JPH02224239A - Plasma etching device - Google Patents

Abstract

PURPOSE:To increase etching rate by combining first and second cathodes with a high frequency power source so as to put it in electrode structure to strengthen the interference during discharge by high frequency voltage. CONSTITUTION:This is equipped with a first cathode, on which a substance 4 to be etched is placed, a second cathode 2, which is provided opposite to this, and high frequency power sources 16-19, which apply high frequency voltage to the first and second cathodes 1 and 2 so as to generate plasma by flow discharge and accelerate ions to the first and second cathodes 1 and 2. And it is made in such electrode structure as to strengthen the interference during discharge by high frequency voltage by combining the first and second cathodes 1 and 2 with the high frequency power sources 16-19. As a result, the plasma density near the substance 4 to be etched increases, and the current density of ions entering the substance 4 to be etched increases. Hereby, etching rate can be increased, and the disturbance of incident direction of ions can be suppressed surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma etching apparatus used for microfabrication in the manufacturing process of semiconductor devices.

[Prior art] In the microfabrication process of the semiconductor device manufacturing process,
Plasma etching methods that utilize high-frequency glow discharge of reactive gases are mainly used.

In particular, in processes that require precise control of processing dimensions or processing shapes, the workpiece (semiconductor wafer) is placed on a cathode to which a high frequency is applied, and the cathode surface is generated when the cathode is biased to a negative voltage. Reactive ion etching method (Reac
tive ion etching (RIE) has become mainstream.

The characteristics of etching in the old E method vary depending on the type and amount of radicals generated in the gas phase, and the energy and density of ions incident on the cathode on which the object to be etched is placed. However, under normal conditions, the processing speed is at most a few tens of nanometers per inch, and if the high frequency power is increased to further increase the etching rate,
Not only does the amount of radicals and the ion current density increase, but also the ion energy increases, which causes problems such as lowering the selectivity of the etching mask and underlying layer and damaging the semiconductor crystal.

Therefore, in order to increase manufacturing speed, large-sized equipment capable of etching multiple semiconductor wafers simultaneously has become necessary.

In addition, in the RIE method, as the processing becomes finer, the problem is that the processed shape is disturbed by ions whose direction is disordered, which is caused by the collision between accelerated ions and neutral gas in the ion sheath near the cathode. It's here.

In order to solve these problems, a so-called magnetron-type etching apparatus has been proposed, which applies a magnetic field in combination with a high-frequency electric field to generate plasma, and improves the etching rate through the interaction of these fields. An example of such a device is shown in US Pat. No. 4,422,896 to Walter H., C1ass et al. Also, JP-A-57-159 by Haruo Okano et al.
No. 026 also discloses such a device.

In these devices, by applying a magnetic field perpendicular to a high-frequency electric field, electrons drift in a direction perpendicular to the electric and magnetic fields, resulting in active collisions with gas and an increase in the plasma density of the discharge. The increase in the plasma density of the discharge is
Since the current density of ions incident on the processed sample placed on the cathode is increased, it is possible to increase the current density by 10
A two-fold increase in etching rate can be seen.

Therefore, etching using these devices can basically achieve a sufficient processing speed even when processing a single sheet, so that the devices can be downsized.

Furthermore, devices using coils as means for applying a magnetic field are also known. Kim Kyung-sik et al.'s paper, RSIO2 high-speed etching, 7th Dry Process Symposium, p. 95 (19
85) An example is given in J. JP-A-63-1/530 by Owen Wilkinson also discloses a magnetron-type device using a coil as a magnetic field neutralization means.

Additionally, devices aimed at independently controlling ion energy, current density, or radical concentration are described in Japanese Patent Publication No. 12346/1982 and the paper Masaaki 5.
ato, Yoshfnobu Ar1ta, Dou
bJe-source Excited Reac
tive Ion Etching and
Its^pplication to Submi
cron Trench EtchingExte
Abstracts of the
18th (19861 inter-national)
Conference on 5solid 5tat
e Devices and Materials, T
okyo, 233 (198δ). Here, a three-electrode plasma is used, in which a cathode on which the object to be etched is placed and another cathode opposed thereto, and a grid made of a mesh or perforated plate as a common anode between both cathodes. An etching device is used.

FIG. 12 is a schematic diagram illustrating the above-mentioned three-electrode plasma etching apparatus. In this plasma etching apparatus, after the inside of the vacuum chamber 21 is evacuated by the vacuum pump 9, a reaction gas is introduced into the vacuum chamber 21 from the gas introduction system 8, and the high frequency power supplies 6 and 7 are used to evacuate the inside of the vacuum chamber 21. When high frequency power is applied to the cathodes 1 and 2, the reactive gas is decomposed and ionized, plasma is generated, and the object to be etched 4 placed on the cathode 1 is
is etched. 3 is a grid provided between cathode 1 and cathode 2; 5 is a blocking capacitor provided between the high frequency power supplies 6 and 7 and the cathodes 1 and 2.

In this apparatus, the discharge area on the cathode 2 side facing the cathode 1 is separated by a grid 3 from the discharge area on the cathode 1 side where the object to be etched 4 is placed. By applying a high frequency voltage to the cathode 2, gas decomposition and ionization are promoted, and the generated ions pass through the grid 3 and reach the cathode 1 on which the object to be etched 4 is placed.
increasing the density of active species and plasma density present in the side discharge region.

Therefore, the amount of ion current and active species incident on the object to be etched 4 can be increased, so that the etching rate can be increased by 2 to 4 times as compared to a general opposed electrode type plasma etching apparatus.

In addition, as the ion current density increases, the width of the ion sheath formed on the surface of the object to be etched 4 decreases, and it is possible to suppress the disturbance in the direction of the ions that occurs when the ions collide with gas molecules within the ion sheath. can. Therefore, in a submicron region such as a width of 0.25 μm, processing can be performed to a depth of about 10 times the width, and an excellent processed shape can be obtained.

[Problems to be Solved by the Invention] However, in a magnetron RIE device that uses a permanent magnet as a magnetic field applying means, the magnetic field applied by the permanent magnet is fixed, so there is no freedom to change the etching conditions. There was a problem that the intensity was considerably reduced. For example, it has been impossible to independently control the energy of ions and their current density. Another problem is that precise control for achieving etching uniformity cannot be performed.

Devices that use coils as magnetic field application means have a greater degree of freedom in etching conditions than devices that use permanent magnets, but it is difficult to independently control ion energy and current density.

Not limited to the above example, in various magnetron etching devices that involve temporal fluctuations in the magnetic field, such as physically moving a coil or permanent magnet or temporally varying the current flowing through the coil, the high-frequency electric field changes over time. Since the change in the magnetic field is very slow compared to the change in the magnetic field, the discharge state changes as the magnetic field changes, and this change causes changes in the energy and directionality of the ions, resulting in element damage or deterioration of the processed shape.

In addition, in the conventional three-electrode etching apparatus, the degree of freedom in etching conditions is increased, making it possible to independently control the ion energy and current density, and there is no temporal variation in the discharge state. Although no element damage or deterioration of the machined shape due to fluctuations in discharge conditions was observed,
In terms of processing speed, it was not sufficient compared to the magnetron type.

The reason for this is that the plasma generated in the discharge area on the cathode 2 side diffuses into the discharge area on the cathode 2 side via the grid 3, so a considerable amount of the plasma generated in the discharge area on the cathode 2 side is etched onto the object to be etched. Therefore, even if the high-frequency power applied to the cathode 2 is increased, the increase in the ion current density incident on the object to be etched 4 reaches saturation. . There was also the problem that slight uneven etching occurred due to the influence of grid 3.

The present invention has been made to solve the above-mentioned problems, and it is possible to increase the processing speed by increasing the etching rate, to reliably suppress disturbances in the direction of ion incidence, and to reduce the ion energy. It is an object of the present invention to provide a plasma etching apparatus which eliminates temporal fluctuations in etching and reduces ion energy so as to cause less damage to an object to be etched.

[Means for Solving the Problem] In order to achieve such an object, the present invention includes a first cathode on which an object to be etched is placed;
A high frequency voltage is applied to a second cathode provided opposite to the first cathode, and the first and second cathodes to generate plasma by glow discharge and direct ions toward the first and second cathodes. The first and second cathodes are combined with the high frequency power source to form an electrode configuration that enhances interference between discharges caused by the high frequency voltage.

At this time, the frequencies of the high-frequency voltages applied to the first and second cathodes from the high-frequency power supply are equal, and the phase between the high-frequency voltages applied to both cathodes is made variable.

Further, as for the electrode configuration, the distance between the first cathode and the second cathode is set to 6 co+ or less. In this case, the phase of the high frequency voltage applied to the second cathode is between 1/4 and 1/4 wavelength with respect to the phase of the high frequency voltage applied to the second cathode.

Further, in the present invention, a first cathode on which an object to be etched is placed, a second cathode provided opposite to the first cathode, and a high frequency applied to the first and second cathodes. It includes a high frequency power source that applies a voltage to generate plasma by glow discharge and accelerate ions toward the first and second cathodes, and a magnetic field applying means that strengthens interference between the discharges caused by the high frequency voltage.

At this time, the frequencies of the high frequency voltages applied from the high frequency power source to the first and second cathodes are equal, and the phase between the high frequency voltages applied to both cathodes is variable.

Further, the magnetic field applying means applies a magnetic field such that lines of magnetic force pass near the first and second cathodes. In this case, the phase of the high frequency voltage applied to the second cathode is advanced by 0 to 1/2 wavelength with respect to the phase of the high frequency voltage applied to the first cathode.

A grid is provided near the second cathode and opposite the first cathode. Further, an anode is provided opposite to the first cathode and is grounded,
The second cathode is an annular object provided between the first cathode and the anode.

At this time, as the magnetic field applying means, a first magnetic field generating coil provided near the first cathode and on the opposite side to the side where the second cathode exists, and a first magnetic field generating coil provided near the second cathode and on the opposite side to the side where the second cathode is present. A device comprising a second magnetic field generating coil provided on the opposite side to the side where the cathode is present, and a coil power source that flows current in opposite directions to the first and second magnetic field generating coils. Use.

At this time, as the magnetic field applying means, a first magnetic field generating coil provided near the first cathode and on the opposite side from the anode, and a first magnetic field generating coil provided near the second cathode and having an outer diameter that is opposite to the anode. a second magnetic field generating coil smaller than the inner diameter of the second cathode; a third magnetic field generating coil provided around the second magnetic field generating coil and having an inner diameter larger than the outer diameter of the second cathode; and a coil power source that allows current to flow in the same direction through the third magnetic field generating coil, and through which current flows in the opposite direction to the current flowing through the first and third coils through the second magnetic field generating coil. Use what you do.

At this time, the magnetic field applying means further includes a first magnetic field generating coil provided near the first cathode and on the opposite side of the anode, and a first magnetic field generating coil provided around the first magnetic field generating coil. The second coil has a larger diameter than the magnetic field generating coil.
a third magnetic field generating coil provided near the second cathode and having an outer diameter smaller than the inner diameter of the second cathode; A current in the same direction is passed through the fourth magnetic field generating coil whose inner diameter is larger than the outer diameter of the second cathode, the first magnetic field generating coil and the fourth magnetic field generating coil, and the second
The third magnetic field generating coil is equipped with a coil power source that allows current to flow in the opposite direction to the current flowing through the first and fourth coils.

[Function] In the present invention, by providing a means for strengthening the interference between the discharges caused by the high frequency voltage applied to the first and second cathodes, or by using an electrode configuration, the plasma near the object to be etched is reduced. As the density increases, the ion current density incident on the object to be etched increases.

Furthermore, by equalizing the frequencies of the high frequency voltages applied to the first and second cathodes from the high frequency power source, it is possible to prevent temporal fluctuations in the high frequency voltages applied to the first and second cathodes, Furthermore, by controlling the phase of the high-frequency voltage applied to the second cathode to an optimal value with respect to the phase of the first high-frequency voltage, the plasma density near the object to be etched is increased, and ions incident on the object to be etched are Current density can be increased.

If the means for increasing the interference between discharges caused by high-frequency voltage is an electrode configuration in which the distance between the first cathode and the second cathode is 6 cm or less, the plasma is confined in a narrow region and the plasma density increases. Also, by having both cathodes facing each other without a grid between them,
When plasma interference due to the high frequency voltage applied to both cathodes increases and the phase between the high frequency voltages applied to both cathodes falls within the range of -i/4 to 1/4 wavelength,
The plasma density near the object to be etched increases, and the density of ion current incident on the object to be etched increases. moreover,
Since there is no grid, minute etching unevenness caused by the grid does not occur.

If the means for intensifying the interference between the discharges caused by the high-frequency voltage is a magnetic field applying means for applying a 641 field such that magnetic lines of force pass near the first and second cathodes,
The plasma is confined by the magnetic field and the plasma density increases. Furthermore, since the electrons move along magnetic lines of force, plasma interference due to the high-frequency voltage applied to both cathodes increases, causing the phase of the high-frequency voltage applied to the second cathode to change from that of the high-frequency voltage applied to the first cathode. O for the phase
If the wavelength is advanced by 1/2, the plasma density near the object to be etched increases, and the density of the ion current incident on the object to be etched increases.

Further, as the above-described magnetic field applying means, a first magnetic field generating coil provided near the first cathode and on the opposite side to the side where the second cathode is present, and a first magnetic field generating coil provided near the second cathode and on the opposite side to the side where the second cathode is present. A second magnetic field generating coil provided on the opposite side to the side where the first cathode is present, and a coil power supply that flows currents in opposite directions to the first and second magnetic field generating coils. When a cathode is used, a surface is formed in which the component of the magnetic flux density of the generated magnetic field in the direction perpendicular to the electrode surface (Z-direction component) is zero, and this surface where the Z-direction component is zero is the second cathode. The electrode surface of the first cathode is located on the side opposite to the side where the first cathode exists, or the surface where the Z direction component becomes zero is the electrode surface of the first cathode and opposite to the side where the second cathode exists. If placed at the sides, the electrons will perform a circular drift motion about the axes of the first and second quads.

The second cathode is an annular object provided between the first cathode and the anode; If a magnetic field applying means is provided that applies a magnetic field such that lines of magnetic force pass near the annular second cathode, since there is a grounded anode facing the first cathode, the first cathode and the anode The uniformity of the potential of the plasma confined in the first cathode in the plane direction of the first cathode is higher than that of conventional devices, and it is necessary to insert the conventional grid to ensure uniformity of the plasma potential. disappears. Therefore, the plasma generated by the high frequency power applied to the annular second cathode is effectively guided to the vicinity of the first cathode, increasing the density of ion current incident on the object to be etched. moreover,
Since no grid is used, slight non-uniformity in plasma density caused by the grid is eliminated.

Further, at this time, a first magnetic field generating coil is provided as a magnetic field applying means near the first cathode and on the opposite side of the anode, and a first magnetic field generating coil is provided near the annular second cathode and the outer diameter of the second coil is provided near the first cathode and on the opposite side of the anode. a second magnetic field generating coil smaller than the inner diameter of the cathode; a third magnetic field generating coil provided around the second magnetic field generating coil and having an inner diameter larger than the outer diameter of the second cathode; A coil power source is provided that supplies current in the same direction to the first and third magnetic field generation coils, and supplies current in the opposite direction to the current that is supplied to the first and third coils in the second magnetic field generation coil. When using a device equipped with a coil, if a current is passed through the coil so that the lines of magnetic force that run almost parallel to the first cathode are also almost parallel to the annular second electrode, the current will flow on both cathodes. The discharge becomes a magnetron type, which promotes collision between gas and electrons and increases plasma density. Then, since the electrons move along the lines of magnetic force, the plasma interference due to the high frequency voltage applied to both cathodes increases. When the phase of the high-frequency voltage applied to the annular second cathode is advanced by 0 to 1/2 wavelength with respect to the phase of the high-frequency voltage applied to the first cathode, the plasma density near the object to be etched increases. , the ion current density incident on the object to be etched increases. Furthermore, since the lines of magnetic force pass in the radial direction of the object to be etched, the movement of electrons in that direction is facilitated, and the uniformity of the plasma density on the object to be etched is improved.

Similarly, the magnetic field applying means includes a first magnetic field generating coil provided near the first cathode and on the opposite side of the anode, and a first magnetic field generating coil provided around the first magnetic field generating coil and applied to the first magnetic field generating coil. a second magnetic field generating coil having a diameter larger than that of the generating coil; a third magnetic field generating coil provided near the annular second cathode and having an outer diameter smaller than the inner diameter of the second cathode; A fourth cathode is provided around the magnetic field generating coil and has an inner diameter larger than the outer diameter of the second cathode.
a first magnetic field generating coil and a fourth magnetic field generating coil.
A coil power supply is provided for passing current in the same direction through the magnetic field generating coils, and passing current in the opposite direction to the current flowing through the first and fourth coils in the second and third magnetic field generating coils. When three coils are used, if the current is passed through the coils so that the lines of magnetic force that pass almost parallel to the first cathode are also almost parallel to the second electrode, Although similar effects can be obtained, the configuration with four coils can more completely align the magnetic lines of force in parallel to the first and second cathodes, thereby improving the uniformity of plasma density.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 shows a schematic configuration of a plasma etching apparatus according to a first embodiment of the present invention. In FIG. 1, the same parts as in FIG. 11 are given the same reference numerals. High frequency amplifiers 16 and 1 are connected to the first cathode 1 and the second cathode 2, respectively.
/ is connected via a blocking capacitor 5. High frequency amplifiers 16 and 1/ are connected to an oscillator 18, and a phase controller 19 is provided between high frequency amplifier 1/ and oscillator 18. The high frequency amplifier 16, the 1/1 oscillator 18, and the phase controller 19 constitute a high frequency power source.

Next, by thermally oxidizing the single crystal silicon, a film thickness of 50
A 5i02 film with a thickness of 0 nm was formed, and the 5in2 film was patterned using a photolithography process and a dry etching process to form a pattern of the 5i02 film on single-crystal silicon as the object to be etched 4, as shown in FIG. A case where etching is performed using a plasma etching apparatus will be explained.

The distance between cathodes 1 and 2 should be 6 cm or less, for example 3 ca.
+ First, the inside of the vacuum chamber 21 is evacuated by the vacuum pump 9, and then 305 CCM of a reaction gas, for example, chlorine gas, is introduced into the vacuum chamber 21 from the gas introduction system 8, and the pressure inside the vacuum chamber is set to 0.5 Pa.

Next, the frequency is increased to 13 by the high frequency amplifier 16 and 1/
．． A high frequency power of 56 MH2 and a power of 150 W is applied to cathodes 1 and 2. At this time, cathodes 1 and 2
The frequencies of the high-frequency voltages applied to the excavator 18 are the same, and the phase of the high-frequency voltage can be changed arbitrarily by the phase controller 19. Due to the glow discharge generated in the vacuum chamber 21 by the application of high frequency power, the reactive gas is decomposed and ionized, plasma is generated, and the object to be etched 4 is etched.

In this case, by bringing the cathodes 1 and 2 closer together, the power consumed per unit volume increases and the plasma density increases. In this plasma etching apparatus, power is supplied from the oscillator 18 to the high frequency amplifier 16 and the high frequency amplifier 1/, so that the frequencies of the high frequency voltages applied to the cathodes 1 and 2 are equal, so that damage to the object 4 to be etched is prevented. It never gets bigger.

When the frequencies of the high-frequency voltages applied to the cathodes 1 and 2 are not equal, beats occur in the plasma due to the frequency difference, and the high-frequency voltages applied to the cathodes 1 and 2 fluctuate as shown in FIG. Since the frequency of the fluctuation is low enough for the ions to follow, the maximum energy of the ions becomes high and the damage to the object 4 to be etched increases.

On the other hand, when the frequencies of the high-frequency voltages applied to cathodes 1 and 2 are equal, no beat occurs in the plasma, and the high-frequency voltages applied to cathodes 1 and 2 do not vary over time. Therefore, the maximum energy of the ions does not become large and the damage to the object 4 to be etched does not become large.

Furthermore, by changing the phase of the high frequency voltage applied to the cathode 2 with respect to the high frequency voltage applied to the cathode 1, the interference between discharges can be changed by the high frequency voltage applied to the cathodes 1 and 2, thus The plasma density can be varied and the plasma density distribution between the cathodes can be varied.

FIG. 3 shows the relationship between the phase difference, self-bias voltage, and emission intensity in the first embodiment of the present invention.

Curve A shows the relationship between the phase difference between the high frequency voltage applied to cathode 2 and the high frequency voltage applied to cathode 1 and the self-bias voltage (DC voltage component) generated at cathode 1. Curve B shows the relationship between the phase difference between the high frequency voltage applied to cathode 2 and the high frequency voltage applied to cathode 1 and the self-bias voltage generated at cathode 2.

Curve C shows the relationship between this phase difference and the emission intensity of chlorine radicals, which are reactive species.The emission wavelength of chlorine radicals is 725.
．． There are 6ni.

The curved line shows the relationship between the above-mentioned phase difference and the emission intensity of silicon, which is a reaction product. The emission wavelength of silicon is 251.6 nm.

As can be seen from curves A, B, C, and D, the self-bias voltage and emission intensity change greatly depending on the phase difference, and the self-bias voltage is minimized when the phase difference is between 1/4 and 1/4 wavelength. The luminous intensity becomes maximum. Since the self-bias voltage decreases as the plasma density increases, when the phase difference is between 1/4 and 1/4, the interference between the discharges caused by the high-frequency voltage applied to both cathodes becomes stronger and the plasma density reaches its maximum. I understand.

Then, the self-bias voltage of cathode 1 is the same as that of cathode 2.
The phase of the high frequency voltage applied to the cathode 1 is minimum on the advanced side with respect to the phase of the high frequency voltage applied to the cathode 1, and the self-bias voltage of the cathode 2 is opposite. This phenomenon is considered to be an effect of electron flow due to changes in potential distribution in the plasma, and is explained as follows.

Figure 4 shows the ion sheath and plasma. Figure 5 is the 4th
The waveform of the high frequency voltage (vl) applied to the ion sheath 103 on the cathode 1, the waveform of the high frequency voltage (VC) applied to the ion sheath 101 on the cathode 2, and the plasma potential near the ion sheath 103 on the cathode 1 shown in the figure. This is a waveform of the difference (Vb) between the plasma potential near the ion sheath on the cathode 2 and the plasma potential near the ion sheath on the cathode 2. 102 is plasma.

When there is no phase difference in the high frequency voltage (θ = 0), no potential difference occurs (Vb = O), whereas when the phase of the high frequency voltage applied to the cathode 2 advances (θ = π/4)
, Vb is almost in phase with V and is opposite to vc.

Focusing on the movement of electrons, Vb increases when (2) substantially matches the potential of the cathode, electrons gather on the cathode 2 side, and the plasma density near the object to be etched 4 increases. Conversely, when the phase of the high frequency voltage applied to the cathode 2 is delayed (θ=-π/4), electrons gather near the cathode 2 and the plasma density near the object to be etched 4 decreases.

Therefore, when the phase of the high frequency voltage applied to the cathode 2 is slightly ahead of the phase of the high frequency voltage applied to the cathode 1, etching can be performed with the maximum ion current density and the minimum ion energy.

The major difference from the conventional three-pole type device is that the grid 3 (see FIG. 11) is removed. When grid 3 is provided, the discharges from cathodes 1 and 2 are separated by the grid, each having an independent space, and interfering with each other through the holes in the grid, whereas in this device, the discharge space is shared. Therefore, the increase in overall plasma density is more noticeable than the effect of electron flow.

Therefore, the etching rate increases, the disturbance in the direction of ion incidence is reliably suppressed, and the ion energy (corresponding to the self-bias voltage) decreases.
Damage to the object 4 to be etched is reduced.

When silicon was etched with a phase difference of, for example, 0.1 wavelength, an etching rate of %290 nm/lll1n was obtained, and a selectivity with respect to 5j02 of 13 was obtained. Although this etching rate was slightly lower than that of other examples described later in which a magnetic field was applied, a practical etching rate was obtained.

The uniformity of the etching rate was also less than ±2%, and since no grid was used, no uneven etching was observed. The uniformity of etching is determined by the uniformity of the plasma density and the uniformity of the plasma potential on the object to be etched 4, but since no magnetic field is applied in this device, there are few changes due to these etching conditions, and it is possible to optimize the processed shape. Even when hydrogen was mixed with a gas other than chlorine gas, such as 5jC14, or when the high frequency power applied to cathodes 1 and 2 was changed, no deterioration in etching uniformity was observed.

In the above embodiment, the cathode spacing is 3CI.
11, but the narrower the interval, the higher the plasma density, the lower the self-bias voltage, and the higher the etching rate. However, if the width is too narrow, the ion sheaths generated on both cathodes will contact each other, making the discharge unstable and reducing the uniformity of etching. Additionally, it becomes difficult to start the discharge.

Further, in the above embodiment, the pressure of the vacuum chamber 21 was set to 0.5 Pa, but the pressure of the vacuum chamber 21 was set to 0.5 Pa.
．． It is good also as 1-100Pa. Furthermore, although chlorine gas or a mixed gas of St(:14 and hydrogen) was used as the etching gas, the effect is exactly the same even if other halogen-containing gases or oxygen-containing gases are used and the object to be etched is changed.

Embodiment 2 FIG. 6 shows a schematic configuration of a plasma etching apparatus according to a second embodiment of the present invention. In FIG. 6, the same parts as in FIG. 1 are given the same reference numerals. In Figure 2, 10 is the first
This magnetic field generating coil is provided near the first cathode 1 on the opposite side to the side where the second cathode 2 is present. 11 is a second magnetic field generating coil, and the first cathode 1. the second cathode 2 on the side opposite to the side where there is
It is located near the. Reference numerals 12 and 13 are coil power supplies that supply current to the magnetic field generation coils 10 and 11, and the magnetic field generation coils 10 and 11 and the coil power supplies 12 and 13 constitute a magnetic field application means.

Next, by thermally oxidizing the single crystal silicon, a film thickness of 1 μm was obtained.
5iO11@ of m is formed and the 5in2 film is patterned by a photolithography process and a dry etching process to form a pattern of Sin on single crystal silicon as the object to be etched 4 as shown in the sixth example. A case where etching is performed using a plasma etching apparatus will be explained.

First, the inside of the vacuum chamber 21 is evacuated by the vacuum pump 9, and then 405 CCM of a reaction gas, for example, chlorine gas, is introduced into the vacuum chamber 21 from the gas introduction system 8, and the pressure inside the vacuum chamber 21 is set to 0.5 Pa. Coils for generating magnetic fields by coil power supplies 12 and 13, respectively.
Flow currents in opposite directions through O and 11.

The current values passed through the magnetic field generating coils 10 and 11 are, for example, 9000 turns and 1400 OA turns, respectively. By flowing this current, a magnetic field is applied such that the magnetic flux density on the cathode 1 is several tens to several hundreds of Gauss and the lines of magnetic force pass near the cathodes 1 and 2.

Next, the cathodes 1 and 2 are connected to each other by the high frequency power supplies 6 and 7.
The frequency is 13.58MH2 and the power is 100W each.
and a high frequency of 300W is applied. Then, the chlorine gas, which is a reactive gas, is decomposed and ionized to generate plasma, and the object to be etched 4 is etched.

In this case, the electrons in the plasma undergo cyclotron motion around the magnetic field lines, making it difficult for the electrons to move in the direction perpendicular to the magnetic field, and the plasma is confined. The density increases, the ion current density incident on the object to be etched 4 increases, and the etching rate increases. Further, since the ion sheath width is reduced, disturbance in the direction of ion incidence is suppressed, and the ion energy is also reduced, so damage to the object 4 to be etched is reduced.

When etching was performed using the plasma etching apparatus shown in Fig. 6, the ion current density was several 100 μA/ca + and the etching rate was approximately 1100 n/win when no magnetic field was applied, whereas when a magnetic field was applied, the etching rate was approximately 1100 n/win. When this happens, the ion current density is approximately 1 m^/C111
2. The etching rate was about 400 nm/min.

The function of the grid 3 in the apparatus shown in FIG. 6 will be explained. When the grid 3 is not provided, electrons are difficult to move in the direction across the lines of magnetic force, and the high-frequency current flows toward the inner wall of the vacuum chamber 21, so the closer you get to the center of the cathode 1, the more the electrons flow toward the inner wall of the vacuum chamber 21. Electrical resistance increases. Ions are heavier than electrons, so they are less affected by magnetic fields, so their electrical resistance does not increase. Due to this difference between electrons and ions, the potential of the plasma decreases closer to the center of the cathode 1, and the acceleration energy of ions decreases closer to the center of the cathode 1, resulting in a lower etching rate.

On the other hand, when a magnetic field is applied and the grid 3 is provided,
Since the grid 3 crosses the lines of magnetic force, it is in a direction in which high-frequency current can easily flow, the plasma potential becomes uniform, and the etching rate also becomes uniform. When a wafer with a diameter of 1.0 cm was etched using the plasma etching apparatus shown in FIG. In some cases, the deviation in etching rate was less than ±2%.

In addition, by flowing currents in opposite directions to the magnetic field generating coils 10 and 11 from the coil power supplies 12 and 13, respectively, the magnetic field becomes a Cubs magnetic field, and the surface where the magnetic flux density in the Z direction becomes zero is the surface of the cathode 1. The lines of magnetic force diverge near this plane.

Since electrons tend to move along magnetic lines of force, plasma converges and diverges along magnetic lines of force. Therefore, by adjusting the current flowing through the magnetic field generating coils 10 and 11, and changing the position of the plane where the magnetic flux density in two directions is τ, the plasma density distribution can be changed.
The in-plane distribution of etching rate can be controlled, and optimum conditions such as etching uniformity can be easily obtained.

When the surface where the magnetic flux density in the Z direction becomes zero is located on the side of the cathode electrode 2 opposite to the side where the cathode 1 is present, the magnetic flux density decreases as the distance from the cathode electrode 1 increases. Further, at this time, the magnetic flux density has a component parallel to the cathode 1, and the lines of magnetic force spread radially from the center of the cathode 1. Moreover, at this time, the direction of the high-frequency electric field is perpendicular to the cathode 2, so the electrons drift near the cathode 2 and perform circular motion around the center of the cathode 1, which prevents collisions between gas molecules and electrons. This increases the plasma density and further increases the etching rate.

Furthermore, since the magnetic flux density near the grid 3 also has a component parallel to the surface of the grid 3, the plasma passing through the grid 3 is mixed by the drift of electrons, and a uniform plasma density is obtained. It is possible to prevent uniformity from occurring. Therefore, slight unevenness in etching caused by holes in the grid 3 can be prevented.

When the surface where the magnetic flux density in the Z direction becomes zero is located on the side of the cathode electrode 1 opposite to the side where the cathode 2 is present, the magnetic flux density decreases as the distance from the cathode electrode 2 increases. Further, at this time, the magnetic flux density has a component parallel to the cathode 1, and the lines of magnetic force spread radially from the center of the cathode 2. Moreover, since the direction of the high-frequency electric field is perpendicular to the cathode 1 at this time, the electrons drift near the cathode 1 and perform circular motion around the center of the cathode 1, so that the plasma is generated near the object 4 to be etched. The density increases and the etching rate further increases.

Furthermore, since the magnetic flux density on the side closer to the object to be etched 4 than the grid 3 also has a component parallel to the surface of the grid 3, the plasma that has passed through the grid 3 is mixed by the drift of electrons, resulting in a uniform plasma density. Therefore, non-uniformity of plasma due to holes in the grid 3 can be prevented. Therefore, slight unevenness in etching caused by holes in the grid 3 can be prevented.

In this embodiment as well, the phase difference between the high frequency voltages applied to the cathodes 1 and 2 changes the interference between the plasmas generated by the respective high frequency voltages. ψ FIG. 7 shows the relationship between the phase difference between the high frequency voltage applied to the cathode 2 and the high frequency voltage applied to the cathode 1 and the self-bias voltage generated at the cathode 1 in the apparatus shown in FIG. 6. As is clear from FIG. 7, when no magnetic field is applied (curve E), there is little interference because of the grid 3, and even if the phase difference changes, the self-bias voltage does not change much. On the other hand, when a magnetic field is applied (curve F), the phase of the high-frequency voltage applied to cathode 2 is 0-1/2 lower than the phase of cathode 1.
When the wavelength is advanced, that is, the phase difference is O~+1/
When there are two wavelengths, the plasma density increases. Conversely, when the phase difference is 0 to -1/2 wavelength, the plasma density near the cathode 1 becomes small.

When a magnetic field is applied in the apparatus shown in Fig. 6, the self-bias voltage is minimized on the side where the phase difference is larger, and the plasma density is lower in curve F in Fig. 7 than in curve A in Fig. 3. It is maximum. This is thought to be because the interference between the discharges caused by the high-frequency voltages applied to each cathode became stronger due to the magnetic field.

Therefore, when a magnetic field is applied, the phase difference controller 19
If the phase difference is O~+1/2 wavelength, the cathode 1
Since the plasma density in the vicinity increases, the etching rate increases, and since the ion energy decreases, damage to the object 4 to be etched is reduced.

In the second embodiment, two magnetic field applying means are used.
Although one set of magnetic field generating coils is used, one set or three or more sets of magnetic field generating coils may be used. Furthermore, in the above embodiment, the pressure inside the vacuum chamber 21 is set to 0.5
Pa, but the pressure inside the vacuum chamber 21 is 0.1 to I
It may also be QOPa. In addition, although chlorine gas was used as the etching gas, the effect is exactly the same even if a halogen-containing gas or an oxygen-containing gas is used and the object to be etched is something other than a 5i02 pattern formed on single crystal silicon. .

Figure 8 shows a schematic configuration of a plasma etching apparatus according to a third embodiment of the present invention. In Figure 8, the same parts as in Figure 6 are given the same reference numerals. 22 is a grounded anode facing the cathode 1. Reference numeral 20 denotes a second annular cathode provided between the cathode 1 and the anode 22, and in this embodiment, a cylindrical second cathode is used. 23 is an insulator for insulating the cathodes 1 and 20 from the ground.

The annular second cathode 20 is arranged so that its axis is substantially perpendicular to the surface of the first cathode 1, and its inner diameter is approximately the same size as the outer diameters of the first cathode 1 and the anode 22. ing.

Next, a case will be described in which the plasma etching apparatus shown in FIG. 8 is used to etch a Si film formed on single crystal Si using a patterned organic resist film as a mask.

First, the inside of the vacuum chamber 21 is evacuated by the vacuum pump 9, and then 505 CCM of a reaction gas, for example C) IF3 gas, is introduced into the vacuum chamber 21 from the gas introduction system 8, and the pressure inside the vacuum chamber is set to 0.8 Pa. At the same time, currents of, for example, 9000 A turns and 1400 OA turns are applied to the magnetic field generating coils 10 and 11 by the coil power supplies 12 and 13, respectively, and the magnetic flux density on the cathode 1 is several tens to hundreds of Gauss. In addition, the lines of magnetic force form a magnetic field passing near the cathode 1 and the cathode 20. Note that the direction in which this magnetic field is formed does not have to be strictly perpendicular to the surface of the cathode 1 as long as it is approximately perpendicular.

Next, the frequency is increased to 13 by the high frequency amplifier 16 and 1/
．． 56MH, power is 150W and 200W respectively
high frequency power is applied to cathodes 1 and 20. Due to the glow discharge generated in the vacuum chamber 21 by the application of high frequency power, the reactive gas is decomposed and ionized, plasma is generated, and the object to be etched 4 is etched.

In this case, the electric field generated by applying high frequency power to the cathode 20 is
0, and the magnetic field has a component parallel to the inner surface of the cathode 20, so the electrons drift in a direction perpendicular to the electric field E and the magnetic flux density B, ie, in the ExB direction, while performing cyclotron motion around the magnetic lines of force. This direction is cathode 2
0, the cathode 1 is circularly orbited along the cathode 1. Therefore, electrons are confined between the cathode 1 and the anode 22 at high density.

In the apparatus shown in FIG. 6 (second embodiment), if there is no grid 3, the plasma potential is lower than the cathode 1.
Since the center of the cathode 1 is very negative, the energy of the ions incident on the object to be etched 4 is low at the center of the cathode 1, making it difficult to ensure uniform etching. Therefore, a grid 3 was inserted to ensure uniformity of the plasma potential.

In the device of this embodiment, an anode 22 is provided opposite to and parallel to the cathode 1 . Since the anode 22 is located in a direction where electrons, which tend to move in the direction of magnetic lines of force, can easily flow, a high frequency current flows between the anode 22 and the cathode 1, and the uniformity of the plasma potential on the surface of the cathode 1 becomes high.

This eliminates the need for a grid, which not only eliminates minute etching unevenness caused by the grid, but also eliminates loss of plasma density due to insertion of the grid.

Therefore, compared to the device shown in FIG. 6, the plasma density increases even if the high frequency applied to the cathode is the same.

Since the ion current density incident on the object to be etched 4 increases, the etching rate increases, and disturbances in the direction of ion incidence are reliably suppressed, and the ion energy decreases, so damage to the object to be etched 4 is reduced. do.

When etching was performed using the plasma etching apparatus shown in Fig. 8, the etching rate was approximately 80 m/a+in when no magnetic field was applied, but increased to approximately 500 nm/l1in when a magnetic field was applied. did.

This was a very large etching rate compared to about 140 nm/layer 1n in the device of the second example shown in FIG. By adjusting the currents flowing through the coils 10 and 11, when the surface where the magnetic flux density in the Z direction becomes zero is located on the opposite side of the card 1 from the side where the cathode 2 is present, the magnetic flux density becomes It has a component parallel to the cathode 1, the magnetic field lines spread radially from the center of the cathode 2, and the direction of the high-frequency electric field is toward the cathode! Since the electrons drift near the cathode 1 and perform circular motion around the center of the cathode 1, the plasma density increases near the object to be etched 4 and the etching rate further increases. Furthermore, the uniformity of etching could be maintained within ±2% on a 10 cm wafer.

Furthermore, in the plasma etching apparatus shown in FIG. 8, the frequencies of the high-frequency voltages applied to the cathodes 1 and 2 are equal, as in the apparatuses of the first and second embodiments shown in FIGS. , the problem of increase in maximum ion energy due to two high-frequency beats does not occur.

Furthermore, when the phase of the high-frequency voltage applied to the cathode 2 is ahead of the high-frequency voltage applied to the cathode 1 by 0 to +1/2 wavelength, the plasma density further increases due to interference' between the two high-frequency waves, as shown in Figure 6. This is similar to the second embodiment shown in .

In the third embodiment, a cylindrical electrode was used as the second cathode 20, but it may be a polygonal cylinder, an elongated cylinder, etc., as long as its axis is perpendicular to the cathode 1. Further, even an incomplete annular electrode in which some parts are not connected can be used without any problems as long as it does not prevent the electron drift caused by EXB from becoming circular.

Furthermore, in the third embodiment, the pressure inside the vacuum chamber 21 was set to 0.8 Pa, but the pressure inside the vacuum chamber 21 may also be set at 0.1-100 Pa, and CHF may be used as the etching gas. However, even if other halogen-containing gases or oxygen-containing gases are used and the object to be etched is changed, the effect is exactly the same.

Further, in the etching apparatus shown in FIG. 8, two sets of coils are used as the magnetic field applying means, but the number of coils may be one or many sets.

Figure 9 is a fourth embodiment of the present invention, and shows a schematic configuration of an apparatus using three sets of coils as magnetic field applying means.
In the figure, the same parts as in FIG. 8 are given the same reference numerals.

24 is a first magnetic field generating coil provided near the cathode 1 and on the opposite side to the side where the anode 22 is located.

25 and 26 are second and third magnetic field generating coils provided on the opposite side of the coil 24 with the anode 22 in between. The axes of the coils 25 and 26 are connected to the cathode 2
0, the outer diameter of the coil 25 is smaller than the inner diameter of the cathode 20, and the inner diameter of the coil 2B is larger than the outer diameter of the cathode 20.

27, 28 and 29 are magnetic field generating coils 24, respectively.
, 25 and 26, and the magnetic field generating coils 24, 25 and 26 and the coil power supplies 27, 28 and 29 constitute a magnetic field applying means. In this embodiment, a current in the same direction is passed through the magnetic field generating coil 24 and the magnetic field generating coil 28, and a current in the opposite direction to the current flowing through the coil 24 and the coil 26 is passed through the magnetic field generating coil 25.

Figure 10 shows a fifth embodiment of the present invention, and shows the schematic configuration of an apparatus using four sets of coils as magnetic field applying means. The same reference numerals are given to the parts, and 30 is a first magnetic field generating coil provided near the cathode 1 and on the opposite side to the side where the anode 22 is located. 31 is a second magnetic field generating coil provided so as to surround the first magnetic field generating coil 30. As shown in FIG.

32 and 33 are third and fourth magnetic field generating coils provided on opposite sides of the coils 30 and 31 with the anode 22 in between. The axes of coil 32 and coil 33 are aligned with cathode 20 , the outer diameter of coil 32 is smaller than the inner diameter of cathode 20 , and the inner diameter of coil 33 is larger than the outer diameter of cathode 20 .

34, 35, 36 and 37 are coil power supplies that supply current to the magnetic field generating coils 30, 31, 32 and 33, respectively;
3 and coil power supplies 34, 35, 38 and 37 constitute magnetic field applying means. In this embodiment, currents in the same direction are passed through the magnetic field generating coils 30 and 33, and currents in the opposite direction to the currents flowing through the magnetic field generating coils 30 and 33 are passed through the magnetic field generating coils 31 and 32. flow.

FIG. 11 shows two sets of coils (the third embodiment shown in FIG. 8), three sets (the fourth embodiment shown in FIG. 9), and four sets (the fourth embodiment shown in FIG. 10). An example of each magnetic field line in the case of Example 5) is shown.

As shown in FIG. 11 (^), when two sets of coils are used, the lines of magnetic force that pass near the cathode 20 and almost parallel to the cathode 20 can only pass across the cathode 1. On the other hand, Fig. 11(B) and Fig. 11(
C) When three and four sets of coils are used, the lines of magnetic force that pass near the cathode 20 and approximately parallel to the cathode 20 also pass approximately parallel to the surface of the cathode 1. be able to. In particular, when four sets of coils are used, the parallelism of the lines of magnetic force to the cathode 1 can be further improved by optimizing the value of the current flowing through the coils.

Using three or four sets of coils as a magnetic field applying means,
When a magnetic field is applied that causes lines of magnetic force to pass approximately parallel to the electrode surfaces of the cathode 1 and cathode 20, electrons cause a drift motion in which they orbit approximately parallel to the electrode surfaces with respect to the cathode 20, causing a magnetron-type discharge. As a result, collisions between gas and electrons are promoted and the plasma density increases.

Further, the electrons cause a circular motion about the center of the electrode with respect to the cathode 1, and a magnetron-type discharge also occurs on the surface of the cathode 1, increasing the plasma density. Furthermore, since the lines of magnetic force pass near the cathodes 1 and 20, the interference between the discharges due to the high frequency voltages applied to each cathode is strengthened, and the phase of the high frequency voltage applied to the cathode 20 is different from that of the high frequency voltage applied to the cathode 1. 0 for phase
When the plasma is advanced by ~1/2 wavelength, the plasma density near the cathode 1 further increases.

As the plasma density increases, the ion current density incident on the object to be etched 4 also increases, so that the etching rate improves. The uniformity of etching is largely related to the parallelism of the lines of magnetic force passing near the cathode 1 to the electrode surface, and the better the parallelism, the better the uniformity of etching. Therefore, by using four sets of coils, it is possible to obtain a magnetic field with better parallelism, thereby improving the uniformity of etching.

The magnetic field in the second to fifth embodiments is basically a static magnetic field and does not involve temporal fluctuations, so fluctuations in the magnetic field do not cause fluctuations in ion energy or disturbance in the direction of ions. The damage is small;
Moreover, it is possible to perform etching with a processed shape with excellent directionality at a high processing speed. [Effects of the Invention] As explained above, in the present invention, etching is performed using a high-frequency voltage applied to the first and second cathodes. By providing a means to strengthen the interference between discharges or using an electrode configuration, the plasma density near the object to be etched increases, and the ion current density incident on the object to be etched increases, so the etching rate increases. Furthermore, disturbances in the direction of ion incidence on the object to be etched are reliably suppressed, and furthermore, since the ion energy is reduced, damage to the object to be etched is reduced.

In addition, since the degree of interference between discharges caused by high-frequency power or high-frequency voltage applied to the first cathode and the second cathode is adjusted, the energy of ions incident on the object to be etched, current density, and radicals can be adjusted. The concentration and the like can be freely controlled, which has the advantage that optimum etching conditions can be easily obtained.

Furthermore, when the plasma etching apparatus according to the present invention is used in the manufacturing process of semiconductor devices, it is possible to perform etching with a finer batten width than before with a high throughput, and damage to the semiconductor device can be reduced. This has the effect that the cost can be reduced and the performance of the semiconductor device can be dramatically improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a plasma etching apparatus according to a first embodiment of the present invention; FIG. 2 is a diagram showing temporal changes in high-frequency voltages when the frequencies of the high-frequency voltages applied to the cathode are not equal; Figure 3 shows the relationship between the phase difference of the high-frequency voltage applied to the cathode 2 with respect to the high-frequency voltage applied to the cathode 1 and the self-bias voltage generated at the cathode 1.2, and the emission of chlorine radicals in the second embodiment of the present invention. FIG. 4 is a diagram showing the ion sheath and plasma in the first embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the intensity and the emission intensity of silicon. FIG. The waveform (Va) of the high-frequency voltage applied to the ion sheath on the cathode 2, the waveform (vc) of the high-frequency voltage applied to the ion sheath on the cathode 2, and the plasma potential near the ion sheath on the cathode 1 and the waveform near the ion sheath on the cathode 2. A diagram showing the waveform (Vb) of the difference from the plasma potential. FIG. 6 is a schematic diagram of the plasma etching apparatus according to the second embodiment of the present invention. FIG. 7 is a diagram showing the cathode 2 according to the second embodiment of the present invention. FIG. 8 is a diagram showing the relationship between the phase difference between the high frequency voltage applied to the cathode 2 and the self-bias voltage generated at the cathode 1. FIG. 9 is a schematic diagram of a plasma etching apparatus according to a fourth embodiment of the present invention. FIG. 10 is a schematic diagram of a plasma etching apparatus according to a fifth embodiment of the present invention. A diagram showing an example of lines of magnetic force when there are two, three, and four sets of magnetic field generating coils. FIG. 12 is a schematic diagram of a conventional three-pole plasma etching apparatus. DESCRIPTION OF SYMBOLS 1...First cathode, 2...Second cathode, 3...Grid, 4...Object to be etched, 5...Blocking capacitor, 6.7...High frequency power supply, 8. ... Gas introduction system, 9... Vacuum pump, 10, 11... Coil for magnetic field generation, 12, 13... Power supply for coil, 16, 1/... High frequency amplifier, 18... Oscillator, 19... Phase controller, 20... Annular second cathode, 21... Vacuum chamber, 22... Anode, 23... Insulator, 24, 25. 26... For magnetic field generation Coil, H, 28,
29... Coil power supply, 30, 31.32.33...-Magnetic field generation coil, 34
, 35.36.37... Coil power supply.

Claims (1)

[Claims] 1) a first cathode on which an object to be etched is placed; a second cathode provided opposite to the first cathode; and the first and second cathodes. Apply a high frequency voltage to the cathode,
A high frequency power source is provided that generates plasma by glow discharge and accelerates ions toward the first and second cathodes, and the first and second cathodes and the high frequency power source are combined to generate a discharge by the high frequency voltage. A plasma etching apparatus characterized by having an electrode configuration that strengthens interference between the plasma etching devices. 2) A claim characterized in that the frequencies of the high-frequency voltages applied from the high-frequency power source to the first and second cathodes are equal, and the phase between the high-frequency voltages applied to both cathodes is variable. 1. The plasma etching apparatus according to 1. 3) The electrode configuration includes the first cathode and the second cathode.
3. The plasma etching apparatus according to claim 2, wherein the distance between the electrode and the cathode is 6 cm or less. 4) The phase of the high frequency voltage applied to the second cathode is between -1/4 and 1/4 wavelength with respect to the phase of the high frequency voltage applied to the second cathode. A plasma etching apparatus according to claim 3. 5) Applying a high frequency voltage to a first cathode on which the object to be etched is placed, a second cathode provided opposite to the first cathode, and the first and second cathodes. death,
It is characterized by comprising: a high frequency power source that generates plasma by glow discharge and accelerates ions toward the first and second cathodes; and a magnetic field applying means that strengthens interference between the discharges caused by the high frequency voltage. Plasma etching equipment. 6) A claim characterized in that the frequencies of the high-frequency voltages applied from the high-frequency power source to the first and second cathodes are equal, and the phase between the high-frequency voltages applied to both cathodes is variable. 5. The plasma etching apparatus according to 5. 7) The plasma etching apparatus according to claim 5, wherein the magnetic field applying means applies a magnetic field such that lines of magnetic force pass near the first and second cathodes. 8) The phase of the high frequency voltage applied to the second cathode is 0 to 1/2 wavelength ahead of the phase of the high frequency voltage applied to the first cathode. plasma etching equipment. 9) The plasma etching apparatus according to claim 5, further comprising a grid provided near the second cathode and facing the first cathode. 10) An anode provided opposite to the first cathode and grounded, wherein the second cathode is an annular object provided between the first cathode and the anode. 6. The plasma etching apparatus according to claim 5. 11) The magnetic field applying means includes a first magnetic field generating coil provided near the first cathode and on the opposite side to the side where the second cathode is present, and near the second cathode. and a second magnetic field generating coil provided on the opposite side to the side where the first cathode is present, and a coil power source that flows current in opposite directions to the first and second magnetic field generating coils. Claim 1 comprising:
The plasma etching apparatus according to 0. 12) The magnetic field applying means includes a first magnetic field generating coil provided near the first cathode and on the opposite side from the anode, and a first magnetic field generating coil provided near the second cathode and having an outer diameter of the second coil. a second magnetic field generating coil smaller than the inner diameter of the cathode; and a third magnetic field generating coil provided around the second magnetic field generating coil and having an inner diameter larger than the outer diameter of the second cathode. Currents in the same direction are passed through the first and third magnetic field generating coils, and currents in the opposite direction to the currents flowing through the first and third coils are passed through the second magnetic field generating coils. 11. The plasma etching apparatus according to claim 10, further comprising: a power supply for a coil to flow the plasma. 13) The magnetic field applying means includes a first magnetic field generating coil provided near the first cathode and on the opposite side of the anode, and a first magnetic field generating coil provided around the first magnetic field generating coil and the first magnetic field generating coil provided near the first cathode and on the opposite side of the anode. The second magnetic field generating coil has a larger diameter than the first magnetic field generating coil.
a third magnetic field generating coil provided near the second cathode and having an outer diameter smaller than the inner diameter of the second cathode; and a third magnetic field generating coil provided around the third magnetic field generating coil. A current in the same direction is passed through a fourth magnetic field generating coil provided and having an inner diameter larger than the outer diameter of the second cathode, the first magnetic field generating coil and the fourth magnetic field generating coil. 11. The magnetic field generating coil according to claim 10, wherein the second and third magnetic field generating coils are equipped with a coil power source that allows current to flow in the opposite direction to the current flowing through the first and fourth coils. Plasma etching equipment.