JPH11297679A - Method and equipment for surface processing of sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible even the superfine processing of elements, by applying high frequency bias voltage to a sample stage independently of generation of plasma, and controlling the ON/OFF of the high frequency bias voltage which is larger than continuous high frequency bias voltage which can provide the same etch rate. SOLUTION: While microwaves are generated into a vacuum container 104 from a magnetron 101, etching gas such as halogen is also introduced into the container. In the vacuum container 104, plasma of the etching gas is generated with the introduction of microwaves. At the same time with introduction of microwaves, the gas pressure is kept constant and microwave power is also supplied continuously and high frequency bias applied to a sample stage is cyclically turned ON and OFF. By turning the high frequency bias ON and OFF, the energy of ions for obtaining the same etch rate for polisilicon can be set high and anisotropy is eliminated. For example, Vpp with continous bias 60 W is 320 V and Vpp with ON/OFF bias peak power 300 W is 1410 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating a surface of a sample, and more particularly to a method and an apparatus suitable for etching a surface of a sample using plasma.

[0002]

2. Description of the Related Art Conventionally, as a means for treating the surface of a semiconductor element, an apparatus for etching a semiconductor element in plasma has been known. Here, a conventional technique will be described using an apparatus called an ECR (Electron Cyclotron Resonance) method as an example. In this method, plasma is generated by microwaves in a vacuum vessel to which a magnetic field is externally applied. Electrons move in a cyclotron due to the magnetic field, and a plasma can be generated efficiently by resonating this frequency with the frequency of the microwave. A high frequency voltage is applied to the sample to accelerate ions incident on the sample such as a semiconductor device. A halogen gas such as chlorine or fluorine is used as a gas to be plasma.

In such a conventional apparatus, Japanese Patent Application Laid-Open No. Hei 6-1513 mainly discloses a technique for improving the precision of processing.
No. 60 (corresponding US Pat. No. 5,352,324)
Is known. In the present invention, the high-frequency voltage applied to the sample is intermittently controlled between on and off, so that the silicon (S
The selectivity between i) and the underlying oxide film can be increased, and the aspect ratio dependency can be reduced. Also, Japanese Patent Application Laid-Open No. 8-33
No. 9989 (corresponding U.S. Pat. No. 5,614,060) teaches that by superimposing intermittent RF bias power short pulses in metal etching,
It is described that the etch residue can be reduced. Also,
Japanese Patent Application Laid-Open No. Sho 62-15473 discloses a method of processing a slope by introducing a gas which causes deposition and etching, and alternately applying a DC bias higher than a predetermined potential and a DC bias lower than a predetermined potential. Is stated.

[0004] Japanese Patent Application Laid-Open No. 60-50923 (corresponding to US Pat. No. 4,579,623) discloses that the amount of etching gas introduced is periodically changed and the application time of a high-frequency voltage is changed. Thus, a method for improving surface treatment characteristics is described. Japanese Patent Publication No. 4-
No. 69415 (corresponding to U.S. Pat. No. 4,808,258) describes a method for improving etching characteristics by modulating a high-frequency voltage applied to a sample. Further, in the specification of US Pat. No. 4,585,516, in a three-electrode type etching apparatus, an etching rate is adjusted by modulating a high-frequency voltage of at least one of high-frequency power supplies connected to two electrodes. A method for improving the uniformity in the wafer plane is described.

[0005]

By the way, with the miniaturization of semiconductor devices, the processing dimensions of lines and spaces corresponding to wirings and electrodes are in the region of 1 μm or less, preferably 0.5 μm or less. In the processing of such a fine pattern, the line becomes gradually thicker, and the problem that the pattern cannot be processed to the design dimensions becomes significant. Further, in addition to the difference in the etching rate between the inside of the fine groove and the relatively wide portion, the difference in shape, that is, the so-called shape microloading becomes remarkable, which hinders the processing.

Furthermore, MOS (metal oxide semiconduct
or) The thickness of the gate oxide film of the transistor is 6 nm or less for memory elements of 256M or more. In such a device, the anisotropy and the selectivity of the base oxide film have a trade-off relationship, which makes processing more difficult.

Many of the above prior arts were invented in the era when the minimum processing size of the element was 1 μm or more, and it has become difficult to respond to processing of finer elements with these techniques. In the processing of such a fine element, it is necessary to assemble under precise process conditions based on the analysis of the relationship between the physical quantity of the plasma and the etching characteristics, and many manufacturers are currently spending much labor here. The constructed process also enables the processing of new devices that are qualitatively different.

An object of the present invention is to provide a method and apparatus for surface treatment of a sample, which can process an element having a processing size of 1 μm or less, preferably 0.5 μm or less in order to meet the demand for miniaturization of a semiconductor element or the like. It is.

[0009]

A feature of the present invention is that a plasma is generated in a processing chamber, and a high frequency bias voltage is applied to a sample stage on which a sample is placed independently of the generation of the plasma, and the same etching rate is applied. The present invention provides a method for surface treatment of a sample in which a high-frequency bias voltage having a Vpp value larger than the Vpp value is applied to a continuous high-frequency bias voltage Vpp obtained as described above.

Another feature of the present invention is that a sample is placed on a sample provided in a vacuum vessel, a processing gas is continuously supplied into the vacuum vessel, and the processing gas is turned into a plasma. Is 100K independently on the sample stage
A high-frequency bias having a frequency equal to or higher than Hz is applied, the high-frequency bias is modulated at a frequency of 100 Hz to 10 KHz, and the sample is subjected to surface processing with a minimum processing dimension of 1 μm or less.

Another feature of the present invention is that a high frequency bias is applied to a sample having a film of a material to be a gate electrode on a gate oxide film having a thickness of 6 nm or less when the sample is etched by plasma. In addition, there is provided a surface treatment method for a sample in which the high-frequency bias is time-modulated.

According to the present invention, in the processing of a fine pattern, the high frequency voltage applied to the sample is repeatedly turned on and off, and the frequency of the high frequency voltage and the combination of the repetition frequency are devised to improve the etching anisotropy. And the selectivity can be increased at the same time. As a result, it is possible to process an element having a processing size of 1 μm or less, preferably 0.5 μm or less. Specifically, due to the narrow band of the energy distribution of ions, there is a problem of fine element processing.
The trade-off between processing anisotropy and selectivity can be eliminated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a plasma etching apparatus to which the present invention is applied. Magnetron 10
1, the automatic matching unit 106, the waveguide 102, and the introduction window 10
Through 3, microwaves are introduced into the vacuum vessel 104. On the other hand, an etching gas such as halogen is introduced into the vacuum vessel 104 via the gas introduction means 100, and plasma of this gas is generated with the introduction of the microwave. The material of the introduction window 103 is a microwave such as quartz or ceramic.
(Electromagnetic waves).

An electromagnet 105 is provided around the vacuum vessel 104.
Is installed. The magnetic field strength of the electromagnet 105 is set so as to cause resonance with the frequency of the microwave. For example, if the frequency is 2.45 GHz, the magnetic field strength is 875 Gauss. At this magnetic field strength, the cyclotron motion of the electrons in the plasma resonates with the frequency of the electromagnetic wave, so that microwave energy is efficiently supplied to the plasma and a high-density plasma is generated.

The sample 107 is set on a sample stage 108. In order to accelerate ions incident on the sample, an rf (radio frequency) bias power supply 109 which is a high frequency power supply
Are connected to the sample stage 108 via a high-pass filter 111. An insulating film 110 such as a ceramic or polymer film is provided on the surface of the sample stage. Further, a DC power supply 112 is connected through a low-pass filter 113.
Is connected, and a voltage is applied to the sample stage 108, whereby the sample is held on the sample stage by electrostatic force.

FIG. 2 shows the gas supply in the vacuum vessel 104 and the magnetron 10 during the etching process by the apparatus shown in FIG.
1, the operation of the rf bias power supply 109 will be described. Gas is supplied as shown in (a), the gas pressure is kept constant at the same time as the start of etching, and microwave power is also supplied continuously as shown in (b). On the other hand, as shown in (c), the rf bias applied to the sample is periodically turned on and off. By providing a period during which ions are accelerated by turning on / off the rf bias, a high-energy ion section and a low-energy ion section are generated during the surface treatment of the sample. Then, as shown in (d), in the low energy ion section, the etching does not proceed, but rather the deposition of the residual reaction product in the gas or plasma occurs.

Next, the relationship between the rf bias frequency, the on / off repetition frequency thereof, and the etching characteristics will be described. 3A and 3B show waveforms of the rf bias, and FIG. 3A shows a waveform corresponding to the etching condition of the present embodiment, in which the rf bias frequency is 100 KHz and the on / off frequency (modulation frequency) is 100 Hz. . (B) is disclosed in Japanese Unexamined Patent Publication No. 6-151360 (corresponding USP 5,35).
2,324), the waveform is when the rf bias frequency is 1 KHz and the on / off frequency (modulation frequency) is 1 Hz.

When an rf bias is applied to the sample stage, a high electric field region (called a sheath) is generated in a region having a thickness of about 1 mm or less from the sample surface, and ions are accelerated in this region. The energy distribution of the accelerated ions is r
It depends on the frequency of the f bias. If the frequency of the rf bias is sufficiently low, the movement of the ions follows the change in the voltage represented by the sine wave, so that the instantaneous value Vx of the voltage (FIG. 3B)
And has the same energy as the energy distribution shown in FIG.
A very wide distribution is obtained as shown in the KHz diagram.

When the frequency of the rf bias increases, the movement of ions cannot follow the fluctuation of the rf bias, so that the energy of the ions gradually converges to the value of the DC component Vdc of the voltage generated when the rf bias is applied. In the meantime, there is a transient state, with a frequency of about 100 KHz to several M
During this period, the energy of the ions is 100 KH in FIG.
As shown in the diagram of z, it has a saddle-shaped distribution having a high energy peak 401 and a low energy peak 402 corresponding to the rf bias amplitude Vpp. This low energy peak 402 has a rf bias of 0 W, ie, rf
This corresponds to the ions that have entered the sheath at the timing when they are not just accelerated due to the change in bias. In addition, while the rf bias is off, the ions are not accelerated, and all ions enter a region corresponding to the low energy peak 402 in FIG.

Next, FIG. 5 shows the result when a fine pattern consisting of lines and spaces is etched on the sample surface using the apparatus shown in FIG. A mixed gas of chlorine (72 sccm) and oxygen (8 sccm) was used as an etching gas, and the pressure inside the vacuum vessel 104 was set to 0.4 Pa. Further, the microwave output from the magnetron 101 is set to 400
W. The structure of the etched semiconductor element is such that the thickness of the gate oxide film 502 on the silicon substrate 501 is 4 nm,
PolySi 503 300 nm thick, resist 50
4 has a thickness of 1 μm and a line and space width of 0.4 μm. FIG. 5 shows an etching shape when the frequency of the bias power supply 109 is 100 KHz and the on / off frequency is 100 Hz. The peak output of the rf bias is 300 W, and the duty ratio (the ratio of the ON period in one cycle) is 20%.

FIG. 6 shows, as a comparative example, the frequency of a bias power supply known in Japanese Patent Application Laid-Open No. 6-151360 (corresponding to US Pat. No. 5,352,324) of 1 KH.
z shows the etching shape when the on / off frequency is 1 Hz. The peak output of the rf bias is 300 W and the duty ratio is 20%.

FIG. 7 shows, as a comparative example, a cross section in the case where the power is set to 60 W by continuous output at an rf bias frequency of 100 KHz. Poly Si under these conditions
Has an etching rate of about 250 nm / min and a selectivity to an oxide film of about 20.

FIGS. 5 to 7 show shapes of the poly Si 503 during etching. The etching according to the method of the invention (FIG. 5) results in vertical sidewalls and a flat etched bottom. In addition, there is no difference in the etching rate between the wide portion 506 and the narrow space portion 505, so that the etch depth is the same.

On the other hand, in the case of etching with a continuous bias shown in the comparative example (FIG. 7), the verticality of the side wall is poor, and the side wall 507 facing the narrow part and the side wall 508 facing the wide part have a wide part. Is worse in verticality. In addition, a fine groove 509 called a subtrench is generated on the etching bottom surface. Further, a difference in the etching rate is generated, and a difference D in the etch depth occurs between the narrow portion and the wide portion.

Further, even if the rf bias is turned on and off, as shown in the comparative example, when the rf bias frequency is low (FIG. 6), the undercut below the resist 504 has better verticality than the continuous bias. Occurs. Also, the verticality is inferior to FIG. 5 to which the method of the present invention is applied.

Next, the cause of the above result will be described. First, in comparison between the on / off of the rf bias (on / off bias) and the continuous application (continuous bias), the same po is obtained by turning on / off the rf bias.
Since the energy of ions for obtaining the ly Si rate can be set high, the anisotropy can be improved. For example, Vpp at a continuous bias of 60 W is 320 V, and Vpp at an on-off bias peak power of 300 W is 1410 V.
Here, the energy of the ions is substantially proportional to the amplitude Vpp of the bias voltage. Therefore, the ion energy can be made higher in the on / off bias than in the continuous bias, so that the perpendicularity is improved.

On the other hand, the verticality is improved by increasing Vpp even in a continuous bias, but the etching rate of the oxide film also increases substantially in proportion to Vpp.
The selectivity between Si and the oxide film becomes low, and it is not suitable when the underlying oxide film is thin as in the etching of the gate electrode of a transistor.

That is, in the on / off bias, by providing an off period for ion acceleration, the number of high energy ions can be reduced, and the perpendicularity can be improved without lowering the selectivity. Further, the sub-trench is generated because the verticality of the side wall is deteriorated, and ions are reflected on the side wall and enter the bottom surface. Accordingly, the sub-trench is reduced by improving the verticality of the side wall, and a flat etched bottom surface can be obtained.

Incidentally, even if the rf bias is turned on and off, rf
When the bias frequency is low, an undercut occurs because a large number of ions having an intermediate region energy exist as shown in FIG. That is, the etching reaction is accelerated by the incidence of ions having energy equal to or higher than a certain threshold. Ions having intermediate region energies promote the etching reaction, but are less directional due to the lower energy, and thus collide with the poly Si sidewall 503 under the resist 504, causing an undercut.

As described above, by setting the rf bias to 100 KHz or more as in the present embodiment, ions of the energy in the intermediate region can be reduced, so that highly anisotropic etching can be performed. That is, in order to increase the anisotropy of the etching, it is necessary to divide the ion energy into two parts, a low energy area that does not contribute to the etching and a high energy area that has a high directivity. The effect of turning the rf bias on and off only shows its true value when it is used at a frequency of 100 KHz or more where the ion energy at the time of on is separated into these two regions.

Next, a second embodiment of the present invention will be described.
First, the rf bias on / off duty ratio and ion energy will be described. FIG.
It shows the relationship between the Si etching rate and the oxide film selectivity, and compares a continuous bias with an on-off bias. In this example, the output of the microwave from the magnetron 101 was 400 W. The output of the bias power supply 109 was 60 W, and the frequency was 800 KHz. Further, the ON / OFF repetition frequency was 1 KHz. The gas was 185 sccm of chlorine and 15 sccm of oxygen, and the pressure was 0.8P.
a. Although the rf bias power is a parameter, in the on / off bias control, the peak power was set to 60 W, and the power was controlled by changing the duty ratio. That is, if the duty ratio is 50%, the power is (at 50% of 60W)
30W.

As can be seen from FIG. 8, in the on / off bias control, the selectivity increases in the region where the duty ratio is 50% or less as compared with the continuous bias. Therefore, even if the ion energy is increased, the anisotropy can be increased without lowering the selectivity. The effect increases as the duty ratio decreases, but if the duty ratio is too low, the poly Si etching rate decreases, so that the duty ratio is practically 5% to 50%.
Range is good.

The reason why the above-described effect is obtained by the on / off control of the rf bias, that is, by the time modulation will be described below.

It is considered that the reason why the selectivity is increased by the on / off bias control is that a reaction product is deposited on the oxide film during the rf bias-off period, thereby lowering the etching rate of the oxide film. In particular, a reaction product of chlorine, oxygen, and silicon tends to deposit on an oxide film in a low temperature region. Since the ion energy incident on the sample surface is low during the off period of the rf bias, the surface temperature decreases. In the meantime, a reaction product is deposited on the oxide film, and a continuous bias at the same Vpp and a Vpp at the same etching rate are obtained.
The selection ratio becomes higher than that of the continuous bias under the condition (1). In the on / off bias control, if the ion energy is further increased beyond these Vpp, the oxide film etching rate increases and the selection ratio becomes the same as that in the continuous bias. However, since the ion energy is high in this region, as shown in the embodiment of FIG. 5, processing with good anisotropy and without sub-trench can be performed. Also, microloading is generally reduced with higher ion energy. Therefore, microloading can be reduced without lowering the selection ratio by the on / off bias control.

Next, conditions of ion energy for increasing anisotropy and reducing subtrench will be described. FIG. 9 is a diagram showing the relationship between the rf bias voltage experimentally obtained and the depth of the subtrench. Here, the sub-trench depth is
This is the depth of the fine groove 509 formed at the bottom of the poly Si groove represented by L in FIG. Next, the allowable depth of the subtrench in the processing of the gate of the transistor is obtained. In the processing of the gate, it is necessary to perform etching while leaving no etching of polySi at the bottom of the groove and leaving a sufficient gate oxide film 502. In a thin region having a gate oxide film of 6 nm or less, the gate oxide film thickness after etching needs to remain at 2 nm or more. Within the time when the remaining thickness becomes 2 nm or more,
If the poly Si corresponding to the sub-trench depth L cannot be etched, an etch residue of the poly Si occurs at the bottom of the groove.

Here, assuming that the etching amount of poly Si that can be etched while the gate oxide film remains 2 nm is an allowable sub-trench depth Lmax (nm), Lmax =
S (d-2). Here, S is the selectivity between poly Si and the oxide film, and d (nm) is the initial thickness of the gate oxide film. This relationship is shown in FIG.

FIG. 11 shows the etched shapes at points A, B, and C in FIG. From FIG. 9 to FIG. 11, the ion energy capable of satisfying both the anisotropy and the remaining amount of the gate oxide film is obtained. First, the verticality of the etched side wall is Vpp of 50.
At 0 V or more, a sufficient level is reached with an element having a minimum processing dimension of 1 μm to 0.1 μm. Vpp from 500V to 1000
At V, the selectivity is in the range of 10 to 5 in the above-described etching using the continuous bias of chlorine and oxygen.

FIG. 10 shows that, for example, when processing a gate oxide film of 6 nm, at a selectivity of 5, the allowable sub-trench depth is about 20 nm. From FIG. 9, it can be seen that the subtrench becomes 20 nm or less in the region where Vpp = 500 V or more, so that if Vpp is set to 500 V or more, it can be processed in calculation. However, if the selectivity is 10 or less, the gate oxide film is etched unless the etching is accurately stopped at the time of the end point of the etching, so that there is no room. Therefore, a method of increasing the selection ratio while keeping Vpp at 500 V is required, that is, a combination with the on / off bias is required.

The physical quantity that directly affects the depth and the selectivity of the subtrench is not Vpp but ion energy. However, since it is actually difficult to measure ion energy, Vpp is an index of ion energy.

Next, the relationship between the ion energy and the high-frequency voltage will be described. When a high-frequency voltage is applied to the sample stage via the plasma, a DC potential is applied to the sample stage so that ions are drawn into the sample stage due to the action of trying to cause a current to flow between the ground (generally, the conductor wall is grounded) and the electrodes. (Hereinafter referred to as Vdc). The ions are accelerated by an electric field in which Vdc and a time-varying high-frequency voltage are superimposed.
The maximum energy obtained by ions changes depending on whether or not it follows the temporal change of the high frequency voltage. Generally, the density of the plasma used for etching is 1 × 10 ¹⁰ / cm ^−3.
Number or more. At this density, the high frequency frequency is 15M
At Hz or lower, during a period in which the high-frequency voltage is negative, that is, during a half cycle of the sine wave, the ions cross the plasma sheath and reach the sample, so that Emax is approximately one half of the voltage amplitude (Vpp / Vpp). It is equal to the value obtained by adding Vdc to 2). Actually, there is a voltage drop in the electric circuit, and Vp
It is known from the measurement that when p is 500 V, Emax becomes 400 eV. Since the essential physical quantity that affects the shape of the etching is not Vpp but ion energy, in order to obtain a shape without a subtrench, the maximum value of ion energy should be 400 eV or more. When the frequency of the high frequency rises and the movement of ions stops following the change in voltage, Emax gradually approaches Vdc. Although the transition period is between the frequency of 15 MHz or more and several tens of MHz, Emax is sufficiently 400 eV or more if Vpp is 800 V or more.

The required Vpp varies depending on the structure of the element and the etching gas, but a good reference is obtained when Vpp is 500 V or more. In the case where the base is thick and the generation of sub-trench does not affect, or in the case where the etching is divided into several steps and applied to the overetch after the completion of the main etch as described later, Vpp can be set to a lower value and 100 V can be used. A degree is enough.

Next, a description will be given of a third embodiment in which the present invention is applied to etching of another material, and the results thereof. As shown in FIG. 12, the sample was a 4 nm oxide film 5 on a silicon substrate 501.
02, a 300 nm poly Si film 503 and an 80 nm tungsten silicide (WSi) film 120 thereon.
The uppermost layer has a patterned silicon nitride film 1202 as a mask. The etching gas was a mixed gas of chlorine (185 sccm) and oxygen (15 sccm), and the pressure was set to 0.8 Pa. Magnetron 101
The output of the microwave from was set to 400W. The frequency of the rf bias power supply 109 is 800 KHz.

FIG. 13 shows a continuous bias 6 as a comparative example.
FIG. 12 shows the etching shape when the power is 0 W and the duty ratio is 20% at the peak output of 300 W in the on / off bias method. Also in this sample, when etching is performed with a continuous bias, the perpendicularity is poor and the microloading is large. On the other hand, in the on / off bias method of the present invention, the verticality of the side wall is improved. Further, in this sample, needle-like protrusions 1203 are observed on the etched surface of poly Si. This is probably poly Si
It is considered that foreign matter at the interface between 503 and WSi 1201 may become a mask, which contributes to the remaining etch.
The on-off bias method can also reduce the density of the needle-like projections.

Next, a description will be given of a fourth embodiment in which the present invention is applied to etching of a metal such as aluminum and the results thereof. As shown in FIG. 14, the sample structure is such that an oxide film (1401) 300 nm and TiN (1402) 100 n are formed on a substrate Si 501.
m, Al (1403) 400 nm, TiN (1404)
75 nm is deposited, and a resist mask (50
4) 1 μm is attached. The line and space dimensions are 0.4 μm. The etching gas is chlorine (80 scc)
m) and BCl ₃ (20 sccm) at a pressure of 1P
a. The output of the microwave power supply 101 was 700 W, and the electrode temperature was 40 ° C. rf bias power supply 109
Was 400 KHz, and the repetition frequency of on / off was 2 KHz.

FIG. 14 shows a case where the peak power is 350 W and the duty ratio is 20% in the on / off bias control.
Shows, as a comparative example, the etching shape when the power is 70 W with continuous bias. With these two power values, the etching rate of aluminum is almost equal. In the sample shown in FIG. 15, the shape microloading is large, and the verticality of the side wall 1405 facing a wide space at the time of continuous bias is particularly deteriorated, but the microloading is suppressed by using the on / off bias control. That is, the anisotropy or microloading of a metal is improved as the ion energy is increased. Therefore, by using the on / off bias control, the ion energy can be set high without lowering the selectivity with respect to the underlying oxide film.

As a method of further utilizing the effects of the present invention, there is a method of dividing the etching process into a plurality of steps. This will be described as a fifth embodiment. FIG. 16 shows a temporal change of a cross-sectional shape when a sample as a workpiece is processed in steps. The structure of the sample is such that a 4-nm oxide film 502, a 200-nm polycrystalline silicon 503, and a 200-nm silicon nitride film 180 are formed on a silicon substrate 501.
1 is deposited, and the silicon nitride film is processed into a desired pattern. The line and space spacing is 250 nm. Normally, a natural oxide film 1802 is provided on the surface of the polycrystalline silicon 503.

Here, the sample having this structure is etched and processed in three steps. Fig. 16 (a)
Is an initial state. In Step 1, first, the natural oxide film 1802 is removed. The etching gas is Cl ₂ (20
0 sccm) and the pressure was set to 0.8 Pa. The output of the microwave power supply 101 was 400 W. rf bias power supply 1
The frequency of 09 is 800 KHz. Since the purpose of this step is to remove a thin natural oxide film, the time is 5 seconds, and the output of the high-frequency voltage power supply 109 is continuously 60 W. FIG. 16B shows a cross section of the sample after step 1 is completed.

Step 2 is etching of the polycrystalline silicon 503 occupying a main part of the processing, and is hereinafter referred to as main etching. Since the shape control of this step is the most important,
In step 2, the rf bias power supply 109 was turned on / off to set the power to 200 W and the duty ratio to 30%. Vpp becomes 1000V. The etching gas was a mixed gas of 185 sccm of chlorine and 15 sccm of oxygen, and the pressure was set to 0.8 Pa. Other conditions were the same as in step 1. Under these conditions, the etching rate of polycrystalline silicon is 300 nm / min, and the selectivity to oxide film is 20. The etching time was 35 seconds. FIG. 16C shows a cross-sectional shape after the completion of Step 2. A side surface perpendicular to the flat bottom without sub-trench is obtained. The time of step 2 is set so that the polysilicon 503 slightly remains.

In the last step 3, since the underlying thin oxide film 502 is exposed, the condition is changed to a condition where the selectivity is high even if the etching rate of polycrystalline silicon is reduced. Specifically, the power of the rf bias power supply 109 is set to 3
0W. Other conditions are the same as in step 2. Under these conditions, the etching rate of polycrystalline silicon is 100 nm.
/ Min, the selection ratio is 50. Etching having a relatively high selectivity after completion of the main etch is called overetch. The etching time was 30 seconds. FIG. 16D shows a cross section after Step 3 is completed. By increasing the selectivity, it is possible to process the polycrystalline silicon 503 without leaving the underlying oxide film sufficiently and without etching remaining. In step 3, the continuous bias is used, but the peak power may be reduced in the on / off bias control.

As described above, by applying the on-off bias control to the processing of the main part of the sample to be etched, that is, the sample to be processed, desired processing can be performed without damaging a very thin underlayer. Become.

Even if the object to be etched is a multi-layered structure of various substances, the number of steps can be increased to perform processing with high accuracy and without shape abnormality. Also, to which step the on / off bias control is applied is appropriately determined according to the element structure, but the on / off bias control enables a condition with a wide process margin. In this embodiment, the etching gas is continuously supplied. However, when the etching is divided into several steps, the gas supply may be discontinuous between the steps.

Next, the structure of an apparatus to which the present invention can be applied will be described. The present invention aims at processing an element having a minimum processing size of 1 μm, preferably 0.5 μm or less, so that the so-called plasma electron density is 1 × 10 ¹⁰ / cm ⁻³ or more, preferably 1 × 10 ¹¹ / cm ³ or more. It is effective when applied to high-density models of cm ^-3 or more. This type of device mainly includes an inductive coupling type device and an ECR type device. In addition, the capacitive coupling type device that has been known for a long time,
Since high-density plasma cannot be generated, the throughput is low.In addition, the plasma density is low, the sheath becomes thick, and the anisotropy is poor due to ion scattering in the sheath. There are problems such as a large amount of scattering, which is not suitable for the present invention.

FIG. 17 shows an inductively coupled device as a sixth embodiment of the present invention. In this apparatus, plasma is generated by inductive coupling using electromagnetic waves having a so-called rf frequency of several hundred KHz to several tens MHz. The vacuum vessel 104 is made of a material that transmits electromagnetic waves, such as alumina and quartz. An electromagnetic coil 201 for generating plasma is wound therearound. An rf power supply 203 is connected to the coil. A sample stage 108 is provided in the vacuum vessel. The sample stage 108 has a sample 107 placed thereon, and is connected to an rf bias power supply 109. The vacuum vessel 104 has an upper lid 207, which may be integrated with the vacuum vessel.

In this type of apparatus, as in the above-described embodiments, the rf bias power supply 109 can be turned on / off to produce the above-described effects. In addition,
In the device shown in FIG.
The effect is the same even if it is installed on the top.

Further, in FIG. 18, as Embodiment 7 of the present invention, an electromagnetic wave and a magnetic field are applied to an electron cyclotron resonance (ECR).
An apparatus provided with a structure for causing the above will be described.

Vacuum container 10 having gas introducing means 100
An electromagnet 105 is disposed around the periphery of the reference numeral 4. The interaction between the electromagnetic wave introduced into the planar antenna plate 205 by the coaxial cable 204 and the magnetic field by the electromagnet 105,
The gas introduced into the vacuum vessel 104 is turned into plasma, and the sample 107 is processed. The sample 107 is placed on a sample stage 108 and is suction-supported by electrostatic suction force. Sample 1
07 is high frequency bias for pulling ions to rf.
The sample stage 1 via the bias power supply 109 and the matching unit 111
08. The voltage for electrostatic attraction is applied by the DC power supply 112. On the planar antenna plate 205,
A 450 MHz plasma generation power supply 211 and a 13.56 MHz antenna bias power supply 213 are connected via a filter 212, and two kinds of frequencies are applied to the flat antenna plate 205. Each power supply is connected to the filter 212 via the matching devices 214 and 215. The coaxial cable 204 and the flat antenna plate 205
It is connected by a substantially conical member, and the coaxial cable 204
The high frequency wave that has propagated through the antenna
5. Here, reference numeral 2
Reference numeral 19 denotes a temperature control inner wall means provided inside the vacuum vessel 104, and reference numeral 227 denotes a temperature control inner wall means provided on the sample stage 108.
7 is an annular member arranged on the outer periphery of
Reference numeral 224 denotes a power supply connected to the annular member 227 to control the plasma distribution, reference numeral 224 denotes a flow path through which a heat medium for controlling the temperature of the sample stage 108 flows, and reference numeral 220 denotes a flow path.
Is a filter for antenna bias, which is provided between the coaxial cable 204 and the ground potential.

In the above-mentioned apparatus, 45 for plasma generation is used.
An electromagnetic wave (microwave) of 0 MHz is applied to the planar antenna plate 20.
5 is fed, the planar antenna plate 205 operates as a planar antenna. The ceiling of the vacuum vessel 104 above the flat antenna plate 205 (in the direction opposite to the plasma generation region) is opposed to the flat antenna plate 205, and the ceiling is grounded to the ground potential. A dielectric 2 made of quartz, alumina, or the like is provided between the ceiling and the flat antenna plate 205.
16 are installed. The diameter, the dielectric material, the thickness, and the like of the planar antenna plate 205 are designed to be such that a 450 MHz electromagnetic wave resonates in the _TM01 mode between the ceiling and the planar antenna plate 205. The 450 MHz electromagnetic wave resonated by such a planar antenna structure passes through the dielectric 216, and is further disposed on the outer peripheral portion of the planar antenna plate 205 by a dielectric ring (here, quartz ring 217 is used because quartz is used). ) Into the plasma. In addition, a part of the electromagnetic wave is
Is propagated as a surface current and is radiated from a portion in contact with the plasma. As described above, the 450 MHz electromagnetic wave fed to the planar antenna plate 205 is efficiently supplied to the outer peripheral space in the vacuum chamber 104 via the dielectric 216 and the quartz ring 217, and is resonated by the magnetic field of the electromagnet 105. In this state, the plasma is easily formed and the plasma is easily maintained.

The flat antenna plate 205 is operated as a flat antenna, and in this embodiment, an electromagnetic wave and a magnetic field are subjected to electron cyclotron resonance. In this case, the intensity of the magnetic field in the plasma generation region is 100 to 200 gauss because the 450 MHz electromagnetic wave and the magnetic field need to have a magnitude that satisfies the electron cyclotron resonance. The electromagnet 105 forms a magnetic field centered on the magnetic field strength. Note that even in the absence of a magnetic field, efficient supply of electromagnetic waves from the planar antenna can be performed, so that plasma can be formed, and the apparatus of this embodiment is not limited to the case where a magnetic field is provided.

A quartz ring 217 is provided around the planar antenna plate 205. The quartz ring 217 has an effect of mitigating a local increase in the electric field intensity around the planar antenna plate 5 or the processing gas supply plate 218 made of silicon, and can make plasma generation uniform.

When utilizing electron cyclotron resonance using a magnetic field, the uniformity of the plasma and the magnetic field conditions are closely related. The electron cyclotron resonance region can be set at an arbitrary position by the electromagnet 105 provided on the outer peripheral portion of the vacuum vessel 104. In the case of the present embodiment, the resonance region uses an electromagnetic wave of 450 MHz.
This is a place where a magnetic field intensity of about 0 to 180 Gauss is generated. This resonance region is a region where the plasma density is high because the plasma is efficiently generated, but is greatly affected by the magnetic field condition. Therefore, by adjusting the position of the electron cyclotron region, the magnetic field gradient (change rate of the magnetic field strength), the shape of the resonance region, etc. so that the plasma density in the etching region becomes uniform, settings suitable for each etching can be made. become.

Also in this type of apparatus, as described in the previous embodiment, the rf bias power supply 109 can be turned on / off to improve the verticality. In the apparatus shown in FIG. 18, it is essential that the frequency band of the plasma generation power supply 211 is an electromagnetic wave in the microwave range of the so-called VHF to UHF band of 100 MHz to 1 GHz, and the additional function described below may not be provided. First, the 13.56 MHz antenna bias power supply 213 connected to the flat antenna plate 205 is for applying a bias to the flat antenna plate 205 to control chemical species in plasma, and is not always necessary. Further, the annular member 222 around the sample stage 108 is provided for controlling the uniformity of plasma, and may not be provided. Further, the planar antenna plate 205 may have a structure outside the vacuum.

Next, as an eighth embodiment of the present invention, an embodiment characterized by a method for adsorbing a sample will be described. As described above, in the present invention, in order to turn on and off the rf bias voltage at high speed and perform high-accuracy etching, the rf bias needs to be transmitted to the sample uniformly and without distortion of the waveform. For that purpose, it is necessary to adsorb the sample to the sample table without a large gap. If there is a gap, the capacitance may cause non-uniformity in how the rf bias is applied. Therefore, it is important for the on / off bias control to be combined with an electrostatic chuck type sample stage as shown in FIG. Further, in the on / off bias control, since the rf bias is turned on / off, there is a possibility that the electrostatic attraction force also varies. Therefore, it is desirable to combine with a bipolar electrostatic adsorption method described below.

FIG. 19 is an enlarged view of a sample stage portion of the above-described etching apparatus having a bipolar electrostatic attraction structure. This sample stage has a second electrode 301 surrounded by an insulating material 302 as an electrode for electrostatic attraction. Here, a DC voltage is applied through a low-pass filter 113.
It should be noted that the sample 107 includes a sample lifting pin 303 and the vertical mechanism 3.
At 04, it can be attached to and detached from the sample table 108. In the sample stage having the monopolar electrostatic adsorption device shown in FIG. 1, the sample cannot be adsorbed unless plasma is generated, but in the sample stage of this embodiment, the sample stage 108 and the second electrode 301 are different. By applying a polar voltage, the sample can be electrostatically attracted without plasma. Therefore, the sample can be adsorbed without being affected by the on / off of the rf bias, and the stability is excellent.

FIG. 20 illustrates a ninth embodiment of the present invention. In this apparatus, microwaves oscillated from a magnetron for generating plasma are simultaneously controlled on / off. In the configuration, a pulse modulator 401 is connected to a microwave power supply 400, and the plasma is turned on / off by a pulse wave 2001 from here. Turning on and off the plasma lowers the electron temperature, which has the effect of reducing damage to the sample due to charged particles. The rf bias power supply 109 has
A positive pulse 2002 may be superimposed during the off period, whereby electrons are drawn into the fine pattern on the sample surface, and damage due to charging can be reduced.

Next, as Embodiment 10, other etching conditions will be described. The conditions described in the above-described embodiments are typical values, and include the processing gas pressure, the type of the processing gas,
The on / off bias control in the present invention is effective even if the power value for plasma generation changes. However, considering the etching rate and the selectivity, it is desirable to use it in the range described below. First, in a mixed gas of chlorine and oxygen mainly used for etching polySi and a multilayer film thereof, a suitable flow rate of oxygen is 0 to 50% at a chlorine flow rate of 20 sccm to 1000 sccm. If the amount of mixed oxygen is further increased, the etching rate of poly Si becomes extremely slow. The pressure is 0.1 Pa to 10
Pa is appropriate. The etching gas is chlorine and HBr.
Also in the case of using a mixed gas of oxygen and oxygen, the flow rates of chlorine and HBr are respectively 20 sccm to 1000 sccm, and the mixing ratio of oxygen is 0% to 50%.

For etching a metal wiring such as Al, chlorine, a mixed gas of chlorine and BCl _3, a mixed gas of chlorine and HCl, or a mixed gas of chlorine, BCl ₃ and HCl is suitable. In this case, the flow rate of chlorine and HCl is 20 sccm to 1000 sccm, respectively, and the mixing ratio of BCl ₃ is 0% to 50%. Further, a rare gas such as CH ₄ or argon may be mixed with these gases.

The density of the plasma is determined by the power of the power supply for generating the plasma, and is closely related to the etching rate. In order to obtain a practical speed, the power for the plasma generation space, that is, the volume between the sample stage and the electrode is 0.01 W / c.
It is good to be more than c. On the other hand, if the plasma density is too high, electrical damage to the device becomes a problem.
It is better to be not more than c.

The frequency of the bias power supply applied to the sample is preferably between 100 KHz and 100 MHz. Although the band of ion energy can be narrowed even at a frequency higher than this, there is a problem that plasma is easily generated by a bias power supply. On / off bias repetition frequency is 100
When the frequency is less than Hz, the on / off time is too long, and the etched side wall is not smooth. If the repetition frequency is high, it becomes technically difficult to create a power supply.

The present invention is particularly effective in the processing of fine patterns in which the distance between lines and spaces is 0.5 μm or less. In the gate electrode, the thickness of the underlying oxide film is 6
This is processing of a sample having a size of nm or less.

As described above, the present invention has the following features.

The Vpp value of the continuous high-frequency bias voltage obtained at the same etching rate is controlled by turning on / off a high-frequency bias voltage having a Vpp value larger than the Vpp value, so that the selection ratio is not impaired. The anisotropy can be improved.

The frequency of the high frequency bias voltage is 15 MHz
By setting the Vpp value of the high-frequency bias voltage to 500 V or higher, the subtrench can be reduced and the anisotropy can be increased.

The frequency of the high frequency bias voltage is 15 MHz
If it is larger, the Vpp value of the high frequency bias voltage is set to 8
When the voltage is set to 00 V or more, the subtrench can be reduced and the anisotropy can be increased.

By setting the on-duty of the high frequency bias voltage to 5% to 50%, the effect of improving the selectivity can be more remarkable.

The process from the start to the end of the surface treatment of the sample is divided into a plurality of steps, and the high frequency bias voltage is turned on / off in at least one of the steps, so that a region having a high selectivity or a region having a high anisotropy can be selectively used. Therefore, the processing accuracy can be further improved.

A plurality of steps are divided into a first half in which the processing speed ratio with the base material is relatively small, and a second half in which the processing speed ratio is relatively large, and the high frequency bias voltage is turned on and off in at least the first half step. In particular, a region with high anisotropy in on / off control can be effectively used, and the processed shape can be improved.

By switching the steps according to time, complicated multilayer films can be etched accurately with simple switching control.

Independently of plasma generation, 100K
Applying a high-frequency bias of a frequency of at least 100 Hz, modulating the high-frequency bias at a frequency of 100 Hz to 10 KHz,
By subjecting the sample to surface processing with a minimum processing dimension of 1 μm or less, the band of ion energy can be narrowed, the effect of on / off bias can be more effectively obtained, and fine processing can be performed.

The electron density of the plasma is 1 × 10 ¹⁰ / c
By using high-density plasma of m ⁻³ or more, processing with high throughput can be performed.

By using a mixed gas of chlorine and oxygen as the processing gas, etching with a higher selectivity between poly Si and an oxide film can be performed.

The processing gas is converted into plasma using microwaves, and a high-frequency bias having a frequency of 100 kHz or more and 10 MHz or less is applied to the sample table independently of the plasma generation.
By performing on / off control of the high-frequency bias at a frequency of 100 Hz to 10 KHz and setting the Vpp value of the high-frequency bias voltage at the time of on to 100 V or more to perform surface processing of the sample, etching with high throughput and high selectivity can be performed.

When the plasma is ECR plasma using microwaves of 2.45 GHz, a magnetron can be used as a power source, so that the above-described effects can be obtained while keeping the apparatus price low.

When the plasma is an ECR plasma using a microwave of 100 MHz to 1 GHz, the above-mentioned effects can be obtained with a larger-diameter and uniform plasma because the microwave has a longer wavelength.

A sample having a pattern with a minimum processing dimension of 1 μm or less is held by electrostatic attraction, and a high-frequency bias applied to the sample is time-modulated independently of plasma generation.
On / off control was performed by plasma treatment of the sample
Since the rf bias can be uniformly and efficiently transmitted to the sample, a sample with a fine pattern can be processed with high accuracy and high reliability.

By holding the sample by dipole electrostatic adsorption, a constant adsorption force can be obtained irrespective of the on / off state of the rf bias, and the processing reliability is further improved.

A thin oxide film is obtained by subjecting a sample having a film of a material to be a gate electrode on a gate oxide film having a thickness of 6 nm or less to plasma processing by time-modulating a high frequency bias applied independently of plasma generation. , The upper layer film can be etched.

By applying on / off control of a high-frequency bias to a sample in which the film of the material to be the gate electrode is a polycrystalline silicon film or a multilayer film having a polycrystalline silicon film, it is possible to perform highly anisotropic processing. it can.

In the on / off control of the high-frequency bias in these embodiments, the application of the high-frequency bias voltage is stopped during the off-period of the high-frequency bias, the output of the high-frequency bias voltage is set to 0 V, or the off-period of the high-frequency bias is off. The application of small voltages in a range that does not affect the effect is included in the on / off control or time modulation of the high frequency bias voltage of the present invention.

[0089]

As described above, according to the present invention, in order to meet the demand for miniaturization of a semiconductor device, the processing dimension is reduced to one.
It is possible to provide a surface treatment method and apparatus for a semiconductor device capable of processing a device having a size of not more than 0.5 μm, preferably not more than 0.5 μm.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation at the time of etching by the apparatus of FIG. 1;

FIG. 3 is a diagram showing a relationship between an rf bias power supply frequency and an on / off frequency in the device of FIG. 1;

FIG. 4 is a diagram showing an ion energy distribution.

FIG. 5 is a cross-sectional view of a sample processed by applying the present invention.

FIG. 6 is a cross-sectional view of a sample during processing in a comparative example.

FIG. 7 is a cross-sectional view of a sample during processing in a comparative example.

FIG. 8 is a diagram showing a relationship between a poly Si etching rate and a selectivity.

FIG. 9 is a diagram showing a relationship between rf bias voltage amplitude and sub-trench depth.

FIG. 10 is a diagram showing a relationship between a gate oxide film thickness and an allowable sub-trench depth.

FIG. 11 is a cross-sectional view of a sample at the time of etching.

FIG. 12 is a cross-sectional view of a sample during processing to which the present invention is applied.

FIG. 13 is a cross-sectional view of a sample during processing in a comparative example.

FIG. 14 is a cross-sectional view of a sample during processing to which the present invention is applied.

FIG. 15 is a cross-sectional view of a sample during processing in a comparative example.

FIG. 16 is an overall configuration diagram of an apparatus according to another embodiment of the present invention.

FIG. 17 is an overall configuration diagram of an apparatus according to another embodiment of the present invention.

FIG. 18 is a cross-sectional view of a sample during processing to which another embodiment of the present invention is applied.

FIG. 19 is an enlarged view of a sample stage of an apparatus according to another embodiment of the present invention.

FIG. 20 is an overall configuration diagram of an apparatus according to another embodiment of the present invention.

[Explanation of symbols]

100: gas introduction tube, 101: microwave power supply, 102: waveguide, 103: introduction window, 104: vacuum vessel, 105: magnet, 106: plasma, 107: sample, 108: sample stage, 109: high frequency voltage power supply , 110: voltage waveform, 201: substrate Si, 202: oxide film, 203 ...
poly Si, 204 ... mask, 304 ... WSi, 405 ... W, 503 ... p-type poly
Si, 504 ... n-type poly Si,

 ──────────────────────────────────────────────────の Continuing on the front page (72) Tokuo Kure, Inventor 1-280 Higashi Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Masayuki Kojima 5-20-1, Josuihonmachi, Kodaira-shi, Tokyo Semiconductor Company, Hitachi, Ltd.

Claims (23)

[Claims] 1. A method for generating plasma in a processing chamber,
A high-frequency bias voltage is applied to a sample stage on which a sample is placed independently of the generation of the plasma, and a Vpp value of a continuous high-frequency bias voltage with the same etching rate is obtained.
A method for surface treatment of a sample, characterized in that a high-frequency bias voltage given a Vpp value larger than the Vpp value is turned on / off. 2. The method according to claim 1, wherein the high frequency bias voltage has a frequency of 15 MHz or less and the high frequency bias voltage has a Vpp value of 500 V or more. 3. The method according to claim 1, wherein the frequency of the high frequency bias voltage is higher than 15 MHz, and the Vpp value of the high frequency bias voltage is 800 V or more. 4. The method according to claim 1, wherein the on-duty of the high frequency bias voltage is set to 5 to 50%. 5. The method according to claim 1, wherein a period from the start to the end of the surface treatment of the sample is divided into a plurality of steps, and the high-frequency bias voltage is turned on / off in at least one of the steps. 6. The method according to claim 5, wherein the plurality of steps are divided into a first half in which the processing speed ratio with the base material is relatively small, and a second half in which the processing speed ratio is relatively large. A surface treatment method for a sample, wherein the high-frequency bias voltage is on / off controlled. 7. The method according to claim 6, wherein the switching of the steps is performed according to time. 8. A method for disposing a sample on a sample stage provided in a vacuum container, continuously supplying a processing gas into the vacuum container, and converting the processing gas into plasma, independently of the plasma generation. A high frequency bias having a frequency of 100 KHz or more is applied to the table, and the high frequency bias is
A surface treatment method for a sample, comprising modulating the sample at a frequency of z to 10 KHz to perform surface processing on the sample with a minimum processing dimension of 1 μm or less. 9. The method according to claim 8, wherein the plasma is a high-density plasma having an electron density of 1 × 10 ¹⁰ electrons / cm ⁻³ or more. 10. The method according to claim 8, wherein the processing gas is a mixed gas of chlorine and oxygen. 11. A sample is placed on a sample stage provided in a vacuum vessel, a processing gas is continuously supplied into the vacuum vessel, and the processing gas is turned into plasma using microwaves. Is 100K independently on the sample stage
A high frequency bias having a frequency of 10 MHz or more and a frequency of 10 Hz to 10 MHz is applied.
A surface treatment method for a sample, comprising: performing on / off control at a frequency of; 12. The method according to claim 11, wherein the plasma is an ECR plasma using a microwave of 2.45 GHz. 13. The method according to claim 11, wherein the plasma is 1
A surface treatment method for a sample which is an ECR plasma using a microwave of 00 MHz to 1 GHz. 14. A sample having a pattern with a minimum processing size of 1 μm or less held by electrostatic adsorption on a sample table provided in a vacuum vessel is generated by continuously supplying a processing gas into said vacuum vessel. When performing an etching process using the plasma, a high-frequency bias is applied to the sample stage independently of the plasma generation, the high-frequency bias is time-modulated, and the sample is processed. Processing method. 15. The method according to claim 14, wherein the electrostatic adsorption of the sample is a dipole electrostatic adsorption. 16. A high-frequency bias is applied to a sample having a film of a material to be a gate electrode formed on a gate oxide film having a thickness of 6 nm or less when the sample is etched by plasma. A surface treatment method for a sample, which comprises performing time modulation. 17. The method according to claim 16, wherein the film of the material to be the gate electrode is a polycrystalline silicon film or a multilayer film having a polycrystalline silicon film. 18. A sample stage provided in a vacuum vessel, on which a sample to be surface-treated is placed, processing gas supply means for continuously supplying a processing gas for generating plasma into the vacuum vessel, A plasma generating means for generating high-density plasma in a vacuum vessel, a bias power supply for applying a bias voltage of 100 KHz or more to the sample table independently of the plasma generation, and a frequency of 100 Hz to 10 KHz. A sample surface treatment apparatus, comprising: a pulse frequency control unit that modulates the surface of the sample by performing a surface treatment with a minimum processing dimension of 1 μm or less on the sample placed on the sample stage. 19. The surface treatment apparatus according to claim 18, wherein when the frequency of the high-frequency power supply is 15 MHz or less, the amplitude of the high-frequency voltage can be output at 500 V or more, and when it is higher than 15 MHz, 800 V or more can be output. 20. A surface treatment apparatus according to claim 18, wherein said high-density plasma is generated by any one of ECR, SECR, and IPC. 21. A sample stage provided in a vacuum vessel for mounting a sample to be surface-treated, processing gas supply means for continuously supplying a processing gas for generating plasma into the vacuum vessel, A plasma generating means for generating high-density plasma in the vacuum vessel by using a wave;
And a pulse frequency control means for modulating the bias power at a frequency of 100 Hz to 10 KHz. The amplitude of the high frequency voltage as the bias power is set to 100.
V. The surface treatment apparatus for a sample, wherein the surface treatment is V or more. 22. An apparatus according to claim 21, wherein said plasma generation means uses a microwave having a frequency of 2.45 GHz and utilizes electron cyclotron resonance. 23. An apparatus according to claim 21, wherein said plasma generating means uses a microwave having a frequency of 100 MHz to 1 GHz and utilizes electron cyclotron resonance.