JPH0727894B2 - Discharge reactor using rotating magnetic field - Google Patents

Description

TECHNICAL FIELD The present invention relates to the manufacture of semiconductor devices such as ICs and LSIs, and more particularly to a discharge reaction device using a rotating magnetic field suitable for a dry etching device.

(Prior Art) With the increase in the integration of semiconductor integrated circuits, the miniaturization of devices is required, and the development of three-dimensional integrated circuits is being advanced. ing.

Since the concept of the dry etching method using a rotating magnetic field was announced by Hyman of IBM in 1981,
It has been widely used as a method for increasing the plasma density together with the triode reactive ion etching apparatus.

In the magnetron system in which the electric field and the magnetic field are orthogonal to each other, the electrons turn by a so-called magnetron motion in a direction (E × B) perpendicular to the plane formed by the electric field and the magnetic field due to the synergistic effect of the electric field and the magnetic field. , Electrons collide with molecules, improving the ionization efficiency and increasing the etching rate. Also, the mobility of electrons is significantly reduced by the magnetic field, and the electron current that reaches the electrode that is in the DC floating state is reduced, so the self-bias is lowered and the ion energy that collides with the electrode can be lowered, and the wafer surface can be reduced. Damage to can be reduced.

In an apparatus using a rotating magnetic field, high density plasma is rotated on a wafer by rotating a magnetic field generated by two or three pairs of electromagnetic coils to promote ionization of the plasma.

(Problems to be Solved by the Invention) However, the above-mentioned conventional device has the following problems.

First of all, the diameter of wafers is increasing to a maximum diameter of 8 inches, etc., and it is necessary to have a large electromagnetic coil each with a diameter of 1 m or more in order to give a uniform magnetic field on these large diameter wafers. Becomes When such a large size is used, it becomes unusable in the current semiconductor manufacturing line in consideration of the floor occupying area of the device and the work space.

Secondly, regardless of the magnetic field strength distribution, in the parallel plate electrode type magnetron device, the electrons move in the E × B direction as described above, so that the plasma becomes dense in the same direction. In such a plasma state, when the magnetic force direction is north, the plasma potential on the wafer is almost uniform in the north-south direction, but in the east-west direction, the plasma potential on the east side is higher than that on the west side. In the case of controlling the etching shape and etching rate by the directionality and strength of the ions, such as reactive ion etching, the ions are accelerated in the plasma dark part by the sum of the plasma potential and the self-bias and collide with the film to be etched. Also, the ion current Ji is Ji = eniμi
As indicated by E, it changes in proportion to the product of ion density and ion mobility. That is, the collision strength and amount of ions in the east peripheral portion are larger than those in the central portion and the west peripheral portion with respect to the magnetic field, and the etching rate is significantly nonuniform. The density phenomenon of plasma mainly depends on the magnetic field strength and reaction pressure. In particular, in order to realize the high aspect ratio and extremely small pattern size-dependent etching required for next-generation devices, etching in a low-pressure atmosphere is indispensable, and the density phenomenon due to the magnetic field becomes remarkable. Further, not only the etching rate but also the ion collision strength in the outer peripheral portion of the wafer is higher than that in the central portion, so that the wafer is more likely to be damaged by ion irradiation, and depending on the device, the yield in the peripheral portion is significantly reduced.

Furthermore, the conventional technique is not suitable for a large-diameter wafer because the damage is large due to the difference in etching rate between the periphery of the wafer to be etched and the central portion and the periodic change in ion energy in the peripheral portion. This makes it difficult to independently change the magnetic field and pressure, and the process window for uniformity tends to be very narrow.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress the movement of electrons in plasma to make the plasma potential distribution uniform and to improve the etching rate in a wafer as a dry etching apparatus. It is possible to improve the uniformity of the surface pressure of the wafer and improve the plasma resistance.
It is an object of the present invention to provide a discharge reaction device using a rotating magnetic field that can generate a uniform film as a CVD device.

(Means for Solving the Problems) In the present invention according to the above object, a vacuum chamber containing an electrode, a gas supply means for supplying a predetermined gas into the vacuum chamber, and an exhaust means for exhausting the gas in the vacuum chamber. In a discharge reaction device using a rotating magnetic field, which is provided around a vacuum chamber and has an electromagnetic coil that generates a rotating magnetic field that rotates in a plane perpendicular to the direction of the electric field, the electrode on which the object to be treated is placed. Synchronized with the rotation of the rotating magnetic field so that the electric potential of the multiple magnetic field that is placed around the west side of the rotating magnetic field is higher than that of the west side of the rotating magnetic field when viewed from the direction of the electric field. It is characterized in that a control electrode whose potential is controlled is provided.

(Operation) If the magnetic field is simply rotated, the plasma potential on the east side with respect to the north direction of the rotating magnetic field becomes higher when viewed from the direction of the electric field as described above.

When the potential of the control electrode arranged around the electrode on which the object to be processed is placed is increased, the plasma potential of the surrounding is increased. Therefore, the plasma potential can be made uniform by controlling the potential so that the potential of the control electrode located on the west side with respect to the north direction of the rotating magnetic field is always higher than the potential of the control electrode located on the east side.

(Embodiment) A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view of the dry etching apparatus 10, and FIG. 2 is a front sectional view.

In the figure, 14 is a vacuum chamber, a gas supply port (not shown) for introducing an etching gas such as CF ₄ and a gas exhaust port (not shown) for exhausting the inside of the vacuum chamber 14 to set a required pressure. Have. The gas supply port is connected to a gas supply source via a valve, and the gas discharge port is connected to an exhaust pump via a valve.

Reference numeral 16 denotes a wafer (object to be processed) arranged in the vacuum chamber 14.
17) A non-grounded electrode for placement, to which a high frequency power source 20 is connected via a matching circuit 18 and high frequency power is applied. Reference numeral 22 is a ground electrode provided on the upper wall surface of the vacuum chamber and is grounded.

1.1 'and 2.2' are two pairs of electromagnetic coils arranged so as to surround the vacuum chamber 14, in which a current with a phase difference of 90 ° is applied and a direction orthogonal to the electric field between the non-grounded electrode 16 and the grounded electrode 22. Rotate the synthetic magnetic field generated in the. The rotation speed of this rotating magnetic field is low, and it is set to about 1 rotation in 2 seconds.

By applying a rotating magnetic field in this way, a high-density plasma can be rotated on the wafer 17, but as described above, when the magnetic field direction is north, the plasma potential is higher in the east side than in the west side. However, even if the magnetic field is rotated, the plasma rotates on the wafer 17 while the density of the plasma is generated, so that the above-mentioned problems occur.

In this embodiment, four control electrodes A, C, B and D are arranged around the non-grounded electrode 16 so that their upper surfaces are substantially the same as the upper surface of the wafer 17 placed on the non-grounded electrode 16. . twenty three,
24 is an insulator.

A DC power source is connected to each of the four control electrodes A, C, B, and D via a low-pass filter, and a pulsating voltage with a phase difference of 90 ° is applied. This pulsating voltage is set to be displaced in synchronization with the rotation of the magnetic field. That is, if the magnetic field rotates once every 2 seconds, the frequency of the pulsating voltage is set to 1/2 Hz. For example, the pulsating voltage applied to the control electrodes A, B, C, and D can be a sinusoidal pulsating voltage. If the direction of the magnetic field as seen from the direction of the magnetic field with respect to the rotation of the magnetic field is the north side, the potential of the control electrode located on the west side is high and the potential of the control electrode located on the east side is low, and the cycles are synchronized. .

It is configured as described above.

Next, the operation of this device will be described.

First, an etching gas such as CF ₄ gas is introduced into the vacuum chamber 14 from the gas supply port, and the inside of the vacuum chamber 14 is changed to 10 ^-2.
[Torr] is maintained and high frequency power (1kW, 13.5
(MHz) is applied, a discharge is generated between the non-grounded electrode 16 and the grounded electrode 22, and plasma is generated. On the other hand, an alternating current is applied to the two pairs of electromagnetic coils 1.1 'and 2.2' to rotate the composite magnetic field. This synthetic magnetic field is generated in the direction orthogonal to the electric field, so that the electrons make a magnetron swirling motion and enhance the ionization efficiency.

On the other hand, as described above, the four control electrodes A, B, C, D
A pulsating current is applied to.

For example, when the driver setting values of the electromagnetic coils 1.1 'and 2.2' are (1, 0), the magnetic field indicates A, and at the same time, the potential of the control electrode B on the west side is the highest with respect to the direction of the magnetic field, and The control electrode D has the lowest potential. Further, when the driver setting values of the electromagnetic coils 1.1 'and 2.2' are (.707, .707), the magnetic field is directed in a direction rotated by 45 ° clockwise from the above position, and at this time, the potentials of the control electrodes A and B are changed. Is high and the potentials of the control electrode C and the control electrode D are low. That is, in synchronization with the rotation of the magnetic field, the potentials of the four control electrodes A, B, C, and D are always higher in the west side control electrode than in the east side control electrode with respect to the magnetic field direction (north). To be displaced.

When a positive potential is applied to the control electrodes A, B, C and D, the plasma potential in the vicinity of the control electrode rises in proportion to the potential of that electrode,
On the contrary, when the potential is negative, the ion current increases and the plasma potential decreases. This is because the DC electrode acts as a source of electrons or removes excess electrons. That is, the movement of electrons in the E × B direction in plasma can be suppressed or controlled.

Therefore, as described above, the potentials of the four control electrodes A, B, C, and D are displaced so that the control electrode on the west side is always higher than the control electrode on the east side with respect to the direction of the magnetic field (north). By doing so, it is possible to eliminate the bias of the plasma potential toward the east side due to only the rotating magnetic field, thereby making the distribution of the plasma potential uniform,
The etching rate within the wafer becomes more uniform, and the breakdown voltage on the wafer surface improves.

The plasma potential can be easily adjusted by adjusting the potentials of the four control electrodes A, B, C, and D. As a result of the optimum potential adjustment, the plasma potential between north and south and east and west was significantly improved to within ± 10 V at a position 4 inches from the center of the wafer. Further, at the same time, the uniformity of the etching rate in the wafer surface was ± 10% in the region of 10 mm from the edge in the past, but it is 5 m from the edge in this embodiment.
It was ± 3.5% excluding the part of m, which was within the allowable range.

Although the four control electrodes A, B, C and D are arranged in the above-mentioned embodiment, for example, if the number of electrodes is increased to eight, the plasma potential can be controlled more easily and can be made uniform.

Further, although the high frequency power supply is used in the above embodiment, a direct current power supply may be used, and the direct current power supply can simplify the structure of the apparatus.

Further, although the dry etching apparatus has been described as an example in the above embodiment, it is needless to say that it can also be used as a plasma CVD apparatus.

Although the present invention has been variously described with reference to the preferred embodiments, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. That is.

(Effect of the invention) As described above, according to the present invention, the movement of electrons in plasma can be controlled and the distribution of plasma potential can be made uniform. It is possible to more uniformly improve the pressure resistance of the surface of the object to be processed, and it is possible to form a film having a uniform thickness on the surface of the object to be processed by using the plasma CVD apparatus.

[Brief description of drawings]

FIG. 1 is a plan view of the dry etching apparatus, and FIG. 2 is a front sectional view thereof. 10: Dry etching device, 14: Vacuum chamber, 16
...... Ungrounded electrode, 17 ・ ・ ・ Wafer, 20 …… High frequency power supply, 22
...... Ground electrode, 1.1 ', 2.2' ...... Electromagnetic coil, A, B,
C, D ... Control electrodes.

Claims (1)

[Claims] 1. A vacuum chamber containing an electrode, a gas supply means for supplying a predetermined gas into the vacuum chamber, an exhaust means for exhausting the gas in the vacuum chamber, and a vacuum chamber provided around the vacuum chamber for generating an electric field. In a discharge reaction device using a rotating magnetic field, which comprises an electromagnetic coil for generating a rotating magnetic field rotating in a plane perpendicular to the direction, a plurality of objects are placed around the electrode on which the object to be treated is placed,
The potential is controlled in synchronization with the rotation of the rotating magnetic field so that the potential of the west side of the rotating magnetic field is higher than the east side of the rotating magnetic field when viewed from the direction of the electric field. A discharge reaction device using a rotating magnetic field, characterized in that a control electrode is provided.