JPS6182434A - Plasma treating device - Google Patents

Abstract

PURPOSE:To etch a sample uniformly at a high speed or to form a film of uniform thickness by generating a traveling magnetic field on the surface side of the sample on a cathode, and virtually uniformly scanning a high density plasma region on the sample in one direction. CONSTITUTION:Reactive gas such as, for example CF4 is fed from a gas inlet 13a into an etching chamber 12, which is held in high vacuum, and when a high frequency power is applied to a cathode 12, a glow discharge is generated between the cathode 12 and an anode to generate a low density plasma region 61. When an AC current is flowed to a coil 30, magnetron discharges of large, intermediate and small values of displaced phases occur, electrons collide repeatedly many times with CF4 molecules while moving in a cycloid motion in ExB direction to generate a high density plasma region 62 along a pole gap. Since this region 62 moves periodically toward a traveling magnetic field in one direction, the integrated value of the sample 18 while exposed with the region 62 becomes constant on the entire surface of the sample. Thus, the entire sample is etched uniformly at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a plasma processing apparatus used for manufacturing semiconductor devices, and more particularly to a plasma processing apparatus that performs dry etching, film formation, etc. at high speed.

[Technical background of the invention and its problems]

In recent years, semiconductor integrated circuits have become increasingly miniaturized, and recently, ultra-fine elements with a minimum dimension of 1 to 2 [μm] have been prototyped and developed. Such microfabrication usually involves introducing a reactive gas such as CF4 or CCl2 into an evacuated container with parallel plate electrodes, and applying high-frequency power to the electrode (cathode) on which the sample is placed. Negative DC self-bias (cathode drop voltage) generated at this cathode, causing a glow discharge
In so-called reactive ion etching (RIE), positive ions in plasma are accelerated and irradiated perpendicularly onto a sample, and the sample is etched by a physicochemical reaction.
1 on Etching) method is used.

However, since this RIE using parallel plate electrodes utilizes a glow discharge with a relatively low gas dissociation effect, the etching rate of Si02 using, for example, CF4 + H2 gas is at most 300 to 400 [people/ll1in]. Si with a thickness of 1 [μm] such as contact holes etc.
It took several tens of minutes or more to etch 02, which was extremely inconvenient in terms of mass production. Therefore, it is desired to increase the etching speed.

In response to this problem, the present inventors have developed a dry etching apparatus which enables high-speed etching by magnetron discharge by providing a magnetic field generating means made of a permanent magnet under the cathode to which high-frequency power is applied (Japanese Patent Laid-Open No. 57-98678). The principle of this device is that, as shown in FIG. 10, electrons 5 are caused to move in a cycloid by a magnetic field 3 generated in a magnetic pole gap 2 forming a closed loop of a permanent magnet 1 and an electric field 4 perpendicular to this magnetic field 3.
The purpose is to significantly increase the frequency of collisions with the introduced reactive gas and generate a large amount of reactive ions.

Note that 6 in the figure indicates a sample to be etched.

As a result, a large number of ions are perpendicularly incident on the sample 6, achieving high-speed anisotropic etching.

However, this type of device has the following problems. That is, if the magnetic pole gap 2 is kept stationary, only the high-density magnetron discharge region 7 generated in a track shape will be etched, but in order to uniformly etch the entire sample 6! ! It is necessary to scan the magnetic pole gap larger than the major axis of the sample 6. Figure 11 shows that Si is heated by CF4 gas.
FIG. 3 is a characteristic diagram showing the results of measuring the etching rate when etching O2 as a function of the distance from the sample edge. At this time, the magnetic pole gap 2 was kept stationary at a distance of 30 [mm] from the edge of the sample 6, as shown in FIG. It can be seen from FIG. 11 that near the edge of the sample, etching for 10 seconds results in etching of about 1000 to 2000 mm, and that the etching rate becomes slower as the area is further inward from the edge of the sample. Even if the return time of the scanning is as fast as, for example, 0.05 seconds, it is equivalent to keeping the magnetic pole gap 2 stationary on both sides of the sample 6 for 2 seconds in about 80 scans.
Therefore, with this number of scans, the depth of the sample edge etched in the state shown in FIG. 12 becomes a value close to 500 [people]. Such fast etching in the surrounding area becomes a factor that reduces the uniform etching performance of the entire sample. One possible way to prevent this is to widen the scanning width of the magnetic pole gap 2, but in this case, this will lead to an increase in the size of the device and a decrease in the etching speed, which may lead to the need for larger diameters (6 inches or more) in the future.
It becomes difficult to respond to

In addition, the above-mentioned problem is not limited to etching, but also plasma CV.
The same can be said for film formation by D or sputtering deposition. For example, in the case of sputtering deposition, when forming a film using parallel plate electrodes, placing the target as a sample on the cathode and the wafer on which the film is to be formed on the anode, the target on the cathode may not be etched uniformly. The film formed on the wafer becomes non-uniform, making it impossible to form a uniform film, and shortening the life of the target.

[Purpose of the invention]

The purpose of the present invention is to avoid increasing the size of the device configuration; 1.
It is an object of the present invention to provide a plasma processing apparatus capable of uniformly etching or sputtering a sample at high speed or forming a film of uniform thickness on the sample, and capable of sufficiently coping with the increase in the diameter of the sample.

[Summary of the invention]

The gist of the present invention is to use a magnetic field generating means that electrically generates a magnetic field that can be continuously moved in a predetermined direction in place of the above-mentioned permanent magnet having a magnetic pole gap.

That is, the present invention provides a plasma processing chamber equipped with a cathode to which high-frequency power is applied and a sample placed on the surface side, and an anode arranged opposite to the cathode; , means for exhausting the processing blank;
Consisting of a magnetic core and a plurality of coils wound around the magnetic core through which alternating currents of mutually different phases are passed, the coils are arranged opposite to the back side of the cathode outside the processing chamber, and apply a magnetic field to the front side of the cathode. The device is equipped with a magnetic field generator that continuously moves this magnetic field in one direction, and a means for reversing the direction of movement of the magnetic field, and the magnetic field generator generates a traveling magnetic field toward the surface of the sample on the cathode. The device is designed to scan a virtual high-density plasma region uniformly over the sample in one direction.

〔Effect of the invention〕

According to the present invention, since the high-density plasma region is always scanned in one direction (and the opposite direction) by the magnetic field generating means consisting of a magnetic core and a plurality of coils, the sample to be etched is placed on the cathode as a sample. When placed, the entire sample can be etched at high speed. In addition, there is no disadvantage that the etching speed near the edge of the sample becomes particularly high as in the case where the magnetic pole spacing is reciprocally scanned, and the entire sample can be etched uniformly. Furthermore, when a sample on which a film is to be formed is placed on the cathode, the uniformity of the film can be improved. Furthermore, when the target as a sample is placed on the cathode and the member on which the film is to be formed is placed on the anode, the target is etched quickly and uniformly, so the film can be formed uniformly and quickly on the sample. .

Further, since the scanning of the high-density plasma can be performed electrically, that is, the magnetic field can be continuously moved in one direction while the magnetic field generating means is fixed, it is possible to downsize the device configuration. In general, for the above reasons, no mechanically movable parts are required, and reliability can be improved. Therefore, it is extremely useful in the field of semiconductor manufacturing technology, and can sufficiently cope with increasing the diameter of the sample.

Furthermore, by reversing the moving direction of the magnetic field at least once during processing, it is possible to solve the problem of magnetic field strength non-uniformity when using a linear motor stator such as ring winding or two-phase winding.

[Embodiments of the invention]

FIG. 1 is a schematic diagram showing a dry etching apparatus according to a first embodiment of the present invention. In the figure, 11 is a grounded container, and the inside of this container 11 is a plasma processing chamber 13 (which is emptied by etching by a shade 8i12) and a magnetic field generator storage chamber 14.
It is separated into

High frequency power from a high frequency power source 16 is applied to the cathode 12 via a matching circuit 15 . Further, the cathode 12 is cooled by a water-cooled tube 17, and this water-cooled tube 17 is used as a lead for the above-mentioned power application. Etching chamber 1
3 is provided with a gas inlet 13a for introducing a reactive gas such as CF4, and a gas exhaust port 13b for exhausting the gas. The sample 18 to be etched is placed on the cathode 12 in the etching chamber 13. Incidentally, the anode opposite to the cathode 12 is formed of the earthen wall of the etching chamber 13.

On the other hand, in the magnetic field generator storage v14, a magnetic field generator 40 consisting of a magnetic core 20 and a coil 30 made up of several dozen or more thin conductive wires is arranged facing the lower surface of the cathode 12. Here, the magnetic core 20 is made of laminated thin plates of magnetic material as shown in FIG. is longer than the major axis of the sample 18, and similarly, the length of the magnetic core 20 in the direction orthogonal to the groove 21 is also longer than the sample 18. A water-cooled plate 22 having a water channel inside is attached to the lower surface of the magnetic core 20, and cooling water is passed through the water-cooled plate 22 through a water-cooled pipe 23 connected to this water-cooled plate 22, thereby cooling the magnetic core 20. It has become something that In general, in order to incorporate one side of the coil 30 into the groove 21 of the magnetic core 20 after manufacturing the coil 30, the magnetic core 20 has a structure that can be divided into a comb-shaped core 20a and a back core 20b. Further, the coil 30 consists of first to third coils 31a, 31b, and 31c, as shown in FIG. 3(1).
), the magnetic core 20 is periodically wound in a ring manner in the groove 21 of the magnetic core 20. That is, the coil 31a is wound around the magnetic core 20 so that one side is embedded in the groove 21 and the other side is located on the opposite side of the groove 21, and is further connected in series to each of the three grooves 21. Other coils 31b, 31
The same applies to And these coils 31a
, 31b, and 31c, three-phase alternating currents having different phases are passed through the switch circuit 25. Note that the switch circuit 25 switches the polarity of the three-phase alternating current U, V, and W.

Here, each of the above: +il 31 a, 31 b, 31 c
When three-phase alternating currents with phases different by 120 degrees are passed through,
On the magnetic field generator 40, that is, on the cathode 12, as shown in FIG.
a), the magnetic flux density B is given by the following equation:
occurs.

B-BOCO8 (ω is 1πX/τ)... ■However, ω-2πf; Angular frequency of power supply [rad/sea]
, ff; frequency [Hz], t; time [sec], X:
Distance [a+] from the reference point on the surface of the magnetic core, τ; pole pitch [jIa+]. As shown in the figure, the pole pitch is a half wavelength of the magnetic flux density, that is, the length of a half period. As is clear from the above equation, B is a traveling magnetic field that moves to the right in the paper with time (Figure 3 (a) shows the relationship at 1-0). Furthermore, when any two circuits, for example U and ■, are switched by the switch circuit 25, the traveling magnetic field moves to the left in the drawing. By the way, is Fig. 3(b) the arrow in Fig. 2? ! It is a cross-sectional schematic diagram corresponding to the AA cross section. Therefore, the magnetic core 20 is placed on the cathode 12 surface.
A parallel magnetic field with varying strengths is generated in the horizontal direction, making it appear as if the area is also moving. That is, the tenth
As explained in the figure, a high-density plasma region is generated on the cathode 12, and this plasma region continuously moves in one direction.

Furthermore, by switching between any two circuits using the switch circuit 25, the moving direction of the plasma region is reversed.

The magnetic field generator storage chamber 14 also includes a gas exhaust port 14a.
is provided in the storage chamber 14, and the magnetic field generator 40 is located inside the storage chamber 14.
The gas is evacuated to a high vacuum of 10 torr or less through a gas exhaust port 14a to prevent discharge caused by the gas. Further, a gate valve 52 driven by a solenoid valve 51 is provided between the storage "ff114" and the etching chamber 13, and the gate valve 52 shuts off each chamber 13 and 14 during etching. In Fig. 4, 53 indicates an insulator such as fluororesin, and 54 indicates an O-ring seal.

The operation of this device configured in this way will be explained.

First, a reactive gas such as CF4 is introduced into the etching chamber 12 from the gas inlet 13a, and after maintaining the inside of the etching chamber 12 at 10' [torr], high frequency power (13.56 MHz) is applied to the cathode 12. Then, the cathode 12
A glow discharge is generated between the etching chamber 13 and the anode (earth wall of the etching chamber 13), and a low-density plasma region 6) is generated. At the same time, when an alternating current is passed through the coil 30, the electric field E and the magnetic field B, which are orthogonal to each other, act on each other in each magnetic pole gap, resulting in a magnitude that is out of phase with each other as shown in the figure.

A medium to small magnetron discharge is generated, and the electrons repeatedly collide with CF4 molecules many times while performing cycloidal motion in the EX8 direction, forming a high-density plasma region 62! 1 occurs along the magnetic pole gap. Since this high-density plasma region 62 moves periodically due to the magnetic field traveling in one direction as explained in FIG. 3, the integral value while the sample 18 is exposed to the high-density plasma region 62 is constant over the entire surface of the sample. Become. For this reason,
The entire surface of the sample is etched uniformly and at high speed. Also, during the above etching process, the switch circuit 2
5, the direction of the traveling magnetic field was reversed at an interval of about once per second.

In this way, according to the present apparatus, the sample 18 can be etched uniformly at high speed by the action of the magnetic field generator 40. Furthermore, the size of the magnetic field generator 40 only needs to be slightly larger than the sample 18, so that the apparatus does not become larger. In addition, since no mechanical moving parts are required, reliability can be improved, and from this, the device it1! The structure can be made smaller. In addition, in this apparatus, the sample 18 is always exposed to the high-density plasma region 62, so the sample 18
Even if the diameter of the magnetic pole 8 is increased, the decrease in the etching rate is extremely small, and an etching rate (approximately 5 μu/min) close to that obtained when the magnetic pole gap is kept stationary can be obtained.

Furthermore, the apparatus of this embodiment has the following advantages compared to the plasma processing apparatus previously proposed by the present inventors (Japanese Patent Application No. 17796/1982, Patent Application No. 150202/1982). be.

That is, in the device of the prior application, the three-phase alternating current was passed directly through the coil 30 without using the switch circuit 25, so the direction of movement of the magnetic field was unidirectional. Then, the moving direction of the magnetic field is from left to right in Fig. 1,
When an experiment was conducted under the same conditions as in this example, the results shown in Figure 13 (
As shown in a), the strength of the magnetic field tended to be high on the left side of the magnetic core and low on the right side. Further, as shown in FIG. 2(b), the etching distribution was accordingly faster on the left side and slower on the right side. The details of this cause are not clear, but for example, if the traveling direction of the magnetic field is to the left from the cloth on the paper, the magnetic field on the right side will be high and low on the left side, contrary to the above case, so ring winding or double layer This is considered to be a characteristic when using a linear motor stator such as winding.

In contrast, in the device of this embodiment, when the direction of the traveling magnetic field is reversed at an interval of once per second by the switch circuit 25, the above-mentioned non-uniform magnetic field portions (both ends of the sample) cancel each other out. As a result, good uniform etching characteristics were obtained as shown in FIG. Therefore, the etching uniformity can be further improved than in the previous application.

FIG. 5 is a schematic diagram showing a dry etching apparatus according to a second embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the previously described embodiments in the way the coil 30 is wound. That is, in this embodiment, the coil 30a has three phases.

Coils 30a, 30b, and 30c were wound periodically so that a predetermined number (two) of grooves were sandwiched between different grooves of coils 30b and 30c. That is, a three-phase AC two-phase wound coil was used. Of course, even with such a configuration, the same effects as in the previous embodiment can be obtained.

FIG. 6 is a block diagram of main parts for explaining a third embodiment of the present invention. This embodiment differs from the first embodiment described above in that a Helmholtz coil 71 is provided on the cathode 12.
．． 72, and the rest is exactly the same as the previous embodiment.

With such a configuration, the Helmholtz coil 71.7
By passing a current through the sample 18, the magnetic field strength on the surface of the sample 18 can be increased. This increases the horizontal magnetic field on the sample surface, which has the advantage of significantly lowering the ion acceleration voltage and reducing radiation damage (Y).

Horiike, H,0kano; Jpn, J.
AI) I) I 1) hYs.

20 (1981) L817).

FIG. 7 is a schematic diagram showing a dry etching apparatus according to a fourth embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the first embodiment in that the magnetic field generator 40 is placed in the atmosphere. That is, in the apparatus having the magnetic field generator 40 described above, even if the magnitude of the magnetic field generated in the magnetic pole gap and the magnitude of the high-frequency power are sufficiently reduced, it is possible to obtain an etching rate that is significantly higher than that of the conventional apparatus. Make the thickness sufficiently thick (1ojI11
(above), and there is almost no risk that the magnetic field generator 4o will discharge even without providing a particularly high vacuum magnetic field generator storage chamber 14.

Therefore, in this embodiment, not only can the same effects as the previous embodiments be obtained, but also there are advantages such as the ability to further simplify the device configuration.

FIG. 8 is a schematic configuration diagram showing a dry etching apparatus according to a fifth embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the first embodiment in that a magnetic material is embedded in the outer periphery of the cathode 12. That is, an iron plate 80 is embedded in the upper surface of the cathode 12 so as to surround the area outside the area where the sample 18 is placed.

With such a configuration, even if the end of the magnetic pole gap is under the iron plate 80, most of the magnetic lines of force will pass through the iron plate 80, which has high magnetic permeability, and the magnetic field will be on the iron plate color 0. does not occur. Therefore, the high-density plasma region 62 around the sample 18 is removed. Therefore, it is possible to improve the uniformity in the direction of the traveling magnetic field, and it is possible to obtain a more uniform etching rate.

Note that the present invention is not limited to the embodiments described above. For example, the coil of the magnetic field generator is not limited to a three-phase winding, but may be any one having two or more phases, and preferably three phases.
It is sufficient if it has n phases (n is a positive integer). That is, the magnetic field generator may be any device as long as it includes a magnetic core and a plurality of coils, generates a magnetic field on the cathode, and can continuously move this magnetic field in one direction. Further, the size of the grooves formed in the magnetic core, the intervals between the grooves, etc. can be changed as appropriate depending on the specifications.

Furthermore, the current flowing through the coil is not limited to three-phase alternating current, but may be any alternating current that corresponds to the number of phases of the coil, that is, two or more phase alternating current. Here, as the number of coils and alternating current phases increases, a more uniform magnetic field distribution can be obtained.

Furthermore, instead of the switch circuit, any circuit can be used as long as it can change the phase of the current flowing through the coil and reverse the direction of movement of the magnetic field. Alternatively, a plurality of samples may be etched simultaneously by forming the cathode in a track shape and the magnetic field generator in a track shape as shown in FIG. This can improve agricultural productivity. Roughly speaking, if a means for preventing the sample from falling is added, it is also possible to reverse the vertical relationship of each embodiment apparatus. Also,
It goes without saying that the sample is not limited to 5 iOz and can be applied to etching various films.

In addition, the device of the present invention is not limited to etching, but also plasma CVD.
It can also be applied to film formation, such as sputtering deposition, or ashing treatment. However, in the case of sputtering deposition, it is necessary to place a target as a sample on the cathode and place a member on which a film is to be formed on the anode. In this case, the target is uniformly etched at high speed in the same manner as the etching of the sample to be etched, so that the film can be formed on the sample at a high speed, and the thickness of the formed film can be made uniform. can do. In general, as in the case of etching, the magnetic field can be moved in one direction while the magnetic field generator is fixed, so the device configuration can be made smaller, and reliability can be improved because no mechanical moving parts are required. . Further, the excited gas introduced into the plasma processing chamber may be adjusted as appropriate depending on the type of the sample to be etched, the sample to be deposited, or the target on the cathode.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

1 to 4 are for explaining a dry etching apparatus according to a first embodiment of the present invention, respectively.
The figure is a schematic diagram showing the overall configuration, Figure 2 is a perspective view showing the magnetic core structure, Figure 3 is a schematic diagram showing how the coil is wound and the generated magnetic field, and Figure 4V is a case where the direction of magnetic field movement is reversed. FIG. 5 is a schematic configuration diagram showing the second embodiment of the present invention, FIG. 6 is a configuration diagram of main parts for explaining the third embodiment of the present invention, and FIG. The figure is a schematic configuration diagram showing a fourth embodiment of the present invention,
FIG. 8 is a schematic configuration diagram showing the fifth embodiment of the present invention, and FIG.
The figure is a main part configuration diagram for explaining a modified example, and Figures 10 to 12 are for explaining the problems of the conventional method. Figure 10 is a perspective view showing the principle of a dry etching device using magnetron discharge. Figure 11 is a characteristic diagram showing the relationship between the sample position and etching depth, Figure 12 is a schematic diagram showing the relationship between the magnetic pole gap and the sample position, and Figure 13 is a characteristic diagram showing the relationship between the sample position and the etching depth. Processing equipment (patent application 1987-177)
96, Japanese Patent Application No. 59-150202). 11... Etching container, 12... Cathode, 13...
- Etching space (plasma processing chamber), 13a... gas inlet, 13b, 14a... gas exhaust port, 14...
Magnetic field generator storage space, 15...Matching circuit, 16.
. . . High frequency power supply, 17. . . Water-cooled tube, 18.. Sample to be etched, 2o.・
...Switch circuit, 30.30a, 3 l b, 31
c...Coil, 6)...Low density plasma region, 62
...High-density plasma processing chamber, 71.72...Helmholtz coil, 80...iron plate. Applicant's agent Patent attorney Takehiko Suzue 956 Figure 7 v W Figure 9 Figure 10 Figure 12

Claims (8)

[Claims] (1) A plasma processing chamber equipped with a cathode to which high-frequency power is applied and a sample placed, and an anode arranged opposite to the cathode, a means for introducing an excited gas into the processing chamber, and an inside of the processing chamber. a magnetic core disposed opposite to the cathode outside the processing chamber; and a plurality of coils wound around the magnetic core through which alternating currents of mutually different phases are passed, and the coils are arranged on the sample in a predetermined direction. A plasma processing apparatus comprising: a magnetic field generating means for generating a continuously moving magnetic field; and a means for reversing the moving direction of the magnetic field. (2) The plasma processing apparatus according to claim 1, wherein the excited gas is a reactive gas, and the sample placed on the cathode is etched by this gas. (3) The plasma processing apparatus according to claim 1, wherein a film is formed on the surface of the sample placed on the cathode by vapor phase growth. (4) The sample placed on the cathode is a target that serves as a raw material for film formation, and a film is formed on the member placed on the anode by sputtering the target. The plasma processing apparatus according to scope 1. (5) The magnetic core has a comb-like cross section and is arranged such that its plurality of grooves face the cathode, and each coil has one side embedded in the groove and the other side on the opposite side of the groove. 2. The plasma processing apparatus according to claim 1, wherein the magnetic core is wound around a ring winding located therein. (6) The magnetic core has a comb-shaped cross section and is arranged such that the plurality of grooves thereof face the cathode, and each coil is wound periodically with a predetermined number of grooves sandwiched between different grooves. A plasma processing apparatus according to claim 1, characterized in that: (7) The plasma according to claim 1, wherein the plurality of coils constitute 3n-phase (n is a positive integer) coils, and a 3n-phase alternating current is passed through these coils. Processing equipment. (8) The means for reversing the moving direction of the magnetic field includes the 3n
8. The plasma processing apparatus according to claim 7, comprising a switch circuit for switching the phase of the 3n-phase alternating current flowing through the phase coils.