JP3086362B2 - Plasma processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a plasma processing apparatus.

[0002]

2. Description of the Related Art Generally, in a semiconductor product manufacturing process, a semiconductor wafer is subjected to a CVD process, an etching process, a sputtering process, and the like. A plasma processing device is used as an apparatus for performing such various processes. May be As an example of this type of conventional plasma processing apparatus, two flat electrodes are installed in parallel in a processing container made of, for example, aluminum or the like, and the upper electrode is grounded, and the lower electrode is connected to a high-frequency power supply. To apply RF power and to support the wafer. Then, plasma is induced by introducing an etching gas between the two electrodes, and plasma processing is performed on the wafer.

Referring to FIG. 4, an upper electrode 4 is disposed in a processing vessel 2 made of aluminum or the like, and a lower electrode 6 as a susceptor is provided below the upper electrode 4. A high frequency power supply 8 is connected. An electrostatic chuck 10 is provided on the upper surface of the lower electrode 6, and the semiconductor wafer W is electrostatically attracted to the surface. The lower electrode 6 is supported on a susceptor support 14 having a cooling jacket 12, and cools the lower electrode 6 heated during plasma processing.

The upper electrode 4 is provided with a processing gas supply header 16 for supplying a processing gas to the processing space S. A plurality of gas holes 18 formed in the upper electrode 4 form a shower to the processing space S. A processing gas is supplied. When plasma processing is performed, a processing gas is supplied to the processing space S while supplying high-frequency power between the upper and lower electrodes 4 and 6, and the processing space S is maintained at a predetermined reduced pressure.
Then, a plasma is generated, and a plasma process such as etching is performed on the wafer surface.

[0005]

By the way, taking as an example the case where etching is performed as plasma processing, in this etching processing, the lower the pressure of the gas atmosphere (process pressure) in the processing space S, the lower the processing pressure. It is known that it is suitable for fine processing.
When forming an M memory, it is necessary to perform etching with a line width of about 0.8 μm, so the process pressure is maintained at about 1.7 Torr. With the miniaturization of processing, for example, when manufacturing a 16M DRAM memory, fine processing with a line width of about 0.5 μm must be performed. In this case, the process pressure is reduced to about 0.5 μm.
It is necessary to set to about 25 Torr.

Usually, the processing gas is supplied to the processing gas supply header 16.
When the gas flows out of the processing space S through the gas holes 8 through the gas holes 8, the gas pressure in the header 16 is somewhat higher than that in the processing space S due to the resistance received from the gas holes 18 and the like.
However, as described above, the process pressure is set to about 0.25T.
At a pressure as low as orr, the atmospheric pressure in the header 16 also becomes correspondingly considerably low, so that plasma discharge occurs not only in the processing space S but also in the header 16. As described above, when the plasma micro-discharge occurs in the header 16, the surface of the aluminum material constituting the header 16 is hit by the active ions or the like by the plasma to generate particles, which flow to the processing space S side and flow to the wafer. There was a problem of adhesion. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a plasma processing apparatus that suppresses plasma discharge in a header by increasing resistance when a processing gas flows out.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of supplying a processing gas to a processing space through a first gas hole formed in an electrode having a processing gas supply header. In a plasma processing apparatus for performing plasma processing on an object to be processed held on an electrode to be processed, the processing is performed so that plasma discharge does not occur in the processing gas supply header .
Pressure in the processing gas supply header and processing pressure in the processing space
Means for providing a pressure difference between the processing gas supply header
It is configured to be provided inside .

[0008]

According to the present invention, as described above, the processing gas supplies a pressure difference from the processing gas supply header .
The pressure by ie resistance applying means so that the flow out through the first gas holes into the processing space in a state of being suppressed. The resistance applying means comprises, for example, a cooling plate having a second gas hole. By changing the thickness of the cooling plate or the diameter of the second gas hole or the first gas hole, the resistance to the processing gas flowing out is reduced. It can be arbitrarily selected.
In this case, even if the process gas pressure in the processing space S is set to 0.5 Torr or less in order to perform fine processing, the pressure in the header becomes 0.5 due to the resistance by the resistance applying means.
The value in the header becomes slightly higher than Torr, and the state in the header deviates from Paschen's law indicating a state for generating plasma discharge. Thus, the generation of plasma in the header is suppressed. It becomes possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the plasma processing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. 1 is a sectional view showing an embodiment of the plasma processing apparatus according to the present invention, FIG. 2 is an enlarged sectional view showing the vicinity of an upper electrode of the apparatus shown in FIG. 1, and FIG. 3 shows the resistance applying means shown in FIG. It is a top view. In this embodiment, a plasma etching apparatus will be described as an example of a plasma processing apparatus.

As shown in the figure, the plasma etching apparatus has a processing vessel 18 formed into a cylindrical shape by a conductor such as aluminum, and the processing vessel 18 is grounded. A pair of electrodes vertically spaced apart, for example, about 20 to 30 mm, that is, an upper electrode 20 and a lower electrode 22 are arranged in parallel in the processing container 18, and the space between these electrodes constitutes a plasma processing space S. Is done. The lower electrode 22 as a susceptor is formed in a substantially columnar shape by using, for example, alumite-treated aluminum or the like, and is capable of mounting an object to be processed, for example, a semiconductor wafer W, on a flat upper end portion thereof. And
A ring-shaped clamper member 24 is provided on an upper peripheral portion of the lower electrode 22, and is configured to engage with a peripheral edge portion of the wafer W and fix it to the lower electrode 22.

The lower electrode 22 is connected to, for example, an insulating tube 26 penetrating from the lower part of the processing vessel.
A wiring 28 connected to the lower electrode 22 is inserted therein, and a matching unit 30 and a first high-frequency power supply 32 of 13.56 MHz, for example, are connected to the wiring 28. Note that the insulating tube 26 itself may be formed of a conductor, and high-frequency power may be supplied to the tube by a skin effect.
In this case, it is configured to ensure insulation between the pipe 26 and each member through which the pipe 26 passes. A lower portion of the lower electrode 22 is provided with a first grounding electrode 36 for reinforcing grounding via an insulator 34 made of ceramics having a thickness of several tens of mm, for example, and this electrode 36 is reliably grounded. The first ground electrode 36 has a thickness of several tens, for example.
mm of good conductor aluminum or the like, and the lower electrode 22
Is formed in a container shape so as to cover substantially the entire lower portion thereof via the insulator 34.

A slight gap S1 is formed between the lower surface of the insulator 34 and the upper surface of the first ground electrode 36, and the lower surface of the peripheral portion of the insulator 34 and the peripheral edge of the first ground electrode 36 are formed. An O-ring 38 is annularly interposed between the upper end and the inside to seal the inside of the gap S1. And, in this gap S1,
A gas introduction passage 40 for introducing an insulating gas is connected from the lower side, and the gap S1 is filled with, for example, 1 atm of air to allow a space between the lower electrode 22 and the first ground electrode 36 to be formed. An insulating gas layer 42 for improving insulation is formed.

A metal susceptor support 44 is provided below the lower electrode 22, and the lower portion is supported by an annular chamber bottom ring 46 attached to the container. The susceptor support 44 is formed by combining a plurality of aluminum members, for example, conductive members so that they are in surface contact with each other. And Further, the lower electrode 22
Inside, a lower cooling jacket 48 for flowing the refrigerant along the circumferential direction is formed.
Is connected to a refrigerant introduction passage 50 and a refrigerant discharge passage (not shown) for introducing and discharging a cooling refrigerant from below.

On the other hand, the upper electrode 20 is formed into a disk shape by using, for example, amorphous carbon or aluminum, and a processing gas supply header 51 made of, for example, aluminum is provided on the upper portion thereof. A recess 52 is formed. Then, the upper electrode 20
The entire side of the supply header 51 is covered with an electrical insulator 54 made of, for example, ceramic or quartz, and the entire upper electrode is supported on the processing container 18 side.

The upper electrode 20 is connected to, for example, 40 through a matching unit 56 including a variable capacitor or the like.
A second high frequency power supply 58 for generating a high frequency of MHz is connected, and is configured to apply a high frequency power to the upper electrode 20. Therefore, in the present embodiment, high-frequency power is supplied to both the upper electrode 20 and the lower electrode 22 to constitute a so-called top-and-bottom type plasma processing apparatus. On the side of the upper electrode 20, a ring-shaped second ground electrode 60 made of, for example, aluminum is provided between the side walls of the processing chamber 18 via an insulator 54, for example. The ground electrode 60 is reliably grounded.

The lower surface of the second ground electrode 60 facing the processing space S is, for example, subjected to an alumite treatment. In order to prevent the ground electrode 60 from being damaged by plasma discharge, A protective layer 62 made of, for example, Al ₂ O _{3 having} good corrosion resistance and insulation properties is formed. The lower end of the ground electrode 60 is set so as to be substantially flush with the lower end of the upper electrode 20 located inside the ground electrode 60, thereby preventing generation of unnecessary deposits.

The second ground electrode 60 can be inserted and removed upward by removing the ceiling portion 18A of the processing vessel 18. When necessary, the second ground electrode 60 can be removed.
Are configured to be easily exchanged. The processing gas supply header 51 is for supplying a processing gas (process gas) to the plasma processing space S, and includes a gas introduction passage 68 for introducing an etching gas from an etching gas source 66. Are linked. At the tip of the header 51, a hollow header chamber 64 expanded in the horizontal direction along the extension of the plate-like upper electrode 20 is provided.
Are formed. As shown in FIG.
The plate-shaped upper electrode 20 is attached to the lower end opening of the lower electrode 4, and the processing space S is formed from the header chamber 64 through the first gas holes 70 formed in the upper electrode 20 at equal pitches.
It is designed to leak out.

In this embodiment, for example, 16 MDRA
Atmospheric pressure in the processing space S is set to 0.5 Torr or less in order to perform ultra-fine processing required for manufacturing M. In this case, the atmosphere flows out to prevent a pressure drop in the header chamber 64. Resistance applying means 72 as means for applying a pressure difference, which is a feature of the present invention for applying resistance to the processing gas.
Is formed. Specifically, the resistance applying means 72 has a plate-shaped resistance plate 74 made of, for example, aluminum or the like. The plate 74 is provided between the opening edge of the header chamber 64 and the upper electrode 20. , Bolts 76 and the like. The resistance plate 74 has a plurality of second gas holes 78 formed at an equal pitch so as to communicate with the first gas holes 70 formed in the upper electrode 20. A plan view at this time is shown in FIG. The first gas holes 70 and the second gas holes 78 are formed at substantially the same pitch over substantially the entire surface of the upper electrode 20 and the resistance plate 74, respectively. The processing space S is determined by the diameter D1 of the hole 70, the thickness H1 of the second gas hole 78 and the resistance plate 74, and by appropriately selecting these values.
Can be set higher than the process pressure by a predetermined pressure difference.

In this case, the atmosphere state in the header chamber 64 is set so as to deviate from Paschen's law indicating the limit of the occurrence of plasma discharge. This Paschen's law shows the relationship between the discharge starting voltage V, the pressure P in the discharge space, and the distance L from the electrode to the discharge space. Set the above parameters. Specifically, in order to increase the pressure in the header chamber 64, the diameter D1 of the first gas hole 70 is set to 0.5 mm,
8, the diameter D2 is set to about 2.0 mm and the second
The pitch L1 of the gas holes 78 is set to about 6.35 mm, and the thickness H1 of the resistance plate 74 that determines the distance from the upper electrode 20 is set to about 17 mm, so that plasma discharge does not occur. ing. Further, the resistance plate 74 is configured to also have a function as a cooling plate for cooling the upper electrode 20 by cooling heat from an upper cooling jacket 80 provided on the processing gas supply header 51 for flowing a refrigerant. I have. Further, in the header chamber 64, two baffle plates 84 having a large number of flow holes 82 and arranged horizontally are provided at appropriate intervals in the vertical direction. The gas is uniformly diffused in the header chamber 64.

Then, on a part of the side wall of the processing vessel 18,
An exhaust passage 86 for exhausting the atmosphere in the container is connected. In addition, a gate valve 8 is provided on the other side wall of the container.
A load lock chamber 92 having a transfer arm 90 therein is communicated with the inside through 8, so that the wafer W can be loaded and unloaded without breaking the vacuum in the processing container 18. A gate valve 94 is also provided on the opposite side wall of the load lock chamber 92 to transfer a wafer to and from a wafer transfer system (not shown).

Next, the operation of this embodiment configured as described above will be described. First, both the inside of the load lock chamber 92 and the inside of the processing chamber 18 are evacuated, and the unprocessed wafer W held by the transfer arm 90 in the load lock chamber 92 is transferred through the gate valve 88 to the processing chamber 18. The wafer W is securely fixed on the lower electrode 22 by the clamper member 24.

Then, the processing gas supplied to the header chamber 60 of the processing gas supply header 51 by supplying the etching gas into the gas introduction passage 68 is provided to the second gas hole 78 provided in the resistance plate 74 and the upper electrode 20. The gas is introduced into the processing vessel 18 through the first gas hole 70 and the inside of the processing vessel 18 is evacuated through the exhaust passage 86 to maintain the inside of the vessel 18 at a predetermined low-pressure atmosphere while the upper electrode 20 A high frequency of, for example, 40 MHz is applied from the second high frequency power supply 58, and a high frequency power of, for example, 13.56 MHz is applied to the lower electrode 22 from the first high frequency power supply 32. As a result, a plasma discharge is generated between the upper electrode 20 and the lower electrode 22, plasma is induced from the etching gas in the processing space S, and radicals in the generated plasma adhere to the surface of the wafer W to chemically react. Etching by reaction is performed, and ions decomposed in the plasma are accelerated by an electric field formed between the electrodes 20 and 22 to collide with the wafer W, for example, to etch a polysilicon film.

When a plasma is generated by generating a discharge between the upper and lower electrodes 20 and 22, the impedance of each of the high-frequency power supplies 32 and 58 and the discharge system, for example, the capacitance formed between the upper and lower electrodes are reduced. Impedance, capacitive impedance formed between the upper electrode 20 and the second ground electrode 60 disposed on the outer peripheral side, between the lower electrode 32 and the first ground electrode 36 disposed on the outer peripheral side. If the coupling impedance such as the formed capacitive impedance or the capacitive impedance formed between the container and the container located farther away is not equal, stable discharge does not occur. Matching units 30 and 56 composed of, for example, variable capacitors connected in series to the high-frequency power supplies 32 and 58.
Is appropriately adjusted, and impedance matching is performed. In this case, the main discharge occurs between the upper and lower electrodes 20 and 22 as in the conventional device, but the undesirable and unnecessary discharge that cannot be avoided is caused by the second electrode provided closer to the upper electrode 20 and the vessel wall. And between the lower electrode 22 and the first ground electrode 36 provided closer to the container wall.

As described above, the upper electrode 20 and the lower electrode 2
Since the first and second ground electrodes 36 and 60 are arranged closer to the inner wall 2 and closer to the inner wall of the container to strengthen the ground, an unnecessary discharge is generated between them. The return efficiency of the matching at the start is improved, and the impedance can be quickly stabilized without fluctuation. Accordingly, the impedance adjustment by the matching units 30 and 56 can be performed more quickly than in the case of the conventional apparatus, and the process can immediately proceed to the etching process, so that the etching process efficiency can be greatly improved.

As described above, the lower electrode 22 is connected to the first ground electrode 36 via the insulator 34 as described above.
And the ground is strengthened, unnecessary electric charges of the lower electrode 22 are generated via the ceramic insulator 34 having a predetermined dielectric constant or directly between the two members as unnecessary electric discharge. This escapes from one ground electrode 36. Therefore, not only can impedance adjustment be performed quickly, but also stable plasma discharge can be maintained. Further, an insulating gas layer 42 filled with, for example, a gas (air) of 1 atm is interposed in a gap S1 between the insulator 34 and the first ground electrode 36 covering the lower portion thereof, so that an insulating property between them is provided. Can be further improved.

Further, in this embodiment, for example, 16M
The atmospheric pressure in the processing space S is set to, for example, 0.5 Torr or less, which is lower than that of the conventional process, in order to perform ultra-fine processing required for manufacturing a DRAM. The inside of the header chamber 64 communicating through the gas holes 70, 78 is also depressurized at a correspondingly slightly higher pressure than the process pressure, and a plasma micro-discharge may occur in the header chamber 64. . However, in this embodiment, the diameters D1 and D2 of the first gas holes 70 formed in the upper electrode 20 and the second gas holes 78 formed in the resistance plate 74, the pitch L1 of these gas holes 70 and 78, the resistance By appropriately selecting the value of the thickness H1 of the plate 74 or the like, the resistance to the gas flow is imparted to slightly increase the atmospheric pressure in the header chamber 64, and the gas state deviates from the plasma discharge region according to Paschen's law. It is located in the place. As a result, plasma micro-discharge does not occur in the header chamber 64,
Therefore, according to the conventional apparatus, there is no generation of particles of aluminum, which is a material of the inner wall of the container, which is generated due to the plasma discharge in the header chamber, and the yield of the product can be improved.

Here, the results when the pressures in the header chambers of the conventional apparatus and the apparatus of the present embodiment are simulated when the process pressure (the pressure in the processing space S) is set to 0.57 Torr will be described. The setting conditions were as follows: in the conventional apparatus, the plate thickness of the upper electrode and the diameter of the gas hole were 3 mm, respectively.
0.8 mm, the thickness of the resistance plate, and the diameter of the gas hole are 7 mm and 1.8 mm, respectively. In this embodiment, the thickness of the upper electrode and the diameter of the gas hole are 3 mm, respectively.
0.5 mm, the thickness of the resistance plate, and the diameter of the gas hole were 17 mm and 2.0 mm, respectively. Gas flow rate 50
When variously changed to ６００600 SCCM, the results shown in Table 1 below were obtained.

[0028]

[Table 1]

In Table 1, the value in parentheses indicates the pressure increase value (differential pressure) with respect to the process pressure. According to this example, in this embodiment, at each flow rate, the differential pressure in the header chamber with respect to the process pressure is considerably higher in all cases than in the case of the conventional apparatus, so that the plasma micro-discharge is hardly generated. Turns out.

Further, when a test was actually performed using the conventional apparatus and the apparatus of this embodiment, the following results were obtained. The test conditions were as follows: In the case of the conventional device, the diameter of the gas hole was 120 m.
m, the pitch of the gas holes is 3.175 mm, and the thickness of the resistance plate is 11 mm. In the case of the apparatus of this embodiment, the diameter of the gas holes is 120 mm, which is the same as the conventional apparatus, and the pitch of the gas holes is doubled. The thickness was set to 35 mm, and the thickness of the resistance plate was slightly increased to 17 mm. Then, the process pressure was set to 0.25 Torr, and CH gas was used as the processing gas.
The F ₃ 20 SCCM, a CF ₄ 20 SCCM, the Ar 4
00SCCM each, wafer gap 0.9c
m, and plasma treatment was performed for 3 minutes at a high frequency power of 800 W.

As a result, the impurity concentration of aluminum becomes
1350 × 10 ¹⁰ atoms / cm ^{2 in} the case of the conventional device
However, in the case of this embodiment, 62 × 10 ¹⁰ atoms
/ Cm ² . As a result, the contamination amount of the present example was two orders of magnitude lower than that of the conventional apparatus, and it was found that as a result of suppressing the plasma micro-discharge, the effect of suppressing the generation of particles was remarkably exhibited. In the above embodiment, the diameter of each gas hole, the pitch of these gas holes, the thickness of the resistance plate, etc. are merely examples, and various values can be selected so as to prevent plasma micro-discharge in the header chamber. Of course.

In the above embodiment, the upper electrode 2
0 to the lower electrode 22 and 13.56 to the lower electrode 22.
Although a high frequency of MHz was applied, the set of these frequencies is not limited. For example, the set of the frequency of the upper electrode and the set of the frequency of the lower electrode are respectively 1 MHz and 380 K, for example.
Hz, 13.56MHz and 13.56MHz, 380K
Hz and 380 KHz can be variously changed.

Further, in the above embodiment, the upper electrode 2
The case of applying a high-frequency power to the direction between 0 and the lower electrode 22, that is, a so-called top-and-bottom method has been described. However, the present invention is not limited to this. Needless to say, the present invention can be applied to a so-called bottom-only system or a so-called top-only system in which high-frequency power is applied only to the upper electrode 20 and the lower electrode 22 is grounded.

In the above embodiment, a plasma etching apparatus has been described as an example of a plasma processing apparatus. However, the present invention is not limited to this, and other plasma processing apparatuses such as a plasma ashing apparatus, a plasma CVD apparatus, and a plasma etching apparatus may be used. Of course, the present invention can be applied to a sputtering apparatus or the like.

[0035]

As described above, according to the plasma processing apparatus of the present invention, the following excellent functions and effects can be exhibited. Since the pressure in the supply header is made higher than that in the processing space by providing the resistance applying means, even if the pressure in the processing space is set to 0.5 Torr or less, it is possible to suppress the occurrence of plasma micro-discharge in the supply header. In addition, generation of particles can be significantly suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is an enlarged sectional view showing the vicinity of an upper electrode of the device shown in FIG.

FIG. 3 is a plan view showing a resistance applying unit shown in FIG. 2;

FIG. 4 is a schematic sectional view showing a conventional plasma processing apparatus.

[Explanation of symbols]

 Reference Signs List 18 processing container 20 upper electrode 22 lower electrode 32 first high-frequency power supply 51 processing gas supply header 58 second high-frequency power supply 64 header chamber 66 etching gas source 68 gas introduction passage 70 first gas hole 72 resistance applying means 74 resistance plate 78 Second gas hole 82 Baffle plate S Processing space W Workpiece (semiconductor wafer)

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shozo Hosoda 2381, Kita-Shimojo, Fujii-machi, Nirasaki-shi, Yamanashi Pref. Tokyo Electron Yamanashi Co., Ltd. Hei 1-17429 (JP, A) JP-A-62-172716 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3065 H01L 21/205 H01L 21/31 C23C 14 / 34 C23C 16/50-16/517 C23F 4/00

Claims (4)

(57) [Claims] 1. A plasma processing for supplying a processing gas to a processing space via a first gas hole formed in an electrode having a processing gas supply header, and performing a plasma processing on an object to be processed held on an opposite electrode. In the apparatus, the processing is performed so that plasma discharge does not occur in the processing gas supply header .
Of the pressure in the gas supply header and the processing pressure in the processing space.
Means for providing a pressure difference between the processing gas supply headers.
The plasma processing apparatus characterized by configured as provided. 2. The means for providing a pressure difference is a plate having a second gas hole, the plate being provided with the first gas hole .
Located upstream of the gas hole in the gas flow direction
The plasma processing apparatus according to claim 1, wherein the are. 3. The processing pressure in the processing space is 0.5 To
rr or less.
Plasma processing equipment . 4. The means for providing a pressure difference comprises changing at least a thickness of the resistance plate, a pitch of the first or second gas holes, and a hole diameter of the first or second gas holes. the plasma processing apparatus according to claim 2 or claim 3, wherein the configured to vary the resistance to process gas the flow.