JPH06333850A - Plasma processing device - Google Patents

Abstract

PURPOSE:To provide a plasma processing device which suppresses plasma discharge in the header by increasing resistance at the time of flowing out processing gas. CONSTITUTION:A plasma processing device is permitted to perform plasma processing on a subject W held by an electrode 22 to be processed while suppling a processing space S with processing gas through a first gas hole 70 formed on an electrode 20, which faces the electrode 22 and is provided with a processing gas suppling header 51. A resistance providing means 72 is provided so as to provide processing gas which flows out from the header with resistance. Thus, the atmosphere in the header is allowed to be in the conditions outside of the electric discharge area of the Paschen's law, and slight plasma discharge in the header is prevented even when the process pressure is 0.5Torr or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in plasma processing equipment.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of semiconductor products, a semiconductor wafer is subjected to a CVD process, an etching process, a sputtering process and the like. A plasma processing apparatus is used as an apparatus for performing such various kinds of processing. May be As an example of this type of conventional plasma processing apparatus, for example, two flat plate-type electrodes are installed in parallel in a processing container made of aluminum or the like, and the upper electrode therein is grounded, while the lower electrode is provided with a high-frequency power source. As a result, RF power is applied and the wafer is supported by the RF power. Then, an etching gas is introduced between both electrodes to induce plasma, and the wafer is subjected to plasma processing.

Explaining this with reference to FIG. 4, an upper electrode 4 is arranged in a processing container 2 made of aluminum or the like, and a lower electrode 6 as a susceptor is installed below the upper electrode 4, and the lower electrode 6 is provided with the lower electrode 6. A high frequency power source 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 of the electrostatic chuck 10. 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.

Further, the upper electrode 4 is provided with a processing gas supply header 16 for supplying the processing gas to the processing space S, and a shower shape is provided from the numerous gas holes 18 formed therein to the processing space S. Processing gas is supplied. When performing the plasma processing, the 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 under a predetermined reduced pressure.
Plasma is generated on the wafer surface, and plasma processing such as etching is performed on the wafer surface.

[0005]

By the way, in the case where etching is performed as the plasma treatment, for example, in this etching treatment, the lower the gas atmosphere pressure (process pressure) in the treatment space S is, It is known to be suitable for microfabrication, for example, 4MDRA
When forming the 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, in the case of manufacturing a memory of 16M DRAM, fine processing with a line width of about 0.5 μm must be performed. In this case, the process pressure is about 0.
It is necessary to set it to about 25 Torr.

Generally, the processing gas is the processing gas supply header 16
Although the gas pressure in the header 16 is somewhat higher than that in the processing space S side due to the resistance received from the gas holes 18 and the like when flowing out from the processing space S to the processing space S through the gas hole 8,
However, as described above, the process pressure is about 0.25T.
When the pressure is as low as orr, the atmospheric pressure in the header 16 correspondingly becomes considerably low, so that plasma discharge occurs not only in the processing space S but also in the header 16. As described above, when a minute discharge of plasma occurs in the header 16, the surface of the aluminum material forming the header 16 is hit by the activated ions by the plasma to generate particles, which flow toward the processing space S and are transferred to the wafer. There was a problem of adhesion. The present invention has been made to pay attention to the above problems and to solve them effectively. 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 problems, the present invention opposes a processing gas by supplying a processing gas to a processing space through a first gas hole formed in an electrode having a processing gas supply header. In the plasma processing apparatus for performing plasma processing on the object to be processed held by the electrode, the processing pressure of the processing space is supplied to the processing gas flowing from the processing gas supply header to the processing space through the gas hole. 0.
When the pressure is set to 5 Torr or less, a resistance applying means for applying resistance is formed in the supply header so that plasma discharge does not occur.

[0008]

Since the present invention is configured as described above, the processing gas from the processing gas supply header flows into the processing space through the first gas hole in a state where the pressure is suppressed by the resistance applying means. It will be. The resistance applying means is composed of, for example, a cooling plate having a second gas hole, and the resistance to the processing gas flowing out is changed by changing the thickness of the cooling plate or the hole diameter of the second gas hole or the first gas hole. 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 for performing fine processing, the pressure in the header is slightly higher than 0.5 Torr due to the resistance of the resistance applying means. The state in the header deviates from the Paschen's law, which indicates the state for generating plasma discharge, and it is possible to suppress the generation of plasma in the header.

[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 the 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 the plasma processing apparatus.

As shown in the drawing, the plasma etching apparatus has a processing container 18 formed in a cylindrical shape by a conductor such as aluminum, and the processing container 18 is grounded. A pair of electrodes, that is, an upper electrode 20 and a lower electrode 22, which are vertically separated from each other by, for example, about 20 to 30 mm, are arranged in parallel in the processing container 18, and a plasma processing space S is formed between these electrodes. To be done. The lower electrode 22 as a susceptor is formed into a substantially columnar shape by, for example, alumite-treated aluminum or the like, and an object to be processed, for example, a semiconductor wafer W can be mounted on the upper end flat portion thereof. And
A ring-shaped clamper member 24 is provided around the upper portion of the lower electrode 22 so that the clamper member 24 can be engaged with the peripheral portion of the wafer W and fixed to the lower electrode 22.

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

A small 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 of the portion and the upper end of the portion to seal the inside of the gap S1. And, in this gap S1,
A gas introduction passage 40 for introducing the insulating gas is connected from below, and the gap S1 is filled with air of, for example, 1 atm to provide a space between the lower electrode 22 and the first ground electrode 36. An insulating gas layer 42 for improving the insulating property is formed.

A metal susceptor support base 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 base 44 is formed by combining a plurality of aluminum members, which are conductive members, so that they are in surface contact with each other, and as a whole, the impedance in the ground line is made as small as possible to make the grounding strong. I am trying. In addition, the lower electrode 22
Inside, a lower cooling jacket 48 for flowing a refrigerant is formed along the circumferential direction thereof.
A refrigerant introduction passage 50 and a refrigerant discharge passage (not shown) for introducing and discharging the cooling refrigerant from below are connected to the.

On the other hand, the upper electrode 20 is formed into a disk shape from, for example, amorphous carbon or aluminum, and a processing gas supply header 51 made of, for example, aluminum is provided on the upper part of the upper electrode 20 and its side portion is engaged. A recess 52 is formed. Then, this upper electrode 20
The entire side portion 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, for example, 40 through a matching unit 56 including a variable capacitor or the like.
A second high frequency power source 58 that generates a high frequency of MHz is connected and configured to apply high frequency power to the upper electrode 20. Therefore, in this embodiment, high-frequency power is supplied to both the upper electrode 20 and the lower electrode 22, and the so-called top-and-bottom plasma processing apparatus is configured. In addition, a ring-shaped second grounding electrode 60 made of, for example, aluminum is provided between the side wall of the processing container 18 and a side wall of the upper electrode 20 via an insulator 54. The ground electrode 60 is surely grounded.

The lower surface of the second ground electrode 60, which faces the processing space S, is subjected to, for example, alumite treatment, and 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 insulating properties is formed. The lower end portion of the ground electrode 60 is set to be substantially flush with the lower end portion 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 in the upward direction by removing the ceiling portion 18A of the processing container 18, and the ground electrode 60 can be inserted when necessary.
Are configured to be easily replaced. 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 connected. In addition, a hollow header chamber 64 that is horizontally expanded at the tip of the header 51 along the expansion of the plate-shaped upper electrode 20.
Are formed. As shown in FIG. 2, this header chamber 6
The plate-shaped upper electrode 20 is attached to the lower end opening end of No. 4 and the processing space S is removed from the header chamber 64 through the first gas holes 70 formed in the upper electrode 20 at a large number at equal pitches.
It is supposed to leak to.

In this embodiment, for example, 16 MDRA
The atmospheric pressure of the processing space S is set to 0.5 Torr or less in order to perform the ultra-fine processing required to manufacture M, but in this case, it flows out in order to prevent the pressure drop in the header chamber 64. A resistance imparting means 72, which is a feature of the present invention and imparts resistance to the processing gas, is formed. Specifically, the resistance applying means 72 has a plate-like resistance plate 74 made of, for example, aluminum or the like, and 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 large number of second gas holes 78 formed at equal pitches 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 equal intervals over substantially the entire surfaces of the upper electrode 20 and the resistance plate 74, respectively.
The resistance to the processing gas flowing therethrough is as follows: the diameter D1 of the first gas hole 70, the second gas hole 78, and the resistance plate 7.
The pressure in the header chamber 64 can be set higher than the process pressure in the processing space S by a predetermined pressure difference by appropriately determining these values.

In this case, the atmosphere inside the header chamber 64 is set so as to deviate from the Paschen's law, which indicates the limit of plasma discharge. This Paschen's law shows the relationship between the discharge starting voltage V, the pressure P of the discharge space, and the distance L from the electrode to the discharge space, so that it is outside the discharge generation region represented by these relationships. 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, and the diameter of the second gas hole 7 is set to 0.5 mm.
The diameter D2 of 8 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 the upper cooling jacket 80 provided in the processing gas supply header 51 for flowing the refrigerant. There is. Further, in the header chamber 64, two baffle plates 84 having a large number of through holes 82 and arranged in the horizontal direction are provided vertically separated from each other as appropriate, and a process introduced from the gas introduction passage 68 is provided. The gas is adapted to be uniformly diffused in the header chamber 64.

Then, on a part of the side wall of the processing container 18,
An exhaust passage 86 for discharging the atmosphere in the container is connected. A load lock chamber 92 having a transfer arm 90 therein is communicated with the other side wall of the container via a gate ben 88, and the wafer W can be loaded and unloaded without breaking the vacuum in the processing container 18. Is configured to do. A gate ben 94 is also provided on the opposite side wall of the load lock chamber 92 to transfer the wafer to and from a wafer transfer system (not shown).

Next, the operation of this embodiment configured as described above will be described. First, the inside of the load lock chamber 92 and the inside of the processing container 18 are both in a vacuum state, and the unprocessed wafer W held by the transfer arm 90 inside the load lock chamber 92 is processed via the gate bend 88.
The wafer W is loaded into the inside and is securely fixed onto the lower electrode 22 by the clamper member 24.

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

By the way, when a discharge is generated between the upper and lower electrodes 20 and 22, and a plasma is started up, the impedance of each high-frequency power source 32 and 58 and the discharge system, for example, the capacitance formed between the upper and lower electrodes, are set. 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 capacitive impedances formed or the coupling impedances such as the capacitive impedances formed with the container wall located further away are not equal, stable discharge does not occur, so at the beginning of discharge each Matching units 30 and 56, which are connected in series to the high-frequency power sources 32 and 58, and which include variable capacitors, for example.
Are appropriately adjusted to perform impedance matching. In this case, the main discharge is generated between the upper and lower electrodes 20 and 22 as in the conventional device, but the undesired and undesired unnecessary discharge is the second electrode provided closer to the upper electrode 20 and the container wall. Ground electrode 60 and between the lower electrode 22 and the first ground electrode 36 provided closer to the container wall.

Thus, the upper electrode 20 and the lower electrode 2
By disposing the first and second ground electrodes 36 and 60 in the vicinity of 2 nearer to the inner wall of the container to strengthen the grounding, an unnecessary discharge is generated between them. The matching return efficiency at the start becomes good, and it becomes possible to quickly stabilize the impedance without changing it. Therefore, 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 etching process can be immediately started, so that the etching process efficiency can be significantly improved.

As for the lower electrode 22, the lower portion of the lower electrode 22 is connected to the first ground electrode 36 via the insulator 34 as described above.
Since the ground is reinforced by covering with, the unnecessary electric charge of the lower electrode 22 is directly generated between the two members through the ceramic insulator 34 having a predetermined dielectric constant or as an unnecessary electric discharge. It will escape from the first ground electrode 36. Therefore, not only the impedance can be adjusted quickly, but also stable plasma discharge can be maintained. In addition, an insulating gas layer 42 filled with a gas (air) of 1 atm, for example, is interposed in the gap S1 between the insulator 34 and the first ground electrode 36 covering the lower part thereof, and therefore the insulating property between them is provided. Can be further improved.

Further, in this embodiment, for example, 16M
The atmospheric pressure of the processing space S is set to, for example, 0.5 Torr or less, which is lower than that in the conventional process, in order to perform the ultra-fine processing required for manufacturing the DRAM. The inside of the header chamber 64 communicating with each other through the gas holes 70 and 78 is also in a decompressed state correspondingly to a pressure slightly higher than the process pressure, and there is a possibility that a plasma micro-discharge will occur in the header chamber 64. . However, in the present 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, and the resistance. By appropriately selecting the thickness H1 of the plate 74 or the like, resistance is added to the gas flow to slightly increase the atmospheric pressure in the header chamber 64, and this gas state is removed 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, particles of aluminum, which is a material for the inner wall of the container, which is generated due to the plasma discharge in the header chamber, are not generated, and the yield of products can be improved.

Here, the results of simulating the pressure inside the header chamber of the conventional apparatus and the apparatus of this embodiment when the process pressure (pressure in the processing space S) is set to 0.57 Torr will be described. As for the setting conditions, in the conventional device, the plate thickness of the upper electrode and the diameter of the gas holes are 3 mm,
0.8 mm, the thickness of the resistance plate and the diameter of the gas holes are 7 mm and 1.8 mm, respectively. In this embodiment, the thickness of the upper electrode and the diameter of the gas holes are 3 mm, respectively.
The thickness of the resistance plate was 0.5 mm, and the diameter of the gas hole was 17 mm and 2.0 mm, respectively. Gas flow rate is 50
When variously changed to ˜600 SCCM, the results shown in Table 1 below were obtained.

[0028]

[Table 1]

In Table 1, the value in parentheses indicates a pressure increase value (differential pressure) with respect to the process pressure. According to this, in the present embodiment, at each flow rate, the differential pressure in the header chamber with respect to the process pressure is considerably higher than in the case of the conventional apparatus, and it is in a state in which plasma micro-discharge is unlikely to occur. Turns out.

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

As a result, the impurity concentration of aluminum is
In the case of the conventional device, 1350 × 10 ¹⁰ atoms / cm ²
However, in the case of this embodiment, 62 × 10 ¹⁰ atoms
Was / cm ² . As a result, it was found that the amount of contamination in this example was two orders of magnitude lower than that in the conventional device, and as a result of suppressing the minute discharge of plasma, the effect of suppressing particle generation was remarkably exhibited. In the above-mentioned 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 numerical values can be selected so as not to cause plasma micro-discharge in the header chamber. Of course.

In the above embodiment, the upper electrode 2
40MHz high frequency to 0, 13.56 to the lower electrode 22
A high frequency of MHz was applied to each, but the set of these frequencies is not limited. For example, the set of frequencies of the upper electrode and the lower electrode is, for example, 1 MHz and 380 K, respectively.
Hz, 13.56MHz and 13.56MHz, 380K
Various changes such as Hz and 380 KHz can be made.

Further, in the above embodiment, the upper electrode 2
Although a so-called top-and-bottom system in which a high-frequency power source is applied to the opposite sides of 0 and the lower electrode 22 has been described, the present invention is not limited to this. For example, the high-frequency power source is applied only to the lower electrode 22 and the upper electrode 20 is grounded. Needless to say, it is applicable to a so-called bottom-only method, or conversely, a so-called top-only method in which a high frequency power is applied only to the upper electrode 20 and the lower electrode 22 is grounded.

Although the plasma etching apparatus has been described as an example of the plasma processing apparatus in the above embodiment, 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 processing apparatus can be used. Of course, it can also be applied to a sputtering device or the like.

[0035]

As described above, according to the plasma processing apparatus of the present invention, the following excellent operational effects can be exhibited. Since the resistance applying means is provided to make the pressure in the supply header higher than that in the processing space, it is possible to suppress generation of plasma micro discharge in the supply header even if the pressure in the processing space is set to 0.5 Torr or less. The generation of particles can be greatly suppressed.

[Brief description of drawings]

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

FIG. 2 is an enlarged cross-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.

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

[Explanation of symbols]

 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 imparting means 74 resistance plate 78 Second gas hole 82 Baffle plate S Processing space W Object to be processed (semiconductor wafer)

Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location H05H 1/46 9014-2G (72) Inventor Yutaka Miura 2-3-3 Nishishinjuku, Shinjuku-ku, Tokyo Tokyo Electron Incorporated (72) Inventor Shozo Hosoda 1 2381 Kitashitajo, Fujii-cho, Nirasaki-shi, Yamanashi Tokyo Electron Yamanashi Ltd.

Claims (3)

[Claims] 1. A plasma treatment in which a treatment gas is supplied to a treatment space through a first gas hole formed in an electrode having a treatment gas supply header, and a plasma treatment is performed on an object to be treated held by an opposite electrode. In the apparatus, the processing pressure in the processing space is 0.5 with respect to the processing gas flowing from the processing gas supply header into the processing space through the gas holes.
A plasma processing apparatus, characterized in that a resistance applying means for applying a resistance is formed in the supply header so as not to generate a plasma discharge when set to Torr or less. 2. The plasma processing apparatus according to claim 1, wherein the resistance applying unit has a resistance plate provided on the processing gas supply header side of the electrode having the second gas hole. 3. The distribution means changes at least the thickness of the resistance plate, the pitch of the first or second gas holes, and the hole diameter of the first or second gas holes. 3. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is configured to change the resistance to the processing gas to be processed.