JP2012199429A - Electrode plate for plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate for a plasma processing apparatus which prevents the reverse flow of plasma to prevent the damage of a cooling plate and enables plasma processing to be uniformly performed on a surface of a processed substrate.SOLUTION: An electrode plate 3 is provided with multiple vent holes 11 penetrating through the electrode plate 3 in the thickness direction. Each vent hole 11 is formed by creating communication between a first hole part 21 having a large diameter and a second hole part 22 having a smaller diameter than the first hole part 21. The first hole parts 21 open on a radiation surface 3a on the processed substrate side. The lengths B of the second hole parts 22 of the vent holes 11 disposed at a center part of the electrode plate 3 are set so as to be shorter than the lengths of the second hole parts 22 of the vent holes 11 disposed at an outer peripheral part of the electrode plate 3.

Description

  The present invention relates to an electrode plate for a plasma processing apparatus that discharges a plasma generating gas while passing it in the thickness direction in the plasma processing apparatus.

  A plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process has, for example, an upper electrode and a lower electrode connected to a high-frequency power source disposed in a chamber facing each other in the vertical direction, With the substrate to be processed disposed on the electrode, plasma is generated by applying a high-frequency voltage while etching gas is circulated from the air hole formed in the upper electrode toward the substrate to be processed, and etching is performed on the substrate to be processed. And the like.

As the upper electrode used in this plasma processing apparatus, a laminated electrode plate is generally used in which a silicon electrode plate is fixed to a cooling plate and overlapped, and the heat of the electrode plate rising during the plasma processing is cooled. It is configured to dissipate heat through the plate.
The vent hole provided in the electrode plate is usually formed in parallel with the thickness direction (see Patent Document 1), but by repeatedly performing the plasma treatment, the portion exposed to the plasma is scraped and consumed. For this reason, the diameter of the vent hole changes greatly. In particular, the opening facing the substrate to be processed on the plasma generation region side of the air hole is eroded. Along with this, a part of the plasma flows back against the flow of the etching gas, and when the plasma enters from the vent hole toward the back surface of the electrode plate, a part of the cooling plate is sputtered and the substrate to be processed is contaminated. There is a risk of being.

  Therefore, in order to prevent the plasma from reaching the cooling plate and prevent damage to the cooling plate and contamination of the substrate to be processed, Patent Document 2 discloses vertical pores formed parallel to the thickness direction of the electrode plate. An electrode plate having vent holes formed with inclined pores formed to be inclined with respect to the thickness direction, and further connecting inclined pores having different inclinations with respect to the thickness direction of the electrode plate. An electrode plate having a formed air hole has been proposed. Patent Document 3 proposes an electrode plate having a ventilation hole in which the tip of the vertical pore is extended from the connection portion between the vertical pore and the inclined pore.

In addition, in the electrode plate in which the same diameter vent holes are uniformly provided, the etching gas is supplied from the upper center of the electrode plate, so that the flow of the etching gas through the electrode plate is different from the outer peripheral portion of the electrode plate. Compared to the center, it is denser. Therefore, there is a problem that the plasma density in the outer peripheral portion is lower than that in the central portion of the electrode plate, and the in-plane uniformity of the etching depth is deteriorated.
Therefore, in Patent Document 4, etching is performed at the outer peripheral portion and the central portion by increasing the hole diameter of the vent hole at the outer peripheral portion rather than the central portion of the electrode plate and increasing the amount of etching gas supplied from the outer peripheral portion. An electrode plate that makes the gas supply amount uniform has been proposed.

JP 2003-289064 A JP 2002-246371 A JP 2008-60197 A JP-A-6-204181

However, as in Patent Document 2 and Patent Document 3, inclined pores that are inclined with respect to the thickness direction of the electrode plate are difficult to match the joints, so the shape of the joints of a plurality of vent holes provided in the electrode plate May become uneven. If the joints of the air holes are formed unevenly, the flow of the etching gas becomes non-uniform, the etching depth varies depending on the location of the substrate to be processed, and there is a possibility that uniform etching processing cannot be performed on the entire substrate to be processed. .
Further, in Patent Document 4, the size of the hole diameter of the air hole is changed between the central part and the outer peripheral part, and the flow of the etching gas can be made uniform. When a part of the cooling plate is sputtered back and sputtered, the substrate to be processed may be contaminated.

  The present invention has been made in view of such circumstances, and it is possible to prevent the reverse flow of the plasma and prevent the cooling plate from being damaged, and to perform the in-plane uniform plasma processing on the substrate to be processed. An electrode plate for a plasma processing apparatus is provided.

  The electrode plate of the present invention is an electrode plate for a plasma processing apparatus disposed opposite to a substrate to be processed in the plasma processing apparatus, and is provided with a plurality of vent holes penetrating in the thickness direction. A first hole portion having a large diameter and a second hole portion having a diameter smaller than that of the first hole portion are formed to communicate with each other, and the first hole portion opens toward the substrate to be processed, and the plasma processing is performed. The second hole portion of the vent hole disposed in the center of the electrode plate for apparatus is shorter than the second hole portion of the vent hole disposed in the outer peripheral portion of the electrode plate for plasma processing apparatus. It is characterized by being set.

Since the vent hole is constituted by the first hole portion and the second hole portion, the back flow of plasma is prevented by the second hole portion having a small hole diameter, and the plasma is prevented from reaching the cooling plate through each vent hole. Can do. In addition, since the central portion having the long second hole portion has a larger flow resistance of the etching gas than the outer peripheral portion, the etching gas is less likely to flow in the central portion than the outer peripheral portion. As a result, the flow of the etching gas can be kept uniform, and the plasma density can be made uniform. Therefore, a uniform etching process can be performed on the entire substrate to be processed.
The vent hole is not only configured to form a step by arranging a large-diameter first hole portion on the substrate to be processed and a small-diameter second hole portion on the opposite side, and the first hole portion is formed on both sides of the electrode plate. Can be arranged, and a small-diameter second hole portion can be provided between the first hole portions.
In any case, since the first hole is opened on the substrate to be processed, even if the surface of the electrode plate on the substrate to be processed is consumed, the second hole having a small diameter remains without being consumed. Therefore, the back flow of plasma can be reliably prevented.

In the electrode plate of the present invention, the vent hole may be provided so as to penetrate in parallel to the thickness direction.
Since the air holes are formed in parallel with the thickness direction of the electrode plate, they can be easily formed by drilling or the like.
Furthermore, in the electrode plate of the present invention, it is preferable that the hole diameters of the first holes are all the same, and the hole diameters of the second holes are all the same.
In the case of the above-mentioned Patent Document 4, since the hole diameter is different for each position of the vent hole, a large number of drills having different diameters are necessary. However, in the present invention, the first hole portion and the second hole portion are different. Since it can be formed by changing only the length without changing the diameter of each hole, two types of drills can be used for various types of vent holes.

In the electrode plate of the present invention, the length of the first hole portion of the vent hole disposed in the central portion is A, the length of the second hole portion is B, and the first of the vent holes disposed in the outer peripheral portion. When the length of the hole is C and the length of the second hole is D, (B / A) / (D / C) is preferably set to 1.2 or more and 3.5 or less.
When the air holes are set in this way, the flow of the etching gas from the air holes of the electrode plate can be kept uniform, so that the difference in etching depth between the central portion and the outer peripheral portion of the substrate to be processed is reduced. And plasma processing can be performed uniformly.

  According to the present invention, it is possible to prevent the reverse flow of the plasma and prevent the cooling plate from being damaged, to keep the etching gas flow uniform, and to perform the in-plane uniform plasma processing on the substrate to be processed.

The electrode plate of 1st Embodiment of this invention is shown, (a) is a front view, (b) is a principal part expanded sectional view. It is a schematic block diagram which shows the example of the plasma processing apparatus in which the electrode plate of FIG. 1 is used.

Hereinafter, embodiments of the electrode plate of the present invention will be described with reference to the drawings.
First, a plasma etching apparatus 1 will be described as a plasma processing apparatus using this electrode plate.
As shown in the schematic cross-sectional view of FIG. 2, the plasma etching apparatus 1 is provided with an electrode plate (upper electrode) 3 in the upper part of the vacuum chamber 2 and a pedestal (lower electrode) 4 that can be moved up and down in the lower part. Are provided in parallel with the electrode plate 3 at a distance from each other. In this case, the upper electrode plate 3 is supported in an insulated state by the insulator 5 with respect to the wall of the vacuum chamber 2, and the electrostatic chuck 6 and the silicon-made surrounding material are placed on the mount 4. A support ring 7 is provided, and a wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with the peripheral edge supported by the support ring 7. Further, an etching gas supply pipe 9 is provided in the upper part of the vacuum chamber 2, and the etching gas sent from the etching gas supply pipe 9 passes through the diffusion member 10, and then the air holes 11 provided in the electrode plate 3. Through the discharge port 12 on the side of the vacuum chamber 2 and discharged to the outside. On the other hand, a high frequency voltage is applied between the electrode plate 3 and the gantry 4 by a high frequency power source 13.

  The electrode plate 3 is formed in a disk shape with silicon, and a cooling plate 14 made of aluminum or the like having excellent thermal conductivity is fixed to the back surface of the electrode plate 3. The cooling plate 14 also has a vent hole in the electrode plate 3. Through holes 15 are formed at the same pitch as the air holes 11 so as to communicate with the air holes 11. The electrode plate 3 is fixed in the plasma processing apparatus 1 by screwing or the like with the back surface in contact with the cooling plate. The detailed structure of the electrode plate 3 will be described later.

In the plasma etching apparatus 1, when an etching gas is supplied by applying a high-frequency voltage from a high-frequency power source 13, the etching gas passes through the diffusion member 10, passes through the vent holes 11 provided in the electrode plate 3, and is then connected to the electrode plate 3. Is released into a space between the pedestal 4 and the gantry 4 and becomes plasma in this space, hits the wafer 8, and the surface of the wafer 8 is etched by sputtering, that is, physical reaction and chemical reaction of the etching gas. .
Further, for the purpose of uniformly etching the wafer 8, the generated plasma is concentrated on the central portion of the wafer 8, and is prevented from diffusing to the outer peripheral portion, thereby generating a uniform plasma between the electrode plate 3 and the wafer 8. In order to generate the plasma, the plasma generation region 16 is usually surrounded by a silicon shield ring 17.

Next, the detailed structure of the electrode plate 3 will be described with reference to the drawings.
The electrode plate 3 of this embodiment is formed in a disk shape from single crystal silicon, columnar crystal silicon, or polycrystalline silicon, and is provided with a plurality of vent holes 11 penetrating in parallel with the thickness direction. As shown in FIG. 1A, a large number of vent holes 11 are provided side by side on a plurality of concentric circles (pitch p1 to p9) having different diameters.

  In addition, as shown in FIG. 1B, the vent hole 11 includes a first hole portion 21 having a large diameter and a second hole portion 22 having a diameter smaller than that of the first hole portion 21 communicating with each other on the same axis. Is formed. The first hole portion 21 opens in the radiation surface 3a of the electrode plate 3 on the wafer 8 side, and the second hole portion 22 opens in the opposite surface 3b of the radiation surface 3a.

In addition, the vent holes 11 have different lengths B of the second hole portions 22 between the central portion and the outer peripheral portion of the electrode plate 3, and the vent holes 11 arranged at the central portion of the electrode plate 3 have different lengths B. The two holes 22 are set shorter than the second holes 11 of the air holes 11 arranged on the outer periphery of the electrode plate 3.
In the present embodiment, two types of vent holes 11a and 11b having different lengths of the second hole portion 22 are provided, and the second hole portion 22 is disposed on the pitches p1 to p4 of the outer peripheral portion of the electrode plate 3. Is provided with a short vent hole 11b, and a vent hole 11a having a long second hole portion 22 on the central pitches p5 to p9. The vent holes 11a and 11b are formed in the outer peripheral portion where the length of the first hole portion 21 of the vent hole 11a disposed at the central portion is A and the length of the second hole portion 22 is B. When the length of the first hole portion 21 of the pore 11b is C and the length of the second hole portion 22 is D, the length ratio B / A of the central portion with respect to the length ratio D / C of the outer peripheral portion. The ratio (B / A) / (D / C) is set to be 1.2 or more and 3.5 or less.

  In the present embodiment, the vent holes 11a and 11b are processed by a drill. For example, for the electrode plate 3 having a plate thickness t of 10 mm, the hole diameter d1 of the first hole portion 21 is 0.5 mm, the hole diameter d2 of the second hole portion 22 is 0.3 mm, and the air holes 11a and 11b are configured.

  In the electrode plate 3 configured in this manner, the backflow of plasma is prevented by the second hole portion 22 having a small hole diameter provided in each air hole 11, and the plasma reaches the cooling plate 14 through each air hole 11. Can be prevented. In addition, since the flow resistance of the etching gas is larger in the central portion of the electrode plate 3 having the long second hole portion 22 than in the outer peripheral portion, the etching gas is less likely to flow in the central portion than in the outer peripheral portion. The flow of the etching gas can be kept uniform from the central portion to the outer peripheral portion, and the plasma density can be made uniform. Therefore, a uniform etching process can be performed on the entire wafer 8.

  Further, since the air holes 11 are formed in parallel with the thickness direction of the electrode plate 3, they can be easily formed by drilling or the like. The vent hole formed in this way is formed by changing only the length without changing the inner diameter of each of the first hole portion and the second hole portion. It is possible to deal with various types of ventilation holes with different lengths.

In order to confirm the effect of the present invention, an electrode plate having vent holes in which the length of the second hole portion was made different between the outer peripheral portion and the central portion was manufactured, and the etching uniformity of these wafers was evaluated.
The electrode plate is manufactured using a single crystal silicon disk having an outer diameter of 380 mm and a thickness of 10 mm. The diameter of the first hole is 0.5 mm and the second hole is formed on the single crystal silicon disk. Each vent hole was formed with a hole diameter of 0.3 mm. Further, vent holes corresponding to the conditions shown in Table 1 were provided with the range of the electrode plate having a diameter of 320 mm or less as the central portion and the range exceeding the diameter of 150 mm as the outer peripheral portion.
The processing of each air hole may be either non-contact processing using a laser or machining using a diamond drill, but in this example, processing using a diamond drill was selected.

Next, the electrode plate produced as described above is attached to a plasma etching apparatus as shown in FIG. 2, and a wafer on which a SiO ₂ layer has been formed in advance by a CVD method is attached oppositely and etched under the following conditions. The test was conducted.
(Etching conditions)
Wafer size: φ300mm
Chamber pressure: 26.7 Pa (200 mTorr)
Etching gas composition: 90 sccm CHF ₃ +4 sccm O ₂ +150 sccm He
High frequency power: 2kW
Frequency: 20kHz
Treatment time: 200 hours Note that sccm is an abbreviation for standard cc / min, and is a flow rate per minute (cc) normalized at a constant temperature such as 0 ° C. or 25 ° C. at 1 atm (atmospheric pressure 1013 Pa). Say.

Then, the wafer after etching of the SiO ₂ layer of the wafer surface in such a condition, the central portion etching depth X and the outer periphery etching depth Y were measured. The etching uniformity of the wafer was evaluated by obtaining a value of (X−Y) / X × 100 (%) from the measured values of the etching depths X and Y. The evaluation results are shown in Table 1.

  As can be seen from Table 1, by setting the length B of the second hole so that the outer peripheral portion is shorter than the central portion of the electrode plate, the etching uniformity value is 1% or less. be able to. That is, the difference in etching depth between the central portion and the outer peripheral portion of the wafer can be reduced, and plasma processing can be performed uniformly. Further, the ratio (B / A) / (D / C) of the vent hole length ratio B / A in the central portion of the electrode plate to the vent hole length ratio D / C in the outer peripheral portion is 1.2 or more. By setting the value to be 3.5 or less, the etching uniformity value can be less than 1%, and the etching uniformity can be further improved.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, in the above-described embodiment, the vent hole 11 is provided with a step by arranging the large-diameter first hole portion 21 on the radiation surface 3a side of the electrode plate 3 and the small-diameter second hole portion 22 on the opposite surface 3b side. However, the first hole 21 may be disposed on both sides of the electrode plate 3, and the second hole 22 having a small diameter may be provided between the first holes 21. Also in this case, since the first hole 21 is opened on the radiation surface 3a side, even if the radiation surface 3a side of the electrode plate 3 is consumed, the second hole portion 22 having a small diameter remains without being consumed. In this way, it is possible to reliably prevent the plasma from rising.

  In addition, the ratio (B / A) / (D / C) of the vent hole length ratio B / A in the central portion of the electrode plate and the vent hole length ratio D / C in the outer peripheral portion is at least the most central. The ratio of the ratio B / A at the vent hole at the position and the ratio D / C at the vent hole at the outermost peripheral position is 1.2 or more and 3.5 or less, and the ratio between them is a step according to the radial position. Alternatively, the gradual ratio may be changed.

DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus 2 Vacuum chamber 3 Electrode plate 3a Radiation surface 3b Opposite surface 4 Base 5 Insulator 6 Electrostatic chuck 7 Support ring 8 Wafer 9 Etching gas supply pipe 10 Diffusion member 11, 11a, 11b Vent hole 12 Exhaust port 13 High frequency Power supply 14 Cooling plate 15 Through hole 16 Plasma generation region 17 Shield ring 21 First hole 22 Second hole

Claims (4)

  An electrode plate for a plasma processing apparatus disposed opposite to a substrate to be processed in a plasma processing apparatus, comprising a plurality of vent holes penetrating in a thickness direction, wherein the vent hole is a first hole portion having a large diameter. And a second hole portion having a diameter smaller than that of the first hole portion, and the first hole portion opens toward the substrate to be processed, and a central portion of the electrode plate for the plasma processing apparatus The second hole portion of the vent hole disposed in the air hole is set shorter than the second hole portion of the vent hole disposed in the outer peripheral portion of the electrode plate for the plasma processing apparatus. An electrode plate for a plasma processing apparatus.   The electrode plate for a plasma processing apparatus according to claim 1, wherein the vent hole is provided so as to penetrate in parallel to the thickness direction.   3. The plasma processing apparatus according to claim 1, wherein each of the first holes has the same diameter, and each of the second holes has the same diameter. Electrode plate. The length of the first hole portion of the vent hole arranged in the central portion is A, the length of the second hole portion is B, the length of the first hole portion of the vent hole arranged in the outer peripheral portion is C, 4. When the length of the two holes is D, (B / A) / (D / C) is set to 1.2 or more and 3.5 or less. The electrode plate for a plasma processing apparatus according to claim 1.

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