JP6485270B2 - Electrode plate for plasma processing equipment - Google Patents

Description

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

  A plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process has a pair of electrodes connected to a high-frequency power source in a chamber, for example, vertically arranged, and the lower electrodes In a state where the substrate to be processed is disposed on the substrate, plasma is generated by applying a high frequency voltage while flowing an etching gas from the plurality of air holes formed in the upper electrode toward the substrate to be processed, and the substrate is processed. It is configured to perform a process such as etching.

  As an upper electrode used in this plasma processing apparatus, an electrode plate having a plurality of vent holes having the same diameter is generally used. However, as the electrode plate is used, the side of the substrate to be processed is etched by being exposed to plasma, and the inner wall of the vent hole is etched by the plasma flowing into the vent hole. At this time, the central portion is more easily etched than the outer peripheral portion of the electrode plate. For this reason, as the usage time of the electrode plate becomes longer, the amount of etching gas flowing from each vent hole is biased, and the plasma processing amount to the substrate to be processed is also biased to perform in-plane uniform processing. become unable.

  In this regard, Patent Document 1 discloses that the diameter of the air holes in the inner peripheral region is larger than the air holes in the outer peripheral region and the outer peripheral region in which the air hole (small diameter hole) of the electrode plate is formed. Thus, the flow rate of the etching gas ejected from the group of vent holes in the outer peripheral region and the flow rate of the etching gas ejected from the group of vent holes in the inner peripheral region are substantially equal on the surface of the substrate to be processed, and the etching rate is the entire surface. It is described that a semiconductor wafer that is kept uniform and uniformly etched can be obtained with a high yield. Also, although the electrode plate vents are etched over time, the difference in hole diameters between the vent holes in both regions is maintained for a long time, so the electrode plate replacement frequency is reduced and the etching process productivity is improved. . Further, in Patent Document 1, the maximum hole diameter of the vent hole in the inner region is preferably 25 μm (0.025 mm) or more larger than the maximum hole diameter of the vent hole in the outer peripheral region, and less than 25 μm. However, it is described that the difference in the hole diameter is too small and the difference in the flow rate of the etching gas becomes large, so that uniform etching is difficult.

  Patent Document 2 describes that air holes are formed at equal pitches on three circumferences centered on the center of the electrode plate, and the diameter of the air holes is reduced as the distance from the center of the electrode plate increases. As a result, the gas distribution in the lower part of the reaction vessel is made uniform in combination with the gas flowing out from the outside of the electrode plate, the gas distribution on the surface of the substrate to be processed (wafer) is made uniform, and stable etching is performed. It is described that processing is performed.

Japanese Patent Laid-Open No. 11-54488 JP-A-62-51223

  As described in Patent Document 1 or Patent Document 2, various measures have been taken for the electrode plate in order to improve the in-plane uniformity of the plasma treatment, but in order to improve the yield of the product, Further improvement is required.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an electrode plate for a plasma processing apparatus capable of performing in-plane uniform plasma processing on a substrate to be processed.

  The present invention is an electrode plate for a plasma processing apparatus provided with a plurality of ventilation holes penetrating in the thickness direction of the electrode plate, wherein the ventilation holes have at least three or more rounds from the center to the outer periphery of the electrode plate. Are arranged on the circumference of concentric circles, and the average hole diameter of the air holes formed on the innermost circumference on the center side of the electrode plate is 0.1 mm or more and 3.0 mm or less in diameter. The inner and outer diameter difference between the average hole diameter of the air holes formed on the circumference and the average hole diameter of the air holes formed on the outermost periphery is 0.010 mm or more and 0.025 mm or less. The air hole having a diameter difference of 0.004 mm or less is formed in the air holes, and the air holes having the same diameter are gradually reduced from the central part to the outer peripheral part without continuous three or more rounds. Are lined up.

By forming the hole diameter from the center to the outer periphery of the electrode plate in a stepwise manner and by gradually reducing the diameter of the air holes without continuation of three or more rounds, the flow of the etching gas is central. It can be made uniform from the portion to the outer peripheral portion, and the uniformity of the plasma processing can be improved.
If the difference between the inner and outer diameters of the average hole diameter of the vent holes on the innermost periphery and the average hole diameter of the vent holes on the outermost periphery is less than 0.010 mm, it is sufficient to make the flow rate of the etching gas uniform from the center to the outer periphery. The effect is not obtained. On the other hand, even when the difference between the inner and outer diameters exceeds 0.025 mm, the flow rate of the etching gas cannot be made uniform from the central part to the outer peripheral part, and the uniformity of the plasma processing is lowered. In addition, even when the difference in the average hole diameter between the adjacent holes on the circumference exceeds 0.004 mm, or when the holes having the same diameter are continued three or more times, the flow rate of the etching gas varies, resulting in plasma. Reduce processing uniformity.

  According to the present invention, the etching gas can be uniformly distributed from the center portion to the outer peripheral portion of the electrode plate, and the in-plane uniform plasma treatment can be performed on the substrate to be processed.

It is a top view which shows embodiment of the electrode plate for plasma processing apparatuses of this invention. It is principal part sectional drawing from the center part of the electrode plate for plasma processing apparatuses shown in FIG. 1 to an outer peripheral part. It is a schematic block diagram which shows an example of the plasma etching apparatus with which the electrode plate for plasma processing apparatuses is used.

Hereinafter, embodiments of an electrode plate for a plasma processing apparatus of the present invention will be described with reference to the drawings.
First, a plasma etching apparatus will be described as a plasma processing apparatus in which an electrode plate 1 for plasma processing apparatus (hereinafter referred to as an electrode plate) is used. As shown in FIG. 3, the plasma etching apparatus 100 is provided with an electrode plate (upper electrode) 1 on the upper side in the vacuum chamber 2 and a gantry (lower electrode) 4 that can move up and down on the lower side. And in parallel with each other. In this case, the upper electrode plate 1 is supported in an insulated state with respect to the wall of the vacuum chamber 2 by the insulator 3, and the electrostatic chuck 5 and the silicon support surrounding the periphery are provided on the gantry 4. A ring (6) is provided, and a wafer (substrate to be processed) 7 is placed on the electrostatic chuck (5) with the peripheral edge supported by the support ring (6). Further, an etching gas supply pipe 21 is provided on the upper side of the vacuum chamber 2, and the etching gas sent from the etching gas supply pipe 21 passes through the diffusion member 8 and then passes through the electrode plate 1. It is configured to flow toward the wafer 7 through the pores 11 and to be discharged to the outside from the discharge port 22 on the side of the vacuum chamber 2. On the other hand, a high frequency voltage is applied between the electrode plate 1 and the gantry 4 by a high frequency power source 9.

  A cooling plate 15 made of aluminum or the like having excellent heat conductivity is fixed to the back surface of the electrode plate 1. The cooling plate 15 is also formed with through holes 16 at the same pitch as the air holes 11 so as to communicate with the air holes 11 of the electrode plate 1. The electrode plate 1 is fixed in the plasma etching apparatus 100 by screwing or the like with the back surface in contact with the cooling plate 15.

  The electrode plate 1 of the present embodiment is formed of a single crystal silicon, columnar crystal silicon, or polycrystalline silicon, for example, into a circular plate having a thickness of about 5 to 20 mm and a diameter of about 100 to 600 mm. As shown in FIGS. 1 and 2, several hundred to 3,000 vent holes 11 are formed in parallel with the thickness direction at a pitch of several mm to 10 mm, and each vent hole 11 is an electrode plate. They are arranged on the circumferences s1 to s11 of concentric circles of at least 3 rounds from the central part of 1 to the outer circumference. In addition, each air hole 11 is formed such that the difference Δd in average diameter between adjacent air holes 11 on the circumference is 0.004 mm or less, and the air holes 11 having the same diameter do not continue three or more times. The vent holes 11 whose diameters are reduced in stages from the center to the outer periphery of the electrode plate 1 are arranged. The average hole diameter d1 of the air holes 11 formed on the circumference s1 that is the innermost circumference on the center side of the electrode plate 1 having the largest diameter is set to a diameter of 0.1 mm or more and 3.0 mm or less. The difference between the inner and outer diameters of the average hole diameter d1 of the vent holes 11 formed on s1 and the average hole diameter d11 of the vent holes 11 formed on the outermost circumference s11 is 0.010 mm or more and 0.025 mm or less. .

  The average hole diameter will be specifically described. For example, in the electrode plate 1 shown in FIG. 1, since four vent holes 11 are formed on the circumference s1, the average of the vent holes 11 on the circumference s1. The hole diameter d1 is a value obtained by averaging the hole diameters of these four vent holes 11. Since 32 vent holes 11 are formed on the circumference s5, the average hole diameter d5 of the vent holes 11 on the circumference s5 is a value obtained by averaging the diameters of the 32 vent holes 11. .

  Each of the air holes 11 of the electrode plate 1 configured as described above is formed by, for example, forming a plurality of through holes penetrating in the thickness direction by drilling in the base plate to be the electrode plate 1 and etching after drilling It is formed by processing. The through hole is formed by drilling after processing the through hole on the circumference s1 on the center side of the electrode plate 1, and then machining the through hole on the circumference s2 adjacent to the circumference s1. Processing is preferably performed in order from the innermost circumference s1 on the center side of the electrode plate 1 to the outermost circumference s11 on the outer circumference side, such as processing a through hole on s3. In this way, by processing the through hole that becomes the air hole 11 from the center side of the electrode plate 1 to the outer peripheral side, even when wear of the cutting edge of the drill is accompanied, from the central side toward the outer peripheral side. The reduced through-hole can be easily processed.

As described above, the diameter of the air holes 11 is gradually reduced from the center part to the outer peripheral part of the electrode plate 1 and the air holes 11 having the same diameter are gradually reduced in diameter without continuing three or more rounds. Thus, the flow of the etching gas can be made uniform from the center portion of the electrode plate 1 to the outer peripheral portion, and the uniformity of the plasma processing can be improved.
If the difference between the inner and outer diameters of the average hole diameter d1 of the vent holes 11 on the innermost periphery (circumference s1) and the average hole diameter d11 of the vent holes 11 on the outermost periphery (circumference s11) is less than 0.010 mm, the etching gas The sufficient effect of equalizing the flow rate from the center to the outer periphery of the electrode plate 1 cannot be obtained. On the other hand, even when the difference between the inner and outer diameters exceeds 0.025 mm, the flow rate of the etching gas cannot be made uniform from the central portion to the outer peripheral portion of the electrode plate 1, and the uniformity of the plasma processing is lowered. In addition, when the diameter difference Δd of the average hole diameters of the adjacent air holes 11 on the adjacent circumference exceeds 0.004 mm, or when the air holes 11 having the same diameter are continued three or more times, the flow rate of the etching gas varies. Occurs, reducing the uniformity of the plasma treatment.

Next, in order to confirm the effect of the present invention, as shown in Table 1, a plurality of electrode plates in which the diameters of the air holes are changed are prepared, and a wafer (substrate to be processed) is formed using each of the prepared electrode plates. Etching was performed.
Each electrode plate is formed of a disk-shaped base plate having a thickness of 10 mm and a diameter of 400 mm, and a vent hole having a diameter of 0.470 mm or more and 0.510 mm or less is formed within the range of the diameter of the base plate of 300 mm. As shown in FIG. 1, the air holes are formed side by side on the respective concentric circles s <b> 1 to s <b> 11 constituted by 11 circles s <b> 1 to s <b> 11. The number of vent holes on each of the circumferences s1 to s11 is 4 on the innermost circumference s1, 10 on the circumference s2, 16 on the circumference s3, and 24 on the circumference s4. 32 on circumference s5, 40 on circumference s6, 48 on circumference s7, 60 on circumference s8, 72 on circumference s9, 80 on circumference s10, and 100 pieces were formed on the outermost circumference s11, and a total of 486 ventilation holes were formed for each electrode plate. The average hole diameters d1 to d11 of the air holes on the circumferences s1 to s11 of each electrode plate are as shown in Table 1.

  The “inner / outer diameter difference (d1−d11)” in Table 1 is the difference between the average hole diameter d1 of the vent holes on the innermost circumference s1 and the average hole diameter d11 of the vent holes on the outermost circumference s11. (D1-d11). Further, the “maximum adjacent diameter difference Δdmax” is the difference Δd in the average hole diameter of the adjacent vent holes on the circumference, that is, the difference (d1−d2), (d2) between the average hole diameters of the adjacent vent holes on the circumference. -D3), (d3-d4), (d4-d5), (d5-d6), (d6-d7), (d7-d8), (d8-d9), (d9-d10), (d10-d11) ).

Then, using each electrode plate, a chamber internal pressure: 10 ⁻¹ Torr, a gas flow rate ratio: 90 sccm CHF ₃ +4 sccmO ₂ +150 sccm He, high frequency power: 300 W, etching on a wafer having a diameter of 152 mm with a SiO ₂ layer formed by CVD. Time: 1.0 min. Plasma etching was performed under the conditions described above. Then, the etching uniformity of each wafer was measured. The results are shown in Table 1.
Note that the etching uniformity of the wafer is measured by measuring the depth A at the deepest etched portion of the wafer and measuring the depth B at the shallowest etched portion. This is a value obtained by substituting into the formula of ((A−B) / B) × 100 (%).

As can be seen from Table 1, the diameter of the air holes is gradually reduced from the center part to the outer periphery of the electrode plate, and the air holes having the same diameter are formed by gradually reducing the diameter without continuing three or more rounds. The etching uniformity of the plasma treatment can be improved.
Further, the inner / outer diameter difference (d1−d11) between the average hole diameter d1 of the vent holes on the innermost circumference (circumference s1) and the average hole diameter d11 of the vent holes on the outermost circumference (circumference s11) is less than 0.010 mm ( In Conventional Example 1), a sufficient effect of making the flow rate of the etching gas uniform from the center to the outer periphery of the electrode plate could not be obtained, and the etching uniformity was lowered. On the other hand, even when the inner / outer diameter difference (d1-d11) exceeds 0.025 mm (Comparative Examples 1 to 4), the etching gas flow rate cannot be made uniform from the center to the outer periphery of the electrode plate, and the etching is uniform. Decreased. Moreover, when the diameter difference Δd of the average hole diameters of the adjacent vent holes on the circumference exceeds 0.004 mm (Comparative Examples 1 to 4), or when the vent holes having the same diameter are continued three or more times (Comparative Example 4). However, it was found that the flow rate of the etching gas varies and the etching uniformity is lowered.

  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.

1 Electrode plate (electrode plate for plasma processing equipment)
2 Vacuum chamber 3 Insulator 4 Base 5 Electrostatic chuck 6 Support ring 7 Wafer (substrate to be processed)
8 Diffusion member 10 High frequency power supply 15 Cooling plate

Claims (1)

An electrode plate for a plasma processing apparatus provided with a plurality of ventilation holes penetrating in the thickness direction of the electrode plate,
The vents are arranged on a circumference of at least three or more concentric circles from the center to the outer periphery of the electrode plate;
The average hole diameter of the air holes formed on the innermost circumference on the center side of the electrode plate is 0.1 mm or more in diameter and 3.0 mm or less in diameter,
The inner and outer diameter difference between the average hole diameter of the vent holes formed on the innermost periphery and the average hole diameter of the vent holes formed on the outermost periphery is 0.010 mm or more and 0.025 mm or less,
The difference between the average hole diameters of the vent holes on adjacent circumferences is 0.004 mm or less, and the vent holes of the same diameter are formed in a stepwise manner from the center to the outer periphery without continuing three or more rounds. An electrode plate for a plasma processing apparatus, wherein the reduced-diameter vent holes are arranged.

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