Silicon electrode plate for plasma processing device and manufacturing method thereof

Abstract

To provide a silicon electrode plate for a plasma processing device.SOLUTION: A silicon electrode plate for a plasma processing device comprises a plurality of slit-shaped gas flow paths 11, which penetrate in a plate thickness direction D1 from a first surface 301 to a second surface 302 located opposite the first surface 301, at a center, an outer periphery, and an intermediate portion of the silicon electrode plate, respectively. The gas flow paths 11 are formed to have an aspect ratio of 10 or more and 80 or less, the aspect ratio being obtained by dividing a depth C from an inlet 111 on the first surface 301 to an outlet 112 on the second surface 302 by a slit width A, and an average number n1 of the sum of chippings with a width of 0.1 mm or more formed on the linear long edge and arc-shaped short edge of the inlet 111 and outlet 112 of one gas flow path 11 is 3 or less (n1≤3).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a silicon electrode plate for a plasma processing apparatus and a method for manufacturing the same. [Background technology]

[0002] Silicon electrode plates for plasma processing equipment such as plasma etching have gas flow paths through which plasma processing gas flows, and if the gas pressure inside these gas flow paths increases, abnormal discharge occurs. As a countermeasure against this abnormal discharge, the gas flow paths of the electrode plate disclosed in Patent Document 1 consist of multiple gas holes extending in the plate thickness direction and slit-shaped gas grooves provided downstream of these gas holes, and the gas grooves suppress increases in gas pressure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-117711 A, paragraphs 0060 to 0062, Figure 5 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the applied high-frequency power has increased dramatically in plasma processing equipment to improve wafer processing speed and accuracy. Therefore, there is a demand for thicker silicon electrode plates, which are consumable materials, to extend their lifespan. Meanwhile, in slit-shaped gas flow channels, the slit width cannot be widened to suppress discharge, and the aspect ratio (depth / slit width) of the slit width to the gas flow channel depth is on the rise.

[0005] Patent Document 1 describes forming slit-shaped gas grooves using laser processing or cutter processing, but silicon is a typically brittle material, and it is extremely difficult to form slit-shaped gas grooves with high aspect ratios in a silicon plate using a cutter. If significant processing damage remains in the gas flow paths of the fabricated silicon electrode plate, it can cause abnormal discharge and particle generation, making it difficult to perform plasma processing effectively. Furthermore, laser processing generally involves difficulty in controlling the processing depth in the depth direction when the processing depth is deep (5 mm or more), making it difficult to consistently form slit shapes and resulting in rough areas inside the gas flow paths.

[0006] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a silicon electrode plate for a plasma processing apparatus and a method for manufacturing the same. [Means for solving the problem]

[0007] The silicon electrode plate for a plasma processing apparatus of the present invention is formed from silicon into a plate shape having first and second circular surfaces parallel to each other, and has gas flow paths penetrating in the plate thickness direction from the first surface to the second surface located opposite the first surface, at four or more different angular positions around the center of the plane, near the center and near the periphery of the silicon electrode plate, respectively. At least the portion of the gas flow path that opens to an outlet of the second surface is formed as a slit-shaped flow path having an opening end consisting of a pair of long edges that are parallel to each other along the plane direction of the second surface and an arc-shaped short edge connecting the ends of the long edges. The slit-shaped flow path is formed so that an aspect ratio (C / A) obtained by dividing the depth C from the outlet by the slit width A, which is the distance between the long edges, is 10 or more and 80 or less, and the average number n1 of chippings having a width of 0.1 mm or more formed at the opening end of the gas flow path at the outlet is 3 or less per slit-shaped flow path (n1≦3).

[0008] Chipping confirmation method: From the plurality of gas flow paths near the center of the silicon electrode plate, one gas flow path is selected from the four positions to designate a central selected flow path, and from the plurality of gas flow paths near the periphery of the silicon electrode plate, one gas flow path is selected from the four positions to designate a peripheral selected flow path, the outlet of each of the central selected flow paths is observed to identify the total number of chippings n111, n112, n113, n114, the outlet of each of the peripheral selected flow paths is observed to identify the total number of chippings n121, n122, n123, n124, and the average of the total number of chippings n111, n112, n113, n114 of the central selected flow paths and the total number of chippings n121, n122, n123, n124 of the peripheral selected flow paths is designated as the average value n1 of the total number of chippings of one of the gas flow paths.

[0009] [Slit width A] The average value of the distance between the long edges of the outlets of the gas flow passage is defined as the slit width A.

[0010] Aspect Ratio An aspect ratio of 10 or more and 80 or less can prevent abnormal discharge within the gas flow path and enable the silicon electrode plate to be used for a long period of time. The aspect ratio is preferably 20 or more and 60 or less. If the aspect ratio is less than 10, abnormal discharge occurs due to a large slit width A of the gas flow path or a small depth C of the gas flow path, while if it exceeds 80, poor gas flow will result in increased pressure within the gas flow path, causing abnormal discharge.

[0011] [Chipping] By keeping the average number of chippings n1 at 3 or less, particle generation during plasma processing can be prevented. In this specification, "chipping" refers to a location at the outlet of a gas flow path where the long edge, short edge, or both the long edge and short edge of a slit-shaped flow path are missing a width W11 of 0.1 mm or more. This width W11 is the dimension along the long edge or short edge. The number of chippings is determined by, for example, scanning the long edge and short edge of the outlet of the gas flow path with an optical microscope, counting the number of locations missing a width W11 of 0.1 mm or more, and measuring eight slit-shaped flow paths.

[0012] In the silicon electrode plate for a plasma processing apparatus of the present invention, preferably, the gas flow path is formed by dividing the slit-shaped flow path at the short edge, and one of the two flow path segments for roughness confirmation is selected, and the average value m1 of the arithmetic mean roughness Ra measured in the plate thickness direction at the first wall surface portion extending from the long edge included in the selected flow path segment for roughness confirmation is 3.2 μm or less.

[0013] [Average value of arithmetic mean roughness Ra of gas flow passages m1] By ensuring that the average value m1 of the arithmetic mean roughness Ra of each gas flow path is 3.2 μm or less, particle generation and abnormal discharge during plasma processing can be prevented. In this invention, the "average value m1" is the average value of the arithmetic mean roughness Ra of the first wall surface portion measured three times for one roughness confirmation flow path segment. The arithmetic mean roughness Ra is measured over a linear range of 4 mm from the second surface in the thickness direction. The gas flow path is divided at the short edge, and any one of the two first wall surface portions that emerge is used to measure the roughness.

[0014] In the silicon electrode plate for plasma processing equipment of the present invention, it is preferable that the gas flow path is divided at the long edge, and one of two crack confirmation flow path segments is selected, and in each cross section of the first wall surface portion extending from the two long edges included in the selected crack confirmation flow path segment, when six fields of view with a radius of 0.3 mm are observed, centered on points 1 mm, 2 mm, and 3 mm deep from the outlet, the total number n2 of cracks 0.05 mm or longer included in the six fields of view is 1 or less.

[0015] In the silicon electrode plate, the number of cracks is one or less (n2≦1), which further reduces the generation of particles during plasma processing. The cross section of the first wall surface portion is parallel to the plate thickness direction and the short direction perpendicular to the longitudinal direction of the outlet.

[0016] In the silicon electrode plate for a plasma processing apparatus of the present invention, the slit-shaped flow path is formed over the entire length of the gas flow path, and when the distance between the long edges of the inlets of the first surface in the gas flow path is a1, the distance between the long edges of the outlets is a2, the maximum distance between the short edges of the inlets is b1, and the maximum distance between the short edges of the outlets is b2, it is preferable that the gas flow path has a ratio r1 in the following formula (1) and a ratio r2 in the following formula (2) of 0.01 or less:

[0017]

number

[0018] where b1 is the maximum spacing between the short edges of the inlet and b2 is the maximum spacing between the short edges of the outlet. Ratio r1 relates to the difference between the spacings a1 and a2 between the long edges of the inlet and outlet of the gas flow path, and ratio r2 relates to the difference between the spacings b1 and b2 between the short edges of the inlet and outlet of the gas flow path.

[0019] When the two ratios r1 and r2 are 0.01 or less, the cross section of the gas flow path is uniform along its length, making it difficult for gas to stagnate in the flow path, and the pressure inside the gas flow path is steadily reduced, further preventing abnormal discharge during plasma processing.

[0020] In the silicon electrode plate for a plasma processing apparatus of the present invention, the slit-shaped flow path may be inclined with respect to the plate thickness direction.

[0021] In the silicon electrode plate for a plasma processing apparatus of the present invention, it is preferable that the difference between the distance between the long edges at the outlet and the diameter of an imaginary circle along the short edges is 0.05 mm or less.

[0022] In the silicon electrode plate for a plasma processing apparatus of the present invention, the gas flow path may be bent at a bending portion located midway along the plate thickness direction, and the slit-shaped flow path may be formed at least from the bending portion to the outlet.

[0023] In the silicon electrode plate for a plasma processing apparatus of the present invention, the gas flow path may comprise the slit-shaped flow path and an inlet-side flow path that opens to the inlet of the first surface, is connected to the slit-shaped flow path, and has a cross-section different from the cross-section of the slit-shaped flow path.

[0024] In this case, the inlet-side flow path can be formed by a hole having a cross section such as a circular or slit-like shape, or can be formed by a plurality of holes. The cross section of the inlet-side flow path may be larger than the cross section of the slit-like flow path.

[0025] The method for manufacturing a silicon electrode plate for a plasma processing apparatus according to the present invention includes a through-hole forming step of forming a plurality of through-holes in a disk-shaped silicon substrate plate, the through-holes extending in the plate thickness direction from a circular first processed surface to a second processed surface opposite the first processed surface, an etching step of etching the substrate plate after the through-hole forming step by immersing it in an etching solution, and a finishing step of finishing the first processed surface and the second processed surface of the substrate plate after the etching step. The through-hole forming step includes a slit forming step of forming a slit hole having an opening end consisting of a pair of parallel long edges extending along the surface direction of the second processed surface and an arc-shaped short edge connecting the ends of the long edges. The slit forming step also includes a round-hole forming step of forming two or more round holes in the second processed surface, and a groove processing step of forming a groove connecting the two or more round holes by transversely feeding a rotary tool having a side cutting edge in a direction connecting the two or more round holes.

[0026] In the through-hole forming process of the silicon electrode plate manufacturing method of the present invention, after forming a round hole in the base plate, the rotary tool is moved laterally to form a slit hole. Furthermore, processing damage remaining in the through-hole is reduced by the etching and polishing processes.

[0027] In the method for manufacturing a silicon electrode plate for a plasma processing apparatus of the present invention, the slit hole may be formed over the entire length of the through hole, and the slit hole forming process may include, instead of the round hole forming process and the groove machining process, a wire penetration process for forming a penetration portion for inserting a wire that penetrates from the first machined surface to the second machined surface, and an electric discharge machining process for passing an electric discharge wire through the penetration portion and further discharging the electric discharge wire to move the base plate and the wire relatively in the surface direction of the base plate, thereby forming the slit hole.

[0028] In addition, the slit hole forming process may include, instead of the round hole forming process and the groove machining process, a process of performing die-sinking electrical discharge machining in which an electrode shaped to the interior of the slit hole is fed in the thickness direction from the second machining surface of the base plate. [Effects of the Invention]

[0029] According to the present invention, the slit-shaped gas flow path has a high aspect ratio, which can suppress abnormal discharge, and the state of the outlet of the slit-shaped flow path suppresses chipping and internal roughness as processing damage, which can reduce particle generation during plasma processing, thereby enabling optimal plasma processing of wafers. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a diagram showing a plasma etching apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a plan view showing an inlet of a gas flow path formed on a first surface of a silicon electrode plate. [Figure 3] FIG. 10 is a plan view showing the outlets of the gas flow channels formed on the second surface of the silicon electrode plate. [Figure 4] 3 is a partial cross-sectional view of the silicon electrode plate taken along line s1-s1 in FIG. 2. FIG. [Figure 5] 3 is a partial cross-sectional view of the silicon electrode plate taken along line s2-s2 in FIG. 2. [Figure 6] 10A and 10B are plan views showing different arrangement examples of the outlet of the gas flow path. [Figure 7] 10A and 10B are plan views showing further different arrangement examples of the outlets of the gas flow paths. [Figure 8] FIG. 10 is a diagram illustrating chipping formed at the inlet of a gas flow path. [Figure 9] 10A and 10B are diagrams illustrating chipping formed at the outlet of a gas flow path. [Figure 10] FIG. 10 is a partial cross-sectional view of the gas flow path illustrating a crack formed in a portion of the first wall surface portion of the gas flow path near the outlet. [Figure 11] FIG. 11 is a partially enlarged view of FIG. [Figure 12] FIG. 10 is an enlarged view showing exaggerated long and short edges of the outlet of the slit-shaped flow channel. [Figure 13]1A and 1B show an example in which gas flow paths are arranged at an angle, with (a) being a plan view and (b) being a cross-sectional view taken along line s1-s1 in (a). [Figure 14] 14A and 14B show an example in which the gas flow passages are arranged so as to be inclined in a direction different from that of FIG. 13, where (a) is a plan view and (b) is a cross-sectional view taken along line s2-s2 of (a). [Figure 15] FIG. 10 shows an example in which the gas flow path is bent midway through the plate thickness, where (a) is a plan view and (b) is a cross-sectional view taken along line s1-s1 in (a). [Figure 16] FIG. 10 shows an example in which the inlet side of the gas flow path is formed as a round fine hole and the outlet side is formed as a slit-shaped flow path, where (a) is a plan view and (b) is a cross-sectional view taken along line s2-s2 in (a). [Figure 17] 1A and 1B show an example in which the outlet side of the gas flow path is formed as a slit-shaped flow path with a larger cross-sectional area than the inlet side, where (a) is a plan view and (b) is a cross-sectional view taken along line s2-s2 in (a). [Figure 18] 17 shows an example in which the outlet side of the gas flow path is formed as a slit-shaped flow path with a smaller cross-sectional area than the inlet side. (a) is a plan view, and (b) is a cross-sectional view along the s2-s2 line in (a). DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a plasma etching apparatus 1 according to an embodiment of the present invention has a silicon electrode plate (hereinafter referred to as the electrode plate) 3 serving as an upper electrode provided at the top of a vacuum chamber 2, and a vertically movable stand 4 serving as a lower electrode provided at the bottom parallel to and spaced from the electrode plate 3.

[0032] The upper electrode plate 3 is supported by an insulator 5 in an insulated state relative to the wall of the vacuum chamber 2, and an electrostatic chuck 6 and a silicon support ring 7 surrounding the electrostatic chuck 6 are provided on the pedestal 4. A wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with its peripheral region supported by the support ring 7. An etching gas supply pipe 9 is provided at the top of the vacuum chamber 2. The etching gas sent from this etching gas supply pipe 9 is diffused by a diffusion member 10, then flows through an upstream gas flow path 15 provided in a cooling plate 14 made of aluminum or the like with excellent thermal conductivity and a gas flow path 11 provided in the electrode plate 3, toward the wafer 8, and is discharged to the outside from an exhaust port 12 on the side of the vacuum chamber 2.

[0033] This plasma etching apparatus 1 is provided with a high-frequency power supply 13 that applies a high-frequency voltage between the electrode plate 3 and the stand 4. When etching gas is released into the space S between the electrode plate 3 and the stand 4 and a high-frequency voltage is applied from the high-frequency power supply 13, the etching gas turns into plasma in this space S and impinges on the wafer 8. The surface of the wafer 8 is etched by sputtering, i.e., a physical reaction, caused by this plasma and a chemical reaction of the etching gas.

[0034] Furthermore, in order to perform uniform etching of the wafer 8, the generated plasma is concentrated at the center of the wafer 8 and prevented from diffusing to the periphery, thereby generating uniform plasma between the electrode plate 3 and the wafer 8. In this manner, the plasma generation region 16 is usually surrounded by a silicon shield ring 17.

[0035] [Electrode plate 3] The electrode plate 3 is made of single crystal silicon, columnar silicon, or polycrystalline silicon, and is formed in a disk shape with a circular first surface that contacts the cooling plate 14 and a circular second surface that is located on the opposite side of the first surface and faces the wafer 8.

[0036] The dimensions of the electrode plate 3 are not limited, but for example, the diameter is 150.0 mm or more and 450.0 mm or less, and the thickness is 5.0 mm or more and 30.0 mm or less.

[0037] A plurality of gas flow paths 11 each penetrate from the first surface 301 to the second surface 302 , with an inlet 111 of each gas flow path 11 provided in the first surface 301 and an outlet 112 of each gas flow path 11 provided in the second surface 302 .

[0038] FIG. 2 is a plan view of one gas flow channel 11 as seen from the first surface side of the electrode plate. The gas flow channel 11 is formed like a slit in plan view. The inlet (opening end) 111 of the first surface 301 of the gas flow channel 11 is formed from a pair of linear long edges 111A extending parallel to each other and a pair of short edges 111B connecting the ends of the long edges 111A and forming an arc-like shape. FIG. 3 is a plan view of the outlet (opening end) 112 located opposite the inlet 111. The outlet 112 of the second surface 302, like the inlet 111, is also formed from a pair of long edges 112A extending parallel to each other and a pair of short edges 112B connecting the ends of the long edges 112A and forming an arc-like shape. The dashed-double-dot lines in FIGS. 2 and 3 represent the edges of the rectangular regions around the inlet 111 and the outlet 112, which are part of the first surface 301 and the second surface 302, respectively.

[0039] As shown in FIGS. 4 and 5, each gas flow path 11 includes a pair of flat first wall portions 113A extending parallel from the long edge 111A of the inlet 111 to the long edge 112A of the outlet 112, and a pair of curved second wall portions 113B extending from the short edge 111B of the inlet 111 to the short edge 112B of the outlet 112. The first and second wall portions 113A and 113B extend in the thickness direction D1 of the electrode plate. In other words, in this embodiment, a slit-shaped flow path (equivalent to the gas flow path 11 in this case) is formed over the entire length of the gas flow path 11. The dashed-dotted line in FIG. 5 indicates the boundary between the first wall portion 113A and the second wall portion 113B.

[0040] [Gas flow path slit width A] 4, the minimum distance between long edges 111A of inlets 111 of gas flow channel 11 is defined as a1, the minimum distance between long edges 112A of outlets 112 is defined as a2, and the average value of distance a1 and distance a2 is defined as slit width A of gas flow channel 11. Slit width A is 0.1 mm or more and 1.2 mm or less, preferably 0.3 mm or more and 1.0 mm or less, for example, 0.5 mm.

[0041] [Gas flow path slit length B] 5, the maximum distance between the short edges 111B of the inlets 111 of the gas flow path 11 is defined as b1, the maximum distance between the short edges 112B of the outlets 112 is defined as b2, and the average of these distances b1 and b2 is defined as the slit length B of the gas flow path 11. The slit length B is 0.3 mm or more and 20.0 mm or less, preferably 0.5 mm or more and 15.0 mm or less, for example, 2.0 mm or more and 10.0 mm or less. The slit length B is set to be greater than the slit width A (B>A).

[0042] [Gas flow path depth C] In the electrode plate 3, a first surface 301 on which an inlet 111 of the gas flow path 11 is provided and a second surface 302 on which an outlet 112 of the gas flow path 11 is provided are formed in parallel, and a plate thickness direction D1 of the electrode plate 3 shown in Fig. 4 is a direction perpendicular to the first surface 301 and the second surface 302. The gas flow path 11 extends in this plate thickness direction D1, and a depth C of the gas flow path 11 from the inlet 111 to the outlet 112 is, for example, 5.0 mm or more and 30.0 mm or less, preferably 10.0 mm or more and 25.0 mm or less, for example, 10.0 mm or more and 20.0 mm or less.

[0043] [Aspect Ratio] If the ratio (=C / A) of the depth C of the gas flow path 11 divided by the slit width A is defined as the aspect ratio, the aspect ratio is 10 or more and 80 or less, and preferably 20 or more and 60 or less. An aspect ratio of 10 or more and 80 or less prevents discharge and enables the electrode plate 3 to be used for a long period of time. If the aspect ratio is less than 10, the slit width A of the gas flow path 11 is small or the depth C of the gas flow path 11 is small, causing abnormal discharge in the gas flow path 11. If the aspect ratio exceeds 80, the gas flow deteriorates, causing the pressure in the gas flow path 11 to rise and making abnormal discharge more likely to occur.

[0044] Although slit-shaped gas flow channels 11 formed with such a high aspect ratio are formed in the electrode plate 3, the number and arrangement of the gas flow channels 11 are not limited. Figures 6(a) and 6(b) and 7(a) and 7(b) show examples of planar arrangements of the gas flow channels 11. Both Figures 6 and 7 show the second surface 302 of the electrode plate 3, and the electrode plate 3 and second surface 302 that are common to both are given the same reference numerals and will not be described again. The gas flow channels also have a common shape, and are designated by reference numerals 11A and 11B in Figure 6(b) for distinction, but will be described as reference numeral 11 in the other cases.

[0045] For example, as shown in Fig. 6(a), the longitudinal directions of the slits of the gas flow paths 11 may be set to the same direction in each gas flow path 11. In the example shown in Fig. 6(a), the longitudinal directions of the slits of each gas flow path 11 are all oriented in the left-right direction of Fig. 6(a) and are arranged parallel to each other.

[0046] In FIG. 6(b), gas flow paths 11A whose longitudinal direction is oriented in the vertical direction and gas flow paths 11B whose longitudinal direction is oriented in the horizontal direction are alternately arranged.

[0047] In FIG. 7(a), the longitudinal direction of the gas flow channels 11 is arranged radially from the center of the circular electrode plate 3.

[0048] In FIG. 7(b), the longitudinal direction of the slits of the gas flow passage 11 is arranged in the circumferential direction of the circular electrode plate 3.

[0049] In any of these arrangements, if the second surface 302 is divided into a circular plate central portion S1 including the center, an annular outer peripheral portion S2 near the periphery of the second surface 302, and an annular intermediate portion S3 between the plate central portion S1 and the outer peripheral portion S2, the plate central portion S1, intermediate portion S3, and outer peripheral portion S2 each have a plurality of slit-shaped gas flow channels. The plate central portion S1 has gas flow channels 11 at four or more different angular positions around the center (areas indicated by C1 to C4 at 90° intervals in the illustrated example) near the center of the electrode plate 3. The outer peripheral portion S2 has gas flow channels 11 at four or more different angular positions (C1 to C4) around the center near the periphery of the electrode plate 3. Thus, the electrode plate 3 has slit-shaped gas flow channels at four or more different angular positions around the center near both the center and the periphery of the electrode plate 3. When the length from the center to the periphery of the electrode plate 3 is expressed as a percentage, the center of the plate is 0% or more The range may be 40% or less, the intermediate portion may be more than 40% and less than 60%, and the outer peripheral portion may be in the range of 60% or more and 100% or less.

[0050] It is also possible to combine the gas flow path arrangements shown in Figures 6 and 7 (for example, arranging the slits so that their longitudinal directions are in the same direction near the center and arranging them so that they are in the circumferential direction near the periphery).

[0051] [Dimensional difference between inlet and outlet] Furthermore, in each gas flow path 11 of the electrode plate 3, the ratio r1 in the following formula (eq1) and the ratio r2 in the following formula (eq2) are 0.01 or less, preferably 0.005 or less, and more preferably 0.001 or less. While not particularly limited, the ratios r1 and r2 may be 0.000001 or more, 0.00001 or more, or 0.0001 or more. By having the ratios r1 and r2 be 0.01 or less, the occurrence of discharge during plasma processing can be further prevented. If the ratio r1 or r2 exceeds 0.01, the gas flow path 11 becomes tapered, which makes it easier for plasma to penetrate into the gas flow path 11, making it difficult to suppress abnormal discharge.

[0052]

number

[0053] The ratio r1 is the absolute value of the difference between the spacing a1 between the long edges 111A of the inlets 111 and the spacing a2 between the long edges 112A of the outlets 112, divided by the depth C.

[0054]

number

[0055] The ratio r2 is the absolute value of the difference between the spacing b1 between the short edges 111B of the inlets 111 and the spacing b2 between the short edges 112B of the outlets 112, divided by the depth C.

[0056] Next, chipping, surface roughness, and cracks as conditions of the gas flow passage 11 will be described.

[0057] [Chipping] As shown in FIGS. 4 and 5, the long edge 111A and the short edge 111B of the inlet 111 of the gas flow channel 11 have an angular cross section. As shown in FIG. 8, the portion of the inlet 111 of the gas flow channel 11 where the angular long edge 111A and / or the short edge 111B are missing and the width W11 is 0.1 mm or more is defined as a tipping 20. The width W11 of the tipping 20 is the dimension along the long edge 111A and the short edge 111B. In the tipping 20 of FIG. 8 where a portion of the long edge 111A is missing, the width W11 is the dimension along the long edge 111A between ends P11 and P12 where the tipping 20 connects to the long edge 111A. In the tipping 20 of FIG. 8 where a portion of the short edge 111B is missing, the width W11 is the dimension along the short edge 111B between ends P21 and P22 where the tipping 20 connects to the short edge 111B. As shown in FIG. 9, at the outlet 112 of the gas flow path 11, the long edge 112A and / or the short edge 112B is chipped, and the chipping 20 occurs at a location with a width W11 of 0.1 mm or more.

[0058] The electrode plate 3 of this embodiment is characterized in that the average number n1 of chippings 20 in one gas flow path 11 is 3 or less (n1≦3). By having 3 or less chippings 20, the generation of particles is suppressed in plasma processing using the electrode plate 3, and plasma processing can be performed appropriately. If the number of chippings 20 exceeds 3, a large number of particles will be generated. Note that the average number n1 of chippings 20 in one gas flow path 11 is more preferably 2 or less, and even more preferably 1 or less.

[0059] [How to check for chipping] The average value n1 of chippings 20 is determined as follows. First, one gas flow path is selected from each of the four regions C1 to C4 in the central portion S1 of the electrode plate 3, and these are designated as central selected flow paths to be observed. The chippings at the outlets 112 of these central selected flow paths are checked, and the total number of chippings for each of the four central selected flow paths is determined as n111, n112, n113, and n114. Taking the total number n111 as an example, the total number n111 is the number of chippings provided at the outlet 112 of one central selected flow path. Next, one gas flow path is selected from each of the four regions C1 to C4 in the peripheral portion S2 of the electrode plate 3, and these are designated as peripheral selected flow paths to be observed. The chippings at the outlets 112 of these peripheral selected flow paths are checked, and the total number of chippings for each of the four peripheral selected flow paths is determined as n121, n122, n123, and n124. Taking the total number n121 as an example, the total number n121 is the number of tippings provided at the outlet 112 of one peripheral selected flow path. The average value of the eight points, including the numbers of tippings n111, n112, n113, and n114 in the central selected flow path and the numbers of tippings n121, n122, n123, and n124 in the peripheral selected flow path, is defined as n1.

[0060] [Surface roughness of gas flow path 11] The average value m1 of the roughness Ra (arithmetic mean roughness) of each gas flow channel 11 is 3.2 μm or less, preferably 3.0 μm or less, and more preferably 1.8 μm or less. While not particularly limited, the average value m1 may be 0.01 μm or more, 0.05 μm or more, or even 0.1 μm or more. The arithmetic mean roughness Ra is measured three times using a stylus-type roughness measuring instrument, and the average value m1 of the arithmetic mean roughness Ra obtained from each measurement represents the surface roughness of the gas flow channel 11. Two roughness confirmation flow channel segments are created by dividing the gas flow channel 11 at the short edges 111B and 112B along line s2-s2 in Figure 2. One of these segments is selected, and the first wall surface 113A included in the selected roughness confirmation flow channel segment is used for roughness measurement. The arithmetic mean roughness Ra is measured by moving a stylus in contact with the first wall surface 113A by 4 mm in the thickness direction D1 of the electrode plate 3. If the average value m1 exceeds 3.2 μm, abnormal discharge and particle generation cannot be suppressed.

[0061] [crack] In the electrode plate 3, preferably, one of two crack-checking flow path segments formed by dividing each gas flow path 11 at the first wall surface portion 113A is selected, and the cross section of each of the two first wall surface portions 113A included in the selected crack-checking flow path segment is observed with an optical microscope at depths of 1 mm, 2 mm, and 3 mm from the outlet 112. The total number n2 of cracks 0.05 mm or longer in six fields of view is 1 or less, and more preferably 0. The total number n2 of cracks in the electrode plate is specified as follows: The observation points are selected at 1 mm, 2 mm, and 3 mm from the outlet 112 because they are close to the plasma generation region 16 and have a significant impact on particle generation.

[0062] The cross section of the first wall surface portion 113A is a longitudinal cross section of the gas flow path 11 taken along an imaginary plane s3 indicated by a dashed line in FIG. 9 . This imaginary plane s3 passes through the center O of the outlet 112 and is parallel to the plate thickness direction D1 and the short-side direction D3 of the outlet 112. The cross section of the first wall surface portion 113A is also parallel to the plate thickness direction D1 and the short-side direction D3. When the gas flow path 11 is divided along the imaginary plane s3, two crack confirmation flow path segments are produced, and each of these crack confirmation flow path segments has two first wall surface portions 113A. One of the two crack confirmation flow path segments is selected, and the two first wall surface portions 113A (hereinafter, the symbols x1 and x2 may be added in parentheses to distinguish between these first wall surface portions 113A) included in the selected crack confirmation flow path segment are observed using an optical microscope.

[0063] First, the observation fields centered at depths of 1 mm, 2 mm, and 3 mm from the outlet 112 of one of the first wall surface portions 113A (x1) shown in FIG. 10 are designated v11, v21, and v31. Each observation field is defined as a circle with a radius of 0.3 mm using an optical microscope at a magnification of 100. Then, the cross section of the first wall surface portion 113A within the field of view of the optical microscope is observed, and cracks with a length of 0.05 mm or more are counted. For example, as shown in FIG. 11, if cracks 30 with a length L of 0.05 mm or more are confirmed in the observation field v11 at a depth of 1 mm, the number of cracks 30 in the observation field v11 at a depth of 1 mm is designated n211. Similarly, the number of cracks 30 in the observation field v21 at a depth of 2 mm is designated n221, and the number of cracks 30 in the observation field v31 at a depth of 3 mm is designated n231.

[0064] Next, the crack observation performed on one first wall surface portion 113A(x1) is similarly performed on the other first wall surface portion 113A(x2). On the other first wall surface portion 113A(x2), observation fields centered on positions 1 mm, 2 mm, and 3 mm deep from the outlet 112 are designated v12, v22, and v32, the number of cracks 30 in the observation field v12 at a depth of 1 mm is designated n212, the number of cracks 30 in the observation field v22 at a depth of 2 mm is designated n222, and the number of cracks 30 in the observation field v32 at a depth of 3 mm is designated n232, and the sum of the numbers of cracks 30 confirmed on one first wall surface portion 113A(x1) and the other first wall surface portion 113A(x2) is designated as the total number n2 (= n211 + n221 + n231 + n212 + n222 + n232) of observed gas flow paths 11.

[0065] Since the number of cracks on the electrode plate 3 is one or less (n2≦1), the generation of particles during plasma processing using the electrode plate 3 can be further reduced.

[0066] [Manufacturing method] The method for manufacturing an electrode plate includes an ingot formation process for producing a silicon ingot for the electrode plate, a slicing process for slicing the silicon ingot, a contour processing process for processing a base plate sliced ​​from the ingot into a disk shape, a through-hole formation process for forming a plurality of through-holes in the base plate that has undergone the contour processing process, an etching process for immersing the base plate that has undergone the through-hole formation process in an etching solution to etch it, and a finishing process for finishing both surfaces of the base plate that has undergone the etching process.

[0067] In the ingot formation process, silicon ingots made of single crystal silicon, columnar crystal silicon, or polycrystalline silicon are formed into cylindrical, block-shaped, or other shapes by the Czochralski method, casting, or other methods. When electrical discharge machining is performed in the through-hole formation process described below, the impurity concentration of the silicon ingot is adjusted to 1×10 so that the substrate has conductivity. 14 atoms / cm 3 More than 1×10 21 atoms / cm 3 It is desirable to produce it under the following control.

[0068] In the slicing process, a silicon ingot is cut using a diamond abrasive band saw or wire saw to form a base plate.

[0069] In the outer shape processing step, the outer shape of the base plate is processed by cutting. The base plate has a through-hole formation portion of a predetermined thickness in which a through-hole for a slit through which gas flows is to be formed, and a peripheral portion formed around this through-hole formation portion. The sizes and cross-sectional shapes of the portion where the through hole is to be formed and the peripheral portion are not limited, but for example, after undergoing the external processing step, the base plate will have a circular first processed surface where one side of the portion where the through hole is to be formed and one side of the peripheral portion are flush with each other, a circular second processed surface consisting of the other side of the portion where the through hole is to be formed, and an annular third processed surface consisting of the other side of the peripheral portion and formed radially outwardly shifted from the second processed surface, with the peripheral side being thinner and the cross section being formed in a stepped shape.

[0070] In the through-hole forming step, a plurality of slit-shaped through-holes are formed in the base plate by, for example, milling, wire electric discharge machining, or die-sinking electric discharge machining, as described below.

[0071] [Milling] The milling process includes a round hole forming process in which two or more round holes that penetrate the base plate are formed using a rotary tool with a tip blade, and a groove processing process in which a rotary tool with a side blade is fed laterally from the position of one of the round holes to the other round hole to form a groove that penetrates the base plate.

[0072] In the round hole forming process, the rotary tool is moved in the direction of its center line to penetrate the base plate. This forms round holes extending in the thickness direction D1 of the base plate. The rotary tool is passed from the first processing surface to the second processing surface. In this case, it is preferable to form round holes at positions that will be both ends of the desired slit-shaped gas flow path. Therefore, two round holes are usually formed, but they may also be formed at a position between them. These round holes are provided to reduce the load during the subsequent groove processing process, and two to about 20 round holes may be formed in a row.

[0073] In the groove processing step, the rotary tool is fed laterally from the position of the round hole to widen the round hole laterally and form a groove that penetrates the base plate, thereby completing a slit-shaped through hole. When round holes are formed at both ends of the desired slit-shaped through flow path, the rotary tool is fed laterally from the position of one round hole to the other round hole to process so as to connect both round holes. When two or more round holes are formed, the rotary tool is fed laterally along the row so as to connect these round holes laterally.

[0074] The elongated rotary tools used in the round hole forming process and the groove machining process may be, for example, end mills, but a drill may be used in the round hole forming process and an end mill may be used in the groove machining process, and it is preferable to use diamond-electroplated tools for these.

[0075] If the thickness of the base plate is, for example, 5.0 mm or more, there is a risk that the long and thin rotary tool may break, so it is advisable to perform the milling process by changing the length of the end mill, for example.

[0076] If the base plate is thick, in the round hole forming step, a hole may be formed with a rotary tool from the first processing surface to partway in the plate thickness direction D1 of the base plate, and then the rotary tool may be inserted from the second processing surface to penetrate the base plate. Also, in the groove processing step, if the base plate is thick, a groove may be formed from the first processing surface to partway through the thickness, and then the rotary tool may be inserted from the second processing surface to reach the previously formed groove to form a slit-shaped through hole.

[0077] Furthermore, in the through-hole forming process, additional processing may be performed on the through-hole formed with the rotary tool. For example, laser processing is performed on the interior of the through-hole within a range of 5 mm deep from the opening on both sides of the base plate to remove chipping and cracks. In particular, when the rotary tool penetrates the base plate, the opening formed on the surface where the tip of the rotary tool exits is more likely to develop chipping than the opening on the surface where the tip enters. Therefore, additional processing is preferably performed on the opening where the tip exits. Furthermore, if a round hole is formed with a drill and then a slit-shaped through-hole is formed by additional processing to form a notch with an end mill, the opening of the through-hole on the first machined surface or the second machined surface may not extend straight but may be curved. Therefore, performing laser processing or electric discharge machining on the through-hole improves (decreases) the ratios r1 and r2. Furthermore, if the curved wall surface formed in the round hole forming process and the flat wall surface formed in the groove machining process are connected via a stepped connection, this stepped portion may be removed with a laser so that the inside of the through hole is composed of a curved wall surface and a flat wall surface that connects to the end of this curved surface. This additional processing can suppress the occurrence of abnormal discharge.

[0078] In this case, because the processing is performed in separate steps of forming a round hole and machining a groove, the short edges 112B formed in the round hole forming step and the long edges 112A formed in the groove machining step may be misaligned, as shown in an exaggerated manner in Figure 12. Therefore, it is preferable to process the second surface 302 so that the difference between the spacing a2 between the long edges 112A at the outlet 112 and the diameter d of an imaginary circle C1 along the short edges 112B (|d-a2|: the absolute value of the difference between d and a2, which is referred to as the difference in slit width G) is 0.05 mm or less. The diameter d of the imaginary circle C1 along the short edges 112B is the diameter d of the imaginary circle formed by extending the short edges 112B, which are usually semicircular in plan view. Since two short edges 112B are formed on the left and right sides, the difference G between the diameter d of the imaginary circle C1 formed by each of the short edges 112B and the distance a2 between the long edges 112A is calculated and set so that both are 0.05 mm or less. By setting the difference G between the diameter d and the distance a2 between the long edges 112A (difference in slit width) to 0.05 mm or less, the step is suppressed, and the occurrence of abnormal discharge can be suppressed.

[0079] [Wire EDM] Wire electric discharge machining includes a wire penetration process in which a penetration portion for inserting an electric discharge wire (hereinafter simply referred to as wire) into a base plate is formed, and an electric discharge machining process in which the wire of an electric discharge machine is passed through the penetration portion and then the wire is discharged to form a slit-shaped through hole.

[0080] The wire passing step involves forming a hole for passing the wire using, for example, a drill, a small-hole electric discharge machine, or a laser machine.

[0081] In the electrical discharge machining process, the base plate is set in a wire electrical discharge machine, with the electrical discharge wire passing through the through-hole of the base plate. The base plate is then machined by wire electrical discharge while the base plate and the wire are moved relative to each other in the surface direction of the base plate. Note that electrical discharge machining may be performed multiple times while relaxing the electrical discharge conditions until the opposing machining plane of the inner surface of the through hole achieves the desired surface roughness (arithmetic mean roughness Ra of 0.1 μm to 3.2 μm). Furthermore, when using wire material containing copper or zinc, it is preferable to remove metal adhering to the machined surface by acid washing with sulfuric acid, nitric acid, or the like after electrical discharge machining.

[0082] In the wire-passing step, a pass-through portion smaller than the imaginary circle formed by the short edges of the slit may be formed, and the entire slit-shaped through hole may be formed by wire electric discharge machining while widening the diameter of the pass-through portion. Alternatively, after forming a pair of round holes that form the short edges in the round hole forming step, a groove machining step connecting these round holes may be performed by wire electric discharge machining. In this case, too, as shown in Figure 12, the difference G between the diameter d of the imaginary circle C1 formed by the short edges and the distance a2 between the long edges 112A (the difference in slit width) is processed to be 0.05 mm or less.

[0083] [Die-sinker EDM] In die-sinking electrical discharge machining, an electrode shaped to resemble a slit-shaped through-hole is formed from graphite or the like, and the electrode is discharged to melt the base plate, transferring the electrode shape to the base plate. When the base plate is thin, die-sinking electrical discharge machining is performed on one side of the base plate. However, when the base plate is thick, die-sinking electrical discharge machining may be performed on a first machining surface to form a groove partway along the thickness direction D1 of the base plate, and then die-sinking electrical discharge machining may be performed on a second machining surface to form a hole that reaches the previously formed groove, forming a slit-shaped through-hole that penetrates the base plate. When using an electrode such as copper, it is preferable to remove any metal adhering to the machining surface by acid washing after machining.

[0084] The etching process involves immersing the base plate in an etching solution to remove processing damage such as depressions formed on the first processed surface, second processed surface and inner surfaces of the multiple through holes of the base plate, as well as removing processing damage such as chipping off part of the edge of the opening of the through holes.

[0085] The etching solution is, for example, a mixed acid solution. The mixed acid solution is a mixture of hydrofluoric acid (HF), nitric acid (HNO3), and acetic acid (CH3COOH), and preferably contains 5% to 30% hydrofluoric acid, 10% to 60% nitric acid, and 5% to 50% acetic acid, with the remainder being pure water. While etching can remove processing damage, a long etching time can increase dimensional variation, so the etching depth is preferably 10 μm to 100 μm. Through the etching process, through-holes are formed in the gas flow passages 11, and a first processed surface is formed on the first surface 301.

[0086] In the finishing process, the first processed surface is polished to form a first surface 301 that contacts the cooling plate 14, and the second processed surface is polished to form a second surface 302 that faces the wafer 8. In the finishing process, the first processed surface and the second processed surface of the substrate are polished while a slurry (polishing liquid) containing an abrasive such as colloidal silica or diamond abrasive grains is supplied onto a rotating polishing pad. The finishing process also includes a cleaning process in which the substrate is washed with running water or the like after being polished. The cleaning process may be ultrasonic cleaning or cleaning using an acid, alkali, or surfactant. After the finishing process, the electrode plate 3 is completed.

[0087] In the electrode plate 3 of this embodiment, the high aspect ratio slit-shaped gas flow path 11 is formed so that the average number of chippings n1 on the edges of the inlet 111 and outlet 112 for the plasma processing gas is 3 or less, and the average value m1 of the arithmetic mean roughness Ra of the internal first wall surface portion 113A is 3.2 μm or less, thereby reducing the generation of particles during plasma processing, and allowing the plasma processing to be performed favorably.

[0088] The present invention can be practiced without being limited to the above-described and illustrated examples. 13 to 18 show other configurations of the gas flow path. In these figures, the electrode plates and their first and second surfaces are given the same reference numerals to simplify the explanation.

[0089] 13 is formed as a slit-shaped flow path overall, but is formed to be inclined with respect to the plate thickness direction of the electrode plate 3. In this case, the longitudinal direction of the slit is not changed, and the angle between the first wall surface portion 113A continuing from the long edge and the second surface 302 of the electrode plate 3 is inclined in a direction that forms an acute angle.

[0090] 14 also has slit-shaped flow paths that are inclined in the thickness direction of the electrode plate 3, but unlike in FIG. 13, the angle between a first wall surface portion 113A continuing from a long edge 112A and a second surface 302 of the electrode plate 3 remains a right angle, and a second wall surface portion 113B continuing from a short edge 112B is disposed at an incline with respect to the second surface 302. Moreover, as shown in FIG. 14(a), in the gas flow paths 202, the longitudinal directions of the slits on the first surface 301 side and the slits on the second surface 302 side are the same when viewed from the first surface 301 or the second surface 302.

[0091] 15 is formed as a slit-shaped flow path overall, but a bent portion 204 is formed midway through the thickness of the electrode plate 3. In this case, the longitudinal direction of the slit is not changed, and from the bent portion 204 to the outlet 112, the first wall surface portion 113A is formed at a right angle to the second surface 302 of the electrode plate 3, and from the bent portion 204 to the inlet 111, the angle formed by the first wall surface portion 205A connected to the first wall surface portion 113A on the outlet 112 side and the first surface 301 of the electrode plate 3 is an acute angle.

[0092] 16, the gas flow path 211 is formed as a slit-shaped flow path 212 from midway in the thickness direction of the electrode plate 3 toward the second surface 302, but two small round holes 213 with circular cross sections are formed on the first surface 301 side. These small round holes 213 are connected near both ends of the slit of the slit-shaped flow path 212. Reference numeral 214 denotes a cross-sectionally changing portion located midway in the thickness direction of the gas flow path 211, and in the embodiment shown in FIG. 16, the slit-shaped flow path of the present invention refers to the flow path from this cross-sectionally changing portion 214 toward the second surface 302.

[0093] 17, the cross-sectional area of ​​the slit changes midway in the thickness direction of the electrode plate 3. In the illustrated example, the cross-sectional area of ​​the slit-shaped flow path 216 on the outlet 112 side is larger than the cross-sectional area of ​​the slit-shaped flow path 217 on the inlet 111 side. In this case, the slit changes in both the longitudinal and lateral directions. Reference numeral 218 denotes a cross-sectional change portion located midway in the thickness direction of the gas flow path 215, and the slit-shaped flow path of the present invention refers to the flow path from this cross-sectional change portion 218 to the second surface 302 side.

[0094] 17, the gas flow path 221 shown in Fig. 18 is formed such that the cross-sectional area of ​​the slit-shaped flow path 222 on the outlet 112 side is smaller than the cross-sectional area of ​​the slit-shaped flow path 223 on the inlet 111 side. Reference numeral 224 denotes a cross-sectional change portion located midway in the plate thickness direction of the gas flow path 221, and the slit-shaped flow path of the present invention refers to the flow path from this cross-sectional change portion 224 to the second surface 302 side.

[0095] 13 to 18, in the configuration in which the flow path is bent partway through the thickness of the electrode plate 3 (FIG. 15) or in the configuration in which the cross-sectional area of ​​the flow path changes (FIGS. 16 to 18), the flow path from the bent portion 204 or the cross-sectional change portion 214, 218, 224 to the outlet 112 side of the second surface 302 of the electrode plate 3 is defined as the slit-shaped flow path of the present invention. In this slit-shaped flow path, the slit width A (equal to a2) and depth C are defined within the depth range, and chipping and cracks are also considered to occur in this slit-shaped flow path on the outlet 112 side.

[0096] Furthermore, as shown in Figures 16 to 18, when a bend or a cross-sectional change portion is formed at a midpoint in the plate thickness direction in the gas flow path, the flow path that opens to the first surface 301 is defined as the inlet-side flow path, in contrast to the slit-shaped flow path that is the outlet-side flow path.

[0097] 16, when the inlet-side flow path is formed of a round fine hole 213 and is not slit-shaped, the process of forming a slit hole is performed only on the outlet-side flow path. Therefore, in the present invention, the process of forming a slit hole in the through-hole forming process is particularly referred to as the slit hole forming process, and when slit holes are formed throughout the entire thickness of the electrode plate as in FIGS. 4 and 13, this slit hole forming process is performed throughout the entire thickness of the electrode plate. In the examples shown in FIGS. 15, 17, and 18, the process of forming the outlet-side flow path is also particularly referred to as the slit hole forming process. [Example]

[0098] The samples were electrode plates, each made of a circular substrate of different thickness, with multiple slit-shaped gas flow paths formed by varying the processing method, shape, and dimensions of the gas flow paths. Using these, Si wafers were subjected to plasma processing, and the number of particles adhering to the Si wafers after plasma processing was counted.

[0099] The method for manufacturing an electrode plate includes a slicing process for slicing a silicon ingot, a contour processing process for processing the base plate sliced ​​from the silicon ingot into a disk shape of a predetermined thickness, a through-hole forming process for forming a plurality of through-holes in the base plate that has undergone the contour processing process, an etching process for immersing the base plate that has undergone the through-hole forming process in an aqueous mixed acid solution for etching, and a finishing process for finishing both surfaces of the base plate that has undergone the etching process.

[0100] Each sample was processed so that the thickness of the base plate varied in the external processing step, and in the through-hole forming step, slit-shaped through-holes were formed by either milling, wire electric discharge machining, die-sinker electric discharge machining, or water jet machining, with the same treatment being applied in the etching and finishing steps.

[0101] The water jet processing was carried out using the abrasive jet method, which involves adding abrasive grains to high-pressure water. Garnet was used as the abrasive grains. After forming the through-hole, the gas flow path was formed by scanning the nozzle to obtain the desired shape.

[0102] The mixed acid solution used in the etching process consisted of 12% hydrofluoric acid (HF), 30% nitric acid (HNO3), 35% acetic acid (CH3COOH), and the remainder was pure water. The etching depth was set to 10 μm.

[0103] In the finishing process, both sides of the substrate were polished by supplying a slurry (polishing liquid) containing abrasive grains (colloidal silica) onto a rotating polishing pad. After polishing, the substrate was washed with running water.

[0104] After this finishing process, a φ300 mm electrode plate was completed. The processing method and shape of the gas flow path for each sample are shown in Table 1. In Table 1, "straight" indicates that the gas flow path is formed along the thickness direction of the electrode plate, and "20° diagonal straight" indicates that the gas flow path is formed straight and inclined at 20° relative to the thickness direction of the electrode plate.

[0105] After the electrode plate was completed, the dimensions of any one of the slit-shaped gas flow paths were measured. The dimensions of the gas flow path were measured as follows: a1, the minimum distance between the first long edges of the gas inlet; a2, the minimum distance between the second long edges of the outlet; b1, the maximum distance between the first short edges of the gas inlet; b2, the maximum distance between the second long edges of the outlet; and depth C. The difference between the diameter d of the imaginary circle of the short edges at the outlet and the distance a2 between the long edges (slit width difference G) was also measured.

[0106] These measurements were made using a CNC image measuring machine manufactured by Mitutoyo Corporation. The electrode plate is a circular plate with both sides formed flat from the center to the periphery, and the first side where the gas flow path inlet is provided is parallel to the second side where the gas flow path outlet is provided, so the plate thickness of the electrode plate was measured and this was taken as depth C.

[0107] Furthermore, the slit width A of the gas flow path, which is the average value of the intervals a1 and a2, the slit length B of the gas flow path, which is the average value of the intervals b1 and b2, and the aspect ratio (=C / A) were calculated.

[0108] In addition, the measured values ​​a1, a2, b1, b2, and C of the gas flow paths are inserted into the above equations (eq1) and (eq2) to find the ratios r1 and r2 of each gas flow path, and the larger value of these (hereinafter referred to as the ratio r max In this case, the calculated value was rounded off to three decimal places and shown in Table 1.

[0109] The slit width A, slit length B, aspect ratio and ratio r of the gas flow path of each sample max The difference in slit width G is shown in Table 1.

[0110] (Check for processing damage) The gas flow path of each sample was observed to check the number of chippings and cracks, and the internal surface roughness (arithmetic mean roughness).

[0111] (chipping) For chipping, four randomly selected from the multiple gas flow paths near the center of the electrode plate were designated as central selected flow paths, and four randomly selected from the multiple gas flow paths near the end of the electrode plate were designated as peripheral selected flow paths. These were used as the observation subjects, and the inlet and outlet edges of these first surfaces were observed using an optical microscope at a magnification of 20. The observed inlet and outlet edges each consisted of two straight long edges and two arc-shaped short edges. The total number of chippings n111, n112, n113, and n114 with a width W11 of 0.1 mm or more was determined for each central selected flow path, and the total number of chippings n121, n122, n123, and n124 with a width w11 of 0.1 mm or more was determined for each peripheral selected flow path. Then, the total number of chippings in the central selected flow path n111, n112, n113, and n114 and the total number of chippings in the peripheral selected flow path n121, n122, n123, and n124 were compared for a total of eight points, n1 (= (n111 + n112 + n113 + n114 + n121 + n122 + n123 + n124) / 8). When chipping occurs, it occurs in the same way in almost all gas flow paths, so checking eight gas flow paths is sufficient, and increasing the number beyond that does not result in a large difference in the average value.

[0112] (crack) In the cross section of any one gas flow path, six fields of view (V11, V21, V31, V12, V22, and V32) with a radius of 0.3 mm were observed using an optical microscope at a magnification of 100, centered on points 1 mm, 2 mm, and 3 mm deep from the outlet on the second surface, as shown in Figure 8. The numbers of cracks counted in each field of view, n211, n221, n231, n212, n222, and n232, were added together to obtain the total number of cracks in the observed gas flow path, n2 (= n211 + n221 + n231 + n212 + n222 + n232).

[0113] Before observing the cross sections of the gas flow path at depths of 1 mm, 2 mm, and 3 mm with an optical microscope, they were etched by immersing them in an etching solution, known as Secco solution, which is made of dichromic acid and hydrofluoric acid, and the etching depth was 5 μm. The total number of cracks, n2, for each sample is shown in Table 1.

[0114] (surface roughness inside the gas passage) An arbitrary gas flow path was cut at the location of the two second wall portions, and the arithmetic mean roughness Ra of an arbitrary first wall portion of the two first wall portions that appeared was measured. This measurement was performed using a surface roughness measuring instrument (model number: SURFTEST SV-3200) manufactured by Mitutoyo Corporation. With the stylus in contact with the first wall portion, it was moved in the thickness direction of the electrode plate, with a linear distance of 4 mm as the measurement range. Three measurements were performed, and the arithmetic mean roughness Ra was calculated for each. The average value m1 of these arithmetic mean roughnesses Ra was used as an index of the surface roughness of the sample gas flow path. Table 1 shows the average value m1 of the surface roughness (arithmetic mean roughness) Ra of the gas flow path of each sample.

[0115] (Evaluation of particle count) Under the conditions below, etching gas was introduced from the upstream gas flow path of the cooling plate through the gas flow path of the electrode plate into the plasma generation region, plasma was generated by applying voltage, and wafers were etched continuously for one hour, and the number of particles generated during this process was counted.

[0116] The plasma etching conditions are as follows: Wafer size: φ150mm Pressure inside the chamber: 3Pa Etching gas composition: Ar: 200 sccm, CF4: 100 sccm, O2: 5 sccm High frequency power: HF 1200W, LF 150W Note that sccm is an abbreviation for standard cc / min, and refers to the flow rate (cc) per minute normalized at 1 atm (atmospheric pressure 1013 Pa) and a constant temperature such as 0°C or 25°C.

[0117] The number of particles was determined by counting particles of 0.5 μm or larger adhering to the silicon wafer using a microscope. The number of particles obtained during plasma etching using each sample is shown in Table 1.

[0118] The breaking strength was also measured. Five strength evaluation specimens (10 mm wide x 40 mm long) were taken from each silicon plate (electrode plate) with holes drilled, each large enough to fit one hole. The breaking strength was measured at room temperature using a Shimadzu AG-X autograph, and the average value was calculated. A silicon plate (electrode plate) with the same shape but no holes drilled was also prepared as a comparison specimen, and was measured in the same way as the test specimens. Those with a breaking strength of 50% or more compared to the comparison specimen were rated as "good," and those with a breaking strength of less than 50% were rated as "poor," as shown in Table 1.

[0119] [Table 1]

[0120] In the electrode plates of Examples 1 to 13, even though the gas flow paths were formed as slits with high aspect ratios, each gas flow path was formed by either milling, wire electrical discharge machining, or die-sinker electrical discharge machining, and chipping was three or less. Because processing damage to the inlets and outlets, which has a significant impact on particle generation, was reduced in this way, plasma etching using the electrode plates of Examples 1 to 13 was able to sufficiently suppress particle generation, allowing for suitable plasma processing of wafers. The breakdown strength was also good.

[0121] Furthermore, in Examples 1 to 10, 12, and 13, in addition to having three or fewer chips, the average surface roughness m1 was 3.2 μm or less, which enabled further reduction in particle generation compared to Example 11. Among these samples, Examples 1 to 5, 7 to 10, 12, and 13 also had three or fewer cracks, which enabled further reduction in particle generation compared to Examples 6 and 11.

[0122] In the electrode plates of Comparative Examples 1 to 3, the gas flow paths are formed by water jets.

[0123] In Comparative Example 1, the aspect ratio of the slit-shaped gas flow path was 25, but there were five chippings and six cracks, and the average surface roughness m1 was 4.8 μm, indicating that the gas flow path had significant processing damage from the manufacturing process. Therefore, plasma etching using the electrode plate of Comparative Example 1 generated a large number of particles. It can be seen that processing damage to the gas flow path processed with a water jet cannot be reduced to a level that allows suitable plasma processing, even if etching and finishing processes are performed.

[0124] The electrode plate of Comparative Example 2, like the electrode plate of Comparative Example 1, had slit-shaped gas flow paths with an aspect ratio of 25, but had 10 chippings, 5 cracks, and an average surface roughness m1 of 4.2 μm, indicating that there was a lot of processing damage remaining from forming the gas flow paths, and many particles were also generated.

[0125] The electrode plate of Comparative Example 3 has a higher aspect ratio of 40 compared to the electrode plates of Comparative Examples 1 and 2, and the ratio r max is the ratio r of Comparative Examples 1 and 2 max Compared to the previous example, the condition has worsened. There were also 10 chips, 5 cracks, and the average surface roughness m1 was 4.8 μm. These remaining processing damages caused a large amount of particles to be generated. In Table 1, the number of particles is so large that it has not been measured and is abbreviated by indicating it as a "-" (hyphen). Furthermore, all of the comparative examples had insufficient breaking strength due to the presence of chipping and cracks and poor shape precision, and were rated "poor."

[0126] In addition, examples were also produced in which a bent section or a cross-sectionally changing section was formed midway through the gas flow path. The gas flow path of Example 21 is formed perpendicular to the second surface 302 on the outlet side, and from the intermediate bend to the inlet side, it is inclined at an angle of 20° with respect to the plate thickness direction. The gas flow path of Example 22 is formed as a slit-shaped flow path overall, but the slit-shaped flow path on the inlet side is formed to have a smaller cross-sectional area than the slit-shaped flow path on the outlet side. The gas flow path of Example 23 is the opposite of Example 22, in that the slit-shaped flow path on the inlet side is formed to have a larger cross-sectional area than the slit-shaped flow path on the outlet side. The gas flow path of Example 24 has two round narrow holes on the inlet side and a slit-shaped flow path on the outlet side. These examples were also evaluated in the same manner as in Table 1. These results are shown in Table 2.

[0127] [Table 2]

[0128] In each example in Table 2, the aspect ratio of the slit-shaped flow path at the outlet was 10 or more and 80 or less, and the average total number of chippings was 3 or less. In addition, the average value m1 of the arithmetic mean roughness Ra was 3.2 μm or less, the total number of cracks was 1 or less, and the number of particles generated was small. The fracture strength also showed good results. [Explanation of symbols]

[0129] 1. Plasma etching equipment (plasma processing equipment) 3 Electrode plate (silicon electrode plate) 301 Front page 302 Second side 11 Gas flow path 111 Entrance 111A long edge 111B Short edge 112 Exit 112A long edge 112B Short edge 113A First wall section 113B Second wall section 20 Chipping 30 Crack 201,202,203,211,215,221 Gas flow path 204 Bend 205A First wall section 213 Round small hole 214,218,224 Cross-sectional change section 215 Gas flow path 212,216,217,222,223 Slit-shaped channel D1 Thickness direction D2 Longitudinal direction D3 Short side direction

Claims

1. the gas passage is formed in a plate shape from silicon and has a first surface and a second surface that are parallel to each other and are circular, and the gas passage penetrates in a plate thickness direction from the first surface to a second surface located opposite the first surface, and is provided at four or more different angular positions around the center of the plane near the center and near the periphery of the plane, at least a portion of the gas flow path that opens to an outlet of the second surface is formed as a slit-shaped flow path having an opening end that is made up of a pair of long edges that are parallel to each other along a surface direction of the second surface and arc-shaped short edges that connect the ends of the long edges, The slit-shaped flow path is formed such that an aspect ratio (C / A) of 10 or more and 80 or less is obtained by dividing a depth C from the outlet by a slit width A, which is the distance between the long edges, and an average value n1 of the total number of chippings having a width of 0.1 mm or more formed at the opening end at the outlet of the gas flow path is 3 or less per slit-shaped flow path (n1≦3).

2. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the gas flow path is formed by selecting any one of two roughness confirmation flow path segments formed by dividing the slit-shaped flow path at the short edge, and the average value m1 of the arithmetic mean roughness Ra measured in the plate thickness direction in a first wall surface portion extending from the long edge included in the selected roughness confirmation flow path segment is 3.2 μm or less.

3. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the gas flow path is formed by selecting any one of two flow path segments formed by dividing the gas flow path at the long edge, and observing six fields of view with a radius of 0.3 mm centered on points 1 mm, 2 mm, and 3 mm deep from the outlet in each cross section of the first wall surface portion extending from the two long edges included in the selected flow path segment, the total number n2 of cracks having a length of 0.05 mm or more included in the six fields of view is 1 or less.

4. When the slit-shaped flow path is formed over the entire length of the gas flow path, the distance between the long edges of the inlets of the first surface of the gas flow path is a1, the distance between the long edges of the outlets is a2, the maximum distance between the short edges of the inlets is b1, and the maximum distance between the short edges of the outlets is b2, then:

2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the gas flow passage has a ratio r1 of the following formula (1) and a ratio r2 of the following formula (2) of 0.01 or less: [Equation 1] where a1 is the smallest spacing between the long edges of the inlet, a2 is the smallest spacing between the long edges of the outlet, b1 is the largest spacing between the short edges of the inlet, and b2 is the largest spacing between the short edges of the outlet.

5. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the slit-shaped flow passage is inclined with respect to the thickness direction of the plate.

6. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the difference between the distance between said long edges at said outlet and the diameter of an imaginary circle along said short edges is 0.05 mm or less.

7. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the gas flow path is bent at a bending portion at a midpoint in the plate thickness direction, and the slit-shaped flow path is formed at least from the bending portion to the outlet.

8. 2. The silicon electrode plate for a plasma processing apparatus according to claim 1, wherein the gas flow path comprises the slit-shaped flow path and an inlet-side flow path that opens to an inlet on the first surface, is connected to the slit-shaped flow path, and has a cross section different from the cross section of the slit-shaped flow path.

9. a through-hole forming step of forming a plurality of through-holes in a disk-shaped silicon substrate, the through-holes extending in a thickness direction from a circular first processed surface to a second processed surface located opposite to the first processed surface; an etching step of immersing the base plate that has undergone the through-hole forming step in an etching solution to etch it; A finishing process for finishing the first processed surface and the second processed surface of the base plate that has undergone the etching process, The through hole forming step includes: a slit hole forming step of forming at least a portion of the through hole that opens onto the second processing surface into a slit hole having an opening end that is made up of a pair of long edges that are parallel to each other along a surface direction of the second processing surface and an arc-shaped short edge that connects the ends of the long edges, The slit hole forming step includes: a round hole forming step of forming two or more round holes from the second processed surface; a groove machining step of forming a groove connecting both of the round holes by feeding a rotary tool having a side blade laterally in a direction connecting the two or more round holes.

10. The slit hole is formed over the entire length of the through hole, and the slit hole forming step is performed by replacing the round hole forming step and the groove processing step. a wire penetration step of forming a wire insertion hole that penetrates from the first processing surface to the second processing surface; 10. The method for manufacturing a silicon electrode plate for a plasma processing apparatus according to claim 9, further comprising an electric discharge machining step of passing an electric discharge wire through the through-hole and discharging the electric discharge wire to move the base plate and the electric discharge wire relatively in a surface direction of the base plate, thereby forming the slit hole.

11. The slit hole forming step is performed by replacing the round hole forming step and the groove processing step.

10. The method for manufacturing a silicon electrode plate for a plasma processing apparatus according to claim 9, further comprising a step of performing die-sinking electrical discharge machining in which an electrode shaped to the inside shape of the slit hole is fed in the thickness direction from the second machining surface of the base plate.

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