JP2013016532A - Method of manufacturing silicon parts, and silicon parts for etching process apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize selection of silicon scraps which is used in manufacturing silicon parts for an etching process apparatus.SOLUTION: A method of manufacturing silicon parts for an etching process apparatus recycles silicon scraps to manufacture silicon parts to be disposed in the etching process apparatus. The method includes the steps of: measuring dopant content in the silicon scraps; calculating an input amount of the silicon scraps, silicon raw material, and dopant based on the measured dopant content and a target value; melting the calculated amount of the silicon scraps, the silicon material, and the dopant by inputting them into a crucible; cooling and solidifying the molten material; producing polycrystal silicon by removing a portion thereof including at least an upper surface of the solidified material; and manufacturing the silicon parts from the produced polycrystal silicon.

Description

  The present invention relates to a method for manufacturing a silicon part and a silicon part for an etching apparatus.

  In the etching processing apparatus, various silicon films on a silicon semiconductor wafer (hereinafter referred to as a wafer) are etched. For various parts arranged in the etching processing apparatus, silicon parts are used so as not to affect the process. For example, in an etching processing apparatus, silicon parts are arranged on a focus ring surrounding a wafer placed on a mounting table. In addition, silicon parts are also arranged on the electrode plate of the counter electrode provided to face the mounting table.

  Since silicon parts placed in the etching processing apparatus are exposed to plasma during the process, they are consumed and deteriorated, and the shape thereof gradually changes. If you continue to use silicon parts that have undergone changes, process reproducibility will deteriorate. Therefore, a silicon part that has been worn out and deteriorated to some extent is considered to have reached the end of its life and is discarded as industrial waste. On the other hand, since expensive single crystal silicon has been conventionally used for such silicon parts for an etching processing apparatus, it has been a factor in increasing the cost of consumables associated with the running of the etching processing apparatus.

  Therefore, in recent years, a polycrystalline silicon material has been used for silicon parts. For example, Patent Document 1 proposes a manufacturing method for recovering silicon waste material and manufacturing polycrystalline silicon from the recovered silicon waste material.

JP 2011-71361 A

  However, even when polycrystalline silicon is manufactured by the above-described manufacturing method, for example, a high-purity and expensive silicon material of 99.99999999% (hereinafter also referred to as 11N) has been used. Therefore, there is a limit to reducing the material cost even when a silicon part is manufactured using a polycrystalline silicon material instead of a single crystal.

  In view of the above-described problems, the present invention provides an etching process capable of reducing material costs and effectively utilizing resources by optimizing the selection of silicon waste materials used for silicon parts for etching processing apparatuses. It is an object of the present invention to provide a method for manufacturing a silicon part for an apparatus and a silicon part.

  In order to solve the above-described problems, according to an aspect of the present invention, there is provided a method for manufacturing a silicon part for an etching processing apparatus, in which a silicon part disposed in the etching processing apparatus is regenerated from a silicon waste material. The step of putting the silicon waste material or the material containing the silicon waste material into a crucible and melting, the step of cooling and solidifying the melted material, and the part including at least the upper surface of the solidified material is excised There is provided a method for producing a silicon part, comprising the steps of producing polycrystalline silicon, and producing the silicon part from the produced polycrystalline silicon.

  The silicon waste material may be put into a crucible after washing with a predetermined etching solution.

  The silicon waste material or the material containing the silicon waste material may be put into the crucible in which a predetermined type of release material is applied to the inner wall.

  Depending on the type of mold release material, the solidified material is cut so that the cut portion is 20 mm or less from the surface, or the cut portion is 15 mm or less from the surface. The upper surface of the material may be cut so that the surface other than the upper surface is blasted.

The release material may be any one of Si ₃ N ₄ , SiC, SiO ₂ , and SiN.

  The material containing the silicon waste material is composed of the input amount of the silicon waste material, the input amount of the silicon raw material, and impurities, and the content rate of the impurities measured by measuring the content ratio of the recovered silicon waste material. And the target value of the resistance value of the final product, the input amount of the silicon waste material input to the crucible, the input amount of the silicon raw material, and the input amount of the impurity may be determined.

  The target value of the resistance value of the final product may be any value in the range of 1 to 4 Ωcm.

  In order to solve the above-mentioned problem, according to another aspect of the present invention, boron-doped P-type polycrystalline silicon having a purity of 99.999% or more or a purity of 99.999% A silicon part for an etching processing apparatus manufactured from polycrystalline silicon produced by regenerating a material containing the above silicon waste material is provided.

  The silicon part may be manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that a resistance value is 0.01 to 100 Ωcm.

  The silicon part may be manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that a resistance value is 1 to 4 Ωcm.

  The silicon part may be manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that a resistance value is 60 to 90 Ωcm.

  The silicon part may be manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that the upper limit of the resistance value is 0.02 Ωcm or less.

  As described above, according to the present invention, it is possible to reduce material costs and to effectively use resources by optimizing the selection of silicon waste materials used for silicon parts for etching processing apparatuses. A method of manufacturing a silicon part for an etching processing apparatus and a silicon part for an etching processing apparatus can be provided.

It is a flowchart which shows the manufacturing method of the silicon components for the etching processing apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the measurement process in the manufacturing method which concerns on one Embodiment. It is the longitudinal cross-sectional view which showed the manufacturing apparatus which concerns on one Embodiment. It is a figure for demonstrating the manufacturing method which concerns on one Embodiment. It is a figure which shows the resistance value of the polycrystalline silicon material which concerns on one Embodiment, and a polycrystalline silicon material. It is a longitudinal cross-sectional view of the etching processing apparatus which has arrange | positioned the silicon parts which concern on one Embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the following, a method for manufacturing a silicon part for an etching apparatus according to an embodiment of the present invention will be described, and then an etching apparatus using the silicon part will be described.

(Introduction)
Silicon components are used as various components arranged in the etching processing apparatus. For example, as shown in FIG. 6, in the etching processing apparatus 10, silicon parts are used for the focus ring 21 surrounding the wafer W mounted on the mounting table 20 and the ground ring 22 surrounding the insulating plate 12. Yes. Silicon parts are also arranged on the electrode plate 31 of the counter electrode 30 facing the mounting table 20.

  A single crystal or polycrystal made of polysilicon (Poly Si) is used for the silicon part. Polysilicon manufacturers for etching processing equipment often produce polycrystals having a purity of about 99.9999999 (9N) to 99.99999999999 (11N). On the other hand, polysilicon manufacturers for solar use often produce polycrystals having a purity of about 99.9999 (5N) to 99.9999999 (9N). Generally, polycrystals having a purity of 99.9999 (6N) or more when silicon waste material is not used and 99.999 (5N) or more when silicon waste material is used (in the case of a recycled product) are generated.

  In the following embodiments, P-type polycrystalline silicon doped with boron is produced by regenerating a silicon waste material having a purity of 5N or more or a material containing silicon waste material having a purity of 5N or more to produce polycrystalline silicon. And used for silicon parts for an etching apparatus.

  Silicone scrap materials such as used focus ring 21, ground ring 22, electrode plate 31, etc. can be used in the method of manufacturing silicon parts for the etching processing apparatus.

  Specific examples of the silicon waste material include those generated in the process of manufacturing silicon parts for an etching processing apparatus. For example, as shown in FIG. 4, an inner cylindrical portion 100c pulled out when manufacturing the top tail 100a and the bottom tail 100b, the focus ring 21 and the ground ring 22 of the ingot 100 manufactured when manufacturing the silicon ingot. The outer peripheral portion 110 of the ingot 100 can be used. Also, silicon scraps that are damaged during the production, such as scratches or chips, those whose dimensions are out of specification, and those whose electrical characteristics such as resistance value are out of specification, can be used.

  In the present embodiment, a silicon part is manufactured using a material obtained by mixing a silicon raw material that is a virgin material with a silicon waste material that is a recycled material as described above. The manufacturing method will be described with reference to the flowchart of FIG.

  Silicon parts can be manufactured using a manufacturing apparatus 50 shown in FIG. In the manufacturing apparatus 50, a quartz crucible 55 is built in a chamber C, and carbon heaters 60 are provided above, below, and laterally. In the crucible 55, a raw material of polysilicon including silicon waste material is charged. The carbon heater 60 is used for dissolving polysilicon raw materials. The manufacturing apparatus 50 is also provided with a cooling mechanism (not shown) so as to cool the raw material in the crucible 55.

(Manufacturing method of silicon parts for etching processing equipment)
<1. Waste material recovery process>
In the present embodiment, first, silicon waste materials such as the used focus ring 21, the ground ring 22, and the used electrode plate 31 as described above are collected (step 105).

<2. Cleaning process>
Next, the recovered silicon waste material is washed (step 110). Specifically, when the etching solution is an acid, etching is performed with a mixed solution of HF, HNO _3, and CH ₃ COOH. When the etching solution is alkaline, etching is performed with KOH or a mixed solution of KOH and H ₂ O ₂ . Contamination on the outside of the silicon waste material needs to be removed by 60 microns or more in the case of acid etching, and 30 microns or more in the case of alkali etching.

  In addition, the silicon | silicone waste material to be used does not originate in the used silicon | silicone components, but the said washing | cleaning process can be abbreviate | omitted in the case of the silicon waste material which generate | occur | produced in the middle of manufacture.

<3. Measurement process>
Next, a measurement process for measuring the electrical characteristics (in this embodiment, electrical resistance) and mass of the cleaned silicon waste material and determining the content of impurities such as boron in the silicon waste material is performed (step 115). A specific measurement process is shown in FIG. In silicon parts for etching processing apparatuses, there are differences in electrical characteristics (for example, electrical resistance values) required from the nature of the parts.

  For example, as shown in FIG. 5, in the case of a P-type polycrystalline silicon material doped with boron, a focus ring 21 (FR), an electrode plate 31 (CEL), a ground ring 22 (G-Ring), a ring protect, etc. The target value of electrical resistance that can be applied to almost all silicon parts for etching processing apparatuses such as (Ring Protect) is 0.01 to 100 Ωcm (Case 4).

  Among them, for example, when silicon parts are applied to the focus ring 21 (FR) and the electrode plate 31 (CEL: O-CEL, I-CEL), the target value of the electrical resistance of the final product is 1 to 4 Ωcm. (Case 1).

  Further, for example, when a silicon part is applied to the focus ring 21 (FR), the target value of the electrical resistance of the final product may be greater than 0 Ωcm and 0.02 Ωcm or less (Case 2).

  For example, when a silicon part is applied to the electrode plate 31 (CEL), the target value of the electrical resistance of the final product may be 60 to 90 Ωcm (Case 3).

  In this way, it is desirable to change the best resistance value (target value) depending on the position and function of the silicon part attached to the etching processing apparatus 10.

(Measuring method)
In FIG. 2, first, the content of impurities in the silicon waste material is measured (step 205). A predetermined amount of impurities such as boron is added when an ingot is manufactured according to an electrical resistance value or the like required for each silicon part for an etching processing apparatus. In the above measurement step, the content of this impurity is determined by measuring the electrical resistance value with a four-probe measuring instrument or the like and measuring the mass with a precision weighing or the like.

  Next, based on the impurity content obtained in the above measurement step and the target value of the electrical characteristics of the final product (electrical resistance in this embodiment), the amount of silicon waste input, the amount of silicon raw material input, the impurity Is determined (step 210).

As described above, silicon parts for an etching processing apparatus have different electrical characteristics such as an electric resistance value required from the position and function of the parts. In the following description, as shown in the upper diagram of FIG. 5, it is a P-type polycrystalline silicon doped with boron, and the target value of the resistance value is any value in the range of 1 to 4 Ωcm, and the purity is Polycrystalline silicon which does not contain 99.999% (5N) or more of Si ₃ N ₄ , SiC, SiO _{2 and the} like is regenerated as a silicon part.

  Based on the target value of the electrical resistance, the input amount of silicon waste material, the input amount of silicon raw material, and the input amount of impurities are determined from the weight of the silicon waste material and the content of impurities. In addition, when the amount of silicon is satisfied with only silicon waste material, the amount of silicon raw material input may be zero. In addition, when the amount of impurities is satisfied only by the impurities contained in the silicon waste material, the amount of injected impurities may become zero.

<3. Input and dissolution process>
Returning to FIG. 1, next, the determined amounts of silicon waste, silicon raw material, and impurities (dope material) are charged into the crucible 55 (step 120: see FIG. 4A), and 1400 ° C. by a carbon heater. The material in the crucible 55 is melted by heating to the extent (step 125: see FIG. 4B).

Next, the material in the crucible 55 is cooled by a cooling mechanism (not shown) provided in the manufacturing apparatus 50 (step 130: see FIG. 4C). Since the mold release material is applied to the inner wall of the crucible 55, the crucible 55 and the silicon material are easily separated when contracting when the silicon material in the crucible is hardened. Thereby, the crack of the silicon material when the silicon material is solidified can be prevented. The release material can be selected from any of Si ₃ N ₄ , SiC, SiO ₂ , and SiN. It is necessary to select a release material that does not become a particle source in the etching processing apparatus.

Next, the crucible 55 is broken to take out the regenerated silicon material from the silicon waste material, and the surface is cut (step 135: see D in FIG. 4). There is a possibility that Si ₃ N ₄ , SiC, SiO ₂ , SiN and the like are contained in the vicinity of the surface of the silicon material due to the action of the release material. Therefore, the surface is cut so that the regenerated silicon material does not contain inclusions as a particle source, and the polycrystal of the silicon material near the crucible 55 is not used. Thereby, the mold release material applied to the crucible 55 mixed in the manufacturing process can be removed from the regenerated silicon material.

Here, in order to take the release material, the entire surface (six surfaces) of the regenerated silicon material is cut by 20 mm. The cutting of the solidified silicon material is preferably changed according to the type of the release material. For example, when the type of the release material is Si ₃ N ₄ , the entire surface of the silicon material is cut so that a portion to be cut is 20 mm or less from the surface.

For example, when the type of the release material is SiO ₂ , only the upper surface of the silicon material is cut so that the portion to be cut is 15 mm or less from the surface on the upper surface of the silicon material. Since the upper surface of the material is dirty in this way, it is cut by 15 mm, but the surface other than the upper surface is cut by 30 μm by blasting.

  Thereby, the polycrystalline silicon of purity 5N or more can be produced | generated from silicon waste material. Then, the silicon ingot manufactured in this process is machined to obtain a predetermined shape, thereby manufacturing a silicon part for a new etching processing apparatus, such as a silicon focus ring or a silicon electrode plate. Can do.

As described above, in the present embodiment, silicon parts applicable to the etching processing apparatus are regenerated by optimizing the selection and manufacturing method of silicon waste materials used for the silicon parts for the etching processing apparatus. can do.

  In particular, in this embodiment, it is possible to regenerate used silicon parts for etching processing apparatuses and the like that have been discarded as industrial waste, and to manufacture new silicon parts for etching processing apparatuses. According to this, since silicon waste is included in the raw material, material costs can be reduced and resources can be effectively utilized. Therefore, it is possible to reduce the cost of consumables for the etching processing apparatus as compared with the conventional case, reduce the amount of industrial waste generated, and improve the environment.

  Currently, the size that can be produced with a single crystal is up to approximately 460 mm. In the future, the required wafer size will be larger and larger than the size that can be produced by a single crystal. In this case, polycrystal must be used. Polycrystals are cheaper than single crystals. Furthermore, in this embodiment, not only the polysilicon waste material for the etching processing apparatus but also the polysilicon waste material for the solar panel can be used as the silicon waste material. Thus, by expanding the material selection range other than single crystal silicon, it is possible to more effectively use recycled materials and reduce material costs.

(Etching processing equipment)
Finally, the configuration of an etching processing apparatus equipped with newly regenerated silicon parts will be described with reference to FIG. FIG. 6 is a longitudinal sectional view of the etching processing apparatus. The etching processing apparatus 10 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates face each other vertically and are connected to a plasma forming power source.

  The etching processing apparatus 10 has a processing chamber 11 made of, for example, aluminum whose surface is anodized and formed into a cylindrical shape. The processing chamber 11 is grounded. A substantially cylindrical susceptor support 13 for mounting the wafer W is provided on the bottom of the processing chamber 11 via an insulating plate 12 such as ceramics. On the susceptor support 13, a mounting table 20 that also serves as a lower electrode is provided.

  A refrigerant chamber 14 is provided inside the susceptor support 13, and the refrigerant is introduced into the refrigerant chamber 14 via a refrigerant introduction pipe, circulated, and discharged from the refrigerant discharge pipe. Then, the cold heat is transferred to the wafer W through the mounting table 20, and the wafer W is adjusted to a desired temperature.

  The mounting table 20 is formed in a disk shape having a convex upper central portion, and an electrostatic chuck 15 having a circular shape and the same diameter as the wafer W is provided thereon. The electrostatic chuck 15 electrostatically attracts the wafer W by, for example, Coulomb force by applying a desired DC voltage to the electrodes disposed between the insulating materials.

  A gas passage 16 for supplying a heat transfer medium (for example, He gas) is formed on the back surface of the wafer W in the insulating plate 12, the susceptor support base 13, the mounting base 20, and the electrostatic chuck 15. The cold heat of the mounting table 20 is transmitted to the wafer W through the heat transfer medium so that the wafer W is maintained at a predetermined temperature.

  An annular focus ring 21 is disposed at the upper peripheral edge of the mounting table 20 so as to surround the wafer W mounted on the electrostatic chuck 15. A ground ring 22 is disposed on the outer periphery of the insulating plate 12. The focus ring 21 and the ground ring 22 are made of silicon, and the silicon focus ring 21 and the ground ring 22 are one of silicon parts for an etching processing apparatus to which the regeneration method according to this embodiment is applied. .

  An upper electrode 30 is provided above the mounting table 20 so as to face the mounting table 20 in parallel. The upper electrode 30 is supported on the upper part of the processing chamber 11. The upper electrode 30 includes an electrode plate 31 and an electrode support 32 made of a conductive material that supports the electrode plate 31. The electrode plate 31 has a number of ejection holes and forms a surface facing the mounting table 20. In the etching processing apparatus 10, the electrode plate 31 is made of silicon, and the silicon electrode plate 31 is one of silicon parts for the etching processing apparatus to which the regeneration method according to the present embodiment is applied. . Note that a DC power source (not shown) is connected to the upper electrode 30. A direct current supplied from a direct current power source is applied to the upper electrode 30 and flows to the ground through the ground ring 22.

  A gas inlet is provided at the center of the electrode support 32 in the upper electrode 30, and a processing gas supply source 33 is connected to the gas inlet. An etching gas or the like for plasma etching processing is supplied from the processing gas supply source 33.

  An exhaust device 35 is connected to the bottom of the processing chamber 11 via an exhaust pipe 34. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the processing chamber 11 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. A gate valve 36 is provided on the side wall of the processing chamber 11, and the wafer W is transferred to and from an adjacent load lock chamber (not shown) with the gate valve 36 opened.

  A first high-frequency power source 40 is connected to the upper electrode 30, and a matching device 41 is inserted in the power supply line. The first high frequency power supply 40 has a frequency in the range of 27 to 150 MHz, for example. In this way, by applying high frequency high frequency power, it is possible to form a high density plasma in a preferable dissociated state in the processing chamber 11.

  A second high-frequency power source 50 is connected to the mounting table 20 as the lower electrode, and a matching unit 51 is inserted in the power supply line. The second high frequency power supply 50 has a lower frequency range than the first high frequency power supply 40. By applying high-frequency power having a frequency in such a range, an appropriate ion action can be given without damaging the wafer W that is the substrate to be processed. The frequency of the second high frequency power supply 50 is preferably in the range of 1 to 20 MHz, for example.

  The example of the etching processing apparatus 10 to which the silicon focus ring 21, the silicon ground ring 22, the silicon electrode plate 31, and the like formed from the regenerated polycrystalline silicon have been described above.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can make various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the case where the silicon parts for the etching processing apparatus are the silicon focus ring, the silicon ground ring, and the silicon electrode plate has been described. However, other silicon parts for the etching processing apparatus are used. Can be applied in the same manner. Moreover, in the said embodiment, although content of an impurity was calculated | required by the measurement of electrical resistance and mass, you may obtain | require content of an impurity from another electrical property.

  In addition, traceability management is important in the recycling of silicon parts using silicon scrap. For example, the manufacturing process has identification information of silicon waste material and silicon raw material after cleaning silicon waste material, and identifies which silicon waste material (recycled material) and which silicon material (virgin material) is used. Can be done.

DESCRIPTION OF SYMBOLS 10 Etching processing apparatus 11 Processing chamber 20 Mounting stand 21 Focus ring 22 Ground ring 30 Upper electrode 31 Electrode plate 50 Manufacturing apparatus 55 Crucible 60 Carbon heater 100 Ingot C Chamber

Claims (12)

A silicon part manufacturing method for an etching processing apparatus for regenerating and manufacturing a silicon part disposed in an etching processing apparatus from silicon waste material,
A step of charging the silicon waste material or the material containing the silicon waste material into a crucible, and melting;
Cooling and solidifying the dissolved material;
Cutting the portion including at least the upper surface of the consolidated material to produce polycrystalline silicon;
Producing the silicon part from the generated polycrystalline silicon;
The manufacturing method of the components made from silicon | silicone characterized by the above-mentioned.   2. The method of manufacturing a silicon part according to claim 1, wherein the silicon waste material is poured into a crucible after being washed with a predetermined etching solution.   3. The silicon component according to claim 1, wherein the silicon waste material or the material containing the silicon waste material is put into the crucible in which a predetermined type of release material is applied to an inner wall. 4. Production method.   Depending on the type of mold release material, the solidified material is cut so that the cut portion is 20 mm or less from the surface, or the cut portion is 15 mm or less from the surface. 4. The method of manufacturing a silicon part according to claim 3, wherein the upper surface of the material is cut so that the surface other than the upper surface is blasted. 5. The method for manufacturing a silicon part according to claim ₃ , wherein the release material is any one of Si ₃ N ₄ , SiC, SiO ₂ , and SiN. The material containing the silicon waste material consists of the input amount of the silicon waste material, the input amount of the silicon raw material, and impurities,
Measure the content of impurities in the recovered silicon waste material, and based on the measured impurity content and the target value of the resistance value of the final product, the amount of silicon waste material to be charged into the crucible, and the silicon raw material The method for manufacturing a silicon part according to claim 1, wherein an input amount of said impurity and an input amount of said impurity are determined.   The method for manufacturing a silicon part according to claim 6, wherein the target value of the resistance value of the final product is any value in the range of 1 to 4 Ωcm.   P-type polycrystalline silicon doped with boron, which is produced by regenerating a silicon waste material having a purity of 99.999% or more or a material containing silicon waste material having a purity of 99.999% or more Silicon parts for etching equipment manufactured from   The etching processing apparatus according to claim 8, wherein the silicon part is manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that a resistance value is 0.01 to 100 Ωcm. Silicon parts for use.   The said silicon | silicone components are manufactured from the polycrystal silicon produced | generated by reproducing | regenerating the silicon waste material or the material containing silicon waste material so that a resistance value may be 1-4 ohm-cm. Silicon parts.   The said silicon | silicone components are manufactured from the polycrystal silicon produced | generated by reproducing | regenerating the silicon waste material or the material containing silicon waste material so that a resistance value may be set to 60-90 ohm-cm. Silicon parts.   The etching process according to claim 8, wherein the silicon part is manufactured from polycrystalline silicon produced by regenerating a silicon waste material or a material containing silicon waste material so that an upper limit of a resistance value is 0.02 Ωcm or less. Silicon parts for equipment.

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