Electrode plate for plasma processing apparatus and method for manufacturing same

Abstract

To provide a thick electrode plate capable of suppressing variation in resistivity value during plasma processing, performing uniform plasma processing, and achieving a long life.SOLUTION: A manufacturing method for an electrode plate for a plasma processing device includes a slicing step of forming a base plate made of silicon with a thickness of 15 mm or more and 35 mm or less, a vent hole forming step for forming a plurality of vent holes penetrating the base plate so that the ratio of the sum of the volumes of the vent holes to the volume of the base plate is 0.04 or more and less than 1.0, a heat treatment step for applying a heat treatment by cooling at a rate of 100°C / minute or more and 180°C / minute or less after heating the base plate in which the vent holes are formed to a temperature of 550°C or more.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Plasma processing apparatuses, such as plasma etching apparatuses and plasma CVD apparatuses, used in semiconductor device manufacturing processes, are configured such that a pair of electrodes connected to a high-frequency power source are arranged, for example, facing each other in a vertical direction within a chamber, with a substrate to be processed placed on the lower electrode, and a high-frequency voltage is applied while a processing gas is passed toward the substrate to be processed through ventilation holes formed in the upper electrode to generate plasma, thereby performing processing such as etching on the substrate to be processed.

[0003] The electrode plate used in this plasma processing apparatus is prepared by cutting an ingot made of single crystal silicon, columnar crystalline silicon, or the like into a thin disk shape, and then finishing it through machining such as forming ventilation holes, etching for surface polishing, polishing, etc. Also, in order to perform uniform plasma processing on the substrate to be processed, the electrode plate is required to have little variation in resistivity within its surface.

[0004] Patent Document 1 discloses that when manufacturing an electrode plate made of P-type silicon, the method includes a first heat treatment step in which the silicon material is held at a temperature of 550°C to 700°C for 30 to 120 minutes, and then cooled at a rate of 100°C / min to 180°C / min, and a second heat treatment step in which the silicon material is held at a temperature of 300°C to 350°C for 20 to 30 hours, and then cooled, after the first heat treatment step, and then an air hole forming step and a finishing step to manufacture the electrode plate. In this case, the thickness of the electrode plate is described as 5 mm to 20 mm.

[0005] Patent Document 2 discloses that after forming vent holes in a base plate obtained from a silicon ingot, the base plate is etched to remove surface damage, and then a donor killing process is carried out at a temperature of 400 to 1000° C. to stabilize the resistance. Patent Document 2 does not disclose the thickness of the resulting electrode plate or the diameter of the vent holes.

[0006] Patent Document 3 discloses that a porous silicon carbide sintered body substrate (base plate) made mainly of α-SiC with an open porosity of 10-40% and a 6H-type crystal structure is drilled to form a large number of gas introduction holes (vent holes), and then the sintered body is heat-treated in an inert gas atmosphere at 1500-2300°C for 10-600 minutes to re-sinter the grain boundary parts weakened by the drilling on the inner wall of the holes, thereby suppressing the generation of particles. It is described that this electrode plate has a diameter of 100-300 mmφ and a thickness of 1-5 mmt, and that the resistivity is preferably 10 Ω·cm or less. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-133537 A [Patent Document 2] Special Publication No. 2010-519763 [Patent Document 3] JP 2001-7082 A Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional electrode plates have a thickness of 5 mm to 20 mm as described in Patent Document 1, but in recent years, there has been a demand to increase the thickness of electrode plates in order to extend their lifespan. In such cases, it is difficult to make the resistivity uniform using conventional methods.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide an electrode plate for a plasma processing apparatus and a manufacturing method thereof that can suppress variations in resistivity during plasma processing, even in the case of a thick electrode plate, thereby enabling uniform plasma processing and achieving a long service life. [Means for solving the problem]

[0010] The method for manufacturing an electrode plate for a plasma processing apparatus of the present invention includes a slicing step of forming a base plate having a thickness of 15 mm or more and 35 mm or less from a silicon ingot, a ventilation hole forming step of forming a large number of ventilation holes penetrating the base plate so that the ratio of the total volume of the ventilation holes to the volume of the base plate is 0.04% or more and less than 1.0%, and a heat treatment step of heating the base plate with the ventilation holes formed therein to a temperature of 550°C or more, and then cooling it at a rate of 100°C / min or more and 180°C / min or less.

[0011] In order to suppress the variation in the resistivity, the oxygen donors can be reduced and the resistivity stabilized by rapidly cooling after heating. If the electrode plate is thick, the effects of heating and rapid cooling do not easily reach the inside. In this manufacturing method, the base plate is heat-treated after the formation of ventilation holes at a predetermined volume ratio. The presence of the ventilation holes at a predetermined volume ratio allows the plate to be heated evenly throughout the heat treatment, and the plate can be rapidly cooled throughout the interior. % If the volume ratio is less than 1.0, the effect of heating and quenching does not reach the inside, and the resistivity value is not stable. % If the volume ratio of the vent holes is more than this, the process gas may get around the electrode plate, and particles may be easily generated.The volume ratio of the vent holes is preferably 0.05% or more and 0.8% or less.

[0012] In addition, if the cooling rate during heat treatment is less than 100°C / min, the donor suppression effect is reduced and the resistivity value is not stable. If it exceeds 180°C / min, there is a risk of cracking in the electrode plate. The cooling rate is preferably 110°C / min or more and 180°C / min or less. In addition, it is preferable to apply this method to electrode plates having a thickness of more than 20 mm, and it is particularly effective for electrode plates having a thickness of 25 mm or more. If the thickness of the electrode plate exceeds 35 mm, it becomes difficult to stabilize the resistivity value. Silicon ingots are also produced from single crystal silicon, columnar silicon or polycrystalline silicon.

[0013] In the method for manufacturing an electrode plate for a plasma processing apparatus, it is preferable to have an etching step of etching the surface of the base plate after the heat treatment step. By etching, not only can the processing damage layer be removed, but also an oxide film that may be formed on the surface of the base plate during the heat treatment can be removed, and the generation of particles can be further suppressed.

[0014] The electrode plate for a plasma processing apparatus of the present invention is made of silicon, has a thickness of 15 mm or more and 35 mm or less, and has a ratio of the total volume of the vent holes to the volume of the electrode plate of 0.04. % Above 1.0 % The in-plane variation of resistivity is less than 0.1Ω cm or more The resistivity is 1.5 Ω·cm or less. It is preferable that the variation in resistivity is 3 Ω·cm or less. If the variation in resistivity is small, the plasma generated during plasma processing is stable, which reduces the defective rate of the processed plate and also leads to uniform wear of the electrode plate, which is advantageous for extending the life of the plate. Effect of the Invention

[0015] According to the present invention, even in the case of a thick electrode plate, the variation in resistivity during plasma processing can be suppressed, uniform plasma processing can be performed, and a longer life can be achieved. [Brief description of the drawings]

[0016] [Figure 1] 1A and 1B show an electrode plate for a plasma processing apparatus according to an embodiment of the present invention, in which FIG. [Diagram 2] 4 is a flowchart illustrating a method for manufacturing an electrode plate for a plasma processing apparatus according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an electrode plate for a plasma processing apparatus and a manufacturing method thereof according to the present invention will be described with reference to the drawings. The electrode plate for plasma processing apparatus (hereinafter simply referred to as electrode plate) 11 of this embodiment is formed of single crystal silicon, columnar silicon, or polycrystalline silicon in a disk shape having a thickness of 15 mm to 35 mm and a diameter of 200 mm to 600 mm, as shown in Fig. 1. In addition, this electrode plate 11 has hundreds to thousands of vent holes 21 formed in parallel to each other in the thickness direction at a pitch of several mm to 10 mm. Each vent hole 21 is formed by drilling or laser processing, and the ratio of the total volume of the vent holes 21 to the volume of the electrode plate 11 (hereinafter referred to as volume ratio) is set to 0.04% or more and less than 1.0%. The ends of the vent holes 21 may be chamfered, and the volume is measured including the chamfered parts. Furthermore, the electrode plate 11 has an in-plane variation in resistivity of 1.5 Ω·cm or less.

[0018] Electrode plate 11 configured in this manner is manufactured through, for example, as shown in the flowchart of FIG. 2, an ingot formation process in which a silicon ingot such as single crystal silicon is formed, a slicing process in which the silicon ingot is thinly cut (sliced) into disks to form a plate-shaped base plate, a contour processing process in which the outer periphery of the base plate is cut to form a base plate with a specified outer diameter, an air hole formation process in which a large number of air holes 21 are formed in the base plate after the contour processing, a heat treatment process in which the base plate with air holes 21 formed therein is heat treated, an etching process in which the base plate after the heat treatment is etched, and a finishing process such as polishing the surface after the etching process.

[0019] In the ingot formation step, a silicon ingot having a cylindrical shape, a block shape, or the like is formed from single crystal silicon, columnar crystal silicon, or polycrystalline silicon by a method such as the Czochralski method or a casting method.

[0020] In the slicing process, the material is cut into thin disk-shaped base plates using a diamond band saw, wire saw, etc. After cutting, both sides are ground to reduce the amount of damage caused by the process. In the outer shape processing, the outer shape of the base plate is processed by cutting to form it into a disk shape that will be the outer shape of the intended electrode plate 11.

[0021] In the vent hole forming process, a drill is lowered parallel to the thickness direction from one surface side of the base plate, or a laser is irradiated, to process the vent holes 21 one by one. In this vent hole forming process, several hundred to several thousand vent holes 21 are formed as described above, and the total volume of these vent holes 21 is formed so that the volume ratio of the volume of the base plate to the volume of the base plate is 0.04 or more and less than 1.0. For example, when 606 vent holes 21 with an inner diameter of 0.8 mm are formed in a base plate with a diameter of 380 mm, the volume ratio is 0.27.

[0022] After the plurality of vent holes 21 are formed in the base plate in the vent hole forming step, in the heat treatment step, the base plate with the vent holes 21 formed therein is placed in a heating furnace and heated to a temperature of 550°C or higher in an inert atmosphere such as an argon atmosphere. For example, the base plate is heated to a temperature of 550°C or higher and 1000°C or lower. After maintaining the peak temperature for 4 hours to 16 hours, the base plate is removed from the heating furnace and rapidly cooled by blowing cold air or the like. The cooling rate at that time is 100°C / min or higher and 180°C / min or lower. In particular, when cooling in a temperature range of around 450°C, electrons are released from the oxygen in the base plate, which becomes a donor and causes the resistivity value to vary. Therefore, by passing through that temperature range quickly, the release of electrons is suppressed, and as a result, the variation in the resistivity value is suppressed.

[0023] In this heat treatment process, since a large number of ventilation holes 21 are formed in the base plate in the ventilation hole forming process prior to this, the base plate is heated evenly to the inside during heating, and the entire base plate is rapidly cooled during quenching, effectively suppressing the emission of electrons and suppressing the variation in resistivity. The cooling rate is preferably 110°C / min or more and 180°C / min or less. This heat treatment also has the effect of removing distortions that occur in the preceding slicing and venting steps.

[0024] The etching process is performed by immersing the base plate in an acid etching solution. For example, hydrofluoric acid (HF), nitric acid (HNO3), and acetic acid (CH3COOH) are mixed together to form hydronitric acid-acetic acid. The immersion time in the etching solution is 10 to 95 minutes. An oxide film is formed on the surface by cooling in the heat treatment process in the air, and this is removed in the etching process. In addition, processing damage such as microcracks on the inner surface of the ventilation hole 21 formed in the ventilation hole forming process can also be removed.

[0025] In the finishing process, both sides of the base plate are polished while supplying a slurry (polishing liquid) containing abrasives such as colloidal silica and diamond abrasive grains onto a rotating polishing pad. After polishing, the base plate is washed with running water or the like to be finished as an electrode plate 11. Ultrasonic cleaning may also be performed.

[0026] The electrode plate 11 manufactured in this manner is subjected to a heat treatment process after the vent hole forming process, and since the vent holes 21 are present at a volume ratio of 0.04 or more and less than 1.0, the electrode plate 11 is heated evenly to the inside during the heat treatment and can be rapidly cooled to the inside. This makes it possible to manufacture an electrode plate 11 with a small in-plane variation in resistivity of 1.5 Ω cm or less, and a uniform process can be performed by stable plasma processing. If the volume ratio of the ventilation holes 21 is less than 0.04, the effects of heating and quenching do not easily reach the inside, and the resistivity value is not stable. If the volume ratio is 1.0 or more, the process gas will get around the electrode plate 11, generating particles. The volume ratio of the ventilation holes 21 is preferably 0.05 or more and 0.8 or less. Also, the in-plane variation in resistivity value is preferably 3 Ω cm or less.

[0027] The present invention is not limited to the configuration of the above embodiment, and various changes can be made to the details of the configuration without departing from the spirit of the present invention. All the vent holes 21 may be formed to have the same inner diameter, or the inner diameter may vary depending on the position on the electrode plate 11. Also, the vent holes 21 on the front and back sides of the electrode plate 11 may have different inner diameters. EXAMPLES

[0028] A single crystal silicon ingot was sliced ​​to form a base plate of various thicknesses with an outer diameter of 380 mm, and the electrode plate was fabricated through a vent hole forming process, a heat treatment process, an etching process, and a finishing process. The inner diameter of the vent hole and its volume ratio to the volume of the electrode plate were as shown in Table 1. The vent hole was formed in a straight shape with a uniform inner diameter. The inner diameter was measured by a three-dimensional measuring machine for the opening of the vent hole on the surface of the electrode plate, and the volume was calculated by measuring the thickness of the electrode plate. In addition, an electrode plate without a vent hole was also fabricated for comparison (Comparative Example 2). The heat treatment involved heating to 630° C. and cooling at the cooling rates shown in Table 1. A comparative example was also produced that was not heat treated (Comparative Example 1). For these electrode plates, the in-plane variation in resistivity and the number of particles generated during plasma processing were measured, and the service life was evaluated. The resistivity was measured by the four-probe method with a probe placed on the surface of the electrode plate, and the difference between the maximum and minimum values ​​measured at three points on the surface of the electrode plate was taken as the variation. The number of particles generated was measured by attaching the electrode plate to the sputtering device. Chamber pressure: 10 -1 Torr Etching gas composition: 90sccmCHF3+ 4sccmO2+ 150sccmHe High frequency power: 2kW Vacuum frequency: 20kCycle Sputtering was carried out continuously for 100 hours under the above conditions, and the number of particles was counted using a particle counter. Samples with 100 or more particles were rated as "no good" samples, and samples with less than 100 particles were rated as "good." The service life was judged based on the time of use, with 500 hours of use being rated as "good" and less than 500 hours being rated as "poor." The overall evaluation was as follows: "A" if the resistivity was 1.5 Ω cm or less and the number of particles generated and the service life were both "good", "B" if the resistivity was 1.5 Ω cm or more, the number of particles generated was "good" and the service life was "good", and "C" if the resistivity exceeded 1.5 Ω cm, the number of particles generated was "poor", or the service life was "poor". Comparative Example 2 was rated "-" because no air vents were formed and had no properties as an electrode, and was rated "C".

[0029] The results are shown in Table 1. Note that only the resistivity was measured for Comparative Example 2 in which no vent holes were formed, and that for Comparative Example 6, cracks were generated during the heat treatment, so measurements below the resistivity were not performed.

[0030] [Table 1]

[0031] In Table 1, in Examples 1 to 6, the variation in resistivity was small, at 1.3 Ω·cm or less, when the thickness was 15 mm or more and 30 mm or less. In addition, the generation of particles was small, and the life was sufficient.

[0032] In contrast, in Comparative Example 1, since no heat treatment was performed, the variation in resistivity was as large as 1.8 Ω·cm, and therefore uniform plasma treatment could not be performed. Comparative Example 2 is an electrode plate without vent holes, and even after heat treatment, the variation in resistivity was as large as 1.6 Ω·cm. Comparative Example 3 had a large volume ratio of vent holes of 1.0, so the variation in resistivity was small, but many particles were generated, and the overall evaluation was C. Comparative Example 4 had a large thickness of 40 mm and a small cooling rate during heat treatment of 80°C / min, so the variation in resistivity was large as 1.7. Comparative Example 5 had a small cooling rate during heat treatment of 50°C / min, so the variation in resistivity was large as 1.8. Comparative Example 6 had a large cooling rate during heat treatment of 200°C / min, so cracks occurred during cooling. All of the conventional examples were thin, at 13 mm, had small variations in resistivity, and no particle generation was observed, but had a short lifespan due to wear. [Explanation of symbols]

[0033] 11 Electrode plate 21 Ventilation hole

Claims

1. 1. A method for manufacturing an electrode plate for a plasma processing apparatus, comprising: a slicing step for forming a silicon base plate having a thickness of 15 mm or more and 35 mm or less; a vent hole forming step for forming a large number of vent holes penetrating the base plate such that the ratio of the total volume of the vent holes to the volume of the base plate is 0.04% or more and less than 1.0%; and a heat treatment step for heating the base plate with the vent holes formed therein to a temperature of 550° C. or more and then cooling at a rate of 100° C. / min. or more and 180° C. / min. or less.

2. 2. The method for manufacturing an electrode plate for a plasma processing apparatus according to claim 1, further comprising an etching step of etching the surface of said base plate after said heat treatment step.

3. An electrode plate for a plasma processing apparatus, characterized in that it is made of silicon, has a thickness of 15 mm or more and 35 mm or less, the ratio of the total volume of the air holes to the volume of the electrode plate is 0.04% or more and less than 1.0%, and the in-plane variation of the resistivity, which is the difference between the maximum and minimum resistivity values ​​measured at three points on the plane of the electrode plate, is 0.1 Ω-cm or more and 1.5 Ω-cm or less.

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