JP2015191970A - Electrode plate for plasma processing apparatus and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode plate for plasma processing apparatus with large diameter composed of single crystal silicon, and to provide a manufacturing method therefor.SOLUTION: A method of manufacturing an electrode plate for plasma processing apparatus having a diameter of 500 mm or more has a heat treatment step (S1) for heat treating a silicon ingot of single crystal silicon by heating it at a temperature rising rate of 1°C/min or less up to a temperature range of 1100°C-1250°C, keeping it in that temperature range for 10 min or more, and then cooling it at a cooling rate of 1°C/min or less to 250°C, and a slice step (S2) for forming a disc-shaped base plate by cutting the silicon ingot subjected to the heat treatment.

Description

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

  A plasma processing apparatus such as a plasma etching apparatus or a plasma CVD apparatus used in a semiconductor device manufacturing process has a pair of electrodes connected to a high-frequency power source in a chamber, for example, vertically arranged, and the lower electrode With the substrate to be processed disposed thereon, plasma is generated by applying a high-frequency voltage while flowing an etching gas from the air hole formed in the upper electrode toward the substrate to be processed, and etching is performed on the substrate to be processed. It is set as the structure which processes.

As the upper electrode used in this plasma processing apparatus, a laminated electrode plate is generally used in which a silicon electrode plate is fixed to a cooling plate and overlapped. The heat of the electrode plate rising during the plasma processing is cooled. It is configured to dissipate heat through the plate.
As this type of silicon electrode plate, as described in Patent Document 1, an electrode plate made of single crystal silicon, polycrystalline silicon, or columnar crystal silicon is known. A single crystal silicon electrode plate produced by thinly cutting an ingot made of single crystal silicon pulled up by the Larski method (CZ method) into a substantially disc shape with a diamond band saw or the like is often used.

Japanese Patent No. 4517363

  However, in recent years, the diameter of silicon wafers subjected to plasma processing has been increased, and accordingly, the electrode plate has to be made larger. However, it is not easy to produce an electrode plate from a large-diameter silicon ingot made of single crystal silicon.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a large-diameter electrode plate for a plasma processing apparatus made of single crystal silicon and a method for manufacturing the same.

  The present invention relates to a method of manufacturing an electrode plate for a plasma processing apparatus having a diameter of 500 mm or more, wherein the temperature of a silicon ingot of single crystal silicon is increased by 1 ° C./min or less to a temperature range of 1100 ° C. to 1250 ° C. Heating at a rate and holding at that temperature range for 10 minutes or more, followed by cooling to 250 ° C. at a temperature lowering rate of 1 ° C./minute or less, and cutting the silicon ingot after the heat treatment And a slicing step for forming a disk-shaped base plate.

As the diameter of the single crystal silicon ingot increases, the internal strain that exists inside the silicon ingot also increases, and when the base plate is formed by cutting the silicon ingot as in the conventional case, the base plate is not chipped or cracked. It sometimes occurred. Further, since the warped base plate is warped, in order to use it as an electrode plate, it is necessary to polish the surface of the base plate to remove the warped portion and to process it flat. For this reason, when cutting a disk-shaped base plate from a silicon ingot, it is necessary to cut it thicker than the thickness of the electrode plate to be produced in consideration of the warp amount of the base plate after cutting, which is a manufacturing cost. Led to an increase.
In this regard, in the method for manufacturing an electrode plate for a plasma processing apparatus of the present invention, the internal strain of the silicon ingot is removed by performing heat treatment under the above conditions before cutting the silicon ingot, that is, before the slicing step. Therefore, it is possible to prevent the base plate from being cracked or chipped in the subsequent slicing step, and to manufacture a large-diameter electrode plate made of single crystal silicon. In addition, since the base plate can be prevented from warping, the material usage rate of the electrode plate can be improved.
Moreover, in the electrode plate manufactured in this way, the in-plane variation of the specific resistance value can be reduced, and the plasma processing on the substrate to be processed can be performed uniformly.
In the heat treatment step, if the temperature at which the silicon ingot is heated and held is less than 1100 ° C., if the holding time is less than 10 minutes, and the rate of cooling exceeds 1 ° C./minute, the internal strain will be sufficient. Cannot be removed, and cracks and chips generated in the base plate in the subsequent slicing step cannot be prevented. Further, when the heating and holding temperature exceeds 1250 ° C., the silicon ingot is distorted due to its own weight, and in the worst case, the shape of the silicon ingot may not be maintained in strength.

The electrode plate for a plasma processing apparatus of the present invention is an electrode plate for a plasma processing apparatus manufactured by the above-described method for manufacturing an electrode plate for a plasma processing apparatus, and is formed in a disk shape having a diameter of 500 mm or more from single crystal silicon. The in-plane variation of the specific resistance value is 10 Ω · cm or less.
The in-plane variation of the specific resistance value is measured at a plurality of locations including the center position in the surface direction of the electrode plate, the outer peripheral position, and the intermediate position between the central position and the outer peripheral position, and the maximum and minimum specific resistance values thereof are measured. It is calculated from the difference between the two.

  According to the present invention, it is possible to form a large-diameter plasma processing apparatus electrode plate made of single crystal silicon, and to reduce in-plane variation in specific resistance value of the electrode plate.

It is a flowchart explaining the manufacturing method of the electrode plate for plasma processing apparatuses of embodiment of this invention. It is a schematic block diagram which shows an example of the plasma processing apparatus with which the electrode plate for plasma processing apparatuses of this embodiment is used. It is a top view of the electrode plate explaining the measurement position of a specific resistance value.

Hereinafter, embodiments of an electrode plate for a plasma processing apparatus and a method for manufacturing the same according to the present invention will be described with reference to the drawings.
First, a plasma etching apparatus 100 will be described as a plasma processing apparatus using this electrode plate for a plasma processing apparatus (hereinafter referred to as an electrode plate).
As shown in FIG. 2, the plasma etching apparatus 100 is provided with an electrode plate (upper electrode) 3 on the upper side in the vacuum chamber 2, and a gantry (lower electrode) 4 that can move up and down on the lower side. And in parallel with each other. In this case, the upper electrode plate 3 is supported in an insulated state with respect to the wall of the vacuum chamber 2 by the insulator 5, and the electrostatic chuck 6 and the silicon support surrounding the periphery are provided on the gantry 4. A ring (7) is provided, and a wafer (substrate to be processed) 8 is placed on the electrostatic chuck 6 with the peripheral edge supported by the support ring (7).

  Further, an etching gas supply pipe 21 is provided on the upper side of the vacuum chamber 2, and the etching gas sent from the etching gas supply pipe 21 passes through the diffusion member 9 and then passes through the electrode plate 3. It is made to flow toward the wafer 8 through the pores 31 and is discharged to the outside from the discharge port 22 on the side of the vacuum chamber 2. On the other hand, a high frequency voltage is applied between the electrode plate 3 and the gantry 4 by a high frequency power source 10.

  A cooling plate 11 made of aluminum or the like having excellent heat conductivity is fixed to the back surface of the electrode plate 3. The cooling plate 11 is also formed with through holes 12 at the same pitch as the air holes 31 so as to communicate with the air holes 31 of the electrode plate 3. The electrode plate 3 is fixed in the plasma etching apparatus 100 by screwing or the like with the back surface in contact with the cooling plate 11.

  The electrode plate 3 of the present embodiment is formed of a single crystal silicon into a large-diameter disk having a thickness of 10 mm to 15 mm and a diameter of 500 mm or more, for example. In addition, the electrode plate 3 is formed so that about several hundred to 3,000 vent holes 31 are penetrated in parallel in the thickness direction in a state of being arranged vertically and horizontally at a pitch of about several mm to 40 mm. Each of the air holes 31 is formed by drilling or laser processing. For example, the air holes 31 are formed with a hole diameter of 0.5 mm and a pitch of 25 mm with respect to the electrode plate 3 having a thickness of 12 mm and a diameter of 530 mm.

  As shown in the flow diagram of FIG. 1, the electrode plate 3 configured in this manner is a disk having a heat treatment step (S1) in which a single crystal silicon ingot is heat treated, and the silicon ingot after the heat treatment is cut into a disc. The base plate is manufactured through a slicing step (S2) for forming a base plate and a vent hole forming step (S3) for processing a plurality of vent holes in the base plate. A silicon ingot made of single crystal silicon and having a diameter of 500 mm or more is formed by the Czochralski method.

  The manufacturing process of the electrode plate 3 will be described in detail. First, a silicon ingot made of single crystal silicon having a diameter of 500 mm or more is heated to a temperature range of 1100 ° C. to 1250 ° C. at a temperature rising rate of 1 ° C./min. Then, after holding in the temperature range for 10 minutes or more, heat treatment is performed by cooling to 250 ° C. at a temperature lowering rate of 1 ° C./min or less (heat treatment step: S1). The silicon ingot after the heat treatment is thinly cut into a substantially disc shape with a diamond band saw or the like to form a base plate (slicing step: S2).

  Finally, the air holes 31 are processed one by one to finish the electrode plate 3 by lowering the drill parallel to the thickness direction from one surface side of the base plate or performing laser irradiation on each base plate. (Vent hole forming step: S3). In addition, in order to remove so-called microcracks that are generated on the inner surface of the air hole 31 by drilling, the electrode plate may be immersed in an etching solution for a certain period of time to perform an etching process.

  Thus, in the manufacturing method of the electrode plate of this embodiment, the silicon ingot of single crystal silicon is heated at a temperature rising rate of 1 ° C./min or less to a temperature range of 1100 ° C. to 1250 ° C., The internal strain of the silicon ingot is removed by performing a heat treatment step (S1) for cooling to 250 ° C. at a temperature lowering rate of 1 ° C./min or less after holding in that temperature range for 10 minutes or more. As a result, at the time of cutting the silicon ingot, cracks and chips were easily generated at the cut end portion of the silicon ingot, but it is possible to smoothly cut from the start to the end of the cut.

Therefore, in the subsequent slicing step (S2), the base plate can be prevented from being cracked or chipped, and a large-diameter electrode plate made of single crystal silicon can be manufactured. In addition, since the base plate can be prevented from warping, the material usage rate of the electrode plate can be improved.
Further, in the electrode plate manufactured in this way, the in-plane variation of the specific resistance value can be reduced, so that it is possible to uniformly perform the plasma processing on the substrate to be processed.
In the heat treatment step (S1), when the temperature at which the silicon ingot is heated and held is less than 1100 ° C., when the holding time is less than 10 minutes, and when the rate of temperature drop exceeds 1 ° C./minute, it is sufficient In addition, internal strain cannot be removed, and cracks and chips generated in the base plate in the subsequent slicing step (S2) cannot be prevented. Further, when the heating and holding temperature exceeds 1250 ° C., the silicon ingot is distorted due to its own weight, and in the worst case, the shape of the silicon ingot may not be maintained in strength.

In order to confirm the effects of the present invention, samples of the base plates of the present invention and comparative examples were prepared.
Each sample formed a base plate having a thickness of 12 mm by cutting a silicon ingot made of single crystal silicon having a diameter of 540 mm.

About the sample of this invention example 1-3 and the comparative examples 1-3, after cut | disconnecting a base plate, after heat-processing, before cut | disconnecting a silicon ingot. Samples of Invention Examples 1 to 3 were heated to 1175 ° C. at a rate of 1 ° C./min, held at 1175 ° C. for 10 minutes, and then cooled to 250 ° C. at a rate of 1 ° C./min. It was. On the other hand, the samples of Comparative Examples 1 to 3 were heated to 1175 ° C. at a rate of 2 ° C./min, held at 1175 ° C. for 10 minutes, and then cooled to 250 ° C. at a rate of 2 ° C./min. went. For the samples of Comparative Examples 4 to 6, the sample was heated to 1050 ° C. at a rate of 1 ° C./min, held at 1050 ° C. for 10 minutes, and then cooled to 250 ° C. at a rate of 1 ° C./min. went.
About the sample of Comparative Examples 7-9, the base plate was cut out, without performing a heat treatment process with respect to a silicon ingot.

And as shown in FIG. 3, about the base plate 30 of each sample, in the position of three places of the center position a of the surface direction of the base plate surface, the outer peripheral position b, and the intermediate position c of the center position a and the outer peripheral position b. The specific resistance value was measured. Further, the in-plane variation of the specific resistance value is determined by the maximum value and the minimum value among the three specific resistance values at each of the center position a, the outer peripheral position b, and the intermediate position c between the central position a and the outer peripheral position b. It calculated | required from the difference (PV value). Moreover, the presence or absence of the crack and chip | tip which arose in the base plate was confirmed.
Table 1 shows the results.

  As can be seen from Table 1, the samples of Invention Examples 1 to 3 could be produced without causing cracks or chipping in the base plate when the silicon ingot was cut. Moreover, it was confirmed that the samples of Invention Examples 1 to 3 had reduced variation in specific resistance value (PV value) compared to the samples of Comparative Examples 1 to 9.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

2 Vacuum chamber 3 Electrode plate (upper electrode)
4 frame (lower electrode)
5 Insulator 6 Electrostatic chuck 7 Support ring 8 Wafer (substrate to be processed)
9 Diffusion member 10 High frequency power source 11 Cooling plate 12 Through hole 21 Etching gas supply pipe 22 Discharge port 30 Base plate 31 Vent hole 100 Plasma etching apparatus (plasma processing apparatus)

Claims (2)

A method of manufacturing an electrode plate for a plasma processing apparatus having a diameter of 500 mm or more,
A silicon ingot made of single crystal silicon is heated to a temperature range of 1100 ° C. or more and 1250 ° C. or less at a temperature rising rate of 1 ° C./min and held at the temperature range for 10 minutes or more, and then at a temperature falling rate of 1 ° C./min or less. A heat treatment step of performing heat treatment by cooling to 250 ° C .;
And a slicing step of cutting the heat-treated silicon ingot to form a disk-shaped base plate.   An electrode plate for a plasma processing apparatus manufactured by the method for manufacturing an electrode plate for a plasma processing apparatus according to claim 1, wherein the electrode plate is formed in a disk shape having a diameter of 500 mm or more from single crystal silicon, and has an in-plane variation in specific resistance value. Is 10 Ω · cm or less, an electrode plate for a plasma processing apparatus.

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