JP6684403B2 - Method for repairing silicon single crystal member - Google Patents

Description

  The present invention relates to a method for repairing a silicon single crystal member. More particularly, it relates to a method of growing a silicon single crystal on the surface of a used silicon single crystal member to repair the member.

  A dry etching apparatus using plasma is used as an etching apparatus in manufacturing a semiconductor integrated device such as an LSI. In this device, when a wafer to be etched is placed on the cathode of a flat electrode and an etching gas is introduced into the device, a high-frequency oscillator applies a high-frequency voltage between a counter electrode (anode) and a cathode. A plasma of etching gas is generated between the electrodes. Positive ions, which are active gas in plasma, are incident on the surface of the wafer for etching.

  Inside the dry etching apparatus, silicon parts are used because metal contamination occurs when using metal parts. Typical silicon parts include a donut-shaped focus ring surrounding a wafer to be etched, a ground ring surrounding a lower electrode, an upper electrode plate, and protective members above and below the etching chamber. Of these, the focus ring and the like need to have a larger diameter than the wafer to be etched, and the ones currently used for 300 mm wafers are expensive because they are made from silicon crystal ingots having a diameter of 320 mm or more. . In addition, if the crystal has a grain boundary, particles are likely to be generated from the grain boundary. Therefore, single crystal silicon having no grain boundary is required, which is more expensive.

  The surface of the silicon component installed in the dry etching apparatus is gradually etched and thinned as it is used. When the thickness becomes thinner than a certain level, it is discarded as scrap silicon, and a method of reusing has been required.

  As a method of regenerating the focus ring and the like, after cleaning the silicon waste material, determining the silicon raw material and impurities to be added by measuring the content of impurities, melted in a crucible, to prepare a polycrystalline silicon ingot, A method for manufacturing a new focus ring or the like has been proposed (Patent Document 1). Further, regarding the reuse of the silicon substrate, a plurality of scrap wafers subjected to a predetermined pretreatment are piled up and aligned in a cylindrical shape, and the scrap wafers are heated at 400 to 1350 ° C. in a heating furnace, and the scrap wafers are diffusion-bonded to each other. A method for producing a recycled ingot has been proposed (Patent Document 2).

JP, 2013-16532, A JP, 2008-218993, A

  However, in all of the above methods, the entire silicon waste material is melted, which requires a large amount of energy and time, and also costs. Furthermore, the method of Patent Document 1 can only obtain polycrystalline silicon. The recycled ingot obtained by the method of Patent Document 2 is said to be in a state that it can be used as a single crystal, but it is also mentioned that a crystal interface or an oxide film may be formed at the bonding surface between scrap wafers. However, it is not suitable for dry etching applications.

  Therefore, an object of the present invention is to provide a method for repairing a used silicon single crystal member more quickly with less energy.

That is, the present invention is as follows.
[1] (1) A step of placing a silicon piece on the surface of the used silicon single crystal member,
(2) heating the mounted silicon piece from the upper side to melt the silicon piece and the surface of the silicon single crystal member in contact with the silicon piece; and (3) step (2) A step of cooling the melt produced in the step of growing a silicon single crystal,
A method of repairing a used silicon single crystal member, comprising:
[2] The method according to [1], wherein in the step (2), heating is performed by light heating.
[3] The method according to [2], wherein the light heating is performed by a xenon lamp or a halogen lamp.
[4] Step (2) includes an auxiliary heating step of auxiliary heating the used silicon single crystal member from below, the auxiliary heating being started before the heating of the silicon piece, and in step (3) The method according to any one of [1] to [3], wherein the auxiliary heating is stopped after the heating of the silicon piece is stopped.
[5] The method according to any one of [2] to [4], wherein the step (2) is carried out while scanning the surface of the used silicon single crystal member and the surface of the silicon piece with condensed light.
[6] The method according to [5], wherein the scanning speed is such that molten silicon is always present in the light collecting region.
[7] The step (1) further includes a step of placing a solid piece for dopant on the surface of the silicon piece, and the step (2) further includes a step of melting the solid piece. The method according to any one of claims 1 to 6.
[8] The method according to any one of [1] to [7], wherein the used silicon single crystal member is a focus ring, a ground ring, or an electrode plate of a dry etching device.

  According to the method of the present invention, since a used silicon single crystal member is locally melted only in the vicinity of its surface, the member can be repaired more quickly with less energy. As a result, it becomes possible to reuse the silicon member that has been conventionally discarded as scrap silicon, leading to a reduction in consumables cost.

It is a schematic diagram explaining the 1st embodiment of the method of the present invention. It is a schematic sectional drawing explaining 2nd Embodiment of the method of this invention.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a first embodiment of the method of the present invention. Here, as the used silicon single crystal member 1, for example, a ring-shaped member such as a focus ring of a dry etching apparatus is horizontally arranged and processed. The silicon piece 2 is placed on the surface of the focus ring to be repaired, and the heating means 3 heats the silicon piece 2 from above.

  The used silicon single crystal member 1 (hereinafter sometimes referred to as “member 1”) is not limited to a specific type as long as it is a single crystal, and its manufacturing method, purity, crystal orientation, shape, etc. may be arbitrary. Good. Examples of used members in the dry etching apparatus include a focus ring, a ground ring, and an electrode plate.

  In the used member 1 of the dry etching apparatus, the surface of the member 1 may be roughened by etching and contaminants such as metal may be attached. Therefore, it is preferable that the surface is etched with a mixed solution of hydrofluoric acid and nitric acid or the like to be a mirror surface prior to the repair and then subjected to the repair. As the mixed liquid, a chemical polishing liquid (hydrofluoric acid (49%): nitric acid (70%): acetic acid (100%) = 3: 5: 3) specified in JIS H0609 can be used.

  The silicon piece 2 is placed on the surface of the portion of the member 1 to be repaired, and it may be a specific one of the portions to be repaired or the entire surface. For example, when it is desired to restore the entire surface of a used focus ring, the focus ring is placed horizontally, and a square silicon piece having a plate shape whose one side is approximately the width of the ring is placed on the focus ring. The one side is placed along the inner circumference of the ring so as to minimize the gap between the silicon pieces.

The silicon piece 2 may be either single crystal or polycrystal. The thickness and size of the silicon piece 2 can be appropriately determined depending on the size and shape of the member 1 to be repaired, the desired thickness for crystal growth, the heating means 3, and the like. When the light heating means capable of condensing light is used as the heating means 3 and the condensing size is 10 to 30 mm in diameter, the silicon piece 2 has a thickness of 0.1 mm to 10 mm and a size of 1 × 1 mm to 50 × 50 mm. Preferably there is. When the thickness exceeds the upper limit value, when the silicon piece 2 is heated, the lower part of the silicon piece 2 is not sufficiently melted, or even if it is melted, it takes time until the silicon piece 2 is completely melted. When it is desired to grow it, the time required for repair is long, which is not preferable. When it is desired to grow the silicon single crystal to a thickness of 10 mm or more, it is preferable to repeat the crystal growth a plurality of times to increase the thickness. On the other hand, when the thickness is less than the lower limit value, the silicon piece 2 may move due to the flow of argon gas for adjusting the atmosphere during heating. Regarding the size, if the size is less than the lower limit value, the specific surface area (cm ⁻¹ ) of the silicon piece 2 becomes large, the surface is oxidized, and the silicon piece 2 is easily contaminated by metal adhesion or the like. On the other hand, if it is larger than the upper limit, it becomes difficult to uniformly melt the entire silicon piece 2. The horizontal cross section of the silicon piece 2 does not have to be square, and may have any shape such as a rectangle or a circle suitable for the above-mentioned converging size, depending on the object to be repaired.

  Some silicon parts used in a dry etching apparatus have a specific resistance specified as a specification. In order to adjust the resistance, a solid piece for dopant, for example, a simple piece of boron, an alloy of silicon and boron (SiB), an alloy of silicon and phosphorus (SiP), or the like is placed on the silicon piece 2 together with the silicon piece 2. The member 1 may be doped by placing it in the melt and incorporating it into the silicon melt. Note that elemental boron has a higher melting point than silicon, but is melted by reacting with a silicon melt and incorporated into silicon.

  The mounted silicon piece 2 is optionally heated together with the solid piece for dopant to heat the silicon piece 2 and the surface of the member 1 in contact with the silicon piece 2. The “upper side” does not have to be an upper side in the vertical direction with respect to the silicon piece 2 as shown in FIG. 1, and may be an obliquely upper side. Since heating is performed from the upper side, the silicon piece 2 is first melted and a silicon melt is generated. The melt rolls like a droplet on the member 1 when the surface of the member 1 below is not melted, but spreads when the surface of the member 1 melts. The depth of the melted portion in the member 1 depends on the degree of damage on the surface, but it is sufficient if it is about 0.1 to 1 mm from the surface of the member. Thus, the melting of the member 1 may be local, which is much more economical and efficient than melting the entire member as in the prior art.

  The heating means 3 is not particularly limited as long as it can locally heat a target portion. Preferably, a light heating means, for example, various lamps or a laser, is used because it is possible to focus on the heated portion and it is easy to change the heating amount according to the supplied power. As the lamp, a xenon lamp or a halogen lamp which is generally used in an infrared crystal growth apparatus can be used. The output is preferably about 1 to 30 kW.

  The heating time differs depending on the output of the heating means 3, the size and thickness of the silicon piece 2, and the like, but was about 2 to 5 minutes in the case of the 28 × 28 × 2 mm silicon piece used in the examples described later. .

  When the above lamp is used, the light is condensed onto the silicon piece 2 to be melted by using a condensing means 4 such as a hyperboloidal mirror. At this time, the heating power may be increased by stacking a plurality of or a plurality of types of heating means 3 on the same silicon piece 2 and focusing the light. Before the silicon is melted, the light collecting position and the area of the light collecting area are adjusted according to the position of the member 1, and when the silicon melt is generated and begins to spread, the area of the light collecting area is adjusted accordingly. It is preferable to adjust. The area is preferably 60 to 100% of the area of the silicon melt. In addition, since the silicon melt has a property of easily gathering at the highest temperature, it is preferable to move the light collecting region with respect to the melt so that the melt spreads with a uniform thickness. For example, when the member 1 has a ring shape, one or both of the heating means 3 and the member 1 are moved so that the light collecting region moves in the radial direction of the ring at a predetermined speed over the width of the ring.

  Next, in step (3), the melt produced in step (2) is cooled, and the melted silicon is single-crystallized along the single-crystal direction of the member 1. At this time, the cooling rate of the member 1 is controlled to be approximately 1 to 10 ° C./min in the temperature range from the melting point of silicon (about 1400 ° C.), which is a temperature range in which dislocations in the crystal can move, to 700 ° C. Preferably. If it is less than the lower limit, the cooling time becomes long and the repair efficiency is poor. On the other hand, if it exceeds the upper limit, dislocations in the silicon crystal tend to increase. The cooling rate can be controlled by gradually decreasing the output of the heating means 3 after the melting of silicon is completed and stopping the heating after the silicon melt is no longer observed.

  FIG. 2 is a schematic sectional view for explaining the second embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and a description thereof will be omitted. In the present embodiment, a plurality of silicon pieces 2 are placed over the entire surface of the member 1, and the member 1 is placed so that the light from the heating means 3 scans the surface of the silicon piece 2 and the surface of the member 1. Repair is performed in the chamber 6 while rotating.

  The chamber 6 is provided with a quartz window 7 through which light from the light heating means 3 is irradiated onto the silicon piece 2, and the member 1 is rotated at a constant speed by a rotary table 9 rotated by a motor 11. , So that the condensing area of the light heating means scans over the surface of the silicon piece 2 and the member 1. The scanning speed varies depending on the size of the member 1, the size of the silicon piece 2, the output of the heating means 3, the converging area, etc., but is adjusted so that the silicon melt is always present in the converging area. Preferably. If the scanning is too fast and the focusing region is moved to a portion where no silicon melt is present, the melting of silicon tends to be insufficient and the cooling rate of the melt tends to be too fast. On the other hand, if it is too slow, not only the repair efficiency deteriorates, but also the melting amount on the surface of the member 1 increases more than necessary. For example, in Examples described later, a ring-shaped silicon single crystal member 1 having an outer diameter of 390 mm, an inner diameter of 330 mm and a thickness of 5 mm was rotated at an angular velocity of 3 degrees / minute.

  The turntable 9 is arranged on the X, Y-stage 12. The X, Y-stage 12 moves the member 1 in the X, Y-directions to equalize the thickness of the silicon melt as described in the first embodiment. For example, when the member 1 has a ring shape, the member 1 is moved in the X and Y-directions so that the light collecting region repeatedly scans within the width of the ring in the radial direction of the ring at a predetermined speed. With the movement of the heating part, the silicon melt moves so as to follow the heating center, and it is possible to realize crystal growth with a uniform thickness without forming a lump.

  When the member 1 is locally heated as described above, the member 1 may be distorted due to a temperature difference between the heating region and a portion adjacent thereto, which may cause an increase in crystal defects such as dislocation. In this embodiment, in order to reduce this temperature difference, the entire member 1 is heated from below by the auxiliary heating means 5 to a temperature lower than the melting point of silicon, for example, 800 to 1300 ° C. The auxiliary heating is started before the heating of the silicon piece 2 is started, the heating of the silicon piece 2 is started after the member 1 reaches the above temperature, and is continued while the silicon piece 2 is heated. Then, in step (3), the heating of the silicon piece 2 is stopped, that is, the heating means 3 is turned off, and then the heating is stopped. As the auxiliary heating means 5, a general resistance heater using a heating wire such as Kanthal (iron-chromium-aluminum alloy) or a ceramic such as SiC can be used. In FIG. 2, the auxiliary heating means 5 is provided at the location corresponding to the light converging region, but the location is not limited to this and may be at another location.

  As the heating part moves, the temperature of the silicon melt in the part that has passed the heating part gradually decreases while emitting radiant heat, and the silicon melt begins to become single crystals in accordance with the crystal orientation of the member 1. After melting the last piece of silicon on member 1, the heating temperature is lowered. The cooling rate of the member 1 at this time is as described above with respect to the first embodiment. By continuing the rotation of the member 1 while reducing the output of the heating means 3, turning off the heating means 3 and then turning off the auxiliary heating means 5, it is possible to suppress an increase in dislocation density due to thermal strain, an increase in internal strain, and the like. be able to.

  In the method of the present invention, it is preferable that the steps (2) and (3) are performed in the chamber 6 in an argon atmosphere of 10 to 200 torr (about 1333-26664 Pa) in order to prevent the oxidation of silicon. The argon gas is supplied in the direction shown by the arrow from an argon gas inlet 8 to which a gas cylinder or the like (not shown) is connected, and is exhausted by an exhaust pump 10. Oxidation can be prevented by reducing the pressure without using the argon gas. However, reducing the pressure causes evaporation of silicon, which may stain the inside of the chamber 6, which is not preferable. Oxidation can also be prevented by nitrogen gas, but this is not desirable because nitriding of silicon occurs at 1200 ° C or higher.

  The member 1 obtained by the above method can be used as it is, but is preferably polished. The polishing method is not particularly limited and may be a conventional method such as lapping or buffing. Further, after polishing, the surface may be etched to remove processing strain. As the etching solution, a chemical polishing solution (hydrofluoric acid (49%): nitric acid (70%): acetic acid (100%) = 3: 5: 3) specified in JIS H0609 can be used.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to the examples.
Using a device as shown in FIG. 2, a single crystal having a thickness of about 2 mm is formed on the surface of a ring-shaped silicon single crystal member 1 having an outer diameter of 390 mm, an inner diameter of 330 mm and a thickness of 5 mm, which has been used in a dry etching device. It was raised and repaired to a thickness of about 7 mm.

  As a pretreatment, the surface of this member 1 was etched by about 50 μm with a mixed solution of hydrofluoric acid (49%): nitric acid (70%): acetic acid (100%) = 3: 5: 3. After the member 1 was washed and dried, it was placed on the turntable 9. A plurality of 28 × 28 × 2 mm silicon pieces 2 were arranged on the surface of the member 1 with one side thereof along the inner circumference of the member 1 so that there were as few gaps as possible. The inside of the chamber 6 was evacuated and argon gas was caused to flow at 5 L / min, so that the inside of the chamber 6 was set to an argon gas atmosphere of about 100 torr (1333.2 Pa).

  A SiC heater 5 (manufactured by Nippon Siliconit Co., Ltd.) installed in the chamber 6 heats a part of the member 1 from the lower part of the member 1 so that the maximum temperature of the upper surface of the member before irradiation with the heating means 3 becomes 1200 ° C. did. Then, a 5 kW xenon lamp (manufactured by USHIO INC.) Was used as the heating means 3 and a hyperboloid mirror was used as the light converging means 4, and the silicon piece 2 was heated from above. The position of the lamp in the hyperboloidal mirror and the distance between the hyperboloidal mirror and the member 1 are moved so that the light condensing area of the xenon lamp becomes a circle having a diameter of about 20 mm at the surface of the member 1. Therefore, it was adjusted in advance. After the lamp was turned on, the position of the member 1 was adjusted by moving the chamber 6 together with the chamber 6 on the X, Y-stage 12 so that the light collecting region was located at the center of one piece of silicon 2. After the adjustment, as the output of the lamp was increased, the silicon pieces were first melted, but the surface of the member 1 was not melted, and the melted melt did not spread and was curled near the width center of the member. When the output was further increased, the surface of the member 1 below the melt melted, and the melt formed by melting the silicon pieces 2 spread to the surface of the member 1. Therefore, by adjusting the output of the xenon lamp, the melted portion on the member 1 is formed into a circular shape having a diameter of about 25 mm.

  Next, while rotating the member 1 in the radial direction by 2.5 mm width at a speed of 10 mm / min so as to cover the silicon piece 2 having a width of 28 mm from end to end, the rotary table 9 is rotated by 3 degrees. It was rotated and moved at an angular velocity of / min. Due to the movement of the member 1, the silicon pieces 2 are sequentially melted when entering the light collecting area, and a silicon melt is constantly present in the light collecting area, and gradually crystallized when leaving the light collecting area. . When all the silicon pieces 2 were completely melted after the member 1 made a round, the movement in the radial direction was stopped and the rotation was continued while the intensity of the xenon lamp was weakened to 2.5 kW for 3 minutes. Disappeared. After confirming that the melted portion was gone, the xenon lamp was turned off. Then, the SiC heater 5 was turned off. The time required for all steps was about 2 hours and 10 minutes except for the pretreatment.

  After the member 1 was cooled to room temperature, it was taken out from the chamber 6, and the surface on which the crystal was grown was lap-polished with abrasive grains of alumina (No. 1500: average particle diameter of about 8 μm), and hydrofluoric acid (49%): nitric acid (70%). %): Acetic acid (100%) = 3: 5: 3 by etching the surface by about 50 μm, a silicon member having a thickness of 6.5 mm could be regenerated.

  In the same manner as in Example 1, a silicon member having a thickness of 6.3 mm was created.

[Evaluation]
Both silicon members were cut to perform crystal evaluation. In order to see defects, according to JIS standard H0609 test method (crystal defects of silicon by selective etching method), solution B (hydrofluoric acid (49%): nitric acid (70%): acetic acid (100%): water = 1: 12.7). : 3: 5.7) and observed, grain boundaries were not seen and it was found to be a single crystal. The dislocation density of both was about 10 ⁵ / cm ² .

  The method of the present invention can rapidly repair a used single crystal silicon member with significantly lower energy than conventional ones.

1 Used silicon single crystal member 2 Silicon piece 3 Heating means 4 Condensing means 5 Auxiliary heating means 6 Chamber 7 Quartz window 8 Argon gas inlet 9 Rotating table 10 Exhaust pump 11 Motor 12 X, Y-stage

Claims (8)

(1) a step of placing a silicon piece on the surface of a used silicon single crystal member,
(2) heating the mounted silicon piece from the upper side to melt the silicon piece and the surface of the silicon single crystal member in contact with the silicon piece; and (3) step (2) A step of cooling the melt produced in the step of growing a silicon single crystal,
A method of repairing a used silicon single crystal member, comprising:   The method according to claim 1, wherein in step (2), the heating is performed by light heating.   The method according to claim 2, wherein the light heating is performed by a xenon lamp or a halogen lamp.   Step (2) includes an auxiliary heating step of auxiliary heating the used silicon single crystal member from below, the auxiliary heating being started before the heating of the silicon piece, and the silicon piece in step (3). 4. A method according to any one of claims 1 to 3, characterized in that the auxiliary heating is stopped after the heating of (1) has been stopped.   The method according to claim 2, wherein step (2) is performed while scanning the surface of the used silicon single crystal member and the surface of the silicon piece with focused light.   6. The method of claim 5, wherein the speed of the scan is such that molten silicon is always present in the light collection area.   The step (1) further includes placing a solid piece for dopant on the surface of the silicon piece, and the step (2) further includes melting the solid piece. Item 7. The method according to any one of Items 1 to 6.   8. The method according to claim 1, wherein the used silicon single crystal member is a focus ring, a ground ring, or an electrode plate of a dry etching device.

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