JPH06315828A - Beveling method for cut-resistant material - Google Patents

Abstract

PURPOSE:To perform electrolytic polishing and abrasive polishing at the same time by providing a nonwoven fabric containing abrasive grains on an auxiliary electrode side when coating the outer periphery edge section of a disk-like cut-resistant material with an electrolyte, applying voltage between a main electrode and the auxiliary electrode, and applying electrolytic polishing to the edge section. CONSTITUTION:A disk-like silicon wafer A is supported on a rotary shaft body 1 rotated around the vertical axis by a chuck device 2, a needle-like main electrode is arranged at the prescribed position corresponding to the outer periphery edge section B of the wafer A, and an auxiliary electrode 4 rotated by a hollow rotary shaft section 7 is arranged at a position in the upstream apart by the prescribed distance in the rotating direction. The auxiliary electrode 4 has a hollow disk-like box body 5 formed with many electrolyte feed holes 6 on a lower wall face section 5, and a nonwoven fabric 8 containing many abrasive grains G is provided on the lower wall face section 5a. The wafer A and the auxiliary electrode 4 are rotated, an electrolyte seeps from the auxiliary electrode 4, voltage is applied between both electrodes, and electrolytic polishing is applied to the outer periphery edge section B of the wafer A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beveling method for polishing an outer peripheral edge portion of a disc-shaped difficult-to-cut material by an electrolytic polishing method.

[0002]

2. Description of the Related Art Heretofore, as insulating difficult-to-cut materials, there are ceramic materials formed by processing alumina, zirconia, silicon carbide, etc., and also glass, silicon wafers cut out from silicon ingots, etc.

By the way, such a difficult-to-cut material has properties of being hard and brittle, and in order to be used for mechanical parts and semiconductor parts, it must be mechanically processed, and such processing is carried out. Therefore, it is necessary to use, for example, a diamond tool, which has a drawback that the processing cost is high.

Therefore, recently, there has been proposed a method for electrically processing the above-mentioned difficult-to-cut material, that is, a processing method by electrolytic polishing, utilizing an electrolytic discharge action generated in an electrochemical solution, that is, an electrolytic solution.

This electrolytic polishing method is a method of processing a difficult-to-cut material by a thermochemical action associated with an electrolytic discharge action, and can process the difficult-to-cut material at a lower cost than that using a diamond tool, for example. It is a product.

By the way, as shown in FIG. 3, for example, when making a hole in a difficult-to-cut material by this electrolytic polishing method, first, in an electrolytic solution D obtained by dissolving an electrolyte in water,
The workpiece F, which is a difficult-to-cut material, is dipped, and the rod-shaped main electrode 31 is formed so that its tip end contacts the processing position of the workpiece F, and the plate-shaped auxiliary electrode 32 is formed on the workpiece F. It is placed in the electrolytic solution D at a position slightly away from.

Next, a power source 33 is connected between the electrodes 31 and 32 to apply a DC or AC voltage V having a predetermined value, and the tip of the main electrode 31 is pressed against the workpiece F side.
At this time, the electrolytic strength E near the main electrode 31 increases as the voltage increases, and as the electrolytic strength E increases, the current I flowing in the electrolytic solution D is increased as shown by the solid line f in FIG.
Is increased and the electrolytic action proceeds.

By the way, as shown in FIG. 4A, no change occurs in the vicinity of the main electrode 31 between the passivity region when the current I does not flow and when the current I is low, but the current I does not flow. When the electrolysis is increased and starts, as shown in FIG. 4 (b), minute bubbles such as hydrogen H ₂ , oxygen O ₂ and air are generated in the vicinity of the main electrode 31 so as to surround the main electrode 31. start.

Then, as the current I increases, as shown in FIG.
As shown in FIG. 4C, when the bubbles gradually become larger and start to float and the current I further increases, as shown in FIG. 4D, the generation of bubbles becomes more intense due to electrolysis, and the main electrode 31 becomes larger. The amount of air bubbles that float around the surface increases with the surrounding area.

Further, when the electric current I increases more than in the case of FIG. 4D, if the electrolytic strength E near the main electrode 31 exceeds the dielectric breakdown strength of bubbles, so-called dielectric breakdown occurs, and FIG. 4E. As shown in, a large number of fine bubbles are generated due to the dielectric breakdown, and at this time, the current I sharply decreases and
Discharge light emission and heat generation occur.

Due to the heat generation, the thermochemical action on the workpiece F becomes remarkable, and this action causes the workpiece F to be perforated. The removal amount W of the workpiece F at this time is as shown by the solid line g in FIG.

In FIG. 3, reference numeral 41 is a floating fine bubble, and 42 is a fine bubble generated by dielectric breakdown.
When the edge portion of the outer peripheral portion of the silicon wafer is polished as a workpiece by such an electrolytic polishing method,
As shown in FIG. 5, a silicon wafer in which an auxiliary electrode 53 is inserted and arranged in a container 51 in which an electrolytic solution D is placed and which is supported on a rotation support shaft 54 side (hereinafter, simply referred to as wafer A)
By immersing part of A in the electrolytic solution D and bringing the tip of the main electrode 52 into contact with the outer peripheral edge portion B of the wafer A to cause discharge between the main electrode 52 and the electrolytic solution D, The edge portion B had been polished.

[0013]

By the way, according to the electrolytic polishing method as described above, only the vicinity of the surface is polished, and, for example, when scratches such as processing marks are made in the pretreatment step, There was a problem that polishing was not enough and the scratch could not be completely removed.

Therefore, an object of the present invention is to provide a method for beveling a difficult-to-cut material which can solve the above problems.

[0015]

In order to solve the above-mentioned problems, a method of beveling a difficult-to-cut material according to the present invention is to apply an electrolytic solution to the outer peripheral edge portion of a disk-shaped difficult-to-cut material that is rotatably supported. Then, the main electrode and the auxiliary electrode are brought into contact with the outer peripheral edge portion coated with this electrolytic solution, and a voltage is applied between these electrodes via the electrolytic solution, so that the discharge heat generated at the tip of the main electrode causes , When polishing the outer peripheral edge of the difficult-to-cut material, use a disk-shaped box body that is hollow as the auxiliary electrode and has an electrolyte supply hole formed on the wall surface on the side in contact with the difficult-to-cut material In addition, by disposing a non-woven fabric containing abrasive grains on this wall surface, and by supplying the electrolytic solution into the auxiliary electrode and pressing the non-woven fabric side to the outer peripheral edge portion, the outer peripheral edge portion of the difficult-to-cut material is polished by a processing method. is there.

[0016]

According to the above-described beveling processing method for each difficult-to-cut material, when electropolishing is performed by applying a voltage between the main electrode and the auxiliary electrode through the electrolytic solution, abrasive grains are provided on the auxiliary electrode side. Since the contained non-woven fabric is provided, it is possible to perform the abrasive grain polishing simultaneously with the electrolytic polishing of the difficult-to-cut material.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiments described below, the case of polishing a silicon wafer (an example of a difficult-to-cut material, which may be applied to a material made of, for example, a ceramic material or a glass material) will be described.

In FIGS. 1 and 2, reference numeral 1 is a rotation for rotatably supporting a disk-shaped silicon wafer (hereinafter, simply referred to as a wafer) A via a chuck device (for example, a magnet type) A in a horizontal plane. The shaft is rotated by a rotary drive device (not shown) such as a motor.

A needle-shaped main electrode 3 is arranged at a predetermined position corresponding to the outer peripheral edge B of the wafer A, and
At a position on the hand side that is separated by a predetermined distance in the rotation direction,
The auxiliary electrode 4 is arranged.

The auxiliary electrode 4 has a hollow disk-shaped box body 5 in which a large number of electrolyte solution supply holes 6 are formed in a lower wall surface section 5a, and a central portion of an upper wall surface section 5b of the disk-shaped box body 5. It is composed of a hollow rotating shaft portion 7 projecting upward from above, and a nonwoven fabric 8 attached to the lower wall surface portion 5a of the disk-shaped box body 5 and containing a large number of abrasive grains G.

The auxiliary electrode 4 is rotatably held by a holding device (not shown), and is rotated by the rotation driving device 11 at a predetermined speed around the rotary shaft portion 7. There is.

The rotary drive device 11 has a driven gear 12 fitted and fixed to the rotary shaft portion 7, a drive gear 13 meshed with the driven gear 12, and a motor (not shown) for rotating the drive gear 13. ) And is composed of.

Further, the rotary shaft portion 7 of the auxiliary electrode 4 is
For example, the electrolytic solution supply pipe 14 via a rotary joint (not shown)
The electrolytic solution D is supplied to the inside of the disk-shaped box body 5 from the hollow portion of the rotating shaft portion 7.

Further, a power source 9 is connected between the main electrode 3 and the auxiliary electrode 4 so that a predetermined voltage (DC voltage, AC voltage, pulse voltage or the like) is applied. Since the auxiliary electrode 4 rotates, the auxiliary electrode 4 side and the power source 9 side are in contact with the current collecting brush 10 that is in sliding contact with the rotating shaft portion 7.
Are electrically connected via.

Therefore, in the above structure, the wafer A is
When polishing the outer peripheral edge portion B, the wafer A is first held on the rotary shaft 1 side via the chuck device 2. Next, the electrolytic solution (acid, alkali, neutral liquid, etc.) D is supplied to the auxiliary electrode 4 side through the electrolytic solution supply pipe 14 so that the electrolytic solution D oozes from the surface of the nonwoven fabric 8. .

Next, as shown by arrows a and b, both electrodes 3 and 4 are rotated so that the facing portions are opposite to each other, and the auxiliary electrode 4 side is lightly pressed to the wafer A side. Then, the nonwoven fabric 8 is brought into sliding contact with the outer peripheral edge portion B of the wafer A, and a predetermined voltage is applied between the electrodes 3 and 4.

Then, on the outer peripheral edge portion B of the wafer A,
The electrolytic solution D exuded from the non-woven fabric 8 is applied, a current flows between the electrodes 3 and 4 through the electrolytic solution D, and a discharge is generated at the tip of the main electrode 3. The outer peripheral edge portion B of the wafer A is subjected to thermal processing (processing by thermal melting or thermochemical reaction) by heat, and abrasive grains are simultaneously polished by the non-woven fabric 8 that is brought into sliding contact with a predetermined pressing force. Be seen. The thickness of the electrolytic solution D applied on the surface of the wafer A is about 0.1 mm, so that the tip of the main electrode 3 is discharged without directly contacting the surface of the wafer A.

As described above, since the abrasive grain polishing using the non-woven fabric containing the abrasive grains is performed simultaneously with the electrolytic polishing, the polishing thickness can be made sufficiently thick unlike the conventional case where only the electrolytic polishing is performed. For example, 3 generated in the pretreatment process
It is possible to reliably remove the machining streaks with a depth of about 5 μm.

Further, the working degree can be controlled by adjusting the applied voltage, the number of revolutions of the wafer and the auxiliary electrode, and the diameter of the abrasive grains contained on the non-woven fabric side. Further, since the electrolytic solution may be simply applied to the wafer, the consumption of the electrolytic solution itself can be small, and since it is wet polishing, generation of dust can be suppressed.

Here, a specific processing example will be described.
A silicon wafer having a diameter of 4 inches was used as a difficult-to-cut material which is a workpiece.

A tungsten needle with a diameter of 0.3 mm is used as the main electrode, and a copper plate with a diameter of 100 m is used as the auxiliary electrode.
I made and used the one of m. Also, as processing conditions,
Use 10% neutral salt electrolyte and apply voltage of DC200V
The wafer rotation speed was 1 to 100 rpm, and the auxiliary electrode rotation speed was 1 to 200 rpm.

Under the above conditions, the wafer was subjected to beveling processing, that is, chamfering, for about 1 minute. As a result, it was confirmed that the polishing was sufficient to remove the processing scratches. By the way, in the above-described embodiment, the structure in which one side of the wafer is polished has been described, but by arranging the auxiliary electrodes on both sides of the wafer, the outer peripheral edge portions of both sides can be simultaneously polished.

In the above embodiment, the needle-shaped electrode was used as the main electrode, but a rod-shaped electrode, a comb-shaped electrode, or a plate-shaped electrode can also be used.

[0034]

As described above, according to the beveling processing method of the present invention, when a voltage is applied between the main electrode and the auxiliary electrode through the electrolytic solution to perform electrolytic polishing, the auxiliary electrode side is ground. Since the non-woven material containing particles is provided, the hard-to-cut material can be electrolytically polished and abrasive-grain polished at the same time. Therefore, even if the surface of the hard-to-cut material has deep scratches, it can be reliably removed.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view illustrating a method of beveling a difficult-to-cut material according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a method of beveling a difficult-to-cut material in the example.

FIG. 3 is a sectional view of relevant parts for explaining the principle of electrolytic polishing in a conventional example.

FIG. 4 is a graph showing the relationship between the current and electrolytic strength and the removal amount of the workpiece for explaining the principle of the same electrolytic polishing.

FIG. 5 is a partially cutaway perspective view illustrating a beveling method for a difficult-to-cut material in a conventional example.

[Explanation of symbols]

 A Wafer B Outer peripheral edge D Electrolyte G Abrasive grains 1 Rotating shaft body 3 Main electrode 4 Auxiliary electrode 5 Disc box 6 Supply hole 7 Rotating shaft 8 Nonwoven fabric 9 Power supply 14 Electrolyte supply pipe

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masanori Tsukahara, 5-3-8 Nishikujo, Konohana-ku, Osaka-shi, Osaka Prefecture (72) Hitachi Shipbuilding Co., Ltd. (72) Akio Komura 5--9, Nishikujo, Konohana-ku, Osaka No. 28 in Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. An electrolytic solution is applied to an outer peripheral edge of a disc-shaped difficult-to-cut material rotatably supported, and a main electrode and an auxiliary electrode are brought into contact with the outer peripheral edge applied with the electrolytic solution. , Voltage is applied between these electrodes via the electrolytic solution,
When the outer peripheral edge of the difficult-to-cut material is polished by the discharge heat generated at the tip of the main electrode, an electrolyte supply hole is formed in the wall surface of the side that is hollow as the auxiliary electrode and is in contact with the difficult-to-cut material. Using a disk-shaped box body in which is formed, a non-woven fabric containing abrasive grains is placed on this wall surface, and an electrolyte solution is supplied to the auxiliary electrode and the non-woven fabric side is pressed against the outer peripheral edge portion to make difficult cutting. A method for beveling a difficult-to-cut material, which comprises polishing an outer peripheral edge portion of the material.