JPH06315829A - Beveling method for cut-resistant material - Google Patents

Abstract

PURPOSE:To prevent the excessive sticking of an electrolyte and prevent the roughing on the surface of a wafer by providing an electrolyte coating member on an auxiliary electrode when coating the outer periphery edge section of a disk-like cut-resistant material with the 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 rotated around the vertical axis by a chuck device 2, a disk-like main electrode 3 is arranged at a 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 9 is arranged at a position in the upstream apart by the prescribed distance in the rotating direction. The auxiliary electrode 4 has a hollow box body formed with many electrode feed holes 6 on a front wall section 5a, a sponge body 7 is provided on the front side of the box body 5, and a storage section 8 of an electrolyte D is provided at the lower section. The wafer A and both electrodes 3, 4 are rotated, the electrolyte D seeps from the auxiliary electrode 4, voltage is applied between both electrodes 3, 4, and electrolytic polishing is applied to the outer periphery edge section B.

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 peripheral edge B was polished.

[0013]

By the way, according to the electrolytic polishing method as described above, since the wafer A is immersed in the electrolytic solution D and rotated, as shown in FIG. The electrolytic solution D also adheres to the peripheral portion C, and a thermochemical reaction also occurs in the peripheral portion C due to discharge heat, which causes a problem that the surface of the peripheral portion C is roughened.

As a method for solving such a problem, it is conceivable to cover a portion other than the outer peripheral edge portion B with a coating material such as insulating paint, but in the case of processing a large amount,
This is not practical because the coating material must be coated on each sheet.

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.

[0016]

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 portion of the difficult-to-cut material, use a disk-shaped electrode that is rotated as the main electrode, and make it hollow as an auxiliary electrode and on the wall portion on the side that contacts the difficult-to-cut material. A box-shaped body having a supply hole for the electrolytic solution is used, and a coating member for the electrolytic solution is arranged on the wall portion where the supply hole is formed, and the coating member is used for supplying the electrolytic solution into the auxiliary electrode. The outer edge of the difficult-to-cut material by pressing against the outer edge. It is a processing method for.

[0017]

[Operation] According to the above beveling method for difficult-to-cut materials,
With the coating member provided on the auxiliary electrode, the electrolytic solution is applied only to the outer peripheral edge portion of the difficult-to-cut material to be polished, so that the electrolytic solution does not adhere to an excessive portion and also serves as the main electrode. Since a rotating disk-shaped material is used, it is possible to perform mechanical polishing as well as electrolytic polishing of difficult-to-cut materials.

[0018]

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 through a chuck device (for example, vacuum type) 2 in a horizontal plane. The shaft is rotated by a rotary drive device (not shown) such as a motor.

A disk-shaped main electrode 3 is arranged at a predetermined position corresponding to the outer peripheral edge B of the wafer A, and an auxiliary electrode 4 is provided at a position on the hand side which is separated by a predetermined distance in the rotation direction. It is arranged.

The auxiliary electrode 4 is arranged on the front side of the front wall portion 5a of the hollow box-shaped body 5 having a large number of electrolyte supply holes 6 formed in the front wall portion 5a. It is composed of a sponge body (one example of a coating member) 7 for applying an electrolytic solution, and an electrolytic solution storage portion 8 provided in the lower portion of the box-shaped body 5, and also on a rear wall portion 5b of the box-shaped body 5. An electrolytic solution supply pipe 9 for supplying the electrolytic solution D is connected to the inside of the box-shaped body 5, and an electrolytic solution discharge pipe 10 is connected to the bottom wall of the storage section 8.

A power source 11 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 main electrode 3 rotates, the main electrode 3 side and the power source 11 side are electrically connected to each other via the current collecting brush 12 that is in sliding contact with the rotating shaft portion 3a.

Therefore, in the above structure, the wafer A
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 9, and exudes from the surface of the sponge body 7.

Next, the main electrode 3 and the wafer A are separated by arrows a,
As indicated by b, the parts facing each other are rotated so as to be opposite to each other, and the electrolyte D is supplied to the auxiliary electrode 4 while being lightly pressed to the wafer A side.

Then, the sponge body 7 is dented and comes into sliding contact with the outer peripheral edge portion B of the wafer A from both sides. To be done.

When a predetermined voltage is applied between the electrodes 3 and 4 in this state, a current flows between the electrodes 3 and 4 through the electrolytic solution D applied to the outer peripheral edge portion B, and the main electrode Three
An electric discharge is generated at a contact portion (in this case, it is almost in a point contact state), and the discharge heat causes the outer peripheral edge portion B of the wafer A to be thermally processed (processing by thermal melting or thermochemical reaction). At the same time, the sliding contact of the main electrode 3 simultaneously performs mechanical polishing by mechanical abrasion.

Thus, the auxiliary electrode 4 allows the wafer A
Since the electrolytic solution D is applied only to the outer peripheral edge portion B which is the polished portion of the electrolytic solution, the electrolytic solution is applied to an extra portion as compared with the conventional case where a part of the difficult-to-cut material is immersed in the electrolytic solution. It is possible to prevent the surface from being roughened, except for the peripheral edge portion.

Further, since mechanical polishing is performed simultaneously with electrolytic polishing, the polishing thickness can be made sufficiently thick, unlike the case of only electrolytic polishing. For example, the depth of about 3 to 5 μm generated in the pretreatment step can be achieved. The processing streaks of can be reliably removed.

Furthermore, by adjusting the applied voltage, the number of rotations of the wafer and the main electrode, and the pressing force of the main electrode,
The degree of processing can be controlled. 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 work piece. Further, as the main electrode, a tungsten plate material having a diameter of 30 mm is used, as a processing condition, an electrolytic solution of 10% neutral salt is used, an applied voltage is DC 200 V, a rotation speed of the wafer is 1 to 100 rpm,
The rotation speed of the auxiliary electrode was 200 rpm.

When the beveling process, that is, the chamfering process, was carried out for about 1 minute under the above conditions, no corrosion was observed in the parts other than the outer peripheral edge part, and sufficient polishing was confirmed to be able to remove the processing scratches. It was

By the way, although a sponge body is used as the coating member in the above-mentioned embodiment, a non-woven fabric may be used, for example.

[0033]

As described above, according to the beveling processing method of the present invention, when electropolishing is performed by applying a voltage between the main electrode and the auxiliary electrode through the electrolytic solution, it is difficult to make the auxiliary electrode side. Since the coating member for coating the electrolytic solution is provided on the outer peripheral edge of the cutting material, the electrolytic solution is prevented from adhering to an extra portion as compared with the case where a part of the difficult-to-cut material is immersed in the electrolytic solution. Therefore, it is possible to prevent the surface other than the outer peripheral edge portion from being roughened.

Further, since the rotating disk-shaped one is used as the main electrode, the difficult-to-cut material can be subjected to electrolytic polishing and mechanical polishing at the same time. But you can definitely get rid of it.

[Brief description of drawings]

FIG. 1 is a 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.

FIG. 6 is a side view illustrating a polished state of a silicon wafer polished by a conventional beveling method.

[Explanation of symbols]

 A Wafer B Outer peripheral edge D Electrolyte 1 Rotating shaft 3 Main electrode 4 Auxiliary electrode 5 Box-like body 6 Supply hole 7 Sponge body 9 Electrolyte supply pipe 11 Power supply

 ─────────────────────────────────────────────────── ─── 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, a disk-shaped electrode that is rotated as the main electrode is used, and it is made hollow and difficult as the auxiliary electrode. While using a box-shaped body in which the supply hole for the electrolytic solution is formed in the wall portion on the side in contact with the cutting material, the coating member for the electrolytic solution is arranged in the wall portion in which the supply hole is formed, and the above-mentioned auxiliary A beveling method for a difficult-to-cut material, comprising supplying an electrolytic solution into an electrode and pressing an application member against the outer-edge material to polish the outer-edge material.