JPH06315826A - Beveling method for silicon wafer - Google Patents

Abstract

PURPOSE:To prevent the fused lump of silicon from being entangled at the electrode tip section by specifying the on/off-time of the applied voltage when dipping a silicon wafer in an electrolyte, applying the prescribed voltage between a main electrode and an auxiliary electrode, and electrolytically polishing an edge section. CONSTITUTION:An electrolyte C is put in a container 1, and a disk-like silicon wafer A is rotated around the horizontal axis while it is partially dipped in the electrolyte C. A rod-like main electrode 2 is brought near to or into contact with the outer periphery of the wafer A, DC or AC voltage is applied between the main electrode 2 and an auxiliary electrode 3 inserted and arranged in the container 1, and the edge section B of the wafer A is electrolytically polished. The on-time of the voltage applied between the electrodes 2, 3 is set to 50ms or below at the time of electrolytic polishing, and the off-time is set to 0.5ms or above. When the excitation is repeated in this set excitation time, the fused lump of silicon is prevented from being entangled at the electrode tip section.

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 silicon wafer by an electrolytic polishing method.

[0002]

2. Description of the Related Art Conventionally, a silicon wafer cut out from a silicon ingot has a hard and brittle property, and in order to use it for a semiconductor component, it must be mechanically processed. In order to apply, it is necessary to use, for example, a diamond tool, which has a drawback that the processing cost is high.

Therefore, recently, a method of electrically processing a silicon wafer, that is, a processing method by electropolishing has been proposed, 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 silicon wafer by a thermochemical action associated with an electrolytic discharge action, and can process the silicon wafer at a low cost as compared with, for example, a method using a diamond tool.

By the way, as shown in FIG. 2, when the workpiece D is drilled by this electrolytic polishing method, first, in an electrolytic solution C obtained by dissolving an electrolyte in water,
While immersing the workpiece D, the rod-shaped main electrode 11 is made to have its tip end brought close to or in contact with the processing position of the workpiece D, and the plate-shaped auxiliary electrode 12 is used for the workpiece D.
It is placed in the electrolytic solution C at a position slightly away from.

Next, a power source 13 is connected between the electrodes 11 and 12 to apply a DC or AC voltage V having a predetermined value, and the tip of the main electrode 11 is pressed against the workpiece D side.
At this time, the electrolytic strength E in the vicinity of the main electrode 11 rises as the voltage rises, and as the electrolytic strength E rises, the current I flowing in the electrolytic solution C as shown by the solid line f in FIG.
Is increased and the electrolytic action proceeds.

By the way, as shown in FIG. 3A, no change occurs in the vicinity of the main electrode 11 when the current I does not flow and when the current I is small, but the current I does not flow. When the electrolysis is increased and starts, as shown in FIG. 3B, minute bubbles such as hydrogen H ₂ , oxygen O ₂ and air are generated in the vicinity of the main electrode 11 so as to surround the main electrode 11. start.

Then, as the current I increases, as shown in FIG.
As shown in FIG. 3C, when the bubbles gradually increase and start to float and the current I further increases, as shown in FIG. The amount of air bubbles that float around the surface increases with the surrounding area.

Further, when the electric current I increases more than that in the case of FIG. 3D, if the electrolytic strength E near the main electrode 11 exceeds the dielectric breakdown strength of bubbles, so-called dielectric breakdown occurs, and FIG. 3E. 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.

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

In FIG. 2, reference numeral 21 is a floating fine bubble, and 22 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. 4, in the container 1 containing the electrolytic solution C,
A plate-shaped auxiliary electrode 3 is inserted and arranged, and a part of a silicon wafer (hereinafter, simply referred to as wafer A) A supported on the rotating shaft body 4 side is immersed in an electrolytic solution C, and at the outer peripheral edge portion B of the wafer A. The edge portion B is polished by bringing the tip portions of the rod-shaped main electrodes 2 closer to or in contact with each other to cause discharge between the main electrodes 2 and the electrolytic solution C.

[0012]

By the way, when the outer peripheral edge portion B of the wafer A is polished by the electrolytic polishing method described above, the wafer A is excessively heated by the discharge heat, the silicon is melted, and the main electrode 2 May get entangled at the tip of the. In such a state, not only the melting and wear of the main electrode 2 becomes severe, but also a melted silicon block adheres to the wafer A again, causing a problem that the polished surface becomes uneven.

Therefore, an object of the present invention is to provide a method for beveling a silicon wafer which can solve the above problems.

[0014]

In order to solve the above problems, a method for beveling a silicon wafer according to the present invention is
Insert the auxiliary electrode into the container containing the electrolytic solution, immerse and rotate the disk-shaped silicon wafer in the electrolytic solution, and bring the main electrode close to or in contact with the edge of the disk-shaped silicon wafer. This is a processing method in which, when a voltage is applied to electropolish the edge portion, the on time of the voltage applied between the electrodes is set to 50 milliseconds or less and the off time is set to 0.5 milliseconds or more.

[0015]

[Function] According to the above-described beveling processing method for a silicon wafer, when a voltage is applied between both electrodes, the ON time is set to 50 milliseconds or less and the OFF time is set to 0.5 milliseconds or more. It is possible to prevent the molten mass of silicon from being entangled at the tip of the electrode.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The characteristic of the silicon wafer beveling processing method in this embodiment is a method of controlling the on / off time of the voltage applied to both electrodes in the same processing method as the conventional method. Since they are the same as those described in the example, the same parts are designated by the same reference numerals and the description thereof will be omitted.

That is, the electrolytic solution C is put in the container 1, and a silicon wafer (hereinafter, simply referred to as a wafer) A.
While inserting and rotating a part of the wafer A, a rod-shaped main electrode 2 is brought close to or in contact with the outer peripheral portion of the wafer A, and a DC or The edge portion B of the wafer A is electrolytically polished by applying an AC voltage.

The time during which the predetermined voltage is applied between the electrodes 2 and 3 during the electropolishing is controlled as follows. That is, as shown in FIG. 1, the applied on-time is set to 50 milliseconds or less and the non-applied off time is set to 0.5 millisecond or more, and such a cycle is continuously repeated.

When the on-time exceeds 50 ms, molten lumps of silicon are entangled in the tip of the electrode, and white light emission is observed. When the off-time is shorter than 0.5 ms, the tip of the electrode also has an off-time. Although the molten mass of silicon is entangled and observed as white light emission, white light emission is not observed at the tip of the electrode within the on / off time of this embodiment described above. That is, the molten mass of silicon is not entangled.

By the way, in the above embodiment, the rod-shaped electrode is shown as the main electrode, but it can be applied to the case of a needle-shaped electrode, a comb-shaped electrode or a plate-shaped electrode.

[0021]

As described above, according to the beveling method for a silicon wafer of the present invention, when a voltage is applied between both electrodes, the ON time is set to 50 milliseconds or less, and
Since the off time is set to 0.5 milliseconds or more, it is possible to prevent the molten mass of silicon from being entangled at the tip of the electrode, and thus to prevent re-adhesion of the molten mass of silicon. The degree of electrode wear can be reduced.

[Brief description of drawings]

FIG. 1 is a time chart diagram showing ON / OFF time of an applied voltage in a beveling processing method for a silicon wafer according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of essential parts for explaining the principle of electrolytic polishing in a conventional example.

FIG. 3 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. 4 is a cross-sectional view illustrating a method of beveling a silicon wafer according to a conventional example.

[Explanation of symbols]

 A Silicon wafer C Electrolyte 1 Container 2 Main electrode 3 Auxiliary electrode 4 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 auxiliary electrode is inserted into a container containing an electrolytic solution, and a disk-shaped silicon wafer is immersed in the electrolytic solution and rotated, and a main electrode is brought close to or in contact with the edge portion thereof, When applying a predetermined voltage between both electrodes and electropolishing the edge portion, the on time of the voltage applied between the electrodes is set to 50 milliseconds or less, and the off time is
A method for beveling a silicon wafer, which is characterized by being 0.5 ms or more.