JPS594030A - Method and device for slicing semiconductor ingot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION In the manufacture of integrated circuits, a large single crystal in the form of an elongated cylindrical ingot is typically made from a material such as silicon,9 and this ingot is sliced into a number of thin wafers. Create. Conventionally known methods of slicing wafers are not fully satisfactory in the following respects. That is, it takes a long time to slice a single sea urchin from an ingot, and most such slicing methods create kerfs of considerable width, thereby wasting material. Moreover, since the wafer surface is extremely rough, even more extensive surface polishing is required. For these reasons, improved methods of slicing ingots to form wafers are highly desired in the art.

The present invention relates to a method and apparatus for cutting silicon, rumanium, glass, ceramic materials, gallium arsenide, and other solid materials that dissolve in or react with molten salts. A reactive chemical, such as molten sodium hydroxide, is applied to the desired portion of the workpiece by a traveling flexible member, preferably a wire or cable. The hot molten salt reacts with the workpiece ingot and The desired portion of the piece dissolves rapidly.

A method of cutting an ingot with a wire using a high temperature etching agent to make a wafer is well known.
tillo U.S. Patent No. 3.9/! ;, No. 770. A method of etching silicon using an aqueous solution of boiling hydroxide is also known.
Such a method is described in U.S. Pat. No. 3.0'l/, 22A (
Pennington) and 3rd. '1gl,,g
No. 9 (Rosvold) K is listed.

tθ0~6 consisting of sodium peroxide and sodium nitride
A method of etching a silicon carbide surface using a melt at 00°C is described in US Patent No. 3. Dakohari No. 56 (Ebert
et al) and a method for electrically desorbing silicon in acid is described in US Pat.
all).

Other prior patents related to the present invention include U.S. Pat.
Gener), and US Pat.
7, 07g, , 2/q (Chang).

and the same No. 3. /g'1.399 issue (5chnable
et al). US Patent @ 3. /3o,7
No. 3g (Faust et al) discloses the use of sodium hydroxide or potassium hydroxide as an electrolyte between a rotating disk and a tungsten ingot.

Although some of these conventional methods and devices can cut the workpiece into the desired wafer, the cutting process results in significant kerf loss and waste of expensive semiconductor material. become. Others cause significant subsurface damage to the workpiece, which causes
It is necessary to thoroughly polish the work piece.

These conventional methods of slicing wafers by bringing the workpiece into direct contact with the cutting member not only exacerbate the problem of kerf losses described above, but also cause the cutting member to be damaged due to the mechanical friction required to make the cut. It has the disadvantage that it is subject to continuous stress, wears out, and eventually breaks. Another problem with conventional methods and equipment used to cut ingots is that most of them are sensitive to the type of donut or tip used in the semiconductor. That is, certain dopants create corrosion pits on the surface of the workpiece and/or cause wide variations in cutting speed. This is probably because it is difficult for current to pass through the semiconductor itself. Furthermore, most of the conventional methods and devices have seven other significant drawbacks. That is, it takes at least 70 to 30 hours to cut seven wafers.

The above 5 antillo% is the acid etching solution.
A method for slicing a wafer is disclosed in which the etchant is applied to the circumferential surface of a rotating etchant application wheel from which the etchant is directed outwardly toward a crystal boule. The etchant is heated by a wire carrying an electric current.

The relative motion between the pool and the wheels and wires is
This is done by moving the pool back and forth or by moving wheels and wires. In contrast, according to the present invention, the reactive fluid is ignited by the wire itself.

The wire is moved continuously against the ingot, the wire being electrically heated and raising the temperature of the molten salt to a predetermined value.

It is an object of the present invention to provide a method and apparatus that significantly reduces the time required to cut 'solid materials such as silicon ingots.

Another object of the invention is to provide a method and apparatus for cutting solid materials, such as silicon ingots, which minimizes kerf loss during cutting.

Yet another object of the invention is to provide a method and apparatus for cutting solid materials, such as silicon ingots, that minimize or eliminate subsurface damage to the workpiece during cutting. be.

Another object of the invention is to provide a method and apparatus for cutting solid materials, such as silicon ingots, that substantially eliminates the need for polishing the workpiece.

Another object of the present invention is to provide a method and apparatus for cutting solid materials, such as silicon ingots, that eliminates or reduces problems such as stress, breakage, and wear of the cutting member.

The above and other objects and effects of the present invention will become more apparent from the following examples explained and explained with reference to the accompanying drawings.

Embodiments of the present invention shown in the drawings will be described below.

An apparatus and method for cutting various molten salt-reactive solid materials includes a workpiece 1 consisting of an ingot held in a workpiece holder or cradle 2. The reel 3 is provided with a continuous electrically conductive wire freeze or cable 4. To operate this device, the wire is wound onto the take-up reel 7 while in contact with the ingot 1. Where the wire 4 comes into contact with the ingot 1, the wire is heated by the current flowing from the power source 8 through the electrical contacts 5 and 5'. At the same time, molten sodium hydroxide (
The wire 4 is coated with a reactive chemical such as (but not limited to). chemicals when the wire comes into contact with the ingot.

Nozzle 20 in such a position that the wire is wetted with molten salt.
applied to the wire.

A chemical reaction occurs between the molten salt covering the wire 4 and the silicon crystal workpiece 1, and the workpiece 1 is locally dissolved. Experiments have shown that the cutting of the workpiece is done by a chemical reaction and not by an l1m contact process between the wire 4 and the workpiece 1.

This is because the width of the resulting kerf was found to be somewhat larger than the diameter of the wire. Therefore, the work piece 1 can be cut at high speed with almost no stress or wear on the wire 4, and with little or no damage to the kerf on the ingot 1.

When carrying out this method, the wire 4 is moved by winding the wire from the reel 3 onto the winding reel 7. It is preferable that the wire is formed in an endless loop of four wires.

In this case, all the wires are transferred from the supply reel 3 to the winding loquat IJ-
Once wound on the lure, the wire 4 can be returned from the reel 7 to the reel 3. Advantageously, the wire 4 can impart a reciprocating motion to the ingot 1 superimposed on the above-mentioned translational motion.

The above cutting process is carried out by a cradle 2 holding a work piece 1.
can be performed continuously by moving the wire 4 in a constant and controlled manner in the direction of the wire 4.

This vertical movement of the cradle 2 and the ingot 1 is caused by the rotation of the screw 10 in threaded engagement with the stationary nut 11 by the motor 8 via the gear transmission 9, thereby moving the ingot 1 in the direction of the cutting member 4. This is achieved by moving at a constant speed.

The flexible member 4 can also be comprised of a braided or twisted cable to facilitate the penetration of heated molten salt into the inner surfaces and cavities of the workpiece 1. Similarly, cutting member 4! -2 Constructed of wires containing hard inert particles or knurled wires or roughened wires to facilitate the transport of hot molten salts into the surface depressions of the workpiece. According to yet another embodiment of the invention, inert insoluble particles are dispersed in a liquid hot molten salt, which
The wire 4 acts so that it does not come into direct contact with the work piece.
It is possible to create a space between the workpiece 1 and the work piece 1 in which a liquid molten salt can enter.

Minimize melting of the work piece in undesirable areas by keeping the temperature of the ingot itself below the reaction temperature of the salt used as a chemical reactant in the area where the slicing operation takes place. Needless to say, it can be done. The temperature of the pressure and heating wires is kept high enough to ensure that the chemical reactants in the groove are effective and dissolve the crystalline material.

It is also within the scope of the invention to use a eutectic mixture of salts rather than a single salt. A feature of this eutectic mixture is that its melting point is extremely low and that the reaction method p is zero or almost zero when the temperature of the molten mixture is slightly above its melting point. This makes it possible to increase the temperature of the mixture locally at the desired cutting area to such a temperature that the mixture reacts with the material of the workpiece.This allows it to remain molten during use and locally Salt can be used to effectively carry out the cutting operation only when heated to a temperature of 100 mL, making it easier to transport such salt mixtures to the kerf groove, from which the spent waste can be removed. It becomes easier to remove the product.

Although preferred embodiments of the invention have been described herein, not all equivalent embodiments of the invention are described herein. It is to be understood that the terminology used is intended to be descriptive and not limiting, and that various modifications may be made within the scope of the invention.

[Brief explanation of the drawing]

The accompanying drawings show exemplary embodiments of the device according to the invention. １・・・・・・・・・Working piece, ２・・・・・・・・・
・Cradle, 3・・・・・・ Reel, 4・
・・・・・・・・・ Wire, 5.5′・・・・・・・・・
・Contactor, 6...High temperature chemicals, 7
・・・・・・・・・Take-up reel.

Claims (1)

[Claims] () A method of manufacturing a thin wafer by slicing a crystalline implant; passing the crystalline material through a flexible tensile member through a kerf formed during the slicing operation; A molten salt or a mixture of salts capable of chemically reacting with and dissolving the salt is deposited on the flexible member, and the flexible member directs the molten salt into the kerfs of the ingot. The above method, characterized in that the method comprises: transporting. (2) The method according to claim 1, wherein the flexible member is electrically conductive and heated by passing an electric current through the flexible member. (3) Maintaining the temperature of the entire ingot below the melting point of the salt applied to the flexible member and maintaining the temperature of the flexible member sufficiently high that at the point where the flexible member and the ingot material come into contact; 2. The method according to claim 1, wherein only the salt retains its reactivity. (4) Claims 1 and 2 in which the reciprocating motion of the flexible member along the direction of motion is superimposed on its translational motion.
The method described in Section 3 or Section 3. (5) In an apparatus for manufacturing a wafer by slicing a crystal ingot: means for moving a flexible tensile member in a direction substantially perpendicular to the axis of the ingot while in contact with the ingot; a flexible member K, comprising means for continuously applying a molten salt capable of dissolving said ingot material, and means for continuously moving said ingot and said flexible member in directions facing each other. The above equipment. (6) Claim 5 further comprising means for heating the flexible member before the flexible member is fused with the ingot.
Apparatus described in section. (Force) The device according to claim 6, wherein the flexible member is a wire. (81 The device according to claim 5 or 6, wherein the flexible member is a multi-strand. (9) 7. The device of claim 3 or 6, wherein the flexible member comprises immobilized insoluble particles. Claim 6, wherein the OI molten salt comprises inert solid insoluble particles. The device according to claim 5 or claim 6. αυ The device according to claim 5 or claim 6, wherein the flexible member has a rough outer surface. The apparatus a according to claim 5 or 6, which is