JPH09248719A - Cutting method and device of semiconductor ingot for epitaxial wafer semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a cutting margin to reduce the cutting time by applying a voltage between each wire and a semiconductor ingot for every wire of wire electrode to thereby generate electric discharge, resulting in cutting of the ingot into several pieces. SOLUTION: A wire electrode 9 is wound around between a guide roller 4, 5 through an aligning roller 13 and moves along a guide groove in order to reach a take-up reel 14, and a plurality of wires of wire electrode 9 are formed in parallel between the roller 4, 5. A d.c. power source voltage is applied between each wire of the electrode 9 and a semiconductor ingot 7, then the ingot 7 mounted on a work table 6 is raised, and the ingot 7 is cut into several pieces with a specified thickness by electric discharge machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a semiconductor ingot and a device therefor when a thin wafer is manufactured from a semiconductor ingot such as single crystal silicon for an epitaxial wafer.
In particular, the present invention relates to a semiconductor ingot for an epitaxial wafer which is cut by electric discharge between the wire electrode and the device, and a device therefor.

[0002]

2. Description of the Related Art Conventionally, when a silicon wafer for LSI is cut out from an ingot such as single crystal silicon for epitaxial wafer, for example, high-purity polycrystalline silicon is melted in a quartz crucible and seed crystals are added thereto. For example, by the Czochralski method, the seed crystal and the crucible were rotated in opposite directions and pulled up, and then the outer diameter was ground and the orientation flat was processed. The most common method is to cut out.

The inner peripheral slicer has a thickness of 300 to 300, for example.
The blade is made of a hollow disc-shaped stainless steel blade having a diameter of 350 μm, and an electrodeposition layer of diamond abrasive grains is formed on the inner circumference of the blade. Then, tension is applied to the outer circumference of the blade to rotate the blade with increased rigidity, and the ingot is cut by grinding.

On the other hand, in recent years, a large number of wires wound between wire guide rollers are pressed against an ingot, abrasives or abrasive grains are supplied while reciprocating the wires, and a large number are cut at a time by polishing. Wire saw processing technology has attracted attention (for example, Journal of Precision Engineering Vo
l.60, No.2, 1994, P.182-187).

[0005]

In the method of cutting a semiconductor ingot by the above inner peripheral slicer, a wafer is cut into 1 pieces.
Since the cutting is performed for individual sheets, there is a problem that the efficiency is low, and since the cutting is performed by the inner circumference of the blade, it cannot be applied to a semiconductor ingot which has a tendency to have a large diameter (for example, 12 inches or more) in recent years. The reason for this is that it is impossible to produce a blade having an inner diameter larger than the above size.

Further, the portion of the semiconductor ingot corresponding to the thickness dimension of the blade of the inner peripheral slicer disappears as so-called chips, so that the thickness dimension of the blade must be made as small as possible. However, it is almost impossible to form the thickness of the blade to be smaller than the above-mentioned size because of the strength of the blade. For this reason, there are problems that the material yield for wafer manufacturing is significantly reduced and the manufacturing cost is inevitably increased.

On the other hand, the cutting method using the wire saw has an advantage that the cutting width can be reduced to, for example, about 100 to 250 μm as compared with the cutting method using the inner peripheral slicer, and the material yield can be improved. However, there are problems such that the time required for cutting is long and the processing of a slurry in which abrasives or abrasive grains and chips are mixed is complicated.

Further, the wire may be broken during processing, and in such a case, it takes a relatively long time to recover, and in terms of running cost such as abrasive grain cost and wire cost, the inner circumference is There is a problem that it is more expensive than a slicer. Further, there is a problem that the accuracy of off-angle cutting is not sufficient.

In both the inner peripheral slicer and the wire saw, the cutting is based on the mechanical processing principle by grinding or polishing (lap). When cutting a semiconductor ingot, which has a remarkable increase in diameter in recent years,
There is a problem that the energy required for cutting work becomes large.

The present invention solves the above-mentioned problems existing in the prior art, has a small cutting margin, a small energy required for cutting, a short cutting time, a high material yield, and a cutting cost. An object of the present invention is to provide a semiconductor ingot cutting method for an epitaxial wafer and a device therefor which can be reduced.

[0011]

In order to solve the above-mentioned problems, in the first aspect of the invention, first, a wire electrode is stretched and supported between support members so as to be capable of running in the longitudinal direction, and the wire electrodes are stretched between these support members. The wire electrode to be supported is configured such that there are a plurality of strips, the semiconductor ingot is relatively moved in a direction orthogonal to the traveling direction of the wire electrode, and each strip and the semiconductor ingot for each strip of the wire electrode. A technical means is adopted in which a voltage is applied between them to generate a discharge and simultaneously cut the semiconductor ingot into three or more pieces.

Next, in a second aspect of the invention, a plurality of guide rollers are rotatably arranged parallel to each other along an axis line at a predetermined interval, and a wire electrode is wound between these guide rollers to form a plurality of strips. A wire electrode is formed so that it can travel in the longitudinal direction, and a processing table is provided in which the semiconductor ingot is movable between the guide rollers in a direction orthogonal to the running direction of the wire electrode, and is electrically connected to a discharge power source. The present invention employs a technical means in which a current-carrying member is provided so as to be in contact with each strip of the wire electrode, and a voltage is applied between each strip of the wire electrode and the semiconductor ingot to generate a discharge and cut.

In the second aspect of the invention, a plurality of guide grooves are provided on the outer circumference of the guide roller so that the wire electrode is continuously moved from the supply reel to the take-up reel by sequentially moving through the guide groove. A plurality of threads may be wound in parallel between the guide rollers.

Further, in this case, a plurality of sets of continuous wire electrodes may be arranged in parallel and wound around the respective guide rollers, and each set of continuous wire electrodes may be electrically insulated.

Further, in the above invention, the current-carrying member may be provided immediately before and immediately after the semiconductor ingot in the traveling direction of the wire electrode. With the above configuration, the semiconductor ingot can be cut by the discharge phenomenon caused by applying a voltage between the wire electrode and the semiconductor ingot that is the workpiece. That is, the cutting proceeds by repeating the heat generation of the cutting target portion of the semiconductor ingot, the rapid vaporization of the working liquid, and the rapid vaporization of the working liquid, and the scattering of the melting portion due to the expansion due to the flow of electrons accompanying the discharge for each pulse of the applied voltage. Of.

As a result, the electric energy required for cutting is small and the portion to be cut is cooled by the working liquid, so that the semiconductor ingot can be easily cut without causing undesired thermal alteration. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a main part perspective view showing an apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a base, which is installed on the floor surface, and a column 2 is erected on one end of the base 1. Next, 3 is a wire electrode supporting device, which is provided on the side surface of the column 2,
The two guide rollers 4 and 5 are formed so as to rotatably support the axes parallel to each other and at a predetermined interval.

A working table 6 is provided below the wire electrode supporting device 3 and is movable along the side surface of the column 2 in the vertical direction (Z direction) and the horizontal direction (X direction). . Reference numeral 7 denotes a semiconductor ingot, which is detachably attached to the processing table 6 via an appropriate supporting jig. Reference numeral 8 denotes a processing liquid tank, which is provided on the processing table 6 so as to surround the semiconductor ingot 7.

Next, 9 is a wire electrode, which comprises a plurality of supply reels 10 provided on the column 2 and an intermediate roller 1
1, the guide rollers 4 and 5 are wound around the guide rollers 4 and 5 through the alignment rollers 12 and 13 so as to reach the take-up reel 14 through the column 2. In this case, the guide roller 4 is a driving roller and the guide roller 5 is a driven roller.

FIG. 2 shows the wire electrode supporting device 3 in FIG.
FIG. 3 is an explanatory diagram of a main part configuration showing a traveling path of the wire electrode 9 and the same portions are denoted by the same reference numerals as those in FIG. In FIG. 2, reference numerals 15 and 16 denote wire guides, which are formed of a hard material such as diamond or sapphire, are provided immediately before and after the semiconductor ingot 7 in the traveling direction of the wire electrode 9, and contact the wire electrode 9,
And it is arranged so that it can be tensioned.

Reference numerals 17 and 18 denote current-carrying members, which are made of a conductive hard material and contact the wire electrode 9 between the guide roller 4 and the wire guide 15 and between the guide roller 5 and the wire guide 16, respectively. However, a predetermined voltage can be applied to this. Reference numeral 19 is a guide roller, and 20 is a tension roller, which are provided near the running end of the electrode wire 9. Reference numeral 21 is a take-up device, which is provided so as to urge the guide roller 5 outward and applies a predetermined tension to the wire electrode 9.

FIG. 3 is an enlarged side view of essential parts showing the guide rollers 4 and 5 in FIG. 2, and FIG. 4 is an enlarged sectional view of the guide groove in FIG. 3 and 4, a plurality of guide grooves 22 are formed on the outer circumference of the guide rollers 4 and 5 at equal pitches in the axial direction, and an insulating member 23 is provided for each of the guide grooves 22. . The pitch dimension between the guide grooves 22, 22 is set in correspondence with the dimension of the cutting width of the semiconductor ingot 7 (see FIG. 2).

2 to 4, the wire electrode 9 is formed so as to be continuous from the winding start end to the winding end. That is, the wire electrode 9 is a supply reel (not shown,
Although it is wound around the guide rollers 4 and 5 via the aligning roller 13 from the reference numeral 10 in FIG. 1, the guide groove 22 shown in FIGS. 3 and 4 is sequentially moved to reach the take-up reel 14. A plurality of threads are formed in parallel between the guide rollers 4 and 5.

And the continuous wire electrode 9 as described above.
When a plurality of sets are used, each set of wire electrodes 9 is held in an electrically insulated state via the insulating member 23 shown in FIG. Note that the current-carrying members 17 and 18, like the guide rollers 4 and 5, are also configured to be in an insulating state for each set of wire electrodes 9. The energizing members 17 and 18 and the wire guides 15 and 16 may be rotatable or non-rotatable.

FIG. 5 is an explanatory view showing a connection state between the discharge power source and the wire electrode in the embodiment of the present invention, and the same portions are denoted by the same reference numerals as those in FIGS. 1 to 4.
5, the wire electrodes 9a, 9b, 9c ..., The current-carrying members 17a, 17b, 17c ..., 18a, 18b, 18c ...
Are insulated from each other.

Next, reference numerals 24a, 24b, 24c ... Are DC power supplies, and one terminal has transistors 25a, 25b, 2
5c, and resistors 26a, 26b, 26c, ..., Conducting members 17a, 18a; 17b, 18b; 17c, 18 respectively.
, and the other terminals are connected to the semiconductor ingot 7, respectively. 27a, 27b, 27c ... Are oscillation circuits, respectively, which are connected to the transistors 25a, 25b, 25c.

With the above structure, the wire electrode 9 is wound from the supply reel 10 to the take-up reel 1 as shown in FIGS.
4 up to DC power source 24a as shown in FIG.
If a voltage of 24 to 24c is applied between the wire electrodes 9a to 9c and the semiconductor ingot 7 and the semiconductor ingot 7 mounted on the processing table 6 shown in FIG. 1 is raised, the semiconductor ingot 7 has a predetermined thickness. Can be cut by electrical discharge machining.

In this case, N consecutive wire electrodes 9 are
By winding the wire guides 4 and 5 so that n semiconductor ingots 7 face each other, it is possible to simultaneously cut (N × n) wafers by raising the processing table 6 once. After finishing one cutting process, the processing table 6
By moving a predetermined amount in the X direction, the cutting operation is performed again.

[0029]

EXAMPLE With the apparatus shown in FIG. 1, crystal orientation <111
>, P type (boron), specific electric resistance of 0.015 Ω · cm, and a single crystal silicon ingot having a diameter of 100 mm were cut.
In this case, a wire electrode 9 having a diameter of 150 μm and an iron core plated with brass (CSX manufactured by Fujikura Electric Wire) is used.
A power supply voltage of 20 V and a pulse current of 0.1 A were applied. The pitch between the wire electrodes 9, 9 is 900 μm, and 5 hours for 1 hour.
The cutting was completed in 8 minutes.

As a result of evaluating the cut wafer, the thickness dimension was measured at the center of the wafer and at four peripheral portions.
The maximum dimensional difference between the parts was 5.2 to 7.5 μm. Further, when the displacement in the wafer surface was measured, the maximum displacement difference in the feeding direction of the ingot (Z direction in FIG. 1) was 5.2 to 5.
3 μm (standard deviation 1.35 to 1.42 μm), maximum displacement difference in the running direction of the wire electrode 5.7 to 7.4 μm (standard deviation 1.36)
Was about 2.26 μm).

As a result, it was confirmed that in the feed direction of the ingot, the so-called drum phenomenon that the central portion peculiar to the wire electric discharge machining is recessed was hardly recognized, and the in-plane displacement was small in the traveling direction of the wire electrode. Was done. The depth of cracks generated on the wafer could be suppressed to 25 μm or less, and the kerf loss could be 201 μm.

[0032]

Since the present invention has the structure and operation as described above, the use of a wire electrode having a minute diameter can further reduce the kerf loss of 250 μm in the case of a wire saw, which is the minimum value in the prior art, by 20%. Therefore, the material yield for wafer production can be significantly improved. Further, the cutting time can be shortened to about 10% as compared with the conventional wire saw, and there is an effect that the wafer manufacturing cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a perspective view of essential parts showing an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part configuration showing traveling paths of a wire electrode supporting device 3 and a wire electrode 9 in FIG.

FIG. 3 is an enlarged side view of essential parts showing guide rollers 4 and 5 in FIG.

FIG. 4 is an enlarged cross-sectional view of the guide groove in FIG.

FIG. 5 is an explanatory diagram showing a connection state between a discharge power source and a wire electrode according to the embodiment of the present invention.

[Explanation of symbols]

 4, 5 Guide roller 7 Semiconductor ingot 9, 9a, 9b, 9c Wire electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuka Kuroda, Daigo 150, Odaira, Nishigokawa-mura, Nishishirakawa-gun, Fukushima Prefecture Shirakawa Lab, Shin-Etsu Semiconductor Co., Ltd. (72) Fumihiko Hasegawa Nishigo-mura, Nishishirakawa-gun, Fukushima Prefecture Odakura, Ohira 150, Shin-Etsu Semiconductor Co., Ltd., Semiconductor Shirakawa Laboratory (72) Inventor, Shoji Nimura, 283 Shimohirama, Sachi-ku, Kawasaki, Kanagawa

Claims (5)

[Claims] 1. A wire electrode is stretched and supported between support members so as to be capable of running in the longitudinal direction, and a plurality of wire electrodes stretched and supported between these support members are provided, and the wire electrode is run. The semiconductor ingot is relatively moved in a direction orthogonal to the direction, and a voltage is applied between each strip of the wire electrode and the semiconductor ingot to generate a discharge so that three or more semiconductor ingots are simultaneously formed. A method for cutting a semiconductor ingot for an epitaxial wafer, which comprises cutting into individual pieces. 2. A plurality of guide rollers are rotatably arranged parallel to an axis line at a predetermined interval and a wire electrode is wound between these guide rollers so that a plurality of wire electrodes can run in the longitudinal direction. And a machining table in which the semiconductor ingot is formed to be movable between the guide rollers in a direction orthogonal to the traveling direction of the wire electrode, and a current-carrying member electrically connected to a discharge power source is provided on the wire electrode. The apparatus for cutting a semiconductor ingot for an epitaxial wafer, which is provided so as to be in contact with each strip of the wire electrode, and applies a voltage between each strip of the wire electrode and the semiconductor ingot to generate a discharge for cutting. 3. A plurality of guide grooves are provided on the outer periphery of the guide roller, and a plurality of wire electrodes are continuously moved from the supply reel to the guide groove to reach the take-up reel. The semiconductor ingot cutting device for an epitaxial wafer according to claim 2, wherein the strips are wound so as to be parallel to each other. 4. A structure in which a plurality of continuous wire electrodes are arranged in parallel and wound around guide rollers, respectively, and each continuous wire electrode group is electrically insulated. A semiconductor ingot cutting device for an epitaxial wafer as described above. 5. The semiconductor ingot cutting device for an epitaxial wafer according to claim 2, wherein a current-carrying member is provided immediately before and immediately after the semiconductor ingot in the traveling direction of the wire electrode.