JPH07232319A - Method for slicing ingot - Google Patents

Abstract

PURPOSE:To simply remove a damaged layer generated at the time of grooving by a method wherein grooves are formed on the outer peripheral surface of an ingot, and the outer peripheral surface of the ingot and the inner parts of the grooves are etched. CONSTITUTION:An ingot 1 chucked by a chucking part is rotated at a predetermined speed. A grooving part 2 is moved to the ingot 1. Grooving blades 2a are pressed against the outer peripheral surface of the ingot 1. Grooves 5 are gradually formed on the outer peripheral surface of the ingot 1 at intervals of the grooving blades 2a. Next, the outer peripheral surface of the ingot 1 is etched for the removal of a damaged layer. The grooves 5 of the ingot 1 and cutting wires are set accurately in an axial direction. After that, while the cutting wires are run in a fixed direction by actuating a wire drive part, the cutting wires gradually cut the ingot 1 along the grooves 5. In this manner, the damaged layer formed at the time of machining by the grooving blades 2a is removed by etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ingot slicing method for slicing an ingot having various shapes such as a disc, a square, a polygon and the like to form a wafer for a semiconductor integrated circuit, a solar cell or the like.

[0002]

2. Description of the Related Art A wafer is obtained by cutting a silicon single crystal into thin slices and grinding the surface. Single crystal silicon wafers are widely used in various applications, for example, as a raw material for solar cells and as a raw material for various integrated circuits. The diameter of the single crystal silicon wafer is gradually increasing with the improvement of the single crystal pulling technique. As a wafer for integrated circuits, for example, surface mirror polishing, photoresist coating, pattern baking, and other numerous steps are required before it becomes a final product.
Handling is performed each time. However, since the wafer is a thin single-crystal plate, it is extremely likely to be chipped, and there is a problem that if something touches a sharp edge during handling, the edge will be chipped or the wafer will be severely broken.
Therefore, the edges of both sides of the wafer are beveled in advance to reduce the corners.

Conventionally, the beveling machine (BM ') shown in FIG. 12 mechanically grinds both edges of the wafer (8') with a grindstone. Countless fine cracks are generated, forming a so-called damage layer (S '). This damage layer (S ') is not only easy to chip, but also serves as a place for storing impurities.
At present, it is considered to be a problem because it causes impurities to be mixed in the subsequent process. or,
The handling of a large amount of dust generated during beveling is also a problem in the subsequent process.

On the other hand, in applications such as solar cells, a p-type single crystal silicon wafer (8a ') which is not subjected to edge masking treatment is processed by a method such as vapor phase diffusion, coating diffusion or ion implantation to obtain the wafer (8a'). Although the n layer (n +) is formed on the surface of the wafer, in the above method, the formation of the n layer (n +) spreads not only to the front surface of the wafer (8a ') but also to the side surface and the back surface. Therefore, after the pn junction formation is completed, the edge of the wafer (8a ′) is shaved off over the entire circumference to expose the p layer over the entire circumference of the wafer edge (junction separation) work (for this method, for example,
There are side etching by plasma, side etching by chemical solution, and side etching by laser. ) Is performed, and after that, the wiring electrodes are formed on both front and back surfaces of the wafer (9 ′) through texture etching. (Processing process shown by the line on the left side of FIG. 13)

As another method, a masking agent is applied to the edge of the wafer (8a ') by brushing or spraying as in the processing method shown by the line on the right side of FIG.
(7 ') is formed into a wafer (8') with an edge coating, and an n layer (n +) is formed in that state, and then the masking layer (7 ') is removed to remove the n layer (n +). Formed wafer
There is also a step of forming wiring electrodes on both front and back surfaces of the wafer (9 ′) through (9 ′) and texture etching.

As described above, in the process of manufacturing a semiconductor integrated circuit wafer, the process for bevelling is specially required for each wafer as described above, and in manufacturing a solar cell wafer, Masking layer (7 ')
When using a wafer (8a ') without forming
Side etching and peripheral cutting with plasma, chemicals, and laser are necessary, or when edge masking is performed, an edge masking process is required for each wafer, which makes the manufacturing process very complicated. There's a problem.

Further, since there is no cut on the surface at the start of cutting the ingot, the problem that the cutting blade swings until the cut is made and becomes stable, and even if the cut is stable, if the cut position is not accurate, a wafer thickness error may occur. There is a problem that will occur. In addition, in the case of wire cutting, there is a problem that the cutting direction slightly sways with respect to the running direction of the wire, which causes waviness or warpage on the processed surface of the wafer.

[0008]

The problem to be solved by the present invention is to eliminate the beveling step required for each wafer at the time of manufacturing a wafer for a semiconductor integrated circuit. It is possible to easily eliminate the damage layer in the solar cell. When manufacturing a solar cell wafer, side etching by plasma or chemical solution or laser in the junction / separation work of the pn junction formation without the wafer edge masking process is performed. Elimination of peripheral cutting work, elimination of edge-masking process for each wafer when edge masking is performed during production of wafers for solar cells, elimination of wobbling of the cutting blade at the start of ingot cutting, and wafer thickness Eliminate errors and waviness and warpage of the processed surface A.

[0009]

According to a first method of slicing an ingot according to the present invention, as described in claim 1, a groove (5) is formed on the outer periphery of the ingot (1), and then the ingot is formed. The outer peripheral surface of (1) and the inside of the groove (5) are etched, and after that, the ingot (1) is cut along the groove (5) to form a wafer (8a).

As a result, the cutting blade (2a) at the time of starting the cutting of the ingot (1) can be inserted into the groove (5) to start the cutting, so that the wobbling of the cutting blade (2a) can be eliminated. Moreover, since it is possible to cut along the groove (5) during cutting, it is possible to eliminate the thickness error of the wafer (8a) and the waviness and warpage of the processed surface. Further, since the groove (5) is formed and then the outer peripheral surface of the ingot (1) and the inside of the groove (5) are etched, the damage layer (6) generated during the groove processing will be removed. . In addition, since the groove processing is performed in advance, when the wafer (8a) is sliced, its outer peripheral shape becomes the same shape as when the beveling processing is performed,
It is possible to eliminate the conventionally required beveling process for each wafer.

A second method of slicing an ingot according to the present invention is, as set forth in claim 2, in which a groove (5) is formed on the outer periphery of the ingot (1), and then the outer peripheral surface of the ingot (1) is formed. Then, the inside of the groove (5) is etched, and after that, a masking layer (7) is formed on the outer peripheral surface of the ingot (1) and the surface of the groove (5), and then the ingot (1) is formed along the groove (5). ) Is cut to form a wafer (8) whose edge portion is covered with the masking layer (7).

In this case, in addition to the above-mentioned operation, since the wafers (8) whose edge portions are covered with the masking layer (7) can be mass-produced at one time, one wafer at a time can be produced as in the conventional case. There is no need to perform edge masking, and the masking process can be eliminated.

[0013]

The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows an ingot groove processing device (A) used in the present invention.
FIG. 2 is a front view of the ingot cutting device used in the present invention.
FIG. 3B is a side view of FIG. 3B, and FIG. 3 is a partially enlarged perspective view of the ingot cut state by the device (B). In FIG. 1, the ingot (1) is chucked by the chuck part (3) from both sides and is rotated by the rotation drive part (4).

The grooved portion (2) is composed of a group of disk-shaped grooved blades (2a) arranged at regular intervals and a blade shaft (2b) for supporting the bladed blades (2a). It is arranged so as to face the outer peripheral surface. Grooving blade of this embodiment
(2a) is a thin disk-shaped, fine diamond powder is attached to the surface thereof, and the outer peripheral edge thereof is sharply formed in a triangular cross section as shown in FIG. The setting interval of the grooving blade (2a) is not particularly limited, but one example is an ingot (1) having a diameter of 4 inches.
In the case of, the distance is about 500 to 600 micron millimeters. Further, the thickness of the groove processing blade (2a) is about 200 μm in the case of the ingot (1) having a diameter of 4 inches.

As shown in FIG. 1, the ingot (1) chucked by the chuck portion (3) is rotated at a predetermined speed to move the grooved portion (2) to the ingot (1) side, and the grooved blade ( 2
Press a) against the outer peripheral surface of the ingot (1) to form a grooved blade.
Grooves (5) are gradually formed on the outer peripheral surface of the ingot (1) at intervals of (2a). The groove processing part (2) is separated from the ingot (1) at the place where the groove (5) is formed to a predetermined depth, and then the rotation drive part (4) is stopped and the chuck part (3) is removed to remove the ingot.
(1) is taken out from the ingot groove processing device (A). This state is shown in FIG.

Further, FIG. 6 shows details of groove processing. As can be seen from Fig. 6, the grooved blade (2
That is, the damage layer (6) is formed during processing by a). As mentioned above, the damage layer (6) is a layer in which extremely minute cracks are formed innumerably, and it is not only easy to chip, but also becomes a place to store impurities, which causes impurities to be mixed in the subsequent process and is removed. There is a need.

When grooving is completed in this way, the ingot is
The outer peripheral surface of (1) is etched to remove the damaged layer (6). A mixed acid is generally used as the etching liquid.
When etching is performed, the damage layer (6) is removed and the groove (5) is removed.
The sharp edges of the groove are melted and removed, and as shown in Fig. 7, the groove (5)
Has a somewhat rounded shape. A virtual line shows an etched portion. As a result, the beveling effect without the damage layer (6) can be obtained.

As the next step of etching, the present invention has the following two processing methods. Slice the ingot (1) along the groove (5) as it is to make a wafer (8a) without edge coating,
A mask material is applied to the outer peripheral surface of the ingot (1) and the surface of the groove (5) to form a masking layer (7), and then, a method of cutting the ingot (1) along the groove (5) and There is.

First, the cutting of the ingot (1) on which the masking layer (7) is formed will be described. When the etching of the outer peripheral surface of the ingot (1) and the surface of the groove (5) is completed as described above, a mask material is applied to the outer peripheral surface of the ingot (1), and the outer peripheral surface of the ingot (1) and the groove (5). A masking layer (7) is formed on the surface of the. The mask material for forming the masking layer (7) needs to be a material having alkali resistance and acid resistance for the next treatment. As the mask material, for example, a material such as water glass is used. In the case of firing in a firing furnace, heat resistance is also required, and in that case, an alumina-based mask material is used. The feature of the alumina-based mask material is that it is excellent in heat resistance, and it is 1,649 ° C for a general alumina-based mask material. (Product name: Ceramabond 503 A maskable alumina-based mask material, with a cure temperature as low as 120 ° C and heat resistance up to 1,649 ° C. Ceramabond 552 Alumina-based mask material. Ceramabond 569 Alumina-based mask material It has a heat-resistant temperature of 1649 ° C and is characterized by not containing sodium and being resistant to moisture. It can be processed at room temperature and does not require heat cure.Ultra Temp 516 This is a mask material based on zirconia, unlike the above-mentioned alumina type. , And has excellent affinity with silicon, and the upper limit of heat resistance is 2400 ° C.) Figure 8 shows a masking layer on the surface of the ingot (1) and groove (5).
The enlarged cross-section shows the one in which (7) is formed.

Thus, the outer peripheral surface of the ingot (1) and the groove
After forming the masking layer (7) on the surface of (5), the ingot (1) is sliced. Figure 2 is an ingot cutting device
It is a side view of (B). The ingot (1) is fixed to the graphite ingot mount (10) with an adhesive (13). The ingot mount (10) is attached to the carriage (11) and the carriage (1
1) slides on the moving base (12). The moving amount of the moving base (11) is controlled by the set screw (17).

A wire guide roller (15) is arranged above the ingot (1), and the cutting wire (1) is arranged around the wire guide roller (15) in accordance with the interval of the groove (5).
4) is lined up. The wire (14) is thinner than the groove (5). (16) is a wire drive unit, and the wire drive unit (1
By driving 6), the cutting wire 14 will run in a fixed direction.

The moving base (12) is installed on the angle adjusting base (21), and the angle adjusting base (21) is installed on the elevating base (23) via the angle adjusting bearing (22). (2
5) is an angle adjustment drive unit attached to the lifting base (22), the rotation axis of which is attached to the angle adjustment base (21).
Ingot by operating the angle adjustment drive (25)
The angle of (1) is adjusted.

A lifting guide (24) and a lifting screw (18) are installed on the lifting base (23), and the ingot (1) can be lifted by operating the lifting screw (18). It has become.

FIG. 3 is an enlarged perspective view of the sliced state of the ingot (1). First, use the set screw (17) to ingot
The groove (5) of (1) and the cutting wire (14) are accurately set in the axial direction, and at the same time, the angle adjustment drive section (25) is operated to adjust the angle, and the groove (5) of the ingot (1) is adjusted. Set the cutting wire (14) and the angle wire correctly.
After that, the wire driving unit (16) is operated to move the cutting wire (14) in a fixed direction. Then, lift screw (1
8) is operated to raise the ingot (1), and the ingot (1) is gradually raised while the cutting wire (14) is fitted exactly in the groove (5). As shown in FIG. 9, as the ingot (1) rises, the cutting wire (14) gradually cuts the ingot (1) along the groove (5).

At the time of cutting, a grinding liquid (19) containing abrasive grains is constantly supplied to the sliced portion of the ingot (1), and when the cutting wire (14) runs in the groove (5), the action of the abrasive grains causes the ingot to move. (1) will be gradually cut off. As the abrasive grains, for example, fine diamond powder, carborundum powder or corundum powder is used. As the cutting wire (14), for example, an ultrafine piano wire or a hardened ultrafine steel wire is used.

Since the groove (5) is formed around the entire circumference of the ingot (1), the cutting wire (14) is along the groove (5) (in other words, without coming off the groove (5)).
(1) will be cut with an accurate width.

When the rise of the ingot (1) reaches the upper limit, the cutting of the ingot (1) by the cutting wire (14) is completed. As a result, a large number of cut wafers (8) are erected on the ingot mount (10). Remove the ingot mount (10) from the transfer base (11), then remove the adhesive (13) and place the wafer (8) on the ingot mount (10).
To remove the ingot (1) and complete the cutting work.
As a result, the wafer (8) having the masking layer (7) formed on the outer peripheral edge thereof as shown in FIG. 4 (e) can be mass-produced at one time.

Next, the slice of the wafer (8a) on which the masking layer (7) is not formed will be described. In this case, as shown in FIG. 4, when the etching step of (c) is completed, the ingot (1) is fixed to the ingot mount (10) with the adhesive (13), and the ingot is processed by the same method as described above. (1) is cut along the groove (5) to obtain a wafer (8a) without the masking layer (7).

The ingot (1) has a columnar shape as shown in FIG. 4, or an orientation flat (not shown), or a corner portion having a slightly arcuate shape as shown in FIG. There is a prismatic solar cell for solar cells. The method of forming the groove (5) for the ingot (1) having a columnar shape or orientation flat is
Although it can be performed by the rotary cutting method as shown in FIG. 1, in the case of a prismatic column, the groove cutting cannot be performed by the rotary cutting method.
It is necessary to perform a profiling process in which the grooved portion (2) is moved according to the shape of the outer peripheral surface of the ingot (1).

In the copying method, although not shown, the copying arm is brought into contact with the outer circumference of the ingot (1) and the ingot (1) is rotated to move the copying arm along the outer peripheral surface of the ingot (1). The grooved portion (2) to which the grooved blades (2a) group is attached is connected to the copying arm, whereby grooves (5) are formed at predetermined intervals on the outer peripheral surface of the ingot (1). Will be. Other not shown,
Instead of the blade (2a), it is also possible to use a comb-tooth-shaped grooved portion having a bite-shaped blade formed at its tip.
Reference numeral (20) is a grinding blade, and the ingot (1) is formed into a perfect circular columnar object or a prismatic object having rounded corners as shown in FIG.

As described above, in the wafer (8) formed by slicing and having the edge coating, the n layer (n +) is formed on the surface of the wafer (8) as it is, and then the masking layer (7). Is removed to form a wafer (not shown) on which an n layer (n +) is formed, and further, through texture etching, wiring electrodes are formed on both front and back surfaces of the wafer.

On the other hand, a wafer without edge coating
In (8a), after the formation of the pn junction, the edge of the wafer (8a) is shaved off over the entire circumference to perform the junction separation work for exposing the p layer over the entire circumference of the wafer edge. Wiring electrodes are formed on both front and back surfaces of a wafer (not shown) through texture etching.

Further, a wafer (8
The wafers (8) with edge coating (8) also have the same shape as that of the outer peripheral edge thereof which has been previously beveled, so that it is not necessary to perform the bevelling work independently, which leads to simplification of the process. Further, when the edge coating is applied, the edge is excellent in impact resistance, so that the chipping or cracking of the edge can be effectively prevented.

[0034]

As described above, according to the present invention, the groove is formed on the outer circumference of the ingot, and then the outer peripheral surface of the ingot and the inside of the groove are etched. Therefore, the damage layer generated during the groove processing can be easily eliminated. Since the ingot is cut along the groove to form a wafer, it is possible to eliminate the beveling process which is conventionally required for each wafer at the time of manufacturing a semiconductor integrated circuit wafer, and the beveled wafer is produced. Has the advantage that it can be produced easily and in large quantities. Furthermore, since the ingot is cut along the groove, there is an advantage that the wobbling of the cutting blade at the time of starting the cutting of the ingot can be eliminated, and the thickness error of the wafer and the waviness and warpage of the processed surface can be eliminated.

Further, since the masking layer is formed on the outer peripheral surface of the ingot and the surface of the groove, the ingot is cut along the groove, so that a wafer whose edge portion is covered with the masking layer can be easily and mass produced. Therefore, there is an advantage that the conventional edge masking process for each wafer can be eliminated.

[Brief description of drawings]

FIG. 1 is a front view of an ingot groove processing device used in the present invention.

FIG. 2 is a side view of the ingot cutting device used in the present invention.

FIG. 3 is an enlarged perspective view of the present invention when an ingot is cut.

FIG. 4 is a process explanatory diagram of a processing method according to the present invention.

FIG. 5 is a partially enlarged sectional view of an ingot according to the present invention.

FIG. 6 is a partially enlarged cross-sectional view of a groove formed on the outer peripheral surface of the ingot according to the present invention.

FIG. 7 is a partially enlarged cross-sectional view of a case where the surfaces of the ingot and the groove according to the present invention are etched.

FIG. 8 is a partially enlarged sectional view when a masking layer is formed on the surface of the ingot and the groove according to the present invention.

FIG. 9 is a partially enlarged cross-sectional view of an ingot according to the present invention in a cut state.

FIG. 10 is a partially enlarged sectional view of a wafer formed by cutting an ingot according to the present invention.

FIG. 11 is a process explanatory view of another ingot cutting example of the present invention.

FIG. 12 is an explanatory diagram of a conventional beveling method.

FIG. 13 is an explanatory diagram of conventional wafer processing.

[Explanation of symbols]

 (A)… Ingot grooving device (B)… Ingot cutting device (1)… Ingot (2)… Grooving part (2a)… Grooving blade (3)… Chuck part (4)… Rotation drive part (5) … Groove (6)… Damage layer (7)… Masking layer (8)… Wafer with edge masking layer (8a)… Wafer without edge masking layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Haruyuki Kinan 3-6-16 Yanaka, Taito-ku, Tokyo M Setek Co., Ltd. (72) Hiroyuki Saito 3-16-16 Yanaka, Taito-ku, Tokyo M SETEK Co., Ltd.

Claims (4)

[Claims] 1. A groove is formed on the outer periphery of an ingot,
Subsequently, the outer peripheral surface of the ingot and the inside of the groove are etched,
Then, the ingot slicing method is characterized in that the wafer is formed by cutting the ingot along the groove. 2. A groove is formed on the outer circumference of the ingot,
Subsequently, the outer peripheral surface of the ingot and the inside of the groove are etched,
After that, a masking layer is formed on the outer peripheral surface of the ingot and the surface of the groove, and subsequently the ingot is cut along the groove to form a wafer whose edge portion is covered with the masking layer. How to slice an ingot. 3. The method for slicing an ingot according to claim 1 or 2, wherein the ingot has a cylindrical shape or a substantially cylindrical shape having an oriental flat surface. 4. The ingot slicing method according to claim 1, wherein the ingot has a prismatic shape.