JP2006239795A - Manufacturing method of semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor substrate, absorbing frictional heat generated in cutting a semiconductor ingot to restrain worsening of cutting accuracy and surface roughness and the occurrence of micro-cracks. <P>SOLUTION: In this manufacturing method of a semiconductor substrate, a wire 3 to which abrasive grains are fixed is moved to run, and the semiconductor ingot 1 is pressed from above the wire 3 to cut the semiconductor ingot 1 and form a semiconductor substrate. The semiconductor ingot 1 is cut while a coolant for cooling is supplied at least to the top side of the semiconductor ingot 1 and the inlet side and the outlet side where the wire 3 bites the semiconductor ingot 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor substrate manufacturing method for manufacturing a semiconductor substrate by cutting a semiconductor ingot using a wire to which abrasive grains are fixed.

  Conventionally, when a semiconductor substrate for a solar cell is formed of polycrystalline silicon or the like, for example, a polycrystalline silicon ingot is formed by a casting method, and the semiconductor ingot is formed by cutting the ingot into predetermined dimensions. After bonding to a glass, carbon material, or resin-made slice base with an epoxy-based adhesive or the like, it was cut into a plurality of sheets so as to have a predetermined thickness.

  As a method for cutting in this way, a cutting method using an outer peripheral blade, an inner peripheral blade or the like, or a cutting method using a wire saw is known. In particular, the cutting method using a wire saw can cut a large number of semiconductor ingots at the same time, with high cutting accuracy and less kerf loss (cutting loss), compared to the method using an outer peripheral blade or inner peripheral blade. It is preferably used.

  FIG. 6 shows a cutting method using a commonly used wire saw device. As shown in FIG. 6, a semiconductor ingot 1 bonded to a slice base 2 is installed, and a single wire 3 made of a piano wire or the like having a diameter of about 80 to 200 μm and having abrasive grains fixed by plating or resin or the like is wired. The supply reel 7 is wound around a plurality of grooves in which the wire 3 is fitted at regular intervals provided on the main roller 5 and arranged parallel to each other. Then, one or a plurality of semiconductor ingots 1 are gradually lowered toward the wires 3 and pressed against the semiconductor ingots 1 while moving the wires 3 stretched between the two main rollers 5 at a high speed. Then, the semiconductor ingot 1 is cut to produce a semiconductor substrate.

  As a cutting method using a wire saw, in addition to the method using the abrasive fixed wire shown here, abrasive grains such as SiC are mixed with oil or water to make a slurry, and this slurry is used as a normal wire (piano wire). A loose abrasive wire saw that is fed to and cut into a known shape is known.

The cutting method using the free abrasive wire is calculated from the wire diameter and the grain size because there are abrasive grains attached around the wire and abrasive grains brought in due to the viscosity of the slurry and the inertia of the wire running at high speed. However, according to the cutting method using an abrasive fixed wire, the abrasive grain size around the wire is determined, and it is possible to bring in more abrasive grains. Therefore, there is an advantage that cutting performance is high and kerf loss can be reduced.
JP 2000-296455 A JP 2000-158318 A

  The cutting method using a wire saw has the advantages as described above, but when the wire is pressed against the semiconductor ingot while running at high speed and the semiconductor ingot is cut, friction heat is generated in the cut portion, and the cut portion of the semiconductor ingot is generated by the friction heat. When the temperature is high, there are problems that the cutting accuracy is deteriorated and microcracks or the like are generated in the formed semiconductor substrate.

  In order to solve this problem, in a wire saw apparatus using an abrasive fixed wire saw, oil or water is directly applied to a contact portion between a semiconductor ingot and a wire in order to absorb frictional heat generated when the semiconductor ingot is cut. A method of supplying a main coolant liquid is shown (see Patent Document 1 and Patent Document 2).

  However, semiconductor substrates used for solar cells and the like are generally rectangular in shape, and are formed by slicing a rectangular semiconductor ingot. In particular, when cutting a 10 mm square or larger cuboid semiconductor ingot with an abrasive wire, it is possible to eliminate the problem that the cutting accuracy deteriorates or microcracks or the like are generated in the formed semiconductor substrate. could not.

  As a result of the study by the inventors, the following facts were found. The method disclosed in Patent Document 1 is a case where a cylindrical semiconductor ingot is cut, and the cutting distance by the wire is not constant, and the cutting distance becomes short at the start and end of ingot cutting. Therefore, frictional heat can be absorbed by supplying the coolant directly to the contact portion between the semiconductor ingot and the wire. However, when cutting a rectangular large semiconductor ingot, the cutting distance does not always change, so the cooling capacity of the coolant liquid brought into the cutting part is reduced, and especially the frictional heat can be absorbed sufficiently near the wire outlet. The problem of not being possible arises.

  In Patent Document 2, since the semiconductor ingot 1 placed below the wire 3 is raised and cut as shown in FIG. 7, the coolant liquid is supplied to the cut surface, which causes the above problem. Is expected to be resolved. However, the inventors have examined that when cutting a semiconductor ingot having a large rectangular shape, the cut portion of the semiconductor ingot becomes a groove shape as the cutting progresses, so that the supplied coolant liquid accumulates, It has been found that there is a problem that the surface roughness is deteriorated due to the vibration of the wire running at high speed due to the pressure.

  Therefore, an attempt was made to lower the coolant temperature in order to increase the cooling capacity of the coolant liquid and increase the cooling performance of the semiconductor ingot. However, the wire 3 is overcooled, and the life of the wire 3 is reduced due to thermal fatigue. It turns out that there is a fear. In addition, an attempt was made to increase the flow rate of the coolant liquid, but it was also found that the surface roughness is likely to deteriorate because the wire running at high speed is shaken by the pressure of the coolant liquid.

  The present invention has been made in view of such conventional problems, and absorbs frictional heat generated when cutting a semiconductor ingot, thereby suppressing cutting accuracy, deterioration of surface roughness, and generation of microcracks. An object of the present invention is to provide a method of manufacturing a semiconductor substrate that can be manufactured.

  In order to achieve the above object, a method of manufacturing a semiconductor substrate according to claim 1 of the present invention moves and runs a wire to which abrasive grains are fixed, and presses the semiconductor ingot from above the wire, thereby the semiconductor ingot. A semiconductor substrate manufacturing method for forming a semiconductor substrate by cutting at least a coolant for cooling at a top portion side of the semiconductor ingot and an inlet portion side and an outlet portion side into which the wire is cut into the semiconductor ingot. The semiconductor ingot was cut while supplying the liquid.

  A semiconductor substrate manufacturing method according to claim 2 of the present invention is the semiconductor substrate manufacturing method according to claim 1, wherein a top side of the semiconductor ingot is attached to a slice base, and through the slice base, The coolant liquid was supplied.

  A semiconductor substrate manufacturing method according to claim 3 of the present invention is the semiconductor substrate manufacturing method according to claim 1 or 2, wherein the semiconductor ingot has a rectangular cut surface.

  As described above, according to the method for manufacturing a semiconductor substrate of the present invention, the wire on which the abrasive grains are fixed is moved and moved, and the semiconductor ingot is pressed from above the wire to cut the semiconductor ingot. A method of manufacturing a semiconductor substrate for forming a substrate, at least while supplying a coolant liquid for cooling to the top side of the semiconductor ingot and the inlet side and the outlet side where the wire cuts into the semiconductor ingot, Since this semiconductor ingot is cut, the coolant liquid for cooling is supplied from the top of the semiconductor ingot so as to cover the entire semiconductor ingot, and the entire semiconductor ingot is efficiently cooled. As a result, the frictional heat generated at the cut portion is efficiently absorbed, so that the cutting accuracy is prevented from being deteriorated, and the problem that microcracks or the like are generated in the formed semiconductor substrate can be suppressed.

  Furthermore, even if the coolant liquid supplied is at a low temperature, the coolant liquid takes the heat from the semiconductor ingot and reaches the wire through the side of the semiconductor ingot. It is possible to prevent a decrease in life.

  Further, since the semiconductor ingot is lowered from above the wire and pressed against the wire for cutting, the coolant liquid supplied to the cut portion is less likely to accumulate. And since a coolant liquid is not supplied directly to a cut surface, it is less likely that the wire running at high speed will be shaken, and the problem that the surface roughness deteriorates can also be reduced.

  Further, the top side of the semiconductor ingot is attached to the slice base, and if the coolant liquid is supplied through the slice base, the semiconductor ingot can be cut while being stably held, and the semiconductor ingot The coolant liquid can be supplied in a stable and reproducible manner regardless of the shape of the semiconductor substrate, and the semiconductor substrate can be manufactured with a stable quality.

  Since the manufacturing method of the semiconductor substrate according to the present invention as described above can sufficiently exhibit the cooling effect of the coolant liquid, the cutting length is from the beginning to the end, particularly like a semiconductor ingot having a rectangular cutting surface. When the object to be cut is not changed, the effect is sufficiently exhibited. Therefore, when cutting a rectangular parallelepiped large-sized semiconductor ingot suitably used for a solar cell element, it is possible to suppress the generation of microcracks and the like and manufacture a high-quality semiconductor substrate.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a perspective view of a wire saw device according to a method for manufacturing a semiconductor substrate of the present invention, and FIG. 2 shows a positional relationship with a wire when a semiconductor ingot is cut with the wire saw device. In the figure, 1 is a semiconductor ingot, 2 is a slice base, 3 is a wire to which abrasive grains are fixed, 4 is a coolant supply nozzle, 5 is a main roller, 6 is a dip tank, 7 is a wire supply reel, and 8 is an end. It is a material entrainment prevention plate.

  The rectangular parallelepiped semiconductor ingot 1 to be cut is formed by cutting a polycrystalline silicon ingot formed by, for example, a casting method into a rectangular parallelepiped having a predetermined size, for example, 150 × 150 × 300 mm. One or a plurality of these semiconductor ingots 1 are arranged on a slice base 2 made of a material such as a carbon material, glass, or resin, and are bonded by an adhesive or the like.

  For example, the wire 3 is a piano wire mainly composed of iron or an iron alloy having a diameter of about 80 to 200 μm, and an abrasive grain having an average particle size of 10 to 20 μm formed of diamond or SiC is plated with, for example, nickel, copper, or chromium. Or fixed by a resin adhesive such as a resin. The wires 3 are supplied from a wire supply reel 7 and are wound and arranged in a groove having a predetermined interval provided on a main roller 5 described later.

  The main roller 5 is made of, for example, urethane rubber or the like, and a plurality of grooves in which the wires 3 are fitted at predetermined intervals are formed on the surface thereof. The thickness of the semiconductor substrate as the final product is determined by the relationship between the groove interval and the diameter of the wire 5.

  By rotating the main roller 5 at a predetermined rotation speed, the wire 3 can be moved and traveled, and is usually traveled at a high speed so as to be about 400 to 800 m / min.

  In this way, the semiconductor ingot 1 is cut by gradually lowering the semiconductor ingot 1 from above the wire 3 and pressing it against the wire 3 while moving the wire 3 to which the abrasive grains for cutting are fixed at high speed. Thus, a plurality of semiconductor substrates can be obtained. The end material entrainment prevention plate 8 is provided to prevent the end material of the semiconductor substrate that may fall during cutting from being entrained in the main roller 5, and if it cannot be prevented, the dip tank 6 is provided. Is provided. The dip tank 6 also has a purpose of collecting chips and coolant liquid during cutting.

  FIG. 3 shows a schematic view of cutting a semiconductor ingot by carrying out the semiconductor substrate manufacturing method of the present invention using the wire saw apparatus shown in FIG. In order to realize the method for manufacturing a semiconductor substrate of the present invention, the wire saw device is provided with a coolant liquid supply nozzle 4 on the top of the semiconductor ingot, and at least a coolant liquid for cooling is supplied from the coolant liquid supply nozzle 4 to the semiconductor ingot 1. The semiconductor ingot 1 is cut while being supplied to the top side and the inlet side and the outlet side where the wire 3 is cut into the semiconductor ingot 1. As shown in FIG. 3, when the semiconductor ingot 1 has a rectangular parallelepiped shape, the inlet side and the outlet side into which the wire 3 is cut are two opposite surfaces of the semiconductor ingot 1 that are orthogonal to the traveling direction of the wire 3.

According to such a configuration of the present invention, the coolant liquid is supplied from the top of the semiconductor ingot 1 instead of supplying the coolant liquid to the cutting portion and absorbing the frictional heat, so that the entire ingot can be cooled. It becomes possible. In particular, when the semiconductor ingot is silicon, since the thermal conductivity of silicon is as high as about 80 (W · m ⁻¹ · K ⁻¹ ), the entire semiconductor ingot can be sufficiently cooled, and a cut portion of the semiconductor ingot 1 can be obtained. It is possible to efficiently absorb the frictional heat generated by the above and suppress the temperature rise of the semiconductor ingot. As a result, it is possible to prevent the cutting accuracy from deteriorating and to suppress the problem that microcracks or the like are generated in the formed semiconductor substrate.

  In addition, when the rectangular parallelepiped semiconductor ingot 1 is used, the coolant is supplied to both side surfaces of the semiconductor ingot 1 perpendicular to the traveling direction of the wire 3, and the side surface of the semiconductor ingot 1 is removed while taking heat from the semiconductor ingot 1. Then, it reaches the wire 3 whose temperature has risen due to frictional heat and cools.

  Further, when the coolant liquid is supplied directly to the contact portion between the semiconductor ingot 1 and the wire 3, the wire 3 is overcooled when the coolant liquid is lowered to increase the cooling performance of the semiconductor ingot 1, and the wire 3 is changed due to thermal fatigue. In the case of the present invention, even if the coolant temperature is lowered, the coolant liquid passes through the wire 3 in a state where heat is taken from the semiconductor ingot 1, so that the wire is overcooled. Therefore, thermal fatigue can be suppressed, the life of the wire 3 can be prevented from being reduced, and the semiconductor ingot 1 can be efficiently cooled.

  Further, since the semiconductor ingot 1 is lowered from above the wire 3 and pressed against the wire 3 to be cut, the coolant liquid supplied to the cut portion is less likely to accumulate. And since coolant liquid is not supplied directly to a cut surface, even if the flow rate of coolant liquid is increased, the wire 3 that travels at high speed is less likely to be shaken, and the problem that surface roughness deteriorates can also be reduced. .

  As the coolant liquid, oil or water is used, but water is preferable in consideration of cooling performance and influence on the environment, and it is used in the range of 5 to 30 ° C. Moreover, you may add a rust preventive agent to coolant liquid in order to suppress rust, such as a wire. The supplied coolant liquid is once stored in the dip tank 6, circulated through the pipe, removed impurities such as semiconductor ingot chips contained in the coolant liquid, temperature controlled, and again supplied to the coolant liquid supply nozzle 4. It may be supplied.

  The above is the description of the basic configuration of the present invention. Next, a more preferable aspect will be described.

  As shown in FIGS. 1 and 2, it is preferable that the top side of the semiconductor ingot 1 is attached to a slice base 2, and the coolant liquid is supplied through the slice base 2. Since the slice base 2 has a thickness of about 10 to 30 mm, the semiconductor ingot 1 can be sufficiently cooled even when the coolant liquid is applied to the slice base 2. Therefore, the semiconductor ingot 1 can be cut while being held stably, and the coolant liquid can be supplied in a stable and reproducible state regardless of the shape of the semiconductor ingot 1. A substrate can be manufactured. In addition, in order to improve cooling property, you may provide a slit in the slice base 2 so that coolant liquid may be supplied directly to the upper part of a semiconductor ingot.

  One coolant liquid supply nozzle 4 may be provided in the upper part of the semiconductor ingot. However, in order to reliably supply the coolant liquid to the semiconductor ingot 1, it is preferable to provide it at a plurality of locations, for example, as shown in FIG. Further, it is desirable to provide the coolant liquid supply nozzle 4 at the upper part of both side surfaces of the semiconductor ingot. As shown in FIG. 4, it is desirable to provide the coolant liquid supply nozzles 4 at three locations corresponding to the top side of the semiconductor ingot 1 and the inlet side and the outlet side where the wire 3 cuts into the semiconductor ingot 1.

  Furthermore, it is more preferable to supply the coolant liquid to all four side surfaces of the semiconductor ingot and cut the semiconductor ingot. For example, as shown in FIG. 5, by installing the coolant liquid supply nozzle so as to surround the periphery of the semiconductor ingot 1, the coolant liquid is supplied to all four side surfaces of the semiconductor ingot. The entire ingot is cooled, and frictional heat generated at the cut portion of the semiconductor ingot 1 can be efficiently absorbed to suppress a temperature rise.

  Since the manufacturing method of the semiconductor substrate according to the present invention as described above can sufficiently exhibit the cooling effect of the coolant liquid, the cutting length is from the beginning to the end, particularly like a semiconductor ingot having a rectangular cutting surface. It is suitable for cutting an object that does not change, for example, a large-sized silicon ingot having a rectangular parallelepiped shape for a solar cell element. When the coolant is sprayed to the semiconductor ingot in the horizontal direction from the coolant supply nozzle arranged in parallel with the wire as in the prior art as shown in FIG. 7, the cutting distance is always longer than the cylindrical semiconductor ingot. This is because the frictional heat cannot be sufficiently absorbed, but the entire semiconductor ingot can be cooled and the frictional heat can be sufficiently absorbed by using the method of the present invention.

  It should be noted that the embodiment of the present invention is not limited to the above-described example, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  For example, the semiconductor ingot 1 may be inclined and provided in order to efficiently supply the coolant liquid in the wire entry direction of the semiconductor ingot.

  Further, as long as the coolant liquid is supplied to the top side of the semiconductor ingot and the inlet side and the outlet side where the wire is cut into the semiconductor ingot, the position and number of the coolant liquid supply nozzles are not limited.

  Further, in the above description, the example of performing the semiconductor substrate manufacturing method of the present invention using a multi-wire saw device that cuts a semiconductor ingot by arranging a plurality of wires at a predetermined interval has been described. However, even if a single-type wire saw device that performs cutting with a single wire is used, the method for manufacturing a semiconductor substrate of the present invention can be used, and the effects of the present invention are excellently achieved.

  First, a polycrystalline silicon ingot is prepared as a semiconductor ingot 1 of 150 mm square * L = 300 mm and bonded to the slice base 2. Then, one sample of the semiconductor silicon ingot 1 bonded to the slice base 2 is set in the wire saw device according to the method for manufacturing the semiconductor substrate of the present invention shown in FIG. 1, and the top side of the semiconductor ingot 1 and the semiconductor The coolant liquid supply nozzle 4 is provided at the position shown in FIG. 4 so that the coolant liquid is supplied to the inlet side and the outlet side where the wire 3 cuts into the ingot 1. Moreover, the wire 3 used the abrasive grain fixed wire which fixed the diamond abrasive grain with an average particle diameter of 10 micrometers to the piano wire which has a diameter of 180 micrometers by nickel plating.

  Thereafter, the coolant liquid supply nozzle 4 moves the semiconductor ingot 1 downward while supplying coolant liquid mainly composed of water to both side surfaces of the semiconductor ingot perpendicular to the traveling direction of the slice base 2 and the wire 3. A semiconductor substrate having a thickness of 300 μm was formed by pressing against the wire 3 running at a high speed of 700 m / min, cutting, and washing.

  As a comparative example, one semiconductor ingot made of polycrystalline silicon was set in the wire saw apparatus shown in FIG. 6, and a coolant liquid supply nozzle 4 was provided near the cutting of the semiconductor ingot 1. Moreover, the wire 3 used for a wire saw apparatus used the abrasive grain fixed wire which fixed the diamond abrasive grain with an average particle diameter of 10 micrometers to the piano wire which has a diameter of 180 micrometers by nickel plating. Then, while supplying the coolant directly to the contact portion between the semiconductor ingot 1 and the wire 3, the semiconductor ingot 1 is moved downward and pressed against the wire 3 running at a high speed of 700 m / min for cutting and cleaning. Thus, a semiconductor substrate having a thickness of 300 μm was formed.

In both the example and the comparative example, the surface roughness (surface roughness Ra, thickness variation of one sliced semiconductor substrate TTV, waviness WCM) is measured when the flow rate of the coolant is changed to 60 to 140 L / min. went. Table 1 shows the results for each coolant flow rate. Ra, TTV, and WCM indicate the average value of one semiconductor ingot. Ra is an arithmetic average roughness defined by JIS B0601 (2001), and TTV is one of the measures for showing the flatness of a semiconductor substrate. The WCM is the maximum wave swell defined by JIS B0610.

  According to Table 1, the surface roughness Ra, the thickness variation TTV of one sliced semiconductor substrate, and the swell WCM are obtained by slicing the semiconductor substrate obtained by slicing with the wire saw device of the example at each coolant flow rate. Good surface roughness was obtained compared to the comparative example.

  In addition, since the cooling performance of the semiconductor ingot is improved by increasing the flow rate of the coolant liquid, good surface roughness (Ra, TTV, WCM) can be obtained in the comparative examples and examples. When increased to 120 and 140 L / min, the wire running at a high speed in the comparative example was shaken, so the surface roughness was the same as or worsened when the coolant flow rate was 100 L / min. On the other hand, in the Example which concerns on this invention, in order to cool a semiconductor ingot efficiently, without shaking a wire, the further favorable surface roughness was obtained.

It is a schematic perspective view which shows the wire saw apparatus which concerns on the manufacturing method of the semiconductor substrate of this invention. It is a figure which shows the positional relationship of the semiconductor ingot adhere | attached with the slice base and the wire for cutting in the manufacturing method of the semiconductor substrate of this invention. It is a schematic diagram explaining the manufacturing method of the semiconductor of this invention using the wire saw apparatus shown in FIG. It is a schematic diagram explaining the manufacturing method of the semiconductor of this invention using another example of a wire saw apparatus. It is a figure which shows the positional relationship of the coolant supply nozzle and semiconductor ingot which concern on this invention, (a) is a top view, (b) is a side view. It is the schematic which shows an example of the conventional wire saw apparatus. It is the schematic which shows the other example of the conventional wire saw apparatus.

Explanation of symbols

1: Semiconductor ingot 2: Slice base 3: Wire 4: Coolant liquid supply nozzle 5: Main roller 6: Dip tank 7: Wire supply reel 8: End material entrainment prevention plate

Claims (3)

A method of manufacturing a semiconductor substrate in which a wire having abrasive grains fixed thereon is moved and traveled, a semiconductor ingot is pressed from above the wire, and the semiconductor ingot is cut to form a semiconductor substrate,
At least a semiconductor substrate in which the semiconductor ingot is cut while supplying a coolant liquid for cooling to the top side of the semiconductor ingot and the inlet side and the outlet side where the wire cuts into the semiconductor ingot. Production method. The semiconductor substrate manufacturing method according to claim 1, wherein a top side of the semiconductor ingot is attached to a slice base, and the coolant liquid is supplied through the slice base. The method of manufacturing a semiconductor substrate according to claim 1, wherein the semiconductor ingot has a rectangular cut surface.

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