JP2012033762A - Method and equipment for manufacturing semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and equipment for manufacturing a semiconductor wafer, capable of suppressing a change in cut shape of the wafer due to the influence of frictional heat generated between a wire and a work.SOLUTION: A method for manufacturing a semiconductor wafer, in which a work 17 is cut by using wire saws 11 formed by winding wires 13 around a plurality of rollers 12 to manufacture the wafer, the method comprises: providing cutting sections 16 of the wire saws 11 so as to be immersed in a slurry tank 18 filled with a slurry 15; providing a slurry supply pipe 20 above the wires 13 of the cutting sections 16, for blowing the slurry 15; providing a work 17 in the slurry tank 18 below the wires 13 of the cutting sections 16, so as to be immersed in the slurry 15; pressing the work 17 against the wires 13 of the cutting sections 16 above the work 17; blowing the slurry 15 from the slurry supply pipe 20 to the cutting sections 16; cutting the work 17; and circulating the slurry 15 from the slurry tank 18 into the slurry supply pipe 20 through a temperature control tank 21.

Description

  The present invention relates to a semiconductor wafer manufacturing method and apparatus for manufacturing a GaAs crystal by slicing using a wire saw.

  A semiconductor wafer of GaAs crystal is manufactured by producing a single crystal ingot by crystal growth, slicing (cutting) it with a method such as inner peripheral edge slicing or wire saw slicing, and further chamfering / polishing to make a disk-shaped Processed into a mirror wafer.

  In recent years when single crystal ingots have become larger in diameter, cutting with a wire saw has become the mainstream.

  The basic structure of a conventional wire saw is shown in FIG.

  The wire saw 31 is formed by winding a wire 33 around a plurality of rollers 32, a wire 33 of a cutting part 35 of the wire saw 31, a slurry supply pipe 38 for supplying a slurry 37 to the work 36, a work 36 and a cutting part 35. A pressing means 39 for pressing the workpiece 36 against the wire 33 is provided.

  The roller 32 is provided with a plurality of wire grooves 40 for fixing the position and interval of the wire 33, and the wire 33 is spirally wound around the plurality of rollers 32 while being fitted in the wire groove 40, and both ends thereof are , Connected to a take-up reel (not shown).

  The pressing unit 39 includes a jig 41 for holding the workpiece 36 on the pressing unit 39, and the workpiece 36 is held on the pressing unit 39 via the jig 41.

  Slurry 37 comprising abrasive grains for cutting and coolant for cooling the workpiece is sprayed from the slurry supply pipe 38 to the wire 33 and the workpiece 36 of the cutting portion 35, and the wire 33 is reciprocated by rotating the roller 32 forward and backward. The workpiece 36 is lifted by the pressing means 39 and pressed against the wire 33 of the cutting portion 35, thereby cutting the workpiece 36 into a wafer shape.

  Products manufactured using cut wafers are not only damaged in appearance, but also have limitations on the surface shape after mirroring in polishing operations, such as warpage and fine irregularities on the surface. However, the standard value varies, but it is common knowledge that the smoother the semiconductor wafer, the higher the quality of the product can be produced. In the process of processing, it is necessary to establish a processing method that does not cause the occurrence of surface shape variation.

  In particular, the warp shape and unevenness that occurred on both sides of the wafer during the initial operation of slicing the single crystal ingot is transferred to the back surface (after polishing, the warp shape and unevenness remaining on the back surface are reflected when the restraint from the fixing jig is released. The thickness of the wafer so that unevenness does not occur on both sides of the wafer even when the wafer is cut. Is required to be uniform.

  In the wire saw 31, heat is generated due to friction between the wire 33 and the workpiece 36 to be cut. Therefore, when this heat is transferred to the roller 32 through the wire 33, the roller 32 expands, and the wire provided on the roller 32. There is a possibility that the gap between the grooves 40 is deviated and the gap between the wires 33 is changed to change the wafer thickness from the set dimension.

  Further, when cutting the workpiece 36 made of a cylindrical ingot or the like, the frictional heat generated along with the change in the length of the contact portion between the wire 33 and the workpiece 36 increases and decreases, so the wire wound around the roller 32 The interval between the 33s varies, which causes a variation in the thickness of the wafer after cutting.

  In order to reduce the variation in wafer thickness due to this temperature change, the wire saw 31 is subjected to temperature control of the slurry 37 sprayed from the slurry supply pipe 38 to generate a heat source (that is, a contact portion between the workpiece 36 and the wire 33). Etc.) may be provided to provide a slurry temperature control device (not shown) that suppresses changes in the dimensions of the wire saw 31 and the wafer.

  Note that prior art document information related to the invention of this application includes the following.

Japanese Patent No. 3923107 Japanese Patent No. 3635870

  As described above, the wire saw may be provided with a temperature control device that controls the temperature of the slurry. However, in the conventional structure, the temperature control device does not directly control the temperature of the heat source. Since precise and quick temperature control cannot be performed with respect to the temperature change, it is impossible to avoid a deviation in the wafer thickness of several μm.

  Particularly in recent years, with the improvement of slicing technology, the diameter and length of single crystal ingots to be sliced have been further increased in order to improve the productivity of wafers, so the contact portion between the wire and workpiece has become longer. As a result, it becomes more difficult to quickly control the temperature of the heat source, and it becomes difficult to satisfy the uniformity of the wafer thickness and the flatness of the wafer surface at the same time.

  The present invention has been made to solve the above problems, and a method for manufacturing a semiconductor wafer capable of suppressing the change in the cutting shape of the semiconductor wafer due to the influence of frictional heat generated between the wire and the workpiece, and the method thereof A device is provided.

  In order to achieve the above object, the present invention provides a method of manufacturing a semiconductor wafer in which a wire is wound between a plurality of rollers and a workpiece is manufactured by cutting a workpiece. Provided by immersing in the accumulated slurry tank, and providing a slurry supply pipe for spraying the slurry above the wire of the cutting part, and providing the work soaked in the slurry in the slurry tank below the wire of the cutting part Then, the workpiece is pressed against the wire of the cutting part above it, and the slurry is blown from the slurry supply pipe to the cutting part for cutting, and the slurry in the slurry tank is passed through the temperature control tank to the slurry supply pipe A method for manufacturing a semiconductor wafer, characterized in that the semiconductor wafer is circulated.

  The slurry stored in the slurry tank is circulated to a temperature control tank capable of temperature control, the slurry is supplied from the temperature control tank to the slurry supply pipe, and the temperature of the workpiece and the wire of the cutting unit is controlled. May be.

  The wire saw and the slurry tank may be separated from each other when installing and removing the workpiece.

  Further, the present invention provides a wire saw in which a wire is wound between a plurality of rollers, and in a semiconductor wafer manufacturing apparatus for manufacturing a wafer by cutting a workpiece, the slurry is stored so that the cutting portion of the wire saw is immersed in the slurry. A slurry tank provided, a slurry supply pipe provided above the wire of the cutting part and spraying the slurry, and holding the workpiece so as to be immersed in the slurry in a slurry tank below the wire of the cutting part, and above Pressing means for pressing the workpiece against the wire of the cutting portion, a temperature control tank for controlling the temperature of the slurry stored in the slurry tank, and supplying the slurry in the slurry tank via the temperature control tank A semiconductor wafer manufacturing apparatus comprising a circulating means for circulating in a tube.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the cutting shape of a semiconductor wafer changes under the influence of the frictional heat which generate | occur | produces between a wire and a workpiece | work.

It is a block diagram which shows embodiment of this invention. It is a figure which shows the effect of this invention. It is a perspective view which shows the structure of the conventional wire saw.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  FIG. 1 shows a configuration of an apparatus for cutting a semiconductor wafer using a wire saw 11 according to the present embodiment.

  The wire saw 11 is formed by winding a wire 13 around three rollers 12, a slurry tank 18 that accumulates the slurry 15, immerses the cutting portion 16 of the wire saw 11 in the slurry 15, and immerses and holds the workpiece 17 in the slurry 15; Pressure means 19 provided in the slurry tank 18 to press the workpiece 17 against the wire 13 of the cutting portion 16, a slurry supply pipe 20 that sprays the slurry 15 onto the wire 13 and the workpiece 17 of the cutting portion 16, and temperature adjustment of the slurry 15. A temperature control tank 21 is provided, and a circulation means 22 that circulates the slurry 15 stored in the slurry tank 18 to the slurry supply pipe 20 through the temperature control tank 21.

  As in the conventional structure shown in FIG. 3, a plurality of wire grooves 23 are formed in the roller 12 at intervals of a dimension at which the workpiece 17 (single crystal ingot) is desired to be cut, and the wires 13 are fitted into the wire grooves 23 while being fitted 3. The two rollers 12 are spirally wound, and both ends thereof are connected to a take-up reel (not shown).

  The slurry tank 18 provided below the wire saw 11 is shaped and dimensioned so that the cutting portion 16 of the wire saw 11 can be immersed in the slurry 15 while holding the workpiece 17 and the pressing means 19 inside.

  The wire saw 11 and the slurry tank 18 are provided so as to be close to and away from each other. When the work 17 is installed and removed from the slurry tank 18, the wire saw 11 and the slurry tank 18 are separated and the work 17 is cut. When doing so, the wire saw 11 and the slurry tank 18 are brought close to each other.

  The slurry supply pipe 20 is provided above the wire 13 of the cutting portion 16, and the slurry 15 in which abrasive grains are suspended is blown to the lower wire 13 and the work 17 during the cutting operation, and the slurry 15 is applied to the slurry tank 18. It is made to accumulate.

  The pressing means 19 provided in the slurry tank 18 includes a jig 24 for fixing the work 17. The work 17 is fixed to the pressing means 19 via the jig 24, and the slurry 15 is placed in the slurry tank 18. Soaked and held.

  In the present invention, the pressing means 19 is not particularly limited. For example, an actuator capable of moving up and down may be used.

  The circulation means 22 includes a pipe 22a for connecting the slurry tank 18 and the temperature control tank 21, a pipe 22b for connecting the temperature control tank 21 and the slurry supply pipe 20, and a pipe 22b for the slurry 15 in the temperature control tank 21. And a liquid feed pump 22p provided in the temperature control tank 21 to feed the slurry to the slurry supply pipe 20 at a predetermined pressure.

  Further, the temperature control tank 21 includes a temperature measuring means for detecting the temperature of the slurry 15 and a temperature control means for controlling the temperature of the slurry 15 to a set temperature.

  Next, a method for cutting a single crystal ingot according to the present embodiment will be described.

  First, the wire saw 11 and the slurry tank 18 are separated from each other, the workpiece 17 (single crystal ingot) is fixed to the pressing means 19 via the jig 24, and then the wire saw 11 and the slurry tank 18 are brought close to each other.

  Since the wire saw 11 and the slurry tank 18 are provided close to and away from each other, the work 17 can be easily installed and removed.

  Thereafter, the slurry 15 whose temperature is controlled by the temperature control tank 21 is circulated to the slurry supply pipe 20 by the circulation means 22, and the slurry 15 is sprayed from the slurry supply pipe 20 to the wire 13 and the workpiece 17 of the cutting portion 16, and While rotating the wire 13, the work 17 is pressed against the wire 13 of the cutting portion 16 by the pressing means 19 to start cutting.

  The roller 12 is driven so that the wire 13 reciprocates by switching between normal rotation and reverse rotation. However, if the wire 13 travels at the same position, disconnection due to wear may occur at an early stage, and therefore winding (not shown) is performed. The new wire 13 is fed forward little by little from the reel (for example, the new wire 13 is supplied by 20 cm by the operation of moving forward 50 cm and returning 30 cm).

  The slurry 15 sprayed onto the wire 13 and the workpiece 17 of the cutting unit 16 includes cutting abrasive grains. The abrasive grains are rolled between the wire 13 and the workpiece 17 to cut the workpiece 17, and the pressing means 19 Furthermore, the workpiece 17 is cut by pressing the workpiece 17 against the wire 13 of the cutting portion 16.

  At this time, the wire 13 and the workpiece 17 generate frictional heat, but the cutting portion 16 and the workpiece 17 are immersed and held in the slurry 15 in the slurry tank 18 in which the slurry 15 is accumulated, and the frictional heat is transmitted to the roller 12. The temperature is controlled so as not to heat.

  Here, the difference between the conventional wire saw 31 and the wire saw 11 according to the present embodiment will be described in detail below.

  In the structure of the conventional wire saw 31 (FIG. 3), the slurry 37 mainly supplies cutting abrasive grains and cools the work 36 that has generated heat. The slurry 37 supplied to the wire 33 and the workpiece 36 is stored in a slurry tank installed outside the wire saw 31 by a system such as drainage of a sink, and the temperature is controlled by an external temperature control tank, and the slurry supply pipe is again formed. 38 is fed.

  Other than the slurry 37 sprayed on the wire 33 and the workpiece 36 of the cutting part 35 are immediately discharged out of the apparatus, the cooling effect on the cutting part 35 is low, and the slurry 37 discharged to the outside of the wire saw 31 and the cutting part 35 A temperature difference is generated between the wire 33 and the workpiece 36.

  Therefore, there is a time difference from when the temperature control tank detects that the temperature of the wire 33 and the roller 32 has been increased by heat transfer from the cutting unit 35 through the slurry 37 until the temperature control of the slurry 37 starts. At the same time, since it takes a response time until the temperature of the workpiece 36 and the wire 33 is actually cooled after the temperature control of the slurry 37 is started to cool the workpiece 36 and the wire 33 whose temperature has increased, the workpiece serving as a heat source is also required. Since the temperature of the wire 36 and the wire 33 cannot be quickly controlled, the change in the cutting shape of the wafer due to the temperature change cannot be completely suppressed, but only to be relaxed.

  Further, in recent years, when cutting a workpiece 36 (single crystal ingot) having a large diameter and a long length, the length of the contact portion between the wire 33 and the workpiece 36 changes with the progress of the cutting. The temperature change of the frictional heat generated during the work increases and decreases, and the dimensional variation of the semiconductor wafer cutting shape increases.

  On the other hand, in the structure of the wire saw 11 according to the present invention (FIG. 1), the slurry 15 sprayed from the slurry supply pipe 20 is accumulated and the wire 13 of the cutting portion 16 is stored in order to reduce the thermal fluctuation of the wire 13 and the roller 12. A slurry tank 18 for holding the workpiece 17 inside is provided, and the wire 13 of the cutting portion 16 and the workpiece 17 are immersed in the slurry 15 to perform the cutting operation of the workpiece 17.

  Since a large amount of the slurry 15 is stored in the slurry tank 18, the frictional heat generated between the wire 13 of the cutting portion 16 and the work 17 is quickly and sufficiently generated by the slurry 15 stored in the slurry tank 18. Heat transfer and thermal expansion to the roller 12 can be suppressed by cooling, and a change in the cutting shape due to a dimensional change in the wire groove 23 can be suppressed.

  Further, since the temperature of the wire 13 and the workpiece 17 of the cutting unit 16 is substantially the same as the temperature of the slurry 15 stored in the slurry tank 18, the temperature adjustment tank 21 changes the temperature of the wire 13 and the workpiece 17 via the slurry 15. Thus, the temperature control of the slurry 15 can be started quickly, and the responsiveness to the change in the cutting shape of the workpiece 17 due to frictional heat can be improved.

  Thereby, even when cutting the workpiece 17 having a large diameter and a long length, it is possible to realize a cutting accuracy of several μm.

  When the cutting is completed (that is, when the workpiece 17 is cut into a wafer shape), the workpiece 17 is lowered by the pressing means 19 while the rotation of the roller 12 and the circulation of the slurry 15 are stopped. In order to remove 17 from the slurry tank 18, the wire saw 11 and the slurry tank 18 are separated from each other.

  Since the wire saw 11 and the slurry tank 18 are provided so as to be close to and away from each other, the workpiece 17 can be easily taken out from the slurry tank 18.

  As described above, according to the method and apparatus for manufacturing a semiconductor wafer according to the present invention, when the workpiece 17 is cut, the wire 13 of the cutting portion 16 and the workpiece 17 are immersed and held in the slurry 15 in the slurry tank 18. As a result, the frictional heat generated between the wire 13 and the workpiece 17 can be sufficiently cooled by the slurry 15 stored in the slurry tank 18, and the temperature of the slurry 15 whose temperature has changed can be quickly increased by the temperature adjustment tank 21. Since it can be controlled, dimensional fluctuations of the roller 12 and the wire groove 23 due to heat transfer of frictional heat can be suppressed, and cutting accuracy can be improved even in a large-diameter / long workpiece (single crystal ingot).

  In addition, since the amount of wafer grinding necessary for obtaining a mirror surface is reduced in the polishing process after cutting, the working efficiency of the polishing process and the yield of the single crystal ingot can be improved.

  Examples of the present invention will be described below.

  In FIG. 2, a 4-inch GaAs single crystal ingot was cut into a wafer shape, and an error profile (ie, surface roughness) from the set thickness of the wafer thickness was measured from one end to the other end in the radial direction of the wafer. The results are shown, wherein (a) shows the wire saw according to the present invention, and (b) shows the error profile of the wafer cut using the conventional wire saw.

  As shown in FIG. 2 (b), when a wire saw having a conventional structure is used, frictional heat generated in the wire and workpiece at the cutting portion during cutting, and dimensional change of the roller due to the heat transfer cannot be suppressed. Because the responsiveness to the temperature change of the frictional heat accompanying the change in the length of the part is low, the wafer surface becomes rough, and the difference between the thickness of the thickest part and the thinnest part of the wafer is increased to 10 μm or more. I understand.

  On the other hand, as shown in FIG. 2 (a), when the wire saw according to the present invention is used, during the cutting, the slurry accumulated in the slurry tank promotes cooling of the frictional heat generated in the wire and workpiece of the cutting part. Since the frictional heat generated from the heat source is immediately transferred to the slurry, the temperature control response is high, so the variation in wafer thickness is low (that is, the flatness of the wafer is high), and the thickest part and the It can be seen that a large-diameter wafer having a high-quality surface shape can be manufactured with a difference in thickness of the thin part of about 8 μm.

DESCRIPTION OF SYMBOLS 11 Wire saw 12 Roller 13 Wire 15 Slurry 16 Cutting part 17 Work 18 Slurry tank 20 Slurry supply pipe 21 Temperature control tank

Claims (4)

  In a semiconductor wafer manufacturing method for manufacturing a wafer by cutting a workpiece with a wire saw formed by winding a wire between a plurality of rollers, the cutting portion of the wire saw is provided by being immersed in a slurry tank in which slurry is accumulated, A slurry supply pipe for spraying the slurry is provided above the wire of the cutting part, and the work is immersed in the slurry in a slurry tank below the wire of the cutting part, and the wire of the cutting part above the wire is The semiconductor is characterized in that a workpiece is pressed and the slurry is blown from the slurry supply pipe to the cutting portion to be cut, and the slurry in the slurry tank is circulated to the slurry supply pipe through a temperature control tank. Wafer manufacturing method.   The slurry stored in the slurry tank is circulated to a temperature control tank capable of temperature control, the slurry is supplied from the temperature control tank to the slurry supply pipe, and the temperature of the workpiece and the wire of the cutting unit is controlled. A method for producing a semiconductor wafer according to claim 1.   The method for manufacturing a semiconductor wafer according to claim 1 or 2, wherein the wire saw and the slurry tank are separated from each other when the workpiece is set and taken out.   In a semiconductor wafer manufacturing apparatus that manufactures a wafer by cutting a workpiece with a wire saw formed by winding a wire between a plurality of rollers, a slurry tank provided to accumulate slurry and immerse the cutting portion of the wire saw in the slurry; A slurry supply pipe that is provided above the wire of the cutting portion and sprays the slurry, and holds the workpiece so as to be immersed in the slurry in a slurry tank below the wire of the cutting portion. Pressing means for pressing the workpiece against the wire, a temperature control tank for controlling the temperature of the slurry stored in the slurry tank, and circulation for circulating the slurry in the slurry tank to the slurry supply pipe via the temperature control tank Means for manufacturing a semiconductor wafer.

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