JP2007281176A - Slicing method of semiconductor ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce kerf loss and a margin by further scaling down grains than a present grain size, and to improve manufacturing efficiency and maintain the quality of a wafer by improving the yield of the wafer. <P>SOLUTION: A semiconductor ingot is sliced using abrasive grains within a range other than No.2000 or lower and No.3000 or more. In this case, in order to increase a compulsive force when the semiconductor is pressed on the wire, a slicing median velocity is set at a slicing velocity of not less than 415 μm/min, and the semiconductor ingot is sliced. Specifically, when the diameter of the wire has a value lower than 0.14 mm and larger than 0.12 mm, the tensile load is set at a value lower than 2.3 kg/f and larger than 2.1 kg/f; and when the diameter of the wire has a value not more than 0.12 mm, the tensile load is set at a value not more than 2.1 kg/f. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for cutting a semiconductor ingot, and more particularly to a method for cutting a single crystal silicon ingot using a wire saw device.

  In the silicon wafer cutting process, the single crystal silicon ingot is cut by a wire saw device. That is, a slurry containing abrasive grains is supplied to the cutting portion of the single crystal silicon ingot, and while the tensile load is applied to the wire that is wound around the roller, the silicon ingot is relatively moved in the direction of pressing the wire against the wire. Then, a plurality of silicon wafers are acquired. In the longitudinal direction of the roller, a wire is wound at a predetermined pitch, and as shown in FIG. 1 (b), a wafer having a thickness corresponding to the roller pitch length, where the ingot is pressed The number of silicon wafers 1 a corresponding to the number of wire turns is simultaneously generated from one silicon ingot 1.

  In the cutting process, in order to improve the yield of silicon wafer production by improving the acquisition rate of silicon wafers, it is required to reduce “g / piece” to minimize the production loss. Here, “g / sheet” is a value obtained by dividing the weight of the silicon ingot by the number of silicon wafers acquired from the silicon ingot.

  It has been found that the kerf loss (cutting allowance) can be reduced in order to reduce “g / sheet”.

  FIG. 1A conceptually shows a state where the ingot 1 is cut into the wafer 1 a by the wire 6. Since the abrasive grains 31 in the slurry are interposed between the wire 6 and the cut surface, the kerf loss (cutting allowance) adds the wire diameter of the wire 6 to twice the grain diameter of the abrasive grains. Length. Further, as shown in FIG. 1B, since it is necessary to secure a machining allowance for performing processing such as etching in the subsequent process of the cutting process, the manufacturing loss increases as the machining allowance increases.

  Further, it is ideal that the wafer 1a produced by cutting has a completely flat cut surface, and the flatness (TTV value) and surface roughness (Ra value) are as small as possible. desirable.

  If the flatness (TTV value) and surface roughness (Ra value) of the cut surface of the wafer 1a (the surface of the wafer 1a) show large values, it will take time and labor for the lapping process, etching process, polishing process, etc. In short, the manufacturing efficiency of the wafer is impaired.

  Further, as shown in FIG. 2, periodic irregularities called “waviness” may occur on the cut surface of the wafer 1a.

  Further, as shown in FIG. 3, the wafer 1a may have a warp called warp as shown in FIG.

  When “undulation” or warp occurs, time and labor are required for the subsequent lapping process, etching process, polishing process, etc., and the wafer production efficiency is impaired.

  In addition, the warp direction and thickness may vary between individual wafers 1a obtained from silicon ingots. If these variations occur, time and labor are required for the lapping process, etching process, polishing process, etc. in the subsequent processes. However, the manufacturing efficiency of the wafer is impaired.

As can be seen from FIG. 1, the smaller the grain size of the abrasive grains 31 and the smaller the wire diameter of the wire 6, the smaller the production loss, the smaller "g / sheet", and the yield can be improved. Further, the smaller the grain size of the abrasive grains 31, the smaller the damage given to the surface of the cut wafer 1a, the smaller the machining allowance in the subsequent process performed to remove the damaged layer, and the reduction of manufacturing loss. Contribute.

  As described above, in the cutting process, it is understood that using the wire 6 having a small wire diameter and using the abrasive grain 31 having a small particle diameter can reduce the manufacturing loss and improve the yield. Yes.

  For this reason, for the purpose of reducing kerf loss, the abrasive grains 31 and the wires 6 have been thinned.

  However, as the grain size of the abrasive grains 31 is reduced and the count of the abrasive grains 31 is increased, the abrasive grains 31 are more easily clogged between the wire 6 and the cut surface, the sharpness is worsened, and the cutting speed is reduced. The conventional technical common sense is that the quality of the cut surface of the wafer 1a deteriorates.

  That is, as the count of the abrasive grains 31, conventionally, those corresponding to # 600 to # 1500 have been used in JIS. However, when the abrasive grains 31 with a count higher than this are used, the waviness increases and the surface roughness ( Conventional technical common sense is that a quality problem such as a high (Ra value) is predicted.

  The present invention has been made in view of such a situation, and by further miniaturizing the abrasive grains than those of the current grain size, the kerf loss and the machining allowance are reduced, and the wafer acquisition rate is improved. Thus, an object of the present invention is to improve manufacturing efficiency and maintain wafer quality.

The first invention is
A slurry containing abrasive grains is supplied to the cutting portion of the semiconductor ingot, and a tensile load is applied to the wire that is wound around the roller while being moved relative to the wire at a predetermined cutting speed in the direction of pressing the semiconductor ingot against the wire. In the semiconductor ingot cutting method that cuts the semiconductor ingot,
When cutting a semiconductor ingot using a count of abrasive grains in a range excluding 2000 or less and 3000 or more,
A semiconductor ingot cutting method for cutting a semiconductor ingot by setting the cutting center speed to a cutting speed of 415 μm / min or more in order to increase the forcing force when the semiconductor is pressed against the wire. To do.

The second invention is the first invention,
When the wire diameter is 0.14 mm or less and a value exceeding 0.12 mm, the tensile load is set to a value exceeding 2.3 kg / f and exceeding 2.1 kg / f,
When the wire diameter is 0.12 mm or less, the tensile load is set to 2.1 kg / f or less.

The third invention is the first invention,
Two or more semiconductor ingots to be cut are arranged in a line along the longitudinal direction of the roller.

  That is, when the present inventor increases the count of the abrasive grains 31 to a range excluding the 2000th and below and the 3000th and beyond, the cutting ability of the abrasive grains 31 is improved against the conventional technical common sense. However, it was found that if the other conditions remain the same as the conventional conditions, the amount of deflection is reduced and the quality of the warp is degraded. The decrease in the amount of bending of the wire is considered to be caused by the fact that the forcing force of the wire 6 is weakened. If the cutting center speed is increased to increase the forcing force of the wire 6, warp I thought the quality would improve.

  As shown in FIGS. 16A and 16B, if the cutting center speed is set to 415 μm / min or more, the average value AVE of the warp size and the variation σ of the warp size become below the reference level, It was confirmed that it reached below the quality standard level of the wafer surface.

  Further, in the case of sticking two, a particularly high quality improvement effect was observed.

  Therefore, according to the present invention, it is possible to reduce the kerf loss and the machining allowance by making the abrasive grains finer, the wafer acquisition rate is improved, and the wafer manufacturing efficiency is improved. In addition, the quality of the warp is improved, so that the quality of the wafer can be maintained.

  Embodiments of a method for cutting a semiconductor ingot according to the present invention will be described below with reference to the drawings. In the present embodiment, it is assumed that a silicon wafer 1a having a diameter of 200 mm is manufactured. However, the present embodiment can be similarly applied when manufacturing a wafer having an arbitrary diameter such as a silicon wafer having a diameter of 300 mm.

  FIG. 4 is a perspective view showing the configuration of the wire saw device of the embodiment. FIG. 5 is a view showing a state in which the silicon ingot 1 is cut by the wire 6, and is a view of the silicon ingot 1 as viewed from the cut surface direction.

  As shown in these drawings, the rollers 7, 8, 9 are arranged at a predetermined distance so that the longitudinal axis directions of the processing rollers 7, 8, 9 coincide with the longitudinal axis direction of the silicon ingot 1. The processing rollers 7 and 8 are disposed on the upper side in the figure, and the processing roller 9 is disposed on the lower side in the figure. A wire 6 is wound around each of the rollers 7, 8, 9. The wire 6 is fed to the rollers 7, 8, and 9 by the feeding reel 10 and wound by a winding reel (not shown). The feeding reel 10 is driven by a reel driving motor 11.

  A wire 6 is wound around each of the rollers 7, 8 and 9 at a constant pitch along the longitudinal direction of the roller. The distance between the roller pitches is set to a length corresponding to the thickness of the wafer 1a (FIG. 1B).

  Further, a constant tension, that is, a constant tensile load (tension; kg / f) is applied to the wire 6 between the rollers 7, 8, 9 by the tension adjusting mechanism. That is, a tension adjusting guide roller 12 is provided between the feed-side reel 10 and the rollers 7, 8, 9, and the wire 6 is wound around the tension adjusting guide roller 12. The position of the tension adjusting guide roller 12 is adjustable, and the tensile load of the wire 6 is adjusted by adjusting the position of the tension adjusting guide roller 12. For example, the actual tensile load of the wire 6 is detected by a sensor, and the position of the tension adjusting guide roller 12 is adjusted so that a desired constant tensile load can be obtained using the detection result of the sensor as a feedback amount. .

  A rotating shaft of a roller driving motor 13 is connected to any one of the processing rollers 7, 8, 9. When the roller driving motor 13 is rotationally driven, for example, the seven processing rollers are rotationally driven, and accordingly, the other rollers 8 and 9 are driven to rotate and the wire 6 travels.

  In FIG. 5, the rollers 7, 8, and 9 rotate in the left direction, so that the wire 6 travels counterclockwise. As the wire 6 travels in one direction (left direction), the wire 6 is taken up by the take-up reel. When the wire 6 is fed leftward at a predetermined amount and at a predetermined constant speed, the traveling speed is reduced and temporarily stopped, and the roller driving motor 13 is rotationally driven in the reverse direction (rightward). The take-up reel functions as a feed reel, and the wire 6 runs in the reverse direction (right direction). When the traveling speed of the wire 6 increases and reaches a constant speed, the wire 6 travels while maintaining a predetermined amount and a predetermined constant speed in the same manner as when traveling in the left direction. Thereafter, the same cycle is repeated. Such reciprocation of the wire 6 is taken as one cycle, and the silicon ingot 1 is cut. The number of reciprocations of the wire 6 per minute (60 s) is referred to as the number of wire cycles. The number of wire cycles is, for example, 1 (times / min). Also, the time from when the speed of the wire 6 decreases until it temporarily stops, travels in the reverse direction, and reaches a predetermined constant speed is called a wire variable speed. The wire variable speed is, for example, 3 to 6 s. Moreover, the average value of the speed which the wire 6 drive | works is called a wire average linear velocity, for example, is 500-650 (m / min).

  As described above, the wire 6 cuts the silicon ingot 1 while reciprocating. Since the wire 6 wears as the time for reciprocating the wire 6 and cutting the silicon ingot 1 increases, the feeding reel 10 feeds out the new wire 6 at a predetermined new wire supply rate (m / min). . The new wire 6 supplied from the feeding reel 10 is taken up by the take-up reel.

  The ingot 1 is bonded to a work plate 2 made of graphite. The work plate 2 is bonded to the set plate 3. When the ingot 1 is bonded to the work plate 2 and the work plate 2 is bonded to the set plate 3, the posture of the ingot 1 is adjusted so that the cutting direction of the ingot 1 coincides with the crystal plane. That is, the direction of the central axis of the ingot 1 is adjusted so that the crystal orientation of the ingot 1 is perpendicular to the cutting direction of the wire 6. The set plate 3 is attached to the lifting base 4. The lifting base 4 is moved up and down in the vertical direction in FIG. 5 by a lifting motor (not shown).

  A slurry supply pipe 14 is disposed above the processing rollers 7 and 8. A supply port 14a is opened in the slurry supply pipe 14, and the slurry 30 including the abrasive grains 31 is discharged from the supply port 14a. The slurry supply pipe 14 is freely accessible in the vicinity of the cut portion of the ingot 1 by a moving mechanism.

  Here, the slurry 30 is, for example, mineral oil (PS-LW-50), a slurry specific gravity of 1.48 to 1.54 (g / cc), and a slurry viscosity of 160 to 260 (cp, 25 ° C., 20 rpm) is used. The particle size of the abrasive grains 31 will be described later.

  The slurry 30 supplied to the cutting site between the wire 6 and the ingot 1 is collected in the slurry tank 15. The slurry 30 collected in the slurry tank 15 is sucked by the pump, discharged from the pump, and supplied to the slurry supply pipe 14 again. The slurry 30 absorbs heat generated when the ingot 1 is cut and rises in temperature. Therefore, the recovered slurry 30 is cooled to a certain temperature by a heat exchanger, and then the slurry supply pipe 14 is cooled. To be supplied.

  Next, a cutting operation performed by the wire saw device having the above-described configuration will be described.

  The elevating motor is driven and controlled, the elevating base 4 is lowered, and the ingot 1 is pressed against the wire 6 between the pair of processing rollers 7 and 8. Further, the roller driving motor 13 is driven and controlled so that the wire 6 travels. Thereby, the cutting process of the ingot 1 is performed. At this time, the slurry supply pipe 14 is approaching the vicinity of the cutting portion of the ingot 1. The slurry 30 is supplied to the cutting part of the ingot 1 against which the wire 6 is pressed from the supply port 14a. For this reason, the ingot 1 is gradually cut by the lapping action. Since the wire 6 is wound at a predetermined pitch in the longitudinal axis direction of the processing rollers 7 and 8, the roller has a thickness corresponding to the pitch length and is pressed against the ingot 1 The number of silicon wafers 1 a corresponding to the number of windings 7 and 8 is generated from one ingot 1.

  The raising / lowering motor is driven and controlled so that the cutting speed (μm / min) changes according to the progress of the cutting process of the ingot 1. The cutting start speed when cutting the outer periphery of the ingot 1 at the start of cutting, the cutting center speed when cutting the central portion of the ingot 1, and the outer periphery of the ingot 1 after cutting the central portion of the ingot 1 Different speeds are set for each stage, such as the cutting end speed when cutting. For example, the cutting start speed is 700 to 830 μm / min, the cutting center speed is 400 to 450 μm / min, and the cutting end speed is set to 400 to 620 μm / min.

  When the cutting process of the ingot 1 is completed, the elevating base 4 is raised, and the sliced ingot 1 is moved to the original retracted position. The cutting temperature is adjusted to a constant value of, for example, 25 ° C. or less, and one ingot 1 is cut in a cutting time of 6.5 (H / time), for example.

  Next, a method for determining the count (average particle diameter) of the abrasive grains 31 contained in the slurry 30 used in the wire saw apparatus will be described.

  First, abrasive grains 31 having various sizes such as # 1000, # 1500, # 2000, # 2500, and # 3000 are prepared.

  FIG. 6 shows the volume particle size distribution for each number such as # 2000, # 2500, and # 3000. The horizontal axis in FIG. 6 is the particle size (μm), and the vertical axis indicates the volume ratio (frequency) (%) of the grain size of the abrasive grains 31 in the total volume. FIG. 6A shows the distribution as a line graph, and FIG. 6B shows the distribution as a bar graph.

  FIG. 12A shows the particle size distribution shown in FIG. 6 in a table.

  FIG. 12B shows the results of measuring D3%, D50%, and D94% for each number such as # 2000, # 2500, and # 3000.

  Furthermore, FIG.12 (c) shows the result of having measured the maximum value, the average value, and the minimum value of the particle size for each number such as # 2000, # 2500, and # 3000.

  Accordingly, # 2000 (No. 2000) means that the average value of the particle diameter is 4 ± 0.5 (μm), the maximum value is 13 (μm), and the minimum value is in the range of 2 (μm). # 2500 (2500) is the average particle size of 5.6 ± 0.5 (μm), the maximum value is 16 (μm), and the minimum value is 3 (μm). The particle size distribution within the range is # 3000 (No. 3000). The average value of the particle size is 6.9 ± 0.5 (μm), the maximum value is 19 (μm), and the minimum value is It is defined as a particle size distribution that falls within a range of 4 (μm).

  Next, the silicon ingot 1 is cut with a wire saw device using the slurry 30 containing the abrasive grains 31 of each count, and the surface roughness (Ra value) of the surface of the wafer 1a after cutting is measured.

  FIG. 7 shows measurement points (1) to (9) of each part of the surface of the silicon wafer 1a. The left side in the figure is the side to which a new wire 6 is supplied (new line side), and the right side in the figure is the side on which the new line is wound. The upper side in the figure is the cutting end side of the wafer 1a, and the lower side in the figure is the cutting start side of the wafer 1a.

  (1), (2), (3), (8), (9) are the respective measurement points in the wafer diameter direction, and indicate the respective measurement points from the new line side to the winding side. (4), (5), (3), (6), and (7) are the respective measurement locations in the wafer diameter direction, each from the upper side (cutting end side) to the lower side (cutting start side). Indicates the measurement location. The central portion of the wafer 1a corresponds to the measurement location (3).

  The measurement conditions are as follows.

Measuring device Surfcoder: SE-30H (manufactured by Kosaka Laboratory)
Condition Vertical magnification 5000
Horizontal magnification 20
Measurement length 2.5mm
Cut-off value λc = 0.25mm
Measurement speed 0.1mm / s

8 and 9 show the measurement results.

  8A and 8B show the maximum surface roughness value Rmax for each measurement location on the surface of the wafer 1a. FIG. 8A shows the relationship between each measurement point (1), (2), (3), (8), (9) from the new line side to the winding side and the maximum surface roughness value Rmax. Is shown for each count of the abrasive grains 31. FIG. 8 (b) shows the measurement points (4), (5), (3), (6), (7) from the upper side (cutting end side) to the lower side (cutting start side) and rough surface. The relationship with the maximum value Rmax is shown for each count of the abrasive grains 31.

  9A and 9B show the average value Ra of the surface roughness for each measurement location on the surface of the wafer 1a. FIG. 9A shows the relationship between each measurement point (1), (2), (3), (8), (9) from the new line side to the winding side and the surface roughness average value Ra. Is shown for each count of the abrasive grains 31. FIG. 9B shows the surface roughness from the upper side (cutting end side) to the lower side (cutting start side) (4), (5), (3), (6), (7). The relationship with the average value Ra is shown for each count of the abrasive grains 31.

  Here, paying attention to the central portion of the wafer 1a, that is, the measurement location (3), the number of the abrasive grains 31 from # 1000 to # 2500 corresponds to the increase in the number of the abrasive grains 31, that is, the grains of the abrasive grains 31. The surface roughness tends to decrease as the diameter decreases. However, when the count of the abrasive grains 31 is # 3000 (or more), the surface roughness is conversely increased and deteriorated. Then, it was confirmed that the tendency shown in FIGS. 8 and 9 is a universal tendency regardless of the wire diameter of the wire 6.

  Thus, by obtaining the relationship between the count of the abrasive grains 31 in advance and the surface roughness of the wafer center portion of the cut silicon wafer 1a, the surface roughness of the wafer center portion is compared for each count of the abrasive grains 31. Thus, it is possible to select the proper abrasive grain 31 count, that is, the abrasive grain 31 whose surface roughness value at the center of the wafer is below a predetermined threshold value. Specifically, the abrasive grains 31 in the range excluding # 2000 or less and # 3000 or more are selected as the counts of the abrasive grains 31 in which the kerf loss is reduced and the surface roughness of the wafer central portion is reduced.

  When the wire saw device of the embodiment was cut under the following conditions using the slurry 30 containing the abrasive grains with counts in the selected range # 2000 to # 3000, for example, the abrasive grains 31 of # 2500, the surface roughness described above was obtained. In addition to the above, improvement in swell, warp, flatness, etc. was observed as compared with the case of using # 1000 abrasive grains 31.

(Example 1)
Count # 2500 of abrasive grain 31
Wire 6 diameter 0.14mm
Tensile load of wire 2.3 kg / f

(Example 2)
Count # 2500 of abrasive grain 31
Wire 6 diameter 0.12mm
Tensile load of wire 6 2.1kg / f

Hereinafter, conditions when # 1000 abrasive grains 31 are used are listed as comparative examples of Examples 1 and 2.

(Comparative Example 1)
Count of abrasive grain # 1000
Wire 6 diameter 0.14mm
Tensile load of wire 6 2.5kg / f

(Comparative Example 2)
Count of abrasive grain # 1000
Wire 6 diameter 0.12mm
Tensile load of wire 2.3 kg / f

FIGS. 10A and 10B show photographs of the surface of the wafer 1a after cutting. FIG. 10A shows the surface of the wafer 1a cut using the # 2500 abrasive grains 31, and the direction cut by the wire 6 is indicated by an arrow. FIG. 10B shows the surface of the wafer 1 a cut using the # 1000 abrasive grains 31.

  10 (a) and FIG. 10 (b), when # 1000 abrasive grain 31 is used, it can be seen from the photograph that waviness is clearly generated, but # 2500 abrasive grain 31 When using, almost no swell is seen.

  FIG. 11 further shows the measurement results by nanotopography. 11 (a), 11 (b), and 11 (c) show the distribution of the undulation size at 0.5 mm square, 2.0 mm square, and 10 mm square, respectively. 0.0 mm square and 10 mm square waviness, and the vertical axis represents a percentage. FIG. 11A shows the distribution of the undulation size at 0.5 mm square in comparison with # 2500 and # 1000. FIG. 11B shows the waviness size distribution at 2.0 mm square in comparison with # 2500 and # 1000. FIG. 11C shows the distribution of the undulation size at 10 mm square in comparison with # 2500 and # 1000.

  From FIG. 11, it is apparent that the variation in waviness on the surface of the wafer 1a is smaller when the # 1500 abrasive grain 31 is used than when the # 1000 abrasive grain 31 is used. .

  As described above, conventionally, those corresponding to # 600 to # 1500 are used in JIS, and when the abrasive grain 31 having a higher count is used, the waviness increases and the surface roughness (Ra value) is large. Although it has been common knowledge in the prior art that problems such as showing a value are predicted, applying the method according to the present embodiment ensures that the surface roughness, etc. Quality can be improved.

  Next, what the inventor has found about the relationship between the count of the abrasive grains 31 and the cutting speed will be described.

  As described above, in the conventional technical common sense, when the count of the abrasive grains 31 is increased and the grain size is reduced, the sharpness is deteriorated due to clogging, and the cutting ability (cutting force) is reduced.

  However, as a result of experiments by the present inventors, when the abrasive grains 31 having a small diameter such as # 2000 to # 3000 are used, the abrasive grains 31 are likely to adhere to the wire 6, and the number and density of adhesion increase. As a result, the cutting ability was rather improved.

  However, the improvement of the cutting ability due to such fine graining of the abrasive grains (# 2000 to # 3000) has resulted in a decrease in the amount of bending of the wire 6 and a quality deterioration related to warp.

  FIG. 13 is a diagram for explaining the amount of deflection.

  That is, as shown in FIG. 13A, when a tensile load T (kg / f) is applied to the wire 6 having a wire diameter D (mm), the wire 6 is deformed from a solid line state to a broken line state, The wire 6 extends in the length direction with an elongation rate ε (%).

  As shown in FIG. 13B, when the ingot 1 is pressed against the wire 6 between the rollers 7 and 8 and is cut, the wire 6 has a distance L (mm) between the rollers 7 and 8 and an elongation rate. It bends in the pressing direction with a bend amount (elongation length) δ according to ε.

  When the abrasive grains 31 of # 2000 to # 3000 were used and were cut under the same cutting speed conditions as when using the conventional count (# 600 to # 1500) abrasive grains, the cutting ability of the abrasive grains 31 was as described above. Since it was improved compared to the prior art, an experimental result was obtained that the amount of deflection was smaller than that of the prior art. And, due to this decrease in the amount of deflection, the experimental results show that the warp value (average value), the warp size variation, and the warp direction (warp direction) variation are larger than before. Obtained.

  In particular, compared to the case where one ingot 1 is bonded to the work plate 2, the two ingots 1, 1 are arranged in a line along the longitudinal direction of the rollers 7, 8, 9. The result that the deterioration of the quality regarding the warp mentioned above was remarkable in the case of two sticking adhere | attached on the work plate 2 was obtained.

  Fig.14 (a) is a figure explaining 2 sticking.

  As shown in FIG. 14 (a), in the two-ply bonding, the two ingots 1 and 1 are arranged in a line along the longitudinal direction of the rollers 7, 8, and 9. In the case of one sticking, one ingot 1 is arranged in the same posture instead of the two ingots 1 and 1 in FIG.

  FIG. 14B shows the relationship between the direction in which the wire 6 is wound around the rollers 7, 8, and 9 and the ingot 1. As shown in FIG. 14 (b), the end of the rollers 7, 8, and 9 on the side where the new wire 6 is supplied is called the new line side (see FIG. 7) and used for cutting. The end on the side where the wire 6 is wound is referred to as the winding side. Correspondingly, the end of the ingot 1 corresponding to the new line side of the rollers 7, 8, 9 is called the new line side, and the end of the ingot 1 corresponding to the winding side of the rollers 7, 8, 9 is It is called the winding side. The direction from the new line side to the winding side (the direction in which the wire 6 is wound) is referred to as a wire feeding direction. In the case of the two ingots 1 and 1, the ingot 1 disposed on the new line side of the rollers 7, 8 and 9 is referred to as “first” (FIG. 14A). The ingot 1 arranged on the winding side of 8 and 9 is referred to as a “second” (FIG. 14B).

  FIG. 14 (c) uses # 2000 to # 3000 abrasive grains 31, and the ingot 1 is subjected to the same cutting speed conditions (hereinafter referred to as conventional conditions) when using the conventional count (# 600 to # 1500) abrasive grains. The state of the warp of each wafer 1a acquired from the ingot 1 when cut is schematically shown.

  As shown in FIG. 14C, it can be seen that the warp directions of the respective wafers 1a obtained from one ingot 1 are not aligned, and the variation in the warp direction is large. The same applies to the case of two ingots 1 and 1 attached.

  FIG. 15A shows the warp size of each wafer 1a obtained when the single ingot 1 is cut under the conventional conditions, with the wire feed direction as the horizontal axis. As shown in FIG. 15A, the warp size of the wafer 1a decreases from the new line side toward the winding side, and it can be seen that the warp size varies. Further, even when viewed in terms of the average value of the warp size, it has not reached a level that can satisfy the standard quality of the wafer.

  FIG. 15B shows the warp size of each wafer 1a obtained when the two ingots 1 and 1 are cut under the conventional conditions, with the wire feed direction as the horizontal axis. As shown in FIG. 15B, the size of the warp is as follows between the wafer 1a obtained from the first ingot 1 on the new line side and the wafer 1a obtained from the second ingot 1 on the take-up side. It can be seen that the size varies greatly and the warp size varies from ingot to ingot. Further, even when viewed in terms of the average value of the warp size, it has not reached a level that can satisfy the standard quality of the wafer.

  As described above, the present inventor increases the count of the abrasive grains 31 to a range excluding the 2000th and below and the 3000th and beyond, thereby reducing the cutting ability of the abrasive grains 31 to the conventional technical common sense. On the contrary, it has been found that if the other conditions remain the same as the conventional conditions, the amount of deflection is reduced and the quality of warp is deteriorated.

  The decrease in the amount of bending of the wire is considered to be caused by the fact that the forcing force of the wire 6 is weakened. If the cutting center speed is increased to increase the forcing force of the wire 6, warp I thought the quality would improve.

  Each condition of this Example 3 and Comparative Example 3 with respect to this Example 3 is listed below.

(Example 3)
Abrasive count # 2500
Cutting center speed 415μm / min or more Wire diameter φ0.12mm to φ0.14mm
Tensile load 2.1kg / f ～ 2.3kg / f

(Comparative Example 3)
Abrasive count # 2500
Cutting center speed 400μm / min
Wire diameter φ0.12mm to φ0.14mm
Tensile load 2.1kg / f ～ 2.3kg / f

The cutting start speed was set to about 800 to 810 μm / min, and the cutting end speed was set to about 600 to 610 μm / min.

  The cutting center speed of 400 μm / min in Comparative Example 3 is the cutting speed set when using the conventional count (# 600 to # 1500) abrasive grains (conventional conditions).

  In the case of Comparative Example 3, the results shown in FIG. 14C, FIG. 15A, and FIG. 15B described above are obtained, and the average value of the warp, the variation in the direction of the warp, and the size of the warp are obtained. The variation was so great that the quality standard level could not be satisfied.

  On the other hand, when the test was performed under the conditions of the present Example 3, FIG. 14 (d) corresponds to FIGS. 14 (c), 15 (a), and 15 (b) of Comparative Example 3, respectively. The results shown in FIGS. 15C and 15D were obtained.

  FIG. 14C showing the result of Comparative Example 3 and FIG. 14D showing the result of Example 3 are obtained from one ingot 1 in the case of Example 3. It can be seen that the warp directions of the respective wafers 1a are almost uniform and the variation in the warp direction is greatly improved as compared with Comparative Example 3. The same applies to the case of two ingots 1 and 1 attached.

  Comparing FIG. 15A showing the result of Comparative Example 3 with FIG. 15C showing the result of Example 3, in the case of Example 3, the size of the warp is in the wire feed direction. It can be seen that the warp size variation was greatly improved as compared with Comparative Example 3, since the portions were almost uniform. Also, the average value of the warp was smaller than that of Comparative Example 3, and was below the standard level of quality.

  When comparing FIG. 15B showing the result of Comparative Example 3 with FIG. 15D showing the result of Example 3, in the case of Example 3, the second ingot 1 on the winding side is compared. The warp size of each wafer 1a acquired from the first ingot 1 and the warp size of each wafer 1a acquired from the first ingot 1 on the new line side are substantially the same size and are evenly aligned. It can be seen that the variation in the warp size was greatly improved as compared with Comparative Example 3. Moreover, the average value of the warp was also small in Comparative Example 3, and was below the standard level of quality.

  In Example 3, # 2500 count abrasive grains 31 are used. However, except for # 2000 or less, for count abrasive grains 31 except # 3000 or more, the cutting center speed is increased from the conventional condition. As a result, when it was set to at least 415 μm / min or more, the warp-related quality was improved as compared with Comparative Example 3.

  In Example 3, the wire 6 having a wire diameter of φ0.12 mm to φ0.14 mm is used and the tensile load is set to 2.1 kg / f to 2.3 kg / f. Even when the wire 6 is set to a tensile load other than this, the warp quality is improved as compared with Comparative Example 3 if the cutting center speed is increased from the conventional condition to at least 415 μm / min. The result was obtained.

  Next, the quality improvement effect on the warp was examined by changing the cutting speed.

  In the experiment, the cutting center speed was changed in the range of 400 to 450 μm / min, and the average value AVE of the warp size and the warp size variation σ of each wafer 1a were obtained.

  The experimental results are shown in FIG.

  16A and 16B, the horizontal axis is the cutting center speed (400 to 450 μm / min), the vertical axis is the warp size (μm), and the relationship between the cutting center speed and the warp size. It is the graph which showed.

  FIG. 16A shows the relationship between the cutting center speed and the warp size under the condition that the wire 6 having a wire diameter of φ0.12 mm is used and the tensile load is set to 2.1 kg / f.

  FIG. 16B shows the relationship between the cutting center speed and the warp size under the condition that the wire 6 having a wire diameter of 0.14 mm is used and the tensile load is set to 2.3 kg / f.

  Abrasive grains 31 of # 2500 were used. The counts were changed in a range excluding # 2000 and below except # 2000 and above, but the tendency shown in FIGS. 16 (a) and 16 (b) was the same.

  As can be seen from FIGS. 16A and 16B, if the cutting center speed is set to 415 μm / min or more, the average value AVE of the warp size and the variation σ of the warp size become below the reference level, It was confirmed that it reached below the quality standard level of the wafer surface.

  Next, what the inventor has found about the relationship between the count of the abrasive grains 31 and the tensile load will be described.

  As described above, the present inventor has found that the improvement of the cutting ability due to the finer abrasive grains (# 2000 to # 3000) results in a decrease in the amount of bending of the wire 6 and a deterioration in the quality related to warp. I got the knowledge. The condition of not only the central cutting speed but also the tensile load was the same. When cutting was performed under the conventional conditions, the amount of deflection was reduced, and the deterioration of quality related to warp was confirmed.

  In other words, the # 31 to # 3000 abrasive grains 31 are used, the ingot 1 is cut under the same tensile load conditions (hereinafter, conventional conditions) as when using the conventional count (# 600 to # 1500) abrasive grains, and the ingot 1 When measuring the warp of each wafer 1a obtained from the above, results similar to those shown in FIG. 14 (c), FIG. 15 (a), and FIG. The result that it deteriorated rather than the time of use was obtained.

  As described above, the present inventor increases the count of the abrasive grains 31 to a range excluding the 2000th and below and the 3000th and beyond, thereby reducing the cutting ability of the abrasive grains 31 to the conventional technical common sense. On the contrary, it has been found that if the other conditions remain the same as the conventional conditions, the amount of deflection is reduced and the quality of warp is deteriorated.

  The decrease in the amount of bending of the wire is considered to be caused by the strong repulsive force of the wire 6, and the wire diameter of the wire 6 is reduced in order to reduce the repulsive force of the wire 6. It was thought that the quality related to warp would improve if the tensile load was reduced.

  The conditions of Examples 4 and 5 and Comparative Examples 4 and 5 are listed below. In Example 4 and Comparative Example 4, the wire 6 having a wire diameter of φ0.14 mm was used, and in Example 5 and Comparative Example 5, the wire 6 having a wire diameter of φ0.12 mm was used.

Example 4
Abrasive count # 2500
Wire diameter φ0.14mm
Tensile load 2.3kg / f or less Cutting center speed 415μm / min
(Example 5)
Abrasive count # 2500
Wire diameter φ0.12mm
Tensile load 2.1kg / f or less Cutting center speed 415μm / min
(Comparative Example 4)
Abrasive count # 2500
Wire diameter φ0.14mm
Tensile load 2.5kg / f or less Cutting center speed 415μm / min
(Comparative Example 5)
Abrasive count # 2500
Wire diameter φ0.12mm
Tensile load 2.5kg / f or less Cutting center speed 415μm / min
The tensile load of 2.5 kg / f in Comparative Examples 4 and 5 is the cutting speed set when using the conventional count (# 600 to # 1500) abrasive grains (conventional conditions).

  In the case of Comparative Examples 4 and 5, the results shown in FIG. 14C, FIG. 15A, and FIG. 15B are obtained. The average value of the warp, the variation in the direction of the warp, the size of the warp The variation was so great that the quality standard level could not be satisfied.

  On the other hand, when the test was conducted under the conditions of Examples 4 and 5, the results shown in FIGS. 14 (d), 15 (c), and 15 (d) were obtained.

  14 (d), 15 (c) and 15 (d) showing the results of Examples 4 and 5 and FIGS. 14 (c), 15 (a) and 15 (d) showing the results of Comparative Examples 4 and 5. As can be seen by comparing (b) with each other, as described above, the warp direction variation, the warp size variation, and the average value of the warp are implemented in both cases of one-ply and two-ply. The example was improved as compared with the comparative example, and it was confirmed that the quality concerning the warp reached below the reference level.

  In Examples 4 and 5, # 2500 count abrasive grains 31 are used. However, except for # 2000 or less, the count abrasive grains 31 except # 3000 or more have a tensile load higher than that of the conventional condition. As a result, the warp quality was improved as compared with Comparative Examples 4 and 5.

  In Examples 4 and 5, the cutting center speed is set to 415 μm / min. However, even if the cutting center speed is lower than this, the cutting speed is equal to or higher than the conventional condition (400 μm / min). Compared with Comparative Examples 4 and 5, the quality related to warp is improved.

  Next, the effect of improving the warp quality was examined by changing the magnitude of the tensile load.

  In the experiment, the tensile load of the wire 6 was measured when the wire diameter was 0.12 mm. When the wire diameter is changed from 2.3 to 1.8 kg / f and the wire 6 has a diameter of 0.14 mm. The average value AVE of the warp size of each wafer 1a and the variation σ of the warp size were obtained by changing the pressure in the range of 2.5 to 2.1 kg / f.

  The experimental results are shown in FIG.

  17 (a) and 17 (b), the horizontal axis indicates the tensile load of the wire 6 (FIG. 17 (a) is 2.3 to 1.8 kg / f, and FIG. 17 (b) is 2.5 to 2.1 kg. / f), the vertical axis is the warp size (μm), and is a graph showing the relationship between the tensile load of the wire 6 and the warp size.

  FIG. 17A shows the relationship between the tensile load and the warp size when the wire 6 having a wire diameter of φ0.12 mm is used.

  FIG. 17B shows the relationship between the tensile load and the warp size when the wire 6 having a wire diameter of 0.14 mm is used.

  Abrasive grains 31 of # 2500 were used. The counts were changed in the range excluding # 2000 and below except for # 2000 and below, but the tendency shown in FIGS. 17A and 17B was the same.

  As can be seen from FIGS. 17A and 17B, when the wire diameter of the wire 6 is φ0.12 mm, the tensile load is set to 2.1 kg / f or less, and the wire diameter of the wire 6 is φ0.14 mm. If the tensile load is set to 2.3 kg / f or less, it has been confirmed that the average value AVE of the warp size and the variation σ of the warp size are below the quality standard level for the warp. Furthermore, when experimenting by changing the wire diameter of the wire 6, when the wire diameter of the wire 6 is φ0.14 mm or less and exceeds φ0.12 mm, the tensile load is set to 2.3 kg / f or less, When the wire diameter of the wire 6 is φ0.12 mm or less, if the tensile load is set to 2.1 kg / f or less, the average value AVE of the warp size and the variation σ of the warp size are below the reference level. It was confirmed that

  Further, FIGS. 18A and 18B are experimental results when the count of the abrasive grains 31 is # 2500 and the wire diameter of the wire 6 is φ0.12 mm. FIG. 18A shows a tensile load of 2 The average value AVE of the warp size at 3 kg / f and the variation σ of the warp size were measured for each number of cuts. FIG. 18B shows the tensile load of 2.1 kg / f. This is a result of measuring the average value AVE of the warp size and the variation σ of the warp size at each cutting frequency.

  In FIGS. 18A and 18B, the horizontal axis indicates the number of cuts, the vertical axis indicates the warp size, and the range of the warp size (maximum) of each wafer 1a obtained by one cutting. Value to minimum value) and the average value of warp sizes (indicated by black circles ●).

  Further, the experiment was similarly performed when the wire diameter of the wire 6 was increased to φ0.14 and the tensile load was increased to 2.5 kg / f (conventional condition). FIG. 18C shows the measurement results when the count of the abrasive grains 31 is # 2500, the wire diameter of the wire 6 is φ0.14 mm, and the tensile load is 2.5 kg / f (conventional conditions).

  As can be seen by comparing these FIGS. 18 (a), (b), and (c), the conditions of Example 5 described above (the wire diameter of the wire 6 is 0.12 mm, the tensile load is 2.1 kg / f or less). In the case of the adapted FIG. 18 (b), both the average value AVE of the warp size and the variation σ of the warp size are greatly improved compared to the case (FIGS. 18 (a) and (c)). I can see that In the experiment, one piece and two pieces were mixed and cut several times, but in the case of two pieces, a result that the effect was particularly remarkable was obtained.

  18A and 18C are out of the conditions of Examples 4 and 5, but as the wire diameter of the wire 6 is reduced from φ0.14 mm to φ0.12 mm (FIG. 18C → FIG. 18). 18 (a)), by reducing the tensile load from 2.5 kg / f (conventional condition) to 2.3 kg / f (FIG. 18 (c) → FIG. 18 (a)), the average value of the warp size It can be seen that the variation σ in the size of AVE and warp is reduced, and the quality is improved.

  From the above, when cutting the ingot 1 using the wire 6 having a linear φ of 0.14 mm or less and using the abrasive grains 31 excluding # 3000 except for # 2000 or less, the ingot 1 is attached to the wire 6. In order to reduce the repulsive force when pressed, the tensile load is lower than 2.5 kg / f and becomes lower as the wire diameter becomes smaller (for example, φ0.14 mm → φ0.12 mm). Applying a load (for example, 2.5 kg / f (conventional condition) → 2.3 kg / f; or 2.3 kg / f → 2.1 kg / f) to the wire 6 is necessary to improve the quality of the warp. It can be concluded that there is.

  Further, when the fourth and fifth embodiments described above are combined with the third embodiment, the effect of quality improvement regarding the warp is further enhanced. That is, when the cutting center speed is set to 415 μm / min or more, and the wire diameter of the wire 6 is φ0.14 mm or less and exceeds φ0.12 mm, the tensile load is 2.3 kg / f or less and 2.1 kg / If the wire 6 is set to a value exceeding f and the wire diameter is φ0.12 mm or less, if cutting is performed under the condition that the tensile load is set to 2.1 kg / f or less, the cutting center speed is the conventional condition. The warp-related quality is further improved as compared with the case of (400 μm / min) (the tensile load is the same as above).

  As described above, according to this embodiment, by reducing the size of the abrasive grains 31 further than that of the current grain size, the kerf loss and the machining allowance can be reduced, and the wafer acquisition rate is improved. Manufacturing efficiency is improved. In addition, as described above, it has become possible to maintain the quality of the wafer, contrary to the conventional technical common sense.

  The present invention can be similarly applied to cutting not only silicon but also other semiconductor ingots such as gallium arsenide.

FIGS. 1A and 1B are diagrams for explaining kerf loss and conceptually showing how an ingot is cut into a wafer by a wire. FIG. 2 is a diagram for explaining the swell. FIG. 3 is a diagram for explaining warp. FIG. 4 is a perspective view showing the configuration of the wire saw device of the embodiment. FIG. 5 is a diagram showing a state where the silicon ingot is cut by the wire, and is a view of the silicon ingot viewed from the cut surface direction. 6 (a) and 6 (b) are diagrams showing volume particle size distributions by abrasive count. FIG. 7 is a view showing measurement points (1) to (9) of each part of the surface of the silicon wafer. FIGS. 8A and 8B are graphs showing the maximum surface roughness value for each measurement location on the surface of the wafer. FIGS. 9A and 9B are graphs showing the average surface roughness for each measurement location on the surface of the wafer. FIGS. 10A and 10B are photographs taken of the surface of the wafer after cutting. FIGS. 11A, 11B, and 11C are graphs showing measurement results by nanotopography. 12A, 12B, and 12C are tables corresponding to FIGS. 6A and 6B. FIGS. 13A and 13B are diagrams showing a state of deformation when a tensile load is applied to the wire. FIGS. 14A and 14B are diagrams for explaining the relationship between the direction in which the wire is wound, the roller, and the ingot. FIGS. 14C and 14D are wafers obtained from the ingot. It is the figure which showed typically the direction of warp. FIGS. 15A, 15B, 15C and 15D are graphs showing the relationship between the wire feed direction and the warp size. FIGS. 16A and 16B are graphs showing the relationship between the cutting center speed, the warp size (average value), and the warp size variation. FIGS. 17A and 17B are graphs showing the relationship between tensile load, warp size (average value), and warp size variation. FIGS. 18A, 18B, and 18C are graphs showing the relationship between the number of cuts, the average value of warp, and variation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Silicon ingot 1a Silicon wafer 6 Wire 30 Slurry 31 Abrasive grain

Claims (3)

A slurry containing abrasive grains is supplied to the cutting portion of the semiconductor ingot, and a tensile load is applied to the wire that is wound around the roller while being moved relative to the wire at a predetermined cutting speed in the direction of pressing the semiconductor ingot against the wire. In the semiconductor ingot cutting method that cuts the semiconductor ingot,
When cutting a semiconductor ingot using a count of abrasive grains in a range excluding 2000 or less and 3000 or more,
A method for cutting a semiconductor ingot in which the semiconductor ingot is cut by setting the cutting center speed to a cutting speed of 415 μm / min or more in order to increase the forcing force when the semiconductor is pressed against the wire. When the wire diameter is 0.14 mm or less and a value exceeding 0.12 mm, the tensile load is set to a value exceeding 2.3 kg / f and exceeding 2.1 kg / f,
2. The method of cutting a semiconductor ingot according to claim 1, wherein when the wire diameter is 0.12 mm or less, the tensile load is set to 2.1 kg / f or less. 2. The semiconductor ingot cutting method according to claim 1, wherein two or more semiconductor ingots to be cut are arranged in a line along the longitudinal direction of the roller.

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