JP6424703B2 - Method of manufacturing silicon wafer - Google Patents

Description

  In the present invention, a cylindrical silicon single crystal ingot grown by floating zone method (Floating Zone method, hereinafter referred to as FZ method) or Czochralski method (Czochralski method, hereinafter referred to as CZ method) is sliced. The present invention relates to a method of manufacturing a silicon wafer.

  Conventionally, the holder holds and bonds the cylindrical semiconductor single crystal ingot while rotating the semiconductor single crystal ingot by a predetermined rotation angle around a crystal axis of the ingot different from the central axis of the cylinder of the ingot. A slicing method of a semiconductor single crystal ingot sliced by a cutting device is disclosed (see, for example, Patent Document 1). In this method of slicing a semiconductor single crystal ingot, a predetermined rotation angle when the ingot is adhered and held by a holder is determined such that the amount of warpage of the wafer sliced by the cutting device becomes a predetermined amount. Further, the correlation between the change in the amount of warpage of the wafer with respect to the change in the predetermined rotation angle is determined in advance by experiment, and the predetermined rotation angle can be determined from the correlation. In addition, a predetermined rotation angle when the ingot is adhered and held by the holder may be determined so that the warpage amount of the wafer sliced by the cutting device is minimized. Furthermore, when a rotation reference portion (orientation flat) is formed in the ingot and a perpendicular drawn from the crystal axis of the ingot to the rotation reference portion (orientation flat) is used as a reference line, the predetermined rotation angle with respect to this reference line is 35 to 75 Degree, 105 to 145 degrees, 215 to 255 degrees, or within the range of 285 to 325 degrees.

  In the method of slicing a semiconductor single crystal ingot configured as above, before the cylindrical semiconductor single crystal ingot is adhered and held by the holder of the cutting apparatus, first, the ingot is subjected to the crystal axis of the ingot different from the central axis of the cylinder. The ingot is then held adhesively by the holder in a state of being rotated by a predetermined rotation angle about the crystal axis. At this time, since the predetermined rotation angle about the crystal axis is determined so that the warpage amount of the sliced wafer becomes a predetermined amount by the cutting apparatus, the warpage amount of the wafer after slicing the ingot can be reduced. In addition, the correlation between the change in the amount of warpage of the wafer to the change in the predetermined rotation angle is determined in advance by experiment, and the predetermined rotation angle is determined from this correlation so that the amount of warpage of the wafer is minimized. The amount of warpage of the wafer after slicing can be further reduced. In addition, a perpendicular drawn from the crystal axis of the ingot to the orientation flat (rotation reference portion) is used as a reference line, and a predetermined rotation angle with respect to this reference line is 35 to 75 degrees, 105 to 145 degrees, 215 to 255 degrees, or When the temperature is set within the range of 325 degrees, the amount of warpage of the wafer after cutting the ingot is approximately the desired amount.

JP-A-2014-195025 (claims 1 to 3 and 5, paragraphs [0015] to [0017] and [0019], FIGS. 1 to 7)

  In the method of slicing a semiconductor single crystal ingot disclosed in the above-mentioned conventional patent document 1, orientation flat positions at which the crystal structures are equivalent can be set at three locations at equal intervals around the central axis of the ingot. An orientation flat was selected by selecting any one of the positions to form an orientation flat, and the ingot was sliced based on the orientation flat. However, when the ingot is sliced by this method, the amount of warpage decreases in the obtained wafer obtained by slicing a certain ingot, the amount of warpage increases in the wafer obtained by slicing another ingot, and the amount of warpage of the wafer is There has been a problem that the grown ingots, that is, the batches vary.

  An object of the present invention is a silicon wafer in which the warpage amount of a wafer does not vary for each grown ingot, that is, for each batch, so that the warpage amount of all manufactured wafers can be reduced and the quality regarding the warpage of the wafer can be improved. It is to provide a manufacturing method of Another object of the present invention is to provide a method of manufacturing a silicon wafer capable of making the distribution of in-plane resistivity of the wafer substantially uniform.

According to a first aspect of the present invention, there is provided a method of producing a silicon wafer by growing a cylindrical single crystal silicon ingot by FZ method or CZ method and slicing this ingot to produce a silicon wafer. A cylindrical ingot is grown in a state in which the axis is inclined at a predetermined angle within the range of 1 degree to 6 degrees from the direction of the <111> crystal axis, and the ingot of the crystal growth line appearing on the outer peripheral surface of the ingot is grown. The orientation flat position is identified based on the remaining crystal habit lines excluding the three crystal habit lines appearing at intervals of 120 degrees with respect to the central axis, and the original is inclined by the above-mentioned predetermined angle based on the orientation flat position. And slicing the ingot.

The second aspect of the present invention is the invention based on the first aspect , and further, in producing a plurality of silicon single crystal ingots, the amount of warpage of the wafer by using a seed crystal having the same axial tilt direction. The ingot is fixed and sliced without repeatedly determining the slicing direction of the ingot.

In the method of manufacturing a silicon wafer according to the first aspect of the present invention, the circular axis of the cylindrical ingot is inclined at a predetermined angle within the range of 1 degree to 6 degrees from the direction of the <111> crystal axis. The columnar ingot is grown, and among the crystal growth lines appearing on the outer peripheral surface of the ingot, the orientation is based on the remaining crystal growth lines except for the three crystal growth lines appearing at intervals of 120 degrees around the central axis of the ingot. The flat position is specified, and the ingot is sliced by restoring the above-mentioned predetermined angle based on the orientation flat position. That is, since each crystal habit line has a specific positional relationship with respect to each orientation flat position, one specific orientation flat position with respect to one specific crystal habit line of a plurality of crystal habit lines is Correspondingly, an orientation flat is formed at this specific one orientation flat position, and the ingot is sliced by returning the above-mentioned predetermined angle based on the orientation flat. As a result, the cleavage plane does not appear in the slicing direction during slicing of the ingot, and a cutting tool such as a wire does not deviate in the direction of the cleavage plane, so the amount of warpage of the wafer obtained by slicing the ingot is It is possible to reduce the amount of warpage of all wafers manufactured without variation among the produced ingots, that is, each batch, and to improve the quality regarding the warpage of the wafers.

  On the other hand, if a cylindrical ingot whose central axis is not tilted with respect to the <111> crystal axis is grown by the CZ method, the horizontal interatomic bonds perpendicular to the central axis of the ingot are strong, so The growth rate is fast. Here, since the solidification interface of the ingot is usually an upwardly convex curved surface, the solidification speed at the horizontal top is faster than other portions. Then, if doping with an element such as phosphorus or arsenic, the faster the solidification rate, the less the doping element ejected from the ingot to the melt, and the segregation coefficient becomes larger. Therefore, the concentration of the doping element is near the center of the ingot. The effect on the distribution of the in-plane resistivity of the wafer obtained by slicing the ingot after heightening is low resistance at the center of the ingot with high doping element concentration, and the in-plane resistivity at the center of the wafer is Very small. However, when growing an ingot whose central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis, the portion with high solidification speed, that is, the high concentration portion of the doping element Because the in-plane resistivity distribution of the wafer is affected by the movement from side to side, the resistance is low at the ring-like position surrounding the center of the ingot, and the in-plane resistivity decreases at the center of the wafer. Be suppressed. And, in the ingot whose central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis, the in-plane resistivity of the wafer becomes extremely small and the in-plane resistivity decreases at the central portion of the wafer. Due to the effects of suppression, the concentration increase in the center of the ingot is alleviated. As a result, the concentration distribution of the doping element in the radial direction of the ingot whose central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis is the ingot whose central axis is not inclined with respect to the <111> crystal axis In this case, the distribution of the in-plane resistivity of the wafer can be made substantially uniform because the uniformity is made remarkably.

  In addition, when an ingot whose central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis is grown by the FZ method, the facet is a portion formed near the center of the ingot and rapidly solidified with a relatively large volume. As the temperature in the outer region, i.e., in each part of the off-facet area, is different, there is less overcooling in this whole off-facet area. As a result, step (step) growth from the off-facet region to the central portion is less likely to occur, and facet growth in the central portion of the silicon melt can be suppressed. For this reason, although doping with an element such as phosphorus or arsenic usually takes a relatively large amount of dopant during facet growth, in the present invention, it is possible to suppress facet growth in the central portion of the silicon melt, so Can reduce the amount of As a result, the resistivity at the central portion of the wafer obtained by slicing the ingot is increased, so that the distribution of the in-plane resistivity of the wafer can be made substantially uniform.

In the method of manufacturing a silicon wafer according to the second aspect of the present invention, in manufacturing a plurality of silicon single crystal ingots, the amount of warpage of the wafer is minimized by using seed crystals having the same axial tilt direction. The ingot is fixed and sliced without repeatedly determining the slicing direction. That is, when using seed crystals having the same axial tilt direction, since the specific orientation flat position of the ingot is always the same position without changing from batch to batch, after forming the orientation flat at this orientation flat position, The ingot can be sliced quickly simply by fixing the ingot to a cutting device in which the fixing position of the ingot and the mounting angle of the cutting tool are set. As a result, since it is not necessary to obtain the slicing direction for each grown ingot, the fixing time of the ingot can be shortened.

It is a principal part front view which shows the state which it is going to slice the silicon single crystal ingot for silicon wafer manufacture of this invention 1st Embodiment with the wire of a wire saw apparatus. It is a principal part perspective view which shows the state which is going to slice the ingot with the wire of a wire saw apparatus. (A) is a block diagram showing a state in which the crystal axis coincides with the central axis of the cylinder of a generally crystalline ingot, extends in a direction perpendicular to the central axis of the cylinder and the crystal axis, and wires are wired; FIG. 7 is a block diagram of the ingot showing a state in which the crystal axis is inclined at a predetermined angle with respect to the central axis of the ingot of the inclined crystal ingot, and (c) is a wire extending in a direction perpendicular to the crystal axis of the ingot of the inclined crystal. It is a block diagram which shows the state which carried out wiring. It is a schematic diagram which shows an example of the inclining direction of the ingot of an inclination crystal | crystallization. It is a stereographic view of a normal crystal ingot. FIG. 5 is a stereographic view of a tilted crystal ingot. (A) is a perspective view of a wafer showing a mechanism in which a cleavage surface appears in the cutting direction during cutting of the ingot by the wire and the wire is deviated in the direction of this cleavage surface; (b) is a cut after a large warpage has occurred It is a side view of a wafer. (A) is a perspective view of a wafer showing a mechanism in which a cleavage plane does not appear in the cutting direction during cutting of the ingot by the wire and the wire advances straight in the cutting direction; (b) is a wafer after cutting in which no warpage occurs Side view of FIG. (A) is a front view of the ingot showing that the cleavage plane of the ingot is parallel to the wire mark on the surface of the ingot, (b) shows a state where the cleavage plane of the ingot is inclined to the crystal axis of the ingot It is a longitudinal cross-sectional view of the ingot shown, (c) is a longitudinal cross-sectional view of the ingot which shows that a wire deviates in the direction of a cleavage plane. (A) is a front view of the ingot showing that the cleavage plane of the ingot is parallel to the wire mark on the surface of the ingot, (b) shows a state in which the cleavage plane of the ingot is parallel to the crystal axis of the ingot It is a longitudinal cross-sectional view of an ingot, and (c) is a longitudinal cross-sectional view of an ingot which shows that a wire goes straight in a cutting direction. It is a block diagram which shows the state which has identified three orientation flat positions 1 to 3 respectively using X-rays. It is a block diagram which shows the state which is measuring the inclination value of the X direction and the Y direction with respect to three orientation flat positions 1-3 using X ray, respectively. It is a principal part perspective view which shows the state which is slicing the silicon monocrystal ingot for silicon wafer manufacture of this invention 2nd Embodiment with the band saw of a band saw apparatus. It is a figure which shows the change of the curvature amount of a wafer when the sticking rotation angle to the slicing stand of the ingot of Example 1 is changed, respectively. It is a figure which shows distribution of the curvature amount of a wafer when changing the orientation flat position of an ingot and setting slice cutting time to 1.0 (au). It is a figure which shows distribution of the curvature amount of a wafer when changing the orientation flat position of an ingot and setting slice cutting time to 1.3 (au). It is a figure which shows the change of the deviation | shift amount from the average value of the in-plane resistivity of a silicon wafer with respect to the change of the surface position of the silicon wafer which sliced the ingot of the normal crystal. It is a figure which shows the change of the deviation | shift amount from the average value of the in-plane resistivity of a silicon wafer with respect to the change of the surface position of the silicon wafer which sliced the ingot of the inclination crystal | crystallization.

  Next, an embodiment of the present invention will be described based on the drawings.

First Embodiment
The method for producing a silicon wafer of the present invention includes the steps of growing a cylindrical silicon single crystal ingot by the FZ method or the CZ method, and slicing the ingot to produce a silicon wafer. On the outer peripheral surface of the cylindrical ingot, there appear a plurality of crystal habit lines spaced in the circumferential direction on the outer peripheral surface of the ingot and extending in the longitudinal direction of the ingot. In the present invention, the slice direction of the ingot which minimizes the amount of warpage of the wafer is determined based on a specific one of the plurality of crystal habits. Further, as the ingot, an ingot of an inclined crystal grown using an axially inclined seed crystal is used, or an ingot of a normal crystal grown using an ordinary seed crystal which does not incline a crystal axis is used. Furthermore, the number of crystal habit lines appearing on the outer peripheral surface of the inclined crystal ingot is usually different from the number of crystal habit lines appearing on the external peripheral surface of the crystal ingot. That is, in a normal crystal ingot, the central axis of a cylindrical ingot coincides with the crystal axis, while in a tilted crystal ingot, the central axis of a cylindrical ingot is specified from the direction of the crystal axis. It is inclined by an angle, and the number of crystal habit lines increases or decreases depending on the inclined angle and the inclined direction. For this reason, it is possible to determine the slicing direction of the ingot which minimizes the amount of warpage of the wafer, based on the crystal growth line which is increased or decreased by using the axially inclined seed crystal in growing the ingot.

  Specifically, when growing an ingot of a normal crystal in which the central axis of the cylindrical ingot is made to coincide with the <111> crystal axis as shown in FIG. 4, the cylindrical ingot is formed as shown in FIG. Six crystal habit lines 1 to 6 appear on the outer peripheral surface. Of the six crystal growth lines 1 to 6, three crystal growth lines 1 to 3 appear at intervals of 120 degrees around the central axis of the cylindrical ingot, and the remaining three crystal growth lines 4 to 6 Are at positions different from the above three crystal growth lines 1 to 3 and appear at intervals of 120 degrees around the central axis of the cylindrical ingot. On the other hand, as shown in FIG. 4, the central axis of the cylindrical ingot is a predetermined angle within the range of 1 degree or more and 6 degrees or less in the direction of <110> crystal axis from the direction of <111> crystal axis, for example When a cylindrical ingot is grown in a state of being inclined at 3 degrees and 30 minutes, four crystal habit lines 1 to 4 appear on the outer peripheral surface of the cylindrical ingot as shown in FIG. Of the four crystal growth lines 1 to 4, three crystal growth lines 1 to 3 appear at intervals of 120 degrees around the central axis of the cylindrical ingot, and the remaining one crystal growth line 4 is the above-described one. It appears at a position different from the three crystal habit lines. Here, the reason why the inclination angle of the central axis of the ingot of the inclined crystal is limited within the range of 1 degree or more and 6 degrees or less from the direction of the <111> crystal axis is that the distribution of the in-plane resistivity of the wafer is less than 1 degree. If the angle is more than 6 degrees, the tilt angle at the time of slicing the cylindrical ingot becomes too large, and the yield is lowered due to the ovalization of the wafer.

  From the above, among the four crystal growth lines 1 to 4 appearing on the outer peripheral surface of the inclined crystal ingot, the remainder excluding the three crystal growth lines 1 to 3 appearing at an interval of 120 degrees around the central axis of the ingot. The orientation flat position can be specified on the basis of one crystal habit line 4 and the ingot is sliced by returning the predetermined angle which is inclined based on the orientation flat position. In the tilted crystal ingot, the central axis of the cylindrical ingot is not from the direction of the <111> crystal axis to the direction of the <110> crystal axis, but from the direction of the <111> crystal axis to the direction of the <112> crystal axis It is also possible to grow a cylindrical ingot in a state of being inclined by a predetermined angle (FIG. 4).

  On the other hand, as shown in FIGS. 1 and 2, a wire saw device is used as a cutting device 20 for slicing and cutting the ingot 11 in this embodiment. The wire saw device 20 includes a holder 23 for bonding and holding the ingot 11, first and second main rollers 21 and 22 having parallel central axes and disposed in the same horizontal plane, and first and second A single sub-roller 24 provided below the main rollers 21, 22 and at an intermediate position between the first and second main rollers 21, 22 and the first and second main rollers 21, 22 and a single sub-roller 24 And a lifting device 27 for moving the holder 23 up and down. Further, on the outer peripheral surface of the first and second main rollers 21 and 22 and the single sub roller 24, a predetermined distance is opened in the axial direction of each of the rollers 21, 22 and 24, that is, the wafer 12 (see FIG. And a plurality of ring grooves (not shown) extending in the circumferential direction at intervals in the axial direction of the respective rollers 21, 22, 24 by the thickness of FIG. The wire 26 is a single long wire wound around a delivery bobbin 28 (FIG. 2), and the wire 26 delivered from the delivery bobbin 28 has a single unit with the first and second main rollers 21, 22. In order to be accommodated sequentially from each ring groove on one end side of the sub roller 24 to each ring groove on the other end side, the rollers 21, 22, 24 are substantially in the shape of an inverted triangle and wound spirally to be stretched. After being installed, it is configured to be taken up on the take-up bobbin 29 (FIG. 2).

  The holder 23 has a slicing table 23a bonded to the ingot 11 and a work plate 23b for holding the slicing table 23a (FIGS. 1 and 2). The slicing table 23a is made of the same material as the ingot 11, or made of glass, ceramic, carbon, resin or the like, but carbon, resin or the like is often used in consideration of cost and ease of molding. Further, as the adhesive, an epoxy resin, a thermoplastic wax or the like is used, and the work plate 23b is mainly formed of SUS. The elevating device 27 further includes a support member 27a extending in the vertical direction, and a horizontal member 27b attached to the support member 27a so as to be capable of raising and lowering and holding the holder 23 on the lower surface of the tip. Thus, the ingot 11 bonded to the holder 23 is configured to be able to be lifted and lowered by the lifting device 27.

  A method of slicing and cutting the silicon single crystal ingot 11 using the wire saw device 20 configured as described above will be described. First, the wire 26 is wound and stretched between the first and second main rollers 21 and 22 and the single sub roller 24. Thus, among the wires 26, the wire 26 stretched horizontally between the first and second main rollers 21 and 22 is made horizontal by the rotation of the first and second main rollers 21 and 22 and the single sub roller 24. Move in the direction. Then, the ingot 11 is bonded to a slicing table 23a attached to the lower end surface of the horizontal member 27b of the lifting device 27 via a work plate 23b.

  Here, as shown in FIG. 4, the central axis of the cylindrical ingot is a predetermined angle within the range of 1 degree or more and 6 degrees or less in the direction of <110> crystal axis from the direction of <111> crystal axis, for example, 3 The method of growing a cylindrical ingot in the state which inclined only 30 degrees, and adhere | attaching this ingot to a slicing base is demonstrated. First, among the four crystal growth lines 1 to 4 (FIG. 6) appearing on the outer peripheral surface of the ingot, the remaining three crystal growth lines 1 to 3 appearing at intervals of 120 degrees around the central axis of the ingot are excluded. Based on one crystal habit line 4, an orientation flat position is specified by X-ray diffraction method or light image method described later, and an orientation flat is formed at this orientation flat position. That is, since the four crystal growth lines 1 to 4 have a specific positional relationship with respect to the three orientation flat positions, one of the four crystal growth lines 1 to 4 has a specific crystal growth line 4 , And a specific one orientation flat position corresponds to form an orientation flat at this particular one orientation flat position. Next, the ingot is bonded to the slicing table in a state of being restored by the above-mentioned predetermined angle based on the orientation flat. Specifically, since the central axis 11a of the cylindrical ingot 11 is inclined by a predetermined angle with respect to the crystal axis 11b (FIG. 3 (b)), it differs from the central axis 11a of the cylindrical ingot 11 After the ingot is placed on a rotary table so that the ingot can be rotated about the crystal axis 11b of the ingot 11 (FIG. 3 (c)), the ingot 11 is centered on the crystal axis 11b and predetermined based on the orientation flat. It adheres to the slice stand 23b in the state which rotated only angle.

  At this time, a vertical line drawn from the crystal axis 11b of the ingot 11 to the orientation flat 11c is a predetermined rotation angle about the crystal axis 11b as a reference line 11d, and a predetermined rotation angle θ (see FIGS. It is preferable to set FIG. 8) in the range of 40 to 60 degrees, and more preferably in the range of 45 to 55 degrees. Here, the reason why the predetermined rotation angle θ with respect to the reference line 11d is limited to the above range is that the wire 26 is easily deviated in the direction of the cleavage plane 11e of the ingot 11, and the wafer obtained by slicing this ingot 11 This is because the variation of the amount of warpage of 12 becomes large. The range of the predetermined rotation angle θ with respect to the reference line 11d is the same as in the case of an ordinary crystal ingot.

  Next, the ingot 11 is above the wire 26 stretched horizontally between the first and second main rollers 21 and 22 and passes through the central axes of the first and second main rollers 21 and 22. The crystal axis 11b of the ingot 11 is moved between the vertical lines so as to be substantially parallel to the central axes of the first and second main rollers 21 and 22 (FIGS. 1 and 2). At this time, the vertical plane including the crystal axis 11b of the ingot 11 is made perpendicular to the extending direction of the wire 26 between the first and second main rollers 21 and 22 (FIG. 3 (c)). In other words, the crystal axis 11 b of the ingot 11 is orthogonal to the plane formed by the wire 26 between the first and second main rollers 21 and 22 and the cutting direction of the ingot 11 by the wire 26. Further, in this state, the ingot 11 is sliced by moving the ingot 11 vertically to a position crossing the wire 26 moving in the horizontal direction. As a result, the cleavage plane does not appear in the slicing direction during slicing of the ingot, and a cutting tool such as a wire does not deviate in the direction of the cleavage plane, so the amount of warpage of the wafer obtained by slicing the ingot is It is possible to reduce the amount of warpage of all wafers manufactured without variation among the produced ingots, that is, each batch, and to improve the quality regarding the warpage of the wafers.

  Even if the cleavage plane 11e of the ingot 11 is parallel to the wire mark 11f on the surface of the wafer 12, the amount of warpage of the wafer 12 obtained by slicing the ingot 11 is different. The reason is described based on FIG. 7 to FIG. As shown in FIGS. 9A and 10A, even if the cleavage surface 11e of the ingot 11 is parallel to the wire marks 11f on the surface of the ingot 11, the cleavage surface 11e of the ingot 11 is as shown in FIG. As shown in FIG. 10, there are cases in which the crystal is inclined with respect to the crystal axis 11b of the ingot 11 and cases in which the crystal is parallel to the crystal axis 11b of the ingot 11 as shown in FIG. Then, when the cleavage plane 11e of the ingot 11 is inclined with respect to the crystal axis 11b of the ingot 11 (FIG. 9 (b)), when the ingot 11 is sliced, the wire 26 is broken arrow in FIG. 7 (a) and FIG. The ingot 11 is easily deviated from the cutting direction shown by the solid line arrow of (c), in the direction shown by the solid line arrow of FIG. 7A and the broken line arrow of FIG. When the cleavage plane 11e of the ingot 11 is parallel to the crystal axis 11b of the ingot 11 (FIG. 10 (b)), when the ingot 11 is sliced, the wire 26 becomes a broken arrow in FIG. 8 (a) and FIG. It is hard to deviate with respect to the cutting direction shown by the solid line arrow, and advances straight in the cutting direction. As a result, even if the cleavage plane 11e of the ingot 11 is parallel to the wire mark 11f on the surface of the ingot 11 (FIG. 9 (a)), the cleavage plane 11e of the ingot 11 is the ingot 11 as shown in FIG. When the wafer 12 is inclined with respect to the crystal axis 11b of the above, the wafer 12 obtained by slicing the ingot 11 is warped as shown in FIG. 7 (b). On the other hand, even if the cleavage plane 11e of the ingot 11 is parallel to the wire mark 11f on the surface of the ingot 11 (FIG. 10 (a)), the cleavage plane 11e of the ingot 11 is the ingot as shown in FIG. If it is parallel to the 11 crystal axes 11b, the wafer 12 obtained by slicing this ingot 11 does not warp as shown in FIG. 8 (b).

  Moreover, it is preferable to dope elements, such as phosphorus and arsenic, to the ingot of the inclined crystal in which the central axis inclines 1 degree or more and 6 degrees or less with respect to a <111> crystal axis. In the case of growing an ingot by the CZ method, it is preferable to dope an element such as phosphorus, arsenic or antimony, and in the case of growing an ingot by the FZ method, it is preferable to dope the element such as phosphorus. The doping of these elements alleviates the high concentration in the center of the ingot, so the concentration distribution of the doping element in the radial direction of the ingot of the inclined crystal is such that the central axis is inclined relative to the <111> crystal axis. It is much more uniform than the conventional crystal ingot. As a result, the distribution of in-plane resistivity of the wafer can be made substantially uniform.

  That is, when an ingot of a normal crystal in which the central axis is not inclined with respect to the <111> crystal axis is grown by the CZ method, the lateral interatomic bond perpendicular to the central axis of the ingot is strong. The crystal growth rate is fast. Here, since the solidification interface of the ingot is usually an upwardly convex curved surface, the solidification speed at the horizontal top is faster than other portions. Then, if doping with an element such as phosphorus or arsenic, the faster the solidification rate, the less the doping element ejected from the ingot to the melt, and the segregation coefficient becomes larger. Therefore, the concentration of the doping element is near the center of the ingot. The effect on the distribution of the in-plane resistivity of the wafer obtained by slicing the ingot after heightening is low resistance at the center of the ingot with high doping element concentration, and the in-plane resistivity at the center of the wafer is Very small. However, when growing an ingot of inclined crystal whose central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis, the portion with high solidification speed, ie, the high concentration portion of the doping element The in-plane resistivity distribution of the wafer is low resistance at the ring-like position surrounding the center of the ingot, and the in-plane resistivity at the center of the wafer is low. The decrease in And, in the ingot of inclined crystal, the influence of extremely small in-plane resistivity of the wafer and the influence of suppressing the decrease of in-plane resistivity at the central portion of the wafer are combined, and the height at the central portion of the ingot is high. Concentration is mitigated. As a result, the concentration distribution of the doping element in the radial direction of the ingot of the inclined crystal is made much more uniform than that of the crystal ingot, so that the distribution of the in-plane resistivity of the wafer can be made substantially uniform.

  In addition, when an ingot of a tilted crystal in which the central axis is inclined at 1 degree or more and 6 degrees or less with respect to the <111> crystal axis is grown by the FZ method, it is formed near the center of the ingot and rapidly solidified in a relatively large volume. Since the temperature in the area outside a facet, that is, in each part of the off-facet area is different, overcooling in this whole off-facet area is less. As a result, step (step) growth from the off-facet region to the central portion is less likely to occur, and facet growth in the central portion of the silicon melt can be suppressed. For this reason, although doping with an element such as phosphorus or arsenic usually takes a relatively large amount of dopant during facet growth, in the present invention, it is possible to suppress facet growth in the central portion of the silicon melt, so Can reduce the amount of As a result, the resistivity at the central portion of the wafer obtained by slicing the ingot is increased, so that the distribution of the in-plane resistivity of the wafer can be made substantially uniform.

  Furthermore, in the case of producing a plurality of ingots, it is preferable to use a seed crystal whose axial tilt direction is the same. Thus, the ingot can be fixed and sliced without repeatedly determining the ingot slicing direction that minimizes the amount of warpage of the wafer. Specifically, when a seed crystal with the same axial tilt direction is used, an orientation flat is formed at this orientation flat position because the specific orientation flat position of the ingot is always the same position without changing from batch to batch. Later, the ingot can be sliced quickly simply by fixing the ingot in a cutting device in which the fixing position of the ingot and the mounting angle of the cutting tool have already been set. As a result, since it is not necessary to obtain the slicing direction for each grown ingot, the fixing time of the ingot can be shortened.

  On the other hand, in the case of an ordinary crystalline ingot, since it can not be limited to the crystal growth line for specifying the orientation flat position, one orientation flat position which minimizes the amount of warpage of the wafer can be ingot by X-ray diffraction or optical imaging. Identify above. Then, the slicing direction of the ingot is determined based on the identified orientation flat position. Further, even in the case of the ingot of the inclined crystal, it is possible to specify one orientation flat position on the ingot, which minimizes the amount of warpage of the wafer, by X-ray diffraction method or optical image method as in the normal crystal ingot. it can.

  Here, in the case where the orientation flat position of the ingot 11 is specified by the X-ray diffraction method, the X-ray diffractometer 31 shown in FIGS. 11 and 12 is used. The X-ray diffraction apparatus 31 generates an X-ray and irradiates the ingot 11 in a horizontal plane with an X-ray irradiation unit 31a, a rotatable table (not shown) supporting the ingot 11, and the ingot 11 And an X-ray detection unit 31b which receives diffracted diffracted X-rays and detects the intensity of the diffracted X-rays. In the X-ray diffraction apparatus 31, the X-ray irradiator 31a and the X-ray detector 31b are arranged in advance so as to correspond to the Bragg angle at which X-ray diffraction by a predetermined crystal plane of the ingot 11 occurs. Further, the cylindrical ingot 11 is mounted on the table so that its central axis 11a is vertically oriented and can be rotated about the central axis 11a of the ingot 11, or its central axis 11a is oriented horizontally and ingot The direction of the end face of 11 is mounted on the table so as to be changeable in the horizontal plane. The Bragg angle is a condition that gives the diffraction angle of X-rays by the crystal lattice derived by Bragg.

  In order to specify one orientation flat position 1 on the ingot 11 by using the X-ray diffractometer 31, first, as shown in FIG. 11, the central axis 11a of the ingot 11 is oriented in the vertical direction and the rotation of the table is The ingot 11 is placed on a table in a state coincident with the axis, and while irradiating X-rays from the X-ray irradiation unit 31a toward the outer peripheral surface of the ingot 11, this table is rotated and diffracted X-rays by a predetermined crystal plane Is stopped at a position detected by the X-ray detection unit 31b, and the diffraction angle of X-rays corresponding to the rotational position of the table is determined. At the remaining two orientation flat positions 2 and 3, the X-ray diffraction angles are respectively determined in the same manner as described above. As a result, since three orientation flat positions 1 to 3 can be specified on the ingot 11, the three orientation flat positions 1 to 3 are marked.

  Next, as shown in FIG. 12, with the central axis 11a of the ingot 11 oriented in the horizontal direction and the central axis 11a of the ingot 11 aligned with the rotational central axis of the table, the ingot 11 is attached to the table. At this time, one of three orientation flat positions 1 to 3 on the ingot 11 is positioned at the top of the ingot 11, and the end face of the ingot 11 is the Y direction and the horizontal direction is the X direction. Set orthogonal coordinates. Then, while irradiating the X-ray from the X-ray irradiation unit 31a to the end face of the ingot 11, the table is rotated to stop at a position where diffracted X-rays due to a predetermined crystal plane can be detected by the X-ray detection unit 31b. Deviations of the X-ray diffraction angle in the X-direction and the Y-direction corresponding to the rotational position of. The remaining two orientation flats 2 and 3 are also positioned on the top of the ingot 11 in the same manner as above, and the X-direction and Y-direction deviations of the X-ray diffraction angles corresponding to the rotational position of the table are respectively Ask. Although the deviations of the diffraction angles in the X direction and the Y direction obtained in this manner are different values on the crystal structure, the combined values obtained by combining the deviations in the X direction and the Y direction are substantially the same. This synthetic value is usually about 0 degree in a crystal ingot, and in the case of a tilted crystal ingot, it substantially coincides with the tilt angle of the crystal axis.

  Since the three orientation flat positions 1 to 3 can be specified respectively by the deviation of the diffraction angles in the X direction and the Y direction, one of the three orientation flat positions 1 to 3 is tested in advance. An orientation flat 11c is formed in 1 and the amount of warpage of the wafer 12 obtained by slicing the ingot 11 is measured with reference to the orientation flat 11c. The amount of warpage of the wafer 12 is also measured in the same manner as above for the remaining two orientation flat positions 2 and 3. Thereby, the reference orientation flat position 3 when the amount of warpage of the wafer 12 becomes the smallest can be specified by the deviation of the diffraction angles in the X direction and the Y direction. Therefore, in the mass production of the ingot 11, three orientation flat positions 1 to 3 are determined by the X-ray diffraction method, and the reference orientation flat position 3 at which the amount of warpage of the wafer 12 becomes the smallest is the X direction and the Y direction. The amount of warpage of the wafer 12 can be reduced by identifying an orientation flat 11c at the identified orientation flat position and slicing the ingot 11 on the basis of the orientation flat 11c. The orientation flat position may be specified not by X-ray diffraction but by optical imaging. In this light imaging method, spots of light are applied to the outer peripheral surface and the end face of the ingot, and the image of the reflected light is visually aligned with the crystal orientation.

Second Embodiment
FIG. 12 shows a second embodiment of the present invention. In FIG. 12, the same reference numerals as in FIG. 1 denote the same parts. In this embodiment, a band saw device 50 is used as a cutting device. The band saw device 50 includes first and second pulleys 51 and 52 provided at predetermined intervals with the first and second vertical shafts 51 a and 52 b as rotation centers, and the first and second pulleys 51 and 52. And a band-like blade 53 which is wound around the belt. The blade 53 includes an endless belt 53a formed in a ring shape by a metal band plate and a cutting blade 53b formed by electrodeposition of diamond particles on the lower edge of the belt 53a. Thus, by rotational driving of the first pulley 51, the first and second pulleys 51 and 52 are made to circulate in one direction at high speed. Further, on both sides of a portion (linearly moving portion) 53c of the blade 53 which linearly moves in one direction between the first and second pulleys 51 and 52, the first and second portions 53c of the linear moving portion 53c are restrained. The second blade fasteners 61 and 62 are disposed. The first and second blade fasteners 61 and 62 are configured to sandwich the blade 53 from both sides with a carbon shoe (not shown) and to hold the blade 53 in contact with a posture parallel to the cutting direction. . In FIG. 8, a holder for bonding and holding the ingot 11 is not shown. Except for the above, the configuration is the same as that of the first embodiment.

  A method of slicing and cutting the silicon single crystal ingot 11 using the band saw device 50 configured as described above will be described. First, the ingot 11 is disposed below the linear movement portion 53 c of the blade 53 so as to be orthogonal to the blade 53. Next, the first and second pulleys 51 and 52 are lowered in the vertical direction in a state in which the blade 53 circulates in one direction, and the ingot 11 is cut by the cutting blade 53 b of the linear movement portion 53 c of the blade 53. The operations other than the above are substantially the same as the operations of the first embodiment, and thus the description thereof will not be repeated.

  Next, an example of the present invention will be described in detail along with a comparative example.

Example 1
As shown in FIGS. 1 and 2, first, a cylindrical ingot 11 having a diameter of 150 mm and having a central axis not inclined with respect to the <111> crystal axis was grown by the FZ method. Since the three orientation flat positions 1 to 3 (FIG. 5) can be specified on the ingot 11 by determining the deviation of the diffraction angles in the X and Y directions at the end face of the ingot 11 with the X-ray diffractometer, Of the three orientation flat positions 1 to 3 experimentally, the reference orientation flat position 3 at which the amount of warpage of the wafer 11 is the smallest is specified by the deviation of the diffraction angles in the X and Y directions. Then, an orientation flat 11c (FIGS. 7 and 8) was formed at the identified orientation flat position 3. Next, the ingot 11 was bonded to the slicing table 23a of the wire saw device 20 (FIG. 1 and FIG. 2) while being rotated by a predetermined rotation angle about the crystal axis 11b of the ingot 11 (FIG. 3A). Here, when the perpendicular drawn from the crystal axis 11b of the ingot 11 to the orientation flat 11c is a reference line 11d, the predetermined rotation angle is a rotation angle θ (FIGS. 7 and 8) with respect to the reference line 11d.

  Next, the ingot 11 is disposed above the wire 26 stretched horizontally between the first and second main rollers 21 and 22 of the wire saw device 20, and each of the first and second main rollers 21 and 22 The crystal axis 11b of the ingot 11 is moved so as to be substantially parallel to the central axes of the first and second main rollers 21 and 22 between vertical lines passing through the central axis (FIGS. 1 and 2). At this time, the vertical plane including the crystal axis 11b of the ingot 11 was made orthogonal to the extending direction of the wire 26 between the first and second main rollers 21 and 22 (FIG. 3A). Furthermore, the ingot 11 was sliced by moving the ingot 11 vertically to a position crossing the wire 26 moving in the horizontal direction, thereby slicing the ingot 11 into a wafer 12 (FIGS. 7 and 8). The above-mentioned predetermined rotation angle θ was adjusted to a predetermined angle within the range of 27 degrees to 85 degrees, and the ingot 11 was sliced in the same manner as described above to produce a wafer 12. These wafers 11 are referred to as Example 1.

<Test 1 and Evaluation>
The amount of warpage of the wafer of Example 1 was measured. The amount of warpage of these wafers is assumed to be a plane passing 3 points on the back surface of the wafer at an inner position of 3 mm inside from the outer peripheral edge of the wafer and at 120 ° intervals around the crystal axis of the wafer. Among the magnitudes of warpage of the wafer measured from this plane, this was the maximum value. The results are shown in FIG.

  As apparent from FIG. 14, when the predetermined rotation angle θ is less than 40 degrees or exceeds 60 degrees, the warpage amount of the wafer is increased, but the predetermined rotation angle θ is in the range of 40 degrees to 60 degrees. Then, the amount of warpage of the wafer decreased, and when the predetermined rotation angle θ was in the range of 45 degrees to 55 degrees, the amount of warpage of the wafer further decreased.

Example 2
As shown in FIGS. 1 and 2, first, a cylindrical ingot 11 having a diameter of 150 mm and a central axis inclined at 3 degrees and 30 minutes with respect to a <111> crystal axis was grown by the FZ method. Four crystal habit lines 1 to 4 appeared on the outer peripheral surface of this ingot (FIG. 6). Then, among the four crystal growth lines 1 to 4 appearing on the outer peripheral surface of the ingot, the remaining one crystal except the three crystal growth lines 1 to 3 appearing at an interval of 120 degrees around the central axis of the ingot. The orientation flat position 3 among the three orientation flat positions 1 to 3 was specified with reference to the ridge line 4, and an orientation flat 11c (FIGS. 7 and 8) was formed at the orientation flat position 3. Then, since the central axis 11a of the cylindrical ingot 11 is inclined at a predetermined angle with respect to the crystal axis 11b (FIG. 3 (b)), the ingot 11 is different from the central axis 11a of the cylindrical ingot 11 After the ingot is placed on the rotary table so that the ingot can rotate about the crystal axis 11b (FIG. 3 (c)), the ingot 11 is centered on the crystal axis 11b and at a predetermined angle based on the orientation flat 11c. It was adhered to the slice table 23 b of the wire saw device 20 in a rotated state. Here, when the perpendicular drawn from the crystal axis 11b of the ingot 11 to the orientation flat 11c is the reference line 11d, the predetermined rotation angle is the rotation angle θ (FIGS. 7 and 8) with respect to the reference line 11d. The rotation angle θ was 50 degrees.

  Next, the ingot 11 is disposed above the wire 26 stretched horizontally between the first and second main rollers 21 and 22 of the wire saw device 20, and each of the first and second main rollers 21 and 22 The crystal axis 11b of the ingot 11 is moved so as to be substantially parallel to the central axes of the first and second main rollers 21 and 22 between vertical lines passing through the central axis (FIGS. 1 and 2). At this time, the vertical plane including the crystal axis 11b of the ingot 11 was made orthogonal to the extending direction of the wire 26 between the first and second main rollers 21 and 22 (FIG. 3 (c)). Furthermore, the ingot 11 was sliced by moving the ingot 11 vertically to a position crossing the wire 26 moving in the horizontal direction, thereby slicing the ingot 11 into a wafer 12 (FIGS. 7 and 8). In addition, the slice cutting time by the wire saw apparatus 20 of the ingot 11 was 1.0 au (arbitrary unit: arbitrary unit). Further, five ingots 11 were pulled up, and one wafer 12 was produced from each ingot 11 to produce a total of five wafers.

Example 3
Five wafers were produced in the same manner as in Example 2 except that the slicing time of the ingot by the wire saw device was set to 1.3 au. These wafers are referred to as Example 3.

Comparative Example 1
An orientation flat is formed at orientation flat position 1 among three orientation flat positions 1 to 3 (FIG. 6), and it is bonded to the slice table in a state rotated by a predetermined angle (50 degrees) with reference to this orientation flat Five wafers were produced in the same manner as in Example 2 except for the above. These wafers are referred to as Comparative Example 1.

Comparative Example 2
An orientation flat is formed at orientation flat position 2 among three orientation flat positions 1 to 3 (FIG. 6), and it is bonded to the slice base in a state rotated by a predetermined angle (50 degrees) with reference to this orientation flat Five wafers were produced in the same manner as in Example 2 except for the above. These wafers are referred to as Comparative Example 2.

Comparative Example 3
Five wafers were manufactured in the same manner as in Comparative Example 1 except that the slicing time of the ingot by the wire saw device was set to 1.3 au. These wafers are referred to as Comparative Example 3.

Comparative Example 4
Five wafers were produced in the same manner as in Comparative Example 2 except that the slicing time of the ingot by the wire saw device was 1.3 au. These wafers are referred to as Comparative Example 4.

<Test 2 and Evaluation>
The amounts of warpage of the wafers of Examples 2 and 3 and Comparative Examples 1 to 4 were measured. The amount of warpage of these wafers was measured in the same manner as in Test 1. The results are shown in FIG. 15 and FIG. In FIG. 15 and FIG. 16, "ori-flat" is an abbreviation of "orientation flat".

  As apparent from FIG. 15, the warpage amount of the wafer was large in Comparative Examples 1 and 2, whereas the warpage amount of the wafer was small in Example 2. Further, as apparent from FIG. 16, in the comparative examples 3 and 4, although the variation of the warpage amount of the wafer was small, the warpage amount of the wafer was still large, while the warpage amount of the wafer was small in the third embodiment. And, the variation in the amount of warpage of the wafer also decreased. As a result, it has been found that the warpage amount of the wafer does not vary for each grown ingot, that is, for each batch, so that the warpage amount of all the manufactured wafers can be reduced and the quality regarding the warpage of the wafer can be improved.

Example 4
Among the plurality of ingots (normal crystal ingots) of Example 1, four wafers sliced by using an ingot having a predetermined angle of 50 degrees to be rotated when bonding the ingots to a slicing base of a wire saw device It is referred to as Example 4. However, phosphorus was doped into the ingot.

Example 5
Four wafers were manufactured in the same manner as in Example 2 except that the ingot (ingot of inclined crystal) of Example 2 was doped with a phosphorus element. These wafers are referred to as Example 5.

<Test 3>
The amount of deviation from the average value of the in-plane resistivity of the wafers of Examples 4 and 5 was determined. Specifically, it entered a position 5 mm inward from the left edge of the wafer, an intermediate position between the left edge and the center of the wafer, a center of the wafer, an intermediate position between the right edge and the center of the wafer, and 5 mm inward from the right edge of the wafer The resistivity was measured at each position, and after calculating the average value of these measured values, the amount of deviation from the average value of each resistivity was determined. The amount of deviation is defined as the amount of deviation from the average value of the in-plane resistivity of the wafer. The resistivity was measured by the four-point probe method. Moreover, RRG (Radial Resistivity Gradient) of the wafer of Examples 4 and 5 was calculated. Specifically, it entered a position 5 mm inward from the left edge of the wafer, an intermediate position between the left edge and the center of the wafer, a center of the wafer, an intermediate position between the right edge and the center of the wafer, and 5 mm inward from the right edge of the wafer The resistivity was measured at each position, and the distribution width of these measured values was calculated, and then the distribution width was divided by the minimum value of the measured values and calculated by multiplying by 100. These calculated values are respectively referred to as "RRG". The results are shown in FIG. 17 and FIG.

  As apparent from FIGS. 17 and 18, in the wafer obtained by slicing the normal crystal ingot of Example 4, the amount of deviation from the average value of the in-plane resistivity of the wafer is up to 9% on the plus side and on the minus side. In the wafer obtained by slicing the ingot of the tilted crystal of Example 5, the amount of deviation from the average value of the in-plane resistivity of the wafer was approximately the same as the maximum value of 9% on the positive side, while the maximum was 17%. However, on the minus side it decreased by up to 12%. In addition, in the wafer obtained by slicing the normal crystal ingot of Example 4 with RRG of about 35%, the wafer obtained with sliced ingot of the inclined crystal of Example 5 with RRG decreased to about 20%. The As a result, it was found that the distribution of in-plane resistivity of the wafer becomes more uniform when using a wafer obtained by slicing an ingot of inclined crystal than a wafer obtained by slicing an ingot of normal crystal.

11 Silicon single crystal ingot 11a Central axis of cylindrical ingot 11b Crystal axis of cylindrical ingot 11c Orientation flat

Claims (2)

In a method for producing a silicon wafer, wherein a cylindrical silicon single crystal ingot is grown by FZ method or CZ method, and the ingot is sliced to produce a silicon wafer,
The cylindrical ingot is grown in a state in which the central axis of the cylindrical ingot is inclined by a predetermined angle within the range of 1 degree to 6 degrees from the direction of the <111> crystal axis,
Among the crystal growth lines appearing on the outer peripheral surface of the ingot, the orientation flat position is specified based on the remaining crystal growth lines excluding the three crystal growth lines appearing at intervals of 120 degrees around the central axis of the ingot;
A method of manufacturing a silicon wafer, wherein the ingot is sliced by returning it by a predetermined angle based on the orientation flat position. In manufacturing a plurality of silicon single crystal ingots, by using seed crystals having the same axial tilt direction, the ingot is fixed and sliced without repeatedly determining the slice direction of the ingot which minimizes the warpage of the wafer. method for producing a silicon wafer according to claim 1 Symbol mounting to.

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