SI substrate production process

Abstract

Silicon substrate manufacturing process for producing a silicon substrate from one silicon ingot (2) in which a crystal plane (100) has been made into a flat surface, the silicon substrate manufacturing process comprising: a separating band formation step comprising forming a separating band (38) by positioning a focal point (FP) of a laser beam (LB) with a wavelength transparent to silicon at a depth from the flat surface equal to the thickness of the silicon substrate to be produced, and irradiating the silicon ingot (2) with the laser beam (LB) while moving the focal point (FP) and the silicon ingot (2) relative to each other in a direction <110> parallel to a line of intersection (12) where a crystal plane {100} and a crystal plane {111} intersect, or in a direction [110] perpendicular to the line of intersection; a setup step involving the execution of an adjustment of the focal point (FP) and the silicon ingot (2) relative to each other in a direction perpendicular to a direction in which the separating band (38) is formed; and a wafer fabrication step with a repeated execution of the separating strip formation step and the setup step to form as a whole a separating layer (40) parallel to the crystal plane (100) inside the silicon ingot (2) and to separate the silicon substrate from the silicon ingot (2) at the separating layer (40) in order to produce the silicon substrate.

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a Si substrate manufacturing process for producing a Si substrate from a Si ingot. DESCRIPTION OF THE RELATED STATE OF THE ART

[0002] A wafer, in which several components, such as integrated circuits (ICs) and large-area integrated circuits (LSIs), are arranged on the top surface of a silicon substrate in such a way that they are separated from each other by several intersecting, planned separation lines, is divided into individual component chips by a dicing device or a laser processing device. The respective component chips obtained by this division are used for electronic equipment, such as portable phones and personal computers.

[0003] A silicon substrate (Si substrate) is formed by cutting a Si ingot to a thickness of approximately 1 mm using a cutting device having an inner diameter blade, a wire saw or similar, lapping and polishing (see, for example, the patent application JP 2000 - 94 221 A).

[0004] Furthermore, patent application JP 2015-32771A discloses a wafer manufacturing process for producing a wafer by separating a single-crystal ingot, taking into account the crystal axis of the ingot. Information on the structure of diamonds is disclosed at Wikipedia: Diamond structure. 2018-08-10. URL: https: / / de.wikipedia.org / w / index.php?title=Diamantstruktur&old id=179905288. The patent application DE 10 2019 214 897 A1 relates to a diamond substrate manufacturing process comprising a step for forming a band-shaped separating layer by applying a laser beam to a diamond ingot while moving relative to each other the diamond ingot and a focal point of the laser beam in a

[110] direction perpendicular to a (110) plane, in order to form a band-shaped separating layer which extends inside the diamond ingot in the

[110] direction.US Patent 6 211 488 B1 also relates to a process in which a non-metallic substrate is separated by microcracks and their targeted propagation. SUMMARY OF THE INVENTION

[0005] However, the kerf allowance of the inner diameter blade and the wire saw is comparatively small, approximately 1 mm. Therefore, when Si substrates are produced from a Si ingot using the inner diameter blade or the wire saw, the problem arises that the amount of material used for Si substrates is approximately 1 / 3 of the Si ingot, resulting in low productivity.

[0006] Consequently, it is an object of the present invention to provide a Si substrate manufacturing process that enables the efficient production of a Si substrate from a Si ingot.

[0007] In accordance with one aspect of the present invention, a silicon substrate fabrication method is provided for producing a silicon substrate from a silicon ingot in which a crystal plane (100) has been made into a flat surface. The silicon substrate fabrication method comprises a separation band formation step, in which a separation band is formed by positioning a focal point of a laser beam having a wavelength transparent to silicon at a depth from the flat surface equal to the thickness of the silicon substrate to be produced, and irradiating the silicon ingot with the laser beam while moving the focal point and the silicon ingot relative to each other in a certain direction. <110> parallel to a line of intersection where a crystal plane {100} and a crystal plane {111} intersect, or in a direction

[110] perpendicular to the line of intersection;a setup step comprising performing a setup of the focal point and the Si ingot relative to each other in a direction perpendicular to a direction in which the separating band is formed; and a wafer fabrication step comprising a repeated execution of the separating band formation step and the setup step to form a separating layer parallel to the crystal plane (100) as a whole inside the Si ingot, and separating the Si substrate from the Si ingot at the separating layer to produce the Si substrate.

[0008] Preferably, the laser beam is caused to branch into several laser beams in an alignment direction to form respective focal points. In the alignment step, it is preferred that the alignment be carried out in such a way that the separating bands that are adjacent are in contact with each other. Preferably, the Si substrate fabrication process further comprises a planarization step involving planarizing the crystal plane (100) of the Si ingot prior to the separating band formation step.

[0009] In accordance with the present invention, it becomes possible to efficiently produce the Si substrates from the Si ingot.

[0010] The above and other tasks, features and advantages of the present invention and the manner of its implementation will become clearer by studying the following description and attached claims, with reference to the accompanying drawings, which show a preferred embodiment of the invention, and the invention itself will be best understood by this. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a perspective view of a Si ingot; Fig. 1B is a top view of the Fig. 1A illustrated Si ingots; Fig. 2A is a perspective view of another Si ingot; Fig. 2B is a top view of the in Fig. 2A illustrated Si ingots; Fig. Figure 3 is a schematic diagram of a laser processing device; Fig. 4A is a perspective view illustrating a state in which a separating tape training step is being performed; Fig. Figure 4B is a front view illustrating the state in which the separating tape training step is performed; Fig. 5A is a sectional view of a Si ingot in which separating bands are formed; Fig. 5B is an enlarged view from one of the separating strips. Fig. 5A; Fig. Figure 6 is a graph illustrating a relationship between the number of branches of a laser beam and the length of a crack; Fig. Figure 7 is a graph illustrating a relationship between the distance between the focal points of branched laser beams and the length of the crack; Fig. Figure 8 is a graph illustrating a relationship between machining feed rate and crack length; Fig. Figure 9 is a graph illustrating a relationship between the output power of the laser beam and the crack length; Fig. Figure 10A is a perspective view illustrating a state in which the Si ingot is positioned under a separating device; Fig. Figure 10B is a perspective view illustrating a state in which a separation step is performed using the separation device; Fig. Figure 10C is a perspective view of the Si ingot and a Si substrate; Fig. Figure 11 is a schematic sectional view illustrating a state in which the separation step is carried out by applying ultrasonic waves to the Si ingot in which a separation layer is formed; Fig. Figure 12 is a perspective view illustrating a state in which a wafer grinding step is being performed; and Fig. Figure 13 is a perspective view illustrating a state in which a planarization step is being performed. DETAILED DESCRIPTION OF THE PREFERRED EXECUTION FORM

[0011] A preferred embodiment of the Si substrate production process of the present invention is described below with reference to the drawings. Fig. 1A and Fig. Figure 1B illustrates a silicon ingot (Si ingot) 2 with which the Si substrate fabrication process of the present invention can be carried out. The Si ingot 2 is formed as a whole with a circular column shape and has a circular first end face 4, which is obtained by making a crystal plane (100) into a flat surface, a circular second end face 6 on a side opposite the first end face 4, and a circumferential surface 8 arranged between the first end face 4 and the second end face 6. A flat, rectangular alignment plane 10 is formed in the circumferential surface 8 of the Si ingot 2. The alignment plane 10 is positioned such that an angle of 45° is formed with respect to a line of intersection 12 at which the crystal plane {100} and a crystal plane {111} intersect.

[0012] As in the Fig. 2A and Fig. As illustrated in Figure 2B, a notch 14 extending in an axial direction can be formed in the circumferential surface 8 of the Si ingot 2 instead of the alignment plane 10. As shown by reference to Fig. As is clear from Figure 2B, the notch 14 is positioned such that the angle formed between a tangent 16 at the notch 14 and the intersection line 12 is 45°. The following description describes a method for producing a Si substrate from the Si ingot 2 in which the alignment plane 10 is formed.

[0013] In the present embodiment, a separating band formation step is first carried out in which a separating band is formed by positioning a focal point of a laser beam with a wavelength that is transparent to Si at a depth equal to the thickness of a Si substrate to be produced, from the flat surface (first end surface 4) and irradiating the Si ingot 2 with the laser beam while moving the focal point and the Si ingot 2 relative to each other in a direction. <110> parallel to the intersection line 12, where the crystal plane {100} and the crystal plane {111} intersect, or in a direction

[110] perpendicular to the intersection line 12.

[0014] The separating tape training step can be carried out, for example, using a laser processing device 18, which is partly integrated into the Fig. 3 and Fig. Figure 4A illustrates this. The laser processing device 18 includes a holding table 20, which holds the Si ingot 2, and a laser beam irradiation unit 22, which irradiates the Si ingot 2 held by the holding table 20 with a pulsed laser beam LB.

[0015] The holding table 20 is rotatable about an axis extending in an upward-downward direction and is configured to be able to rotate in an X-axis direction that extends into the Fig. 3, Fig. 4A and Fig. 4B is indicated by an arrow X, and in a Y-axis direction (in the Fig. 3, Fig. 4A and Fig. 4B (direction indicated by an arrow Y) to move back and forth perpendicular to the X-axis direction. Furthermore, the holding table 20 is configured to be movable from a processing area of ​​the laser processing device 18 to a processing area of ​​a cutting device 42 and a grinding device 62, which will be described later. The plane defined by the X-axis direction and the Y-axis direction is essentially horizontal.

[0016] Referring to Fig. 3 The laser beam irradiation unit 22 includes a laser oscillator 24, which emits a pulsed laser beam LB with a wavelength that is transparent to Si, a damper 26, which sets an output power of the pulsed laser beam LB emitted by the laser oscillator 24, and a spatial light modulator 28, which causes the pulsed laser beam LB, whose output power has been set by the damper 26, to branch into several (for example 5) beams at predetermined intervals in the Y-axis direction. The laser beam irradiation unit 22 further includes a mirror 30, which reflects the pulsed laser beams LB that have been branched by the spatial light modulator 28 and changes their optical path direction, and a laser condenser 32, which focuses the pulsed laser beam LB that has been reflected by the mirror 30 and irradiates the Si ingot 2 with the pulsed laser beam LB.

[0017] In the separating tape training step, the Si-Ingot 2 is first attached to an upper surface of the holding table 20 using a suitable adhesive (for example, an epoxy resin-based adhesive) positioned between the two surfaces. Alternatively, several suction holes can be formed in the upper surface of the holding table 20, and the Si-Ingot 2 can be held in place by suction.

[0018] The Si-ingot 2 is imaged from above by an imaging unit (not illustrated) of the laser processing device 18, and the holding table 20 is rotated and moved based on an image of the Si-ingot 2 acquired by the imaging unit. This sets the orientation of the Si-ingot 2 to a predetermined orientation and adjusts the positions of the Si-ingot 2 and the laser capacitor 32 in the XY plane. When the orientation of the Si-ingot 2, as shown in Fig. As illustrated in Figure 4A, when a predetermined orientation is set, the setting is carried out in such a way that an angle formed between the X-axis direction and the alignment plane 10 becomes 45°, and the direction <110> is aligned with the X-axis direction parallel to the intersection line 12 where the crystal plane {100} and the crystal plane (111} intersect.

[0019] Subsequently, the laser condenser 32 is raised and lowered by a focal point position adjusting means of the laser processing device 18 (not illustrated), and a focal point FP (see Fig. 4B) The pulsed laser beam LB is positioned from the first end surface 4, which is a flat surface, at a depth equal to the thickness of a Si substrate to be produced. The pulsed laser beam LB of the present embodiment is caused to branch into several beams at predetermined intervals in the Y-axis direction by the spatial light modulator 28, and the focal points FP of the branched pulsed laser beams LB are positioned at the same depth.

[0020] While the holding table 20 is moved in the X-axis direction at a predetermined feeding speed, which corresponds to the direction <110> parallel to the one in the Fig. 1B and Fig. The Si ingot 2 is aligned with the section line 12 shown in Figure 2B, where the crystal plane {100} and the crystal plane {111} intersect. Subsequently, the Si ingot 2 is irradiated with the pulsed laser beam LB from the laser condenser 32 with a wavelength that is transparent to Si. As shown in the Fig. 5A and Fig. As illustrated in Figure 5B, a crystal structure near five focal points FP of the pulsed laser beam LB is refracted, and a dividing band 38, in which cracks 36 extend isotropically from a part 34 where the crystal structure is refracted along a (111) plane, is refracted along the <110> -direction (X-axis direction). In the present embodiment, the focal point FP and the Si ingot 2 are formed in the direction <110> The separating band 38 is moved parallel to the cutting line 12 relative to each other, where the crystal plane {100} and the crystal plane {111} intersect. However, the separating band 38 is also formed similarly to the one described above if the focal point FP and the Si ingot 2 are moved relative to each other in the direction

[110] perpendicular to the cutting line 12. In the separating band formation step, the laser condenser 32 can be moved in the X-axis direction instead of the holding table 20.Furthermore, in the present embodiment, the Si ingot 2 is irradiated with several beams branched off from the pulsed laser beam LB. However, the Si ingot 2 can be irradiated with the pulsed laser beam LB without causing the pulsed laser beam LB to branch.

[0021] The following adjustment step involves adjusting the focal point FP and the Si ingot 2 relative to the direction perpendicular to the direction in which the separating strip 38 is formed. In the adjustment step of the present embodiment, the holding table 20 is adjusted by a predetermined adjustment amount Li (see Fig. 4A) in the Y-axis direction perpendicular to the <110> -direction (X-axis direction) in which the separating strip 38 is formed. During the adjustment step, the laser condenser 32 can be adjusted instead of the holding table 20.

[0022] Subsequently, a wafer manufacturing step is carried out in which the separating layer formation step and the setting step are repeated to form a separating layer parallel to the crystal plane (100) as a whole inside the Si ingot 2, and a Si substrate is separated from the Si ingot 2 at the separating layer to produce the Si substrate.

[0023] By repeatedly performing the separating belt training step and the positioning step, as described in Fig. Figure 5A illustrates the formation of a separating layer 40 inside the Si ingot 2, which is composed of several separating bands 38 and in which the strength is reduced. The cracks 36 of each separating band 38 extend along the (111) plane. However, as can be seen by reference to Fig. As can be understood from 5A, the separating layer 40, which is made up of the several separating bands 38, is as a whole parallel to the first end surface 4.

[0024] A slight gap may be present between the cracks 36 of adjacent separating bands 38. However, the aligning is preferably carried out in such a way that the adjacent separating bands 38 are in contact with each other during the aligning step. This can cause the adjacent separating bands 38 to bond together and further reduce the strength of the separating layer 40. Thus, separating a Si substrate from the Si ingot 2 is simplified in the separation step described later.

[0025] It is desirable to use the following processing conditions as processing conditions adapted to form a separating layer 40. The present inventor et al. have carried out experiments under various conditions. As a result, they have found that when the separating layer 38 is formed under the following processing conditions, the cracks 36 of the separating layer 38 become longer and therefore the application rate Li can be chosen to be longer, thus reducing the time required to form the separating layer 40. Wavelength of the laser beam: 1342 nm Average output power of the laser beam before branching: 2.5 W Number of branched laser beams: 5 (based on the result of Experiment 1 described below) Distance between focal points of the branched laser beams: 10 µm (based on the result of Experiment 2 described below) Repetition rate: 60 kHz Feed rate: 300 mm / s (based on the result of Experiment 3 described below) Setting amount: 320 µm (based on the result of Experiment 4 described below)

[0026] With reference to the Fig. Sections 6 to 9 describe the results of experiments carried out by the present inventor, etc., concerning the formation of the separating layer. During various changes to the number of branches of the pulsed laser beam, the distance between the focal points of the branched laser beams, the relative feed rate of the Si ingot and the focal points, and the output power of the pulsed laser beam, the present inventor, etc.The length of the crack in the separation band was measured while the focal points of the pulsed laser beam with a wavelength transparent to Si were positioned from the top end face (top end face obtained by making the crystal plane (100) a flat surface) at a depth equal to the thickness of a Si substrate to be produced, and the Si ingot was irradiated with the pulsed laser beam while the focal points and the Si ingot were in the direction <110> The objects were moved parallel to the intersection line relative to each other, where the crystal plane {100} and the crystal plane {111} intersect. With the exception of the parameters that were changed in each experiment as described below, the processing conditions were set in the same way as the processing conditions described above, and a description of the processing conditions, except for the changed parameters, is omitted. < Experiment 1 >

[0027] Fig. Figure 6 illustrates the measurement result of the crack length of the separating strip in the Y-axis direction when the average output power per beam after branching was set to 0.5 W and the number of branches of the pulsed laser beam was changed. In the cases where the number of branches was 3, 4, and 5, the crack length was as shown in Figure 6. Fig. Figure 6 illustrates that the duration was longer when the number of branches of the pulsed laser beam was higher. < Experiment 2 >

[0028] Fig. Figure 7 illustrates the measurement result of the crack length of the separating strip in the Y-axis direction when the distance between the focal points of the branched pulsed laser beams has been changed (black circle markings). As in Fig. As illustrated in Figure 7, the length of the crack was at its maximum when the distance between the focal points of the branched pulsed laser beams was 10 µm. Furthermore, it is illustrated Fig. Figure 7, as a comparative example, also shows a result in which the Si ingot was irradiated with the pulsed laser beam while the focal points and the Si ingot were moved relative to each other in a direction parallel to the alignment plane (cross markings). As by reference to Fig. As is understandable in section 7, the length of the crack will be longer regardless of the distance between the focal points of the branched pulsed laser beams if the focal points and the Si ingot are in the direction <110> parallel to the line of intersection where the crystal plane {100} and the crystal plane {111} intersect (black circle markings), relative to each other, as if the foci and the Si ingot had been moved parallel to the alignment plane relative to each other (cross markings). < Experiment 3 >

[0029] Fig. Figure 8 illustrates the measurement result of the crack length of the separation strip in the Y-axis direction when the relative feed rate of the Si ingot and the focal points has been changed. As by reference to Fig. As is understandable in section 8, the crack length was at its maximum when the feed rate was set to 300 mm / s. The objective of experiment 3 was to determine the optimal feed rate. Consequently, the process was performed with the number of branches of the pulsed laser beam set to 3 and with the average output power of the pulsed laser beam set to 1.8 W (average output power: 0.5 W per beam after branching). < Experiment 4 >

[0030] Fig. Figure 9 illustrates the measurement result of the crack length of the separating strip in the Y-axis direction when the average output power of the pulsed laser beam was changed before branching. Fig. 9. A line graph, indicated by black circles, corresponds to the case where the number of branches was 5 and the foci and the Si ingot were moved relative to each other in the direction <110> parallel to the line of intersection where the crystal plane {100} and the crystal plane (111} intersect. A line graph indicated by crosses corresponds to the case where the number of branches was 5 and the foci and the Si ingot were moved relative to each other parallel to the alignment plane. A line graph indicated by triangles corresponds to the case where the number of branches was 3 and the foci and the Si ingot were moved relative to each other in the direction <110> parallel to the line of intersection where the crystal plane {100} and the crystal plane {111} intersect.

[0031] Out of Fig. 9. The following facts become clear: (1) the crack became longer when the output power of the pulsed laser beam was higher, (2) the crack became longer when the number of branches was greater, and (3) the crack became longer when the focal points and the Si ingot were moved relative to each other in the direction <110> parallel to the line of intersection where the crystal plane {100} and the crystal plane {111} intersect, rather than when the focal points and the Si ingot were moved relative to each other parallel to the alignment plane. As by reference to Fig. 9 Furthermore, it is understandable that the length of the crack in the line graph indicated by the black circle markings was at its maximum when the output power was 2.5 W.

[0032] To return to the explanation of the wafer manufacturing step, after the formation of the separating layer 40 inside the Si ingot 2, a Si substrate is separated from the Si ingot 2 at the separating layer 40 to produce the Si substrate. The separation of the Si substrate from the Si ingot 2 at the separating layer 40 can be carried out, for example, by using the separation device 42, which is located in the Fig. 10A and Fig. 10B is illustrated.

[0033] As in the Fig. 10A and Fig. As illustrated in Figure 10B, the separating device 42 includes an arm 44 extending substantially in a horizontal direction and a motor 46 attached to a head of the arm 44. A suction cup 48 with a circular plate shape is rotatably coupled about an axis to a lower surface of the motor 46, which extends in the upward-downward direction. The suction cup 48, which is configured to cause suction adhesion of a workpiece to a lower surface thereof, includes an ultrasonic vibration application device (not illustrated) that applies ultrasonic vibrations to the lower surface of the suction cup 48.

[0034] The explanation will be given with reference to the Fig. 10A to 10C continued. After the separating layer 40 has formed inside the Si ingot 2, the holding table 20, which holds the Si ingot 2, is moved to a lower side of the suction cup 48. Subsequently, the arm 44 is lowered, and, as in Fig. Figure 10B illustrates how a suction force is exerted on the lower surface of the suction holder 48 at the first end surface 4 (the end surface closer to the interface 40) of the Si ingot 2. Subsequently, the ultrasonic vibration application device is actuated to apply ultrasonic vibrations to the lower surface of the suction holder 48. Additionally, the suction holder 48 is rotated by the motor 46. As shown in Fig. As illustrated in Figure 10C, using the separating layer 40 as a starting point, a Si substrate 50 (wafer) can be separated from the Si ingot 2 in order to produce the Si substrate 50.

[0035] If the Si substrate 50 is to be separated from the Si ingot 2 at the separation layer 40, a further step can be taken in Fig. The separating device 52 illustrated in section 11 can be used. The one in Fig. 11 Illustrated separating device 52 includes a water tank 54, a rod 56 which is arranged in the water tank 54 in such a way that it is able to be raised and lowered, and an ultrasonic oscillation component 58 which is attached to a lower end of the rod 56.

[0036] If the Si substrate 50 is to be separated from the Si ingot 2 using the separation device 52, the Si ingot 2 is immersed in water 60 in the water tank 54. The rod 56 is then moved to position the ultrasonic oscillation component 58 just above the first end face 4 of the Si ingot 2. A distance of approximately 1 mm between the first end face 4 of the Si ingot 2 and the ultrasonic oscillation component 58 is sufficient. By oscillating ultrasonic waves from the ultrasonic oscillation component 58 stimulating the separation layer 40 through a layer of water 60, the Si substrate 50 can then be separated from the Si ingot 2, using the separation layer 40 as the starting point.

[0037] After the wafer fabrication step has been carried out, a wafer grinding step is performed by grinding a parting line 50a of the Si substrate 50 to planarize the parting line 50a. The wafer grinding step can be, as partly described in Fig. Figure 12 illustrates this, for example, by using the grinding device 62. The grinding device 62 includes a clamping table 64, which holds the Si substrate 50 under suction, and an abrasive 66, which grinds the Si substrate 50 held by the clamping table 64. The clamping table 64, which holds the Si substrate 50 under suction at one of its upper surfaces, is rotatable about an axis extending in the upward-downward direction.

[0038] As in Fig. As illustrated in Figure 12, the grinding element 66 includes a spindle 68, which is configured to rotate with its axial center in the up-down direction, and a disc holder 70, which is attached to a lower end of the spindle 68 and has a circular plate shape. An annular grinding wheel 74 is attached to a lower surface of the disc holder 70 by bolts 72. Several abrasive grinding stones 76 are attached to an outer circumferential edge portion of a lower surface of the grinding wheel 74 and are arranged in a ring at intervals in a circumferential direction.

[0039] The explanation is given with reference to Fig. 12 continued. In the wafer grinding step, a substrate 78 with a circular plate shape is first attached to a surface of the Si substrate 50 on a side opposite the parting line 50a using a suitable adhesive. Subsequently, the Si substrate 50 together with the substrate 78, with the parting line 50a of the Si substrate 50 facing upwards, is held by suction through the upper surface of the clamping table 64. The clamping table 64 is then rotated counterclockwise at a predetermined speed (for example, 300 rpm) in the direction viewed from above. Furthermore, the spindle 68 is rotated counterclockwise at a predetermined speed (for example, 6000 rpm) in the direction viewed from above.The spindle 68 is then lowered by a lifting / lowering device (not illustrated) of the grinding device 62, and the abrasive grinding stones 76 are brought into contact with the parting line 50a of the Si substrate 50. After the abrasive grinding stones 76 have been brought into contact with the parting line 50a of the Si substrate 50, the spindle 68 is then lowered at a predetermined grinding feed rate (for example, 1.0 µm / s). This allows the parting line 50a of the Si substrate 50 to be ground, and the Si substrate 50 to be planarized. After the parting line 50a has been ground, the planarized parting line 50a can be polished using a suitable polishing device until a desired surface roughness is obtained.

[0040] After the wafer manufacturing step was performed before, after or simultaneously with the wafer grinding step, a planarization step was further carried out by grinding a parting surface 4' of the Si ingot 2 from which the Si substrate 50 had been separated in order to planarize the crystal plane (100).

[0041] If the planarization step is performed before or after the wafer grinding step, the planarization step can be carried out using the abrasive 66 of the grinding device 62 described above. If the planarization step is carried out using the abrasive 66, the clamping table 64 is first separated from the position under the abrasive 66, and then the holding table 20, which holds the Si ingot 2, is separated as shown in Fig. 13 illustrates, moved to the position under the abrasive 66.

[0042] Similar to grinding the parting line 50a of the Si substrate 50, the holding table 20 is subsequently rotated counterclockwise (viewed from above), and the spindle 68 is rotated counterclockwise (viewed from above). The spindle 68 is then lowered, and the abrasive grinding stones 76 are brought into contact with the parting line 4' of the Si ingot 2. The spindle 68 is then lowered at a predetermined grinding feed rate. This allows the parting line 4' of the Si ingot 2 to be ground, and the crystal plane (100) of the Si ingot 2 to be planarized. The planarization step can be performed simultaneously with the wafer grinding step by using another grinding device with an abrasive similar to that of the grinding device 62.After the dividing surface 4' has been ground, the planarized crystal plane (100) can also be polished until a desired surface roughness is obtained by using a suitable polishing device.

[0043] After the planarization step has been performed, the separating belt formation step, setup step, wafer fabrication step, wafer grinding step, and planarization step described above are repeated to produce several Si substrates 50 from the Si ingot 2. In the present embodiment, an example is described in which the Si substrate fabrication process begins with the separating belt formation step, since the first end face 4 of the Si ingot 2 is a surface obtained by making the crystal plane (100) a flat surface. However, the Si substrate fabrication process can begin with the planarization step even if the first end face 4 of the Si ingot 2 is not a surface obtained by making the crystal plane (100) a flat surface.

[0044] In the Si substrate fabrication process of the present embodiment, the Si ingot 2 is irradiated with the pulsed laser beam LB, as described above, to form the separating layer 40, and the Si substrate 50 is separated from the Si ingot 2 using the separating layer 40 as the starting point. Therefore, no cutting is required, and it becomes possible to efficiently fabricate the Si substrates 50 from the Si ingot 2.

[0045] The present invention is not limited to the details of the preferred embodiment described above. The scope of protection of the invention is defined by the attached claims, and all modifications and adaptations that fall within the equivalent scope of protection of the claims are therefore encompassed by the invention.

Claims

[1] Silicon substrate manufacturing process for producing a silicon substrate from one silicon ingot (2) in which a crystal plane (100) has been made into a flat surface, the silicon substrate manufacturing process comprising: a separating band formation step comprising forming a separating band (38) by positioning a focal point (FP) of a laser beam (LB) with a wavelength transparent to silicon at a depth from the flat surface equal to the thickness of the silicon substrate to be produced, and irradiating the silicon ingot (2) with the laser beam (LB) while moving the focal point (FP) and the silicon ingot (2) relative to each other in a direction <110> parallel to a line of intersection (12) where a crystal plane {100} and a crystal plane {111} intersect, or in a direction [110] perpendicular to the line of intersection; a setup step involving the execution of an adjustment of the focal point (FP) and the silicon ingot (2) relative to each other in a direction perpendicular to a direction in which the separating band (38) is formed; and a wafer fabrication step with a repeated execution of the separating strip formation step and the setup step to form as a whole a separating layer (40) parallel to the crystal plane (100) inside the silicon ingot (2) and to separate the silicon substrate from the silicon ingot (2) at the separating layer (40) in order to produce the silicon substrate. [2] Silicon substrate manufacturing method according to claim 1, wherein the laser beam (LB) is caused to branch into multiple laser beams (LB) in the direction of the tilt in order to form corresponding focal points (FP). [3] Silicon substrate manufacturing method according to claim 1 or 2, wherein during the sizing step the sizing is carried out in such a way that the separating strips (38) which are adjacent are in contact with each other. [4] Silicon substrate manufacturing process according to any one of the preceding claims, further comprising: a planarization step with a planarization of the crystal plane (100) of the silicon ingot (2) prior to the separating band formation step.

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