How to separate the board

Abstract

To provide a substrate separation method capable of forming a separation original point at a position to be processed.SOLUTION: A substrate separation method for separating a substrate having a first surface and a second surface opposite to the first surface at least into two sheets, comprises: a separation original point formation step 102 of positioning a light focal point of a laser beam of a wavelength having transmissivity with respect to the substrate at an inner part of the substrate and radiating a laser beam while relatively moving a light focal point and the substrate along a first direction to form a peeling layer; an indexing feeding step 104 of relatively moving the light focal point and the substrate in a second direction orthogonal to the first direction; and a pressing member covering and providing step 101 of covering and providing a pressing member having the transmissivity with respect to the wavelength of the laser beam in a manner to press the first surface before the separation original point formation step 102.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for separating a substrate. [Background technology]

[0002] Wafers on which semiconductor devices are formed are generally formed by slicing an ingot with a cutting device such as a wire saw, and then undergoing processes such as lapping and polishing (see, for example, Patent Document 1).

[0003] However, the method disclosed in Patent Document 1 has a problem in that the cutting amount by the wire saw is large, so that most of the ingot is discarded, which is uneconomical.

[0004] Therefore, a technology has been proposed in which a laser beam having a wavelength that is transparent to the ingot is focused inside the ingot and irradiated to form a peeling layer having a thickness equivalent to the thickness of the wafer to be produced (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-94221 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-111143 [Patent Document 3] Patent application No. 2020-128469 Summary of the Invention [Problem to be solved by the invention]

[0006] However, peeling starting from the peeling layer is not easy, and ultrasonic waves must be applied through a water layer, which increases the amount of water used and increases costs.

[0007] Another issue is that separation becomes impossible in processes that do not require the use of water, such as when dividing a wafer on which devices are formed into two wafers.

[0008] Therefore, an attempt was made to improve the peeling force by performing processing under conditions of strong processing force, but a new problem emerged in that the wafer began to peel during processing, causing significant warping, and processing could not be performed in the desired position, resulting in processing defects such as cracks.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for separating a substrate that can form a separation starting point at a position where processing is desired. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, a substrate separation method of the present invention is a method for separating a substrate having a first surface and a second surface opposite to the first surface into at least two pieces, the method comprising: a separation start point forming step of positioning a focal point of a laser beam having a wavelength that is transparent to the substrate inside the substrate, and irradiating the laser beam while moving the focal point and the substrate relatively along a first direction to form a separation start point; and an indexing step of moving the focal point and the substrate relatively in a second direction orthogonal to the first direction, and further comprising a pressing member covering step of covering the first surface side with a pressing member that is transparent to the wavelength of the laser beam so as to press the first surface side before the separation start point forming step. The separation start point forming step and the indexing and feeding step are repeated to form the separation start points at intervals that allow the substrate to be separated on the first surface side and the second surface side without applying an external force to the inside of the substrate, and in the separation start point forming step, the substrate is pressed by the pressing member while being irradiated with the laser beam to form the separation start points. It is characterized by: In the substrate separation method, the pressing member covering step may include adhering the center of a tape attached to an annular frame having an inner diameter larger than the outer diameter of the substrate at its outer edge to the second surface of the substrate, adhering the center of a second tape, which is the pressing member having an outer diameter larger than the outer diameter of the substrate and smaller than the inner diameter of the frame, to the first surface of the substrate, and adhering the outer edge of the second tape to the tape.

[0011] In the method for separating a substrate, the substrate may include a Si ingot, and the laser beam may be irradiated onto the Si ingot while branching in a direction perpendicular to the first direction.

[0012] In the method for separating a substrate, the pressing member may include a tape that is transparent to the wavelength of the laser beam.

[0013] The substrate separation method may further include a separation step in which the separation starting point forming step and the indexing and feeding step are repeated while the substrate is held on a chuck table to form separation starting points throughout the interior of the substrate, and then the substrate is separated into a substrate on the first surface side and a substrate on the second surface side, and a grinding step in which, after the separation step, the surface of the substrate on the second surface side held on the chuck table is ground. [Effects of the Invention]

[0014] The present invention has an effect of being able to form a separation starting point at a position where processing is desired. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a substrate to be processed by the substrate separation method according to the first embodiment. [Figure 2] FIG. 2 is a flowchart showing the flow of the substrate separation method according to the first embodiment. [Figure 3] FIG. 3 is a perspective view showing a pressing member covering step of the substrate separation method shown in FIG. [Figure 4] FIG. 4 is a side view, partially in section, schematically showing the separation starting point forming step of the substrate separation method shown in FIG. [Figure 5] FIG. 5 is a perspective view schematically showing a separation starting point forming step of the substrate separation method shown in FIG. [Figure 6] FIG. 6 is a perspective view schematically showing a separation start point forming step after the first indexing and feeding step of the substrate separation method shown in FIG. [Figure 7] FIG. 7 is a side view, partly in section, schematically showing the separation step of the substrate separation method shown in FIG. [Figure 8]FIG. 8 is a side view, partially in section, schematically showing the grinding step of the substrate separation method shown in FIG. [Figure 9] FIG. 9 is a perspective view showing a pressing member covering step of the substrate separation method according to the second embodiment. [Figure 10] FIG. 10 is a side view, partially in section, schematically showing the separation starting point forming step of the substrate separation method according to the second embodiment. [Figure 11] FIG. 11 is a perspective view of a Si ingot to be processed by the substrate separation method according to the modified example of the first and second embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0017] [Embodiment 1] A substrate separation method according to a first embodiment of the present invention will be described with reference to the drawings. The substrate separation method according to the first embodiment is a method for processing a substrate 1 shown in Fig. 1. First, the substrate 1 to be processed by the separation method according to the first embodiment will be described. Fig. 1 is a perspective view showing a substrate to be processed by the substrate separation method according to the first embodiment.

[0018] (substrate) The substrate 1 to be processed in the substrate separation method according to the first embodiment is made of silicon. The substrate 1 has a circular and flat first surface 2, a circular and flat second surface 3 opposite the first surface 2, and a peripheral surface 4 connecting the first surface 2 and the second surface 3, and is formed into a disk shape as a whole. The first surface 2 and the second surface 3 of the substrate 1 are parallel to each other. The substrate 1 also has a notch 5 cut into the peripheral surface 4 to indicate the crystal orientation. In the first embodiment, the thickness of the substrate 1 is 775 μm.

[0019] (Substrate separation method) Next, a method for separating the substrate will be described. Fig. 2 is a flowchart showing the flow of the method for separating the substrate according to embodiment 1. The method for separating the substrate according to embodiment 1 is a method for separating the substrate 1 shown in Fig. 1 into at least two pieces, and as shown in Fig. 2, includes a pressing member covering step 101, a separation start point forming step 102, an indexing and feeding step 104, a separating step 105, and a grinding step 106.

[0020] (Pressing member covering step) Figure 3 is a perspective view showing a pressing member covering step of the substrate separation method shown in Figure 2. Pressing member covering step 101 is a step, prior to separation start point forming step 102, in which tape 20, which is a pressing member that is transparent to the wavelength of laser beam 31 (shown in Figure 4) that will be irradiated onto substrate 1 in separation start point forming step 102, is laid down so as to press tape 20 against first surface 2 of substrate 1.

[0021] In embodiment 1, in pressing member covering step 101, as shown in Fig. 3, a disk-shaped tape 20 is attached to an annular frame 21 having an outer diameter larger than that of the substrate 1 and an inner diameter larger than that of the substrate 1 at its outer edge, and the center of the disk-shaped tape 20 is attached to the first surface 2 of the substrate 1. In embodiment 1, the tape 20 is made of an adhesive and flexible resin, and includes an adhesive layer attached to the substrate 1 and the frame 21, and a base layer laminated with the adhesive layer and made of a non-adhesive and flexible resin. In embodiment 1, the tape 20 is a pressing member that presses the first surface 2 side of the substrate 1.

[0022] (Separation origin formation step) Figure 4 is a side view, partially in cross section, schematically showing the separation starting point forming step of the substrate separation method shown in Figure 2. Figure 5 is a perspective view schematically showing the separation starting point forming step of the substrate separation method shown in Figure 2. The separation starting point forming step 102 is a step in which a focal point 32 of a laser beam 31 having a wavelength that is transparent to the substrate 1 is positioned inside the substrate 1, and the laser beam 31 is irradiated while the focal point 32 and the substrate 1 are moved relatively along a first direction 8 to form a peeling layer 6 that is a separation starting point.

[0023] In the first embodiment, in the separation starting point forming step 102, the processing device 30 shown in Fig. 4 suction-holds the second surface 3 of the substrate 1 on the holding surface 34 of the chuck table 33, and clamps the frame 21 with a plurality of clamp portions 35 around the chuck table 33. At this time, in the first embodiment, the tape 20 is positioned above the substrate 1. In the first embodiment, in the separation starting point forming step 102, the processing device 30 shown in Fig. 4 uses an imaging unit to capture an image of the substrate 1 held on the chuck table 33, and performs alignment to align the substrate 1 with a laser beam irradiation unit 36 ​​that irradiates a laser beam 31.

[0024] In the first embodiment, in the separation starting point forming step 102, the processing device 30 positions the laser beam irradiation unit 36 ​​above one end of the outer edge of the substrate 1 in the X-axis direction, which is the processing feed direction, and positions a tangent 7 (shown by a dashed line in FIG. 1) of the position where the notch 5 of the substrate 1 held by the chuck table 33 is formed, parallel to the X-axis direction. The processing feed direction is the direction in which the processing device 30 moves the chuck table 33 while irradiating the substrate 1 with the laser beam 31 from the laser beam irradiation unit 36.

[0025] In the separation starting point forming step 102, as shown in FIG. 4, the processing device 30 sets the focal point 32 at a depth 37 corresponding to the thickness of the substrate 1-1 on the first surface 2 side of the substrate 1 to be separated within the substrate 1, and then irradiates the tape 20 and the substrate 1 with a laser beam 31 having a wavelength that is transparent to the tape 20 and the substrate 1 from the laser beam irradiation unit 36 ​​while moving the chuck table 33 horizontally along a first direction 8 parallel to the tangent line 7 so that the other end of the substrate 1 in the X-axis direction faces downward from the laser beam irradiation unit 36. In the first embodiment, in the separation starting point forming step 102, the processing device 30 splits the laser beam 31 emitted from the laser oscillator into multiple beams using a beam splitting unit (not shown) of the laser beam irradiation unit, and irradiates the substrate 1 with multiple focal points 32 arranged in a second direction 9 perpendicular to the first direction 8, as shown in FIG. 5. Note that the clamp unit 35 is omitted in FIG. 5.

[0026] In the separation starting point forming step 102, when the substrate 1 is irradiated with a laser beam 31 of a wavelength having transparency with a focal point 32 set inside, a modified portion 6-1 and a peeling layer 6 including cracks extending from the modified portion 6-1 are formed inside the substrate 1 near the focal point 32. In the separation starting point forming step 102, the processing device 30 forms the peeling layer 6 from one end to the other end in the X-axis direction of the outer edge of the substrate 1, and then stops irradiating the laser beam 31 from the laser beam irradiation unit 36.

[0027] The processing device 30 determines whether a control unit (not shown) or the like has formed the release layer 6 throughout the aforementioned depth 37 inside the substrate 1 (step 103). Formation of the release layer 6 throughout the aforementioned depth 37 inside the substrate 1 means that modified portions 6-1 of the release layer 6 have been formed at intervals that allow the substrate 1 to be peeled off between the first surface 2 and the second surface 3 without the application of external force. If the control unit (not shown) or the like determines that the release layer 6 has not been formed throughout the aforementioned depth 37 inside the substrate 1 (step 103: No), the processing device 30 proceeds to indexing and feeding step 104.

[0028] (indexing feed step) FIG. 6 is a perspective view schematically showing a separation start point forming step after the first indexing and feeding step of the substrate separation method shown in FIG.

[0029] The indexing step 104 is a step of relatively moving the focal point 32 and the substrate 1 in a second direction perpendicular to the first direction 8. In the indexing step 104, the processing device 30 moves the chuck table 33 in the second direction 9, i.e., the Y-axis direction, and also moves it in the first direction 8, i.e., the X-axis direction, to position the laser beam irradiation unit 36 ​​at a position shown by a dotted line in FIG. 6 , adjacent to the position where the peeling layer 6 has already been formed on the substrate 1 and above one end of the outer edge of the substrate 1 in the X-axis direction. Note that in the indexing step 104 as well, the processing device 30 positions the tangent 7 of the position where the notch 5 of the substrate 1 held by the chuck table 33 was formed, i.e., the first direction 8, parallel to the X-axis direction, and returns to the separation start point forming step 102.

[0030] 6 , the processing device 30 sets the focal point 32 at the depth 37 described above, and irradiates the substrate 1 with the laser beam 31 branched from the laser beam irradiation unit 36 ​​while moving the chuck table 33 along the first direction 8 so that the other end of the substrate 1 in the X-axis direction faces downward from the laser beam irradiation unit 36, thereby forming a peeling layer 6 including a modified portion 6-1 and cracks inside the substrate 1. In the separation starting point forming step 102, the processing device 30 forms the peeling layer 6 from one end to the other end of the substrate 1 in the X-axis direction, and then stops irradiating the laser beam 31 from the laser beam irradiation unit 36.

[0031] The processing device 30 again determines whether the control unit etc. has formed the peeling layer 6 over the entire depth 37 inside the substrate 1 (step 103), and if it determines that the peeling layer 6 has not been formed over the entire depth 37 inside the substrate 1 (step 103: No), it proceeds to the indexing and feeding step 104, and after performing the indexing and feeding step 104, it again performs the separation starting point formation step 102.

[0032] In this way, the processing device 30 repeats the indexing and feeding step 104 and the separation start point forming step 102 until the peeling layer 6 is formed throughout the entire depth 37 inside the substrate 1. In the first embodiment, typical processing conditions for the separation start point forming step 102 and the indexing and feeding step 104 of the processing device 30 are as follows:

[0033] Laser beam 31 wavelength: 1342 nm Repetition frequency of laser beam 31: 60 kHz Average power of laser beam 31 before branching: 2.0W Number of branches of laser beam 31: 5 Processing feed rate: 420mm / s Index amount: 50 μm The index amount is the distance by which the laser beam irradiation unit 36 ​​and the chuck table 33 are moved relatively in the Y-axis direction in the indexing feed step 104 .

[0034] When the control unit or the like of the processing device 30 determines that the peeling layer 6 has been formed throughout the entire depth 37 inside the substrate 1 (step 103: Yes), the processing device 30 proceeds to separation step 105. When the peeling layer 6 is formed throughout the entire depth 37 inside the substrate 1, the peeling layer 6 includes the modified portion 6-1 and cracks described above, and therefore, separation into the first surface 2 side and the second surface 3 side is facilitated starting from the peeling layer 6 (boundary).

[0035] In addition, in the separation starting point formation step 102, a laser beam 31 is irradiated through the tape 20 to form a peeling layer 6 inside the substrate 1, so that the substrate 1 is pressed against the holding surface 34 of the chuck table 33 with the tape 20 while the laser beam 31 is irradiated to form the peeling layer 6.

[0036] (separation step) Fig. 7 is a side view, partially in cross section, schematically showing the separation step of the substrate separation method shown in Fig. 2. In separation step 105, separation start point forming step 102 and indexing step 104 are repeated while substrate 1 is held on chuck table 33, forming peeling layer 6, which serves as a separation start point, throughout the entire interior of substrate 1, and then separating substrate 1 into substrate 1-1 on the first surface 2 side and substrate 1-2 on the second surface 3 side.

[0037] In the first embodiment, in the separation step 105, the processing device 30 releases the clamping of the frame 21 by the clamp unit 35 while the second surface 3 side of the substrate 1 is held by suction on the chuck table 33, and a transport unit (not shown) holds the frame 21 and the like and raises the frame 21 and the tape 20 in a direction away from the holding surface 34 of the chuck table 33. Then, as shown in FIG. 7 , the substrate 1 is separated into the substrate 1-2 on the second surface 3 side held by suction on the chuck table 33 and the substrate 1-1 on the first surface 2 side attached to the tape 20, starting from the release layer 6.

[0038] (Grinding step) Fig. 8 is a side view, partially in cross section, schematically showing the grinding step of the substrate separation method shown in Fig. 2. Grinding step 106 is a step of grinding surface 3-1, which is the peeled surface of substrate 1-2 on second surface 3 of substrate 1 held on chuck table 33, peeled from substrate 1-1 on first surface 2.

[0039] In embodiment 1, in the grinding step 106, as shown in FIG. 8, the processing device 30 rotates the grinding wheel 39 around its axis using the spindle 38 and rotates the chuck table 33 around its axis, and while supplying grinding water (not shown), such as pure water, the grinding stone 40 of the grinding wheel 39 is brought into contact with the surface 3-1 of the substrate 1-2 on the second surface 3 side and moved toward the chuck table 33 at a predetermined feed rate, and grinds with the grinding stone 40 to flatten the surface 3-1 of the substrate 1-2 on the second surface 3 side.

[0040] In the first embodiment, the processing device 30 uses the same chuck table 33 throughout the separation start point forming step 102, the indexing and feeding step 104, and the separation step 105, and forms the peeling layer 6 without releasing the suction hold, and then grinds it. Generally, a thin substrate 1-2 warps when the suction hold is released, but since cracks remain on the surface or inside the substrate 1-2 after peeling, there is a risk that the cracks will extend along with the warping, causing the substrate 1-2 to break.

[0041] Therefore, in embodiment 1, after forming the peeling layer 6 without releasing the suction hold throughout the separation starting point formation step 102, the indexing feed step 104, and the separation step 105, the surface 3-1 of the substrate 1-2 is ground and flattened, thereby suppressing the propagation of the crack and preventing the substrate 1-2 from breaking.

[0042] In addition, the substrate 1-2 on the first surface 2 side separated starting from the peeling layer 6 of the substrate 1 has the peeled surface 2-1 peeled from the second surface 3 side ground by a separate grinding device or the like to be flattened.

[0043] As described above, in the substrate separation method according to embodiment 1, laser beam 31 is applied to substrate 1 while substrate 1 is pressed against holding surface 34 of chuck table 33 with tape 20, which makes it possible to suppress warping of substrate 1-2, particularly on the first surface 2 side, after peeling layer 6 is formed, and form peeling layer 6 in an appropriate position. As a result, the substrate separation method according to embodiment 1 has the effect of suppressing a reduction in processing defects and forming peeling layer 6, which is the separation starting point, at a desired processing position.

[0044] Furthermore, the substrate separation method according to embodiment 1 can form an appropriate peeling layer 6 without being affected by warping even under processing conditions with a strong processing force, and therefore has the effect of allowing the substrate 1 to be separated starting from the peeling layer 6 simply by lifting the tape 20 and separating it from the substrate 1, without applying ultrasonic vibrations to the substrate 1 through the use of water, thereby easily separating the substrate 1.

[0045] [Embodiment 2] Next, a substrate separation method according to embodiment 2 will be described with reference to the drawings. Fig. 9 is a perspective view showing a pressing member covering step of the substrate separation method according to embodiment 2. Fig. 10 is a side view, partially in cross section, showing a separation start point forming step of the substrate separation method according to embodiment 2. In Figs. 9 and 10, the same parts as those in embodiment 1 are designated by the same reference numerals, and their description will be omitted.

[0046] The method for separating the substrate according to the second embodiment is the same as the method for separating the substrate according to the first embodiment, except that second tape 22, which is a pressing member, is used.

[0047] In the substrate separation method according to the second embodiment, in the pressing member covering step 101, the center of tape 20, which has been attached to the outer edge of frame 21, is attached to second surface 3 of substrate 1, and the center of second tape 22, which has an outer diameter larger than the outer diameter of substrate 1 and smaller than the inner diameter of frame 21, is attached to first surface 2 of substrate 1, and the outer edge of second tape 22 is attached to tape 20, as shown in Fig. 9 . Second tape 22 presses against first surface 2 of substrate 1. Note that second tape 22 may be made of a resin that is non-adhesive, flexible, and transparent to the wavelength of laser beam 31.

[0048] 10 , in the separation starting point forming step 102, the processing device 30 suction-holds the second surface 3 of the substrate 1 on the holding surface 34 of the chuck table 33 via the tape 20, and irradiates the laser beam 31 through the second tape 22 in the same manner as in the first embodiment, to form a peeling layer 6 inside the substrate 1. For this reason, in the substrate separation method according to the second embodiment, in the separation starting point forming step 102, the processing device 30 irradiates the laser beam 31 while pressing the substrate 1 against the holding surface 34 of the chuck table 33 with the second tape 22.

[0049] In the substrate separation method of embodiment 2, the substrate 1 is pressed against the holding surface 34 of the chuck table 33 with the second tape 22 while the laser beam 31 is applied, thereby suppressing warping, particularly on the first surface 2 side, after the peeling layer 6 is formed, and allowing the peeling layer 6 to be formed in an appropriate position.As with embodiment 1, this has the effect of allowing the peeling layer 6, which is the separation starting point, to be formed at the desired processing position without causing processing defects.

[0050] Furthermore, the substrate separation method according to embodiment 2 can form an appropriate peeling layer 6 without being affected by warping even under processing conditions with a strong processing force, and therefore has the effect of easily separating the substrate 1 by simply peeling the second tape 22 from the tape 20 and lifting it away from the substrate 1, without applying ultrasonic vibrations to the substrate 1 through the use of water, thereby enabling the substrate 1 to be separated starting from the peeling layer 6.

[0051] In the substrate separation methods according to the first and second embodiments, a direction parallel to a tangent 7 at the position where the notch 5 is formed is defined as a first direction 8, and the chuck table 33 is moved horizontally along the direction parallel to the tangent 7 while irradiating the laser beam 31 to form a peeling layer 6 including a modified portion 6-1 and a crack inside the substrate 1. However, in the present invention, a direction tilted 45 degrees from the direction parallel to the tangent 7 at the position where the notch 5 is formed may be defined as the first direction 8, and the chuck table 33 may be moved horizontally along the direction tilted 45 degrees from the direction parallel to the tangent 7 while irradiating the laser beam 31 to form a peeling layer 6 including a modified portion 6-1 and a crack inside the substrate 1. In this case, the cracks are more likely to extend, which has the effect of further increasing the index amount and shortening the processing time.

[0052] [Modification] Next, a substrate separation method according to a modification of the first embodiment and the second embodiment will be described with reference to the drawings. Fig. 11 is a perspective view of a Si ingot that is the processing target of the substrate separation method according to the modification of the first embodiment and the second embodiment. In Fig. 11, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

[0053] In the substrate separation method according to the modified example, the processing object is a Si ingot 11 (corresponding to a substrate) shown in FIG. 11, and a portion of the Si ingot 11 on the first surface 12 side is separated as a wafer substrate. The Si ingot 11 shown in FIG. 11 is made of Si (silicon) and is formed in a cylindrical shape as a whole. In the first embodiment, the Si ingot 11 has a circular and flat first surface 12, a circular and flat second surface 13 opposite the first surface 12, and a peripheral surface 14 connecting the first surface 12 and the second surface 13, and the first surface 12 is a crystal plane {100}. The Si ingot 11 has a flat, rectangular orientation flat 15 indicating the crystal orientation formed on the peripheral surface 14.

[0054] In the substrate separation method according to the modified example, in separation starting point formation step 102, Si ingot 11 is suction-held on holding surface 34 of chuck table 33, and the angle between the X-axis direction and orientation flat 10 is adjusted to be 45°. In the substrate separation method according to the modified example, in separation starting point formation step 102, chuck table 33 is moved in the X-axis direction, i.e., first direction 8, while irradiating laser beam 31 onto Si ingot 11, as in embodiment 1, etc., to form peeling layer 6 inside Si ingot 11.

[0055] In the substrate separation method according to the modified example, in the separation starting point formation step 102, the Si ingot 11 is pressed against the holding surface 34 of the chuck table 33 with the tape 20 or the second tape 22 while being irradiated with the laser beam 31, as in the first or second embodiment.

[0056] In the substrate separation method according to the modified example, the Si ingot 11 is pressed against the holding surface 34 of the chuck table 33 with the tape 20 or the second tape 22 while being irradiated with the laser beam 31, thereby suppressing warping on the first surface 2 side and achieving the effect of forming a separation starting point at the desired processing position without causing processing defects, as in the first embodiment, etc.

[0057] In the substrate separation method according to the modified example, in the separation start point formation step 102, the angle between the X-axis direction and the orientation flat 10 is adjusted to 45°, and the chuck table 33 is moved in the X-axis direction, i.e., the first direction 8, while irradiating the Si ingot 11 with the laser beam 31, as in the first embodiment, to form a peeling layer 6 inside the Si ingot 11. However, in the present invention, the processing feed direction is not limited to the directions described in the embodiment and modified example, whether for the Si ingot 11 or the substrate 1. Furthermore, if the chuck table 33 is moved in a direction tilted 45 degrees from a direction parallel to the orientation flat 15 during processing, the crack tends to extend, and therefore the index amount can be increased and the processing time can be shortened.

[0058] The present invention is not limited to the above-described embodiments. In other words, various modifications can be made without departing from the gist of the present invention. In the present invention, the laser beam irradiation unit 36 ​​that irradiates the laser beam 31 preferably includes a phase modulation element (Lcos-SLM: Liquid Crystal on Silicon-Spatial Light Modulator) that cancels aberrations caused by the tapes 20 and 22 that serve as pressing members. In the present invention, the pressing members are not limited to the tapes 20 and 22, and may be, for example, a hard substrate (glass substrate) that is transparent to the wavelength of the laser beam 31. [Explanation of symbols]

[0059] 1 board 1-1 First surface side substrate 1-2 Second surface side substrate 2. First Side 3. Second Side 3-1 Surface 6 Peeling layer (starting point of separation) 8 First Direction 9 Second Direction 11 Si ingot (substrate) 12 First Side 13 Second Side 20 Tape (pressing member) 22 Second tape (pressing member) 31 Laser Beam 32 Focusing point 101 Pressing member covering step 102 Separation origin formation step 104 Indexing feed step 105 Separation Step 106 Grinding Step

Claims

1. A method for separating a substrate, the method comprising: separating a substrate having a first surface and a second surface opposite to the first surface, into at least two substrates, the method comprising: a separation starting point forming step of positioning a focal point of a laser beam having a wavelength that is transparent to the substrate inside the substrate, and irradiating the laser beam while moving the focal point and the substrate relatively along a first direction to form a separation starting point; an indexing step of relatively moving the focal point and the substrate in a second direction perpendicular to the first direction; Before the separation origin forming step, a pressing member covering step of covering the first surface side with a pressing member that is transparent to the wavelength of the laser beam, the separation start point forming step and the indexing and feeding step are repeated to form the separation start points at intervals that allow the substrate to be separated on the first surface side and the second surface side without applying an external force to the inside of the substrate, and in the separation start point forming step, the substrate is pressed by the pressing member while being irradiated with the laser beam to form the separation start points. How to separate the board.

2. The pressing member covering step is characterized in that the center of a tape attached to an annular frame whose outer edge has an inner diameter larger than the outer diameter of the substrate is attached to the second surface of the substrate, the center of a second tape, which is the pressing member and has an outer diameter larger than the outer diameter of the substrate and smaller than the inner diameter of the frame, is attached to the first surface of the substrate, and the outer edge of the second tape is attached to the tape. The method for separating a substrate according to claim 1 .

3. the substrate comprises a Si ingot; the laser beam is irradiated onto the Si ingot in a state where the laser beam is branched in a direction perpendicular to the first direction. The method for separating a substrate according to claim 1 or 2.

4. The pressing member is 4. The method for separating substrates according to claim 1, further comprising the step of: providing a tape that is transparent to the wavelength of the laser beam.

5. a separating step of repeating the separation origin forming step and the indexing and feeding step while the substrate is held on a chuck table to form separation origins throughout the interior of the substrate, and then separating the substrate into a substrate on the first surface side and a substrate on the second surface side; a grinding step of grinding the surface of the substrate on the second surface side held by the chuck table after the separating step; The method for separating a substrate according to claim 1 , further comprising:

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