Laser processing method, manufacturing method of substrate, and laser processing device

Abstract

To form a separation layer, which is appropriate to be cleaved, inside of an ingot.SOLUTION: A laser processing method for forming a separation layer inside of an ingot by utilizing a laser beam having a wavelength, which is transmitted through a material of the ingot, includes: a substrate manufacture step of manufacturing a substrate by separating a portion, which is positioned at the side of one face of the ingot, from the ingot; a substrate evaluation step of evaluating the substrate for acquiring information relating to optical characteristics in each of a plurality of regions at the side of one face of the ingot; a setting step of setting for each of the plurality of regions an irradiation condition of the laser beam by referring to the information after the substrate evaluation step; and a separation layer formation step of forming the separation layer inside of the ingot by irradiating the ingot with the laser beam from the side of one face in a state where a focal point in which the laser beam is focused is positioned inside of the ingot after the setting step.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a laser processing method for forming a separation layer inside an ingot by utilizing a laser beam having a wavelength that transmits through the ingot material, a substrate manufacturing method for producing a substrate from an ingot by utilizing this laser beam, and a laser processing apparatus for forming a separation layer inside an ingot by utilizing this laser beam. [Background technology]

[0002] Semiconductor device chips are generally manufactured using disk-shaped substrates. The substrates are manufactured, for example, by cutting out cylindrical semiconductor ingots using a wire saw. However, when manufacturing substrates in this manner, most of the ingot is lost as kerf loss, which increases the cost of chips manufactured from the substrates.

[0003] Furthermore, the single crystal SiC (silicon carbide) used as a material for power devices is hard. In this case, it takes a long time to cut a substrate from a single crystal SiC ingot using a wire saw. Therefore, in this case, the throughput when manufacturing substrates from the ingot tends to be low.

[0004] In consideration of these points, a method for manufacturing a substrate from an ingot using a laser beam has been proposed (see, for example, Patent Document 1). In this method, a laser beam having a wavelength that transmits through the material of the ingot is irradiated onto the ingot so that the focal point of the laser beam is positioned inside the ingot.

[0005] As a result, a separation layer is formed inside the ingot, which includes a modified portion and a crack extending from the modified portion. When an external force is applied to the ingot with the separation layer formed, the crack extends further. As a result, the ingot is cleaved at the separation layer to produce a substrate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-111143 A Summary of the Invention [Problem to be solved by the invention]

[0007] Ingots are generally doped with impurities such as nitrogen to impart electrical conductivity, but the ingot may not be doped uniformly with such impurities and may contain multiple regions with different impurity concentrations.

[0008] For example, the impurity concentration in an atomically flat region called a facet region formed during the growth process of single crystal SiC is higher than in other regions (non-facet regions). Regions with high impurity concentrations such as facet regions have a higher absorption rate of a laser beam, i.e., a lower transmittance, compared to non-facet regions.

[0009] Therefore, when a separation layer is formed by irradiating an ingot including facet regions and non-facet regions with a laser beam under certain irradiation conditions, the distribution of modified parts and cracks in the separation layer varies, i.e., the density of modified parts and cracks is relatively low in the facet regions included in the ingot.

[0010] In this case, it is difficult to cleave the separation layer in the facet region even if an external force is applied to the ingot. Even if the ingot can be cleaved at the separation layer, the surface (separation surface) of the manufactured substrate that is separated from the ingot is likely to have large irregularities. Therefore, in this case, a large amount of the substrate needs to be removed to flatten the separation surface of the substrate, and the cost of the chip manufactured from the substrate increases.

[0011] In view of these points, an object of the present invention is to provide a laser processing method and laser processing apparatus capable of forming a separation layer suitable for cleavage inside an ingot, and a substrate manufacturing method for manufacturing a substrate from the ingot by cleaving the ingot at the separation layer. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a laser processing method for forming a separation layer inside an ingot by utilizing a laser beam having a wavelength that transmits through an ingot material, the laser processing method comprising: a substrate manufacturing step of manufacturing a substrate by separating a portion located on one side of the ingot from the ingot; a substrate evaluation step of evaluating the substrate after the substrate manufacturing step to obtain information regarding optical properties of each of a plurality of regions on the one side of the ingot; a setting step of setting irradiation conditions of the laser beam for each of the plurality of regions by referring to the information after the substrate evaluation step; and a separation layer formation step of forming the separation layer inside the ingot by irradiating the ingot with the laser beam from the one side with a focusing point at which the laser beam is focused positioned inside the ingot.

[0013] Preferably, in the substrate evaluation step, the substrate is irradiated with light and the luminance of the light transmitted through the substrate is measured.

[0014] According to another aspect of the present invention, there is provided a method for producing a substrate from an ingot by utilizing a laser beam having a wavelength that transmits through a material of the ingot, the method comprising: a first substrate production step of producing a first substrate by separating a portion located on one side of the ingot from the ingot; a first substrate evaluation step of evaluating the first substrate after the first substrate production step to obtain information about optical properties of each of a plurality of regions on the one side of the ingot; a setting step of setting irradiation conditions of the laser beam for each of the plurality of regions by referring to the information after the first substrate evaluation step; a separation layer formation step of forming a separation layer inside the ingot by irradiating the ingot with the laser beam from the one side with a focusing point at which the laser beam is focused positioned inside the ingot; and a second substrate production step of cleaving the ingot at the separation layer after the separation layer formation step to produce a second substrate.

[0015] According to yet another aspect of the present invention, there is provided a laser processing apparatus for forming a separation layer inside an ingot by using a laser beam having a wavelength that transmits through a material of the ingot, the laser processing apparatus comprising: a holding table for holding the ingot; a laser beam irradiation unit for irradiating the ingot with the laser beam from one side of the ingot held by the holding table; and a controller for controlling the laser beam irradiation unit, wherein the controller has a memory for storing information relating to optical characteristics and irradiation conditions of the laser beam in association with each other; and a processor for setting the irradiation conditions for forming the separation layer inside the ingot for each of a plurality of regions on the one side by referring to the information for each of a plurality of regions on the one side obtained by evaluating a substrate produced by separating a portion located on the one side of the ingot from the ingot, and then controlling the laser beam irradiation unit to irradiate the plurality of regions with the laser beam in accordance with the irradiation conditions set for each of the plurality of regions.

[0016] It is preferable that the laser processing apparatus of the present invention further includes a separation unit for cleaving the ingot at the separation layer to produce the substrate. Effect of the Invention

[0017] In the present invention, the irradiation conditions of the laser beam for forming a separation layer inside the ingot are set for each of the multiple regions on one side of the ingot by referring to information on the optical characteristics of each of the multiple regions on one side of the ingot, thereby making it possible to form a suitable separation layer inside the ingot. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1(A) is a front view that shows a schematic diagram of an example of an ingot, and FIG. 1(B) is a top view that shows a schematic diagram of the ingot shown in FIG. 1(A). [Diagram 2] FIG. 2 is a flow chart that illustrates a schematic example of a laser processing method. [Diagram 3] FIG. 3 is a side view that illustrates a substrate evaluation process. [Figure 4] FIG. 4 is a diagram illustrating an example of an image. [Diagram 5] FIG. 5 is a perspective view illustrating an example of a laser processing device. [Figure 6] FIG. 6 is a diagram showing a schematic view of a laser beam traveling inside the laser processing device. [Figure 7] FIG. 7 is a flow chart that illustrates a schematic example of a method for manufacturing a substrate. [Figure 8] 8(A) and 8(B) are side views each showing a schematic view of a second substrate manufacturing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a front view showing an example of an ingot used in manufacturing a substrate, and Fig. 1(B) is a top view showing the ingot shown in Fig. 1(A).

[0020] 1(A) and 1(B) is made of cylindrical single crystal SiC having a generally parallel upper surface (one surface) 11a and lower surface (other surface) 11b. This ingot 11 is manufactured, for example, by using epitaxial growth so that the c-axis 11c of the single crystal SiC is slightly inclined with respect to a perpendicular line 11d between the one surface 11a and the other surface 11b.

[0021] The angle (off angle) α between the c-axis 11c and the perpendicular line 11d is, for example, 1° to 6° (typically, 4°). Two flat portions, i.e., a primary orientation flat 13 and a secondary orientation flat 15, are formed on the side surface of the ingot 11 to indicate the crystal orientation of the single crystal SiC.

[0022] The primary orientation flat 13 is longer than the secondary orientation flat 15. In addition, the secondary orientation flat 15 is formed so as to be parallel to the intersection line where a plane parallel to the c-plane 11e of the single crystal SiC intersects with the one face 11a or the other face 11b.

[0023] Furthermore, ingot 11 is doped with impurities such as nitrogen to impart electrical conductivity. Ingot 11 also includes facet region 11f, which is a region that is flat at the atomic level, and non-facet region 11g, which is a region other than facet region 11f.

[0024] The impurity concentration in the facet region 11f is higher than the impurity concentration in the non-facet region 11g. In FIG. 1B, the boundary between the facet region 11f and the non-facet region 11g is shown by a dotted line, but this boundary line is an imaginary line. Therefore, such a dotted line does not exist in the actual ingot 11.

[0025] Furthermore, the material of the ingot 11 is not limited to single crystal SiC, but may be other semiconductors such as single crystal Si (silicon), or may be LiTaO3 (lithium tantalate: LT) or GaN (gallium nitride).

[0026] In addition, one or both of the primary orientation flat 13 and the secondary orientation flat 15 may not be formed on the side surface of the ingot 11. Alternatively, a notch may be formed on the side surface of the ingot 11 in place of the primary orientation flat 13 and the secondary orientation flat 15.

[0027] 2 is a flow chart showing a schematic example of a laser processing method for forming a separation layer inside the ingot 11 by using a laser beam having a wavelength that transmits the material of the ingot 11. In this method, first, a portion of the ingot 11 located on one surface 11a side is separated from the ingot 11 to produce a substrate (substrate production process S1).

[0028] In this substrate manufacturing process S1, for example, a wire saw is used to cut out a portion located on one surface 11a side of ingot 11 to manufacture the substrate. Alternatively, in this substrate manufacturing process S1, a laser beam having a wavelength that transmits through the material of ingot 11 may be used to form a separation layer inside the ingot, and then the ingot may be cleaved at the separation layer to manufacture the substrate.

[0029] In addition, the surface (separation surface) of the substrate produced in the substrate production process S1 that is separated from the ingot 11 may be subjected to grinding and / or polishing, etc., in order to flatten the separation surface. Similarly, one surface 11a of the ingot 11 after the substrate is produced, i.e., the surface (separation surface) that is newly exposed in association with the production of the substrate, may also be subjected to grinding and / or polishing, etc., in order to flatten the separation surface.

[0030] After the substrate manufacturing process S1, the substrate is evaluated to obtain information about the optical characteristics in each of a plurality of regions on one surface 11a of the ingot 11 (substrate evaluation process S2). Fig. 3 is a side view showing a schematic view of the substrate evaluation process S2. This substrate evaluation process S2 is performed, for example, in an evaluation device 2 shown in Fig. 3.

[0031] The evaluation device 2 has a table 4, a light source 6 provided below the table 4, and a camera 8 provided above the table 4 so as to face the light source 6 across the table 4. The table 4 is made of a material, such as glass, that transmits light L, such as visible light, irradiated upward from the light source 6.

[0032] When the substrate evaluation step S2 is performed in the evaluation device 2, first, the substrate 17 manufactured in the substrate manufacturing step S1 is placed on the table 4 so that the substrate 17 is positioned between the light source 6 and the camera 8. Then, the camera 8 captures an image of the substrate 17 in a state where the light source 6 is irradiating the substrate 17 with light L directed upward.

[0033] This forms an image based on the light L transmitted through the substrate 17. Specifically, the camera 8 measures the luminance of the light L for each of a plurality of regions (specifically, the facet region 17a and the non-facet region 17b) included in the substrate 17 to form data, and the camera 8 forms an image based on this data.

[0034] In addition, the camera 8 may form an image that is binarized based on the brightness of the light L measured for each of a plurality of regions, i.e., an image in which regions where the brightness of the measured light L is higher than a threshold brightness are displayed, for example, in white, and regions where the brightness is lower are displayed, for example, in black.

[0035] 4 is a diagram showing a schematic example of this binarized image. Specifically, in this case, facet regions 17a of substrate 17, which have a lower transmittance for light L than non-facet regions 17b, are displayed in black, and an image is formed in which non-facet regions 17b are displayed in white.

[0036] In addition, camera 8 may form a multi-valued image based on the brightness of light L measured for each of the multiple regions, i.e., an image in which each of the multiple regions is displayed in one of colors classified into multiple gradations (specifically, three or more gradations) depending on the brightness of the measured light L.

[0037] The arrangement of multiple regions in substrate 17 (specifically, facet regions 17a and non-facet regions 17b) corresponds to the arrangement of multiple regions on one surface 11a of ingot 11 (specifically, facet regions 11f and non-facet regions 11g).

[0038] Therefore, in this substrate evaluation process S2, information regarding the optical characteristics of each of the multiple regions on one surface 11a of the ingot 11 (specifically, data regarding the brightness of light L transmitted through each of the facet regions 17a and non-facet regions 17b) can be obtained.

[0039] In the substrate evaluation step S2, the luminance of the light L reflected by the substrate 17 may be measured instead of the luminance of the light L transmitted through the substrate 17. In this case, the image of the substrate 17 by the camera 8 is captured in a state in which the light L is irradiated onto the substrate from the light source 6 positioned on the same side as the camera 8 when viewed from the substrate 17.

[0040] After the substrate evaluation process S2, the irradiation conditions of the laser beam to be irradiated to the ingot 11 are set for each of multiple regions on one surface 11a of the ingot 11 by referring to the information acquired in the substrate evaluation process S2 (setting process S3), and then, with the focusing point where the laser beam is focused positioned inside the ingot 11, the laser beam is irradiated to the ingot 11 from the one surface 11a side of the ingot 11 to form a separation layer inside the ingot 11 (separation layer formation process S4).

[0041] The setting step S3 and the separation layer forming step S4 are performed, for example, in a laser processing apparatus 10 shown in Fig. 5. Specifically, the setting step S3 is performed in a controller 60 built into the laser processing apparatus 10, and the separation layer forming step S4 is performed by the controller 60 controlling the laser beam irradiation unit 48 and the like provided in the laser processing apparatus 10.

[0042] In addition, the X-axis direction and the Y-axis direction shown in Fig. 5 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction. In Fig. 5, some components of the laser processing device are shown as blocks.

[0043] The laser processing apparatus 10 has a base 12 that supports each of the components. A horizontal movement mechanism 14 is disposed on the upper surface of the base 12. The horizontal movement mechanism 14 is fixed to the upper surface of the base 12 and has a pair of Y-axis guide rails 16 that extend along the Y-axis direction.

[0044] A Y-axis moving plate 18 is connected to the upper part of the pair of Y-axis guide rails 16 in a manner that allows it to slide along the pair of Y-axis guide rails 16. A screw shaft 20 extending along the Y-axis direction is disposed between the pair of Y-axis guide rails 16. A motor 22 for rotating the screw shaft 20 is connected to one end of the screw shaft 20.

[0045] A nut (not shown) that accommodates balls that roll on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 on which the helical groove is formed, thereby forming a ball screw. That is, when the screw shaft 20 rotates, the balls circulate inside the nut, and the nut moves along the Y-axis direction.

[0046] In addition, this nut is fixed to the underside of the Y-axis moving plate 18. Therefore, when the screw shaft 20 is rotated by the motor 22, the Y-axis moving plate 18 moves along the Y-axis direction together with the nut.

[0047] A pair of X-axis guide rails 24 extending along the X-axis direction are fixed to the upper surface of the Y-axis moving plate 18. An X-axis moving plate 26 is connected to the upper part of the pair of X-axis guide rails 24 in a manner that allows it to slide along the pair of X-axis guide rails 24.

[0048] A screw shaft 28 extending along the X-axis direction is disposed between the pair of X-axis guide rails 24. A motor 30 for rotating the screw shaft 20 is connected to one end of the screw shaft 28.

[0049] A nut (not shown) that accommodates balls that roll on the surface of the rotating screw shaft 28 is provided on the surface of the screw shaft 28 on which the helical groove is formed, thereby forming a ball screw. That is, when the screw shaft 28 rotates, the balls circulate inside the nut, and the nut moves along the X-axis direction.

[0050] Moreover, this nut is fixed to the underside of the X-axis moving plate 26. Therefore, when the screw shaft 28 is rotated by the motor 30, the X-axis moving plate 26 moves along the X-axis direction together with the nut.

[0051] A cylindrical table base 32 is disposed on the upper surface side of the X-axis moving plate 26. A holding table 34 for holding the ingot 11 is provided on the upper portion of the table base 32. The holding table 34 has a generally flat circular upper surface (holding surface), and a porous plate 34a is exposed on this holding surface.

[0052] Furthermore, the porous plate 34a communicates with a suction source (not shown) such as an ejector through a communication passage formed inside the holding table 34. When the suction source is operated, a suction force acts on the space near the holding surface of the holding table 34. Therefore, when the suction source is operated with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the holding table 34.

[0053] Furthermore, the holding table 34 is connected to a rotation mechanism including a pulley, a motor, etc. When this rotation mechanism is operated, the holding table 34 rotates about a rotation axis that passes through the center of the holding surface of the holding table 34 and is aligned in the Z-axis direction.

[0054] A support structure 36 having a side surface generally parallel to the Y-axis direction is provided near the horizontal movement mechanism 14. A vertical movement mechanism 38 is disposed on the side surface of the support structure 36. The vertical movement mechanism 38 is fixed to the side surface of the support structure 36 and has a pair of Z-axis guide rails 40 extending along the Z-axis direction.

[0055] A Z-axis moving plate 42 is connected to the side of the pair of Z-axis guide rails 40 that is farther from the support structure 36, in a manner that allows it to slide along the pair of Z-axis guide rails 40. A screw shaft (not shown) extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 40. A motor 44 for rotating the screw shaft is connected to one end of the screw shaft.

[0056] A nut (not shown) that houses balls that roll on the surface of the rotating screw shaft is provided on the surface of the screw shaft where the spiral grooves are formed, forming a ball screw. In other words, when the screw shaft rotates, the balls circulate inside the nut, causing the nut to move along the Z-axis direction.

[0057] In addition, this nut is fixed to the side surface of the Z-axis moving plate 42 that is closer to the support structure 36. Therefore, when the screw shaft is rotated by the motor 44, the Z-axis moving plate 42 moves along the Z-axis direction together with the nut.

[0058] A support 46 is fixed to the side of the Z-axis moving plate 42 away from the support structure 36. The support 46 is connected to a laser beam irradiation unit 48 for irradiating the ingot 11 held by the holding table 34 with a laser beam.

[0059] Fig. 6 is a diagram showing a schematic view of the laser beam LB traveling inside the laser processing apparatus 10. In Fig. 6, some of the components of the laser beam application unit 48 are shown by blocks.

[0060] As shown in Figures 5 and 6, the laser beam irradiation unit 48 includes, for example, a laser oscillator 50 fixed to the base 12, a cylindrical housing 52 whose base end is supported by the support 46 and extends along the Y-axis direction, and a head 54 provided at the tip of the housing 52.

[0061] The laser oscillator 50 has a laser medium suitable for laser oscillation, such as Nd:YAG, etc. The laser oscillator 50 has a wavelength (for example, 1064 nm or 1342 nm) that transmits through the material of the ingot 11, and emits a pulsed laser beam LB.

[0062] The housing 52 accommodates part of the optical system that constitutes the laser beam irradiation unit 48, for example, mirrors 52a and 52b shown in FIG.

[0063] The head 54 houses another part of the optical system constituting the laser beam irradiation unit 48, for example, a mirror 54a and a condenser lens 54b. The laser beam LB guided in the housing 52 has its path changed downward by the mirror 54a, and is condensed by the condenser lens 54b to a height corresponding to the ingot 11 held by the holding table 34.

[0064] 5, a camera 56 is provided at a position adjacent to the head 54 in the X-axis direction. A cover (not shown) that covers the above-mentioned components is provided on the base 12, and a touch panel 58 that serves as a user interface is provided on one surface of the cover.

[0065] The touch panel 58 is configured by, for example, an input device such as a capacitive touch sensor or a resistive touch sensor, and a display device such as a liquid crystal display or an organic EL (Electro Luminescence) display.

[0066] The operations of the components of the laser processing apparatus 10 described above are controlled by a controller 60 built into the laser processing apparatus 10. The controller 60 includes a processor 60a and a memory 60b.

[0067] The processor 60a is configured, for example, by a CPU (Central Processing Unit) etc. The memory 60b is configured, for example, by a volatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory) and a non-volatile memory such as an SSD (Solid State Drive) (NAND type flash memory) or an HDD (Hard Disk Drive) (magnetic storage device).

[0068] The memory 60b stores various information (specifically, data, programs, etc.) used by the processor 60a. For example, the memory 60b stores information related to optical characteristics (for example, multi-level brightness) and irradiation conditions of the laser beam LB in association with each other. The irradiation conditions of the laser beam LB include, for example, the height of the focal point where the laser beam LB is focused, the output (power) of the laser beam LB, or the frequency of the laser beam LB and a pulse pitch set according to the moving speed of the holding table 34.

[0069] Furthermore, the processor 60a controls the components of the laser processing apparatus 10 so as to read out from the memory 60b and execute a program for forming a separation layer inside the ingot 11 by utilizing the laser beam LB, for example.

[0070] When the setting step S3 is performed in the laser processing apparatus 10, first, the information acquired in the substrate evaluation step S2 (specifically, the brightness data of the light L transmitted through each of the facet region 17a and the non-facet region 17b) is input to the controller 60. Then, when this information is input to the controller 60, the processor 60a sets the irradiation conditions of the laser beam LB for each of the multiple regions on the one surface 11a of the ingot 11 based on the data stored in the memory 60b.

[0071] For example, in this setting step S3, the irradiation conditions of the laser beam are set so that the output (power) of the laser beam irradiated to the region (specifically, the facet region 11f) where the luminance of the measured light L is relatively low is relatively high. Specifically, in this setting step S3, for example, the outputs of the laser beam irradiated to the facet region 11f and the non-facet region 11g are set to 10 W and 6 W, respectively.

[0072] When performing the separation layer forming step S4 in the laser processing apparatus 10, first, the ingot 11 is placed on the holding table 34 so that one surface 11a of the ingot 11 faces upward and covers the porous plate 34a. Then, a suction source communicating with the porous plate 34a is operated so that the ingot 11 is held on the holding surface of the holding table 34.

[0073] Next, the camera 56 is operated to capture an image of the ingot 11 and form an image. Next, with reference to this image, for example, the holding table 34 is rotated so that the primary orientation flat 13 is parallel to the Y-axis direction. Next, the head 54 is raised and lowered so that the focal point at which the laser beam LB emitted from the head 54 is focused is positioned at a predetermined depth from one surface 11a of the ingot 11.

[0074] Next, a laser beam LB is applied to the ingot 11 under irradiation conditions set for each of a plurality of regions (specifically, the facet region 11f and the non-facet region 11g) on ​​the one surface 11a of the ingot 11 to form a separation layer. Specifically, the separation layer is formed in the following order.

[0075] First, the holding table 34 is moved along the X-axis direction and / or the Y-axis direction so that a linear region (first region) near one end of the ingot 11 in the Y-axis direction is positioned in the X-axis direction when viewed in a plan view from the head 54. Next, while emitting a laser beam LB from the head 54, the holding table 34 is moved along the X-axis direction so that the focal point at which the laser beam LB is focused passes from one end to the other end of the ingot 11 in the X-axis direction. As a result, a separation layer including a modified portion and a crack extending from the modified portion is formed in the first region of the ingot 11.

[0076] The first region of the ingot 11 is, for example, entirely non-faceted region 11g. In this case, the processor 60a controls the laser beam irradiation unit 48 so that the laser beam LB is irradiated according to the irradiation conditions set for the non-faceted region 11g in the setting step S3 (for example, with an output of 6 W).

[0077] Next, the holding table 34 is moved along the Y-axis direction so that the head 54 is positioned in the X-axis direction when viewed from a region of the ingot 11 that has already been irradiated with the laser beam LB, i.e., a region (second region) slightly separated in the Y-axis direction from the first region, in a plan view. Next, while emitting the laser beam LB from the head 54, the holding table 34 is moved along the X-axis direction so that the focal point at which the laser beam LB is focused passes from the other end to one end in the X-axis direction of the ingot 11. As a result, a separation layer including a modified portion and a crack extending from the modified portion is formed in the second region of the ingot 11.

[0078] The second region of the ingot 11 is also, for example, entirely non-faceted region 11g. In this case, the processor 60a controls the laser beam irradiation unit 48 so that the laser beam LB is irradiated while maintaining the irradiation conditions set for the non-faceted region 11g in the setting step S3.

[0079] Next, the holding table 34 is moved along the Y-axis direction so that the region of the ingot 11 that has already been irradiated with the laser beam LB, i.e., a region (third region) slightly separated in the Y-axis direction from the second region, is positioned in the X-axis direction as seen in a plan view from the head 54. Furthermore, the above-mentioned operation is repeated until irradiation of the region of the ingot 11 near the other end in the Y-axis direction with the laser beam LB is completed.

[0080] Here, when the ingot 11 is irradiated with the laser beam LB in this manner, there is a timing during which the laser beam LB is irradiated to the facet region 11f. At this timing, the processor 60a controls the laser beam irradiation unit 48 so that the laser beam LB is irradiated to the facet region 11f according to the irradiation conditions set for the facet region 11f in the setting step S3 (for example, with the output of the laser beam LB set to 10 W).

[0081] 2, by referring to information on the optical characteristics (e.g., data on the luminance of light L transmitted through each of facet region 11f and non-facet region 11g) of each of multiple regions on one surface 11a of ingot 11 (specifically, facet region 11f and non-facet region 11g), irradiation conditions of laser beam LB for forming a separation layer inside ingot 11 are set for each of the multiple regions. As a result, in this method, it is possible to form a suitable separation layer inside ingot 11.

[0082] The above-mentioned laser processing method and the laser processing apparatus are each an aspect of the present invention, and the laser processing method and the laser processing apparatus of the present invention are not limited to the above. For example, in the laser processing method of the present invention, the substrate manufacturing step S1 and / or the substrate evaluation step S2 may be performed using the laser processing apparatus 10.

[0083] Specifically, the substrate manufacturing step S1 may use a laser processing device 10 to form a separation layer inside the ingot 11, and then cleave the ingot 11 at the separation layer to manufacture the substrate 17. The substrate evaluation step S2 may be performed using an image formed by a camera 56 capturing an image of the substrate 17 held by the holding table 34.

[0084] Furthermore, in the laser processing apparatus of the present invention, in addition to the components of the laser processing apparatus 10, at least some of the components of the evaluation device 2 may be provided. For example, the laser processing apparatus of the present invention may have a table 4 and a light source 6 in addition to the components of the laser processing apparatus 10. In this case, the substrate evaluation step S2 is performed by placing the substrate 17 on the table 4 so as to position the substrate 17 directly above the light source 6, and then using an image formed by the camera 56 capturing an image of the substrate 17 while the light source 6 is irradiating the substrate 17 upward.

[0085] The present invention may also be a method for manufacturing a substrate, which is carried out by utilizing the above-mentioned laser processing method. Fig. 7 is a flow chart that shows a schematic example of such a method for manufacturing a substrate. In this method, the above-mentioned substrate manufacturing step (first substrate manufacturing step) S1, substrate evaluation step (first substrate evaluation step) S2, setting step S3, and separation layer forming step S4 are carried out in this order.

[0086] After the separation layer forming step S4, the ingot 11 is cleaved at the separation layer to produce another substrate (second substrate) (second substrate production step S5). Each of Figs. 8(A) and 8(B) is a side view showing the second substrate production step S5. This second substrate production step S5 is performed in a separation apparatus 62 shown in Figs. 8(A) and 8(B).

[0087] The separating apparatus 62 includes a holding table 64 for holding the ingot 11. The holding table 64 has a generally flat circular upper surface (holding surface), and a porous plate (not shown) is exposed on the holding surface.

[0088] The porous plate also communicates with a holding table side suction source (not shown) such as an ejector through a communication passage formed inside the holding table 64. When the holding table side suction source is operated, a suction force acts on the space near the holding surface of the holding table 64. Therefore, when the holding table side suction source is operated with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the holding table 64.

[0089] A separation unit 66 is provided above the holding table 64. This separation unit 66 has a suction plate 68 with a plurality of suction ports formed on the lower surface. The plurality of suction ports communicate with a separation unit side suction source such as a vacuum pump via suction paths formed inside the suction plate 68. When the separation unit side suction source is operated, a suction force acts on the space near the lower surface of the suction plate 68.

[0090] A vertical movement mechanism 70 is connected to the upper surface of the suction plate 68. The vertical movement mechanism 70 includes, for example, a ball screw and a motor. When the vertical movement mechanism 70 is operated, the suction plate 68 moves in the vertical direction.

[0091] When the second substrate manufacturing process S5 is carried out in the separation apparatus 62, first, the ingot 11 is placed on the holding table 64 so that one surface 11a of the ingot 11, inside which the separation layer 19 has been formed, faces upward and covers the porous plate of the holding table 64. Then, the holding table side suction source communicating with the porous plate is operated so that the ingot 11 is held on the holding surface of the holding table 64.

[0092] Next, the suction plate 68 is lowered so that the lower surface of the suction plate 68 contacts the one surface 11a of the ingot 11 (see FIG. 8(A)). Next, the peeling unit side suction mechanism is operated so that the one surface 11a side of the ingot 11 is sucked upward. Next, the suction plate 68 is raised so as to separate the suction plate 68 from the holding table 64 (see FIG. 8(B)).

[0093] This applies an external force to ingot 11 that separates one surface 11a and the other surface 11b of ingot 11, further expanding the cracks contained in separation layer 19. As a result, ingot 11 is cleaved at separation layer 19, and a substrate (second substrate) 21 different from substrate (first substrate) 17 manufactured in substrate manufacturing process (first substrate manufacturing process) S1 is manufactured.

[0094] In addition, the separation device 62 may be used to separate the substrate 21 from the ingot 11 by sucking the substrate 21, which has already been separated from the ingot 11 and is placed on the ingot 11, upward.

[0095] Furthermore, the thickness of first substrate 17 manufactured in first substrate manufacturing process S1 is not limited. For example, first substrate 17 having a thickness equivalent to that of second substrate 21 is manufactured in first substrate manufacturing process S1. In this case, it is preferable that not only second substrate 21 but also first substrate 17 can be used to manufacture chips.

[0096] Alternatively, first substrate manufacturing step S1 may manufacture first substrate 17 having a thickness 1 / 2, preferably 1 / 4, and more preferably 1 / 8 or less of that of second substrate 21. This is preferable in that the amount of ingot 11 that is discarded without being used to manufacture chips can be reduced.

[0097] Additionally, the second substrate manufacturing process S5 may be performed by any method. For example, in the second substrate manufacturing process S5, an external force may be applied to the ingot 11 so as to drive a wedge into the separation layer 19 from a side surface of the ingot 11, thereby separating the one surface 11a side and the other surface 11b side of the ingot 11.

[0098] Furthermore, in the laser processing apparatus of the present invention, at least some of the components of the separating device 62 may be provided in addition to the components of the laser processing apparatus 10. For example, the laser processing apparatus of the present invention may have a separating unit 66 in addition to the components of the laser processing apparatus 10. In this case, the second substrate manufacturing process S5 may be performed in the laser processing apparatus having the separating unit 66.

[0099] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0100] 2: Evaluation device 4: Table 6:Light source 8: Camera 10: Laser processing equipment 11: Ingot (11a: Top surface (one side), 11b: Bottom surface (other side), 11c: c axis) (11d: perpendicular line, 11e: c surface) (11f: faceted area, 11g: non-faceted area) 12: Foundation 13: Primary orientation flat 14: Horizontal movement mechanism 15: Secondary orientation flat 16: Y-axis guide rail 17: Substrate (first substrate) (17a: facet region, 17b: non-facet region) 18: Y-axis moving plate 19: Separation layer 20: Screw shaft 21: Substrate (second substrate) 22: Motor 24: X-axis guide rail 26: X-axis moving plate 28: Screw shaft 30:Motor 32: Table base 34: Holding table (34a: Porous plate) 36: Support structure 38: Vertical movement mechanism 40: Z-axis guide rail 42: Z-axis moving plate 44: Motor 46: Support equipment 48: Laser beam irradiation unit 50: Laser oscillator 52: Housing (52a, 52b: mirror) 54: Head (54a: mirror, 54b: condenser lens) 56: Camera 58: Touch panel 60: controller (60a: processor, 60b: memory) 62: Separation device 64: Holding table 66: Separation unit 68: Suction plate 70: Vertical movement mechanism

Claims

1. A laser processing method for forming a separation layer inside an ingot by using a laser beam having a wavelength that transmits through the material of the ingot, comprising: a substrate manufacturing process for manufacturing a substrate by separating a portion of the ingot located on one side of the ingot from the ingot; a substrate evaluation step of evaluating the substrate after the substrate manufacturing step to obtain information regarding optical properties in each of a plurality of regions on one side of the ingot; a setting step of setting the irradiation conditions of the laser beam for each of the plurality of regions by referring to the information after the substrate evaluation step; a separation layer forming step of forming the separation layer inside the ingot by irradiating the ingot with the laser beam from the one surface side in a state where a focusing point of the laser beam is positioned inside the ingot after the setting step; A laser processing method comprising:

2. 2. The laser processing method according to claim 1, wherein said substrate evaluation step comprises measuring the luminance of light transmitted through said substrate while irradiating said substrate with light.

3. A method for manufacturing a substrate, comprising the steps of: manufacturing a substrate from an ingot by utilizing a laser beam having a wavelength that transmits through the material of the ingot; a first substrate manufacturing process for manufacturing a first substrate by separating a portion of the ingot located on one side of the ingot from the ingot; a first substrate evaluation step of evaluating the first substrate after the first substrate manufacturing step to obtain information regarding optical properties in each of a plurality of regions on one side of the ingot; a setting step of setting irradiation conditions of the laser beam for each of the plurality of regions by referring to the information after the first substrate evaluation step; a separation layer forming step of forming a separation layer inside the ingot by irradiating the ingot with the laser beam from the one surface side while positioning a focusing point of the laser beam inside the ingot after the setting step; a second substrate manufacturing step of cleaving the ingot at the separation layer to manufacture a second substrate after the separation layer forming step; A method for manufacturing a substrate comprising the steps of:

4. A laser processing apparatus for forming a separation layer inside an ingot by utilizing a laser beam having a wavelength that transmits through the material of the ingot, a holding table for holding the ingot; a laser beam irradiation unit for irradiating the ingot with the laser beam from one side of the ingot held by the holding table; A controller for controlling the laser beam irradiation unit, The controller a memory that stores information regarding optical characteristics and irradiation conditions of the laser beam in association with each other; a processor that sets the irradiation conditions for forming the separation layer inside the ingot for each of a plurality of regions on the one side by referring to the information in each of the plurality of regions on the one side obtained by evaluating a substrate produced by separating a portion located on the one side of the ingot from the ingot, and then controls the laser beam irradiation unit to irradiate the plurality of regions with the laser beam in accordance with the irradiation conditions set for each of the plurality of regions.

5. The laser processing apparatus according to claim 4 , further comprising a separation unit for cleaving the ingot at the separation layer to produce the substrate.

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