Method for processing carbon-containing single crystal substrate

Abstract

To at least partially remove a product produced by irradiating a carbon-containing single crystal substrate containing carbon as a main component of single crystal with a laser beam.SOLUTION: A method for processing a carbon-containing single crystal substrate containing carbon as the main component of a single crystal includes: a processed groove forming step of forming a processed groove by emitting a first laser beam having a wavelength absorbed by the carbon-containing single crystal substrate along a division-planned line set on one surface of the carbon-containing single crystal substrate, and a heating step of emitting a second laser beam along the processed groove, the second laser beam transmitting through the carbon-containing single crystal substrate, and having a wavelength absorbed by a product which has a structure different from that of the material constituting the carbon-containing single crystal substrate, contains carbon, and is produced in the processed groove forming step, thereby reacting the product produced in the processed groove forming step and located at least inside the processed groove with oxygen, thereby vaporizing and removing the product.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for processing a carbon-containing single crystal substrate that contains carbon as a main component of the single crystal. [Background technology]

[0002] 2. Description of the Related Art In recent years, the use of diamond substrates, which have superior physical properties such as dielectric strength and thermal conductivity compared to single crystal silicon substrates, in semiconductor devices has been attracting attention (see, for example, Patent Document 1).

[0003] Incidentally, when manufacturing semiconductor device chips by dividing an ordinary semiconductor substrate such as a single crystal silicon substrate, for example, a cutting device having a spindle with a cutting blade attached to the tip thereof is used.

[0004] However, when a semiconductor substrate with high Mohs hardness such as a diamond substrate is cut by a cutting device, the cutting blade is severely worn, which causes problems such as (i) the shape of the cut surface of the substrate changes as cutting proceeds, and (ii) the cutting blade needs to be frequently replaced, which increases the cost of the cutting process.

[0005] Therefore, instead of using a cutting blade, a method has been considered in which a laser beam having a wavelength that is absorbed by a semiconductor substrate having a relatively high Mohs hardness is irradiated along the intended dividing line of the semiconductor substrate, and a laser processed groove is formed in the semiconductor substrate by ablation processing, thereby dividing the semiconductor substrate (see, for example, Patent Document 2).

[0006] However, when a diamond substrate is irradiated with a laser beam, part of the diamond is carbonized, generating graphite and other products. These graphite and other products adhere to the bottom and side surfaces of the laser-processed grooves formed along the intended dividing lines, and may change the electrical characteristics of the semiconductor device.

[0007] Therefore, the products such as graphite may cause product defects in semiconductor device chips. A similar problem may occur when a laser beam is irradiated onto a silicon carbide substrate, which contains carbon as the main component of the single crystal. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2015-57824 A [Patent Document 2] Japanese Patent Application Publication No. 10-305420 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above problems, and aims to provide a processing method capable of improving the yield of semiconductor device chips by at least partially removing a product generated by irradiating a carbon-containing single crystal substrate, such as a diamond substrate, a silicon carbide substrate, etc., which contains carbon as the main component of the single crystal, with a laser beam. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a method for processing a carbon-containing single crystal substrate containing carbon as a main component of the single crystal, the method comprising: a machining groove forming step of forming a machining groove by irradiating a first laser beam having a wavelength absorbed by the carbon-containing single crystal substrate along a planned division line set on one surface of the carbon-containing single crystal substrate; and a heating step of irradiating along the machining groove with a second laser beam which transmits through the carbon-containing single crystal substrate but has a structure different from that of a material constituting the carbon-containing single crystal substrate, contains carbon, and has a wavelength which is absorbed by a product generated in the machining groove forming step, thereby causing the product generated in the machining groove and located at least inside the machining groove to react with oxygen and vaporize, thereby removing the product.

[0011] Preferably, in the groove forming step, the carbon-containing single crystal substrate is cut by forming the groove penetrating from the one surface of the carbon-containing single crystal substrate to the other surface located opposite to the one surface.

[0012] Also, preferably, in the groove forming step, the groove having a depth that does not reach the other surface of the carbon-containing single crystal substrate located opposite to the one surface is formed without cutting the carbon-containing single crystal substrate, and the method for processing the carbon-containing single crystal substrate further includes a breaking step of breaking the carbon-containing single crystal substrate by applying an external force to a remaining region of the carbon-containing single crystal substrate that overlaps with the groove in the thickness direction of the carbon-containing single crystal substrate before or after the heating step.

[0013] According to another aspect of the present invention, there is provided a method for processing a carbon-containing single crystal substrate containing carbon as a main component of a single crystal, the method comprising: a laser beam irradiation step of irradiating a pulsed first laser beam having a wavelength that transmits through the carbon-containing single crystal substrate along a planned division line set on the carbon-containing single crystal substrate to form a fragile region inside the carbon-containing single crystal substrate having a reduced mechanical strength compared to a region of the carbon-containing single crystal substrate not irradiated with the first laser beam; a dividing step of dividing the carbon-containing single crystal substrate along the planned division line by applying an external force to the carbon-containing single crystal substrate after the laser beam irradiation step; and a heating step of irradiating at least the fractured surface of the carbon-containing single crystal substrate exposed by the division step with a second laser beam that transmits through the carbon-containing single crystal substrate but has a structure different from that of a material constituting the carbon-containing single crystal substrate, contains carbon, and has a wavelength that is absorbed by a product generated in the laser beam irradiation step, thereby causing the product to react with oxygen and vaporize and remove the product.

[0014] Preferably, the second laser beam irradiated to the carbon-containing single crystal substrate in the heating step has a wavelength of not less than 9.0 μm and not more than 11.0 μm.

[0015] Also preferably, the carbon-containing single crystal substrate is a diamond substrate.

[0016] Also preferably, the carbon-containing single crystal substrate is a silicon carbide substrate.

[0017] Also preferably, the product contains graphite or amorphous carbon. Effect of the Invention

[0018] In a method for processing a carbon-containing single crystal substrate according to one embodiment of the present invention, a product generated by irradiating a carbon-containing single crystal substrate with a first laser beam is irradiated with a second laser beam having a wavelength absorbed by the product, and the product is removed by reacting with oxygen and vaporizing it. Therefore, the yield of semiconductor device chips can be improved compared to a case in which the product is not removed with the second laser beam. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a flow diagram of a processing method according to the first embodiment. [Diagram 2] FIG. [Diagram 3] FIG. 3(A) is a diagram showing a process for forming a processed groove, and FIG. 3(B) is a cross-sectional view of the division groove. [Figure 4] 4(A) and 4(B) are diagrams illustrating the heating step. [Diagram 5] FIG. 5(A) is a flow diagram of a processing method according to the second embodiment, and FIG. 5(B) is a flow diagram of a processing method according to a modified example of the second embodiment. [Figure 6] FIG. 6(A) is a diagram showing a process for forming a processed groove, and FIG. 6(B) is a cross-sectional view of a half-cut groove. [Figure 7] FIG. 7(A) is a diagram showing an expansion device, and FIG. 7(B) is a diagram showing a breaking process. [Figure 8]FIG. 8(A) is a diagram showing a braking device, and FIG. 8(B) is a diagram showing a modified example of the breaking process. [Figure 9] FIG. 11 is a flow diagram of a processing method according to a third embodiment. [Figure 10] FIG. 13 is a diagram showing a laser beam irradiation process. [Figure 11] FIG. 4 is a cross-sectional view of the carbon-containing single crystal substrate after a dividing step. [Figure 12] FIG. [Figure 13] FIG. 13 is a diagram showing a laser beam irradiation step according to the fourth embodiment. [Figure 14] FIG. 14(A) is a perspective view showing the structure of one shield tunnel, and FIG. 14(B) is a cross-sectional view of a portion of a carbon-containing single crystal substrate showing a plurality of shield tunnels. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] (First embodiment) An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a method for processing a carbon-containing single crystal substrate 11 (see Fig. 2) according to a first embodiment. In the first embodiment, the carbon-containing single crystal substrate 11 is processed in the order of a processed groove forming step S10 and a heating step S20.

[0021] 2 is a perspective view of a workpiece unit 21 including a carbon-containing single crystal substrate 11. In this embodiment, the carbon-containing single crystal substrate 11 is a diamond substrate. The diamond substrate is generally a synthetic diamond, but may be a natural diamond.

[0022] The method for producing the diamond substrate, which is a synthetic diamond, is not particularly limited, and may be a gas phase synthesis method such as CVD, or a high temperature and high pressure synthesis method. The diamond substrate is a cubic single crystal substrate mainly composed of carbon (C), but may contain n-type impurities such as phosphorus (P), p-type impurities such as boron (B), and other impurities.

[0023] The diamond substrate is, for example, a disk-shaped substrate having a thickness of 500 μm and a diameter of 5 mm, but the thickness, diameter and shape of the diamond substrate are not particularly limited. The diamond substrate may be a rectangular plate.

[0024] The carbon-containing single crystal substrate 11 may be a silicon carbide substrate. The method for producing the silicon carbide substrate is not particularly limited. The silicon carbide substrate is mainly composed of both silicon (Si) and carbon (C) and is generally a hexagonal single crystal substrate.

[0025] The silicon carbide substrate may contain n-type impurities such as phosphorus (P) and nitrogen (N), p-type impurities such as aluminum (Al) and boron (B), other impurities, etc. The silicon carbide substrate is, for example, disk-shaped with a thickness of 350 μm and a diameter of 150 mm.

[0026] However, the thickness, diameter, and shape of the silicon carbide substrate are not particularly limited. The silicon carbide substrate may be a rectangular plate. The carbon-containing single crystal substrate 11 may be a single crystal substrate of other materials as long as it contains carbon (C) as a main component.

[0027] 2, the carbon-containing single crystal substrate 11 of this embodiment has a disk shape. On a front surface (one surface) 11a of the carbon-containing single crystal substrate 11, a plurality of division lines 13 are set in a lattice pattern.

[0028] Devices 15 such as LEDs (Light Emitting Diodes) and ICs (Integrated Circuits) are formed in each region defined by the plurality of division lines 13. The carbon-containing single crystal substrate 11 is fixed to a metal annular frame 17 via a resin dicing tape 19.

[0029] Specifically, with the carbon-containing single crystal substrate 11 placed in the opening 17a of the annular frame 17, a dicing tape 19 is attached to the back surface (other surface) 11b of the carbon-containing single crystal substrate 11 and to one surface of the annular frame 17, so that the carbon-containing single crystal substrate 11 is fixed to the annular frame 17 via the dicing tape 19.

[0030] The dicing tape 19 is a thin film and has flexibility. The dicing tape 19 can be plastically deformed by being stretched in the radial direction. The dicing tape 19 has a laminated structure of, for example, a base layer and an adhesive layer (i.e., a glue layer).

[0031] The base layer is made of a resin such as polyolefin (PO), etc. An adhesive layer made of an adhesive resin such as an ultraviolet (UV) curable resin is formed on the entirety or part of one surface of the base layer.

[0032] The dicing tape 19 is not limited to a laminated structure of a base layer and an adhesive layer. The dicing tape 19 may have only a base layer without an adhesive layer. The base layer is made of a thermoplastic resin such as polyolefin.

[0033] By thermocompression bonding such a dicing tape 19 to the carbon-containing single crystal substrate 11, the dicing tape 19 can be attached to the carbon-containing single crystal substrate 11 without using an adhesive layer.

[0034] Not using an adhesive layer has the advantage that no adhesive layer remains on the carbon-containing single crystal substrate 11 after peeling off the dicing tape 19. In this case, the dicing tape 19 may or may not have an adhesive layer in the region in contact with the annular frame 17.

[0035] In this embodiment, the carbon-containing single crystal substrate 11 is supported by the annular frame 17 via a dicing tape 19 in the form of a workpiece unit 21, and a groove forming step S10 and a heating step S20 are performed on the carbon-containing single crystal substrate 11.

[0036] In the groove forming process S10, a laser processing device 2 (see FIG. 3(A)) is used. The laser processing device 2 has a disk-shaped chuck table 4 for suction-holding the workpiece unit 21 with negative pressure. As shown in FIG. 3(A), the chuck table 4 has a disk-shaped frame.

[0037] A disk-shaped recess is formed at the top and center of the frame, and a disk-shaped porous plate having an outer diameter approximately the same as the inner diameter of the recess is fixed in the recess. The upper surfaces of the frame and the porous plate are approximately flush with each other, and form a holding surface 4a for suction-holding the carbon-containing single crystal substrate 11 via the dicing tape 19.

[0038] The chuck table 4 is configured to be movable along the X-axis direction (machining feed direction) by a moving mechanism including a first ball screw (not shown), and to be movable along the Y-axis direction (indexing feed direction) by a moving mechanism including a second ball screw (not shown).

[0039] Furthermore, the chuck table 4 is configured to be rotatable around a predetermined rotation axis that is approximately parallel to the Z-axis direction (vertical direction) by a motor (not shown). Note that the X-axis direction, the Y-axis direction, and the Z-axis direction described in this specification are perpendicular to each other.

[0040] A plurality of clamp units (not shown) that are opened and closed by an air actuator are provided on the outer periphery of the chuck table 4. The plurality of clamp units clamp the annular frame 17 of the workpiece unit 21 that is suction-held on the holding surface 4a.

[0041] A condenser 8 of the laser beam irradiation unit 6 is disposed above the holding surface 4a. The laser beam irradiation unit 6 has a laser oscillator (not shown). A pulsed laser beam L1 (first laser beam) is emitted from the laser oscillator. Note that the laser beam L1 in this embodiment is a pulsed wave, but may be a continuous wave.

[0042] The laser oscillator includes a laser medium (e.g., Yb:YAG crystal) and an excitation light source (not shown) such as a lamp that irradiates the laser medium with excitation light. When the laser beam L1 is a pulse wave, the laser oscillator further includes, for example, a Q switch (not shown) that controls the timing at which the laser beam L1 is emitted.

[0043] Instead of a Q switch, an electro-optic modulator (EOM) may be controlled by an electrical signal to convert a continuous wave incident on the modulator into a pulse wave, or a pulse wave may be emitted from a laser oscillator using other means.

[0044] The laser beam L1 has a wavelength (e.g., 1030 nm) that is absorbed by the carbon-containing single crystal substrate 11. The condenser 8 includes a mirror, a condenser lens (neither of which are shown), and the like. The laser beam L1 is irradiated from the condenser 8 toward the holding surface 4a substantially perpendicularly to the holding surface 4a.

[0045] A microscope camera unit (not shown) is provided near the condenser 8 and is used to identify the orientation, position, etc. of the planned division line 13. The microscope camera unit and the laser beam irradiation unit 6 are configured to be movable along the Z-axis direction by a ball screw type Z-axis direction moving mechanism (not shown).

[0046] Here, the groove forming step S10 will be described. Fig. 3(A) is a diagram showing the groove forming step S10. For convenience of explanation, the device 15 is omitted from Fig. 3(A). In the groove forming step S10, first, the carbon-containing single crystal substrate 11 is suction-held by the holding surface 4a.

[0047] Thereafter, the orientation of the chuck table 4 is adjusted using the microscope camera unit so that one of the planned division lines 13 is approximately parallel to the X-axis direction. Next, with the height of the focal point of the laser beam L1 being set to be approximately the same as the height of the surface 11a, the carbon-containing single crystal substrate 11 and the chuck table 4 are moved relatively along the X-axis direction.

[0048] For example, while the condenser 8 is kept stationary, the chuck table 4 is moved along the X-axis direction at a predetermined processing feed rate. In this manner, the laser beam L1 is irradiated onto the carbon-containing single crystal substrate 11 along one planned division line 13, thereby forming a division groove (machined groove) 23 in the carbon-containing single crystal substrate 11 by ablation processing.

[0049] An example of the processing conditions in the groove forming step S10 is shown below. The following example is the processing condition when a diamond substrate having a thickness of 500 μm and a diameter of 5 mm is used as the carbon-containing single crystal substrate 11.

[0050] Laser beam wavelength: 1030nm Average power output: 80W Repetition frequency: 2000kHz Machining feed speed: 100mm / s Number of passes: 90

[0051] The number of passes shown in the processing conditions means the number of times the focal point of a laser beam (for example, the laser beam L1) is moved from one end of one of the planned division lines 13 to the other end thereof.

[0052] When the number of passes is two or more, the height position of the focal point of the laser beam L1 may be gradually moved closer to the rear surface 11b from the front surface 11a according to the number of passes. That is, among the multiple passes, the focal point in the first pass may be moved closest to the front surface 11a, and the focal point in the last pass may be moved closest to the rear surface 11b.

[0053] The division grooves 23 formed in the processed groove forming step S10 of this embodiment are so-called full-cut grooves, and penetrate from the front surface 11a of the carbon-containing single crystal substrate 11 to the back surface 11b located opposite to the front surface 11a. In other words, the division grooves 23 cut the carbon-containing single crystal substrate 11 along the intended division lines 13.

[0054] After forming the division groove 23 on one of the division lines 13, the light collector 8 and the chuck table 4 are moved relatively along the Y-axis direction by a predetermined index amount. Then, division grooves 23 are formed in the same manner on other division lines 13 adjacent in the Y-axis direction to the division line 13 on which the division groove 23 was formed immediately before.

[0055] After the division grooves 23 are formed along all of the division lines 13 along the X-axis direction in this manner, the chuck table 4 is rotated approximately 90 degrees. Then, in the same manner, the division grooves 23 are formed along all of the division lines 13 along the X-axis direction. As a result, the carbon-containing single crystal substrate 11 is divided into a plurality of semiconductor device chips 27 (see FIG. 3(B)).

[0056] In the groove forming step S10, the carbon in the carbon-containing single crystal substrate 11 is carbonized to produce a product 25 that has a crystal structure different from the material constituting the carbon-containing single crystal substrate 11 and contains carbon (C).

[0057] The product 25 is a non-diamond (i.e., an allotrope of carbon other than diamond), such as graphite. However, the product 25 is not limited to graphite. The product 25 may also include amorphous carbon.

[0058] Fig. 3(B) is a cross-sectional view of the dividing groove 23 when the carbon-containing single crystal substrate 11 is cut so as to transversely cross the longitudinal direction of the dividing groove 23. Particulate products 25 shown in Fig. 3(B) are located inside the dividing groove 23, such as on the bottom and side surfaces, and on the opening edges of the dividing groove 23. Such products 25 may cause product defects in the semiconductor device chip 27.

[0059] Therefore, in this embodiment, after the groove forming step S10, the by-product 25 is removed in the heating step S20 using a laser processing device 12 (see FIG. 4(A)). The laser processing device 12 has a chuck table 14 having substantially the same structure as the chuck table 4 described above.

[0060] The chuck table 14 has a holding surface 14a and is configured to be movable along the X-axis direction and the Y-axis direction by a moving mechanism including two ball screws (not shown). Furthermore, the chuck table 14 is configured to be rotatable about a predetermined rotation axis approximately parallel to the Z-axis direction by a motor (not shown).

[0061] In addition, a plurality of clamp units (not shown) that are opened and closed by an air actuator are provided on the outer periphery of the chuck table 14. A condenser 18 of a laser beam irradiation unit 16 is disposed above the holding surface 14a. The laser beam irradiation unit 16 in this embodiment is a so-called carbon dioxide laser.

[0062] The laser beam irradiation unit 16 has a laser oscillator (not shown). A laser beam L2 (second laser beam) is emitted from the laser oscillator. The laser oscillator includes a discharge tube (not shown) that functions as an optical resonator.

[0063] The discharge tube is filled with carbon dioxide gas. A highly reflective total reflector is disposed at one end of the discharge tube, and a semi-reflective mirror is disposed at the other end of the discharge tube. The discharge tube is also provided with a pair of electrode plates to which a high-frequency voltage is applied.

[0064] The filled gas that has been converted into plasma by the discharge is emitted to the outside through the semi-reflecting mirror. When the laser beam L2 is a pulse wave (i.e., pulsed), a Q switch or the like for controlling the timing of oscillation is further provided in the laser oscillator.

[0065] The laser beam L2 has a wavelength that is transmitted through the carbon-containing single crystal substrate 11 but is absorbed by the product 25. Such a laser beam L2 has a wavelength of, for example, 9.0 μm or more and 11.0 μm or less.

[0066] In this embodiment, a carbon dioxide gas laser is used, and therefore the wavelength of the laser beam L2 is 9.4 μm or 10.6 μm. The laser beam L2 in this embodiment is a pulsed wave, but may be a continuous wave. In either case, the laser beam L2 is irradiated from the condenser 18 toward the holding surface 14a in a direction substantially perpendicular to the holding surface 14a.

[0067] A microscope camera unit (not shown) is provided near the condenser 18. The laser beam irradiation unit 16 and the microscope camera unit are configured to be movable along the Z-axis direction by a ball screw type Z-axis direction moving mechanism (not shown).

[0068] Here, the heating step S20 will be described. Figures 4(A) and 4(B) are diagrams showing the heating step S20. For ease of explanation, device 15 is omitted in Figure 4(A). In the heating step S20, first, carbon-containing single crystal substrate 11 is suction-held by holding surface 14a.

[0069] Thereafter, the orientation of the chuck table 14 is adjusted using the microscope camera unit so that one of the planned division lines 13 is approximately parallel to the X-axis direction. Next, in a state in which the height of the focal point of the laser beam L2 is shifted from the height position of the surface 11a (i.e., in a defocused state), the carbon-containing single crystal substrate 11 and the chuck table 14 are moved relatively along the X-axis direction.

[0070] For example, while the condenser 18 is kept stationary, the chuck table 14 is moved along the X-axis direction at a predetermined processing feed rate. In this manner, the laser beam L2 is irradiated along one of the division grooves 23, whereby oxygen gas (O2) reacts with the product 25, and the product 25 is vaporized.

[0071] Specifically, the chuck table 14 is placed in air at room temperature and pressure, or in a space where oxygen gas is supplied at a predetermined flow rate as atmospheric gas, and the product 25 is reacted using the laser beam L2.

[0072] This removes the by-products 25 from inside the dividing groove 23 and from the opening edge of the dividing groove 23 (i.e., at least inside the dividing groove 23). By defocusing the laser beam L2, the laser beam L2 can be irradiated not only to the inside of the dividing groove 23 but also to the vicinity of the opening edge of the dividing groove 23. This helps to remove the by-products 25 efficiently.

[0073] An example of the processing conditions for the heating step S20 when the laser beam L2 is a continuous wave and when it is a pulse wave is shown below. The following example shows the processing conditions when a diamond substrate having a thickness of 500 μm and a diameter of 5 mm is used as the carbon-containing single crystal substrate 11.

[0074] (In the case of pulse waves) Laser beam wavelength: 9.4μm or 10.6μm Average power output: 100W Repetition frequency: 10kHz Machining feed speed: 100mm / s Number of passes: 1 or more

[0075] (For continuous wave) Laser beam wavelength: 9.4μm or 10.6μm Output: 100W Machining feed speed: 100mm / s Number of passes: 1 or more

[0076] After irradiating one of the dividing grooves 23 with the laser beam L2, the collector 18 and the chuck table 14 are moved relatively in the Y-axis direction, so that the by-products 25 are similarly removed from the other dividing grooves 23 adjacent in the Y-axis direction to the dividing groove 23 irradiated with the laser beam L2.

[0077] After removing the by-products 25 from all the division grooves 23 along the X-axis direction in this manner, the chuck table 14 is rotated approximately 90 degrees. Then, in the same manner, the by-products 25 are removed from all the division grooves 23 along the X-axis direction.

[0078] In this embodiment, since the by-products 25 that may cause product defects in the semiconductor device chips 27 are removed in the heating step S20, the yield of the semiconductor device chips 27 can be improved compared to the case where the by-products 25 are not removed.

[0079] In the heating step S20, it is not essential to defocus the laser beam L2. The focal point of the laser beam L2 may be positioned on the surface 11a of the carbon-containing single crystal substrate 11, or on the bottom or side surface of the division groove 23.

[0080] When the diameter of the focal point of the laser beam L2 is relatively large, equal to or larger than the width of the dividing groove 23, the height position of the focal point of the laser beam L2 may be near the opening edge of the dividing groove 23. In addition, the traveling direction of the laser beam L2 may be tilted with respect to the surface 11a, so that only the side surface of the dividing groove 23 is selectively irradiated with the laser beam L2.

[0081] The oblique incidence of the laser beam L2 can be achieved, for example, by using an LCOS-SLM (Liquid Crystal on Silicon - Spatial Light Modulator) with the optical axis of the focusing lens 18a in the collector 18 perpendicular to the holding surface 14a, or by simply tilting the optical axis of the focusing lens 18a.

[0082] Furthermore, the laser beam L2 does not necessarily have to be focused at a single point, and may be branched along (i) the X-axis direction, (ii) the Y-axis direction, or (iii) a predetermined direction intersecting the X-axis and Y-axis directions of the laser processing apparatus 12.

[0083] The laser beam L2 can be split using a DOE (Diffractive Optical Element), an LCOS-SLM, or the like arranged on the optical path of the laser beam L2. Note that the shape of the focal point of the laser beam L2 is not limited to a circle, and may be an ellipse, a rectangle, or the like.

[0084] When a silicon carbide substrate having a thickness of 350 μm and a diameter of 150 mm is used as the carbon-containing single crystal substrate 11, an example of the processing conditions in the groove forming step S10 is as follows. In addition, in the heating step S20, either the above-mentioned continuous wave processing conditions or the pulse wave processing conditions can be used.

[0085] Laser beam wavelength: 343 nm (i.e., the third harmonic of the 1030 nm wavelength) Average power: 6W Repetition frequency: 10kHz Machining feed speed: 80mm / s Number of passes: 36

[0086] In the first embodiment, the heating step S20 is performed after the groove forming step S10, but the groove forming step S10 and the heating step S20 may be performed in parallel. In this case, for example, a laser processing device (not shown) including a laser beam irradiation unit 6 (see FIG. 3(A)) and a laser beam irradiation unit 16 (see FIG. 4(A)) is used.

[0087] During laser processing, the condenser 8 and the condenser 18 are arranged along the X-axis direction so that the focal point of the laser beam L1 reaches the carbon-containing single crystal substrate 11 earlier than the focal point of the laser beam L2, and the chuck table (corresponding to the above-mentioned chuck tables 4 and 14) is moved relative to the carbon-containing single crystal substrate 11.

[0088] For example, by moving the focal points of the laser beam L2 so that the focal point of the laser beam L1 follows the focal point of the laser beam L1, the heating step S20 can be performed while performing the groove forming step S10.

[0089] In other words, the groove forming step S10 and the heating step S20 can be performed simultaneously. This can shorten the time required for laser processing. Even when the groove forming step S10 and the heating step S20 are performed simultaneously, the number of passes is not particularly limited and can be 2 or more.

[0090] Alternatively, the focal points of the laser beam L1 and the focal points of the laser beam L2 may be positioned at substantially the same position, and the focal points and the chuck table may be moved relatively to each other.

[0091] When the focal point of the laser beam L1 and the focal point of the laser beam L2 are positioned at approximately the same position, for example, the product 25 formed in the first pass is removed by the laser beam L2 in the second pass.

[0092] Furthermore, for example, when the diameter of the focal point of the laser beam L2 is larger than the diameter of the focal point of the laser beam L1, by approximately matching the center of the focal point of the laser beam L1 and the center of the focal point of the laser beam L2, the product 25 formed in the first pass can also be removed by the first pass laser beam L2.

[0093] Incidentally, the laser beam irradiation unit 6 may be disposed above the chuck table, and the laser beam irradiation unit 16 may be disposed below the chuck table. In this case, the chuck table is made of a material that is transparent or translucent to the laser beam L2, and has a holding member with a substantially flat upper surface.

[0094] Examples of such materials include glass such as quartz glass and a single crystal substrate of zinc selenide (ZnSe). A plurality of suction holes, through which negative pressure for suctioning and holding the workpiece unit 21 is transmitted, are arranged at approximately equal intervals along the circumferential direction of the holding member on the outer periphery of the holding member.

[0095] During laser processing, the laser beam irradiation unit 6 irradiates the carbon-containing single crystal substrate 11 with a laser beam L1, and the laser beam irradiation unit 16 irradiates the carbon-containing single crystal substrate 11 with a laser beam L2 via the chuck table.

[0096] During laser processing, for example, the focal points of the laser beam L1 are moved so that the focal point of the laser beam L2 follows the focal point of the laser beam L1. Alternatively, the focal points of the laser beam L1 and the focal point of the laser beam L2 may be positioned at substantially the same position, and the focal points and the chuck table may be moved relatively.

[0097] Of course, when the chuck table has the above-mentioned holding member, the laser beam application unit 16 can be disposed above the chuck table, and the laser beam application unit 6 can be disposed below the chuck table.

[0098] Second Embodiment Next, a method for processing a carbon-containing single crystal substrate 11 according to a second embodiment will be described with reference to Fig. 5(A) to Fig. 8(B). Fig. 5(A) is a flow diagram of the processing method according to the second embodiment.

[0099] In the second embodiment, in the groove forming process S12, a half-cut groove (groove) 31 is formed using a laser beam L1 (see FIG. 6(A)), and then in the heating process S20, a laser beam L2 is used to remove the product 25.

[0100] Then, in the breaking step S30 after the heating step S20, an external force is applied to a remaining region 33 (see FIG. 6(A)) of the carbon-containing single crystal substrate 11 located between the half-cut groove 31 and the back surface 11b, thereby breaking the carbon-containing single crystal substrate 11 along the intended split line 13.

[0101] 5(B) is a flow diagram of a processing method according to a modified example of the second embodiment. In this modified example, after forming a half-cut groove 31 using a laser beam L1 in a processed groove forming step S12, a breaking step S14 is performed before a heating step S20, and a heating step S20 is performed using a laser beam L2 after the breaking step S14.

[0102] First, the flow shown in Fig. 5(A) will be described. Fig. 6(A) is a diagram showing a groove forming step S12 in the second embodiment. In the groove forming step S12, half-cut grooves 31 having a depth that does not cut the carbon-containing single crystal substrate 11 are formed along each of the planned division lines 13.

[0103] In this specification, the half-cut groove 31 has a depth that does not reach from the front surface 11a to the back surface 11b, and does not necessarily have a depth that is exactly half the depth of the carbon-containing single crystal substrate 11 in the thickness direction 11c of the carbon-containing single crystal substrate 11.

[0104] The groove forming step S12 is performed in substantially the same manner as the groove forming step S10 using the laser processing device 2. An example of the processing conditions for the groove forming step S12 is shown below. The following example is the processing condition when a diamond substrate having a thickness of 500 μm and a diameter of 5 mm is used as the carbon-containing single crystal substrate 11.

[0105] Laser beam wavelength: 1030nm Average power output: 80W Repetition frequency: 2000kHz Machining feed speed: 100mm / s Number of passes: 45

[0106] When the number of passes is two or more, the height position of the focal point of the laser beam L1 may be gradually moved closer to the rear surface 11b from the front surface 11a according to the number of passes. That is, among the multiple passes, the focal point in the first pass may be moved closest to the front surface 11a, and the focal point in the last pass may be moved closest to the rear surface 11b.

[0107] Fig. 6(B) is a cross-sectional view of the half-cut groove 31 formed in the processed groove forming step S12. In Fig. 6(B), the carbon-containing single crystal substrate 11 is cut at a plane arranged so as to cross the longitudinal direction of the half-cut groove 31.

[0108] As a result of the groove forming process S12, a product 25 adheres to the bottom, side, etc. of the dividing groove 23, which is inside the dividing groove 23, and to the opening edge of the dividing groove 23. Therefore, after the groove forming process S12, the product 25 is removed using a laser processing device 12 (heating process S20).

[0109] Although not shown, in the second embodiment, the heating step S20 is performed in the same manner as described in Fig. 4(A) and Fig. 4(B). As the processing conditions, the above-mentioned pulse wave or continuous wave processing conditions can be adopted.

[0110] After removing the product 25 in the heating step S20, an external force is applied to the remaining region 33 overlapping with the half-cut groove 31 in the thickness direction 11c using an expansion device 20 (see FIG. 7(A)), thereby breaking the carbon-containing single crystal substrate 11 (breaking step S30).

[0111] 7(A) is a diagram showing the expansion device 20. The expansion device 20 has multiple legs 22. A ring-shaped support part 24 is fixed to the upper ends of the multiple legs 22. A plurality of clamp units 26 are provided on the outer periphery of the support part 24.

[0112] The clamp units 26 are disposed at substantially regular intervals at different positions in the circumferential direction of the support portion 24. A push-up device 28 that pushes up the dicing tape 19 of the workpiece unit 21 from below is provided inside the multiple legs 22.

[0113] The push-up device 28 has a plurality of legs 28a that are extendable and retractable along the height direction 20a of the expansion device 20. A cylindrical roller 28b is provided at the upper end of each leg 28a. In FIG. 7(A), the height position of the upper end of each roller 28b is disposed at approximately the same height as the upper end of the support part 24.

[0114] Fig. 7(B) is a diagram showing the breaking step S30. In the breaking step S30, first, as shown in Fig. 7(A), the workpiece unit 21 is placed on the expansion device 20 so that the surface 11a of the carbon-containing single crystal substrate 11 is exposed upward, and the annular frame 17 is fixed by a plurality of clamp units 26.

[0115] At this time, the annular frame 17 is supported on the upper surface of the support portion 24, and the outer side surfaces of the multiple rollers 28b contact the area on the lower surface of the dicing tape 19 between the outer peripheral edge of the carbon-containing single crystal substrate 11 and the inner peripheral edge of the annular frame 17.

[0116] Next, the legs 28a of the push-up device 28 are raised to position the rollers 28b at a predetermined height position higher than the support portion 24. By raising the rollers 28b to the predetermined height position, the dicing tape 19 is expanded radially.

[0117] As a result, the carbon-containing single crystal substrate 11 is subjected to tensile stress in a direction that advances radially from the center in the radial direction of the dicing tape 19, and is broken at the remaining region 33 where the mechanical strength is reduced. As a result, the carbon-containing single crystal substrate 11 is divided into a plurality of semiconductor device chips 27.

[0118] In the second embodiment, the by-products 25 that may cause product defects in the semiconductor device chips 27 are also removed in the heating step S20, so that the yield of the semiconductor device chips 27 can be improved compared to the case where the by-products 25 are not removed.

[0119] Next, the flow shown in Fig. 5(B) will be described. In the modified example shown in Fig. 5(B), after forming a half-cut groove 31 in the carbon-containing single crystal substrate 11 in the groove forming process S12, the above-mentioned expansion device 20 is used to perform the breaking process S14, and then, in the heating process S20, the laser beam L2 is irradiated into the gap between the semiconductor device chips 27 to remove the by-product 25.

[0120] The distance between the semiconductor device chips 27 after the breaking step S14 is larger than the width of the half-cut groove 31. Therefore, in the heating step S20, after irradiating one side of the division line 13 in the width direction with the laser beam L2, the other side of the division line 13 in the width direction may be irradiated with the laser beam L2.

[0121] When a silicon carbide substrate having a thickness of 350 μm and a diameter of 150 mm is used as the carbon-containing single crystal substrate 11, an example of the processing conditions in the groove forming step S12 is as follows.

[0122] Laser beam wavelength: 343 nm (i.e., the third harmonic of the 1030 nm wavelength) Average power: 6W Repetition frequency: 10kHz Machining feed speed: 80mm / s Number of passes: 18

[0123] In addition, in the heating step S20 after the groove forming step S12, either the continuous wave processing conditions or the pulse wave processing conditions described above can be used.

[0124] Incidentally, in the breaking steps S30 and S14, a braking device 30 may be used in place of the above-mentioned expanding device 20. Fig. 8(A) is a diagram showing the braking device 30. The braking device 30 has a pair of support blades 32.

[0125] Each of the pair of support blades 32 is a flat plate with a substantially flat upper end. Between the pair of support blades 32 and above the pair of support blades 32, a pressing blade 34 is provided in a manner movable along the height direction 30a of the breaking device 30.

[0126] The lower end of the pressing blade 34 is sharper than the upper end of the support blade 32. The lower end of the pressing blade 34 may be disposed approximately parallel to the upper end of the support blade 32, or may be disposed obliquely so as to gradually move away from the upper end of the support blade 32 along the depth direction of the paper.

[0127] Between the pair of support blades 32 and below the upper ends of the pair of support blades 32, a microscope camera unit (not shown) for capturing an image of the carbon-containing single crystal substrate 11 is provided.

[0128] Before performing the breaking steps S30 and S14 using the breaking apparatus 30, in order to reduce damage to the device 15, first, the front surface 11a side of the carbon-containing single crystal substrate 11 is covered with a protective tape 35 made of resin.

[0129] Next, the workpiece unit 21 is supported by the pair of supporting blades 32 so that the front surface 11a faces downward (i.e., the back surface 11b faces upward). Then, an image of the front surface 11a side is captured by the microscope camera unit.

[0130] Based on the image obtained by imaging, the positions of the pair of supporting blades 32 and the pressing blade 34 relative to the half-cut groove 31 are adjusted, and the pressing blade 34 is positioned directly above the remaining region 33. Next, as shown in Fig. 8(B), the pressing blade 34 is lowered to apply a downward force to the carbon-containing single crystal substrate 11 via the dicing tape 19.

[0131] 8(B) is a diagram showing a modified example of the breaking steps S30 and S14. A bending stress generated in the carbon-containing single crystal substrate 11 causes a crack to extend from the bottom surface of the half-cut groove 31 to the back surface 11b, and the remaining region 33 breaks.

[0132] As a result, the carbon-containing single crystal substrate 11 is divided along the intended division lines 13. By breaking the remaining regions 33 similarly along all of the intended division lines 13, the carbon-containing single crystal substrate 11 is divided into a plurality of semiconductor device chips 27. After the breaking steps S30 and S14, the protective tape 35 is peeled off from the surface 11a.

[0133] Incidentally, instead of having a pair of support blades 32 and pressing blade 34, the breaking device 30 may be provided with a substantially flat table (not shown) and a pressing roller (not shown) arranged on the table and having a longitudinal portion equal to or larger than the diameter of the carbon-containing single crystal substrate 11.

[0134] In the breaking steps S30 and S14, the workpiece unit 21 is placed on the table so that the dicing tape 19 is exposed upward and the protective tape 35 is in contact with the table. Then, a pressure roller is pressed against the dicing tape 19 and rolled, thereby applying a downward force to the entire carbon-containing single crystal substrate 11.

[0135] Bending stress occurring in the carbon-containing single crystal substrate 11 causes cracks to form from the bottom surface of the half-cut groove 31 to the back surface 11b, and the remaining region 33 is fractured. As the remaining region 33 is fractured along all of the planned division lines 13, the carbon-containing single crystal substrate 11 is divided into a plurality of semiconductor device chips 27.

[0136] Incidentally, after performing the breaking step S30 with the breaking device 30, or after performing the breaking step S14 and the heating step S20 with the breaking device 30, the spacing between the semiconductor device chips 27 may be widened using the expansion device 20 so that the semiconductor device chips 27 can be easily picked up.

[0137] (Third embodiment) Next, a third embodiment will be described with reference to Fig. 9 to Fig. 12. Fig. 9 is a flow diagram of a processing method according to the third embodiment. In the third embodiment, the steps of a laser beam irradiation step S16, a division step S18, and a heating step S20 are performed in this order.

[0138] In the laser beam irradiation step S16, a laser processing apparatus 42 that is substantially the same as the above-mentioned laser processing apparatus 2 is used (see FIG. 10). Like the laser processing apparatus 2, the laser processing apparatus 42 also has a chuck table 4, a laser beam irradiation unit 6, and the like.

[0139] However, the laser beam irradiation unit 6 of the laser processing device 42 emits a pulsed laser beam L having a wavelength that is transmitted through the carbon-containing single crystal substrate 11. 1´ The carbon-containing single crystal substrate 11 is irradiated with a laser beam L (first laser beam) along each of the division lines 13. 1´A weakened region 37 having a reduced mechanical strength compared to the non-irradiated region is formed inside the carbon-containing single crystal substrate 11 (see FIG. 10).

[0140] Laser beam L 1´ The laser beam L has a wavelength of 1030 nm or 1064 nm and is transmitted through both the diamond substrate and the silicon carbide substrate. 1´ The transmittance does not necessarily have to be 100%.

[0141] In one example, a laser beam L on a diamond substrate 1´ The transmittance of the laser beam L to the silicon carbide substrate is about 70%. 1´ The transmittance is about 15%.

[0142] Laser beam L 1´ When the laser medium is, for example, a Yb:YAG crystal, the laser beam L 1´ has a wavelength of 1064 nm, a Nd:YAG crystal, for example, is used as the laser medium.

[0143] Fig. 10 is a diagram showing the laser beam irradiation step S16. For convenience of explanation, the device 15 is omitted in Fig. 10. In the laser beam irradiation step S16, a dicing tape 19 is attached to the front surface 11a side of the carbon-containing single crystal substrate 11 and one surface of the annular frame 17.

[0144] Then, the front surface 11a side is suction-held by the holding surface 4a so that the back surface 11b is exposed upward. After that, based on an image obtained by capturing an image of the front surface 11a side using a microscope camera unit, the orientation of the chuck table 4 is adjusted so that one planned division line 13 is approximately parallel to the X-axis direction.

[0145] Then, the laser beam L 1´With the height of the focal point of the beam being positioned at a predetermined height corresponding to the interior of the carbon-containing single crystal substrate 11, the carbon-containing single crystal substrate 11 and the chuck table 4 are moved relatively along the X-axis direction.

[0146] For example, while the condenser 8 is stationary, the chuck table 4 is moved along the X-axis direction at a predetermined processing feed rate. In this manner, the laser beam L is aligned along one of the planned division lines 13. 1´ The carbon-containing single crystal substrate 11 is irradiated with the light to form a weakened region 37.

[0147] The weak area 37 is 1´ 10. The modified region is a region having a different crystallinity from the non-irradiated region, and includes a modified region shown in white in FIG. 10 and cracks extending from the modified region to the front surface 11a and the back surface 11b. In the laser beam irradiation step S16, the above-mentioned product 25 is generated in the vicinity of the fragile region 37.

[0148] An example of the processing conditions in the laser beam irradiation step S16 is shown below. The following example is the processing condition when a diamond substrate having a thickness of 500 μm and a diameter of 5 mm is used as the carbon-containing single crystal substrate 11.

[0149] Laser beam wavelength: 1030nm or 1064nm Average output: 2W Repetition frequency: 50kHz Machining feed speed: 400mm / s Number of passes: 8

[0150] In the laser beam irradiation step S16, a processing method called SD (Stealth Dicing) is adopted, and a laser beam L having a lower average power than the laser beam L1 used in the groove formation step S10 of the first and second embodiments is used. 1´ By using this method, multiphoton absorption occurs near the focal point rather than ablation, resulting in the formation of the weakened region 37 described above.

[0151] In addition, when the number of passes is two or more, the laser beam L 1´ The height position of the light collecting point may be gradually moved closer from the front surface 11a to the back surface 11b. That is, among the multiple passes, the light collecting point in the first pass may be moved closest to the front surface 11a, and the light collecting point in the last pass may be moved closest to the back surface 11b.

[0152] After the laser beam irradiation step S16, a circular tape 39 (see FIG. 11) is attached to the back surface 11b and one surface of the annular frame 17, and the dicing tape 19 on the front surface 11a side is peeled off. The tape 39 can be plastically deformed by being stretched in the radial direction using the above-mentioned expansion device 20.

[0153] Next, a dividing step S18 is performed using the expansion device 20. In the dividing step S18, an external force is applied to the carbon-containing single crystal substrate 11 to divide the carbon-containing single crystal substrate 11 into a plurality of semiconductor device chips 27 along each of the planned dividing lines 13, as shown in FIG.

[0154] 11 is a cross-sectional view of the carbon-containing single crystal substrate 11 after the dividing step S18. In the dividing step S18, the carbon-containing single crystal substrate 11 may be divided by a breaking device 30 using a pressing blade 34 or a roller instead of the expanding device 20 alone, and then the spacing between the multiple semiconductor device chips 27 may be widened by the expanding device 20.

[0155] In addition, when the dicing tape 19 is plastically deformable, the dicing tape 19 may be stretched and expanded by the expansion device 20 without attaching the tape 39 to the back surface 11b. In addition, the laser beam irradiation step S16 may be performed with the dicing tape 19 attached to the back surface 11b, and then, in the division step S18, the dicing tape 19 may be expanded by the expansion device 20.

[0156] 11, the product 25 generated in the laser beam irradiation step S16 remains on the fractured surface 11d of the carbon-containing single crystal substrate 11 exposed in the dividing step S18. Therefore, after the dividing step S18, the heating step S20 is performed using the above-mentioned laser processing device 12.

[0157] 12 is a diagram showing a heating step S20. In the heating step S20, at least the fractured surface 11d is irradiated with a laser beam L2, so that the product 25 remaining on the fractured surface 11d reacts with oxygen and is vaporized. As a result, the product 25 is removed.

[0158] Of course, a part of the laser beam L2 in the heating step S20 may be irradiated onto the surface 11a. In the third embodiment, the heating step S20 is performed in the same manner as described in Figures 4(A) and 4(B). The processing conditions may be the above-mentioned pulse wave or continuous wave processing conditions.

[0159] In the third embodiment, the by-products 25 that may cause product defects in the semiconductor device chips 27 are removed in the heating step S20, so that the yield of the semiconductor device chips 27 can be improved compared to the case where the by-products 25 are not removed.

[0160] When a silicon carbide substrate having a thickness of 350 μm and a diameter of 150 mm is used as the carbon-containing single crystal substrate 11, an example of the processing conditions in the laser beam irradiation step S16 is as follows.

[0161] Laser beam wavelength: 1030nm or 1064nm Average power output: 1W Repetition frequency: 50kHz Machining feed speed: 600mm / s Number of passes: 2

[0162] In addition, in the heating step S20 after the laser beam irradiation step S16, either the continuous wave processing conditions or the pulse wave processing conditions described above can be used.

[0163] (Fourth embodiment) Next, a fourth embodiment will be described with reference to Fig. 13, Fig. 14(A) and Fig. 14(B). In the fourth embodiment, each step is performed according to the flow shown in Fig. 9. In the fourth embodiment, in the laser beam irradiation step S16, a weak region 41 different from the weak region 37 shown in Fig. 10 is formed inside the carbon-containing single crystal substrate 11 (see Fig. 13).

[0164] The fourth embodiment differs from the third embodiment in this respect, but the dividing step S18 and the heating step S20 are the same as those of the third embodiment. Therefore, the following mainly describes the laser beam irradiation step S16 in the fourth embodiment.

[0165] The laser beam irradiation step S16 of the fourth embodiment also uses the above-mentioned laser processing apparatus 42. Fig. 13 is a diagram showing the laser beam irradiation step S16 according to the fourth embodiment. Note that in Fig. 13, the device 15 is omitted, and hatching on the cross section of the carbon-containing single crystal substrate 11 is omitted.

[0166] In addition, in the laser beam irradiation process S16 of the fourth embodiment, unlike FIG. 10 of the third embodiment, the back surface 11b side is suction-held by the holding surface 4a via the dicing tape 19 so that the front surface 11a is exposed.

[0167] In the laser beam irradiation step S16, the laser beam irradiation unit 6 of the laser processing device 42 irradiates a pulsed laser beam L having a wavelength that transmits the carbon-containing single crystal substrate 11. 1´´ By irradiating the carbon-containing single crystal substrate 11 with the (first laser beam) along each of the intended dividing lines 13, a weakened region 41 having reduced mechanical strength is formed inside the carbon-containing single crystal substrate 11.

[0168] An example of the processing conditions in the laser beam irradiation step S16 is shown below. The following example is the processing condition when a diamond substrate having a thickness of 500 μm and a diameter of 5 mm is used as the carbon-containing single crystal substrate 11.

[0169] Laser beam wavelength: 1064nm Average power: 4W Repetition frequency: 10kHz Machining feed speed: 400mm / s Number of passes: 7

[0170] In addition, when the number of passes is two or more, the laser beam L 1´´ The height position of the light collecting point may be gradually moved closer from the front surface 11a to the back surface 11b. That is, among the multiple passes, the light collecting point in the first pass may be moved closest to the front surface 11a, and the light collecting point in the last pass may be moved closest to the back surface 11b.

[0171] The weak area 41 is 1´´ The weak region 41 has a plurality of shield tunnels 43 (see FIG. 14(A)).

[0172] Fig. 14(A) is a perspective view showing the structure of one shield tunnel 43. Note that in Fig. 14(A), a part of the carbon-containing single crystal substrate 11 in the thickness direction 11c is omitted. Each shield tunnel 43 has a pore 43a formed along the thickness direction 11c.

[0173] The fine hole 43a is an elongated space having a substantially cylindrical shape with a diameter of about 1 μm, and for example, penetrates from the front surface 11a to the back surface 11b. However, when the number of passes is set to two or more, the laser beam L is focused while gradually moving the depth position of the focal point closer to the back surface 11b. 1´´ The carbon-containing single crystal substrate 11 is processed with the above.

[0174] In this case, even if the repetition frequency and the processing feed rate are constant, the fine holes 43a may not completely overlap in the thickness direction of the carbon-containing single crystal substrate 11. The shield tunnel 43 has an affected region 43b formed so as to surround the side surface of the fine hole 43a.

[0175] The affected region 43b is, for example, a substantially cylindrical region having a diameter of about 5 μm to about 20 μm. The affected region 43b is formed by irradiating a part of the carbon-containing single crystal substrate 11 with the laser beam L. 1´´ The affected region 43b is a region whose crystal structure has changed due to the energy received from the source. For example, the affected region 43b is an amorphous region or a polycrystalline region.

[0176] In the laser beam irradiation step S16, a processing method called LEAF (Laser Enhanced Ablation Filling) is adopted. The laser beam L used in the laser beam irradiation step S16 of the third embodiment 1´ A laser beam L with a high average power compared to 1´´ By using this, the pores 43a and the altered regions 43b are formed by ablation.

[0177] Fig. 14(B) is a cross-sectional view of a portion of the carbon-containing single crystal substrate 11, showing a plurality of shield tunnels 43 formed along the intended dividing line 13. Note that in Fig. 14(B), a portion of the carbon-containing single crystal substrate 11 in the thickness direction 11c is omitted.

[0178] 14(B), the altered regions 43b of the two shield tunnels 43 adjacent to each other along the planned split line 13 are connected to each other, but the two altered regions 43b may be separated from each other. In other words, a single crystal region may remain between the two shield tunnels 43 adjacent to each other along the planned split line 13.

[0179] After the laser beam irradiation step S16, the division step S18 is performed using the expansion device 20. However, in the division step S18, as described above, instead of using the expansion device 20 alone, the carbon-containing single crystal substrate 11 may be divided by a breaking device 30 using a pressing blade 34 or a roller, and then the spacing between the multiple semiconductor device chips 27 may be widened by the expansion device 20.

[0180] The product 25 generated in the laser beam irradiation step S16 remains on the fractured surface 11d of the carbon-containing single crystal substrate 11 exposed by the dividing step S18. Therefore, after the dividing step S18, the heating step S20 is performed using the above-mentioned laser processing apparatus 12 (see FIG. 12).

[0181] In the heating step S20, at least the fractured surfaces 11d are irradiated with a laser beam L2, so that the by-products 25 remaining on the fractured surfaces 11d react with oxygen and are vaporized, thereby removing the by-products 25.

[0182] In the fourth embodiment, the heating step S20 is performed in the same manner as described in Fig. 4(A) and Fig. 4(B). As the processing conditions, the above-mentioned pulse wave or continuous wave processing conditions can be adopted.

[0183] In the fourth embodiment, since the by-products 25 that may cause product defects in the semiconductor device chips 27 are removed in the heating step S20, the yield of the semiconductor device chips 27 can be improved compared to the case where the by-products 25 are not removed.

[0184] When a silicon carbide substrate having a thickness of 350 μm and a diameter of 150 mm is used as the carbon-containing single crystal substrate 11, an example of the processing conditions in the laser beam irradiation step S16 is as follows.

[0185] Laser beam wavelength: 1064nm Average power: 4W Repetition frequency: 10kHz Machining feed speed: 400mm / s Number of passes: 7

[0186] In addition, in the heating step S20 after the laser beam irradiation step S16, either the continuous wave processing conditions or the pulse wave processing conditions described above can be adopted. In addition, the structures, methods, etc. according to the above-mentioned embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. [Explanation of symbols]

[0187] 2: laser processing device, 4: chuck table, 4a: holding surface 6: Laser beam irradiation unit, 8: Condenser 11: Carbon-containing single crystal substrate 11a: front surface (one side), 11b: back surface (other side), 11c: thickness direction, 11d: cut surface 12: laser processing device, 14: chuck table, 14a: holding surface 13: Planned division line, 15: Device 16: laser beam irradiation unit, 18: condenser, 18a: condenser lens 17: annular frame, 17a: opening 19: dicing tape, 21: workpiece unit 20: extension device, 20a: height direction, 22: legs, 24: support 23: Dividing groove (processing groove) 25:Product 26: Clamp unit 27: Semiconductor device chip 28: push-up device, 28a: legs, 28b: roller 30: braking device, 30a: height direction, 32: support blade, 34: pressing blade 31: half-cut groove (machined groove), 33: remaining area, 35: protective tape 37: Weak area, 39: Tape 41: Vulnerable area 42: Laser processing equipment 43: Shield tunnel, 43a: Hole, 43b: Deterioration area L1,L 1´ ,L 1´´ : Laser beam (first laser beam) L2: Laser beam (second laser beam) S10,S12: Machining groove forming process S14, S30: Breaking process S16: Laser beam irradiation process S18:Dividing process S20: Heating process

Claims

1. A method for processing a carbon-containing single crystal substrate containing carbon as a main component of the single crystal, comprising the steps of: a groove forming step of forming a groove by irradiating a first laser beam having a wavelength absorbed by the carbon-containing single crystal substrate along a division line set on one surface of the carbon-containing single crystal substrate; a heating step of irradiating a second laser beam along the groove, the second laser beam having a wavelength that is transmitted through the carbon-containing single crystal substrate but has a structure different from that of the material constituting the carbon-containing single crystal substrate, contains carbon, and is absorbed by the product generated in the groove formation step, thereby reacting the product generated in the groove formation step and positioned at least inside the groove with oxygen to vaporize it and remove it; A method for processing a carbon-containing single crystal substrate, comprising:

2. 2. The method for processing a carbon-containing single crystal substrate according to claim 1, wherein in the groove forming step, the carbon-containing single crystal substrate is cut by forming the groove penetrating from the one surface of the carbon-containing single crystal substrate to the other surface located opposite to the one surface.

3. In the groove forming step, the groove is formed without cutting the carbon-containing single crystal substrate, the groove having a depth that does not reach the other surface of the carbon-containing single crystal substrate located on the opposite side to the one surface, 2. The method for processing a carbon-containing single crystal substrate according to claim 1, further comprising a breaking step of breaking the carbon-containing single crystal substrate by applying an external force to a remaining region of the carbon-containing single crystal substrate that overlaps with the processed groove in a thickness direction of the carbon-containing single crystal substrate before or after the heating step.

4. A method for processing a carbon-containing single crystal substrate containing carbon as a main component of the single crystal, comprising the steps of: a laser beam irradiation step of irradiating a carbon-containing single crystal substrate with a pulsed first laser beam having a wavelength that transmits through the carbon-containing single crystal substrate along a planned division line set on the carbon-containing single crystal substrate, thereby forming a brittle region inside the carbon-containing single crystal substrate, the brittle region having a reduced mechanical strength compared to a region of the carbon-containing single crystal substrate that is not irradiated with the first laser beam; a dividing step of dividing the carbon-containing single crystal substrate along the dividing lines by applying an external force to the carbon-containing single crystal substrate after the laser beam irradiation step; a heating step of irradiating at least the cut surface of the carbon-containing single crystal substrate exposed by the dividing step with a second laser beam, the second laser beam having a wavelength that is transmitted through the carbon-containing single crystal substrate but has a structure different from that of the material constituting the carbon-containing single crystal substrate, contains carbon, and is absorbed by the product generated in the laser beam irradiation step, thereby reacting the product with oxygen to vaporize it and remove it; A method for processing a carbon-containing single crystal substrate, comprising:

5. 5. The method for processing a carbon-containing single crystal substrate according to claim 1, wherein the second laser beam irradiated to the carbon-containing single crystal substrate in the heating step has a wavelength of 9.0 μm or more and 11.0 μm or less.

6. 5. The method for processing a carbon-containing single crystal substrate according to claim 1, wherein the carbon-containing single crystal substrate is a diamond substrate.

7. 5. The method for processing a carbon-containing single crystal substrate according to claim 1, wherein the carbon-containing single crystal substrate is a silicon carbide substrate.

8. 5. The method for processing a carbon-containing single crystal substrate according to claim 1, wherein the product contains graphite or amorphous carbon.

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