Processing method for plate-shaped materials

Abstract

To allow a determination of resistivity corresponded to the processability of a plate-like material without processing the plate-like material.SOLUTION: A detection method of resistivity is a detection method of resistivity for detecting the resistivity of a plate-like material having a back surface and a front surface on the side opposite to the back surface, and comprises: an interference waveform acquisition step 1005 of acquiring an interference waveform of light radiated from a light source to the back surface of the plate-like material and reflected by the back surface, and light reflected by the front surface after transmitted through the back surface; and an estimation step 1006 of estimating the resistivity of the plate-like material on the basis of the interference waveform acquired in the interference waveform acquisition step 1005.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention , board relates to a method for processing a shaped object.

Background Art

[0002] In order to generate chips from a semiconductor wafer, a technique has been proposed in which a laser beam having permeability to the wafer is irradiated to form a modified layer inside the wafer, which is a plate-shaped object, and the wafer is divided starting from the modified layer with reduced strength and the like (see, for example, Patent Document 1).

[0003] When forming the modified layer, if the wafer is doped with impurities, the transmittance and refractive index of the laser beam vary depending on the amount of the doped impurities and the like. For this reason, even for wafers of the same thickness, there are problems such that the position of the condensing point changes and a modified layer cannot be formed at an appropriate position, or the absorption of the laser beam increases and a modified layer cannot be formed at a deep position in the thickness direction.

[0004] In response to the above problems, a method for processing a wafer capable of forming a modified layer under appropriate processing conditions corresponding to the impurities added to the wafer has been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the method disclosed in Patent Document 2 described above has a problem that processing must be performed on the outer peripheral surplus region in advance.

[0007] Since the electrical resistivity changes when impurities are added to a wafer, methods are used to pre-measure the resistivity using measuring instruments such as resistivity meters. However, this presents a challenge because it requires selecting wafers according to the measured resistivity, making management complicated.

[0008] This invention has been made in view of the above problems, and its purpose is to make it possible to determine the resistivity corresponding to the processability of a plate-shaped material without processing the plate-shaped material. board The objective is to provide a method for processing shaped materials. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the objectives, the present invention The processing method for plate-shaped materials is: It has a first surface and a second surface opposite to the first surface. A method for processing a plate-like material, the A method for detecting the resistivity of a plate-shaped object, Applicable The method includes: an interference waveform acquisition step in which light is shone from a light source onto the first surface of a plate-like object, and an interference waveform is obtained between the light reflected from the first surface and the light that passes through the first surface and is reflected from the second surface; and an estimation step in which the resistivity of the plate-like object is estimated based on the interference waveform obtained in the interference waveform acquisition step. The process involves a resistivity detection step of detecting the resistivity of a plate-shaped object using a resistivity detection method, a processing condition selection step of selecting processing conditions corresponding to the resistivity, and a laser beam irradiation step of irradiating the plate-shaped object with a laser beam under the processing conditions selected in the processing condition selection step, wherein the processing condition selection step selects processing conditions that make it difficult to form a modified layer as the resistivity of the plate-shaped object increases. It is characterized by the following:

[0010] The aforementioned Processing method for plate-shaped materials In this estimation step, the resistivity of the plate-like object may be estimated based on the maximum value of the interference waveform obtained in the interference waveform acquisition step.

[0011] The aforementioned Processing method for plate-shaped materials The method further includes a storage step in which the interference waveform acquisition step is performed on plate-like objects having various resistivities, and resistivity information is stored in advance, linking the resistivity of each plate-like object with the maximum value of the interference waveform corresponding to that resistivity. The estimation step may then calculate the resistivity of the plate-like object based on the resistivity information stored in the storage step.

[0012] The aforementioned Processing method for plate-shaped materialsIn this case, in the estimation step, the interference waveform acquired in the interference waveform acquisition step may be Fourier-transformed, and the resistivity of the plate-like object may be estimated based on the maximum value of the waveform after the transformation.

[0013] The above-mentioned Processing method for plate-shaped materials Further includes a storage step of performing the interference waveform acquisition step on plate-like objects having various resistivities in advance, associating the resistivity of each plate-like object with the maximum value of the waveform obtained by Fourier-transforming the interference waveform corresponding to the resistivity, and storing the resistivity information. The estimation step may calculate the resistivity of the plate-like object inversely based on the resistivity information stored in the storage step.

[0015] In the processing method of the plate-like object, after performing the resistivity detection step, a determination step of determining whether the plate-like object having the detected resistivity can be processed by irradiating the laser beam may be further included.

Effect of the Invention

[0016] The present invention has the effect of enabling the determination of the resistivity corresponding to the workability of the plate-like object without processing the plate-like object.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a perspective view of the plate-like object that is the detection target of the resistivity detection method and the processing target of the plate-like object processing method according to Embodiment 1. [Figure 2] FIG. 2 is a perspective view of the plate-like object shown in FIG. 1 as viewed from the back side. [Figure 3] FIG. 3 is a perspective view showing a configuration example of a laser processing apparatus that implements the resistivity detection method and the plate-like object processing method according to Embodiment 1. [Figure 4] FIG. 4 is a diagram schematically showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG. 3. [Figure 5] FIG. 5 is a diagram schematically showing the configuration of the spectroscopic interferometer of the laser processing apparatus shown in FIG. 3. [Figure 6]FIG. 6 is a diagram showing an example of an interference waveform acquired by the spectroscopic interferometer shown in FIG. 5. [Figure 7] FIG. 7 is a diagram showing resistivity information stored in the storage unit of the control unit of the laser processing apparatus shown in FIG. 3. [Figure 8] FIG. 8 is a diagram showing determination conditions stored in the storage unit of the control unit of the laser processing apparatus shown in FIG. 3. [Figure 9] FIG. 9 is a flowchart showing the flow of the method for processing a plate-like object according to Embodiment 1. [Figure 10] FIG. 10 is a flowchart showing the flow of the method for measuring resistivity according to Embodiment 1. [Figure 11] FIG. 11 is a diagram showing resistivity information stored in the storage unit of the control unit of a laser processing apparatus that implements a method for detecting resistivity and a method for processing a plate-like object according to a modification of Embodiment 1. [Figure 12] FIG. 12 is a diagram showing an example of a waveform obtained by Fourier-transforming an interference waveform acquired by a spectroscopic interferometer of a laser processing apparatus that implements a method for detecting resistivity and a method for processing a plate-like object according to a modification of Embodiment 1. [Figure 13] FIG. 13 is a perspective view showing a configuration example of a laser processing apparatus that implements a method for detecting resistivity and a method for processing a plate-like object according to Embodiment 2. [Figure 14] FIG. 14 is a flowchart showing the flow of the method for measuring resistivity according to Embodiment 2. Embodiments for Carrying Out the Invention

[0018] Embodiments (embodiment forms) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0019] [Embodiment 1] A resistivity detection method and a plate-like material processing method according to Embodiment 1 of the present invention will be described based on the drawings. Figure 1 is a perspective view of the plate-like material to be detected in the resistivity detection method and the plate-like material to be processed in the processing method according to Embodiment 1. Figure 2 is a perspective view of the plate-like material shown in Figure 1, viewed from the back side.

[0020] The plate-shaped object 1 of the resistivity detection method and the plate-shaped object processing method according to Embodiment 1 is a disc-shaped semiconductor wafer or optical device wafer with a substrate 2 made of silicon, gallium arsenide, or SiC (silicon carbide), etc. As shown in Figure 1, the plate-shaped object 1 has multiple intersecting division lines 4 set on the second surface 3, and a device 5 is formed in the region partitioned by the division lines 4.

[0021] Device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor memory device).

[0022] Furthermore, in Embodiment 1, the plate-like object 1 has notches 6 indicating the crystal orientation formed on its outer edge, as shown in Figures 1 and 2. Various doping materials are added to the substrate 2 to form the plate-like object 1. The electrical resistance, or resistivity, of the plate-like object 1 changes depending on the amount of doping material added to the substrate 2. In Embodiment 1, the plate-like object 1 is divided into individual devices 5 by, for example, irradiating the back surface 7, which is the first surface opposite the front surface 3, along the division line 4. That is, the plate-like object 1 has a back surface 7, which is the first surface, and a front surface 3, which is the second surface opposite the back surface 7.

[0023] (Laser processing equipment) Next, a laser processing apparatus for implementing the resistivity detection method and plate-shaped material processing method according to Embodiment 1 will be described. Figure 3 is a perspective view showing an example of the configuration of a laser processing apparatus for implementing the resistivity detection method and plate-shaped material processing method according to Embodiment 1. Figure 4 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in Figure 3.

[0024] The laser processing apparatus 10 shown in Figure 3 is a processing apparatus that sets a focal point 22 inside the substrate 2 of a pulsed laser beam 21 with a wavelength that is transparent to the substrate 2 constituting the plate-shaped object 1, from the back surface 7 of the plate-shaped object 1, and irradiates the laser beam 21 along the division line 4 to form a modified layer 8 (shown in Figure 4) inside the substrate 2 along the division line 4.

[0025] The modified layer 8 refers to a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding area. Examples include melted regions, cracked regions, dielectric breakdown regions, refractive index change regions, and regions where these regions are mixed. The mechanical strength of the modified layer 8 is lower than that of other parts. Furthermore, the less resistivity of the plate-like material 1, the more difficult it becomes to form the modified layer 8 inside the substrate 2, and the more resistivity of the plate-like material 1, the easier it becomes to form the modified layer 8 inside the substrate 2.

[0026] As shown in Figure 3, the laser processing apparatus 10 comprises a holding table 11 for holding a plate-shaped object 1, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 40, a spectroscopic interferometer 50, and a control unit 100.

[0027] The holding table 11 holds the plate-shaped object 1 with a holding surface 12 parallel to the horizontal direction. The holding surface 12 is a disc shape formed from porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a suction path (not shown). The holding table 11 holds the plate-shaped object 1 placed on the holding surface 12 by suction, as the surface 3 is placed on the holding surface 12 and the holding surface 12 is sucked by the vacuum suction source.

[0028] Furthermore, the holding table 11 is rotated by the rotational movement unit 33 of the moving unit 30 around an axis that is perpendicular to the holding surface 12 and parallel to the Z-axis direction which is also parallel to the vertical direction. Together with the rotational movement unit 33, the holding table 11 is moved in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and moved in the Y-axis direction parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The holding table 11 is moved by the moving unit 30 between the processing area below the laser beam irradiation unit 20 and the loading / unloading area away from below the laser beam irradiation unit 20 where the plate-shaped object 1 is loaded and unloaded.

[0029] The moving unit 30 moves the holding table 11 and the focal point 22 of the laser beam 21 irradiated by the laser beam irradiation unit 20 relative to each other in the X-axis direction, Y-axis direction, Z-axis direction, and an axis parallel to the Z-axis direction. The X-axis direction and Y-axis direction are mutually orthogonal and parallel to the holding surface 12 (i.e., the horizontal direction). The Z-axis direction is perpendicular to both the X-axis direction and the Y-axis direction.

[0030] The moving unit 30 includes an X-axis moving unit 31, which is a machining feed unit that moves the holding table 11 in the X-axis direction; a Y-axis moving unit 32, which is an indexing feed unit that moves the holding table 11 in the Y-axis direction; a rotational moving unit 33 that rotates the holding table 11 around an axis parallel to the Z-axis direction; and a Z-axis moving unit 34 that moves the focal point 22 of the laser beam 21 of the laser beam irradiation unit 20 in the Z-axis direction.

[0031] The Y-axis movement unit 32 is an indexing feed unit that moves the holding table 11 and the focusing point 22 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the Y-axis direction. In Embodiment 1, the Y-axis movement unit 32 is installed on the main body 13 of the laser processing apparatus 10. The Y-axis movement unit 32 supports the movable plate 16 that supports the X-axis movement unit 31 so as to be movable in the Y-axis direction.

[0032] The X-axis movement unit 31 is a machining feed unit that moves the holding table 11 and the focusing point 22 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the X-axis direction. The X-axis movement unit 31 is mounted on a movement plate 16. The X-axis movement unit 31 supports a second movement plate 17 that is movable in the X-axis direction, and the second movement plate 17 supports a rotational movement unit 33 that rotates the holding table 11 around an axis parallel to the Z-axis direction. The second movement plate 17 supports the rotational movement unit 33 and the holding table 11. The rotational movement unit 33 supports the holding table 11.

[0033] The Z-axis movement unit 34 is a feed unit that moves the holding table 11 and the focusing point 22 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the Z-axis direction. The Z-axis movement unit 34 is installed on an upright column 14 that is erected from the main body of the device 13. The Z-axis movement unit 34 supports a support column 15, which has a focusing lens 24 (described later) of the laser beam irradiation unit 20 positioned at its tip, so as to be movable in the Z-axis direction.

[0034] The X-axis movement unit 31 includes a well-known ball screw that is rotatable around its axis and moves the second movement plate 17 in the X-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the second movement plate 17 so as to be movable in the X-axis direction. The Y-axis movement unit 32 includes a well-known ball screw that is rotatable around its axis and moves the movement plate 16 in the Y-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the movement plate 16 so as to be movable in the Y-axis direction. The Z-axis movement unit 34 includes a well-known ball screw that is rotatable around its axis and moves the support column 15 in the Z-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the support column 15 so as to be movable in the Z-axis direction. The rotational movement unit 33 includes a motor that rotates the holding table 11 around its axis, etc.

[0035] Furthermore, the laser processing apparatus 10 includes an X-axis position detection unit (not shown) for detecting the position of the holding table 11 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the holding table 11 in the Y-axis direction, and a Z-axis position detection unit (not shown) for detecting the position of the support column 15 in the Z-axis direction. Each position detection unit outputs the detection result to the control unit 100.

[0036] The laser beam irradiation unit 20 is a processing unit that focuses and irradiates a plate-shaped object 1 held on the holding surface 12 of the holding table 11 with a pulsed laser beam 21 to perform laser processing on the plate-shaped object 1. In Embodiment 1, a part of the laser beam irradiation unit 20 is positioned at the tip of a support column 15, which is supported by a Z-axis movement unit 34 installed on an upright column 14 erected from the main body of the apparatus 13, as shown in Figure 1.

[0037] As shown in Figure 4, the laser beam irradiation unit 20 includes a laser oscillator 23 that emits a pulsed laser beam 21, and a focusing lens 24 that focuses the laser beam 21 emitted from the laser oscillator 23 and irradiates the plate-shaped object 1. In Embodiment 1, the laser beam irradiation unit 20 includes a mirror 25 that reflects the laser beam 21 emitted from the laser oscillator 23 toward the focusing lens 24.

[0038] The imaging unit 40 images the plate-shaped object 1 held on the holding table 11. The imaging unit 40 is an infrared camera equipped with an image sensor such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor, whose objective lens images objects facing each other in the Z-axis direction. In Embodiment 1, as shown in Figure 1, the imaging unit 40 is positioned at the tip of the support column 15, with its objective lens aligned with the focusing lens 24 of the laser beam irradiation unit 20 along the X-axis direction.

[0039] The imaging unit 40 acquires the image captured by the image sensor and outputs the acquired image to the control unit 100. The imaging unit 40 also images the plate-shaped object 1 held on the holding surface 12 of the holding table 11 to acquire an image for performing alignment between the plate-shaped object 1 and the laser beam irradiation unit 20, and outputs the acquired image to the control unit 100.

[0040] (Spectroscopic interferometer) Next, the spectroscopic interferometer 50 will be described. Figure 5 is a schematic diagram showing the configuration of the spectroscopic interferometer of the laser processing apparatus shown in Figure 3. Figure 6 is a diagram showing an example of interference waveform acquired by the spectroscopic interferometer shown in Figure 5.

[0041] As shown in Figure 5, the spectroscopic interferometer 50 irradiates a plate-shaped object 1 held on a holding table 11 with light 52 from a light source 51. The spectroscopic interferometer 50 acquires an interference waveform 60 (exemplified in Figure 6) of light 52 reflected from the back surface 7 (hereinafter referred to as reference numeral 521) and light 52 transmitted through the back surface 7 and reflected from the front surface 3 (hereinafter referred to as reference numeral 522). As shown in Figure 5, the spectroscopic interferometer 50 comprises a light source 51 that emits light 52, a sensor head 53 facing the holding surface 12 of the holding table 11, a diffraction grating 54, and a line sensor 55.

[0042] In Embodiment 1, the light source 51 is an SLD (Super Luminescent Diode) light source that emits light 52 with a wavelength of 1250 nm to 1350 nm. The sensor head 53 transmits the light 52 emitted by the light source 51 and irradiates the plate-shaped object 1 held on the holding table 11, and also guides the interference light of the light 521 reflected from the back surface 7 of the plate-shaped object 1 and the light 522 that has passed through the back surface 7 and reflected from the front surface 3 to the diffraction grating 54.

[0043] The diffraction grating 54 diffracts the interference light of light 521 and light 522 at different angles for each wavelength and reflects it toward the line sensor 55, thereby spectrally separating the light 521 and 522 by wavelength. The line sensor 55 has image sensors arranged in a straight line, and each image sensor receives the light 523 spectrally separated by the diffraction grating 54. The line sensor 55 outputs information indicating the intensity of the light 523 received by each image sensor toward the control unit 100.

[0044] The spectrophotometer 50 irradiates a plate-shaped object 1 held on a holding table 11 with light 52 from a light source 51. The interference light of light 521 reflected from the back surface 7 and light 522 transmitted through the back surface 7 and reflected from the front surface 3 is spectrally separated by wavelength using a diffraction grating 54. The spectrally separated light 523 is received by each image sensor of the line sensor 55 to acquire the interference waveform 60 shown in Figure 6, and the acquired interference waveform 60 is output to the control unit 100. In Figure 6, the horizontal axis indicates the position of each image sensor, and the vertical axis indicates the intensity of the light 523 received by each image sensor. The maximum value 61 of the intensity of the light 523 in the interference waveform 60 exemplified in Figure 6 corresponds to the resistivity of the plate-shaped object 1 irradiated with light 52 by the spectrophotometer 50.

[0045] Next, the control unit 100 will be described. Figure 7 shows the resistivity information stored in the memory unit of the control unit of the laser processing apparatus shown in Figure 3. Figure 8 shows the decision conditions stored in the memory unit of the control unit of the laser processing apparatus shown in Figure 3.

[0046] The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 10 to cause the laser processing apparatus 10 to perform processing operations on the plate-shaped object 1. The control unit 100 is a computer having an arithmetic processing unit with a microprocessor such as a CPU (central processing unit), a storage device with memory such as ROM (read-only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing unit of the control unit 100 performs calculations according to the computer program stored in the storage device and outputs control signals for controlling the laser processing apparatus 10 to the above-mentioned components of the laser processing apparatus 10 via the input / output interface device, thereby realizing the function of the control unit 100.

[0047] The laser processing apparatus 10 also includes a display unit 110, which is a display means consisting of a liquid crystal display device that displays the status of processing operations and images, an input unit 120, which is an input means used by the operator to input processing conditions, and a notification unit (not shown). The display unit 110, the input unit 120, and the notification unit are connected to the control unit 100. The input unit 120 consists of a touch panel provided on the display unit 110. The notification unit notifies the operator by emitting at least one of sound, light, or a message on the display unit 110.

[0048] Furthermore, as shown in Figure 3, the control unit 100 includes a processing control unit 101 and a storage unit 102. The processing control unit 101 controls each of the above-mentioned components of the laser processing apparatus 10 to cause each component of the laser processing apparatus 10 to perform processing operations on the plate-shaped object 1.

[0049] The memory unit 102 stores the resistivity information 70 shown in Figure 7 and the judgment conditions 80 shown in Figure 8.

[0050] The resistivity information 70 links the resistivity of multiple plate-like objects 1 made of the same material and thickness with the maximum value 61 of the interference waveform 60 corresponding to that resistivity, showing the relationship between them. In other words, the resistivity information 70 establishes a one-to-one correspondence between the resistivity of multiple plate-like objects 1 made of the same material and thickness and the maximum value 61 of the interference waveform 60 corresponding to that resistivity. In Figure 7, the resistivity information 70 shows the resistivity of multiple plate-like objects 1 made of the same material and thickness on the horizontal axis, and the maximum value 61 of the interference waveform 60 on the vertical axis.

[0051] The resistivity information 70 is obtained by irradiating multiple plate-like objects 1 of the same material and thickness with known resistivity using a spectroscopic interferometer 50 to acquire interference waveforms 60, and then approximating the known resistivity with the measured value 72 of the maximum value 61 of the interference waveform 60 using the least squares method or the like. The memory unit 102 stores the resistivity information 70 corresponding to each material and thickness of the plate-like object 1. In this way, the resistivity information 70 is obtained by acquiring interference waveforms 60 from plate-like objects 1 with various resistivity, and linking the resistivity of each plate-like object 1 with the maximum value 61 of the interference waveform 60 corresponding to that resistivity.

[0052] The judgment condition 80 shown in Figure 8 is a condition for determining the processing conditions based on the resistivity of the plate-shaped object 1 to be processed, which is determined from the maximum value 61 of the interference waveform 60 acquired by the spectroscopic interferometer 50 and the resistivity information 70. In Embodiment 1, the judgment condition 80 stipulates that processing is not possible if the resistivity of the plate-shaped object 1 is less than a predetermined first value. Furthermore, the judgment condition 80 stipulates that if the resistivity of the plate-shaped object 1 is greater than or equal to the first value and less than a predetermined second value, processing will be performed using the processing conditions set by the operator (labeled as processing condition 81 in Figure 8). Furthermore, the judgment condition 80 stipulates that if the resistivity of the plate-shaped object 1 is greater than or equal to the second value and less than a predetermined third value, processing will be performed using processing condition 82.

[0053] Furthermore, the second value is greater than the first value, and the third value is greater than the second value. Also, processing condition 82 is a condition that makes it easier to form the modified layer 8 than processing condition 81 set by the operator. For example, processing condition 82 may involve reducing the output of the laser beam 21 or reducing the number of modified layers 8 formed in the thickness direction on the same planned division line 4 than processing condition 81 set by the operator. Thus, the judgment condition 80 stipulates that, for resistivity that allows processing of the plate-like object 1, processing should be performed under processing conditions 81 and 82, which make it more difficult to form the modified layer 8 as the resistivity increases, since it becomes easier to form the modified layer 8 as the resistivity increases.

[0054] The functions of the processing control unit 101 are realized by the arithmetic processing unit performing calculations according to the computer program stored in the memory device. The functions of the storage unit 102 are realized by the memory device described above.

[0055] (Method for processing plate-like materials and method for measuring resistivity) Next, the processing method for a plate-like material and the method for measuring its resistivity according to Embodiment 1 will be described. Figure 9 is a flowchart showing the flow of the processing method for a plate-like material according to Embodiment 1. Figure 10 is a flowchart showing the flow of the method for measuring its resistivity according to Embodiment 1. The processing method for a plate-like material according to Embodiment 1 is also the processing operation of the laser processing apparatus 10.

[0056] The plate-shaped material processing method according to Embodiment 1 is a method for processing the plate-shaped material 1 described above. The plate-shaped material processing method begins when the processing control unit 101 of the control unit 100 of the laser processing apparatus 10 registers the processing conditions input by the operator by operating the input unit 120, etc., the surface 3 side of the plate-shaped material 1 is placed on the holding surface 12 of the holding table 11, and the processing control unit 101 of the control unit 100 receives a processing start instruction from the operator. The processing conditions include the material and thickness of the plate-shaped material 1 to be processed. As shown in Figure 9, the plate-shaped material processing method involves performing a resistivity detection step 1001, a judgment step 1002, a processing condition selection step 1003, and a laser beam irradiation step 1004.

[0057] (Resistivity detection step) The resistivity detection step 1001 is a step to detect the resistivity 71 (shown in Figure 7) of the plate-shaped object 1 to be processed, with its surface 3 side placed on the holding surface 12 of the holding table 11, using the resistivity measurement method according to Embodiment 1. The resistivity detection step 1001, i.e., the resistivity measurement method according to Embodiment 1, is also a method for detecting the resistivity of the plate-shaped object 1 with its surface 3 side placed on the holding surface 12 of the holding table 11. The resistivity detection step 1001, i.e., the resistivity measurement method according to Embodiment 1, includes an interference waveform acquisition step 1005 and an estimation step 1006, as shown in Figure 10.

[0058] (Interference waveform acquisition step) Interference waveform acquisition step 1005 is a step in which light 52 from the light source 51 is irradiated onto the back surface 7 of the plate-shaped object 1, and an interference waveform 60 is acquired between the light 521 reflected from the back surface 7 and the light 522 that passes through the back surface 7 and is reflected from the front surface 3. In interference waveform acquisition step 1005, the laser processing apparatus 10 has a processing control unit 101 of the control unit 100 that uses suction to hold the front surface 3 of the plate-shaped object 1 to the holding surface 12 of the holding table 11, and controls the moving unit 30 to move the holding table 11 toward the processing area, while also positioning the plate-shaped object 1 below the spectroscopic interferometer 50.

[0059] In interference waveform acquisition step 1005, the laser processing apparatus 10 controls the processing control unit 101 of the control unit 100 to emit light 52 from the light source 51 and irradiate the plate-shaped object 1. At the same time, the interference light of light 521 reflected from the back surface 7 and light 522 reflected from the front surface 3 is spectrally separated by the diffraction grating 54 and received by the line sensor 55. In interference waveform acquisition step 1005, the laser processing apparatus 10 uses the spectroscopic interferometer 50 to receive the interference light of light 521 and light 522 with the line sensor 55, acquires the interference waveform 60, and outputs the acquired interference waveform 60 to the control unit 100.

[0060] (Estimated step) Estimation step 1006 is a step in which the resistivity 71 of the plate-shaped object 1 to be processed is estimated based on the interference waveform 60 acquired in interference waveform acquisition step 1005. In estimation step 1006, the laser processing apparatus 10 has a processing control unit 101 that extracts a maximum value 61 from the interference waveform 60 and reads resistivity information 70 of the plate-shaped object 1 of the material and thickness specified in the processing conditions from the storage unit 102. In estimation step 1006, the laser processing apparatus 10 has a processing control unit 101 that extracts a resistivity 71 corresponding to the maximum value 61 extracted from the interference waveform 60 in the resistivity information 70 read from the storage unit 102, for example. Thus, in estimation step 1006, the processing control unit 101 of the control unit 100 estimates the resistivity 71 of the plate-shaped object 1 to be processed based on the maximum value 61 of the interference waveform 60 acquired in interference waveform acquisition step 1005, and in estimation, it also calculates the resistivity 71 of the plate-shaped object 1 to be processed based on the resistivity information 70 stored in the storage unit 102.

[0061] (Decision-making step) The determination step 1002 is a step in which, after performing the resistivity detection step 1001, it is determined whether or not it is possible to process the plate-shaped object 1 to be processed, which has the detected resistivity 71, by irradiating it with a laser beam 21. In Embodiment 1, in the determination step 1002, the processing control unit 101 of the control unit 100 reads the determination condition 80 from the storage unit 102 and determines whether or not the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is less than a first value, and then determines whether or not processing is possible.

[0062] In Embodiment 1, in the determination step 1002, if the processing control unit 101 of the control unit 100 determines that the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is less than the first value, it determines that processing of the plate-shaped object 1 to be processed by irradiating it with the laser beam 21 is not possible (determination step 1002: No). In Embodiment 1, if the processing control unit 101 of the control unit 100 determines in the determination step 1002 that processing of the plate-shaped object 1 to be processed by irradiating it with the laser beam 21 is not possible, it notifies the notification unit (step 1010) and terminates the processing method for the plate-shaped object.

[0063] Furthermore, in Embodiment 1, in the determination step 1002, if the processing control unit 101 of the control unit 100 determines that the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is not less than the first value, then it determines that processing is possible by irradiating the plate-shaped object 1 to be processed with the laser beam 21 (determination step 1002: Yes). In Embodiment 1, if the processing control unit 101 of the control unit 100 determines in the determination step 1002 that processing is possible by irradiating the plate-shaped object 1 to be processed with the laser beam 21, then the process proceeds to the processing condition selection step 1003.

[0064] (Processing condition selection step) The machining condition selection step 1003 is a step in which machining conditions corresponding to the resistivity estimated in the estimation step 1006 are selected. In the machining condition selection step 1003, the machining control unit 101 of the control unit 100 determines whether the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is greater than or equal to a first value and less than a second value, or greater than or equal to a second value and less than a third value.

[0065] In the machining condition selection step 1003, if the machining control unit 101 of the control unit 100 determines that the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is greater than or equal to the first value and less than the second value, it refers to the determination condition 80 and selects the machining condition 81 set by the operator. Also in the machining condition selection step 1003, if the machining control unit 101 of the control unit 100 determines that the resistivity 71 estimated in the estimation step 1006, i.e., the resistivity 71 detected in the resistivity detection step 1001, is greater than or equal to the second value and less than the third value, it refers to the determination condition 80 and selects the machining condition 82.

[0066] (Laser beam irradiation step) The laser beam irradiation step 1004 is a step in which the laser beam 21 is irradiated onto the plate-shaped object 1 to be processed using the processing conditions 81 and 82 selected in the processing condition selection step 1003 to perform processing. In the laser beam irradiation step 1004, the processing control unit 101 of the control unit 100 of the laser processing apparatus 10 controls the moving unit 30 to position the plate-shaped object 1 to be processed below the imaging unit 40, and causes the imaging unit 40 to image the back surface 7 of the plate-shaped object 1.

[0067] In the laser beam irradiation step 1004, the laser processing apparatus 10 detects the division line 4 from the image captured and acquired by the imaging unit 40 using the processing control unit 101 of the control unit 100, and performs alignment to align the division line 4 with the laser beam irradiation unit 20. In the laser beam irradiation step 1004, the laser processing apparatus 10, using the processing control unit 101 of the control unit 100, positions the focal point 22 of the laser beam 21, which has a wavelength that is transparent to the plate-shaped object 1, inside the substrate 2, as shown in Figure 4, based on the processing conditions 81, 82, etc. selected in the processing condition selection step 1003, and irradiates the plate-shaped object 1 with a pulsed laser beam 21 along the division line 4 from the back surface 7 side of the plate-shaped object 1 while relatively moving the holding table 11 and the laser beam irradiation unit 20 along the division line 4.

[0068] As a result, as shown in Figure 4, a modified layer 8 is formed inside the substrate 2 along the planned division lines 4 because the wavelength of the laser beam 21 is transparent to the plate-shaped object 1. In the laser beam irradiation step 1004, once the modified layer 8 has formed inside the substrate 2 along all the planned division lines 4, the laser processing apparatus 10 stops irradiating the laser beam 21 from the laser beam irradiation unit 20, moves the holding table 11 to the loading / unloading area, and then stops the suction holding of the holding surface 12, thereby ending the processing method, i.e., the processing operation, of the plate-shaped object.

[0069] The resistivity detection method and plate-shaped object processing method according to Embodiment 1 described above involves pre-storing resistivity information 70 in the memory unit 102 of the laser processing apparatus 10, which links the resistivity of the plate-shaped object 1 with the maximum value 61 of the interference waveform 60. The interference waveform 60 of the plate-shaped object 1 to be processed is acquired, and the resistivity 71 of the plate-shaped object 1 to be processed is estimated based on the acquired maximum value 61 of the interference waveform 60 and the resistivity information 70. As a result, the resistivity detection method and plate-shaped object processing method according to Embodiment 1 has the effect of making it possible to determine the resistivity 71 corresponding to the processability of the plate-shaped object 1 without processing the plate-shaped object 1.

[0070] [Variation] A resistivity detection method and a plate-shaped material processing method according to a modified embodiment 1 of the present invention will be described with reference to the drawings. Figure 11 is a diagram showing resistivity information stored in the memory unit of the control unit of a laser processing apparatus that implements the resistivity detection method and plate-shaped material processing method according to a modified embodiment 1. Figure 12 is a diagram showing an example of a waveform obtained by performing a Fourier transform on the interference waveform acquired by the spectroscopic interferometer of a laser processing apparatus that implements the resistivity detection method and plate-shaped material processing method according to a modified embodiment 1.

[0071] The resistivity detection method and plate-shaped material processing method according to a modified embodiment of Embodiment 1 are the same as Embodiment 1, except that the control unit 100 of the laser processing apparatus 10 stores resistivity information 70-1 shown in Figure 11 in the storage unit 102 in advance instead of resistivity information 70, and in the estimation step 1006, the resistivity 71 of the plate-shaped material 1 is estimated based on the maximum value 61-1 of the waveform 60-1 shown in Figure 12, which is obtained by Fourier transforming the interference waveform 60 acquired in the interference waveform acquisition step 1005, and the resistivity information 70-1.

[0072] The resistivity information 70-1 links the resistivity of multiple plate-like objects 1 made of the same material and thickness with the maximum value 61-1 of the waveform 60-1 exemplified in Figure 12, which is obtained by Fourier transforming the interference waveform 60 corresponding to the resistivity, and shows the relationship between them. In other words, the resistivity information 70 establishes a one-to-one correspondence between the resistivity of multiple plate-like objects 1 made of the same material and thickness and the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the interference waveform 60 corresponding to the resistivity. Note that in the resistivity information 70-1 shown in Figure 11, the horizontal axis shows the resistivity of multiple plate-like objects 1 made of the same material and thickness, and the vertical axis shows the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the interference waveform 60. Also, in the waveform 60-1 shown in Figure 12, the horizontal axis shows the height of the back surface 7 of the plate-like object 1, and the vertical axis shows the signal strength.

[0073] The resistivity information 70-1 is obtained by approximating the known resistivity and the measured value 72-1 of the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the interference waveform 60 with the known resistivity by irradiating multiple plate-like objects 1 of the same material and thickness with known resistivity using a spectroscopic interferometer 50 to acquire interference waveforms 60. The memory unit 102 stores resistivity information 70-1 corresponding to the material and thickness of each plate-like object 1, similar to Embodiment 1. Thus, the resistivity information 70-1 is obtained by Fourier transforming the interference waveforms 60 acquired from plate-like objects 1 with various resistivity, and linking the resistivity of each plate-like object 1 with the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the interference waveform 60 corresponding to that resistivity.

[0074] In the resistivity detection method and plate-shaped material processing method according to a modified embodiment of Embodiment 1, in estimation step 1006, the processing control unit 101 of the laser processing apparatus 10 performs a Fourier transform on the interference waveform 60 acquired from the plate-shaped material 1 to be processed in interference waveform acquisition step 1005. In the modified embodiment of Embodiment 1, in estimation step 1006, the processing control unit 101 of the laser processing apparatus 10 extracts the maximum value 61-1 from the Fourier-transformed waveform 60-1 and reads the resistivity information 70-1 of the plate-shaped material 1 with the material and thickness specified in the processing conditions from the storage unit 102.

[0075] In a modified example of Embodiment 1, in estimation step 1006, the laser processing apparatus 10 extracts the resistivity 71 corresponding to the maximum value 61-1 extracted from the waveform 60-1 in the resistivity information 70-1 read from the storage unit 102 by the processing control unit 101 of the control unit 100. Thus, in estimation step 1006, the processing control unit 101 of the control unit 100 performs a Fourier transform on the interference waveform 60 acquired in interference waveform acquisition step 1005, and estimates the resistivity 71 of the plate-shaped object 1 to be processed based on the transformed waveform 60-1. During estimation, the resistivity 71 of the plate-shaped object 1 to be processed is calculated in reverse based on the resistivity information 70-1 stored in the storage unit 102.

[0076] The resistivity detection method and plate-shaped material processing method according to a modified embodiment of Embodiment 1 involves pre-storing resistivity information 70-1 in the memory unit 102 of the laser processing apparatus 10, which links the resistivity of the plate-shaped material 1 with the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the interference waveform 60. The interference waveform 60 of the plate-shaped material 1 to be processed is acquired, and the resistivity 71 of the plate-shaped material 1 to be processed is estimated based on the maximum value 61-1 of the waveform 60-1 obtained by Fourier transforming the acquired interference waveform 60 and the resistivity information 70-1. Thus, similar to Embodiment 1, it is possible to determine the resistivity 71 corresponding to the processability of the plate-shaped material 1 without processing the plate-shaped material 1.

[0077] [Embodiment 2] A resistivity detection method and a plate-like material processing method according to Embodiment 2 of the present invention will be described with reference to the drawings. Figure 13 is a perspective view showing an example of the configuration of a laser processing apparatus for implementing the resistivity detection method and plate-like material processing method according to Embodiment 2. Figure 14 is a flowchart showing the flow of the resistivity measurement method according to Embodiment 2. Note that in Figures 13 and 14, the same reference numerals are used for the same parts as in Embodiment 1, and their descriptions are omitted.

[0078] The resistivity detection method and plate-shaped material processing method according to Embodiment 2 are identical to Embodiment 1 and its modified form, except that the control unit 100 of the laser processing apparatus 10 is equipped with an information acquisition unit 103, and the resistivity detection step 1001, i.e., the resistivity detection method, of the plate-shaped material processing method is different. The information acquisition unit 103 of the control unit 100 acquires resistivity information 70, 70-1 and stores it in the storage unit 102. The function of the information acquisition unit 103 is realized by the arithmetic processing unit performing arithmetic processing according to a computer program stored in the storage device.

[0079] The resistivity detection method and plate-shaped object processing method according to Embodiment 2 further comprises a storage step 1007, as shown in Figure 14, in the resistivity detection step 1001, i.e., the resistivity detection method. The storage step 1007 is a step in which the resistivity detection step 1001 of Embodiment 1 is performed on plate-shaped objects 1 having various resistivities, and resistivity information 70, 70-1 is stored in the storage unit 102 in advance. In the storage step 1007, the laser processing apparatus 10 has an information acquisition unit 103 of the control unit 100 that sequentially holds a plurality of plate-shaped objects 1 made of the same material and thickness as the plate-shaped object 1 to be processed, and whose resistivities are known, on the holding surface 12 of the holding table 11, and acquires the interference waveform 60 of each plate-shaped object 1 with a spectroscopic interferometer 50.

[0080] In Embodiment 2, in estimation step 1006, the laser processing apparatus 10, in the same manner as in Embodiment 1 and its modified form, uses the processing control unit 101 of the control unit 100 to calculate the resistivity 71 of the plate-shaped object 1 to be processed based on the resistivity information 70, 70-1 stored in storage step 1007. Also in Embodiment 2, in estimation step 1006, the laser processing apparatus 10, in the same manner as in Embodiment 1 and its modified form, uses the processing control unit 101 of the control unit 100 to perform a Fourier transform on the interference waveform 60 acquired in interference waveform acquisition step 1005, and estimates the resistivity of the plate-shaped object based on the maximum value 61-1 of the waveform 60-1 after the Fourier transform.

[0081] The resistivity detection method and plate-shaped material processing method according to Embodiment 2 involves storing resistivity information 70 and 70-1 in a storage step 1007, acquiring the interference waveform 60 of the plate-shaped material 1 to be processed, and estimating the resistivity 71 of the plate-shaped material 1 to be processed based on the maximum value 61 of the acquired interference waveform 60 or the maximum value 61-1 of the waveform 60-1 after the Fourier transform and the resistivity information 70-1. Therefore, similar to Embodiment 1, it has the effect of being able to determine the resistivity 71 corresponding to the processability of the plate-shaped material 1 without processing the plate-shaped material 1.

[0082] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core of the present invention. For example, in the present invention, only the resistivity measurement method, i.e., the interference waveform acquisition step 1005 and the estimation step 1006, or only the storage step 1007, the interference waveform acquisition step 1005 and the estimation step 1006 may be performed, and the judgment step 1002, the processing condition selection step 1003 and the laser beam irradiation step 1004 may not necessarily be performed. Furthermore, in the present invention, resistivity information 70, 70-1 for multiple plate-like objects 1 of the same material and thickness with known resistivity may be acquired for each different thickness, and the acquired resistivity information 70, 70-1 for each of the multiple thicknesses may be stored in the storage unit 102 of the laser processing apparatus 10. In this case, it becomes possible to estimate the resistivity 71 of plate-like objects 1 of various thicknesses. [Explanation of Symbols]

[0083] 1. Plate-like object 3. Surface (Second surface) 7 Reverse side (first side) 21 Laser beam 51 Light source 52 light 60 Interference Waveforms 60-1 Waveform 61, 61-1 Maximum value 70,70-1 Resistivity information 71 Resistivity 81,82 Processing conditions 521 Light (light reflected from the first surface) 522 Light (light reflected from the second surface) 1001 Resistivity detection step 1002 Decision Step 1003 Processing Condition Selection Step 1004 Laser beam irradiation step 1005 Interference waveform acquisition step 1006 Estimated Step 1007 Memory Steps

Claims

1. A method for processing a plate-shaped object having a first surface and a second surface opposite to the first surface, A resistivity detection method for detecting the resistivity of a plate-shaped object, comprising: an interference waveform acquisition step of irradiating the first surface of the plate-shaped object with light from a light source and acquiring an interference waveform of light reflected from the first surface and light transmitted through the first surface and reflected from the second surface; and an estimation step of estimating the resistivity of the plate-shaped object based on the interference waveform acquired in the interference waveform acquisition step, A machining condition selection step for selecting machining conditions corresponding to the resistivity, A laser beam irradiation step is performed by irradiating the plate-shaped object with a laser beam using the processing conditions selected in the processing condition selection step, In addition to implementing the following, A method for processing a plate-like material, characterized in that, in the processing condition selection step, processing conditions are selected such that it becomes more difficult to form a modified layer as the resistivity of the plate-like material increases.

2. The method for processing a plate-shaped object according to claim 1, characterized in that the estimation step estimates the resistivity of the plate-shaped object based on the maximum value of the interference waveform obtained in the interference waveform acquisition step.

3. The interference waveform acquisition step is performed on plate-shaped objects having various resistivities, and the system further includes a storage step in which resistivity information is pre-stored, linking the resistivity of each plate-shaped object with the maximum value of the interference waveform corresponding to that resistivity. The method for processing a plate-like material according to claim 2, characterized in that the estimation step calculates the resistivity of the plate-like material based on the resistivity information stored in the storage step.

4. The method for processing a plate-shaped object according to claim 1, characterized in that the estimation step involves performing a Fourier transform on the interference waveform acquired in the interference waveform acquisition step, and estimating the resistivity of the plate-shaped object based on the maximum value of the transformed waveform.

5. The interference waveform acquisition step is performed on plate-like objects having various resistivities, and the resistivity information is further stored in advance, linking the resistivity of each plate-like object with the maximum value of the waveform obtained by Fourier transforming the interference waveform corresponding to that resistivity. The method for processing a plate-like material according to claim 4, characterized in that the estimation step calculates the resistivity of the plate-like material based on the resistivity information stored in the storage step.

6. A method for processing a plate-shaped object according to any one of claims 1 to 5, further comprising a determination step of determining whether or not it is possible to process a plate-shaped object having the detected resistivity by irradiating it with the laser beam, after performing the resistivity detection step.

Images