Laser Processing Equipment

Abstract

To improve productivity in a wafer manufacturing technology where an ingot is sliced by laser beam to obtain a wafer.SOLUTION: A laser processing device (3) comprises: a transmitter (80); a collector (88); an optical system (83); and a control part (9). The collector is arranged opposite to a top face (2a) of an ingot (2) in a high direction of the ingot so that laser bean emitted from the transmitter is radiated on the top face of the ingot to condensate the laser beam inside of the ingot. The optical system arranged in a laser optical path (BL) between the transmitter and the collector, includes: a detection part (833) which detects alignment status of optical axis in the laser optical path; and an optical axis alignment mechanism (831) which can adjust the alignment status based on the detection result of the detection part. The control part controls the optical axis alignment mechanism based on the detection result of the detection part.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus that irradiates an ingot with a laser beam in order to obtain a wafer from the ingot. [Background technology]

[0002] Patent Document 1 discloses a wafer production method for producing a wafer from a single crystal SiC ingot, and a laser processing device used in the wafer production method. The wafer production method includes a step of producing a peeled surface, and a step of producing a wafer by peeling the wafer using the peeled surface as an interface. In the step of producing the peeled surface, the focal point of a laser beam having a wavelength that is transparent to SiC is positioned at a depth corresponding to the thickness of the wafer to be produced, and the laser beam is irradiated while being relatively fed in a direction perpendicular to the direction in which the off-angle is formed, thereby forming a separation layer consisting of a modified layer and cracks extending from the modified layer along the c-plane. Then, the separation layer formation process is performed multiple times with index feeding in the direction in which the off-angle is formed, to produce the peeled surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6723877 Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of laser processing device, if an error, fluctuation, or variation occurs in the depth of the focal point of the laser beam, the amount of grinding or polishing required for the peeled surface increases, which leads to a deterioration in material yield and a decrease in productivity. Examples of factors that cause this include misalignment of the optical axis due to vibration or heat during operation of the device. The present invention has been made in consideration of the above-mentioned circumstances. That is, the present invention makes it possible to improve productivity compared to the conventional technology in wafer manufacturing, for example, in which wafers are obtained from an ingot by so-called laser slicing. [Means for solving the problem]

[0005] The laser processing apparatus (3) described in claim 1 is configured to irradiate a transparent laser beam to an ingot top surface (2a), which is an end surface on one side in the height direction of the ingot, in order to obtain a wafer (1) from the ingot (2). This laser processing device is An oscillator (80) which is a source of the laser beam; a collector (88) disposed opposite the top surface of the ingot along the height direction so that the laser beam emitted from the oscillator is irradiated onto the top surface of the ingot to collect the laser beam inside the ingot; an optical system (83) provided in a laser optical path (BL) between the transmitter and the collector, the optical system (83) including a detection unit (833) for detecting an alignment state of an optical axis in the laser optical path, and an optical axis alignment mechanism (831) configured to operate so as to adjust the alignment state based on a detection result of the detection unit; a control unit (9) that adjusts the alignment state by controlling the operation of the optical axis alignment mechanism based on the detection result of the detection unit; a chuck (4) provided to support the ingot by joining with an ingot bottom surface (2b), which is the other end surface of the ingot in the height direction; a chuck moving mechanism (5) that is provided so as to be able to move a chuck table (50) that fixedly supports the chuck in an in-plane direction that intersects with the height direction; A main support base (62) that supports at least the chuck moving mechanism; Equipped with picture, The main support table has an active vibration suppression device (62c) that operates in response to the operation of the chuck moving mechanism. Claim to 4The described laser processing apparatus (3) is configured to irradiate a transparent laser beam onto an ingot top surface (2a), which is an end surface on one side in the height direction of the ingot, in order to obtain a wafer (1) from the ingot (2). This laser processing device is An oscillator (80) which is a source of the laser beam; a collector (88) disposed opposite the top surface of the ingot along the height direction so that the laser beam emitted from the oscillator is irradiated onto the top surface of the ingot to collect the laser beam inside the ingot; an optical system (83) provided in a laser optical path (BL) between the transmitter and the collector; a chuck (4) provided to support the ingot by joining with an ingot bottom surface (2b), which is the other end surface of the ingot in the height direction; a chuck moving mechanism (5) that is provided so as to be able to move a chuck table (50) that fixedly supports the chuck in an in-plane direction that intersects with the height direction; A main support base (62) that supports at least the chuck moving mechanism; Equipped with The main support table has an active vibration suppression device (62c) that operates in response to the operation of the chuck moving mechanism. do.

[0006] In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the reference symbol. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing an overview of a wafer manufacturing method using a laser processing apparatus according to an embodiment of the present invention; [Diagram 2]1 is a side view showing a schematic configuration of a laser processing apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a plan view showing a schematic configuration of the optical system shown in FIG. 2. [Figure 4] FIG. 3 is a conceptual diagram showing an overview of optical alignment in the optical system shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings. Note that, if various modified examples applicable to one embodiment are inserted in the middle of a series of explanations regarding the embodiment, understanding of the embodiment may be hindered. For this reason, the modified examples are not inserted in the middle of a series of explanations regarding the embodiment, but are explained together after that. In addition, the description of each drawing and the description of the device configuration and its functions and operations described below corresponding thereto are simplified to briefly explain the contents of the present invention, and do not limit the contents of the present invention in any way. For this reason, it goes without saying that each drawing does not necessarily match a diagram showing a specific configuration that is actually manufactured and sold. In other words, it goes without saying that the present invention should not be interpreted as being limited by the description of each drawing and the description of the device configuration and its functions and operations described below corresponding thereto, unless the applicant explicitly limits it through the prosecution history of this application.

[0009] (Wafer Manufacturing Overview) Referring to FIG. 1, the wafer 1 is obtained by slicing an ingot 2 that is substantially cylindrical in side view, that is, dividing it in the height direction, and is formed in a substantially circular thin plate shape in plan view. That is, the wafer 1 has a substantially cylindrical end face surrounding a central axis L. Similarly, the ingot 2 has a substantially cylindrical side face surrounding the central axis L. The central axis L is a virtual straight line that is parallel to the substantially cylindrical end face of the wafer 1 and the substantially cylindrical side face of the ingot 2, and passes through the axial center of the wafer 1 and the ingot 2. Note that, from the viewpoint of simplifying the illustration and explanation, the so-called orientation flat that is usually provided on the wafer 1 and the ingot 2 is not illustrated or explained in this specification.

[0010] In order to simplify the following description, the right-handed XYZ coordinate system is set as shown in the figure for convenience. In the right-handed XYZ coordinate system, the Z axis is parallel to the central axis L and is a direction that defines the wafer thickness and ingot height. That is, the Z axis direction corresponds to the thickness direction of the wafer 1 or the height direction of the ingot 2. The X axis and the Y axis are assumed to be approximately parallel to the main surface of the wafer 1 and the end surface of the ingot 2. The "main surface" is a surface that is perpendicular to the plate thickness direction of a plate-like object such as the wafer 1, and may also be referred to as the "upper surface", "lower surface", "bottom surface", or "plate surface". The direction along the main surface of the wafer 1 or the upper and lower end surfaces of the ingot 2, that is, any direction that intersects with the Z axis direction, may be referred to as the "in-plane direction" hereinafter. Typically, the main surface of the wafer 1 and the upper and lower end surfaces of the ingot 2 are approximately horizontal surfaces that are approximately perpendicular to the Z axis. Therefore, typically, an "in-plane direction" is any direction perpendicular to the Z axis, i.e., any direction parallel to the XY plane.

[0011] The wafer 1 has a pair of main surfaces, that is, a wafer front surface 1a and a wafer back surface 1b, which are substantially perpendicular to the central axis L. Similarly, the ingot 2 has a pair of end surfaces, that is, an ingot top surface 2a and an ingot bottom surface 2b, which are substantially perpendicular to the central axis L. A wafer manufacturing method for obtaining the wafer 1 from the ingot 2 includes the following steps as main processes.

[0012] (1) Peeling layer forming process: While moving the irradiation position PR of the laser beam B having a predetermined degree of transparency to the ingot 2 in the in-plane direction, the laser beam B is irradiated to the ingot top surface 2a, which is the end surface on one side in the height direction of the ingot 2. As a result, a peeling layer 2c is formed at a depth corresponding to the thickness of the wafer 1 from the ingot top surface 2a. The peeling layer 2c is composed of a modified layer in which SiC is modified by the irradiation of the laser beam B and cracks extending from this modified layer, and corresponds to the "separation layer" in Patent Document 1. Here, the "predetermined degree of transparency" is a degree of transparency that allows the focal point BP of the laser beam B to be formed at a depth corresponding to the thickness of the wafer 1 from the ingot top surface 2a inside the ingot 2. In addition, the "depth corresponding to the thickness of the wafer 1" is a dimension obtained by adding a thickness corresponding to a processing allowance in a wafer flattening process or the like described later to the thickness of the wafer 1 (i.e., a target thickness value) of the wafer 1, which is a finished product. It can also be called the "depth corresponding to the thickness of the wafer 1". The irradiation position PR of the laser beam B in the in-plane direction on the ingot top surface 2a, which is the laser irradiation surface, is scanned in a scanning direction Ds parallel to the X-axis direction, as in the forward scanning Sc1 and the return scanning Sc2 shown in FIG. 1. In addition, the irradiation position PR is index-fed in a line feed direction Df parallel to the Y-axis direction every time it is scanned once in the scanning direction Ds by the forward scanning Sc1 or the return scanning Sc2. Both the line feed direction Df and the scanning direction Ds are in-plane directions (i.e., directions along the ingot top surface 2a) and are perpendicular to each other. The peeling layer forming step forms a wafer precursor 2d between the ingot top surface 2a and the peeling layer 2c. The peeling layer 2c forms a peeling surface 2e, which is an interface when the wafer precursor 2d is peeled off from the ingot 2.

[0013] (2) Wafer peeling process: The wafer precursor 2d is peeled off from the ingot 2 at the peeling layer 2c, i.e., the peeling surface 2e, to generate the wafer 1. The back surface 1b of the wafer immediately after peeling has rough unevenness (i.e., to the extent that grinding or polishing is required) due to the peeling surface 2e.

[0014] (3) Wafer planarization process: Of the wafer front surface 1a, which is the main surface of the wafer 1, and the wafer back surface 1b, at least the wafer back surface 1b, which has unevenness due to the peeled surface 2e, is planarized to obtain a final wafer 1 having an epi-ready main surface. In the wafer planarization process, in addition to general grinding stone polishing and CMP, ECMG and ECMP can be used. Note that CMP is an abbreviation for Chemical Mechanical Polishing. ECMG is an abbreviation for Electro-Chemical Mechanical Grinding. ECMP is an abbreviation for Electro-Chemical Mechanical Polishing. The wafer planarization process can be performed by using one of these selectable multiple types of planarization methods alone, or by appropriately combining multiple methods.

[0015] (4) Ingot flattening process: The ingot top surface 2a newly generated after peeling off the wafer precursor 2d has rough unevenness (i.e., roughness requiring grinding or polishing) due to the peeling layer 2c and peeling off by the wafer peeling process. Therefore, the ingot top surface 2a is flattened, i.e., mirror-finished, so that the ingot 2 that has been subjected to the wafer peeling process can be reused in the peeling layer forming process. In the ingot flattening process, in addition to general grindstone polishing and CMP, ECMG and ECMP can be used. The ingot flattening process can also be performed by using one of these selectable flattening methods alone or by appropriately combining multiple methods.

[0016] (Laser processing equipment) 2 and 3 show a schematic configuration of the laser processing device 3 used in the peeling layer forming process. The configuration of the laser processing device 3 will be described below with reference to FIG. 2 and FIG. 3. The laser processing device 3 is configured to irradiate a laser beam B having transparency to the ingot top surface 2a, which is an end surface on one side in the height direction of the ingot 2, in order to obtain a wafer 1 from the ingot 2. Specifically, as shown in FIG. 2, the laser processing device 3 includes a chuck 4, a chuck moving mechanism 5, a support means 6, a measuring device 7, a laser irradiation device 8, and a control unit 9. Each part constituting the laser processing device 3 will be described below in order. Note that the right-handed XYZ coordinates shown in FIG. 2 and FIG. 3 are displayed so as to match the right-handed XYZ coordinates shown in FIG. 1. In addition, in this embodiment, the positive direction of the Z axis is assumed to point vertically upward. In other words, the negative direction of the Z axis is assumed to be the same direction as or approximately the same direction as the direction of gravity.

[0017] (Chuck) First, referring to FIG. 2, the chuck 4 is provided to support the ingot 2 with the ingot top surface 2a exposed upward by bonding with the ingot bottom surface 2b, which is the other end surface in the height direction of the ingot 2. Specifically, the chuck 4 has a chuck surface 41 exposed upward when the ingot 2 is not supported. The chuck surface 41 bonded with the ingot bottom surface 2b has good flatness and is provided so as to be approximately parallel to the XY plane. The chuck 4 is adapted to fixedly support the ingot 2 on the chuck surface 41 by a well-known method (i.e., for example, suction or adhesion by negative pressure). The chuck 4 is fixedly supported on the upper surface of a chuck table 50 provided in the chuck moving mechanism 5.

[0018] (Chuck movement mechanism) The chuck moving mechanism 5 is configured to be movable in an in-plane direction while fixedly supporting the chuck 4. Specifically, the chuck moving mechanism 5 includes a chuck table 50, a first slide mechanism 51, and a second slide mechanism 52. The chuck table 50 is formed in a plate shape having a plate thickness direction in the Z-axis direction, and fixedly supports the chuck 4 on a main surface exposed upward by screwing, bonding, or the like. The first slide mechanism 51 is configured to be capable of reciprocating the chuck table 50 in a first direction, which is an in-plane direction, i.e., the X-axis direction. The second slide mechanism 52 is configured to be capable of reciprocating the chuck table 50 in a second direction, which is an in-plane direction and different from the first direction, i.e., the Y-axis direction. Specifically, the first slide mechanism 51 and the second slide mechanism 52 each have a configuration as a so-called ball screw-driven uniaxial stage.

[0019] (Support means) The support means 6 forming the basic structure of the laser processing device 3 has an oscillator support table 61 and a main support table 62. The oscillator support table 61 and the main support table 62 are provided separately and independently from each other so that direct vibration transmission does not occur. The main support table 62 is configured to support the chuck moving mechanism 5 and the measuring device 7 from below, and to support a part of the laser irradiation device 8. Specifically, the main support table 62 has a surface plate portion 62a, a pedestal portion 62b, and an active vibration control device 62c. As the surface plate portion 62a, for example, a stone surface plate that is less affected by deformation and dimensional change due to temperature change and has excellent physical and mechanical strength can be suitably used. Such a stone surface plate can be formed of, for example, granite (i.e., mica stone) or the like. The surface plate portion 62a on which the chuck moving mechanism 5 and the like are placed is formed in a thick plate shape, and the levelness of the upper and lower plate surfaces is precisely finished. The base portion 62a is supported from below by a base portion 62b having an active vibration suppression device 62c having a vibration suppression function. The active vibration suppression device 62c has a known configuration and is provided so as to operate in response to the operation of the chuck moving mechanism 5.

[0020] (Measuring Equipment) The measuring device 7 is a device that measures the ingot height, which is the height of the ingot 2 to be processed by the laser processing device 3, and is disposed on one side (i.e., the Y-axis negative side in the configuration example shown in FIG. 2) of the range in which the chuck table 50 can be moved along the Y-axis direction by the second slide mechanism 52. That is, the measuring device 7 and the laser irradiating device 8 are provided adjacent to each other along the Y-axis direction. The laser processing device 3 is configured to irradiate the ingot top surface 2a with a laser beam B having transparency by the laser irradiating device 8 based on the ingot height measured by the measuring device 7 in order to obtain a wafer 1 from the ingot 2.

[0021] (Laser irradiation device) The laser irradiation device 8 is disposed on the other side (i.e., the Y-axis positive side in the configuration example shown in FIG. 2) of the range in which the chuck table 50 can be moved by the second slide mechanism 52 in the Y-axis direction. The laser irradiation device 8 is configured to irradiate the laser beam B output from an oscillator 80, which is a source of the laser beam B, downward in the figure toward the ingot 2 held by the chuck 4. Specifically, the laser irradiation device 8 includes the oscillator 80, a first introduction mirror 81, a second introduction mirror 82, an optical system 83, an optical system stage 84, an optical system guide body 85, a stage moving mechanism 86, a stage position scale 87, and a condenser 88. The configuration of each part constituting the laser irradiation device 8 will be described below in order.

[0022] The transmitter 80 is supported in a vibration-proof manner by a transmitter support base 61 different from the main support base 62, and is provided so as to emit the laser beam B in a substantially horizontal direction. The first introduction mirror 81 is a reflecting mirror provided so as to have the same optical axis height as the transmitter 80, and is provided so as to change the traveling direction of the laser beam B emitted from the transmitter 80 from a substantially horizontal direction to a substantially vertical direction toward the second introduction mirror 82 above. The first introduction mirror 81 is fixedly supported by the main support base 62 so as to be adjustable in tilt angle. The second introduction mirror 82 is a reflecting mirror provided so as to have the same optical axis height as the optical system 83, and is provided so as to change the traveling direction of the laser beam B from the first introduction mirror 81 to a substantially horizontal direction toward the optical system 83. The second introduction mirror 82 is provided so as to be adjustable in tilt angle, and is supported by the main support base 62 by being fixed to an optical system stage 84 that supports the optical system 83 from below. That is, the transmitter 80 is provided so as to have a different optical axis height from the optical system 83.

[0023] The optical system 83 is provided in the laser light path BL between the transmitter 80 and the condenser 88. The configuration of the optical system 83 will be described in detail later. The optical system 83 is installed on the upper main surface of an optical system stage 84 formed in a plate shape having a plate thickness direction in the Z-axis direction by a material such as a metal having rigidity. That is, the optical system 83 is supported from below by the optical system stage 84. The optical system stage 84 is provided with through holes through which a plurality of optical system guide bodies 85, which are rod-shaped members extending in the Z-axis direction, penetrate. The optical system guide body 85 is provided so that its lower end is supported by the main support base 62 and its upper end penetrates the optical system stage 84 and protrudes upward by a predetermined amount. At least four optical system guide bodies 85 are arranged so as to be located on the corners or sides of a rectangle in a plan view seen from above with a line of sight parallel to the Z-axis direction. The optical system stage 84 is provided so as to be movable up and down along the Z-axis direction while being guided by the plurality of optical system guide bodies 85. The stage moving mechanism 86 is a ball screw mechanism configured to move the optical system stage 84 up and down in the Z-axis direction, i.e., along the height direction of the ingot 2. The stage position scale 87 is configured as a linear scale for detecting the position of the optical system stage 84 in the Z-axis direction.

[0024] The condenser 88 is supported by the optical system stage 84 so as to move up and down together with the optical system 83 and the optical system stage 84 by driving the stage moving mechanism 86. The condenser 88 is equipped with an optical element such as an objective lens, and is configured to form a focal point BP at a predetermined depth from the ingot top surface 2a when the laser beam B is irradiated toward the ingot 2 located below. That is, the condenser 88 is arranged to face the ingot top surface 2a along the height direction of the ingot 2 so that when the chuck table 50 reaches a predetermined processing area while the chuck 4 is supporting the ingot 2, the laser beam B emitted from the transmitter 80 is irradiated to the ingot top surface 2a, and the laser beam B is condensed inside the ingot 2. In this way, the laser irradiation device 8 has a configuration in which the laser beam B emitted from the transmitter 80 on the first floor is launched upward toward the second floor by the first introduction mirror 81, introduced into the optical system 83 located on the second floor by the second introduction mirror 82, and shot down downward by the condenser 88.

[0025] (optical system) Hereinafter, the configuration of each part constituting the optical system 83 will be described with reference to Fig. 3 in addition to Fig. 2. As shown in Fig. 3, the optical system 83 includes an optical axis alignment mechanism 831, a beam profiler 832, a detection unit 833, a beam characteristic adjustment unit 834, and a switching unit 835.

[0026] The optical axis alignment mechanism 831 is configured to operate so as to adjust the alignment state of the optical axis inside the optical system 83 in the laser optical path BL based on the detection result of the detection unit 833 described later. Specifically, the optical axis alignment mechanism 831 includes a first optical axis adjustment mirror 831a, a first optical axis adjustment actuator 831b, a second optical axis adjustment mirror 831c, and a second optical axis adjustment actuator 831d. The first optical axis adjustment mirror 831a is a reflecting mirror provided to change the traveling direction of the laser beam B that has passed through the second introduction mirror 82 toward the second optical axis adjustment mirror 831c, and is provided so that the tilt angle can be adjusted around two axes by the operation of the first optical axis adjustment actuator 831b. The second optical axis adjustment mirror 831c is a reflecting mirror provided to change the traveling direction of the laser beam B that has passed through the first optical axis adjustment mirror 831a toward the beam characteristic adjustment unit 834, and is provided so that the tilt angle can be adjusted around two axes by the operation of the second optical axis adjustment actuator 831d. The first optical axis adjustment actuator 831b and the second optical axis adjustment actuator 831d may be configured using, for example, a piezo motor or the like. The beam profiler 832 is provided so as to be able to detect the beam intensity and spatial distribution of the laser beam B. In this embodiment, the beam profiler 832 is disposed at a position between the second optical axis adjustment mirror 831c and the beam characteristics adjustment unit 834 in the laser optical path BL, more specifically, at a position between the second optical axis adjustment mirror 831c and the first beam splitter 833a in the detection unit 833.

[0027] The detection unit 833 is provided to detect the alignment state of the optical axis inside the optical system 83 in the laser optical path BL. Specifically, the detection unit 833 includes a first beam splitter 833a, a second beam splitter 833b, a first detector 833c, and a second detector 833d. The first beam splitter 833a is provided at a position between the second optical axis adjustment mirror 831c and the beam characteristic adjustment unit 834 in the laser optical path BL, more specifically, at a position between the beam profiler 832 and the beam characteristic adjustment unit 834. The first beam splitter 833a is provided to pass most of the laser beam B (for example, about 90%) that has passed through the second optical axis adjustment mirror 831c toward the beam characteristic adjustment unit 834, and to allow the remaining portion (for example, about 10%) to proceed toward the second beam splitter 833b. The second beam splitter 833b is provided so as to pass half of the laser beam B introduced from the first beam splitter 833a toward the first detector 833c and to cause the remaining half to proceed toward the second detector 833d. The first detector 833c and the second detector 833d are, for example, two-dimensional optical sensors made of CMOS or CCD, and are configured to generate an output according to the position and intensity of the received laser beam B. CMOS is an abbreviation for Complementary Metal Oxide Semiconductor. CCD is an abbreviation for Charge Coupled Device.

[0028] The beam characteristic adjustment unit 834 has a function of adjusting beam characteristics of the laser beam B other than the optical axis. Specifically, the beam characteristic adjustment unit 834 includes, for example, a beam expander that expands the beam diameter of the laser beam B, a spatial light modulator that modulates the laser beam B, and the like. The switching unit 835 is provided in the laser optical path BL so as to be capable of switching between traveling of the laser beam B to the condenser 88 and blocking the laser beam B. The switching unit 835 can be configured with, for example, a shutter, a polarizing plate, an acousto-optic element (i.e., AOM), an electro-optic modulator (i.e., EOM), and the like. AOM is an abbreviation for Acousto-Optic Modulator. EOM is an abbreviation for Electro-Optic Modulator.

[0029] (Control unit) 2 again, the control unit 9 is provided to control the overall operation of the laser processing apparatus 3. In this embodiment, the control unit 9 has a configuration as a so-called microcomputer equipped with a processor and a memory, and controls the operation of each part in the laser processing apparatus 3 by reading and starting a program prestored in the memory by the processor. The "memory" is a non-transient tangible storage medium such as a ROM, a magnetic disk, an optical disk, a flash memory, etc. At least one processor and one memory are provided.

[0030] The control unit 9 controls the operation of the first slide mechanism 51 and the second slide mechanism 52 in the chuck moving mechanism 5 to move and set the position of the chuck 4, i.e., the ingot 2, to a desired position in the XY plane. The control unit 9 also controls the operation of the measuring device 7 to measure the ingot height, and controls the operation of the stage moving mechanism 86 based on the ingot height measured by the measuring device 7 to adjust the position of the condenser 88 in the Z-axis direction in order to adjust the focal position of the laser beam B.

[0031] The control unit 9 is adapted to control the generation and stopping of the laser beam B in the transmitter 80. In addition, the control unit 9 is adapted to control the switching unit 835 to switch between traveling of the laser beam B to the condenser 88 and blocking it.

[0032] The control unit 9 also controls the operation of each unit in the optical system 83 to adjust the beam shape, optical axis, and the like of the laser beam B. Specifically, the control unit 9 acquires a detection result of the alignment state of the optical axis in the laser optical path BL based on the output of the detection unit 833, i.e., the first detector 833c and the second detector 833d. The control unit 9 then adjusts the alignment state of the optical axis in the laser optical path BL by controlling the operation of the optical axis alignment mechanism 831 based on the detection result of the detection unit 833. Furthermore, the control unit 9 as an output state acquisition unit acquires a time-dependent fluctuation state of the output of the laser beam B irradiated from the collector 88 to the ingot top surface 2a based on the output of the beam profiler 832 and / or the detection unit 833.

[0033] (operation) Hereinafter, an outline of the operation of the laser processing device 3 having the above-mentioned configuration will be described together with the effects achieved by this configuration with reference to the drawings.

[0034] First, the control unit 9 controls the operation of the second slide mechanism 52 in the chuck moving mechanism 5 to set the position of the chuck table 50 in the Y-axis direction within the measurement area, as shown in Fig. 2. In the measurement area, the ingot 2 fixed to the chuck 4 is positioned directly below a measurement unit (not shown) provided in the measurement device 7. Then, in this measurement area, the control unit 9 measures the ingot height by the measurement device 7.

[0035] When the measurement of the ingot height is completed, the control unit 9 controls the operation of the second slide mechanism 52 in the chuck movement mechanism 5 to set the position of the chuck table 50 in the Y-axis direction within the processing area. In the processing area, the ingot 2 fixed to the chuck 4 is located directly below the condenser 88. Then, the control unit 9 controls the operation of the stage movement mechanism 86 based on the measurement result of the ingot height to set the height of the condenser 88, i.e., the position in the Z-axis direction, so that the depth of the focal point BP from the ingot top surface 2a is a predetermined depth. Then, the control unit 9 irradiates the ingot top surface 2a with the laser beam B while controlling the operation of the first slide mechanism 51 and the second slide mechanism 52 in the chuck movement mechanism 5 to form a peeling layer 2c.

[0036] FIG. 1 shows the irradiation and scanning of the laser beam B on the ingot 2. Since the illustration shows the relative movement of the condenser 88 and the irradiation position PR with respect to the ingot 2, the condenser 88 and the irradiation position PR appear to move in the XY direction. However, in reality, in the laser processing device 3 according to this embodiment, the condenser 88, i.e., the irradiation position PR, is stationary in the XY direction. Meanwhile, the ingot 2 moves in the XY direction by the operation of the chuck movement mechanism 5. As shown in FIG. 1, in the peeling layer formation process, an outward scan Sc1 in which the condenser 88 moves relative to the ingot 2 in a first direction parallel to the X axis, and a return scan Sc2 in which the condenser 88 moves relative to the ingot 2 in a second direction parallel to the X axis and opposite to the first direction, are alternately repeated. In addition, between the outward scan Sc1 and the return scan Sc2, an index feed is performed in which the chuck table 50 is fed a predetermined small amount in the Y axis direction. The irradiation of the laser beam B is performed intermittently within the region of the ingot top surface 2a during at least one of the forward scan Sc1 and the return scan Sc2. That is, during one forward scan Sc1 and / or return scan Sc2, irradiation of the laser beam B is performed multiple times at predetermined intervals. Note that the scanning of the laser beam B during one forward scan Sc1 or return scan Sc2 is hereinafter referred to as "laser scanning".

[0037] In laser slicing, which requires high precision, if there is an error, fluctuation, or variation in the depth of the focal point BP of the laser beam B from the top surface 2a of the ingot, the processing cost for grinding and polishing the peeled surface 2e increases, and the yield of the material deteriorates, resulting in a decrease in productivity. Examples of such factors include misalignment of the optical axis caused by vibrations and heat during operation of the device. The misalignment of the optical axis caused by vibrations and heat during operation of the device changes from moment to moment. For this reason, it is necessary to adjust the optical axis in real time simultaneously with processing, but such an apparatus configuration has not yet been proposed in the field of laser slicing.

[0038] In adjusting the optical axis, it is important to consider whether the optical axis is perpendicular to the top surface 2a of the ingot and whether the beam spot shape at the processing point is appropriate. The basis of these adjustments is which point in space the laser beam B should pass through and at what angle it should be emitted. Figure 4 shows an overview of the optical axis adjustment of the laser beam B passing through the first optical axis adjustment mirror 831a and the second optical axis adjustment mirror 831c. As shown in Figure 4, it is possible to monitor the optical axis adjustment state by detecting the beam positions Σ1[x1,y1] and Σ2[x2,y2], which are the passing points of the laser beam B on the virtual planes Σ1 and Σ2 set at different positions in the traveling direction of the laser beam B that has passed through the second optical axis adjustment mirror 831c.

[0039] Therefore, in this embodiment, as shown in Fig. 3, a detection unit 833 is provided inside the optical system 83 in the laser optical path BL, and an alignment state of the optical axis in the optical system 83 in the laser optical path BL is detected using a first beam splitter 833a and a second beam splitter 833b provided at different positions in the detection unit 833, and a first detector 833c and a second detector 833d provided corresponding to the first beam splitter 833a and the second detector 833d. With this configuration, the control unit 9 can detect the alignment state of the optical axis in the laser optical path BL in real time using the detection unit 833, and can correct the alignment state of the optical axis in real time by controlling the operation of the optical axis alignment mechanism 831 based on the detection result. Therefore, according to this embodiment, it is possible to improve productivity more than ever in the wafer manufacturing technology in which a wafer 1 is obtained from an ingot 2 by laser slicing.

[0040] In addition, the depth of the focal point BP of the laser beam B may vary due to a change in the output of the laser beam B. In this embodiment, the control unit 9 acquires the time-dependent change in the output of the laser beam B irradiated from the condenser 88 to the ingot top surface 2a. When forming the peeling layer 2c, the laser beam B is irradiated in pulses at predetermined time intervals while the ingot 2 and the condenser 88 move relatively in the in-plane direction. Therefore, the control unit 9 can obtain surface information of the output distribution of the laser beam B by monitoring the output of the laser beam B for each of the multiple irradiation positions PR arranged two-dimensionally. Such surface information corresponds to the grinding and polishing processing allowance of the wafer back surface 1b corresponding to the peeling surface 2e. Therefore, according to this embodiment, it is possible to control the grinding and polishing processing allowance for each wafer 1.

[0041] When forming the peeling layer 2c, the laser beam B is irradiated in a pulsed manner as described above. In addition, in the forward scanning Sc1 and the backward scanning Sc2, the laser beam B is not usually irradiated outside the range of the ingot top surface 2a in the in-plane direction. Furthermore, the laser beam B may be irradiated only in one of the forward scanning Sc1 and the backward scanning Sc2. In this regard, in this type of laser processing device 3, a device configuration or function for stabilizing the output of the laser beam B is usually installed, but when the emission of the laser beam B is controlled on and off by the oscillator 80, it takes a certain amount of time from the start of irradiation until the output stabilizes. That is, the rise of the output when it is on is not an ideal rectangular wave shape, and it is normal for a rise time lag or overshoot to occur in the output as a transient phenomenon during the rise period. Therefore, in this embodiment, the on and off of the irradiation of the laser beam B is controlled using a switching unit 835 provided in the laser optical path BL that can switch between traveling to the condenser 88 and blocking the laser beam B. Specifically, while the oscillator 80 continuously emits the laser beam B, the switching unit 835 can be used to switch between traveling of the laser beam B to the condenser 88, i.e., the top surface 2a of the ingot, and blocking the laser beam B. This makes it possible to effectively suppress errors, fluctuations, and variations in the depth of the condensing point BP of the laser beam B caused by fluctuations in the output of the laser beam B.

[0042] When forming a peeling layer 2c on the ingot 2 by irradiating the laser beam B while driving the chuck moving mechanism 5, which is an XY stage, the number of reciprocating movements of the chuck table 50 in the X-axis direction for laser scanning becomes very large. For this reason, from the viewpoint of improving productivity, it is essential to perform the laser scanning as quickly as possible. On the other hand, vibration occurs when the chuck moving mechanism 5 is driven. Therefore, if the laser scanning is performed at high speed to shorten the cycle time, there is a concern that the optical axis may be misaligned due to the influence of vibration. In this regard, in the conventional concept, the vibration control unit itself is closed in control, and the control input for vibration control is created from the signal of the displacement sensor or the like that the unit has. For this reason, the timing of starting vibration control is inevitably delayed with respect to the occurrence of vibration due to acceleration and deceleration. Therefore, in this embodiment, the main support table 62 that supports the chuck moving mechanism 5 is provided with an active vibration control device 62c that operates in response to the operation of the chuck moving mechanism 5. The control unit 9 controls the operation of the active vibration damping device 62c together with the operation of the chuck moving mechanism 5, and controls the vibration damping operation in the active vibration damping device 62c using known information on acceleration and deceleration in the chuck moving mechanism 5. This makes it possible to perform vibration damping without time delay, and can effectively suppress errors, fluctuations, and variations in the depth of the focal point BP of the laser beam B.

[0043] When active vibration control is performed, the vibration of the point to be controlled approaches zero, and in exchange, vibration occurs in other parts. That is, in this embodiment, the vibration of the chuck table 50, i.e., the ingot 2, is controlled, while vibration occurs in other parts. At this time, if the transmitter 80 is mounted on the vibrating body, it will lead to damage, so two places, the transmitter 80 and the processing part, are targets for vibration isolation. However, if the first introduction mirror 81, which is a mirror for launching the laser beam B, is attached to the mounting side of the transmitter 80, the first introduction mirror 81 vibrates while the second introduction mirror 82 does not vibrate, so the laser beam B entering the optical system 83 will vibrate. In this regard, in this embodiment, the first introduction mirror 81 and the second introduction mirror 82 are mounted on the same vibrating body, so that the largest vibration in the X-axis direction can be canceled. Then, by removing only the minute vibrations that remain after this by the optical axis alignment mechanism 831, it is possible to effectively suppress the misalignment of the optical axis and the error, fluctuation, and variation in the depth of the focal point BP of the laser beam B caused by the influence of the vibrations accompanying the driving of the chuck moving mechanism 5.

[0044] (Modification) The present invention is not limited to the above embodiment. Therefore, the above embodiment can be modified as appropriate. Representative modified examples will be described below. In the following description of the modified examples, differences from the above embodiment will be mainly described. In addition, the same reference numerals are used for parts that are the same or equivalent to each other in the above embodiment and the modified examples. Therefore, in the following description of the modified examples, the description of the above embodiment can be appropriately used for components having the same reference numerals as the above embodiment, unless there is a technical contradiction or special additional explanation.

[0045] The present invention is not limited to the specific configurations shown in the above embodiments. For example, the positive direction of the Z axis does not have to be vertically upward. In other words, the positive direction of the Z axis may be a direction that intersects with the vertically upward direction, which is the opposite direction to the direction of gravity.

[0046] The first slide mechanism 51 may be configured to be capable of moving the chuck table 50 in the X and Y directions. In other words, unlike the second slide mechanism 52 which is a coarse movement mechanism capable of moving the chuck table 50 in the Y-axis direction over a relatively long distance, the first slide mechanism 51, which has a relatively short movable range approximately equal to the outer diameter of the ingot 2, may be given the function of a fine movement mechanism in the Y-axis direction. This allows the feed amount of the chuck table 50, i.e., the ingot 2, in the Y-axis direction to be controlled more precisely during measurement by the measuring device 7 and during processing by the laser irradiation device 8.

[0047] There is no particular limitation on the types of motors for the first slide mechanism 51, the second slide mechanism 52, the stage moving mechanism 86, etc. That is, for example, a linear motor may be used.

[0048] The function of the control unit 9 to control the operation of the active vibration damping device 62c may be provided on the side of a controller (not shown) built into the active vibration damping device 62c itself.

[0049] The configuration of the optical system 83 is not limited to the specific example shown in the above embodiment. That is, for example, the reflecting mirrors provided in the optical axis alignment mechanism 831 are not limited to two, the first optical axis adjustment mirror 831a and the second optical axis adjustment mirror 831c, as in the above embodiment. Similarly, the set of the mirror for adjusting the optical axis and the actuator is not limited to two sets as in the above embodiment. The second beam splitter 833b may be provided between the beam characteristic adjustment unit 834 and the condenser 88. The interposition position of the switching unit 835 may be between the second introduction mirror 82 and the first optical axis adjustment mirror 831a as shown in FIG. 3, between the second optical axis adjustment mirror 831c and the beam characteristic adjustment unit 834, within the beam characteristic adjustment unit 834, or between the beam characteristic adjustment unit 834 and the condenser 88.

[0050] In the above description, a plurality of components that were formed seamlessly and integrally with each other may be formed by bonding separate members together. Similarly, a plurality of components that were formed by bonding separate members together may be formed seamlessly and integrally with each other. Furthermore, in the above description, a plurality of components that were formed from the same material may be formed from different materials together. Similarly, a plurality of components that were formed from different materials together may be formed from the same material together.

[0051] Needless to say, the elements constituting the above-mentioned embodiment are not necessarily essential, except when expressly stated as essential or when considered to be obviously essential in principle. Furthermore, when the numbers, amounts, ranges, etc. of the components are mentioned, the present invention is not limited to the specific values, except when expressly stated as essential or when clearly limited to a specific value in principle. Similarly, when the shapes, directions, positional relationships, etc. of the components are mentioned, the present invention is not limited to the shapes, directions, positional relationships, etc., except when expressly stated as essential or when clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0052] The modified examples are not limited to the above examples. In addition, multiple modified examples may be combined with each other unless technically inconsistent. [Explanation of symbols]

[0053] 1 wafer 2 Ingots 2a Top surface of ingot 3 Laser processing equipment 80 Transmitter 83 Optical system 831 Optical axis alignment mechanism 833 Detector 88 Concentrator 9. Control Unit

Claims

1. A laser processing device (3) for irradiating a laser beam having transparency onto a top surface (2a) of an ingot (2), which is an end surface on one side in a height direction of the ingot, in order to obtain a wafer (1) from the ingot, comprising: An oscillator (80) which is a source of the laser beam; a collector (88) disposed opposite the top surface of the ingot along the height direction so that the laser beam emitted from the oscillator is irradiated onto the top surface of the ingot to collect the laser beam inside the ingot; an optical system (83) provided in a laser optical path (BL) between the transmitter and the collector, the optical system (83) including a detection unit (833) for detecting an alignment state of an optical axis in the laser optical path, and an optical axis alignment mechanism (831) configured to operate so as to adjust the alignment state based on a detection result of the detection unit; A control unit (9) that adjusts the alignment state by controlling the operation of the optical axis alignment mechanism based on the detection result of the detection unit; a chuck (4) configured to support the ingot by joining with an ingot bottom surface (2b), which is the other end surface of the ingot in the height direction; a chuck moving mechanism (5) that is provided so as to be able to move a chuck table (50) that fixedly supports the chuck in an in-plane direction that intersects with the height direction; A main support base (62) that supports at least the chuck moving mechanism; Equipped with The main support table has an active vibration control device (62c) that operates in response to the operation of the chuck moving mechanism. Laser processing equipment.

2. the control unit acquires a time-dependent fluctuation state of the output of the laser beam irradiated from the collector onto the top surface of the ingot.

2. The laser processing apparatus according to claim 1.

3. The laser beam may further include a switching unit (835) provided in the laser optical path so as to be capable of switching between traveling to the condenser and blocking the laser beam; The control unit controls switching between propagation and blocking of the laser beam to the condenser in the switching unit.

3. The laser processing apparatus according to claim 1 or 2.

4. A laser processing device (3) for irradiating a laser beam having transparency onto a top surface (2a) of an ingot (2), which is an end surface on one side in a height direction of the ingot, in order to obtain a wafer (1) from the ingot, comprising: An oscillator (80) which is a source of the laser beam; a collector (88) disposed opposite the top surface of the ingot along the height direction so that the laser beam emitted from the oscillator is irradiated onto the top surface of the ingot to collect the laser beam inside the ingot; an optical system (83) provided in a laser optical path (BL) between the transmitter and the collector; a chuck (4) configured to support the ingot by joining with an ingot bottom surface (2b), which is the other end surface of the ingot in the height direction; a chuck moving mechanism (5) that is provided so as to be able to move a chuck table (50) that fixedly supports the chuck in an in-plane direction that intersects with the height direction; A main support base (62) that supports at least the chuck moving mechanism; Equipped with The main support table has an active vibration control device (62c) that operates in response to the operation of the chuck moving mechanism. Laser processing equipment.

5. The transmitter is supported by a transmitter support base (61) different from the main support base, and is disposed so that the optical axis height is different from that of the optical system, a first introduction mirror (81) which is a reflecting mirror provided so as to be at the same optical axis height as the transmitter; A second introduction mirror (82) which is a reflecting mirror provided so as to be at the same optical axis height as the optical system; Further equipped with the first introduction mirror and the second introduction mirror are supported by the main support base, the first introduction mirror is provided to direct the laser beam emitted from the oscillator to the second introduction mirror, The second introduction mirror is provided to direct the laser beam from the first introduction mirror to the optical system. The laser processing device according to any one of claims 1 to 4.

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