Laser processing apparatus

Abstract

To provide a laser processing apparatus capable of suppressing misalignment between laser beams due to stage position.SOLUTION: A laser processing apparatus according to the embodiment comprises: an optical system having a laser light-emitting laser light source, an optical forming element forming a processing laser light from the laser light and a focusing lens for focusing processing laser light onto the workpiece; a stage holding the workpiece; a transfer mechanism for transferring the workpiece; a base plate arranging the transfer mechanism; a deformation measurement mechanism for measuring the amount of deformation of the base plate; and a posture adjustment mechanism for applying stress to the base plate to restore the deformation amount based on the results measured by the deformation measurement mechanism.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a laser processing apparatus. [Background technology]

[0002] In the field of semiconductors, wafers (semiconductor wafers) are known that form multiple devices using a laminate consisting of a low-dielectric-constant insulating film (low-k film) and a functional film that forms circuits on the surface of a substrate such as silicon.

[0003] In such a wafer, a plurality of devices are partitioned in a lattice pattern by lattice streets, and the individual devices are manufactured by dividing the wafer along the planned dividing lines.

[0004] Low-k films tend to peel easily, so dicing using a blade can result in the film peeling off. To address this issue, there is a method in which two first grooves that divide the low-k film are formed on both sides of the intended separation area using laser ablation, and then a second groove is formed between the two first grooves.

[0005] When performing laser processing on a workpiece, it is required that the processing time be short and that the thermal impact on divided devices be suppressed. To shorten the processing time, it is possible to perform the processing in one pass, but in this case the energy per beam must be increased. Increasing the energy per beam makes it easier for heat to be generated during laser processing, increasing the impact on the device. On the other hand, in order to reduce the thermal impact on the device, it is possible to reduce the energy per beam and perform laser processing in multiple passes. However, in this case it becomes difficult to shorten the processing time.

[0006] Patent Document 1 discloses a laser processing device that, as a technology capable of maintaining the processing quality of the processed groove while preventing an increase in takt time, includes a branching element that branches a second laser beam into multiple branched beams along the processing feed direction, and a second condenser lens that focuses the multiple branched beams branched by the branching element onto the street to be processed. The laser processing device satisfies the following relationship: L is the branching distance, which is the distance between adjacent leading and trailing spots among the spots of each branched beam focused onto the street by the second condenser lens; V is the processing speed, which is the speed of relative movement; and τ is the time until the trailing spot overlaps the processing position of the leading spot. When τ1 is the threshold time at which a deterioration in the processing quality of the second groove occurs, the device satisfies the following relationship: τ=L / V. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-71402 Summary of the Invention [Problem to be solved by the invention]

[0008] The stage on which the workpiece (wafer) is placed is placed on a base plate supported by a platform. Changing the position of the stage for laser processing fluctuates the load distribution on the base plate, which deforms the base plate and causes misalignment at the processing point. When a single laser light source is used to form the first and second grooves, the misalignment at each processing point is roughly the same even if the stage position causes deformation in the device's posture or optical system. However, when processing is performed using multiple branched laser beams, as in Patent Document 1, the processing point (spot) position differs in the processing direction, so the laser beam misalignment due to the stage position is not uniform. Depending on the stage position, the laser beam misalignment at each processing point differs. Furthermore, when multiple laser light sources are used, there are two or more optical paths to each processing point, and therefore the laser beam misalignment due to the stage position is independent of each other. Similarly, the laser beam misalignment at each processing point differs depending on the stage position.

[0009] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a laser processing apparatus that can suppress deviations between laser beams due to stage positions. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention proposes the following means. <1> The laser processing apparatus according to aspect 1 of the present invention comprises: a laser light source that emits laser light; a light forming element that forms a processed laser beam from the laser beam; a condenser lens that condenses the processing laser light onto a workpiece; an optical system comprising: a stage for fixing the workpiece; a movement mechanism that moves the stage; a base plate on which the movement mechanism is disposed; a deformation amount measuring mechanism for measuring the deformation amount of the base plate; an attitude adjustment mechanism that applies stress to the base plate so as to return the amount of deformation to its original value based on the result of measurement by the deformation amount measurement mechanism; Equipped with. <2> A second aspect of the present invention is the laser processing apparatus of the first aspect, The optical system may include a sensing means for measuring a deviation of the optical system. <3> A third aspect of the present invention is the laser processing apparatus of the second aspect, Based on the results measured by the deformation amount measuring mechanism, stress may be applied to the base plate to restore the deformation amount, and then the posture adjustment may be completed by confirming that the deviation has been corrected by the sensing means. <4> A fourth aspect of the present invention may be such that, in the laser processing apparatus of the second or third aspect, a deviation derived from the position of the stage is detected from among the deviations, and the attitude adjustment mechanism is operated based on the deviation derived from the position. [Effects of the Invention]

[0011] According to the above aspects of the present invention, it is possible to provide a laser processing device that can suppress deviations between the laser beams due to the stage position. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic perspective view of a laser processing device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the area surrounded by the two-dot chain line in FIG. [Figure 3] FIG. 2 is a plan view of a wafer that is a workpiece. [Figure 4] FIG. 10 is an explanatory diagram for explaining laser processing along the outgoing direction X1. [Figure 5] 10 is an explanatory diagram for explaining laser processing along the backward direction X2. FIG. [Figure 6] FIG. 2 is a plan view of the laser processing apparatus of FIG. [Figure 7] FIG. 1 is a block diagram illustrating an example of a laser optical system. [Figure 8]10A and 10B are diagrams for explaining the deviation amount and deviation angle of laser light; [Figure 9] 1 is a flowchart of a laser processing method according to an embodiment of the present invention. [Figure 10] FIG. 10 is a schematic perspective view of a first modified example of the laser processing device. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser processing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0014] [Laser processing overview] In this embodiment, the laser processing time can be shortened by splitting the processing laser beam emitted from the laser light source into multiple beams. Furthermore, the deformation of the base plate caused by the movement of the stage position (fluctuation in load distribution) during processing is measured by the deformation amount measurement mechanism, and based on the measurement results by the deformation amount measurement mechanism, stress is applied to the base plate using the posture adjustment mechanism to restore the deformation (deformation amount) of the base plate. This reduces the misalignment between the laser beams.

[0015] First Embodiment [Laser processing equipment] Next, an example of a laser processing apparatus will be described with reference to Figures 1 and 2. Figure 2 is an enlarged view of the area surrounded by the two-dot chain line in Figure 1 near the attitude adjustment mechanism 70A. Enlarged views near the other attitude adjustment mechanisms 70B and 70C are omitted, but the same reference numerals are used for the components of the other attitude adjustment mechanisms 70B and 70C.

[0016] FIG. 1 is a schematic perspective view of a laser processing apparatus according to one embodiment of the present invention. As shown in FIG. 1, the laser processing apparatus 1 performs laser processing (laser ablation processing) on ​​a wafer W1 as a pre-process before dividing the wafer W1 into a plurality of chips C (see FIG. 3). Here, the X direction, Y direction, and Z direction in the figure are defined. The X direction and Y direction are directions along the surface W1a of the wafer W1, which will be described later. The Y direction is a direction that intersects (e.g., is perpendicular to) the X direction. The Z direction is a direction that intersects (e.g., is perpendicular to) the X direction and the Y direction, and is the thickness direction of the wafer W1. The X direction corresponds to the processing feed direction in the present invention.

[0017] Figure 3 is a plan view of a wafer W1, which is a workpiece. As shown in Figure 3, the wafer W1 is a laminate in which a low-k film and a functional film that forms a circuit are laminated on the surface of a substrate such as silicon. The wafer W1 is divided into multiple regions by multiple streets S (planned division lines) arranged in a grid pattern. Each of these divided regions is provided with a device D that constitutes a chip C.

[0018] The laser processing device 1 performs laser processing on the wafer W1 along each street S, as indicated by the parenthesized numbers (1) to (4) in the figure, thereby removing the low-k film, part of the base material, etc.

[0019] At this time, in order to reduce the processing time of the laser processing of the wafer W1, the laser processing apparatus 1 may alternately switch the relative movement direction when moving the laser optical system 14 described below in the X direction relative to the wafer W1 for each street S.

[0020] For example, when laser processing is performed along odd-numbered streets S such as those indicated by parenthesized numbers (1) and (3) in Fig. 3, the laser optical system 14 is moved relative to the wafer W1 in a forward direction X1, which is one side in the X direction. When laser processing is performed along even-numbered streets S such as those indicated by parenthesized numbers (2) and (4) in Fig. 3, the laser optical system 14 is moved relative to the wafer W1 in a backward direction X2, which is opposite to the forward direction X1.

[0021] FIG. 4 is an explanatory diagram for explaining laser processing along the forward direction X1. 5 is an explanatory diagram for explaining laser processing along the even-numbered backward direction X2. As shown in FIGS. 4 and 5, in this embodiment, the laser processing involves simultaneously (concurrently) performing edge cutting processing to form two parallel, thin first grooves G1 along the street S so as not to affect the chip side with processing effects, and hollowing processing to remove unnecessary material inside the first grooves G1 to expose the base material (e.g., silicon) and form second grooves G2. The edge cutting processing is laser processing performed using two first processing laser beams (split lasers) LA1, and forms two parallel edge cutting grooves G1 (two first grooves G1; ablation grooves) along the street S.

[0022] The hollowing process is a laser process for forming a hollow groove G2 (second groove; ablation groove) between the two edge cutting grooves G1 formed in the edge cutting process. In this embodiment, the hollowing process is performed using a second processing laser beam (line laser) LB1 having a larger diameter than the two first processing laser beams LA1.

[0023] In the laser processing device 1, in either case where the laser optical system 14 is moved relative to the wafer W1 in the forward direction X1 or in the backward direction X2, the edge cutting process is performed before the hollowing process.

[0024] FIG. 6 is a plan view of the laser processing apparatus 1 of FIG. 1. For the sake of explanation, FIG. 6 omits the control device 10, the laser optical system 14, the optical system base 81, and the like. As shown in FIGS. 1 and 6 , the laser processing apparatus 1 includes the control device 10, the laser optical system 14, the microscope 20, the Y-axis movement mechanism 30, the X-axis movement mechanism 40, the Z-axis movement mechanism 50, the rotation mechanism 60, the attitude adjustment mechanisms 70A, 70B, and 70C, the deformation amount measurement mechanisms 75A, 75B, and 75C, the base plate 80, the optical system base 81, and the support portions 91, 91B, and 91C. The laser processing apparatus 1 is installed on a stand 90. The optical system base 81 is provided on the base plate 80. The laser optical system 14 is fixed to the upper part of the optical system base 81.

[0025] Under the control of the control device 10, the stage ST moves along the X, Y, and Z directions and rotates around the Z axis by a Y-axis movement mechanism 30, an X-axis movement mechanism 40, a Z-axis movement mechanism 50, and a rotation mechanism 60. The Y-axis movement mechanism 30, the X-axis movement mechanism 40, the Z-axis movement mechanism 50, and the rotation mechanism 60 are an example of a movement mechanism 100 that moves the stage ST relatively.

[0026] The first laser light source 12A emits a first laser light LA, which is a pulsed laser light having conditions (such as the wavelength, pulse width, and repetition frequency of the laser light) suitable for edge cutting processing, to the laser optical system 14. The second laser light source 12B emits a second laser light LB, which is a pulsed laser light having conditions (such as the wavelength, pulse width, and repetition frequency of the laser light) suitable for center cutting processing, to the laser optical system 14.

[0027] The laser optical system 14 forms two first processing laser beams LA1 for edge cutting from the first laser beam LA. The laser optical system 14 also forms one or more second processing laser beams LB1 for center cutting from the second laser beam LB. The laser optical system 14 then emits (irradiates) the two first processing laser beams LA1 from the first condenser lens 16 toward the street S. The laser optical system 14 also selectively emits (irradiates) the second processing laser beam LB1 from the second condenser lenses 18A, 18B toward the street S under the control of the control device 10. The laser optical system 14 may be moved in the Y direction and the Z direction by an optical system moving mechanism (not shown) under the control of the control device 10.

[0028] The microscope 20 is fixed to the laser optical system 14 and moves integrally with the laser optical system 14. The microscope 20 photographs an alignment reference (not shown) formed on the wafer W1 before the edge cutting and hollowing processes. The microscope 20 also photographs the two first grooves G1 and second grooves G2 formed along the street S by the edge cutting and hollowing processes. The photographed image (image data) taken by the microscope 20 is output to the control device 10, and is displayed by the control device 10 on a monitor (not shown).

[0029] In this embodiment, the moving mechanism 100 includes a Y-axis moving mechanism 30, an X-axis moving mechanism 40, a Z-axis moving mechanism 50, and a rotation mechanism 60, and moves the stage ST in the X, Y, and Z directions and rotates it about a rotation axis under the control of the control device 10. This allows the moving mechanism 100 to move the laser optical system 14 relative to the stage ST and the wafer W1. Note that the method of relative movement is not particularly limited as long as it is possible to move the laser optical system 14 relative to the stage ST (wafer W1) in each direction (including rotation).

[0030] By relatively moving the stage ST using the movement mechanism 100, it is possible to align the laser optical system 14 with the processing start end, which is one end of the street S to be processed, and to relatively move the laser optical system 14 in the X direction (the outgoing direction X1 side or the returning direction X2 side) along the street S. In addition, by driving the movement mechanism 100 and rotating the stage ST by 90°, it is possible to make each street S along the Y direction of the wafer W1 parallel to the X direction, which is the processing feed direction.

[0031] Y-axis movement mechanism 30 is disposed on base plate 80. Y-axis movement mechanism 30 includes Y-axis motor 31, Y-axis ball screw 32, two Y-axis rails 33 disposed in parallel on base plate 80, a Y-axis guide (not shown) disposed on Y-axis rails 33, and a Y-axis table 34 placed on the Y-axis guide. Y-axis table 34 moves linearly in the Y-axis direction along Y-axis rails 33 by Y-axis ball screw 32 driven by Y-axis motor 31 under the control of control device 10.

[0032] The X-axis movement mechanism 40 is disposed on the Y-axis table 34. The X-axis movement mechanism 40 includes an X-axis motor 41, an X-axis ball screw 42, two X-axis rails 43 that are perpendicular to the Y-axis rails 33 and disposed parallel to the Y-axis table 34, an X-axis guide (not shown) disposed on the X-axis rails 43, and an X-axis table 44 placed on the X-axis guide. The X-axis table 44 moves linearly in the X-axis direction along the X-axis rails 43 by the X-axis ball screw 42 driven by the X-axis motor 41 under the control of the control device 10.

[0033] A Z-axis movement mechanism 50 is disposed on X-axis table 44. Z-axis movement mechanism 50 includes a motor (not shown), a Z-axis ball screw (not shown), a Z-axis base (not shown) that is provided perpendicular to X-axis table 44, a Z-axis rail (not shown) that is provided on the Z-axis base, a Z-axis guide that is attached to the Z-axis rail, and a Z-axis table (not shown) that is provided on the Z-axis guide so as to be movable in the Z-axis direction along the Z-axis rail. The Z-axis table moves in the Z-axis direction along the Z-axis rail by a Z-axis ball screw that is driven by the Z-axis motor under the control of control device 10.

[0034] A rotation mechanism 60 is disposed on the Z-axis table. The rotation mechanism 60 rotates the stage ST, which is a support table used to rotate the wafer W1, around the θ-axis. The rotation mechanism 60 is, for example, a motor (not shown) and a shaft (not shown) that is rotated by the motor. Here, the θ-axis is a rotation axis that is oriented in a direction parallel to the Z-axis.

[0035] The deformation measurement mechanisms 75A, 75B, and 75C are disposed, for example, between the base plate 80 and the platform 90. The deformation measurement mechanisms 75A, 75B, and 75C measure the deformation of the base plate 80 due to changes in load distribution caused by the operation of the movement mechanism. When the movement mechanism 100 moves the stage ST, the load distribution on the base plate 80 changes, causing the base plate 80 to deform. The deformation measurement mechanisms 75A, 75B, and 75C measure the deformation of the base plate due to this change in load distribution. The more deformation measurement mechanisms there are, the easier it is to grasp the deformation distribution of the base plate 80. The deformation measurement mechanisms 75A, 75B, and 75C are preferably disposed point-symmetrically or line-symmetrically with the supports 91A, 91B, and 91C that support the base plate 80, with respect to a predetermined object. This arrangement facilitates adjusting the posture of the base plate 80. The base plate in this embodiment is, for example, rectangular, and in this case, the center or the axis of symmetry of the rectangle is the object.

[0036] The deformation amount measuring mechanisms 75A, 75B, and 75C may be arranged on the side of the base plate 80 or on the side of the pedestal 90. The deformation amount measuring mechanisms 75A, 75B, and 75C are, for example, strain gauges capable of measuring the strain of the base plate 80, or laser displacement meters capable of measuring the relative position of the base plate 80 and the pedestal 90. The measured deformation amount of the base plate is sent to the control device 10.

[0037] The attitude adjustment mechanisms 70A, 70B, and 70C apply stress to the base plate 80 to restore the deformation of the base plate 80 based on the results of measurements by the deformation measurement mechanisms 75A, 75B, and 75C. The attitude adjustment mechanisms 70, 70B, and 70C are arranged near the deformation measurement mechanisms 75A, 75B, and 75C. In the present embodiment, the attitude adjustment mechanism 70A is arranged near the deformation measurement mechanism 75A, the attitude adjustment mechanism 70B is arranged near the deformation measurement mechanism 75B, and the attitude adjustment mechanism 70C is arranged near the deformation measurement mechanism 75C. By arranging the attitude adjustment mechanisms 70A, 70B, and 70C in this manner, it is possible to easily adjust the attitude of the base plate 80.

[0038] 2, the attitude adjustment mechanism 70A includes a gantry-side fixed part 71A fixed to the gantry 90, an actuator fixed part 72A arranged on the gantry-side fixed part 71A, a base plate-side fixed part 73A fixed to the base plate 80, and an actuator movable part 74A arranged on the base plate-side fixed part 73A. The actuator fixed part 72A and the actuator movable part 74A constitute one actuator. Examples of the actuator include a linear motor, an electric actuator, a hydraulic cylinder, and an air cylinder.

[0039] The attitude adjustment mechanism 70B includes a gantry-side fixed part 71B fixed to the gantry 90, an actuator fixed part 72B arranged on the gantry-side fixed part 71B, a base plate-side fixed part 73B fixed to the base plate 80, and an actuator movable part 74B arranged on the base plate-side fixed part 73B. The actuator fixed part 72B and the actuator movable part 74B constitute one actuator. The actuator can be the same as that of the attitude adjustment mechanism 70A.

[0040] The attitude adjustment mechanism 70C includes a gantry-side fixed part 71C fixed to the gantry 90, an actuator fixed part 72C arranged on the gantry-side fixed part 71C, a base plate-side fixed part 73C fixed to the base plate 80, and an actuator movable part 74C arranged on the base plate-side fixed part 73C. The actuator fixed part 72C and the actuator movable part 74C constitute one actuator. The actuator can be the same as that of the attitude adjustment mechanism 70A.

[0041] When the deviation in the position of the laser beam measured by the first sensing means and the second sensing means described below exceeds a threshold value, the control device 10 controls the attitude adjustment mechanisms 70A, 70B, and 70C based on the results of measurement by the deformation amount measurement mechanisms 75A, 75B, and 75C to apply stress to the base plate 80 so as to restore the deformation of the base plate 80. This makes it possible to reduce the deviation of the laser beam due to the variation in stress distribution depending on the position of the stage ST.

[0042] The control device 10 is configured, for example, by a personal computer and includes various processors (e.g., a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit)), a memory, and a storage device. The various functions of the control device 10 may be implemented by a single processor, or by multiple processors of the same or different types. For example, the control device 10 may be configured by a host device such as a personal computer (PC), a control device (motor driver, sequencer, controller, etc.) for the movement mechanism 100, and control devices (motor driver, sequencer, controller, etc.) for the attitude adjustment mechanisms 70A, 70B, and 70C. The control device 10 comprehensively controls the operations of the first laser light source 12A, the second laser light source 12B, the laser optical system 14, the movement mechanism 100, the deformation amount measurement mechanisms 75A, 75B, and 75C, and the attitude adjustment mechanisms 70A, 70B, and 70C.

[0043] [Laser optics] Next, an example of the laser optical system 14 will be described with reference to FIG. 7. FIG. 7 is a block diagram showing an example of the laser optical system. The first condenser lens 16 in FIG. 1 is disposed between the second condenser lens 18A and the second condenser lens 18B. In other words, the second condenser lenses 18A and 18B are disposed so as to sandwich the first condenser lens 16 therebetween. The second condenser lens 18A is disposed on the backward direction X2 side of the first condenser lens 16. The second condenser lens 18B is disposed on the forward direction X1 side of the first condenser lens 16. The state of the second laser light LB on the second condenser lens 18A side and the second condenser lens 18B side is the same, and in the following description, the second condenser lenses 18A and 18B will be described as the second condenser lens 18.

[0044] The laser optical system 14 includes a first laser light source 12A that emits a first laser beam LA, a first sensing means SSA that measures the positional deviation of at least one of the first laser beam LA and the first processing laser beam LA1 due to deformation of the base plate 80, a first light forming element 22A that forms two first processing laser beams LA1 from the first laser beam LA, a first focusing lens 16 that focuses the first processing laser beam LA1 on the workpiece, a second laser light source 12B that emits a second laser beam, a second sensing means SSB that measures the positional deviation of at least one of the second laser beam LB and the second processing laser beam LB1 due to deformation of the base plate 80, a second light forming element 22B that forms one or more second processing laser beams LB1 from the second laser beam LB, and a second focusing lens 18 that focuses the second processing laser beam LB1 on the workpiece. The first laser light source 12A and the second laser light source 12B are examples of laser light sources. The first light forming element 22A and the second light forming element 22B are examples of light forming elements. The first condenser lens 16 and the second condenser lens 18 are examples of condenser lenses. The first sensing means SSA and the second sensing means SSB are examples of sensing means that measure misalignment of the optical system. The laser optical system 14 is an example of an optical system.

[0045] The first sensing means SSA includes a first sensor unit SAU and a second sensor unit SA1U. The first sensor unit SAU is disposed on the optical path between the first laser light source 12A and the first light forming element 22A. The first sensor unit SAU includes a first mirror MAa that reflects the first laser light LA, and a first sensor SA that measures the deviation of the transmitted light LAT of the first laser light that has passed through the first mirror MAa. The first mirror MAa is an example of a mirror. The first sensor SA is an example of a sensor. The second sensor unit SA1U is disposed on the optical path between the first light forming element 22A and the first focusing lens 16. The second sensor unit SA1U includes a second mirror MA1a that reflects the first processing laser beam LA1 and a second sensor SA1 that measures the deviation of the transmitted light LA1T of the first processing laser beam that has passed through the second mirror MA1a. In this embodiment, the deviation of the positions of the laser beam and the processing laser beam is measured by measuring the deviation of the position of the transmitted light of the laser beam and the transmitted light of the processing laser beam. The second mirror MA1a is an example of a mirror. The second sensor SA1 is an example of a sensor.

[0046] The second sensing means SSB includes a third sensor unit SBU and a fourth sensor unit SB1U. The third sensor unit SBU is disposed on the optical path between the second laser light source 12B and the second light forming element 22B. The third sensor unit SBU includes a third mirror MBa that reflects the second laser light LB, and a third sensor SB that measures the deviation of the transmitted light LBT of the second laser light that has passed through the third mirror MBa. The third mirror MBa is an example of a mirror. The third sensor SB is an example of a sensor. The fourth sensor unit SB1U is disposed on the optical path between the second light forming element 22B and the second condenser lens 18. The fourth sensor unit SB1U includes a fourth mirror MB1a that reflects the second processing laser beam LB1 and a fourth sensor SB1 that measures the deviation of the transmitted light B1T of the second processing laser beam that has passed through the fourth mirror MB1a. The fourth mirror MB1a is an example of a mirror. The fourth sensor SB1 is an example of a sensor.

[0047] The first mirror MAa is disposed on the optical path between the first laser light source 12A and the mirror MAb. The first mirror MAa reflects the first laser light LA ​​incident from the first laser light source 12A toward the mirror MAb. When the first laser light LA ​​is reflected by the first mirror MAa, a small amount of transmitted light LAT is generated behind the first mirror MAa. This transmitted light LAT of the first laser light LA ​​is incident on the first sensor SA.

[0048] The first sensor SA measures the deviation of the position of the first laser beam LA due to the deformation of the base plate 80 caused by the movement of the stage ST. The first sensor SA is, for example, a position sensor detector (PSD, position detection sensor). This makes it possible to detect the deviation of the position of the first laser beam LA due to the deformation of the base plate 80. The measured deviation of the position of the first laser beam LA is sent to the control device 10.

[0049] The mirror MAb is disposed on the optical path between the first mirror MAa and the first light forming element 22 A. The mirror MAb reflects the first laser beam LA reflected by the first mirror MAa toward the first light forming element 22 A.

[0050] The first light forming element 22A is disposed on the optical path between the mirror MAb and the mirror MA1b. The first light forming element 22A forms two first processing laser beams LA1 from the incident first laser beam LA and emits them toward the mirror MA1b. As a result, the two first processing laser beams LA1 are focused on the street S (on the outward and return paths) by the first focusing lens 16, and two spots (also referred to as focused points or processing points) spaced apart in the Y direction are formed on the street S.

[0051] The first light forming element 22A may be, for example, a diffractive optical element, a refractive optical element, a prism, or a combination thereof. A diffractive optical element (DOE) may also be used as the first light forming element 22A. The optical paths of the two first processing laser beams LA1 from the first light forming element 22A to the first condenser lens 16 are omitted from the illustration.

[0052] The mirror MA1b is disposed on the optical path between the second mirror MA1a and the first light forming element 22A. The mirror MA1b reflects the two first processing laser beams LA1 incident from the first light forming element 22A to the second mirror MA1a.

[0053] The second mirror MA1a is disposed on the optical path between the first focusing lens 16 and the mirror MA1b. The second mirror MA1a reflects the first processing laser beam LA1 toward the first focusing lens 16. When the second mirror MA1a reflects the first processing laser beam LA1, a small amount of transmitted light LA1T is generated behind the second mirror MA1a. This transmitted light LA1T of the first processing laser beam LA1 is incident on the second sensor SA1.

[0054] The second sensor SA1 measures the positional deviation of the first processing laser beam LA1 due to deformation of the base plate 80. The second sensor SA1 is, for example, a position sensor detector. This allows the positional deviation of the first processing laser beam LA1 due to deformation of the base plate 80 to be detected. The measured positional deviation of the first processing laser beam LA1 is sent to the control device 10. The control device 10 can also calculate the angular deviation of the first processing laser beam LA1 using the following equation (1) based on the positional deviation measured by the first sensor SA and the second sensor SA1. In the following equation (1), θ represents the angular deviation, B represents the amount of positional deviation, and A represents the optical path length. For example, as shown in FIG. 8, it is preferable to arrange the first laser light source 12A and the first sensor SA so that the optical path length between the first sensor SA and the second sensor SA1 is equal to the optical path length between the first sensor SA and the second sensor SA1. By using the first sensor SA and the second sensor SA1, the angular deviation θ can be measured from the deviation amount B measured by the first sensor SA and the deviation amount B′ measured by the second sensor SA1. B = A × tanθ (1)

[0055] The third mirror MBa is disposed on the optical path between the second laser light source 12B and the mirror MBb. The third mirror MBa reflects the second laser light LB incident from the second laser light source 12B toward the mirror MBb. When the second laser light LB is reflected by the third mirror MBa, a small amount of transmitted light LBT is generated behind the third mirror MBa. This transmitted light LBT of the second laser light LB is incident on the third sensor SB.

[0056] The third sensor SB measures the deviation of the position of the second laser light LB due to the deformation of the base plate 80. The third sensor SB is, for example, a position sensor detector. This makes it possible to detect the deviation of the position of the second laser light LB due to the deformation of the base plate 80. The measured deviation of the position of the second laser light LB is sent to the control device 10.

[0057] The mirror MBb is disposed on the optical path between the third mirror MBa and the second light forming element 22B. The mirror MBb reflects the second laser light LB reflected by the third mirror MBa toward the second light forming element 22B.

[0058] The second light forming element 22B is disposed on the optical path between the mirror MBb and the mirror MB1b. The second light forming element 22B forms a second processing laser beam LB1 corresponding to one or more hollowing processes from the incident second laser beam LB and emits the second processing laser beam LB1 toward the mirror MB1b. As a result, the second processing laser beam LB1 forms one or more rectangular (or other shapes such as circular) spots between the two edge-cutting grooves G1 on the wafer W1, which is the workpiece. The width of this spot in the Y direction is adjusted to match the spacing between the two edge-cutting grooves G1. Note that when there are multiple spots, the spots of the second processing laser beam LB1 are spaced apart in the X direction.

[0059] The second light forming element 22B may be, for example, a mask, a diffractive optical element, a refractive optical element, a prism, or a combination thereof. When two or more second processing laser beams are formed, a diffractive optical element (DOE) may be used as the second light forming element 22B. Note that the following description will be given taking as an example a case where one second processing laser beam LB1 is formed from the second light forming element 22B.

[0060] The mirror MB1b is disposed on the optical path between the fourth mirror MB1a and the second light forming element 22B. The mirror MB1b reflects one or more second processing laser beams LB1 incident from the second light forming element 22B to the fourth mirror MB1a.

[0061] The fourth mirror MB1a is disposed on the optical path between the second focusing lens 18 and the mirror MB1b. The fourth mirror MB1a reflects the second processing laser beam LB1 toward the second focusing lens 18. When the second processing laser beam LB1 is reflected by the fourth mirror MB1a, a small amount of transmitted light LB1T is generated behind the fourth mirror MB1a. This transmitted light LB1T of the second processing laser beam LB1 is incident on the fourth sensor SB1.

[0062] The fourth sensor SB1 measures the positional deviation of the second processing laser beam LB1 due to deformation of the base plate 80. The fourth sensor SB1 is, for example, a position sensor detector. This allows the positional deviation of the second processing laser beam LB1 due to deformation of the base plate 80 to be detected. The measured positional deviation of the second processing laser beam LB1 is sent to the control device 10. The control device 10 can also calculate the angular deviation of the second processing laser beam LB1 using the above formula (1) based on the positional deviations measured by the third sensor SB and the fourth sensor SB1. For example, by arranging the optical path lengths between the second laser light source 12B and the third sensor SB and the third sensor SB1 so that they are equal, the angular deviation can be measured from the deviation amount measured by the third sensor SB and the deviation amount measured by the fourth sensor SB1.

[0063] The second focusing lens 18 focuses the incident second processing laser beam LB1 onto the wafer W1, which is the workpiece, thereby forming one or more spots (also referred to as focusing points or processing points) on the street S.

[0064] The above has described the laser processing device 1 according to this embodiment. With the laser processing device 1, it is possible to suppress deviations between the laser beams due to the position of the stage ST.

[0065] In this embodiment, the deviation of the laser light is measured and attitude control is performed based on the first sensing means SSA and the second sensing means SSB, but if the relationship between the deviation due to the position of the stage ST and the amount of deformation of the base plate 80 is known in advance, the attitude adjustment mechanisms 70A, 70B, 70C may be operated so that the amount of deformation measured by the deformation amount measuring mechanisms 75A, 75B, 75C is less than a predetermined threshold value.

[0066] In this embodiment, the first sensor unit SAU, the third sensor unit SBU, the second sensor unit SA1U, and the fourth sensor unit SB1U are each composed of a reflecting mirror and a sensor for measuring positional deviation. However, a lens may be placed on the optical path between the reflecting mirror and the sensor. The distance between the lens and the sensor is preferably the focal length of the lens. In this case, the angular deviation can be calculated using the following two equations: f in equation (2) is the focal length of the lens, B is the deviation of the laser beam, and θ is the angular deviation of the laser beam. A shift in the laser beam entering the lens is not reflected in the deviation of the focal point, but the angle is converted into a deviation corresponding to the focal length of the lens. This makes it possible to detect only the angular component. Note that angular deviation can cause a problem in that the irradiation position on the workpiece changes when the laser enters the focusing lens. Positional deviation can cause a problem in that the irradiation position does not change when the laser enters the focusing lens, but the shape formed by light-generating elements such as diffractive optical elements is affected by the positional deviation. Therefore, it is important to measure both angular and positional deviations. B = f × tanθ (2)

[0067] Although four sensor units (first sensor unit SAU, third sensor unit SBU, second sensor unit SA1U, and fourth sensor unit SB1U) are arranged on the optical path, the number of sensor units is not limited to this number. For example, only the first sensor unit SAU and the third sensor unit SBU may be arranged. In this case, the first sensor unit SAU may be arranged at the position of the second sensor unit SA1U, and the third sensor unit SBU may be arranged at the position of the fourth sensor unit SB1U. Furthermore, five or more sensor units may be arranged.

[0068] The first sensor SA, the third sensor SB, the second sensor SA1, and the fourth sensor SB1 may all be cameras, or the first sensor SA, the second sensor SA1, the third sensor SB, and the fourth sensor SB1 may all be position detective sensors, or a combination of cameras and position detective sensors may be used as the first sensor SA, the second sensor SA1, the third sensor SB, and the fourth sensor SB1.

[0069] In this embodiment, the first laser light source 12A and the second laser light source 12B are used and the deviation of the laser light position is detected by each of them, but attitude control may be started by detecting the deviation of only one of the laser light sources, the first laser light source 12A and the second laser light source 12B. In other words, the attitude may be controlled based on the measurement result of at least one of the first sensing means SSA and the second sensing means SSB.

[0070] The laser processing apparatus 1 may detect positional and angular deviations of the laser beam to perform attitude control instead of measuring the amount of deformation of the base plate 80 using the deformation amount measuring mechanisms 75A, 75B, and 75C.

[0071] [Laser processing method] Next, a laser processing method using the laser processing device 1 according to this embodiment will be described. FIG. 9 is a flowchart of the laser processing method according to this embodiment. Here, a method for processing one street S using the first sensing device SSA and the second sensing device SSB will be described as an example. Laser processing can be performed in the same manner until all streets S are processed. In processing the street S, first, the laser beam emission position (spot) is adjusted, and then the first laser beam LA and the second laser beam LB are emitted from the first laser beam source 12A and the second laser beam source 12B (step S1). Next, measurement of the laser beam deviations (positional deviation and angular deviation) by the first sensor unit SAU, the third sensor unit SBU, the second sensor unit SA1U, and the fourth sensor unit SB1U is started (step S2). The control device 10 records the values ​​of the stationary state before the stage ST is moved by the movement mechanism 100 as initial values. The control device 10 also records the deformation amounts of the deformation measurement mechanisms 75A, 75B, and 75C at the positions of the stage ST before movement as initial values. Next, the moving mechanism 100 starts moving the stage ST along the street S (step S3). While the stage ST is moving, it is determined whether the deviation of the laser beam measured by the first sensor unit SAU, the third sensor unit SBU, the second sensor unit SA1U, and the fourth sensor unit SB1U exceeds a threshold (step S4). Of the deviations of the laser beam, it is preferable to detect the deviation of the laser beam due to the position of the stage ST (deviation due to the position of the stage), and operate the attitude adjustment mechanisms 70A, 70B, and 70C based on the deviation due to the position of the stage. For example, the deviation of the laser beam due to the position of the stage ST (deviation due to the stage) is detected, and when the deviation due to the stage exceeds a threshold, the attitude adjustment mechanisms 70A, 70B, and 70C are operated. Next, a method for detecting deviation of the laser beam due to the position of the stage ST will be described. Deviation of the laser beam due to the position of the stage ST is repeatable. Therefore, deviation for each position of the stage ST can be predicted in advance from measurements or results of previous measurements, and the deviation of the laser beam can be monitored using the first sensing means SSA or the like to detect deviation due to the position of the stage ST. Alternatively, deviation due to vibration has a different frequency from deviation due to the position of the stage ST, so deviation due to the stage position can be detected by applying a filter that can remove frequency deviation due to the vibration component to the detection results of the deviation component. If the deviation of the laser beam is less than the threshold, the posture adjustment mechanisms 70A, 70B, and 70C are not operated, and the movement of the stage ST continues (step S4: YES). If the deviation is equal to or greater than the threshold (step S4: NO), the posture adjustment mechanisms 70A, 70B, and 70C are operated to restore the deformation of the base plate 80 caused by the movement of the stage ST (step S5). This makes it possible to suppress deviation of the laser beam due to the stage position. If the processing of the planned processing area (street S) is completed (step S6: YES), the laser processing ends. If the processing of the planned processing area is not completed (step S6: NO), the movement of the stage ST by the movement mechanism 100 continues (step S3).

[0072] (Attitude control method) Next, the attitude control of step S5 will be described. In the attitude control method, first, the deformation amount of the base plate 80 is measured by the deformation amount measuring mechanisms 75A, 75B, and 75C. The attitude adjustment mechanisms 70A, 70B, and 70C are operated based on the measured deformation amount of the base plate 80 so that the deformation amount becomes an initial value. In this way, it is possible to suppress deviation of the laser beam due to the position of the stage ST. Furthermore, in the laser processing method, instead of measuring the deformation amount of the base plate 80 by the deformation amount measuring mechanisms 75A, 75B, and 75C, attitude control may be performed by detecting positional and angular deviations of the laser beam.

[0073] In the posture control of step S5, it is preferable to apply stress to the base plate 80 so as to restore the deformation of the base plate 80 based on the results of measurement by the deformation amount measurement mechanisms 75A, 75B, and 75C, and then complete the posture adjustment by confirming that the deviation caused by the stage position has been corrected by the sensing means. This makes it possible to further suppress deviation of the laser light due to the position of the stage ST.

[0074] In the laser processing method and attitude control method of this embodiment, the first sensing means SSA and the second sensing means SSB are used to measure the deviation of the laser beam, and when the deviation of the laser beam is equal to or greater than a threshold, the attitude adjustment mechanisms 70A, 70B, and 70C are activated. However, if the relationship between the deviation due to the position of the stage ST and the deformation amount of the base plate 80 is known in advance, the attitude adjustment mechanisms 70A, 70B, and 70C may be activated when the deformation amount measured by the deformation amount measuring mechanisms 75A, 75B, and 75C is equal to or greater than a predetermined threshold. In this case, for example, in step S2, instead of measuring the laser beam, measurement of the deformation amount of the base plate 80 may be started, and in step S4, it may be determined whether the deformation amount of the base plate 80 is equal to or greater than a threshold.

[0075] (Laser processing device variation 1) Next, a laser processing apparatus 1A, which is a first modified example of the laser processing apparatus, will be described with reference to Fig. 10. Fig. 10 is a perspective view of the laser processing apparatus 1A. As shown in Fig. 10, the laser processing apparatus 1A includes a control device 10, a laser optical system 14, a microscope 20, a Y-axis movement mechanism 30, an X-axis movement mechanism 40, a Z-axis movement mechanism 50, a rotation mechanism 60, attitude adjustment mechanisms 70A, 70B, and 70C, deformation amount measurement mechanisms 75A, 75B, and 75C, a base plate 80, optical system bases 81A and 81B, and support portions 91, 91B, and 91C. The laser processing apparatus 1 is installed on a stand 90.

[0076] The laser optical system 14 is disposed on the optical system base 81A and the optical system base 81B. Even when there are two optical system bases as in the laser processing apparatus 1A, it is possible to suppress misalignment between the laser beams due to the position of the stage ST.

[0077] The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, and the above-described modifications can be combined as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0078] 1 laser processing device, 10 control device, 12A first laser light source, 12B second laser light source, 30 Y-axis movement mechanism 30, 40 X-axis movement mechanism, 50 Z-axis movement mechanism, 60 rotation mechanism, 100 movement mechanism

Claims

1. a laser light source that emits laser light; a light forming element that forms a processed laser beam from the laser beam; a condenser lens that condenses the processing laser light onto a workpiece; an optical system comprising: a stage for fixing the workpiece; a movement mechanism that moves the stage; a base plate on which the movement mechanism is disposed; a deformation amount measuring mechanism for measuring the deformation amount of the base plate; an attitude adjustment mechanism that applies stress to the base plate so as to return the amount of deformation to its original value based on the result of measurement by the deformation amount measurement mechanism; A laser processing device comprising:

2. 2. The laser processing device according to claim 1, wherein said optical system comprises sensing means for measuring a deviation of said optical system.

3. 3. The laser processing apparatus according to claim 2, wherein stress is applied to the base plate so as to return the deformation amount to its original value based on the result measured by the deformation amount measuring mechanism, and then posture adjustment is completed by confirming that the deviation has been corrected by the sensing means.

4. 4. The laser processing apparatus according to claim 2, wherein a deviation resulting from the position of the stage is detected from among the deviations, and the attitude adjustment mechanism is operated based on the deviation resulting from the position.

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