Optical devices

Abstract

An optical device capable of forming a fine modified region at a higher speed than conventional devices is provided. [Solution] An optical device 100A that forms a fine modified region on a workpiece 9 using pulsed laser light 1, the optical device 100A comprising: an afocal optical system 3 having a first convex lens system 31 and a second convex lens system 32 arranged along the direction of propagation of the pulsed laser light 1; an optical system 2 that has a rotating mirror 4 arranged at the position of the common focus CF of the first convex lens system 31 and the second convex lens system 32 and emits a convergent beam 10 from the second convex lens system 32; and a control unit 5 that has the function of scanning the convergent beam 20 on the workpiece 9 along a predetermined beam scanning direction 15 by controlling the reciprocating rotational movement of the rotating mirror 4.

Description

[Technical Field]

[0001] One aspect of the present invention is an optical device to Regarding. [Background technology]

[0002] In recent years, there has been a demand for even higher integration of semiconductor packages, and because it is not easy to further miniaturize wiring in the so-called front-end process, interest in so-called back-end processes is growing. One such technology is chiplet. This is a technology in which small semiconductor chips, each with its own assigned function, are combined like blocks and placed in a single package. An interposer (intermediate substrate) is used to connect semiconductor chips together. The interposer uses a glass substrate or similar, and has many fine through-glass vias (TGVs) formed within its surface to ensure electrical continuity between the circuits on the front and back.

[0003] To form a large number of fine through-holes in an interposer, a stage on which the workpiece is mounted is moved appropriately while irradiating the workpiece with a converging pulsed laser beam to form fine modified regions (hereinafter referred to as "fine modified regions") at a large number of predetermined locations, and then wet-etching the workpiece with a hydrofluoric acid-based etching solution or the like to form a large number of fine through-holes from the fine modified regions. In this case, if a converging pulsed laser beam generated using, for example, an axicon lens is used as the converging pulsed laser beam, a Bessel beam region with an extremely high aspect ratio can be generated, thereby forming high-quality fine modified regions with a more uniform diameter than conventional ones across the depth direction (thickness direction) of the workpiece, and ultimately high-quality fine through-holes with a more uniform diameter than conventional ones across the depth direction (thickness direction) of the interposer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-136442 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technical field of forming fine modified regions in workpieces, there is a challenge of wanting to form fine modified regions faster than before, and this challenge does not exist only when using convergent pulsed laser light generated using an axicon lens. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical device and a method for forming a fine modified region that are capable of forming a fine modified region at a higher speed than conventional methods. [Means for solving the problem]

[0006] [1] An optical device according to one aspect of the present application is an optical device that forms a finely modified region on a workpiece using laser light, and includes an afocal optical system having a first convex lens system and a second convex lens system arranged along the direction of propagation of the laser light, and a rotating mirror arranged at the common focal position of the first convex lens system and the second convex lens system, and emits a convergent beam from the second convex lens system, and a control unit that has the function of scanning the convergent beam on the workpiece along a predetermined beam scanning direction by controlling the reciprocating rotation of the rotating mirror.

[0007]

[17] Another aspect of the present application provides an optical device for forming a finely modified region on a workpiece using pulsed laser light, the optical device comprising: a focusing optical system for forming a convergent beam from the pulsed laser light; a control unit for scanning the convergent beam on the workpiece along a predetermined beam scanning direction; and a stage for placing the workpiece, the stage being configured to be movable along predetermined main scanning and sub-scanning directions that are perpendicular to each other in a plane parallel to a placing surface, wherein the control unit has the function of scanning the convergent beam along the beam scanning direction while moving the stage along the main scanning direction with the beam scanning direction and the sub-scanning direction tilted by a predetermined angle (α), thereby forming a spot train of the pulsed laser light along the sub-scanning direction on the workpiece.

[0008]

[23] A method for forming a fine modified region according to another aspect of the present application includes: A method for forming a fine modified region in a workpiece by scanning a convergent beam formed from pulsed laser light along a predetermined beam scanning direction on the workpiece, the workpiece being placed on a stage configured to be movable along predetermined main scanning and sub-scanning directions that are orthogonal to each other in a plane parallel to a mounting surface, the method comprising: With the beam scanning direction and the sub-scanning direction tilted by a predetermined angle (α), the stage is moved along the main scanning direction while the convergent beam is scanned along the beam scanning direction, thereby forming a spot train of the pulsed laser light on the workpiece along the sub-scanning direction.

[0009] According to the optical device of the above aspect, it is possible to form fine modified regions at a higher speed than conventional methods. Also, according to the optical device and the fine modified region forming method of another aspect of the present application, it is possible to form a large number of fine modified regions at a higher speed than conventional methods. [Brief explanation of the drawings]

[0010] [Figure 1]1A and 1B are diagrams illustrating an overview of an optical device 100A according to a first embodiment. [Figure 2] 2A and 2B are diagrams illustrating the configuration of an afocal optical system 3 in the optical device 100A. [Figure 3] 10A and 10B are diagrams illustrating a method of forming a spot train over the entire processing target area 95. [Figure 4] 10A and 10B are diagrams for explaining a method of forming a spot train along the sub-scanning direction in an "outgoing spot train formation region." [Figure 5] 10A and 10B are diagrams for explaining a two-dimensional spot train formation method in the "outbound spot train formation region." [Figure 6] 10A and 10B are diagrams for explaining a two-dimensional spot train formation method in the "returning spot train formation region." [Figure 7] 10A and 10B are diagrams for explaining a method of forming spot trains along the sub-scanning direction in a "returning spot train forming region." [Figure 8] 10A and 10B are diagrams for explaining another method of forming spot trains along the sub-scanning direction in the "returning spot train forming region." [Figure 9] 3A and 3B are diagrams illustrating the configuration of a second convex lens system 32. [Figure 10] 1 is a diagram showing the in-plane light intensity distribution of a convergent beam 10. FIG. [Figure 11] 3 is a diagram for explaining the beam shift amount of a convergent beam 10 and the maximum effective swing angle of a rotating mirror 4. FIG. [Figure 12] 10 is a diagram showing the relationship between the maximum effective swing angle θ of the rotating mirror 4 and the spot quality. [Figure 13] FIG. 2 is a diagram showing how wave trains of pulsed laser light 1 are superimposed over time. [Figure 14] 3A and 3B are diagrams illustrating the configuration of a rotating mirror 4. FIG. [Figure 15] A chart showing the simulation results for productivity. [Figure 16] FIG. 10 is a diagram illustrating an overview of an optical device 100B according to a second embodiment. [Figure 17]FIG. 10 is a diagram illustrating an overview of an optical device 100C according to a third embodiment. [Figure 18] FIG. 10 is a diagram illustrating an overview of an optical device 100D according to a fourth embodiment. [Figure 19] FIG. 10 is a diagram illustrating an overview of an optical device 100E according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes optical devices (100A to 100D) and methods for forming fine modified regions according to one aspect of the present invention, using the drawings. Note that each drawing is a schematic diagram and does not necessarily accurately reflect an actual optical device. Furthermore, each embodiment does not limit the scope of the claims. Furthermore, not all of the components and combinations thereof described in each embodiment are necessarily essential to the present invention. Furthermore, the same reference numerals are used across embodiments for components that are considered to be substantially equivalent, and repeated explanations may be omitted (there may be some overlapping explanations).

[0012] [Embodiment 1] In embodiment 1, the optical device of the present invention will be described by taking as an example an optical device that uses pulsed laser light as laser light. Figures 1 to 15 are diagrams shown to explain an optical device 100A according to embodiment 1. Figure 1 is a diagram shown to explain the overview of optical device 100A, and Figure 2 is a diagram shown to explain the configuration of afocal optical system 3 in optical device 100A.

[0013] Note that Figure 1 and Figures 16 to 18 described below are figures shown to explain the overview of the optical device (optical devices 100A, 100B, 100C, 100D), and therefore the first convex lens system 31 and the second convex lens system 32 are shown as simple convex lenses, while in Figure 2 and Figures 9 and 13 described below, the first convex lens system 31 and the second convex lens system 32 are shown as convex lenses having specific lens shapes.

[0014] In addition, in FIG. 1 and FIG. 17 described later, optical devices (100A, 100C) are described using an example in which the focal length f2 of the second convex lens system 32 is shorter than the focal length f1 of the first convex lens system 31, and in FIG. 2 and FIGS. 16 and 18 described later, optical devices (100B, 100D) are described using an example in which the focal length f2 of the second convex lens system 32 is the same as the focal length f1 of the first convex lens system 31.

[0015] [Optical device 100A] 1 and 2 , the optical device 100A according to the first embodiment is an optical device 100A that forms a fine modified region on a workpiece 9 using a pulsed laser beam 1. The optical device 100A according to the first embodiment includes an afocal optical system 3 having a first convex lens system 31 and a second convex lens system 32 arranged along the traveling direction of the pulsed laser beam 1, and a rotating mirror 4 arranged at a common focal point CF of the first convex lens system 31 and the second convex lens system 32, an optical system 2 that emits a convergent beam 10 from the second convex lens system 32, and a control unit 5 that has a function of scanning the convergent beam 10 on the workpiece 9 along a predetermined beam scanning direction 15 by controlling the reciprocating rotation of the rotating mirror 4.

[0016] The optical system 2 includes one axicon lens 21. In Fig. 2, symbol (a) indicates the position onto which the convergent beam 10 is irradiated when the rotating mirror 4 is at the maximum effective swing angle position on the clockwise side, symbol (c) indicates the position onto which the convergent beam 10 is irradiated when the rotating mirror 4 is at the maximum effective swing angle position on the counterclockwise side, and symbol (c) indicates a position intermediate between symbols (a) and (c) (see Fig. 10(a) described later).

[0017] When the pulsed laser beam 1 passes through the axicon lens 21, the outer diameter of the annulus gradually decreases and it converges at the focal position F on the incident side of the first convex lens system 31 to form the first Bessel beam region 11a. The first Bessel beam region 11a is a region formed along the optical axis AX with an extremely high optical energy density. The same applies to the "Bessel beam region 11 formed in the vicinity of the workpiece 9" described later.

[0018] Thereafter, the pulsed laser light 1 passes through the first convex lens system 31, is reflected by the rotating mirror 4, and further passes through the second convex lens system 32, and is then irradiated onto the workpiece 9 placed on the stage 6. At this time, the initial Bessel beam region 11a is relayed to the vicinity of the workpiece 9 by the afocal optical system 3 having the first convex lens system 31 and the second convex lens system 32, and becomes the Bessel beam region 11.

[0019] In the optical device 100A, the control unit 5 controls the reciprocating rotation of the rotating mirror 4, and the convergent beam 10 emitted from the second convex lens system 32 scans the workpiece 9 along a predetermined beam scanning direction 15. The rotating mirror 4 is configured to rotate reciprocatingly around a rotation axis RAx that passes through a common focal point CF of the first convex lens system 31 and the second convex lens system 32. FIGS. 1 and 2 show the beam scanning direction 15 when an angle α, which will be described later, is set to 0 degrees. The same applies to FIGS. 16 to 18, which will be described later.

[0020] Therefore, in the optical device 100A according to the first embodiment, the convergent beam 10 that has passed through the second convex lens system 32 is a convergent beam generated using an axicon lens, and therefore a Bessel beam region 11 having an extremely high aspect ratio is formed in the vicinity of the workpiece 9. Therefore, the optical device 100A according to the first embodiment can form a high-quality fine modified region that has a more uniform diameter across the depth direction (thickness direction) of the workpiece than conventionally.

[0021] Furthermore, in the optical device 100A according to the first embodiment, the convergent beam 10 is scanned on the workpiece 9 along a predetermined beam scanning direction by the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation. Therefore, the optical device 100A according to the first embodiment can form a large number of fine modified regions on the workpiece at higher speeds than conventional methods.

[0022] In the optical device 100A according to the first embodiment, the focal length f1 of the first convex lens system 31 and the focal length f2 of the second convex lens system 32 can be set arbitrarily. In Fig. 1, the focal length f2 of the second convex lens system 32 is set shorter than the focal length f1 of the first convex lens system 31, and in Fig. 2, the focal length f2 of the second convex lens system 32 is set the same as the focal length f1 of the first convex lens system 31.

[0023] As shown in FIG. 1, when the focal length f2 of the second convex lens system 32 is set shorter than the focal length f1 of the first convex lens system 31, the diameter of the fine modified region can be made smaller.

[0024] In contrast to this, as shown in FIG. 2, when the focal length f2 of the second convex lens system 32 is set to be the same as the focal length f1 of the first convex lens system 31, the first convex lens system 31 and the second convex lens system 32 can be configured to be the same, and the length of the initial Bessel beam region 11a can be made the same as the length of the Bessel beam region 11 formed in the vicinity of the workpiece.

[0025] Here, the components of the optical device 100A and the terms used in the description will be explained. [Optical axis Ax] The optical axis Ax indicated by the dashed-dotted line is the optical axis of the optical device 100A. The optical axis Ax is the optical axis Ax along which light actually passes until it enters the axicon lens 21, but is a virtual optical axis along which light may not actually pass after passing through the axicon lens 21. As described above, the pulsed laser light 1 does not pass through the optical axis Ax of the first convex lens system 31, the rotating mirror 4, and the second convex lens system 32, but passes through the annular region indicated by the dashed line.

[0026] [Pulse laser light 1] The "pulse laser light 1" refers to a pulse laser light having a pulse width of, for example, nanoseconds, picoseconds, or femtoseconds.

[0027] [First convex lens system 31 and second convex lens system 32] The first convex lens system 31 and the second convex lens system 32 are lenses that make up an afocal optical system. The first convex lens system 31 (or the second convex lens system 32) includes not only a single convex lens or a lens made up of a combination of multiple convex lenses, but also a lens made up of a combination of a convex lens and a concave lens that functions as a convex lens overall. The "rotating mirror 4" is provided at the common focal point CF of the first convex lens system 31 and the second convex lens system 32, and is configured to be rotatable back and forth by a rotary drive motor. Galvanometer mirrors in which the rotating mirror 4 and the rotary drive motor are integrated are available on the market. The "workpiece 9" is, for example, a glass substrate.

[0028] [Area through which pulsed laser light 1 passes or is reflected] 1 and 2, the pulsed laser light 1 becomes an annular light beam, passes through the first convex lens system 31, is reflected by the rotating mirror 4, and passes through the second convex lens system 32 (see the areas surrounded by dashed lines in FIGS. 1 and 2). The area surrounded by dashed lines is an annular area centered on the optical axis Ax when viewed along the optical axis Ax in the first convex lens system 31, an annular area centered on the optical axis Ax when viewed along the optical axis Ax in the rotating mirror 4, and an annular area centered on the optical axis Ax when viewed along the optical axis Ax in the second convex lens system 32. Note that the term annular includes an ellipse, an oval, a short circle, a perfect circle, etc.

[0029] [Convergent beam 10] In the first embodiment, the pulsed laser light 1 after passing through the second convex lens system 42 becomes a convergent beam 10, with the outer diameter of the beam decreasing along the traveling direction. The convergent beam forms a Bessel beam region 11 in the vicinity of the workpiece 9.

[0030] [Control unit 5] The control unit 5 (specific circuits and the like are not shown) is composed of, for example, a logic circuit, a microcomputer, etc. The microcomputer is a computer that mainly includes a CPU (Central Processing Unit) and is composed of ROM, RAM, input / output ports, interfaces, etc. The control unit 5 performs various controls (rotation control of the stage 6 and movement control in the main scanning direction or sub-scanning direction, rotation control of the rotating mirror 4, emission control of the pulsed laser beam 1, etc.) using instructions pre-stored in the ROM. The control unit 5 may perform the above-mentioned movement control of the stage 6, rotation control of the rotating mirror 4, and emission control of the pulsed laser beam 1 using rotation information of the rotating mirror 4 from a rotation state detection encoder (not shown).

[0031] [Optical system 2] In the optical device 100A of the first embodiment, the optical system 2 includes one axicon lens 21, as described above. Here, an "axicon lens" is a conical lens. The downstream axicon lens 22 used in the optical devices 100B and 100D in FIGS. 16 and 18, which will be described later, does not need to be entirely conical. It is sufficient that the area through which the pulsed laser beam 1 passes is a part of a cone, and for example, the cone may be a cone with its apex cut off. The cone of the axicon lens 21 in the optical device 100A may be located on either the exit side or the entrance side of the pulsed laser beam 1.

[0032] The optical device 100A, in which the focusing optical system 2 is composed of "one axicon lens 21," is a simple optical device with a small number of parts.

[0033] [Method of forming a spot train by scanning with a convergent beam 10] A method for forming a spot train by scanning the convergent beam 10 in the optical device 100A will be described using Figures 3 to 5. Figure 3 is a diagram shown to explain a method for forming a spot train over the entire processing target area 95. Figure 4 is a diagram shown to explain a method for forming a spot train along the sub-scanning direction in the "outgoing spot train formation area". Figure 5 is a diagram shown to explain a method for two-dimensionally forming a spot train in the "outgoing spot train formation area". In Figures 3 to 5, the X axis is an axis along the main scanning direction, the Y axis is an axis along the sub-scanning direction, and the Z axis is an axis perpendicular to the X and Y axes.

[0034] As described above, the optical device 100A according to the first embodiment further includes the stage 9 on which the workpiece 9 is placed (see FIGS. 1 and 2). The stage 9 is configured to be movable along predetermined mutually orthogonal main scanning directions (X-axis direction) and sub-scanning directions (Y-axis direction) within a plane parallel to the placement surface (within the XY plane) (see FIGS. 3 to 5).

[0035] Before explaining the method for forming a spot array over the entire processing area 95 (see Figure 3), we will explain the method for forming a spot array along the sub-scanning direction with reference to Figure 4, and then we will explain the method for forming a spot array two-dimensionally with reference to Figure 5.

[0036] In the optical device 100A according to the first embodiment, as shown in Fig. 4, the control unit 5 rotates the stage 6 or the rotary shaft 42 of the rotary mirror 4 so that the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) are tilted at a predetermined angle (α) (see Fig. 4(a)), and then scans the convergent beam 10 along the beam scanning direction 15 while gradually moving the stage 6 along the main scanning direction (X-axis direction) (see Figs. 4(b) to 4(d)), thereby forming a train of spots (P01, P02, P03, ...) on the workpiece 9 along the sub-scanning direction (Y-axis direction). The step of forming the train of spots along the sub-scanning direction is specifically performed as follows.

[0037] [Method of forming a spot row along the sub-scanning direction] First, the control unit 5 moves the stage 6 to an initial position and rotates the rotating mirror 4 to the maximum swing angle position on the clockwise side (see FIG. 11(a) described later), and then starts controlling the movement of the stage 6 along the main scanning direction and the rotation of the rotating mirror 4 around the rotation axis RAx (see FIG. 4(a)). At this time, the control unit 5 synchronizes the movement of the stage 6 and the rotation of the rotating mirror 4 using a rotation position detection encoder (not shown).

[0038] After that, at time t1 after passing time t0, the stage 6 moves leftward from its position at time t0, and the rotating mirror 4 rotates counterclockwise by a predetermined angle (forward rotation). As a result, the convergent beam 10 is irradiated onto a predetermined position on the workpiece 9, and a spot P01 is formed at that position (see FIG. 4(b)). The rotational position (swing angle position) of the rotating mirror 4 at time t1 becomes the maximum effective swing angle position.

[0039] After that, at time t2, the stage 6 moves leftward from its position at time t1, and the rotating mirror 4 rotates counterclockwise by a predetermined angle (forward rotation). As a result, the convergent beam 10 is irradiated onto a predetermined position on the workpiece 9 (a position where the spots P01 and P02 are aligned in the sub-scanning direction), and the spot P02 is formed at that position (see FIG. 4(c)).

[0040] After that, at time t3, the stage 6 moves leftward from its position at time t2, and the rotating mirror 4 rotates counterclockwise by a predetermined angle (forward rotation). As a result, the converging beam 10 is irradiated onto a predetermined position on the workpiece 9 (a position where spots P01 to P03 are aligned in the sub-scanning direction), and spot P03 is formed at that position (see FIG. 4(d)).

[0041] In this way, by repeating the formation of spots along the sub-scanning direction, a row of spots (P01, P02, P03, . . . ) extending in the sub-scanning direction is formed on the workpiece 9.

[0042] [Method for two-dimensionally forming a spot train in the "outbound spot train forming region"] Next, a method for two-dimensionally forming a spot train in the "outgoing spot train forming region" will be described with reference to FIG. First, the first spot train is formed along the sub-scanning direction (the leftmost spot train in Figure 5, hereinafter referred to as the first spot train). Next, when the formation of the first spot train is completed, the rotating mirror 4 rotates in the reverse direction (clockwise) to return to the maximum clockwise swing angle position for forming the next spot train along the sub-scanning direction (hereinafter referred to as the next spot train), and then forms the next spot train in the same manner as above. Note that the stage 6 always moves at a constant speed along the main scanning direction (from right to left in this case), and by repeating the above spot train formation, many spot trains are formed in a dual manner within the "outgoing spot train formation region" (see Figures 3 and 5).

[0043] As described above, in the optical device 100A according to the first embodiment, the control unit 5 repeats the operation of forming a spot train by the pulsed laser beam 1 along the sub-scanning direction while moving the stage 6 along the main scanning direction with the beam scanning direction 15 and the sub-scanning direction tilted by a predetermined angle (α), thereby forming a spot train two-dimensionally within the processing target region 95 of the workpiece 9. At this time, the control unit 5 synchronizes the movement of the stage 6 along the main scanning direction with the reciprocating rotation of the rotary mirror 4 about the rotation axis RAx.

[0044] Therefore, in the optical device 100A according to the first embodiment, spots are formed dually in the "outgoing spot train formation region" while the stage 6 is moved once in the main scanning direction (see FIG. 5). As a result, the optical device 100A according to the first embodiment can form a large number of fine modified regions on the workpiece at higher speeds than conventional methods.

[0045] [Method of forming a spot array over the entire processing target area 95] 3 and 5, a method for forming a spot train over the entire processing target area 95 will be described. First, by using the method shown in FIGS. 3 and 5, a spot train is formed two-dimensionally by forming a spot train from left to right in a certain "outbound spot train formation region" (e.g., outbound spot train formation region R1 in FIG. 3). Then, when the formation of the spot train in that region is completed, the control unit 5 (temporarily suspends the formation of the spot train) moves the stage 6 along the sub-scanning direction to the next processing region, the "returning spot train formation region" (e.g., returning spot train formation region R2 in FIG. 3), and then forms a spot train two-dimensionally in that region by forming a spot train from right to left. At this time, as shown in FIG. 4 and FIG. 7 (described later), a spot train is formed two-dimensionally in the "returning spot train formation region" under the condition that the angle α between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is opposite to that in the "outbound spot train formation region."

[0046] After completing the formation of the spot train in the "returning spot train formation region," the control unit 5 (temporarily suspends spot formation) moves the stage 6 along the sub-scanning direction to the next processing region, the "next outgoing spot train formation region" (e.g., outgoing spot train formation region R3 in FIG. 3), and then forms a spot train from left to right in that region, thereby forming a two-dimensional spot train. At this time, the spot train along the sub-scanning direction is formed two-dimensionally in the "outgoing spot train formation region" under the condition that the angle between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is opposite to that in the "returning spot train formation region." By repeating these steps, multiple spot trains are formed throughout the entire processing target region 95 of the workpiece 9.

[0047] In this way, in the optical device 100A according to the first embodiment, the operation of forming a train of spots two-dimensionally on the workpiece is repeated while intermittently moving the stage 6 in the sub-scanning direction and while reciprocating the stage 6 in the main scanning direction. As a result, the optical device 100A according to the first embodiment can form a train of spots over the entire processing target region 95 on the workpiece 9.

[0048] Fig. 6 is a diagram shown to explain a method for two-dimensionally forming spot trains in the "returning spot train formation region." Fig. 7 is a diagram shown to explain a method for forming spot trains along the sub-scanning direction in the "returning spot train formation region." In optical device 100A according to embodiment 1, if a spot train is formed in the "returning spot train formation region" in the same way as in the "outgoing spot train formation region," it is not possible to form a spot train along the sub-scanning direction (Y-axis direction) because stage 6 moves in the opposite direction (from left to right). Therefore, in optical device 100A according to embodiment 1, a spot train (P11, P12, P13, ...) is formed two-dimensionally in the "returning spot train formation region" under the condition that the angle between beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is opposite to that in the "outgoing spot train formation region," as shown in Figures 6 and 7.

[0049] In this way, in the optical device 100A according to embodiment 1, the angle between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is reversed in the "outbound spot train formation area" and the "returning spot train formation area", and therefore, according to the optical device 100A according to embodiment 1, the spot train can be correctly formed along the sub-scanning direction in both the "outbound spot train formation area" and the "returning spot train formation area".

[0050] FIG. 8 is a diagram shown to explain another method of forming spot trains along the sub-scanning direction in the "returning spot train forming region." In optical device 100A according to embodiment 1, in the "outgoing spot train formation region," spot trains (P01, P02, P03,...) may be formed in the forward direction along the sub-scanning direction as shown in Fig. 4, and in the "returning spot train formation region," spot trains (P11, P12, P13,...) may be formed in the reverse direction along the sub-scanning direction as shown in Fig. 8. Even in this case, spot trains can be correctly formed along the sub-scanning direction in both the "outgoing spot train formation region" and the "returning spot train formation region."

[0051] [Second convex lens system 32] Fig. 9 is a diagram shown to explain the configuration of the second convex lens system 32. Fig. 9 shows a ray tracing diagram of light L passing through the second convex lens 32 when the beam shift amount is ±0 mm. In the optical device 100A according to the first embodiment, the performance requirements for the second convex lens system 32 are satisfied when the second convex lens system 32 is configured as shown in FIG. 9 so that, when the rotating mirror 4 is disposed virtually perpendicular to the optical axis of the second convex lens system 32, a divergent light beam L having an optical axis parallel to the optical axis 32Ax of the second convex lens system 32, which is emitted from a predetermined point within the region of the rotating mirror 4 through which the pulsed laser beam 1 passes toward the region of the second convex lens system 32 through which the pulsed laser beam 1 passes, becomes parallel after passing through the second convex lens system 32.

[0052] Therefore, in the optical device 100A according to the first embodiment, taking the above into consideration, the second convex lens system 32 was designed under the following conditions: the refractive index n of the second convex lens system 32 was set to 1.45, the wavelength λ of the pulsed laser light 1 was set to 1030 nm, the predetermined angle was set to 25.3 degrees, and the incident beam diameter on the workpiece 9 was set to 2.9 mm. Using the designed second convex lens system 32, the in-plane light intensity distribution of the convergent beam 10 in the vicinity of the workpiece 9 was obtained by optical simulation. The predetermined angle was set to 25.3 degrees in order to set the diameter of the convergent beam 10 in the vicinity of the workpiece 9 to 2 μm, and the incident beam diameter on the workpiece 9 was set to 2.9 mm because an incident beam diameter of 2.9 mm allows the Bessel beam region 11 to cover the thickness (e.g., 1 mm) of the workpiece 9.

[0053] FIG. 10 is a diagram showing the in-plane light intensity distribution of the convergent beam 10. FIG. 10(a) is a diagram showing the in-plane light intensity distribution of the convergent beam 10 when the beam shift amount (half angle) (maximum beam shift amount (half angle)) is +2.5 mm, FIG. 10(b) is a diagram showing the in-plane light intensity distribution of the convergent beam 10 when the beam shift amount (half angle) is ±0 mm, and FIG. 10(c) is a diagram showing the in-plane light intensity distribution of the convergent beam 10 when the beam shift amount (half angle) is −2.5 mm. In FIG. 10, the in-plane light intensity distribution of the convergent beam 10 is the in-plane light intensity distribution of the convergent beam 10 in the vicinity of the workpiece 10, in other words, the in-plane light intensity distribution in the Bessel beam region 11. FIG. 11 is a diagram shown to explain the beam shift amount of the convergent beam 10 and the swing angle of the rotating mirror 4. FIG. 11(a) is a diagram for explaining the beam shift amount of the convergent beam 10, and FIG. 11(b) is a diagram for explaining the swing angle of the rotating mirror 4. As shown in FIG.

[0054] As can be seen from FIG. 10 , it was confirmed that the optical device 100A according to the first embodiment maintains an appropriate in-plane light intensity distribution (spot quality) of the convergent beam 10 within a beam shift amount (half angle) range of ±2.5 mm. Here, the maximum beam shift amount (full angle) refers to the effective scanning range of the convergent beam 10, as shown in FIG. 11( a), and the maximum beam shift amount (half angle) refers to the distance from the center of the effective scanning range of the convergent beam 10 to the maximum beam shift position. The maximum beam shift amount (full angle) corresponds to the effective swing angle (full angle) of the rotating mirror 4 shown in FIG. 11( b), and the maximum beam shift amount (half angle) corresponds to the maximum effective swing angle (half angle) of the rotating mirror 4. The maximum swing angle (full angle) of the rotating mirror 4 corresponds to the reciprocating rotation range of the rotating mirror 4, and the effective swing angle (full angle) of the rotating mirror 4 refers to the swing angle obtained by excluding the folding range from the maximum swing angle (full angle) of the rotating mirror 4.

[0055] The reason why the beam shift amount (half angle) is set within the range of ±2.5 mm is as follows: Referring to Fig. 3, when the processing target area 95 of the workpiece 9 is 500 mm x 500 mm and this is divided into 100 in the Y-axis direction to form 50 forward spot train formation areas and 50 backward spot train formation areas, the width along the sub-scanning direction of the forward spot train formation area or the backward spot train formation area is taken into consideration to be 5 mm.

[0056] In the optical device 100A according to the first embodiment, if there is a large difference between the optical path length L1 of the longest optical path from the focal point on the entrance side of the afocal optical system 3 to the focal point on the exit side and the optical path length L2 of the shortest optical path, the quality of the spot formed near the workpiece 9 will deteriorate accordingly. Therefore, in the optical device 100A according to the first embodiment, the maximum effective swing angle θ of the rotating mirror 4 is reduced to shorten the optical path difference L1-L2, thereby suppressing the deterioration of the spot quality.

[0057] Fig. 12 is a diagram showing the relationship between the maximum effective deflection angle θ of the rotating mirror 4 and the spot quality. In Fig. 12, the "in-plane light intensity distribution characteristics of the convergent beam 10 at the spot" is used as the "spot quality".

[0058] As shown in FIG. 12, in the optical device 100A of embodiment 1, when the wavelength λ of the pulsed laser light is 1030 nm, the spot quality deteriorates when the maximum effective deflection angle θ is greater than ±1.5 degrees (see Test Examples 1 to 3), but it was confirmed that the deterioration of the spot quality is suppressed when the maximum effective deflection angle θ is set to ±0.75 degrees (see Test Example 4). This shows that deterioration of spot quality is suppressed when "(maximum effective swing angle θ of rotating mirror 4) / (wavelength λ / 1030 of laser light)"≦1". Note that with the optical device 100A of embodiment 1, even when the wavelength λ of the pulsed laser light is 515 nm, the spot quality deteriorates when the maximum effective swing angle θ is greater than ±0.75 degrees (see Test Examples 5 to 7), but it was confirmed that deterioration of spot quality is suppressed when the maximum effective swing angle θ is set to ±0.37 degrees (see Test Example 8). This shows that deterioration of spot quality is suppressed when "(maximum effective swing angle θ of rotating mirror 4) / (wavelength λ / 1030 of laser light)"≦1".

[0059] As described above, the optical device 1 according to the first embodiment can maintain the in-plane light intensity distribution (spot quality) of the convergent beam 10 at an appropriate level within a beam shift amount range of ±2.5 mm. However, even in this case, depending on the design of the second convex lens system 32, the overlap state of the pulsed laser beam 1 wave train that reaches the focus on the output side via the longest optical path from the focus on the input side to the focus on the output side of the afocal optical system 3 and the pulsed laser beam 1 wave train that reaches the focus on the output side via the shortest optical path may decrease over time. If this occurs, the light intensity effective for forming the finely modified region decreases, thereby degrading the spot quality.

[0060] FIG. 13 is a diagram showing how wave trains of pulsed laser beam 11 are superimposed over time. The upper part of FIG. 13 shows how the pulse length of pulsed laser beam 1 is changed over time, while the lower part of FIG. 13 illustrates the first light to reach workpiece 9 after passing through afocal optical system 3 (light that has passed through an optical path with optical path length L2) and the last light to reach workpiece 9 (light that has passed through an optical path with optical path length L1). FIG. 13 shows the superimposed wave trains using an example in which the "optical path difference L1-L2," described below, is 0.244 mm. The "optical path difference L1-L2" was set to 0.244 mm to clearly illustrate the superimposed wave trains; as described below, the "optical path difference L1-L2" can also be made shorter.

[0061] In this case, as can be seen from FIG. 13, when the pulse length of pulsed laser light 1 is 400 fSec (femtoseconds), the wave train length is 0.120 mm, and the temporal overlap ratio between the first arriving light (optical path length L2) and the last arriving light (optical path length L1) is 0%. Furthermore, when the pulse length is 1 pSec (picoseconds), the wave train length is 0.300 mm, and the temporal overlap ratio is 19%. Furthermore, when the pulse length is 5 pSec (picoseconds), the wave train length is 1.499 mm, and the temporal overlap ratio is 84%. Furthermore, when the pulse length is 10 pSec (picoseconds), the wave train length is 2.998 mm, and the temporal overlap ratio is 92%.

[0062] In the optical device 100A according to the first embodiment, even when the rotating mirror 4 is at the maximum tilt angle position, the afocal optical system 3 must ensure that the wave trains of the pulsed laser beam 1 that reach the exit-side focus through the longest optical path (optical path length L1) and the wave trains of the pulsed laser beam 1 that reach the exit-side focus through the shortest optical path (optical path length L2) among the optical paths from the entrance-side focus to the exit-side focus of the afocal optical system 3 are at least partially overlapped in time. To achieve this, pulsed laser beams having a pulse length of approximately 0.8 pSec or more are used. In the optical device 100A according to the first embodiment, it is preferable that the wave trains of the two pulsed laser beams 1 overlap by 50% or more in time, and even more preferably by 75% or more in time. To achieve this, pulsed laser beams having a pulse length of approximately 2.5 pSec or more and pulsed laser beams having a pulse length of approximately 4 pSec or more are used. As mentioned above, the difference between the optical path length L1 and the optical path length L2 can be reduced or even made zero by changing the design (refractive index, thickness, surface shape) of the second convex lens 32.

[0063] [Rotating mirror 4] Fig. 14 is a diagram illustrating the configuration of the rotating mirror 4. Figs. 14(a) to 14(d) are plan views of the rotating mirror 4. Fig. 14(e) is a front view of the rotating mirror 4 shown in Fig. 14(a) as viewed along the rotation axis RAx. In Fig. 14, reference numeral 41 denotes a rotation drive motor, reference numeral 42 denotes a rotating shaft, reference numeral 44 denotes an annular reflective region, reference numeral 45 denotes an inner region inside the annular reflective region 44, the two-dot chain line indicated by reference numeral 46 denotes the boundary between the annular reflective region 44 and the inner region 45, and reference numeral 48 denotes a hole or cavity.

[0064] The rotating mirror 4 may have an entire mirror surface in which the inner region 45 of the annular reflective region 44 is also a mirror surface, as shown in Fig. 14(a), or may have an annular mirror surface in which the entire inner region 45 of the annular reflective region 44 is removed, as shown in Fig. 14(b), or may have a structure in which part of the inner region 45 of the annular reflective region 44 is absent (or removed), as shown in Fig. 14(c) and Fig. 14(d). Note that Fig. 14(c) has a structure in which the rotating shaft 42 extends into the inner region 45 of the annular reflective region 44, and Fig. 14(d) has a structure in which a number of holes are provided in the inner region 45 of the annular reflective region 44.

[0065] The rotating mirror 4 has an elliptical mirror surface as shown in FIG. 14(a) because the area that reflects the convergent beam 10 during use has an elliptical shape when viewed perpendicular to the mirror surface. This reduces the area and weight compared to a circular mirror surface. Alternatively, the rotating mirror 4 may have a structure in which all or part of the inside of the area that reflects the convergent beam 10 during use (annular reflection area 44) is removed, as shown in FIGS. 14(b) to 14(d). This further reduces the weight of the rotating mirror 14 (particularly the mirror surface). This allows for faster rotation of the rotating mirror 4, which in turn increases the speed at which spots are formed and the speed at which fine modified regions are formed.

[0066] [Productivity simulation] As described above, with the optical device 100A according to the first embodiment, it was found that spot quality could be maintained by enlarging the optical system and reducing the effective deflection angle, even under conditions where the beam shift amount (half angle) was ±2.5 mm (see Test Examples 4 and 8 in FIG. 12). On the other hand, it was also found that spot quality could be maintained even when the optical system was downsized by correspondingly reducing the beam shift amount. However, reducing the beam shift amount narrows the width of the outward spot train formation region and outward spot train formation region in the sub-scanning direction, as shown in FIG. 3, reducing productivity. Therefore, in this simulation, we investigated how small the optical system could be made while maintaining spot quality and maintaining a certain level of productivity. In this case, we used the optical device according to the comparative example shown in Table 1 as a benchmark. The optical device according to the comparative example was an apparatus that one-dimensionally forms one row of spots in one main scanning direction by moving the stage along the main scanning direction without scanning the convergent beam along the sub-scanning direction. Table 1 shows the specifications for forming spots over the entire processing target area using the optical device according to the comparative example.

[0067] [Table 1] ---------------------------------------------------------------------------------- Scanning of the convergent beam 10: No (only movement of the stage 6) Shape of processing area 95: Square shape with length and width of 500 mm Number of spots formed: 1 million (1000 formed at 0.5 mm intervals along the main scanning direction, and 1000 lines formed at 0.5 mm intervals along the sub-scanning direction) Movement speed of stage 6 along the main scanning direction: 200 mm / sec Effective efficiency: 70% Main scanning time along the main scanning direction: 3.571 seconds Processing time per substrate: 3571 seconds (approximately 60 minutes) ----------------------------------------------------------------------------------

[0068] Comparative Example In the comparative example, 1,000 spots are formed one-dimensionally with one scan along the main scanning direction. Therefore, to form spots over the entire processing target area 95, it is necessary to scan 1,000 times in the main scanning direction while shifting the scans at 0.5 mm intervals in the sub-scanning direction. Therefore, since one scan in the main scanning direction takes 3.571 seconds, a processing time of 3,571 seconds (approximately 60 minutes) is required for the entire processing target area 95. This was used as the benchmark.

[0069] [Example] Therefore, in the example, the goal was to reduce the processing time for the entire processing target region 95 to less than half that of the comparative example (i.e., 30 minutes). Fig. 15 is a chart showing the simulation results regarding productivity.

[0070] Simulations were performed by setting the wavelength of the pulsed laser light 1 (laser wavelength λ) to two types, 1030 nm and half that, 515 nm, and changing the maximum beam shift amount (Test Examples 9 to 16).

[0071] The spot diameter (diameter of the first dark ring) formed on the glass substrate is approximately 2 μm when the wavelength is 1030 nm, and approximately 1 μm (half the diameter when the wavelength is 1030 nm) when the wavelength is 515 nm. The spot is formed in a concentric pattern with alternating bright and dark areas. The first dark ring is the dark ring that first forms outside the central bright area.

[0072] The maximum effective deflection angle (half angle) θ is ±0.75 degrees when the wavelength is 1030 nm (Test Examples 9 to 12), and is half that, ±0.37 degrees, when the wavelength is 515 nm (Test Examples 13 to 16).

[0073] The maximum beam shift amount (full angle) corresponds to the scanning width in the sub-scanning direction, that is, the width of the spot row in one main scanning pass (scanning width in the sub-scanning direction).

[0074] Simulations were performed by changing the maximum beam shift amount. 1. When the wavelength of pulsed laser light 1 is 1030 nm When the maximum beam shift amount (full angle) d is set to 5 mm, the substrate processing time (the time it takes to form spots P on the entire glass substrate) is 6 minutes. This is 0.1 times the time of the comparative example. This is because 10 spot rows (compared to 1 in the conventional method) can be formed along the sub-scanning direction in one main scan. The size of the rotating mirror 4 is 82.1 mm on the short side and 116.0 mm on the long side (Test Example 9).

[0075] When the maximum beam shift amount (full angle) d is set to 2.5 mm, the substrate processing time is 12 minutes, which is approximately 0.2 times the time of the comparative example. The size of the rotating mirror 4 is 41.0 mm in short side and 58.0 mm in long side (Test Example 10). When the maximum beam shift amount (full angle) d is set to 1.25 mm, the substrate processing time is 24 minutes, compared to approximately 0.4 hours in the comparative example. The size of the rotating mirror 4 is 20.5 mm on the short side and 29.0 mm on the long side (Test Example 11). When the maximum beam shift amount (full angle) d is set to 0.63 mm, the substrate processing time is 48 minutes, which is approximately 0.8 times the time of the comparative example. The size of the rotating mirror 4 is 10.3 mm on the short side and 14.5 mm on the long side (Test Example 12).

[0076] 2. When the wavelength of pulsed laser light 1 is 515 nm When the maximum effective beam shift amount d (full angle) is set to 2.50 mm, the substrate processing time is 12 minutes, which is approximately 0.2 times the time of the comparative example. The size of the rotating mirror 4 is 82.1 mm in short side and 116.0 mm in long side (Test Example 13). When the maximum effective beam shift amount d (full angle) is set to 1.25 mm, the substrate processing time is 24 minutes, which is approximately 0.4 times the time of the comparative example. The size of the rotating mirror 4 is 41.0 mm in short side and 58.0 mm in long side (Test Example 14). When the maximum effective beam shift amount (full angle) d is set to 0.63 mm, the substrate processing time is 48 minutes, which is approximately 0.8 times the time of the comparative example. The size of the rotating mirror 4 is 20.5 mm in short side and 29.0 mm in long side (Test Example 15). When the maximum effective beam shift amount d (full angle) is set to 0.31 mm, the substrate processing time is 96 minutes, which is approximately 1.6 times longer than the comparative example. The size of the rotating mirror 4 is 10.3 mm on the short side and 14.5 mm on the long side (additional test example 16).

[0077] As shown in Figure 15, increasing the maximum effective beam shift (full angle) allows the size of the optical system to be reduced, but productivity decreases. When aiming for a substrate processing time of 30 minutes or less, which is half the substrate processing time (benchmark) in the comparative example, it was found that the target could be achieved even if the maximum effective beam shift was reduced to 1.25 mm, for both 1030 nm and 515 nm.

[0078] [Embodiments 2 to 4] Optical devices 100B to 100D according to embodiments 2 to 4 are basically the same as the optical device 100A according to embodiment 1, but differ mainly in the optical system 2, and will be described in order.

[0079] [Embodiment 2] Fig. 16 is a diagram for explaining an overview of an optical device 100B according to embodiment 2. As shown in Fig. 16, the optical device 100B according to embodiment 2 basically has the same configuration as the optical device 100A according to embodiment 1, but differs in that the optical system 2 includes two axicon lenses (axicon lenses 21 and 22) provided along the traveling direction of the pulsed laser beam 1.

[0080] The pulsed laser light 1 generates a first Bessel beam region 11a when it passes through the first axicon lens 21. Then, it generates a next Bessel beam region 11b when it passes through the next axicon lens 22. The next Bessel beam region 11b is then relayed by the afocal optical system 3 to become the Bessel beam region 11 in the vicinity of the workpiece 9.

[0081] [Effects of the Second Embodiment] As described above, the optical system 2 of the optical device 100B according to the second embodiment is different from that of the optical device 100A according to the first embodiment. However, the convergent beam 10 is scanned on the workpiece 9 along a predetermined beam scanning direction by the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation. Therefore, similar to the optical device 100A according to the first embodiment, a large number of fine modified regions can be formed on the workpiece at higher speeds than conventionally possible.

[0082] Furthermore, according to the optical device 100B of the second embodiment, the optical system 2 includes two axicon lenses 21 and 22 arranged along the traveling direction of the pulsed laser beam 1, which has the advantage of making it easier to adjust the size (diameter, length) of the Bessel beam region 11 than in the case of the optical device 100A of the first embodiment.

[0083] [Embodiment 3] Fig. 17 is a diagram illustrating an overview of an optical device 100C according to embodiment 3. As shown in Fig. 17, the optical device 100C according to embodiment 3 basically has the same configuration as the optical device 100A according to embodiment 1, but differs in that the optical system 2 further includes a lens system 25 that adjusts the size (diameter, length) of the Bessel beam region 11 generated near the target object 9.

[0084] 17, when the pulsed laser beam 1 passes through the axicon lens 21, the outer diameter of the annulus gradually decreases (the light beams become parallel within the annulus), converges once near the initial Bessel beam region 11a, and then diverges. The optical device 100C according to the third embodiment further includes, at the position of the convergence portion, a lens system 25 that adjusts the size (diameter, length) of the Bessel beam region 11 generated near the workpiece 9. Therefore, the optical device 100C according to the third embodiment has an advantage that it is easier to adjust the size (diameter, length) of the Bessel beam region 11 generated near the workpiece 9 than the optical device 100A according to the first embodiment.

[0085] If the lens system 25 is a convex lens system, the thickness of the annulus (the width of the annulus along the diameter direction) gradually decreases after passing through the lens system 25, and the size (diameter, length) of the Bessel beam region 11 decreases.

[0086] [Effects of the Third Embodiment] As described above, the optical system 2 of the optical device 100C according to the third embodiment is different from that of the optical device 100A according to the first embodiment. However, the convergent beam 10 is scanned on the workpiece 9 along a predetermined beam scanning direction by the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation. Therefore, as in the case of the optical device 100A according to the first embodiment, a large number of fine modified regions can be formed on the workpiece at higher speeds than conventionally possible.

[0087] Furthermore, according to the optical device 100C of the third embodiment, the optical system 2 further includes a lens system 25 that adjusts the size (diameter, length) of the Bessel beam region 11 generated near the workpiece 9, which has the effect of making it easier to adjust the size (diameter, length) of the Bessel beam region 11 than in the case of the optical device 100A of the first embodiment.

[0088] [Embodiment 4] Fig. 18 is a diagram illustrating an overview of an optical device 100D according to embodiment 4. As shown in Fig. 18, the optical device 100D according to embodiment 4 basically has the same configuration as the optical device 100B according to embodiment 2, but differs in that the optical system 2 further includes a lens system 25 that adjusts the length of a Bessel beam region 11 of the convergent beam 10 generated in the vicinity of the workpiece 9.

[0089] [Effects of the fourth embodiment] As described above, the optical system 2 of the optical device 100D according to the fourth embodiment is different from that of the optical device 100B according to the second embodiment. However, the convergent beam 10 scans the workpiece 9 along a predetermined beam scanning direction due to the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation. Therefore, similar to the optical device 100B according to the second embodiment, a large number of fine modified regions can be formed on the workpiece at higher speeds than conventional methods.

[0090] Furthermore, according to the optical device 100D of the fourth embodiment, the optical system 2 further includes a lens system 25 that adjusts the size (diameter, length) of the Bessel beam region 11 generated near the workpiece 9, which has the effect of making it easier to adjust the size (diameter, length) of the Bessel beam region 11 than in the case of the optical device 100B of the second embodiment.

[0091] Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment. The present invention can be embodied in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0092] (1) In the above-described embodiment, a pulsed laser beam is used as the laser beam, but the present invention is not limited to this. A CW laser beam may also be used as the laser beam. In this case, a linear fine modified region in plan view can be formed instead of a spot-shaped fine modified region in plan view.

[0093] (2) In the above embodiment, an optical device is used in which the convergent beam 10 scans the workpiece 9 along a predetermined beam scanning direction by controlling the reciprocating rotation of a rotating mirror (hereinafter, this is referred to as a rotating mirror system), but the present invention is not limited to this. Fig. 19 is a diagram for explaining an overview of an optical device 100E according to a modified example. The present invention can also scan the convergent beam 10 along a predetermined beam scanning direction on the workpiece 9 using an optical device as shown in FIG. 19 (for example, optical device 100E, which uses as its optical system an optical system 102 including a first axicon lens 121 and a second axicon lens 122 arranged along the traveling direction of the pulsed laser beam 1 and a mirror 104 arranged between the first axicon lens 121 and the second axicon lens 122 for reflecting the laser beam, and which emits the convergent beam 10 from the second axicon lens 122, and which uses as its control unit a control unit 105 having a function of scanning the convergent beam 10 along a predetermined beam scanning direction 15 on the workpiece 9 by controlling the reciprocating motion of the mirror 4 and the second axicon lens 122). Therefore, the optical device of the present invention also includes the following optical devices A to F and a fine modified region forming method G. In the optical device 100E according to the modified example, the mirror 104 and the second axicon lens 122 are attached to a housing 131 and are reciprocated along the beam scanning direction 15 by a voice coil motor 107.

[0094] A: An optical device 100A for forming a fine modified region on a workpiece 9 using pulsed laser light 1, the optical device comprising: a focusing optical system 2 for forming a convergent beam 10 from the pulsed laser light 1; a control unit 5 for scanning the convergent beam 10 on the workpiece along a predetermined beam scanning direction 15; and a stage 6 for placing the workpiece 9, the stage 6 being configured to be movable along predetermined main scanning and sub-scanning directions that are perpendicular to each other in a plane parallel to the placing surface, wherein the control unit 5 has the function of scanning the convergent beam 10 along the beam scanning direction 15 on the workpiece while moving the stage 6 along the main scanning direction with the beam scanning direction 15 and the sub-scanning direction tilted by a predetermined angle (α), thereby forming a spot train by the pulsed laser light 1 on the workpiece along the sub-scanning direction.

[0095] B: An optical device in which the control unit 5 has the function of forming a spot train by the pulsed laser light 1 two-dimensionally (in strips) on the workpiece by repeating the operation of forming the spot train on the workpiece along the sub-scanning direction while moving the stage 6 along the main scanning direction.

[0096] C: The control unit 5 repeats the operation of forming the spot train two-dimensionally on the workpiece while intermittently moving the stage 6 along the sub-scanning direction and while reciprocating the stage 6 along the main scanning direction, thereby forming the spot train over the entire area to be processed on the workpiece.

[0097] D: An optical device in which the control unit 5 has a function of forming the spot sequence on the workpiece along the sub-scanning direction while the angle between the beam scanning direction 15 and the sub-scanning direction is reversed on the outbound and return paths of the reciprocating movement.

[0098] E: An optical device in which the control unit 5 has the function of forming the spot train in a forward direction along the sub-scanning direction on the workpiece during the outgoing path of the reciprocating movement, and forming the spot train in a reverse direction along the sub-scanning direction on the workpiece during the return path of the reciprocating movement.

[0099] F: An optical device in which the convergent beam is emitted when the operating speed of the reciprocating motion is constant under the control of the control unit.

[0100] G: A method for forming a fine modified region in a workpiece 9 placed on a stage 6 configured to be movable along predetermined main scanning and sub-scanning directions that are perpendicular to each other in a plane parallel to the mounting surface, by scanning a convergent beam 10 formed from pulsed laser light 1 along a predetermined beam scanning direction 15 on the workpiece 9, wherein the beam scanning direction 15 and the sub-scanning direction are tilted at a predetermined angle (α), thereby forming a series of spots by the pulsed laser light 1 on the workpiece along the sub-scanning direction.

[0101] (3) In the above embodiment, the maximum number of spots is formed on the workpiece 9. However, instead of forming the maximum number of spots, any number of spots may be formed. In this case, spots may be formed only at any desired positions.

[0102] (4) In the above embodiment, when scanning on the outbound path is completed, scanning is performed on the adjacent return path (see FIG. 3, etc.). However, if there is no spot P to be formed on the adjacent return path, scanning on that return path may not be performed, and the stage 6 may move to the return path where the spot P to be formed is located (by moving the stage 6 relatively) and scan on the return path. The actual movement path of the spot is optimized to minimize the time based on the processing data.

[0103] (5) In the above embodiment, the spot train is formed in a direction parallel to the sub-scanning direction (a direction perpendicular to the main scanning direction), but it may be formed in an oblique direction that is not parallel to the sub-scanning direction. [Explanation of symbols]

[0104] 1...pulse laser light, 10...convergent beam, 11...Bessel beam region, 11a...first Bessel beam region, 11b...next Bessel beam region, 15...beam scanning direction, 2, 102...optical system, 21, 22, 121, 122...axicon lens, 25...lens system, 3...afocal optical system, 31...first convex lens system, 32...second convex lens system, 32Ax...optical axis of second convex lens system, 4...rotating mirror, 41...rotation drive motor, 42...rotating shaft, 44...annular reflection region , 45...inner region, 46...boundary between annular reflection region 44 and inner region 45, 48...hole, 5, 105...controller, 6...stage, 9...workpiece, 95...processing target region, 100A, 100B, 100C, 100D, 100E...optical device, 104...mirror, 107...voice coil motor, 131...casing, f1...focal length of first convex lens system, f2...focal length of second convex lens system, P...spot, Ax...optical axis of optical device, F...focus, CF...common focus, RAx...rotation center axis, α...angle

Claims

1. An optical device for forming a fine modified region on a workpiece using laser light, an afocal optical system having a first convex lens system and a second convex lens system arranged along the traveling direction of the laser light, and an optical system having a rotating mirror arranged at a common focal position of the first convex lens system and the second convex lens system, and emitting a convergent beam from the second convex lens system; an optical device comprising a control unit having a function of scanning the convergent beam along a predetermined beam scanning direction on the workpiece by controlling the reciprocating rotational movement of the rotating mirror;

2. 2. The optical device according to claim 1, The optical device, wherein the laser light is a pulsed laser light.

3. 2. The optical device according to claim 1, The optical system includes an axicon lens.

4. 2. The optical device according to claim 1, The optical system includes two axicon lenses arranged along a traveling direction of the laser light.

5. 2. The optical device according to claim 1, An optical device, wherein the focal length of the second convex lens system is shorter than the focal length of the first convex lens system.

6. 5. The optical device according to claim 3, The optical system further includes a lens system that adjusts the length of a Bessel beam region formed by the convergent beam emitted from the second convex lens system.

7. 2. The optical device according to claim 1, The second convex lens system is configured such that, when the rotating mirror is positioned virtually perpendicular to the optical axis of the second convex lens system, a divergent light beam having an optical axis parallel to the optical axis of the second convex lens system, which is emitted from a predetermined point within the area of ​​the rotating mirror through which the laser light passes toward the area of ​​the second convex lens system through which the laser light passes, becomes parallel after passing through the second convex lens system.

8. 2. The optical device according to claim 1, An optical device, wherein the maximum effective swing angle (half angle) θ (degrees) of the rotating mirror and the wavelength λ (nm) of the laser light satisfy the following relationship: (θ) / (λ / 1030)≦1

9. 2. The optical device according to claim 1, The rotating mirror has a structure in which all or part of the inside of an annular reflective area that reflects the laser light during use is absent.

10. 3. The optical device according to claim 2, The afocal optical system is an optical device configured such that, even when the rotating mirror is at the maximum effective swing angle position, a wave train of the pulsed laser light that reaches the focus on the exit side via the optical path with the longest optical path length among the optical paths from the focus on the entrance side to the focus on the exit side of the afocal optical system and a wave train of the pulsed laser light that reaches the focus on the exit side via the optical path with the shortest optical path length are overlapped, even if only partially, in terms of time.

11. 3. The optical device according to claim 2, a stage for placing the workpiece thereon, the stage being configured to be movable along predetermined main scanning and sub-scanning directions that are orthogonal to each other within a plane parallel to the placement surface; the control unit has a function of forming a train of spots by the pulsed laser light on the workpiece along the sub-scanning direction by scanning the convergent beam along the beam scanning direction while moving the stage along the main scanning direction in a state in which the rotation axis of the stage or the rotating mirror is rotated so that the beam scanning direction and the sub-scanning direction are tilted by a predetermined angle (α).

12. 12. The optical device according to claim 11, the control unit has a function of forming a spot train by the pulsed laser light on the workpiece in two dimensions by repeating the operation of forming the spot train on the workpiece in the sub-scanning direction while moving the stage in the main scanning direction.

13. 13. The optical device according to claim 12, the control unit repeats the operation of forming the spot train two-dimensionally on the workpiece while intermittently moving the stage along the sub-scanning direction and while moving the stage back and forth along the main scanning direction, thereby forming the spot train over the entire area to be processed on the workpiece.

14. 14. The optical device according to claim 13, the control unit has a function of forming the spot sequence on the workpiece along the sub-scanning direction while the angle between the beam scanning direction and the sub-scanning direction is reversed on the outbound and return paths of the reciprocating movement.

15. 14. The optical device according to claim 13, The control unit has a function of forming the spot train in a forward direction along the sub-scanning direction on the workpiece during the outbound path of the reciprocating movement, and forming the spot train in a reverse direction along the sub-scanning direction on the workpiece during the return path of the reciprocating movement.

16. 2. The optical device according to claim 1, The optical device, wherein the convergent beam is emitted when the reciprocating motion speed is constant under the control of the control unit.

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