Optical device and method for forming a micro-modified region

Abstract

The present invention provides an optical device capable of forming micro-modified regions at a faster rate than conventional methods. [Solution] An optical device 100A for forming a micro-modified region on a workpiece 9 using pulsed laser light 1, comprising: an afocal optical system 3 having a first convex lens system 31 and a second convex lens system 32 provided along the direction of propagation of the pulsed laser light 1; an optical system 2 having a rotating mirror 4 provided at the position of the common focal point CF of the first convex lens system 31 and the second convex lens system 32, and emitting a convergent beam 10 from the second convex lens system 32; and a control unit 5 having 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 relates to an optical device and a method for forming a fine modified region. [Background Art]

[0002] In recent years, further higher integration of semiconductor packages has been demanded, and since further miniaturization of wiring in the so-called pre-process is not easy, interest in the so-called post-process has been increasing. Among these is Chiplet technology. This is a technology in which small semiconductor chips each with functions assigned according to their roles are combined like blocks and housed in a single package. An interposer (intermediate substrate) is used for connection between semiconductor chips. A glass substrate or the like is used for the interposer, and a large number of fine through holes (TGV: Through Glass Vias) are formed in the plane to achieve conduction between circuits on the front and back sides.

[0003] To form a large number of fine through holes in an interposer, convergent pulsed laser light is irradiated onto a workpiece while appropriately moving a stage on which the workpiece is mounted, so as to form fine modified regions (hereinafter referred to as "fine modified regions") at a plurality of predetermined locations. Subsequently, wet etching of the workpiece is performed using a hydrofluoric acid-based etching solution or the like to form a large number of fine through holes from the fine modified regions at the plurality of locations. In this case, if convergent pulsed laser light generated using, for example, an axicon lens is used as the convergent pulsed laser light, a Bessel beam region having an extremely high aspect ratio can be generated. Therefore, a high-quality fine modified region having a more uniform diameter than conventional ones along the depth direction (thickness direction) of the workpiece, and consequently, a high-quality fine through hole having a more uniform diameter than conventional ones along the depth direction (thickness direction) of the interposer can be formed (see, for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-136442 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the field of technology for forming micro-modified regions in workpieces, there is a challenge in forming these micro-modified regions at a faster speed than before, and this challenge is not unique to the use of focused pulsed laser light generated using an axicon lens. Therefore, the present invention aims to provide an optical device and a method for forming a micro-modified region that can form a micro-modified region at a faster speed than conventional methods. [Means for solving the problem]

[0006] [1] An optical device relating to one aspect of the present invention is an optical device that forms a micro-modified region on a workpiece using laser light, comprising an afocal optical system having a first convex lens system and a second convex lens system provided along the direction of propagation of the laser light, an optical system having a rotating mirror provided at the common focal position of the first convex lens system and the second convex lens system, which emits a focusing beam from the second convex lens system, and a control unit which has the function of scanning the focusing beam on the workpiece along a predetermined beam scanning direction by controlling the reciprocating rotational movement of the rotating mirror.

[0007]

[17] An optical device relating to another aspect of the present invention is an optical device for forming a micro-modified region on a workpiece using pulsed laser light, comprising: a focusing optical system for forming a focusing beam from the pulsed laser light; a control unit for scanning the focusing beam on the workpiece along a predetermined beam scanning direction; and a stage for placing the workpiece, the stage configured to be movable along a predetermined main scanning direction and sub-scanning direction which are mutually orthogonal in a plane parallel to the placement surface, wherein the control unit has the function of forming a spot row of pulsed laser light on the workpiece along the sub-scanning direction by scanning the focusing 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).

[0008]

[23] A method for forming a micro-modified region relating to another aspect of the present application is: A method for forming a micro-modified region on a workpiece, wherein the workpiece is placed on a stage configured to be movable along predetermined main scanning directions and sub-scanning directions that are mutually orthogonal in a plane parallel to the mounting surface, and a focusing beam formed from pulsed laser light is scanned along a predetermined beam scanning direction, thereby forming a micro-modified region on the workpiece. With the beam scanning direction and the sub-scanning direction tilted by a predetermined angle (α), the converging beam is scanned along the beam scanning direction while the stage is moved along the main scanning direction, thereby forming a row of spots on the workpiece along the sub-scanning direction using the pulsed laser light.

[0009] According to the optical device relating to one aspect described above, it is possible to form micro-modified regions at a faster speed than conventional methods. Furthermore, according to the optical device relating to the other aspect of this application and the method for forming micro-modified regions described above, it is possible to form a large number of micro-modified regions at a faster speed than conventional methods. [Brief explanation of the drawing]

[0010] [Figure 1]A diagram illustrating the outline of the optical device 100A according to Embodiment 1. [Figure 2] This diagram illustrates the configuration of the afocal optical system 3 in the optical device 100A. [Figure 3] This diagram illustrates the method for forming a series of spots across the entire processing area 95. [Figure 4] This figure illustrates the method for forming a spot row along the sub-scanning direction in the "forward path spot row formation region". [Figure 5] This diagram illustrates the two-dimensional method of forming the spot array in the "forward path spot array formation region." [Figure 6] This diagram illustrates the two-dimensional formation method of the spot array in the "return path spot array formation region." [Figure 7] This figure illustrates the method of forming a spot row along the sub-scanning direction in the "return path spot row formation region". [Figure 8] This figure illustrates how to form other spot rows along the sub-scanning direction in the "return path spot row formation region". [Figure 9] This diagram illustrates the configuration of the second convex lens system 32. [Figure 10] This figure shows the in-plane light intensity distribution of the focusing beam 10. [Figure 11] This figure illustrates the beam shift amount of the converging beam 10 and the maximum effective swing angle of the rotating mirror 4. [Figure 12] A diagram showing the relationship between the maximum effective swing angle θ of the rotating mirror 4 and the quality of the spot. [Figure 13] A diagram showing how the wave feeds of pulsed laser light 1 are superimposed over time. [Figure 14] A diagram illustrating the configuration of the rotating mirror 4. [Figure 15] A chart showing the simulation results regarding productivity. [Figure 16] A diagram illustrating the outline of the optical device 100B according to Embodiment 2. [Figure 17]A diagram shown for explaining the outline of an optical device 100C according to Embodiment 3. [Figure 18] A diagram shown for explaining the outline of an optical device 100D according to Embodiment 4. [Figure 19] A diagram shown for explaining the outline of an optical device 100E according to a modification. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an optical device (100A to 100D) and a method for forming a fine modified region according to one aspect of the present invention will be described with reference to the drawings. Each drawing is a schematic diagram and does not necessarily strictly reflect an actual optical device. In addition, each embodiment does not limit the scope of the claims. Furthermore, not all of the constituent elements and combinations thereof described in each embodiment are necessarily essential to the present invention. Constituent elements that can be regarded as substantially equivalent are denoted by the same reference numerals across embodiments, and repeated description may be omitted (some descriptions may overlap).

[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. FIGS. 1 to 15 are diagrams shown for explaining an optical device 100A according to Embodiment 1. FIG. 1 is a diagram shown for explaining the outline of the optical device 100A, and FIG. 2 is a diagram shown for explaining the configuration of an afocal optical system 3 in the optical device 100A.

[0013] Note that, since FIG. 1 and FIGS. 16 to 18 described later are diagrams shown for explaining the outline of optical devices (optical devices 100A, 100B, 100C, 100D), the first convex lens system 31 and the second convex lens system 32 are illustrated as simple convex lenses. In FIG. 2 and FIGS. 9 and 13 described later, the first convex lens system 31 and the second convex lens system 32 are illustrated as convex lenses having specific lens shapes.

[0014] Furthermore, in Figure 1 and Figure 17 (described later), the optical apparatus (100A, 100C) is explained using the example where 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, while in Figure 2 and Figures 16 and 18 (described later), the optical apparatus (100B, 100D) is explained using the example where 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] The optical device 100A according to Embodiment 1 is an optical device 100A that forms a micro-modified region on a workpiece 9 using pulsed laser light 1. As shown in Figures 1 and 2, the optical device 100A according to Embodiment 1 includes 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, and an optical system 2 having a rotating mirror 4 provided at the common focal point CF of the first convex lens system 31 and the second convex lens system 32, and emitting a convergent beam 10 from the second convex lens system 32, and a control unit 5 that controls the reciprocating rotational movement of the rotating mirror 4 to scan the convergent beam 10 on the workpiece 9 along a predetermined beam scanning direction 15.

[0016] The optical system 2 includes one axicon lens 21. In Figure 2, the symbol (a) indicates the position where the focusing beam 10 is projected when the rotating mirror 4 is at its maximum effective swing angle position in the clockwise direction, the symbol (c) indicates the position where the focusing beam 10 is projected when the rotating mirror 4 is at its maximum effective swing angle position in the counterclockwise direction, and the symbol (c) indicates a position intermediate between the symbols (a) and (c) (see Figure 10(a) described later).

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

[0018] Subsequently, the pulsed laser light 1 passes through the first convex lens system 31, is reflected by the rotating mirror 4, and then passes through the second convex lens system 32 before being 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, becoming the Bessel beam region 11.

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

[0020] Therefore, in the optical device 100A according to Embodiment 1, the convergent beam 10 that has passed through the second convex lens system 32 is a convergent beam generated using an axicon lens, so a Bessel beam region 11 with an extremely high aspect ratio is formed near the workpiece 9. For this reason, the optical device 100A according to Embodiment 1 can form a high-quality micro-modification region with a more uniform diameter than conventional methods over the depth direction (thickness direction) of the workpiece.

[0021] Furthermore, in the optical device 100A according to Embodiment 1, the converging 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, with the optical device 100A according to Embodiment 1, a large number of fine modification regions can be formed on the workpiece at a faster speed than in the conventional method.

[0022] In the optical device 100A according to Embodiment 1, 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 Figure 1, 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, while in Figure 2, 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.

[0023] As shown in Figure 1, if the focal length f2 of the second convex lens system 32 is made shorter than the focal length f1 of the first convex lens system 31, the diameter of the micro-modification region can be made smaller.

[0024] In contrast, as shown in Figure 2, if the focal length f2 of the second convex lens system 32 is made 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 made to have the same configuration, and the length of the initial bessel beam region 11a and the bessel beam region 11 formed near the workpiece can be made to be the same length.

[0025] Here, we will explain the components of the optical device 100A described above, as well as the terminology used in the explanation. [Optical axis Ax] The optical axis Ax, indicated by the dashed line, is the optical axis of the optical device 100A. The optical axis Ax is the optical axis through which light actually passes until it enters the axicon lens 21, but after passing through the axicon lens 21, it is a virtual optical axis through which light may not actually pass. As described above, the pulsed laser light 1 does not pass through the optical axis Ax point 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] [Pulsed laser light 1] "Pulsed laser light 1" refers to pulsed laser light with pulse widths such as nanoseconds, picoseconds, and 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 constitute 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 multiple convex lenses, but also a lens made up of a convex lens and a concave lens that functions as a convex lens as a whole. The "rotating mirror 4" is positioned at the common focal point CF of the first convex lens system 31 and the second convex lens system 32, and is configured to reciprocate rotationally by a rotation drive motor. A galvanometer mirror in which the rotating mirror 4 and the rotation drive motor are integrated is available on the market. The "workpiece 9" is, for example, a glass substrate.

[0028] [Region through which pulsed laser light 1 passes or is reflected] As shown in Figures 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 area enclosed by the dashed line in Figures 1 and 2). The area enclosed by the dashed line is an annular region centered on the optical axis Ax when viewed along the optical axis Ax in the first convex lens system 31, an annular region centered on the point where the reflective surface of the rotating mirror 4 intersects the optical axis Ax in the rotating mirror 4, and an annular region centered on the optical axis Ax when viewed along the optical axis Ax in the second convex lens system 32. Note that the annular shape includes ellipses, ovals, short circles, and perfect circles.

[0029] [Converging beam 10] In Embodiment 1, the pulsed laser light 1, after passing through the second convex lens system 42, becomes a focused beam 10 as the outer diameter of the beam decreases along the direction of propagation. The focused beam forms a Bessel beam region 11 near the workpiece 9.

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

[0031] [Optical system 2] In the optical device 100A of Embodiment 1, the optical system 2 includes one axicon lens 21, as described above. Here, "axicon lens" is a cone-shaped lens. Note that the subsequent axicon lenses 22 used in the optical devices 100B and 100D shown in Figures 16 and 18, which will be described later, do not need to be entirely cone-shaped. It is sufficient that the region through which the pulsed laser light 1 passes is part of a cone; for example, it may be a cone with the top portion of the cone cut off. The cone of the axicon lens 21 of optical device 100A may be on either the output side or the input side of the pulsed laser light 1.

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

[0033] [Method for forming a spot row by scanning a convergent beam 10] Figures 3 to 5 illustrate the method of forming a spot row by scanning the focusing beam 10 in the optical device 100A. Figure 3 is a diagram illustrating the method of forming a spot row over the entire processing area 95. Figure 4 is a diagram illustrating the method of forming a spot row along the sub-scanning direction in the "forward spot row formation area". Figure 5 is a diagram illustrating the two-dimensional method of forming a spot row in the "forward spot row formation area". In Figures 3 to 5, the X-axis is the axis along the main scanning direction, the Y-axis is the axis along the sub-scanning direction, and the Z-axis is the axis perpendicular to the X-axis and Y-axis.

[0034] As described above, the optical device 100A according to Embodiment 1 further comprises a stage 9 for placing the workpiece 9 (see Figures 1 and 2). The stage 9 is configured to be movable along predetermined mutually orthogonal main scanning direction (X-axis direction) and sub-scanning direction (Y-axis direction) in a plane parallel to the mounting surface (XY plane) (see Figures 3 to 5).

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

[0036] In the optical device 100A according to Embodiment 1, the control unit 5 rotates the stage 6 or the rotating mirror 4's rotation axis 42 so that the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) are tilted by a predetermined angle (α) (see Figure 4(a)), and then gradually moves the stage 6 along the main scanning direction (X-axis direction) while scanning the converging beam 10 along the beam scanning direction 15 (see Figures 4(b) to 4(d)) to form a row of spots (P01, P02, P03, ...) on the workpiece 9 along the sub-scanning direction (Y-axis direction). Specifically, the step of forming a row of spots along the sub-scanning direction is carried out as follows.

[0037] [Method for forming a spot row along the sub-scanning direction] First, the control unit 5 moves the stage 6 to its initial position and rotates the rotating mirror 4 to its maximum clockwise swing angle position (see Figure 11(a) described later). Then, it starts controlling the movement of the stage 6 along the main scanning direction and the rotation of the rotating mirror around the rotation axis RAx (see Figure 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] Subsequently, after time t0, at time t1, the stage 6 moves to the left of its position at time t0, and the rotating mirror 4 rotates counterclockwise by a predetermined angle (forward rotation). As a result, the focusing beam 10 is irradiated onto a predetermined position on the workpiece 9, and a spot P01 is formed at that position (see Figure 4(b)). The rotational position (swing angle position) of the rotating mirror 4 at time t1 becomes the maximum effective swing angle position.

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

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

[0041] In this way, by repeatedly forming spots along the sub-scanning direction, a series of spots (P01, P02, P03, ...) extending in the direction of the sub-scanning direction are formed on the workpiece 9.

[0042] [Method for forming a two-dimensional spot train in the "outbound spot train formation region"] Next, with reference to Figure 5, a two-dimensional method for forming the spot array in the "forward path spot array formation region" will be explained. First, the first row of spots (the leftmost row of spots in Figure 5, hereinafter referred to as the first row of spots) is formed along the sub-scanning direction. Next, once the formation of the first row of spots is complete, the rotating mirror 4 rotates in the reverse direction (clockwise) to return to the position of maximum clockwise swing angle for forming the next row of spots (hereinafter referred to as the next row of spots) along the sub-scanning direction, and then forms the next row of spots in the same manner as above. The stage 6 is always moving at a constant speed along the main scanning direction (in this case, from right to left), and by repeating the above row formation, a large number of row of spots are formed in a binary manner within the "forward row of spot formation region" (see Figures 3 and 5).

[0043] Thus, in the optical device 100A according to Embodiment 1, the control unit 5 tilts the beam scanning direction 15 and the sub-scanning direction by a predetermined angle (α), moves the stage 6 along the main scanning direction, and repeatedly performs the operation of forming a spot row with pulsed laser light 1 along the sub-scanning direction, thereby forming a spot row two-dimensionally within the processing area 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 rotating mirror 4 around the rotation axis RAx.

[0044] Therefore, in the optical device 100A according to Embodiment 1, while the stage 6 is moved once in the main scanning direction, spots are formed bidirectionally within the "forward path spot row formation region" (see Figure 5). As a result, the optical device 100A according to Embodiment 1 can form a large number of micro-modification regions on the workpiece at a faster speed than conventional methods.

[0045] [Method for forming a spot row across the entire processing area 95] Referring again to Figures 3 and 5, the method for forming a spot row over the entire area 95 to be processed will be explained. First, a spot row is formed two-dimensionally in a certain "forward spot row formation region" (for example, the forward spot row formation region R1 in Figure 3) by forming a spot row from left to right using the method shown in Figures 3 and 5. Once the formation of the spot row in that region is complete, the control unit 5 (temporarily interrupts the formation of the spot row) moves the stage 6 along the sub-scanning direction to the next processing region, the "return spot row formation region" (for example, the return spot row formation region R2 in Figure 3), and then forms a spot row two-dimensionally in that region by forming a spot row from right to left. At this time, as shown in Figure 4 and Figure 7 described later, the spot row is formed two-dimensionally in the "return spot row formation region" under the condition that the angle α between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is the opposite of the forward spot row formation direction in the "forward spot row formation region".

[0046] Once the formation of the spot rows in the "return spot row formation region" is complete, the control unit 5 (temporarily interrupts spot formation) moves the stage 6 along the sub-scanning direction to the next processing region, the "next forward spot row formation region" (for example, the forward spot row formation region R3 in Figure 3), and then forms the spot rows in that region from left to right, thereby forming the spot rows two-dimensionally. At this time, the formation of the spot rows along the sub-scanning direction is performed under the condition that the angle between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is the opposite of that in the "return spot row formation region," and the spot rows are formed two-dimensionally in the "forward spot row formation region." By repeating these steps, a large number of spot rows are formed across the entire processing area 95 of the workpiece 9.

[0047] Thus, in the optical device 100A according to Embodiment 1, the operation of forming a two-dimensional row of spots on the workpiece is repeated while intermittently moving the stage 6 along the sub-scanning direction and while reciprocating the stage 6 along the main scanning direction. As a result, with the optical device 100A according to Embodiment 1, a row of spots can be formed over the entire processing area 95 of the workpiece 9.

[0048] Figure 6 is a diagram illustrating the two-dimensional formation method of spot rows in the "return path spot row formation region". Figure 7 is a diagram illustrating the formation method of spot rows along the sub-scanning direction in the "return path spot row formation region". In the optical device 100A according to Embodiment 1, if the spot row is formed in the "return path spot row formation region" in the same way as in the "forward path spot row formation region," the stage 6 is moving in the reverse direction (from left to right), making it impossible to form a spot row along the sub-scanning direction (Y-axis direction). Therefore, in the optical device 100A according to Embodiment 1, as shown in Figures 6 and 7, the spot row (P11, P12, P13...) is formed two-dimensionally in the "return path spot row formation region" under the condition that the angle between the beam scanning direction 15 and the sub-scanning direction (Y-axis direction) is the opposite of that in the "forward path spot row formation region."

[0049] Thus, 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 between the "forward spot row formation region" and the "return spot row formation region" when forming the spot row. Therefore, according to the optical device 100A according to Embodiment 1, the spot row can be correctly formed along the sub-scanning direction in both the "forward spot row formation region" and the "return spot row formation region".

[0050] Figure 8 is a diagram illustrating how other spot rows are formed along the sub-scanning direction in the "return path spot row formation region". In the optical device 100A according to Embodiment 1, in the "forward spot row formation region," spot rows (P01, P02, P03...) may be formed in the forward direction along the sub-scanning direction as shown in Figure 4, and in the "return spot row formation region," spot rows (P11, P12, P13...) may be formed in the reverse direction along the sub-scanning direction as shown in Figure 8. Even in this way, spot rows can be correctly formed along the sub-scanning direction in both the "forward spot row formation region" and the "return spot row formation region."

[0051] [Second convex lens system 32] Figure 9 is a diagram illustrating the configuration of the second convex lens system 32. In Figure 9, the ray tracing diagram of light L passing through the second convex lens 32 is shown when the beam shift amount is ±0 mm. In the optical device 100A according to Embodiment 1, the required performance of the second convex lens system 32 is satisfied when the second convex lens system 32 is configured such that, as shown in Figure 9, "when the rotating mirror 4 is virtually positioned perpendicular to the optical axis of the second convex lens system 32, a divergent luminous flux L having an optical axis parallel to the optical axis 32Ax of the second convex lens system 32 is emitted from a predetermined point within the region through which the pulsed laser light 1 of the rotating mirror 4 passes into the region through which the pulsed laser light 1 of the second convex lens system 32 passes, and becomes parallel after passing through the second convex lens system 32."

[0052] Therefore, in the optical device 100A according to Embodiment 1, taking the above into consideration, the second convex lens system 32 was designed under the conditions that the refractive index n of the second convex lens system 32 was 1.45, the wavelength λ of the pulsed laser light 1 was 1030 nm, the predetermined angle was 25.3 degrees, and the incident beam diameter to the workpiece 9 was 2.9 mm. Using the designed second convex lens system 32, the in-plane light intensity distribution of the convergent beam 10 near the workpiece 9 was determined by optical simulation. The predetermined angle was set to 25.3 degrees in order to make the diameter of the convergent beam 10 2 μm near the workpiece 9, and the incident beam diameter to the workpiece 9 was set to 2.9 mm because if the incident beam diameter is 2.9 mm, the Bessel beam region 11 can cover the thickness of the workpiece 9 (for example, 1 mm).

[0053] Figure 10 shows the in-plane light intensity distribution of the focusing beam 10. Figure 10(a) shows the in-plane light intensity distribution of the focusing beam 10 when the beam shift amount (half-angle) (maximum beam shift amount (half-angle)) is +2.5 mm, Figure 10(b) shows the in-plane light intensity distribution of the focusing beam 10 when the beam shift amount (half-angle) is ±0 mm, and Figure 10(c) shows the in-plane light intensity distribution of the focusing beam 10 when the beam shift amount (half-angle) is -2.5 mm. In Figure 10, the in-plane light intensity distribution of the focusing beam 10 is the in-plane light intensity distribution of the focusing beam 10 in the vicinity of the workpiece 10, or in other words, the in-plane light intensity distribution in the bessel beam region 11. Figure 11 is shown to explain the beam shift amount of the focusing beam 10 and the swing angle of the rotating mirror 4. Figure 11(a) is shown to illustrate the beam shift amount of the focusing beam 10, and Figure 11(b) is shown to illustrate the swing angle of the rotating mirror 4.

[0054] In the optical device 100A according to Embodiment 1, as can be seen from Figure 10, it was confirmed that the in-plane light intensity distribution (spot quality) of the focusing beam 10 could be maintained appropriately within a beam shift amount (half-angle) of ±2.5 mm. Here, the maximum beam shift amount (full-angle) is the effective scanning range of the focusing beam 10, as shown in Figure 11(a), and the maximum beam shift amount (half-angle) is the distance from the center position of the effective scanning range of the focusing 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 Figure 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 is the swing angle obtained by subtracting the folding range from the maximum swing angle (full-angle) of the rotating mirror 4.

[0055] The reason for setting the beam shift amount (half-angle) within ±2.5 mm is as follows: Referring to Figure 3, when the processing area 95 of the workpiece 9 is set to 500 mm × 500 mm and divided into 100 sections in the Y-axis direction, resulting in 50 forward spot row formation areas and 50 return spot row formation areas, it was considered that the width along the sub-scanning direction of either the forward spot row formation area or the return spot row formation area would be 5 mm.

[0056] In the optical device 100A according to Embodiment 1, if the difference between the optical path length L1 of the longest optical path from the incident focal point to the exit focal point of the afocal optical system 3 and the optical path length L2 of the shortest optical path is large, the quality of the spot formed near the workpiece 9 will deteriorate accordingly. Therefore, in the optical device 100A according to Embodiment 1, the deterioration of spot quality is suppressed by reducing the maximum effective swing angle θ of the rotating mirror 4 and shortening the optical path difference L1-L2.

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

[0058] As shown in Figure 12, in the optical device 100A according to Embodiment 1, when the wavelength λ of the pulsed laser light is 1030 nm, the spot quality deteriorates when the maximum effective swing angle θ is greater than ±1.5 degrees (see Test Examples 1-3). However, it was confirmed that the deterioration of spot quality is suppressed when the maximum effective swing angle θ is set to ±0.75 degrees (see Test Example 4). From this, it was found that the deterioration of spot quality is suppressed when "(maximum effective swing angle θ of the rotating mirror 4) / (wavelength λ of the laser light / 10³)" ≤ 1. Furthermore, in the optical device 100A according to 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 5-7), but it was confirmed that the deterioration of spot quality is suppressed when the maximum effective swing angle θ is set to ±0.37 degrees (see Test Example 8). From this, it was found that the deterioration of spot quality is suppressed when "(maximum effective swing angle θ of the rotating mirror 4) / (wavelength λ of the laser light / 10³)" ≤ 1.

[0059] As described above, the optical device 1 according to Embodiment 1 makes it possible to maintain an appropriate in-plane light intensity distribution (spot quality) of the focusing beam 10 within a beam shift range of ±2.5 mm. However, even in this case, depending on the design of the second convex lens system 32, the superposition of the pulsed laser light 1 waves reaching the exit focal point via the longest optical path and the pulsed laser light 1 waves reaching the exit focal point via the shortest optical path may decrease over time. When this happens, the light intensity effective for forming the fine modification region decreases, resulting in a decrease in spot quality.

[0060] Figure 13 shows how the wave chain of pulsed laser light 11 is superimposed in time. The upper part of Figure 13 shows how the pulse length of the pulsed laser light 1 is changed and how the pulse chain is superimposed in time. The lower part of Figure 13 explains the light that first reaches the workpiece 9 after passing through the afocal optical system 3 (light that has passed through the optical path with optical path length L2) and the light that reaches it last (light that has passed through the optical path with optical path length L1). In Figure 13, the superposition state of the wave chain is shown using the case where the "optical path length difference L1-L2", which will be described later, is 0.244 mm as an example. 0.244 mm was chosen as the "optical path length difference L1-L2" to make the wave chain superposition easier to understand, and as will be described later, the "optical path length difference L1-L2" can be made shorter.

[0061] In this case, as can be seen from Figure 13, when the pulse length of pulsed laser light 1 is 400 fSec (femtoseconds), the wave 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%. When the pulse length is 1 pSec (picosecond), the wave length is 0.300 mm, and the above temporal overlap ratio is 19%. When the pulse length is 5 pSec (picoseconds), the wave length is 1.499 mm, and the temporal overlap ratio is 84%. When the pulse length is 10 pSec (picoseconds), the wave length is 2.998 mm, and the temporal overlap ratio is 92%.

[0062] In the optical device 100A according to Embodiment 1, even when the rotating mirror 4 is at its maximum swing angle position, the afocal optical system 3 requires that the wave feed of pulsed laser light 1 reaching the exiting focal point via the longest optical path (optical path length L1) and the wave feed of pulsed laser light 1 reaching the exiting focal point via the shortest optical path (optical path length L2) overlap at least partially in time. To achieve this, pulsed laser light with a pulse length of approximately 0.8 pSec or more is used. In the optical device 100A according to Embodiment 1, it is preferable that the wave feeds of both pulsed laser light 1 overlap by 50% or more in time, and even more preferable that they overlap by 75% or more in time. To achieve this, pulsed laser light with a pulse length of approximately 2.5 pSec or more and pulsed laser light with a pulse length of approximately 4 pSec or more are used, respectively. As mentioned above, the difference between the optical path length L1 and the optical path length L2 can be reduced, or even reduced to zero, by designing the second convex lens 32 (refractive index, thickness, surface shape).

[0063] [Rotating Mirror 4] Figure 14 is a diagram illustrating the configuration of the rotating mirror 4. Figures 14(a) to 14(d) are plan views of the rotating mirror 4. Figure 14(e) is a front view of the rotating mirror 4 shown in Figure 14(a) along the rotation axis RAx. In Figure 14, reference numeral 41 indicates a motor for rotational drive, reference numeral 42 indicates a rotating shaft, reference numeral 44 indicates an annular reflective region, reference numeral 45 indicates an inner region inside the annular reflective region 44, the dashed line indicated by reference numeral 46 indicates the boundary between the annular reflective region 44 and the inner region 45, and reference numeral 48 indicates a hole or cavity.

[0064] The rotating mirror 4 may have a full mirror surface, as shown in Figure 14(a), where the inner region 45 of the annular reflective region 44 is also a mirror surface; or, as shown in Figure 14(b), where the entire inner region 45 of the annular reflective region 44 is removed from the annular mirror surface; or, as shown in Figures 14(c) and 14(d), where a part of the inner region 45 of the annular reflective region 44 is missing (or removed). Note that Figure 14(c) shows a structure in which the rotating shaft 42 extends into the inner region 45 of the annular reflective region 44, and Figure 14(d) shows 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 oval shape when the region that reflects the converging beam 10 during use is viewed along the direction perpendicular to the mirror surface. As shown in Figure 14(a), the mirror surface is oval-shaped. This reduces the area and weight compared to a circular mirror surface. The rotating mirror 4 may also have a structure in which all or part of the area that reflects the converging beam 10 during use (annular reflection region 44) is absent. This further reduces the weight of the rotating mirror 14 (especially the mirror surface). As a result, the rotational operation of the rotating mirror 4 can be increased in speed, which in turn increases the spot formation speed and the formation speed of the fine modification region.

[0066] [Productivity simulation] According to the optical device 100A of Embodiment 1, as described above, it was found that even under the condition of a beam shift amount (half-angle) of ±2.5 mm, the quality of the spots can be maintained by increasing the size of the optical system and decreasing the effective swing angle (see Test Examples 4 and 8 in Figure 12). On the other hand, it has also been found that even if the optical system is made smaller, the quality of the spots can be maintained by decreasing the beam shift amount accordingly. However, when the beam shift amount is reduced, the width of the forward spot row formation region and the forward spot row formation region along the sub-scanning direction shown in Figure 3 becomes narrower, and productivity decreases. Therefore, in this simulation, we investigated how small the optical system can be while maintaining a predetermined productivity while maintaining the quality of the spots. In this case, the optical device of the comparative example shown in Table 1 was used as a benchmark. The optical device of the comparative example is a device that forms one row of spots one-dimensionally in one main scan direction by moving the stage along the main scan direction without scanning the converging beam along the sub-scanning direction. Table 1 is a table showing the specifications when spots are formed over the entire processing area using the optical device of the comparative example.

[0067] [Table 1] ------------------------------------------------------------------ Scanning of convergent beam 10: Do not scan (only move stage 6) Shape of the processing area 95: A square shape with dimensions of 500mm x 500mm. Number of spots to form: 1 million (1,000 spots are formed at 0.5 mm intervals along the main scanning direction, and these are then arranged in 1,000 rows at 0.5 mm intervals along the sub-scanning direction) Stage 6 movement speed along the main scanning direction: 200 mm / second Effective efficiency: 70% Main scan time along the main scan direction: 3.571 seconds Processing time per circuit board: 3571 seconds (approximately 60 minutes) ------------------------------------------------------------------

[0068] [Comparative Example] In the comparative example, 1000 spots are formed one-dimensionally with a single scan along the main scanning direction. Therefore, to form spots across the entire workpiece area 95, it is necessary to scan 1000 times in the main scanning direction while shifting by 0.5 mm in the sub-scanning direction. Since the scanning time for one scan in the main scanning direction is 3.571 seconds, the total processing time for the entire workpiece area 95 is 3571 seconds (approximately 60 minutes). This was used as the benchmark.

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

[0070] Simulations were conducted by varying the maximum beam shift amount, etc., using two different wavelengths for pulsed laser light 1 (laser wavelength λ): 1030 nm and half of that, 515 nm (Experimental Examples 9-16).

[0071] The diameter of the spot formed on the glass substrate (the diameter of the first dark ring) 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 alternating concentric circles of bright and dark areas. The first dark ring is the dark ring that first forms outside the central bright area.

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

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

[0074] We performed simulations by varying the maximum beam shift amount. 1. When the wavelength of pulsed laser light 1 is 1030 nm When the maximum beam shift amount (total angle) d is set to 5 mm, the substrate processing time (time to form spots P across the entire glass substrate) becomes 6 minutes. This is 0.1 times the time of the comparative example. This is because 10 spot rows (compared to 1 conventionally) can be formed along the sub-scanning direction in a single 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 (total angle) d is set to 2.5 mm, the substrate processing time becomes 12 minutes. This is approximately 0.2 times the time of the comparative example. The size of the rotating mirror 4 is 41.0 mm on the short side and 58.0 mm on the long side (Test Example 10). When the maximum beam shift amount (total angle) d is set to 1.25 mm, the substrate processing time becomes 24 minutes. This is approximately 0.4 times the time in the comparative example. The four rotating mirror sizes are 20.5 mm on the short side and 29.0 mm on the long side (Test Example 11). When the maximum beam shift amount (total angle) d is set to 0.63 mm, the substrate processing time becomes 48 minutes. This is approximately 0.8 times the time of the comparative example. The four rotating mirror sizes are 10.3 mm for the short side and 14.5 mm for 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 (total angle) is set to 2.50 mm, the substrate processing time becomes 12 minutes. This is approximately 0.2 times the time of the comparative example. 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 13). When the maximum effective beam shift amount d (total angle) is set to 1.25 mm, the substrate processing time is 24 minutes. This is approximately 0.4 times the time of the comparative example. The size of the rotating mirror 4 is 41.0 mm on the short side and 58.0 mm on the long side (Test Example 14). When the maximum effective beam shift amount (total angle) d is set to 0.63 mm, the substrate processing time becomes 48 minutes. This is approximately 0.8 times the time of 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 15). When the maximum effective beam shift amount d (total angle) is set to 0.31 mm, the substrate processing time becomes 96 minutes. This is approximately 1.6 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 (additional, test example 16).

[0077] As shown in Figure 15, increasing the maximum effective beam shift (full angle) allows for a reduction in the size of the optical system, 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 met even when the maximum effective beam shift was reduced to 1.25 mm, in both the 1030 nm and 515 nm cases.

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

[0079] [Embodiment 2] Figure 16 is a diagram illustrating the outline of 100B according to Embodiment 2. As shown in Figure 16, the optical device 100B according to Embodiment 2 has basically 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, 22) provided along the direction of propagation of the pulsed laser light 1.

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

[0081] [Effects of Embodiment 2] Thus, although the optical system 2 of the optical device 100B according to Embodiment 2 differs from that of the optical device 100A according to Embodiment 1, the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation, causes the converging beam 10 to be scanned on the workpiece 9 along a predetermined beam scanning direction. Therefore, similar to the optical device 100A according to Embodiment 1, a large number of fine modification regions can be formed on the workpiece at a faster rate than conventional methods.

[0082] Furthermore, according to the optical device 100B of Embodiment 2, since the optical system 2 includes two axicon lenses 21 and 22 provided along the direction of propagation of the pulsed laser light 1, there is also the effect that it is easier to adjust the size (diameter, length) of the Bessel beam region 11 compared to the optical device 100A of Embodiment 1.

[0083] [Embodiment 3] Figure 17 is a diagram illustrating the outline of the optical device 100C according to Embodiment 3. As shown in Figure 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 object to be worked on 9.

[0084] Referring to Figure 17, when the pulsed laser light 1 passes through the axicon lens 21, the outer diameter of the ring gradually decreases (parallel rays within the ring), and after converging near the initial Bessel beam region 11a, it diverges. The optical device 100C according to Embodiment 3 further has a lens system 25 at the position of the converging section that adjusts the size (diameter, length) of the Bessel beam region 11 generated near the workpiece 9. Therefore, the optical device 100C according to Embodiment 3 has the effect of making it 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 Embodiment 1.

[0085] Furthermore, if the lens system 25 is changed to a convex lens system, the thickness of the ring (the width of the ring along the diameter) gradually decreases after passing through the lens system 25, so the size (diameter, length) of the Bessel beam region 11 becomes smaller.

[0086] [Effects of Embodiment 3] As described above, although the optical system 2 of the optical device 100C according to Embodiment 3 differs from that of the optical device 100A according to Embodiment 1, the converging beam 10 is scanned on the workpiece 9 along a predetermined beam scanning direction by the reciprocating rotation operation of the rotating mirror 4, which is capable of high-speed reciprocating rotation. Therefore, similar to the optical device 100A according to Embodiment 1, a large number of fine modification regions can be formed on the workpiece at a faster speed than conventional methods.

[0087] Furthermore, according to the optical device 100C of Embodiment 3, 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. Therefore, it has the effect of making it easier to adjust the size (diameter, length) of the Bessel beam region 11 compared to the optical device 100A of Embodiment 1.

[0088] [Embodiment 4] Figure 18 is a diagram illustrating the outline of the optical device 100D according to Embodiment 4. As shown in Figure 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 the Bessel beam region 11 generated near the workpiece 9 of the converging beam 10.

[0089] [Effects of Embodiment 4] Thus, although the optical system 2 of the optical device 100D according to Embodiment 4 differs from that of the optical device 100B according to Embodiment 2, the reciprocating rotation of the rotating mirror 4, which is capable of high-speed reciprocating rotation, causes the converging beam 10 to be scanned on the workpiece 9 along a predetermined beam scanning direction. Therefore, similar to the optical device 100B according to Embodiment 2, a large number of fine modification regions can be formed on the workpiece at a faster speed than conventional methods.

[0090] Furthermore, according to the optical device 100D of Embodiment 4, 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. This has the effect of making it easier to adjust the size (diameter, length) of the Bessel beam region 11 compared to the optical device 100B of Embodiment 2.

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

[0092] (1) In the embodiments described above, pulsed laser light was used as the laser light, but the present invention is not limited thereto. CW laser light can also be used as the laser light. In this case, instead of a spot-shaped micro-modification region in a plan view, a linear micro-modification region in a plan view can be formed.

[0093] (2) In the above embodiment, an optical device is used that scans the convergent beam 10 over the workpiece 9 along a predetermined beam scanning direction by controlling the reciprocating rotational movement of a rotating mirror (hereinafter referred to as the rotating mirror method), but the present invention is not limited thereto. Figure 19 is a diagram that illustrates the outline of an optical device 100E according to a modified example. The present invention also allows the convergent beam 10 to be scanned on the workpiece 9 along a predetermined beam scanning direction using an optical device as shown in Figure 19 (for example, an optical device 100E having an optical system comprising a first axicon lens 121 and a second axicon lens 122 provided along the direction of propagation of pulsed laser light 1, and a mirror 104 provided between the first axicon lens 121 and the second axicon lens 122 to reflect laser light, and using an optical system 102 that emits a convergent beam 10 from the second axicon lens 122, and using a control unit 105 that controls the reciprocating motion of the mirror 4 and the second axicon lens 122 to scan the convergent beam 10 along a predetermined beam scanning direction 15 on the workpiece 9). Therefore, the optical device of the present invention also includes the following optical devices A to F and the micro-modification region formation method G. In the modified optical device 100E, the mirror 104 and the second axicon lens 122 are mounted on the housing 131 and reciprocate along the beam scanning direction 15 by a voice coil motor 107.

[0094] A: An optical device 100A for forming a fine modification region on a workpiece 9 using pulsed laser light 1, comprising: a focusing optical system 2 for forming a focusing beam 10 from the pulsed laser light 1; a control unit 5 for scanning the focusing 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 move along a predetermined main scanning direction and sub-scanning direction which are mutually orthogonal in a plane parallel to the placement surface, wherein the control unit 5 has the function of forming a spot row of pulsed laser light 1 on the workpiece along the sub-scanning direction by scanning the focusing beam 10 along the beam scanning direction 15 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).

[0095] B: The control unit 5 is an optical device that has the function of forming a row of spots on the workpiece in two dimensions (in a strip shape) by repeatedly moving the stage 6 along the main scan direction and forming a row of spots on the workpiece with the pulsed laser light 1 along the sub-scan direction.

[0096] C: The control unit 5 has the function of forming the spot rows in a two-dimensional manner on the workpiece by repeatedly moving the stage 6 intermittently along the sub-scanning direction and moving the stage 6 back and forth along the main scanning direction, thereby forming the spot rows over the entire area to be processed on the workpiece.

[0097] D: The control unit 5 is an optical device that has the function of forming the spot row on the workpiece along the sub-scanning direction, with the angle between the beam scanning direction 15 and the sub-scanning direction being opposite in forward and reverse directions during the forward and return movements of the reciprocating motion.

[0098] E: An optical device having the function of forming the spot rows in the forward direction along the sub-scanning direction on the workpiece during the forward movement of the reciprocating motion, and forming the spot rows in the reverse direction along the sub-scanning direction on the workpiece during the return movement of the reciprocating motion.

[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 micro-modified region on a workpiece 9 placed on a stage 6 configured to be movable along predetermined main scanning directions and sub-scanning directions that are mutually orthogonal 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, wherein the beam scanning direction 15 is tilted by a predetermined angle (α) between the beam scanning direction 15 and the sub-scanning direction, thereby forming a row of spots by the pulsed laser light 1 on the workpiece along the sub-scanning direction.

[0101] (3) In the above embodiment, the case in which the maximum number of spots are formed on the workpiece 9 was described as an example, but instead of forming the maximum number of spots, any number of spots may be formed. In this case, spots only need to be formed at arbitrary positions.

[0102] (4) In the above embodiment, once scanning on the forward path is completed, scanning is performed on the adjacent return path (see Figure 3, etc.). However, if there are no spots P to be formed on the adjacent return path, scanning on that return path may be omitted, and the stage 6 may move to a return path where there are spots P to be formed (the stage 6 moves relatively) and perform scanning on that return path. The actual spot movement path is optimized to be the shortest possible time based on the processing data.

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

[0104] 1...Pulsed laser light, 10...Converging 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 the double convex lens system, 4...Rotating mirror, 41...Motor for rotation drive, 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...Control unit, 6...Stage, 9...Workpiece, 95...Processing area, 100A,100B,100C,100D,100E...Optical device, 104...Mirror, 107...Voice coil motor, 131...Housing, f1...Focal length of the first convex lens system, f2...Focal length of the second convex lens system, P...Spot, Ax...Optical axis of the optical device, F...Focus, CF...Common focus, RAx...Rotation center axis, α...Angle

Claims

1. An optical device that uses laser light to form a micro-modified region on a workpiece, An afocal optical system having a first convex lens system and a second convex lens system provided along the direction of propagation of the laser light, and an optical system having a rotating mirror provided at the common focal position of the first convex lens system and the second convex lens system, which emits a focusing beam from the second convex lens system, An optical device comprising a control unit having the function of scanning the converging beam over the workpiece along a predetermined beam scanning direction by controlling the reciprocating rotational movement of the rotating mirror.

2. In the optical apparatus described in claim 1, The laser light is pulsed laser light, and the optical device is such that

3. In the optical apparatus described in claim 1, The optical system is an optical device that includes one axicon lens.

4. In the optical apparatus described in claim 1, The optical system is an optical device that includes two axicon lenses arranged along the direction of propagation of the laser light.

5. In the optical apparatus described in claim 1, An optical device in which the focal length of a second convex lens system is shorter than the focal length of a first convex lens system.

6. In the optical apparatus according to claim 3 or 4, The optical system further comprises a lens system for adjusting the length of the Bessel beam region formed by the converging beam emitted from the second convex lens system.

7. In the optical apparatus described in claim 1, The second convex lens system is configured such that, when the rotating mirror is virtually perpendicular to the optical axis of the second convex lens system, a divergent luminous beam having an optical axis parallel to the optical axis of the second convex lens system, emitted from a predetermined point within the region through which the laser light passes in the rotating mirror toward the region through which the laser light passes in the second convex lens system, becomes parallel after passing through the second convex lens system.

8. In the optical apparatus described in claim 1, An optical device in which 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. In the optical apparatus described in claim 1, The rotating mirror is an optical device having a structure in which all or part of the inside of the annular reflective region that reflects the laser light during use is missing.

10. In the optical apparatus described in claim 2, The afocal optical system is configured such that, even when the rotating mirror is in the position of the maximum effective swing angle, the wave feed of the pulsed laser light that reaches the focal point on the exit side via the longest optical path and the wave feed of the pulsed laser light that reaches the focal point on the exit side via the shortest optical path are superimposed in time, at least partially.

11. In the optical apparatus described in claim 2, A stage for placing the workpiece, further comprising a stage configured to be movable along predetermined main scanning directions and sub-scanning directions that are mutually orthogonal in a plane parallel to the mounting surface, The control unit has the function of forming a spot row of 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, with the rotation axis of the stage or the rotating mirror rotated such that the beam scanning direction and the sub-scanning direction are tilted by a predetermined angle (α).

12. In the optical apparatus according to claim 11, The control unit has the function of forming a two-dimensional spot array on a workpiece by repeatedly moving the stage along the main scanning direction and forming a spot array on the workpiece along the sub-scanning direction using the pulsed laser light.

13. In the optical apparatus according to claim 12, The control unit has the function of forming the spot rows in a two-dimensional manner on the workpiece by repeatedly moving the stage intermittently along the sub-scanning direction and moving the stage back and forth along the main scanning direction, thereby forming the spot rows over the entire area to be processed on the workpiece.

14. In the optical apparatus according to claim 13, The control unit has the function of forming the spot row on the workpiece along the sub-scanning direction, with the angle between the beam scanning direction and the sub-scanning direction being opposite in forward and reverse directions during the forward and return movements of the reciprocating motion.

15. In the optical apparatus according to claim 13, The control unit has the function of forming the spot rows on the workpiece in the forward direction along the sub-scanning direction during the forward movement of the reciprocating motion, and forming the spot rows on the workpiece in the reverse direction along the sub-scanning direction during the return movement of the reciprocating motion.

16. In the optical apparatus described in claim 1, The optical device emits the convergent beam when the operating speed of the reciprocating motion is constant, under the control of the control unit.

17. An optical device that uses pulsed laser light to form a micro-modified region on a workpiece, A focusing optical system that forms a focused beam from the pulsed laser light, A control unit that scans the convergent beam on the workpiece along a predetermined beam scanning direction, A stage for placing the workpiece, comprising a stage configured to be movable along predetermined main scanning directions and sub-scanning directions that are mutually orthogonal in a plane parallel to the mounting surface, The control unit has the function of forming a spot row of 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 with the beam scanning direction and the sub-scanning direction tilted by a predetermined angle (α).

18. In the optical apparatus according to claim 17, The control unit has the function of forming a two-dimensional spot array on a workpiece by repeatedly moving the stage along the main scan and forming a spot array on the workpiece along the sub-scan direction using the pulsed laser light.

19. In the optical apparatus according to claim 18, The control unit has the function of forming the spot rows in a two-dimensional manner on the workpiece by repeatedly moving the stage intermittently along the sub-scanning direction and moving the stage back and forth along the main scanning direction, thereby forming the spot rows over the entire area to be processed on the workpiece.

20. In the optical apparatus according to claim 19, The control unit has the function of forming the spot row on the workpiece along the sub-scanning direction, with the angle between the beam scanning direction and the sub-scanning direction being opposite in forward and reverse directions during the forward and return movements of the reciprocating motion.

21. In the optical apparatus according to claim 19, The control unit has the function of forming the spot rows on the workpiece in the forward direction along the sub-scanning direction during the forward movement of the reciprocating motion, and forming the spot rows on the workpiece in the reverse direction along the sub-scanning direction during the return movement of the reciprocating motion.

22. In the optical apparatus according to claim 17, The optical device emits the convergent beam when the operating speed of the reciprocating motion is constant, under the control of the control unit.

23. A method for forming a micro-modified region on a workpiece, wherein the workpiece is placed on a stage configured to be movable along predetermined main scanning directions and sub-scanning directions that are mutually orthogonal in a plane parallel to the mounting surface, and a focusing beam formed from pulsed laser light is scanned along a predetermined beam scanning direction, thereby forming a micro-modified region on the workpiece. A method for forming a micro-modified region, wherein the beam scanning direction and the sub-scanning direction are tilted by a predetermined angle (α), and the stage is moved along the main scanning direction while scanning the converging beam along the beam scanning direction, thereby forming a row of spots by the pulsed laser light along the sub-scanning direction on the workpiece.

Images