Laser processing device

Abstract

To provide a laser processing device that can emit laser light with a nearly constant intensity to a work-piece.SOLUTION: A laser processing device 10 comprises: a laser light source 12 that emits laser light 11; a work-piece holding part 13 that holds a work-piece 22; and a relatively moving part 14 that relatively moves an emission spot 11a of the laser light 11 emitted from the laser light source 12 and the work-piece holding part 13. While the relatively moving part 14 makes the emission spot 11a cross a surface to be processed 22a, the laser light source 12 emits the laser light 11 to the emission spot 11a and emits the laser light 11 to the surface to be processed 22a, so as to perform laser-processing to the surface to be processed 22a. A preprocessing emission section 23, in which the laser light source 12 emits the laser light 11 just before the emission spot 11a reaches the surface to be processed 22a, is formed on a passage on which the emission spot 11a crosses the surface to be processed 22a.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus that irradiates a substrate with laser light to perform processing such as trimming. [Background technology]

[0002] A known technology is to form a wiring circuit pattern of electronic circuits on a substrate called a wafer or workpiece, and then bond or adhere (forming an electrically conductive part while fixing in a state where it will not fall off or shift in position due to external forces, in other words, mounting) components such as semiconductor devices and resistors (called chips) onto that wiring circuit pattern using a bonding material such as solder or resin.

[0003] Among the mounted chip components, any that are found to have poor bonding or malfunction are removed (trimmed) and then remounted (so-called repair).

[0004] In this repair, a technique is known in which a mounted electronic component is irradiated with laser light to heat the electronic component and melt a thermoplastic bonding material such as solder, and then the electronic component is adsorbed and trimmed, or the chip itself is burned and trimmed (for example, Patent Document 1).

[0005] 5, a laser processing apparatus 100 for performing trimming using a laser beam includes a laser oscillator 102 having a laser diode (laser light source) 102a, a workpiece holder 103, and a relative moving unit 104. With the workpiece holder 103 holding a workpiece 106, the relative moving unit 104 moves the workpiece holder 103 in the XY directions, thereby moving an irradiation spot 101a, which is a point of arrival of the laser beam 101 irradiated from the laser oscillator 102, relative to the workpiece 106. When the irradiation spot 101a is positioned on a chip 105 to be trimmed, the laser oscillator 102 emits the laser beam 101, whereby the chip 105 is irradiated with the laser beam 101, and the chip 105 is removed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-164310 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to reliably remove electronic components in trimming with a laser beam, it is desirable for the intensity of the laser beam to be approximately constant. However, a laser light source has a lifespan, and in handling laser beams, it is generally not necessary to irradiate the laser beam at unnecessary times.

[0008] Specifically, in laser processing of the workpiece 106 shown in Fig. 6, when the irradiation spot 101a of the laser light is moved relatively in a substantially zigzag manner by repeating the action of crossing in the X-axis direction and the shifting action in the Y-axis direction as shown by the arrow, and the laser light 101 is irradiated when the irradiation spot 101a is positioned at the position shown by the circle in Fig. 5 to remove the chip 105, the laser light 101 is not irradiated with the irradiation spot 101a on the chip 105 that is not to be removed, and the laser light 101 is not irradiated basically even when the irradiation spot 101a is positioned in a part other than the area where the chip 105 exists. At this time, it is assumed that the emission of the laser light 101 from the laser oscillator 102 is stopped.

[0009] On the other hand, the intensity of the laser light 101 emitted from the laser oscillator 102 becomes stable only after the laser oscillator 102 oscillates continuously for a predetermined period of time. Specifically, as shown in Fig. 7(a), the intensity increases steadily immediately after the start of oscillation, then decreases and stabilizes at a predetermined intensity.

[0010] Here, even after the intensity of the laser beam 101 becomes stable, when the oscillation of the laser source 102a of the laser oscillator 102 is stopped, the intensity of the laser beam 101 at the time of restarting the oscillation fluctuates, as if tracing back the increase and decrease in the intensity of the laser beam 101 occurring at the beginning of the oscillation. Therefore, as shown in Fig. 7(b) and Fig. 7(c), there is a problem that the amount of fluctuation in the intensity of the laser beam 101 differs depending on the oscillation stop time. On the other hand, the intensity of the laser beam 101 can be corrected from a predetermined value to a different predetermined value by providing a correction means such as an acousto-optic modulator (AOM) 107 in the optical path of the laser beam 101 as shown in Fig. 5, but when the amount of fluctuation in the intensity of the laser beam 101 differs depending on the oscillation stop time as in the above problem, countless correction settings are required in the correction means, and it is practically difficult to perform processing with the laser beam 101 having a substantially constant intensity.

[0011] SUMMARY OF THE PRESENT EMBODIMENT In view of the above problems, an object of the present invention is to provide a laser processing apparatus capable of irradiating a processing object with laser light of a substantially constant intensity. [Means for solving the problem]

[0012] In order to solve the above problems, the laser processing apparatus of the present invention comprises a laser light source that emits laser light, a workpiece holding section that holds a workpiece, and a relative movement section that relatively moves the irradiation spot of the laser light emitted from the laser light source and the workpiece holding section, and is a laser processing apparatus that performs laser processing on the workpiece surface by causing the laser light source to emit laser light to the irradiation spot while the relative movement section moves the irradiation spot across the workpiece surface, and irradiating the laser light onto the workpiece surface, and is characterized in that, on the path along which the irradiation spot crosses the workpiece surface, a pre-processing emission section is provided in which the laser light source emits laser light before the irradiation spot reaches the workpiece surface.

[0013] According to the laser processing apparatus of the present invention, a pre-processing emission section is provided, so that the intensity of the laser light can be stabilized at an approximately constant intensity when the irradiation spot reaches the surface to be processed, and laser processing can be performed at an approximately constant intensity.

[0014] It is also preferable that the irradiation spot crosses the work surface a plurality of times, and the pre-processing emission section is provided on each path along which the irradiation spot crosses the work surface.

[0015] The laser beam may further include a reach blocking section that blocks the laser beam from reaching the irradiation spot, and the reach blocking section may block the laser beam from reaching at least a part of the pre-processing emission section.

[0016] In this way, while the laser light is emitted, it is possible to avoid irradiating the irradiation spots where no processing is required with the laser light. Effect of the Invention

[0017] The laser processing apparatus of the present invention can irradiate the processing object with laser light of approximately constant intensity. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a laser processing device according to an embodiment of the present invention. [Diagram 2] 10A and 10B are diagrams illustrating a state in which irradiation of laser light is blocked in the laser processing apparatus of the present embodiment. [Diagram 3] 1A to 1C are diagrams illustrating a laser processing method using the laser processing apparatus of the present embodiment. [Figure 4] 4 is a graph showing a transition of the intensity of a laser beam in a laser processing method using the laser processing apparatus of the present invention. [Diagram 5] FIG. 1 is a diagram illustrating a conventional laser processing device. [Figure 6] 1A to 1C are diagrams illustrating a laser processing method using a conventional laser processing device. [Figure 7] 1A to 1C are diagrams for explaining problems in a conventional laser processing method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The laser processing apparatus of the present invention will be described with reference to FIG.

[0020] The laser processing device 10 includes a laser oscillator 12 that emits laser light 11, a workpiece holding unit 13 that holds a workpiece 22, a relative movement unit 14 that can move the workpiece holding unit 13 in at least the X-axis and Y-axis directions, and a control unit 30. By irradiating the laser light 11 to the workpiece surface 22a of the workpiece 22 held by the workpiece holding unit 13, the workpiece surface 22a is processed by the energy of the laser light 11.

[0021] Moreover, a processing object 21 is formed on the processing surface 22a of the workpiece 22, and in the laser processing in this embodiment, the processing object 21 is irradiated with the laser light 11 to burn or alter the processing object 21. This is also called trimming. In this embodiment, the processing object 22 is a semiconductor wafer, and will also be called a wafer 22 in the following description. In this embodiment, the processing object 21 is, for example, a semiconductor chip or a micro LED, and will also be called a chip 21 in the following description. The processing object may also be a wiring pattern, etc.

[0022] The laser oscillator 12 is a device that irradiates laser light 11 such as an excimer laser, which is an active energy ray, and is fixedly provided on the laser processing device 10. In this embodiment, the laser oscillator 12 intermittently emits spot-shaped laser light 11, and the irradiation position of the laser light 11 in the X-axis direction and the Y-axis direction is adjusted via mirrors such as mirrors 15a to 15c. In addition, an acousto-optical modulator (not shown) that modulates the laser light 11 by the acousto-optical effect, and an optical system including an expander lens, a collimator lens, etc. (not shown) are provided between the laser oscillator 12 and the mirror 15a.

[0023] In addition, mirrors 15a and 15b surrounded by a two-dot dashed line in FIG. 1 are attached to a common frame and are movable together in the Z-axis direction. By moving these in the Z-axis direction, the focal position of laser light 11 in the vicinity of wafer 22 in the Z-axis direction can be adjusted.

[0024] In this description, an area on the workpiece surface 22a of the wafer 22 held by the workpiece holder 13 to be irradiated with the laser beam 11 during one emission of the laser beam 11 is referred to as the irradiation spot 11a, and the laser beam 11 is irradiated while changing the position of the irradiation spot 11a in the XY directions by relatively moving the laser oscillator 12 and the wafer 22 by the relative moving unit 14. This allows selective irradiation of the chips 21 arranged on the workpiece surface 22a of the wafer 22, and trimming of the predetermined chips 21.

[0025] The laser oscillator 12 includes a laser diode 12a and a variable attenuator 12b.

[0026] The laser diode 12a is a source of the laser light 11, and oscillates when power is supplied to generate the laser light 11. In this description, the laser diode 12a is also referred to as a laser light source 12a.

[0027] The variable attenuator 12b is an element also called an attenuator (ATT), and is an optical system that attenuates the intensity of the laser light 11 emitted from the laser light source 12a. The variable attenuator 12b can adjust the degree of attenuation of the intensity of the laser light 11, and by adjusting this degree of attenuation, the intensity of the laser light 11 that has passed through the variable attenuator 12b can be adjusted.

[0028] Near the laser oscillator 12, there is provided an arrival blocking section 16 that blocks the laser light 11 emitted from the laser oscillator 12 from reaching the processing surface 22a of the wafer 22 held by the workpiece holder 13. In this embodiment, the arrival blocking section 16 is a shutter, and is also referred to as the shutter 16 in the following description. When the shutter 16 is in an open state, the laser light 11 emitted from the laser oscillator 12 passes through an opening formed in the shutter 16 and reaches the irradiation spot 11a on the processing surface 22a. On the other hand, when the shutter 16 is in a closed state, the path of the laser light 11 is blocked by the shutter 16 as shown in FIG. 2, and the laser light 11 does not reach the irradiation spot 11a. This allows the laser oscillator 12 to continuously emit the laser light 11, while irradiating the irradiation spot 11a with the laser light 11 at any timing.

[0029] Here, when the path of the laser beam 11 is blocked by the shutter 16 or when the laser beam 11 itself is not emitted from the laser oscillator 12, the laser beam 11 does not actually reach the workpiece surface 22a, but even in such a case, in this description, the area where the laser beam 11 would have reached if the laser beam 11 had been emitted and its path had not been blocked is referred to as the irradiation spot 11a. Therefore, in laser trimming such as in this embodiment, irradiation spots 11a irradiated with the laser beam 11 and irradiation spots 11a not irradiated with the laser beam 11 may coexist.

[0030] The workpiece holder 13 is a suction table, and holds the back surface of the wafer 22 (the surface opposite to the surface to be processed 22a) by suction.

[0031] The relative moving unit 14 moves the workpiece holding unit 13 in the X-axis and Y-axis directions, and is configured, for example, with a linear guide and a motor, and its operation is controlled by the control unit 30. When the relative moving unit 14 moves the workpiece holding unit 13, the wafer 22 and the laser oscillator 12 held by the workpiece holding unit 13 move relatively in the X-axis and Y-axis directions. The relative moving unit 14 may also be movable in the Z direction, and its height may be adjusted according to the thickness of the wafer 22 or the chip 21.

[0032] The control unit 30 has a computer, a sequencer, etc., and controls operations such as the emission of laser light 11 from the laser oscillator 12, the opening and closing of the shutter 16, suction in the workpiece holding unit 13, and the movement of the workpiece holding unit 13 in the XY directions by the relative movement unit 14.

[0033] The control unit 30 also has a storage device for storing various information, which is made up of a hard disk, RAM, ROM, or other memory, and stores data such as the intensity of the laser light 11, the emission interval, the moving speed and trajectory of the irradiation spot 11a, etc., for laser processing of a predetermined wafer 22. Other data necessary for laser processing are also stored in the storage device.

[0034] A laser processing method in the laser processing apparatus 10 having the above configuration will be described with reference to FIG.

[0035] In the laser processing device 10 of this embodiment, the relative position of the irradiation spot 11a with respect to the wafer 22 is changed by driving the relative moving part 14, while the shutter 16 is opened at an arbitrary timing, and the laser light 11 is irradiated onto the processing surface 22a. Specifically, the shutter 16 is opened at a timing when the irradiation spot 11a is positioned on a chip 21 of the processing target (target to be trimmed) shown by a solid circle in Fig. 3, and the chip 21 is irradiated with the laser light 11, burning it off. This allows trimming of only the arbitrary chip 21.

[0036] At this time, as shown in Fig. 3, the trajectory of the irradiation spot 11a is a substantially zigzag shape in which an operation of crossing the wafer 22 in the X-axis direction (also called scanning movement) and an operation of moving in the Y-axis direction by a short distance equal to the Y-axis dimension of one irradiation spot (also called shift movement) are alternately performed. That is, the scanning movement is repeated multiple times. In this description, the direction in which the operation of crossing the wafer 22 is performed and the direction in which the shift movement is performed are also called the first direction and the second direction, respectively. That is, in this description, the X-axis direction is the first direction and the Y-axis direction is the second direction.

[0037] In addition, in this embodiment, the distance that the irradiation spot 11a moves during each scanning movement is uniform, and the area covered by the irradiation spot 11a through the scanning movement and shift movement is approximately rectangular and encompasses the processed surface 22a of the wafer 22.

[0038] During each scan movement, the laser oscillator 12 emits the laser light 11 at each irradiation spot 11a including the portion indicated by the dashed circle as well as the solid circle in Fig. 3. On the other hand, at the timing when the irradiation spot 11a is located at the position indicated by the dashed circle, the shutter 16 is closed and the laser light 11 is blocked. On the other hand, at the timing when the irradiation spot 11a is located at the position indicated by the solid circle, the shutter 16 is opened and the laser light 11 reaches the work surface 22a. As a result, even if the emission of the laser light 11 from the laser oscillator 12 is continuous, the laser light 11 can be irradiated onto the work surface 22a only at an arbitrary position to perform trimming.

[0039] Here, the linear path of each scanning movement is composed of a section just before the irradiation spot 11a reaches the workpiece surface 22a, a section where the irradiation spot 11a is located on the workpiece surface 22a, and a section after the irradiation spot 11a has passed through the workpiece surface 22a.

[0040] On the other hand, when the scanning movement is performed continuously as in the present embodiment, the section after the irradiation spot 11a passes through the workpiece surface 22a can also be regarded as the section before the irradiation spot 11a reaches the workpiece surface 22a in the next scanning movement. In this case, the path of the section before the irradiation spot 11a reaches the workpiece surface 22a, excluding the first scanning movement, is a path that turns back at the shift movement part.

[0041] Here, in this embodiment, as described above, the laser oscillator 12 emits laser light 11 at each irradiation spot 11a including the portion indicated by the dashed circle in Figure 3 (the portion corresponding to the section before the irradiation spot 11a reaches the workpiece surface 22a).

[0042] In this embodiment, the emission of the laser light 11 from the laser oscillator 12 is stopped only during the shift movement between the scanning movements.

[0043] In this description, regardless of whether the shutter 16 is open or closed, the section before the irradiation spot 11a reaches the workpiece surface 22a and where the laser oscillator 12 emits the laser light 11 is called the pre-processing emission section 23. In addition, in the multiple pre-processing emission sections 23 associated with multiple scan movements, they are called the pre-processing emission section 23a, the pre-processing emission section 23b, the pre-processing emission section 23c, the pre-processing emission section 23d, and the pre-processing emission section 23e in order from the first scan movement. In addition, after the pre-processing emission section 23b, which is a path with a turn-back shape, the sections before turning back are distinguished by adding 1 to the end of the code, and the sections after turning back are distinguished by adding 2 to the end of the code, such as the pre-processing emission section 23b1 and the pre-processing emission section 23b2.

[0044] FIG. 4 shows the transition of the intensity of the laser beam 11 while the laser beam 11 is being emitted in this embodiment described above.

[0045] In this embodiment, when the scanning movement and the shifting movement of the irradiation spot 11a are alternately repeated, the emission of the laser light 11 is stopped only for a very short time when the relative moving part 14 shifts. In Fig. 4, the portions where the waveform is cut off are the portions where the shifting movement occurs, and the portions sandwiching these shifting movement portions are, for example, the pre-processing emission section 23b1 and the pre-processing emission section 23b2.

[0046] Here, when the emission of the laser light 11 starts at the start of the first scanning movement, the intensity of the laser light 11 increases steadily immediately after the start of the scanning movement as shown in FIG. 4, and then the intensity decreases before stabilizing at a predetermined intensity.

[0047] Furthermore, even if the emission is stopped for a short period of time during the shift movement (specifically, about 200 milliseconds), the intensity of the laser light 11 when oscillation is restarted fluctuates, retracing the increase and decrease in the intensity of the laser light 11 that occurs at the beginning of emission described above.

[0048] In contrast, in the present invention, a pre-processing emission section 23a is provided, and although the optical path is blocked by the closing operation of the shutter 16, the laser beam 11 is emitted for a predetermined time before the irradiation spot 11a reaches the processed surface 22a. Therefore, when the irradiation spot 11a reaches the processed surface 22a, the intensity of the laser beam 11 can be kept substantially constant and stable.

[0049] In addition, for example, in the first and second scan movements, in the present invention, pre-processing emission sections 23b1 and 23b2 are provided, and although the optical path is blocked by the closing operation of the shutter 16, the laser beam 11 is emitted in most of the path before the irradiation spot 11a is positioned on the processed surface 22a. Therefore, the time during which the emission of the laser beam 11 is stopped is very short, and the fluctuation in the laser intensity accompanying the stop of the emission of the laser beam 11 is very small.

[0050] Furthermore, in this embodiment, as shown in Fig. 3, the distance that the irradiation spot 11a moves in each scanning movement is uniform, and the area covered by the irradiation spot 11a by the scanning movement and the shifting movement is a substantially rectangular shape that includes the processing surface 22a of the wafer 22. This forms a section after turning back in each scanning movement and before reaching the processing surface 22a. Then, the laser light 11 is emitted in these sections to form the pre-processing emission sections 23b2, c2, d2, and e2. That is, a pre-processing emission section is provided for each of the scanning movements that are performed multiple times.

[0051] This allows the laser intensity, which has fluctuated due to the shift movement in each scan movement, to return to a stable value within this pre-processing emission section, and the intensity of the laser beam 11 can be stabilized at a substantially constant intensity when the irradiation spot 11a reaches the workpiece surface 22a. As a result, the intensity of the laser beam 11 used for laser processing of the workpiece surface 22a can always be kept at a stable value.

[0052] In addition, the pre-processing emission sections 23b1, c1, d1, and e1 are provided before the return, and the oscillation of the laser light source 12a is stopped only during the shift movement, so that the oscillation stop time of the laser light source 12a can be made substantially constant. Therefore, even if the laser intensity is corrected using an acousto-optic modulator, the setting can be made easily.

[0053] The above-described laser processing device makes it possible to irradiate the processing object with laser light of a substantially constant intensity.

[0054] Here, the laser processing device of the present invention is not limited to the above-described form and may be of other forms within the scope of the present invention. For example, in the above description, the laser processing device of the present invention is applied to laser trimming, but it is not limited to this and may be applied to other process devices using lasers. For example, the laser processing device may be a transfer device that irradiates a laser toward a chip held on a transfer substrate and transfers the chip from the transfer substrate to a transferee substrate.

[0055] In the above description, the emission of the laser light 11 is stopped at the timing of the shift movement, but the emission of the laser light 11 may be continued without this stop period. In that case, the intensity of the laser light 11 at the time of restarting the oscillation as shown in Fig. 4 will not fluctuate, and the intensity of the laser light 11 will be approximately constant except at the start of the first scanning movement.

[0056] In the above description, for example, the pre-processing emission section 23b1 and the pre-processing emission section 23b2 are provided, and the time during which the emission of the laser light 11 is stopped is a very short time during the shift movement, but if the intensity of the laser light 11 can be sufficiently restored to a stable value by the time it reaches the processed surface 22a by only emitting the laser light 11 after turning back in each scan movement, the emission of the laser light 11 may be stopped until the irradiation spot 11a passes through the processed surface 22a in the previous scan movement and turns back. That is, only the pre-processing emission section 23b2 may be provided without the pre-processing emission section 23b1.

[0057] In the above description, the laser light is irradiated only to an arbitrary chip on the wafer, but the present invention is not limited to this, and may be irradiated to the entire surface to be processed with the laser light. Even in this case, the pre-processing emission section is provided in each scanning movement as described above, so that the entire surface to be processed can be irradiated with the laser light of a substantially constant intensity. In this case, a form in which no arrival blocking section such as a shutter is provided may be considered.

[0058] Furthermore, the locus of the irradiation spot caused by the relative movement of the laser oscillator and the wafer does not necessarily have to be substantially zigzag. [Explanation of symbols]

[0059] 10 Laser processing equipment 11 Laser light 11a Irradiation spot 12 Laser Oscillator 12a Laser diode (laser light source) 12b Variable attenuator (intensity adjustment section) 13 Workpiece holding part 14 Relative moving part 15a, 15b, 15c Mirror 16 Shutter (reach blocking part) 21 Chip 22 Wafer (workpiece) 22a Processed surface 23a, b, c, d, e Unprocessed emission section 23b1, 23c1, 23d1, 23e1 Pre-processing exit section 23b2, 23c2, 23d2, 23e2 Unprocessed emission section 30 Control section 100 Laser processing equipment 101 Laser light 101a Irradiation spot 102 Laser Oscillator 102a Laser light source 103 Workpiece holding part 104 Relative moving part 105 Chips 106 Wafer (workpiece) 107 Acousto-optical element

Claims

1. A laser light source that emits laser light; A workpiece holding portion that holds a workpiece; a relative moving unit that moves an irradiation spot of the laser light emitted from the laser light source relative to the workpiece holding unit; Equipped with a laser processing apparatus for performing laser processing on a surface to be processed by irradiating the surface to be processed with the laser light source by emitting a laser light to the irradiation spot while the relative moving part is moving the irradiation spot across the surface to be processed, A laser processing apparatus characterized in that, on a path along which the irradiation spot crosses the workpiece surface, a pre-processing emission section is provided in which the laser light source emits laser light before the irradiation spot reaches the workpiece surface.

2. 2. The laser processing device according to claim 1, wherein the irradiation spot crosses the workpiece surface a plurality of times, and the pre-processing emission section is provided on each path along which the irradiation spot crosses the workpiece surface.

3. 2. The laser processing apparatus according to claim 1, further comprising a reach blocking section that blocks the laser light from reaching the irradiation spot, the reach blocking section blocking the laser light in at least a portion of the pre-processing emission section.

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