Laser processing equipment

Abstract

To provide a laser processing device which can make a laser beam be perpendicularly incident on a workpiece while a size increase of the device and contamination of a lens with debris are prevented.SOLUTION: In a laser processing device, a laser beam emission unit 20 has: a laser oscillator 22 that emits a laser beam 21; an fθ main lens 27 that condenses a laser beam 21 emitted from the laser oscillator 22 and emits it to a workpiece 100 held on a holding table 10; a scanning unit 30 that is disposed on an optical path between the laser oscillator 22 and the fθ main lens 27 and scans the laser beam 21 to guide it to the fθ main lens 27; and an fθ sub-lens 26 that is disposed on an optical path between the laser oscillator 22 and the scanning unit 30 and changes the laser beam 21 from parallel light to diffused light.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] As a method for dividing a semiconductor wafer having a functional layer such as a low-k film laminated on its surface into chips, a processing method has been proposed in which the laminated functional layer is removed by irradiating the wafer with a laser beam, and then the wafer is divided by cutting using a cutting blade (see Patent Document 1).

[0003] However, this method requires multiple irradiations of the laser beam to form a groove of sufficient width in order to prevent molten material such as debris generated by the irradiation of the laser beam from being sufficiently removed and filling back into the groove, resulting in poor productivity.

[0004] To solve this problem, a laser processing device has been developed that places a scanning optical system that scans a laser beam between the laser oscillator and the collector, and irradiates the laser beam while scanning it in the Y-axis direction (width direction of the processing groove) and the X-axis direction (processing feed direction), thereby enabling efficient processing while preventing the molten material from filling back in (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-064231 A [Patent Document 2] JP 2016-068149 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when processing is performed while scanning a laser beam as in the above-mentioned laser processing device, an fθ lens is generally used as a condenser. Here, if the distance from the fθ lens to the processing point is short, the lens will be contaminated by scattering of molten material such as debris, so it is required to position the distance from the lens to the processing point, i.e., the position of the back focal point of the fθ lens, as far away as possible from the fθ lens.

[0007] On the other hand, in order to make the laser beam perpendicular to the wafer, it is necessary to place a mirror in the scanning optical system at the front focal position of the fθ lens. However, if the distance between the fθ lens and the scan mirror is too close, the fθ lens may vibrate due to the high speed operation of the scan mirror. Therefore, it is preferable to position the front focal position as far away as possible from the fθ lens.

[0008] However, it is difficult to achieve all of these simultaneously, and there are physical limitations. Therefore, we considered a method to increase the distance between the f-theta lens and the scan mirror by forming an intermediate image, but this would result in the f-theta lens itself becoming larger, leading to a problem of the device becoming bulky.

[0009] The present invention has been made in consideration of these problems, and its object is to provide a laser processing apparatus that can make a laser beam perpendicular to the workpiece while suppressing the enlargement of the apparatus and the contamination of the lens by debris. [Means for solving the problem]

[0010] In order to solve the above problems and achieve the object, the laser processing apparatus of the present invention is a laser processing apparatus including a holding table for holding a workpiece, a laser beam irradiating unit for condensing and irradiating a pulsed laser beam onto the workpiece held on the holding table to process it, and a moving unit for relatively moving the holding table and the focal point of the laser beam, the laser beam irradiating unit including a laser oscillator for emitting a laser beam, an fθ main lens for condensing the laser beam emitted from the laser oscillator and irradiating it onto the workpiece held on the holding table, a scan unit disposed on the optical path between the laser oscillator and the fθ main lens for scanning the laser beam and guiding it to the fθ main lens, and an fθ secondary lens disposed on the optical path between the laser oscillator and the scan unit for changing the laser beam from a parallel beam to a diverging beam. The fθ main lens and the fθ secondary lens are unitized with a fixed distance and position relative to the scan unit, and the scan unit reflects the laser beam, which has been converted into diffuse light by the fθ secondary lens, toward the fθ main lens with a scan mirror. The present invention is characterized by the above.

[0011] In the laser processing apparatus of the present invention, the front focal point of the fθ main lens may be positioned on a scan mirror on which the laser beam is incident from the fθ secondary lens in the scan unit.

[0013] In addition, in the laser processing apparatus of the present invention, the scan unit may be disposed inside a chamber, and the fθ main lens and the fθ secondary lens may be arranged like windows that transmit the laser beam while separating the inside of the chamber from the surrounding environment. Effect of the Invention

[0014] The present invention makes it possible to make a laser beam perpendicularly incident on a workpiece while suppressing an increase in the size of the apparatus and suppressing contamination of the lens by debris. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing device according to an embodiment. [Diagram 2]FIG. 2 is an explanatory diagram illustrating a schematic configuration of a laser beam irradiation unit of the laser processing apparatus shown in FIG. [Diagram 3] FIG. 3 is an explanatory diagram showing an example of the front focus and the rear focus of the fθ main lens in the laser beam irradiation unit shown in FIG. [Figure 4] FIG. 4 is an explanatory diagram showing an example of the front focus and the rear focus of the fθ main lens in the laser beam irradiation unit of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0017] [Embodiment] First, the configuration of a laser processing device 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of the configuration of a laser processing device 1 according to an embodiment. In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on a horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction. In the laser processing device 1 of the embodiment, the processing feed direction is the X-axis direction, and the indexing feed direction is the Y-axis direction.

[0018] 1, the laser processing apparatus 1 includes a holding table 10, a laser beam emitting unit 20, a moving unit 40, a display unit 50, and a control unit 60. The laser processing apparatus 1 according to the embodiment is an apparatus that processes the workpiece 100 by irradiating the workpiece 100 held on the holding table 10 with a pulsed laser beam 21 by the laser beam emitting unit 20. The processing of the workpiece 100 by the laser processing apparatus 1 is, for example, groove processing for forming grooves on the surface of the workpiece 100, or cutting processing for cutting the workpiece 100 along a planned division line.

[0019] In the embodiment, the workpiece 100 is made of silicon (Si), sapphire (Al 2 O 3 ), gallium arsenide (GaAs), silicon carbide (SiC), or lithium tantalate (LiTa 3 The workpiece 100 is a wafer such as a disk-shaped semiconductor device wafer or an optical device wafer, using a substrate 101 such as a semiconductor wafer or an optical device wafer. Note that the workpiece 100 is not limited to the embodiment, and does not have to be disk-shaped in the present invention.

[0020] The workpiece 100 has division lines 103 set in a grid pattern on a surface 102 of a substrate 101, and devices 104 formed in areas partitioned by the division lines 103. The devices 104 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), or image sensors such as CCDs (Charge Coupled Devices) or CMOSs ​​(Complementary Metal Oxide Semiconductors). The workpiece 100 is supported within an opening of the frame 110, with, for example, a ring-shaped frame 110 attached thereto and an adhesive tape 111 having a diameter larger than the outer diameter of the workpiece 100 attached to a back surface 105 of the workpiece 100.

[0021] The holding table 10 holds the workpiece 100 on a holding surface 11. The holding surface 11 is a disk shape made of porous ceramics or the like. In the embodiment, the holding surface 11 is a plane parallel to the horizontal direction. The holding surface 11 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 10 holds the workpiece 100 placed on the holding surface 11 by suction. A plurality of clamps 12 are arranged around the holding table 10 to clamp a frame 110 that supports the workpiece 100.

[0022] The holding table 10 is rotated around an axis parallel to the Z-axis direction by a rotation unit 13. The rotation unit 13 is supported by an X-axis direction moving plate 14. The rotation unit 13 and the holding table 10 are moved in the X-axis direction by an X-axis direction moving unit 41 of the moving unit 40 via the X-axis direction moving plate 14. The rotation unit 13 and the holding table 10 are moved in the Y-axis direction by a Y-axis direction moving unit 42 of the moving unit 40 via the X-axis direction moving plate 14, the X-axis direction moving unit 41 and the Y-axis direction moving plate 15.

[0023] The laser beam irradiation unit 20 is a unit that irradiates the workpiece 100 held on the holding table 10 with a pulsed laser beam 21 having a predetermined wavelength for processing the workpiece 100. In the embodiment, a part of the laser beam irradiation unit 20 is supported on the tip of a support column 4 whose base end is attached to an erect wall 3 erected from the apparatus main body 2. The detailed configuration of the laser beam irradiation unit 20 will be described later.

[0024] The moving unit 40 is a unit that relatively moves the holding table 10 and the focal point 211 (see FIG. 3) of the laser beam 21 irradiated from the laser beam irradiation unit 20. The moving unit 40 includes an X-axis direction moving unit 41 and a Y-axis direction moving unit .

[0025] The X-axis direction moving unit 41 is a unit that relatively moves the holding table 10 and the focal point 211 (see FIG. 3) of the laser beam 21 irradiated from the laser beam irradiation unit 20 in the X-axis direction, which is the processing feed direction. In the embodiment, the X-axis direction moving unit 41 moves the holding table 10 in the X-axis direction. In the embodiment, the X-axis direction moving unit 41 is installed on the apparatus body 2 of the laser processing apparatus 1. The X-axis direction moving unit 41 supports the X-axis direction moving plate 14 so as to be freely movable in the X-axis direction.

[0026] The Y-axis direction moving unit 42 is a unit that relatively moves the holding table 10 and the focal point 211 (see FIG. 3) of the laser beam 21 irradiated from the laser beam irradiation unit 20 in the Y-axis direction, which is the indexing feed direction. In the embodiment, the Y-axis direction moving unit 42 moves the holding table 10 in the Y-axis direction. In the embodiment, the Y-axis direction moving unit 42 is installed on the apparatus body 2 of the laser processing apparatus 1. The Y-axis direction moving unit 42 supports the Y-axis direction moving plate 15 so that it can be moved freely in the Y-axis direction.

[0027] Each of the X-axis direction moving unit 41 and the Y-axis direction moving unit 42 includes, for example, a well-known ball screw, a well-known pulse motor, and a well-known guide rail. The ball screw is provided so as to be rotatable about its axis. The pulse motor rotates the ball screw about its axis. The guide rail of the X-axis direction moving unit 41 is provided so as to be fixed to the Y-axis direction moving plate 15, and supports the X-axis direction moving plate 14 so as to be movably in the X-axis direction. The guide rail of the Y-axis direction moving unit 42 is provided so as to be fixed to the device body 2, and supports the Y-axis direction moving plate 15 so as to be movably in the Y-axis direction.

[0028] The display unit 50 is a display section configured by a liquid crystal display device or the like. The display unit 50 displays, for example, a setting screen for processing conditions, the state of the workpiece 100 captured by an imaging unit (not shown), the state of the processing operation, and the like on the display surface 51. When the display surface 51 of the display unit 50 includes a touch panel, the display unit 50 may include an input unit. The input unit can receive various operations such as an operator registering processing content information. The input unit may be an external input device such as a keyboard. The display unit 50 switches information and images displayed on the display surface 51 by operations from the input unit or the like. The display unit 50 may include an alarm device. The alarm device emits at least one of sound and light to notify the operator of the laser processing device 1 of predetermined alarm information. The alarm device may be an external alarm device such as a speaker or a light-emitting device.

[0029] The control unit 60 controls each of the above-mentioned components of the laser processing apparatus 1, and causes the laser processing apparatus 1 to execute a processing operation on the workpiece 100. The control unit 60 is a computer including an arithmetic processing device as a calculation means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing device includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The arithmetic processing device performs various calculations based on a predetermined program stored in the storage device. The arithmetic processing device outputs various control signals to each of the above-mentioned components via the input / output interface device according to the calculation results, thereby controlling the laser processing apparatus 1.

[0030] Next, a detailed description will be given of the configuration of the laser beam irradiation unit 20. Fig. 2 is an explanatory diagram for explaining a schematic configuration of the laser beam irradiation unit 20 of the laser processing apparatus 1 shown in Fig. 1. As shown in Fig. 2, the laser beam irradiation unit 20 has a laser oscillator 22, an acousto-optic deflector (AOD) 23, mirrors 24 and 25, an fθ secondary lens 26, an fθ main lens 27, a scan unit 30, and a chamber 33.

[0031] The laser oscillator 22 emits a laser beam 21 having a predetermined wavelength for processing the workpiece 100. The laser beam 21 irradiated by the laser beam irradiation unit 20 may be a laser beam having a wavelength that is transparent to the workpiece 100, or may be a laser beam having a wavelength that is absorbent to the workpiece 100.

[0032] When a predetermined high frequency is applied to the acousto-optical element 23, the acousto-optical element 23 deflects the optical axis of the laser beam 21 emitted from the laser oscillator 22 in a predetermined direction (the Y-axis direction in this embodiment) to perform scanning. The acousto-optical element 23 adjusts the angle at which the optical axis of the laser beam 21 is deflected in accordance with the frequency of the applied high frequency. As a result, the laser beam 21 is scanned in the Y-axis direction.

[0033] In the embodiment, the mirrors 24 and 25 are provided on the optical path between the acousto-optical element 23 and the fθ secondary lens 26. The mirrors 24 and 25 propagate the laser beam 21 emitted from the laser oscillator 22 and polarized by the acousto-optical element 23 to the fθ secondary lens 26.

[0034] The fθ secondary lens 26 is provided on the optical path between the laser oscillator 22 and the fθ main lens 27. In the embodiment, the fθ secondary lens 26 is provided on the optical path between the mirror 25 and the scan unit 30. In the embodiment, the laser beam 21 polarized by the acousto-optical element 23 is incident on the fθ secondary lens 26. The fθ secondary lens 26 changes the incident laser beam 21 from parallel light to divergent light. The fθ secondary lens 26 may be a single lens or a compound lens.

[0035] The laser beam 21 scanned by the scan unit 30 is incident on the fθ main lens 27. The fθ main lens 27 collects the laser beam 21 emitted from the laser oscillator 22 and irradiates the workpiece 100 held on the holding table 10. The fθ main lens 27 is a composite lens made up of a combination of multiple lenses.

[0036] The scan unit 30 is disposed on the optical path between the laser oscillator 22 and the fθ main lens 27, and is a unit that scans the laser beam 21 and guides it to the fθ main lens 27. In the embodiment, the scan unit 30 includes a polygon scanner. The scan unit 30 includes a scan mirror 31 and a scan motor 32.

[0037] The scan mirror 31 is provided so as to be rotatable or swingable around an axis parallel to the indexing feed direction (Y-axis direction). In the embodiment, the scan mirror 31 is provided on each side of a polygonal prism (in the embodiment, an octagonal prism) that rotates around its axis. The axis of the scan mirror 31 is held by a mirror holder (not shown). The front focal point 271 (see FIG. 3) of the fθ main lens 27 is positioned on the scan mirror 31 where the laser beam 21 is incident from the fθ secondary lens 26 in the scan unit 30. The scan motor 32 outputs a rotational driving force for rotating or swinging the scan mirror 31 around its axis.

[0038] The scan unit 30 reflects the laser beam 21, which has been converted into diffuse light by the fθ secondary lens 26, in a direction parallel to the XZ plane toward the fθ main lens 27 using the scan mirror 31, and rotates the scan mirror 31 around an axis parallel to the Y-axis direction, thereby scanning the laser beam 21 in the X-axis direction.

[0039] The chamber 33 has the scan unit 30 disposed therein. In the embodiment, the fθ secondary lens 26 and the fθ main lens 27 are fixed to the chamber 33. The chamber 33 functions as a lens holder for the fθ secondary lens 26 and the fθ main lens 27. As a result, the fθ secondary lens 26 and the fθ main lens 27 are unitized with their relative distance and relative position fixed. In addition, the fθ secondary lens 26 and the fθ main lens 27 are arranged in a window-like manner that transmits the laser beam 21 in the wall that separates the inside of the chamber 33 from the surrounding environment.

[0040] Next, the effect of the fθ secondary lens 26 will be described. Fig. 3 is an explanatory diagram showing an example of the front focus 271 and the rear focus 272 of the fθ main lens 27 in the laser beam irradiation unit 20 shown in Fig. 2. Fig. 4 is an explanatory diagram showing an example of the front focus 271-1 and the rear focus 272-1 of the fθ main lens 27 in the laser beam irradiation unit of the comparative example.

[0041] 4, the parallel laser beam 21 is reflected by the scan mirror 31 and enters the fθ main lens 27. Therefore, the position of the rear focal point 272-1 of the fθ main lens 27 is equal to the position of the focal point 211-1 of the laser beam 21.

[0042] 3, the laser beam 21 converted into diffuse light by the fθ secondary lens 26 is reflected by the scan mirror 31 and enters the fθ main lens 27. Therefore, the focal point 211 of the laser beam 21 is positioned at a position farther away from the fθ main lens 27 than the rear focal point 272 of the fθ main lens 27.

[0043] 4, that is, in the case where the laser beam 21 of parallel light is incident, the distance from the fθ main lens 27 to the front focal point 271-1 is equal to the distance from the fθ main lens 27 to the rear focal point 272-1. In contrast, the distance from the fθ main lens 27 to the front focal point 271 of the fθ main lens 27 in the embodiment shown in Fig. 3 is longer than the distance from the fθ main lens 27 to the front focal point 271-1 (see Fig. 4) in the case where the laser beam 21 of parallel light is incident.

[0044] Here, in order to make the laser beam 21 perpendicularly incident on the workpiece 100, the position of the front focal point 271 of the fθ main lens 27 needs to be positioned on the scan mirror 31 on which the laser beam 21 is incident from the fθ secondary lens 26. Therefore, in the laser beam irradiation unit of the comparative example shown in FIG. 4, in order to make the laser beam 21 perpendicularly incident on the workpiece 100, it is necessary to make the distance between the scan mirror 31 and the fθ main lens 27 shorter than the state shown in FIG. 4. However, if the distance between the scan mirror 31 and the fθ main lens 27 is made shorter, there is a possibility that the fθ main lens 27 will vibrate due to the influence of the high-speed rotation of the scan unit 30.

[0045] 3, the laser beam irradiation unit 20 has an fθ secondary lens 26 that changes the laser beam 21 incident on the scan mirror 31 of the scan unit 30 into diffused light, so that the distance between the focal point 211 of the laser beam 21 positioned at the processing point on the workpiece 100 and the fθ main lens 27 can be made greater than the distance between the fθ main lens 27 and the rear focal point 272. In addition, the fθ secondary lens 26 eliminates the need to consider the position of the rear focal point 272 of the fθ main lens 27 in the laser beam irradiation unit 20, improving design freedom and allowing the distance of the front focal point 271 of the fθ main lens 27 to be increased.

[0046] As described above, the laser processing apparatus 1 according to the embodiment can focus the laser beam 21 behind the position (rear focal point 272) where the laser beam 21 is focused when parallel light is incident, by making the laser beam 21 enter the fθ main lens 27 in a diffused state using the fθ secondary lens 26. This allows the distance from the fθ main lens 27 to the processing point to be increased. In addition, since it is not necessary to take into consideration the position of the rear focal point 272 of the fθ main lens 27, the design freedom of the fθ main lens 27 is improved, and the front focal point 271 of the fθ main lens 27 can be designed to be away from the fθ main lens 27.

[0047] Therefore, even if the scan mirror 31 and the fθ main lens 27 are placed at positions sufficiently apart so as not to be affected by the high-speed rotation of the scan mirror 31, the front focal point 271 of the fθ main lens 27 can be positioned on the scan mirror 31. This allows the laser beam 21 to be perpendicularly incident on the workpiece 100 while suppressing enlargement of the entire apparatus and contamination of the fθ main lens 27 by debris.

[0048] It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced in various modified forms without departing from the gist of the present invention. [Explanation of symbols]

[0049] 1 Laser processing equipment 10 Holding table 20 Laser beam irradiation unit 21 Laser Beam 211, 211-1 Focus point 22 Laser Oscillator 26 fθ secondary lens 27 fθ main lens 271, 271-1 anterior focus 272, 272-1 posterior focus 30 Scan Unit 31 Scan Mirror 33 Chamber 40 Mobile Units 100 Workpiece

Claims

1. A holding table for holding the workpiece; a laser beam irradiation unit that irradiates a workpiece held on the holding table with a focused pulsed laser beam to process the workpiece; a moving unit for relatively moving the holding table and the focal point of the laser beam; A laser processing apparatus comprising: The laser beam irradiation unit includes: A laser oscillator that emits a laser beam; an fθ main lens that collects the laser beam emitted from the laser oscillator and irradiates the laser beam onto the workpiece held on the holding table; a scan unit disposed on an optical path between the laser oscillator and the main fθ lens, for scanning the laser beam and guiding it to the main fθ lens; an fθ lens disposed on an optical path between the laser oscillator and the scan unit to change the laser beam from a parallel beam to a divergent beam; having The fθ main lens and the fθ secondary lens are unitized with a fixed distance and position relative to the scan unit, The scan unit is characterized in that the laser beam converted into a diffused light by the fθ secondary lens is reflected by a scan mirror toward the fθ main lens. Laser processing equipment.

2. The front focal point of the fθ primary lens is positioned on a scan mirror on which the laser beam is incident from the fθ secondary lens in the scan unit. The laser processing apparatus according to claim 1.

3. The scanning unit is disposed within the chamber, The fθ main lens and the fθ secondary lens are arranged like a window that transmits the laser beam while separating the inside of the chamber from the surrounding environment.

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

Images