Laser processing equipment

Abstract

[Problem] To provide a laser processing apparatus that can achieve high-precision processing. [Solution] The laser beam irradiation unit of the laser processing apparatus includes: a laser oscillator that emits a laser beam; a characteristic conversion optical element that converts the characteristics of the laser beam emitted from the laser oscillator; a reflector and a focusing lens that guide the laser beam to the workpiece; a detection unit that detects the water retention state of the characteristic conversion optical element; and a drying unit that dries the characteristic conversion optical element.

Description

[Technical Field]

[0001] This invention relates to a laser processing apparatus. [Previous Technology]

[0002] Techniques for processing workpieces such as semiconductor wafers or optical element wafers by irradiating them with laser beams are already widespread (see, for example, Patent Document 1 and Patent Document 2).

[0003] In the processing of the workpiece, the basic wavelength, namely 1064nm (IR, infrared), is the primary wavelength, and various wavelengths of laser beams such as the second harmonic, namely 532nm (Green), the third harmonic, namely 355nm (UV, ultraviolet), and the fourth harmonic, namely 266nm (DUV, far ultraviolet), are used, and the selection is made according to the application.

[0004] Among them, short-wavelength UV or DUV laser beams can reduce the laser focusing diameter at the irradiation position, so high-precision processing is expected. In addition, due to their high absorption rate and high light energy for various materials, they can also be expected to be applied to materials that were previously difficult to process, and are therefore attracting attention.

[0005] Various optical elements are incorporated into the laser processing apparatus used to perform this type of processing. These include: laser crystals for oscillating and outputting laser light; wavelength conversion optical elements for converting the wavelength of the laser beam; wavelength plates for converting the polarization direction; mirrors for converting the deflection direction of the beam; and lenses for focusing the beam into a parallel beam, i.e., converting the focusing angle of the beam, etc.

[0006] For example, Nd:YAG, ND:YVO4, and titanium sapphire are commonly used as laser crystals. Furthermore, CLBO (cesium lithium borate, CsLiB6O10) crystals have become increasingly common in recent years for wavelength conversion optical elements used for DUV output (see, for example, Patent Document 3). Moreover, wavelength plates, mirrors, lenses, etc., are often made of transparent materials coated with dielectric multilayer films to improve their reflective or transmissive properties. [Conventional Art Documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2014-143285 [Patent Document 2] Japanese Patent Application Publication No. 2004-072052 [Patent Document 3] Japanese Patent Application Publication No. 2000-292819 [Summary of the Invention]

[0008] [Problem to be Solved by the Invention] However, these optical elements are known to deteriorate due to moisture in the air. For example, if moisture is adsorbed on the dielectric multilayer film, the spectral dispersive characteristics of the mirror or wavelength plate will change, the reflectivity or transmittance will change, the amount of light irradiated by the laser beam onto the workpiece will decrease, and the processing quality will be reduced. Furthermore, the CLBO crystal used in wavelength conversion optical elements is deliquescent. As a result, the CLBO crystal deteriorates due to retaining moisture in the air, adversely affecting the profile of the laser beam after crystallization, and reducing the processing quality.

[0009] Therefore, the aforementioned optical components require frequent replacement or maintenance, which may lead to reduced productivity due to longer downtime of the processing equipment.

[0010] Therefore, the object of the present invention is to provide a laser processing apparatus that can achieve high-precision processing.

[0011] [Technical Means for Solving the Problem] According to the present invention, a laser processing apparatus is provided, comprising: a holding stage for holding a workpiece; a laser beam irradiation unit for irradiating the workpiece held on the holding stage with a laser beam; and a controller, wherein the laser beam irradiation unit comprises: a laser oscillator having a first optical element for emitting a laser beam; a characteristic conversion optical element for converting the characteristics of the laser beam emitted from the laser oscillator; a second optical element for guiding the characteristic-converted laser beam to the workpiece; a detection unit for detecting the water retention state of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator; and a drying unit for drying any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator.

[0012] Preferably, when the water retention state of any of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator detected by the detection unit is greater than a predetermined value, the controller performs drying of the first optical element, the characteristic conversion optical element, and any of the optical elements of the laser oscillator by the drying unit.

[0013] Preferably, the laser beam irradiation unit has at least two characteristic conversion optical elements, the at least two characteristic conversion optical elements comprising: a first characteristic conversion optical element disposed in the optical path of the laser beam; and a second characteristic conversion optical element configured to replace the first characteristic conversion optical element. If the controller determines that the first characteristic conversion optical element needs to be dried, it moves the first characteristic conversion optical element out of the optical path of the laser beam and moves the second characteristic conversion optical element into the optical path of the laser beam. While the first characteristic conversion optical element is dried by the drying unit, the second characteristic conversion optical element is used to convert the characteristics of the laser beam to process the workpiece.

[0014] Preferably, the detection unit includes: a light source that emits light in the infrared region; and a detection unit that detects light emitted from the light source and transmitted through any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator, and the controller determines the water retention state of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator based on the transmittance of the light emitted from the light source.

[0015] Preferably, the characteristic conversion optical element is a wavelength conversion optical element that converts the characteristics, i.e., the wavelength, of the laser beam emitted from the laser oscillator.

[0016] Preferably, the wavelength conversion optical element is a CLBO crystal.

[0017] [Effect of the Invention] The present invention enables high-precision machining.

Implementation Method

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the constituent elements described below include those readily conceived by those skilled in the art to which this invention pertains, and those substantially the same. Moreover, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications to the configuration can be made without departing from the spirit of the present invention.

[0020] [First Embodiment] A laser processing apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG1 is a perspective view showing an example of the configuration of the laser processing apparatus of the first embodiment. FIG2 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG1.

[0021] The laser processing apparatus 1 of the first embodiment is a processing apparatus for performing laser processing on a workpiece 200. The workpiece 200 to be processed by the laser processing apparatus 1 of the first embodiment is a wafer such as a disc-shaped semiconductor wafer having a substrate, a laser beam absorbing layer deposited on the front side of the substrate, and a component layer deposited on the laser beam absorbing layer. In the first embodiment, the substrate is made of a transparent material such as sapphire and is formed into a disc shape. The laser beam absorbing layer is made of resin, and in the first embodiment, it is made of polyimide.

[0022] The component layer has components formed in the area divided by multiple intersecting predetermined dividing lines. The components are, for example, integrated circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration), power components, MEMS (Micro Electro Mechanical Systems) or various memory devices (semiconductor memory devices).

[0023] The aforementioned workpiece 200 is subjected to a so-called laser lift-off process, in which a transfer substrate 201 made of glass is attached to the component layer divided according to each component through an adhesive layer, the focus point is set on the laser beam absorption layer, and a laser beam 21 with a wavelength that has penetrability to the substrate is irradiated through the substrate to the entire surface, thereby destroying the laser beam absorption layer and peeling the components off the substrate.

[0024] Furthermore, in the first embodiment, the workpiece 200 is attached to the element layer by means of an adhesive layer, and the transfer substrate 201 is attached to a circular adhesive film 202 with a diameter larger than that of the workpiece 200. An annular frame 203 with an inner diameter larger than that of the workpiece 200 is attached to the outer periphery of the adhesive film 202 and supported in the opening on the inner side of the annular frame 203.

[0025] The laser processing apparatus 1 shown in FIG1 is a processing apparatus that performs laser peeling processing on the workpiece 200 by setting the focusing point of a pulsed laser beam 21 with a wavelength that has penetrability to the substrate of the workpiece 200 on the laser beam absorption layer from the back side of the substrate of the workpiece 200, and irradiating the entire surface of the workpiece 200 with the laser beam 21. As shown in FIG1, the laser processing apparatus 1 includes: a holding stage 10, which holds the workpiece 200, a laser beam irradiation unit 20, a moving unit 30, a camera unit 40, and a controller 100.

[0026] The holding table 10 holds the workpiece 200 with a holding surface 11 parallel to the horizontal direction. The holding surface 11 is a disc shape formed of porous ceramic or the like, and is connected to a vacuum suction source (not shown) through a suction path (not shown). The holding table 10 holds the workpiece 200 placed on the holding surface 11 by being attracted by the vacuum suction source. A plurality of clamping parts 12 are arranged around the holding table 10, which clamp the frame 203 supporting the workpiece 200 in the opening.

[0027] Furthermore, the holding table 10 rotates about an axis orthogonal to the holding surface 11 and parallel to the Z-axis direction via the rotational movement unit 33 of the moving unit 30. The Z-axis direction is parallel to the vertical direction. The holding table 10 moves together with the rotational movement unit 33 in the X-axis direction (equivalent to the processing direction) parallel to the horizontal direction via the X-axis movement unit 31 of the moving unit 30, and in the Y-axis direction (parallel to the horizontal direction and orthogonal to the X-axis direction) via the Y-axis movement unit 32. The holding table 10 moves across the processing area below the laser beam irradiation unit 20 and away from the area below the laser beam irradiation unit 20 to move the workpiece 200 in and out.

[0028] The laser beam irradiation unit 20 is a laser beam irradiation means that focuses and irradiates the workpiece 200 held on the holding table 10 with a pulsed laser beam 21. In the first embodiment, as shown in FIG1, a part of the laser beam irradiation unit 20 is moved in the Z-axis direction by means of a Z-axis moving unit 34, which is disposed on the standing wall 3 erected from the device body 2.

[0029] The laser beam irradiation unit 20 irradiates the workpiece 200 held on the holding stage 10 with a laser beam 21 of a wavelength that is penetrable to the substrate. As shown in FIG2, the laser beam irradiation unit 20 includes: a laser oscillator 22 that emits a pulsed laser beam 21-1; a wavelength conversion optical element 23 (equivalent to a characteristic conversion optical element) that converts the wavelength (equivalent to a characteristic) of the laser beam 21-1 emitted from the laser oscillator 22; and a focusing lens 24 that focuses the wavelength-converted laser beam 21 by the wavelength conversion optical element 23 onto the workpiece 200. Furthermore, in the first embodiment, the laser beam irradiation unit 20 includes: a reflector 25 that reflects the laser beam 21-1 emitted from the laser oscillator 22 toward the wavelength conversion optical element 23.

[0030] The laser oscillator 22 includes a crystal 221, which is an optical element constituting the laser medium of the oscillating laser beam 21-1. The crystal 221 is, for example, constructed from YAG (Yittrium Aluminum Garnet, Y3Al5O12) crystal, yttrium orthovanadate (YVO4) crystal, or titanite (Ti, Al2O3) crystal. In the first embodiment, the laser oscillator 22 oscillates IR light with a wavelength of 1064 nm. The IR light is converted into green light with a wavelength of 532 nm by the BBO (β-BaB2O4) crystal 222 and emitted as the laser beam 21-1. Furthermore, in this invention, the BBO crystal 222 may also exist in the same housing as the laser oscillator 22.

[0031] The wavelength conversion optical element 23 is positioned at a conversion position to convert the wavelength of the laser beam 21-1 emitted from the laser oscillator 22 into a shorter wavelength laser beam 21, and then emits the converted laser beam 21 toward the condenser lens 24. Furthermore, the conversion position refers to the position where the wavelength conversion optical element 23 is located in the optical path of the laser beam 21-1 emitted from the laser oscillator 22, and converts the wavelength of the laser beam 21-1 into a shorter wavelength laser beam 21.

[0032] In the first embodiment, the wavelength conversion optical element 23 is constructed from CLBO (cesium lithium borate, CsLiB 6O 10) crystal and is housed within an internally sealed box-shaped container 231. The CLBO crystal constituting the wavelength conversion optical element 23 is hygroscopic. In the first embodiment, the wavelength conversion optical element 23 converts a second harmonic (green) laser beam 21-1 with a wavelength of 532 nm into a fourth harmonic (DUV, far ultraviolet) laser beam 21 with a wavelength of 266 nm. Furthermore, the container 231 includes windows for transmitting the laser beams 21-1 and 21.

[0033] The condenser lens 24 is positioned opposite the holding surface 11 of the holding stage 10 in the Z-axis direction. The condenser lens 24 is a condensing optical element that focuses and irradiates the workpiece 200 held on the holding stage 10 with a pulsed laser beam 21. The condenser lens 24 transmits the laser beam 21 emitted from the laser oscillator 22, reflected by the mirror 25, and wavelength-converted by the wavelength-converting optical element 23, and focuses the laser beam 21 at a focusing point (as shown in FIG2, etc.). Furthermore, in the first embodiment, the condenser lens 24 focuses the focusing point of the laser beam 21 onto the laser beam absorption layer of the workpiece 200 held on the holding surface 11 of the holding stage 10.

[0034] Furthermore, the reflector 25 and the condenser lens 24 are optical elements that guide the laser beams 21-1 and 21 to the workpiece 200. In the first embodiment, the laser beam irradiation unit 20 is an optical element that guides the laser beams 21-1 and 21, which have undergone wavelength conversion by the wavelength conversion optical element 23, to the workpiece 200, and is equipped with the reflector 25 and the condenser lens 24. However, in this invention, for example, it is not limited to the reflector 25 and the condenser lens 24, but may also be equipped with various optical elements such as the scanning optical system that constitutes the scanning laser beams 21-1 and 21.

[0035] Furthermore, as shown in FIG2, the laser beam irradiation unit 20 includes a drying unit 26, a detection unit 27, and an optical element moving unit 28. The drying unit 26 is a unit for drying the wavelength conversion optical element 23 inside the container 231. In the first embodiment, the drying unit 26 is a unit that heats the wavelength conversion optical element 23 to 150°C while continuously allowing dry air from a dry air supply source to flow into the container 231. In the first embodiment, the drying unit 26 includes a heating means that heats the wavelength conversion optical element 23 inside the container 231 to 150°C; and a mechanism that continuously allows dry air from a dry air supply source to flow into the container 231. The heating means heats the wavelength conversion optical element 23 to 150°C and continuously allows dry air from a dry air supply source to flow into the container 231, thereby drying the wavelength conversion optical element 23 inside the container 231. Furthermore, in this invention, the drying unit 26 may also include a heating means for heating the contents of the container 231 to, for example, 150°C, and a pump for degassing the contents of the container 231. In this case, in the drying unit 26, the heating means heats the wavelength conversion optical element 23 to 150°C within the container 231, and the pump degasses the contents of the container 231, thereby drying the wavelength conversion optical element 23 within the container 231.

[0036] The detection unit 27 detects the water retention state of the wavelength conversion optical element 23. The water retention state refers to the degree to which the wavelength conversion optical element 23 absorbs water (water vapor) from the air. In the first embodiment, the detection unit 27 includes: a light source 271, a bandpass filter 272, and a detection unit 273.

[0037] The light source 271 emits detection light 274 to the wavelength conversion optical element 23, which is positioned at the detection position away from the conversion position, i.e., from the optical path of the laser beam 21-1. The light source 271 irradiates the wavelength conversion optical element 23, which is positioned at the detection position, with the detection light 274 (light in the infrared region) having a center wavelength of 2800 nm, i.e., a wavenumber of 3600 cm⁻¹. Furthermore, the reason why the light source 271 irradiates the wavelength conversion optical element 23, which is positioned at the detection position, with the detection light 274 having a center wavelength of 2800 nm, i.e., a wavenumber of 3600 cm⁻¹, is that water molecules easily absorb the detection light 274 with a center wavelength of 2800 nm, i.e., a wavenumber of 3600 cm⁻¹, and thus easily detect the water retention state of the wavelength conversion optical element 23. The light source 271 can be, for example, a 2800W LED manufactured by THORLABS.

[0038] Therefore, the detection light 274 irradiated by the light source 271 onto the wavelength conversion optical element 23 will decrease as the water retention state of the wavelength conversion optical element 23 increases (the amount of water absorbed by the wavelength conversion optical element 23 increases), and the amount of light transmitted through the wavelength conversion optical element 23, i.e., the transmittance, decreases. Conversely, the detection light 274 irradiated by the light source 271 onto the wavelength conversion optical element 23 will increase as the water retention state of the wavelength conversion optical element 23 decreases (the amount of water absorbed by the wavelength conversion optical element 23 decreases). Furthermore, in this invention, the detection light 274 emitted by the light source 271 of the detection unit 27 only needs to have infrared absorption by water molecules, and is not limited to the first embodiment.

[0039] However, the wavelength range of the light source 271 is wide, sometimes reaching wavelengths where infrared absorption by water molecules is relatively small. For example, in the first embodiment, the infrared absorption by water molecules is limited to 3550 cm⁻¹ to 3650 cm⁻¹. In contrast, the wavenumber range of the light source 271 reaches 3400 cm⁻¹ to 3800 cm⁻¹, including wavelengths of light that are not sufficiently absorbed by water molecules. As a result, even if the water retention state of the wavelength conversion optical element 23 shows a small change, the transmittance of infrared light sometimes does not change sufficiently. In this case, by inserting a bandpass filter that transmits light only in a narrow wavelength range into the optical path, the detection sensitivity of the water retention state can be improved.

[0040] For example, in the first embodiment, a bandpass filter 272 is disposed between the wavelength conversion optical element 23 and the detection unit 273. In the first embodiment, the bandpass filter 272 transmits light with a wavelength number between 3500 cm⁻¹ and 3700 cm⁻¹, but does not transmit light with other wavelength numbers. The bandpass filter 272 transmits the detection light 274 with a wavelength number between 3500 cm⁻¹ and 3700 cm⁻¹ transmitted by the wavelength conversion optical element 23 toward the detection unit 273, but does not transmit detection light 274 with other wavelength numbers. As a result, the proportion of infrared light absorbed by water molecules in the infrared light irradiating the wavelength conversion optical element 23 increases, and the detection sensitivity of the water-retaining state is improved. Furthermore, although the detection unit 27 is equipped with a bandpass filter 272 in the first embodiment to improve the detection sensitivity of the water-retaining state, it may not be equipped with a bandpass filter 272 in cases where improved detection sensitivity is not required or where the wavelength range of the light source is sufficiently narrow.

[0041] The detection unit 273 receives detection light 274 emitted from the light source 271 and sequentially transmitted through the wavelength conversion optical element 23 and the bandpass filter 272 positioned at the detection position, detects the amount of light received by the detection light 274, and outputs information indicating the amount of light received by the detection light 274 to the controller 100. In the first embodiment, the detection unit 273 is a photodiode that receives infrared light with wavelengths from 1 μm to 10.6 μm and outputs information indicating the amount of infrared light received to the controller 100. For example, the detection unit 273 can use a VML8T4 manufactured by THORLABS.

[0042] In the detection unit 27, the detection section 273 receives detection light 274 that is irradiated from the light source 271 and transmitted to the wavelength conversion optical element 23 positioned at the detection position, and outputs information indicating the amount of light received to the controller 100, thereby detecting the state quantity that changes in response to the water retention state of the wavelength conversion optical element 23, and outputting the detection result to the controller 100.

[0043] The optical element moving unit 28 moves the wavelength conversion optical element 23 across the conversion position and the detection position. The conversion position is located on the optical path of the laser beam 21-1, where the wavelength conversion optical element 23 inside the container 231 is irradiated by the laser beam 21-1 and undergoes wavelength conversion, and the wavelength conversion optical element 23 emits the wavelength-converted laser beam 21 towards the condenser lens 24. Furthermore, the conversion position is also a position where the wavelength conversion optical element 23 is not irradiated by the detection light 274 from the light source 271.

[0044] The detection position is the position of the wavelength conversion optical element 23 that is away from the optical path of the laser beam 21-1 and does not irradiate the wavelength conversion optical element 23 inside the container 231 with the laser beam 21-1. Furthermore, the detection position is also the position of the wavelength conversion optical element 23 that irradiates the wavelength conversion optical element 23 with the detection light 274 from the light source 271 and transmits the detection light 274 toward the bandpass filter 272 and the detection unit 273.

[0045] In the first embodiment, the optical element moving unit 28 moves the container 231 that has contained the wavelength conversion optical element 23, so that the wavelength conversion optical element 23 moves across the conversion position and the detection position.

[0046] The laser beam irradiation unit 20 performs laser stripping processing, wherein the laser stripping processing is to irradiate the substrate of the workpiece 200 held on the holding table 10 with a laser beam 21 having a penetrating wavelength, thereby destroying the laser beam absorption layer of the workpiece 200 and peeling the element off the substrate.

[0047] The moving unit 30 shown in FIG1 moves the holding stage 10 and the focusing point of the laser beam 21 irradiated by the laser beam irradiation unit 20 relative to each other in the X-axis direction, Y-axis direction, Z-axis direction, and about an axis parallel to the Z-axis direction. The X-axis and Y-axis directions are mutually orthogonal and parallel to the holding surface 11 (i.e., the horizontal direction). The Z-axis direction is orthogonal to the X-axis and Y-axis directions, i.e., the holding surface 11. The moving unit 30 includes: an X-axis moving unit 31, which is a machining feed unit that moves the holding stage 10 in the X-axis direction; a Y-axis moving unit 32, which is an indexing feed unit that moves the holding stage 10 in the Y-axis direction; a rotational moving unit 33, which rotates the holding stage 10 about an axis parallel to the Z-axis direction; and a Z-axis moving unit 34, which moves a portion of the laser beam irradiation unit 20 in the Z-axis direction.

[0048] The Y-axis moving unit 32 is a unit that indexes and feeds the stage 10 relative to the focusing point of the laser beam 21 of the laser beam irradiation unit 20. In the first embodiment, the Y-axis moving unit 32 is provided on the device body 2 of the laser processing apparatus 1. The Y-axis moving unit 32 supports the moving plate 4, which already supports the X-axis moving unit 31, and allows it to move freely in the Y-axis direction.

[0049] The X-axis moving unit 31 is a feeding means for processing the stage 10 relative to the focusing point of the laser beam 21 of the laser beam irradiation unit 20. The X-axis moving unit 31 is mounted on the moving plate 4. The X-axis moving unit 31 supports the second moving plate 5, which already supports the rotating moving unit 33, in a freely movable manner in the X-axis direction. The rotating moving unit 3 rotates the stage 10 about an axis parallel to the Z-axis direction. The second moving plate 5 supports the rotating moving unit 33 and the stage 10. The rotating moving unit 33 supports the stage 10.

[0050] The X-axis moving unit 31, Y-axis moving unit 32, and Z-axis moving unit 34 include: a conventional ball screw configured to rotate freely about an axis; a conventional pulse motor that rotates the ball screw about an axis; and a conventional guide rail that supports the moving plates 4 and 5 and the focusing lens 24 included in the laser beam irradiation unit 20 in a freely movable manner in the X-axis, Y-axis, or Z-axis direction. The rotary moving unit 33 includes a motor that rotates the holding stage 10 about an axis.

[0051] Furthermore, the laser processing apparatus 1 includes: an X-axis position detection unit (not shown) for detecting the X-axis position of the holding stage 10; a Y-axis position detection unit (not shown) for detecting the Y-axis position of the holding stage 10; and a Z-axis position detection unit (not shown) for detecting the Z-axis position of the laser beam irradiation unit 20. Each position detection unit outputs the detection result to the controller 100.

[0052] The imaging unit 40 captures images of the workpiece 200 held on the holding stage 10. The imaging unit 40 includes an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) imaging element that captures images of an object facing the objective lens in the Z-axis direction. In the first embodiment, the imaging unit 40 is mounted via a laser beam irradiation unit 20 and is positioned such that the objective lens and the condenser lens 24 are arranged along the X-axis direction.

[0053] The camera unit 40 acquires the image captured by the camera element and outputs the acquired image to the controller 100. In addition, the camera unit 40 captures the workpiece 200 held on the holding surface 11 of the holding stage 10 and acquires an image for performing alignment, wherein the alignment is performed to align the workpiece 200 with the laser beam irradiation unit 20.

[0054] The controller 100 controls each of the aforementioned components of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform laser processing operations on the workpiece 200. Furthermore, the controller 100 is a computer, which includes: an arithmetic processing unit having a microprocessor such as a CPU (central processing unit); a memory unit having memory such as ROM (read-only memory) or RAM (random access memory); and an input / output interface device. The arithmetic processing unit of the controller 100 performs arithmetic processing according to a computer program stored in the memory unit, and outputs control signals for controlling the laser processing apparatus 1 to the aforementioned components of the laser processing apparatus 1 through the input / output interface device, thereby realizing the function of the controller 100.

[0055] Furthermore, the laser processing apparatus 1 includes a display unit 110 and an input unit, etc. The display unit 110 is a display means constituted by a liquid crystal display device or the like that displaying the status or image of the processing operation, etc., and the input unit is an input means used by the operator to input processing conditions, etc. The display unit 110 and the input unit are connected to the controller 100. The input unit is constituted by at least one of an external input device such as a touch panel and a keyboard provided on the display unit 110.

[0056] Furthermore, as shown in FIG1, the controller 100 includes a memory unit 101 and a determination unit 102. The memory unit 101 stores the following light quantity: the amount of light emitted by the light source 271 after the detection light 274 has been transmitted through the bandpass filter 272 when the wavelength conversion optical element 23 is not irradiated with the detection light 274. In the first embodiment, the memory unit 101 stores the following light quantity: the amount of light emitted by the light source 271 after the wavelength conversion optical element 23 has been positioned in the conversion position and the detection light 274 has been transmitted through the bandpass filter 272.

[0057] The determination unit 102 determines the water retention state of the wavelength conversion optical element 23 based on the transmittance of the detection light 274 emitted from the light source 271. The determination unit 102 calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23 based on the following light amounts: the light amount stored in the memory unit 101; and the light amount received by the detection unit 273 when the detection light 274 emitted from the light source 271 has been transmitted to the wavelength conversion optical element 23 and the bandpass filter 272 positioned at the detection position.

[0058] Furthermore, in the first embodiment, the determination unit 102 sets the light intensity when the detection light 274 is not irradiated by the wavelength conversion optical element 23 but the detection unit 273 receives the detection light 274 irradiated by the light source 271 and transmitted through the bandpass filter 272 to 100%, and sets the light intensity when the detection unit 273 does not receive the detection light 274 to 0%, and calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23 (equivalent to a water-retaining state). The determination unit 102 determines the water-retaining state of the wavelength conversion optical element 23 by determining whether the calculated transmittance of the detection light 274 is above a predetermined value. Furthermore, in the first embodiment, the predetermined value is set to, for example, 13%. However, considering the wavelength range of the bandpass filter 272 or the light source 271, a value other than this value may also be set.

[0059] If the determination unit 102 determines that the transmittance of the calculated detection light 274 is above a predetermined value, then the wavelength conversion optical element 23 is suitable for processing the workpiece 200, and the drying unit 26 is not operated. If the determination unit 102 determines that the transmittance of the calculated detection light 274 is less than a predetermined value, then the determination unit 102 determines that the water retention of the wavelength conversion optical element 23 is greater than a certain water retention amount, i.e., a predetermined value, and the wavelength conversion optical element 23 is not suitable for processing the workpiece 200, then the drying unit 26 is operated to dry the wavelength conversion optical element 23.

[0060] Furthermore, the function of the memory unit 101 is realized by means of the aforementioned memory device. Also, the function of the determination unit 102 is realized by means of the arithmetic processing device performing arithmetic processing according to the computer program stored in the memory device.

[0061] Next, the processing operation of the laser processing apparatus 1 configured as described above will be explained. In the laser processing apparatus 1, the controller 100 receives and registers the processing conditions input by the operator, and places the transfer substrate 201 of the component layer attached to the workpiece 200 on the holding surface 11 of the holding table 10, which is positioned in the transfer-in / transfer-out area. If the controller 100 receives a start instruction for the processing operation from the operator, the laser processing apparatus 1 begins the processing operation.

[0062] During the processing operation, in the laser processing apparatus 1, the controller 100 attracts and holds the workpiece 200 on the holding surface 11 of the holding stage 10, and the clamping part 12 clamps the frame 203. During the processing operation, in the laser processing apparatus 1, the controller 100 positions the wavelength conversion optical element 23 at the conversion position. During the processing operation, in the laser processing apparatus 1, the controller 100 controls the moving unit 30 to move the holding stage 10 to the processing area, and the camera unit 40 captures an image of the workpiece 200 attracted and held on the holding stage 10, and performs alignment.

[0063] During the processing operation, the laser processing apparatus 1 sets the focusing point of the laser beam irradiation unit 20 on the laser beam absorption layer, and while moving the holding stage 10 relative to the focusing point of the laser beam irradiation unit 20, a pulsed laser beam 21 is irradiated from the back side of the substrate of the workpiece 200.

[0064] In the first embodiment, during the processing operation, the laser processing apparatus 1 irradiates the laser beam 21 across the entire surface of the workpiece 200 with the laser beam absorption layer, thereby destroying the laser beam absorption layer across the entire surface of the workpiece 200.

[0065] During the processing operation, if the laser processing apparatus 1 crosses the entire surface of the workpiece 200 and destroys the laser beam absorption layer, the irradiation of the laser beam 21 is stopped, and the holding table 10 is moved to the loading / unloading area. During the processing operation, the laser processing apparatus 1 positions the holding table 10 in the loading / unloading area, stops the attraction and holding of the workpiece 200 by the holding table 10, releases the clamping of the frame 203 of the clamping part 12, and ends the processing operation.

[0066] Furthermore, in the laser processing apparatus 1, the controller 100 periodically positions the wavelength conversion optical element 23 at the detection position, and illuminates the wavelength conversion optical element 23 with detection light 274 from the light source 271. The detection unit 273 receives the detection light 274 that has been transmitted through the wavelength conversion optical element 23 and the bandpass filter 272. In the laser processing apparatus 1, the determination unit 102 of the controller 100 calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23 based on the following light amounts: the light amount stored in the memory unit 101; and the light amount received by the detection unit 273 from the light source 271 that has been transmitted through the wavelength conversion optical element 23 and the bandpass filter 272 positioned at the detection position.

[0067] The determination unit 102 of the controller 100 determines whether the transmittance of the calculated detection light 274 is above a preset value. If the transmittance of the calculated detection light 274 is above the preset value, the controller 100 determines that the wavelength conversion optical element 23 is suitable for processing the workpiece 200, and does not operate the drying unit 26. The controller 100 positions the wavelength conversion optical element 23 in the conversion position and performs the processing operation. If the determination unit 102 of the controller 100 determines that the transmittance of the calculated detection light 274 is less than a preset value, that is, the water retention is greater than a predetermined amount, the controller 100 determines that the wavelength conversion optical element 23 is not suitable for processing the workpiece 200. The controller 100 maintains the wavelength conversion optical element 23 in the detection position and operates the drying unit 26 to dry the wavelength conversion optical element 23.

[0068] If the determination unit 102 of the controller 100 determines that the calculated transmittance of the detection light 274 is less than a preset predetermined value and activates the drying unit 26, then during each predetermined period (e.g., two weeks), the drying unit 26 is stopped, the detection light 274 is irradiated from the light source 271, the determination unit 102 calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23, and determines whether the transmittance of the detection light 274 calculated by the determination unit 102 is greater than or equal to the preset predetermined value. In this manner, in the first embodiment, when the detection unit 27 detects that the water retention state of the wavelength conversion optical element 23 is greater than a predetermined value, the determination unit 102 of the controller 100 performs drying of the wavelength conversion optical element 23 by the drying unit 26. Furthermore, the laser processing apparatus 1 operates the drying unit 26 and interrupts the processing operation until the transmittance of the detection light 274 of the wavelength conversion optical element 23 reaches or exceeds the preset predetermined value.

[0069] Furthermore, in the first embodiment, although the drying unit 26 is operated and the processing operation is interrupted until the transmittance of the detection light 274 of the wavelength conversion optical element 23 reaches or exceeds a predetermined value, in this invention, if it is determined that the transmittance of the detection light 274 is less than the predetermined value, the wavelength conversion optical element 23 can be maintained in the conversion position, the drying unit 26 can be operated, and while the wavelength conversion optical element 23 is dried, the workpiece 200 is irradiated with the laser beam 21 to process the workpiece 200. Furthermore, in this invention, the predetermined period can be freely set. For example, in this invention, if it is confirmed that the water retention state has improved to a certain extent, the predetermined period can be freely set by calculating how long it takes for the transmittance to reach or exceed the predetermined value. The predetermined period can be set by the operator or automatically calculated and set by the controller 100 or the like.

[0070] The laser processing apparatus 1 of the first embodiment described above is equipped with a detection unit 27 for detecting the moisture retention state of the wavelength conversion optical element 23, and a drying unit 26 for drying the wavelength conversion optical element 23 if the moisture retention state detected by the detection unit 27 is greater than a certain amount of moisture. Therefore, adverse effects on processing quality caused by deliquescence can be prevented. As a result, the laser processing apparatus 1 can achieve high-precision processing.

[0071] Furthermore, in the laser processing apparatus 1 of the first embodiment, a bandpass filter 272 is provided before the detection section 273 of the detection unit 27, thereby improving the detection sensitivity of the detection section 273.

[0072] [Second Embodiment] A laser processing apparatus according to a second embodiment of the present invention will be described with reference to the figures. FIG3 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus of the second embodiment. In addition, the same reference numerals are used for the same parts as in the first embodiment in FIG3 and the description is omitted.

[0073] As shown in FIG3, the laser beam irradiation unit 20-2 of the laser processing apparatus 1 of the second embodiment includes: a first wavelength conversion optical element 23-1 and a second wavelength conversion optical element 23-2 as wavelength conversion optical elements 23; and a first drying unit 26-1 and a second drying unit 26-2 as drying units 26. The wavelength conversion optical elements 23-1 and 23-2 have the same configuration as the wavelength conversion optical element 23 of the first embodiment, and are respectively housed in the container 231. In addition, the container 231 also has the same configuration as the container 231 that houses the wavelength conversion optical element 23 of the first embodiment. Similar to the first embodiment, when the wavelength conversion optical elements 23-1 and 23-2 are housed, the optical element moving unit 28 moves across the conversion position and the detection position.

[0074] Thus, in the second embodiment, the laser beam irradiation unit 20-2 has at least two wavelength conversion optical elements 23-1 and 23-2, the at least two wavelength conversion optical elements 23-1 and 23-2 comprising: a first wavelength conversion optical element 23-1, which is disposed in the optical path of the laser beam 21-1; and a second wavelength conversion optical element 23-2, which can be disposed in the optical path of the laser beam 21-1 interchangeably with the first wavelength conversion optical element 23-1.

[0075] Drying units 26-1 and 26-2 have the same configuration as drying unit 26 in the first embodiment, and correspond one-to-one with wavelength conversion optical elements 23-1 and 23-2, and dry the corresponding wavelength conversion optical elements 23-1 and 23-2. Furthermore, in this invention, one drying unit may be connected to both wavelength conversion optical elements 23-1 and 23-2.

[0076] In the laser processing apparatus 1, during the processing operation, the controller 100 positions one of the wavelength conversion optical elements 23-1 and 23-2 in a conversion position and the other in a detection position to perform the processing operation. In the laser processing apparatus 1, the controller 100 periodically positions either of the wavelength conversion optical elements 23-1 and 23-2 in the detection position, illuminates the wavelength conversion optical element 23 with detection light 274 from the light source 271, and receives the detection light 274 that has been transmitted through the wavelength conversion optical element 23 and the bandpass filter 272 through the detection unit 273.

[0077] In the laser processing apparatus 1, the determination unit 102 of the controller 100 calculates the transmittance of the detection light 274 of one of the wavelength conversion optical elements 23-1 and 23-2 based on the following light amounts: the light amount stored in the memory unit 101; and the light amount received by the detection unit 273 when the light emitted by the light source 271 has been transmitted through the detection light 274 of one of the wavelength conversion optical elements 23-1 and 23-2 positioned at the detection position and the bandpass filter 272.

[0078] The determination unit 102 of the controller 100 maintains one of the wavelength conversion optical elements 23-1 and 23-2, whose transmittance of the detection light 274 calculated by the controller is less than a predetermined value, in the detection position, operates the drying unit 26 to dry one of the wavelength conversion optical elements 23-1 and 23-2, and positions the other in the conversion position to perform the processing operation.

[0079] Thus, in the second embodiment, if the determination unit 102 of the controller 100 determines that the first wavelength conversion optical element 23-1 needs to be dried, the first wavelength conversion optical element 23-1 is dried by the first drying unit 26-1, and the laser beam 21-1 is converted by the second wavelength conversion optical element 23-2 to process the workpiece 200.

[0080] Similar to the first embodiment, the laser processing apparatus 1 of the second embodiment includes a detection unit 27 for detecting the moisture retention state of the wavelength conversion optical element 23. It also includes drying units 26-1 and 26-2 that dry the wavelength conversion optical elements 23-1 and 23-2 if the moisture retention state detected by the detection unit 27 exceeds a certain amount of moisture. Therefore, adverse effects on processing quality caused by deliquescence can be prevented. As a result, the laser processing apparatus 1 achieves high-precision processing.

[0081] Furthermore, in the second embodiment of the laser processing apparatus 1, during the drying of one of the wavelength conversion optical elements 23-1 and 23-2, the other is positioned in the conversion position to perform the processing operation, thus eliminating downtime and contributing to the improvement of productivity.

[0082] Next, the inventors of the present invention have confirmed the effectiveness of the laser processing apparatus 1 of the first embodiment. The results are shown in FIG4 and Table 1 below. Furthermore, FIG4 is a graph showing the transmittance spectrum of the wavelength conversion optical element of the laser processing apparatus shown in FIG1 before and after drying.

[0083] [Table 1]

[0084] During the verification, the transmittance spectrum of the wavelength conversion optical element 23 before and after drying was measured using a Fourier transform infrared spectrometer. Subsequently, simulations were performed with and without a bandpass filter 272 to measure the transmittance of the wavelength conversion optical element 23 before and after drying, which should be detected using detection light 274 with a center wavenumber of 3600 cm⁻¹.

[0085] The horizontal axis of Figure 4 represents the wavenumber of light, and the vertical axis of Figure 4 represents the transmittance of the wavelength conversion optical element 23. In Figure 4, the transmittance of the wavelength conversion optical element 23 before drying is represented by a dashed line, and the transmittance after drying is represented by a solid line. Furthermore, the area filled with thick dots represents the wavelength region of the light source, and the area filled with thin dots represents the wavelength region transmitted by the bandpass filter 272.

[0086] Furthermore, Table 1 shows the transmittance of the wavelength conversion optical element 23 before and after drying, which should be detected by the detection light 274 with a center wavenumber of 3600 cm⁻¹, in the case with and without the bandpass filter 272.

[0087] According to Figure 4, the transmittance of the detection light 274 with wavenumbers of 3400 cm⁻¹ and 3600 cm⁻¹ before drying is almost zero, while the transmittance of the detection light 274 with wavenumber of 3400 cm⁻¹ after drying is about 6% and about 12%.

[0088] Based on these spectra, as shown in the "With bandpass filter" column of Table 1, the transmittance detected in the first embodiment was simulated to be 5% before drying and 15% after drying. That is, the transmittance was estimated to increase by 3 times due to drying. From these results, it can be seen that the detection unit 27 can detect the water retention state of the wavelength conversion optical element 23.

[0089] On the other hand, as shown in Table 1, without the bandpass filter 272, the transmittance of the detection light 274 before and after drying was simulated to be 9% and 12%, respectively. That is, the increase in transmittance caused by drying was estimated to be only 1.3 times. From this result, it can be seen that the detection unit 27 can improve the sensitivity of the detection section 273 by having the bandpass filter 272.

[0090] Furthermore, the present invention is not limited to the above-described embodiments. That is, various modifications and implementations can be made without departing from the spirit of the present invention. In addition, in the first embodiment, the water retention state of the wavelength conversion optical elements 23, 23-1, and 23-2 is detected, and if it exceeds a certain water retention amount, the drying units 26, 26-1, and 26-2 dry them. However, in the present invention, the crystallization of the laser oscillator 22 and the water retention state of various optical elements can also be detected, and if they exceed a certain water retention amount, the drying units 26, 26-1, and 26-2 dry them. That is, in the present invention, as long as the detection unit 27 detects the water retention state of the crystallization 221 of the laser oscillator 22, the wavelength conversion optical elements 23, 23-1, and 23-2, and any of the optical elements, the drying units 26, 26-1, and 26-2 can dry the crystallization 221 of the laser oscillator 22, the wavelength conversion optical elements 23, 23-1, and 23-2, and any of the optical elements.

[0091] That is, in this invention, as long as the determination unit 102 of the controller 100 detects that the water retention state of any one of the crystal 221 of the laser oscillator 22, the wavelength conversion optical element 23, 23-1, 23-2 and the optical element detected by the detection unit 27 is greater than a predetermined value, the drying unit 26, 26-1, 26-2 can perform drying of any one of the crystal 221 of the laser oscillator 22, the wavelength conversion optical element 23, 23-1, 23-2 and the optical element. Furthermore, in this invention, as long as the detection unit 273 of the detection unit 27 detects the detection light 274 of any one of the crystal 221 of the transmission laser oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, and the optical element, the determination unit 102 of the controller 100 can determine the water retention status of any one of the crystal 221 of the laser oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, and the optical element based on the transmittance of the detection light 274 emitted from the light source 271.

[0092] Furthermore, in the above embodiment, although the laser processing apparatus 1 performs laser stripping processing on the workpiece 200, in the present invention, it can also perform laser processing that completely cuts off the workpiece 200 along the predetermined dividing line, or laser processing that forms a processing groove on the workpiece 200 along the predetermined dividing line.

[0093] Furthermore, in this invention, the optical element may also be a lens, a mirror, a wavelength plate, or other optical element coated with a dielectric multilayer film, the properties of which would change if moisture were retained. Furthermore, in this invention, the optical element may also be a laser crystal such as Nd:YAG, ND:YVO4, or titanium sapphire. Furthermore, in this invention, the optical element may also be a BBO crystal 222. In addition, in this invention, the optical element is included in the optical system of the laser processing apparatus 1 and is also included inside the laser oscillator 22.

[0094] Furthermore, in the above embodiment, the characteristic conversion optical element is described as a wavelength conversion optical element 23, 23-1, 23-2 that converts the characteristics, i.e., the wavelength, of the laser beam 21-1 emitted from the laser oscillator 22. However, in the present invention, the characteristic conversion optical element may also be an optical element that converts characteristics other than the wavelength of the laser beam 21-1, etc. That is, the present invention can also be applied to processing apparatuses that do not have wavelength conversion optical elements 23, 23-1, 23-2. [Simplified Explanation of the Diagram]

[0018] FIG1 is a perspective view showing a configuration example of the laser processing apparatus according to the first embodiment. FIG2 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG1. ​​FIG3 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus according to the second embodiment. FIG4 is a graph showing the transmittance spectrum of the wavelength conversion optical element of the laser processing apparatus shown in FIG1 before and after drying.

Claims

1. A laser processing apparatus comprising: a holding stage for holding a workpiece; a laser beam irradiation unit for irradiating the workpiece held on the holding stage with a laser beam; and a controller, wherein... The laser beam irradiation unit includes: a laser oscillator having a first optical element for emitting a laser beam; a characteristic conversion optical element for converting the characteristics of the laser beam emitted from the laser oscillator; a second optical element for guiding the characteristic-converted laser beam to the workpiece; a detection unit for detecting the water retention status of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator; and a drying unit for drying any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator.

2. The laser processing apparatus as described in claim 1, wherein, When the water retention state of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator detected by the detection unit is greater than a predetermined value, the controller performs drying of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator by the drying unit.

3. The laser processing apparatus as described in claim 1, wherein, The laser beam irradiation unit has at least two characteristic conversion optical elements, the at least two characteristic conversion optical elements including: a first characteristic conversion optical element, which is disposed in the optical path of the laser beam; The controller also includes a second characteristic conversion optical element, which is configured to replace the first characteristic conversion optical element. If the controller determines that the first characteristic conversion optical element needs to be dried, it moves the first characteristic conversion optical element out of the optical path of the laser beam and moves the second characteristic conversion optical element into the optical path of the laser beam. While the first characteristic conversion optical element is dried by the drying unit, the second characteristic conversion optical element is used to convert the characteristics of the laser beam to process the workpiece.

4. The laser processing apparatus as described in claim 1, wherein, The detection unit includes: a light source that emits light in the infrared region; and a detection unit that detects light emitted from the light source and transmitted through any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator. The controller determines the water retention status of any one of the first optical element, the characteristic conversion optical element, and the second optical element of the laser oscillator based on the transmittance of the light emitted from the light source.

5. The laser processing apparatus as described in claim 1, wherein, The characteristic conversion optical element is a wavelength conversion optical element that converts the characteristics, i.e., the wavelength, of the laser beam emitted from the laser oscillator.

6. The laser processing apparatus as described in claim 5, wherein, The wavelength conversion optical element is made of CLBO crystal.

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