Laser processing equipment

Abstract

To provide a laser machining device which enables highly accurate machining.SOLUTION: A laser machining device 1 comprises: a holding table 10 for holding a workpiece 200; a laser beam irradiation unit 20 for irradiating the workpiece 200 held on the holding table 10 with a laser beam 21; and a control unit for controlling respective components, with the laser beam irradiation unit 20 comprising an oscillator 22 for emitting a laser beam 21-1, a characteristics conversion optical element 23 for converting the characteristics of the laser beam 21-1 emitted by the oscillator 22, and a mirror 25 and a condenser lens 24 as optical elements for guiding the laser beams 21,21-1 to the workpiece 200. In addition, it comprises a detection unit 27 for detecting a water retention state of the characteristics conversion optical element 23 and a drying unit 26 for drying the characteristics conversion optical element 23.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] BACKGROUND ART Techniques for processing workpieces such as semiconductor wafers and optical device wafers by irradiating them with a laser beam are becoming widespread (see, for example, Patent Documents 1 and 2).

[0003] Laser beams of various wavelengths are used to process workpieces, including the fundamental wavelength of 1064 nm (IR: infrared), its second harmonic of 532 nm (Green), its third harmonic of 355 nm (UV: ultraviolet), and its fourth harmonic of 266 nm (DUV: far ultraviolet), and are selected according to the application.

[0004] In particular, short-wavelength UV and DUV laser beams are attracting attention because they can reduce the laser focus diameter at the irradiation position, which is expected to enable highly accurate processing.In addition, they have high absorption rates and high optical energy for various materials, which means they can be applied to materials that were previously difficult to process.

[0005] Laser processing equipment for achieving this type of processing incorporates various optical elements, such as a laser crystal for oscillating and outputting the laser, a wavelength conversion optical element for converting the wavelength of the laser beam, a wave plate for converting the polarization direction, a mirror for changing the beam deflection direction, and a lens for focusing a parallel beam, i.e., for changing the beam focusing angle.

[0006] For example, Nd:YAG, ND:YVO4, titanium sapphire, etc. are often used as laser crystals. In recent years, CLBO (cesium lithium borate: CsLiBO) has been used as a wavelength conversion optical element for outputting DUV. 10) crystals are often used (see, for example, Patent Document 3). Furthermore, for wave plates, mirrors, lenses, etc., transparent materials coated with a dielectric multilayer film are often used to improve their reflection and transmission characteristics. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-143285 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-072052 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-292819 Summary of the Invention [Problem to be solved by the invention]

[0008] However, these optical elements are known to deteriorate due to moisture in the air. For example, when moisture is adsorbed onto the dielectric multilayer film of a mirror or wave plate, its spectral characteristics change, resulting in changes in reflectance and transmittance, reducing the amount of laser beam light irradiated onto the workpiece and degrading processing quality. Furthermore, CLBO crystal, a wavelength conversion optical element, exhibits deliquescence. As a result, CLBO crystal deteriorates by retaining moisture in the air, adversely affecting the profile of the laser beam after passing through the crystal and degrading processing quality.

[0009] Therefore, the optical elements described above require frequent replacement and maintenance, which increases the downtime of the processing device and leads to a decrease in productivity.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laser processing device that can achieve high-precision processing. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the object, the laser processing apparatus of the present invention is a laser processing apparatus comprising a holding table for holding a workpiece, a laser beam irradiation unit for irradiating a laser beam onto the workpiece held on the holding table, and a control unit for controlling each component, wherein the laser beam irradiation unit comprises an oscillator for emitting a laser beam, a characteristic conversion optical element for converting the characteristics of the laser beam emitted from the oscillator, and an optical element for guiding the laser beam to the workpiece, and further comprises a detection unit for detecting a water retention state of any of the optical element of the oscillator, the characteristic conversion optical element, and the optical element, and a drying unit for drying any of the optical element of the oscillator, the characteristic conversion optical element, and the optical element. The control unit controls the drying unit to dry any one of the optical element of the oscillator, the characteristic conversion optical element, and the optical element when the moisture retention state of any one of the optical element of the oscillator, the characteristic conversion optical element, and the optical element detected by the detection unit exceeds a predetermined value. It is characterized by the following.

[0013] In the laser processing apparatus, the laser beam irradiation unit has at least two characteristic conversion optical elements including a first characteristic conversion optical element arranged in the optical path of the laser beam and a second characteristic conversion optical element that is replaceable with the first characteristic conversion optical element, and when the control unit 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, and while drying the first characteristic conversion optical element with the drying unit, it may convert the characteristics of the laser beam using the second characteristic conversion optical element to process the workpiece.

[0014] In the laser processing device, the detection unit includes a light source that emits light in the infrared region, and a detection section that detects light that is emitted from the light source and that has passed through either the optical element of the oscillator, the characteristic conversion optical element, or the optical element, and the control unit may determine the water retention state of either the optical element of the oscillator, the characteristic conversion optical element, or the optical element based on the transmittance of the light emitted from the light source.

[0015] In the laser processing device, the characteristic conversion optical element may be a wavelength conversion optical element that converts the wavelength, which is a characteristic of the laser beam emitted from the oscillator.

[0016] In the laser processing device, the wavelength conversion optical element may be a CLBO crystal. [Effects of the Invention]

[0017] The present invention has an effect of enabling high-precision machining to be realized. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing device according to the first embodiment. [Figure 2] FIG. 2 is a diagram schematically showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG. [Figure 3] FIG. 3 is a diagram schematically showing the configuration of a laser beam irradiation unit of a laser processing apparatus according to the second embodiment. [Figure 4] FIG. 4 is a diagram showing the transmittance spectra of the wavelength conversion optical element of the laser processing apparatus shown in FIG. 1 before and after drying. DETAILED DESCRIPTION OF THE INVENTION

[0019] Modes (embodiments) 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 embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0020] [Embodiment 1] A laser processing apparatus according to a first 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 the laser processing apparatus according to the first embodiment. Fig. 2 is a diagram schematically showing the configuration of a laser beam irradiation unit of the laser processing apparatus shown in Fig. 1.

[0021] The laser processing apparatus 1 according to the first embodiment is a processing apparatus that performs laser processing on a workpiece 200. The workpiece 200 to be processed by the laser processing apparatus 1 according to the first embodiment is a wafer such as a disk-shaped semiconductor wafer that includes a substrate, a laser beam absorption layer laminated on the surface of the substrate, and a device layer laminated on the laser beam absorption layer. In the first embodiment, the substrate is made of a transparent material such as sapphire and is formed in a disk shape. The laser beam absorption layer is made of resin, and in the first embodiment, is made of polyimide.

[0022] The device layer has devices formed in areas partitioned by a plurality of intersecting planned division lines, such as integrated circuits (ICs) or large-scale integration (LSIs), power devices, microelectromechanical systems (MEMSs), or various types of memories (semiconductor memory devices).

[0023] The workpiece 200 described above is subjected to so-called laser lift-off processing, in which a transfer substrate 201 made of glass is attached via an adhesive layer to a device layer divided into individual devices, and a laser beam 21 having a focal point set in the laser beam absorption layer and a wavelength that is transparent to the substrate is irradiated onto the entire surface through the substrate, thereby destroying the laser beam absorption layer and peeling the device from the substrate.

[0024] In addition, in embodiment 1, the workpiece 200 has a transfer substrate 201 attached to the device layer by an adhesive layer, a circular tape 202 having a larger diameter than the workpiece 200 attached to the transfer substrate 201 side, and an annular frame 203 having an inner diameter larger than the outer diameter of the workpiece 200 attached to the outer peripheral edge of the tape 202, and is supported within the inner opening of the annular frame 203.

[0025] 1 is a processing apparatus that performs laser lift-off processing on the workpiece 200 by setting the focal point of a pulsed laser beam 21, having a wavelength that is transparent to the substrate constituting the workpiece 200, on a laser beam absorption layer from the back side of the substrate of the workpiece 200, and irradiating the entire surface with the laser beam 21, thereby peeling off a device from the substrate of the workpiece 200. As shown in FIG. 1, the laser processing apparatus 1 has a holding table 10 that holds the workpiece 200, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 40, and a control unit 100.

[0026] The holding table 10 holds the workpiece 200 on a holding surface 11 that is parallel to the horizontal direction. The holding surface 11 is disk-shaped and made of porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a suction path (not shown). The holding table 10 is sucked by the vacuum suction source to suction-hold the workpiece 200 placed on the holding surface 11. A plurality of clamps 12 are arranged around the holding table 10 to clamp a frame 203 that supports the workpiece 200 in an opening.

[0027] Furthermore, the holding table 10 is rotated by the rotational movement unit 33 of the movement unit 30 about an axis that is perpendicular to the holding surface 11 and parallel to the Z-axis direction that is parallel to the vertical direction. The holding table 10, together with the rotational movement unit 33, is moved by the X-axis movement unit 31 of the movement unit 30 in the X-axis direction (corresponding to the machining proceeding direction) that is parallel to the horizontal direction, and is moved by the Y-axis movement unit 32 in the Y-axis direction that is parallel to the horizontal direction and perpendicular to the X-axis direction. The holding table 10 is moved by the movement unit 30 between a machining area below the laser beam irradiation unit 20 and a carry-in / out area that is away from below the laser beam irradiation unit 20 and where the workpiece 200 is carried in and out.

[0028] The laser beam irradiation unit 20 is a laser beam irradiation means that focuses and irradiates a pulsed laser beam 21 onto a workpiece 200 held on a holding table 10. In the first embodiment, a part of the laser beam irradiation unit 20 is moved in the Z-axis direction by a Z-axis moving unit 34 that is disposed on an upright wall 3 that stands upright from the apparatus main body 2, as shown in FIG.

[0029] The laser beam irradiation unit 20 irradiates a laser beam 21 having a wavelength that is transparent to the substrate of the workpiece 200 held on the holding table 10, thereby laser processing the workpiece 200. As shown in Fig. 2, the laser beam irradiation unit 20 includes an oscillator 22 that emits a pulsed laser beam 21-1, a wavelength conversion optical element 23 (corresponding to a characteristic conversion optical element) that converts the wavelength (corresponding to a characteristic) of the laser beam 21-1 emitted from the oscillator 22, and a condenser lens 24 that collects the laser beam 21 whose wavelength has been converted by the wavelength conversion optical element 23 and irradiates the workpiece 200. In addition, in the first embodiment, the laser beam irradiation unit 20 includes a mirror 25 that reflects the laser beam 21-1 emitted from the oscillator 22 toward the wavelength conversion optical element 23.

[0030] The oscillator 22 includes a crystal 221, which is an optical element constituting a laser medium for emitting the laser beam 21-1. The crystal 221 is, for example, YAG (Yttrium Aluminum Garnet: YAlO 12 ) crystal, yttrium orthovanadate (YVO4) crystal, titanium sapphire (Ti:Al2O3) crystal, or the like. In the first embodiment, the oscillator 22 emits IR light with a wavelength of 1064 nm. The IR light is converted into Green light with a wavelength of 532 nm via a BBO (β-BaB2O4) crystal 222, which is then emitted as the laser beam 21-1. In the present invention, the BBO crystal 222 may be present in the same housing as the oscillator 22.

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

[0032] In the first embodiment, the wavelength conversion optical element 23 is made of CLBO (cesium lithium borate: CsLiBO 10 ) crystal and is housed in a box-shaped cell 231 with the inside sealed. The CLBO crystal that constitutes the wavelength conversion optical element 23 is deliquescent. In the first embodiment, the wavelength conversion optical element 23 converts a second harmonic (Green) laser beam 21-1 having a wavelength of 532 nm into a fourth harmonic (DUV: far ultraviolet) laser beam 21 having a wavelength of 266 nm. The cell 231 is provided with a window or the like that allows the laser beams 21-1 and 21 to pass through.

[0033] The condensing lens 24 is disposed at a position opposite to the holding surface 11 of the holding table 10 in the Z-axis direction. The condensing lens 24 is a focusing optical element that focuses and irradiates the pulsed laser beam 21 onto the workpiece 200 held on the holding table 10. The condensing lens 24 transmits the laser beam 21 that is emitted from the oscillator 22, reflected by the mirror 25, and wavelength-converted by the wavelength conversion optical element 23, and focuses the laser beam 21 at a focal point (shown in FIG. 2, etc.). In the first embodiment, the condensing lens 24 focuses the focal point of the laser beam 21 on a laser beam absorption layer of the workpiece 200 held on the holding surface 11 of the holding table 10.

[0034] The mirror 25 and the condenser lens 24 are optical elements that guide the laser beams 21-1, 21 to the workpiece 200. In the embodiment, the laser beam irradiation unit 20 includes the mirror 25 and the condenser lens 24 as optical elements that guide the laser beams 21-1, 21 wavelength-converted by the wavelength conversion optical element 23 to the workpiece 200. However, in the present invention, the optical elements are not limited to the mirror 25 and the condenser lens 24, and various optical elements that constitute a scanning optical system that scans the laser beams 21-1, 21 may be included.

[0035] 2, 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 dries the wavelength conversion optical element 23 in the cell 231. In the first embodiment, the drying unit 26 heats the wavelength conversion optical element 23 up to 150°C while continuously flowing dry air from a dry air supply source into the cell 231. In the first embodiment, the drying unit 26 includes a heating means for heating the wavelength conversion optical element 23 in the cell 231 up to 150°C, and a mechanism for continuously flowing dry air from the dry air supply source into the cell 231. The heating means heats the wavelength conversion optical element 23 up to 150°C, and continuously flows dry air from the dry air supply source into the cell 231, thereby drying the wavelength conversion optical element 23 in the cell 231. In the present invention, the drying unit 26 may include a heating means for heating the inside of the cell 231 to, for example, 150°C, and a pump for degassing the inside of the cell 231. In this case, the drying unit 26 dries the wavelength conversion optical element 23 in the cell 231 by using the heating means to heat the wavelength conversion optical element 23 in the cell 231 to 150°C and degassing the inside of the cell 231 with the pump.

[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 has absorbed 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 section 273.

[0037] The light source 271 emits detection light 274 to the wavelength conversion optical element 23 located at a conversion position, i.e., a detection position spaced apart from the optical path of the laser beam 21-1. The light source 271 emits detection light 274 having a center wavelength of 2800 nm, i.e., a wave number of 3600 cm. -1 The light source 271 emits detection light 274 (light in the infrared region) having a center wavelength of 2800 nm, i.e., a wave number of 3600 cm. -1 The detection light 274 is irradiated onto the wavelength conversion optical element 23 positioned at the detection position because the water molecules have a central wavelength of 2800 nm, i.e., a wave number of 3600 cm -1This is because the light source 271 easily absorbs the detection light 274, making it easy to detect the water retention state of the wavelength conversion optical element 23. The light source 271 may be, for example, an LED 2800W manufactured by THORLABS.

[0038] For this reason, the amount of light that passes through the wavelength conversion optical element 23, i.e., the transmittance, of the detection light 274 irradiated onto the wavelength conversion optical element 23 by the light source 271 decreases as the water retention state of the wavelength conversion optical element 23 increases (the amount of water taken in by the wavelength conversion optical element 23 increases). The amount of light that passes through the wavelength conversion optical element 23, i.e., the transmittance, of the detection light 274 irradiated onto the wavelength conversion optical element 23 by the light source 271 increases as the water retention state of the wavelength conversion optical element 23 decreases (the amount of water taken in by the wavelength conversion optical element 23 decreases). Note that, in the present invention, the detection light 274 emitted by the light source 271 of the detection unit 27 may be any light that is capable of infrared absorption by water molecules, and is not limited to that of embodiment 1.

[0039] The wavelength range of the light source 271 is wide and may extend to a wavelength range where infrared absorption by water molecules is small. For example, in the first embodiment, infrared absorption by water molecules is large at 3550 cm -1 ~3650cm -1 In contrast, the wavenumber range of Illuminant 271 is limited to 3400 cm -1 ~3800cm -1 The infrared light includes wavelengths 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 slight change, the transmittance of infrared light may not change sufficiently. In this case, the sensitivity of detecting the water retention state can be improved by inserting a bandpass filter that transmits only light in a narrow wavelength range into the optical path.

[0040] For example, in the first embodiment, the 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 is a filter having a wave number of 3500 cm -1 From 3700cm -1The bandpass filter 272 transmits light having a wavenumber between 3500 cm and 4500 cm, and does not transmit light having other wavenumbers. -1 From 3700cm -1 The detection unit 27 transmits the detection light 274 between wavenumbers toward the detection unit 273, and does not transmit the detection light 274 of other wavenumbers. As a result, the proportion of the amount of infrared light absorbed by water molecules among the infrared light irradiated onto the wavelength conversion optical element 23 increases, and the detection sensitivity of the water retention state improves. Note that, in the first embodiment, the detection unit 27 includes the bandpass filter 272 to improve the detection sensitivity of the water retention state, but the bandpass filter 272 may not be included 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 that is emitted from the light source 271 and that is transmitted through the wavelength conversion optical element 23 positioned at the detection position and the bandpass filter 272 in that order, detects the amount of the received detection light 274, and outputs information indicating the amount of the received detection light 274 to the control unit 100. In the first embodiment, the detection unit 273 is a photodiode that receives infrared light having a wavelength of 1 μm to 10.6 μm and outputs information indicating the amount of the received infrared light to the control unit 100. For example, a VML8T4 manufactured by THORLABS can be used as the detection unit 273.

[0042] The detection unit 27 receives detection light 274 that is irradiated from the light source 271 by the detection section 273 and that has passed through the wavelength conversion optical element 23 positioned at the detection position, and outputs information indicating the amount of light received to the control unit 100, thereby detecting a state quantity that changes depending on the water retention state of the wavelength conversion optical element 23, and outputs the detected result to the control unit 100.

[0043] The optical element moving unit 28 moves the wavelength conversion optical element 23 between a conversion position and a detection position. The conversion position is located on the optical path of the laser beam 21-1, and is a position of the wavelength conversion optical element 23 where the laser beam 21-1 is irradiated onto the wavelength conversion optical element 23 in the cell 231, wavelength-converts the laser beam 21-1, and the wavelength-converted laser beam 21 is emitted toward the condenser lens 24. The conversion position is also a position of the wavelength conversion optical element 23 where the detection light 274 from the light source 271 is not irradiated onto the wavelength conversion optical element 23.

[0044] The detection position is a position of the wavelength conversion optical element 23 that is away from the optical path of the laser beam 21-1 and where the laser beam 21-1 is not irradiated onto the wavelength conversion optical element 23 in the cell 231. The detection position is also a position of the wavelength conversion optical element 23 where the detection light 274 from the light source 271 is irradiated onto the wavelength conversion optical element 23 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 cell 231 that houses the wavelength conversion optical element 23, and moves the wavelength conversion optical element 23 between the conversion position and the detection position.

[0046] The laser beam irradiation unit 20 irradiates the workpiece 200 held on the holding table 10 with a laser beam 21 having a wavelength that is transparent to the substrate of the workpiece 200, destroying the laser beam absorption layer of the workpiece 200 and performing laser lift-off processing to peel the device off from the substrate.

[0047] The moving unit 30 relatively moves the holding table 10 and the focal point of the laser beam 21 emitted by the laser beam application unit 20 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and the Y-axis direction are perpendicular to each other and parallel to the holding surface 11 (i.e., the horizontal direction). The Z-axis direction is perpendicular to the X-axis direction and the Y-axis direction, i.e., the holding surface 11. The moving unit 30 includes an X-axis moving unit 31 which is a processing feed unit that moves the holding table 10 in the X-axis direction, a Y-axis moving unit 32 which is an indexing feed unit that moves the holding table 10 in the Y-axis direction, a rotational moving unit 33 that rotates the holding table 10 around an axis parallel to the Z-axis direction, and a Z-axis moving unit 34 that moves a part of the laser beam application unit 20 in the Z-axis direction.

[0048] The Y-axis moving unit 32 is a unit that indexes and moves the holding table 10 relative to the focal point of the laser beam 21 of the laser beam irradiation unit 20. In the first embodiment, the Y-axis moving unit 32 is installed on the device body 2 of the laser processing device 1. The Y-axis moving unit 32 supports the moving plate 4 that supports the X-axis moving unit 31 so that the moving plate 4 is movable in the Y-axis direction.

[0049] The X-axis moving unit 31 is a feed means that relatively feeds the holding table 10 and the focal point of the laser beam 21 of the laser beam irradiation unit 20 for processing. The X-axis moving unit 31 is installed on the moving plate 4. The X-axis moving unit 31 supports a second moving plate 5 that supports a rotational moving unit 33 that rotates the holding table 10 around an axis parallel to the Z-axis direction, so that the second moving plate 5 can move freely in the X-axis direction. The second moving plate 5 supports the rotational moving unit 33 and the holding table 10. The rotational moving unit 33 supports the holding table 10.

[0050] The X-axis moving unit 31, the Y-axis moving unit 32, and the Z-axis moving unit 34 each include a well-known ball screw rotatably mounted about its axis, a well-known pulse motor for rotating the ball screw about its axis, and well-known guide rails for supporting the moving plates 4 and 5 and the condenser lens 24 included in the laser beam irradiation unit 20 so that they can move in the X-axis, Y-axis, or Z-axis direction. The rotational moving unit 33 includes a motor for rotating the holding table 10 about its axis, etc.

[0051] The laser processing device 1 also includes an X-axis position detection unit (not shown) for detecting the position of the holding table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the holding table 10 in the Y-axis direction, and a Z-axis position detection unit (not shown) for detecting the position of the laser beam irradiation unit 20 in the Z-axis direction. Each position detection unit outputs the detection result to the control unit 100.

[0052] The imaging unit 40 captures an image of the workpiece 200 held on the holding table 10. The imaging unit 40 includes an imaging element such as a CCD (Charge Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element that captures an image of an object facing the objective lens in the Z-axis direction. In the first embodiment, the imaging unit 40 is attached by the laser beam irradiation unit 20, and is disposed at a position where the objective lens is aligned with the condenser lens 24 along the X-axis direction.

[0053] The imaging unit 40 acquires the image captured by the imaging element and outputs the acquired image to the control unit 100. The imaging unit 40 also captures an image of the workpiece 200 held on the holding surface 11 of the holding table 10 and acquires an image for performing alignment between the workpiece 200 and the laser beam irradiation unit 20.

[0054] The control unit 100 controls each of the above-mentioned components of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform laser processing operations on the workpiece 200. The control unit 100 is a computer having an arithmetic processing device with a microprocessor such as a CPU (central processing unit), a storage device with memory such as a ROM (read only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the functions of the control unit 100.

[0055] The laser processing device 1 also includes a display unit 110, which is a display means configured with a liquid crystal display device or the like that displays the status of the processing operation, images, etc., and an input unit, which 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 control unit 100. The input unit is configured with at least one of a touch panel provided on the display unit 110 and an external input device such as a keyboard.

[0056] 1, the control unit 100 includes a storage unit 101 and a determination unit 102. The storage unit 101 stores the amount of light when the detection unit 273 receives the detection light 274 that is emitted by the light source 271 and transmitted through the band-pass filter 272 without irradiating the detection light 274 onto the wavelength conversion optical element 23. In the first embodiment, the storage unit 101 stores the amount of light when the detection unit 273 receives the detection light 274 that is emitted by the light source 271 and transmitted through the band-pass filter 272 when the wavelength conversion optical element 23 is positioned at the conversion position.

[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 amount of light stored in the storage unit 101 and the amount of light received by the detection unit 273 after the detection light 274 is emitted by the light source 271 and transmitted through the wavelength conversion optical element 23 positioned at the detection position and the bandpass filter 272.

[0058] In the first embodiment, the determination unit 102 calculates the transmittance (corresponding to the water retention state) of the detection light 274 of the wavelength conversion optical element 23 by setting the amount of light when the detection unit 273 receives the detection light 274 irradiated by the light source 271 and transmitted through the bandpass filter 272 as 100% without irradiating the wavelength conversion optical element 23 stored in the storage unit 101 with the detection light 274, and the amount of light when the detection unit 273 does not receive the detection light 274 as 0%. The determination unit 102 determines the water retention state of the wavelength conversion optical element 23 by determining whether the calculated transmittance of the detection light 274 is equal to or greater than a predetermined value. In the first embodiment, the predetermined value is set to, for example, 13%. However, it may be set to a value other than this in consideration of the wavelength ranges of the bandpass filter 272 and the light source 271, etc.

[0059] If the determination unit 102 determines that the calculated transmittance of the detection light 274 is equal to or greater than a predetermined value, it determines that the wavelength conversion optical element 23 is suitable for processing the workpiece 200, and does not operate the drying unit 26. If the determination unit 102 determines that the calculated transmittance of the detection light 274 is less than a predetermined value, it determines that the water retention state of the wavelength conversion optical element 23 exceeds a predetermined value that is a certain amount of water retention, and determines that the wavelength conversion optical element 23 is not suitable for processing the workpiece 200, and operates the drying unit 26 to dry the wavelength conversion optical element 23.

[0060] The function of the storage unit 101 is realized by the above-mentioned storage device, and the function of the determination unit 102 is realized by the arithmetic processing unit performing arithmetic processing in accordance with a computer program stored in the storage device.

[0061] Next, we will explain the processing operation of the laser processing apparatus 1 configured as described above. In the laser processing apparatus 1, the control unit 100 accepts and registers processing conditions input by an operator, and the transfer substrate 201 attached to the device layer of the workpiece 200 is placed on the holding surface 11 of the holding table 10 positioned in the carry-in / out area. When the control unit 100 accepts an instruction to start the processing operation from the operator, the laser processing apparatus 1 starts the processing operation.

[0062] In the processing operation, the control unit 100 of the laser processing apparatus 1 sucks and holds the workpiece 200 on the holding surface 11 of the holding table 10, and causes the clamp section 12 to clamp the frame 203. In the processing operation, the control unit 100 of the laser processing apparatus 1 positions the wavelength conversion optical element 23 at the conversion position. In the processing operation, the control unit 100 controls the moving unit 30 to move the holding table 10 to the processing area, and the imaging unit 40 captures an image of the workpiece 200 sucked and held on the holding table 10 to obtain the image, thereby performing alignment.

[0063] During the processing operation, the laser processing device 1 sets the focal point of the laser beam irradiation unit 20 at the laser beam absorption layer, and irradiates a pulsed laser beam 21 from the back side of the substrate of the workpiece 200 while moving the holding table 10 and the focal point of the laser beam irradiation unit 20 relative to each other.

[0064] In the first embodiment, in the processing operation, the laser processing device 1 irradiates the laser beam 21 onto the laser beam absorption layer over the entire surface of the workpiece 200 to destroy the laser beam absorption layer over the entire surface of the workpiece 200.

[0065] In the processing operation, when the laser beam absorption layer is destroyed over the entire surface of the workpiece 200, the laser processing device 1 stops irradiating the laser beam 21 and moves the holding table 10 to the carry-in / out area. In the processing operation, the laser processing device 1 positions the holding table 10 in the carry-in / out area, stops suction holding of the workpiece 200 on the holding table 10, releases the clamping of the frame 203 of the clamp unit 12, and ends the processing operation.

[0066] Furthermore, in the laser processing apparatus 1, the control unit 100 periodically positions the wavelength conversion optical element 23 at the detection position, irradiates the wavelength conversion optical element 23 with detection light 274 from the light source 271, and receives the detection light 274 that has passed through the wavelength conversion optical element 23 and the bandpass filter 272 at the detection unit 273. In the laser processing apparatus 1, the determination unit 102 of the control unit 100 calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23 based on the light amount stored in the memory unit 101 and the light amount when the detection unit 273 receives the detection light 274 that has been emitted by the light source 271 and passed through the wavelength conversion optical element 23 positioned at the detection position and the bandpass filter 272.

[0067] The determination unit 102 of the control unit 100 determines whether the calculated transmittance of the detection light 274 is equal to or greater than a predetermined value, and if it determines that the calculated transmittance of the detection light 274 is equal to or greater than the predetermined value, it determines that the wavelength conversion optical element 23 is suitable for processing the workpiece 200, and positions the wavelength conversion optical element 23 at the conversion position without operating the drying unit 26, and performs the processing operation. If the determination unit 102 of the control unit 100 determines that the calculated transmittance of the detection light 274 is less than the predetermined value, that is, the water retention state exceeds a predetermined amount, it determines that the wavelength conversion optical element 23 is not suitable for processing the workpiece 200, and operates the drying unit 26 while keeping the wavelength conversion optical element 23 positioned at the detection position, to dry the wavelength conversion optical element 23.

[0068] When the determination unit 102 of the control unit 100 determines that the calculated transmittance of the detection light 274 is less than a predetermined value and operates the drying unit 26, the determination unit 102 stops the drying unit 26, irradiates the detection light 274 from the light source 271, calculates the transmittance of the detection light 274 of the wavelength conversion optical element 23 by the light source 271, and determines whether the transmittance of the detection light 274 calculated by the determination unit 102 is equal to or greater than the predetermined value. Thus, in the first embodiment, when the water retention state of the wavelength conversion optical element 23 detected by the detection unit 27 exceeds a predetermined value, the determination unit 102 of the control unit 100 causes the drying unit 26 to dry the wavelength conversion optical element 23. Furthermore, the laser processing apparatus 1 operates the drying unit 26 and suspends processing until the transmittance of the detection light 274 of the wavelength conversion optical element 23 becomes equal to or greater than the predetermined value.

[0069] In the first embodiment, the drying unit 26 is operated and the processing operation is suspended until the transmittance of the detection light 274 of the wavelength conversion optical element 23 reaches or exceeds a predetermined value. However, in the present invention, if it is determined that the transmittance of the detection light 274 is less than the predetermined value, the drying unit 26 may be operated while the wavelength conversion optical element 23 is positioned at the conversion position, and the laser beam 21 may be irradiated onto the workpiece 200 while drying the wavelength conversion optical element 23, thereby processing the workpiece 200. In the present invention, the predetermined period can be freely set. For example, in the present invention, once it is confirmed that the water retention state has improved to a certain extent, the time required for the transmittance to reach or exceed the predetermined value can be calculated and the predetermined period can be freely set. The predetermined period may be set by an operator or automatically calculated and set by the control unit 100 or the like.

[0070] As described above, the laser processing apparatus 1 according to the first embodiment is equipped with the detection unit 27 that detects the water retention state of the wavelength conversion optical element 23, and the drying unit 26 that dries the wavelength conversion optical element 23 when the water retention state detected by the detection unit 27 exceeds a certain water retention amount, thereby preventing adverse effects on processing quality due to deliquescence. As a result, the laser processing apparatus 1 has the effect of being able to achieve high-precision processing.

[0071] Furthermore, in the laser processing device 1 according to the first embodiment, the bandpass filter 272 is arranged in front of the detection section 273 of the detection unit 27, so that the detection sensitivity of the detection section 273 can be improved.

[0072] [Embodiment 2] A laser processing apparatus according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 3 is a diagram schematically showing the configuration of a laser beam irradiation unit of the laser processing apparatus according to the second embodiment. In Fig. 3, the same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0073] 3, the laser beam irradiation unit 20-2 of the laser processing apparatus 1 according to the second embodiment includes a first wavelength conversion optical element 23-1 and a second wavelength conversion optical element 23-2 as the wavelength conversion optical element 23, and a first drying unit 26-1 and a second drying unit 26-2 as the 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 each housed in a cell 231. The cell 231 also has the same configuration as the cell 231 housing the wavelength conversion optical element 23 of the first embodiment, and is moved between a conversion position and a detection position by an optical element moving unit 28 while housing the wavelength conversion optical elements 23-1 and 23-2, as in the first embodiment.

[0074] Thus, in embodiment 2, the laser beam irradiation unit 20-2 has at least two wavelength conversion optical elements 23-1, 23-2 including a first wavelength conversion optical element 23-1 arranged in the optical path of the laser beam 21-1 and a second wavelength conversion optical element 23-2 arranged in the optical path of the laser beam 21-1 so as to be interchangeable with the first wavelength conversion optical element 23-1.

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

[0076] In the laser processing apparatus 1, the control unit 100 performs processing operations by positioning one of the wavelength conversion optical elements 23-1, 23-2 at a conversion position and the other at a detection position. In the laser processing apparatus 1, the control unit 100 periodically positions one of the wavelength conversion optical elements 23-1, 23-2 at the detection position, irradiates the wavelength conversion optical element 23 with detection light 274 from the light source 271, and receives the detection light 274 that has passed through the wavelength conversion optical element 23 and the bandpass filter 272 at the detection unit 273.

[0077] In the laser processing apparatus 1, the judgment section 102 of the control unit 100 calculates the transmittance of the detection light 274 from one of the wavelength conversion optical elements 23-1, 23-2 based on the amount of light stored in the memory section 101 and the amount of light when the detection section 273 receives the detection light 274 that is emitted by the light source 271 and transmitted through one of the wavelength conversion optical elements 23-1, 23-2 positioned at the detection position and the bandpass filter 272.

[0078] The judgment section 102 of the control unit 100 operates the drying unit 26 while positioning one of the wavelength conversion optical elements 23-1, 23-2, which has been determined to have a transmittance of the calculated detection light 274 less than a predetermined value, at the detection position, to dry one of the wavelength conversion optical elements 23-1, 23-2, and positions the other at the conversion position to perform the processing operation.

[0079] Thus, in the second embodiment, when the judgment section 102 of the control unit 100 determines that the first wavelength conversion optical element 23-1 needs to be dried, the judgment section 102 dries the first wavelength conversion optical element 23-1 by the first drying unit 26-1, while converting the wavelength of the laser beam 21-1 using the second wavelength conversion optical element 23-2 to process the workpiece 200.

[0080] The laser processing apparatus 1 according to the second embodiment is provided with the detection unit 27 for detecting the water retention state of the wavelength conversion optical element 23, as in the first embodiment, and drying units 26-1 and 26-2 for drying the wavelength conversion optical elements 23-1 and 23-2 when the water retention state detected by the detection unit 27 exceeds a certain water retention amount, thereby preventing adverse effects on processing quality due to deliquescence. As a result, the laser processing apparatus 1 has the effect of being able to achieve high-precision processing.

[0081] Furthermore, the laser processing apparatus 1 according to the second embodiment performs processing operations by positioning one of the wavelength conversion optical elements 23-1, 23-2 at the conversion position while the other is drying, thereby eliminating downtime and contributing to improved productivity.

[0082] Next, the inventors of the present invention confirmed the effects of the laser processing apparatus 1 of embodiment 1. The results are shown in Fig. 4 and the following Table 1. Fig. 4 is a diagram showing the transmittance spectra of the wavelength conversion optical element of the laser processing apparatus shown in Fig. 1 before and after drying.

[0083] [Table 1]

[0084] For confirmation, the transmittance spectrum of the wavelength conversion optical element 23 before and after drying was measured using a Fourier transform infrared spectrophotometer. -1 The transmittance of the wavelength conversion optical element 23 before and after drying, which would be detected using the detection light 274, was simulated with and without the bandpass filter 272.

[0085] The horizontal axis of Fig. 4 represents the wavenumber of light, and the vertical axis of Fig. 4 represents the transmittance of the wavelength conversion optical element 23. In Fig. 4, the dashed line represents the transmittance of the wavelength conversion optical element 23 before drying, and the solid line represents the transmittance after drying. Furthermore, the area filled with coarse dots represents the wavelength range of the light source, and the area filled with fine dots represents the wavelength range transmitted by the bandpass filter 272.

[0086] Table 1 also shows the central wave number of 3600 cm -1 2 shows the transmittance of the wavelength conversion optical element 23 before and after drying, which would be detected using the detection light 274, with and without the bandpass filter 272.

[0087] According to Figure 4, the wave number before drying was 3400 cm -1 and 3600 cm -1 The transmittance of the detection light 274 is almost zero, while the wave number after drying is 3400 cm -1 The transmittance of the detection light 274 is about 6%, and the wave number is 3600 cm -1 The transmittance of the detection light 274 was about 12%.

[0088] From these spectra, as shown in the "With bandpass filter" column in Table 1, the transmittance detected in embodiment 1 was simulated to be 5% before drying and 15% after drying. In other words, it was estimated that the transmittance increased three times by drying. These results made it clear that the detection unit 27 can detect the moisture retention state of the wavelength conversion optical element 23.

[0089] On the other hand, as shown in Table 1, when there was no bandpass filter 272, the transmittance of the detection light 274 before and after drying was simulated to be 9% and 12%, respectively. In other words, the increase in transmittance due to drying was estimated to be only 1.3 times. This result revealed that the sensitivity of the detection section 273 can be improved by providing the detection unit 27 with the bandpass filter 272.

[0090] The present invention is not limited to the above-described embodiment. In other words, various modifications can be made without departing from the gist of the present invention. In the first embodiment, the moisture retention state of the wavelength conversion optical elements 23, 23-1, and 23-2 is detected, and the drying units 26, 26-1, and 26-2 dry the elements when a certain moisture retention amount is exceeded. However, in the present invention, the moisture retention state of the crystal of the oscillator 22 and various optical elements may be detected, and the drying units 26, 26-1, and 26-2 dry the elements when a certain moisture retention amount is exceeded. That is, in the present invention, the detection unit 27 detects the moisture retention state of any of the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, and 23-2, and the optical elements, and the drying units 26, 26-1, and 26-2 dry any of the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, and 23-2, and the optical elements.

[0091] That is, in the present invention, when the moisture retention state of any of the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, and the optical elements detected by the detection unit 27 exceeds a predetermined value, the judgment section 102 of the control unit 100 causes the drying units 26, 26-1, 26-2 to dry any of the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, and the optical elements. Furthermore, in the present invention, the detection section 273 of the detection unit 27 detects the detection light 274 that has passed through the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, or any one of the optical elements, and the determination section 102 of the control unit 100 determines the water retention state of the crystal 221 of the oscillator 22, the wavelength conversion optical elements 23, 23-1, 23-2, or any one of the optical elements based on the transmittance of the detection light 274 emitted from the light source 271.

[0092] Furthermore, in the above embodiment, the laser processing apparatus 1 performs laser lift-off processing on the workpiece 200, but in the present invention, laser processing may be performed to fully cut the workpiece 200 along the planned dividing line, or to form a processed groove in the workpiece 200 along the planned dividing line.

[0093] In the present invention, the optical element may be a lens, mirror, wave plate, or other optical element coated with a dielectric multilayer film or the like whose properties change when wet. In the present invention, the optical element may be a laser crystal such as Nd:YAG, ND:YVO4, or titanium sapphire. In the present invention, the optical element may be a BBO crystal 222. In the present invention, optical elements are included in both the optical system of the laser processing apparatus 1 and the inside of the oscillator 22.

[0094] Furthermore, in the above embodiment, an example is described in which the characteristic conversion optical element is the wavelength conversion optical element 23, 23-1, or 23-2 that converts the wavelength, which is a characteristic of the laser beam 21-1 emitted from the oscillator 22. However, in the present invention, the characteristic conversion optical element may be an optical element that converts a characteristic other than the wavelength of the laser beam 21-1, etc. In other words, the present invention may also be applied to a processing apparatus that does not have the wavelength conversion optical element 23, 23-1, or 23-1. [Explanation of symbols]

[0095] 1. Laser processing equipment 10 Holding table 20 Laser beam irradiation unit 21 Laser Beam 21-1 Laser beam 22 Oscillator 23 Wavelength conversion optical element (characteristic conversion optical element) 23-1 First wavelength conversion optical element (wavelength conversion optical element, characteristic conversion optical element) 23-2 Second wavelength conversion optical element (wavelength conversion optical element, characteristic conversion optical element) 24 Condenser lens (optical element) 25 Mirror (optical element) 26 Drying Unit 27 Detection Unit 100 control unit 200 Workpiece 221 Crystals (Optical Elements) 271 Light source 273 Detection Unit 274 Detection light (infrared light)

Claims

1. a holding table for holding the workpiece; a laser beam irradiation unit that irradiates a laser beam onto the workpiece held on the holding table; a control unit for controlling each component; A laser processing device comprising: The laser beam irradiation unit comprises: an oscillator that emits a laser beam; a characteristic conversion optical element that converts the characteristics of the laser beam emitted from the oscillator; an optical element for directing a laser beam to the workpiece; Equipped with a detection unit that detects a water retention state of any of the optical element of the oscillator, the characteristic conversion optical element, and the optical element; a drying unit that dries any one of the optical element of the oscillator, the characteristic converting optical element, and the optical element; The control unit When the water retention state of any of the optical element of the oscillator, the characteristic conversion optical element, and the optical element detected by the detection unit exceeds a predetermined value, A laser processing apparatus characterized in that the drying unit dries any one of the optical element of the oscillator, the characteristic converting optical element, and the optical element.

2. The laser beam irradiation unit comprises: a first characteristic conversion optical element disposed in the optical path of the laser beam; The optical system has at least two characteristic conversion optical elements including a second characteristic conversion optical element that is provided interchangeably with the first characteristic conversion optical element, The control unit When it is determined that the first characteristic conversion optical element needs to be dried, moving the first characteristic conversion optical element out of the optical path of the laser beam and moving the second characteristic conversion optical element into the optical path of the laser beam; 2. The laser processing apparatus according to claim 1, wherein the first characteristic conversion optical element is dried by the drying unit while the second characteristic conversion optical element is used to convert the characteristics of the laser beam and process the workpiece.

3. The detection unit comprises: a light source that emits light in the infrared region; a detection unit that detects light that is emitted from the light source and that has passed through any one of the optical element of the oscillator, the characteristic conversion optical element, and the optical element; The control unit 3. The laser processing device according to claim 1, wherein the moisture retention state of any one of the optical element of the oscillator, the characteristic converting optical element and the optical element is determined based on the transmittance of the light emitted from the light source.

4. 4. The laser processing device according to claim 1, wherein the characteristic conversion optical element is a wavelength conversion optical element that converts the wavelength, which is a characteristic of the laser beam emitted from the oscillator.

5. 5. The laser processing device according to claim 4, wherein the wavelength conversion optical element is a CLBO crystal.

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