Laser Processing Equipment

Abstract

To quickly laser process products suitable for mass production, such as semiconductor wafers and radial sliding bearings, into a desired shape or state. [Solution] A laser processing apparatus 100 performs laser processing by irradiating one surface of a rotationally symmetric irradiation object W with laser light. The laser processing apparatus 100 includes a laser light source 210, 260 capable of emitting laser light, and a first optical element 224, 274 that changes the direction of the laser light emitted from the laser light source 210, 260 to a direction different from the emission direction. The laser processing apparatus 100 also includes a second optical element 226, 276 that includes a drive mechanism that scans the laser light emitted from the first optical element 224, 274 in the circumferential direction of the irradiation object W.

Description

[Technical Field]

[0001] The present invention relates to a laser processing device, and more particularly to a laser processing device suitable for use in planarizing a surface of a semiconductor wafer where chips are to be formed, or for processing the inner surface of a cylindrical bearing. [Background technology]

[0002] Wafer processing, which forms circuits on semiconductor wafers, often includes a process of forming a flat surface with minimal surface roughness on the front or back surface of the wafer. Traditionally, this process has been carried out using a grinding wheel or polishing pad. However, if the grinding wheel or polishing pad wears unevenly during grinding or polishing of the wafer surface, the flatness of the processed surface is distorted, resulting in a deterioration in quality.

[0003] To solve this problem, Patent Document 1 performs the following three steps on the planned cutting positions, which are positions where the semiconductor wafer will be divided into chips: a step of grinding or polishing the back surface of the wafer to flatten it before laser processing, a step of irradiating the front and back surfaces of the wafer placed upside down with a laser to check the flatness of the back surface, and a step of irradiating the laser from the back surface to the planned cutting positions of the wafer, with the focal point aligned inside the wafer.

[0004] Patent Document 2 discloses a laser annealing method that achieves consistent processing quality. In the laser annealing method described in this publication, a semiconductor wafer with an uneven front surface is prepared, and a filler is filled into the concave side of the front surface. The semiconductor wafer filled with the filler is held on an annealing table with the front surface facing the annealing table, and a laser beam is irradiated onto the back surface of the held semiconductor wafer to perform annealing.

[0005] Patent Document 3 also discloses annealing defects formed on a wafer. The system described in this publication includes a CO2-based line formation system configured to form a first line image on the wafer surface with an optical power of 2000 W to 3000 W. The first line image is scanned across the wafer surface, locally raising the temperature to a defect annealing temperature. The system further includes a visible wavelength line formation system, which forms a second line image and locally raises the wafer surface temperature to a spike annealing temperature. The spike annealing reduces deleterious pattern effects and improves temperature uniformity and the resulting annealing uniformity.

[0006] Meanwhile, Patent Document 4 discloses a method for machining the inner surface of a cylinder in which grooves are formed with high dimensional accuracy on the inner surface of a small-diameter cylinder. In this publication, a laser beam is focused using a focusing lens and reflected by a small reflecting mirror installed inside the bearing sleeve, and then focused on the inner surface of the bearing sleeve. By moving and rotating the bearing sleeve in the axial and circumferential directions, the focal point is moved on the inner surface of the bearing sleeve, and grooves are formed on the inner surface of the bearing sleeve. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-121677 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-143833 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-105470 [Patent Document 4] Japanese Patent Application Publication No. 6-315784 Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional grinding or polishing methods using grinding stones or polishing pads to flatten the front or back surface of a wafer have the following problems: unevenness on the surface due to uneven wear; abrasive grains turn into wear powder due to wear of the grinding stone, which can cause unacceptable unevenness on the surface that has been finished to have minimal unevenness; and there is also the risk that part of the processing stress during processing may remain in the wafer as residual stress. Furthermore, the more the surface unevenness is reduced, the longer the processing time required.

[0009] In the method of Patent Document 1, to solve such problems, lighting means are placed above the front surface and on the periphery of the back surface of an inverted wafer to check the flatness of the back surface of the wafer, and then the laser processing is performed by aligning the light focusing point inside the wafer at the planned cutting position. Since the laser irradiation of the entire wafer from the back surface side is for imaging to check the flatness and to determine whether or not diffuse reflection occurs, it is not configured to irradiate the front or back surface of the wafer with laser light at a uniform intensity for a uniform short time and perform planarization annealing of the irradiated surface for only a short time to improve processing efficiency.

[0010] In the wafer annealing apparatus described in Patent Document 2, the wafer is held upside down and a laser beam is focused on the backside. The laser beam has a predetermined elongated shape, and the light intensity distribution is uniform within the elongated shape. In this apparatus, the laser beam position is fixed, so in order to anneal the entire wafer surface, the wafer must be constantly moved within the wafer beam range, and the annealing table on which the laser is placed must be moved two-dimensionally or three-dimensionally. This movement and positioning is performed using a general three-dimensional table or three-dimensional +θ table, which takes time to position, resulting in reduced wafer processing throughput.

[0011] Furthermore, in the defect annealing apparatus described in Patent Document 3, a laser beam from a light source is guided obliquely to the wafer surface via multiple mirrors, and the laser beam is irradiated onto defects formed on the wafer. In this apparatus, the folding mirror optical system is variable to change the laser irradiation angle onto the wafer, so in order to irradiate the laser beam onto a desired position on the wafer, the folding mirror optical system must be highly controlled, which makes the optical system complicated.

[0012] On the other hand, in Patent Document 4, a small mirror is placed inside a bearing sleeve to form a groove on the inner surface of the bearing. In this processing device, the small mirror is placed inside the sleeve, so the size is limited to the size where the mirror can fit into the sleeve with a gap. Therefore, in order to process the inner surface of an extremely small bearing, a tiny and complex jig is required to hold the mirror in a position where it does not interfere with the movement of the sleeve.

[0013] The present invention has been made in consideration of the above-mentioned drawbacks of the conventional technology, and aims to enable rapid laser processing of products suitable for mass production, such as semiconductor wafers and radial sliding bearings, into a desired shape or state. In particular, in the case of semiconductor wafers, the object is to enable rapid planarization and uniform annealing of the front or back surface of the wafer, and in the case of small bearing parts, the object is to enable processing of the inner surface into a desired shape in a short period of time. [Means for solving the problem]

[0014] The present inventors have found that the above problems can be solved by the following configuration.

[0015] [1] A laser processing apparatus that irradiates one surface of an irradiation object, which is a semiconductor wafer, with laser light to perform rotationally symmetric laser processing, comprising: a laser light source capable of emitting laser light; a first optical element that changes the direction of the laser light emitted from the laser light source to a direction different from the emission direction; a second optical element that includes a mechanism for controlling the laser light emitted from the first optical element to scan in the circumferential direction of the irradiation object; and focusing means that focuses the laser light emitted from the second optical element, wherein the first and second optical elements are wedge prisms that each include a fixed wedge prism and a translation control mechanism and / or a rotation control mechanism, and the focusing means is a focusing lens consisting of a number of microlenses arranged concentrically. [2] The laser processing apparatus according to [1], characterized in that the one surface is either the surface on which the circuit of the semiconductor wafer is formed or the opposite surface, and the laser light emitted from the laser light source is irradiated onto the object to be irradiated to anneal the one surface. [3] The laser processing device according to [2], characterized in that a galvanometer scanner and an f-θ lens are disposed between the second optical element and the irradiation object. [4] The laser processing apparatus according to [1] or [2], characterized in that it has two sets of the laser light source, the first optical element, and the second optical element, and the sets of the laser light source, the first optical element, and the second optical element are arranged symmetrically at positions opposite each other across the object to be irradiated, and a galvanometer scanner and an f-θ lens are arranged between one of the second optical elements and the object to be irradiated. [5] A laser processing apparatus according to any one of [1] to [4], further comprising first and second reflecting means for reflecting the laser light emitted from the second optical element, and the focusing means for focusing the laser light reflected by the reflecting means. [6] The laser processing device according to [1] or [2], wherein the one surface is the rear side of the side on which the laser light source is arranged.

[0016] Another aspect of the present invention is characterized in that a laser processing device that performs laser processing by irradiating one surface of an object to be irradiated with laser light in a rotationally symmetric manner comprises a laser light source capable of emitting laser light, a first optical element that changes the direction of the laser light emitted from the laser light source to a direction different from the emission direction, and a second optical element that includes a mechanism for scanning and controlling the laser light emitted from the first optical element in a circumferential direction of the object to be irradiated.

[0017] In this feature, it is preferable that the first and second optical elements are wedge prisms each including a wedge prism and a translation control mechanism and / or a rotation control mechanism, the irradiation object is a semiconductor wafer, the one surface is either a surface of the semiconductor wafer on which a circuit is formed or the opposite surface, and the laser light emitted from the laser light source is irradiated onto the irradiation object to anneal the one surface, and it is also preferable that the first and second optical elements are wedge prisms each including a wedge prism and a translation control mechanism and / or a rotation control mechanism, the one surface of the irradiation object is a sleeve-shaped inner peripheral surface, and the laser light emitted from the laser light source is irradiated onto the irradiation object to form a groove on the one surface.

[0018] In the above features, a galvanometer scanner and an f-θ lens may be disposed between the second optical element and the object to be irradiated, or two sets of the laser light source, the first optical element, and the second optical element may be provided, and the sets of the laser light source, the first optical element, and the second optical element may be disposed symmetrically at positions opposite to each other across the object to be irradiated, and a galvanometer scanner and an f-θ lens may be disposed between one of the second optical elements and the object to be irradiated.

[0019] Furthermore, in the above-mentioned features, first and second reflecting means for reflecting the laser light emitted from the second optical element and focusing means for focusing the laser light reflected by these reflecting means may be provided, and two sets of the galvanometer scanner and the f-θ lens may be provided, and the sets of the galvanometer scanner and the f-θ lens may be disposed symmetrically between the second optical element and the irradiation object. [Effects of the Invention]

[0020] According to the present invention, by rotating the optical component at a variable speed, it is possible to instantly change the position of the laser light emitted from the laser light source and irradiate it at the desired position on a wafer or bearing component, etc., making it possible to process products suitable for mass production, such as semiconductor wafers and radial sliding bearings, with high precision and in a short time. In particular, in the case of semiconductor wafers, the front or back surface of the wafer can be quickly flattened and uniformly annealed. In the case of small bearing components, the inner surface can be quickly processed into the desired shape. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of an embodiment of a laser processing device according to the present invention; [Figure 2] 2A to 2C are diagrams illustrating the operation of an optical element provided in the laser processing apparatus shown in FIG. [Figure 3] FIG. 2 is a block diagram of the laser processing device shown in FIG. [Figure 4] FIG. 10 is a schematic diagram of another embodiment of the laser processing device according to the present invention. [Figure 5] 5A to 5C are diagrams illustrating an example of processing performed by the laser processing device shown in FIG. 4. [Figure 6] FIG. 5 is a block diagram of the laser processing device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Several embodiments of the laser processing apparatus according to the present invention will be described below with reference to the drawings. Fig. 1 is a schematic front view of one embodiment of the laser processing apparatus 100. The laser processing apparatus 100 of this embodiment is used in combination with, for example, a wafer chamfering apparatus equipped with an XYZ-θ table (not shown).

[0023] A semiconductor wafer W is sucked downward into a suction unit 240 of a processing device such as a wafer chamfering device, with the circuit-formed surface facing downward. Main parts of a laser processing device 100, which have approximately the same configuration, are arranged above and below the semiconductor wafer W. That is, as the main part of the laser processing device 100 located on the upper side, a laser light source 210 is fixedly arranged at the top directly above the wafer W. The laser light source 210 emits a pulsed laser, and the intensity, timing, etc. of the emitted laser light 110 are controlled by a laser light source control unit 212.

[0024] A beam expander 222 is fixedly disposed below the laser light source 210, and the beam expander 222 expands the laser light 110 emitted from the laser light source 210 to a predetermined intensity and a predetermined spot diameter. An optical element (movable part) 220 having a plurality of prisms is disposed below the beam expander 222.

[0025] The optical element 220 is a component for determining a specific irradiation position on the wafer W, which is a workpiece, and includes two types of wedge prisms 224 and 226, each shaped like a diagonally cut cylinder. The upper wedge prism 224 is a first optical element and is used to adjust the irradiation angle, as will be described in detail later. It includes an upper prism (fixed prism) 224a and a lower prism 224b spaced apart in the optical axis direction, and the spacing between the upper prism 224a and the lower prism 224b is variably controlled by a translation control unit 232. In the upper wedge prism 224, the translation control unit 232 changes the distance in the optical axis direction between the upper prism 224a and the lower prism 224b, thereby making it possible to change the position on the wafer W in a direction perpendicular to the optical axis of the laser beam 110, i.e., in the radial direction.

[0026] The wedge prism 226 located on the lower side, which is the second optical element, is used for the radius of the rotational operation circle, which will be described in detail later, and includes an upper prism (fixed prism) 226a and a lower prism 226b spaced apart from each other in the optical axis direction. The distance between the upper prism 226a and the lower prism 226b is variably controlled by a translation control unit 234, and the rotation of the upper prism 226a and the lower prism 226b around the optical axis is controlled by a rotation control unit 236. The rotation control unit 236 drives the rotation of the upper prism 226a and the lower prism 226b, thereby controlling the irradiation position of the laser light in the circumferential direction of the wafer W. In other words, to irradiate the surface of the wafer W in a circular pattern, the wedge prism 226 may be rotated continuously one or more times. The translation control unit 232 of the upper wedge prism 224 and the translation control unit 234 and rotation control unit 236 of the lower wedge prism 226 constitute the optical element control unit 230.

[0027] A laser light source 260, a beam expander 272, and an optical element 270, which have substantially the same configuration as the laser light source 210, the beam expander 222, and the optical element 220, are arranged symmetrically below the wafer W with the wafer W in between. That is, above the laser light source 260, a beam expander 272 that diffuses the laser light 110 is arranged, and above that, an optical element (movable part) 270 having a plurality of prisms is arranged. The laser light source 260 is a light source that emits a pulsed laser, and the intensity, timing, etc. of the emitted laser light 110 are controlled by a laser light source control unit 262.

[0028] The optical element 270 includes two types of wedge prisms 274, 276, each having a shape formed by cutting a cylinder at an angle. The lower wedge prism 274 includes an upper prism 274b and a lower prism (fixed prism) 274a spaced apart in the optical axis direction, and the distance between the upper prism 274b and the lower prism (fixed prism) 274a is variably controlled by a translation control unit 282.

[0029] The upper wedge prism 276 includes an upper prism 276b and a lower prism 276a spaced apart from each other in the optical axis direction, and the distance therebetween is variably controlled by a translation control unit 284, and their rotation is controlled by a rotation control unit 286. The translation control unit 282 of the lower wedge prism 274 and the translation control unit 284 and rotation control unit 286 of the upper wedge prism 276 constitute the optical element control unit 230. By the optical element control unit 230 controlling the prisms 274a to 276b that constitute the optical element 270, it becomes possible to irradiate the wafer W evenly with laser light in a concentric pattern from the inner diameter side to the outer diameter side, or vice versa.

[0030] Next, around the suction section 240 of the processing device that holds the wafer W by suction, there are arranged optical elements that guide the laser light 110 emitted from the laser light source 210 at the top of the laser processing device 100 to the back side of the wafer W, and optical elements that also guide the laser light 110 emitted from the laser light source 260 at the bottom to the back side of the wafer W. These optical elements form an optical element 250.

[0031] Specifically, a cylindrical portion 254a of the reflecting mirror 254 is disposed at a radial distance from the outer circumferential edge of the wafer W, and a truncated cone-shaped cone portion 254b of the reflecting mirror 254 is connected to the bottom end of the cylindrical portion 254a. Furthermore, a condenser lens 252 is disposed in a ring shape at a position above the cone portion 254b and spaced downward from the wafer W.

[0032] On the other hand, in order to focus the laser beam 110 emitted from the lower laser light source 260, an f-θ lens 256 is disposed at a position corresponding to the center position of the wafer W, approximately at the position of the opening of the reflecting mirror, and a galvanometer scanner 258 is disposed below and spaced apart from the f-θ lens 256. The rotation and the like of the f-θ lens 256 and the galvanometer scanner 258 are driven and controlled by a drive control unit 288. By arranging the optical elements in this manner, the upper laser light source 210 is suitable for irradiating the laser beam mainly on the outer diameter side of the wafer W, and the lower laser light source 260 is suitable for irradiating the laser beam mainly on the center side of the wafer W. Therefore, when the wafer diameter is small, the laser processing apparatus 100 may be provided with only the lower configuration.

[0033] The laser light sources 210 and 260 are arranged above and below each other to irradiate the center and outer periphery of the wafer W, respectively, in order to enable simultaneous processing and shorten the laser irradiation time, and also because the deflection angle formed by the wedge prism cannot theoretically be made large. Usually, this deflection angle is within a few degrees, and at most 10 degrees.

[0034] The main optical elements provided in the laser processing apparatus 100 shown in Fig. 1 will be described with reference to Fig. 2. Fig. 2 is a diagram for explaining the operation and function of the main optical elements, with Fig. 2(a) being a schematic diagram for explaining the operation of wedge prisms 224 and 226 provided in optical element 220, Fig. 2(b) being a schematic diagram for explaining the function of reflecting mirror 254, Fig. 2(c) being a schematic diagram for explaining the function of condenser lens 252 and a cross-sectional view of part A in Fig. 2(e) showing condenser lens 252, and Fig. 2(d) being a schematic diagram for explaining how concentric circular scanning trajectories are obtained on wafer W.

[0035] As described above, the optical element 220 includes two sets of wedge prisms 224, 226, each of which includes two prisms 224a, 224b; 226a, 226b spaced apart from each other. The relative positions of the prisms 224a to 226b are variable, and although not shown in FIG. 2(a), their positions are controlled by the optical element control unit 230. That is, in the upper wedge prism 224, the upper prism 224a is fixed and the lower prism 224b is moved, thereby varying the relative positions of the prisms in the optical axis direction.

[0036] For example, the lower prism 224b is translated T in the optical axis direction relative to the upper prism 224a from the position indicated by the solid line to the position indicated by the dashed line. RL1 Then, the laser light 110 that has reached the optical element 220 from the laser light source 210 via the beam expander 222 changes its radial position (position perpendicular to the optical axis) in the wedge prism 224 from a locus 112a indicated by a chain line located on the central side to a locus 112b indicated by a dashed line located on the outer periphery side.

[0037] In the lower wedge prism 226, similarly to the upper wedge prism 224, at least one of the upper and lower prisms 226a and 226b, in this example the upper prism 226b, is moved in a translational motion T RL2 When the gap between them is changed by rotating the upper and lower prisms 226a and 226b, the change in the radial position of the laser light is expanded. OT1 When the upper wedge prism 224 is rotated, the irradiation locus of the laser light forms a concentric circular locus on the surface of the wafer W. In other words, the trajectories 112a and 112b of the laser light whose radial positions are changed by the upper wedge prism 224 change from the circular irradiation light locus 114a indicated by the dashed line on the surface of the wafer W to the circular irradiation light locus 114b indicated by the broken line.

[0038] Therefore, by changing the relative distance in the optical axis direction between the prisms 224a to 226b of the upper and lower wedge prisms 224, 226 and simultaneously rotating the prisms 226a, 226b of the lower wedge prism 226, it becomes possible to irradiate the entire surface of the wafer W with laser light. Note that, as shown in Fig. 1, the wafer W in this embodiment is placed with its back side facing down and the back side is processed, so the laser light from the laser light source 210 arranged above cannot be used as is. For this reason, a reflecting mirror 254 is used.

[0039] As shown in FIG. 2(b), the reflecting mirror 254 includes a cylindrical portion 254a having a diameter larger than the diameter of the wafer W and a truncated conical portion 254b connected at the bottom end of the cylindrical portion 254a and having an opening 254c in the center. The inner surfaces of these portions 254a and 254b are the portions of the reflecting mirror 254 that function as mirrors. The laser beam 116 emitted from the optical element 220 reaches the reflecting mirror 254 at an angle to the optical axis, first colliding with the inner surface of the cylindrical portion 254a of the reflecting mirror 254 and becoming a reflected beam 116a, which then colliding with the inclined surface of the conical portion 254b. The reflecting mirror 254 is set so that the reflected beam 116b becomes a laser beam oriented in the optical axis direction, positioned radially inward from the outer edge of the wafer W and outward from the opening 254c of the reflecting mirror 254. This allows the laser light to be evenly irradiated onto the wafer W from the exit port 254d of the reflecting mirror 254 from the position on the wafer W corresponding to the opening 254c of the reflecting mirror 254 to the outer diameter position of the wafer W.

[0040] The reflected light 116b may include laser light diffused by the two reflecting surfaces 254a, 254b. Therefore, to make the laser light more parallel to the optical axis, a ring-shaped condenser lens 252 having a width at least extending from the position on the wafer W corresponding to the opening 254c of the reflecting mirror 254 to the outer diameter position of the wafer W is provided near the set position of the wafer W and spaced apart from the wafer W. As shown in FIG. 2(c), the condenser lens 252 is composed of a number of microlenses 252a arranged concentrically, and the microlenses 252a are arranged adjacent to each other on the same circumference. The laser light emitted from the laser light source 210 passes through optical elements and reflecting mirrors (not shown) and is condensed by the condenser lens 252 composed of the microlenses 252a to form an irradiation area with a predetermined spot diameter on the wafer W. FIG. 2(d) shows that laser beams 118a and 118b parallel to the optical axis formed through the condenser lens 252 form concentric irradiation beam trajectories 114a and 114b on the wafer W surface.

[0041] Next, the operation of the laser processing apparatus 100 configured as described above will be described with reference to FIGS. 1 and 3. FIG. 3 is a block diagram showing the configuration of the laser processing apparatus 100. The laser processing apparatus 100 anneals the backside of the wafer W on which semiconductor circuits have been formed to remove residual stress and flatten the wafer W surface after the circuits have been formed. Conventionally, flattening has been achieved by mechanical processing, primarily grinding and chemical treatment, but this required additional processing, such as treatment of residual stress and waste liquids during processing. In this embodiment, annealing the backside of the wafer W by laser irradiation prevents cracks and chips from occurring in the subsequent thinning process, improves processing uniformity, and enables high-throughput processing.

[0042] The control units that drive and control the optical elements of the laser processing apparatus 100 are generally integrated and arranged in a housing as a laser processing control device 200. First, the wafer W to be processed is transported to the suction unit 240 using the drive control unit 150 of a processing apparatus such as a grinding apparatus, and the wafer W is sucked with its backside facing downward. Next, a laser beam 110 is emitted downward from the upper laser light source 210, and a laser beam 110 is emitted upward from the lower laser light source 260. At this time, the output timing and intensity of the laser beams are controlled by laser beam source control units 212 and 262. In the initial state, the upper laser beam 110 that has passed through the optical elements irradiates an outer peripheral region of the wafer W, and the lower laser beam 110 that has passed through the optical elements irradiates a central region of the wafer W.

[0043] For the laser beam 110 emitted from the upper laser light source 210, the optical element control unit 230 adjusts and controls the wedge prisms 224 and 226 of the optical element 220 to determine the incident angle, which is the incident deflection angle on the wedge prism 226, and the radial position (radius of the rotational scanning circle) of the laser beam emitted from the wedge prism 226. This determines the incident position of the laser beam on the reflecting mirror 254. The laser beam deflected by the reflecting mirror 254 is focused by a focusing lens 252 corresponding to the shape of the wafer W and irradiates the wafer surface as irradiation light substantially perpendicular to the wafer surface. When laser irradiation at a certain radius is completed, the irradiation position is changed to the next radial position. Therefore, the optical element control unit 230 adjusts and controls the optical axis positions of the prisms 224a to 226b constituting the wedge prisms 224 and 226 of the optical element 220. The amount of change in the optical axis position ultimately corresponds to the radial pitch of the laser irradiation positions on the wafer W. By repeating the radial movement of the laser irradiation position, that is, the movement of each of the prisms 224a to 226b in the optical axis direction, laser irradiation of the entire outer peripheral region of the wafer W is completed.

[0044] On the other hand, for the laser beam 110 emitted from the lower laser light source 260, the optical element control unit 280 adjusts and controls the wedge prisms 274 and 276 included in the optical element 270 to determine the angle of incidence on the wedge prism 276 and the radial position (radius of the rotational scanning circle) of the laser beam emitted from the wedge prism 276. Next, the optical element control unit 280 drives and controls the galvanometer scanner 258 and the f-θ lens 256 to focus the laser beam that has passed through the optical element 270 and irradiate the central region of the wafer W with the laser beam substantially perpendicularly. For this lower laser beam 110, once laser irradiation at a certain radius is completed, the irradiation position is also changed to the next radial position. For this reason, the optical element control unit 280 adjusts and controls the optical axis positions of the prisms 274a to 276b that constitute the wedge prisms 274 and 276. By repeatedly moving the laser irradiation position in the radial direction, i.e., by repeatedly moving each of the prisms 274a to 276b in the optical axis direction, laser irradiation of the entire central region of the wafer W is completed. Note that a condenser lens such as the condenser lens 252 may be used as the lower focusing means instead of the galvanometer scanner 258 and the f-θ lens 256. In this case, the shape of the condenser lens is a disk corresponding to the center of the wafer W.

[0045] In the above operation, the wedge prisms 226, 276 are rotated and controlled at high speed. This allows the laser beam 110 emitted from the upper laser light source 210 to concentrically irradiate a portion at a predetermined radius position within the outer peripheral region of the wafer W, and the laser beam 110 emitted from the lower laser light source 260 to concentrically irradiate a portion at a predetermined radius position within the central region of the wafer W. As is clear from the above, when the diameter of the wafer W is small, the processing amount per wafer W is small, so laser processing can also be performed using only the laser light source 260 arranged on the lower side in FIG. 1.

[0046] As described above, according to this embodiment, it is possible to perform highly accurate and uniform processing over the entire surface of the wafer. As a result, it is possible to maintain high quality of the wafer. Furthermore, since processing is performed under atmospheric pressure and no special chemicals are required, there is no need for waste liquid disposal or consumables, and processing can be performed cleanly and at low cost.

[0047] Another embodiment of the laser processing apparatus 102 according to the present invention will be described with reference to Figures 4 to 6. Figure 4 is a schematic diagram of the laser processing apparatus 102 corresponding to Figure 1, Figure 5 is a diagram showing some examples of processing patterns, and Figure 6 is a block diagram showing the configuration of the laser processing apparatus 102 corresponding to Figure 3. K is, for example, a radial sliding bearing having a sleeve-shaped inner peripheral surface, and for example, a spiral groove is formed on the inner peripheral surface of the radial sliding bearing. Parts similar to those in the embodiment shown in Figures 1 to 3 are given the same numbers with the digit in the hundreds place changed. That is, reference numerals 210 and 310 similarly indicate laser light sources. Some of the parts are similar to those in the embodiment shown in Figure 1, so their explanation will be omitted to avoid complication.

[0048] Work W K Since the workpiece W has a cylindrical configuration, the cylindrical axis is arranged in the vertical direction, and the outer periphery of the cylindrical axis is fixed and held by the holding part 340 of the processing device. K The laser light 110 is emitted from the laser light sources 310 and 360 arranged above and below the workpiece W. K 1, the laser beam can be directly irradiated to the same position on the inner surface of the workpiece W, which differs from the embodiment shown in FIG. 1 in this respect. Also, due to this difference, a reflecting mirror is not required on the upper side of the laser processing device 102. The focusing means is composed of an f-θ lens 352, a galvano scanner 354, and a drive control unit 338 for these, instead of a focusing lens. Similarly, on the lower side, the focusing means is composed of an f-θ lens 392, a galvano scanner 394, and a drive control unit 388 for these. K The lower part is the work W K Since it is configured symmetrically with the upper part across from it, its explanation will be omitted.

[0049] Work W K Since the spiral groove is machined on the workpiece W, the holding unit 340 of the machining device is controlled by the translation control unit 162 and the rotation control unit 164 of the drive control unit 160 (see FIG. 4) of the machining device so as to move up and down in synchronization with the rotation of the wedge prisms 326, 376 of the upper and lower optical elements 320, 390. K 5(a) shows a case where the holder 340 is not moved up and down during laser processing, that is, the workpiece W is not moved up and down during laser processing. K The workpiece W is stationary, and laser beams 122 and 124 are emitted from the upper and lower laser light sources 310 and 360 shown in FIG. 4 through the upper and lower openings 132. K The irradiation point on the inner wall 134 is the same point. By rotating the wedge prisms 326 and 376, the work W K The irradiation point on the inner wall 134 moves to form an irradiation locus 142. The laser intensity is adjusted to form a desired circumferential groove at the irradiation locus 142.

[0050] In FIG. 5(b), the laser beam is irradiated from only one laser source 310, and the workpiece W is irradiated in synchronization with the change in the circumferential irradiation position of the laser beam. K Moves downward in parallel with T RL3 In addition to the progress of the processing state, the workpiece W is irradiated with the laser beam 122b in the early stage of processing. K The bottom of the workpiece W is being machined, but as time passes, K moves downward, and the work W is K This results in a spiral irradiation locus 144, and by adjusting and controlling the intensity of the laser light, a spiral groove is formed at the irradiation locus 144.

[0051] FIG. 5(c) shows an example in which laser beams 124a and 124b from a laser light source 360 ​​are added to the embodiment shown in FIG. 5(b). K is synchronized with the rotation of the upper and lower laser beams and moves in a translational motion. RL4As a result, two spiral irradiation loci 144, 146 are obtained. These two spiral irradiation loci 144, 146 are intersecting spiral irradiation loci 144, 146, and intersecting spiral grooves are formed by adjusting and controlling the laser light intensity.

[0052] Figure 5(d) shows the workpiece W K The laser beam is irradiated from the upper and lower laser light sources while the workpiece W is fixed and held in place, and the configuration and operation of the laser processing device are the same as those of the embodiment shown in Fig. 5(a). However, the laser processing content is different from that of the embodiment shown in Fig. 5(a). In the previous embodiments, grooves were formed on the inner surface of a cylindrical workpiece W, but in this example, K A ring-shaped or sheet-shaped adherend 136 is laser welded or melt-bonded to the inner wall 134 of the groove. By using minute protrusions as the adherend, the opposite effect to that of the groove can be obtained.

[0053] The examples shown in Figure 5 are particularly suitable for cases where the opening diameter is too small to insert a processing tool, or where the processing tool is too small to maintain its strength, etc. For example, they are suitable for processing bearings for high-speed printers and radial bearings for microturbines.

[0054] As explained above, according to the above embodiment, it is possible to irradiate the processing area with laser light at high speed, and the processing time can be shortened compared to the conventional method. Furthermore, since processing is possible within the range that the laser light can reach, it becomes possible to process grooves inside small holes, which have been difficult to process until now, and to weld micro parts inside small holes. [Explanation of symbols]

[0055] 100, 102...laser processing device, 110...laser light, 112a, 112b...laser light trajectory, 114a, 114b...irradiation light trajectory, 116...laser light, 116a, 116b...reflected light, 118a, 118b...laser light (parallel to the optical axis), 122, 122a, 122b...(upper) laser light, 124, 124a, 124b...(lower) laser light, 132...opening, 134...inner wall, 136...adhered object, 142, 144, 146...irradiation trajectory, 150, 160...(processing device) drive control unit, 162...translation control unit, 164...rotation control unit, 200...laser processing control device, 210... Laser light source, 212...laser light source control unit, 220...optical element, 222...beam expander, 224...wedge prism (for adjusting irradiation angle), 224a...upper prism (fixed prism), 224b...lower prism, 226...wedge prism (for rotating operation circle), 226a...upper prism (fixed prism), 226b...lower prism, 230...optical element control unit, 232...translation control unit, 234...translation control unit, 236...rotation control unit, 240...suction unit (of processing device), 250...optical element, 252...condenser lens, 252a...microlens, 254...reflection mirror, 254a ...Reflective surface (cylindrical portion), 254b...Reflective surface (conical portion), 254c...Aperture, 256...f-θ lens, 258...Galvano scanner, 260...Laser light source, 262...Laser light source control unit, 270...Optical element (movable portion), 272...Beam expander, 274...Wedge prism, 274a...Lower prism, 274b...Upper prism, 276...Wedge prism, 276a...Lower prism, 276b...Upper prism, 280...Optical element control unit, 282, 284...Translation control unit, 286...Rotation control unit, 288...Drive control unit, 300...Optical element control unit, 310...Laser light source, 3 12...Laser light source control unit, 320...Optical element (movable part), 322...Beam expander, 324...Wedge prism (for adjusting irradiation angle), 324a...Upper prism (fixed prism), 324b...Lower prism, 326...Wedge prism (for rotating operation circle), 326a...Upper prism (fixed prism), 326b...Lower prism, 330...Optical element control unit, 332, 334...Translation control unit, 336...Rotation control unit, 338...Drive control unit, 340...Holding unit (of processing device), 350...Optical element, 352...f-θ lens, 354...Galvano scanner, 360...Laser light source,362...laser light source control unit, 370...optical element, 372...beam expander, 374...wedge prism (for adjusting irradiation angle), 374a...lower prism (fixed prism), 374b...upper prism, 376...wedge prism (for rotation operation circle), 376a...lower prism (fixed prism), 376b...upper prism, 380...optical element control unit, 382, ​​384...translation control unit, 386...rotation control unit, 388...drive control unit, 390...optical element, 392...f-θ lens, 394...galvanometer scanner, R, OT1 …Rotational motion, T RL1 , T RL2 , T RL3 , T RL4 ...translation, W...wafer, W K …Work

Claims

1. A laser processing apparatus for performing rotationally symmetric laser processing by irradiating one surface of an irradiation object, which is a semiconductor wafer, with laser light, a laser light source capable of emitting laser light; a first optical element that changes the direction of the laser light emitted from the laser light source to a direction different from the emission direction and scans the laser light in a radial direction of the semiconductor wafer; a second optical element that scans the laser light emitted from the first optical element in a circumferential direction of the semiconductor wafer; and focusing means that focuses the laser light emitted from the second optical element, the first and second optical elements are respectively a fixed wedge prism and a wedge prism including a translation control mechanism and / or a rotation control mechanism; the focusing means is a focusing lens made up of a number of microlenses arranged concentrically, A laser processing device in which the first and second optical elements irradiate the semiconductor wafer with laser light from its inner diameter side to its outer diameter side or vice versa via a condenser lens.

2. 2. The laser processing apparatus according to claim 1, wherein the one surface is either the surface on which a circuit of the semiconductor wafer is formed or the opposite surface, and the laser light emitted from the laser light source is irradiated onto the object to be annealed.

3. 3. The laser processing apparatus according to claim 1, further comprising first and second reflecting means for reflecting the laser light emitted from the second optical element, and the focusing means focuses the laser light reflected by the reflecting means.

4. 3. The laser processing device according to claim 1, wherein the one surface is a rear side on which the laser light source is disposed.

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