JP6989392B2 - How to process plate-shaped objects - Google Patents

Description

The present invention relates to a method for processing a plate-shaped object such as a wafer, which is subjected to laser processing.

Generally, along the planned division line of a wafer (plate-shaped object), a laser beam is irradiated at a focusing point inside the wafer to form a modified layer inside the wafer, and the modified layer is broken. A processing method for dividing into individual device chips from a starting point is known (see, for example, Patent Document 1). In this type of processing method, since a modified layer is formed inside the wafer and divided, it is possible to suppress machining waste compared to the method of cutting with a cutting blade along the planned division line, and the cutting allowance. It is possible to realize the narrowing of the line, and by extension, to narrow the pre-formed division scheduled line.

Japanese Patent No. 3408805

By the way, in the method of forming a modified layer inside the wafer, in order to prevent diffused reflection of the laser beam on the incident surface, it is possible to flatten the incident surface (for example, the back surface) of the plate-like object before laser processing. preferable. Generally, flattening is performed by a grinding wheel or a polishing pad. For example, when the machined surface of the grinding wheel or the polishing pad is unevenly worn, flattening can be performed to improve the flatness of the wafer. It is also expected to collapse. If laser processing is performed while the wafer is not flat, the relative position of the wafer in the thickness direction with respect to the focusing point of the laser beam changes, so there is a risk that the modified layer cannot be formed at a uniform depth inside the wafer. be.

The present invention has been made in view of the above, and an object of the present invention is to provide a method for processing a plate-like material capable of forming a modified layer at a uniform depth position.

In order to solve the above-mentioned problems and achieve the object, the present invention is a method for processing a plate-shaped material in which laser processing is performed on the plate-shaped material, and the back surface of the plate-shaped material is ground or polished to be flattened. After performing the flattening step, the first light is irradiated from the front surface side of the plate-shaped object, and the amount of light is smaller than that of the first light from the back surface side of the plate-shaped object. While irradiating the light of 2, the back surface of the plate-shaped object is imaged by an imaging means to form an image, and the flatness confirmation is confirmed based on the captured image to confirm whether the back surface of the plate-shaped object is flat. After performing the step and the flatness confirmation step, the back surface of the plate-shaped object is in a state where the focusing point of the laser beam having a wavelength that is transparent to the plate-shaped object is positioned inside the plate-shaped object. It is provided with a modified layer forming step of irradiating the laser beam with the laser beam to form a modified layer inside the plate-shaped object.

According to this configuration, after performing a flattening step for flattening the back surface of a plate-like object, it is confirmed that the back surface is flat by performing a flatness confirmation step for confirming whether the back surface is flat. It is possible to carry out the modified layer forming step only on the plate-like material that has been formed. Therefore, uniform laser processing can be applied to the plate-shaped object, and the modified layer can be formed at a uniform depth position inside the plate-shaped object. Further, in the flatness confirmation step, by irradiating the first light from the front surface side of the plate-shaped object, the back surface of the plate-shaped object is imaged blacker than the surroundings. Further, by irradiating the back surface of the plate-shaped object with a second light having a smaller amount of light than the first light, the shadow of the captured image on the back surface can be emphasized, so that it is easy to check whether the back surface is flat. Can be confirmed.

In this configuration, if it is confirmed in the flatness confirmation step that the back surface of the plate-like object is not flat, a re-flattening step of grinding or polishing the back surface of the plate-like object to flatten it may be further provided. According to this configuration, since the back surface of the plate-shaped object can be flattened again by the re-flattening step, the modified layer can be more reliably formed at a uniform depth position inside the plate-shaped object.

Further, after performing the modified layer forming step, a thinning step may be provided in which the back surface of the plate-shaped object is ground to be thinned to a predetermined thickness. According to this configuration, a grinding load is applied to the modified layer when grinding to a predetermined thickness, so that cracks starting from the modified layer are generated inside the plate-shaped material to form the plate-shaped material. Can be split.

Further, the flattening step may be performed by a flattening apparatus, and the flattening confirmation step and the modified layer forming step may be performed by a laser processing apparatus. According to this configuration, the modified layer can be formed as it is on the plate-shaped material whose flatness has been confirmed by the laser processing apparatus, so that the productivity is prevented from being impaired.

Further, even if the flatness confirmation step confirms that the back surface of the plate-shaped object is not flat when there is a portion having higher brightness than others in the back surface region of the plate-shaped object in the captured image. good. According to this configuration, it is possible to accurately confirm whether or not the back surface of the plate-shaped object is flattened by the luminance distribution on the back surface of the plate-shaped object in the captured image.

Further, in the flatness confirmation step, pattern matching processing is performed between the reference image of a plate-like object having a flat back surface and the captured image, and when the similarity of these images does not reach a predetermined threshold value, the flatness confirmation step is performed. It may be confirmed that the back surface of the plate-like object is not flat. According to this configuration, it is possible to accurately confirm whether or not the back surface of the plate-shaped object is flattened by the pattern matching process between the reference image and the captured image.

According to the present invention, it is confirmed that the back surface is flat by performing a flattening step for flattening the back surface of the plate-like object and then performing a flatness confirmation step for confirming whether the back surface is flat. It is possible to carry out the modified layer forming step only on the plate-like material that has been formed. Therefore, uniform laser processing can be applied to the plate-shaped object, and the modified layer can be formed at a uniform depth position inside the plate-shaped object.

FIG. 1 is a perspective view of a wafer, which is an example of a plate-shaped object to be processed. FIG. 2 is a perspective view of a configuration example of a grinding and polishing apparatus used in the method for processing a plate-shaped object according to the present embodiment. FIG. 3 is a perspective view of a configuration example of a laser processing apparatus used in the method for processing a plate-shaped object according to the present embodiment. FIG. 4 is a schematic cross-sectional view showing the structure of the flattening confirmation unit provided in the laser processing apparatus. FIG. 5 is a flowchart showing a procedure of a method for processing a plate-shaped object. FIG. 6 is a side view showing an outline of the flattening step. FIG. 7 is an example of a captured image that is confirmed to be flat in the flatness confirmation step. FIG. 8 is an example of a captured image that is confirmed not to be flat in the flatness confirmation step. FIG. 9 is a side view showing an outline of the reflattening step. FIG. 10 is a side view showing an outline of the modified layer forming step. FIG. 11 is a side view showing an outline of the thinning step.

An embodiment (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. In addition, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

A method for processing a plate-shaped object according to the present embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of a wafer, which is an example of a plate-shaped object to be processed. FIG. 2 is a perspective view of a configuration example of a grinding and polishing apparatus used in the method for processing a plate-shaped object according to the present embodiment. FIG. 3 is a perspective view of a configuration example of a laser processing apparatus used in the method for processing a plate-shaped object according to the present embodiment. FIG. 4 is a schematic cross-sectional view showing the structure of the flattening confirmation unit provided in the laser processing apparatus.

In the method for processing a plate-shaped material according to the present embodiment, a laser beam is irradiated from the back surface 201 side of the wafer 200 as a plate-shaped material to form a modified layer inside the wafer 200, and the modified layer is used as a fracture starting point. It is divided into individual device chips. The wafer 200 is not particularly limited as long as it can irradiate a laser beam to form a modified layer inside. The wafer 200 is, for example, a plate-shaped semiconductor wafer or optical device wafer using silicon, gallium arsenide (GaAs) or the like as a base material, or a plate-shaped inorganic material substrate such as _{glass or a sapphire (Al 2} O _{3) -based plate.} Various processing materials. As shown in FIG. 1, the wafer 200 is a device such as an IC (Integrated Circuit) or an LSI (Large Scale Integration) in a plurality of regions partitioned by a grid-shaped scheduled division line 203 on the surface 202. 204 is formed. As shown in FIG. 2, the wafer 200 is flattened by grinding or polishing the back surface 201 by a grinding / polishing device (flattening device) 1 with the protective member 205 attached to the front surface 202. The protective member 205 is formed of a disk shape having the same size as the wafer 200, and is made of a flexible synthetic resin.

As shown in FIG. 2, the grinding and polishing apparatus 1 includes an apparatus main body 2, a rough grinding unit (grinding means) 3, a finish grinding unit (grinding means) 4, a polishing unit (polishing means) 5, and a polishing unit movement. The mechanism 6, the machining fluid supply unit 7, the four chuck tables 9 (9a to 9d) installed on the turntable 8, the cassettes 11 and 12, the position table 13, the transfer arm 15, and the robot pick. 16, a spinner cleaning device 17, and a control device (control unit) 100 are mainly provided.

The rough grinding unit 3 roughly grinds the back surface 201 of the wafer 200 by pressing the rough grinding wheel 3b mounted on the lower end of the spindle 3a against the back surface 201 of the wafer 200 held by the chuck table 9 while rotating the rough grinding wheel 3b. Process. Similarly, the finish grinding unit 4 finishes on the back surface 201 of the wafer 200 by pressing the finish grinding wheel 4b mounted on the spindle 4a against the back surface 201 of the wafer 200 after the rough grinding while rotating the finish grinding wheel 4b. Grind.

The polishing unit 5 presses the back surface 201 of the wafer 200 after the finish grinding process held on the chuck table 9 while rotating the polishing pad 5b mounted on the lower end of the spindle 5a, thereby pressing the back surface 201 of the wafer 200. Is polished. The polishing pad 5b is deformed according to the shape of the wafer 200 to be polished, and the lower surface of the polishing pad 5b comes into contact with the back surface 201 of the wafer 200 to become the polishing surface of the back surface 201.

In the present embodiment, the work of grinding or polishing the back surface 201 of the wafer 200 to flatten it is carried out by using the rough grinding unit 3, the finish grinding unit 4, or the polishing unit 5. The flattening is for removing the oxide film formed on the back surface 201 of the wafer 200 and the scratches (unevenness) generated on the back surface 201, and the surface roughness Ra defined by the JIS standard (B0601) is defined. For example, processing that satisfies the condition of Ra ≦ 0.1 (μm), more preferably Ra ≦ 0.02 (μm).

The polishing unit moving mechanism 6 may move the polishing unit 5 in the horizontal direction (the radial direction of the polishing pad 5b, the X-axis direction in FIG. 2) and the vertical direction (the axial direction of the spindle 5a, the Z-axis direction in FIG. 2). can. The processing liquid supply unit 7 selectively supplies the polishing liquid and the cleaning liquid to the back surface 201 of the wafer 200 after the grinding process at the time of the polishing process. The processing liquid supply unit 7 is connected to the upper end portion of the polishing unit 5 via the processing liquid supply path 72, and supplies the polishing liquid or the cleaning liquid to the polishing unit 5.

The turntable 8 is a disk-shaped table provided on the upper surface of the apparatus main body 2, is provided so as to be rotatable in the horizontal direction, and is rotationally driven at a predetermined timing. On the turntable 8, for example, four chuck tables 9 (9a to 9d) are arranged at equal intervals with a phase angle of, for example, 90 degrees. The chuck table 9 vacuum-sucks and holds the wafer 200 placed on the holding surface.

The chuck table 9 is rotationally driven by a motor around a rotation shaft (not shown) during grinding and polishing. Such a chuck table 9 moves and orbits in the order of the carry-in / carry-out area A, the rough grinding area B, the finish grinding area C, and the polishing area D by the rotation of the turntable 8.

The cassettes 11 and 12 are containers for a wafer 200 having a plurality of slots. One cassette 11 accommodates the wafer 200 before grinding or flattening, and the other cassette 12 accommodates the wafer 200 after polishing or flattening. The position table 13 is a table on which the wafer 200 taken out from the cassette 11 is temporarily placed and the center of the wafer 200 is aligned.

The transport arm 15 is configured to be movable in the horizontal direction (Y-axis direction), and transports the wafer 200 placed on the position table 13 before grinding and polishing or before flattening to the carry-in / carry-out area A. It is placed on the positioned chuck table 9a. Further, the transfer arm 15 conveys the polished or flattened wafer 200 placed on the chuck table 9a located in the carry-in / carry-out area A and places it on the spinner table of the spinner cleaning device 17.

The robot pick 16 includes a wafer holding portion (for example, a U-shaped hand) 16A, and the wafer holding portion 16A sucks and holds the back surface 201 of the wafer 200 and conveys the robot pick 16. Specifically, the robot pick 16 conveys the wafer 200 before grinding and polishing or flattening from the cassette 11 to the position table 13. Further, the wafer 200 after polishing or flattening is conveyed from the spinner cleaning device 17 to the cassette 12. The spinner cleaning device 17 cleans the polished wafer 200 to remove contamination such as grinding debris and polishing debris adhering to the ground and polished machined surface.

The control device 100 controls each of the above-mentioned components constituting the grinding and polishing device 1. That is, the control device 100 causes the grinding and polishing device 1 to perform the grinding and polishing operation and the flattening processing operation on the wafer 200. The control device 100 is a computer capable of executing a computer program.

On the other hand, the laser processing apparatus 101 confirms whether the back surface 201 is flat with respect to the wafer 200 whose back surface 201 is flattened by the grinding and polishing apparatus 1, and irradiates the back surface 201 with a laser beam to irradiate the wafer 200 with a laser beam. It forms a modified layer inside. The modified layer is a region where the density, refractive index, mechanical strength and other physical properties are different from those of the surrounding base material, for example, a melt processing region, a crack region, a dielectric breakdown region, and a refraction. The rate change region and the region where these regions are mixed.

As shown in FIG. 3, the laser processing apparatus 101 includes an apparatus main body 102, a chuck table 110, a laser irradiation unit 120, an X-axis moving unit (machining feed unit) 130, and a Y-axis moving unit 140 (indexing feed unit). ), A flattening confirmation unit 150, a transport unit 160, and a control device (control unit) 170.

The chuck table 110 holds the wafer 200 when performing laser machining on the wafer 200. In this configuration, the wafer 200 is held on the chuck table 110 in a form in which the protective member 205 is attached. The chuck table 110 has a holding surface 111 on which the wafer 200 is placed and sucked.

The laser irradiation unit 120 is fixed to the wall unit 103 of the apparatus main body 102, and irradiates the laser beam toward the wafer 200 held by the chuck table 110. The laser irradiation unit 120 includes an irradiation head 121 that irradiates a laser beam toward the wafer 200, an image pickup unit 122 that is arranged side by side with the irradiation head 121 in the X-axis direction (processing feed direction), these irradiation heads 121, and the irradiation head 121. It includes a main body unit 123 that holds the image pickup unit 122.

The X-axis moving unit 130 moves the chuck table 110 along the X-axis direction. The X-axis moving portion 130 includes a ball screw 131 extending in the X-axis direction, a guide rail 132 arranged in parallel with the ball screw 131, and a pulse motor 133 connected to one end of the ball screw 131 to rotate the ball screw 131. And a slide plate 134 having a nut (not shown) whose lower portion is in sliding contact with the guide rail 132 and screwed into the ball screw 131. The slide plate 134 moves in the X-axis direction guided by the guide rail 132 as the ball screw 131 rotates. Further, a rotation drive unit 135 having a pulse motor (not shown) inside is fixed to the slide plate 134, and the rotation drive unit 135 can rotate the chuck table 110 by a predetermined angle. In the present embodiment, for example, based on the image of the wafer 200 captured by the imaging unit 122, the chuck table 110 (the chuck table 110) so that the scheduled division lines 203 (FIG. 1) intersecting each other face each other in the X-axis direction and the Y-axis direction, respectively. Wafer 200) is rotated.

The Y-axis moving unit 140 moves the chuck table 110 along the Y-axis direction (indexing feed direction). The Y-axis moving portion 140 includes a ball screw 141 extending in the Y-axis direction, a guide rail 142 arranged in parallel with the ball screw 141, and a pulse motor 143 connected to one end of the ball screw 141 to rotate the ball screw 141. And a slide plate 144 having a nut (not shown) whose lower portion is in sliding contact with the guide rail 142 and screwed into the ball screw 141. The Y-axis moving portion 140 is placed on the apparatus main body 102, and the slide plate 144 is guided by the guide rail 142 and moves in the Y-axis direction as the ball screw 141 rotates. The X-axis moving portion 130 described above is arranged on the slide plate 144, and the X-axis moving portion 130 also moves in the same direction as the slide plate 144 moves in the Y-axis direction.

The flattening confirmation unit 150 confirms whether or not the back surface 201 of the wafer 200 is flattened by the grinding and polishing apparatus 1, and is arranged adjacent to the apparatus main body 102. As shown in FIG. 3, the flattening confirmation unit 150 includes a main body portion 151, a holding table 152 arranged on the upper surface of the main body portion 151, and a plurality of firsts arranged in an annular shape around the holding table 152. The lighting means 153 and the image pickup unit (imaging means) 154 arranged vertically above the holding table 152 are provided. As shown in FIG. 4, the holding table 152 includes a holding portion 152A formed of a porous ceramic having a diameter smaller than that of the wafer 200, and a suction path 152B communicating with the holding portion 152A, and the suction path 152B has a suction path 152B. , The suction source 155 is connected. Further, the holding table 152 includes an annular groove 152C formed around the holding portion 152A, and a plurality of first lighting means 153 are arranged in the annular groove 152C. The first lighting means 153 emits visible light toward the light transmitting member 152D that covers the annular groove 152C, and for example, an incandescent light bulb or an LED is used. The light transmitting member 152D is made of a transparent or translucent member capable of transmitting light, has an outer diameter larger than the diameter of the wafer 200, and has an inner diameter smaller than the diameter of the wafer 200. Is formed in. The outer peripheral edge of the wafer 200 is placed on the surface of the light transmitting member 152D. The surface of the holding portion 152A and the surface of the light transmitting member 152D are provided on the same plane. The first light 153A emitted from the first lighting means 153 travels outside the outer peripheral edge of the wafer 200 and reaches the image pickup unit 154.

The image pickup unit 154 is arranged vertically above the holding table 152 and takes an image of the wafer 200 held by the holding table 152. The image pickup unit 154 is a camera in which, for example, a CCD (Charge Coupled Device) image sensor that captures visible light is housed in the case 154A. The imaging unit 154 captures the back surface 201 of the wafer 200 to generate an captured image, and the captured image is transmitted to the control device 170 at any time. Further, a plurality of second lighting means 156 are arranged around the case 154A of the image pickup unit 154. The second lighting means 156 is oblique illumination that irradiates the back surface 201 of the wafer 200 held on the holding table 152 with the second light 156A, and for example, an incandescent light bulb or an LED is used. In the present embodiment, the second light 156A is set to have a smaller light amount (luminous flux) than the first light 153A.

The transport unit 160 transports the wafer 200 to and from the chuck table 110 and the holding table 152 of the flattening confirmation unit 150. The transport portion 160 is fixed to the wall portion 103 of the apparatus main body 102, and is connected to a ball screw 161 extending in the X-axis direction, a guide rail 162 arranged in parallel with the ball screw 161 and one end of the ball screw 161. It is provided with a pulse motor 163 for rotating the ball screw 161 and a slide plate 164 having a nut (not shown) internally provided with a nut (not shown) having one end slidingly contacting the guide rail 162 and screwing into the ball screw 161. In the transport unit 160, the slide plate 164 is guided by the guide rail 162 as the ball screw 161 rotates, and moves in the X-axis direction. A holding portion 165 that attracts and holds the wafer 200 is provided at the lower end portion of the slide plate 164.

The control device 170 includes an arithmetic processing unit 171 having a microprocessor such as a CPU (central processing unit), a storage unit 172 having a memory such as a ROM (read only memory) or a RAM (random access memory), and input / output. It has an interface device. The arithmetic processing unit 171 executes a computer program stored in the ROM on the RAM to generate a control signal for controlling the laser processing apparatus 101, and the generated control signal is passed through the input / output interface apparatus. It is output to each component of the laser processing apparatus 101.

Further, the storage unit 172 stores an image captured by the image pickup unit 154 of the flattening confirmation unit 150 as an image of the back surface 201 of the wafer 200 at any time, and the arithmetic processing unit 171 stores the image taken by the arithmetic processing unit 171 on the wafer 200 based on the image. It is determined whether or not the back surface 201 is flat. Further, a display unit 173 for displaying an captured image is connected to the control device 170.

Next, a method for processing a plate-shaped object according to the present embodiment will be described. FIG. 5 is a flowchart showing a procedure of a method for processing a plate-shaped object. First, the back surface 201 of the wafer 200 is flattened (step S1; flattening step). Specifically, with the protective member 205 attached to the surface 202 of the wafer 200, the protective member 205 is held on the chuck table 9 of the grinding and polishing apparatus 1 to rotate the turntable 8. Then, as shown in FIG. 2, the chuck table 9 is positioned in the rough grinding unit 3, and the back surface 201 of the wafer 200 is roughly ground by the rough grinding unit 3. When the rough grinding is completed, the turntable 8 is rotated to position the chuck table 9 in the finish grinding unit 4, and the finish grinding unit 4 finish grinds the back surface 201 of the wafer 200. When performing these rough grinding and finish grinding, for example, the chuck table 9 is rotated at 300 (rpm), while the wheels of the rough grinding unit 3 and the finish grinding unit 4 are rotated at 6000 (rpm). Further, when the finish grinding is completed, the turntable 8 is rotated and positioned in the polishing unit 5 as shown in FIG. 6, and the back surface 201 of the wafer 200 is flattened by the polishing unit 5. In this case, for example, the chuck table 9 is rotated at 300 (rpm), while the polishing pad 5b of the polishing unit 5 is rotated at 1500 (rpm). By executing this polishing for a predetermined time, the back surface 201 of the wafer 200 is flattened. In the present embodiment, when flattening, the back surface 201 of the wafer 200 is subjected to each step of rough grinding, finish grinding and polishing, but the present invention is not limited to this, and the steps of rough grinding and finish grinding are not limited to this. You may end with.

Next, it is confirmed whether or not the back surface 201 of the wafer 200 is flattened (step S2; flatness confirmation step). In the present embodiment, the wafer 200 is transferred from the grinding and polishing apparatus 1 to the laser processing apparatus 101 together with the protective member 205, and the wafer 200 is transferred to the holding table 152 of the flattening confirmation unit 150 of the laser processing apparatus 101 via the protective member 205. Is placed. Next, as shown in FIG. 4, the back surface 201 of the wafer 200 is imaged by the image pickup unit 154 while lighting the first lighting means 153 and the second lighting means 156, respectively.

The imaging unit 154 captures the back surface 201 of the wafer 200 to generate an captured image, and transmits the captured image to the control device 170. The transmitted captured image is stored in the storage unit 172, and the arithmetic processing unit 171 determines whether or not the back surface 201 of the wafer 200 is flat based on the captured image. Specifically, the arithmetic processing unit 171 detects the luminance distribution in the back surface 201 region of the wafer 200 in the captured image, and confirms that the luminance is not flat when there is a portion whose brightness is higher than a predetermined threshold value than the other portions. do. For example, in the captured image 300 of the example of FIG. 7, the luminance distribution in the back surface 201 region of the wafer 200 is almost uniform, and there is no portion having high luminance above a predetermined threshold value, so that the back surface 201 of the wafer 200 is Confirm that it is flat (step S2; OK). On the other hand, in the captured image 301 of the example of FIG. 8, the brightness of the peripheral portion 201A of the back surface 201 of the wafer 200 is higher than that of the central portion 201B (other portion). Therefore, when the brightness of the peripheral portion 201A is higher than that of the central portion 201B by a predetermined threshold value or more, it is confirmed that the back surface 201 of the wafer 200 is not flat (step S2; NG).

Of the first light 153A emitted from the first lighting means 153, the light emitted outside the outer peripheral edge of the wafer 200 reaches the image pickup unit 154, so that the outer peripheral edge of the wafer 200 becomes brighter and contours are formed. Make it stand out. Further, the back surface 201 of the wafer 200 is irradiated with the second light 156A emitted from the second lighting means 156. The second light 156A is oblique light that is weaker (less light) than the first light 153A. Therefore, when the back surface 201 of the wafer 200 is flat, the second light 156A is totally reflected by the back surface 201 and does not reach the image pickup unit 154. As a result, the captured image 300 having a substantially uniform luminance distribution in the back surface 201 region of the wafer 200 is generated. On the other hand, when the back surface 201 of the wafer 200 is not flat, the second light 156A is diffusely reflected by the back surface 201, so that a part of the diffusely reflected second light 156A reaches the image pickup unit 154. As a result, the captured image 301 in which the brightness distribution is uneven and the shadow is reflected is generated.

In the present embodiment, the control device 170 is connected to a display unit 173 that displays a captured image. Therefore, by displaying the captured images 300 and 301 on the display unit 173, the operator may see the captured images 300 and 301 displayed and confirm whether or not the back surface 201 of the wafer 200 is flat.

When it is confirmed that the back surface 201 of the wafer 200 is not flat in this flatness confirmation step (step S2; NG), the back surface 201 of the wafer 200 is ground or polished again to be flattened (step S3; again). Flattening step). In the present embodiment, the wafer 200 is transferred from the laser processing device 101 to the grinding and polishing device 1 again together with the protective member 205, and the wafer 200 is held by the chuck table 9 of the grinding and polishing device 1 via the protective member 205. Here, in the re-flattening step S3, the conditions of the grinding wheels 3b and 4b of the rough grinding unit 3 and the finish grinding unit 4 and the polishing pad 5b of the polishing unit 5 are adjusted by dressing, and then the flattening step S1 is performed. The back surface 201 of the wafer 200 is flattened again under the same processing conditions. In the previous flattening step S1, the back surface 201 of the wafer 200 is subjected to the rough grinding, finish grinding, and polishing steps. Therefore, as shown in FIG. 9, the chuck table 9 is used as the rough grinding unit 3 and the finish grinding unit. Rough grinding and finish grinding of the back surface 201 of the wafer 200 are carried out under the same grinding conditions. After that, as shown in FIG. 6, the chuck table 9 is positioned in the polishing unit 5, and the back surface 201 of the wafer 200 is polished under the same polishing conditions. When the previous flattening step S1 is completed in the rough grinding and finish grinding steps, the reflattening step S3 also carries out the rough grinding and finish grinding steps. After executing this re-flattening step, the process is returned to step S2 again, and it is confirmed whether or not the back surface 201 of the wafer 200 has been flattened.

On the other hand, when it is confirmed that the back surface 201 of the wafer 200 is flat (step S2; OK), the back surface 201 of the wafer 200 is irradiated with a laser beam to form a modified layer inside the wafer 200. (Step S4; Modified layer forming step). In the present embodiment, the wafer 200 is transferred together with the protective member 205 from the holding table 152 of the flattening confirmation unit 150 in the laser processing apparatus 101 onto the chuck table 110 by using the holding unit 165 of the transport unit 160. In this case, as shown in FIG. 10, the wafer 200 is held on the chuck table 110 via the protective member 205 with the back surface 201 side exposed upward.

Subsequently, the laser processing apparatus 101 performs alignment of the wafer 200 held on the chuck table 110. After that, while relatively moving the chuck table 110 and the laser irradiation unit 120, as shown in FIG. 10, the wavelength having transparency from the back surface 201 of the wafer 200 held by the chuck table 110 to the wafer 200 ( For example, a laser beam 125 having a wavelength of 1064 nm) is irradiated along the scheduled division line 203 (FIG. 1) by aligning the focusing point 125A inside the wafer 200. Then, the modified layer 206 along the scheduled division line 203 is formed inside the wafer 200. When the modified layer 206 is formed, laser processing is performed inside the wafer 200 under the condition that cracks 207 extending from the modified layer 206 in the thickness direction of the wafer 200 are generated. Therefore, inside the wafer 200, cracks 207 extending from the modified layer 206 in the thickness direction of the wafer 200 are generated. The crack 207 is formed, for example, to have a length similar to a predetermined thickness when the wafer 200 is thinned.

Generally, it is known that the laser processing apparatus 101 has a higher processing capacity per unit time than the grinding and polishing apparatus 1. In this configuration, the flattening confirmation unit 150 is provided in the laser processing apparatus 101, and the modified layer 206 can be formed by laser processing as it is on the wafer 200 for which the flatness has been confirmed, so that the productivity (throughput) can be improved. It can be prevented from being damaged.

Next, the back surface 201 of the wafer 200 is ground and polished to be thinned to a predetermined thickness (step S5; thinning step). In the present embodiment, the wafer 200 is transferred from the laser processing device 101 to the grinding and polishing device 1 again together with the protective member 205, and the wafer 200 is held by the chuck table 9 of the grinding and polishing device 1 via the protective member 205. Next, the wafer 200 held by the chuck table 9 is positioned in the rough grinding unit 3 by the rotation of the turntable 8, and as shown in FIG. 11, the rough grinding unit 3 is in a state where the chuck table 9 is rotated. The rough grinding wheel 3b of No. 1 is rotated and lowered, and the rotating rough grinding wheel 3b is brought into contact with the back surface 201 of the wafer 200 to perform rough grinding. When the rough grinding is completed, the turntable 8 is rotated to position the chuck table 9 in the finish grinding unit 4, and the finish grinding unit 4 finish grinds the back surface 201 of the wafer 200. Further, when the finish grinding is completed, the turntable 8 is rotated and positioned in the polishing unit 5, the back surface 201 of the wafer 200 is polished by the polishing unit 5, and finally the wafer 200 is thinned to a predetermined thickness d. The thickness of the wafer 200 is measured, for example, by using a contact-type thickness measuring gauge at a portion where the back surface 201 of the wafer 200 is exposed (a portion where the wafer 200 and the grinding wheel or polishing pad do not overlap). The thinning step S5 is not limited to being carried out by rough grinding, finish grinding and polishing, but may be carried out by rough grinding and finish grinding.

A crack 207 is formed in the wafer 200 from the modified layer 206 to at least the surface 202 of the wafer 200. Therefore, when the wafer 200 is thinned, the wafer 200 is divided along the scheduled division line 203 by these cracks 207, and a plurality of chips having a predetermined thickness d are formed. The formed plurality of chips are supported by the protective member 205. In the present embodiment, the wafer 200 is laser-machined to generate cracks 207 extending from the modified layer 206 in the thickness direction of the wafer 200, and when the wafer 200 is thinned, the wafer 200 is divided by these cracks 207. However, it is not limited to this. For example, the modified layer 206 is formed by laser processing on the wafer 200, and the grinding load when thinning the wafer 200 causes cracks starting from the modified layer 206 inside the wafer 200, and the planned division line 203. The wafer 200 may be divided along the above.

Next, another embodiment of the flatness confirmation step described above will be described. In the above-described embodiment, the arithmetic processing unit 171 detects the luminance distribution in the back surface 201 region of the wafer 200 in the captured image, and is not flat when there is a portion whose brightness is higher than the other portion by a predetermined threshold value or more. However, in this other embodiment, the arithmetic processing unit 171 confirms whether the back surface 201 of the wafer 200 is flat by the pattern matching process between the reference image and the captured image of the wafer 200 acquired in advance. ..

Specifically, a reference wafer (not shown) having a flat back surface is formed, and the back surface of the reference wafer is imaged in advance to acquire a reference image (not shown). This reference image is imaged under the same imaging conditions by using the imaging unit 154 of the flattening confirmation unit 150 described above, and is stored in the storage unit 172. The arithmetic processing unit 171 calculates the similarity (matching degree) between the reference image stored in the storage unit 172 and the captured images 300 and 301, and the similarity reaches a predetermined threshold value. For example, it is confirmed that the back surface 201 of the wafer 200 is flat, and if the predetermined threshold value is not reached, it is confirmed that the back surface 201 of the wafer 200 is not flat. For the similarity, for example, the correlation value of the normalized correlation method can be used, but the value calculated by the existing method may also be used. Further, the similarity between the reference image and the captured image may be calculated by comparing the entire wafer, but an image of an equivalent portion (for example, a partial region including the outer peripheral edge of the wafer 200) is cut out and these are cut out. It may be calculated by comparison.

As described above, in the processing method of the wafer 200 of the present embodiment, the flattening step S1 for flattening the back surface 201 of the wafer 200 by grinding or polishing, and the flattening step S1 are performed, and then the wafer 200 is processed from the surface 202 side. While irradiating the light 153A of No. 1 and irradiating the second light 156A, which has a smaller amount of light than the first light 153A, from the back surface 201 side of the wafer 200, the back surface 201 of the wafer 200 is imaged by the imaging unit 154 and captured. After performing the flatness confirmation step S2 for confirming whether the back surface 201 of the wafer 200 is flat based on the captured image and the flatness confirmation step S2, a laser having a wavelength that is transparent to the wafer 200. A modified layer forming step of irradiating the back surface 201 of the wafer 200 with the laser beam 125 to form the modified layer 206 inside the wafer 200 with the condensing point 125A of the beam 125 positioned inside the wafer 200. It is provided with S4. According to this configuration, the back surface 201 is flat by performing the flattening step S1 for flattening the back surface 201 of the wafer 200 and then performing the flatness confirmation step S2 for confirming whether the back surface 201 is flat. The modified layer forming step S4 can be carried out only on the wafer 200 confirmed to be. Therefore, uniform laser processing can be applied to the back surface 201 of the wafer 200, and the modified layer 206 can be formed at a uniform depth position inside the wafer 200. Further, in the flatness confirmation step S2, by irradiating the first light 153A from the front surface 202 side of the wafer 200, the back surface 201 of the wafer 200 is imaged blacker than the surroundings. Further, by irradiating the back surface 201 of the wafer 200 with the second light 156A having a light amount smaller than that of the first light 153A, the shadow of the captured image of the back surface 201 can be emphasized, so that the back surface 201 is flat. Can be easily confirmed.

According to the present embodiment, when it is confirmed in the flatness confirmation step S2 that the back surface 201 of the wafer 200 is not flat, the re-flattening step S3 for grinding or polishing the back surface 201 of the wafer 200 to flatten the wafer 200 is further provided. Since the back surface 201 of the wafer 200 can be flattened again by the re-flattening step S3, the modified layer 206 can be more reliably formed at a uniform depth position inside the wafer 200.

According to the present embodiment, after the modified layer forming step S4 is performed, the back surface 201 of the wafer 200 is ground to have a thinning step S5 for thinning to a predetermined thickness d, so that the wafer is ground to a predetermined thickness d. When a grinding load is applied to the modified layer 206, cracks originating from the modified layer 206 are generated inside the wafer 200, and the wafer 200 can be easily divided.

According to the present embodiment, the flattening step S1 is carried out by the grinding and polishing apparatus 1, and the flatness confirmation step S2 and the modified layer forming step S4 are carried out by the laser machining apparatus 101, so that the flattening step S1 is flattened by the laser machining apparatus 101. Since the modified layer 206 can be formed as it is on the confirmed wafer 200, it is possible to prevent the productivity from being impaired.

According to the present embodiment, the flatness confirmation step S2 confirms that the back surface 201 of the wafer 200 is not flat when there is a portion having a higher brightness than the others in the region of the back surface 201 of the wafer 200 in the captured image. Therefore, it is possible to accurately confirm whether or not the back surface 201 of the wafer 200 is flattened.

According to the present embodiment, in the flatness confirmation step S2, pattern matching processing is performed between the reference image of the wafer on which the back surface 201 is formed flat and the captured image, and the similarity of these images does not reach a predetermined threshold value. In order to confirm that the back surface 201 of the wafer 200 is not flat, it is possible to accurately confirm whether or not the back surface 201 of the wafer 200 is flattened by the pattern matching process between the reference image and the captured image.

The present invention is not limited to the above embodiment. That is, it can be variously modified and carried out within a range that does not deviate from the gist of the present invention. For example, in the present embodiment, when the back surface 201 of the wafer 200 is polished or flattened by using the polishing unit 5, a processing liquid is supplied, but the polishing or flattening is performed without using this processing liquid. Dry polishing can also be done.

Further, in the present embodiment, after the modified layer 206 is formed inside the wafer 200 (modified layer forming step S4), the back surface 201 of the wafer 200 is ground to a predetermined thickness d and divided into chips. However, it is not limited to this. For example, the back surface 201 of the wafer 200 thinned to a predetermined thickness d is flattened by grinding or polishing, and when the flattening of the back surface 201 is confirmed, the laser beam 125 is irradiated from the back surface 201 to inside the wafer 200. A modified layer 206 is formed along the planned division line 203. Then, instead of the protective member 205, an expand tape is attached to the surface 202 of the wafer 200, and the expand tape is expanded while holding the peripheral edge of the expand tape to be formed along the planned division line 203. It is also possible to apply tension to the modified layer 206 to divide the wafer 200 along the scheduled division line 203. In this case, the thinning step is executed before the flattening step, and a new division step is executed after the modified layer forming step.

Further, in the present embodiment, the laser processing apparatus 101 is provided with the flattening confirmation unit 150, but the chuck table 110 of the laser processing apparatus 101 has the same configuration as the holding table 152 of the flattening confirmation unit 150. At the same time, for example, a line sensor camera and a second lighting means may be arranged on the movement path in the X-axis direction of the chuck table 110, and the line sensor camera may be used to capture an image of the back surface 201 of the wafer 200.

1 Grinding and polishing equipment (flat processing equipment)
3 Rough grinding unit 3b Rough grinding wheel 4 Finish grinding unit 4b Finish grinding wheel 5 Polishing unit 5b Polishing pad 9, 9a, 9b, 9c, 9d Chuck table 100 Control device 101 Laser processing device 110 Chuck table 120 Laser irradiation unit 121 Irradiation head 125 Laser beam 125A Condensing point 150 Flattening confirmation unit 151 Main body 152 Holding table 153 First lighting means 154 Imaging unit 156 Second lighting means 170 Control device 171 Arithmetic processing unit 172 Storage unit 173 Display unit 200 Waha (board) State)
201 Back side 201A Peripheral part 201B Central part 202 Front side 203 Scheduled division line 204 Device 205 Protective member 206 Modified layer 207 Crack

Claims (6)

It is a processing method for plate-shaped objects that is laser-processed.
A flattening step of grinding or polishing the back surface of the plate-like object to flatten it,
After performing the flattening step, the first light is irradiated from the front surface side of the plate-shaped object, and the second light having a light amount smaller than that of the first light is irradiated from the back surface side of the plate-shaped object. At the same time, a flatness confirmation step in which the back surface of the plate-shaped object is imaged by an imaging means to form an captured image, and whether the back surface of the plate-shaped object is flat based on the captured image,
After performing the flatness confirmation step, with respect to the back surface of the plate-shaped object in a state where the focusing point of the laser beam having a wavelength that is transparent to the plate-shaped object is positioned inside the plate-shaped object. A modified layer forming step of irradiating the laser beam to form a modified layer inside the plate-like object,
A method for processing plate-shaped objects. The plate according to claim 1, further comprising a re-flattening step of grinding or polishing the back surface of the plate-shaped object to flatten it when it is confirmed in the flatness confirmation step that the back surface of the plate-shaped object is not flat. Processing method of the state. The method for processing a plate-shaped material according to claim 1 or 2, further comprising a thinning step of grinding the back surface of the plate-shaped material to thin it to a predetermined thickness after performing the modified layer forming step. The flattening step is carried out in a flattening machine and
The method for processing a plate-like material according to any one of claims 1 to 3, wherein the flatness confirmation step and the modified layer forming step are carried out by a laser processing apparatus. Claims 1 to confirm that the back surface of the plate-shaped object is not flat when there is a portion having a higher brightness than others in the back surface region of the plate-shaped object in the captured image. The method for processing a plate-shaped object according to any one of 4. The flatness confirmation step performs pattern matching processing between a reference image of a plate-like object having a flat back surface and the captured image, and if the similarity of these images does not reach a predetermined threshold value, the plate The method for processing a plate-shaped object according to any one of claims 1 to 4, wherein the back surface of the object is confirmed to be not flat.

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