Method for processing a wafer on which a semiconductor chip is formed, and processing apparatus used therefor.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOKYO SEIMITSU CO LTD
- Filing Date
- 2024-12-09
- Publication Date
- 2026-05-26
Smart Images
Figure 0007866028000001 
Figure 0007866028000002 
Figure 0007866028000003
Abstract
Description
[Technical Field]
[0001] The present invention relates to a method for processing a wafer on which a large number of semiconductor chips are formed on its surface, and to a processing apparatus used therefor, and more particularly to a method for processing a wafer on which semiconductor chips are formed, and a processing apparatus used therefor, which is suitable for wafer thinning or terrace processing, and which utilizes laser irradiation. [Background technology]
[0002] In wafers on which numerous semiconductor chips are formed, a method is used in which a substrate, such as a silicon wafer, is thinned by grinding it from the back side, and then divided into individual semiconductor chips. To prevent cracks and scratches that occur at the periphery of the wafer from propagating to the center of the wafer and reducing the yield of semiconductor chip formation, a terrace grinding process, in which only the periphery is ground to a predetermined thickness, or a process to shape the periphery is performed prior to thinning the wafer.
[0003] Conventional techniques for processing the peripheral edges of wafers are disclosed in Patent Documents 1 and 2. In Patent Document 1, a dicing device is attached to a chuck table to process wafers in order to form small-diameter wafers from large-diameter wafers without using a dedicated processing device, or to create wafers with an easy-to-handle shape from cracked wafers without using a laser processing device. Furthermore, by using not only the rotation of the chuck table, but also the movement of the chuck table in the X-axis direction and the movement of the blade in the Y-axis direction, the wafer is cut into an arbitrary curved shape to obtain a wafer shape that is easy to handle.
[0004] Furthermore, Patent Document 2 describes a wafer edge trimming process in which uneven portions of a wafer with non-uniform thickness are recognized and reprocessed, and processed to a desired cutting depth. Specifically, a rotating cutting blade is lowered from above the wafer, and the wafer is rotated while cutting the outer edge of the wafer to a predetermined depth. At this time, the cutting marks formed on the outer edge are imaged, the depth of the cutting marks for each rotation angle of the wafer is stored, and it is determined whether or not the cutting marks have reached a predetermined depth for each rotation angle, and the portions that have not reached the predetermined depth are cut again.
[0005] Patent Document 3 describes a method of thinning a wafer by grinding the back surface of a wafer on which a semiconductor chip is formed. In this wafer thinning method, to prevent cracks and chips from occurring around the periphery of the semiconductor substrate even when back surface grinding results in a wafer thickness of several tens of micrometers or less, the beveled portion of the wafer is cut to a depth slightly deeper than the target wafer thickness for back surface grinding. Then, a semiconductor element protective tape is attached to the flat surface, cut into a circular shape to match the shape of the flat surface with a cutting tool, and then the back surface of the wafer is ground with a grinding wheel for back surface grinding. This prevents cracks and chips around the wafer caused by the protective tape getting caught or by the remaining knife-edge-shaped bevel. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-54461 [Patent Document 2] Japanese Patent Publication No. 2013-149822 [Patent Document 3] Japanese Patent Publication No. 2000-173961 [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] In the wafer processing apparatus described in Patent Document 1 above, a wafer with chips or other defects is cut off with a dicing blade to produce a smaller diameter wafer. However, the apparatus described in this publication only cuts with a dicing blade and does not take into account the possibility of new cracks developing during processing due to wear of the dicing blade and propagating towards the center. In other words, in wafers where the processing area is crystalline, there are many places where the processing orientation and the crystal orientation differ, so if it is processed mechanically with a dicing blade, there is a risk that micro-cracks such as chipping will occur in unexpected directions.
[0008] The wafer processing method described in Patent Document 2 involves cutting the same location multiple times with a cutting blade in accordance with changes in wafer thickness. However, even in the method described in this publication, since the wafer is processed mechanically with a cutting blade, there is a risk that microscopic cracks such as chipping may occur in unexpected directions due to differences between the crystal orientation and the processing direction.
[0009] Furthermore, Patent Document 3 describes a method of back-surface grinding of a wafer in which protective tape is applied and then the peripheral edge is cut with a cutting tool. However, even in the method described in this publication, a wafer with a crystalline orientation is simply being cut with a cutting tool, so if the processing direction and the crystal orientation of the wafer differ, and tool wear is added to this, there is a risk that the wafer may chip or develop microcracks in unexpected directions.
[0010] The present invention has been made in view of the shortcomings of the prior art described above, and its purpose is to process the peripheral edge of a wafer with a semiconductor chip formed on it to a desired shape with high precision, even when wear of tools such as grinding wheels and cutting tools is expected to occur when cutting or grinding the peripheral edge of the wafer on which the semiconductor chip is formed, by making the cutting depth uniform or preventing the occurrence of chipping. [Means for solving the problem]
[0011] In a processing method for processing the peripheral portion of a semiconductor wafer having a circuit formed on its surface, the features of the present invention for achieving the above object include: a step of bringing a processing tool rotating at high speed into contact with the semiconductor wafer rotating at low speed to cut or grind the peripheral portion of the semiconductor wafer; and a step of irradiating a laser beam in the vicinity of the position where the processing tool contacts the semiconductor wafer rotating at low speed, at a processing planned position before processing the semiconductor wafer, to melt and amorphize the surface of the processing planned position. The processing planned position is on the rear side in the rotation direction of the semiconductor wafer from the position where the processing tool is disposed, and is a position having a surface that the processing tool has not yet contacted. The control device controls to cut or grind only the processing planned position that has undergone the laser beam irradiation step.
[0012] And in this feature, instead of the processing planned position on the rear side in the rotation direction of the semiconductor wafer from the position where the processing tool is disposed, a position after processing the semiconductor wafer on the front side in the rotation direction of the semiconductor wafer, where the frictional heat generated during the processing is substantially not completely dissipated, is set as the processing planned position. In the first pass for cutting or grinding the processing planned position, it is preferable to irradiate the laser beam to the processing planned position in advance.
[0013] Further, when the semiconductor wafer is composed of at least any one of a Si substrate, a sapphire substrate, a GaN substrate, a SiC substrate, a lithium tantalate substrate, and a lithium niobate substrate, it is preferable that the laser beam is a pulsed laser beam with a long wavelength of 532 nm or more. When the semiconductor wafer is composed of a gallium oxide substrate, it is desirable that the laser beam is an ultraviolet excimer laser beam.
[0014] Another feature of the present invention that achieves the above objective is a processing apparatus for processing a semiconductor wafer on which a large number of semiconductor chips are formed on the surface, comprising: a processing tool that cuts or grinds the peripheral edge of the semiconductor wafer and rotates at high speed; a rotating bed that rotates the semiconductor wafer at low speed; and a control device that controls the rotation of the processing tool and the rotation of the semiconductor wafer, wherein when the peripheral edge of the wafer is processed by the processing tool, a laser beam irradiation device is provided that irradiates the processed surface of the wafer with laser light to melt and amorphous the surface near the position where the processing tool contacts the semiconductor wafer and before the processing tool cuts or grinds, and the control device controls the laser beam irradiation in advance at the processing position that is to be cut or ground by the processing tool.
[0015] In this feature, the laser irradiation device preferably emits pulsed laser light, the laser irradiation device preferably is an ultraviolet excimer laser when the semiconductor wafer is made of a gallium oxide substrate, and the laser irradiation device preferably is capable of emitting long-wavelength pulsed laser light with a wavelength of 532 nm or more when the semiconductor wafer is made of at least one of a Si substrate, a sapphire substrate, a GaN substrate, a SiC substrate, a lithium tantalate substrate, or a lithium niobate substrate. [Effects of the Invention]
[0016] According to the present invention, when cutting or grinding the peripheral edge of a wafer on which a semiconductor chip is formed, the cutting or grinding area is modified by amorphization using laser irradiation before processing. As a result, the cutting or grinding can be performed at the desired processing location, the cutting depth can be made uniform, and chipping can be prevented. This makes it possible to process the peripheral edge of the wafer into the desired shape with high precision. [Brief explanation of the drawing]
[0017] [Figure 1] This is a front view of one embodiment of a wafer processing apparatus for which a semiconductor chip is formed according to the present invention. [Figure 2]This is a top view of the laser processing apparatus, illustrating the arrangement of the laser processing apparatus shown in Figure 1. [Figure 3] This diagram illustrates the procedure of one embodiment of wafer processing according to the present invention. [Figure 4] This is a front view of another embodiment of a wafer processing apparatus for which a semiconductor chip is formed according to the present invention. [Figure 5] Figure 4 is a top view of the laser processing apparatus, illustrating its arrangement. [Figure 6] This figure illustrates the procedure for another embodiment of wafer processing according to the present invention. [Modes for carrying out the invention]
[0018] The following describes a wafer processing apparatus and processing method for wafers on which semiconductor chips are formed according to the present invention, with reference to the drawings. Figure 1 is a front view of one embodiment of a wafer processing apparatus 300, including a wafer chamfering apparatus 100 used for terrace processing of a wafer W on which semiconductor chips are formed. The wafer chamfering apparatus 100 is an apparatus for processing the peripheral edges of wafers W and various brittle plate-like bodies, and can process, for example, Si wafers and compound semiconductors such as sapphire, SiC, GaN, and LT. In the following description of this embodiment, a silicon wafer W will be used as an example of a workpiece processed by the wafer chamfering apparatus 100, but wafers, plate-like bodies, and bonded wafers made of other materials can be processed in the same manner.
[0019] The wafer chamfering apparatus 100 comprises a wafer feeding unit 102 and a grinding unit 104. The wafer feeding unit 102 includes a horizontally positioned base plate 106, on which a pair of Y-axis guide rails 108 are arranged parallel to each other at intervals, and a Y-axis linear guide 110 is placed on each Y-axis guide rail. A Y-axis table 112 is placed on the Y-axis linear guide 110. The Y-axis table 112 moves linearly in the Y direction along the Y-axis guide rails 108 by a Y-axis ball screw 116 driven by a Y-axis motor 114.
[0020] On the Y-axis table 112, a pair of X-axis guide rails 120 are arranged parallel to each other at a distance, perpendicular to the Y-axis guide rail 108, and an X-axis linear guide 122 is placed on each X-axis guide rail 120. An X-axis table 124 is placed on the X-axis linear guide 122. The X-axis table 124 moves linearly in the X direction along the X-axis guide rail 120 by an X-axis ball screw 128 driven by an X-axis motor 126.
[0021] A Z-axis base 130 is mounted perpendicular to the X-axis table 124 on the X-axis table 124, and a Z-axis guide rail 132 is mounted on the Z-axis base 130. A Z-axis linear guide 134 is attached to the Z-axis guide rail 132, and a Z-axis table 136 is mounted on the side of the Z-axis linear guide 134 opposite the Z-axis guide rail so as to be movable in the vertical direction. The Z-axis table 136 is movable in the vertical direction by a Z-axis ball screw 140 driven by a Z-axis motor 138. That is, when the Z-axis motor 138 is driven, the Z-axis ball screw 140 rotates, and the Z-axis table 136 moves up and down along the Z-axis guide rail 132.
[0022] A θ-axis motor 150 is mounted on the Z-axis table 136 to rotate a suction table 160, which serves as a rotating bed used to hold the workpiece. The θ-axis motor 150 is connected to a θ-axis shaft 152, and the suction table 160 is horizontally connected to the upper end of the θ-axis shaft 152. The suction table 160 is a so-called vacuum chuck, and a wafer W, which is the workpiece, is placed on it by vacuum suction, and the wafer W is terrace-machined in that state. Here, the θ-axis is a rotation axis that is parallel to the Z-axis and oriented in the vertical direction.
[0023] In the wafer feeding unit 102 configured in this way, the control device 252 drives the Y-axis motor 114, causing the suction table 160 to move in the Y-direction, which is the left-right direction in Figure 1. Similarly, the control device 252 drives the X-axis motor 126, causing the suction table 160 to move in the X-direction, which is the front-back direction of the paper in Figure 1. In addition, the control device 252 drives the θ-axis motor 150, causing the suction table 160 to rotate at a relatively low speed around the θ-axis, which is parallel to the Z-axis.
[0024] On the other hand, in the grinding unit 104 to which the grinding wheel 180 is attached, a frame 174 is arranged on the base plate 106. An outer perimeter motor 176 is provided on the frame 174, and the outer perimeter motor 176 is connected to a spindle 178. The central axis CH of the spindle 178 is parallel to the Z-axis. The grinding wheel 180 is detachably attached to the lower end of the spindle 178. The spindle 178 is rotated at a relatively high speed by the outer perimeter motor 176. A nozzle 192 for discharging coolant 190 is positioned near the grinding wheel 180, and the coolant 190 is sprayed onto the grinding position where the grinding wheel 180 contacts the workpiece.
[0025] The terrace processing apparatus configured as described above employs the same configuration as the conventional wafer chamfering apparatus 100. However, the present invention is characterized by the use of laser processing in combination with the conventional mechanical grinding process described above. Therefore, a laser processing apparatus 200 is added to the wafer chamfering apparatus 100. The wafer chamfering apparatus 100 equipped with this laser processing apparatus 200 will be referred to as the wafer processing apparatus 300 below.
[0026] In the wafer processing apparatus 300, the laser processing apparatus 200 is positioned near the wafer chamfering apparatus 100. This will be explained using Figure 2. Figure 2 is a top view of the wafer processing apparatus 300, including the main part of the laser processing apparatus 200. In Figure 1, for ease of understanding, the laser processing apparatus 200 is positioned on the opposite side of the grinding unit 104, with the wafer feeding unit 102 in between. However, as shown in Figure 2, the laser processing apparatus 200 is positioned such that the irradiation position is near the position where the grinding wheel 180 contacts the wafer at point W.
[0027] The laser processing apparatus 200 includes a laser light source 210 and a beam splitter 212 that splits the light emitted from the laser light source 210 into two beams. The first beam 220, which is one of the beams split by the beam splitter 212, is positioned in the Z-axis direction via a galvanometer mirror 222 and an f-θ lens 224 to reach the irradiation position P I The light is irradiated onto the end face 242. The other light, the second spectral portion 230, is similarly positioned radially via the galvanometer mirror 232 and the f-θ lens 234 to irradiate position P I The irradiation is directed onto the terrace processing surface 244, which is the position of the wafer W before grinding at the irradiation position P. I These two spectral beams then irradiate surfaces 242 and 244 respectively, heating the wafer W before grinding.
[0028] Depending on the form of the terrace processing, the vertically extending end face 242 formed by the terrace processing may be a conical surface rather than a cylindrical surface. In that case, the first spectral beam 220 is incident on the end face 242 at an angle. Furthermore, if the frictional heat generated during grinding is used in conjunction to further modify the ground surface in the next grinding process, the irradiation position P of the laser beam is used. I This refers to the position before the cooling effect of the coolant 190 progresses, that is, the position immediately after grinding (in the diagram, the wafer rotation direction is to the right, so grinding position P). g It is also possible to place it to the right of that position.
[0029] Each optical component 212, 222, 224, 232, and 234 of the laser processing apparatus 200 is housed within a housing or holder 254, and in this embodiment, these components are positioned on the upper surface of the control device 252 of the wafer chamfering apparatus 100. In other words, the control device 252 also functions as a stand, making effective use of the processing space. The control device 250 of the laser processing apparatus 200 is incorporated above the control device 252 of the wafer chamfering apparatus 100, and controls the emission of laser light from the laser light source 210, as well as the irradiation position and rotation of the galvanometer mirrors 222 and 232.
[0030] The processing method of the present invention, which uses the wafer processing apparatus 300 configured in this way to perform terrace processing on a wafer W, will be explained with reference to Figures 1 to 3. Here, Figure 3 is a diagram showing the terrace processing of the wafer W as a partial front view of the wafer. Figure 3(a) shows the state before terrace processing, Figure 3(b) shows the laser processing state before grinding, and Figure 3(c) shows the state during grinding. Figure 3(d) shows the state after terrace processing is completed. In terrace processing using the wafer chamfering apparatus 100, first the wafer W is placed on the suction table 160 and vacuum-adsorbed. At the same time, the Z-axis motor 138 is driven to adjust the height of the suction table 160 so that the height of the wafer W matches the processing position of the grinding wheel 180, and the X-axis motor 126 is driven to align the θ axis, which is the rotation axis of the wafer W, with the X-axis position of the central axis CH of the grinding wheel 180. At this time, the Y-axis motor 114 is either not driven, or if the wafer W is too close to the grinding wheel 180, it is driven to retract to the retracted position.
[0031] Next, the control device 252 controls the rotation of the outer periphery motor 176 at high speed and the θ-axis motor 150 at low speed so that they move in the same direction. For example, the motors 176 and 150 are controlled to rotate at speeds such that the rotation speed of the grinding wheel 180 attached to the spindle 178 connected to the outer periphery motor 176 is 3000 rpm, and the outer periphery speed of the wafer W is 5 mm / s.
[0032] In this state, the control device 252 drives the Y-axis motor 114 to bring the wafer W closer to the grinding wheel 180 in the Y-axis direction (see Figure 3(a)). When the wafer W approaches the vicinity of the point where it will contact the grinding wheel 180, the rotational speed of the Y-axis motor 114 is reduced, slowing down the feed rate of the wafer W in the Y-axis direction, and bringing the grinding wheel 180 into contact with the wafer W. Subsequently, the feed amount of the wafer W in the Y-axis direction is determined so that it corresponds to the radial grinding width per grinding stroke, and grinding is started over the entire circumference of the wafer W under the determined feed amount (see Figure 3(c)). Once grinding has started, coolant 190 is ejected from the nozzle (cooling liquid supply means) 192 toward the grinding position, removing grinding debris and wear particles from the grinding wheel from the grinding position, and cooling the grinding area.
[0033] The radius grinding width that can be achieved in one grinding pass (per pass) is the desired terrace machining area P. T If the width is greater than or equal to the desired terrace processing area P, once grinding is completed around the entire circumference, the Y-axis motor 114 is driven to retract the wafer W from the grinding position. T If the width is smaller than the specified width, the above process is repeated multiple times (multiple passes). In addition, when performing terrace processing on a wafer in general, multiple grinding passes are required in the thickness direction of the wafer, i.e., in the Z direction. Therefore, the Z-axis motor is driven to move the wafer W in the Z direction by a predetermined Z-axis feed amount to change the grinding height position. Since the height position of the wafer W has changed downward, the Y-axis motor 114 is driven again to contact the wafer W, and grinding is performed with a predetermined Y-axis feed amount to a predetermined radial width. This is repeated until terrace processing is performed on the wafer W to a predetermined thickness (see Figure 3(d)), and then the processing of the next wafer W is moved on. Note that Figure 3(b) shows the laser processing state which will be described in detail below, and the circumferential position of the wafer feed unit 102 is shown differently from the other figures (Figures 3(a), (b), (d)). In the terrace processing described above, the control device 252 controls the grinding speed of the grinding wheel 180, the rotation speed of the wafer W, and the positions of the grinding wheel 180 and the wafer W.
[0034] By the way, when the grinding wheel 180 is brought into contact with the wafer W, friction occurs due to the difference in rotational speed between them, and abrasive grains of high hardness such as diamond scrape off the surface of the wafer W. Therefore, a large frictional force is instantaneously applied to the surface of the wafer W, and in a state where the abrasive grains are not stably held on the grinding wheel 180, that is, in a state where the grinding wheel 180 is worn, the wafer W may be damaged unexpectedly, and there is a risk of generating unfavorable defects.
[0035] Therefore, a portion (processing planned position) P where the grinding wheel 180 is planned to grind T is previously destroyed by laser light to reduce the grinding load by the abrasive grains or to serve as a guide for grinding. That is, by microscopically determining in advance with laser light the location on the wafer W where the abrasive grains will remove, when the abrasive grains pass through that portion, the wafer is peeled off only from the portion microscopically destroyed by the laser light and made amorphous, preventing unintended peeling. This destruction by laser light is microscopic, unlike the destruction by abrasive grains, and since it temporarily melts the wafer W into a liquid phase or a state close thereto and makes it amorphous, the shear stress by the abrasive grains is significantly reduced.
[0036] The state of pre-modifying the wafer W by such laser light is shown in Fig. 3(b). Since it is pre-modification of the wafer W, it is carried out before the grinding process. Therefore, the irradiation position P of the laser light is set at a position behind the wafer W in the rotational direction with respect to the grinding position P g (in the figure, since the wafer W rotates clockwise, to the left of the grinding position P g ). Incidentally, as described above, if the thickness direction position of the wafer W is further changed and grinding is performed after the current grinding process, the laser irradiation position P for pre-modification may be set at the position after the grinding process, that is, at the front position in the rotational direction of the wafer W I . In this case, if the laser irradiation position P I is set at the position immediately after the grinding process where the frictional heat generated by the grinding process can be utilized, the surface of the wafer W can be pre-modified and made amorphous including the frictional heat during grinding before the frictional heat is dissipated by the coolant 190, and the wafer can be effectively pre-modified. I
[0037] The laser processing using the laser processing apparatus 200 shown in this embodiment will be further described below. The laser light is pulsed laser light, and its wavelength is preferably changed according to the material of the wafer W which is the workpiece. When the workpiece is a wafer or substrate made of Si (silicon), sapphire, GaN (gallium nitride), SiC (silicon carbide), LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), etc., it is preferable to use a nanosecond pulsed laser with a relatively long wavelength of 532 nm or more in terms of heat absorption on the terrace processing surface.
[0038] In the case of GaN or SiC substrates or wafers, a highly laser-absorbent fluid material may be applied to the surface of the wafer or substrate before irradiating it with laser light. In this case, a large proportion of the laser light is absorbed by the fluid material before reaching the interior of the wafer W, so the heat generated by the laser light is concentrated at the interface of the wafer W, i.e., the terrace processing surfaces 242 and 244, allowing the wafer W to be melted more effectively and the terrace processing surfaces 242 and 244 to be planarized. On the other hand, in the case of Ga2O3 (gallium oxide), pre-modification of the wafer W is possible by using a short-wavelength ultraviolet excimer laser, for example, with a wavelength of 250-260 nm.
[0039] In this embodiment, the control device 252 controls the process by irradiating the wafer W immediately before grinding with laser light according to a pre-stored program to melt and modify the processing surface before performing terrace processing on the wafer W. This makes it possible to pre-determine the area in which the abrasive grains of the grinding wheel 180 will detach from the wafer W. Therefore, it is possible to prevent unintended parts of the wafer W from being peeled off by the abrasive grains, and to prevent defects such as cracks and chipping on the processed surface. This prevents cracks originating in the terrace area from propagating to the chip area formed on the semiconductor wafer, thereby improving the yield of semiconductor manufacturing.
[0040] Next, another embodiment of the wafer processing on which the semiconductor chip according to the present invention is formed will be described with reference to Figures 4 to 6. The processing in this embodiment is a trimming process, which involves cutting the peripheral edge of the wafer W on which the semiconductor chip is formed. For the trimming process, the tool used is a disc-shaped dicing blade 182. Figure 4 is a front view of the wafer processing apparatus 301 corresponding to Figure 1, and Figure 5 is a top view of the laser processing apparatus 201 portion showing the arrangement of the laser processing apparatus 201. Figure 6 is a diagram illustrating the trimming process, showing the relative relationship between the wafer, the dicing blade 182, and the laser processing apparatus 201.
[0041] Referring to the wafer processing apparatus 301 shown in Figure 4, the wafer chamfering apparatus 100 in Figure 1 was equipped with a grinding unit 104, but the wafer processing apparatus 301 in this embodiment is equipped with a dicing apparatus 101 that has a cutting unit 105 instead. The cutting unit 105 of the dicing apparatus 101 has a configuration almost the same as the grinding unit 104 in Figure 1, but differs from the grinding unit 104 in that the spindle 178 is formed on the horizontal axis and a disc-shaped cutter, the dicing blade 182, is attached to the tip of the spindle 178. In the cutting unit 105, the dicing blade 182 is lowered while rotating at high speed and brought into contact with the wafer W placed on the suction table 160 to cut the peripheral edge of the wafer into a predetermined shape.
[0042] Furthermore, the laser processing apparatus 201 is also simplified compared to the case in Figure 1. The emitted light 216 from the laser light source 210 is redirected by the galvanometer mirror 232 and incident on the f-θ lens 234. The position is then adjusted by the galvanometer mirror 232 and the f-θ lens 234 to form the edge trimming portion or trimming processing portion P of the wafer W. TR It is irradiated (see Figure 6(a)).
[0043] As shown in Figure 5, in this embodiment as well, the laser processing apparatus 201 has a dicing section (trimming section) P using a dicing blade 182. TRIt is positioned in the vicinity of and immediately before the position. That is, since the wafer W is rotating clockwise, the trimming processing part P TR The irradiation position P of the laser processing device 201 is to the left of this position. I It is set.
[0044] The control device 252, according to a pre-stored program, controls the laser processing device 201 to perform trimming on the planned processing location P before dicing the wafer W. TR The process is controlled to melt and amorphize the wafer. As a result, the wafer W is microscopically destroyed, and dicing proceeds from the destroyed areas. This prevents unintended delamination or cracks from propagating to the center of the wafer W.
[0045] Figure 5 shows the laser irradiation position P. I and trimming processing part P TR Since a nozzle 192 for the coolant 190 is positioned between them, the wafer W is cooled after laser irradiation but before dicing. The cooling heat from the coolant 190 is applied to the laser irradiation position P I When transmitted to this position, the efficiency of laser irradiation decreases. If this decrease in efficiency is undesirable, the irradiation position P of the laser processing device 201 can be changed. I trimming processing part P TR It can also be positioned behind it, that is, on the right side in Figure 5.
[0046] In this case, there is an advantage in that the frictional heat generated during dicing, which has not yet been sufficiently dissipated by the coolant 190, can be utilized along with the heat generated by the laser light. However, this method is only effective when dicing is performed multiple times (multiple passes) in the thickness direction of the wafer W, and even in that case, the benefit of pre-modification of the wafer W by laser irradiation cannot be obtained in the first dicing (first processing pass). To avoid this, in the first pass, the wafer is rotated while only laser light is irradiated without dicing, and from the next pass onwards, the control device 252 controls the wafer W to be diced as usual before laser processing is performed.
[0047] Even in this case, the initial wafer modification using laser light cannot utilize the frictional heat generated during dicing, so the laser beam irradiation position P is located behind the dicing area. I When setting this, only the first pass should be on the trimming line L on the wafer W. TR It is desirable to emit a higher-power laser beam along this line.
[0048] Figure 6 shows a wafer processing apparatus 301 equipped with a dicing apparatus 101 and a laser processing apparatus 201. The dicing blade 182 is rotated at high speed, for example, 500 rpm in the R direction (see Figure 5), and the wafer W is rotated at a low speed of 5 mm / s at the outer circumference. The laser is irradiated onto the wafer W at position P. I Irradiate with (Figure 6(a)). Irradiation position P I The trimming line L is used to trim the wafer W using the dicing blade 182. TR It is set to the top. And the irradiation position P I This position is set behind the wafer W in the rotational direction of the wafer W, relative to the dicing position 196 where the dicing blade 182 contacts the wafer W.
[0049] Irradiation position P of the same wafer W I At the dicing position 196, which is further back in the rotational direction of the wafer W, the irradiation position P I The wafer W, which has been modified by laser light, is then cut using the dicing blade 182 (Figure 6(b)). The processes in Figures 6(a) and 6(b) are repeated for the desired number of processing passes. Finally, the wafer W is trimmed to the desired shape, and the trimming process is completed (Figure 6(c)).
[0050] In this embodiment as well, the wafer is irradiated with laser light immediately before dicing to temporarily melt and modify the processing surface into an amorphous state. This makes it possible to microscopically distinguish between the areas to be cut by the dicing blade and the areas that will not be cut. Therefore, it is possible to prevent unintended parts of the wafer W from being cut microscopically, and to prevent defects such as cracks and chipping on the processed surface. This prevents cracks caused by edge trimming from propagating to chips formed on the semiconductor wafer, thereby improving the yield of semiconductor manufacturing.
[0051] Furthermore, if the laser processing described in each of the above embodiments is performed at least before the final step in the terrace processing or trimming process, or before the finishing process, the wafer can be flattened and provided free from cracks and chipping in the next process, such as the thinning process. Therefore, laser processing can be omitted when it is desirable to eliminate the complexity of the processing or when there is little risk of cracks or chipping occurring during intermediate processing. However, since it is difficult to predict the timing of wear on the grinding wheel or dicing blade, it is desirable to use the laser processing shown in each of the above embodiments before each grinding or cutting pass. [Explanation of symbols]
[0052] 100...Wafer chamfering device, 101...Dicing device, 102...Wafer feeding unit, 104...Grinding unit, 105...Cutting unit, 106...Base plate, 108...Y-axis guide rail, 110...Y-axis linear guide, 112...Y-axis table, 114...Y-axis motor, 116...Y-axis ball screw, 120...X-axis guide rail, 122...X-axis linear guide, 124...X-axis table, 126...X-axis motor, 128...X-axis ball screw, 130...Z-axis base, 132...Z-axis guide rail, 134...Z-axis linear guide, 136...Z-axis table, 138...Z-axis motor, 140...Z-axis ball screw, 150...θ-axis motor, 152...θ-axis shaft, 160...Suction table (rotating bed), 174...Stand, 176... Outer circumference motor, 178... Spindle, 180... Grinding wheel (processing tool), 182... Dicing blade (processing tool), 190... Coolant, 192... Coolant supply means (nozzle), 196... Dicing processing position, 200, 201... Laser processing device, 210... Laser light source, 212... Beam splitter, 216... Emitted light, 220... (First) Spectroscopy, 222... Galvano mirror, 224... f-θ lens, 230... (Second) Spectroscopy, 232... Galvano mirror, 234... f-θ lens, 242... (Terrace processing) end face, 244... Terrace processing surface, 250... Control device (for laser processing device), 252... Control device, 254... Holder (housing), 300, 301... Wafer processing device, CH... Central axis, L TR ...trimming line, P I ...(Laser) irradiation position, P g ...grinding position, P T ...Terrace processing section (planned processing location), P TR ...Trimming section (dicing section, planned processing position), R...Rotation direction, W...Wafer
Claims
1. A semiconductor wafer processing method comprising rotating a semiconductor wafer on which a circuit is formed on its surface, and applying a rotating processing tool to the peripheral edge and making multiple cuts in the thickness direction until a target thickness is achieved or until the peripheral edge can be cut, A method for processing a semiconductor wafer, comprising irradiating the semiconductor wafer with laser light of a wavelength corresponding to the material of the semiconductor wafer along the circumferential direction, and repeating the process of amorphousization at a predetermined thickness direction position and processing the amorphous portion of the semiconductor wafer with the processing tool until a target thickness is reached or until the wafer can be cut.
2. A semiconductor wafer processing method comprising rotating a semiconductor wafer on which a circuit is formed on its surface, and processing the peripheral edge by bringing a rotating processing tool into contact with the peripheral edge, At a position in the rotational direction corresponding to the processing position by the aforementioned processing tool, laser light of a wavelength corresponding to the material of the semiconductor wafer is irradiated to make it amorphous. A method for processing a semiconductor wafer, comprising irradiating the laser beam onto a position that is ahead in the rotational direction, corresponding to the processing position, where the frictional heat generated during the processing is substantially not dissipated, and where the processing tool is scheduled to contact the next position.
3. A semiconductor wafer processing apparatus for processing a semiconductor wafer having a circuit formed on its surface by rotating the wafer and bringing a rotating processing tool into contact with the peripheral edge, A semiconductor wafer processing apparatus comprising a laser irradiation device, which irradiates the semiconductor wafer with laser light of a wavelength corresponding to the material of the semiconductor wafer at a position in the rotational direction prior to the processing position by the processing tool to make it amorphous, and irradiates the laser light at a position in the rotational direction prior to the processing position, corresponding to the processing position, where the frictional heat generated in the processing is substantially not dissipated, at a position where the processing tool is scheduled to next contact.
4. A semiconductor wafer processing apparatus for processing a semiconductor wafer having a circuit formed on its surface, by rotating the wafer and bringing a rotating processing tool into contact with the peripheral edge and making multiple cuts in the thickness direction until a target thickness is reached or until the peripheral edge can be cut, A semiconductor wafer processing apparatus configured to irradiate the semiconductor wafer with laser light of a wavelength corresponding to the material of the semiconductor wafer along the circumferential direction, and to repeat the process of amorphousization at a predetermined thickness direction position and processing the amorphous portion of the semiconductor wafer with the processing tool until a target thickness is reached or until the wafer can be cut.