JP7685345B2 - Wafer terrace processing method and processing device used therefor - Google Patents

Description

The present invention relates to a method for laser processing the peripheral portion of a wafer and a processing device used therefor, and in particular to a method for processing a stepped terrace portion formed on the peripheral portion of a wafer using a laser and a processing device used therefor.

In order to prevent chipping from occurring at the edge of a bonded wafer or as a preliminary step to thinning the wafer, the edge of the wafer may be processed to have a stepped shape, a process known as terrace processing. An example of such wafer terrace processing is disclosed in Patent Document 1.

In this publication, in order to reduce the circumferential thickness and variation of the terrace flat portion, in the terracing of a bonded wafer, the circumferential thickness distribution of the peripheral portion of the bonded wafer that has already been terraced is first measured. After that, the in-plane correction conditions that compensate for the variation in the measured circumferential thickness distribution are fed back to the terrace processing conditions, and the terrace portion of the wafer is terraced again based on the fed-back terrace processing conditions. When terrace processing is performed again, the bonded wafer is rotated and processed in the thickness direction, i.e., in the vertical direction, following the processing conditions according to the corrected terrace processing conditions.

In the past, silicon wafer processing typically involves using a combination of a high-speed rotating grinding wheel and a low-speed rotating wafer to grind the edge of the wafer to the desired thickness, and then removing the remaining part in a post-process, etching, to form a terrace. Terraces are formed in this manner, but laser processing may also be used on the chip formation surface of a typical wafer so that the processed surface becomes the desired surface. An example of this type of laser processing is described in Patent Document 2.

In the laser processing method described in Patent Document 2, the objective is to form recesses or through-holes with a large aspect ratio in a SiC wafer while suppressing the generation of debris, and a pulsed laser beam with a wavelength of 500 nm or more, a pulse energy of 50 μJ or less, and a repetition rate of 200 kHz or more is irradiated to form recesses or through-holes in a SiC material. The irradiated area of the pulsed laser beam is then covered with a light absorbing layer with an absorption coefficient of the pulsed laser greater than that of SiC.

Another example of laser processing is described in Patent Document 3. In the laser processing described in this publication, in order to achieve high-precision processing of semiconductor materials that is not possible with RIE or dicing, a fluid substance that has a high absorption rate for the wavelength of the irradiated laser light is brought into contact with the surface of the semiconductor material to be processed, and pulses of laser light are irradiated from the back side of the semiconductor material. At that time, the wavelength of the laser light is set to a wavelength that is outside the optical absorbency of the semiconductor material. This makes it possible to suppress processing scratches such as cracks, chips, and chipping on the groove surface.

JP 2020-131410 A JP 2014-4628 A JP 2014-226685 A

Wafer terrace processing is a process for forming the starting point for thinning in bonded wafers, etc., and its purpose is to eliminate or minimize the effect on the semiconductor chip portion of the thinning process that is carried out afterwards, including the flat portion on which the semiconductor chip is formed. Therefore, it is necessary to avoid chipping, cracks, breaks, etc. in the processed terrace portion as much as possible, and to do so, the terrace portion needs to be flattened.

In the conventional terrace processing described in Patent Document 1, the terrace is processed once, its thickness is measured, and it is processed again according to the distribution of thickness variations, and the relative position of the grinding wheel and the wafer is changed according to the amount of variation. This has the advantage of making the thickness of the terrace more uniform than conventional methods. However, a process of measuring the thickness of the terrace is required until the final processing, and since precise measurement is difficult during grinding due to disturbances, grinding must be stopped for this process, and it takes a long time to process the terrace. Furthermore, although the thickness of the terrace is certainly uniform, the surface after grinding has minute irregularities due to the roughness of the grinding wheel, and these irregularities can cause chipping.

Patent Document 2 describes how debris is reduced in laser processing to form recesses or through holes with a large aspect ratio with high precision. However, what is described in this publication does not take into consideration the fact that laser light is irradiated onto a plane that is almost flat macroscopically, such as a ground wafer, but has minute irregularities formed microscopically, thereby eliminating the irregularities such as grinding marks formed on the flat surface and microscopically flattening the wafer surface.

Patent Document 3 also presents a laser processing method that allows semiconductor materials to be processed with low energy consumption, instead of etching, which requires a mask. In this publication, since laser light is irradiated from the back surface of the semiconductor material, when grinding the top surface of the semiconductor material with a grinding wheel, such as processing of terraces, it is required to perform the laser processing separately from the grinding process, or to process the semiconductor wafer only with the laser processing. In the former case, the processing steps overlap, resulting in a long processing time. On the other hand, in the latter case, there is a limit to the processing depth per pass in laser processing, or the laser output needs to be increased, and in either case, it is difficult to process the wafer to the desired thickness by laser processing alone due to time and equipment limitations.

The present invention was developed in consideration of the above-mentioned problems with the conventional technology, and its purpose is to reduce the unevenness or residual processing stress on the surface of the terrace portion, which are factors that cause defects such as chipping when processing the terrace portion of a semiconductor wafer. In addition to the above-mentioned object, another purpose of the present invention is to achieve flattening of the terrace portion of the wafer without increasing the processing time even when applying laser processing technology.

The present invention, which achieves the above object, is characterized in that the method for processing the peripheral portion of a semiconductor wafer having a circuit formed on its surface includes the steps of bringing a grinding wheel rotating at high speed into contact with the semiconductor wafer rotating at low speed to process the peripheral portion of the wafer into a stepped terrace shape, and irradiating a laser beam to a position of the semiconductor wafer that has been ground, in the direction of rotation, near the position where the grinding wheel contacts the semiconductor wafer rotating at low speed, to melt and flatten the terraced surface of the semiconductor wafer.

In this feature, it is preferable that the irradiation position of the laser light is a position where the processing heat generated in the grinding process is not substantially completely dissipated, and when the semiconductor wafer is composed of at least one of a Si substrate, a sapphire substrate, a GaN substrate, a SiC substrate, a lithium tantalate substrate, and a lithium niobate substrate, the laser light is a pulsed laser light with a long wavelength of 532 nm or more, and when the semiconductor wafer is composed of a gallium oxide substrate, the laser light is preferably an ultraviolet excimer laser light.

Another feature of the present invention, which achieves the above object, is that a processing device for terrace processing a semiconductor wafer having a large number of semiconductor chips formed on its surface includes a grinding wheel that rotates at high speed to grind the peripheral portion of the semiconductor wafer, a rotating bed that rotates the semiconductor wafer at a low speed, and a control device that controls the rotation of the grinding wheel and the rotation of the semiconductor wafer, and a laser light irradiation device is provided that irradiates a laser light that melts and flattens the terrace processed surface of the semiconductor wafer near the position where the grinding wheel contacts the semiconductor wafer and at a position after the grinding wheel has performed the grinding process when the peripheral portion of the semiconductor wafer is terrace processed with the grinding wheel.

In this feature, the laser light irradiation device emits pulsed laser light, and when the semiconductor wafer is made of a gallium oxide substrate, the laser light irradiation device is an ultraviolet excimer laser irradiation device, and 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, and a lithium niobate substrate, it is preferable that the laser light irradiation device is capable of emitting pulsed laser light with a long wavelength of 532 nm or more.

According to the present invention, by combining grinding using a grinding wheel and annealing by irradiating the wafer with a laser in processing the terrace portion of the wafer, it is possible to reduce unevenness or residual processing stress on the surface of the terrace portion, which can cause defects such as chipping. In addition, by arranging the laser processing device adjacent to the grinding device, it is possible to perform grinding and annealing on the same wafer, and it is possible to flatten the terrace portion of the wafer without increasing the processing time of the terrace portion of the wafer.

1 is a front view of an embodiment of a wafer processing apparatus according to the present invention; FIG. 1 is a schematic diagram illustrating the progress of terrace processing. FIG. 2 is a top view of the laser processing apparatus for explaining the arrangement of the laser processing apparatus according to the present invention. 6A and 6B are photographs showing the state of a terraced surface of a wafer before and after laser processing according to the present invention, where (a) shows the state after processing and (b) shows the state before processing. 6A and 6B are photographs showing the state of a terraced surface of a wafer before and after laser processing according to the present invention, where (a) shows the state after processing and (b) shows the state before processing.

The wafer terrace processing device and processing method according to the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an embodiment of a wafer processing device 300 including a wafer chamfering device 100 used for terrace processing of a wafer W. The wafer chamfering device 100 processes the peripheral portion of a wafer W or 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, the workpiece processed by the wafer chamfering device 100 will be described as a bonded wafer W made by laminating and bonding two silicon wafers, but wafers and plate-like bodies made of other materials can also be processed in the same manner.

The wafer chamfering device 100 comprises a wafer feed unit 102 and a grinding unit 104. The wafer feed unit 102 comprises a horizontally arranged base plate 106, on which a pair of Y-axis guide rails 108 are arranged parallel to each other at a distance from each other, and a Y-axis linear guide 110 is disposed 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.

A pair of X-axis guide rails 120 are arranged parallel to each other at a distance from each other on the Y-axis table 112, perpendicular to the Y-axis guide rail 108, and an X-axis linear guide 122 is arranged 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 rails 120 by an X-axis ball screw 128 driven by an X-axis motor 126.

A Z-axis base 130 is provided on the X-axis table 124 perpendicular to the X-axis table 124, and a Z-axis guide rail 132 is provided 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 provided on the opposite side of the Z-axis guide rail surface of the Z-axis linear guide 134 so as to be movable up and down. The Z-axis table 136 is movable up and down 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.

A θ-axis motor 150 is disposed on the Z-axis table 136, which rotates and drives the suction table 160, which is a holding platform used to rotate the workpiece. The θ-axis motor 150 is connected to a θ-axis shaft 152, and the suction table 160 is connected horizontally to the upper end of the θ-axis shaft 152. The suction table 160 is a so-called vacuum chuck, on which the workpiece, a bonded wafer W, is placed by vacuum suction, and the wafer W is terraced in this state. Here, the θ-axis is a rotation axis that faces in the vertical direction parallel to the Z-axis.

In the wafer feed unit 102 configured in this manner, the Y-axis motor 114 is driven and controlled by the control device 252, causing the suction table 160 to move in the Y direction, which is the left-right direction in FIG. 1. Similarly, the X-axis motor 126 is driven and controlled by the control device 252, causing the suction table 160 to move in the X direction, which is the front-to-back direction of the page in FIG. 1. In addition, the θ-axis motor 150 is driven by the control device 252, causing the suction table 160 to rotate at a relatively slow speed around the θ-axis, which is parallel to the Z-axis.

On the other hand, in the grinding unit 104 to which the grinding wheel 180 is attached, a stand 174 is disposed on a base plate 172. Here, the base plate 172 may be integrated with the base plate 106 disposed in the wafer feed unit 102 as shown in FIG. 1, or may be separate. An outer peripheral motor 176 is provided on the stand 174, and the outer peripheral 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 peripheral motor 176. A nozzle (not shown) for ejecting a grinding fluid as a coolant is disposed as necessary, and the grinding fluid is sprayed to the grinding position where the grinding wheel 180 abuts against the workpiece.

Figure 2 shows the state of terrace processing of the wafer W in a partial front view of the wafer. Figure 2(a) shows the state before terrace processing, and Figure 2(b) shows the state during terrace processing. Figure 2(c) shows the state after terrace processing. In terrace processing using the wafer chamfering device 100, the wafer W is first placed on the suction table 160 and vacuum-sucked. At the same time, the Z-axis motor 138 is driven to adjust the height of the suction table 160 to match the height of the wafer W to the processing position of the grinding wheel 180, and the X-axis motor 126 is driven to match the θ-axis, which is the rotation axis of the wafer W, with the X-axis position of the center axis CH of the grinding wheel 180. At this time, the Y-axis motor 114 is not driven, or if the wafer W is too close to the grinding wheel 180, it is driven so that it retreats to the retreat position.

Next, the control device 252 controls the rotation of the outer peripheral motor 176 at a high speed and the θ-axis motor 150 at a low speed so that they move in the same direction. For example, the motors 176 and 150 are controlled so that the rotation speed of the grinding wheel 180 attached to the spindle 178 connected to the outer peripheral motor 176 is 3000 rpm, and the outer peripheral speed of the wafer W is 5 mm/s.

In this state, the control device 252 drives the Y-axis motor 114 to move the wafer W closer to the grinding wheel 180 in the Y-axis direction (see FIG. 2(a)). Then, when the wafer W approaches the vicinity of the point where it contacts the grinding wheel 180, the rotation speed of the Y-axis motor 114 is reduced, the feed speed of the wafer W in the Y-axis direction is decelerated, and the grinding wheel 180 is brought into contact with the wafer W. Then, the feed amount of the wafer W in the Y-axis direction is determined so as to be the radial grinding width per grinding, and grinding of the entire circumference of the wafer W is started at the determined feed amount (see FIG. 2(b)). Once grinding is started, coolant is sprayed from a nozzle toward the grinding position to remove grinding debris and wear powder of the grinding wheel generated by grinding from the grinding position and to cool the grinding area.

If the radial grinding width possible in one grinding (per pass) is equal to or larger than the desired terrace processing width, when grinding is completed over the entire circumference, the Y-axis motor 114 is driven to move the wafer W away from the grinding position. If the radial grinding width possible in one grinding is smaller than the desired terrace processing width, the above is repeated multiple times (multiple passes). In addition, when performing terrace processing on a wafer W, it is generally necessary to perform grinding multiple times in the thickness direction of the wafer W, i.e., in the Z direction, so the Z-axis motor 138 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 abut against the wafer W, and grinding is performed for a predetermined radial width at a predetermined Y-axis feed amount. This is repeated until the wafer W is terraced to a predetermined thickness (see FIG. 2(d)), and the processing of the next wafer W begins. FIG. 2(c) is a diagram showing the laser processing state, the details of which will be described later, and shows the circumferential position of the wafer feed unit 102 differently from the other diagrams (FIGS. 2(a), (b), and (d)). In the above-mentioned terrace processing, 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.

In the above description, the wafer chamfering device 100 is used in the same way as in conventional terrace processing, but the present invention is characterized in that, in addition to the conventional mechanical grinding process described above, laser processing is also used during grinding processing. For this reason, a laser processing device 200 is added to the wafer chamfering device 100. The wafer chamfering device 100 equipped with this laser processing device 200 will be referred to as the wafer processing device 300 below.

With reference to Fig. 1 and Fig. 3 to Fig. 5, terrace processing by the wafer processing apparatus 300 according to the present invention including the laser processing apparatus 200 will be described. Fig. 3 is a top view showing only a part of the wafer processing apparatus 300, showing the relative positional relationship between the wafer chamfering apparatus 100 and the laser processing apparatus 200. Fig. 4 is a photograph showing an enlarged state of the terrace processed surface S _T of the wafer W after the wafer W has been terrace processed, Fig. 4(a) is an enlarged photograph of an example of the terrace processed surface S _T of the wafer W subjected to the wafer processing method according to the present invention, and Fig. 4(b) is an enlarged photograph of an example of the terrace processed surface S _T of the conventional wafer W. Fig. 5 is a cross-sectional photograph (transmission electron microscope TEM image) of the terrace processed portion P _T of the wafer W in Fig. 4, Fig. 5(a) corresponds to Fig. 4(a), and Fig. 5(b) corresponds to Fig. 4(b).

A laser processing device 200 is disposed near the wafer chamfering device 100. In FIG. 1, for ease of understanding, the laser processing device 200 is disposed on the opposite side of the grinding unit 104 across the wafer feed unit 102, but as shown in FIG. 3, the laser processing device 200 is disposed so that the irradiation position is located near the position where the grinding wheel 180 abuts against the wafer W.

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 split beam 220, which is one of the beams split by the beam splitter 212, is adjusted in position in the Z-axis direction via a galvanometer mirror 222 and an f-θ lens 224, and is irradiated onto an end surface 242 at an irradiation position P _I. The second split beam 230, which is the other beam, is similarly adjusted in position in the radial direction via a galvanometer mirror 232 and an f-θ lens 234, and is irradiated onto a terraced surface 244 at an irradiation position P _I. At an irradiation position P _I , which is a position immediately after the grinding of the wafer W is completed, these two split beams irradiate the respective surfaces 242, 244, and heat the wafer W after grinding. Depending on the form of the terrace processing, the end surface 242 that expands in the vertical direction formed by the terrace processing becomes a conical surface rather than a cylindrical surface. In that case, the first split light beam 220 is incident on the end face 242 at an angle.

Each optical component 212, 222, 224, 232, 234 of the laser processing device 200 is disposed in a housing or holder 254, which in this embodiment is disposed on the upper surface of the control device 252 of the wafer chamfering device 100. In other words, the control device 252 also functions as a stand, and aims to make effective use of the processing space. The control device 250 of the laser processing device 200 is incorporated on the upper part of the control device 252 of the wafer chamfering device 100, and controls the emission timing and emission intensity of the laser light from the laser light source 210, the irradiation position and rotation of the galvanometer mirrors 222 and 232, etc.

When grinding a wafer, friction occurs due to the relative movement between the wafer W and the grinding wheel 180 in the tangential direction, and this friction generates frictional heat. When processing the wafer W, frictional heat accelerates tool wear and changes the grinding conditions, so in the past, coolant was sprayed onto the processing area, which also had the effect of removing wear powder and grinding wheel fragments. As a result, the wafer W is rapidly cooled by the coolant.

In the case of the wafer W that has been subjected to such grinding processing, when the terraced surface S _T of the wafer W is observed microscopically, stripes due to the abrasive grains of the grinding wheel 180 are observed along the direction in which the grinding wheel 180 moves, as shown in FIG. 4B. Here, in FIG. 4, the terraced surface S _T is viewed from above the wafer W, and is shown at a magnification of 500 times. Also, as shown in FIG. 5B, in a cross-sectional view of the terraced portion P _T of the wafer W cut in the thickness direction of the wafer W, micro scratches in the thickness direction are observed at multiple points on the surface (three points circled No. 1 to 3 in FIG. 5B). Furthermore, scratches or defects (circled No. 4) are also observed inside the wafer W. Here, in FIG. 5, the wafer W is cut in the thickness direction (line A-A in FIG. 2D), and a carbon layer 262 is formed on the surface of the wafer W to protect the surface. In this embodiment, the wafer W is a Si (silicon) wafer. The sample surface position is indicated by 264.

The reason why the wafer W is subjected to the terrace processing is to prevent cracks or breaks occurring at the periphery of the wafer W from progressing to the center of the wafer W, thereby damaging the circuits formed at the center of the wafer W and reducing the yield of the semiconductor device (chip). However, as a result of the terrace processing, new scratches (No. 1 to 4 in the circled area in FIG. 5(b)) are generated in the terrace processing part P _T as shown in FIG. 4(b) and FIG. 5(b), and these scratches may become a factor in reducing the yield in the subsequent process of forming semiconductor chips from the wafer W. In other words, it cannot be completely excluded that such micro scratches may progress to cracks or breaks that reach the inside of the semiconductor. In addition, since the wafer W is cooled with coolant during the terrace processing, the processing stress during the grinding process is likely to remain as residual stress in the wafer W.

In view of these current problems, in order to effectively melt the semiconductor wafer W after grinding without impeding the grinding process, the present invention provides a laser processing device 200 and locally heats the processed surface S _T of the terrace processing portion P _T , which has an uneven surface, to a flat surface free of minute scratches, and effectively utilizes frictional heat without impeding cooling by the coolant.

In particular, the effect of the laser processing can be further increased or the laser intensity can be reduced by adding the frictional heat generated during the terrace processing to the laser processing, in other words, by performing the laser processing before the frictional heat is sufficiently dissipated. Therefore, in this embodiment, the laser irradiation position PI is disposed in the direction in which the semiconductor wafer W rotates, and is located forward of the grinding processing position _Pg in the rotation direction (on the right side in FIG. 3 since the wafer W rotates clockwise ₎ , preferably immediately after grinding. This reduces the cooling rate by the coolant at the laser irradiation position _PI , and suppresses the occurrence of cracks or the like in the wafer W from the terrace processing portion _PT .

The laser processing using the laser processing device 200 shown in the present invention will be further described below. The laser light is a pulsed laser light, and it is preferable that the wavelength is 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), LiTaO ₃ (lithium tantalate), LiNbO ₃ (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 of the terrace processing surface S _T. In this case, in the case of a GaN or SiC substrate or wafer W, a fluid material with a high laser absorption rate may be applied to the surface of the wafer W or substrate and the laser light may be irradiated. In this case, since a high proportion of the laser light is absorbed by the fluid material before reaching the inside of the wafer W, the heat generated by the laser light is concentrated on the interface of the wafer W, i.e., the terrace processing surface S _T , and the wafer W can be melted more effectively, and the terrace processing surface S _T can be flattened. On the other hand, in the case of Ga ₂ O ₃ (gallium oxide), laser annealing becomes possible by using ultraviolet excimer laser light with a short wavelength, for example, a wavelength of 250 to 260 nm.

As described above, according to the above embodiment of the present invention, in terrace processing, the wafer immediately after grinding is irradiated with laser light to melt the processed surface and release the residual processing stress, so that the uneven surface of the terrace processing part after grinding is flattened and micro-scratches can be eliminated. This makes it possible to prevent cracks caused by the terrace part from progressing to the chip part formed on the semiconductor wafer, and improve the yield of semiconductor manufacturing.

If the above-mentioned laser processing is performed at least in the final grinding pass or finish grinding in terrace processing, the wafer can be provided in a flattened and crack-free state for the next process such as the thinning process. Therefore, laser processing can be omitted when it is desired to eliminate the complexity of the processing, or when rough grinding is performed and finish processing is expected to be performed in the end. However, since it is difficult to predict when the grinding wheel will wear out or when abrasive grains will fall off the grinding wheel, it is more desirable to use laser processing in addition to each grinding pass.

100...wafer chamfering device, 102...wafer feed unit, 104...grinding 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, 172...base plate, 174...frame, 176...periphery motor, 178...spindle, 180...grinding wheel, 200...laser processing device, 210...laser light source, 212...beam splitter, 220...(first) splitter, 222...galvanometer mirror, 224...f-θ lens, 230...(second) splitter, 232...galvanometer mirror, 234...f-θ lens, 242...(terrace processing) end surface, 244...terrace processing surface (S _T ), 250 ... (laser processing device) control device, 252 ... control device, 254 ... holder (housing), 262 ... carbon layer, 264 ... sample surface position, 300 ... wafer processing device, CH ... central axis line, P _I ... laser irradiation position, P _g ... grinding position, P _T ... terrace processing portion, S _T ... terrace processing surface, W ... (semiconductor) wafer

Claims (8)

A wafer terrace processing method for processing a peripheral portion of a semiconductor wafer having a circuit formed on a surface thereof, comprising the steps of:
a step of bringing a grinding wheel rotating at a high speed into contact with the semiconductor wafer rotating at a low speed to terrace the peripheral portion of the wafer in a stepped shape;
and irradiating a laser beam to a position in the direction of rotation where the grinding wheel has come into contact with the semiconductor wafer rotating at a low speed, where the grinding wheel has been placed, to melt and flatten the terraced surface of the semiconductor wafer. The semiconductor wafer terrace processing method according to claim 1, characterized in that the laser light irradiation position is a position where the processing heat generated in the grinding process is not substantially completely dissipated. The method for processing a semiconductor wafer terrace according to claim 1, characterized in that when the semiconductor wafer is composed of at least one of a Si substrate, a sapphire substrate, a GaN substrate, a SiC substrate, a lithium tantalate substrate, and a lithium niobate substrate, the laser light is a pulsed laser light having a long wavelength of 532 nm or more. The method for processing a terrace of a semiconductor wafer according to claim 1, characterized in that when the semiconductor wafer is made of a gallium oxide substrate, the laser light is an ultraviolet excimer laser light. A processing apparatus used for terrace processing of a semiconductor wafer having a large number of semiconductor chips formed on its surface,
a grinding wheel that rotates at high speed to grind the peripheral portion of the semiconductor wafer, a rotating bed that rotates the semiconductor wafer at a low speed, and a control device that controls the rotation of the grinding wheel and the rotation of the semiconductor wafer,
a laser light irradiation device that irradiates a laser beam to melt and flatten the terraced surface of the semiconductor wafer at a position near the position where the grinding wheel contacts the semiconductor wafer and at a position after the grinding wheel has completed grinding processing, when the peripheral portion of the semiconductor wafer is terraced with the grinding wheel. The semiconductor wafer processing device according to claim 5, characterized in that the laser light irradiation device emits pulsed laser light. The semiconductor wafer processing device according to claim 5, characterized in that when the semiconductor wafer is made of a gallium oxide substrate, the laser light irradiation device is an ultraviolet excimer laser irradiation device. The semiconductor wafer processing device according to claim 5, characterized in that when the semiconductor wafer is composed of at least one of a Si substrate, a sapphire substrate, a GaN substrate, a SiC substrate, a lithium tantalate substrate, and a lithium niobate substrate, the laser light irradiation device is capable of emitting a pulsed laser beam with a long wavelength of 532 nm or more.