JP7359980B2 - Laser irradiation repair device and method for repairing the surface of a silicon wafer after grinding - Google Patents

Description

The present invention is applicable to grinding of the surface of various materials such as silicon, sapphire, zirconia, and glass, especially plate-shaped workpieces such as semiconductor wafers and glass panels (these are referred to as "silicon wafers" in this application). Regarding a laser irradiation repair device that repairs and flattens the roughness caused by grinding marks generated on the ground surface and repairs the process-altered layer (returning to a single crystal, etc.), we have developed a laser irradiation repair device that can perform the laser irradiation efficiently. related to the equipment used. In particular, laser irradiation is applied to the surface of the outer peripheral edge and notch of the silicon wafer after grinding to improve the roughness and repair damaged layers resulting in damage such as crack growth in subsequent processes. To provide a technology suitable for suppressing

In recent years, there has been a strong demand for improved wafer quality, and importance has been placed on the processing conditions of wafer edges and notches. Semiconductor wafers such as silicon wafers used for manufacturing semiconductor devices, etc. must be prevented from chipping due to handling. Therefore, chamfering is performed by grinding the edges, and mirror chamfering is performed by polishing. In other words, in the semiconductor manufacturing process, from wafer manufacturing to device manufacturing, quality improvement of edge characteristics has become an essential process.

Silicon and other materials are hard and brittle, and if the edges of the wafer remain sharp during slicing, they will easily break or chip during handling during transportation and alignment in subsequent processing steps, and the resulting fragments may damage the wafer surface. or pollute. To prevent this, the edges and notches of the cut wafer are chamfered using a diamond-coated chamfering grindstone.

In addition, masking printing is performed to form sensor electrodes on the thinner and lighter glass substrates of smartphones and tablets, and the sensor electrodes are then cut. The occurrence of cracks directly affects the edge strength of the glass substrate.

Patent Documents 1, 2, and 3 listed below disclose improved techniques for chamfering such wafers. That is, Patent Document 1 discloses a wafer edge processing device and the like that can shape the outer peripheral edge of a silicon wafer or the like with high precision using an abrasive tape. Further, Patent Document 2 discloses a chamfering device that can eliminate bending deformation of the wafer that occurs when helically grinding the outer peripheral edge of the wafer and improve processing accuracy. Further, Patent Document 3 discloses a chamfering method that can obtain good machined surface roughness in chamfering a notch portion of a notched wafer.

After grinding the outer peripheral edge or notch of a silicon wafer as described above, the surface is conventionally buffed to remove grinding marks and smooth the surface. Since surface portions that have cracks, processing distortions, or have become amorphous cannot be completely removed, the yield will deteriorate due to damage caused by propagation of cracks from such portions of the wafer in subsequent steps. Furthermore, there is a possibility that processing strain and crystal dislocation may be expanded due to polishing pressure (load) during buffing.

Further, since buffing is a polishing process (removal process) by removing a material, when comparing the dimensions immediately after grinding with the dimensions after subsequent buffing, the dimensions after buffing change to some extent. In addition, buffing requires consumables such as polishing thread, polishing liquid, and chemicals, and processes such as cleaning (removal of foreign matter) and drying after polishing, which is costly.

Unlike the above-mentioned mechanical surface repair processing, Patent Document 4 discloses a method of repairing surface defects by irradiating a laser onto a process-affected layer on the surface caused by grinding a single crystal wafer. has been done. However, existing surface modification by laser irradiation is for simple flat surfaces, and it is necessary to irradiate complex shapes and various surface conditions after grinding, or to irradiate while monitoring the irradiation results. Therefore, it has been difficult to perform fast and effective processing.

Patent No. 5700264 JP2017-159421A Japanese Patent Application Publication No. 2005-153129 Japanese Patent Application Publication No. 2008-147639

As mentioned above, when using conventional methods to repair the surface condition of silicon wafers after grinding, buffing cannot completely repair surface defects or maintain the original dimensions strictly, resulting in lower yields. There are other problems, such as poor results (particularly in the notch part), resulting in high costs, and, in the case of laser irradiation, rapid and effective repair results depending on the surface condition and shape after grinding cannot be obtained.

In view of these problems, the object of the present invention is to process a workpiece (referred to as a "silicon wafer" in this application) using a pulsed laser (referred to as a "laser" in this application) with a pulse width on the nanosecond level. An object of the present invention is to provide a processing damage repair device and method.

More specifically, the purpose of the present invention is to provide a technique for repairing (single crystallization, etc.) and roughness improvement (flattening) of a process-affected layer, particularly at the outer peripheral edge portion and/or notch portion of a silicon wafer. It's about doing.

Another object of the present invention is to provide a method and apparatus for diagnosing the scale and condition of a damaged area and performing effective irradiation.

Another object of the present invention is to provide an efficient laser irradiation method and apparatus that can be applied to edges and notches having different shapes.

In other words, the purpose of the present invention is to use a laser to perform efficient surface treatment in a short time (for example, 10 seconds or less in the case of repairing a chamfer), thereby improving product throughput. .

Therefore, an object of the present invention is to check the surface condition and shape of a silicon wafer to be repaired before, during and/or after laser irradiation, and to check the surface condition and shape of the silicon wafer under conditions appropriate to the situation such as distortion and destruction. It is an object of the present invention to enable efficient and effective surface modification by performing laser irradiation.

Another object of the present invention is to completely repair cracks and distortions, improve the mechanical strength of the object to be repaired, and improve the yield of post-processing.

Another object of the present invention is to achieve a process that eliminates the need for consumables such as polishing threads, polishing liquids, and chemicals, as well as cleaning and drying steps, and has a low environmental impact.

Another object of the present invention is to enable a simple process that can be carried out in environments such as atmospheric pressure and room temperature, and does not require other additional raw materials.

Another object of the present invention is to make it possible to perform repairs that maintain the original dimensions (accuracy) by modifying the material by heat treatment based on laser irradiation without removing the material (processed material) to be repaired. It is to be.

The structure of the present invention for achieving the above object is as follows.
[1] A laser irradiation repair device for the surface of a silicon wafer after grinding, comprising a measuring device for measuring at least the surface condition of the silicon wafer, a laser irradiation unit, the relative position of the laser irradiation unit, and the silicon wafer. The laser irradiation unit includes a displacement mechanism that causes displacement, and a control device that controls laser irradiation conditions and/or irradiation atmosphere based on measurement data by the measurement device, and the laser irradiation unit is configured to perform chamfering of the silicon wafer after grinding. A laser irradiation repair device for the surface of a silicon wafer after grinding, which irradiates the outer peripheral edge portion and/or notch portion with a laser beam.
[2] The laser irradiation repair device for the surface of a silicon wafer after grinding according to [1], wherein the laser irradiation unit performs laser irradiation until repair is confirmed based on the measurement result of the surface state.
[3] Laser irradiation of the surface of the silicon wafer after grinding according to [2], wherein the measuring device measures the surface state before, during, and/or after irradiation with the laser. Repair equipment.
[4] A measuring device that measures at least the surface state of the silicon wafer, a laser irradiation unit, a displacement mechanism that displaces the relative position of the laser irradiation unit and the silicon wafer, and based on measurement data by the measuring device. A method for repairing a surface of a silicon wafer after grinding using a laser irradiation repair device comprising: a control device for controlling laser irradiation conditions and/or an irradiation atmosphere; a step of setting the laser irradiation conditions and/or irradiation atmosphere by the control device based on the measurement data by the measurement device; A method for repairing a surface of a silicon wafer after grinding, the method comprising the step of irradiating a chamfered outer peripheral edge portion and/or a notch portion of the silicon wafer with a laser.
[5] The method for repairing a surface of a silicon wafer after grinding according to [4], wherein the laser irradiation step is a step of performing laser irradiation until repair is confirmed based on the measurement result of the surface state.
[6] The silicon wafer according to [5], wherein the step of measuring the surface state is a step of measuring the surface state before the laser irradiation, during and/or after the laser irradiation. How to repair the surface after grinding.

In order to achieve the above object, another aspect of the present invention is a laser irradiation repair device for the surface of a silicon wafer after grinding, the surface state and/or shape of the silicon wafer held in a wafer feeding unit before laser irradiation. a measuring device that measures the surface of the silicon wafer; a laser irradiation unit that irradiates the ground surface of the silicon wafer with a laser beam; and a laser irradiation unit that rotates, moves, or tilts the silicon wafer held by the wafer feeding unit. A displacement mechanism that supports at least one type of displacement operation among the above, and a control device that controls laser irradiation conditions and/or irradiation atmosphere based on measurement data by the measurement device. That is.
In this case, the silicon wafer is held by the wafer feeding unit so as to be able to rotate, move, and tilt at least one of the following.

Further, the wafer feeding unit may be attached to the laser irradiation repair device of the present invention, or may be provided independently, or the wafer feeding unit attached to the grinding unit may also be used in common with the laser irradiation repair device of the present invention. You can do it like this.

Further, in the present invention, it is preferable that the measuring device is configured to measure the surface state and/or shape of the silicon wafer after grinding and before laser irradiation, during laser irradiation, and/or after laser irradiation.

Furthermore, in the above, it is preferable that the laser irradiates the outer circumferential edge portion and/or notch portion of the silicon wafer that has been chamfered by the grinding.

Furthermore, in the above, the measuring device for measuring the surface state and/or shape of the silicon wafer includes an image measuring means, a capacitance change measuring means, a droplet contact angle measuring means, a Raman spectroscopy measuring means, a surface roughness meter. , acoustic measuring means, eddy current characteristics measuring means, reflectance measuring means, X-ray Lang method measuring means, electron beam diffraction measuring means, and SEM measuring means by any one or a combination of two or more. It is preferable that it be configured.

Furthermore, in the above, the laser irradiation unit has an optical mechanism including at least one of a mirror, a galvano mirror, a lens, a prism, a collimator, a polarizer, a beam splitter, and a mask, in addition to the laser light source, It is desirable that the configuration be such that the laser irradiation conditions can be changed.

Furthermore, in the above, it is desirable to include a temperature control device that heats and cools the silicon wafer held in the wafer feeding unit.

Furthermore, in the above, it is desirable to include an atmosphere maintenance device that maintains the gas composition and pressure within a predetermined range in a predetermined processing area surrounding the silicon wafer held in the wafer feeding unit.

Furthermore, in the above, the control device includes a drive device for the wafer feeding unit, a displacement mechanism for the laser irradiation unit, an output characteristic of the laser light source, an operation of the optical mechanism, an operation of the temperature adjustment device, and the atmosphere maintenance device. It is desirable that the controller be configured to control at least one of the following operations.

Furthermore, in the above, in order to irradiate multiple locations on the silicon wafer from various directions with the laser irradiation unit included in the laser irradiation repair device, the laser irradiation repair apparatus further includes at least one beam splitter that splits the laser beam from the laser light source into multiple beams. This is desirable.

Furthermore, in the above, the pair of laser beams separated by the beam splitter are incident on individual galvanometer mirrors, and are further reflected, so that the pair of outer circumferential arc portions of the notch portion of the silicon wafer are illuminated by the respective reflected laser beams. It is desirable to be configured to respectively irradiate and/or respectively irradiate the chamfered slope on the front side and the chamfered slope on the back side of the silicon wafer.

Furthermore, in order to achieve the above object, the present invention provides a method for repairing the surface of a silicon wafer after grinding using a laser irradiation repair device, the method comprising: a step of measuring the surface state and/or shape of the silicon wafer held in the wafer feeding unit by a measuring device; and a step of measuring the surface state and/or shape of the silicon wafer held in the wafer feeding unit, and a step of measuring the surface state and/or shape of the silicon wafer held in the wafer feeding unit, and a step of measuring the surface condition and/or shape of the silicon wafer held in the wafer feeding unit, and a step of measuring the surface condition and/or shape of the silicon wafer held in the wafer feeding unit. A step of setting laser irradiation conditions and/or irradiation atmosphere, and irradiating the ground surface of the silicon wafer with a laser by a laser irradiation unit provided in the laser irradiation repair device according to the settings of the control device. a step of measuring the surface condition of the silicon wafer using the measuring device during and/or after the laser irradiation to confirm whether the surface of the silicon wafer has been repaired; This method is characterized by the step of terminating the irradiation and, if the repair has not been done, restarting or continuing the laser irradiation until the repair is confirmed.

Further, in the above, in the step of irradiating the ground surface of the silicon wafer with a laser by a laser irradiation unit included in the laser irradiation repair apparatus, the outer peripheral edge portion of the silicon wafer chamfered by the grinding and/or Alternatively, it is desirable to irradiate the notch portion with a laser.

Further, in the above, in the step of irradiating the ground surface of the silicon wafer with a laser by a laser irradiation unit provided in the laser irradiation repair apparatus, a displacement mechanism of the laser irradiation unit, an output characteristic of the laser light source, It is desirable to control at least one type of operation of the optical mechanism.

Further, in the above, in the step of irradiating the ground surface of the silicon wafer with a laser beam by a laser irradiation unit provided in the laser irradiation repair apparatus, the laser beam from the laser light source of the laser irradiation unit is split into a plurality of beams. It is desirable to irradiate a plurality of locations on the silicon wafer from various directions with each of the separated laser beams.

Furthermore, in the above, the pair of laser beams separated by the beam splitter are incident on individual galvanometer mirrors, and are further reflected, so that each of the pair of outer circumferential arc portions of the notch portion of the silicon wafer is individually illuminated by each reflected laser beam. It is desirable to be configured to irradiate and/or respectively irradiate a chamfered slope on the front side and a chamfered slope on the back side of the silicon wafer.

Furthermore, in the above, when irradiating a laser to an arcuate portion at the bottom of a recess in a notch portion of the silicon wafer, the center of the radius of curvature of the arcuate portion is placed on the optical path of the laser, and the center of the radius of curvature is set as the center. It is desirable to configure the silicon wafer to be irradiated while rotating the silicon wafer itself and/or rotating the laser irradiation direction.

Furthermore, in the above, when irradiating a straight line part of the recess of the notch part of the silicon wafer with a laser, the silicon wafer is moved in the direction of the straight part while the laser irradiation direction is maintained perpendicular to the straight line part. It is desirable to configure the device so that it can be moved in a straight line along.

The present invention is configured as described above, and the measurement device measures the surface condition and shape of the silicon wafer to confirm and understand the scale and condition of the damaged part due to the grinding process, and then the control device irradiates the laser beam. By controlling the laser irradiation conditions and atmosphere through the unit's displacement mechanism, optical mechanism, temperature control device, etc., and performing effective laser irradiation, efficient repair and planarization of the wafer surface can be performed. becomes possible. In addition, since the laser scanning method can be executed in accordance with the shape, appropriate repair can be performed in a short time.

That is, more specifically, (1) the surface condition after grinding can be investigated before laser irradiation and the laser irradiation can be performed under conditions corresponding to the condition, thereby making it possible to efficiently and effectively modify the surface; (2) Throughput is improved by performing surface treatment in a short time (10 seconds or less) using a laser; (3) There is no need for polishing threads, polishing liquids, chemicals, or cleaning/drying processes, resulting in a low environmental impact. (4) Since it is carried out in an environment such as atmospheric pressure and room temperature, there is no need for additional raw materials, (5) Laser irradiation is a type of heat treatment that modifies the material. (6) Since cracks and distortions can be completely repaired, the mechanical strength of the workpiece is improved and the yield of post-processing is improved. It can be achieved.

A front view showing the main parts of an embodiment of a silicon wafer grinding and repairing device equipped with a laser irradiation repairing device for the surface of a silicon wafer after grinding according to the present invention. A plan view showing the main parts of the entire device in one embodiment of the grinding repair device shown in FIG. A partially enlarged side view showing the state during processing of the outer periphery fine grinding spindle part in the embodiment of the grinding repair device shown in FIG. 1 Cross-sectional view showing the shape of a silicon wafer after processing using conventional technology A cross-sectional view showing the shape of a silicon wafer after grinding in an embodiment of the grinding repair apparatus shown in FIG. An explanatory diagram showing a notch provided on a silicon wafer and its fine grinding and chamfering process. A block diagram showing the relationship between the main components of an embodiment of the laser irradiation repair device according to the present invention An image diagram showing various examples of measuring devices included in the laser irradiation repair device according to the present invention An image diagram showing an example of a mode in which laser irradiation is performed in accordance with the shape of a notch portion of a silicon wafer using the laser irradiation repair device according to the present invention. An image diagram showing several examples of forms in which laser irradiation is performed in accordance with the shape of a notch portion of a silicon wafer using the laser irradiation repair device according to the present invention. Image diagram for explaining an example of laser irradiation conditions in the present invention Flowchart of the laser irradiation repair method according to the present invention Enlarged image to compare the state of the surface layer of a ground silicon wafer before and after laser irradiation Explanatory diagram showing the principle of repairing the surface layer of a silicon wafer by laser irradiation Microscopic photograph of the notch part of a silicon wafer after chamfering and other grinding processes and before laser irradiation A microscopic photograph after laser irradiation treatment was performed on the region after grinding of the notch portion of the silicon wafer shown in FIG. 15 using the laser irradiation repair apparatus and method according to the present invention.

Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 1 is a front view showing the main parts of a grinding and repairing apparatus 1 equipped with a laser irradiation repairing apparatus for the surface of a silicon wafer after grinding according to an embodiment of the present invention.

The grinding repair device 1 includes a wafer feeding unit 20, a grinding unit 10, and a laser irradiation repair device 100 of the present invention. The wafer feeding unit 20 has a silicon wafer W attached thereto, and holds the silicon wafer W so as to be capable of at least one of rotation, movement, and tilting. This wafer feeding unit 20 is used in the same way when performing grinding processing with the grinding unit 10 and when performing laser irradiation with the laser irradiation repair device 100. It may be provided independently of the device 100, or may be provided attached to either of them and shared by both. The grinding unit 10 chamfers and grinds the surface of the silicon wafer W held by the wafer feeding unit 20, particularly the outer peripheral edge portion and notch portion thereof. The laser irradiation repair device 100 irradiates the surface of the ground silicon wafer W with a laser to flatten the surface roughness and repair the process-affected layer.

First, the grinding unit 10 and the wafer feeding unit 20 that perform the grinding process on the silicon wafer W will be explained.

The grinding unit 10 includes a grindstone rotation unit 50, a controller that controls the operation of each part of the grinding unit, and the like.

The drive device 12 of the wafer feeding unit 20 includes a wafer supply/storage section, a wafer cleaning/drying section, a wafer transport means, etc. (not shown), and also includes an X-axis base 21 placed on the main body base 11, two X-axis It has axis guide rails 22, 22, four X-axis linear guides 23, 23, . . . , an X-table 24 that is moved in the X direction in the figure by an X-axis drive mechanism 25 consisting of a ball screw and a stepping motor.

The X table 24 includes two Y-axis guide rails 26, 26, four Y-axis linear guides 27, 27, ..., which are moved in the Y direction in the figure by a Y-axis drive mechanism consisting of a ball screw and a stepping motor (not shown). A Y table 28 is incorporated.

The Y table 28 is guided by two Z-axis guide rails 29, 29 and four Z-axis linear guides (not shown), and is moved in the Z direction in the figure by a Z-axis drive mechanism 30 consisting of a ball screw and a stepping motor. A Z table 31 is incorporated.

A θ-axis motor 32 and a θ spindle 33 are built into the Z table 31, and a wafer table 34 for suctioning and mounting a wafer W (a plate-shaped workpiece) is attached to the θ spindle 33. is rotated in the θ direction in the figure around the wafer table rotation axis CW.

Furthermore, a truing grindstone 41 (hereinafter referred to as truer 41) used for truing a grindstone for finishing chamfering the peripheral edge of the wafer W is attached to the lower part of the wafer table 34 so as to be concentric with the wafer table rotation axis.

The wafer W and truer 41 are rotated in the θ direction in the figure and moved in the X, Y, and Z directions by the wafer feeding unit 20.

The outer circumferential rough grinding device 60 of the grindstone rotation unit 50 is provided with an outer circumferential grindstone spindle 51 to which an outer circumferential rough grinding wheel 52 is attached and rotated around an axis by an outer circumferential grindstone motor (not shown). Furthermore, the grindstone rotation unit 50 has an upper outer periphery precision grinding spindle 54 and an upper outer periphery precision grinding motor 56 attached to a turntable 53 disposed above. Similarly, a lower outer periphery precision grinding spindle 57 and a lower outer periphery precision grinding motor (not shown) are provided on the turntable 53 via a lower fixed frame 59 (shown partially cut away in FIG. 1). The turntable 53 also includes a notch rough grinding wheel 61, a notch rough grinding spindle 62, a notch rough grinding motor 63, a notch fine grinding wheel 64, a notch fine grinding spindle 65, and a notch fine grinding motor 66. is provided.

FIG. 2 is a plan view showing the main parts of the entire grinding and repairing apparatus 1 shown in FIG. The wafers are collected into a wafer cassette 70. This operation is performed by the supply and collection robot 40. A wafer cassette 70 is set on a cassette table 71, and stores a large number of wafers to be chamfered. The supply and collection robot 40 takes out wafers W one by one from the wafer cassette 70 and stores chamfered wafers into the wafer cassette 70.

The supply and collection robot 40 includes a three-axis rotating transfer arm 80, and the transfer arm 80 includes a suction pad (not shown) on its upper surface. The transfer arm 80 holds the wafer W by vacuum suctioning the back surface of the wafer with a suction pad. That is, the transport arm 80 of the supply and collection robot 40 can move back and forth, move up and down, and rotate while holding the wafer W, and the wafer is transported by combining these operations.

The grinding unit 10 is disposed at the front and performs all processes for chamfering the outer periphery of the wafer W, that is, from rough processing to finishing processing. This grinding unit 10 includes a wafer feeding unit 20 and a grindstone rotation unit 50 shown in FIG. The wafer feeding unit 20 is also used for the operation of the laser irradiation repair apparatus 100.

As shown in FIG. 1, the upper outer periphery fine grinding spindle 54 and the lower outer periphery fine grinding spindle 57 rotate the wafer W with their rotation axes inclined at 3 to 15 degrees, preferably 6 to 10 degrees with respect to the rotation axis of the wafer W. Perform finishing machining of the outer periphery chamfering. As a result, helical grinding is performed, and although weak grinding marks are generated in the diagonal direction on the chamfered portion of the wafer W, the effect of improving the surface roughness of the chamfered portion compared to normal grinding can be obtained. However, the grinding method in the grinding unit 10 provided in the grinding repair device 1 according to the present invention is not limited to such a helical grinding method, but also widely includes a normal grinding method along a direction parallel to the main plane of the wafer. included.

FIG. 3 is an enlarged side view of a part of the outer periphery fine grinding spindle section, and also shows the state during processing. The upper outer periphery precision grinding spindle 54 is attached with an upper outer periphery precision grinding wheel (upper grinding wheel) 55-1, which is a chamfering grindstone for finishing grinding the outer periphery of the wafer W, and similarly, the lower outer periphery precision grinding spindle 57 is equipped with a The outer periphery fine grinding wheel (lower grinding wheel) 55-2 and the upper outer periphery fine grinding wheel 55-1 have a gap of about 0.1 to 1 mm, which is smaller than the thickness of the wafer W, so that the rotation axes are approximately concentric. can be attached to.

In addition, the upper outer circumference precision grinding wheel 55-1 and the lower outer circumference precision grinding wheel 55-2 are driven by an upper outer circumference precision grinding spindle 54 and a lower outer circumference precision grinding spindle 57, respectively, so that the rotation directions thereof are reversed, that is, they rotate in the opposite direction. be done. A grinding groove for processing the wafer W is formed by an upper outer circumference fine grinding wheel 55-1 and a lower outer circumference fine grinding wheel 55-2. The gap is provided approximately at the center of the grinding groove in the direction of the rotation axis.

The wafer processing process is performed in the order of slicing → chamfering → lapping → etching → donor killer → fine chamfering, and various cleaning methods are used between steps to remove dirt. Silicon and other materials are hard and brittle, and if the edges of the wafer's outer periphery remain sharp during slicing, they will easily break or chip during handling during transportation and alignment in subsequent processing steps, causing fragments to damage the wafer surface. or pollute. To prevent this, in the chamfering process, the outer peripheral end face of the cut wafer is chamfered using a diamond-coated chamfering grindstone.

The chamfering process may be performed after the lapping process. At this time, it also includes adjusting the diameter of the outer circumference, which has variations, adjusting the length of the width of the orientation flat (OF), and adjusting the dimensions of a minute cutout called a notch.

FIG. 3 also shows the state of the outer circumferential fine grinding spindle part during processing, including the rotational direction and force of the upper outer circumferential fine grinding spindle 54 and the lower outer circumferential fine grinding spindle 57, the inflow and retention of coolant, This shows the relationship between chip evacuation. The upper outer periphery precision grinding spindle 54 rotates counterclockwise (in the direction indicated by arrow A, that is, rotates from left to right in the drawing) and tilts clockwise with respect to the rotation axis of the wafer W, that is, downward from left to right in the drawing. Since the wafer W is inclined to , a force is applied to the wafer W in the direction of arrow A. Since the center of the wafer W is held and the outer periphery is a free end, it can be bent downward by the component force. On the other hand, the lower outer periphery precision grinding spindle 57 rotates clockwise (in the direction indicated by arrow B, that is, rotates from right to left in the drawing) and is tilted upward from right to left in the drawing, so that it Force is applied as shown by arrow B.

Since the gaps between the upper outer periphery fine grinding wheel 55-1 and the lower outer periphery fine grinding wheel 55-2 are symmetrical at the center in the direction of the rotation axis, the wafer W and the upper outer periphery fine grinding wheel 55-1 and the lower outer periphery fine grinding The contact area with the grindstone 55-2 becomes equal. Therefore, the respective grinding resistances are balanced, and no force that would bend the wafer W is generated. Thereby, the wafer W is not bent and deformed from the center to the tip, and the shape accuracy of the machined surface is not affected by the bending deformation.

Arrows C and D indicate the inflow direction of the coolant liquid, and the upper side of the wafer W is from the left side in FIG. Let it flow from the center towards the center. The lower part is caused to flow from the right side and from the outer periphery of the wafer W toward the center along the clockwise direction, which is the rotation direction of the lower outer periphery fine grinding wheel 55-2.

FIG. 4 is a cross-sectional view showing the shape of the wafer W after processing by the conventional technique, showing the shape of the wafer W at the cut position processed by a normal peripheral precision grinding wheel, with a thickness of 740 μm and an upper surface (surface). By bending the wafer W downward, the front side is chamfered. The symmetry between the slope w2 and the chamfered slope w3 on the back side was broken.

On the other hand, FIG. 5 is a cross-sectional view showing the shape of the wafer W after processing using the outer periphery precision grinding spindle of FIG. The shape of the wafer W is shown when the fine grinding wheel 55-1 and the lower outer periphery fine grinding wheel 55-2 are rotated in reverse. When the thickness is 740 μm, the top surface (front surface) has A1 of 290 μm, B1 of 260 μm, and θ1 of 44 degrees, while the bottom surface (back surface) has A2 of 290 μm, B2 of 240 μm, and θ2 of 42 degrees. The symmetry between the chamfered slope w2 and the chamfered slope w3 on the back side is improved, and accuracy is improved.

Note that an orientation flat (abbreviation for orientation flat) or a notch is often formed on the outer periphery of the silicon wafer W to facilitate determination of its crystal orientation and alignment of the wafer. For these wafers, it is also necessary to perform precision grinding and chamfering on the orientation flat or notch portion.

FIG. 6 shows an example of a notch portion and the process of fine grinding and chamfering (finish chamfering) the notch portion. FIG. 6D shows a silicon wafer W and a notch wn formed at one location on its outer periphery. The notch portion wn has a substantially V-shaped notch shape, and both ends and the bottom portion on the outer peripheral side are arcuate.

6(a) to 6(c) show a step of performing fine grinding chamfering (finish chamfering) of the notch portion wn, but before that, the outer periphery of the silicon wafer W is Roughly grind and chamfer. Next, a notch portion wn is formed at one location on the outer circumferential surface of the silicon wafer W using a notch rough grinding wheel 61 shown in FIG. Next, as described above, the outer peripheral chamfered portion of the silicon wafer W is finely ground (finish grinding) by the outer peripheral fine grinding grindstone 55. Next, the turntable 53 is rotated, and the notch precision grinding wheel 64 is positioned at the processing position as shown in FIG. 6(a). In this state, while rotating the notch part fine grinding wheel 64 at high speed, the wafer W is sent in the X and Y directions as shown in FIGS. Perform fine grinding and chamfering. That is, the outer peripheral side corner part of the notch part wn shown in FIG. 6(a) is chamfered by precision grinding in an arc shape with a notch fine grinding grindstone 64, and the corner part on the outer peripheral side of the notch part wn shown in FIG. Fine grinding and chamfering are performed up to the outer peripheral corner on the opposite side shown in 6(c). During this time, the wafer W is not rotated by θ, and the notch portion wn is precisely ground and chamfered by feeding in the X and Y directions.

As described above, the rough grinding and fine grinding operations of the outer peripheral edge portion of the silicon wafer W and the chamfered slopes on the front and back sides of the notch portion by the grinding unit 10 in the grinding repair apparatus 1 are completed.

Next, the configuration and operation of the laser irradiation repair device 100 according to the present invention provided in the grinding repair device 1 will be described with reference to FIG. 1 again. The laser irradiation repair device 100 irradiates a laser onto the ground portion of the silicon wafer W, which has had its outer peripheral edge portion and/or notch portion ground and chamfered by the grinding unit 10 as described above, to flatten the surface roughness. Repairs damaged and processed layers. The laser irradiation repair device 100 includes a laser irradiation unit 101, a measuring device 102, and a control device 103. Further, the wafer feeding unit 20 may be attached to the laser irradiation repair apparatus 100 and may be included as a part thereof.

In addition, in the displacement mechanism 120 in which the laser irradiation unit 101 of the laser irradiation repair apparatus 100 is mounted, each component indicated by reference numerals 121 to 134 is respectively indicated by reference numerals 21 to 34 in the wafer feeding unit 20 of the grinding unit 10. Since the configuration is the same or equivalent to each component shown, the explanation will be omitted here. With these components, the rotary table 135 is configured to be movable in the X, Y, and Z axis directions and rotatable about the axis of the θ spindle 133.

Furthermore, a tilting pedestal 136 is attached to the rotary table 135, and the laser irradiation unit 101 is placed thereon. The tilting frame 136 is tiltably held with respect to the rotary table 135 by a pivot pin 137, and by rotating a cam 138 rotatably provided by a cam pin 139 with a pulse motor or the like (not shown in the figure). The tilting frame 136 rotates around the pivot pin 137. Thereby, the laser irradiation unit 101 can be tilted in the vertical direction, and along with the movement in the X, Y, and Z axis directions and rotation around the axis of the θ spindle 133, it can be tilted toward the silicon wafer W. The laser irradiation direction can be adjusted continuously and constitutes one means for changing the laser irradiation conditions. In the illustrated embodiment, the displacement mechanism 120 is configured to be able to move, rotate, and tilt the laser irradiation unit 101 relative to the silicon wafer W; It may be possible to perform at least one type of displacement operation among rotation and tilting.

The laser irradiation unit 101 is configured to irradiate a laser onto a predetermined surface of the silicon wafer W after being ground, and in the embodiment shown in FIG. Alternatively, the notch portion is configured to be irradiated with laser. As shown in the block diagram of FIG. 7, the laser irradiation unit 101 includes a laser light source 101a and an optical mechanism 101b, and in the illustrated embodiment, the optical mechanism 101b includes a relay mirror 101c and a collimator. 101d, a mask 101e, a condensing lens 101f, a moving table 101g for focal position adjustment, and the like. In this case, the direction of the laser emitted from the laser light source 101a is changed by the relay mirror 101c, the collimator 101d converts the laser beam into a parallel beam of a predetermined diameter, the laser beam travels along the light-shielding mask 101e, and then passes through the condenser lens 101f. As a result, the irradiation target is focused on a predetermined position on the surface of the silicon wafer W. The condensing lens 101f is mounted on a moving table 101g for focal position adjustment, and the position on which the laser is focused coincides with the position on the silicon wafer W to be irradiated. Note that the optical elements constituting the optical mechanism 101b are not limited to the illustrated example, and include at least one of a mirror, a galvano mirror, a lens, a prism, a collimator, a polarizer, a beam splitter, a mask, etc. , any structure may be used as long as the laser irradiation conditions can be adjusted by them. The galvano mirror causes the laser to scan the irradiation target surface by its rotation and vibration.

The laser irradiation repair device 100 further includes a measuring device 102 and a control device 103. Although not shown in FIG. 1, if necessary, as shown in FIG. An atmosphere maintenance device 105 that maintains the gas composition and pressure in a predetermined processing area surrounding the wafer W within a predetermined range is also provided.

As shown in FIG. 1, the measuring device 102 has a main body 102a of the measuring device attached to the silicon wafer W in the vicinity of a portion of the silicon wafer W to be irradiated with a laser via a support 102b attached to the Z table 31 of the wafer feeding unit 20. It is designed to be held in a non-contact state. The measuring instrument body 102a is configured to be able to adjust its position on the support 102b, and preferably, the support 102b is also configured to be movable as appropriate to adjust the surface condition (surface roughness, reflection, etc.) at a desired location on the silicon wafer W. characteristics, scattered light, etc.) and/or shape can be measured.

To measure the surface condition of the silicon wafer W, first, in order to set the irradiation conditions and irradiation atmosphere at the start of laser irradiation, the surface of the silicon wafer W before laser irradiation is measured after grinding the silicon wafer W. Measure the condition etc. In addition, the configuration is such that measurements are taken during laser irradiation to prevent over-irradiation and to monitor the suitability of the irradiation situation, and also after the irradiation to determine the suitability of the irradiation results. is desirable.

It is preferable that the measurement of the surface state and/or shape of the silicon wafer W by the measuring device 102 be performed using a non-destructive method, and specific measuring means include, for example, an image measuring means, a capacitance change measuring means, and a droplet contact angle. Measuring means, Raman spectroscopy measuring means, surface roughness meter, acoustic measuring means, eddy current characteristics measuring means, reflectance measuring means, X-ray Lang method measuring means, electron beam diffraction measuring means, SEM measuring means, etc. It is also recommended to use one of the selected ones or a combination of two or more of them. Among these, some examples will be explained with reference to FIG.

FIG. 8(a) uses an image measurement means, and in order to measure the surface roughness of, for example, the chamfered slope w2 on the front side of the silicon wafer W, a laser beam or light in a desired wavelength range is emitted from the measurement light source 140. is irradiated onto the chamfered slope w2, the image is captured by a detector 141 such as a hyperspectral camera, the surface roughness, etc. is detected by analyzing the image, and the irradiation from the laser irradiation unit 101 is performed based on the detection result. It selects and controls conditions and the like to flatten the chamfered slope w2 and repair the process-affected layer. Machine learning means based on trial experiments, comparison with control samples, etc. may be used to determine surface roughness and the like through such image analysis.

FIG. 8(b) shows a measuring device using capacitance change measuring means. In this case, the electrode 142 is placed close to the outer peripheral end surface w1 and the chamfered slopes w2 and w3 on the front and back sides of the silicon wafer W, and a voltage is applied from the DC power supply 143 between the silicon wafer W and the electrode 142, By detecting the attractive force F caused by the static electricity, the surface roughness of the outer circumferential end surface w1, the chamfered slopes w2 and w3 on the front and back sides, etc. are detected.

FIG. 8(c) shows a measuring device using a droplet contact angle measuring means. In this case, a suitable droplet 144 is attached to, for example, the chamfered slope w2 on the front side of the silicon wafer W, and the contact angle 144a of the droplet 144 with respect to the chamfered slope w2 is measured. This method takes advantage of the fact that the wettability of the chamfered slope w2 changes depending on the level of surface roughness, and the contact angle 144a of the droplet 144 changes accordingly.

In addition to these measurement means, although not shown in the drawings, for example, Raman spectroscopy measurement means may also be used. In that case, by measuring the strain caused by the Raman shift, changes in the internal crystalline state of the silicon wafer W can be detected, and based on this, the level of deterioration due to the grinding process can be determined, and based on the results, the laser irradiation conditions can be adjusted. can be optimally controlled. In addition, it is also possible to use acoustic measurement means to detect non-destructive ultrasonic waves or AE waves, or use a non-contact or contact type surface roughness meter, and eddy current characteristic measurement means to detect It is also possible to determine the level of deterioration due to grinding by measuring the conductivity of the chamfered slope and the like. Furthermore, using various known means such as reflectance measuring means, X-ray Lang method measuring means, electron beam diffraction measuring means, SEM measuring means, etc., the scale and situation of alteration due to grinding on the surface of silicon wafer W can be determined. Based on the results, laser irradiation conditions etc. can be optimally and efficiently adjusted and controlled.

Next, the control device 103 of the laser irradiation repair device 100 has a function of controlling the laser irradiation conditions and/or the irradiation atmosphere based on the measurement data by the measurement device 102. In the embodiment shown in FIG. 1, the control device 103 is provided within the base of the grindstone rotation unit 50, but it can be installed at any location, and can be used as part of the control device for the entire grinding and repair device 1. may be configured.

As shown in the block diagram of FIG. 7, in the illustrated embodiment, the control objects of the control device 103 of the laser irradiation repair apparatus 100 are the drive device 12 of the wafer feeding unit 20, the displacement mechanism 120 of the laser irradiation unit, and the laser Output characteristics of the light source 101a (energy density, etc.), operation of the optical mechanism 101b (laser direction, beam diameter, focal position adjustment, scanning range, frequency, etc.), operation of the temperature adjustment device 104, and atmosphere maintenance device. 105, etc., and these controlled objects are controlled according to a predetermined program based on the measurement data of the measuring device 102.

As described above, the temperature control device 104 may be one that heats and cools the silicon wafer W to eliminate the influence of thermal stress, promotes and optimizes the laser irradiation effect, or the wafer feeding unit 20. In order to eliminate the influence of thermal stress on the laser irradiation unit 101 and the laser irradiation unit 101, a device is provided to keep their temperatures constant.

Further, an atmosphere maintenance device 105 is provided to maintain the gas composition and pressure in a predetermined processing area surrounding the silicon wafer W within a predetermined range, so as to form and maintain an atmosphere with gas components, pressure, etc. suitable for the processing conditions.

Note that a shield mechanism is provided to prevent laser leakage from the processing area, and such a shield mechanism is also controlled by the control device 103 as necessary.

Next, a description will be given of an example of an irradiation mode that allows effective, efficient, and short-time repair in laser irradiation according to the surface condition and shape of a silicon wafer after grinding by the laser irradiation repair apparatus 100. In this case, the irradiation conditions are generally changed according to the surface condition by changing the output characteristics, energy density, etc. of the laser using the laser light source 101a and the optical mechanism 101b. In addition, changes in irradiation depending on the shape of the irradiation area are generally performed by changing the position and posture of the laser irradiation unit and/or the silicon wafer (workpiece), and This is done by changing the attitude of the silicon wafer side and the orientation of mirrors in the optical mechanism. However, the present invention is not limited to these, and it is also possible to select or combine these various means as appropriate depending on the situation.

FIG. 9 shows an example of an irradiation mode according to the present invention that matches the shape of a chamfered notch portion of a silicon wafer W. More specifically, FIG. 9(a) shows two locations, the outer circular arc portions w4 and w5 of the chamfered notch portion wn, simultaneously and in parallel, and FIG. 9(b) [in the figure (a) As shown in the enlarged cross-sectional view taken along line B-B, the optical system is configured to continuously irradiate laser onto the chamfered slope w2 on the front side, the chamfered slope w3 on the back side, and the outer peripheral end surface w1 of the notch part recess. The mechanism is shown. Note that, in FIG. 9A, for convenience of explanation, only the notch portion wn of the silicon wafer W is illustrated in an enlarged manner.

That is, specifically, a pair of lasers L11a and L12a separated by the beam splitter 101m are incident on individual galvanometer mirrors 101n and 101o, and are further reflected, and the notch portion is formed by the respective reflected lasers L11b and L12b. It is configured to irradiate a pair of outer circumferential arc portions w4 and w5 of wn, respectively. At that time, by rotating or reciprocating the galvano mirrors 101n and 101o, the directions of the reflected lasers L11b and L12b are changed, and the chamfered slope w2 on the front side and the chamfered slope on the back side of the outer circumferential arc portions w4 and w5 are scanned. W3 and the outer peripheral end face w1 are simultaneously and efficiently irradiated with laser. In the illustrated embodiment, the galvano mirrors 101n and 101o are parabolic mirrors, and are designed to focus on the outer circumferential arc portions w4 and w5, which are irradiation targets. This focal position can be adjusted by adjusting the laser beam at a stage before entering the beam splitter 101m, for example, by adjusting the moving table 101g of the condenser lens 101f shown in FIG. be. In FIG. 9(a), O1 is the center of the radius of curvature of the circular arc portion w6 at the bottom of the recess of the notch portion wn, and O2 and O3 are the centers of the radius of curvature of the circular arc portions w4 and w5 of the notch portion wn. be. In addition, the uneven shape drawn on the chamfered slope w2 on the front side and the chamfered slope w3 on the back side in FIG. 9(b) is an enlarged image of the surface roughness caused by grinding.

Note that by using such an optical mechanism, laser irradiation can be performed by aligning the focal points of the galvano mirrors 101n and 101o with the chamfered slope of the outer periphery of the rotating silicon wafer W. Chamfered slopes and end faces on the front and back sides of the can be repaired efficiently and effectively, for example, quickly over the entire circumference in less than 10 seconds. As shown in FIG. 9(a), a polarizer 101l and a beam splitter 101k for adjusting the light flux are provided at a stage upstream of the beam splitter 101m in FIG. It is assumed that each optical element connected to the optical mechanism 101b and shown in FIG. 9(a) is also included in the optical mechanism 101b, and the whole constitutes an optical mechanism in the present invention.

Furthermore, FIG. 10A shows another configuration example in which the chamfered slope w2 on the front side, the chamfered slope w3 on the back side, and the end surface w1 on the outer periphery of the silicon wafer W are irradiated simultaneously. That is, a pair of lasers L13a and L14a separated by the beam splitter 101h are incident on individual galvano mirrors 101i and 101j, and are further reflected, and the front side of the silicon wafer W is chamfered by the respective reflected lasers L13b and L14b. A configuration example is shown in which the slope w2 and the chamfered slope w3 on the back side are each irradiated. More specifically, in this irradiation example, the laser emitted from the laser light source 101a shown in FIG. 7 passes through a predetermined optical element in the optical mechanism 101b, and then passes through the beam splitter shown in FIG. 101h, and is separated into two lasers L13a and L14a. Of these, the laser L13a is reflected by the galvanometer mirror 101i placed on its optical path, and is irradiated onto the chamfered slope w2 on the front side of the silicon wafer W. By rotating the galvanometer mirror 101i or rotating within a predetermined angle range, the slope w2 is irradiated with the reflected laser L13b in a scanning manner. Similarly, the laser L14a is reflected by the galvanometer mirror 101j placed on its optical path, and is irradiated onto the chamfered slope w3 on the back side of the silicon wafer W in a scanning manner. At this time, in order to also irradiate the end surface w1 on the outer periphery of the silicon wafer W, the arrangement of each optical element, etc. is adjusted to include the end surface w1 within the scanning range of the galvanometer mirrors 101i and/or 101j. Good too. Alternatively, the entire irradiation target area may be irradiated by changing the direction of the silicon wafer W during the irradiation period. In the example shown in FIG. 10A, the end surface w1 of the outer periphery of the silicon wafer W is irradiated with the transmitted laser L15 of the beam splitter 101h. In this embodiment, the beam splitter 101h and galvano mirrors 101i and 101j are also included in the optical mechanism 101b.

Next, FIG. 10(b) shows a suitable irradiation form when the laser L is irradiated onto the circular arc portion w6 at the bottom of the recess of the notch portion wn of the silicon wafer W. In this case, the center O1 of the radius of curvature of the circular arc portion w6 at the bottom of the recess of the notch portion wn is placed on the optical path of the laser L (in other words, the laser L is set to pass through the center O1), The silicon wafer W itself is irradiated while being rotated around this O1. Alternatively, with the center O1 placed on the optical path of the laser L, the laser irradiation direction may be rotated about this center O1. Thereby, the laser L continues to be irradiated in a state substantially perpendicular to the curved surface of the circular arc portion w6, and an effective and efficient irradiation effect can be obtained. In order to rotate the silicon wafer W around the center O1, for example, the circular arc portion w6 at the bottom of the recess of the notch portion is rotated around the rotation center of the wafer table 34 of the wafer feeding unit 20 of the grinding repair apparatus 1 shown in FIG. The center O1 of the radius of curvature is positioned and the wafer table 34 is rotated.

Next, FIG. 10(c) shows a preferred irradiation form when the laser L is irradiated onto the straight line portion w7 (the same applies to w8) of the recess of the notch portion wn of the silicon wafer W. In this case, the silicon wafer W is moved linearly along the direction of the straight line portion w7 while keeping the irradiation direction of the laser L perpendicular to the straight line portion w7. Thereby, the laser L continues to be irradiated in a state perpendicular to the plane of the straight portion w7, and an effective and efficient irradiation effect can be obtained. In order to linearly move the silicon wafer W along the direction of the straight line portion w7, for example, by using the It can be moved linearly along the direction of the portion w7.

FIG. 11(a) shows an enlarged cross-sectional view of a chamfered portion on the outer periphery of a silicon wafer W to be irradiated with laser according to the present invention, and FIG. 11(b) shows a plan view of a notch portion. . An example of the specifications of suitable irradiation conditions for such an irradiation target is that the laser wavelength λ = 532 nm and the pulse width = 3 to 7 ns (generally 10 ns or less. However, if the damage to the surface of the silicon wafer is large and deep) ), energy per pulse = 60 to 80 μJ, energy density = 0.6 to 0.8 J/cm ² (generally 0.24 to 1.44 J /cm ² ), irradiation area = 0.5 mm x 0.5 mm, and atmospheric pressure = atmospheric pressure.

Next, a method for repairing the surface of a silicon wafer after grinding according to the present invention will be described with reference to FIG. That is, the method according to the present invention is a method for repairing the surface of a silicon wafer W that has been previously ground for chamfering or the like after the grinding.

As shown in FIG. 12, the silicon wafer W to be irradiated with laser according to the present invention is first subjected to at least one of (a) rotating, moving, and tilting the silicon wafer W prior to implementing the method of the present invention. It is attached to the wafer feeding unit 20 that holds the wafer as shown in FIG.

Next, (b) the surface of the silicon wafer W held by the wafer feeding unit 20 is ground by the grinding unit 10; In the grinding, rough grinding and fine grinding are usually performed as described above. The laser irradiation repair method according to the present invention is performed on this ground (that is, after grinding) silicon wafer W.

That is, first, (1) before laser irradiation by the laser irradiation repair device 100, the surface condition and/or Execute the step of measuring the shape.

Next, (2) the control device 103 provided in the laser irradiation repair device 100 executes a step of setting laser irradiation conditions and/or irradiation atmosphere based on the measurement data by the measurement device 102.

Next, (3) a step of irradiating the ground surface of the silicon wafer W with a laser is executed by the laser irradiation unit 101 provided in the laser irradiation repair apparatus 100 according to the setting conditions of the control device 103.

Next, (4) the measuring device 102 measures the surface state of the silicon wafer during and/or after the laser irradiation to confirm whether or not the surface of the silicon wafer has been repaired.

Next, (5) the step of terminating the laser irradiation if the repair has been made, and restarting or continuing the laser irradiation if the repair has not been made is confirmed.

As described above, according to the method of the present invention, laser irradiation according to the surface condition and shape of the silicon wafer W can be efficiently performed. In the step of irradiating the ground surface of the wafer W with a laser, it is possible to suitably perform an operation of irradiating the outer peripheral edge portion and/or notch portion of the silicon wafer W that has been chamfered by the grinding with the laser.

Further, when using the method of the present invention, in the step of irradiating the laser, the displacement mechanism 120 of the laser irradiation unit, the output characteristics (energy density, etc.) of the laser light source 101a, the operation of the optical mechanism 101b (the laser direction, beam diameter, scanning range, frequency, etc.).

In addition, when using the method of the present invention, in order to irradiate a laser according to the shape of the irradiation part of the silicon wafer W obtained by the measuring device 102, a plurality of lasers from the laser light source 101a of the laser irradiation unit 101 are emitted as described above. By irradiating a plurality of parts of the silicon wafer W from various directions with each of the separated laser beams, it is possible to efficiently irradiate outer peripheral parts and notch parts having different shapes.

In addition, when using the method of the present invention, as explained with reference to FIG. 9, the pair of lasers L11a and L12a separated by the beam splitter 101m is made incident on individual galvano mirrors 101n and 101o, and further reflected. The reflected lasers L11b and L12b can simultaneously irradiate the pair of outer circular arc portions w4 and w5 of the notch portion wn of the silicon wafer, respectively, to the notch portion, which was previously difficult to irradiate efficiently and well. It is possible to perform the irradiation operation efficiently.

Furthermore, when using the method of the present invention, as explained with reference to FIG. 10(a), the pair of lasers L13a and L14a separated by the beam splitter 101h are incident on individual galvano mirrors 101i and 101j, respectively, and are further reflected. , it is possible to simultaneously irradiate the chamfered slope w2 on the front side of the silicon wafer and the chamfered slope w3 on the back side of the silicon wafer using the respective reflected lasers L13b and L14b. It is possible to efficiently perform the irradiation operation on the chamfered slope.

Further, when using the method of the present invention, as explained with reference to FIG. 10(b), when the laser L is irradiated onto the circular arc portion w6 at the bottom of the recess of the notch portion wn of the silicon wafer W, the irradiation direction of the laser L is changed. While keeping it constant, the center O1 of the radius of curvature of the circular arc portion w6 at the bottom of the recess of the notch wn is placed on the optical path of the laser L, and the silicon wafer W itself is irradiated while rotating around this O1. This makes it possible to efficiently irradiate the arcuate portion of the bottom of the recess of the notch wn, which has been difficult to irradiate efficiently and well in the past.

Furthermore, when the method of the present invention is used, as explained with reference to FIG. It is possible to linearly move the silicon wafer W along the direction of the straight line portion w7 (w8) while keeping the direction perpendicular to the straight line portion w7 (w8), and conventionally, efficient and good irradiation has been achieved. It is possible to efficiently perform the irradiation operation on the straight part of the recess of the notch part wn, which was difficult to do.

In order to explain the repair effect of laser irradiation on the surface of a silicon wafer after grinding according to the present invention, FIG. An image diagram of the repair is shown. That is, as shown in FIG. 13(a), when the surface of the silicon wafer W is ground, the original surface region of the single crystal layer w9 becomes a process-affected layer and becomes a rough surface having irregularities w10. When this rough surface is irradiated with the laser L, the irradiated surface area melts and becomes a flat surface w11 as shown in FIG. 13(b) due to surface tension, and the area near the surface becomes single crystal again and is repaired. be done. The principle will be explained with reference to FIG.

As shown in FIG. 14(a), in the ground portion of a silicon wafer, a layer near the surface of the processed portion has crystal defects due to machining, resulting in a process-affected layer such as an amorphous layer or a dislocation layer. The laser absorption rate of this processed damaged layer part is significantly higher than that of the single crystal region, so the processed affected layer is melted by laser irradiation (nanosecond pulsed laser) as shown in (b), and is converted to (c) by heat conduction. As the melted region expands as shown, the surface of the melted region becomes flat due to surface tension. When the laser irradiation is stopped, a liquid phase epitaxial crystal grows using the single crystal region as a seed, as shown in (d), and as a result, the lattice defects in the crystal that occurred during the grinding process disappear, and (e) As shown in Figure 2, the portion that has been irradiated with the laser is restored to its original single crystal (see Patent Document 4).

Finally, with reference to FIGS. 15 and 16, the surface conditions of the surface of the silicon wafer after grinding are compared before and after laser irradiation using the laser irradiation repair apparatus and method according to the present invention. The effects of the present invention will now be explained. FIG. 15 is a microscopic photograph of a notch portion of a silicon wafer before laser irradiation after the grinding process has been completed by a grinding repair device equipped with a laser irradiation repair device according to the present invention, and FIG. 3 is a micrograph after laser irradiation treatment is performed on the region after grinding of the notch portion of the silicon wafer shown in FIG.

As shown in FIG. 15, after the grinding process has been completed, there are fine grinding marks (abrasion marks or streaks) on the ground surface including the chamfered slope w2 of the notch part wn of the silicon wafer W before laser irradiation. It is formed. That is, the entire area from one outer circumferential arc portion w4 of the notch portion wn, through the straight line portion w7, the circular arc portion w6 at the bottom of the recess, the other straight line portion w8, to the other outer circumferential arc portion w5. , grinding marks consisting of a large number of fine, approximately parallel uneven striations are formed, resulting in a rough surface. Such grinding marks are formed not only at the notch portion wn shown in the photograph but also on the end face of the outer periphery of the silicon wafer W and the chamfered slope of the outer periphery. Furthermore, damage caused by grinding is not limited to the surface, which can be observed with a microscope, but also extends to the interior, where a region at a certain depth from the surface becomes an amorphous layer or a dislocation layer. I'm reading.

FIG. 16 shows a state in which the surface area of the notch portion of the silicon wafer shown in FIG. 15 after being subjected to laser irradiation treatment using the grinding repair apparatus and method according to the present invention. That is, after the laser irradiation treatment, as described above, from one outer circumferential arc portion w4 of the notch portion wn to the straight line portion w7, the circular arc portion w6 at the bottom of the recess, the other straight line portion w8, and then to the other outer circumference. It can be visually confirmed that the surface of the area up to the side arc portion w5 is a smooth and shiny flat surface as a whole. That is, by irradiating the grinding surface with the laser from various directions under appropriate intensity and other irradiation conditions as described above, while matching the laser to the shape and surface condition of the notch part wn, it is usually possible to achieve uniform and good irradiation. According to the present invention, proper laser irradiation is performed evenly, efficiently, quickly, and effectively on the notch part wn, which is difficult to repair. Repairs will be made.

The present invention has the above-mentioned configuration, and by measuring the surface condition and shape of the silicon wafer with the measuring device, the scale and condition of the damaged part due to the grinding process are confirmed and understood, and then the control device irradiates the laser. By controlling the laser irradiation conditions and atmosphere through the unit's displacement mechanism, optical mechanism, temperature control device, etc., and performing effective laser irradiation, efficient repair and planarization of the wafer surface can be performed. becomes possible. Furthermore, since the laser scanning method can be executed in accordance with the shape, appropriate repair can be performed in a short time.

L...Laser W...Silicon wafer (workpiece material)
w1...Outer periphery or end face of notch recess w2...Front side chamfered slope w3...Back side chamfered slope w4, w5...Outer circumferential circular arc portion of notch portion w6...Circular arc portion of bottom of recess of notch portion w7, w8...notch portion Straight line part of the recess w9...Single crystal layer w10...Irregularities w11...Flat surface wn...Notch part O1...Center of the radius of curvature of the circular arc part at the bottom of the notch part O2, O3...Of the circular arc part on the outer circumferential side of the notch part Center of curvature radius 1...Grinding repair device 10 according to the present invention...Grinding unit 11...Main body base 12...Wafer feed unit drive device 20...Wafer feed unit 21, 121...X-axis base 22, 122...X-axis guide rail 23 , 123...X-axis linear guide 24, 124...X-table 25, 125...X-axis drive mechanism 26, 126...Y-axis guide rail 27, 127...Y-axis linear guide 28, 128...Y-table 29, 129...Z-axis guide Rails 30, 130...Z-axis drive mechanism 31, 131...Z table 32, 132...θ-axis motor 33, 133...θ spindle 34, 134...Wafer table 40...Supply and collection robot 41...Truer 50...Wheelstone rotation unit 51...Outer periphery Grinding wheel spindle 52...Outer circumference rough grinding wheel 53...Turntable 54...Upper outer circumference fine grinding spindle 55...Outer circumference fine grinding wheel 55-1...Upper outer circumference fine grinding wheel (upper grinding wheel)
55-2…Lower outer circumference fine grinding wheel (lower grinding wheel)
56...Upper outer circumference fine grinding motor 57...Lower outer circumference fine grinding spindle 59...Lower fixed frame 60...Outer circumference rough grinding device 61...Notch part rough grinding wheel 62...Notch part rough grinding spindle 63...Notch part rough grinding motor 64...Notch part Fine grinding whetstone 65...notch part fine grinding spindle 66...notch part fine grinding motor 70...wafer cassette 71...cassette table 80...transport arm 100...laser irradiation repair device 101...laser irradiation unit 101a...laser light source 101b...optical mechanism 101c... Relay mirror 101d...Collimator 101e...Mask 101f...Condensing lens 101g...Movement table 101h for focal position adjustment...Beam splitters 101i, 101j...Galvano mirror 101k...Beam splitter 101l...Polarizer 101m...Beam splitters 101n, 101o... Galvanometer mirror 102...Measuring device 102a...Measuring device main body 102b...Strut 103...Control device 104...Temperature adjustment device 105...Atmosphere maintenance device 120...Displacement mechanism 135...Rotary table 136...Tilt frame 137...Spindle pin 138...Cam 139... Cam pin 140...Measurement light source 141...Detector 142...Electrode 143...DC power supply 144...Droplet 144a...Contact angle

Claims (6)

A laser irradiation repair device for the surface of a silicon wafer after grinding,
a measuring device that measures at least a surface condition of a silicon wafer;
a laser irradiation unit,
a displacement mechanism that displaces the relative position of the laser irradiation unit and the silicon wafer;
a control device that controls laser irradiation conditions and/or irradiation atmosphere based on measurement data by the measurement device;
has
The laser irradiation unit is a laser irradiation repair device for a surface of a silicon wafer after grinding, which irradiates a laser beam onto a chamfered outer peripheral edge portion and/or a notch portion of the silicon wafer after grinding. The laser irradiation repair apparatus for the surface of a silicon wafer after grinding according to claim 1, wherein the laser irradiation unit performs laser irradiation until repair is confirmed based on the measurement result of the surface state. 3. The laser irradiation repair device for a surface of a silicon wafer after grinding according to claim 2, wherein the measuring device measures the surface state before irradiation with the laser, during irradiation with the laser, and/or after irradiation with the laser. a measuring device that measures at least a surface condition of a silicon wafer; a laser irradiation unit; a displacement mechanism that displaces the relative position of the laser irradiation unit and the silicon wafer; and laser irradiation based on measurement data by the measuring device. A method for repairing the surface of a silicon wafer after grinding using a laser irradiation repair device having a control device for controlling conditions and/or irradiation atmosphere,
measuring at least a surface state of the silicon wafer with the measuring device;
a step of setting laser irradiation conditions and/or irradiation atmosphere by the control device based on measurement data by the measurement device;
A step of irradiating a chamfered outer peripheral edge portion and/or notch portion of the silicon wafer after grinding with a laser beam by the laser irradiation unit according to the setting conditions of the control device;
A method for repairing a surface of a silicon wafer after grinding, the method comprising: 5. The method for repairing a surface of a silicon wafer after grinding according to claim 4, wherein the laser irradiation step is a step of performing laser irradiation until repair is confirmed based on the measurement result of the surface state. After grinding the silicon wafer according to claim 5, wherein the step of measuring the surface state is a step of measuring the surface state before irradiation with the laser, during irradiation with the laser, and/or after irradiation with the laser. How to repair surfaces.

Images