JP2023052577A - Laser-irradiating restoration device for silicon wafer surface after grinding and restoration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method capable of efficiently, effectively carrying out restoration and roughness planarization of a work-affected layer of a silicon wafer surface after grinding work such as chamfering by pulse laser irradiation.

SOLUTION: A laser-irradiating restoration device (100) is characterized by comprising: a measurement device (102) measuring the surface appearance and/or shape of a silicon wafer (W) held so as to be rotatable, movable and/or tiltable; a laser irradiation unit (101) irradiating the ground surface of the silicon wafer with a laser; a displacement mechanism (120) of the laser irradiation unit; and a controller (103) controlling the irradiation condition and/or irradiation atmosphere of the laser, based on the measurement data of the measurement device. The measurements of the surface appearance and/or shape of the silicon wafer by the measurement device (102) are desirably carried out before, during and after the laser irradiation.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention is applicable to various materials such as silicon, sapphire, zirconia, glass, etc., especially semiconductor wafers, glass panels, and other plate-shaped workpieces (these are referred to as "silicon wafers" in the present application). , regarding a laser irradiation repair device for repairing and flattening the roughness due to grinding marks generated on the ground surface and repairing the work-affected layer (returning to a single crystal, etc.), especially so that the laser irradiation can be performed efficiently related to the device that In particular, laser irradiation is performed on the surface after grinding the outer peripheral edge and notch of the silicon wafer to improve the surface such as improving the roughness and repairing the process-affected layer. To provide a technique suitable for suppressing

In recent years, there has been a strong demand for improved wafer quality, and the processing state of the wafer end face (edge part) and notch part has been emphasized. Therefore, chamfering is performed by grinding edges and the like, and mirror-like chamfering is performed by polishing. In other words, in the semiconductor manufacturing process, from wafer manufacturing to device manufacturing, quality improvement of edge characteristics is an essential process.

Silicon and other materials are hard and brittle, and if the edge of the wafer remains sharp during slicing, it can easily break or chip during handling such as transportation and positioning in subsequent processing steps, and the fragments can damage the wafer surface. pollute. To prevent this, the edges and notches of the cut wafer are chamfered with a diamond-coated chamfering whetstone.

In addition, smartphones and tablets have become thinner and lighter, and masking printing and sensor electrodes are formed on glass substrates, which are then cut. The occurrence of cracks and the like directly affects the edge strength of the glass substrate.

Patent Literatures 1, 2 and 3 listed below disclose techniques for improving such chamfering of wafers. That is, Patent Literature 1 discloses a wafer edge processing apparatus and the like capable of processing the peripheral edge of a silicon wafer or the like with high accuracy using a polishing tape. Further, Patent Document 2 discloses a chamfering apparatus capable of eliminating the bending deformation of the wafer that occurs when the outer peripheral edge of the wafer is helically ground, thereby improving the processing accuracy. Further, Patent Document 3 discloses a chamfering method capable of obtaining a good processed surface roughness in the chamfering of the notch portion of a notched wafer.

After grinding the outer peripheral edge portion of the silicon wafer and grinding the notch portion as described above, the surface is conventionally buffed in order to remove grinding traces on the surface and smooth the surface. Since the surface portion of the wafer has cracks, processing strain, and has become amorphous, it cannot be completely removed. In addition, there is a possibility that the polishing pressure (load) during buffing may increase processing strain and crystal transition.

Also, since buffing is a polishing process (removal process) by removing a material, comparing the dimension immediately after grinding with the dimension after buffing, the dimension after buffing changes 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) after polishing, drying, and the like, which is costly.

Unlike the mechanical surface repair process as described above, Patent Document 4 discloses a method of repairing surface defects by irradiating a laser on a process-affected layer on the surface produced by grinding a single crystal wafer. It is However, the existing surface modification by laser irradiation is for simple planes, and irradiation is performed under conditions according to complex shapes and various surface conditions after grinding, and irradiation while monitoring the irradiation results. It was difficult to process at high speed and effectively because it was not a thing.

Japanese Patent No. 5700264 JP 2017-159421 A JP 2005-153129 A JP 2008-147639 A

As described above, when using the conventional means for repairing the surface condition of silicon wafers after grinding, in the case of buffing, surface defects cannot be completely repaired or the original dimensions cannot be strictly maintained, resulting in a low yield. There are problems such as high costs (particularly for the notch portion), and in the case of laser irradiation, rapid and effective repair results according to the surface condition and shape after grinding cannot be obtained.

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

More specifically, the object of the present invention is to provide a technique for repairing (single crystallization, etc.) and improving roughness (flattening) of a process-affected layer on the outer edge and/or notch of a silicon wafer. to do.

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

Another object of the present invention is to provide an efficient laser irradiation method and apparatus adapted to the shape of edge portions and notch portions having different shapes.

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

Therefore, the object of the present invention is to check the surface state and shape of the silicon wafer to be repaired before, during and/or after laser irradiation, and to perform the repair under conditions according to the situation such as distortion and breakage. It is 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 an object to be repaired, and improve the yield of subsequent processes.

Another object of the present invention is to achieve a process that does not require consumables such as polishing threads, polishing liquids, chemicals, etc., cleaning and drying steps, and has a low environmental impact.

Another object of the present invention is to enable a simple treatment that can be carried out in an environment such as atmospheric pressure or room temperature and that does not require additional raw materials.

In addition, the object of the present invention is to enable repair that maintains the original dimensions (accuracy) by performing modification by heat treatment based on laser irradiation without removing the material (processed material) to be repaired. It is to be.

The configuration of the present invention for achieving the above object is as follows.
[1] A laser irradiation repair apparatus for a ground surface of a silicon wafer, comprising: a measurement apparatus for measuring at least the surface state of the silicon wafer; a laser irradiation unit; and a relative position of the laser irradiation unit and the silicon wafer. A displacement mechanism for displacement and a control device for controlling laser irradiation conditions and/or irradiation atmosphere based on data measured by the measurement device, and the laser irradiation unit is used to chamfer the silicon wafer after grinding. A device for repairing a ground surface of a silicon wafer by laser irradiation, which irradiates a laser to the outer peripheral edge portion and/or the notch portion.
[2] The apparatus for repairing a ground surface of a silicon wafer by laser irradiation according to [1], wherein the laser irradiation unit performs laser irradiation until repair is confirmed based on the measurement result of the surface condition.
[3] Laser irradiation of the ground surface of the silicon wafer according to [2], wherein the measurement device measures the surface state before, during, and/or after the laser irradiation. repair equipment.
[4] A measurement device for measuring at least the surface state of a silicon wafer, a laser irradiation unit, a displacement mechanism for displacing the relative position of the laser irradiation unit and the silicon wafer, and based on measurement data by the measurement device A method for repairing a ground surface of a silicon wafer by a laser irradiation repair apparatus comprising a controller for controlling laser irradiation conditions and/or irradiation atmosphere, wherein at least the surface state of the silicon wafer is measured by the measurement apparatus. a step of setting the laser irradiation conditions and/or irradiation atmosphere based on the measurement data by the measuring device by the control device, and the laser irradiation unit according to the setting conditions of the control device after grinding and a step of irradiating the chamfered outer peripheral edge portion and/or the 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 step of irradiating the laser is a step of irradiating the laser 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, during, and/or after the laser irradiation. method of repairing the surface after grinding of

In order to achieve the above object, another configuration of the present invention is an apparatus for repairing a surface of a silicon wafer by laser irradiation after grinding, comprising: a laser irradiation unit for irradiating the ground surface of the silicon wafer with a laser; and the laser irradiation unit for rotating, moving, and tilting with respect to the silicon wafer held by the wafer feeding unit. and a controller for controlling laser irradiation conditions and/or irradiation atmosphere based on data measured by the measuring device. and
In this case, the silicon wafer is held by the wafer feed unit so that at least one of rotation, movement and tilting is possible.

Further, the wafer feeding unit may be attached to the laser irradiation repairing apparatus 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 repairing apparatus of the present invention. You may do so.

Further, according to the above aspect of the present invention, it is preferable that the measurement 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 desirable that the peripheral edge portion and/or the notch portion chamfered by the grinding of the silicon wafer is configured to be irradiated with a laser.

Further, in the above, the measuring device for measuring the surface state and/or shape of the silicon wafer includes image measuring means, capacitance change measuring means, droplet contact angle measuring means, Raman spectroscopic measuring means, and surface roughness meter. , acoustic measurement means, eddy current characteristic measurement means, reflectance measurement means, X-ray Lang method measurement means, electron beam diffraction measurement means, SEM measurement means, or a combination of two or more preferably configured.

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

Furthermore, in the above, it is desirable to provide a temperature control device for heating and cooling the silicon wafer held by the wafer feeding unit.

Furthermore, in the above, it is desirable to provide an atmosphere maintaining device for keeping the gas composition and pressure in a predetermined processing area surrounding the silicon wafer held by the wafer feeding unit within a predetermined range.

Further, in the above, the control device includes a drive device for the wafer feeding unit, a displacement mechanism for the laser irradiation unit, output characteristics of the laser light source, operation of the optical mechanism, operation of the temperature control device, and the atmosphere maintenance device. is preferably configured to control at least one of the operations of

Furthermore, in the above, in order to irradiate a plurality of locations on the silicon wafer from various directions by a laser irradiation unit provided in the laser irradiation repair apparatus, at least one beam splitter that splits the laser from the laser light source into a plurality of parts is provided. is desirable.

Furthermore, in the above, the pair of laser beams split by the beam splitter are made incident on individual galvanomirrors and further reflected, and the respective reflected laser beams irradiate the pair of outer circular arc portions of the notch portion of the silicon wafer. It is desirable to irradiate each and/or to irradiate a chamfered slope on the front side and a chamfered slope on the back side of the silicon wafer respectively.

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

Furthermore, 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, the outer peripheral edge portion chamfered by the grinding of the silicon wafer and/or Alternatively, it is desirable to irradiate the notch portion with a laser.

Furthermore, 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, the displacement mechanism of the laser irradiation unit, the output characteristics of the laser light source, It is desirable to provide control of at least one of the operations of the optical mechanism.

Furthermore, 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, the laser from the laser light source of the laser irradiation unit is divided 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 lasers that are separated.

Furthermore, in the above, the pair of laser beams split by the beam splitter are made incident on individual galvanomirrors, respectively, and further reflected, and the respective reflected laser beams irradiate the pair of outer circular arc portions of the notch portion of the silicon wafer. It is preferably configured to irradiate and/or irradiate a chamfered slope on the front side and a chamfered slope on the back side of the silicon wafer, respectively.

Furthermore, in the above, when the arc portion of the recess bottom of the notch portion of the silicon wafer is irradiated with the laser, the center of the curvature radius of the arc portion is placed on the optical path of the laser, and the center of the curvature radius is set as the center. It is desirable to irradiate while rotating the silicon wafer itself and/or rotating the laser irradiation direction.

Further, in the above, in the case of irradiating the straight portion of the recess of the notch portion of the silicon wafer with the laser, the silicon wafer is oriented in the direction of the straight portion while the laser irradiation direction is kept perpendicular to the straight portion. It is desirable to configure the linear movement along the .

The present invention is configured as described above. By measuring the surface condition and shape of a silicon wafer with the measuring device, the scale and condition of the damaged portion due to the grinding process can be confirmed and grasped. Efficient wafer surface repair and flattening can be performed by controlling the laser irradiation conditions, atmosphere, etc. via the displacement mechanism, optical mechanism, temperature control device, etc. of the unit and performing effective laser irradiation. becomes possible. In addition, since a laser scanning method suitable for the shape can be executed, proper repair can be performed in a short time.

That is, more specifically, (1) the surface state after grinding is examined before laser irradiation, and the laser irradiation is performed under the conditions corresponding to it, so that the surface can be efficiently and effectively modified. (2) Throughput is improved by performing surface treatment in a short period of time (10 seconds or less) using a laser. (3) Environmental load is small because no polishing thread, polishing liquid, chemicals, or cleaning/drying processes are required. (4) Since it is performed in an environment such as atmospheric pressure and normal temperature, there is no need for additional raw materials, etc. (5) Laser irradiation is a kind of heat treatment modification, (6) Since cracks and distortions can be completely repaired, the mechanical strength of the workpiece is improved, and the yield of post-processes is improved. achievable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a main part of an embodiment of a silicon wafer grinding and repairing apparatus equipped with a laser irradiation repairing apparatus for a ground surface of a silicon wafer according to the present invention; FIG. 2 is a plan view showing main parts of the entire apparatus in one embodiment of the grinding repair apparatus shown in FIG. 1; FIG. 2 is a partially enlarged side view showing a state during processing of an outer peripheral fine-grinding spindle portion in the embodiment of the grinding and repairing apparatus shown in FIG. 1; Cross-sectional view showing the shape of a silicon wafer after processing by conventional technology FIG. 2 is a cross-sectional view showing the shape of a silicon wafer after grinding in the embodiment of the grinding and repairing apparatus shown in FIG. 1; Explanatory drawing showing the notch part provided in the silicon wafer and the process of precision grinding chamfering process FIG. 1 is a block diagram showing the relationship of major components of one embodiment of a laser irradiation repair apparatus according to the present invention; Image diagrams showing various examples of the measuring device provided in the laser irradiation repair device according to the present invention. FIG. 2 is an image diagram showing an example of a form in which laser irradiation is performed according to the shape of a notch portion of a silicon wafer by the laser irradiation repair apparatus according to the present invention. FIG. 2 is an image diagram showing several examples of a form in which laser irradiation is performed according to the shape of the notch portion of a silicon wafer by the laser irradiation repair apparatus according to the present invention. An image diagram for explaining an example of laser irradiation conditions in the present invention. Flowchart of laser irradiation repair method according to the present invention An enlarged image for comparing 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 Photomicrograph of notch part of silicon wafer after grinding process such as chamfering and before laser irradiation 15 is a photomicrograph of the area after grinding of the notch portion of the silicon wafer shown in FIG. 15 after laser irradiation treatment was performed by the laser irradiation repairing apparatus and method according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail 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 a ground surface of a silicon wafer according to one embodiment of the present invention.

The grinding and repairing apparatus 1 includes a wafer feeding unit 20, a grinding unit 10, and a laser irradiation repairing apparatus 100 of the present invention. The wafer feed unit 20 attaches the silicon wafer W thereto and holds the silicon wafer W so that at least one of rotation, movement, and tilting is possible. This wafer feed unit 20 is used in the same way when grinding is performed by the grinding unit 10 and when laser irradiation is performed by the laser irradiation repair device 100. It may be provided independently of the device 100, or may be attached to one 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 the notch portion thereof. The laser irradiation repair apparatus 100 irradiates the ground surface of the silicon wafer W with a laser to smooth the surface roughness and repair the work-affected layer.

First, the grinding unit 10 and the wafer feeding unit 20 for grinding the silicon wafer W will be described.

The grinding unit 10 includes a grindstone rotating unit 50, a controller for controlling the operation of each part of the grinding unit, and the like.

The drive device 12 of the wafer feed unit 20 includes a wafer supply/storage unit, a wafer cleaning/drying unit, wafer transfer means, etc. (not shown), and 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, .

The X table 24 has two Y-axis guide rails 26, 26, four Y-axis linear guides 27, 27, . 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 .theta.-axis motor 32 and a .theta.-spindle 33 are incorporated in the Z table 31. A wafer table 34 is attached to the .theta. is rotated about the wafer table rotation axis CW in the .theta.

Under the wafer table 34, a truing grindstone 41 (hereinafter referred to as a truer 41) used for truing the grindstone for finish chamfering of the peripheral edge of the wafer W is mounted concentrically with the wafer table rotation axis.

By this wafer feeding unit 20, the wafer W and the tool 41 are rotated in the .theta.

An outer peripheral rough grinding device 60 of the grindstone rotating unit 50 is provided with an outer peripheral rough grinding grindstone 52 and an outer peripheral grindstone spindle 51 that is driven to rotate about its axis by an outer peripheral grindstone motor (not shown). Further, the grinding wheel rotating unit 50 has an upper outer peripheral fine grinding spindle 54 and an upper outer peripheral fine grinding motor 56 attached to a turntable 53 arranged above. Similarly, the turntable 53 is provided with a lower peripheral fine grinding spindle 57 and a lower peripheral fine grinding motor (not shown) via a lower fixed frame 59 (partially cut away in FIG. 1). The turntable 53 has 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. It collects in the wafer cassette 70 . This operation is performed by the supply/collection robot 40 . A wafer cassette 70 is set on a cassette table 71 and contains a large number of wafers to be chamfered. The supply/recovery robot 40 takes out the wafers W one by one from the wafer cassette 70 and stores the chamfered wafers in the wafer cassette 70 .

The supply/recovery robot 40 has a three-axis rotary transfer arm 80, and the transfer arm 80 has a suction pad (not shown) on its upper surface. The transfer arm 80 holds the wafer W by vacuum-sucking the rear surface of the wafer with a suction pad. That is, the transfer arm 80 of the supply/recovery robot 40 can move back and forth, move up and down, and turn while holding the wafer W, and the wafer is transferred by combining these movements.

The grinding unit 10 is arranged in the front part, and performs the entire processing of chamfering the outer periphery of the wafer W, that is, from rough processing to finishing processing. The grinding unit 10 is composed of a wafer feed unit 20 and a grindstone rotation unit 50 shown in FIG. The wafer feeding unit 20 is also shared for operating the laser irradiation repair apparatus 100 .

As shown in FIG. 1, the upper and lower outer circumference precision grinding spindles 54 and 57 grind the wafer W in a state in which their rotation axes are inclined 3 to 15 degrees, preferably 6 to 10 degrees, with respect to the rotation axis of the wafer W. Perform finishing of chamfering on the outer circumference. As a result, helical grinding is performed, and although weak grinding marks are generated in the oblique direction on the chamfered portion of the wafer W, the effect of improving the surface roughness of the chamfered portion compared to normal grinding is obtained. However, the grinding method in the grinding unit 10 provided in the grinding and repairing apparatus 1 according to the present invention is not limited to such a helical grinding method, and a normal grinding method along the direction parallel to the main plane of the wafer is widely used. included.

FIG. 3 is an enlarged side view of a part of the peripheral fine-grinding spindle, and also shows the state during machining. An upper peripheral fine grinding wheel (upper grinding wheel) 55-1 is attached to the upper peripheral fine grinding spindle 54 as a chamfering wheel for finish grinding the outer periphery of the wafer W. The outer peripheral precision grinding wheel (lower grinding wheel) 55-2 is positioned so that the upper peripheral fine grinding wheel 55-1 has a gap of about 0.1 to 1 mm smaller than the thickness of the wafer W so that the rotating shaft is substantially concentric. can be attached to

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

The wafer processing process is performed in the order of slicing→chamfering→lapping→etching→donor killer→precise chamfering, and various cleanings are used between processes to remove dirt. Silicon, etc. is hard and fragile, and if the edge of the outer periphery of the wafer remains sharp during slicing, it can easily break or chip during handling such as transportation and positioning in subsequent processing steps, and the fragments can damage the wafer surface. pollute. In order to prevent this, in the chamfering step, the outer peripheral end face of the cut wafer is chamfered with a diamond-coated chamfering whetstone.

The chamfering process may also be performed after the lapping process. At this time, it also includes adjusting the diameter of the outer periphery, which varies, adjusting the width of the orientation flat (OF), and adjusting the size of a very small notch called a notch.

FIG. 3 also shows the state during machining of the outer peripheral precision grinding spindle portion, and the rotational direction and force of the upper peripheral fine grinding spindle 54 and the lower peripheral fine grinding spindle 57, the inflow of the coolant liquid, retention, It shows the relationship of chip discharge. The upper and outer peripheral precision grinding spindle 54 rotates counterclockwise (in the direction indicated by the 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. , a force is applied to the wafer W as indicated by an arrow A. Since the wafer W is held at the center and has a free edge on the outer periphery, it can be bent downward by the force component. On the other hand, the lower outer circumference precision grinding spindle 57 rotates rightward (in the direction indicated by the arrow B, that is, rotates from right to left in the drawing), and is inclined upward from right to left in the drawing. A force is applied as indicated by arrow B.

Since the gap between the upper and lower periphery fine grinding wheel 55-1 and the lower and lower periphery fine grinding wheel 55-2 is symmetrical at the center in the rotation axis direction, the wafer W and the upper and lower periphery fine grinding wheel 55-1 and lower and lower periphery fine grinding are symmetrical. The contact area with the grindstone 55-2 becomes equal. Therefore, the respective grinding resistances are balanced, and no force that bends the wafer W is generated. As a result, the wafer W is not bent from the center to the tip, and the shape accuracy of the processed 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 drawn from the left side in FIG. flow from the center toward the center. The lower side is introduced from the right side toward the center from the outer periphery of the wafer W along the clockwise direction, which is the rotating direction of the lower outer periphery precision grinding wheel 55-2.

FIG. 4 is a cross-sectional view showing the shape of the wafer W after processing according to the prior art, showing the shape of the wafer W at the incision position processed by a normal outer peripheral precision grinding wheel, the thickness of which is 740 μm and the upper surface (surface). A1 is 340 μm, B1 is 300 μm, and θ1 is 43°. The symmetry between the slope w2 and the chamfered slope w3 on the back side was lost.

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 peripheral fine grinding wheel 55-2 are rotated in reverse. With a thickness of 740 μm, A1 on the top surface (surface) is 290 μm, B1 is 260 μm, and θ1 is 44°, while A2 on the bottom surface (back surface) is 290 μm, B2 is 240 μm, and θ2 is 42°. The symmetry between the chamfered slope w2 and the chamfered slope w3 on the back side is improved, and the accuracy is improved.

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 the crystal orientation and alignment of the wafer. For these wafers, the orientation flat or notch portion also needs to be subjected to precision grinding and chamfering.

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

FIGS. 6A to 6C show the process of performing fine grinding chamfering (finishing chamfering) of the notch portion wn. Rough ground chamfering. Next, a notch portion wn is formed at one location on the outer peripheral surface of the silicon wafer W using the notch portion rough grinding grindstone 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 precision grinding wheel 55 . Next, the turntable 53 is rotated to position the notch precision grinding wheel 64 at the processing position as shown in FIG. 6(a). In this state, while rotating the notch fine grinding wheel 64 at high speed, the wafer W is fed in the X and Y directions as shown in FIGS. Perform fine grinding chamfering. That is, the outer corner portion of the notch portion wn shown in FIG. Precise grinding chamfering is performed up to the outer peripheral side corner portion on the opposite side shown in 6(c). During this time, the wafer W is not rotated by .theta., 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 chamfered slopes of the outer peripheral edge portion of the silicon wafer W and the front side and back side of the notch portion by the grinding unit 10 of the grinding and repairing apparatus 1 are completed.

Next, the configuration and operation of the laser irradiation repairing device 100 according to the present invention provided in the grinding repairing device 1 will be described with reference to FIG. 1 again. The laser irradiation repairing apparatus 100 irradiates a laser on the ground portion of the silicon wafer W whose outer peripheral edge portion and/or notch portion has been ground by the grinding unit 10 and has been chamfered as described above, thereby flattening the surface roughness. and restore the work-affected layer. The laser irradiation repair apparatus 100 includes a laser irradiation unit 101 , a measuring device 102 and a control device 103 . Also, the wafer feeding unit 20 may be attached to the laser irradiation repair apparatus 100 and included as a part thereof.

In addition, in the displacement mechanism 120 in which the laser irradiation unit 101 of the laser irradiation repairing apparatus 100 is mounted, respective constituent elements indicated by reference numerals 121 to 134 are respectively indicated by reference numerals 21 to 34 in the wafer feeding unit 20 of the grinding unit 10. Since it has the same or equivalent configuration as each component shown, the description is omitted here. With these constituent elements, the rotary table 135 is configured to be movable in the X, Y, and Z axial directions and to be rotatable around the axis of the θ spindle 133 .

Further, a tilting base 136 is attached on the rotary table 135, and the laser irradiation unit 101 is placed thereon. The tilting base 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), The tilting platform 136 rotates around the pivot pin 137 . As a result, the laser irradiation unit 101 can be vertically tilted, and along with the movement in the X-, Y-, and Z-axis directions and the rotation about the axis of the θ spindle 133, the laser irradiation unit 101 can be tilted toward the silicon wafer W. The direction of laser irradiation can be continuously adjusted, and constitutes one means for changing laser irradiation conditions. In the illustrated embodiment, the displacement mechanism 120 is configured to move, rotate, and tilt the laser irradiation unit 101 with respect to the silicon wafer W. At least one displacement operation out of rotation and tilting may be possible.

The laser irradiation unit 101 is adapted to irradiate a predetermined surface of the silicon wafer W after grinding with a laser. In the embodiment shown in FIG. Alternatively, the notch portion is configured to be irradiated with a laser. As shown in the block diagram of FIG. 7, the laser irradiation unit 101 has a laser light source 101a and an optical mechanism 101b. 101d, a mask 101e, a condenser lens 101f, a moving table 101g for focus position adjustment, and so on. In this case, the laser beam emitted from the laser light source 101a is redirected by the relay mirror 101c, collimated into a parallel beam with a predetermined diameter by the collimator 101d, travels along the light shielding mask 101e, and passes through the condenser lens 101f. is converged to a predetermined position on the surface of the silicon wafer W to be irradiated. The condensing lens 101f is mounted on a moving table 101g for focal position adjustment, and the position to converge the laser is matched with the position on the silicon wafer W to be irradiated. The optical elements that make up the optical mechanism 101b are not limited to the illustrated example, and include at least one of mirrors, galvanomirrors, lenses, prisms, collimators, polarizers, beam splitters, masks, and the like. , as long as they can adjust the laser irradiation conditions. The galvanomirror scans the irradiation target surface with the laser by its rotation and vibration.

The laser irradiation repair apparatus 100 further includes a measuring device 102 and a control device 103 . Although not shown in FIG. 1, as shown in FIG. 7, a temperature control device 104 for heating and cooling the silicon wafer W held by the wafer feeding unit 20 and a silicon An atmosphere maintaining device 105 is also provided for keeping the gas composition and pressure in a predetermined processing area surrounding the wafer W within a predetermined range.

As shown in FIG. 1, the measuring device 102 has a measuring device main body 102a which is attached to the Z table 31 of the wafer feeding unit 20 via a support 102b. is held in a non-contact state. The measuring instrument main body 102a is configured so that its position can be adjusted on the column 102b. properties, scattered light, etc.) and/or shape.

In order to set the irradiation conditions and the irradiation atmosphere at the start of laser irradiation, the surface state of the silicon wafer W is measured after grinding the silicon wafer W and before the laser irradiation. Measure the condition, etc. In addition, to prevent over-irradiation of the laser and to monitor the appropriateness of the irradiation situation, the measurement should be performed during the laser irradiation, and furthermore, the measurement should be performed after the irradiation to determine the appropriateness of the irradiation result. is desirable.

Measurement of the surface state and/or shape of the silicon wafer W by the measuring device 102 is preferably non-destructive. measuring means, Raman spectroscopic measuring means, surface roughness meter, acoustic measuring means, eddy current characteristic 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 selected or a combination of two or more thereof. Some examples of these will be described with reference to FIG.

FIG. 8(a) uses an image measuring 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 light source 140 for measurement. is irradiated on the chamfered slope w2, the image is captured by a detector 141 such as a hyperspectral camera, the surface roughness is detected by analyzing the image, and irradiation from the laser irradiation unit 101 is performed based on the detection result. Conditions and the like are selected and controlled, and the chamfered slope w2 and the like are flattened and the work-affected layer is repaired. Machine learning means based on trial experiments, comparisons with control samples, etc. may be employed for determination of surface roughness and the like by such image analysis.

FIG. 8(b) is a measuring device using capacitance change measuring means. In this case, the electrode 142 is placed close to the outer peripheral end face w1 of the silicon wafer W and the chamfered slopes w2 and w3 on the front and back sides, 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 due to the static electricity, the surface roughness of the outer peripheral end face w1 and the chamfered slopes w2 and w3 on the front and back sides are detected.

FIG. 8(c) shows a measuring device using droplet contact angle measuring means. In this case, a suitable droplet 144 is adhered 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. It utilizes the fact that the wettability changes according to the level of surface roughness of the chamfered slope w2, and the contact angle 144a of the droplet 144 changes accordingly.

As the measuring means, in addition to these, although illustration is omitted, for example, Raman spectroscopic measuring means can also be used. In that case, by measuring the strain from the Raman shift, it is possible to detect the change in the crystal state inside the silicon wafer W, based on it, determine the level of alteration due to grinding, and based on the result, laser irradiation conditions, etc. can be optimally controlled. In addition, it is also possible to detect using ultrasonic waves or AE waves that do not involve destruction by acoustic measurement means, or to use a non-contact or contact-type surface roughness meter. It is also possible to measure the conductivity of the chamfered slope and determine the level of alteration due to grinding. Furthermore, using various known means such as reflectance measurement means, X-ray Lang method measurement means, electron beam diffraction measurement means, SEM measurement means, etc., the scale and state of deterioration due to grinding of the surface of the silicon wafer W can be measured. can be determined, and based on the results, the laser irradiation conditions and the like can be optimally and efficiently adjusted and controlled.

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

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

As the temperature control device 104, as described above, the silicon wafer W can be heated and cooled to eliminate the effects of thermal stress, and the laser irradiation effect can be accelerated and optimized. In order to eliminate the influence of thermal stress on the laser irradiation unit 101 and the laser irradiation unit 101, a device for keeping the temperature thereof constant is provided.

Further, an atmosphere maintaining 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, thereby forming and maintaining an atmosphere with gas components, pressure, etc. suitable for processing conditions.

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, an example of an irradiation form capable of effective, efficient, and short-time repair in laser irradiation according to the surface state and shape of the silicon wafer after grinding by the laser irradiation repair apparatus 100 will be described. In this case, the irradiation conditions are generally changed according to the surface state by changing the laser output characteristics, energy density, etc., using the laser light source 101a and the optical mechanism 101b. In addition, the change of irradiation according to the shape of the irradiation area is generally performed by changing the position and attitude of the laser irradiation unit and/or the silicon wafer (workpiece), and the depth direction of the notch part is changed. This is done by changing the orientation of the silicon wafer side and the direction of mirrors in the optical mechanism. However, it is not limited to these, and it is also possible to appropriately select or combine these various means depending on the situation.

FIG. 9 shows an example of an irradiation pattern according to the present invention that matches the shape of the chamfered notch portion of the silicon wafer W. As shown in FIG. More specifically, in FIG. 9(a), the chamfered notch portion wn has two circular arc portions w4 and w5 on the outer peripheral side in parallel, and FIG. Enlarged cross-sectional view along BB], the chamfered slope w2 on the front side, the chamfered slope w3 on the back side, and the outer peripheral end face w1 of the notch recess can also be continuously irradiated with the laser. Mechanism is shown. In FIG. 9A, only the notch portion wn of the silicon wafer W is enlarged for convenience of explanation.

That is, specifically, a pair of lasers L11a and L12a split by the beam splitter 101m are incident on individual galvanomirrors 101n and 101o, respectively, and are further reflected to form the notch portion by the reflected lasers L11b and L12b. wn are configured to irradiate a pair of outer arc portions w4 and w5, respectively. At this time, by rotating or reciprocatingly rotating the galvanomirrors 101n and 101o, the directions of the reflected lasers L11b and L12b are changed, and the chamfered slopes w2 on the front side and the chamfered slopes on the back side of the outer peripheral arc portions w4 and w5 are scanned. The w3 and the outer peripheral end face w1 are simultaneously and efficiently irradiated with the laser. In the illustrated embodiment, the galvanometer mirrors 101n and 101o are parabolic mirrors, and are designed to focus on the outer arc portions w4 and w5, which are irradiation targets. This focus position can be adjusted by adjusting the moving table 101g of the condenser lens 101f shown in FIG. be. In FIG. 9A, O1 is the center of the radius of curvature of the 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 arc portions w4 and w5 of the notch portion wn. be. The uneven shapes drawn on the chamfered slope w2 on the front side and the chamfered slope w3 on the back side in FIG.

By using such an optical mechanism, if the focal points of the galvanomirrors 101n and 101o are aligned with the chamfered slope of the outer periphery of the rotating silicon wafer W, laser irradiation can be performed not only on the notch portion but also on the outer periphery of the silicon wafer W. The chamfer slopes and end faces on the front and back sides of the can be efficiently and effectively repaired, for example, the entire circumference can be quickly repaired in less than 10 seconds. As shown in FIG. 9(a), a polarizer 101l and a beam splitter 101k for luminous flux adjustment are provided before the beam splitter 101m in FIG. 9(a). 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 the optical mechanism of the present invention.

Further, FIG. 10(a) shows another configuration example in which the chamfered slope w2 on the front side of the silicon wafer W, the chamfered slope w3 on the back side, and the outer peripheral end face w1 of the silicon wafer W are irradiated at the same time. That is, a pair of lasers L13a and L14a split by the beam splitter 101h are made incident on individual galvanomirrors 101i and 101j, respectively, and then reflected to chamfer the front side of the silicon wafer W by the respective reflected lasers L13b and L14b. A configuration example is shown in which the oblique surface w2 and the chamfered oblique surface w3 on the back side are respectively irradiated. More specifically, in this irradiation example, the laser emitted from the laser light source 101a shown in FIG. 101h and split into two lasers L13a and L14a. Among them, the laser L13a is reflected by the galvanomirror 101i placed on the optical path of the laser L13a, and the chamfered slope w2 on the front side of the silicon wafer W is irradiated with the laser L13a. By rotating the galvanomirror 101i or rotating it within a predetermined angle range, the slope w2 is irradiated in a scanning manner by the reflected laser L13b. Similarly, the laser L14a is reflected by the galvanomirror 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 irradiate the end face w1 on the outer periphery of the silicon wafer W, the arrangement of the optical elements is adjusted so that the end face w1 is included in the scanning range of the galvanomirrors 101i and/or 101j. good too. Alternatively, the entire irradiation target area may be irradiated by changing the orientation of the silicon wafer W during the irradiation period. In the example shown in FIG. 10(a), the peripheral end surface w1 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 the galvanomirrors 101i and 101j are also included in the components of the optical mechanism 101b.

Next, FIG. 10(b) shows a suitable irradiation form in the case of irradiating the arc portion w6 at the bottom of the recess of the notch portion wn of the silicon wafer W with the laser L. As shown in FIG. In this case, the center O1 of the radius of curvature of the 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), Irradiation is performed while rotating the silicon wafer W itself around this O1. Alternatively, while the center O1 is placed on the optical path of the laser L, the laser irradiation direction may be rotated around the center O1. As a result, the laser L continues to irradiate in a state substantially perpendicular to the curved surface of the 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 placed at the rotation center of the wafer table 34 of the wafer feeding unit 20 of the grinding and repairing apparatus 1 shown in FIG. The center O1 of the radius of curvature is positioned so that the wafer table 34 is rotated.

Next, FIG. 10(c) shows a suitable irradiation form in the case of irradiating the straight portion w7 (the same applies to w8) of the recess of the notch portion wn of the silicon wafer W with the laser L. As shown in FIG. In this case, the silicon wafer W is linearly moved along the direction of the linear portion w7 while the irradiation direction of the laser L is kept perpendicular to the linear portion w7. As a result, 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 linear portion w7, for example, the X table 24 and the Y table 28 of the wafer feeding unit 20 of the grinding and repairing apparatus 1 shown in FIG. It can be linearly moved along the direction of the portion w7.

FIG. 11(a) shows an enlarged cross-sectional view of the chamfered portion of the outer peripheral portion of the silicon wafer W to be irradiated with laser according to the present invention, and FIG. 11(b) shows a plan view of the notch portion. . An example of the specifications of suitable irradiation conditions for such an irradiation target is as follows: laser wavelength λ = 532 nm, pulse width = 3 to 7 ns (generally 10 ns or less. However, the damage on the surface of the silicon wafer is large and deep. In some cases, up to about 50 ns may be required.), 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×0.5 mm, atmospheric pressure=atmospheric pressure.

Next, referring to FIG. 12, a method for repairing the ground surface of a silicon wafer according to the present invention will be described. That is, the method according to the present invention is a method for repairing the ground surface of a silicon wafer W that has been previously ground for chamfering or the like.

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

Next, (b) the surface of the silicon wafer W held by the wafer feeding unit 20 is ground by the grinding unit 10 . In 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. As shown in FIG.

That is, (1) before laser irradiation by the laser irradiation repair apparatus 100, the surface state and/or A step of measuring the shape is performed.

Next, (2) the controller 103 provided in the laser irradiation repair apparatus 100 performs the step of setting the laser irradiation conditions and/or the irradiation atmosphere based on the measurement data from the measurement device 102 .

Next, (3) a step of irradiating the ground surface of the silicon wafer W with a laser by the laser irradiation unit 101 provided in the laser irradiation repair apparatus 100 is executed 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 laser irradiation if repaired and restarting or continuing laser irradiation until repair is confirmed if not repaired is performed.

As described above, according to the method of the present invention, the laser irradiation unit 101 provided in the laser irradiation repair apparatus 100 can efficiently perform laser irradiation according to the surface state and shape of the silicon wafer W. In the step of irradiating the ground surface of the wafer W with the laser, the operation of irradiating the outer peripheral edge portion and/or the notch portion chamfered by the grinding of the silicon wafer W with the laser can be preferably performed.

Further, according to the method of the present invention, in the step of irradiating the laser, as described above, 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 (laser direction, beam diameter, scanning range, frequency, etc.).

Further, according to the method of the present invention, since the laser is irradiated according to the shape of the irradiated portion of the silicon wafer W acquired by the measuring device 102, as described above, a plurality of laser beams are emitted from the laser light source 101a of the laser irradiation unit 101. It is possible to irradiate a plurality of locations of the silicon wafer W from various directions with each of the laser beams that have been dispersed, so that the outer peripheral portion and the notch portion having different shapes can be efficiently irradiated.

Further, according to the method of the present invention, as explained with reference to FIG. 9, a pair of lasers L11a and L12a split by the beam splitter 101m are made incident on individual galvanomirrors 101n and 101o, respectively, and are further reflected to produce The reflected lasers L11b and L12b can be used to simultaneously irradiate the pair of outer arcuate portions w4 and w5 of the notch portion wn of the silicon wafer, respectively. It is possible to efficiently perform the irradiation operation of

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

Further, according to the method of the present invention, as explained with reference to FIG. While being held constant, the center O1 of the radius of curvature of the arc portion w6 at the bottom of the recess of the notch portion wn is placed on the optical path of the laser L, and the silicon wafer W itself is rotated around this O1 and irradiated. Thus, it is possible to efficiently irradiate the arc portion of the recess bottom of the notch portion wn, which has conventionally been difficult to irradiate efficiently and satisfactorily.

Further, according to the method of the present invention, as described with reference to FIG. It is possible to linearly move the silicon wafer W along the direction of the linear portion w7 (w8) while maintaining the direction perpendicular to the linear portion w7 (w8). It is possible to efficiently irradiate the linear portion of the recess of the notch portion wn, which has been difficult to do.

In FIG. 13, in order to explain the effect of repairing the surface of the silicon wafer W after grinding according to the present invention by laser irradiation, unevenness of the surface layer generated when the surface of the silicon wafer W is ground is flattened by laser irradiation. An image diagram for repairing is shown. That is, as shown in FIG. 13(a), when the surface of the silicon wafer W is ground, the surface region of the original single crystal layer w9 becomes a work-affected layer and becomes a rough surface having irregularities w10. When this rough surface is irradiated with a laser L, the irradiated surface region melts and becomes a flat surface w11 as shown in FIG. be done. The principle will be described with reference to FIG.

As shown in FIG. 14(a), in the ground portion of the silicon wafer, the layer near the surface of the processed portion has crystal defects due to mechanical processing, resulting in a work-affected layer such as an amorphous layer or a dislocation layer. Since the laser absorptance of this work-affected layer portion is significantly higher than that of the single crystal region, as shown in (b), the work-affected layer is melted by irradiation with a laser (nanosecond pulse laser), and is transferred to (c) by heat conduction. As the melted region expands as shown, the surface of the melted region flattens due to surface tension. When the laser irradiation is stopped, as shown in (d), a liquid phase epitaxial crystal grows using the single crystal region as a seed, and as a result, the crystal lattice defect generated during the grinding process disappears, and (e). 2, the portion irradiated with the laser is restored to the original single crystal (see Patent Document 4).

Finally, referring to FIGS. 15 and 16, the surface state of the silicon wafer surface after grinding is compared with that before and after laser irradiation by the laser irradiation repair apparatus and method according to the present invention. The effect of the present invention will be explained by the following. FIG. 15 is a microscope photograph of a notch portion of a silicon wafer before laser irradiation after grinding by a grinding and repairing apparatus equipped with a laser irradiation and repairing apparatus according to the present invention, and FIG. 2 is a micrograph after the region of the notch portion of the silicon wafer shown in FIG.

As shown in FIG. 15, fine grinding marks (scratches or streaks) are present on the ground surface including the chamfered slope w2 of the notch portion wn of the silicon wafer W before laser irradiation after the grinding process is finished. formed. That is, the entire region from one outer peripheral arc portion w4 of the notch portion wn to the other outer peripheral arc portion w5 via the straight portion w7, the recess bottom arc portion w6, the other straight portion w8, and the other outer peripheral arc portion w5. Grinding marks consisting of a large number of fine, substantially parallel uneven streaks are formed, resulting in a rough surface. Such grinding marks are formed not only on the notch portion wn shown in the photograph, but also on the outer peripheral end face and the chamfered slope of the outer periphery of the silicon wafer W. In addition, the damage caused by grinding is not limited to the surface that can be observed with a microscope, and as described above, a region at a predetermined depth from the surface is transformed into an amorphous layer or a dislocation layer, which is a work-affected layer that extends to the inside. I'm listening.

FIG. 16 shows the state after laser irradiation treatment is performed on the surface region of the notch portion of the silicon wafer shown in FIG. That is, after the laser irradiation treatment, as described above, the notch portion wn passes through the arc portion w4 on the outer circumference side to the straight portion w7, the arc portion w6 at the bottom of the recess, the other straight portion w8, and then the other outer circumference. It can be visually recognized that the surface of the area up to the side arc portion w5 is a smooth and glossy flat surface as a whole. That is, by irradiating the ground surface with the laser from various directions under irradiation conditions such as appropriate intensity while adjusting the laser to correspond to the shape and surface condition of the notch portion wn, normally uniform and good irradiation can be obtained. According to the present invention, the notch portion wn, which is difficult to clean, is evenly, uniformly, efficiently, rapidly, and effectively irradiated with a proper laser, and based on the above-mentioned repair principle, the damage caused by grinding is reduced. It is to be repaired.

The present invention has the above configuration, and by measuring the surface condition and shape of the silicon wafer with the measuring device, the scale and condition of the damaged portion due to the grinding process are confirmed and grasped, and the control device controls the laser irradiation. Efficient wafer surface repair and flattening can be performed by controlling the laser irradiation conditions, atmosphere, etc. via the displacement mechanism, optical mechanism, temperature control device, etc. of the unit and performing effective laser irradiation. becomes possible. In addition, since a laser scanning method suitable for the shape can be executed, proper repair can be performed in a short time.

L... Laser W... Silicon wafer (workpiece)
w1: End face of outer circumference or notch recess w2: Chamfered slope on the front side w3: Chamfered slope on the back side w4, w5: Arc portion on the outer peripheral side of the notch portion w6: Arc portion on the bottom of the notch portion w7, w8: Notch portion Straight portion w9 of the recess: single crystal layer w10: unevenness w11: flat surface wn: notch portion O1: centers of the radius of curvature of the arc portion of the bottom of the recess of the notch portion O2, O3: arc portions on the outer peripheral side of the notch portion Curvature radius center 1 Grinding and repairing apparatus according to the present invention 10 Grinding unit 11 Main body base 12 Wafer feeding unit driving device 20 Wafer feeding units 21, 121 X-axis bases 22, 122 X-axis guide rail 23 , 123...X-axis linear guides 24, 124...X-tables 25, 125...X-axis drive mechanisms 26, 126...Y-axis guide rails 27, 127...Y-axis linear guides 28, 128...Y-tables 29, 129...Z-axis guides Rails 30, 130 Z-axis drive mechanisms 31, 131 Z-tables 32, 132 θ-axis motors 33, 133 θ-spindles 34, 134 Wafer table 40 Supply and recovery robot 41 Truer 50 Grindstone rotation unit 51 Periphery Grinding wheel spindle 52 -- Periphery rough grinding wheel 53 -- Turntable 54 -- Upper periphery fine grinding spindle 55 -- Periphery fine grinding wheel 55-1 -- Upper periphery fine grinding wheel (upper grinding wheel)
55-2 ... Lower periphery precision grinding wheel (lower grinding wheel)
56 Upper and outer periphery fine grinding motor 57 Lower and lower periphery fine grinding spindle 59 Lower fixed frame 60 Outer periphery rough grinding device 61 Notch rough grinding wheel 62 Notch rough grinding spindle 63 Notch rough grinding motor 64 Notch Precision grinding wheel 65 Notch precision grinding spindle 66 Notch precision grinding motor 70 Wafer cassette 71 Cassette table 80 Transfer 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 Collecting lens 101g Moving table 101h for adjusting focal position Beam splitters 101i, 101j Galvanomirror 101k Beam splitter 101l Polarizer 101m Beam splitters 101n, 101o Galvanomirror 102 Measuring device 102a Measuring device body 102b Post 103 Control device 104 Temperature control device 105 Atmosphere maintaining device 120 Displacement mechanism 135 Rotary table 136 Tilting base 137 Pivot pin 138 Cam 139 Cam pin 140...Light source for measurement 141...Detector 142...Electrode 143...DC power supply 144...Droplet 144a...Contact angle

Claims (6)

A laser irradiation repair apparatus for the surface of a silicon wafer after grinding,
a measuring device for measuring at least the surface state of a silicon wafer;
a laser irradiation unit;
a displacement mechanism that displaces the relative position between the laser irradiation unit and the silicon wafer;
a control device for controlling laser irradiation conditions and/or irradiation atmosphere based on data measured by the measuring device;
has
The laser irradiation unit is an apparatus for repairing a surface of a silicon wafer after grinding by laser irradiation, wherein the laser irradiation unit irradiates a chamfered outer peripheral edge portion and/or a notch portion of the silicon wafer after grinding. 2. The apparatus for repairing a ground surface of a silicon wafer by laser irradiation according to claim 1, wherein said laser irradiation unit performs laser irradiation until repair is confirmed based on the measurement result of said surface condition. 3. The laser irradiation repair apparatus for a ground surface of a silicon wafer according to claim 2, wherein said measuring device measures said surface state before, during and/or after said laser irradiation. A measurement device for measuring at least the surface state of a silicon wafer, a laser irradiation unit, a displacement mechanism for displacing the relative position of the laser irradiation unit and the silicon wafer, and laser irradiation based on measurement data from the measurement device. A method for repairing a surface of a silicon wafer after grinding by a laser irradiation repairing apparatus having a control device for controlling conditions and/or an irradiation atmosphere,
measuring at least the surface state of the silicon wafer with the measuring device;
a step of setting laser irradiation conditions and/or an irradiation atmosphere by the control device based on data measured by the measurement device;
a step of irradiating the chamfered outer peripheral edge portion and/or the notch portion of the silicon wafer after grinding with laser irradiation 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, comprising: 5. The method of repairing a ground surface of a silicon wafer according to claim 4, wherein said step of irradiating said laser is a step of irradiating said laser until said repair is confirmed based on said measurement result of said surface state. 6. The silicon wafer after grinding according to claim 5, wherein the step of measuring the surface state is a step of measuring the surface state before, during, and/or after the laser irradiation. Surface repair method.

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