JP6932865B1 - Reformer and reformer method for wafer edge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high-quality and high-speed surface treatment by continuously laser scanning with high accuracy even if it has a complicated three-dimensional shape such as a notch in a wafer edge reforming apparatus using laser heat treatment. .. An arc type having an optical system that irradiates a notch portion 4 with a laser beam 5 from a laser light source 10, and the optical system reflects the laser beam 5 and is combined in a dogleg shape on side surfaces to form a concave mirror. A polygon mirror 7 leading to the mirror 9 and a three-dimensional curved body having a plano-convex cross-sectional shape and a curved shape when viewed from above, and condensing the laser beam 5 reflected by the mirror 9 on the notch portion 4. A condenser lens 8 is provided, and the notch portion 4 is scanned and irradiated with the laser beam 5 by rotating the polygon mirror 7. [Selection diagram] Fig. 3

Description

The present invention relates to a reformer that repairs surface defects, which are a processing alteration layer of a wafer surface, and flattens the roughness by laser heat treatment, and in particular, a reformer for a wafer edge portion that irradiates an edge portion with a laser. And the reforming method.

Semiconductor wafers such as silicon wafers used in the manufacture of semiconductor devices and the like are surface-processed by machining processes such as cutting, grinding, lapping, and polling. However, a processed alteration layer is formed on the surface and the inside thereof, and some of the processed alteration layers contain microcracks (microcracks). The removal of internal cracks and the like is mainly performed by chemical and mechanical methods such as etching and chemical mechanical polishing (CMP).

Further, Patent Documents 1 and 2 describe that after performing grinding such as chamfering, repairing a surface-processed altered layer of a silicon wafer and flattening the roughness are efficiently and effectively performed by irradiating a pulse laser. It is described that a laser irradiation unit having an optical mechanism including at least one of a mirror, a galvanometer mirror, a lens, a prism, a collimator, a polarizer, and a beam splitter is used in addition to the laser light source.

Then, when irradiating the arc portion at the bottom of the recess portion of the notch portion with the laser, it is described that the silicon wafer itself is irradiated while being rotated, or the laser irradiation direction is swiveled. Further, it is described that when irradiating a straight portion of a notch portion recess with a laser, a wafer feed unit is used to linearly move a silicon wafer along the direction of the straight portion.

Further, Patent Document 3 discloses a light projecting unit that emits light while moving the angle in an angular manner and a light projecting unit that emits light in order to enable easy and highly accurate arrangement of optical devices constituting the optical scanning device in the laser processing device. It is provided with one or more reflecting portions that reflect the light and guide it on a predetermined scanning line, and scan the laser beam along the scanning line set on the work after reflecting the angularly moving laser beam. The optical scanning apparatus configured in is described.

Japanese Unexamined Patent Publication No. 2020-131218 Japanese Unexamined Patent Publication No. 2020-1410888 Japanese Unexamined Patent Publication No. 2014-16398

In the above-mentioned prior art, those described in Patent Documents 1 and 2 can repair and flatten damage such as grinding marks by grinding. However, the ones described in Patent Documents 1 and 2 move the silicon wafer on the work side to the notch portion having a complicated three-dimensional shape during laser irradiation, and the silicon wafer on the work side is moved to the notch portion uniformly and at high speed. Surface treatment is extremely difficult.

Further, the laser processing apparatus described in Patent Document 3 simplifies the alignment work of the incident optical path and the outgoing optical path, and by extension, the alignment work of the equipment constituting the reflecting portion can be performed easily and with high accuracy. However, if the laser processing apparatus described in Patent Document 3 is simply applied to the notch portion, there is a limit to uniform and high-speed surface treatment on the notch portion as in Patent Documents 1 and 2.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to irradiate a complex three-dimensional shape such as a notch portion with a laser, as a uniform surface treatment, the entire notch portion is continuous (the processed portion is seamless). Laser scanning, high-speed surface treatment, for example, minimizing the movement of the silicon wafer on the work side during laser irradiation and making the incident angle substantially perpendicular to the irradiation surface, and appropriately setting the irradiation conditions It is an object of the present invention to provide a high-quality and high-speed reformer for a wafer edge portion and a reforming method by realizing the determination and the like.

In order to achieve the above object, the present invention has an optical system for irradiating a notch portion with laser light from a laser light source in a wafer edge portion reforming apparatus using laser heat treatment, and the optical system is the laser light. A polygon mirror that reflects light and leads to an arc-shaped mirror that is combined in a dogleg shape to form a concave mirror, and a three-dimensional curved body that has a plano-convex cross-sectional shape and a curved shape when viewed from above. A condensing lens that collects the laser light reflected by the mirror to the notch portion is provided, and the polygon mirror rotates to scan and irradiate the notch portion with the laser light.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, the irradiation section of the notch portion is defined as (1) piece R portion, (2) straight portion, (3) bottom R portion, and (2) straight portion. The laser is divided into a (2') straight line portion having a different inclination direction and a (1') piece R portion symmetrical to the (1) piece R part, and the optical system is three-dimensionally configured for each of a plurality of layers. It is desirable that the light is emitted for each irradiation section by the optical system for each layer.
Further, it is desirable that the reformer of the wafer edge portion using the above laser heat treatment is provided with an attitude control means for controlling the irradiation position so that the laser light is irradiated for each irradiation section by the optical system for each layer. ..

Further, in the reformer of the wafer edge portion using the above laser heat treatment, the (2) straight portion and the (2') straight portion, which are the irradiation sections, determine the distance between the rotation centers of the mirror and the polygon mirror. It is desirable to increase the size so that the laser scanning trajectory is linearly approximated.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, it is desirable to use the laser light source as one unit and split the laser light into the optical system for each layer by a beam splitter.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, it is desirable to use a plurality of the laser light sources to guide the laser light to the optical system for each layer.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, it is desirable to determine the cumulative irradiation energy corresponding to the crystal orientation of the notch portion and irradiate the laser beam.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, it is desirable to change at least one of the energy density, the scan pitch, and the number of irradiations according to the curvature of the notch portion to perform the irradiation.

Further, in the reformer of the wafer edge portion using the above laser heat treatment, it is desirable that the laser light is used in combination with the CW (continuous) laser irradiation in addition to the irradiation of the nanosecond pulse laser.

The present invention is a method for modifying a wafer edge portion using laser heat treatment, in which a polygon mirror that reflects laser light and leads to an arcuate mirror whose side surfaces are combined in a dogleg shape to form a concave mirror and a cross-sectional shape. Is a three-dimensional curved body having a plano-convex shape and a curved shape when viewed from the upper surface, and using an optical system including a condensing lens that collects the laser light reflected by the mirror into a notch portion. By rotating the polygon mirror, the notch portion is scanned and irradiated with the laser beam.

According to the present invention, a polygon mirror that reflects laser light and guides it to an arc-shaped mirror whose side surfaces are combined in a dogleg shape to form a concave mirror, and a plano-convex cross-sectional shape that is curved when viewed from above. It is a three-dimensional curved surface, and the laser beam is scanned into the notch by rotating the polygon mirror using an optical system equipped with a condenser lens that collects the laser light reflected by the mirror into the notch. Even if it is a complicated three-dimensional shape such as a notch part, it is possible to perform laser scanning with high accuracy and continuously (without a break in the processing part), change the irradiation angle, and use the laser. By combining the types, high-quality surface treatment can be performed under conditions suitable for local aspects (states) such as crystal orientation and surface waviness.

It is a figure which shows the shape (notch shape) of a notch part 4, (a) is a plan view, (b) is a cross-sectional view of a dash-dotted line part. Explanatory drawing which shows an example of laser irradiation to the end face T of the notch part 4 by one Embodiment of this invention. A block diagram showing a basic configuration of an optical system according to an embodiment of the present invention. A block diagram showing a basic configuration of an optical system according to an embodiment of the present invention. Explanatory drawing (top view) showing the hierarchical relationship between the irradiation section of the first embodiment and the optical system. Explanatory drawing (structural drawing) showing the hierarchical relationship between the irradiation section of the first embodiment and the optical system. The figure which shows the relationship between the shape of the mirror 9, the condenser lens 8 and the laser beam 5 in each irradiation section. Top view showing the configuration of the optical system of the first embodiment Top view for explaining (1) irradiation to the piece R portion by the one-layer optical system of the first embodiment. Explanatory drawing seen from the cross section explaining the irradiation to (1) piece R part by the 1-layer optical system of 1st Embodiment Top view for explaining (2) irradiation to a straight line portion by the two-layer optical system of the first embodiment. Explanatory drawing seen from the cross section showing the relationship between the two-layer optical system and the 2'layer optical system of the first embodiment. Top view for explaining (3) irradiation of the bottom R portion by the three-layer optical system of the first embodiment. Explanatory drawing seen from the cross section showing the relationship between the three-layer optical system and the 3'layer optical system of the first embodiment. Perspective view illustrating the operation of the attitude control means 12 of the first embodiment. A diagram (structural diagram) for explaining the relationship between the irradiation section of the second embodiment and the hierarchy of the optical system. Top view showing (2) irradiation of a straight line portion by the 2'layer optical system of the second embodiment. Explanatory drawing seen from the cross section showing the relationship between the two-layer optical system and the 2'layer optical system in the second embodiment. Block diagram showing the system configuration in each embodiment

1A and 1B are views showing the shape (notch shape) of the notch portion 4, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view of a alternate long and short dash line portion. The notch shape is a complicated three-dimensional shape, and the irradiation section thereof is (1) one piece R part, (2) straight part, (3) bottom R part, and (2) straight part from the left end of FIG. 1A. It is followed by a (2') straight line portion having a different inclination direction, and a (1') piece R portion symmetrical with the (1) piece R portion. Further, the cross-sectional shape is an end surface T perpendicular to the upper surface 2 or the lower surface 3 of the silicon wafer 1, two R portions R1 and R2 connected to both ends of the end surface T, and two slopes X1 connected to the two R portions, respectively. There is X2. The crystal orientations of the upper surface 2 or lower surface 3 of the silicon wafer 1, the end faces T, the R portions R1 and R2, and the slopes X1 and X2 are also different.

Laser irradiation to the notch portion 4 is performed in each irradiation section having a complicated three-dimensional shape as shown in FIG. 1, and by using optical components and actuators, a uniform and high-speed laser heat treatment is configured. Uniform surface treatment is a continuous (continuously seamless) constant velocity laser scan across the notch 4 (if that is difficult, adjust the laser irradiation energy appropriately for speed changes), shape. Achieved by continuous laser irradiation for changes. High-speed surface treatment is performed by avoiding movement of the work side during laser irradiation as much as possible. Further, the laser irradiation is substantially perpendicular to the processing surface (irradiation surface) (incident angle is 10 to 15 ° or less). Further, the irradiation conditions are determined according to the crystal orientation and shape.

FIG. 2 is an explanatory view showing an example of laser irradiation on the end surface T of the notch portion 4. Irradiation of each part (end face T, R part R1, R2, slope X1, X2) of the notch portion 4 in the thickness direction is fixed by vacuum chucking the wafer, and at least in the pitch direction (up and down with the left and right axes as axes). A chuck table having a rotation axis in the direction of rotation) is rotated around the rotation axis to change the posture. In the laser irradiation of the end surface T of the notch portion 4, the laser scanning trajectory of the laser irradiation portion (1) piece R portion is indicated by arrows a to b as (1) in the drawing.

The laser scanning trajectory to the laser irradiation section (2) straight section is indicated by arrows c to d as (2) in the figure. The laser scanning trajectory to the laser irradiation section (3) bottom R section is indicated by arrows d to e as (3) in the figure. Hereinafter, the laser irradiation to the laser irradiation unit (2') straight portion and the (1') piece R portion is performed in the same manner, and both laser irradiations are performed continuously and perpendicular to the irradiation surface.

However, since the (2') straight part and (1') piece R part are symmetrical with respect to the notch bottom position, they are the same as the (1) piece R part and (2) straight part, but the laser scanning trajectories are on the same plane. If there is, the parts constituting the optical system interfere with each other. For example, (2') the laser scanning trajectory to the straight section (2') interferes with (1) the laser scanning trajectory to the single R portion (1) and (3) the laser scanning trajectory to the bottom R portion (3). do.

In addition, (1') the laser scanning trajectory to the single R portion (1') interferes with (2) the laser scanning trajectory to the straight portion (2) and (3) the laser scanning trajectory to the bottom R portion (3). do. Therefore, since the optical system interferes when the optical system is assembled on the same plane, the optical system is divided into a plurality of layers corresponding to each irradiation section and arranged so that the optical components do not interfere with each other. Further, the (2) straight line portion and the (2') straight line portion approximate the laser scanning trajectory with an arc having a small curvature.

The reformer for the wafer edge portion has the following structure in summary. In the optical system, polygon mirrors (rotating multifaceted mirrors) 6 and 7, mirrors (reflectors) 9, beam splitter 38 and condenser lens 8 are appropriately arranged as deflection elements as optical components, and polygon mirrors 6 and 7 are motors and the like. Rotates and controls at high speed with the actuator of. This enables the optical system to scan the laser irradiation at a constant speed and at a high speed.

The laser beam 5 emitted from the laser light source 10 is continuously scanned at high speed along the notch shape. Further, since the optical system interferes when assembled on the same plane, it is three-dimensionally configured for each of a plurality of layers, and the laser beam 5 is irradiated for each irradiation section by the optical system for each layer. The laser beam 5 is branched for each layer by a beam splitter 38 or the like according to the irradiation section.

The laser beam 5 selects a wavelength, pulsed or continuous (CW) laser depending on the material of the wafer. Further, a plurality of laser beams 5 may be combined. The selected laser beam 5 is deflected by the polygon mirror 7 that rotates at high speed. Next, the laser beam 5 is deflected through the mirror 9 or the like so that the incident angle is substantially perpendicular to the irradiation surface, for example, corresponding to the notch shape. The laser irradiation angle may be adjusted so as to be suitable for the surface condition. Further, the deflected laser beam 5 is condensed by a condenser lens 8 having a shape corresponding to the notch shape, and the notch portion 4 is scanned and irradiated with the laser beam 5.

As described above, the reformer of the wafer edge portion can perform uniform processing (high quality) with high accuracy on the entire notch portion 4 whose shape changes in three dimensions at high speed. Further, it is possible to perform surface treatment under conditions suitable for local aspects (states) such as crystal orientation and surface undulation by changing the irradiation angle of the laser beam 5 or combining the types of the laser beam 5. can.

3 and 4 are configuration diagrams showing the basic configuration of the optical system. FIG. 3 shows the basic configuration of the optical system used in the laser irradiation unit (1) piece R part, (3) bottom R part, and (1') piece R part shown in FIG. 2, and FIG. 4 shows the same (2). ) This is the basic configuration of the optical system used in the straight section and (2') straight section.

In FIG. 3, the laser beam 5 from the laser light source 10 is reflected by the polygon mirrors 6 and 7 rotating at high speed and reaches the mirror 9. The laser beam 5 incident on the mirror 9 becomes a laser scanning trajectory that moves in an arc centered on the rotation center of the polygon mirror 7. The laser beam 5 reflected by the mirror 9 is condensed through the condenser lens 8 and irradiates the notch portion 4.

As shown in the figure, the condenser lens 8 is a three-dimensional curved surface having a plano-convex cross-sectional shape and a curved surface when viewed from the upper surface. FIG. 4 is the same as FIG. 3, but the distance between the rotation centers of the mirror 9 and the polygon mirror 6 is increased, and the laser scanning trajectory is linearly approximated by an arc having a small curvature.

5 and 6 are explanatory views showing the hierarchical relationship between the irradiation section of the laser beam 5 of the first embodiment and the optical system, FIG. 5 is a top view, and FIG. 6 shows a hierarchical structure. In the first embodiment, the entire optical system has one laser light source 10, and the basic configurations of the optical systems shown in FIGS. 3 and 4 are three-dimensionally arranged (particularly, arranged in the height direction) in a plurality of layers. It is composed.

5A and 5B are views of the upper surface of the silicon wafer 1 as viewed from above, and FIG. 5C is a view of the lower surface of the silicon wafer 1 as viewed from below. As shown in FIGS. 5 (a) and 6 (1), the irradiation section of the piece R portion is irradiated with a one-layer optical system. Since the irradiation of the (1') piece R portion is symmetrical with respect to the line passing through the notch bottom and the center of the wafer, the (1') piece R portion is irradiated with the five-layer optical system arranged symmetrically with respect to the one-layer optical system.

As shown in FIGS. 5 (b) and 6 (2), the irradiation section of the straight line portion is irradiated with a two-layer optical system. (2') Irradiation of the straight line portion is symmetrical with respect to the line passing through the notch bottom and the center of the wafer, so irradiation is performed with a four-layer optical system arranged symmetrically with respect to the two-layer optical system. As shown in FIGS. 5 (c) and 6 in the 2'layer optical system, the 2'layer optical system sandwiching the silicon wafer 1 and the 2'layer optical system forming a mirror image are formed on the upper surface side and the lower surface side of the silicon wafer 1. Arrange them in pairs.

Hereinafter, similarly, in the first embodiment, the three-layer optical system and the mirror image of the 3'layer optical system, the four-layer optical system and the mirror image of the 4'layer optical system, and the five-layer optical system and the mirror image of the 5'layer Place the optical system. In the reformer, the laser beam 5 is rotated in the pitch direction by rotating the switching means 11 of each layer (1 to 5, 2'to 5'layer optical system) and the silicon wafer 1, and the irradiation position is set in FIG. 1 (1). The attitude control means 12 for switching between the slopes X1 and X2, the end faces T, and the R portions R1 and R2 shown in b) is provided.

FIG. 7 is a diagram showing the relationship between the shapes of the mirror 9 and the condenser lens 8 and the laser beam 5 in each irradiation section. Fig. (A) shows (1) piece R part, (1') piece R part, figure (b) shows (2) straight part, (2') straight part, and figure (c) shows (3) bottom R part. be. In FIG. 3A, the laser beam 5 is incident on the upper side of the arcuate mirror 9 which is a concave mirror whose side surfaces are combined in a dogleg shape, is reflected on the lower side, and is a condenser lens as shown in FIG. Up to 8. The condenser lens 8 is a three-dimensional curved surface having a plano-convex cross-sectional shape and a curved surface shape when viewed from the upper surface.

In FIG. (B), the curvature seen from the upper surface of the mirror 9 and the condenser lens 8 is an arc smaller than that in FIG. (A), and the laser scanning trajectory of the laser beam 5 is approximated to a straight line. FIG. (C) is the same as FIG. (A), but the curvature (or focal length) seen from the upper surface of the mirror 9 and the condenser lens 8 is (3) the bottom R portion and (1) the piece R portion. Corresponds to the difference in distance.

FIG. 8 is a top view showing the configuration of the optical system of the first embodiment, and shows an example of irradiation of the irradiation section (see FIGS. 1 and 2) of the (1) piece R portion by the one-layer optical system. The laser beam 5 from the laser light source 10 is reflected by the polygon mirrors 6 and 7 rotating at high speed via the polygon mirror 21 and the fixed mirror 23 as the one-layer optical system shown in FIG. 3 and reaches the mirror 9. Irradiation to the notch portion 4 is the same as that described with reference to FIG.

The laser beam 5 from the laser light source 10 is guided to the two-layer optical system via the optical paths of the polygon mirror 21, the rotating mirror 22, the polygon mirror 24, the fixed mirror 25, and the deflection mirror 26. Further, the laser beam 5 is guided to the three-layer optical system via the polygon mirror 21, the rotating mirror 22, the polygon mirror 24, the rotating mirror 27, the rotating mirror 28, the fixed mirror 29, and the deflection mirror 30. Further, the laser beam 5 branched by the rotating mirror 28 is guided to the four-layer optical system via the fixed mirror 31 and the deflection mirror 32. Then, the laser beam 5 branched by the rotating mirror 27 is guided to the five-layer optical system via the fixed mirrors 33 and 34 and the deflection mirror 35.

Switching to the 1- to 5-layer optical system is performed by rotating the polygon mirrors 21 and 24. Further, the mirror 9 and the condenser lens 8 are arranged in an arc centered on the rotation center of the polygon mirror 7. Therefore, the central axis of the polygon mirror 7 coincides with the center of the circle of (1) the piece R portion (see FIGS. 1 and 2).

9 is a top view for explaining (1) irradiation of the piece R portion by the one-layer optical system, FIG. 10 is an explanatory view seen from a cross section, (a) is a cross-sectional view, and (b) is a condenser lens 8. It is a perspective view of. In FIG. 9, the size of the polygon mirrors 6 and 7 is drawn small in order to make the notch portion 4 easy to see. Further, in the irradiation section of the (1') piece R portion, the optical system is arranged as a five-layer optical system symmetrically with the line g passing through the notch bottom and the center of the wafer.

In FIG. 10, the laser beam 5 is folded back at a right angle by the mirror 9 and irradiates the notch portion 4 with the optical axis shifted in the thickness direction of the silicon wafer 1. In (2) the irradiation section of the straight line portion, the curved surface of the mirror 9 is enlarged to bring the laser scanning trajectory closer to the straight line. Further, since the irradiation section of the (2') straight line portion is symmetrical with respect to the line g passing through the notch bottom and the center of the wafer, the same applies.

FIG. 11 is a top view illustrating (2) irradiation of the straight line portion by the two-layer optical system. The laser beam 5 guided to the two-layer optical system by the deflection mirror 26 is guided to the polygon mirror 6 via the mirror 36, the mirror 37, and the beam splitter 38. Irradiation to the notch portion 4 is the same as that described with reference to FIG.

The laser beam 5 branched by the beam splitter 38 is guided to the 2'layer optical system. The central axis of the polygon mirror 7 is (2) arranged on the left side with the vertical bisector f of the straight line portion as a boundary with the center of the wafer as a boundary. The same applies to the 2'layer optical system, and the 2'layer optical system is arranged symmetrically with the silicon wafer 1 interposed therebetween. That is, the 2'layer optical system is mirror-image symmetric with the two-layer optical system, and the palms are put together with the silicon wafer 1 sandwiched between them. The 3'layer optical system, the 4'layer optical system, and the 5'layer optical system have the same arrangement.

FIG. 12 is an explanatory view seen from a cross section showing the relationship between the two-layer optical system and the 2'layer optical system. In FIG. 12, the laser beam 5 branched by the beam splitter 38 is guided to the two-layer optical system (upper side in FIG. 12) on one side and to the 2'layer optical system (lower side in FIG. 12) via the mirror 39. It will be split. Irradiation to the notch portion 4 is performed through the condenser lens 8 in the same manner as described with reference to FIG. 3 in both the two-layer optical system and the 2'layer optical system.

FIG. 13 is a top view illustrating (3) irradiation of the bottom R portion by the three-layer optical system. The laser beam 5 guided to the three-layer optical system by the deflection mirror 30 is guided to the polygon mirror 6 via the mirror 40, the mirror 41, and the beam splitter 42. Irradiation to the notch portion 4 is the same as that described with reference to FIG. The laser beam 5 branched by the beam splitter 42 is guided to the 3'layer optical system. The central axis of the polygon mirror 7 is arranged at the center of the notch bottom. The same applies to the 3'layer optical system, and the 3'layer optical system is arranged symmetrically with the silicon wafer 1 interposed therebetween. That is, the 3'layer optical system is mirror-image symmetric with the 3-layer optical system, and the palms are put together with the silicon wafer 1 sandwiched between them.

FIG. 14 is an explanatory diagram showing the relationship between the three-layer optical system and the 3'layer optical system as seen in cross section. In FIG. 14, the laser beam 5 branched by the beam splitter 42 is guided to the three-layer optical system (upper side in FIG. 14) on one side and to the 3'layer optical system (lower side in FIG. 14) via the mirror 43. It will be split. Irradiation to the notch portion 4 is performed through the condenser lens 8 in the same manner as described with reference to FIG. 3 in both the three-layer optical system and the 3'layer optical system.

FIG. 15 is a perspective view illustrating the operation of the attitude control means 12 (see FIG. 6). The attitude control means 12 rotates the silicon wafer 1 in the pitch direction to switch the irradiation position between the slopes X1 and X2, the end faces T, and the R portions R1 and R2 shown in FIG. 1 (b). The silicon wafer 1 is fixed with a vacuum chuck or the like. The attitude control means 12 rotates a table having a rotation axis in the pitch direction as shown in the figure.

Then, the attitude control means 12 changes the attitude of the silicon wafer 1 so that the incident of the laser beam 5 is perpendicular to any of the slopes X1 and X2, the end faces T, and the R portions R1 and R2. With the posture of the silicon wafer 1 fixed, the position adjusting mechanism (for example, a wafer table: not shown) moves the silicon wafer 1 in the Y and Z directions to adjust the irradiation distance and the position.

Irradiation of slopes X1, X2, end faces T, R parts R1 and R2 is continuous (1) single R part, (2) straight part, and (3) bottom R part (see FIG. 1) one line at a time. conduct. Irradiation to the next line on the same surface is carried out by feeding and irradiating at a predetermined scan pitch on the Z axis.

FIG. 16 is a diagram illustrating the relationship between the irradiation section of the laser beam 5 of the second embodiment and the hierarchy of the optical system. In the second embodiment, in order to increase the irradiation energy, two laser light sources 10 and 51 are used in the entire optical system, and the basic configurations of the optical system shown in FIGS. 3 and 4 are three-dimensionally arranged in a plurality of layers. It is composed. For example, in the second embodiment, (2) the laser light source 10 is used separately in the two-layer optical system and the laser light source 51 is used separately in the 2'layer optical system for irradiating the irradiation section of the straight line portion.

Therefore, in the second embodiment, the laser beam 5 is rotated in the pitch direction by rotating the switching means 11 of the 1st to 5th layer optical system, the switching means 50 of the 2'to 5'layer optical system, and the silicon wafer 1 to the irradiation position. Is provided with the attitude control means 12 for switching between the slopes X1 and X2, the end faces T, and the R portions R1 and R2 shown in FIG. 1 (b). Hereinafter, similarly, in the second embodiment, the three-layer optical system and the mirror image of the 3'layer optical system, the four-layer optical system and the mirror image of the 4'layer optical system, and the five-layer optical system and the mirror image of the 5'layer Place the optical system. The laser light sources 10 and 51 are not limited to two units, and a plurality of units may be provided, and the laser light source 10 may be appropriately branched and guided to each optical system, or may be provided for each layer.

FIG. 17 is a top view showing the configuration of the optical system of the second embodiment, and shows irradiation of the (2) straight line portion (see FIGS. 1 and 2) by the 2'layer optical system. The one-layer optical system is the same as that of the first embodiment. The 2'layer optical system is paired with the two-layer optical system and (2) irradiates the linear portion. The laser beam 5 from the laser light source 51 is reflected by the polygon mirrors 6 and 7 rotating at high speed via the polygon mirror 52 and the fixed mirror 53 as the 2'layer optical system shown in FIG. 4 and reaches the mirror 9. Irradiation to the notch portion 4 is the same as that described with reference to FIG.

The laser beam 5 from the laser light source 51 is guided to the 3'layer optical system through the optical paths of the polygon mirror 52, the rotating mirror 54, the polygon mirror 55, the fixed mirror 56, and the deflection mirror 57. Further, the laser beam 5 is guided to the 4'layer optical system via the polygon mirror 52, the rotating mirror 54, the polygon mirror 55, the fixed mirror 58, the rotating mirror 61, the fixed mirror 59, and the deflection mirror 60. Further, the laser beam 5 branched by the rotating mirror 61 is guided to the 5'layer optical system via the fixed mirror 63 and the deflection mirror 62.

FIG. 18 is a cross-sectional explanatory view showing the relationship between the two-layer optical system and the 2'layer optical system in the second embodiment. Since the laser light sources 10 and 51 are used in the second embodiment, the beam splitter 38 (see FIG. 12) of the first embodiment becomes unnecessary. The laser light 5 from the laser light source 10 is guided to the two-layer optical system (upper side in FIG. 18), and the laser light 5 from the laser light source 51 is guided to the 2'layer optical system (lower side in FIG. 18). Irradiation to the notch portion 4 is performed through the condenser lens 8 in the same manner as described with reference to FIG. 3 in both the two-layer optical system and the 2'layer optical system.

FIG. 19 is a block diagram showing a system configuration in each embodiment. The control unit 70 determines the irradiation conditions for the laser light source 10 (see FIGS. 3 and 8) according to the crystal orientation and shape of the irradiation unit, and starts, stops, switches, scan pitch, and the like. Control. For example, the control unit 70 determines the cumulative irradiation energy corresponding to the crystal orientation of the irradiation location (notch portion 4 and other parts) and irradiates the laser beam 5 (for example, a nanosecond pulse laser). The control unit 70 may use CW (continuous) laser irradiation in combination with nanosecond pulse laser irradiation.

In particular, since the crystal orientations of the upper surface 2 or the lower surface 3 of the silicon wafer 1, the end faces T, the slopes X1 and X2 are different, the irradiation conditions corresponding to the crystal orientations are determined. The laser light source 10 is preferably a nanosecond pulse laser having a wavelength of λ = 355, 532, or 785 nm. The energy per pulse width is preferably 0.5 μjoule to 30 μjoule, and the energy density is 0.125 J / cm ² to 7.5 J / cm ^2.

Further, the nanosecond pulse laser irradiates by changing at least one of the energy density, the scan pitch, and the number of irradiations according to the curvature of the irradiation portion. For example, the required irradiation energy has a magnitude relationship of Si (110)> Si (100)> Si (111), and the irradiation conditions corresponding to the crystal orientation are determined. Under the irradiation conditions corresponding to the crystal orientation, the energy of the Si (110) plane is about 1.3 times that of the Si (100) plane, and the energy of the Si (111) plane is about the same as that of the Si (100) plane to 0.7 times. It is used as the irradiation energy of.

Further, the control unit 70 uses polygon mirrors 6, 7 and the like (see FIG. 3 and the like) and rotary mirrors 22, 27 and 28 and the like (see FIG. 8) as the deflection element (actuator) 71 for the irradiation section of the laser beam 5 and the optics. Controls switching of system hierarchy, scan pitch, etc. Further, the control unit 70 commands the posture of the silicon wafer 1 to the posture control means 12 (see FIG. 6) to control the rotation in the pitch direction, the vertical direction, and the horizontal position. The mirror 9 and the like (see FIG. 3 and the like), the condenser lens 8 and the like are fixed.

As described above, the condensing lens 8 is a three-dimensional curved surface having a plano-convex cross-sectional shape and a curved surface shape when viewed from the upper surface, and the laser beam 5 uses an optical system that condenses light on the notch portion 4. Since the deflection element (actuator) 71 controls switching of the irradiation section, the hierarchy of the optical system, the scan pitch, etc., even if it has a complicated three-dimensional shape such as the notch portion 4, it is highly accurate and continuous. It is possible to perform laser scanning on target (without a break in the processing unit). In addition, by changing the irradiation angle or combining the types of lasers, it is possible to perform high-quality and high-speed surface treatment under conditions suitable for local aspects (states) such as crystal orientation and surface waviness. It becomes.

1 ... Silicon wafer 2 ... Top surface 3 ... Bottom surface 4 ... Notch 5 ... Laser beam 6, 7, 21, 24, 52, 55 ... Polygon mirror 8 ... Condensing lens 9, 36, 37, 39, 40, 41, 43 ... Mirrors 10, 51 ... Laser light sources 11, 50 ... Switching means 12 ... Attitude control means 22, 27, 28, 54, 61 ... Rotating mirrors 23, 25, 29, 31, 33, 34, 53, 56, 58, 59. , 63 ... Fixed mirror 26, 30, 32, 35, 57, 60, 62 ... Deflection mirror 38, 42 ... Beam splitter 70 ... Control unit 71 ... Deflection element T ... End surface X1, X2 ... Slope R1, R2 ... R unit f … Vertical bisector

Claims (9)

In a wafer edge reformer using laser heat treatment
It has an optical system that irradiates the notch with laser light from a laser light source.
The optical system is
A polygon mirror that reflects the laser beam and guides it to an arc-shaped mirror whose side surfaces are combined in a dogleg shape to form a concave mirror.
A three-dimensional curved body having a plano-convex cross-sectional shape and a curved shape when viewed from above, and a condensing lens that collects the laser light reflected by the mirror to the notch portion.
By rotating the polygon mirror, the laser beam is scanned and irradiated to the notch portion, and the cumulative irradiation energy corresponding to the crystal orientation of the notch portion is determined to irradiate the laser beam. A featured wafer edge reformer. The irradiation section of the notch portion is divided into (1) piece R portion, (2) straight portion, (3) bottom R portion, (2) straight portion having a different inclination direction from the straight portion, and (1) piece. Divided into (1') piece R parts symmetrical to the R part, the optical system is three-dimensionally configured for each of a plurality of layers, and the laser beam is irradiated for each irradiation section by the optical system for each layer. The reforming device for a wafer edge portion according to claim 1, wherein the wafer edge portion is modified. The reforming device for a wafer edge portion according to claim 2, further comprising an attitude control means for controlling an irradiation position so that the laser beam is irradiated for each irradiation section by the optical system for each layer. The (2) straight line portion and the (2') straight line portion, which are the irradiation sections, are characterized in that the laser scanning trajectory is linearly approximated by increasing the distance between the rotation centers of the mirror and the polygon mirror. The reformer for a wafer edge portion according to claim 2 or 3. The reforming device for a wafer edge portion according to any one of claims 2 to 4, wherein the laser light source is used as one unit, and the laser light is split into the optical system for each layer by a beam splitter. The reformer for a wafer edge portion according to any one of claims 2 to 4, wherein a plurality of the laser light sources are used to guide the laser light to the optical system for each layer. The wafer edge portion according to any one of claims 1 to 6 , wherein at least one of the energy density, the scan pitch, and the number of irradiations is changed according to the curvature of the notch portion. Reformer. The reformer for a wafer edge portion according to any one of claims 1 to 7 , wherein the laser beam is used in combination with the irradiation of a nanosecond pulse laser and CW (continuous) laser irradiation. This is a method for modifying the edge of a wafer using laser heat treatment.
A polygon mirror that reflects laser light and guides it to an arc-shaped mirror that is combined in a dogleg shape to form a concave mirror, and a three-dimensional curved body that has a plano-convex cross-sectional shape and a curved shape when viewed from above. The laser beam is scanned into the notch by rotating the polygon mirror using an optical system including a condensing lens that collects the laser light reflected by the mirror into the notch. A method for modifying a wafer edge portion, which comprises irradiating, determining cumulative irradiation energy corresponding to the crystal orientation of the notch portion, and irradiating the laser beam.

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