JP7139050B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method for dividing a wafer by irradiating the wafer with a laser beam to form a modified layer inside the wafer.

As a method of processing wafers such as semiconductor wafers and optical device wafers, there is known a method of forming a modified layer inside the wafer and then applying an external force to the wafer to divide the wafer into individual chips starting from the modified layer. (See Patent Document 1, for example).

In the processing method described in Patent Document 1, a laser beam having a wavelength that is transparent to the wafer (i.e., that passes through the wafer) is focused on the inside of the wafer by directing the laser beam from the surface side of the wafer to the wafer. By irradiating, a modified layer is formed inside the wafer along the dividing line of the wafer. Then, by applying an external force to the wafer, the wafer is divided with the modified layer as a starting point.

JP 2009-34723 A

In a state in which a polarizing film is provided on the surface of the wafer forming the modified layer, when the wafer is irradiated with a laser beam having a wavelength that passes through the wafer from the surface side of the wafer, the polarizing film absorbs the energy of the laser beam. As a result, the polarizing film may be ablated by the laser beam. The material of the polarizing film that has been ablated becomes debris, and there is a problem that this debris adheres to the condensing lens from which the laser beam is emitted.

In addition, since the energy of the laser beam is partially absorbed by the polarizing film, multiphoton absorption is less likely to occur at the focal point of the laser beam inside the wafer, resulting in insufficient formation of the modified layer by the laser beam. there is a problem. These problems become more pronounced as the focal point of the laser beam approaches the boundary between the wafer and the polarizing film.

Therefore, instead of irradiating the laser beam from the front side of the wafer (that is, from the polarizing film side of the wafer), it is conceivable to irradiate the wafer with the laser beam from the back side of the wafer.

In this case, the front side of the wafer is sucked and held by the holding surface of the chuck table. However, since the polarizing film is very fragile, there is a problem that the polarizing film on the front surface side of the wafer is destroyed when the front surface side of the wafer is suction-held by the holding surface.

The present invention has been made in view of such problems, and prevents debris from adhering to a condenser lens when irradiating a wafer with a laser beam from the front side of the wafer on which a polarizing film is provided, and An object of the present invention is to form a modified layer suitable for dividing a wafer.

According to one aspect of the present invention, there is provided a wafer processing method for dividing a wafer having a polarizing film formed on its surface along a dividing line, wherein the back surface of the wafer, which is opposite to the front surface, is formed into an annular shape. and after the wafer supporting step, the polarizing film is absorptive to the polarizing film from the outer surface side of the polarizing film opposite to the wafer. A laser-processed groove forming step of irradiating a laser beam of a wavelength along the dividing line to form a laser-processed groove that divides the polarizing film; A modified layer is formed inside the wafer by irradiating the wafer along the laser-processed groove with a laser beam having a wavelength that is transmissive to the wafer from the outer surface side of the polarizing film so as to locate a point. and a dividing step of applying an external force to the wafer after the modified layer forming step to divide the wafer along the planned dividing line , wherein the laser processing The width of the laser-processed groove formed in the groove forming step is set to a minimum within a range in which the polarizing film is not damaged in the modified layer forming step. Provided is a wafer processing method for irradiating the wafer with the laser beam whose polarization direction is controlled in the direction of transmission through the polarizing film .

Preferably, the wafer processing method includes, prior to the laser-processed groove forming step, a protective film coating step of applying a liquid material to the outer surface side of the polarizing film to form a protective film; After the step, a protective film removing step of removing the protective film is further included.

Also preferably, the wafer is glass.

In the wafer processing method according to the present invention, the polarizing film formed on the surface of the wafer is partially removed along the dividing lines before forming the modified layer on the wafer along the dividing lines.

Therefore, even if a laser beam is irradiated from the surface side of the wafer when forming the modified layer, the laser beam can reach the inside of the wafer without being absorbed by the polarizing film. In addition, a modified layer in which the strength of the wafer is locally reduced to such an extent that the wafer can be split can be formed inside the wafer.

Furthermore, since the polarizing film is partially removed along the dividing lines, it is possible to prevent the polarizing film from turning into debris and adhering to the condensing lens when forming the modified layer.

FIG. 10 is a perspective view showing a wafer supporting step (S10) of attaching the back side of the wafer to a supporting tape; 1 is a perspective view of a laser processing apparatus in which wafer units are arranged; FIG. FIG. 3(A) is a partial cross-sectional side view showing the wafer before the polarizing film is processed in the laser processing groove forming step (S20), and FIG. 3(B) is a laser processing groove forming step (S20). FIG. 4 is a partial cross-sectional side view showing a wafer after processing a polarizing film; FIG. 4 is a cross-sectional view showing laser-processed grooves formed in a polarizing film; FIG. 5(A) is a partial cross-sectional side view showing the wafer before processing in the modified layer forming step (S30), and FIG. 5(B) shows the wafer after processing in the modified layer forming step (S30) 1 is a partial cross-sectional side view showing a wafer of FIG. It is a partial cross-sectional side view which shows the modified layer formed inside the wafer. FIG. 10 is a partial cross-sectional side view showing a dividing step (S40) for dividing the wafer; 4 is a flowchart of a processing method according to the first embodiment; FIG. 9(A) is a partial cross-sectional side view showing a wafer unit fixed on an expanding device according to the second embodiment, and FIG. 9(B) is a dividing step (S45) according to the second embodiment. It is a partial cross-sectional side view showing the. FIG. 11 is a perspective view of a protective film coating and cleaning apparatus used in the third embodiment; FIG. 11A is a partial cross-sectional side view showing the protective film coating step (S15), and FIG. 11B is a partial cross-sectional side view showing the protective film removing step (S25). 9 is a flow chart of a processing method according to the third embodiment; FIG. 13A is a cross-sectional view of the laminate when the width of the laser-processed groove is sufficiently larger than the diameter of the laser beam on the outer surface of the polarizing film, and FIG. 13B is a cross-sectional view of the outer surface of the polarizing film. FIG. 13C is a cross-sectional view of the laminate in the case where the diameter of the laser beam at the outer surface of the polarizing film is approximately the same as the width of the laser-processed groove, and FIG. is a cross-sectional view of a laminate when is sufficiently small. FIG. 14A is a cross-sectional view of the laminate when the diameter of the laser beam on the outer surface of the polarizing film is approximately the same as the width of the laser-processed groove, and the skirt portion of the laser beam does not pass through the polarizing film. FIG. 14B shows the cross section of the laminate when the diameter of the laser beam on the outer surface of the polarizing film is approximately the same as the width of the laser-processed groove, and the skirt portion of the laser beam passes through the polarizing film. It is a diagram.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. 1 to 7 are diagrams showing steps of a method for processing a wafer 11 according to the first embodiment, apparatuses used for processing, and the like. Moreover, FIG. 8 is a flowchart of the processing method according to the first embodiment.

FIG. 1 is a perspective view showing the wafer support step (S10) of attaching the back surface 11b side of the wafer 11 to the support tape 17b. The support tape 17b made of resin or the like has a diameter larger than the opening of the annular frame 17a. A peripheral portion of the support tape (dicing tape) 17b is attached to an annular frame 17a made of metal, and a central portion of the support tape 17b is exposed at an opening of the frame 17a.

The support tape 17b has, for example, a base layer and an adhesive layer provided over the entire surface of the base layer. The adhesive layer is, for example, an ultraviolet curable resin layer, and exerts strong adhesion to the frame 17a and the like. The adhesive layer of the support tape 17b is exposed through the opening of the frame 17a.

The wafer 11 of the present embodiment is a plate-shaped substrate made of glass that is transparent to visible light (for example, 360 nm or more and 830 nm or less), but the type of glass of the wafer 11 is not particularly limited. The glass of the wafer 11 may be various glasses such as alkali glass, non-alkali glass, soda lime glass, lead glass, borosilicate glass, and quartz glass.

The material, shape, structure, size, etc. of the wafer 11 are not limited. For example, a substrate or the like made of a semiconductor such as silicon, ceramics, resin, metal, or the like can be used as the wafer 11 .

The wafer 11 has a thickness (length in the Z-axis direction) of 100 μm or more and less than 1000 μm, for example. The wafer 11 of this embodiment has a thickness of 730 μm. Moreover, the wafer 11 is formed in a rectangular shape having long sides and short sides in plan view.

In this embodiment, the direction parallel to the long side of the wafer 11 is defined as the first direction, and the direction parallel to the short side of the wafer 11 is defined as the second direction. In FIG. 1, numeral 1 indicates the first direction, and numeral 2 indicates the second direction.

The front surface 11a side of the wafer 11 opposite to the back surface 11b is partitioned into a plurality of regions by a plurality of division lines (street) 11c that cross each other. In the present embodiment, each area partitioned by the planned dividing line 11c is a 20 mm square rectangular area.

Devices and the like are not formed on the surface 11a side of each region in the wafer 11 of this embodiment. Further, the front surface 11a side of the wafer 11 of the present embodiment is partitioned into rectangular regions by the straight dividing lines 11c. The surface 11a side of the wafer 11 may be partitioned into circular regions.

A polarizing film 13 is formed on the entire surface 11 a of the wafer 11 . Like the wafer 11, the polarizing film 13 is also partitioned into a plurality of regions by the dividing lines 11c. The polarizing film 13 has a plurality of convex portions having longitudinal portions along the first direction of the wafer 11 . That is, each of the plurality of protrusions is formed in a stripe shape along the first direction. Two protrusions adjacent in the second direction are provided with a predetermined interval, and a groove is formed between the two protrusions. In FIG. 1, these grooves are indicated by lines in the polarizing film 13. As shown in FIG.

The convex portion of the polarizing film 13 has a laminated structure of a reflective layer that is made of a metal material and reflects light, and an absorption layer that is made of a semiconductor material and is formed on the reflective layer and absorbs light. The polarizing film 13 further includes an oxide film in contact with the surfaces of the projections and the surface 11a of the wafer 11 at the bottoms of the grooves located between the two projections.

The oxide film is formed through an oxidation process such as thermal oxidation after forming a plurality of protrusions on the wafer 11 . The oxide layer is sufficiently thinner than the height of the protrusions, and the oxide layer does not completely fill the grooves between the two protrusions.

The polarizing film 13 of the present embodiment is a so-called wire grid polarizing film made of an inorganic material as described above, but the material, shape, structure, etc. of the polarizing film 13 are not particularly limited. For example, as the polarizing film 13, a polarizing film made of an organic material formed by orienting iodine ions or the like in polyvinyl alcohol (PVA) can be used, or another polarizing film can be used.

In FIG. 1, the polarizing film 13 and the wafer 11 are shown separated in order to explain the dividing line 11c. 13 and wafer 11 form a laminate 15 .

In the wafer support step (S10), the rear surface 11b side of the wafer 11 is attached to the adhesive layer of the support tape 17b exposed at the opening of the frame 17a. As a result, a wafer unit 19 in which the frame 17a, the support tape 17b, and the laminate 15 are integrated is formed (see FIG. 2).

In this embodiment, after the above-described wafer supporting step (S10), the polarizing film 13 is irradiated with a laser beam L1 having an ultraviolet wavelength from the outer surface 13a side of the polarizing film 13 opposite to the wafer 11, The polarizing film 13 is processed. As a result, laser-processed grooves 13b are formed in the polarizing film 13 (laser-processed groove forming step (S20)).

The laser processing groove forming step (S20) is performed using the laser processing device 20A. FIG. 2 is a perspective view of the laser processing apparatus 20A in which the wafer unit 19 is arranged. The laser processing apparatus 20A has a chuck table 28A that holds the wafer unit 19 by suction.

The wafer unit 19 is placed on the upper surface of the chuck table 28A of the laser processing apparatus 20A so that the back surface of the base material layer of the support tape 17b (that is, the surface of the base material layer of the support tape 17b opposite to the adhesive layer) is in contact. placed.

The chuck table 28A has a circular top surface larger than the wafer 11, and the top surface is formed substantially parallel to the X-axis direction and the Y-axis direction. A porous plate made of porous ceramics or the like is provided in the central region of the upper surface of the chuck table 28A.

The porous plate is connected to suction means (not shown) such as a vacuum pump through a suction path (not shown) formed inside the chuck table 28A. The upper surface of the porous plate functions as a holding surface 28Aa (see FIG. 3, etc.) for sucking and holding the wafer 11 by applying the negative pressure of the suction means to the wafer 11 through the porous plate and the suction path.

A moving mechanism (not shown) is provided below the chuck table 28A, and the chuck table 28A can move in the X-axis direction (that is, the processing feed direction) and the Y-axis direction by this moving mechanism. However, it is not necessary to move the chuck table 28A in both the X and Y-axis directions, and the chuck table 28A may be moved only in the X-axis direction.

The chuck table 28A is connected to a rotation drive source (not shown) such as a motor, and can rotate around a rotation axis substantially parallel to the Z-axis direction (vertical direction). By rotating the chuck table 28A by a predetermined angle, the wafer unit 19 sucked and held by the holding surface 28Aa is rotated by the same predetermined angle. Thereby, the orientation of the wafer 11 on the XY plane with respect to the laser processing apparatus 20A is adjusted.

The laser processing apparatus 20A has a laser irradiation unit 22A at a position facing a chuck table 28A. A laser processing head 24A that emits a pulsed laser beam is provided at the tip of the laser irradiation unit 22A. The laser processing head 24A has an internal condenser lens for condensing the laser beam, and the laser beam is emitted from the condenser lens to the outside of the laser processing head 24A.

20 A of laser processing apparatuses of this embodiment irradiate the laser beam L1 of the wavelength which belongs to the wavelength range of an ultraviolet-ray (for example, the wavelength ranges from 10 nm to 400 nm). The laser beam L<b>1 having an ultraviolet wavelength is a laser beam having a wavelength that is absorptive to the polarizing film 13 . The laser beam L1 of the present embodiment is linearly polarized light in which the electric field and the magnetic field oscillate in specific directions with respect to the traveling direction of the laser beam L1. may be

When processing the polarizing film 13, the laser processing apparatus 20A irradiates a laser beam L1 having an ultraviolet wavelength from a laser processing head 24A to ablate a portion of the polarizing film 13. FIG. Note that the wafer 11 is not processed by the laser beam L1 of this embodiment.

The laser irradiation unit 22A further has an imaging unit 26A arranged near the laser processing head 24A. The image of the laminate 15 captured by the imaging unit 26A is used for alignment of the laminate 15 and the laser processing head 24A.

3(A), 3(B), and 4, how the laser processing apparatus 20A is used to form the laser-processed groove 13b, which is the opening of the polarizing film 13, in the laminate 15 will be described. . FIG. 3A is a partial cross-sectional side view showing the wafer 11 before the polarizing film 13 is processed in the laser processing groove forming step (S20), and FIG. 3B is a laser processing groove forming step (S20). ) is a partial cross-sectional side view showing the wafer 11 after the polarizing film 13 has been processed.

In FIG. 3B, the polarizing film 13 located in the depth direction (that is, the second direction) of the paper surface from the laser-processed groove 13b is omitted for easy understanding. FIG. 4 is a cross-sectional view showing a laser-processed groove 13b formed in the polarizing film 13. As shown in FIG.

In the laser processing groove forming step (S20), first, the chuck table 28A is rotated so that the X-axis direction of the laser processing device 20A and the first direction of the wafer 11 are parallel. Then, while moving the laser processing head 24A and the chuck table 28A relative to each other in the X-axis direction, the laser beam L1 is irradiated from the laser processing head 24A to the laminate 15. FIG.

In this embodiment, by moving the chuck table 28A along the X-axis direction so that the wafer 11 is irradiated with the laser beam L1 from one end to the other end in the first direction, the wafer 11 is parallel to the first direction. A laser beam L1 is applied linearly along the dividing line 11c (see FIG. 4).

By irradiating the polarizing film 13 with the laser beam L1, the material forming the polarizing film 13 is ablated to become debris. This debris may fly off the polarizing film 13 and adhere to, for example, the laser processing head 24A.

However, the distance from the tip of the laser processing head 24A to the polarizing film 13 in the laser processing groove forming step (S20) can be sufficiently increased compared to the case of forming the modified layer on the wafer 11. FIG. Therefore, in the laser processing groove forming step (S20), it is possible to prevent debris from adhering to the condensing lens of the laser processing head 24A.

As shown in FIG. 3B, laser-processed grooves 13b are formed by partially removing the polarizing film 13 by irradiating the laser beam L1. The average power of the laser beam L1 is, for example, 1.0 W, and the moving speed of the chuck table 28A during irradiation is, for example, 200 mm/s.

As shown in FIG. 4, by partially removing the polarizing film 13, a laser-processed groove 13b having a predetermined width W in the second direction of the wafer 11 and dividing the polarizing film 13 is formed. The width W is, for example, 100 μm or more and 300 μm or less. Also, the width W may be about 40% of the thickness of the wafer 11 in relation to the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13, which will be described later.

In this embodiment, the laser processing head 24A irradiates the polarizing film 13 with the laser beam L1 so that the laser processing head 24A reciprocates between one end and the other end of the wafer 11 in the first direction at least once (that is, one pass). At this time, the laser beam L1 may be irradiated so that the laser beam L1 partially overlaps in the second direction between the outward path and the return path.

After forming one laser processing groove 13b along the first direction of the wafer 11, the laser processing head 24A is positioned adjacent to the laser processing groove 13b in the second direction of the wafer 11, and similarly, the wafer The polarizing film 13 is linearly irradiated with the laser beam L1 from one end to the other end in the first direction 11 .

In this manner, the polarizing film 13 is linearly irradiated with the laser beam L1 from one end to the other end of the wafer 11 in the first direction at a plurality of different positions on the wafer 11 in the second direction. As a result, laser-processed grooves 13b are formed on all dividing lines 11c parallel to the first direction of the wafer 11 .

Next, the chuck table 28A is rotated by 90 degrees so that the X-axis direction of the laser processing device 20A and the second direction of the wafer 11 are parallel. Then, by moving the chuck table 28A along the X-axis direction so that the laser beam L1 is linearly irradiated from one end to the other end of the wafer 11 in the second direction, the laser beam L1 is directed to the wafer 11 in the second direction. Irradiate along the dividing line 11c parallel to the direction.

By linearly irradiating the polarizing film 13 with the laser beam L1 one after another from one end to the other end of the wafer 11 in the second direction at a plurality of different positions of the wafer 11 in the first direction, Laser-processed grooves 13b are formed on all parallel dividing lines 11c.

After the laser processing groove forming step (S20), a laser processing apparatus 20B different from the laser processing apparatus 20A is used to irradiate the wafer 11 with a laser beam L2 having an infrared wavelength along the laser processing groove 13b. A modified layer is formed inside the wafer 11 .

5(A), 5(B) and 6, using a laser processing apparatus 20B, along the laser-processed grooves 13b formed in the polarizing film 13, reforming is formed on the wafer 11. The layer 11d and the crack 11e will be explained.

The laser processing device 20B has a laser processing unit 22B having substantially the same function as the laser irradiation unit 22A. However, the laser processing unit 22B emits a laser beam L2 having a wavelength belonging to an infrared wavelength band (for example, a wavelength range of 0.75 μm or more and 1000 μm or less) from the laser processing head 24B.

The laser beam L2 having an infrared wavelength is a laser beam having a wavelength that is transparent to the wafer 11, and the wafer 11 is irradiated with this laser beam L2 when the wafer 11 is processed.

In this embodiment, the wafer 11 is irradiated with a laser beam L2 through an opening (laser-processed groove 13b, which will be described later) of the polarizing film 13 to form a modified layer inside the wafer 11 . Note that the laser beam L2 is linearly polarized light in which the electric field and the magnetic field oscillate in specific directions with respect to the traveling direction of the laser beam L2.

The laser processing apparatus 20B also has a chuck table 28B having substantially the same function as the chuck table 28A. The chuck table 28B has a porous plate, and the upper surface of the porous plate functions as a holding surface 28Ba for holding the wafer 11 by suction.

FIG. 5(A) is a partial cross-sectional side view showing the wafer 11 before being processed in the modified layer forming step (S30), and FIG. 5(B) is a modified layer forming step (S30) processed. It is a partial cross-sectional side view which shows the wafer 11 after. 6 is a partial cross-sectional side view showing a modified layer 11d formed inside the wafer 11. As shown in FIG.

In the present embodiment, the wafer 11 is irradiated with the laser beam L2 from the outer surface 13a side of the polarizing film 13 so that the focal point is positioned inside the wafer 11 . The average power of the laser beam L2 is 1.0 W, for example. The laser beam L2 applied to the wafer 11 is condensed at a specific depth position inside the wafer 11 .

Multiphoton absorption occurs at the light condensing point, and the wafer 11 is altered to form a modified layer 11d having reduced mechanical strength and the like. The modified layer 11d is, for example, a region where the wafer 11 is partially melted.

In the modified layer forming step (S30), first, the chuck table 28B is rotated so that the X-axis direction of the laser processing device 20B and the first direction of the wafer 11 are parallel. Then, while moving the laser processing head 24B and the chuck table 28B relative to each other in the X-axis direction, the laser beam L2 is irradiated from the laser processing head 24B to the laminate 15 .

By moving the chuck table 28B along the X-axis direction so that the wafer 11 is irradiated with the laser beam L2 from one end to the other end of the wafer 11 in the first direction, the laser beam L2 is directed to the wafer 11 in the first direction. Linear irradiation is performed along the parallel laser-processed grooves 13b (one-time (that is, one-pass) irradiation of the laser beam L2). The moving speed of the chuck table 28B when irradiating the laser beam L2 is, for example, 500 mm/s.

In this embodiment, the depth position of the condensing point is changed, and the irradiation with the laser beam L2 described above is repeated once. Thereby, the modified layers 11d are formed at different depth positions inside the wafer 11. Next, as shown in FIG. A plurality of modified layers 11d adjacent in the thickness direction of the wafer 11 are connected to each other by irradiating the laser beam L2 5 to 10 times (for example, 8 times) while changing the depth position of the focal point. A modified layer 11d is formed (see FIG. 6).

When forming a plurality of modified layers 11d, cracks 11e are formed extending from the modified layer 11d closest to the surface 11a to the surface 11a. Similarly, a crack 11e extending from the modified layer 11d closest to the back surface 11b to the back surface 11b is formed. Note that in FIG. 6, the division line 11c overlapping the modified layer 11d and the crack 11e in the X-axis direction is omitted.

A laser beam L2 is linearly irradiated along all laser-processed grooves 13b parallel to the first direction of the wafer 11 to form a modified layer 11d below each laser-processed groove 13b. Furthermore, as in the laser processing groove forming step (S20), the chuck table 28B is rotated by 90 degrees so that the X-axis direction of the laser processing device 20B and the second direction of the wafer 11 are parallel, and the laser beam L2 is is irradiated along the laser-processed groove 13 b parallel to the second direction of the wafer 11 .

By linearly irradiating the polarizing film 13 with the laser beam L2 one after another from one end to the other end of the wafer 11 in the second direction at a plurality of different positions on the wafer 11 in the first direction, A modified layer 11d is formed along all parallel laser-processed grooves 13b.

When forming the modified layer 11d, the distance between the condenser lens in the laser processing head 24B and the surface 11a of the wafer 11 is made closer than in the laser processing groove forming step (S20), and the laser beam L2 is directed to the wafer 11. Concentrate light inside.

In this embodiment, since the polarizing film 13 does not exist in the laser-processed groove 13b, even if the polarizing film 13 side of the wafer 11 is irradiated with the laser beam L2, no debris of the polarizing film 13 is generated. Therefore, debris from the polarizing film 13 can be prevented from adhering to the condensing lens in the laser processing head 24B.

After the modified layer forming step (S30), the dividing device (breaking device) 30 is used to apply an external force to the wafer 11 to divide the wafer 11 along the dividing line 11c. FIG. 7 is a partial cross-sectional side view showing the dividing step (S40) for dividing the wafer 11. As shown in FIG.

The dividing step (S40) is performed using, for example, the dividing device 30 shown in FIG. The dividing device 30 of this embodiment has a support base 32 on which the support tape 17b side of the wafer unit 19 is arranged. The dividing device 30 also has a pressing blade 34 that applies stress to the front surface 11a side of the wafer 11 supported by the support base 32 .

In the division step (S40), first, the wafer unit 19 is placed on the support table 32. As shown in FIG. Then, the pressing blade 34 is pressed against the dividing line 11c on the front surface 11a side of the wafer 11 . As a result, the wafer 11 is divided into a plurality of chips 11f (see FIG. 9B) along the modified layer 11d and the cracks 11e (that is, the dividing lines 11c).

In this embodiment, the chuck table does not hold the front surface 11a of the wafer 11 on which the polarizing film 13 is provided. Therefore, it is possible to prevent the polarizing film 13 from being destroyed due to contact with the chuck table.

Each chip 11f formed by dividing the wafer 11 is, for example, a polarizing element used in a projector device. Since the projector device is a device for projecting an image that can be visually recognized by a person on a screen, the wafer 11 is preferably made of glass that is transparent to visible rays.

By the way, it is conceivable that the wafer 11 having the polarizing film 13 is cut and divided by a cutting device instead of the pressing blade 34 . However, during cutting, cutting water supplied to the blade of the cutting device and the contact point between the blade and the wafer 11 (that is, the processing point) also destroys the polarizing film 13 in areas other than the dividing line 11c. Therefore, when dividing the wafer 11 with the polarizing film 13, it is desirable to divide the wafer 11 by a method that does not apply a load to the polarizing film 13 in the regions other than the dividing line 11c, as in the present embodiment.

Next, a second embodiment will be described in which the wafer 11 is split using the expanding device 40 instead of the splitting step (S40) using the splitting device 30. FIG. FIG. 9A is a partial cross-sectional side view showing the wafer unit 19 fixed on the expanding device 40 according to the second embodiment.

The expanding device 40 includes a cylindrical drum 42 having a diameter larger than that of the wafer 11 . The expanding device 40 also includes a frame holding unit 44 including a frame support base 48 provided so as to surround the upper end of the drum 42 from the outer peripheral side.

The frame support 48 has an opening with a diameter larger than the diameter of the drum 42 and is positioned at the same height as the upper end of the drum 42 . Clamps 46 are provided at a plurality of locations on the outer peripheral side of the frame support base 48 .

The wafer unit 19 is fixed by the frame support 48 by placing the wafer unit 19 on the frame support 48 and fixing the frame 17 a of the wafer unit 19 with the clamp 46 .

The frame support 48 is supported by a plurality of rods 50 extending vertically. At the lower end of each rod 50, an air cylinder 52 is provided which is supported by a disk-shaped base (not shown) and moves the rod 50 up and down. When each air cylinder 52 is retracted, the frame support 48 is lowered relative to the drum 42 .

In the dividing step (S45), first, the air cylinder 52 is operated to raise the height of the frame support 48 so that the height of the upper end of the drum 42 of the expanding device 40 and the height of the upper surface of the frame support 48 are aligned. adjust the

Next, the wafer unit 19 unloaded from the laser processing device 20B is placed on the drum 42 and the frame support table 48 of the expanding device 40. As shown in FIG. After that, the frame 17a of the wafer unit 19 is fixed on the frame support table 48 by the clamp 46. As shown in FIG.

Next, the air cylinder 52 is operated to pull down the frame support base 48 of the frame holding unit 44 with respect to the drum 42 . Then, as shown in FIG. 9B, the support tape 17b is expanded in the outer peripheral direction. FIG. 9B is a partial cross-sectional side view showing the dividing step (S45) according to the second embodiment.

When the support tape 17b is expanded in the outer peripheral direction, the wafer 11 supported by the support tape 17b is separated into a plurality of chips 11f, and the intervals between the chips 11f are widened. As a result, the chips 11f are separated from each other in the XY plane direction, so that individual chips 11f can be easily picked up.

In addition, in the modification of the second embodiment, after the dividing step (S40) using the dividing device 30, the expanding device 40 may be used to increase the distance between the chips 11f. This facilitates picking up of individual chips 11f.

Next, a third embodiment will be described in which a water-soluble protective film 61 is formed on the polarizing film 13 before the laser-processed groove forming step (S20), and the protective film 61 is removed after the laser-processed groove forming step (S20). do.

FIG. 10 is a perspective view of a protective film coating/cleaning device 60 used in the third embodiment. FIG. 11A is a partial cross-sectional side view showing the protective film coating step (S15), and FIG. 11B is a partial cross-sectional side view showing the protective film removing step (S25). Moreover, FIG. 12 is a flowchart of the processing method according to the third embodiment.

As shown in FIG. 10, the protective film coating and cleaning apparatus 60 includes a spinner table mechanism 62 having a disk-shaped spinner table 68 . The spinner table 68 includes a holding surface 68a formed of a porous material, and the holding surface 68a is connected to suction means (not shown) via a channel (not shown). The spinner table 68 can suck and hold the wafer 11 placed on the holding surface 68a by applying negative pressure to the suction means.

Four pendulum-type clamping mechanisms 66 for holding the frame 17 a of the wafer unit 19 are provided on the outer periphery of the spinner table 68 . When the number of rotations per unit time of the spinner table 68 is less than or equal to a predetermined value, the claws of the clamping mechanism 66 are separated from the frame 17a. A clamping mechanism 66 is configured to hold down 17a. A predetermined value of the number of rotations per unit time is, for example, 1000 rpm.

A cover member 82 having an opening (not shown) on the lower surface opposite to the spinner table 68 is provided below the spinner table 68 . An output shaft 70 a of a motor 70 for rotating the spinner table 68 is connected through an opening of the cover member 82 below the spinner table 68 .

The motor 70 is housed in a cylindrical housing, and a plurality of (three in this embodiment) support mechanisms 72 are provided around the housing. Each support mechanism 72 has a support leg 74 and an air cylinder 76 connected to the support leg 74 . Each support mechanism 72 supports the motor 70 with a support leg 74 and moves the air cylinder 76 in the vertical direction.

A washing water receiving mechanism 64 is provided around the spinner table 68 and the cover member 82 . The washing water receiving mechanism 64 has a washing water receiving container 78 that temporarily stores used washing water. A plurality of support legs 80 for supporting the cleaning water receiving container 78 are connected below the cleaning water receiving container 78 .

The washing water receiving container 78 has a cylindrical outer wall 78a, a cylindrical inner wall 78b lower than the outer wall 78a and positioned below the cover member 82, and bottom portions of the outer wall 78a and the inner wall 78b. and a ring-shaped bottom wall 78c connecting the .

A part of the bottom wall 78c is provided with a drain port 78d. A drain hose 84 is connected to the drain port 78d, and used wash water temporarily stored in the wash water receiving container 78 is discharged from the drain hose 84 to the outside of the protective film coating and washing device 60. .

The protective film coating/cleaning device 60 has coating means 86 for coating liquid resin on the polarizing film 13 side of the wafer 11 held on the spinner table 68 . The coating means 86 includes a discharge nozzle 88 that discharges the liquid resin toward the wafer 11 held on the spinner table 68 and a substantially L-shaped arm 90 that supports the discharge nozzle 88 .

The coating means 86 further includes a motor (not shown) that swings the arm 90 between a position corresponding to the center of the spinner table 68 and a retracted position outside the spinner table 68 . The discharge nozzle 88 is connected via an arm 90 to a liquid resin supply source (not shown).

Liquid resin is a material for forming the protective film 61 . This liquid resin is, for example, a water-soluble resin such as PVA (polyvinyl alcohol), PEG (polyethylene glycol), or PEO (polyethylene oxide).

The protective film coating/cleaning device 60 has cleaning water supply means 92 for cleaning the laminate 15 . The cleaning water supply means 92 includes a cleaning water nozzle 94 for ejecting cleaning water toward the laminated body 15 after the formation of the laser-processed grooves 13b held by the spinner table 68, and an approximately L-shaped nozzle for supporting the cleaning water nozzle 94. and arm 96 .

The washing water supply means 92 further includes a motor (not shown) that swings the arm 96 between a position corresponding to the center of the spinner table 68 and a retracted position outside the spinner table 68 . The washing water nozzle 94 is connected to a washing water supply source (not shown) via an arm 96 .

The protective film coating/cleaning device 60 further has an air supply means 98 for drying the laminate 15 . The air supply means 98 has an air nozzle 100 for ejecting air toward the cleaned laminate 15 held on the spinner table 68 and a substantially L-shaped arm 102 for supporting the air nozzle 100 .

The air supply means 98 further includes a motor (not shown) that swings the arm 102 between a position corresponding to the center of the spinner table 68 and a retracted position outside the spinner table 68 . Note that the air nozzle 100 is connected to an air supply source (not shown) via an arm 102 .

In this embodiment, before the laser processing groove forming step (S20), a liquid material is applied to the outer surface 13a side of the polarizing film 13 to form the protective film 61 (protective film coating step (S15)) (FIG. 11). (A)).

For example, in the protective film coating step ( S<b>15 ), the back surface 11 b side of the layered product 15 is attracted to the holding surface 68 a and the discharge nozzle 88 of the coating means 86 is moved above the layered product 15 . Thereafter, the spinner table 68 is rotated at 2000 rpm to spin-coat the entire surface of the polarizing film 13 with the discharged water-soluble resin.

After the protective film coating step (S15), the above-described laser processing groove forming step (S20) is performed. Then, after the above-described laser processing groove forming step (S20), cleaning water and air are jetted from the cleaning water supply means 92 and the air supply means 98 to the laminated body 15 to remove the protective film 61 (protective film removing step ( S25)) (see FIG. 11(B)).

For example, in the protective film removing step (S25), the spinner table 68 is rotated at a low speed of 100 rpm to 200 rpm while supplying cleaning water (pure water) and air from the cleaning water nozzle 94 and the air nozzle 100 to the laminate 15, respectively. The laminate 15 is washed.

In this embodiment, by forming the protective film 61 on the polarizing film 13 before forming the laser-processed grooves 13b, the debris of the polarizing film 13 ablated in the laser-processed groove forming step (S20) is not the polarizing film 13. It adheres on the protective film 61 . Therefore, debris can be prevented from adhering to the polarizing film 13 .

Further, after the laser processing groove forming step (S20), by washing away the protective film 61 to which debris of the ablated polarizing film 13 adheres with washing water, the debris can be removed from the laminate 15 together with the protective film 61. .

Next, a modified example in which the conditions of the diameter of the laser beam L2 and the width W of the laser-processed groove 13b are changed will be described. The laser beam L2 has a substantially Gaussian profile, where the horizontal axis is the radial direction of the spot on the surface 11a of the wafer 11 and the vertical axis is the energy.

For example, the diameter of the laser beam L2 is determined by a range from the peak value of the intensity of the laser beam L2 to (1/e ² ) times the peak value (where e is a natural logarithm). Further, outside the diameter of the laser beam L2, there is a skirt portion of the laser beam L2 whose intensity is weaker than that of the inner portion of the diameter.

13(A), 13(B) and 13(C) do not show the skirt portion of the laser beam L2, but show only the inner diameter portion of the laser beam L2. FIG. 13A is a cross-sectional view of the laminate 15 when the width W1 of the laser-processed groove 13b is sufficiently larger than the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13. FIG. In this case, the polarizing film 13 is not ablated by the laser beam L2.

However, in order to make the width W1 larger than the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13, in the laser-processed groove forming step (S20), in order to form one laser-processed groove 13b, the polarizing film 13 It is necessary to increase the number of linear irradiations of the laser beam L1.

Therefore, in order to reduce the number of linear irradiations of the laser beam L1 when forming one linear laser-processed groove 13b, the width W of the laser-processed groove 13b is changed in the modified layer forming step (S30). It may be set to a minimum within a range in which the film 13 is not damaged. Thereby, the processing time in the laser processing groove forming step (S20) can be shortened.

For example, when the modified layer forming step (S30) is performed with a laser beam L2 having a diameter of 100 μm at the outer surface 13a of the polarizing film 13, the minimum laser processing groove 13b that does not damage the polarizing film 13 is is 100 μm. However, the minimum width W2 may change by about ±30% depending on the energy of the laser beam L2, ease of processing of the wafer 11, and the like.

In order to form the laser-processed groove 13b with a width of 100 μm, in the laser-processed groove forming step (S20), for example, the diameter of the laser beam L2 at the outer surface 13a of the polarizing film 13 is 45 μm. Irradiate linearly three times while partially overlapping on the film 13 .

FIG. 13B is a cross-sectional view of the laminate 15 when the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13 is approximately the same as the width W2 of the laser-processed groove 13b. The example of FIG. 13(B) is advantageous in that the time required for the laser processing groove forming step (S20) can be shortened compared to the example of FIG. 13(A).

As a comparative example, FIG. 13C shows a cross-sectional view of the laminate 15 in which the width W3 of the laser-processed groove 13b is sufficiently smaller than the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13. As shown in FIG. In the example of FIG. 13(C), the time required for the laser processing groove forming step (S20) can be shortened compared to the example of FIG. 13(B). This is not preferable because the polarizing film 13 is ablated.

By the way, on the outer surface 13a of the polarizing film 13 irradiated with the laser beam L2, the skirt portion positioned outside the diameter of the laser beam L2 is also irradiated. Since the skirt portion of the laser beam L2 has lower energy than the inner portion of the diameter of the laser beam L2, the polarizing film 13 is not ablated in the modified layer forming step (S30), and the polarizing film 13 may be damaged. is low.

The skirt portion of the laser beam L2 is preferably transmitted through the polarizing film 13 rather than being absorbed or reflected by the polarizing film 13 in the modified layer forming step (S30). Thereby, the energy of the focal point of the laser beam L2 positioned inside the wafer 11 can be further improved.

Since the laser beam L2 is linearly polarized, by adjusting the polarization direction of the laser beam L2 with respect to the polarizing film 13, absorption or reflection and transmission of the laser beam L2 with respect to the polarizing film 13 can be adjusted.

When the polarizing film 13 is the wire grid polarizing film described above, the laser beam L2 is absorbed or reflected by the polarizing film 13 when the extending direction of the stripe-shaped convex portion is parallel to the polarization direction of the laser beam L2. be done.

For example, when the polarization direction of the laser beam L2 is parallel to the extending direction of the protrusions of the wire grid polarizing film, or the polarization direction of the laser beam L2 includes a component parallel to the extending direction of the protrusions of the wire grid polarizing film. , the skirt portion of the laser beam L2 is mostly absorbed or reflected by the polarizing film 13 .

On the other hand, when the polarization direction of the laser beam L2 is orthogonal to the extending direction of the stripe-shaped protrusions, both the inner portion and the skirt portion of the spot diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13 are , passes through the polarizing film 13 .

In the examples of FIGS. 14A and 14B, in order to clarify how the skirt portion L2a of the laser beam L2 is absorbed or reflected by the polarizing film 13, in addition to the diameter of the laser beam L2, the skirt portion L2a is added to the laser beam L2 in FIG. 13(B).

14A, the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13 is substantially the same as the width W2 of the laser-processed groove 13b, and the skirt portion L2a of the laser beam L2 does not pass through the polarizing film 13. 2 is a cross-sectional view of a laminated body 15 in the case of FIG. As described above, the width W2 is the minimum width of the laser-processed groove 13b that does not damage the polarizing film 13. As shown in FIG.

On the other hand, in FIG. 14B, the diameter of the laser beam L2 on the outer surface 13a of the polarizing film 13 is substantially the same as the width W2 of the laser-processed groove 13b, and the skirt portion L2a of the laser beam L2 is polarized. 4 is a cross-sectional view of the laminate 15 when passing through the membrane 13. FIG.

The laser processing head 24B in the example of FIG. 14B has a wavelength plate 24b between a laser oscillator (not shown) and a condenser lens 24a for changing the polarization direction of the laser beam L2. The wave plate 24b is, for example, a λ/2 wave plate (that is, a half-wave plate), and can rotate the polarization direction of the laser beam L2 by an arbitrary angle within a plane perpendicular to the traveling direction of the laser beam L2. .

For example, when the polarization direction of the laser beam L2 is tilted by an angle θ counterclockwise with respect to the optical axis (also referred to as the fast axis) of the λ / 2 wave plate, the laser beam L 2 transmitted through the λ / 2 wave plate is tilted clockwise by an angle θ with respect to the optical axis of the λ/2 wave plate. That is, the polarization direction of the laser beam L2 rotates by an angle 2θ before and after passing through the λ/2 wavelength plate. If the angle θ is 45 degrees, the polarization direction of the laser beam L2 transmitted through the λ/2 wavelength plate is rotated 90 degrees.

The polarization direction of the laser beam L2 emitted from the laser oscillator is predetermined. Therefore, by appropriately rotating the optical axis of the wave plate 24b, the known polarization direction of the laser beam L2 can be rotated within a plane perpendicular to the traveling direction of the laser beam L2. In the example of FIG. 14B, the polarization direction of the laser beam L2 is controlled so that the polarization direction of the laser beam L2 is orthogonal to the extending direction of the projections of the wire grid polarizing film.

In the example of FIG. 14B, since the skirt portion L2a of the laser beam L2 can pass through the polarizing film 13, the energy of the skirt portion L2a of the laser beam L2 can also contribute to the formation of the modified layer 11d. As a result, compared to the case where the skirt portion L2a of the laser beam L2 is absorbed by the polarizing film 13, the processing quality can be improved.

In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention.

REFERENCE SIGNS LIST 11 Wafer 11a Front surface 11b Back surface 11c Scheduled division line (street)
11d modified layer 11e crack 11f chip 13 polarizing film 13a outer surface 13b laser processing groove 15 laminate 17a frame 17b support tape (dicing tape)
19 wafer unit 20A, 20B laser processing device 22A, 22B laser irradiation unit 24A, 24B laser processing head 24a condensing lens 24b wavelength plate 26A imaging unit 28A, 28B chuck table 28Aa, 28Ba holding surface 30 dividing device (braking device)
32 support base 34 pressing blade 40 expanding device 42 drum 44 frame holding unit 46 clamp 48 frame support base 50 rod 52 air cylinder 60 protective film coating and washing device 61 protective film 62 spinner table mechanism 64 washing water receiving mechanism 66 clamp mechanism 68 spinner table 68a holding surface 70 motor 70a output shaft 72 support mechanism 74 support leg 76 air cylinder 78 washing water receiving container 78a outer wall 78b inner wall 78c bottom wall 78d drain port 80 support leg 82 cover member 84 drain hose 86 application means 88 discharge nozzle 90 Arm 92 Washing water supply means 94 Washing water nozzle 96 Arm 98 Air supply means 100 Air nozzle 102 Arm

Claims (3)

A wafer processing method for dividing a wafer having a polarizing film formed on its surface along a dividing line, comprising:
a wafer support step of attaching the back side of the wafer opposite the front side to a support tape attached to an annular frame;
After the wafer supporting step, a laser beam having a wavelength that is absorptive to the polarizing film is irradiated along the dividing line from the outer surface side of the polarizing film opposite to the wafer, and the polarized light is a laser-processed groove forming step of forming a laser-processed groove that divides the film;
After the laser-processed groove forming step, a laser beam having a wavelength that is transmissive to the wafer is emitted along the laser-processed groove from the outer surface side of the polarizing film so as to position the focal point inside the wafer. A modified layer forming step of forming a modified layer inside the wafer by irradiating the wafer;
a dividing step of applying an external force to the wafer after the modified layer forming step to divide the wafer along the planned dividing line;
including
The width of the laser-processed groove formed in the laser-processed groove-forming step is set to a minimum within a range in which the polarizing film is not damaged in the modified layer-forming step,
A method of processing a wafer, wherein, in the modified layer forming step, the wafer is irradiated with the laser beam whose polarization direction is controlled in the direction of transmission through the polarizing film of the wafer. a protective film coating step of applying a liquid material to the outer surface side of the polarizing film to form a protective film before the laser processing groove forming step;
a protective film removing step of removing the protective film after the laser processing groove forming step;
2. The method of processing a wafer according to claim 1, further comprising: 3. The method of processing a wafer according to claim 1, wherein said wafer is glass.

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