JP7086474B2 - Wafer processing method - Google Patents

Description

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

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

In the processing method described in Patent Document 1, the laser beam is transferred from the surface side of the wafer to the wafer so that the laser beam having a wavelength transparent to the wafer (that is, transmitted through the wafer) is focused inside the wafer. Irradiation is performed to form a modified layer inside the wafer along the planned division line of the wafer. Then, by applying an external force to the wafer, the wafer is divided starting from the reformed layer.

When a polarizing film is provided on the surface of the wafer forming the modified layer and the wafer is irradiated with a laser beam having a wavelength transmitted through the wafer from the surface side of the wafer, the polarizing film absorbs the energy of the laser beam. May cause the polarizing film to be ablated by the laser beam. The material of the ablated polarizing film becomes debris, and there is a problem that the debris adheres to the condenser lens from which the laser beam is emitted.

Further, even if the wafer is irradiated with a laser beam having a wavelength transmitted through the wafer from the polarizing film side of the wafer without controlling the polarization state of the laser beam, due to the nature of the polarizing film, only a laser beam having a specific polarizing component can be applied. Since it cannot pass through the polarizing film, the formation of the modified layer inside the wafer becomes incomplete.

When a film of metal, oxide, nitride, organic material, etc. is formed on the semiconductor wafer, the film is irradiated with a laser beam to partially remove the film of metal, etc., and then the semiconductor. A method of forming a modified layer inside a semiconductor wafer along a planned division line of the wafer is known (see, for example, Patent Documents 2 and 3).

Japanese Unexamined Patent Publication No. 2009-34723 Japanese Unexamined Patent Publication No. 2005-116844 Japanese Unexamined Patent Publication No. 2008-277414

When a film such as metal on a semiconductor wafer is partially removed by a laser beam as in Patent Documents 2 and 3, there is a problem that the time required for processing the semiconductor wafer is increased by the time required for this removal step. be.

The present invention has been made in view of the above problems, and an object of the present invention is to efficiently divide a wafer on which a polarizing film is formed.

According to one aspect of the present invention, it is a method of processing a wafer in which a wafer having a polarizing film formed on the surface thereof is divided along a planned division line, and the back surface side of the wafer opposite to the front surface is annular. After the frame support step to be attached to the support tape attached to the frame of the wafer and the frame support step, the polarization direction of the linearly polarized light is controlled so that the linearly polarized laser beam passes through the polarizing film of the wafer. The laser beam having a wavelength transparent to the wafer is irradiated along the planned division line from the outer surface side of the polarizing film located on the opposite side of the wafer so as to position the light collecting point inside. Thereby, after the modified layer forming step of forming the modified layer inside the wafer and the modified layer forming step, an external force is applied to the wafer to divide the wafer along the planned division line. A method for processing a wafer, including a split step, is provided.

Preferably, the method for processing the wafer includes a protective film coating step of applying a liquid protective material to the outer surface side of the polarizing film of the wafer to form a protective film before the modified layer forming step. After the modified layer forming 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 polarization direction of the laser beam is controlled so that the linearly polarized laser beam passes through the polarizing film, so that the laser beam reaches the inside of the wafer without removing the polarizing film. Can be made to. Therefore, the step of removing the polarizing film can be omitted, and the time required for processing the wafer can be shortened.

It is a perspective view which shows the wafer support step (S10) which attaches the back surface side of a wafer to a support tape. It is a perspective view of the wafer unit and the laser processing apparatus in the 1st reforming layer formation step (S20) which forms the reforming layer along the 1st direction of a wafer. It is a figure which shows the state of forming a modified layer on a wafer by controlling the polarization direction of the linear polarization of a laser beam in the first modified layer formation step (S20). It is a perspective view of the wafer unit and the laser processing apparatus in the 2nd reforming layer formation step (S30) which forms the reforming layer along the 2nd direction of a wafer. It is a figure which shows the state of forming the modified layer on a wafer by controlling the polarization direction of the linear polarization of a laser beam in the 2nd modified layer formation step (S30). It is a partial cross-sectional side view which shows the division step (S40) which divides a wafer. It is a flowchart of the processing method which concerns on 1st Embodiment. FIG. 8A is a partial cross-sectional side view showing a wafer unit fixed on the expanding device according to the second embodiment, and FIG. 8B is a division step (S45) according to the second embodiment. It is a partial cross-sectional side view showing. It is a perspective view of the protective film coating cleaning apparatus used in 3rd Embodiment. FIG. 10A is a partial cross-sectional side view showing the protective film coating step (S15), and FIG. 10B is a partial cross-sectional side view showing the first modified layer forming step (S20). Yes, FIG. 10C is a partial cross-sectional side view showing the protective film removing step (S35). It is a flowchart of the processing method which concerns on 3rd Embodiment. It is a partial cross-sectional side view which shows the 1st modified layer formation step (S20) which concerns on a comparative example.

An embodiment according to an aspect of the present invention will be described with reference to the accompanying drawings. 1 to 6 are diagrams showing each step in the processing of the wafer 11 according to the first embodiment, an apparatus used for the processing, and the like. Further, FIG. 7 is a flowchart of the processing method according to the first embodiment.

FIG. 1 is a perspective view showing a wafer support step (S10) in which the back surface 11b side of the wafer 11 is attached 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. The peripheral portion of the support tape (dicing tape) 17b is attached to an annular frame 17a made of metal, and the central portion of the support tape 17b is exposed by the opening of the frame 17a.

The support tape 17b has, for example, a base material layer and an adhesive layer provided on the entire surface of the base material layer. The adhesive layer is, for example, an ultraviolet curable resin layer, and exhibits strong adhesive force against the frame 17a and the like. The adhesive layer of the support tape 17b is exposed in 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 types of glass such as alkaline glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, and quartz glass.

There are no restrictions on the material, shape, structure, size, etc. of the wafer 11. For example, a substrate made of a semiconductor such as silicon, ceramics, resin, metal or the like can be used as the wafer 11.

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

In the present embodiment, the direction parallel to the long side of the wafer 11 is the first direction, and the direction parallel to the short side of the wafer 11 is the second direction. In FIG. 1, the first direction is indicated by a number 1 and the second direction is indicated by a number 2.

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

No device or the like is formed on the surface 11a side of each region of the wafer 11 of the present embodiment. Further, the surface 11a side of the wafer 11 of the present embodiment is divided into a rectangular region by a linear planned division line 11c, but the planned division line 11c is curved and is formed by a curved planned division line 11c. The surface 11a side of the wafer 11 may be partitioned into a circular region.

A polarizing film 13 is formed on the entire surface of the wafer 11 on the surface 11a. Like the wafer 11, the polarizing film 13 is also divided into a plurality of regions by the planned division line 11c. The polarizing film 13 includes a plurality of convex portions having a longitudinal portion along the first direction of the wafer 11. That is, each of the plurality of convex portions is formed in a striped shape along the first direction. Two convex portions adjacent to each other in the second direction are provided at a predetermined interval, and a groove is formed between the two convex portions. In FIG. 1, this groove is shown by a line in the polarizing film 13.

The convex portion of the polarizing film 13 is composed of a laminated structure of a reflective layer formed of a metal material and reflecting light and an absorbing layer formed of a semiconductor material on the reflective layer and absorbing light. The polarizing film 13 further includes an oxide film that is in contact with the surface of the convex portion and the surface 11a of the wafer 11 at the bottom of the groove located between the two convex portions. The oxide film is formed after forming a plurality of convex portions on the wafer 11 and then undergoing an oxidation step such as thermal oxidation. The oxide film is sufficiently thinner than the height of the convex part, and the oxide film does not completely fill the groove between the two convex parts.

The polarizing film 13 of the present embodiment is a so-called wire grid polarizing film formed 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 on polyvinyl alcohol (PVA) can be used, or other polarizing films can also be used.

In FIG. 1, in order to explain the planned division line 11c, the polarizing film 13 and the wafer 11 are shown separately, but the polarizing film 13 is provided in contact with the surface 11a of the wafer 11, and the polarizing film 13 is provided. The 13 and the wafer 11 constitute a laminated body 15.

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

In the present embodiment, after the wafer support step (S10) described above, the laser beam L is applied to the wafer 11 from the outer surface 13a side of the polarizing film 13 opposite to the wafer 11, and the modified layer 11d (FIG. 3) is formed (first modified layer forming step (S20)).

The first modified layer forming step (S20) is performed using the laser processing apparatus 20. FIG. 2 is a perspective view of the wafer unit 19 and the laser processing apparatus 20 in the first modified layer forming step (S20) for forming the modified layer 11d along the first direction of the wafer 11.

FIG. 3 shows the first reformed layer forming step (S20) for forming the reformed layer 11d along the first direction of the wafer 11 and controlling the polarization direction of the linearly polarized laser beam L on the wafer 11. It is a figure which shows the appearance of forming the modified layer 11d. The polarization state of the laser beam L in the present embodiment is linear polarization in which an electric field and a magnetic field vibrate in specific directions with respect to the traveling direction of the laser beam L.

As shown in FIG. 2, on the upper surface of the chuck table 28 of the laser processing apparatus 20, the back surface of the base material layer of the support tape 17b (that is, the surface opposite to the adhesive layer of the base material layer of the support tape 17b) is The wafer unit 19 is arranged so as to be in contact with each other.

The chuck table 28 has a circular upper surface larger than the wafer 11, and the upper 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 28.

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

A moving mechanism (not shown) is provided below the chuck table 28, and the chuck table 28 is indicated by the moving mechanism in the X-axis direction (that is, the machining feed direction, which is indicated by a double-headed arrow in FIG. 2, and is shown in FIG. 3 (Indicated by a symbol below the chuck table 28 inside) and can be moved in the Y-axis direction. However, it is not always necessary to move the chuck table 28 in both the X-axis direction and the Y-axis direction, and the chuck table 28 may be moved only in the X-axis direction.

The chuck table 28 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 28 by a predetermined angle, the wafer unit 19 sucked and held by the holding surface 28a is rotated by the same predetermined angle. As a result, the orientation of the wafer 11 with respect to the laser processing apparatus 20 in the XY plane is adjusted.

In the first reforming layer forming step (S20) shown in FIG. 2, the wafer unit 19 is rotated so that the first direction of the wafer 11 and the X-axis direction of the laser processing apparatus 20 are parallel to each other. The orientation of 11 in the XY plane is adjusted.

A laser irradiation unit 22 that irradiates the wafer 11 with the laser beam L is provided at a position facing the chuck table 28. Further, the laser irradiation unit 22 has a cylindrical laser processing head 24 provided at the tip thereof and whose height direction is substantially parallel to the Z-axis direction. The laser processing head 24 emits a pulsed laser beam L from the lower end on the chuck table 28 side.

The laser irradiation unit 22 further includes an image pickup unit 26 arranged in the vicinity of the laser processing head 24. The image of the laminated body 15 captured by the image pickup unit 26 is used for positioning the laminated body 15 and the laser processing head 24 and the like.

As shown in FIG. 3, the laser irradiation unit 22 has a laser oscillator 22a. The laser beam L emitted from the laser oscillator 22a is incident on the laser processing head 24.

The laser beam L incident on the laser processing head 24 is reflected by the mirror 24c in the laser processing head 24, and its traveling direction changes by approximately 90 degrees. As a result, the laser beam L is incident on the chuck table 28 along the Z-axis direction.

The laser processing head 24 has a condensing lens 24a that collects the laser beam L inside, and the laser beam L is emitted from the condensing lens 24a to the outside of the laser processing head 24. The condensing lens 24a has a function of positioning the condensing point of the laser beam L inside the wafer 11.

The laser beam L has a predetermined wavelength that is transparent to the wafer 11 (that is, passes through the wafer 11). The predetermined wavelength is, for example, about 1064 nm or about 1300 nm. The average power of the laser beam L is, for example, 1.0 W.

The laser processing head 24 has a wave plate 24b between the mirror 24c and the condenser lens 24a. The wave plate 24b of the present embodiment is housed in the laser processing head 24 so that it can rotate in a plane parallel to the XY plane with the central axis of the cylindrical laser processing head 24 as the axis of rotation.

The laser processing head 24 has a rotation mechanism for rotating the wave plate 24b. The rotation angle of this rotation mechanism can be adjusted manually, for example, but may be adjusted by a small rotary actuator formed by MEMS (Micro Electro Mechanical Systems) technology.

The wave plate 24b has a function of changing the polarization direction of the laser beam L. 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 linearly polarized light by an arbitrary angle in a plane perpendicular to the traveling direction of the laser beam L. ..

For example, when the polarization direction of the laser beam L is tilted counterclockwise by an angle θ with respect to the optical axis (also referred to as a high-speed axis) of the λ / 2 wave plate, the laser beam L transmitted through the λ / 2 wave plate. The polarization direction of 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 L rotates by an angle of 2θ before and after the transmission of the λ / 2 wave plate. Assuming that the angle θ is 45 degrees, the polarization direction of the laser beam L transmitted through the λ / 2 wave plate is rotated by 90 degrees.

The polarization direction of the laser beam L emitted from the laser oscillator 22a is predetermined. Therefore, by rotating the optical axis of the wave plate 24b and appropriately adjusting its direction, the polarization direction of the laser beam L can be rotated in a plane perpendicular to the traveling direction of the laser beam L. Thereby, the polarization direction of the laser beam L can be controlled.

By adjusting the polarization direction of the laser beam L with respect to the polarizing film 13 by the wave plate 24b, the laser beam L is absorbed and reflected by the polarizing film 13, and the laser beam L passes through the polarizing film 13. Can be adjusted.

Since the polarizing film 13 of the present embodiment is a wire grid polarizing film, the laser beam L is when the polarization direction of the laser beam L is orthogonal to the stretching direction of the convex portion having a stripe shape (which is also the stretching direction of the groove). Transmits through the polarizing film 13. On the other hand, when the polarization direction of the laser beam L is parallel to the extension direction of the striped convex portion, the laser beam L is absorbed or reflected by the polarizing film 13.

In the first modified layer forming step (S20) shown in FIG. 3, the polarization direction of the laser beam L is orthogonal to the first direction of the wafer 11. As a result, the laser beam L irradiated from the outer surface 13a side passes through the polarizing film 13.

In the first modified layer forming step (S20), first, the chuck table 28 is rotated so that the X-axis direction of the laser processing apparatus 20 and the first direction of the wafer 11 are parallel to each other. Then, while the laser processing head 24 and the chuck table 28 are relatively moved in the X-axis direction, the laser processing head 24 irradiates the laminated body 15 with the laser beam L.

In the present embodiment, the chuck table 28 is moved along the X-axis direction so as to irradiate the laser beam L from one end to the other end of the first direction of the wafer 11 so as to be parallel to the first direction of the wafer 11. The laser beam L is linearly irradiated along the scheduled division line 11c (see FIG. 1) (one-time (that is, one pass) irradiation of the laser beam L). The moving speed of the chuck table 28 when irradiating the laser beam L linearly is, for example, 500 mm / s.

In the present embodiment, the focusing point of the laser beam L transmitted through the polarizing film 13 is positioned at a specific depth inside the wafer 11. Multiphoton absorption occurs at the condensing point, and the wafer 11 is denatured. As a result, the modified layer 11d having reduced mechanical strength and the like is formed. The modified layer 11d is, for example, a region where the wafer 11 is partially melted.

In the present embodiment, the above-mentioned irradiation of the laser beam L is repeated once by changing the depth position of the condensing point. As a result, the modified layer 11d is formed at different depth positions inside the wafer 11. A plurality of modified layers 11d adjacent to each other in the thickness direction of the wafer 11 are connected to each other by irradiating the laser beam L 5 to 10 times (for example, 8 times) by changing the depth position of the condensing point. The modified layer 11d is formed (see FIG. 6).

Next, the second modified layer forming step (S30) will be described. FIG. 4 is a perspective view of the wafer unit 19 and the laser processing apparatus 20 in the second modified layer forming step (S30) for forming the modified layer 11d along the second direction of the wafer 11.

In the second modified layer forming step (S30), the orientation of the chuck table 28 in the first modified layer forming step (S20) is rotated by 90 degrees. As a result, the X-axis direction of the laser processing apparatus 20 and the second direction of the wafer 11 become parallel.

The stretching direction of the convex portion of the polarizing film 13 in the second modified layer forming step (S30) is orthogonal to the stretching direction of the convex portion in the first modified layer forming step (S20) shown in FIG. Therefore, if the polarization direction of the laser beam L is the same as that of the first modified layer forming step (S20), the laser beam L is absorbed or reflected by the polarizing film 13.

Therefore, the wave plate 24b is rotated by 45 degrees by using the rotation mechanism in the laser processing head 24. As a result, the polarization direction of the laser beam L is rotated by 90 degrees in the plane perpendicular to the traveling direction of the laser beam L, and is orthogonal to the stretching direction of the convex portion of the polarizing film 13.

FIG. 5 is a diagram showing a state in which the modified layer 11d is formed on the wafer 11 by controlling the polarization direction of the linear polarization of the laser beam L in the second modified layer forming step (S30). In the present specification, both the first modified layer forming step (S20) and the second modified layer forming step (S30) may be collectively referred to as a modified layer forming step.

In the second modified layer forming step (S30), the polarization direction of the laser beam L is orthogonal to the stretching direction of the convex portion of the polarizing film 13, so that the laser beam L irradiated from the outer surface 13a side of the polarizing film 13 is radiated. It passes through the polarizing film 13.

In the second modified layer forming step (S30), the chuck table 28 is moved along the X-axis direction so as to linearly irradiate the laser beam L from one end to the other end of the wafer 11 in the second direction. Then, the laser beam L is irradiated along the planned division line 11c parallel to the second direction of the wafer 11. The moving direction of the chuck table 28 is indicated by a double-headed arrow in FIG. 4, and is indicated by a symbol below the chuck table 28 in FIG.

By irradiating the laser beam L linearly from one end to the other end of the second direction of the wafer 11 at a plurality of positions different from each other in the first direction of the wafer 11, all the positions parallel to the second direction of the wafer 11 are applied. The modified layer 11d is formed along the planned division line 11c. The moving speed of the chuck table 28 when irradiating the laser beam L linearly is, for example, 500 mm / s.

In the second modified layer forming step (S30), similarly to the first modified layer forming step (S20), the depth position of the condensing point is changed a plurality of times along one scheduled division line 11c. By irradiating the laser beam L, the modified layer 11d is formed at different depth positions inside the wafer 11.

When a plurality of modified layers 11d are formed, cracks 11e extending from the modified layer 11d at the position closest to the surface 11a to the surface 11a are formed. Similarly, a crack 11e extending from the modified layer 11d at the position closest to the back surface 11b to the back surface 11b is formed (see FIG. 6; in FIG. 6, the modified layer 11d and the crack 11e overlap each other in the X-axis direction. The description of the planned division line 11c is omitted).

As described above, in the present embodiment, since the polarization direction of the laser beam L is controlled so that the laser beam L passes through the polarizing film 13, the laser beam L can be placed inside the wafer 11 without removing the polarizing film 13. Can be reached. Therefore, the step of removing the polarizing film 13 can be omitted. Therefore, the time required for processing the wafer 11 can be shortened.

After the reforming layer forming step (S30), an external force is applied to the wafer 11 by using the dividing device (braking device) 30, and the wafer 11 is divided along the planned division line 11c. FIG. 6 is a partial cross-sectional side view showing a division step (S40) for dividing the wafer 11.

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

In the division step (S40), first, the wafer unit 19 is arranged on the support base 32. Then, the pressing blade 34 is pressed against the scheduled division line 11c on the surface 11a side of the wafer 11. As a result, the wafer 11 is divided into a plurality of chips 11f (see FIG. 8B) along the modified layer 11d and the crack 11e (that is, the scheduled division line 11c).

In this embodiment, the surface 11a side of the wafer 11 provided with the polarizing film 13 is not held by the chuck table 28. Therefore, it is possible to prevent the polarizing film 13 from being destroyed by coming into contact with the chuck table 28.

Each chip 11f formed by being divided from 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, glass that is transparent to visible light is suitable as the wafer 11.

By the way, it is also 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, at the time of cutting, the polarizing film 13 in the region other than the planned division line 11c is also destroyed by the cutting water supplied to the blade of the cutting device and the contact point (that is, the processing point) of the blade and the wafer 11. Therefore, when the wafer 11 with the polarizing film 13 is divided, it is desirable to divide the wafer 11 by a method in which the load is not applied to the polarizing film 13 in the region other than the planned division line 11c as in the present embodiment.

By the way, in the present embodiment, the chuck table 28 is rotated 90 degrees in the second modified layer forming step (S30), but in the second modified layer forming step (S30) according to the first modification, the chuck is used. The chuck table 28 may be moved along the Y-axis direction without rotating the table 28 by 90 degrees.

Further, instead of moving the chuck table 28 along the Y-axis direction, in the second modified layer forming step (S30) according to the second modification, the laser machining head 24 is moved along the Y-axis direction. May be good.

In the first and second modifications, if the stretching direction of the convex portion of the polarizing film 13 in the first modified layer forming step (S20) and the polarization direction of the laser beam L are orthogonal to each other, the second modification is performed. In the layer forming step (S30), it is not necessary to rotate the direction of the chuck table 28 and the polarization direction of the laser beam L, respectively.

Further, in the second modified layer forming step (S30) according to the third modification, the polarization direction of the linearly polarized light of the laser beam L may be tilted by 45 degrees with respect to the stretching direction of the convex portion of the polarizing film 13. ..

In the third modification, the energy of the laser beam L forming the modified layer 11d is lower than that of the first embodiment, but the chuck table 28 or laser processing is performed without rotating the polarization direction of the laser beam L by 90 degrees. The modified layer 11d can be formed on the wafer 11 by moving the head 24 along the X-axis and Y-axis directions. Therefore, in the third modification, it is advantageous that the rotation mechanism in the laser processing head 24 becomes unnecessary.

Next, a second embodiment in which the wafer 11 is divided by using the expanding device 40 instead of the dividing step (S40) using the dividing device 30 will be described. FIG. 8A 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 the diameter of the wafer 11. Further, the expanding device 40 includes a frame holding unit 44 including a frame support base 48 provided so as to surround the upper end portion of the drum 42 from the outer peripheral side.

The frame support base 48 has an opening having a diameter larger than the diameter of the drum 42, and is arranged at the same height as the upper end portion of the drum 42. Further, clamps 46 are provided at a plurality of locations on the outer peripheral side of the frame support base 48.

When the wafer unit 19 is placed on the frame support base 48 and the frame 17a of the wafer unit 19 is fixed by the clamp 46, the wafer unit 19 is fixed by the frame support base 48.

The frame support 48 is supported by a plurality of rods 50 extending in the vertical direction. An air cylinder 52 that is supported by a disc-shaped base (not shown) and raises and lowers the rod 50 is provided at the lower end of each rod 50. When each air cylinder 52 is pulled in, the frame support base 48 is pulled down with respect to the drum 42.

In the division step (S45), first, the air cylinder 52 is operated so that the height of the upper end of the drum 42 of the expanding device 40 matches the height of the upper surface of the frame support base 48, and the height of the frame support base 48 is adjusted. To adjust.

Next, the wafer unit 19 carried out from the laser processing device 20 is placed on the drum 42 and the frame support 48 of the expanding device 40. After that, the frame 17a of the wafer unit 19 is fixed on the frame support base 48 by the clamp 46.

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. 8B, the support tape 17b is expanded in the outer peripheral direction. FIG. 8B is a partial cross-sectional side view showing the division 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 distance between the chips 11f is widened. As a result, the chips 11f are separated from each other in the XY plane direction, so that the individual chips 11f can be easily picked up.

In the modified example of the second embodiment, after the division step (S40) using the division device 30, the expansion device 40 may be used to widen the distance between the chips 11f. This facilitates the pickup of the individual chips 11f.

Next, the water-soluble protective film 61 is formed on the polarizing film 13 before the first modified layer forming step (S20), and the protective film 61 is removed after the second modified layer forming step (S30). , The third embodiment will be described.

FIG. 9 is a perspective view of the protective film coating cleaning device 60 used in the third embodiment. FIG. 10A is a partial cross-sectional side view showing the protective film coating step (S15), and FIG. 10B is a partial cross-sectional side view showing the first modified layer forming step (S20). Yes, FIG. 10C is a partial cross-sectional side view showing the protective film removing step (S35). Further, FIG. 11 is a flowchart of the processing method according to the third embodiment.

As shown in FIG. 9, the protective film coating cleaning device 60 includes a spinner table mechanism 62 having a disc-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 a suction means (not shown) via a flow path (not shown). By applying a negative pressure to the suction means, the spinner table 68 can suck and hold the wafer 11 arranged on the holding surface 68a.

On the outer periphery of the spinner table 68, four pendulum type clamp mechanisms 66 for holding the frame 17a of the wafer unit 19 are provided. When the rotation speed of the spinner table 68 per unit time is equal to or less than the predetermined value, the claw portion of the clamp mechanism 66 separates from the frame 17a, and when the rotation speed of the spinner table 68 per unit time is greater than the predetermined value, the claw portion is the frame. The clamp mechanism 66 is configured to hold down 17a. The predetermined value of the number of revolutions per unit time is, for example, 1000 rpm.

Below the spinner table 68, a cover member 82 having an opening (not shown) on the lower surface opposite to the spinner table 68 is provided. Further, below the spinner table 68, an output shaft 70a of a motor 70 that rotationally drives the spinner table 68 is connected via an opening of a cover member 82.

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 by the support legs 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 wash water receiving mechanism 64 has a wash water receiving container 78 for temporarily storing used wash water. A plurality of support legs 80 for supporting the washing water receiving container 78 are connected below the washing water receiving container 78.

The wash water receiving container 78 has a cylindrical outer wall 78a, a cylindrical inner side wall 78b which is lower than the outer wall 78a and is located below the cover member 82, and the bottoms of the outer wall 78a and the inner side wall 78b. It has a ring-shaped bottom wall 78c and a ring-shaped bottom wall 78c.

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

The protective film coating / cleaning device 60 has a coating means 86 for coating the 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 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 central portion of the spinner table 68 and a retracted position outside the spinner table 68. The discharge nozzle 88 is connected to a liquid resin supply source (not shown) via an arm 90.

The liquid resin is a material that forms the protective film 61. This liquid resin is a water-soluble resin such as PVA (poly vinyl alcohol), PEG (poly ethylene glycol), PEO (polyethylene oxide) and the like.

The protective film coating cleaning device 60 has a cleaning water supply means 92 for cleaning the laminated body 15. The washing water supply means 92 includes a washing water nozzle 94 that ejects washing water toward the laminated body 15 after forming the modified layer held on the spinner table 68, and a substantially L-shaped arm that supports the washing water nozzle 94. Includes 96 and.

The wash water supply means 92 further includes a motor (not shown) that swings the arm 96 between a position corresponding to the central portion 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 includes an air supply means 98 for drying the laminated body 15. The air supply means 98 has an air nozzle 100 that ejects air toward the washed laminate 15 held on the spinner table 68, and a substantially L-shaped arm 102 that supports 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 central portion of the spinner table 68 and a retracted position outside the spinner table 68. The air nozzle 100 is connected to an air supply source (not shown) via the arm 102.

In the present embodiment, before the first modified layer 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)). (See FIG. 10 (A)).

For example, in the protective film coating step (S15), the back surface 11b side of the laminated body 15 is adsorbed on the holding surface 68a, and the discharge nozzle 88 of the coating means 86 is moved onto the laminated body 15. Then, the spinner table 68 is rotated at 2000 rpm, and the discharged water-soluble resin is spin-coated on the entire surface of the polarizing film 13.

After the protective film coating step (S15), the above-mentioned first modified layer forming step (S20) and second modified layer forming step (S30) are sequentially performed. Note that FIG. 10B shows the first modified layer forming step (S20) when the protective film 61 is provided on the polarizing film 13, and the moving direction of the chuck table 28 is indicated by double-headed arrows.

By the way, when the polarization direction of the laser beam L is orthogonal to the stretching direction of the convex portion of the polarizing film 13, the laser beam L passes through the polarizing film 13, but the energy density of the transmitted laser beam L ablate the polarizing film 13. It can be expensive enough to do. In this case, a part of the polarizing film 13 is ablated to become debris 13b (see FIG. 12), which is scattered from the polarizing film 13.

In FIG. 10B, the region of the polarizing film 13 that has received energy corresponding to ablation from the laser beam L is indicated by the capital letter A. A part of the polarizing film 13 to be ablated is located directly above the modified layer 11d, and corresponds to the peripheral end portion of the polarizing film 13 of the chip 11f after division. Therefore, even if a part of the polarizing film 13 is ablated, the function of the polarizing film 13 of the chip 11f is not hindered.

After the second modified layer forming step (S30), the protective film 61 is removed by injecting wash water and air from the wash water supply means 92 and the air supply means 98 onto the laminated body 15 (protective film removal step (S35). )) (See FIG. 10 (C)).

For example, in the protective film removing step (S35), the spinner table 68 is rotated at a low rotation speed of 100 rpm to 200 rpm while supplying wash water (pure water) and air from the wash water nozzle 94 and the air nozzle 100 to the laminated body 15, respectively. And wash the laminated body 15. As a result, the protective film 61 is removed together with the debris 13b.

On the other hand, when the protective film 61 is not provided on the polarizing film 13, a part of the polarizing film 13 may be scattered as debris 13b when the laser beam L is irradiated to the laminated body 15. FIG. 12 is a partial cross-sectional side view showing the first modified layer forming step (S20) according to the comparative example.

As described above, in the third embodiment, since the protective film 61 is formed on the polarizing film 13, it is possible to prevent the polarizing film 13 ablated in the modified layer forming steps (S20 and S30) from scattering. This makes it possible to prevent the debris 13b from adhering to the condenser lens 24a of the laser processing head 24.

In addition, the structure, method, and the like according to the above-described embodiment can be appropriately modified and implemented as long as they do not deviate from the scope of the object of the present invention.

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 Debris 15 Laminated body 17a Frame 17b Support tape (dicing tape)
19 Wafer unit 20 Laser processing device 22 Laser irradiation unit 22a Laser oscillator 24 Laser processing head 24a Condensing lens 24b Wave plate 26 Imaging unit 28 Chuck table 28a 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 cleaning device 61 Protective film 62 Spinner table mechanism 64 Cleaning 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 side wall 78b Inner side wall 78c Bottom wall 78d Drain port 80 Support leg 82 Cover member 84 Drain hose 86 Coating 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)

It is a wafer processing method that divides a wafer having a polarizing film formed on its surface along a planned division line.
A frame support step in which the back surface side of the wafer opposite to the front surface is attached to a support tape mounted on an annular frame, and a frame support step.
After the frame support step, the wafer of the polarizing film is controlled so that the direction of polarization of the linear polarization is controlled so that the laser beam of linear polarization passes through the polarizing film, and the focusing point is positioned inside the wafer. A modified layer is formed inside the wafer by irradiating the laser beam having a wavelength transparent to the wafer from the outer surface side located on the opposite side of the wafer along the planned division line. Layer formation step and
After the modified layer forming step, an external force is applied to the wafer to divide the wafer along the planned division line, and a division step.
A method for processing a wafer, which comprises. Prior to the modified layer forming step, a protective film coating step of applying a liquid protective material to the outer surface side of the polarizing film of the wafer to form the protective film.
After the modified layer forming step, a protective film removing step for removing the protective film and a protective film removing step,
The wafer processing method according to claim 1, further comprising. The method for processing a wafer according to claim 1 or 2, wherein the wafer is glass.

Images