JP7350432B2 - Wafer processing method - Google Patents

Description

The present invention relates to a wafer processing method for dividing a wafer, in which a plurality of devices are formed in each region of a surface divided by division lines, into individual device chips.

In the manufacturing process of device chips used in electronic devices such as mobile phones and personal computers, first, a plurality of intersecting dividing lines (street) are set on the surface of a wafer made of a material such as a semiconductor. Then, devices such as ICs (Integrated Circuits), LSIs (Large-Scale Integrations), LEDs (Light Emitting Diodes), etc. are formed in each area divided by the planned dividing line.

After that, an adhesive tape called dicing tape, which is attached to an annular frame having an opening so as to close the opening, is attached to the back or front surface of the wafer, and the wafer, adhesive tape, and annular frame are integrated. form a frame unit. Then, the wafer included in the frame unit is processed and divided along the dividing line to form individual device chips.

For example, a laser processing device is used to divide the wafer. The laser processing device includes a chuck table that holds the wafer via an adhesive tape, and a laser beam having a wavelength that is transparent to the wafer, and irradiates the wafer with a focused point located inside the wafer. Equipped with a laser processing unit.

When dividing a wafer, a frame unit is placed on a chuck table, and the wafer is held on the chuck table via adhesive tape. Then, while the chuck table and the laser processing unit are moved relative to each other in a direction parallel to the upper surface of the chuck table, the laser beam is sequentially irradiated from the laser processing unit onto the wafer along each dividing line.

When the wafer is irradiated with the laser beam, filament-shaped regions called shield tunnels are formed one after another along the planned dividing line. This shield tunnel is composed of a pore extending in the thickness direction of the wafer and an amorphous region surrounding the pore, and serves as a starting point for dividing the wafer (see Patent Document 1).

Thereafter, the frame unit is taken out of the laser processing apparatus and the adhesive tape is expanded radially outward, thereby dividing the wafer and forming individual device chips. When picking up the formed device chip from the adhesive tape, the adhesive tape is previously subjected to a treatment such as irradiation with ultraviolet rays to reduce the adhesive strength of the adhesive tape. As a processing apparatus with high production efficiency for device chips, there is known a processing apparatus that can continuously divide a wafer and irradiate an adhesive tape with ultraviolet rays in one apparatus (see Patent Document 2).

Patent No. 6151557 Patent No. 3076179

The adhesive tape includes, for example, a base layer formed of a vinyl chloride sheet or the like, and an adhesive layer disposed on the base layer. In a laser processing device, a laser beam is irradiated into the inside of a wafer in order to form a shield tunnel on the wafer that serves as a starting point for division. At this time, a part of the leaked light of the laser beam reaches the adhesive layer of the adhesive tape. Then, the adhesive layer of the adhesive tape melts due to the thermal influence of the laser beam irradiation, and a portion of the adhesive layer adheres to the back side or front side of the device chip formed from the wafer.

In this case, even if the adhesive tape is subjected to a treatment such as irradiating ultraviolet rays when picking up the device chip from the adhesive tape, a portion of the adhesive layer remains on the back or front side of the picked up device chip. I end up. Therefore, deterioration in the quality of device chips becomes a problem.

The present invention has been made in view of such problems, and its purpose is to prevent the adhesive layer from adhering to the back side or front side of the device chip to be formed, and to prevent the adhesive layer from adhering to the device chip. An object of the present invention is to provide a wafer processing method that does not cause quality deterioration.

According to one aspect of the present invention, there is provided a wafer processing method for dividing a wafer into individual device chips in which a plurality of devices are formed in each region of a surface partitioned by dividing lines, the method comprising: dividing a wafer into individual device chips; a polyolefin sheet disposing step of disposing a polyolefin sheet without an adhesive layer on the surface; and an integration step of heating the polyolefin sheet and integrating the wafer and the polyolefin sheet by thermocompression bonding. a frame that is formed before or after the integration process, and includes an inner frame having an opening large enough to accommodate the wafer, and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame. a frame supporting step of supporting the polyolefin sheet with the frame by sandwiching the outer periphery of the polyolefin sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame, using A convergence point of a laser beam with a wavelength that is transparent to the wafer is positioned inside the wafer, and the laser beam is irradiated onto the wafer along the planned dividing line to continuously shield the wafer. Provided is a method for processing a wafer, comprising: a dividing step of forming a wafer and dividing the wafer into individual device chips; and a pickup step of picking up the individual device chips from the polyolefin sheet. .

Preferably, in the integration step, the thermocompression bonding is performed by irradiation with infrared rays.

Preferably, in the pickup step, the polyolefin sheet is expanded to widen the distance between the device chips, and the device chips are pushed up from the polyolefin sheet side.

Preferably, the polyolefin sheet is a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet.

Further preferably, in the integration step, the heating temperature is 120°C to 140°C when the polyolefin sheet is the polyethylene sheet, and the heating temperature is 160°C when the polyolefin sheet is the polypropylene sheet. °C to 180 °C, and when the polyolefin sheet is the polystyrene sheet, the heating temperature is 220 °C to 240 °C.

Further, preferably, the wafer is made of Si, GaN, GaAs, or glass.

In a wafer processing method according to one aspect of the present invention, a frame unit and a wafer are integrated using a polyolefin sheet without an adhesive layer without using an adhesive tape having an adhesive layer in the frame unit. The integration step of integrating the polyolefin sheet and the wafer is achieved by thermocompression bonding.

In a wafer processing method according to one aspect of the present invention, a frame includes an inner frame having an opening large enough to accommodate a wafer, and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame. is used. In the frame supporting step, the inner frame is inserted into the opening of the outer frame, and at this time, a polyolefin sheet is sandwiched between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame. The polyolefin sheet can be supported by a frame.

That is, even if the polyolefin sheet does not have an adhesive layer, by performing the integration step and the frame support step, the wafer, the polyolefin sheet, and the frame can be integrated to form a frame unit. .

Thereafter, the wafer is irradiated with a laser beam having a wavelength that is transparent to the wafer, and a shield tunnel is continuously formed along the planned dividing line to divide the wafer. After that, device chips are picked up from the polyolefin sheet. The picked up device chips are each mounted on a predetermined mounting target.

When forming a shield tunnel inside the wafer, the leaked light from the laser beam reaches the polyolefin sheet. However, since the polyolefin sheet does not include an adhesive layer, the adhesive layer does not melt and adhere to the back or front side of the device chip.

That is, according to one aspect of the present invention, since a frame unit can be formed using a polyolefin sheet without an adhesive layer, an adhesive tape with an adhesive layer is not required, and as a result, device problems caused by adhesion of the adhesive layer No deterioration in chip quality occurs.

Therefore, according to one aspect of the present invention, a wafer processing method is provided in which a glue layer is not attached to the back side or the front side of a device chip to be formed, and the quality of the device chip is not deteriorated due to the attachment of the glue layer. be done.

FIG. 1(A) is a perspective view schematically showing the front surface of the wafer, and FIG. 1(B) is a perspective view schematically showing the back surface of the wafer. FIG. 3 is a perspective view schematically showing how the wafer is positioned on the holding surface of the chuck table. FIG. 2 is a perspective view schematically showing a polyolefin sheet disposing step. FIG. 3 is a perspective view schematically showing an example of an integration process. FIG. 3 is a perspective view schematically showing an example of an integration process. FIG. 3 is a perspective view schematically showing an example of an integration process. FIG. 7(A) is a perspective view schematically showing a frame supporting step, and FIG. 7(B) is a perspective view schematically showing a formed frame unit. FIG. 8(A) is a perspective view schematically showing a dividing process, FIG. 8(B) is a sectional view thereof, and FIG. 8(C) is a perspective view schematically showing a shield tunnel. . FIG. 3 is a perspective view schematically showing how the frame unit is carried into the pickup device. FIG. 10(A) is a cross-sectional view schematically showing a frame unit fixed on a frame support, and FIG. 10(B) is a cross-sectional view schematically showing a pickup process.

Embodiments according to one aspect of the present invention will be described with reference to the accompanying drawings. First, a wafer processed by the wafer processing method according to the present embodiment will be described. FIG. 1(A) is a perspective view schematically showing the front surface of the wafer 1, and FIG. 1(B) is a perspective view schematically showing the back surface of the wafer 1.

The wafer 1 is made of, for example, a material such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), GaAs (gallium arsenide), or other semiconductors, or a material such as sapphire, glass, or quartz. It is a substantially disk-shaped substrate made of. Examples of the glass include alkali glass, non-alkali glass, soda lime glass, lead glass, borosilicate glass, and quartz glass.

The surface 1a of the wafer 1 is divided by a plurality of dividing lines 3 arranged in a grid pattern. Furthermore, devices 5 such as ICs, LSIs, and LEDs are formed in each region of the front surface 1a of the wafer 1 divided by the dividing lines 3. In the method for processing a wafer 1 according to the present embodiment, shield tunnels are formed on the wafer 1 consecutively along the dividing line 3, and the wafer 1 is divided using the shield tunnel as a starting point to separate individual device chips. Form.

When forming a shield tunnel in the wafer 1, a laser beam with a wavelength that is transparent to the wafer 1 is irradiated onto the wafer 1 along the planned dividing line 3, and the laser beam is focused inside the wafer 1. let At this time, the laser beam may be irradiated onto the wafer 1 from the front surface 1a side shown in FIG. 1(A), or may be irradiated onto the wafer 1 from the back surface 1b side shown in FIG. 1(B). In addition, when irradiating the wafer 1 with a laser beam from the back side 1b side, the laser beam is transmitted through the wafer 1 using an alignment means equipped with an infrared camera to detect the scheduled dividing line 3 on the front side 1a side, and the laser beam is irradiated along the scheduled dividing line 3 on the front side 1a side. irradiate the laser beam.

Before carrying the wafer 1 into the laser processing apparatus 10 (see FIG. 8(A)) that performs laser processing to form a shield tunnel on the wafer 1, the wafer 1, the polyolefin sheet, and the frame are integrated. Then, a frame unit is formed. The wafer 1 is carried into the laser processing apparatus 10 in the form of a frame unit, and is processed.

Then, by expanding the polyolefin sheet, the wafer 1 can be divided, and individual device chips formed by dividing the wafer 1 are supported by the polyolefin sheet. Thereafter, the polyolefin sheet is further expanded to widen the spacing between the device chips, and the device chips are picked up by a pickup device.

The annular frame 7 (see FIG. 7A, etc.) is made of, for example, a material such as metal, and has an inner frame 7c having an opening large enough to accommodate the wafer 1, and an outer diameter corresponding to the inner frame 7c. It is composed of two members: an outer frame 7a having an opening with a diameter of The inner frame 7c and the outer frame 7a have substantially the same height.

The polyolefin sheet 9 (see FIG. 3, etc.) is a flexible resin sheet, and has flat front and back surfaces. The polyolefin sheet 9 has a diameter larger than the outer diameter of the inner frame 7c of the frame 7, and does not include an adhesive layer. The polyolefin sheet 9 is a polymer sheet synthesized using an alkene as a monomer, and is, for example, a sheet transparent or translucent to visible light, such as a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet. However, the polyolefin sheet 9 is not limited to this, and may be opaque.

Since the polyolefin sheet 9 does not have adhesive properties, it cannot be attached to the wafer 1 at room temperature. However, since the polyolefin sheet 9 has thermoplasticity, when it is heated to a temperature close to its melting point while being bonded to the wafer 1 while applying a predetermined pressure, it can be partially melted and bonded to the wafer 1.

In the method for processing the wafer 1 according to the present embodiment, the polyolefin sheet 9 is bonded to the back surface 1b of the wafer 1 by thermocompression bonding, and the outer peripheral portion of the polyolefin sheet 9 is connected to the outer peripheral wall 7e of the inner frame 7c and the outer peripheral wall 7e of the inner frame 7c. 7a and the inner peripheral wall 7b to form a frame unit.

Next, each step of the method for processing the wafer 1 according to this embodiment will be explained. First, in preparation for integrating the wafer 1 and the polyolefin sheet 9, a polyolefin sheet disposing step is performed. FIG. 2 is a perspective view schematically showing how the wafer 1 is positioned on the holding surface 2a of the chuck table 2. As shown in FIG. 2, the polyolefin sheet disposing process is carried out on a chuck table 2 having a holding surface 2a on the top.

The chuck table 2 includes a porous member having a diameter larger than the outer diameter of the wafer 1 at the upper center. The upper surface of the porous member becomes the holding surface 2a of the chuck table 2. As shown in FIG. 3, the chuck table 2 has an internal exhaust passage whose one end communicates with the porous member, and a suction source 2b is disposed at the other end of the exhaust passage. The exhaust path is provided with a switching part 2c that switches between a communication state and a disconnection state, and when the switching part 2c is in the communication state, the vacuum generated by the suction source 2b is applied to the object placed on the holding surface 2a. Pressure is applied, and the object to be held is suctioned and held on the chuck table 2.

In the polyolefin sheet disposing process, first, as shown in FIG. 2, the wafer 1 is placed on the holding surface 2a of the chuck table 2. At this time, the orientation of the wafer 1 is selected in consideration of whether the surface to be irradiated with the laser beam will be the front surface 1a or the back surface 1b in the dividing step described later. For example, when the surface to be irradiated is the surface 1a, the surface 1a side is directed downward. Further, for example, when the irradiated surface is the back surface 1b, the back surface 1b side is directed downward. Hereinafter, the wafer processing method according to the present embodiment will be described using an example in which the surface 1a is the surface to be irradiated with the laser beam, but the orientation of the wafer 1 is not limited to this.

After the wafer 1 is placed on the holding surface 2a of the chuck table 2, a polyolefin sheet 9 is placed on the back surface 1b (or front surface 1a) of the wafer 1. FIG. 3 is a perspective view schematically showing a polyolefin sheet disposing process. As shown in FIG. 3, a polyolefin sheet 9 is placed on the wafer 1 so as to cover the wafer 1.

In the polyolefin sheet disposing process, a chuck table 2 having a holding surface 2a having a diameter smaller than the diameter of the polyolefin sheet 9 is used. When applying negative pressure from the chuck table 2 to the polyolefin sheet 9 in the later integration process, if the entire holding surface 2a is not covered by the polyolefin sheet 9, the negative pressure will leak from the gap. This is because pressure cannot be applied appropriately to the polyolefin sheet 9.

In the method for processing the wafer 1 according to this embodiment, next, an integration step is performed in which the polyolefin sheet 9 is heated and the wafer 1 and the polyolefin sheet 9 are integrated by thermocompression bonding. FIG. 4 is a perspective view schematically showing an example of the integration process. In FIG. 4, broken lines indicate what is visible through the polyolefin sheet 9, which is transparent or translucent to visible light.

In the integration process, first, the switching part 2c of the chuck table 2 is activated to connect the suction source 2b to the porous member on the upper part of the chuck table 2, and the negative pressure from the suction source 2b is applied to the polyolefin sheet 9. Let it work. Then, the polyolefin sheet 9 is brought into close contact with the wafer 1 due to atmospheric pressure.

Next, the polyolefin sheet 9 is heated while being suctioned by the suction source 2b to carry out thermocompression bonding. For heating the polyolefin sheet 9, for example, as shown in FIG. 4, an infrared lamp 4 disposed above the chuck table 2 is used. The infrared lamp 4 is capable of emitting at least infrared rays 4a of a wavelength that is absorbed by the material of the polyolefin sheet 9.

The infrared lamp 4 is operated to irradiate the polyolefin sheet 9 with infrared rays 4a to heat the polyolefin sheet 9. Then, the polyolefin sheet 9 is bonded to the wafer 1 by thermocompression.

Heating of the polyolefin sheet 9 may be performed by other methods. FIG. 5 is a perspective view schematically showing another example of the integration process. In FIG. 5, broken lines indicate what is visible through the polyolefin sheet 9, which is transparent or translucent to visible light. The integration process shown in FIG. 5 is performed by a heat gun 6 disposed above the chuck table 2.

The heat gun 6 includes a heating means such as a heating wire and a blowing mechanism such as a fan, and can heat and spray air. While applying negative pressure from the suction source 2b to the polyolefin sheet 9, hot air 6a is supplied from above to the polyolefin sheet 9 using the heat gun 6 to heat the polyolefin sheet 9 to a predetermined temperature. is heat-compressed.

Further, the heating of the polyolefin sheet 9 may be carried out by still another method, for example, by pressing the wafer 1 from above with a member heated to a predetermined temperature. FIG. 6 is a perspective view schematically showing another example of the integration process. In FIG. 6, broken lines indicate what is visible through the polyolefin sheet 9, which is transparent or translucent to visible light.

In the integration step shown in FIG. 6, for example, a heat roller 8 having an internal heat source is used. In the integration step shown in FIG. 6, first, negative pressure from the suction source 2b is applied to the polyolefin sheet 9, and the polyolefin sheet 9 is brought into close contact with the wafer 1 by atmospheric pressure.

Thereafter, the heat roller 8 is heated to a predetermined temperature and placed on one end of the holding surface 2a of the chuck table 2. Then, the heat roller 8 is rotated and rolled on the chuck table 2 from the one end to the other end. Then, the polyolefin sheet 9 is bonded to the wafer 1 by thermocompression. At this time, when a force is applied in a direction to push down the polyolefin sheet 9 using the heat roller 8, thermocompression bonding is performed at a pressure higher than atmospheric pressure. Note that it is preferable that the surface of the heat roller 8 be coated with a fluororesin.

Alternatively, the heat roller 8 may be replaced with an iron-like pressing member that is equipped with an internal heat source and has a flat bottom plate to carry out thermocompression bonding of the polyolefin sheet 9. In this case, the pressing member is heated to a predetermined temperature to serve as a hot plate, and the pressing member presses the polyolefin sheet 9 held on the chuck table 2 from above.

When the polyolefin sheet 9 is heated to a temperature close to its melting point by any method, the polyolefin sheet 9 is bonded to the wafer 1 by thermocompression. After thermocompression-bonding the polyolefin sheet 9, the switching part 2c is operated to release the communication state between the porous member of the chuck table 2 and the suction source 2b, and the suction by the chuck table 2 is released.

In addition, when carrying out thermocompression bonding, the polyolefin sheet 9 is preferably heated to a temperature below its melting point. This is because if the heating temperature exceeds the melting point, the polyolefin sheet 9 may melt and become unable to maintain its shape. Further, the polyolefin sheet 9 is preferably heated to a temperature equal to or higher than its softening point. This is because thermocompression bonding cannot be properly performed unless the heating temperature reaches the softening point. That is, the polyolefin sheet 9 is preferably heated to a temperature above its softening point and below its melting point.

Furthermore, some polyolefin sheets 9 may not have a clear softening point. Therefore, when thermocompression bonding is carried out, the polyolefin sheet 9 is preferably heated to a temperature that is 20° C. lower than its melting point and lower than its melting point.

Further, when the polyolefin sheet 9 is a polyethylene sheet, the heating temperature is preferably 120°C to 140°C. Further, when the polyolefin sheet 9 is a polypropylene sheet, the heating temperature is preferably 160°C to 180°C. Further, when the polyolefin sheet 9 is a polystyrene sheet, the heating temperature is preferably 220°C to 240°C.

Here, the heating temperature refers to the temperature of the polyolefin sheet 9 when performing the integration step. For example, heat sources such as an infrared lamp 4, a heat gun 6, a heat roller 8, etc., have models that can set the output temperature, but even if the heat source is used to heat the polyolefin sheet 9, the polyolefin sheet In some cases, the temperature of No. 9 does not reach the set output temperature. Therefore, in order to heat the polyolefin sheet 9 to a predetermined temperature, the output temperature of the heat source may be set higher than the melting point of the polyolefin sheet 9.

In the method for processing the wafer 1 according to this embodiment, a frame support step of supporting the polyolefin sheet 9 with the frame 7 is performed before or after the integration step. FIG. 7(A) is a perspective view schematically showing a frame supporting process. In the frame support process, the outer circumference of the polyolefin sheet 9 is sandwiched between the outer circumferential wall 7e of the inner frame 7c of the frame 7 and the inner circumferential wall 7b of the outer frame 7a of the frame 7, so that the polyolefin sheet 9 is attached to the frame. Supported by 7.

First, the polyolefin sheet 9 is placed on the inner frame 7c. At this time, the position of the polyolefin sheet 9 is determined so that the entire area of the upper surface of the inner frame 7c is covered with the polyolefin sheet 9. Next, the outer frame 7a is placed above the polyolefin sheet 9. At this time, the outer frame 7a is positioned so that the outer circumferential wall 7e of the inner frame 7c and the inner circumferential wall 7b of the outer frame 7a substantially overlap.

Thereafter, the outer frame 7a placed above the polyolefin sheet 9 is pushed down, and the inner frame 7c is housed in the opening of the outer frame 7a. At this time, the outer peripheral portion of the polyolefin sheet 9 is bent by the outer frame 7a, and is held between the outer peripheral wall 7e of the inner frame 7c and the inner peripheral wall 7b of the outer frame 7a. Then, as shown in FIG. 7(B), a frame unit 11 is formed in which the wafer 1, the polyolefin sheet 9, and the frame 7 are integrated. In the frame unit 11, a polyolefin sheet 9 is arranged on the upper surface of the inner frame 7c of the frame 7.

Although a case has been described in which the frame support step is performed after the integration step, the wafer processing method according to this embodiment is not limited to this. For example, the integration process may be performed after the frame support process. In this case, the portion of the polyolefin sheet 9 sandwiched between the inner frame 7c and the outer frame 7a of the frame 7 becomes the outer circumferential wall 7e of the inner frame 7c, the inner circumferential wall 7b of the outer frame 7a, and The polyolefin sheet 9 is supported by the frame 7 with stronger force.

Furthermore, although a case has been described in which the polyolefin sheet 9 is placed on the inner frame 7c of the frame 7 and the outer frame 7a is placed thereon to carry out the frame support process, the wafer processing method according to the present embodiment Then, the inner frame 7c and the outer frame 7a may be replaced.

That is, the polyolefin sheet 9 may be placed on the outer frame 7a, the inner frame 7c may be placed on top of the polyolefin sheet 9, and the inner frame 7c may be pressed from above to accommodate the inner frame 7c in the opening of the outer frame 7a. In this case, in the frame unit that is formed, the polyolefin sheet 9 is in contact with the lower surface of the inner frame 7c, and the wafer 1 is placed in an opening surrounded by the inner circumferential wall 7d of the inner frame 7c.

Next, in the wafer processing method according to the present embodiment, the wafer 1 in the state of the frame unit 11 is laser-processed to form shield tunnels one after another in the wafer 1 along the dividing line 3, and the wafer is A dividing step is performed to divide 1. The dividing step is performed using, for example, a laser processing apparatus shown in FIG. 8(A). FIG. 8(A) is a perspective view schematically showing the dividing process, and FIG. 8(B) is a sectional view schematically showing the dividing process.

The laser processing apparatus 10 includes a laser processing unit 12 that irradiates the wafer 1 with a laser beam 14, and a chuck table (not shown) that holds the wafer 1. The laser processing unit 12 includes a laser oscillator (not shown) capable of emitting a laser beam, and can emit a laser beam 14 having a wavelength that is transparent to the wafer 1 (a wavelength that can be transmitted through the wafer 1). The chuck table can be moved (processing feed) along a direction parallel to the upper surface.

The laser processing unit 12 irradiates the wafer 1 held on the chuck table with a laser beam 14 emitted from the laser oscillator. The processing head 12a included in the laser processing unit 12 has a mechanism for positioning the focal point 12b of the laser beam 14 at a predetermined height position inside the wafer 1. The processing head 12a includes a condensing lens (not shown) inside. The numerical aperture (NA) of the condenser lens is determined so that the value obtained by dividing the numerical aperture (NA) by the refractive index (N) of the wafer 1 falls within the range of 0.05 to 0.2.

When laser processing the wafer 1, the frame unit 11 is placed on a chuck table, and the wafer 1 is held on the chuck table via the polyolefin sheet 9. Next, the chuck table is rotated to align the planned dividing line 3 of the wafer 1 with the processing feed direction of the laser processing device 10. Further, the relative positions of the chuck table and the laser processing unit 12 are adjusted so that the processing head 12a is disposed above the extension line of the planned dividing line 3. Then, the condensing point 12b of the laser beam 14 is positioned at a predetermined height position.

Next, the chuck table and the laser processing unit 12 are moved relative to each other along the processing feed direction parallel to the upper surface of the chuck table while successively irradiating the inside of the wafer 1 with laser beams 14 from the laser processing unit 12. That is, the condensing point 12b of the laser beam 14 is positioned inside the wafer 1, and the laser beam 14 is irradiated onto the wafer 1 along the planned dividing line 3.

Then, filament-shaped regions called shield tunnels 3a are formed one after another along the planned dividing line 3. FIG. 8(B) schematically shows a cross-sectional view of the wafer 1 in which the shield tunnels 3a are continuously formed. Moreover, FIG. 8(C) is a perspective view schematically showing the shield tunnel 3a. The shield tunnel 3a is composed of a pore 3b extending in the thickness direction of the wafer 1 and an amorphous region 3c surrounding the pore 3b. In addition, in FIG. 8(A), the shield tunnels 3a lined up along the planned dividing line 3 are shown by solid lines.

The irradiation conditions of the laser beam 14 in the dividing step are set as follows, for example. However, the irradiation conditions of the laser beam 14 are not limited to these.
Wavelength: 1030nm
Average output: 3W
Repetition frequency: 50kHz
Pulse width: 10ps
Focused spot diameter: φ10μm
Feed speed: 500mm/sec

When the laser beam 14 is irradiated onto the wafer 1 in this manner, shield tunnels 3a are formed in the wafer 1 along the planned dividing line 3 at intervals of 10 μm. Each shield tunnel 3a formed includes a pore 3b with a diameter of about 1 μm and an amorphous region 3c with a diameter of about 10 μm. Therefore, the shield tunnels 3a adjacent to each other have a form in which the amorphous regions 3c are connected to each other, as shown in FIG. 8(B).

After forming the shield tunnel 3a in the wafer 1 along one planned dividing line 3, the chuck table and the laser processing unit 12 are relatively moved in the index feed direction perpendicular to the processing feed direction, and the shield tunnel 3a is formed along one planned dividing line 3. Similarly, the wafer 1 is laser-processed along line 3. After forming the shield tunnels 3a along all the planned dividing lines 3 along one direction, the chuck table is rotated around an axis perpendicular to the holding surface, and the shield tunnels 3a are formed along all the planned dividing lines 3 along the other direction. Similarly, wafer 1 is laser processed.

Here, when the laser processing unit 12 irradiates the wafer 1 with a laser beam 14 to form a shield tunnel 3a, the leaked light of the laser beam 14 reaches the polyolefin sheet 9 below the wafer 1.

For example, when an adhesive tape is used in the frame unit 11 instead of the polyolefin sheet 9, when the adhesive tape's adhesive layer is irradiated with the leaked light of the laser beam 14, the adhesive tape's adhesive layer melts and the wafer 1 is Part of the glue layer adheres to the back surface 1b side. In this case, a portion of the glue layer remains on the back side of the device chip formed by dividing the wafer 1. Therefore, deterioration in the quality of device chips becomes a problem.

In contrast, in the wafer processing method according to the present embodiment, a polyolefin sheet 9 without an adhesive layer is used in the frame unit 11. Therefore, even if the leaked light of the laser beam 14 reaches the polyolefin sheet 9, the adhesive layer will not stick to the back surface 1b of the wafer 1. Therefore, the quality of device chips formed from the wafer 1 is maintained at good quality.

Next, the wafer 1 is divided into device chips by expanding the polyolefin sheet 9 radially outward. Thereafter, a pick-up step is carried out to pick up the individual device chips from the polyolefin sheet 9. A pickup device 16 shown at the bottom of FIG. 9 is used to expand the polyolefin sheet 9. FIG. 9 is a perspective view schematically showing how the frame unit 11 is carried into the pickup device 16.

The pickup device 16 includes a cylindrical drum 18 having a diameter larger than the diameter of the wafer 1 and a frame holding unit 20 including a frame support 22 . The frame support stand 22 of the frame holding unit 20 is provided with an opening having a diameter larger than the diameter of the drum 18, is arranged at the same height as the upper end of the drum 18, and has the upper end of the drum 18 on the outer circumferential side. Surround from. Furthermore, the frame support stand 22 has an outer diameter corresponding to the diameter of the opening of the inner frame 7c that constitutes the frame 7 of the frame unit 11.

Further, the outer peripheral wall of the frame support 22 is provided with, for example, a plurality of suction holes 22a. The frame support 22 can apply negative pressure to the inner frame 7c of the frame 7 positioned on the outer peripheral side of the frame support 22 through the suction hole 22a. When the frame unit 11 is placed on the frame support stand 22 and negative pressure is applied to the inner frame 7c of the frame 7, the frame unit 11 is fixed to the frame support stand 22.

The frame support stand 22 is supported by a plurality of rods 24 extending in the vertical direction, and an air cylinder 26 for raising and lowering the rods 24 is disposed at the lower end of each rod 24. The plurality of air cylinders 26 are supported by a disc-shaped base 28. Actuation of each air cylinder 26 lowers the frame support 22 relative to the drum 18.

A push-up mechanism 30 for pushing up the device chip supported by the polyolefin sheet 9 from below is provided inside the drum 18. Further, above the drum 18, a collet 32 (see FIG. 10(B)) that can suck and hold a device chip is provided. The push-up mechanism 30 and collet 32 are movable in the horizontal direction along the upper surface of the frame support 22. Further, the collet 32 is connected to a suction source 32a (see FIG. 10(B)) via a switching portion 32b (see FIG. 10(B)).

When expanding the polyolefin sheet 9, first operate the air cylinder 26 so that the height of the upper end of the drum 18 of the pickup device 16 matches the height of the upper surface of the frame support 22. Adjust the height. Next, the frame unit 11 carried out from the laser processing device 10 is placed on the drum 18 of the pickup device 16. At this time, the frame support 22 is inserted into the opening of the inner frame 7c of the frame 7, and the inner peripheral wall 7d of the inner frame 7c is made to face the outer peripheral wall of the frame support 22.

Thereafter, the frame 7 of the frame unit 11 is fixed on the frame support 22 by applying negative pressure to the inner frame 7c of the frame 7 from the suction hole 22a of the frame support 22. FIG. 10(A) is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support stand 22. FIG. Shield tunnels 3 a are formed in the wafer 1 and lined up along the dividing line 3 .

Next, the air cylinder 26 is operated to lower the frame support base 22 of the frame holding unit 20 with respect to the drum 18. Then, as shown in FIG. 10(B), the polyolefin sheet 9 is expanded radially outward. FIG. 10(B) is a cross-sectional view schematically showing the expanded polyolefin sheet 9. FIG.

When the polyolefin sheet 9 is expanded, a radially outward force acts on the wafer 1, and the wafer 1 is divided starting from the shield tunnel 3a, forming individual device chips 1c. When the polyolefin sheet 9 is further expanded, the distance between the device chips 1c supported by the polyolefin sheet 9 is increased, making it easier to pick up the individual device chips 1c.

In the wafer processing method according to the present embodiment, after the wafer 1 is divided into individual device chips 1c, a pickup step of picking up the device chips 1c from the polyolefin sheet 9 is carried out. In the pick-up process, the device chip 1c to be picked up is determined, the push-up mechanism 30 is moved below the device chip 1c, and the collet 32 is moved above the device chip 1c.

Thereafter, the pushing up mechanism 30 is operated to push up the device chip 1c from the polyolefin sheet 9 side. Then, the switching unit 32b is operated to connect the collet 32 to the suction source 32a. Then, the device chip 1c is sucked and held by the collet 32, and the device chip 1c is picked up from the polyolefin sheet 9. The picked up individual device chips 1c are then mounted on a predetermined wiring board or the like and used.

For example, when forming the frame unit 11 using adhesive tape, the leakage light of the laser beam 14 irradiated to the wafer 1 in the dividing process reaches the adhesive tape, and the adhesive layer of the adhesive tape is attached to the back side of the device chip. stick. Then, a problem arises in that the quality of the device chip deteriorates due to the adhesion of the glue layer.

On the other hand, according to the wafer processing method according to the present embodiment, it is possible to form the frame unit 11 using the polyolefin sheet 9 without an adhesive layer by thermocompression bonding, so the adhesive tape with an adhesive layer can be used. is not necessary. As a result, the quality of the device chip does not deteriorate due to adhesion of the adhesive layer to the back side.

Note that the present invention is not limited to the description of the above embodiments, and can be implemented with various modifications. For example, in the embodiment described above, the polyolefin sheet 9 is, for example, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, but one embodiment of the present invention is not limited thereto. For example, the polyolefin sheet may be made of other materials, such as a copolymer of propylene and ethylene or an olefin elastomer.

In addition, the structure, method, etc. according to the above embodiments can be modified and implemented as appropriate without departing from the scope of the objective of the present invention.

1 Wafer 1a Front surface 1b Back surface 3 Planned dividing line 3a Shield tunnel 3b Pore 3c Amorphous region 5 Device 7 Frame 7a Outer frame 7b, 7d Inner wall 7c Inner frame 7e Outer wall 9 Polyolefin sheet 11 Frame unit 2 Chuck table 2a Holding surface 2b, 32a Suction source 2c, 32b Switching part 4 Infrared lamp 4a Infrared 6 Heat gun 6a Hot air 8 Heat roller 10 Laser processing device 12 Laser processing unit 12a Processing head 12b Focusing point 14 Laser beam 16 Pick-up device 18 Drum 20 Frame holding Unit 22 Frame support 22a Suction hole 24 Rod 26 Air cylinder 28 Base 30 Push-up mechanism 32 Collet

Claims (6)

A wafer processing method in which a wafer in which a plurality of devices are formed in each region of a surface partitioned by dividing lines is divided into individual device chips, the method comprising:
a polyolefin sheet disposing step of disposing a polyolefin sheet without an adhesive layer on the back surface or the front surface of the wafer;
an integration step of heating the polyolefin sheet and integrating the wafer and the polyolefin sheet by thermocompression bonding;
Before or after the integration step, a frame is used that includes an inner frame having an opening large enough to accommodate the wafer, and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame. a frame supporting step of supporting the polyolefin sheet with the frame by sandwiching the outer periphery of the polyolefin sheet between an outer peripheral wall of the inner frame and an inner peripheral wall of the outer frame;
A convergence point of a laser beam with a wavelength that is transparent to the wafer is positioned inside the wafer, and the laser beam is irradiated onto the wafer along the planned dividing line to continuously shield the wafer. forming a wafer and dividing the wafer into individual device chips;
a pickup step of picking up each of the device chips from the polyolefin sheet;
A wafer processing method comprising: 2. The wafer processing method according to claim 1, wherein the thermocompression bonding is performed by irradiating infrared rays in the integrating step. 2. The method of processing a wafer according to claim 1, wherein in the pickup step, the polyolefin sheet is expanded to widen the distance between each device chip, and the device chips are pushed up from the polyolefin sheet side. 2. The wafer processing method according to claim 1, wherein the polyolefin sheet is one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet. In the integration step, when the polyolefin sheet is the polyethylene sheet, the heating temperature is 120°C to 140°C, and when the polyolefin sheet is the polypropylene sheet, the heating temperature is 160°C to 180°C. 5. The method for processing a wafer according to claim 4, wherein the heating temperature is 220° C. to 240° C. when the polyolefin sheet is the polystyrene sheet. 2. The method of processing a wafer according to claim 1, wherein the wafer is made of one of Si, GaN, GaAs, and glass.

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