JP7242134B2 - 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 respective regions of a surface partitioned by dividing lines, into individual device chips.

2. Description of the Related Art 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 (streets) 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 Integrated circuits), LEDs (Light Emitting Diodes), etc. are formed in the regions defined by the division lines.

After that, an adhesive tape called a dicing tape, which is attached to an annular frame having an opening so as to close the opening, is attached to the back surface or front surface of the wafer, and the wafer, the adhesive tape, and the annular frame are integrated. form a frame unit. Then, by processing and dividing the wafer contained in the frame unit along the planned division lines, individual device chips are formed.

A laser processing apparatus, for example, is used to divide the wafer. A laser processing apparatus includes a chuck table that holds a wafer via an adhesive tape, and a laser processing unit that converges a laser beam having a wavelength that is transmissive to the wafer inside the wafer.

When dividing the wafer, the frame unit is placed on the chuck table, and the wafer is held by the chuck table via the adhesive tape. Then, the wafer is irradiated with the laser beam from the laser processing unit along each dividing line while the chuck table and the laser processing unit are relatively moved along the direction parallel to the upper surface of the chuck table. When the laser beam is focused inside the wafer, a modified layer that serves as a starting point for splitting is formed (see Patent Document 1).

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

Japanese Patent No. 3408805 Japanese Patent No. 3076179

The adhesive tape includes, for example, a base layer made of a vinyl chloride sheet or the like, and an adhesive layer provided on the base layer. In a laser processing apparatus, a laser beam is condensed inside the wafer in order to form a modified layer that serves as a splitting starting point inside the wafer, but part of the leakage light of the laser beam reaches the glue layer of the adhesive tape. . Then, the adhesive layer of the adhesive tape melts due to the thermal effect of the laser beam irradiation, and part of the adhesive layer adheres to the back side or front side of the device chip formed from the wafer.

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

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

According to one aspect of the present invention, there is provided a wafer processing method for dividing a wafer in which a plurality of devices are formed in respective regions of a front surface partitioned by dividing lines into individual device chips, the method comprising: A polyolefin-based sheet disposing step of disposing a polyolefin-based sheet having no glue layer on the surface, and an integration of heating the polyolefin-based sheet and integrating the wafer and the polyolefin-based sheet by thermocompression bonding. and before or after the integration step, a frame composed of an inner frame having an opening large enough to accommodate the wafer, and an outer frame having an opening with a diameter corresponding to the outer diameter of the inner frame. a frame supporting step of supporting the polyolefin-based sheet with the frame by sandwiching the outer periphery of the polyolefin-based sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame; A focal point of a laser beam having a wavelength that is transmissive to the wafer is positioned inside the wafer, and the laser beam is irradiated to the wafer along the dividing line to form a modified layer on the wafer. and a dividing step of dividing the wafer into individual device chips; and a picking-up step of picking up the individual device chips from the polyolefin-based sheet.

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

Preferably, in the pick-up step, the polyolefin-based sheet is expanded to widen the space between the device chips, and the device chips are pushed up from the polyolefin-based sheet side.

Moreover, preferably, the polyolefin-based 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.

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

In the wafer processing method according to one aspect of the present invention, the frame unit and the wafer are integrated using a polyolefin-based sheet having no glue layer, without using an adhesive tape having a glue layer in the frame unit. An integration process for integrating the polyolefin-based sheet and the wafer is realized by thermocompression bonding.

In a wafer processing method according to an aspect of the present invention, a frame is composed of 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. Then, 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. can support the polyolefin-based sheet with a frame.

That is, even if the polyolefin-based sheet does not have a glue layer, the wafer, the polyolefin-based sheet, and the frame can be integrated to form a frame unit by performing the integration step and the frame supporting step. .

After that, the wafer is irradiated with a laser beam having a wavelength that is transmissive to the wafer, and a modified layer is formed inside the wafer along the lines to be divided, thereby dividing the wafer. After that, the device chip is picked up from the polyolefin-based sheet. Each of the picked-up device chips is mounted on a predetermined mounting target.

Leakage light of the laser beam reaches the polyolefin-based sheet when forming the modified layer inside the wafer. However, since the polyolefin-based sheet does not have 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 the frame unit can be formed using a polyolefin-based sheet that does not have a glue layer, an adhesive tape that has a glue layer is not required, and as a result, the device caused by the adhesion of the glue layer Chip quality does not deteriorate.

Therefore, according to one aspect of the present invention, there is provided a wafer processing method in which a glue layer does not adhere to the back or front side of the device chip to be formed, and quality deterioration resulting from the adherence of the glue layer to the device chip does not occur. be done.

FIG. 1A is a perspective view schematically showing the front surface of a wafer, and FIG. 1B is a perspective view schematically showing the rear surface of the wafer. FIG. 4 is a perspective view schematically showing how the wafer is positioned on the holding surface of the chuck table; FIG. 4 is a perspective view schematically showing a polyolefin-based sheet disposing step; It is a perspective view which shows an example of an integration process typically. It is a perspective view which shows an example of an integration process typically. It is a perspective view which shows an example of an integration process typically. FIG. 7A is a perspective view schematically showing the frame supporting process, and FIG. 7B is a perspective view schematically showing the formed frame unit. FIG. 8A is a perspective view schematically showing the dividing step, and FIG. 8B is a cross-sectional view schematically showing the dividing step. FIG. 10 is a perspective view schematically showing loading of the frame unit into the pickup device; FIG. 10(A) is a cross-sectional view schematically showing the frame unit fixed on the frame support, and FIG. 10(B) is a cross-sectional view schematically showing the pickup process.

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

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

The front surface 1a of the wafer 1 is partitioned by a plurality of dividing lines 3 arranged in a lattice. Further, devices 5 such as ICs, LSIs, and LEDs are formed in respective regions defined by dividing lines 3 on the front surface 1a of the wafer 1 . In the method for processing a wafer 1 according to the present embodiment, a modified layer is formed inside the wafer 1 along the dividing line 3, the wafer 1 is divided starting from the modified layer, and individual device chips are obtained. Form.

When forming the modified layer on the wafer 1, the wafer 1 is irradiated with a laser beam having a wavelength that is transmissive to the wafer 1 along the division line 3, and the laser beam is focused inside the wafer 1. light up At this time, the laser beam may be applied to the wafer 1 from the front surface 1a side shown in FIG. 1(A), or may be applied to the wafer 1 from the rear surface 1b side shown in FIG. 1(B). When irradiating the wafer 1 with a laser beam from the rear surface 1b side, an alignment means equipped with an infrared camera is used to transmit the wafer 1 and detect the planned dividing line 3 on the front surface 1a side. to irradiate the laser beam.

Before loading the wafer 1 into a laser processing apparatus 10 (see FIG. 8A) in which laser processing is performed to form a modified layer on the wafer 1, the wafer 1, the polyolefin-based sheet, and the frame are integrated. to form a frame unit. The wafer 1 is loaded into the laser processing apparatus 10 in the state of a frame unit and processed.

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. After that, the polyolefin-based sheet is further expanded to widen the space between the device chips, and the device chips are picked up by a pick-up device.

An annular frame 7 (see FIG. 7A, etc.) is formed of a material such as metal, for example, and corresponds to an inner frame 7c having an opening large enough to accommodate the wafer 1 and an outer diameter of the inner frame 7c. and an outer frame 7a having an opening with a diameter equal to that of the outer frame 7a. The inner frame 7c and the outer frame 7a have substantially the same height.

The polyolefin-based sheet 9 (see FIG. 3, etc.) is a flexible resin-based sheet having 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 have a glue layer. The polyolefin-based sheet 9 is a polymer sheet synthesized using alkene as a monomer, and is, for example, a transparent or translucent sheet to visible light, such as a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet. However, the polyolefin-based sheet 9 is not limited to this, and may be opaque.

The polyolefin-based sheet 9 cannot be adhered to the wafer 1 at room temperature because it does not have adhesiveness. However, since the polyolefin-based sheet 9 has thermoplasticity, it can be partially melted and adhered to the wafer 1 by heating to a temperature near the melting point while being bonded to the wafer 1 while applying a predetermined pressure.

In the method for processing the wafer 1 according to the present embodiment, the polyolefin sheet 9 is adhered to the back surface 1b side 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 frame. A frame unit is formed by sandwiching between the inner peripheral wall 7b of 7a.

Next, each step of the method for processing the wafer 1 according to this embodiment will be described. 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. As shown in FIG. 2, the polyolefin-based sheet placement process is performed on a chuck table 2 having a holding surface 2a on its top.

The chuck table 2 has a porous member with a diameter larger than the outer diameter of the wafer 1 in the upper center. The upper surface of the porous member serves as the holding surface 2a of the chuck table 2. As shown in FIG. As shown in FIG. 3, the chuck table 2 has therein an exhaust path, one end of which communicates with the porous member, and a suction source 2b is arranged on the other end of the exhaust path. The exhaust path is provided with a switching portion 2c for switching between a connected state and a disconnected state. Pressure is applied, and the object to be held is held by suction on the chuck table 2 .

In the polyolefin sheet placement step, first, the wafer 1 is placed on the holding surface 2a of the chuck table 2, as shown in FIG. At this time, the orientation of the wafer 1 is selected in consideration of which of the front surface 1a and the back surface 1b is to be irradiated with the laser beam in the dividing step described later. For example, when the surface to be irradiated is the surface 1a, the surface 1a side faces downward. Further, for example, when the surface to be irradiated 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 by taking as an example the case where the surface to be irradiated with the laser beam is the surface 1a, but the orientation of the wafer 1 is not limited to this.

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

In addition, in the polyolefin-based sheet arranging step, a chuck table 2 having a holding surface 2a with a smaller diameter than the diameter of the polyolefin-based sheet 9 is used. When the chuck table 2 applies negative pressure to the polyolefin-based sheet 9 in the subsequent integration process, the negative pressure will leak through the gaps unless the entire holding surface 2a is covered with the polyolefin-based sheet 9. , the pressure cannot be appropriately applied to the polyolefin-based sheet 9 .

In the method for processing the wafer 1 according to the present embodiment, next, the polyolefin sheet 9 is heated, and an integration step is performed in which 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, the dashed lines indicate what can be seen through the polyolefin-based sheet 9, which is transparent or translucent to visible light.

In the integration step, first, the switching portion 2c of the chuck table 2 is operated to bring the suction source 2b into a communication state in which it is connected to the porous member above the chuck table 2, and the negative pressure from the suction source 2b is applied to the polyolefin sheet 9. act. Then, the polyolefin-based sheet 9 is brought into close contact with the wafer 1 by the atmospheric pressure.

Next, while the polyolefin sheet 9 is being sucked by the suction source 2b, the polyolefin sheet 9 is heated to perform thermocompression bonding. For heating the polyolefin sheet 9, for example, an infrared lamp 4 arranged above the chuck table 2 is used as shown in FIG. The infrared lamp 4 can irradiate infrared rays 4a having a wavelength at least which the material of the polyolefin-based sheet 9 absorbs.

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-based sheet 9 is thermocompression bonded to the wafer 1 .

Heating of the polyolefin-based 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, the dashed lines indicate what can be seen through the polyolefin-based sheet 9, which is transparent or translucent to visible light. The integration process shown in FIG. 5 is performed by a heat gun 6 arranged above the chuck table 2 .

The heat gun 6 includes a heating means such as a heating wire and a blower mechanism such as a fan, and can heat and jet air. While applying a negative pressure from the suction source 2b to the polyolefin sheet 9, the heat gun 6 supplies hot air 6a to the polyolefin sheet 9 from above to heat the polyolefin sheet 9 to a predetermined temperature. It is thermocompression bonded to.

Moreover, the heating of the polyolefin-based sheet 9 may be performed by other methods, 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, the dashed lines indicate what can be seen through the polyolefin-based 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 a heat source inside is used. Also in the integration step shown in FIG. 6, first, a negative pressure is applied to the polyolefin-based sheet 9 by the suction source 2b, and the polyolefin-based sheet 9 is brought into close contact with the wafer 1 by atmospheric pressure.

After that, the heat roller 8 is heated to a predetermined temperature and placed on one end of the holding surface 2 a of the chuck table 2 . Then, the heat roller 8 is rotated to roll the heat roller 8 on the chuck table 2 from the one end to the other end. Then, the polyolefin-based sheet 9 is thermocompression bonded to the wafer 1 . At this time, if a force is applied in the direction of pushing down the polyolefin-based sheet 9 by the heat roller 8, thermocompression bonding is performed at a pressure higher than the atmospheric pressure. Incidentally, it is preferable to coat the surface of the heat roller 8 with a fluorine resin.

Alternatively, the heat roller 8 may be replaced with an iron-like pressing member having a flat bottom plate and having a heat source inside to perform thermocompression bonding of the polyolefin-based sheet 9 . In this case, the pressing member is heated to a predetermined temperature to serve as a hot plate, and the polyolefin sheet 9 held on the chuck table 2 is pressed from above by the pressing member.

When the polyolefin-based sheet 9 is heated to a temperature near its melting point by any method, the polyolefin-based sheet 9 is thermocompression bonded to the wafer 1 . After the polyolefin-based sheet 9 is thermocompressed, the switching portion 2c is actuated to release the state of communication between the porous member of the chuck table 2 and the suction source 2b, thereby releasing the suction by the chuck table 2.

It should be noted that the polyolefin sheet 9 is preferably heated to a temperature below its melting point when the thermocompression bonding is performed. This is because if the heating temperature exceeds the melting point, the polyolefin-based sheet 9 may melt and become unable to maintain the shape of the sheet. Also, the polyolefin-based sheet 9 is preferably heated to a temperature above 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-based sheets 9 may not have a definite softening point. Therefore, the polyolefin sheet 9 is preferably heated to a temperature higher than or equal to 20° C. lower than its melting point and lower than its melting point when performing thermocompression bonding.

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

Here, the heating temperature refers to the temperature of the polyolefin-based sheet 9 during the integration process. For example, models capable of setting the output temperature of heat sources such as infrared lamps 4, heat guns 6, and heat rollers 8 have been put into practical use. In some cases, the temperature of 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 the present embodiment, a frame supporting step of supporting the polyolefin-based sheet 9 with the frame 7 is performed before or after the integrating step. FIG. 7A is a perspective view schematically showing the frame supporting process. In the frame supporting step, the outer periphery of the polyolefin sheet 9 is sandwiched between the outer peripheral wall 7e of the inner frame 7c of the frame 7 and the inner peripheral wall 7b of the outer frame 7a of the frame 7, thereby supporting the polyolefin sheet 9 with the frame. Support with 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 7 c is covered with the polyolefin sheet 9 . Next, the outer frame 7a is put on the polyolefin sheet 9. As shown in FIG. At this time, the position of the outer frame 7a is determined so that the outer peripheral wall 7e of the inner frame 7c and the inner peripheral wall 7b of the outer frame 7a substantially overlap each other.

After that, the outer frame 7a placed above the polyolefin-based sheet 9 is pushed downward to accommodate the inner frame 7c in the opening of the outer frame 7a. At this time, the outer peripheral portion of the polyolefin sheet 9 is folded by the outer frame 7a and sandwiched 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. 7B, a frame unit 11 is formed in which the wafer 1, the polyolefin-based sheet 9, and the frame 7 are integrated. In the frame unit 11, the polyolefin sheet 9 is arranged on the upper surface of the inner frame 7c of the frame 7. As shown in FIG.

Although the case where the frame supporting process is performed after the integration process has been described, 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 part sandwiched between the inner frame 7c and the outer frame 7a of the frame 7 of the polyolefin sheet 9 by heating in the integration process is the outer peripheral wall 7e of the inner frame 7c, the inner peripheral wall 7b of the outer frame 7a, , the polyolefin sheet 9 is supported by the frame 7 with a stronger force.

Also, the case where the polyolefin-based 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 supporting process has been described, but the wafer processing method according to the present embodiment. Then, the inner frame 7c and the outer frame 7a may be interchanged.

That is, the polyolefin sheet 9 may be placed on the outer frame 7a, the inner frame 7c may be placed thereon, and the inner frame 7c may be accommodated in the opening of the outer frame 7a by pressing the inner frame 7c from above. In this case, in the formed frame unit, the polyolefin sheet 9 is in contact with the lower surface of the inner frame 7c, and the wafer 1 is placed in the opening surrounded by the inner peripheral wall 7d of the inner frame 7c.

Next, in the method for processing the wafer 1 according to the present embodiment, the wafer 1 in the state of the frame unit 11 is laser-processed to form a modified layer inside the wafer 1 along the dividing lines 3. A dividing step for dividing the wafer 1 is performed. The dividing step is performed, for example, by a laser processing apparatus shown in FIG. 8(A). FIG. 8A is a perspective view schematically showing the dividing step, and FIG. 8B is a cross-sectional view schematically showing the dividing step.

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 oscillating a laser, and can emit a laser beam 14 having a wavelength that is transmissive to the wafer 1 (a wavelength that can be transmitted through the wafer 1). The chuck table can move (process 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. A processing head 12 a provided in the laser processing unit 12 has a mechanism for positioning a focal point 12 b of the laser beam 14 at a predetermined height inside the wafer 1 .

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

Next, while irradiating the inside of the wafer 1 with a laser beam 14 from the laser processing unit 12, the chuck table and the laser processing unit 12 are relatively moved along the processing feed direction parallel to the upper surface of the chuck table. That is, the focal 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 line 3 to divide. Then, a modified layer 3 a is formed inside the wafer 1 . In addition, in FIG. 8A, the modified layer 3a formed inside the wafer 1 is indicated by a broken line.

The irradiation conditions of the laser beam 14 in the dividing step are set as follows, for example. However, the irradiation condition of the laser beam 14 is not limited to this.
Wavelength: 1064nm
Repetition frequency: 50 kHz
Average output: 1W
Feeding speed: 200mm/sec

After forming the modified layer 3a inside the wafer 1 along one dividing line 3, the chuck table and the laser processing unit 12 are relatively moved in the indexing feed direction perpendicular to the processing feed direction, and another Similarly, the wafer 1 is laser-processed along the division line 3 . After forming the modified layer 3a along all the planned dividing lines 3 along one direction, the chuck table is rotated around the axis perpendicular to the holding surface, and the planned dividing lines 3 along the other direction are formed. Similarly, the wafer 1 is laser-processed along the line.

When the modified layer 3 a is formed by condensing the laser beam 14 inside the wafer 1 by the laser processing unit 12 , the leakage light of the laser beam 14 reaches the polyolefin sheet 9 below the wafer 1 .

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

On the other hand, in the wafer processing method according to the present embodiment, the frame unit 11 uses the polyolefin-based sheet 9 having no adhesive layer. Therefore, even if the leaked light of the laser beam 14 reaches the polyolefin sheet 9, the glue layer does not adhere to the back surface 1b side of the wafer 1. FIG. Therefore, the quality of device chips formed from the wafer 1 is kept good.

Next, by expanding the polyolefin-based sheet 9 radially outward, the wafer 1 is divided to form device chips. After that, a pick-up step is performed to pick up the individual device chips from the polyolefin-based sheet 9 . A pick-up device 16 shown in the lower part of FIG. 9 is used for expanding the polyolefin-based sheet 9 . FIG. 9 is a perspective view schematically showing loading of the frame unit 11 into the pickup device 16. As shown in FIG.

The pickup device 16 includes a cylindrical drum 18 having a diameter larger than that of the wafer 1 and a frame holding unit 20 including a frame support 22 . The frame support base 22 of the frame holding unit 20 has an opening with a diameter larger than the diameter of the drum 18 and is arranged at the same height as the upper end of the drum 18 so that the upper end of the drum 18 faces the outer circumference. surround from Further, the frame support base 22 has an outer diameter corresponding to the diameter of the opening of the inner frame 7c forming the frame 7 of the frame unit 11. As shown in FIG.

Further, the outer peripheral wall of the frame support 22 is provided with, for example, a plurality of suction holes 22a. The frame supporter 22 can apply negative pressure to the inner frame 7c of the frame 7 positioned on the outer peripheral side of the frame supporter 22 through the suction holes 22a. The frame unit 11 is fixed to the frame support base 22 by placing the frame unit 11 on the frame support base 22 and applying negative pressure to the inner frame 7c of the frame 7 .

The frame support base 22 is supported by a plurality of rods 24 extending along the vertical direction, and an air cylinder 26 for raising and lowering the rods 24 is provided at the lower end of each rod 24 . A plurality of air cylinders 26 are supported by a disk-shaped base 28 . Actuation of each air cylinder 26 causes the frame support 22 to be lowered relative to the drum 18 .

Inside the drum 18, a push-up mechanism 30 is arranged to push up the device chip supported by the polyolefin-based sheet 9 from below. A collet 32 (see FIG. 10B) capable of sucking and holding the device chip is arranged above the drum 18 . The push-up mechanism 30 and collet 32 are horizontally movable along the upper surface of the frame support 22 . Also, the collet 32 is connected to a suction source 32a (see FIG. 10B) via a switching portion 32b (see FIG. 10B).

When expanding the polyolefin-based sheet 9, first, the air cylinder 26 is operated so that the height of the upper end of the drum 18 of the pickup device 16 and the height of the upper surface of the frame support 22 are aligned with each other. Adjust the height of the 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 faces the outer peripheral wall of the frame support 22. As shown in FIG.

Thereafter, negative pressure is applied to the inner frame 7c of the frame 7 through the suction holes 22a of the frame support 22 to fix the frame 7 of the frame unit 11 on the frame support 22. As shown in FIG. FIG. 10A is a cross-sectional view schematically showing the frame unit 11 fixed on the frame support base 22. FIG. Inside the wafer 1, a modified layer 3a is formed along the dividing line 3. As shown in FIG.

Next, the air cylinder 26 is actuated to pull the frame support base 22 of the frame holding unit 20 downward 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-based sheet 9. As shown in FIG.

When the polyolefin-based sheet 9 is expanded, a force directed radially outward acts on the wafer 1, and the wafer 1 is divided starting from the modified layer 3a to form individual device chips 1c. When the polyolefin sheet 9 is further expanded, the intervals between the device chips 1c supported by the polyolefin sheet 9 are widened, 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 to form individual device chips 1c, a pick-up step of picking up the device chips 1c from the polyolefin-based sheet 9 is performed. 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.

After that, the push-up mechanism 30 is operated to push up the device chip 1c from the polyolefin sheet 9 side. Then, the switching portion 32b is operated to connect the collet 32 to the suction source 32a. Then, the device chip 1c is held by suction by the collet 32, and the device chip 1c is picked up from the polyolefin-based sheet 9. As shown in FIG. The individual device chips 1c picked up are then mounted on a predetermined wiring board or the like for use.

For example, when the frame unit 11 is formed using an 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 glue layer of the adhesive tape is applied to the back side of the device chip. Stick. Then, there is a problem that the quality of the device chip is deteriorated due to 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-based sheet 9 having no adhesive layer by thermocompression bonding. is unnecessary. As a result, the quality of the device chip does not deteriorate due to adhesion of the glue layer to the back surface.

It should be noted 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 above embodiment, the polyolefin sheet 9 is, for example, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, but one aspect of the present invention is not limited to this. For example, other materials may be used for the polyolefin-based sheet, such as a copolymer of propylene and ethylene, or an olefin-based elastomer.

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 1 wafer 1a front surface 1b back surface 3 dividing line 3a modified layer 5 device 7 frame 7a outer frame 7b, 7d inner peripheral wall 7c inner frame 7e outer peripheral wall 9 polyolefin-based sheet 11 frame unit 2 chuck table 2a holding surface 2b, 32a suction source 2c, 32b switching unit 4 infrared lamp 4a infrared ray 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 pickup device 18 drum 20 frame holding unit 22 frame support base 22a suction hole 24 rod 26 air cylinder 28 base 30 push-up mechanism 32 collet

Claims (6)

A wafer processing method for dividing a wafer in which a plurality of devices are formed in respective regions of a surface partitioned by dividing lines into individual device chips,
A polyolefin-based sheet disposing step of disposing a polyolefin-based sheet having no glue layer on the back surface or the front surface of the wafer;
an integration step of heating the polyolefin-based sheet and integrating the wafer and the polyolefin-based sheet by thermocompression bonding;
Before or after the integration step, a frame is used which is composed of 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-based sheet with the frame by sandwiching the outer periphery of the polyolefin-based sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame;
A focal point of a laser beam having a wavelength that is transmissive to the wafer is positioned inside the wafer, and the laser beam is irradiated to the wafer along the dividing line to form a modified layer on the wafer. and dividing the wafer into individual device chips;
a pick-up step of picking up the individual device chips from the polyolefin-based sheet;
A wafer processing method comprising: 2. The method of processing a wafer according to claim 1, wherein said thermocompression bonding is performed by irradiation of infrared rays in said integrating step. 2. The wafer processing method according to claim 1, wherein in said pick-up step, said polyolefin-based sheet is expanded to widen the space between the device chips, and said device chips are pushed up from said polyolefin-based sheet side. 2. The wafer processing method according to claim 1, wherein said polyolefin sheet is one of a polyethylene sheet, a polypropylene sheet and a polystyrene sheet. 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. to 180° C. when the polyolefin sheet is the polypropylene sheet. 5. The method of processing a wafer according to claim 4, wherein the heating temperature is 220.degree. C. to 240.degree. C. when the polyolefin sheet is the polystyrene sheet. 2. The method of processing a wafer according to claim 1, wherein said wafer is made of any one of Si, GaN, GaAs and glass.

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