JP2020115507A - Wafer processing method - Google Patents

Abstract

To form a device chip without deteriorating quality.SOLUTION: A wafer processing method for dividing a wafer in which a plurality of devices are formed on a surface into individual device chips comprises a polyester-based sheet arranging step, an integrating step, a frame supporting step, a dividing step, and a picking-up step. The polyester-based sheet arranging step arranges a polyester-based sheet on a rear surface of the wafer. The integrating step heats and presses the polyester-based sheet, and integrates the wafer and the polyester-based sheet. The frame supporting step supports the polyester-based sheet by a frame composed of an inner frame including an opening having a size enough to house the wafer and an outer frame including an opening with a diameter corresponding to an outer diameter of the inner frame by holding an outer periphery of the polyester-based sheet between an outer peripheral wall of the inner frame and an inner peripheral wall of the outer frame using the frame. The dividing step divides the wafer into individual device chips. The picking-up step cools the polyester-based sheet, pushes up the device chips, and picks up the device chips.SELECTED DRAWING: Figure 4

Description

The present invention relates to a wafer processing method for dividing a wafer formed in each region of a surface where a plurality of devices are divided by dividing 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 planned 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 respective regions divided by the planned dividing lines.

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

A laser processing device is used to divide the wafer, for example (see Patent Document 1). The laser processing apparatus includes a chuck table that holds the wafer via an adhesive tape, and a laser processing unit that irradiates the wafer with a laser beam having a wavelength that is absorptive to the wafer.

When dividing the wafer, a frame unit is placed on the chuck table and the wafer is held on the chuck table via an adhesive tape. Then, while the chuck table and the laser processing unit are relatively moved along a direction parallel to the upper surface of the chuck table, the laser processing unit irradiates the wafer with the laser beam. When the laser beam is irradiated, a dividing groove is formed in the wafer along each dividing line by ablation, and the wafer is divided.

After that, the frame unit is carried out from the laser processing apparatus, the adhesive tape is subjected to a treatment such as irradiation with ultraviolet rays to reduce the adhesive force of the adhesive tape, and the device chip is picked up. As a processing device with high device chip production efficiency, there is known a processing device capable of continuously dividing a wafer and irradiating an adhesive tape with ultraviolet rays by one device (see Patent Document 2). The device chip picked up from the adhesive tape is mounted on a predetermined wiring board or the like.

JP, 10-305420, A Japanese Patent No. 3076179

The adhesive tape includes, for example, a base material layer formed of a vinyl chloride sheet or the like and a glue layer disposed on the base material layer. In the laser processing apparatus, in order to surely divide the wafer by ablation processing, the wafer is irradiated with the laser beam under the condition that the dividing groove from the front surface to the back surface of the wafer can be surely formed. Therefore, below or around the formed dividing groove, the glue layer of the adhesive tape is melted by the thermal effect of the laser beam irradiation, and a part of the glue layer is formed on the back surface side of the device chip formed from the wafer. Stick to it.

In this case, when the device tape is picked up from the adhesive tape, even if a process such as irradiating the adhesive tape with ultraviolet rays is performed, the part of the glue layer remains on the back surface side of the picked-up device chip. .. Therefore, the deterioration of the quality of the device chip becomes a problem.

The present invention has been made in view of the above problems, and an object thereof is to prevent the adhesive layer from adhering to the back surface side of the device chip to be formed, and to improve the quality derived from the adhesion of the adhesive layer to the device chip. It is an object of the present invention to provide a wafer processing method that does not cause deterioration.

According to one aspect of the present invention, a plurality of devices is a wafer processing method for dividing a wafer formed in each region of the front surface partitioned by a dividing line into individual device chips, and Prior to the step of arranging the polyester sheet, the step of arranging the polyester sheet, the step of heating and pressing the polyester sheet to integrate the wafer with the polyester sheet, Alternatively, later, using a frame composed of an inner frame having an opening having a size capable of accommodating 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 polyester sheet by the frame by sandwiching the outer periphery of the polyester sheet between the outer peripheral wall and the inner peripheral wall of the outer frame, and having absorptivity for the wafer. A dividing step of irradiating the wafer with a laser beam of a wavelength along the dividing line to form dividing grooves to divide the wafer into individual device chips, and an individual step corresponding to each device chip of the polyester sheet In the region of, the wafer is processed by cooling the polyester sheet, pushing up the device chip from the polyester sheet side, and picking up the device chip from the polyester sheet. Will be provided.

Further, preferably, in the pickup step, the polyester sheet is expanded to widen the intervals between the device chips.

Further, preferably, the polyester sheet is either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet.

Further, preferably, in the integration step, the heating temperature is 250° C. to 270° C. when the polyester-based sheet is the polyethylene terephthalate sheet, and the heating temperature is heated when the polyester-based sheet is the polyethylene naphthalate sheet. The temperature is 160°C to 180°C.

Also, preferably, the wafer is made of any one of Si, GaN, GaAs, and glass.

In the wafer processing method according to one aspect of the present invention, the frame and the wafer are integrated by using the adhesive tape having the glue layer in the frame unit, and using the polyester sheet having no glue layer. The integration step of integrating the polyester sheet and the wafer is realized by heating and pressing.

In a wafer processing method according to one aspect of the present invention, a frame including an inner frame having an opening having a size capable of accommodating a wafer and an outer frame having an opening having a diameter corresponding to an 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 polyester sheet is sandwiched between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame. Thus, the polyester sheet can be supported by the frame.

That is, even if the polyester-based sheet does not have a glue layer, the wafer, the polyester-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 divided by irradiating the wafer with a laser beam having a wavelength having an absorptivity to the wafer and forming a dividing groove along the dividing line by ablation. Then, the polyester sheet is cooled in each area corresponding to each device chip of the polyester sheet, the device chip is pushed up from the polyester sheet side, and the device chip is picked up from the polyester sheet. The picked-up device chips are respectively mounted on predetermined mounting targets. When the polyester-based sheet is cooled during pickup, the polyester-based sheet shrinks and the polyester-based sheet is easily peeled off, so that the load on the device chip can be reduced.

When the ablation process is performed on the wafer, the heat generated by the irradiation of the laser beam is transferred to the polyester sheet below and near the dividing groove. However, since the polyester sheet does not have a glue layer, the glue layer does not melt and stick to the back surface side of the device chip.

That is, according to one aspect of the present invention, since the frame unit can be formed by using the polyester-based sheet having no glue layer, the adhesive tape having the glue layer is unnecessary, and as a result, the device caused by the adhesion of the glue layer is obtained. No deterioration of chip quality occurs.

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 surface side of a device chip to be formed and the deterioration of quality due to the adhesion of the glue layer does not occur on the device chip. ..

It is a perspective view which shows a wafer typically. It is a perspective view which shows typically a mode that a wafer is positioned on the holding surface of a chuck table. It is a perspective view which shows the polyester sheet|seat arrangement process typically. It is a perspective view which shows an example of an integration process typically. FIG. 5(A) is a perspective view schematically showing the frame supporting step, and FIG. 5(B) is a perspective view schematically showing the formed frame unit. It is a perspective view which shows a dividing process typically. It is a perspective view which shows typically the carrying in of the frame unit to a pick-up apparatus. FIG. 8A is a sectional view schematically showing the frame unit fixed on the frame support base, and FIG. 8B is a sectional view schematically showing the pickup step.

An embodiment according to an 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 this embodiment will be described. FIG. 1 is a perspective view schematically showing 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 another semiconductor, or a material such as sapphire, glass, or quartz. And a substantially disk-shaped substrate made of. The glass is, for example, alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, quartz glass, or the like.

The front surface 1a of the wafer 1 is divided by a plurality of planned dividing lines 3 arranged in a grid. In addition, devices 5 such as ICs, LSIs, LEDs, etc. are formed in each area of the front surface 1a of the wafer 1 which is divided by the planned dividing line 3. In the method for processing the wafer 1 according to the present embodiment, a dividing groove along the dividing line 3 is formed in the wafer 1 by ablation processing, the wafer 1 is divided, and individual device chips are formed.

Before the wafer 1 is loaded into the laser processing apparatus 6 (see FIG. 6) in which the ablation process is performed, the wafer 1, the polyester sheet, and the frame are integrated to form a frame unit. The wafer 1 is carried into the laser processing apparatus in the state of the frame unit and processed. The formed individual device chips are supported by a polyester sheet. After that, the polyester sheet is expanded to widen the space between the device chips, and the device chips are picked up by the pickup device.

The annular frame 7 (see FIG. 5(A), etc.) is formed of, for example, a material such as a metal, and corresponds to an inner frame 7c having an opening having a size capable of accommodating the wafer 1, and an outer diameter of the inner frame 7c. And an outer frame 7a having an opening of the same diameter. The inner frame 7c and the outer frame 7a have substantially the same height.

The polyester-based sheet 9 (see FIG. 3 and the like) is a flexible resin-based sheet and has flat front and back surfaces. The polyester sheet 9 has a diameter larger than the outer diameter of the inner frame 7c of the frame 7 and does not include a glue layer. The polyester sheet 9 is a polymer sheet synthesized by using dicarboxylic acid (compound having two carboxyl groups) and diol (compound having two hydroxyl groups) as monomers, for example, polyethylene terephthalate sheet, or , A sheet such as a polyethylene naphthalate sheet which is transparent or translucent to visible light. However, the polyester sheet 9 is not limited to this, and may be opaque.

Since the polyester sheet 9 does not have adhesiveness, it cannot be attached to the wafer 1 at room temperature. However, since the polyester-based sheet 9 has thermoplasticity, it can be partially melted and adhered to the wafer 1 when heated to a temperature near the melting point while being bonded to the wafer 1 while applying and pressing a predetermined pressure.

In the processing method of the wafer 1 according to the present embodiment, the polyester sheet 9 is adhered to the back surface 1b side of the wafer 1 by heating and pressing, and the outer peripheral portion of the polyester sheet 9 and the outer peripheral wall 7e of the inner frame 7c are separated from the outer peripheral wall 7e. The frame unit is formed by being sandwiched between the frame 7a and the inner peripheral wall 7b.

Next, each step of the method for processing the wafer 1 according to this embodiment will be described. First, in order to prepare the wafer 1 and the polyester sheet 9 to be integrated with each other, a polyester sheet arranging step is performed. FIG. 2 is a perspective view schematically showing how the wafer 1 is positioned on the holding surface 2 a of the chuck table 2. As shown in FIG. 2, the polyester sheet arranging step is performed on the chuck table 2 having the holding surface 2a on the upper portion.

The chuck table 2 includes a porous member having a diameter larger than the outer diameter of the wafer 1 at the center of the upper portion. 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 exhaust passage inside which one end communicates with the porous member, and a suction source 2b is arranged on the other end side of the exhaust passage. A switching unit 2c for switching between a communication state and a disconnection state is provided in the exhaust passage, and when the switching unit 2c is in the communication state, a negative force generated by the suction source 2b is generated on the held object placed on the holding surface 2a. The pressure acts and the held object is suction-held on the chuck table 2.

In the polyester sheet arranging step, first, as shown in FIG. 2, the wafer 1 is placed on the holding surface 2 a of the chuck table 2. At this time, the front surface 1a side of the wafer 1 is turned downward. Next, the polyester sheet 9 is provided on the back surface 1b of the wafer 1. FIG. 3 is a perspective view schematically showing the polyester sheet arranging step. As shown in FIG. 3, a polyester sheet 9 is provided on the wafer 1 so as to cover the wafer 1.

In the polyester sheet arranging step, the chuck table 2 having the holding surface 2a having a diameter smaller than that of the polyester sheet 9 is used. When the negative pressure by the chuck table 2 is applied to the polyester sheet 9 in the later-described integration step, the negative pressure will leak from the gap unless the entire holding surface 2a is covered with the polyester sheet 9. This is because the pressure cannot be properly applied to the polyester sheet 9.

In the method for processing the wafer 1 according to the present embodiment, next, an unifying step of heating and pressing the polyester sheet 9 to integrate the wafer 1 and the polyester sheet 9 is performed. FIG. 4 is a perspective view schematically showing an example of the integration process. In FIG. 4, what can be visually recognized through the polyester sheet 9 that is transparent or translucent to visible light is shown by a broken line.

In the integration step, first, the switching unit 2c of the chuck table 2 is operated to establish a communication state in which the suction source 2b is connected to the porous member above the chuck table 2, and the negative pressure by the suction source 2b is applied to the polyester sheet 9. Let it work. Then, the polyester sheet 9 is brought into close contact with the wafer 1 by the atmospheric pressure.

Next, the polyester sheet 9 is heated and pressed while the polyester sheet 9 is sucked by the suction source 2b. The heating and pressing of the polyester-based sheet 9 are performed, for example, by pressing the wafer 1 from above with a member heated to a predetermined temperature. In the integration step, for example, the heat roller 4 having a heat source inside is used.

The heat roller 4 is heated to a predetermined temperature, and the heat roller 4 is placed on one end of the holding surface 2 a of the chuck table 2. Then, the heat roller 4 is rotated, and the heat roller 4 is rolled on the chuck table 2 from the one end to the other end. Then, the polyester sheet 9 is thermocompression bonded to the wafer 1. At this time, if a force is applied by the heat roller 4 in a direction to push down the polyester sheet 9, thermocompression bonding is performed at a pressure higher than atmospheric pressure. The surface of the heat roller 4 is preferably covered with a fluororesin.

Further, an iron-like pressing member having a heat source inside and having a flat bottom plate may be used in place of the heat roller 4 to heat and press the polyester sheet 9. In this case, the pressing member is heated to a predetermined temperature to form a hot plate, and the polyester sheet 9 held on the chuck table 2 is pressed from above by the pressing member.

After thermocompression-bonding the polyester sheet 9, the switching unit 2c is operated to release the communication state between the porous member of the chuck table 2 and the suction source 2b, and the chuck table 2 releases the suction.

When the thermocompression bonding is performed, the polyester sheet 9 is preferably heated to a temperature below its melting point. This is because if the heating temperature exceeds the melting point, the polyester sheet 9 may melt and the sheet shape may not be maintained. Further, the polyester 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, it is preferable that the polyester sheet 9 is heated to a temperature equal to or higher than its softening point and equal to or lower than its melting point.

Furthermore, some polyester-based sheets 9 may not have a clear softening point. Therefore, when thermocompression bonding is performed, the polyester sheet 9 is preferably heated to a temperature that is 20° C. lower than the melting point thereof and lower than the melting point thereof.

When the polyester sheet 9 is a polyethylene terephthalate sheet, the heating temperature is preferably 250°C to 270°C. When the polyester sheet 9 is a polyethylene naphthalate sheet, the heating temperature is preferably 160°C to 180°C.

Here, the heating temperature refers to the temperature of the polyester sheet 9 when the integration step is performed. For example, although a model capable of setting the output temperature is practically used as a heat source such as the heat roller 4, even if the polyester sheet 9 is heated using the heat source, the temperature of the polyester sheet 9 is set. In some cases, the output temperature may not be reached. Therefore, in order to heat the polyester sheet 9 to a predetermined temperature, the output temperature of the heat source may be set higher than the melting point of the polyester sheet 9.

In the method for processing the wafer 1 according to this embodiment, a frame supporting step of supporting the polyester sheet 9 with the frame 7 is performed before or after the integration step. FIG. 5A is a perspective view schematically showing the frame supporting step. In the frame supporting step, the polyester sheet 9 is held 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 by sandwiching the outer periphery of the polyester sheet 9 in the frame. Support at 7.

First, the polyester sheet 9 is placed on the inner frame 7c. At this time, the position of the polyester sheet 9 is determined so that the entire area of the upper surface of the inner frame 7c is covered with the polyester sheet 9. Next, the outer frame 7a is placed above the polyester sheet 9. 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 with each other.

Then, the outer frame 7a, which is placed above the polyester sheet 9, is pushed down to accommodate the inner frame 7c in the opening of the outer frame 7a. At this time, the outer peripheral portion of the polyester sheet 9 is bent by the outer frame 7a and is 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. 5B, a frame unit 11 in which the wafer 1, the polyester sheet 9, and the frame 7 are integrated is formed. In the frame unit 11, the polyester sheet 9 is arranged on the upper surface of the inner frame 7c of the frame 7.

Although the case where the frame supporting step is performed after the integration step has been described, the wafer processing method according to the present embodiment is not limited to this. For example, the integration step may be performed after the frame supporting step. In this case, the portion sandwiched between the inner frame 7c and the outer frame 7a of the frame 7 of the polyester sheet 9 by the heating in the integration step is the outer peripheral wall 7e of the inner frame 7c, the inner peripheral wall 7b of the outer frame 7a, And the polyester sheet 9 is supported by the frame 7 with a stronger force.

Further, the case where the polyester sheet 9 is placed on the inner frame 7c of the frame 7 and the outer frame 7a is placed on the polyester sheet 9 to carry out the frame supporting step has been described, but the wafer processing method according to the present embodiment is described. Then, the inner frame 7c and the outer frame 7a may be replaced with each other.

That is, the polyester sheet 9 may be arranged on the outer frame 7a, the inner frame 7c may be arranged on the outer frame 7a, and the inner frame 7c may be pressed from above so that the inner frame 7c is accommodated in the opening of the outer frame 7a. In this case, in the formed frame unit, the polyester 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 a wafer 1 according to the present embodiment, the wafer 1 in the state of the frame unit 11 is subjected to ablation processing to form a division groove along the division line 3 to divide the wafer 1. Carry out the dividing step. The dividing step is performed by, for example, the laser processing apparatus shown in FIG. FIG. 6 is a perspective view schematically showing the dividing step.

The laser processing device 6 includes a laser processing unit 8 that ablates the wafer 1, and a chuck table (not shown) that holds the wafer 1. The laser processing unit 8 includes a laser oscillator (not shown) that can oscillate a laser, and can emit a laser beam 10 having a wavelength that has an absorptivity for the wafer 1 (a wavelength that the wafer 1 can absorb). The chuck table can be moved (working feed) along a direction parallel to the upper surface.

The laser processing unit 8 irradiates the laser beam 10 emitted from the laser oscillator onto the wafer 1 held on the chuck table. The processing head 8 a included in the laser processing unit 8 has a mechanism for focusing the laser beam 10 on the wafer 1 at a predetermined height position.

When the wafer 1 is ablated, the frame unit 11 is placed on the chuck table, and the wafer 1 is held on the chuck table via the polyester sheet 9. Then, 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 6. Further, the relative positions of the chuck table and the laser processing unit 8 are adjusted so that the processing head 8a is arranged above the extension line of the planned dividing line 3.

Next, while irradiating the wafer 1 with the laser beam 10 from the laser processing unit 8, the chuck table and the laser processing unit 8 are relatively moved along a processing feed direction parallel to the upper surface of the chuck table. Then, the wafer 1 is irradiated with the laser beam 10 along the planned dividing line 3, and a division groove 3 a along the planned dividing line 3 is formed in the wafer 1 by ablation.

The irradiation conditions of the laser beam 10 in the dividing step are set as follows, for example. However, the irradiation condition of the laser beam 10 is not limited to this.
Wavelength: 355nm
Repetition frequency: 50kHz
Average output: 5W
Feed rate: 200 mm/sec

After performing the ablation process along one division line 3, the chuck table and the laser processing unit 8 are moved relatively in the indexing feed direction perpendicular to the machining feed direction, and along the other division line 3 Similarly, the ablation process of the wafer 1 is performed. After forming the dividing grooves 3a along all the dividing lines 3 along one direction, the chuck table is rotated around an axis perpendicular to the holding surface, and along the dividing lines 3 along the other direction. Then, the wafer 1 is similarly ablated.

When the wafer 1 is ablated along all the planned dividing lines 3 of the wafer 1, the dividing process is completed. When the dividing step is completed and the dividing grooves 3a extending from the front surface 1a to the back surface 1b along all the planned dividing lines 3 are formed on the wafer 1, the wafer 1 is divided and individual device chips are formed.

When the ablation process is performed on the wafer 1 by the laser processing unit 8, processing waste originating from the wafer 1 is generated from the irradiation target portion of the laser beam 10, and the processing scrap is scattered around the irradiation target portion of the wafer 1. Adheres to the surface 1a. Even if the surface 1a of the wafer 1 is cleaned by the cleaning unit described below after the wafer 1 is subjected to the ablation process, it is not easy to completely remove the attached processing waste. If the processing waste remains on the device chip formed from the wafer 1, the quality of the device chip deteriorates.

Therefore, a water-soluble liquid resin that functions as a protective film that protects the surface 1a of the wafer 1 may be applied in advance to the surface 1a of the wafer 1 that is ablated by the laser processing device 6. When the liquid resin is applied to the front surface 1a of the wafer 1, the processing dust scattered during the ablation process adheres to the upper surface of the liquid resin, so that the processing waste does not directly adhere to the front surface 1a of the wafer 1. .. Then, the processing waste is removed together with the liquid resin by the cleaning unit described next.

The laser processing device 6 may include a cleaning unit (not shown). In this case, the wafer 1 ablated by the laser processing unit 8 is transferred to the cleaning unit and cleaned by the cleaning unit. For example, the cleaning unit includes a cleaning table that holds the frame unit 11, and a cleaning water supply nozzle that can reciprocate above the frame unit 11.

The cleaning table is rotated around an axis perpendicular to the holding surface, and while supplying a cleaning liquid such as pure water from the cleaning water supply nozzle to the wafer 1, the cleaning water supply nozzle is horizontally moved along a path passing above the center of the holding surface. By reciprocating in the direction, the front surface 1a side of the wafer 1 can be cleaned.

In the method for processing the wafer 1 according to the present embodiment, next, a pickup step of picking up the individual device chips from the polyester sheet 9 is carried out. In the pickup process, the pickup device 12 shown in the lower part of FIG. 7 is used. FIG. 7 is a perspective view schematically showing the loading of the frame unit 11 into the pickup device 12.

The pickup device 12 includes a cylindrical drum 14 having a diameter larger than the diameter of the wafer 1, and a frame holding unit 16 including a frame support 18. The frame support base 18 of the frame holding unit 16 is provided with an opening having a diameter larger than the diameter of the drum 14, and is arranged at the same height as the upper end of the drum 14, and the upper end of the drum 14 is located on the outer peripheral side. Surround from. Further, the frame support base 18 has an outer diameter of a size corresponding to the diameter of the opening of the inner frame 7c that constitutes the frame 7 of the frame unit 11.

Further, on the outer peripheral wall of the frame support base 18, for example, a plurality of suction holes 18a are provided. The frame support 18 can apply a negative pressure to the inner frame 7c of the frame 7 positioned on the outer peripheral side of the frame support 18 through the suction holes 18a. When the frame unit 11 is placed on the frame support base 18 and a negative pressure is applied to the inner frame 7c of the frame 7, the frame unit 11 is fixed to the frame support base 18.

The frame support base 18 is supported by a plurality of rods 20 extending in the vertical direction, and an air cylinder 22 for raising and lowering the rods 20 is arranged at the lower end of each rod 20. The plurality of air cylinders 22 are supported by a disc-shaped base 24. When each air cylinder 22 is operated, the frame support base 18 is pulled down with respect to the drum 14.

Inside the drum 14, a push-up mechanism 26 that pushes up the device chip supported by the polyester sheet 9 from below is disposed. The push-up mechanism 26 includes a cooling unit 26a including a cooling mechanism such as a Peltier element at the upper end. Further, a collet 28 (see FIG. 8B) capable of suction-holding the device chip is arranged above the drum 14. The push-up mechanism 26 and the collet 28 are movable in the horizontal direction along the upper surface of the frame support 18. Further, the collet 28 is connected to the suction source 28a (see FIG. 8B) via the switching unit 28b (see FIG. 8B).

In the pickup process, first, the height of the frame support 18 is adjusted by operating the air cylinder 22 so that the height of the upper end of the drum 14 of the pickup device 12 and the height of the upper surface of the frame support 18 match. To do. Next, the frame unit 11 carried out from the laser processing device 6 is placed on the drum 14 of the pickup device 12. At this time, the frame support base 18 is inserted into the opening of the inner frame 7c of the frame 7 so that the inner peripheral wall 7d of the inner frame 7c faces the outer peripheral wall of the frame support base 18.

Then, a negative pressure is applied to the inner frame 7c of the frame 7 from the suction holes 18a of the frame support 18 to fix the frame 7 of the frame unit 11 on the frame support 18. FIG. 8A is a sectional view schematically showing the frame unit 11 fixed on the frame support base 18. A dividing groove 3a is formed in the wafer 1 by the dividing step and is divided.

Next, the air cylinder 22 is operated to pull down the frame support base 18 of the frame holding unit 16 with respect to the drum 14. Then, as shown in FIG. 8B, the polyester sheet 9 is expanded in the outer peripheral direction. FIG. 8B is a cross-sectional view schematically showing the pickup process.

When the polyester sheet 9 is expanded in the outer peripheral direction, the intervals between the device chips 1c supported by the polyester sheet 9 are widened. Then, the device chips 1c are less likely to come into contact with each other, and the individual device chips 1c can be easily picked up. Then, the device chip 1c to be picked up is determined, the push-up mechanism 26 is moved below the device chip 1c, and the collet 28 is moved above the device chip 1c.

Then, the cooling unit 26a is operated to reduce the temperature, and the cooling unit 26a is brought into contact with the region of the polyester sheet 9 corresponding to the device chip 1c to cool the region. Further, the push-up mechanism 26 is operated to push up the device chip 1c from the polyester sheet 9 side. Then, the switching unit 28b is operated to communicate the collet 28 with the suction source 28a. Then, the device chip 1c is suction-held by the collet 28, and the device chip 1c is picked up from the polyester sheet 9. The individual device chips 1c thus picked up are then mounted on a predetermined wiring board or the like for use.

When the area of the polyester sheet 9 is cooled by the cooling unit 26a, the polyester sheet 9 contracts, a large stress is generated at the interface between the polyester sheet 9 and the device chip, and peeling is facilitated. Therefore, the load applied to the device chip when peeled from the polyester sheet 9 is reduced.

For example, when the frame unit 11 is formed using an adhesive tape, heat generated by the irradiation of the laser beam 10 in the dividing step is transferred to the adhesive tape, and the glue layer of the adhesive tape is melted and fixed to the back surface side of the device chip. To do. Then, the deterioration of the quality of the device chip due to the adhesion of the glue layer becomes a problem.

On the other hand, according to the wafer processing method of the present embodiment, it is possible to form a frame unit using a polyester-based sheet that does not have a glue layer by thermocompression bonding, so an adhesive tape having a glue layer is not required. Is. As a result, the quality of the device chip does not deteriorate due to the adhesion of the glue layer to the back surface side.

The present invention is not limited to the description of the above embodiment, and can be implemented with various modifications. For example, although the case where the polyester sheet 9 is, for example, a polyethylene terephthalate sheet or a polyethylene naphthalate sheet has been described in the above embodiment, one aspect of the present invention is not limited thereto. For example, other materials may be used for the polyester sheet, and may be a polytrimethylene terephthalate sheet, a polybutylene terephthalate sheet, a polybutylene naphthalate sheet, or the like.

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

1 wafer 1a front surface 1b back surface 3 planned dividing line 3a dividing groove 5 device 7 frame 7a outer frame 7b, 7d inner peripheral wall 7c inner frame 7e outer peripheral wall 9 polyester sheet 11 frame unit 2 chuck table 2a holding surface 2b, 28a suction source 2c , 28b Switching part 4 Heat roller 6 Laser processing device 8 Laser processing unit 8a Processing head 10 Laser beam 12 Pickup device 14 Drum 16 Frame holding unit 18 Frame support base 18a Suction hole 20 Rod 22 Air cylinder 24 Base 26 Push-up mechanism 26a Cooling part 28 Collet

Claims (5)

A method of processing a wafer, wherein a plurality of devices divides a wafer formed in each region of the surface divided by a dividing line into individual device chips,
A polyester sheet arranging step of arranging a polyester sheet on the back surface of the wafer,
An integration step of heating and pressing the polyester-based sheet to integrate the wafer and the polyester-based sheet,
Before or after the integration step, a frame composed of an inner frame having an opening having a size capable of accommodating the wafer and an outer frame having an opening having a diameter corresponding to the outer diameter of the inner frame is used. A frame supporting step of supporting the polyester sheet by the frame by sandwiching the outer periphery of the polyester sheet between the outer peripheral wall of the inner frame and the inner peripheral wall of the outer frame,
A dividing step of irradiating the wafer with a laser beam having a wavelength having an absorptivity to the wafer along the dividing line to form dividing grooves and dividing the wafer into individual device chips;
A pickup step of cooling the polyester sheet in each area corresponding to each device chip of the polyester sheet, pushing up the device chip from the polyester sheet side, and picking up the device chip from the polyester sheet; ,
A method for processing a wafer, comprising: 2. The method of processing a wafer according to claim 1, wherein in the pick-up step, the polyester sheet is expanded to widen intervals between the device chips. 2. The method for processing a wafer according to claim 1, wherein the polyester sheet is either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. In the integration step, the heating temperature is 250° C. to 270° C. when the polyester sheet is the polyethylene terephthalate sheet, and the heating temperature is 160° C. when the polyester sheet is the polyethylene naphthalate sheet. The wafer processing method according to claim 3, wherein the temperature is 180°C. The wafer processing method according to claim 1, wherein the wafer is made of any one of Si, GaN, GaAs, and glass.

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