WAFER PROCESSING METHODS

Abstract

Wafer processing method for dividing a wafer (1) along a plurality of dividing lines (3) to obtain a plurality of individual component chips (1c), wherein the dividing lines (3) are formed on the front side (1a) of the wafer (1) so as to define a plurality of separate regions in which a plurality of components (5) are individually formed, the wafer processing method comprising: a ring frame preparation step of preparing a ring frame (7) having an inner opening (7a) for receiving the wafer (1); a polyester film providing step of positioning the wafer (1) in the inner opening (7a) of the ring frame (7) and providing a polyester film (9) on a back side (1b) of the wafer (1) and on a back side (7c) of the ring frame (7), wherein no adhesive layer is arranged between the polyester film (9) and the wafer (1); a bonding step of heating the polyester film (9) while applying pressure to the polyester film (9) after performing the polyester film providing step, whereby the wafer (1) and the ring frame (7) are bonded by thermocompression bonding via the polyester film (9) to form a frame unit (11) in a state where the front side (1a) of the wafer (1) and the front side (7b) of the ring frame (7) are exposed upward; a dividing step of applying a laser beam to the wafer (1) along each dividing line (3), the laser beam having an absorption wavelength for the wafer (1), after performing the bonding step, thereby forming a dividing groove in the wafer along each dividing line (3) to divide the wafer (1) into the individual component chips (1c); and a picking-up step of heating the polyester film (9) in each region of the polyester film (9) corresponding to a respective component chip (1c), and pushing up each component chip (1c) from the side of the polyester film (9) to pick up each component chip (1c) from the polyester film (9) after performing the dividing step.

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a wafer processing method for dividing a wafer along a plurality of dividing lines to obtain a plurality of individual device chips, wherein the dividing lines are formed on the front side of the wafer to thereby define a plurality of separate regions in which a plurality of devices are individually formed. Description of related technology

[0002] In a manufacturing process for component chips to be used in electronic equipment such as mobile phones and personal computers, a plurality of intersecting division lines (streets) are first arranged on the front side of a wafer made of, for example, a semiconductor, to thereby define a plurality of divided regions on the front side of the wafer. Next, a component such as an integrated circuit (IC), a large-scale integrated circuit (LSI), and a light-emitting diode (LED) is formed in each divided region. Next, a ring frame having an inner opening is prepared in which an adhesive tape called a division tape is preliminarily attached to its outer portion on the ring frame (the back side of the ring frame) so as to close the inner opening of the ring frame.Next, a central portion of the adhesive tape is applied to the back of the wafer so that the wafer is received within the inner opening of the ring frame. In this way, the wafer, the adhesive tape, and the ring frame are bonded together to form a frame unit. The wafer contained within this frame unit is then processed to be divided along each division line to obtain a plurality of individual component chips containing the respective components.

[0003] For example, a laser processing apparatus is used to divide the wafer (see Japanese Patent Application Laid-Open No. JP H10-305420 A). The laser processing apparatus includes a chuck table for holding the wafer via the adhesive tape, and a laser processing unit for applying a laser beam to the wafer held on the chuck table, the laser beam having an absorption wavelength for the wafer. When dividing the wafer using this laser processing apparatus, the frame unit is placed on the chuck table, and the wafer is held on the upper surface of the chuck table via the adhesive tape. In this state, the chuck table and the laser processing unit are relatively moved in a direction parallel to the upper surface of the chuck table. At the same time, the laser beam from the laser processing unit is applied to the wafer.When the laser beam is applied to the wafer, laser ablation occurs to form a dividing groove in the wafer along each dividing line, thereby dividing the wafer along each dividing line.

[0004] Next, the frame assembly is transferred from the laser processing apparatus to another apparatus for applying ultraviolet light to the adhesive tape, thereby reducing the adhesion of the adhesive tape. After that, each component chip is picked up by the adhesive tape. As a processing apparatus capable of manufacturing component chips with high efficiency, there is a laser processing apparatus capable of continuously performing the wafer dividing process and the process of applying ultraviolet light to the adhesive tape (see, for example, Japanese Patent JP 3 076 179 B2). Each component chip picked up by the adhesive tape is next attached to a predetermined wiring substrate or the like.

[0005] Further prior art helpful for understanding the following invention can be found in the following documents: WO 2014 / 157471 A1 relates to a wafer processing belt having a uniform expandability and a property that enables the picking up of device chips. US 2004 / 0 089 515 A1 relates to a method and apparatus for receiving a semiconductor chip, a method and apparatus for removing a semiconductor chip from a dividing band and a method for forming a perforated dividing band. US 2014 / 0 295 646 A1 relates to a partition film with a protective layer forming layer comprising a substrate layer, an adhesive layer and a protective layer forming layer. US 2014 / 0 004 685 A1 concerns laser and plasma etching wafer divisions using UV-curable adhesive tapes. US 2016 / 0 007 479 A1 relates to a chip spacing maintenance apparatus in which the spacing between adjacent device chips is maintained. JP 2003-152056 A relates to a semiconductor element holding device and a method for manufacturing the same. DESCRIPTION OF THE INVENTION

[0006] The adhesive tape includes a base layer made of, for example, a polyvinyl chloride film, and an adhesive layer formed on the base layer. In the laser processing apparatus, the laser beam is applied to the wafer under conditions where each dividing groove can be reliably formed in the wafer to have a depth from the front side to the back side of the wafer, so as to reliably divide the wafer by laser ablation. Consequently, the adhesive layer of the adhesive tape applied to the back side of the wafer is melted by the heat due to the application of the laser beam to the wafer at the position below or around each dividing groove formed in the wafer, and a part of the melted adhesive layer is attached to the back side of each device chip obtained from the wafer.In this case, in the step of picking up each component die from the adhesive tape, ultraviolet light is applied to the adhesive tape to reduce the adhesion of the adhesive tape. However, the melted portion of the adhesive layer adhered to the back of each component die mounted on the adhesive tape still remains on the back of each component die picked up by the adhesive tape. Consequently, the quality of each component die is reduced.

[0007] The present invention has been made in view of such problems, and therefore, an object of the present invention is to provide a wafer processing method that prevents the adhesion of the adhesive layer to the back surface of each device chip obtained from a wafer, thereby suppressing a reduction in the quality of each device chip due to the adhesion of the adhesive layer.

[0008] According to one aspect of the present invention, a wafer processing method is provided for dividing a wafer along a plurality of dividing lines to obtain a plurality of individual component chips, wherein the dividing lines are formed on a front side of the wafer so as to define a plurality of separate regions in which a plurality of components are individually formed. The wafer processing method includes a ring frame preparation step of preparing a ring frame having an inner opening for receiving the wafer, a polyester film provision step of positioning the wafer in the inner opening of the ring frame, and providing a polyester film on a back side of the wafer and on a back side of the ring frame, wherein no adhesive layer is disposed between the polyester film and the wafer,a joining step of heating the polyester film while applying pressure to the polyester film after performing the polyester film providing step, thereby joining the wafer and the ring frame via the polyester film by thermocompression bonding to form a frame unit in a state where the front side of the wafer and the front side of the ring frame are exposed upward; a dividing step of applying a laser beam to the wafer along each dividing line, the laser beam having an absorption wavelength for the wafer, after performing the joining step, thereby forming a dividing groove in the wafer along each dividing line to divide the wafer into the individual component chips; and a receiving step of heating the polyester film in each region of the polyester film corresponding to each component chip.and pushing up each component chip from the side of the polyester film to pick up each component chip from the polyester film after performing the dividing step.

[0009] Preferably, the bonding step includes a step of applying infrared light to the polyester film, thereby performing thermocompression bonding.

[0010] Preferably, the polyester film is larger than the ring frame, and the bonding step includes an additional step of cutting the polyester film after heating the polyester film, thereby removing a part of the polyester film outside the outer periphery of the ring frame.

[0011] Preferably, the receiving step includes a step of expanding the polyester film to thereby increase a distance between respective adjacent components.

[0012] Preferably, the polyester film is formed from a material selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate.

[0013] In the case where the polyester film is formed from polyethylene terephthalate, the polyester film is preferably heated in the range of 250°C to 270°C in the bonding step. In the case where the polyester film is formed from polyethylene naphthalate, the polyester film is preferably heated in the range of 160°C to 180°C in the bonding step.

[0014] Preferably, the wafer is formed from a material selected from the group consisting of silicon, gallium nitride, gallium arsenide and glass.

[0015] In the wafer processing method according to a preferred embodiment of the present invention, the wafer and the ring frame are bonded using the polyester film having no adhesive layer instead of an adhesive tape having an adhesive layer, thereby forming the frame unit consisting of the wafer, the ring frame, and the polyester film bonded together. The bonding step of bonding the wafer and the ring frame via the polyester film is realized by thermocompression bonding. After performing the bonding step, a laser beam having an absorption wavelength for the wafer is applied to the wafer to thereby form a dividing groove in the wafer along each dividing line by laser ablation, so that the wafer is divided along each dividing line to obtain individual device chips attached to the polyester film.Next, in each region of the polyester film corresponding to each component chip, the polyester film is heated. Then, each component chip is pushed up from the side of the polyester film and then picked up by the polyester film. Each picked-up component chip is next attached to a predetermined mounting substrate or the like. Note that if the polyester film is heated during the picking up of each component chip, the adhesion of the polyester film is reduced, and a load applied to each component chip can be reduced.

[0016] When performing laser ablation on the wafer, heat due to the application of the laser beam to the wafer is transferred to the polyester film at the position below or near each dividing line. However, since the polyester film does not have an adhesive layer, there is no problem that the adhesive layer may be melted to be attached to the back surface of each component chip. That is, the frame unit according to one aspect of the present invention can be formed using the polyester film that does not have an adhesive layer, so that an adhesive tape having an adhesive layer is not required. Consequently, it is possible to prevent the problem that the quality of each component chip is degraded due to the adhesion of the adhesive layer to each component chip.

[0017] Thus, the wafer processing method according to one aspect of the present invention can exhibit the effect that the adhesive layer does not adhere to the back surface of each device chip obtained from the wafer, whereby a reduction in the quality of each device chip due to the adhesion of the adhesive layer can be suppressed.

[0018] The above and other objects, features and advantages of the present invention and the mode for carrying them out will become more apparent and the invention itself will be best understood by studying the following description and the appended claims with reference to the attached drawings which show a preferred embodiment of the invention. SHORT DESCRIPTION OF THE FIGURES Fig. 1 is a schematic perspective view of a wafer; Fig. 2 is a schematic perspective view illustrating a manner of positioning the wafer and a ring frame on a holding surface of a chuck table; Fig. 3 is a schematic perspective view illustrating a polyester film providing step; Fig. 4 is a schematic perspective view illustrating a connecting step; Fig. 5 is a schematic perspective view illustrating a modification of the connecting step; Fig. Fig. 6 is a schematic perspective view illustrating another modification of the connecting step; Fig. 7A is a schematic perspective view illustrating a manner of cutting the polyester film after performing the joining step; Fig. 7B is a schematic perspective view of a device formed by performing the Fig. 7A; Fig. 8 is a schematic perspective view illustrating a dividing step; Fig. 9 is a schematic perspective view illustrating a manner of loading the frame unit into a receiving device after performing the dividing step; Fig. 10A is a schematic sectional view illustrating a standby state in which a frame unit is mounted on a support frame in a pickup step using the Fig. 9 shown receiving device is attached to an initial position arranged frame support table; and Fig. 10B is a schematic sectional view illustrating a working state in which the frame support table holding the frame unit with the polyester film is lowered to expand the polyester film in the take-up step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. First, a wafer to be processed by a wafer processing method according to this preferred embodiment will be described. Fig. 1 is a schematic perspective view of a wafer 1. The wafer 1 is a substantially disc-shaped substrate formed of a material such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs). The wafer 1 may be formed of any other semiconductor material. Further, the wafer 1 may be formed of a material such as sapphire, glass, and quartz. Examples of the glass include alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, and quartz glass. The wafer 1 has a front surface 1a and a back surface 1b. A plurality of intersecting dividing lines 3 are formed on the front surface 1a of the wafer 1, thereby respectively defining a plurality of separated regions in which a plurality of devices 5, such as ICs, LSIs, and LEDs, are formed.The intersecting dividing lines 3 consist of a plurality of parallel dividing lines 3 extending in a first direction and a plurality of parallel dividing lines 3 extending in a second direction perpendicular to the first direction. In the processing method for the wafer 1 according to this preferred embodiment, laser ablation is performed to form a plurality of intersecting dividing grooves along the respective intersecting dividing lines 3 in the wafer 1, thereby dividing the wafer 1 into a plurality of individual device chips, each containing the device 5.

[0020] The laser ablation is carried out using a laser processing device 12 (see Fig. 8). Before loading the wafer 1 into the laser processing device 12, the wafer 1 is covered with a polyester film 9 (see Fig. 3) and a ring frame 7 (see Fig. 2) to form a frame unit 11 (see Fig. 8). Thus, the wafer 1 in the form of the frame unit 11 is loaded into the laser processing device 12 and then processed by the laser processing device 12 to obtain the individual component chips, with each component chip being held by the polyester film 9. Thereafter, the polyester film 9 is expanded to thereby increase the spacing between all adjacent component chips. Thereafter, each component chip is picked up using a picking device. The ring frame 7 is formed of a rigid material such as metal and has a circular inner opening 7a having a diameter larger than that of the wafer 1. The outer shape of the ring frame 7 is substantially circular. The ring frame 7 has a front surface 7b and a back surface 7c.When forming the frame unit, the wafer 1 is received in the inner opening 7a of the ring frame 7 and positioned in such a manner that the center of the wafer 1 substantially coincides with the center of the inner opening 7a.

[0021] The polyester film 9 is a flexible (expandable) plastic film and has a flat front side and a flat back side. The polyester film 9 is a circular film having a diameter larger than the outer diameter of the ring frame 7. The polyester film 9 does not have an adhesive layer. The polyester film 9 is a film made of a polymer (polyester) synthesized by polymerizing a dicarboxylic acid (a compound having two carboxyl groups) and a diol (a compound having two hydroxyl groups) as a monomer. Examples of the polyester film 9 include a polyethylene terephthalate film and a polyethylene naphthalate film. The polyester film 9 is transparent or translucent to visible light. As a modification, the polyester film 9 may be opaque. Since the polyester film 9 has no adhesive property, it cannot be adhered to the wafer 1 and the ring frame 7 at room temperature.However, the polyester film 9 is a thermoplastic film, so when the polyester film 9 is heated to a temperature near its melting point under a predetermined pressure in a state where the polyester film 9 is in contact with the wafer 1 and the ring frame 7, the polyester film 9 is melted and thereby bonded to the wafer 1 and the ring frame 7. That is, by applying heat and pressure to the polyester film 9 in the state where the polyester film 9 is in contact with the wafer 1 and the ring frame 7, the polyester film 9 can be bonded to the wafer 1 and the ring frame 7. Thus, in the processing method for the wafer 1 according to this preferred embodiment, both the wafer 1, the ring frame 7, and the polyester film 9 are bonded by thermocompression bonding as mentioned above, thereby forming the frame unit.

[0022] The steps of the processing method for the wafer 1 according to this preferred embodiment will now be described. Before bonding the wafer 1, the polyester film 9, and the ring frame 7, a polyester film supply step is performed using a chuck table 2 having a Fig. 2 has a holding surface 2a shown. Fig. Fig. 2 is a schematic perspective view illustrating a manner of positioning the wafer 1 and the ring frame 7 on the holding surface 2a of the chuck table 2. That is, the polyester film providing step as in Fig. 2 is performed on the holding surface 2a of the chuck table 2. The chuck table 2 has a circular porous member having a diameter larger than the outer diameter of the ring frame 7. The porous member forms a central upper portion of the chuck table 2. The porous member has an upper surface serving as the holding surface 2a of the chuck table 2. A suction line (not shown) is formed in the chuck table 2, one end of the suction line being connected to the porous member. Further, a vacuum source 2b (see Fig. 3) is connected to the other end of the suction line. The suction line is equipped with a selector switch 2c (see Fig. 3) for switching between an ON state and an OFF state. When the ON state is established by the selector switch 2c, a vacuum generated by the vacuum source 2b is applied to a workpiece placed on the holding surface 2a of the chuck table 2, thereby holding the workpiece on the holding table 2 under suction.

[0023] In the polyester film preparation step, first the wafer 1 and the ring frame 7 are prepared as shown in Fig. 2 shown on the holding surface 2a of the chuck table 2. At this time, the front side 1a of the wafer 1 is oriented downwards and the front side 7b of the ring frame 7 is also oriented downwards. In this state, the wafer is positioned in the inner opening 7a of the ring frame 7. Thereafter, as shown in Fig. 3, the polyester film 9 is provided on the back side 1b (upper surface) of the wafer 1 and the back side 7c (upper surface) of the ring frame 7. Fig. Fig. 3 is a schematic perspective view illustrating a manner of providing the polyester film 9 to the wafer 1 and the ring frame 7. That is, as in Fig. 3, the polyester film 9 is provided so as to completely cover the wafer 1 and the ring frame 7. In the polyester film providing step, the diameter of the polyester film 9 is set larger than the diameter of the holding surface 2a of the chuck table 2. Unless the diameter of the polyester film 9 is larger than the diameter of the holding surface 2a, such a problem may occur that when the vacuum is applied from the vacuum source 2b to the holding surface 2a of the chuck table 2 in a bonding step to be performed later, the vacuum may be lost from any gap between the polyester film 9 and the holding surface 2a because the holding surface 2a is not completely covered with the polyester film 9, so that printing cannot be appropriately applied to the polyester film 9.

[0024] Next, in the processing method for the wafer 1 according to this preferred embodiment, a bonding step is performed in such a manner that the polyester film 9 is heated to bond the wafer 1 and the ring frame 7 by thermocompression bonding via the polyester film 9. Fig. 4 is a schematic perspective view illustrating the connecting step according to this preferred embodiment. As in Fig. 4, the transparent or visible light translucent polyester film 9 is provided to cover the wafer 1, the ring frame 7 and the holding surface 2a of the chuck table 2, which are shown in Fig. 4, all shown by dashed lines. In the connecting step, the selector switch 2c is operated to establish the ON state in which the vacuum source 2b is in communication with the porous member of the chuck table 2, that is, the holding surface 2a of the chuck table 2, so that a vacuum generated by the vacuum source 2b is applied to the polyester film 9 provided on the chuck table 2. Accordingly, the polyester film 9 is brought into close contact with the wafer 1 and the ring frame 7 by the atmospheric pressure applied to the upper surface of the polyester film 9.

[0025] Thereafter, the polyester film 9 is heated in a state in which the polyester film 9 is sucked by the vacuum source 2b, thereby performing thermocompression bonding. In this Fig. In the preferred embodiment shown in Fig. 4, heating of the polyester film 9 is effected, for example, by a heat gun 4 provided above the chuck table 2. The heat gun 4 includes a heating means such as a heating wire and an air blowing mechanism such as a fan. Accordingly, the heat gun 9 can heat ambient air and blow the heated air. In a state where the vacuum from the vacuum source 2b is applied to the polyester film 9, the heat gun 4 is operated to supply hot air 4a to the upper surface of the polyester film 9. Accordingly, when the polyester film 9 is heated to a predetermined temperature, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding.

[0026] Another method may be used to heat the polyester film 9. For example, each element heated to a predetermined temperature on the polyester film 9 may be pressed against the wafer 1 and the ring frame 7. Fig. 5 is a schematic perspective view illustrating such a modification of the connecting step. As in Fig. 5, the transparent or visible light translucent polyester film 9 is provided to cover the wafer 1, the ring frame 7 and the holding surface 2a of the chuck table 2, which are shown in Fig. 5 are all represented by dashed lines, completely covered. In this Fig. In the modification shown in Figure 5, a heat roller 6 having a heat source is used. Specifically, first, the vacuum generated by the vacuum source 2b is applied to the polyester film 9, so that the polyester film 9 is brought into close contact with the wafer 1 and the ring frame 7 by the atmospheric pressure applied to the upper surface of the polyester film 9.

[0027] Thereafter, the heat roller 6 is heated to a predetermined temperature and next, at one end located on the outer periphery of the holding surface 2a, as shown in Fig. 5, is placed on the holding surface 2a of the chuck table 2. Thereafter, the heat roller 6 is rotated about its axis to roll over the polyester film 9 from the above one end to another end diametrically opposite to the above one end on the chuck table 2. As a result, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding. In the case where a force for pressing the polyester film 9 is applied from the heat roller 6, the thermocompression bonding is effected at a pressure higher than atmospheric pressure. Preferably, the cylindrical surface of the heat roller 6 is coated with a fluoroplastic. Further, the heat roller 6 may be replaced by an iron-like pressing member having a flat base plate and a heat source.In this case, the printing element is heated to a predetermined temperature to thereby provide a hot plate, which is next pressed onto the polyester film 9 held on the chuck table 2.

[0028] Another method for heating the polyester film 9 can be used in the following manner. Fig. 6 is a schematic perspective view illustrating such another modification of the connecting step. As in Fig. 6, the transparent or visible light translucent polyester film 9 is provided so as to completely cover the wafer 1, the ring frame 7 and the holding surface 2a of the chuck table 2, which in Fig. 6 are all shown by dashed lines. In this Fig. 6, an infrared lamp 8 is provided above the clamping table 2 to heat the polyester film 9. The infrared lamp 8 can apply infrared light 8a, which has an absorption wavelength at least for the material of the polyester film 9. In the embodiment shown in Fig. 6, the vacuum generated by the vacuum source 2b is also first applied to the polyester film 9, so that the polyester film 9 is brought into close contact with the wafer 1 and the ring frame 7 by the atmospheric pressure applied to the upper surface of the polyester film 9. Thereafter, the infrared lamp 8 is actuated to apply the infrared light 8a to the polyester film 9, thereby heating the polyester film 9. As a result, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding.

[0029] When the polyester film 9 is heated to a temperature near its melting point by performing one of the above methods, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding. After bonding the polyester film 9, the selector switch 2c is operated to establish the OFF state in which the connection between the porous member of the chuck table 2 and the vacuum source 2b is severed. Accordingly, the suction holding by the chuck table 2 is terminated.

[0030] Thereafter, the polyester film 9 is circularly cut along the outer circumference of the ring frame 7 to remove an unwanted peripheral portion of the polyester film 9. Fig. 7A is a schematic perspective view illustrating a manner of cutting the polyester film 9. As in Fig. As shown in Fig. 7A, a disc-shaped (annular) cutter 10 is used to cut the polyester film 9. The cutter 10 has a central through-hole 10a into which a rotary shaft 10b is fitted. Accordingly, the cutter 10 is rotatable about the axis of the rotary shaft 10b. First, the cutter 10 is positioned above the annular frame 7. At this time, the rotary shaft 10b is arranged to extend in the radial direction of the chuck table 2. Thereafter, the cutter 10 is lowered until the outer periphery (cutting edge) of the cutter 10 comes into contact with the polyester film 9 placed on the annular frame 7. That is, the polyester film 9 is caught between the cutter 10 and the annular frame 7, so that the polyester film 9 is cut by the cutter 10 to form a cutting trace 9a. Furthermore, the cutter 10 is cut on the polyester film 9 along a circular line formed between the inner circumference of the ring frame 7 (ieoutside of the inner opening 7a of the ring frame 7) and the outer periphery of the ring frame 7, thereby circularly forming the cutting track 9a along the above circular line. As a result, a predetermined central portion of the polyester film 9 is surrounded by the circular cutting track 9a. Thereafter, a remaining outer portion of the polyester film 9 outside the circular cutting track 9a is removed. That is, an undesired outer portion of the polyester film 9, including an outermost portion outside the outer periphery of the ring frame 7, can be removed.

[0031] The cutter 10 can be replaced by an ultrasonic cutter for cutting the polyester film 9. Furthermore, a vibration source for vibrating the cutter 10 at a frequency in an ultrasonic band can be connected to the cutter 10. Furthermore, the polyester film 9 can be cooled during cutting of the polyester film 9 so that it is hardened to facilitate the cutting process. By cutting the polyester film 9 as mentioned above, a Fig. 7B, in which the frame unit 11 consists of the wafer 1, the ring frame 7, and the polyester film 9, which are bonded together. That is, the wafer and the ring frame 7 are bonded together via the polyester film 9 to form the frame unit 11 as shown in Fig. 7B shown. Fig. 7B is a schematic perspective view of the frame unit 11 in a state where the front surface 1a of the wafer and the front surface 7b of the ring frame 7 are exposed upward.

[0032] When performing the thermocompression bonding as mentioned above, the polyester film 9 is preferably heated to a temperature equal to or below the melting point of the polyester film 9. If the heating temperature is higher than the melting point of the polyester film 9, there is a possibility that the polyester film 9 is melted to such an extent that the shape of the polyester film 9 cannot be maintained. Further, the polyester film 9 is preferably heated to a temperature equal to or higher than the softening point of the polyester film 9. If the heating temperature is lower than the softening point of the polyester film 9, the thermocompression bonding cannot be properly performed. Accordingly, the polyester film 9 is preferably heated to a temperature equal to or higher than the softening point of the polyester film 9 and equal to or lower than the melting point of the polyester film 9.Furthermore, there is a case where the softening point of the polyester film 9 may be unknown. To cope with such a case, when performing thermocompression bonding, the polyester film 9 is preferably heated to a temperature equal to or higher than a predetermined temperature and equal to or lower than the melting point of the polyester film 9, wherein the predetermined temperature is 20°C lower than the melting point of the polyester film 9.

[0033] In the case where the polyester film 9 is a polyethylene terephthalate film, the heating temperature in the bonding step is preferably set in the range of 250°C to 270°C. Further, in the case where the polyester film 9 is a polyethylene naphthalate film, the heating temperature in the bonding step is preferably set in the range of 160°C to 180°C.

[0034] The heating temperature is defined herein as the temperature of the polyester film 9 to be heated when performing the bonding step. As the heat sources including the heat gun 4, the heat roller 6, and the infrared lamp 8 mentioned above, some types of heat sources capable of setting an output temperature have been practically used. However, even when such a heat source is used to heat the polyester film 9, the temperature of the polyester film 9 does not reach the above-specified output temperature in some cases. To deal with such a case, the output temperature of the heat source may be set to a temperature higher than the melting point of the polyester film 9 to heat the polyester film 9 to a predetermined temperature.

[0035] After performing the above-mentioned bonding step, a dividing step is performed in such a manner that the wafer 1 in the state of the frame unit 11 is processed by laser ablation to form a plurality of intersecting dividing grooves along the plurality of intersecting dividing lines 3 in the wafer 1, thereby dividing the wafer 1 into individual component chips. The dividing step is performed in this preferred embodiment using a Fig. 8 shown laser processing device 12. Fig. Figure 8 is a schematic perspective view illustrating the dividing step. As shown in Fig. 8, the laser processing apparatus 12 includes a laser processing unit 14 for performing laser ablation on the wafer 1 and a chuck table (not shown) for holding the wafer 1. The laser processing unit 14 includes a laser oscillator (not shown) for generating a laser beam 16 having an absorption wavelength for the wafer 1 (having a wavelength absorbable by the wafer 1). The chuck table has an upper surface as a holding surface for holding the wafer 1. The chuck table is movable in a direction parallel to its upper surface, that is, movable in a feed direction. The laser beam 16 generated by the laser oscillator in the laser processing unit 14 is applied to the wafer 1 held on the chuck table.The laser processing unit 14 further comprises a processing head 14a with a mechanism for focusing the laser beam 16 at a predetermined vertical position in the wafer 1.

[0036] When performing laser ablation on the wafer 1, the frame unit 11 is placed on the chuck table in the state where the front surface 1a of the wafer 1 is exposed upward. Accordingly, the wafer 1 is held on the chuck table via the polyester film 9. Thereafter, the chuck table is rotated to cause the dividing lines 3 extending in the first direction on the front surface 1a of the wafer 1 to be parallel to a feed direction in the laser processing apparatus 12. Further, the chuck table and the laser processing unit 14 are relatively moved to adjust a relative position, thereby positioning the processing head 14a directly above an extension of a predetermined one of the dividing lines 3 extending in the first direction. Thereafter, the laser beam 16 is applied from the processing head 14a to the wafer.At the same time, the chuck table and the laser processing unit 14 are relatively moved in the feed direction parallel to the upper surface of the chuck table. Consequently, the laser beam 16 is applied to the wafer 1 along the predetermined dividing line 3, thereby performing laser ablation along the predetermined dividing line 3. Accordingly, a dividing groove 3a is formed in the wafer 1 along the predetermined dividing line 3 by the laser beam 16. The dividing groove 3a has a depth from the front side 1a to the back side 1b of the wafer 1. In this dividing step, the laser beam 16 can be applied under the following processing conditions. The following processing conditions are only examples. Wavelength: 355 nm Repetition frequency: 50 kHz Average power: 5 W Feed speed: 200 mm / s

[0037] After forming the dividing groove 3a along the predetermined dividing line 3, the chuck table and the laser processing unit 14 are moved in an index direction perpendicular to the feed direction to similarly perform laser ablation along the next dividing line 3 extending in the first direction. Thereafter, laser ablation is similarly performed along all other dividing lines 3 extending in the first direction. Thus, a plurality of similar dividing grooves 3a are formed along all dividing lines 3 extending in the first direction. Thereafter, the chuck table is rotated 90 degrees about its vertical axis perpendicular to its support surface to similarly perform laser ablation along all dividing lines 3 extending in the second direction perpendicular to the first direction.Thus, a plurality of similar dividing grooves 3a are similarly formed along all the dividing lines 3 extending in the second direction. Thus, the plurality of intersecting dividing grooves 3a are formed in the wafer 1 along the respective intersecting dividing lines 3, with a depth from the front side 1a to the back side 1b of the wafer, so that the wafer 1 is divided by these dividing lines 3a to obtain the individual component chips.

[0038] When the laser processing unit 14 is operated to perform laser ablation on the wafer 1, processing dust is generated from the wafer 1 at the position where the laser beam 16 is applied. This processing dust disperses around this laser application position to adhere to the front surface 1a of the wafer 1. Even if the front surface 1a of the wafer 1 is cleaned after performing laser ablation on the wafer 1 using a cleaning unit described below, it is not easy to completely remove this processing dust adhering to the front surface 1a of the wafer 1. If the processing dust remains on each device chip obtained from the wafer 1, the quality of each device chip is degraded.To address this problem, a water-soluble liquid resin may be applied in advance to the front surface 1a of the wafer 1, and this water-soluble liquid resin serves as a protective film for protecting the front surface 1a of the wafer 1. When the liquid resin is applied in advance to the front surface 1a of the wafer 1, the processing dust scattered upon performing laser ablation adheres to the upper surface of the applied liquid resin. That is, the processing dust is prevented from directly adhering to the front surface 1a of the wafer 1. After performing laser ablation, the wafer 1 is cleaned using the cleaning unit. At this time, the processing dust can be removed together with the applied liquid resin upon cleaning the wafer 1.

[0039] That is, the laser processing apparatus 12 may include such a cleaning unit (not shown). In this case, the wafer 1 processed by the laser processing unit 14 as mentioned above is transferred to the cleaning unit and then cleaned by the cleaning unit. For example, the cleaning unit includes a cleaning table having a holding surface for holding the frame unit 11 and a cleaning water nozzle configured to reciprocate horizontally above the frame unit 11 held on the holding surface of the cleaning table. The cleaning water nozzle functions to supply cleaning water such as clean water to the wafer 1. The cleaning table is rotatable about its axis perpendicular to its holding surface. In operation, the cleaning table is rotated about its axis, and at the same time, the cleaning water is supplied from the cleaning water nozzle to the wafer 1.During this supply of cleaning water, the cleaning water nozzle is reciprocated horizontally along a path passing through the position directly above the center of the support surface of the cleaning table. Accordingly, the entire surface of the front side 1a of the wafer 1 can be cleaned by the cleaning water.

[0040] After performing the dividing step or the cleaning step, a picking step is performed to pick up each component chip from the polyester film 9. The picking step is carried out using a Fig. 9 shown receiving device 18. Fig. 9 is a schematic perspective view illustrating a manner of loading the frame unit 11 into the receiving device 18. As in Fig. As shown in Figure 9, the receiving device 18 includes a cylindrical drum 20 and a frame holding unit 22 having a frame support table 26 provided around the cylindrical drum 20. The cylindrical drum 20 has an inner diameter larger than the diameter of the wafer 1 and an outer diameter smaller than the inner diameter of the ring frame 7 (the diameter of the inner opening 7a). The frame support table 26 of the frame holding unit 22 is an annular table having a circular inner opening larger in diameter than the drum 20. That is, the frame support table 26 has an inner diameter larger than the outer diameter of the drum 20. Furthermore, the frame support table 26 has an outer diameter larger than the outer diameter of the ring frame 7.The inner diameter of the frame support table 26 is substantially equal to the inner diameter of the ring frame 7. The frame support table 26 has an upper surface as a support surface for supporting the ring frame 7 via the polyester film 9 thereon. First, the height of the upper surface of the frame support table 26 is set equal to the height of the upper end of the drum 20 (see ). Fig. 10A). Furthermore, the upper end portion of the drum 20 is surrounded by the inner circumference of the ring frame 7 in this initial stage.

[0041] A plurality of clamps 24 are provided on the outer periphery of the frame support table 26. Each clamp 24 functions to hold the ring frame 7 supported on the frame support table 26. That is, when the ring frame 7 of the frame unit 11 is placed on the frame support table 26 via the polyester film 9 and then held by each clamp 24, the frame unit 11 can be fixed to the frame support table 26. The frame support table 26 is supported by a plurality of rods 28 extending in a vertical direction. That is, each rod 28 is connected at its upper end to the lower surface of the frame support table 26. An air cylinder 30 for vertically moving each rod 28 is connected to the lower end of each rod 28. Specifically, the lower end of each rod 28 is connected to a piston (not shown) movably housed in the air cylinder 30. Each air cylinder 30 is supported on a disc-shaped base 32.That is, the lower end of each air cylinder 30 is connected to the upper surface of the disc-shaped base 32. Accordingly, when each air cylinder 30 is actuated in the initial stage, the frame support table 26 is lowered with respect to the drum 20 fixed in place.

[0042] Furthermore, a push-up mechanism 34 for pushing up each component chip supported on the polyester film 9 is provided within the drum 20. The high-pressure mechanism 34 has a heater 34a at its upper end, which comprises a heat source such as a Peltier element or a heating wire. That is, each component chip is configured to be pushed up by the push-up mechanism 34 arranged below the polyester film 9 by blowing the air 34a upwards via the polyester film 9. Furthermore, a gripper 36 (see Fig. 10B), which is capable of holding each component chip under suction, is provided above the drum 20. Both the push-up mechanism 34 and the gripper 36 are movable in a horizontal direction parallel to the upper surface of the frame support table 26. The gripper 36 is connected to the drum 20 via a selector switch 36b (see Fig. 10B) with a vacuum source 36a (see Fig. 10B).

[0043] In the pick-up step, first, each air cylinder 30 in the pick-up jig 18 is actuated to adjust the height of the frame support table 26 so that the height of the upper end of the drum 20 corresponds to the height of the upper surface of the frame support table 26. Next, the frame unit 11 transferred from the laser processing device 12 is placed on the drum 20 and the frame support table 26 in the pick-up jig 18 in a state where the front side 1a of the wafer 1 of the frame unit 11 is facing upward. After that, each clamp 24 is actuated to fix the ring frame 7 of the frame unit 11 to the upper surface of the frame support table 26. Fig. Fig. 10A is a schematic sectional view illustrating a standby state in which the frame unit 11 is fixed to the frame support table 26 set at the initial position. At this time, the plurality of dividing grooves 3a have already been formed in the wafer 1 in the dividing step, so that the wafer 1 has already been divided into a plurality of individual component chips 1c (see Fig. 10B).

[0044] Thereafter, each air cylinder 30 is actuated to lower the frame support table 26 of the frame holding unit 22 with respect to the drum 20. As a result, the polyester film 9 fixed by each clamp 24 to the frame holding unit 22 is clamped as shown in Fig. 10B shown radially outwardly expanded. Fig. Fig. 10B is a schematic sectional view illustrating a processing state in which the frame support table 26 holding the ring frame 7 with the polyester film 9 is lowered to expand the polyester film 9. When the polyester film 9 is expanded radially outward as mentioned above, the distance between adjacent device chips 1c supported on the polyester film 9 becomes Fig. 10B. Accordingly, the contact between the adjacent component chips 1c can be suppressed, and each component chip 1c can be easily picked up. After that, a targeted component chip 1c is selected, and the push-up mechanism 34 is next operated as shown in Fig. 10B to a position directly below this target device chip 1c. In addition, the gripper 36 is also moved as shown in Fig.10B, to a position directly above this target component chip 1c. Thereafter, the heater 34a is operated to raise a temperature and brought into contact with a portion of the polyester film 9 corresponding to the target component chip 1c to heat the portion. Further, the push-up mechanism 34 is operated to push the target component chip 1c up above the polyester film 9. Further, the selector switch 36b is operated to cause the gripper 36 to communicate with the vacuum source 36a. As a result, the target component chip 1c is held under suction by the gripper 36 and thereby picked up by the polyester film 9. Such picking operation is similarly performed for all other component chips 1c. Thereafter, each picked-up component chip 1c is attached to a predetermined wiring substrate or the like for actual use.

[0045] Note that when the portion of the polyester film 9 is heated by, for example, the heater 34a, the corresponding portion is heated at a temperature near a melting point of the polyester film 9. Since the polyester film 9 reduces adhesion during a period in which the polyester film 9 has a temperature near its melting point, a load applied when peeling each device chip from the polyester film 9 is reduced.

[0046] In the case of forming the frame unit 11 using an adhesive tape, heat generated by the application of the laser beam 16 in the dividing step is transferred to the adhesive tape, so that the adhesive layer of the adhesive tape is melted and adhered to the back surface of each device chip. Accordingly, in this case, there is a problem in that the adhesion of the adhesive layer to each device chip causes a deterioration in quality. In comparison, in the wafer processing method according to this preferred embodiment, the frame unit 11 can be formed using the polyester film 9 not having an adhesive layer, and the polyester film 9 is attached to the wafer 1 and the ring frame 7 by thermocompression bonding. That is, an adhesive tape having an adhesive layer is not required.Consequently, it is possible to avoid a deterioration in the quality of each component chip due to the adhesion of the adhesive layer to the back surface of each component chip.

[0047] The present invention is not limited to the above preferred embodiment, but various modifications can be made within the scope of the present invention. For example, while in the above preferred embodiment, the polyester film 9 is selected from a polyethylene terephthalate film and a polyethylene naphthalate film, this is only illustrative. That is, the polyester film usable in the present invention can be formed from any other materials (polyesters), such as polytrimethylene terephthalate, polybutyrene terephthalate, or polybutylene naphthalate.

Claims

[1] A wafer processing method for dividing a wafer (1) along a plurality of dividing lines (3) to obtain a plurality of individual component chips (1c), wherein the dividing lines (3) are formed on the front side (1a) of the wafer (1) so as to define a plurality of separate regions in which a plurality of components (5) are individually formed, the wafer processing method comprising: a ring frame preparation step of preparing a ring frame (7) having an inner opening (7a) for receiving the wafer (1); a polyester film providing step of positioning the wafer (1) in the inner opening (7a) of the ring frame (7) and providing a polyester film (9) on a back side (1b) of the wafer (1) and on a back side (7c) of the ring frame (7), wherein no adhesive layer is arranged between the polyester film (9) and the wafer (1); a bonding step of heating the polyester film (9) while applying pressure to the polyester film (9) after performing the polyester film providing step, whereby the wafer (1) and the ring frame (7) are bonded by thermocompression bonding via the polyester film (9) to form a frame unit (11) in a state in which the front side (1a) of the wafer (1) and the front side (7b) of the ring frame (7) are exposed upward; a dividing step of applying a laser beam to the wafer (1) along each dividing line (3), the laser beam having an absorption wavelength for the wafer (1), after performing the bonding step, whereby a dividing groove is formed in the wafer along each dividing line (3) to divide the wafer (1) into the individual component chips (1c); and a picking-up step of heating the polyester film (9) in each region of the polyester film (9) corresponding to a respective component chip (1c), and pushing up each component chip (1c) from the side of the polyester film (9) to pick up each component chip (1c) from the polyester film (9) after performing the dividing step. [2] The wafer processing method according to claim 1, wherein the bonding step includes a step of applying infrared light to the polyester film (9), thereby performing thermocompression bonding. [3] The wafer processing method according to claim 1 or 2, wherein the polyester film (9) is larger than the ring frame (7), and wherein the joining step comprises an additional step of cutting the polyester film (9) after heating the polyester film (9), thereby removing a part of the polyester film (9) outside an outer periphery of the ring frame (7). [4] A wafer processing method according to any one of the preceding claims, wherein the receiving step includes a step of expanding the polyester film (9) to thereby increase a distance between respective adjacent device chips (1c). [5] A wafer processing method according to any one of the preceding claims, wherein the polyester film (9) is formed of a material selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate. [6] The wafer processing method according to claim 5, wherein the polyester film (9) is formed of polyethylene terephthalate, and the polyester film (9) is heated in the range of 250°C to 270°C in the bonding step. [7] The wafer processing method according to claim 5, wherein the polyester film (9) is formed of polyethylene naphthalate, and the polyester film (9) is heated in the range of 160°C to 180°C in the bonding step. [8] A wafer processing method according to any one of the preceding claims, wherein the wafer (1) is formed of a material selected from the group consisting of silicon, gallium nitride, gallium arsenide and glass.

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