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 a 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 of the ring frame (7) and providing a polyester film (9) on a back side or the front side (1a) of the wafer (1) and on a back side 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 in a state where the wafer (1) and the front side of the ring frame (7) are exposed; a dividing step of positioning a focal point of a laser beam within the wafer (1), the laser beam having a transmission wavelength for the wafer (1), and applying the laser beam to the wafer (1) along each dividing line (3), thereby forming a modified layer in the wafer (1) along each dividing line (3) to divide the wafer (1) into the individual component chips (1c), after performing the bonding step; and a picking-up step of blowing out air from the side of the polyester film (9) to push up each component chip (1c), and picking 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 component 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 components 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 dividing lines (streets) are first arranged on the front side of a wafer made of, for example, a semiconductor, to thereby define a plurality of separated 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 separated region. Thereafter, a ring frame having an inner opening is prepared in which an adhesive tape called a dividing tape is preliminarily attached to its outer portion on 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 or front 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 device is used to divide the wafer. The laser processing device includes a chuck table for holding the wafer via the adhesive tape, and a laser processing unit for focusing a laser beam within the wafer held on the chuck table, the laser beam having a transmission wavelength suitable for the wafer. When dividing the wafer using this laser processing device, 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 along each dividing line.When the laser beam is focused within the wafer, a modified layer serving as a division starting point is formed in the wafer along each division line (see Japanese Patent JP 3 408 805 B2).

[0004] Thereafter, the frame unit is transferred from the laser processing apparatus to another apparatus, and the adhesive tape is expanded in a radially outward direction, so that the wafer is divided into individual component chips. When the thus formed component chips are picked up by the adhesive tape, for example, ultraviolet light is applied to the adhesive tape in advance to thereby reduce 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).

[0005] Further prior art helpful for understanding the present 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 component chips. US 2004 / 0 089 515 A1 relates to a method and a device for receiving a semiconductor chip, a method and a device 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 2016 / 0 007 479 A1 relates to a chip spacing maintenance device 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. PRESENTATION 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 focused within the wafer to form a modified layer serving as a division starting point within the wafer, and a portion of the leakage light of the laser beam reaches the adhesive layer of the adhesive tape. Consequently, the adhesive layer of the adhesive tape attached to the back or front 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 division groove formed in the wafer, and a portion of the melted adhesive layer is attached to the back or front side of each device chip obtained from the wafer.In this case, during the step of picking up each component chip from the adhesive tape, ultraviolet light is applied to the adhesive tape to reduce the adhesiveness of the adhesive tape. However, the melted portion of the adhesive layer adhered to the back or front side of each component chip mounted on the adhesive tape still remains on the back or front side of each component chip picked up by the adhesive tape. Consequently, the quality of each component chip is reduced.

[0007] It is therefore an object of the present invention to provide a wafer processing method that can prevent the adhesion of the adhesive layer to the back surface or the front 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 preparation step of positioning the wafer in the inner opening of the ring frame, and providing a polyester film on a back side or the front 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 bonding step of heating the polyester film while applying pressure to the polyester film after performing the polyester film providing step, thereby bonding the wafer and the ring frame via the polyester film by thermocompression bonding to form a frame unit in a state where the wafer and the front side of the ring frame are exposed; a dividing step of positioning a focal point of a laser beam within the wafer, the laser beam having a transmission wavelength for the wafer, and applying the laser beam to the wafer along each dividing line, thereby forming a modified layer in the wafer along each dividing line to divide the wafer into the individual component chips after performing the bonding step; and a receiving step of blowing air out from the side of the polyester film;to push up each component chip, and picking 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 an 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 adjacent component chips.

[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 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 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 a transmission wavelength for the wafer is applied to the wafer to thereby form a modified layer in the wafer along each dividing line, so that the wafer is divided along each dividing line to obtain individual device chips attached to the polyester film.Then, each component chip is picked up from the polyester film by blowing air from the side of the polyester film to push each component chip up. Each picked-up component chip is then attached to a predetermined mounting substrate or the like. If the target component chip is pushed up by blowing air from the side of the polyester film during picking up of the component chip, the load applied to the component chip during peeling off the component chip from the polyester film can be reduced.

[0016] When forming a modified layer in the wafer, leakage light from the laser beam reaches the polyester film. 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 or front side 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 side or the front side 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. 1A is a schematic perspective view of the front side of a wafer; Fig. Figure 1B is a schematic perspective view of the back side of the 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. 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 illustrated step formed frame unit; Fig. 8A is a schematic perspective view illustrating a dividing step; Fig. 8B is a schematic sectional view illustrating the 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. 1A is a schematic perspective view of the front side of a wafer 1. Fig. 1B is a schematic perspective view of the backside of the wafer. 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. Furthermore, 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 side 1a and a back side 1b. A plurality of intersecting dividing lines 3 are formed on the front side 1a of the wafer 1, thereby respectively defining a plurality of separate regions in which a plurality of devices 5, such as ICs, LSIs, and LEDs, are formed.The intersecting dividing lines 3 are formed from 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, a plurality of modified layers are formed within the wafer along the respective intersecting dividing lines 3 in the wafer 1, thereby dividing the wafer 1 with the modified layers as division starting points into a plurality of individual device chips, each containing the device 5.

[0020] When forming a modified layer in the wafer 1, a laser beam having a transmission wavelength for the wafer 1 is applied to the wafer 1 along each of the dividing lines 3, whereby the laser beam is focused within the wafer 1. At this time, the laser beam can be emitted from the Fig. 1A shown front side 1a or from the Fig. 1B. Note that in a case where the laser beam can be applied to the wafer 1 from the back side 1b, an alignment means with an infrared camera is used to detect each of the dividing lines 3 from the front side 1a through the wafer 1, so that the laser beam is applied to the wafer 1 along each of the dividing lines 3.

[0021] The laser processing for forming a modified layer in the wafer 1 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. Then, the polyester film 9 is expanded to divide the wafer 1, thereby obtaining the individual component chips, with each component chip being supported on the polyester film 9. Thereafter, the polyester film 9 is further expanded to thereby increase the spacing between all adjacent component chips. Thereafter, each component chip is picked up using a pick-up 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.

[0022] 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 i25.

[0023] The polyester film 9 is a thermoplastic film, so that 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.

[0024] 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 preparation 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 shown in Fig. 2 is carried out on the holding surface 2a of the chuck table 2. The chuck table 2 has a circular porous element having a diameter larger than the outer diameter of the ring frame 7. The porous element forms a central upper portion of the chuck table 2. The porous element 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 element. Furthermore, a vacuum source 2b (see Fig. 3) is connected to the other end of the intake line. The intake 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.

[0025] In the polyester film preparation step, first the wafer 1 and the ring frame 7 are prepared as shown in Fig. 2, the wafer is placed on the holding surface 2a of the chuck table 2. In this state, the wafer is positioned in the inner opening 7a of the ring frame 7. At this time, an orientation of the wafer 1 is selected, taking into account whether the front surface 1a or the back surface 1b is an application surface to which the laser beam is to be applied in the later dividing step. For example, in a case where the front surface 1a is selected as the application surface, the front surface 1a is directed downward. Alternatively, for example, in a case where the back surface 1b is selected as the application surface, the back surface 1b is directed downward. A wafer processing method according to the preferred embodiment will be described below, taking the case where the front surface 1a is selected as the application surface of the laser beam as an example. However, the orientation of the wafer 1 is not limited thereto.

[0026] After the wafer 1 and the frame 7 are placed on the holding surface 2a of the chuck table 2, the polyester film 9 is provided on the back surface 1b (or the front surface 1a) (upper surface) of the wafer 1 and the back surface 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 properly applied to the polyester film 9.

[0027] 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. Fig. 4 is a schematic perspective view illustrating the connecting step according to this preferred embodiment. As shown 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.

[0028] Thereafter, the polyester film 9 is heated in a state in which the polyester film 9 is sucked by the vacuum source 2b, whereby thermocompression bonding is performed. 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.

[0029] Another method can be used to heat the polyester film 9. For example, any element heated to a predetermined temperature on the polyester film 9 can be pressed against the wafer 1 and the ring frame 7. Fig. Figure 5 is a schematic perspective view illustrating such a modification of the connecting step. As shown 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, the vacuum created by the vacuum source 2b is 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.

[0030] 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 case 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, a 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 against the polyester film 9 held on the chuck table 2.

[0031] Another different 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 shown 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 represented by dashed lines. In this Fig. In the modification shown in Figure 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. In the modification shown in Figure 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.

[0032] When the polyester film 9 is heated to a temperature near its melting point by performing any of the above processes, 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.

[0033] 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. 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 mark 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 (ieThe cutting tool 9a is guided in a rotational direction by a rotary motion arranged between 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 peripheral portion of the polyester film 9 outside the circular cutting track 9a is removed. That is, an unwanted peripheral portion of the polyester film 9, including an outermost peripheral portion outside the outer periphery of the ring frame 7, can be removed.

[0034] 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 is formed from 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.

[0035] When performing 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.

[0036] 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.

[0037] 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 included in 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.

[0038] 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 a laser beam to form a plurality of modified layers along the plurality of intersecting dividing lines 3 within the wafer 1, thereby dividing the wafer 1 into individual component chips. The dividing step is performed in this preferred embodiment using a Fig. 8A shown laser processing device 12. Fig. 8A is a schematic perspective view illustrating the dividing step. Fig. 8B is a schematic sectional view illustrating the dividing step. As shown in Fig. 8A, the laser processing apparatus 12 includes a laser processing unit 14 for applying a laser beam 16 to 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 the laser beam 16 having a transmission wavelength for the wafer 1 (having a wavelength transmissible to 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 positioning a focal point 14b of the laser beam 16 at a predetermined vertical position within the wafer 1.

[0039] When performing laser processing 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 focal point 14b of the laser beam 16 is positioned at a predetermined vertical position. After that, the laser beam 16 is applied from the laser processing unit 14 inside the wafer.At the same time, the clamping table and the laser processing unit 14 are relatively moved in the feed direction parallel to the upper surface of the clamping table.

[0040] In particular, the focal point 14b of the laser beam 16 is positioned within the wafer 1, and the laser beam 16 is applied to the wafer 1 along the predetermined dividing lines 3. Consequently, the modified layer 3a is formed within the wafer 1. Note that in Fig. 8A, the modified layer 3a formed within the wafer 1 is shown with dashed lines. 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: 1064 nm Repetition frequency: 50 kHz Average power: 1 W Feed speed: 200 mm / s

[0041] After forming the modified layer 3a within the wafer 1 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 processing along the next dividing line 3 extending in the first direction. Thereafter, laser processing is similarly performed along all other dividing lines 3 extending in the first direction. Thus, a plurality of similar modified layers 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 processing along all dividing lines 3 extending in the second direction perpendicular to the first direction.Thus, a plurality of similar modified layers 3a are formed along all the dividing lines 3 extending in the second direction.

[0042] When the laser beam 16 from the laser processing unit 14 is focused inside the wafer 1 to form the modified layer 3a, leakage light of the laser beam 16 reaches the polyester film 9 below the wafer 1. For example, in a case where an adhesive tape is used in the frame unit 11 instead of the polyester film 9, if the leakage light of the laser beam 16 is applied to an adhesive layer of the adhesive tape, the adhesive layer of the adhesive tape is melted, so that a part of the adhesive layer is attached to the back surface 1b of the wafer 1. In this case, the part of the adhesive layer remains on the back surface of each of the device chips formed by dividing the wafer 1. Consequently, a reduction in the quality of each device chip is caused. In comparison, in the wafer processing method according to the present embodiment, the polyester film 9 without an adhesive layer is used in the frame unit 11.Accordingly, even if the leakage light of the laser beam 16 reaches the polyester film 9, the adhesive layer is not adhered to the back surface 1b of the wafer 1. Thus, the quality of each device chip formed from the wafer 1 is advantageously maintained.

[0043] Next, the polyester film 9 is expanded in a radially outward direction, so that the wafer 1 is divided into individual component chips. After performing the dividing step, a picking step is performed to pick up each component chip from the polyester film 9. The polyester film 9 is expanded using a device provided in a lower portion of Fig. 9 shown receiving device 18. Fig. 9 is a schematic perspective view illustrating a manner of loading the frame unit 11 onto 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.

[0044] 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.

[0045] Furthermore, a push-up mechanism 34 is provided for pushing up each component chip supported on the polyester film 9 within the drum 20. The push-up mechanism 34 has a function of blowing out air 34a upward. 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).

[0046] When expanding the polyester film 9, first, each air cylinder 30 in the cradle 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 cradle 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. 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 modified layers 3a have already been formed inside the wafer 1 along the dividing lines 3.

[0047] 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. 10B is a schematic sectional view illustrating the expanded polyester film 9. When the polyester film 9 is expanded, a force is applied in a radially outward direction to the wafer 1, and the wafer 1 is divided with the modified layers 3a as a starting point, thereby forming individual component chips 1c. When the polyester film 9 is further expanded, the distance between adjacent component chips 1c supported on the polyester film 9 becomes Fig. 10B is shown enlarged. Accordingly, each component chip 1c can be easily accommodated.

[0048] In the wafer processing method according to the present embodiment, a picking-up step of picking up the component chips 1c from the polyester film 9 is performed after the wafer 1 has been divided into individual component chips 1c. In the picking-up step, a targeted one of the component chips 1c is selected, and the push-up mechanism 34 is next actuated as shown in Fig. 10B to a position directly below this target component 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 push-up mechanism 34 is operated to push up the target component chip 1c by blowing out the air 34a from the side of the polyester film 9 through 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.When the target device chip 1c is pushed up by blowing out the air 34a from the side of the polyester film 9 toward the device chip 1c when picking up the device chip 1c, a load applied to the device chip 1c when peeling off the device chip 1c from the polyester film 9 is reduced.

[0049] In the case of forming the frame unit 11 using an adhesive tape, the leakage light of the laser beam 16 applied to the wafer 1 reaches the adhesive tape in the dividing step, so that the adhesive layer of the adhesive tape is melted and adhered to the back surface of each component chip. Accordingly, in this case, there is a problem in that the adhesion of the adhesive layer to each component 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 of the quality of each component chip due to the adhesion of the adhesive layer to the back surface of each component chip.

[0050] 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. For example, the polyester film usable in the present invention can be formed from any other materials (polyesters) such as polytrimethylene terephthalate, polybutylene 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 a 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 of the ring frame (7) and providing a polyester film (9) on a back side or the front side (1a) of the wafer (1) and on a back side 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 in a state where the wafer (1) and the front side of the ring frame (7) are exposed; a dividing step of positioning a focal point of a laser beam within the wafer (1), the laser beam having a transmission wavelength for the wafer (1), and applying the laser beam to the wafer (1) along each dividing line (3), thereby forming a modified layer in the wafer (1) along each dividing line (3) to divide the wafer (1) into the individual component chips (1c), after performing the bonding step; and a picking-up step of blowing out air from the side of the polyester film (9) to push up each component chip (1c), and picking 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 comprises a step of expanding the polyester film (9) to thereby increase a distance between 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. [9] A wafer processing method according to any preceding claim, wherein the bonding step comprises a step of supplying hot air to the polyester film (9), thereby performing thermocompression bonding. [10] The wafer processing method according to any one of claims 1-8, wherein the bonding step comprises a step of pressing and heating the polyester film by a heat roller (6), thereby performing thermocompression bonding.

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