Wafer processing processes

Abstract

Wafer processing method for dividing a wafer (1) along multiple division lines (3) to obtain multiple individual component chips (1c), wherein the division lines (3) are formed on the front face (1a) of the wafer (1) such that they define multiple separate areas in which multiple components (5) are individually formed, wherein the wafer processing method comprises: a ring frame preparation step of preparing a ring frame (7) which has an inner opening (7a) for receiving the wafer (1); a polyester film provisioning step of positioning the wafer (1) in the inner opening (7a) of the ring frame (7) and providing a polyester film (9) on a rear side (1b) of the wafer (1) and on a rear side (7c) of the ring frame (7), wherein no adhesive layer is arranged between the polyester film (9) and the wafer (1); a joining step of heating the polyester film (9) during the application of a pressure to the polyester film (9) after performing the polyester film provisioning step, whereby the wafer (1) and the ring frame (7) are joined by thermocompression joining over the polyester film (9) so that they form a frame unit (11) in a state in which the front (1a) of the wafer (1) and the front (7b) of the ring frame (7) are exposed; a division step of cutting the wafer (1) along each division line (3) using a cutting device (12) having a rotatable cutting blade (18), after performing the joining step, thereby dividing the wafer (1) into the individual component chips (1c); and a pickup step of cooling the polyester film (9) in each of the several areas corresponding to each component (5), pushing up each component chip (1c) through the polyester film (9), and picking up each component chip (1c) from the polyester film (9) after performing the division 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 integration (LSI), and a light-emitting diode (LED) is formed in each separated region. Next, 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 (the back side of the ring frame) so as to close the inner opening of the ring frame.Next, a central section 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 multiple individual component chips containing the respective components.

[0003] For example, a cutting device is used to divide the wafer. The cutting device includes a chuck table for holding the wafer via the adhesive tape and a cutting unit for cutting the wafer. The cutting unit includes a cutting blade for cutting the wafer and a spindle for rotating the cutting blade. The cutting blade has a central through-hole, and the spindle is fitted into this central through-hole of the cutting blade, so that the cutting blade and the spindle are rotated as a unit. An annular abrasive section is provided around the outer circumference of the cutting blade to cut the wafer. When cutting the wafer using this cutting 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 spindle is rotated to rotate the cutting blade, and the cutting unit is then lowered to a predetermined height. After that, the chuck table and the cutting unit are moved relatively in a direction parallel to the upper surface of the chuck table. Accordingly, the wafer is cut along each dividing line by the rotating cutting blade, thus dividing the wafer.

[0004] Next, the frame unit is transferred from the cutting device to another device for applying ultraviolet light to the adhesive tape, thereby reducing the adhesion of the adhesive tape. Each component chip is then picked up from the adhesive tape. As a processing device capable of producing component chips with high efficiency, there is a cutting device capable of continuously performing the wafer dividing process and the process of applying ultraviolet light to the adhesive tape (see, for example, Japanese Patent No. 3076179). Each component chip picked up from the adhesive tape is next mounted on a predetermined wiring substrate or the like.

[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. JP 2015-126082 A relates to a semiconductor chip pickup method that can prevent a pitch band from widening. 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. 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. PRESENTATION OF THE INVENTION

[0006] The adhesive tape includes a base layer and an adhesive layer formed on the base layer. When cutting the wafer using the cutting device, the cutting unit is positioned at a predetermined height so that the lower end of the cutting blade reaches a position lower than the lower surface (back surface) of the wafer, thus reliably cutting the wafer. Accordingly, the adhesive layer of the adhesive tape attached to the back surface of the wafer is also cut by the cutting blade at the time the wafer is cut by the cutting blade. As a result, cutting dust emanating from the wafer is generated during wafer cutting, and cutting dust emanating from the adhesive layer is also generated. When cutting the wafer, cutting water is supplied to the wafer and the cutting blade.The cutting dust generated during wafer cutting is absorbed into the cutting water and then dispersed on the front side of the wafer. However, the cutting dust emanating from the adhesive layer may re-adhere to the front side of each component. Furthermore, it is not easy to remove this cutting dust adhering to each component in a cleaning step that must be performed after wafer cutting. Accordingly, if the cutting dust emanating from the adhesive layer adheres to each component formed on the front side of the wafer, a problem arises in that the quality of each component chip may be reduced.

[0007] The present invention has been made in view of the above problem, and therefore, an object of the present invention is to provide a wafer processing method that prevents the adhesion of cutting dust to the front surface of each component when cutting the wafer, and thereby suppresses a reduction in the quality of each component chip.

[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 device chips. The dividing lines are formed on a front side of the wafer to define a plurality of separate regions in which a plurality of devices 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 providing 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 bonding step of heating the polyester film while applying pressure to the polyester film after performing the polyester film providing step, whereby the wafer and the ring frame are bonded 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;a dividing step of cutting the wafer along each dividing line using a cutter having a rotary cutting blade after performing the bonding step, thereby dividing the wafer into the individual component chips; and a picking-up step of cooling the polyester film in each of the plurality of separated regions corresponding to each component chip, pushing up each component chip through the polyester film, and then 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 the outer periphery of the ring frame.

[0011] Preferably, the receiving step includes a step of expanding the polyester film, thereby increasing a distance between all 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 without an 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, the wafer is cut using the cutting blade to be divided into the individual device chips.Next, the polyester film is cooled in each of the plurality of separate regions of the polyester film corresponding to each component chip, and each component chip is pushed up through the polyester film, thereby picking up each component chip from the polyester film. Each picked-up component chip is then attached to a predetermined wiring substrate or the like. Note that when the polyester film is cooled during the picking up of each component chip, the polyester film shrinks, and the polyester film can be easily peeled off the component chip, making it possible to reduce the load applied to each component chip.

[0016] When the wafer is cut using the cutting knife, the polyester film provided below the wafer is also cut by the cutting knife. This means that the wafer and the polyester film bonded to the back of the wafer are cut together by the cutting knife in a state where the front of the wafer is facing upward. Consequently, cutting dust emanating from the polyester film is generated. This cutting dust is absorbed into the cutting water supplied during the wafer cutting process and then distributed on the front of the wafer. However, since the polyester film lacks an adhesive layer, the cutting dust is not attached to the wafer, allowing it to be more reliably removed in a subsequent cleaning step.In this way, the frame unit according to the preferred embodiment of the present invention can be formed by thermocompression bonding using the polyester film that does not have an adhesive layer. Accordingly, no cutting dust emanating from an adhesive layer is generated when dicing the wafer, making it possible to suppress a deterioration in the quality of each component chip due to such cutting dust having adhesion.

[0017] Thus, the wafer processing method according to the preferred embodiment of the present invention can exhibit the effect that cutting dust does not adhere to the front surface of each component when cutting the wafer, and a reduction in the quality of each component chip divided from the wafer 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. 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. 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 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 from a material such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs). The wafer 1 may be formed from any other semiconductor material. Furthermore, the wafer 1 may be formed from a material such as sapphire, glass, and quartz. 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, defining a plurality of separate regions, each of which contains a plurality of components 5, such as ICs and LEDs. 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, the wafer 1 is cut along the intersecting dividing lines 3 and thereby divided into a plurality of individual component chips each containing the plurality of components 5.

[0020] The wafer 1 is cut using a cutting device. Before loading the wafer 1 into the cutting device, the wafer 1 is covered with a polyester film 9 (see Fig. 3) and a ring frame 7 (see Fig. 3) to thereby form a frame unit. Thus, the wafer 1 in the form of such a frame unit is loaded into the cutting device and then cut into the individual component chips in the cutting device, in which each component chip is 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 hydroxy 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 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.

[0023] In the polyester film preparation step, first the wafer 1 and the ring frame 7 are prepared as shown in Fig. 2 is placed 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 properly 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. 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.

[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 for heating the polyester film 9 can be used. For example, each element on the polyester film 9 heated to a predetermined temperature 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.

[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 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, 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 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 Fig. In the modification 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 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 disconnect the porous member of the chuck table 2 from the vacuum source 2b. Accordingly, the suction hold 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. 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 (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 unwanted 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 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] For example, 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. Furthermore, 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, several 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 cut by a cutting knife to obtain individual component chips. The dividing step is performed in this preferred embodiment using a Fig. 8 shown cutting device 12. Fig. Figure 8 is a schematic perspective view illustrating the dividing step. As shown in Fig. As shown in Figure 8, the cutting device 12 includes a cutting unit 14 for cutting a workpiece and a chuck table (not shown) for holding the workpiece. The cutting unit 14 includes a cutting blade 18 having an annular abrasive portion (cutting edge) for cutting the workpiece, and a spindle (not shown) for supporting the cutting blade 18 so as to rotate the cutting blade 18. The cutting blade 18 has a central through-hole for attaching the front end of the spindle. The cutting blade 18 consists of an annular base (terminal) having the above-mentioned central through-hole and an annular abrasive portion provided along the outer periphery of the annular base. The spindle is rotatably supported in a spindle housing 16, and the base end of the spindle is connected to a spindle motor (not shown) housed in the spindle housing 16.Accordingly, the cutting blade 18 can be rotated by operating the spindle motor. The chuck table has an upper surface as a holding surface for holding the wafer 1.

[0036] When the workpiece is cut by the cutting blade 18, heat is generated due to the friction between the cutting blade 18 and the workpiece. Furthermore, when the workpiece is cut by the cutting blade 18, cutting dust is generated from the workpiece. To remove such heat and cutting dust from cutting the workpiece, cutting water, such as clean water, is supplied to the cutting blade 18 and the workpiece during cutting of the workpiece. Accordingly, the cutting unit 14 has a pair of cutting water nozzles 20 for supplying cutting water to the cutting blade 18 and the workpiece, the pair of cutting water nozzles 20 being arranged to face both sides of the cutting blade 18. Fig. 8 only one of the two cutting water nozzles 20 is shown.

[0037] When cutting 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 feeding direction in the cutting device 12. Further, the chuck table and the cutting unit 14 are relatively moved in a direction perpendicular to the feeding direction in a horizontal plane, thereby positioning the cutting blade 18 directly above an extension of a predetermined one of the dividing lines 3 extending in the first direction.

[0038] Thereafter, the spindle is rotated to thereby rotate the cutting blade 18. After that, the cutting unit 14 is lowered to a predetermined height, and the chuck table and the cutting unit 14 are relatively moved in the feed direction parallel to the upper surface of the chuck table. Accordingly, the abrasive portion of the cutting blade 18 being rotated comes into contact with the wafer 1, thereby cutting the wafer 1 along the predetermined dividing line 3 in the feed direction. As a result, a cutting track 3a (groove) is formed along the predetermined dividing line 3 so as to completely cut the wafer 1 and the polyester film 9. After cutting the wafer 1 and the polyester film 9 along the predetermined dividing line 3, the chuck table and the cutting unit 14 are relatively moved in an index direction perpendicular to the feed direction by the pitch of the dividing lines 3.Thereafter, the above cutting process is similarly performed along the next parting line adjacent to the above predetermined parting line 3. After similarly performing the cutting process along all other parting lines 3 extending in the first direction, the chuck table is rotated 90 degrees about its axis perpendicular to the holding surface so that the other parting lines 3 extending in the second direction perpendicular to the first direction become parallel to the feed direction. Thereafter, the above cutting process is similarly performed along all other parting lines 3 extending in the second direction. After performing the cutting process along all other parting lines 3 extending in the second direction, the parting step is completed.

[0039] The cutting device 12 may include a cleaning unit (not shown) provided near the cutting unit 14. That is, the wafer 1 cut by the cutting unit 14 can be transferred to the cutting unit and then cleaned by the cleaning unit. For example, the cleaning unit includes a cleaning table having a support surface for supporting the frame unit 11 and a cleaning water nozzle configured to move horizontally in opposite directions above the frame unit 11 held on the support 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 the support 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 moved horizontally in opposite directions 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] By performing the dividing step as mentioned above, the wafer 1 is divided into the individual component chips still supported by the polyester film 9. When cutting the wafer 1, the cutting unit 14 is positioned at a predetermined height such that the lower end of the cutting blade 18 is at a lower level than the back surface 1b of the wafer 1 to reliably divide the wafer 1. Accordingly, when the wafer 1 is cut by the cutting blade 18, the polyester film 9 bonded to the back surface 1b of the wafer 1 is also cut by the cutting blade 18, so that cutting dust emanating from the polyester film 9 is generated. In the case where an adhesive tape having an adhesive layer is used instead of the polyester film 9 in the frame unit 11, cutting dust emanating from the adhesive layer of the adhesive tape is generated.In this case, the cutting dust is absorbed into the cleaning water supplied from the cleaning water nozzles 20 and then dispersed on the front surface 1a of the wafer 1. The cutting dust emanating from the adhesive layer may re-adhere to the front surface of each component 5. Moreover, it is not easy to remove the cutting dust adhering to the front surface of each component 5 in a cleaning step of cleaning the wafer 1 after the dividing step. If the cutting dust emanating from the adhesive layer adheres to each component 5, a problem arises that the quality of each component chip divided from the wafer 1 is degraded.

[0041] In comparison, the processing method for the wafer 1 according to this preferred embodiment has the following advantage. In this preferred embodiment, instead of an adhesive tape having an adhesive layer, the polyester film 9 not having an adhesive layer is used in the frame unit 11. Even if the cutting dust emanating from the polyester film 9 is generated and then dispersed on the front surface 1a of the wafer 1 when absorbed into the cleaning water, this grinding dust is not attached to the wafer 1 but is reliably removed in the subsequent cleaning step. Accordingly, it is possible to suppress deterioration of each device chip due to the cutting dust.

[0042] 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 22. Fig. Fig. 9 is a schematic perspective view illustrating a manner of loading the frame unit 11 into the receiving device 22. As in Fig. As shown in Figure 9, the receiving device 22 includes a cylindrical drum 24 and a frame holding unit 26 having a frame support table 30 provided around the cylindrical drum 24. The cylindrical drum 24 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 30 of the frame holding unit 26 is an annular table having a circular inner opening larger in diameter than the drum 24. That is, the frame support table 30 has an inner diameter larger than the outer diameter of the drum 24. Furthermore, the frame support table 30 has an outer diameter larger than the outer diameter of the ring frame 7.The inner diameter of the frame support table 30 is substantially equal to the inner diameter of the ring frame 7. The frame support table 30 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 30 is set equal to the height of the upper end of the drum 24 (see ). Fig. 10A). Furthermore, the upper end portion of the drum 24 is surrounded by the inner circumference of the ring frame 7 in this initial step.

[0043] A plurality of clamps 28 are provided on the outer periphery of the frame support table 30. Each clamp 28 functions to hold the ring frame 7 supported on the frame support table 30. That is, when the ring frame 7 of the frame unit 11 is placed on the frame support table 30 via the polyester film 9 and then held by each clamp 28, the frame unit 11 can be fixed to the frame support table 30. The frame support table 30 is supported by a plurality of rods 32 extending in a vertical direction. That is, each rod 32 is connected at its upper end to the lower surface of the frame support table 30. An air cylinder 34 for vertically moving each rod 32 is connected to the lower end of each rod 32. Specifically, the lower end of each rod 32 is connected to a piston (not shown) movably housed in the air cylinder 34. Each air cylinder 34 is supported on a disc-shaped base 36.That is, the lower end of each air cylinder 34 is connected to the upper surface of the disc-shaped base 36. Accordingly, when each air cylinder 34 is actuated in the initial stage, the frame support table 30 is lowered with respect to the drum 24 fixed in place.

[0044] Furthermore, a push-up mechanism 38 for pushing up each component chip supported on the polyester film 9 is provided within the drum 24. The push-up mechanism has a cooling region 38a at its upper end, which has a cooling mechanism such as a Peltier element. This means that each component chip is configured to be pushed up through the polyester film 9 by the push-up mechanism 38 arranged below the polyester film 9. Furthermore, a gripper 40 (see Fig. 10B), which is capable of holding each component chip under suction, is provided above the drums 24. Both the push-up mechanism 38 and the gripper 40 are movable in a horizontal direction parallel to the upper surface of the frame support table 30. The gripper 40 is connected to the drums 24 via a selector switch 40b (see Fig. 10B) with a vacuum source 40a (see Fig. 10B).

[0045] In the pick-up step, first, each air cylinder 34 in the pick-up device 22 is operated to adjust the height of the frame support table 30 so that the height of the upper end of the drum 24 corresponds to the height of the upper surface of the frame support table 30. Next, the frame unit 11 transferred from the cutting device 12 is placed on the drum 24 and the frame support table 30 in the pick-up device 22 in a state where the front side 1a of the wafer 1 of the frame unit 11 is facing upward. After that, each clamp 28 is operated to fix the ring frame 7 of the frame unit 11 to the upper surface of the frame support table 30. 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 30 set at the initial position. At this time, the plurality of cutting tracks 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).

[0046] Thereafter, each air cylinder 34 is actuated to lower the frame support table 30 of the frame holding unit 26 with respect to the drum 24. As a result, the polyester film 9 fixed by each clamp 28 to the frame holding unit 26 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 30 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 component chips 1c supported on the polyester film 9 becomes Fig. 10B is enlarged. 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 38 is next actuated as shown in Fig. 10B to a position directly below this target device chip 1c. In addition, the gripper 40 is also moved as shown in Fig.10B to a position directly above this target component chip 1c. Thereafter, the cooling region 38a is actuated so that its temperature decreases, and the push-up mechanism 38 causes the cooling region 38a to come into contact with a region corresponding to the component chip 1c in the polyester film 9, thereby cooling the region. Further, the push-up mechanism 38 is actuated to push up the target component chip 1c through the polyester film 9. Further, the selector switch 40b is actuated to cause the gripper 40 to communicate with the vacuum source 40a. As a result, the target component chip 1c is held under suction by the gripper 40 and is thereby picked up by the polyester film 9. Such a picking operation is similarly performed for all other component chips 1c. Thereafter, each picked-up component chip 1c is mounted on a predetermined wiring substrate or the like for actual use.

[0047] Note that after the region in the polyester film 9 is cooled by the cooling region 38a, the polyester film 9 shrinks, generating a large stress at an interface between the polyester film 9 and each component. Consequently, it becomes easy to peel each component chip from the polyester film 9. Accordingly, a load applied to the component chip during peeling from the polyester film 9 is reduced.

[0048] In the wafer processing method according to this preferred embodiment mentioned above, the frame unit 11 containing the wafer 1 can be formed with an adhesive layer without using an adhesive tape. Accordingly, when cutting the wafer 1, no cutting dust from the adhesive tape is generated from the adhesive layer, so that this cutting dust does not adhere to each component chip 1c. As a result, there is no possibility of the quality of each component chip 1c being reduced.

[0049] 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, 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 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; a dividing step of cutting the wafer (1) along each dividing line (3) using a cutting device (12) having a rotatable cutting blade (18) after performing the bonding step, thereby dividing the wafer (1) into the individual component chips (1c); and a receiving step of cooling the polyester film (9) in each of the plurality of regions corresponding to each component (5), pushing up each component chip (1c) through the polyester film (9), and receiving 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 all 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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