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 upwards; a division step of applying a laser beam to the wafer (1) along each division line (3), wherein the laser beam has an absorption wavelength for the wafer (1), after performing the joining step, thereby forming a division groove in the wafer (1) along each division line (3) to divide the wafer (1) into the individual component chips (1c); and a pickup step of cooling the polyester film (9) in each area of ​​the polyester film (9) corresponding to a respective component chip (1c), and of pushing up each component chip (1c) from the side of the polyester film (9) in order to pick up each component chip (1c) from the polyester film (9) after performing the division step.

Description

BACKGROUND OF THE INVENTION Technical field

[0001] The present invention relates to a wafer processing method for dividing a wafer along several division lines to obtain several individual component chips, wherein the division lines are formed on the front side of the wafer in order to define several separate areas in which several components are individually formed. Description of the related technique

[0002] In the manufacturing process for electronic components used in devices such as mobile phones and PCs, several intersecting parting lines (roads) are first arranged on the front face of a wafer, for example, made of a semiconductor, to define several separate areas on the wafer's front surface. In each separate area, a component such as an integrated circuit (IC), a large-scale integrated circuit (LSI), or a light-emitting diode (LED) is then formed. Next, a ring frame with an inner opening is prepared. An adhesive strip, called a parting strip, is pre-attached to the outer section of the ring frame (the back of the ring frame) so that it closes the inner opening.Next, a central section of the adhesive strip is attached to the back of the wafer in such a way that the wafer is held in the inner opening of the ring frame. In this way, the wafer, the adhesive strip, and the ring frame are joined together to form a frame unit. The wafer contained within this frame unit is then processed by splitting it along each division line to obtain multiple individual component chips, each containing the respective components.

[0003] For example, a laser processing device is used to split the wafer (see Japanese patent application JP H10-305 420 A). The laser processing device comprises a clamping table for holding the wafer via the adhesive strip and a laser processing unit for applying a laser beam to the wafer held on the clamping table, the laser beam having an absorption wavelength for the wafer. When splitting the wafer using this laser processing device, the frame unit is placed on the clamping table, and the wafer is held by the adhesive strip on the upper surface of the clamping table. In this state, the clamping table and the laser processing unit are moved relative to each other in a direction parallel to the upper surface of the clamping table. Simultaneously, the laser beam is applied to the wafer by the laser processing unit.When the laser beam is applied to the wafer, laser ablation occurs to create a parting groove in the wafer along each parting line, thereby splitting the wafer along each parting line.

[0004] The wafer assembly is then transferred from the laser processing device to another device for applying ultraviolet light to the adhesive tape, thereby reducing the tape's adhesion. Each component chip is then picked up from the adhesive tape. A laser processing device capable of continuously performing the wafer splitting and ultraviolet light application processes is used to manufacture the component chips with high efficiency (see, for example, Japanese patent JP 3 076 179 B2). Each component chip picked up from the adhesive tape is then attached to a predefined wiring substrate or similar.

[0005] Further prior art that may be helpful for understanding the present invention can be found in the following documents: WO 2014 / 157471A1 concerns a wafer processing belt that has a uniform expandability and a property that enables the placement of component chips. US 2014 / 0004685A1 concerns laser and plasma etching wafer splitting using UV-curable adhesive tapes. US 2004 / 0089515A1 relates to a method and apparatus for receiving a semiconductor chip, a method and apparatus for removing a semiconductor chip from a dividing strip, and a method for forming a perforated dividing strip. JP 2015-126082A relates to a semiconductor chip imaging technique that can prevent a dividing band from widening. US 2016 / 0007479A1 relates to a device for maintaining chip spacing, in which the spacing between adjacent component chips is maintained. JP 2003-152056A relates to a semiconductor element holding device and a method for manufacturing it. US 2014 / 0295646A1 relates to a partition film with a protective layer formation layer comprising a substrate layer, an adhesive layer, and a protective layer formation layer. US 2004 / 0 097 053 A1 relates to a grinding machine consisting of at least one clamping table with a suction area and a frame and a grinding device for grinding a semiconductor wafer held on the clamping table. PRESENTATION OF THE INVENTION

[0006] The adhesive tape has a base layer, for example, made of a polyvinyl chloride film, and an adhesive layer formed on the base layer. In the laser processing device, the laser beam is applied to the wafer under conditions that allow each parting groove to be reliably formed in the wafer, with a depth from the front to the back of the wafer, in order to reliably divide the wafer by laser ablation. Consequently, the adhesive layer of the tape, which is attached to the back of the wafer, is melted by the heat generated by the laser beam at the position under or around each parting groove formed in the wafer, and a portion of the molten adhesive layer is bonded to the back of each component chip obtained from the wafer.In this case, during the pick-up of each component chip from the adhesive tape, ultraviolet light is applied to the tape to reduce its adhesion. However, the molten portion of the adhesive layer, which is attached to the back of each component chip, remains on the back of each chip. Consequently, the quality of each component chip is reduced.

[0007] The present invention was made in view of such problems and it is therefore an objective of the present invention to provide a wafer processing method which prevents the adhesion of the adhesive layer to the back of each component chip obtained from a wafer, thereby suppressing a reduction in the quality of each component 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 multiple division lines to obtain multiple individual component chips, wherein the division lines are formed on a front face of the wafer such that they define multiple separate areas in which multiple components are individually formed. The wafer processing method comprises a ring frame preparation step of preparing a ring frame having an inner opening for receiving the wafer, a polyester film provision step of positioning the wafer in the inner opening of the ring frame and providing a polyester film to a rear face of the wafer and to a rear face of the ring frame, wherein no adhesive layer is arranged between the polyester film and the wafer.a joining step of heating the polyester film during the application of a print to the polyester film after performing the polyester film provisioning step, whereby the wafer and the ring frame are joined across the polyester film by a thermocompression joining process, so that they form a frame unit in a state where the front of the wafer and the front of the ring frame are exposed upwards; a severing step of applying a laser beam to the wafers along each severance line, wherein the laser beam has an absorption wavelength for the wafer, after performing the joining step, whereby a severance groove is formed in the wafer along each severance line to divide the wafer into the individual device chips; and a receiving step of cooling the polyester film in each area of ​​the polyester film corresponding to a respective device chip.and of pushing up each component chip from the side of the polyester film in order to pick up each component chip from the polyester film after performing the division step.

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

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

[0011] Preferably, the intake step includes a step of widening the polyester film in order to increase the distance between the respective adjacent building elements.

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

[0013] If the polyester film is made of polyethylene terephthalate, it is preferably heated to between 250°C and 270°C during the bonding step. If the polyester film is made of polyethylene naphthalate, it is preferably heated to between 160°C and 180°C during the bonding step.

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

[0015] In a wafer processing method according to a preferred embodiment of the present invention, the wafer and the ring frame are joined using a polyester film without an adhesive layer instead of an adhesive tape with an adhesive layer, thereby forming the frame unit consisting of the wafer, the ring frame, and the polyester film bonded together. The joining step of connecting the wafer and the ring frame via the polyester film is achieved by thermocompression bonding. After performing the joining step, a laser beam with an absorption wavelength appropriate for the wafer is applied to the wafer to create a parting groove in the wafer along each parting line by means of laser ablation, thus dividing the wafer along each parting line to obtain individual component chips attached to the polyester film.Next, the polyester film is cooled in each area corresponding to a specific component chip. Then, each component chip is pushed up from the side of the polyester film and picked up by the film. Each picked-up component chip is then attached to a predetermined mounting substrate or similar. Note that if the polyester film is cooled during the picking-up of each component chip, the film shrinks, making it easier to peel each component chip from the film and thus reducing the load applied to each component chip.

[0016] When performing laser ablation on a wafer, heat from the laser beam is transferred to the polyester film at the position below or near each division line. However, since the polyester film lacks an adhesive layer, there is no problem with melting the adhesive layer to bond it to the back of each component chip. This means that, according to one aspect of the present invention, the frame assembly can be formed using the polyester film without an adhesive layer, thus eliminating the need for an adhesive strip containing an adhesive layer. Consequently, it is possible to prevent the problem of the adhesive layer's adhesion to each component chip reducing its quality.

[0017] Thus, the wafer processing method according to one aspect of the present invention can have the effect that the adhesive layer does not adhere to the back of each component chip obtained from the wafer, thereby suppressing a reduction in the quality of each component chip due to the adhesion of the adhesive layer.

[0018] The above and further aims, features and advantages of the present invention and the way in which they are realized will become more apparent, and the invention itself will best be understood by studying the following description and the attached claims with reference to the attached drawings, which show a preferred embodiment of the invention. SHORT FIGURE DESCRIPTION Fig. Figure 1 is a schematic perspective view of a wafer; Fig. Figure 2 is a schematic perspective view showing one way of positioning the wafer and a ring frame on a holding surface of a clamping table; Fig. Figure 3 is a schematic perspective view depicting a polyester film supply step; Fig. Figure 4 is a schematic perspective view representing a connecting step; Fig. Figure 5 is a schematic perspective view that represents a variation of the connection step; Fig. Figure 6 is a schematic perspective view, representing a further variation of the connection step; Fig. 7A is a schematic perspective view showing one way of cutting the polyester film after performing the joining step; Fig. 7B is a schematic perspective view of a [project] created by performing the [action] in Fig. 7A shown step formed frame unit; Fig. Figure 8 is a schematic perspective view representing a division step; Fig. Figure 9 is a schematic perspective view showing one way of loading the frame unit into a receiving device after performing the division step; Fig. 10A is a schematic sectional view representing a standby state in which a frame unit is connected to a camera in a recording step using the [missing information]. Fig. 9 shown receiving device is attached to a frame support table arranged in an initial position; and Fig. Figure 10B is a schematic sectional view showing 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 pickup step. DETAILED DESCRIPTION OF THE PREFERRED EXECUTION FORM

[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. Figure 1 is a schematic perspective view of a wafer 1. The wafer 1 is essentially a disk-shaped substrate made of a material such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs). The wafer 1 can be made of any other semiconductor material. Furthermore, the wafer 1 can be made of a material such as sapphire, glass, and quartz. Examples of glass include alkali glass, non-alkali glass, soda-lime glass, lead glass, borosilicate glass, and fused silica. The wafer 1 has a front face 1a and a back face 1b. Several intersecting division lines 3 are formed on the front face 1a of the wafer 1 to define several separate areas in which multiple devices 5, such as ICs, LSIs, and LEDs, are implemented.The intersecting division lines 3 consist of several parallel division lines 3 extending in a first direction and several parallel division lines 3 extending in a second direction perpendicular to the first direction. In the processing method for the wafer 1 according to this preferred embodiment, laser ablation is performed to form several intersecting division grooves along the respective intersecting division lines 3 in the wafer 1, thereby dividing the wafer 1 into several individual component chips, each containing the component 5.

[0020] Laser ablation is performed using a laser processing device 12 (see Fig. 8) Before loading the wafer 1 into the laser processing device 12, the wafer 1 is coated with a polyester film 9 (see Fig. 3) and a ring frame 7 (see Fig. 2) connected to form a frame unit 11 (see Fig. 8) to form. Thus, the wafer 1, in the form of the frame unit 11, is loaded into the laser processing device 12 and then processed by the laser processing device 12 to obtain the individual component chips, with each component chip being held against the polyester film 9. The polyester film 9 is then expanded to increase the spacing between all adjacent component chips. Each component chip is then picked up using a receiving device. The ring frame 7 is made of a rigid material such as metal and has a circular inner opening 7a with a diameter larger than that of the wafer 1. The outer shape of the ring frame 7 is essentially circular. The ring frame 7 has a front 7b and a back 7c.During the formation of the frame unit, the wafer 1 is received in the inner opening 7a of the ring frame 7 and positioned in such a way 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 with a flat front and back surface. The polyester film 9 is a circular film with a diameter larger than the outer diameter of the ring frame 7. The polyester film 9 lacks an adhesive layer. It is a polymer (polyester) film synthesized by polymerizing a dicarboxylic acid (a compound with two carboxyl groups) and a diol (a compound with two hydroxyl groups) as a monomer. Examples of polyester film 9 include polyethylene terephthalate film and polyethylene naphthalate film. The polyester film 9 is transparent or translucent to visible light. As a variation, the polyester film 9 can be opaque. Because the polyester film 9 lacks adhesive properties, it cannot be bonded to the wafer 1 and the ring frame 7 at room temperature.However, the polyester film 9 is a thermoplastic film, so if the polyester film 9 is heated to a temperature near its melting point under a predetermined pressure in a state where it is in contact with the wafer 1 and the ring frame 7, the polyester film 9 melts and is thereby bonded to the wafer 1 and the ring frame 7. This means that the polyester film 9 can be bonded to the wafer 1 and the ring frame 7 by applying heat and pressure while in contact with them. Thus, in the processing method for the wafer 1 according to this preferred embodiment, the wafer 1, the ring frame 7, and the polyester film 9 are all joined by thermocompression bonding as described above, thereby forming the frame unit.

[0022] The steps of the processing procedure for the wafer 1 according to this preferred embodiment are now described. Before joining the wafer 1, the polyester film 9, and the ring frame 7, a polyester film supply step is performed using a clamping table 2, which has a Fig. The holding surface 2a shown in the diagram was carried out. Fig. Figure 2 is a schematic perspective view illustrating one way of positioning the wafer 1 and the ring frame 7 on the holding surface 2a of the clamping table 2. This means that the polyester film supply step is as shown in Fig. The process is carried out on the holding surface 2a of the clamping table 2, as shown in Figure 2. The clamping table 2 has a circular porous element with a diameter larger than the outer diameter of the ring frame 7. The porous element forms a central upper section of the clamping table 2. The porous element has an upper surface that serves as the holding surface 2a of the clamping table 2. A suction line (not shown) is formed in the clamping table 2, with one end of the suction line connected to the porous element. Furthermore, a vacuum source 2b (see Figure 2) is also provided. Fig. 3) connected to the other end of the intake pipe. The intake pipe is connected to a selector switch 2c (see Fig. 3) provided for switching between an ON state and an OFF state. When the ON state is established by selector switch 2c, a vacuum generated by the vacuum source 2b is applied to a workpiece placed on the holding surface 2a of the clamping table 2, thereby holding the workpiece under suction on the holding table 2.

[0023] In the polyester film preparation step, the wafer 1 and the ring frame 7 are first prepared as described in Fig. 2 shown on the holding surface 2a of the clamping table 2. At this point, the front face 1a of the wafer 1 is oriented downwards and the front face 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. Then, as shown in Fig. 3 shown, the polyester film 9 is provided on the back 1b (top surface) of the wafer 1 and the back 7c (top surface) of the ring frame 7. Fig. Figure 3 is a schematic perspective view illustrating one way of supplying the polyester film 9 to the wafer 1 and the ring frame 7. That is, as in Fig. Figure 3 shows that the polyester film 9 is provided such that it completely covers the wafer 1 and the ring frame 7. In the polyester film provisioning step, the diameter of the polyester film 9 is set to be larger than the diameter of the holding surface 2a of the clamping table 2. If the diameter of the polyester film 9 is not larger than the diameter of the holding surface 2a, a problem can arise in which, when the vacuum from the vacuum source 2b is applied to the holding surface 2a of the clamping table 2 in a subsequent joining step, the vacuum can be lost from any gap between the polyester film 9 and the holding surface 2a, since the holding surface 2a is not completely covered by the polyester film 9, and therefore pressure cannot be adequately applied to the polyester film 9.

[0024] In the processing method for the wafer 1 according to this preferred embodiment, a joining step is next carried out in such a way that the polyester film 9 is heated in order to join the wafer 1 and the ring frame 7 by thermocompression joining via the polyester film 9. Fig. Figure 4 is a schematic perspective view illustrating the joining step according to this preferred embodiment. As shown in Fig. As shown in Figure 4, the transparent or visible-light translucent polyester film 9 is designed to cover the wafer 1, the ring frame 7 and the holding surface 2a of the clamping table 2, which is in Fig. All areas shown by dashed lines are completely covered. In the connection step, the selector switch 2c is actuated to establish the ON state, in which the vacuum source 2b is in contact with the porous element of the clamping table 2, i.e., the holding surface 2a of the clamping table 2, so that a vacuum generated by the vacuum source 2b is applied to the polyester film 9 provided on the clamping table 2. Accordingly, the atmospheric pressure applied to the upper surface of the polyester film 9 brings it into close contact with the wafer 1 and the ring frame 7.

[0025] The polyester film 9 is then heated to a state in which it is drawn in by the vacuum source 2b, thereby undergoing a thermocompression bond. In this state Fig. In the preferred embodiment shown in Figure 4, the heating of the polyester film 9 is effected, for example, by a heat gun 4 provided above the clamping table 2. The heat gun 4 has a heating medium, 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. When a vacuum is applied to the polyester film 9 by the vacuum source 2b, the heat gun 4 is operated such that it supplies hot air 4a to the upper surface of the polyester film 9. Accordingly, when the polyester film 9 has been heated to a predetermined temperature, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression.

[0026] Another method can be used to heat the polyester film 9. For example, each 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 one such variation of the connection step. As in Fig. As shown in Figure 5, the transparent or visible-light translucent polyester film 9 is designed to cover the wafer 1, the ring frame 7, and the holding surface 2a of the clamping table 2, which is located in Fig. 5, all represented by dashed lines, are completely covered. In this, Fig. In the modification shown in Figure 5, a heat roller 6, which has a heat source, is used. In particular, the vacuum generated 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] The heating roller 6 is then heated to a predetermined temperature and next, at an end located on the outer circumference of the holding surface 2a, as shown in Fig. As shown in Figure 5, the heating roller 6 is placed on the holding surface 2a of the clamping table 2. The heating roller 6 is then rotated about its axis to roll over the polyester film 9 from one end shown above to another end diametrically opposite the first end shown above. As a result, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding. If a force is applied to press the polyester film 9 by the heating roller 6, the thermocompression bonding is effected at a pressure higher than atmospheric pressure. Preferably, the cylindrical surface of the heating roller 6 is coated with a fluoropolymer. Alternatively, the heating roller 6 can be replaced by an iron-like pressure element having a flat base plate and a heat source.In this case, the printing element is heated to a predetermined temperature to provide a hot plate which is then pressed onto the polyester film 9 held on the clamping table 2.

[0028] Another method for heating the polyester film 9 can be used in the following way. Fig. Figure 6 is a schematic perspective view illustrating one such variation of the connection step. As in Fig. As shown in Figure 6, the transparent or visible-light translucent polyester film 9 is provided such that it completely covers the wafer 1, the ring frame 7 and the holding surface 2a of the clamping table 2, which is shown in Fig. 6 all are represented by dashed lines. In this in 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 emit infrared light 8a, which has an absorption wavelength at least equal to that of the polyester film 9 material. In the modification shown in Fig. In the modification shown in Figure 6, the vacuum generated by the vacuum source 2b is first applied to the polyester film 9, so that the atmospheric pressure applied to the upper surface of the polyester film 9 brings it into close contact with the wafer 1 and the ring frame 7. The infrared lamp 8 is then activated to apply the infrared light 8a to the polyester film 9, thereby heating it. As a result, the polyester film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression.

[0029] When the polyester film 9 is heated to a temperature near its melting point by performing one of the above procedures, it is joined to the wafer 1 and the ring frame 7 by thermocompression. After joining the polyester film 9, the selector switch 2c is actuated to establish the OFF state, in which the connection between the porous element of the clamping table 2 and the vacuum source 2b is broken. Accordingly, the suction holding by the clamping table 2 is terminated.

[0030] Then the polyester film 9 is cut in a circular fashion along the outer circumference of the ring frame 7 in order to remove an unwanted circumferential section of the polyester film 9. Fig. Figure 7A is a schematic perspective view illustrating one method of cutting the polyester film 9. As shown in Fig. As shown in Figure 7A, a disc-shaped (ring-shaped) cutter 10 is used to cut the polyester film 9. The cutter 10 has a central through-hole 10a into which a rotating shaft 10b is fitted. Accordingly, the cutter 10 can be rotated about the axis of the rotating shaft 10b. First, the cutter 10 is positioned above the ring frame 7. At this point, the rotating shaft 10b is positioned so that it extends in the radial direction of the clamping table 2. Then, the cutter 10 is lowered until the outer circumference (cutting edge) of the cutter 10 comes into contact with the polyester film 9 placed on the ring frame 7. That is, the polyester film 9 is trapped between the cutter 10 and the ring frame 7, so that the polyester film 9 is cut by the cutter 10 to form a cut line 9a. Furthermore, the cutter 10 is cut along a circular line on the polyester film 9, which is between the inner circumference of the ring frame 7 (i.e.The tool is positioned outside the inner opening 7a of the ring frame 7 and the outer circumference of the ring frame 7, is guided in a rotating manner, and thereby forms the cutting track 9a along the circular line above. As a result, a predetermined central section of the polyester film 9 is surrounded by the circular cutting track 9a. Subsequently, a remaining outer section of the polyester film 9 outside the circular cutting track 9a is removed. That is, an unwanted outer section of the polyester film 9, including an outermost section outside the outer circumference 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 the ultrasonic range can be connected to the cutter 10. Additionally, the polyester film 9 can be cooled during cutting to harden it and facilitate the cutting process. Cutting the polyester film 9 as described above results in a Fig. Figure 7B shows a frame unit 11, in which the frame unit 11 consists of the wafer 1, the ring frame 7, and the polyester film 9, which are connected to each other. That is, the wafer and the ring frame 7 are connected to each other via the polyester film 9 to form the frame unit 11 as shown in Figure 7B. Fig. 7B is shown to be trained. Fig. 7B is a schematic perspective view of the frame unit 11 in a state in which the front side 1a of the wafer and the front side 7b of the ring frame 7 are exposed upwards.

[0032] When performing thermocompression bonding as described above, the polyester film 9 is preferably heated to a temperature equal to or below its melting point. If the heating temperature is higher than the melting point, there is a possibility that the polyester film 9 will melt to such an extent that its shape cannot be maintained. Furthermore, the polyester film 9 is preferably heated to a temperature equal to or higher than its softening point. If the heating temperature is lower than the softening point, thermocompression bonding cannot be carried out properly. Accordingly, the polyester film 9 is preferably heated to a temperature equal to or higher than its softening point and equal to or lower than its melting point.Furthermore, there is a case in which the softening point of the polyester film 9 may be unknown. To deal with such a case, 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 during the thermocompression bonding process, wherein the predetermined temperature is 20°C lower than the melting point of the polyester film 9.

[0033] If 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, if 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 here as the temperature of the polyester film 9 to be heated during the joining step. Several types of heat sources capable of setting an output temperature have been used, including the heat gun 4, the heat roller 6, and the infrared lamp 8 mentioned above. However, even when such a heat source is used to heat the polyester film 9, in some cases the temperature does not reach the output temperature specified above. To address this, the output temperature of the heat source can be set to a temperature higher than the melting point of the polyester film 9 in order to heat the polyester film 9 to the specified temperature.

[0035] After performing the aforementioned joining step, a division step is carried out such that the wafer 1, in the state of the frame unit 11, is processed by laser ablation to form several intersecting division grooves along the several intersecting division lines 3 in the wafer 1, thereby dividing the wafer 1 into individual component chips. In this preferred embodiment, the division step is performed using a Fig. The laser processing device 12 shown in section 8 was used. Fig. Figure 8 is a schematic perspective view illustrating the division step. As in Fig. As shown in Figure 8, the laser processing device 12 comprises a laser processing unit 14 for performing laser ablation on the wafer 1 and a clamping table (not shown) for holding the wafer 1. The laser processing unit 14 includes a laser oscillator (not shown) for generating a laser beam 16 with an absorption wavelength for the wafer 1 (which has a wavelength that is absorbable by the wafer 1). The clamping table has an upper surface that serves as a holding surface for the wafer 1. The clamping table is movable in a direction parallel to its upper surface, i.e., 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 clamping table.The laser processing unit 14 further comprises a processing head 14a with a mechanism for focusing the laser beam 16 at a predetermined vertical position in the wafer 1.

[0036] During laser ablation of wafer 1, the frame unit 11 is positioned on the clamping table with the front face 1a of wafer 1 exposed. The wafer 1 is held on the clamping table by the polyester film 9. The clamping table is then rotated to align the division lines 3 extending in the first direction on the front face 1a of wafer 1 with a feed direction in the laser processing unit 12. The clamping table and the laser processing unit 14 are then moved relative to establish a position that places the processing head 14a directly above one of the division lines 3 extending in the first direction. Finally, the laser beam 16 is applied to the wafer by the processing head 14a.Simultaneously, the clamping table and the laser processing unit 14 are moved relative to the upper surface of the clamping table in the feed direction. Consequently, the laser beam 16 is applied to the wafer 1 along the predefined division line 3, thereby performing laser ablation along the predefined division line 3. Accordingly, a division groove 3a is formed in the wafer 1 along the predefined division line 3 by the laser beam 16. The division groove 3a has a depth from the front side 1a to the back side 1b of the wafer 1. In this division step, the laser beam 16 can be applied under the following processing conditions. The following processing conditions are only examples. Wavelength: 355 nm Repetition frequency: 50 kHz Average power consumption: 5 W Feed rate: 200 mm / s

[0037] After forming the parting groove 3a along the predefined parting line 3, the clamping table and the laser processing unit 14 are moved in an index direction perpendicular to the feed direction to perform a similar laser ablation along the next parting line 3 extending in the first direction. A similar laser ablation is then performed along all other parting lines 3 extending in the first direction. Thus, several similar parting grooves 3a are formed along all parting lines 3 extending in the first direction. The clamping table is then rotated 90 degrees about its vertical axis perpendicular to its holding surface to perform a similar laser ablation along all parting lines 3 extending in the second direction perpendicular to the first.Thus, several similar division grooves 3a are formed similarly along all division lines 3 extending in the second direction. In this way, the multiple intersecting division grooves 3a with a depth from the front 1a to the back 1b of the wafer are formed in wafer 1 along the respective intersecting division lines 3, so that wafer 1 is divided by these division lines 3a to obtain the individual component chips.

[0038] When the laser processing unit 14 is activated to perform laser ablation on wafer 1, processing dust is generated on wafer 1 at the point where the laser beam 16 is applied. This processing dust spreads around this laser application point and adheres to the front face 1a of wafer 1. Even if the front face 1a of wafer 1 is cleaned after laser ablation using a cleaning unit described below, it is not easy to completely remove this processing dust adhering to the front face 1a of wafer 1. If the processing dust remains on each device chip obtained from wafer 1, the quality of each device chip is reduced.To address this problem, a water-soluble liquid plastic can be pre-applied to the front face 1a of wafer 1, serving as a protective film. When the liquid plastic is pre-applied, any processing dust dispersed during laser ablation adheres to the surface of the applied liquid plastic. This prevents the processing dust from directly bonding to the front face 1a of wafer 1. After laser ablation, wafer 1 is cleaned using the cleaning unit. At this stage, the processing dust is removed along with the applied liquid plastic during cleaning.

[0039] This means that the laser processing device 12 can have such a cleaning unit (not shown). In this case, the wafer 1, processed by the laser processing unit 14 as mentioned above, is transferred to the cleaning unit and then cleaned by the cleaning unit. For example, the cleaning unit has a cleaning table with a holding surface for the frame unit 11 and a cleaning water nozzle designed to be moved horizontally back and forth above the frame unit 11, which is held on the holding surface of the cleaning table. The cleaning water nozzle acts by supplying cleaning water, such as pure water, to the wafer 1. The cleaning table is rotatable about its axis, which is perpendicular to its holding surface. During 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 back and forth along a path that runs through the position directly above the center of the holding surface of the cleaning table. Accordingly, the entire surface of the front face 1a of wafer 1 can be cleaned by the cleaning water.

[0040] After performing the division step or the cleaning step, a pickup step is carried out to pick up each component chip from the polyester film 9. The pickup step is performed using a Fig. 9 shown recording device 18 carried out. Fig. Figure 9 is a schematic perspective view illustrating one way of loading the frame unit 11 into the receiving device 18. As shown in Fig. As shown in Figure 9, the receiving device 18 comprises a cylindrical drum 20 and a frame holding unit 22, which has a frame support table 26 arranged 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 with a larger 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 essentially equal to the inner diameter of the ring frame 7. The frame support table 26 has an upper surface that serves as a support surface for carrying the ring frame 7 over the polyester film 9 on it. Initially, 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 figure ). Fig. 10A). Furthermore, in this initial stage, the upper end section of the drum 20 is surrounded by the inner circumference of the ring frame 7.

[0041] Several clamps 24 are provided on the outer circumference of the frame support table 26. Each clamp 24 acts such that it holds 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 over the polyester film 9 on the frame support table 26 and then held by each clamp 24, the frame unit 11 can be attached to the frame support table 26. The frame support table 26 is supported by several 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) that is movably housed within the air cylinder 30. Each air cylinder 30 is supported on a disc-shaped base 32.This means that 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 relative to the drum 20 which is fixed in place.

[0042] Furthermore, a lifting mechanism 34 is provided for lifting each component chip carried on the polyester film 9 within the drum 20. The high-pressure mechanism 34 has a cooling device 34a at its upper end, which includes a cooling mechanism such as a Peltier element. A gripper 36 is also provided (see Fig. 10B), which is capable of holding each component chip under suction, is provided above the drum 20. Both the lifting 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 controlled by a selector switch 36b (see Fig. 10B) with a vacuum source 36a (see Fig. 10B) connected.

[0043] In the loading step, each air cylinder 30 in the loading device 18 is first 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. Then, the frame unit 11, transferred from the laser processing device 12, is positioned in the loading device 18 with the front face 1a of the wafer 1 of the frame unit 11 facing upwards. Finally, each clamp 24 is actuated to secure the ring frame 7 of the frame unit 11 to the upper surface of the frame support table 26. Fig. Figure 10A is a schematic sectional view showing a standby state in which the frame unit 11 is attached to the frame support table 26, which is set in its initial position. At this point, the multiple division slots 3a have already been formed in the wafer 1 during the division step, so that the wafer 1 has already been divided into several individual component chips 1c (see Figure 10A). Fig. 10B).

[0044] Subsequently, each air cylinder 30 is actuated to lower the frame support table 26 of the frame holding unit 22 relative to the drum 20. As a result, the polyester film 9, attached to the frame holding unit 22 by each clamp 24, is lowered as shown in Fig. 10B shown widened radially outwards. Fig. Figure 10B is a schematic sectional view depicting a machining state in which the frame support table 26, which holds the ring frame 7 with the polyester film 9, is lowered to expand the polyester film 9. As the polyester film 9 expands radially outward as described above, the distance between adjacent component chips 1c, which are supported on the polyester film 9, is as shown in Fig. Figure 10B is shown enlarged. Accordingly, contact between the adjacent component chips 1c can be suppressed and each component chip 1c can be easily picked up. Then a specific component chip 1c is selected and the push-up mechanism 34 is next used as shown. Fig. 10B is moved to a position directly below this target component chip 1c. Furthermore, the gripper 36 is also moved as shown in Fig.The target component chip 1c is moved to a position directly above it, as shown in figure 10B. The cooling device 34a is then activated to reduce the temperature and is brought into contact with an area of ​​the polyester film 9 corresponding to the target component chip 1c to cool that area. The lifting mechanism 34 is then activated to lift the target component chip 1c above the polyester film 9. The selector switch 36b is then activated to connect the gripper 36 to the vacuum source 36a. As a result, the target component chip 1c is held by the gripper 36 under suction and thus picked up by the polyester film 9. This picking-up operation is performed similarly for all other component chips 1c. Each picked-up component chip 1c is then attached to a predetermined wiring substrate or the like for actual use.

[0045] Note that when the area of ​​the polyester film 9 is cooled by the cooling device 34a, the polyester film 9 shrinks and a large stress occurs at an interface between the polyester film 9 and each component chip, making it easy to peel each component chip from the polyester film 9. Accordingly, the load applied to each component chip when peeling it from the polyester film 9 is reduced.

[0046] In the case of forming the frame unit 11 using an adhesive strip, the heat generated by the laser beam 16 during the division step is transferred to the adhesive strip, causing the adhesive layer of the strip to melt and adhere to the back of each component chip. Accordingly, in this case, the adhesion of the adhesive layer to each component chip results in a reduction in quality. In contrast, in the wafer processing method according to this preferred embodiment, the frame unit 11 can be formed using the polyester film 9, which does not have an adhesive layer. The polyester film 9 is attached to the wafer 1 and the ring frame 7 by thermocompression bonding. This means that an adhesive strip with an adhesive layer is not required.Consequently, it is possible to avoid a reduction in the quality of each component chip due to the adhesion of the adhesive layer to the back of each component chip.

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

Claims

[1] 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 upwards; a division step of applying a laser beam to the wafer (1) along each division line (3), wherein the laser beam has an absorption wavelength for the wafer (1), after performing the joining step, thereby forming a division groove in the wafer (1) along each division line (3) to divide the wafer (1) into the individual component chips (1c); and a pickup step of cooling the polyester film (9) in each area of ​​the polyester film (9) corresponding to a respective component chip (1c), and of pushing up each component chip (1c) from the side of the polyester film (9) in order to pick up each component chip (1c) from the polyester film (9) after performing the division step. [2] Wafer processing method according to claim 1, wherein the joining step comprises a step of applying infrared light to the polyester film (9), whereby thermocompression joining is carried out. [3] 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 includes an additional step of cutting the polyester film (9) after heating the polyester film (9), thereby removing a portion of the polyester film (9) outside an outer circumference of the ring frame (7). [4] Wafer processing method according to one of the preceding claims, wherein the receiving step includes a step of widening the polyester film (9) in order to increase the distance between respective adjacent component chips (1c). [5] Wafer processing method according to any of the preceding claims, wherein the polyester film (9) is formed from a material selected from the group consisting of polyethylene terephthalate and polyethylene naphthalate. [6] Wafer processing method according to claim 5, wherein the polyester film (9) is made of polyethylene terephthalate and the polyester film (9) is heated in the bonding step in the range of 250°C to 270°C. [7] Wafer processing method according to claim 5, wherein the polyester film (9) is made of polyethylene naphthalate and the polyester film (9) is heated in the bonding step in the range of 160°C to 180°C. [8] Wafer processing method according to any of the preceding claims, wherein the wafer (1) is formed from a material selected from the group consisting of silicon, gallium nitride, gallium arsenide and glass.

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