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 polyolefin film provisioning step of positioning the wafer (1) in the inner opening (7a) of the ring frame (7) and providing a polyolefin 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 polyolefin film (9) and the wafer (1); a joining step of heating the polyolefin film (9) during the application of pressure to the polyolefin film (9) after performing the polyolefin film provisioning step, whereby the wafer (1) and the ring frame (7) are joined by thermocompression joining over the polyolefin 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 polyolefin film (9) in each of the several areas corresponding to each component chip (1c), pushing up each component chip (1c) through the polyolefin film (9), and picking up each component chip (1c) from the polyolefin 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, one 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 cutting device is used to split the wafer. The cutting device has a clamping table for holding the wafer via the adhesive strip and a cutting unit for cutting the wafer. The cutting unit has 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 spindle rotate as a single 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 clamping table, and the wafer is held by the adhesive strip on the upper surface of the clamping table.In this state, the spindle is rotated to turn the cutting blade, and the cutting unit is then lowered to a predetermined height. Afterward, the clamping table and the cutting unit are moved relative to each other in a direction parallel to the upper surface of the clamping table. Consequently, the wafer is cut along each parting line by the rotating cutting blade, thus splitting the wafer.

[0004] The wafer assembly is then transferred from the cutting device to another device for applying ultraviolet light to the adhesive tape, thereby reducing its adhesion. Each component chip is then picked up from the adhesive tape. A cutting device capable of continuously performing the wafer cutting and ultraviolet light application processes is used as a processing unit for the highly efficient production of component chips (see, for example, Japanese patent JP 3 076 179 B2). Each component chip picked up from the adhesive tape is then mounted onto 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 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. PRESENTATION OF THE INVENTION

[0006] The adhesive tape has a base layer and an adhesive layer formed on the base layer. When the wafer is cut using the cutting device, the cutting unit is positioned at a predetermined height so that the lower end of the cutting blade is lower than the bottom surface (the back side) of the wafer, thus reliably cutting the wafer. Consequently, the adhesive layer of the adhesive tape on the back side of the wafer is also cut by the cutting blade at the moment the wafer is cut. As a result, cutting dust is generated both from the wafer and from the adhesive layer. Cutting water is supplied to the wafer and the cutting blade during the cutting process.The cutting dust generated during wafer slicing is drawn into the cutting fluid and then distributed across the wafer's front surface. However, cutting dust emanating from the adhesive layer can re-adhere to the front surface of each component. Furthermore, removing this adhering cutting dust from each component in a post-slicing cleaning step is not straightforward. Consequently, if cutting dust emanating from the adhesive layer adheres to every component formed on the wafer's front surface, the quality of each component chip can be reduced.

[0007] The present invention was made in view of the above problem and it is therefore an objective of the present invention to provide a wafer processing method which prevents the adhesion of cutting dust to the front of each component during the cutting of 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 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 polyolefin film provision step of positioning the wafer in the inner opening of the ring frame and providing a polyolefin film on a rear face of the wafer and on a rear face of the ring frame, wherein no adhesive layer is arranged between the polyolefin film and the wafer.a joining step of heating the polyolefin film during the application of pressure to the polyolefin film after performing the polyolefin film provisioning step, whereby the wafer and the ring frame are joined via the polyolefin film by thermocompression joining, so that they form a frame unit in a state in which the front of the wafer and the front of the ring frame are exposed; a severing step of cutting the wafer along each severance line using a cutting device having a rotatable cutting blade, after performing the joining step, whereby the wafer is divided into the individual component chips; and a receiving step of cooling the polyolefin film in each of the several separate areas corresponding to each component, pushing up each component chip through the polyolefin film.and then the picking up of each component chip from the polyolefin film after performing the division step.

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

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

[0011] Preferably, the insertion step includes a step of widening the polyolefin film, thereby increasing the distance between all adjacent components.

[0012] Preferably, the polyolefin film is made of a material selected from the group consisting of polyethylene, polypropylene and polystyrene.

[0013] If the polyolefin film is made of polyethylene, it is preferably heated to between 120°C and 140°C during the bonding step. If the polyolefin film is made of polypropylene, it is preferably heated to between 160°C and 180°C during the bonding step. If the polyolefin film is made of polystyrene, it is preferably heated to between 220°C and 240°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 polyolefin 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 polyolefin film bonded together. The joining step of connecting the wafer and the ring frame via the polyolefin film is carried out by thermocompression bonding. After performing the joining step, the wafer is cut using a cutting blade to divide it into individual component chips.The polyolefin film is then cooled in each of the several separate areas corresponding to each component chip, and each component chip is pushed upwards through the polyolefin film, thus being picked up by the film. Each picked-up component chip is then attached to a predetermined wiring substrate or the like. Note that if the polyolefin film is cooled during the picking-up of each component chip, the polyolefin film shrinks and can be easily peeled off, thus making it possible to reduce the load applied to each component chip.

[0016] When the wafer is cut using the cutting blade, the polyolefin film underneath the wafer is also cut by the blade. This means that the wafer and the polyolefin film bonded to the back of the wafer are cut together by the blade in a state where the front of the wafer is facing upwards. Consequently, cutting dust is generated from the polyolefin film. This cutting dust is absorbed by the cutting water, which is supplied during the cutting process and then distributed across the front of the wafer. However, since the polyolefin film lacks an adhesive layer, the cutting dust does not adhere to the wafer, allowing for more reliable removal 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 polyolefin film, which has no adhesive layer. Accordingly, no cutting dust originating from an adhesive layer is generated when the wafer is cut, so that it is possible to suppress a reduction in the quality of each component chip due to such adhesive cutting dust.

[0017] Thus, the wafer processing method according to the preferred embodiment of the present invention can have the effect that cutting dust does not adhere to the front of each component when cutting the wafer, and a reduction in the quality of each component chip split from the wafer can be suppressed.

[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 polyolefin 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 polyolefin 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 polyolefin film is lowered to widen the polyolefin film in the receiving 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 machining process 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. 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, defining several separate regions, each containing several devices 5 such as ICs and LEDs. 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.In the processing method for the wafer 1 according to this preferred embodiment, the wafer 1 is cut along the intersecting division lines 3 and thereby divided into several individual component chips, each containing the several components 5.

[0020] Wafer 1 is cut using a cutting device. Before loading wafer 1 into the cutting device, wafer 1 is coated with a polyolefin film 9 (see Fig. 3) and a ring frame 7 (see Fig. 3) connected to form a frame unit. The wafer 1, in the form of such a frame unit, is loaded into the cutting device and then cut into individual component chips within the cutting device, where each component chip is held against the polyolefin film 9. The polyolefin 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 polyolefin film 9 is a flexible (expandable) plastic film with a flat front and back surface. The polyolefin film 9 is a circular film with a diameter larger than the outer diameter of the ring frame 7. The polyolefin film 9 lacks an adhesive layer. It is a film made of a polymer (polyolefin) synthesized by polymerizing an alkene as a monomer. Examples of polyolefin film 9 include polyethylene film, polypropylene film, and polystyrene film. The polyolefin film 9 is transparent or translucent to visible light. As a variation, the polyolefin film 9 can be opaque. Because the polyolefin film 9 lacks adhesive properties, it cannot be bonded to the wafer 1 and the ring frame 7 at room temperature.However, the polyolefin film 9 is a thermoplastic film, so if the polyolefin 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 polyolefin film 9 melts and is thereby bonded to the wafer 1 and the ring frame 7. This means that the polyolefin 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 polyolefin 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 polyolefin film 9, and the ring frame 7, a polyolefin 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 polyolefin 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 polyolefin 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 polyolefin 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 polyolefin film 9 to the wafer 1 and the ring frame 7. That is, as in Fig. Figure 3 shows that the polyolefin film 9 is provided such that it completely covers the wafer 1 and the ring frame 7. In the polyolefin film provisioning step, the diameter of the polyolefin 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 polyolefin 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 polyolefin film 9 and the holding surface 2a, since the holding surface 2a is not completely covered by the polyolefin film 9, and therefore pressure cannot be adequately applied to the polyolefin 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 polyolefin film 9 is heated in order to join the wafer 1 and the ring frame 7 by thermocompression joining via the polyolefin 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 polyolefin 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 polyolefin film 9 provided on the clamping table 2. Accordingly, the atmospheric pressure applied to the upper surface of the polyolefin film 9 brings the wafer 1 and the ring frame 7 into close contact.

[0025] The polyolefin film 9 is then heated to a state in which it is drawn in by the vacuum source 2b, thereby undergoing thermocompression bonding. In this state Fig. In the preferred embodiment shown in Figure 4, the heating of the polyolefin 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 polyolefin 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 polyolefin film 9. Accordingly, when the polyolefin film 9 has been heated to a predetermined temperature, the polyolefin film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding.

[0026] Another method for heating the polyolefin film 9 can be used. For example, each element heated to a predetermined temperature on the polyolefin 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 polyolefin 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. 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 polyolefin film 9, so that the polyolefin 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 polyolefin 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 the polyolefin film 9 from one end shown above to another end diametrically opposite the first end shown above. As a result, the polyolefin film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression bonding. If a force is applied to press the polyolefin 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 polyolefin film 9 held on the clamping table 2.

[0028] Another method for heating the polyolefin 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 polyolefin 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 polyolefin film 9. The infrared lamp 8 can emit infrared light 8a, which has an absorption wavelength at least equal to that of the polyolefin 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 polyolefin film 9, so that the atmospheric pressure applied to the upper surface of the polyolefin film 9 brings the polyolefin film 9 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 polyolefin film 9, thereby heating it. As a result, the polyolefin film 9 is bonded to the wafer 1 and the ring frame 7 by thermocompression.

[0029] When the polyolefin 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 polyolefin film 9, the selector switch 2c is actuated to disconnect the connection of the porous element of the clamping table 2 to the vacuum source 2b. Accordingly, the suction holding by the clamping table 2 is terminated.

[0030] Then the polyolefin 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 polyolefin film 9. Fig. Figure 7A is a schematic perspective view illustrating one method of cutting the polyolefin film 9. As shown in Fig. As shown in Figure 7A, a disc-shaped (ring-shaped) cutter 10 is used to cut the polyolefin 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 polyolefin film 9 placed on the ring frame 7. That is, the polyolefin film 9 is trapped between the cutter 10 and the ring frame 7, so that the polyolefin film 9 is cut by the cutter 10 to form a cut line 9a. Furthermore, the cutter 10 is guided along a circular line on the polyolefin 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, and is guided in a rotating manner, thereby forming the cutting track 9a along the circular line above. As a result, a predetermined central section of the polyolefin film 9 is surrounded by the circular cutting track 9a. Subsequently, a remaining outer section of the polyolefin film 9 outside the circular cutting track 9a is removed. That is, an unwanted outer section of the polyolefin 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 polyolefin 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 polyolefin film 9 can be cooled during cutting to harden it and facilitate the cutting process. Cutting the polyolefin film 9 as described above results in a Fig. The frame unit 11 shown in Figure 7B is formed, in which the frame unit 11 consists of the wafer 1, the ring frame 7, and the polyolefin film 9, which are connected to each other. That is, the wafer and the ring frame 7 are connected to each other via the polyolefin 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 polyolefin 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 polyolefin film 9 will melt to such an extent that its shape cannot be maintained. Furthermore, the polyolefin 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 polyolefin 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 polyolefin film 9 may be unknown. To deal with such a case, the polyolefin 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 polyolefin film 9 during the thermocompression bonding process, wherein the predetermined temperature is 20°C lower than the melting point of the polyolefin film 9.

[0033] If the polyolefin film 9 is a polyethylene film, the heating temperature in the bonding step is preferably set in the range of 120°C to 140°C. Furthermore, if the polyolefin film 9 is a polypropylene film, the heating temperature in the bonding step is preferably set in the range of 160°C to 180°C. Furthermore, if the polyolefin film 9 is a polystyrene film, the heating temperature in the bonding step is preferably set in the range of 220°C to 240°C.

[0034] The heating temperature is defined here as the temperature of the polyolefin 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 polyolefin 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 polyolefin film 9 in order to heat the polyolefin film 9 to the specified temperature.

[0035] After performing the aforementioned joining step, a dividing step is carried out such that the wafer 1, in the state of the frame unit 11, is cut by a cutting blade to obtain individual component chips. In this preferred embodiment, the dividing step is performed using a Fig. 8 shown cutting device 12 carried out. Fig. Figure 8 is a schematic perspective view illustrating the division step. As in Fig. As shown in Figure 8, the cutting device 12 comprises a cutting unit 14 for cutting a workpiece and a clamping table (not shown) for holding the workpiece. The cutting unit 14 includes a cutting blade 18, which has an annular abrasive section (cutting edge) for cutting the workpiece, and a spindle (not shown) for supporting the cutting blade 18 so that it rotates 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 (connector) having the aforementioned central through-hole and an annular abrasive section extending along the outer circumference of the annular base. The spindle is rotatably mounted in a spindle housing 16, and the base end of the spindle is connected to a spindle motor (not shown) housed within the spindle housing 16.Accordingly, the cutting blade 18 can be rotated by actuating the spindle motor. The clamping table has an upper surface that serves as a holding surface for the wafer 1.

[0036] When the workpiece is cut by the cutting blade 18, heat is generated by the friction between the cutting blade 18 and the workpiece. Furthermore, cutting dust is generated from the workpiece during cutting. To remove this heat and the cutting dust generated during the cutting process, cutting water, such as clean water, is supplied to the cutting blade 18 and the workpiece during the cutting operation. 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 such that they face both sides of the cutting blade 18. Fig. Figure 8 shows only one of the two cutting water nozzles 20.

[0037] During wafer 1 cutting, 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 polyolefin 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 parallel to a feed direction in the cutting device 12. The clamping table and the cutting unit 14 are then moved relative to each other in a horizontal plane perpendicular to the feed direction to position the cutting blade 18 directly above a predetermined extension of the division lines 3 extending in the first direction.

[0038] The spindle is then rotated to turn the cutting blade 18. The cutting unit 14 is then lowered to a predetermined height, and the clamping table and the cutting unit 14 are moved relative to the upper surface of the clamping table in the feed direction. The rotating abrasive section of the cutting blade 18 thus comes into contact with the wafer 1, cutting it along the predetermined parting line 3 in the feed direction. This results in a cut 3a (groove) along the predetermined parting line 3, completely cutting through the wafer 1 and the polyolefin film 9. After cutting the wafer 1 and the polyolefin film 9 along the predetermined parting line 3, the clamping table and the cutting unit 14 are moved relative to it in an index direction perpendicular to the feed direction by the distance of the parting lines 3.The cutting process described above is then carried out similarly along the next division line adjacent to the previously specified division line 3. After performing the cutting process similarly along all other division lines 3 extending in the first direction, the clamping table is rotated 90 degrees about its axis perpendicular to the holding surface, so that the other division lines 3 extending in the second direction, perpendicular to the first, become parallel to the feed direction. The cutting process described above is then carried out similarly along all other division lines 3 extending in the second direction. After performing the cutting process along all other division lines 3 extending in the second direction, the division step is complete.

[0039] The cutting device 12 can include a cleaning unit (not shown) located near the cutting unit 14. This means that 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 has a cleaning table with a holding surface for the frame unit 11 and a cleaning water nozzle that is positioned to move horizontally in opposite directions above the frame unit 11, which is held on the holding surface of the cleaning table. The cleaning water nozzle supplies cleaning water, such as pure water, to the wafer 1. The cleaning table is rotatable about its axis perpendicular to the holding surface. During operation, the cleaning table is rotated about its axis, and simultaneously, 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 that passes 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] By performing the splitting step as described above, wafer 1 is divided into individual component chips, which are still supported by the polyolefin film 9. During the cutting process, the cutting unit 14 is positioned at a predetermined height such that the lower end of the cutting blade 18 is lower than the back side 1b of wafer 1, ensuring reliable splitting. Consequently, when wafer 1 is cut by the cutting blade 18, the polyolefin film 9, which is bonded to the back side 1b of wafer 1, is also cut by the cutting blade 18, generating cutting dust from the polyolefin film 9. If an adhesive tape with an adhesive layer is used in place of the polyolefin film 9 in the frame unit 11, cutting dust from the adhesive tape is generated.In this case, the cutting dust is drawn into the cleaning water supplied by the cleaning water nozzles 20 and then distributed on the front face 1a of wafer 1. The cutting dust emanating from the adhesive layer can re-adhere to the front face of each component 5. Furthermore, it is not easy to remove the cutting dust adhering to the front face of each component 5 in a single cleaning step of wafer 1 after the splitting step. If the cutting dust emanating from the adhesive layer adheres to each component 5, this creates a problem that reduces the quality of each component chip split from wafer 1.

[0041] In comparison, the processing method for wafer 1 according to this preferred embodiment offers the following advantage. In this preferred embodiment, instead of an adhesive tape having an adhesive layer, the polyolefin film 9, which does not have an adhesive layer, is used in the frame unit 11. Even though cutting dust emanating from the polyolefin film 9 is generated and then distributed on the front face 1a of the wafer 1 when it is drawn into the cleaning water, this abrasive dust is not adhered to the wafer 1 but is reliably removed in the subsequent cleaning step. Accordingly, it is possible to suppress any reduction in the quality of each component chip due to the cutting dust.

[0042] After performing the division step or the cleaning step, a pick-up step is carried out to pick up each component chip from the polyolefin film 9. The pick-up step is performed using a Fig. 9 shown recording device 22 was carried out. Fig. Figure 9 is a schematic perspective view illustrating one way of loading the frame unit 11 into the receiving device 22. As shown in Fig. As shown in Figure 9, the receiving device 22 comprises a cylindrical drum 24 and a frame holding unit 26, which has a frame support table 30 arranged 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 with a larger 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 essentially equal to the inner diameter of the ring frame 7. The frame support table 30 has an upper surface that serves as a support surface for carrying the ring frame 7 over the polyolefin film 9 on it. Initially, 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 figure ). Fig. 10A). Furthermore, in this initial step, the upper end section of the drum 24 is surrounded by the inner circumference of the ring frame 7.

[0043] Several clamps 28 are provided on the outer circumference of the frame support table 30. Each clamp 28 acts such that it holds 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 over the polyolefin film 9 on the frame support table 30 and then held by each clamp 28, the frame unit 11 can be attached to the frame support table 30. The frame support table 30 is supported by several 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. In particular, the lower end of each rod 32 is connected to a piston (not shown) that is movably housed in the air cylinder 34. Each air cylinder 34 is supported on a disc-shaped base 36.This means that 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 relative to the drum 24 which is fixed in place.

[0044] Furthermore, a lifting mechanism 38 is provided for lifting each component chip carried on the polyolefin film 9 within the drum 24. The lifting mechanism has a cooling area 38a at its upper end, which includes a cooling mechanism such as a Peltier element. This means that each component chip is arranged so that it is lifted through the polyolefin film 9 by the lifting mechanism 38 located below the polyolefin 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 lifting 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 controlled by a selector switch 40b (see Fig. 10B) with a vacuum source 40a (see Fig. 10B) connected.

[0045] In the pickup step, each air cylinder 34 in the pickup device 22 is first 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. Then, the frame unit 11, transferred by the cutting device 12, is positioned on the drum 24 and the frame support table 30 in the pickup device 22 in a state where the front face 1a of the wafer 1 of the frame unit 11 is oriented upwards. Finally, each clamp 28 is actuated to secure the ring frame 7 of the frame unit 11 to the upper surface of the frame support table 30. 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 30, which is set in its initial position. At this point, the multiple cutting tracks 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).

[0046] Subsequently, each air cylinder 34 is actuated to lower the frame support table 30 of the frame holding unit 26 relative to the drum 24. As a result, the polyolefin film 9, which is attached to the frame holding unit 26 by each clamp 28, 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 30, which holds the ring frame 7 with the polyolefin film 9, is lowered to expand the polyolefin film 9. As the polyolefin film 9 expands radially outward as mentioned above, the distance between adjacent component chips 1c, which are supported on the polyolefin 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 38 is next used as shown. Fig. 10B is moved to a position directly below this target component chip 1c. Furthermore, the gripper 40 is also moved as shown in Fig.The device 1c is moved to a position directly above the target component chip 1c, as shown in the diagram. The cooling area 38a is then activated, causing its temperature to decrease. The lifting mechanism then brings the cooling area 38a into contact with an area corresponding to the component chip 1c in the polyolefin film, thus cooling that area. The lifting mechanism 38 is then activated to push the target component chip 1c up through the polyolefin film 9. The selector switch 40b is then activated to connect the gripper 40 to the vacuum source 40a. As a result, the target component chip 1c is held under suction by the gripper 40 and thus picked up by the polyolefin film 9. This picking-up action 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.

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

[0048] In the wafer processing method according to this preferred embodiment mentioned above, the frame unit 11 containing the wafer 1 can be designed with an adhesive layer without the use of an adhesive tape. Accordingly, no cutting dust from the adhesive tape is generated during the cutting of the wafer 1, so 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 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 polyolefin film 9 is selected from a polyethylene film, a polypropylene film, and a polystyrene film, this is only illustrative. That is to say, the polyolefin film usable in the present invention can be made from any other material (polyolefin), such as a copolymer of polypropylene and ethylene and an olefin elastomer.

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 polyolefin film provisioning step of positioning the wafer (1) in the inner opening (7a) of the ring frame (7) and providing a polyolefin 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 polyolefin film (9) and the wafer (1); a joining step of heating the polyolefin film (9) during the application of pressure to the polyolefin film (9) after performing the polyolefin film provisioning step, whereby the wafer (1) and the ring frame (7) are joined by thermocompression joining over the polyolefin 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 polyolefin film (9) in each of the several areas corresponding to each component chip (1c), pushing up each component chip (1c) through the polyolefin film (9), and picking up each component chip (1c) from the polyolefin 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 polyolefin film (9), whereby thermocompression joining is carried out. [3] Wafer processing method according to claim 1 or 2, wherein the polyolefin film (9) is larger than the ring frame (7) and wherein the joining step includes an additional step of cutting the polyolefin film (9) after heating the polyolefin film (9), thereby removing a portion of the polyolefin 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 polyolefin film (9) in order to increase the distance between all adjacent component chips (1c). [5] Wafer processing method according to any of the preceding claims, wherein the polyolefin film (9) is formed from a material selected from the group consisting of polyethylene, polypropylene and polystyrene. [6] Wafer processing method according to claim 5, wherein the polyolefin film (9) is made of polyethylene and the polyolefin film (9) is heated in the bonding step in the range of 120°C to 140°C. [7] Wafer processing method according to claim 5, wherein the polyolefin film (9) is made of polypropylene and the polyolefin film (9) is heated in the bonding step in the range of 160°C to 180°C. [8] Wafer processing method according to claim 5, wherein the polyolefin film (9) is made of polystyrene and the polyolefin film (9) is heated in the bonding step in the range of 220°C to 240°C. [9] 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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