WAFER PROCESSING METHODS

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 a 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 of the ring frame (7) and providing a polyester film (9) on a back or front (1a) of the wafer (1) and on a back 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) to form a frame unit in a state in which the wafer (1) and the front of the ring frame (7) are exposed; a division step of positioning a focal point of a laser beam within the wafer (1), wherein the laser beam has a transmission wavelength for the wafer (1), and of applying the laser beam to the wafer (1) along each division line (3), thereby forming a modified layer in the wafer (1) along each division line (3) to divide the wafer (1) into the individual component chips (1c), after performing the interconnection step; and a pickup step of cooling the polyester film (9) in each of the several separate areas corresponding to a respective component chip (1c), pushing up each component chip (1c) through the polyester film (9) and then picking 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 to close the inner opening.Next, a central section of the adhesive strip is attached to the back or front 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. The laser processing device comprises a clamping table for holding the wafer via the adhesive strip and a laser processing unit for focusing a laser beam within the wafer held on the clamping table, the laser beam having a transmission wavelength suitable 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 along each split line.When the laser beam is focused within the wafer, a modified layer serving as a division start point is formed in the wafer along each division line (see Japanese patent JP 3 408 805 B2).

[0004] The frame unit is then transferred from the laser processing device to another device, and the adhesive strip is expanded radially outward in one direction, thus dividing the wafer into individual component chips. When the resulting component chips are picked up by the adhesive strip, ultraviolet light is applied to the strip beforehand to reduce its adhesion. Each component chip is then picked up by the adhesive strip. A laser processing device capable of producing the component chips with high efficiency exists that can continuously perform the wafer dividing and ultraviolet light application processes (see, for example, Japanese patent JP 3 076 179 B2).

[0005] Further prior art that may be helpful for understanding the following invention can be found in the following documents: WO 2014 / 157471 A1 concerns a wafer processing belt that has a uniform expandability and a property that enables the pick-up 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 2015-126082 A relates to a semiconductor chip imaging technique that can prevent a dividing band from widening. US 2016 / 0 007 479 A1 relates to a device for maintaining chip spacing, in which the spacing between adjacent component chips is maintained. JP 2003-152056 A 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 device consisting of a clamping table with a suction area and a frame and an abrasive 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 focused within the wafer to form a modified layer that serves as a parting point, and some of the laser beam's leakage light reaches the adhesive layer of the tape. Consequently, the heat generated by the laser beam melts the adhesive layer of the tape, which is attached to the back or front of the wafer, at the position below or around each parting groove formed in the wafer. A portion of the molten adhesive layer is then bonded to the back or front 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 front or back of each component chip, remains on either side of the tape. Consequently, the quality of each component chip is reduced.

[0007] It is therefore an objective of the present invention to provide a wafer processing method that can prevent the adhesion of the adhesive layer to the back or front 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 includes a ring frame preparation step of preparing a ring frame having an inner opening for receiving the wafer, a polyester film provision step of positioning the wafer in the inner opening of the ring frame, and providing a polyester film on a back or front face of the wafer and on a back 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 thermocompression joining, so that they form a frame unit in a state where the wafer and the front of the ring frame are exposed; a division step of positioning a focal point of a laser beam within the wafer, wherein the laser beam has a transmission wavelength for the wafer, and of applying the laser beam to the wafer along each division line, thereby forming a modified layer in the wafer along each division line to divide the wafer into the individual device chips, after performing the joining step; and a receiving step of cooling the polyester film in each of the several separated areas.which correspond to a respective component chip, the pushing up of each component chip through the polyester film, and then the picking up of 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 an outer circumference of the ring frame.

[0011] Preferably, the uptake step includes a step of widening the polyester film in order to increase the distance between adjacent component chips.

[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 heated to between 250°C and 270°C during the bonding step. If the polyester film is made of polyethylene naphthalate, it is 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 a transmission wavelength suitable for the wafer is applied to the wafer to form a modified layer in the wafer along each division line, thus splitting the wafer along each division line to obtain individual component chips attached to the polyester film.The polyester film is then cooled in each of the several separate areas within the film, corresponding to a specific component chip. Each component chip is then pushed up through the polyester film, thus being picked up by the film. Each picked-up component chip is subsequently attached to a predetermined mounting substrate or similar. Note that cooling the polyester film during the pick-up process causes it to shrink, facilitating separation and thus reducing the load applied to each component chip.

[0016] During the formation of a modified layer in the wafer, leakage light from the laser beam reaches the polyester film. However, since the polyester film lacks an adhesive layer, there is no problem with melting the adhesive layer to attach it to the back or front 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 quality of each component chip being reduced by the adhesion of the adhesive layer to each component chip.

[0017] Thus, the wafer processing method according to one aspect of the present invention can have the effect that the adhesive layer does not adhere to the back or front 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. 1A is a schematic perspective view of the front side of a wafer; Fig. 1B is a schematic perspective view of the back of the 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 8A is a schematic perspective view representing a division step; Fig. 8B is a schematic sectional view showing the 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 1A is a schematic perspective view of the front side of a wafer 1. Fig. Figure 1B is a schematic perspective view of the back side of the wafer. 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 side 1a and a back side 1b. Several intersecting division lines 3 are formed on the front side 1a of the wafer 1 to define several separate regions in which multiple devices 5, such as ICs, LSIs, and LEDs, are implemented.The intersecting division lines 3 are formed from 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, several modified layers are formed within the wafer 1 along the respective intersecting division lines 3, thereby dividing the wafer 1, with the modified layers as division start points, into several individual component chips, each containing the component 5.

[0020] During the formation of a modified layer in wafer 1, a laser beam with a transmission wavelength for wafer 1 is applied along each of the division lines 3 onto wafer 1, thereby focusing the laser beam within wafer 1. At this point, the laser beam can be directed from the in Fig. 1A front side 1a or from the side shown in Fig. The laser beam is applied to the back side 1b shown in Figure 1B on the wafer 1. Note that in a case where the laser beam can be applied to the wafer 1 from the back side 1b, an alignment device with an infrared camera is used to detect each of the division lines 3 from the front side 1a through the wafer 1, so that the laser beam is applied to the wafer 1 along each of the division lines 3.

[0021] The laser processing to form a modified layer in the wafer 1 is carried out using a laser processing device 12 (see Fig. 8) Before loading the wafer 1 into the laser processing device 12, the wafer 1 is 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. The polyester film 9 is then expanded to divide the wafer 1, thereby obtaining the individual component chips, each component chip being supported by the polyester film 9. The polyester film 9 is then further 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.

[0022] 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 film made of a polymer (polyester) 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, i25. The polyester film 9 is a thermoplastic film such that, when 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.

[0023] 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.

[0024] In the polyester film preparation step, the wafer 1 and the ring frame 7 are first prepared as described in Fig. The wafer is positioned on the holding surface 2a of the clamping table 2, as shown in Figure 2. In this state, the wafer is positioned in the inner opening 7a of the ring frame 7. At this point, the orientation of the wafer 1 is selected, taking into account whether the front side 1a or the back side 1b is the deposition surface onto which the laser beam is to be applied in the subsequent division step. For example, if the front side 1a is selected as the deposition surface, the front side 1a is oriented downwards. Alternatively, if the back side 1b is selected as the deposition surface, the back side 1b is oriented downwards. A wafer processing method according to the preferred embodiment is described below as an example, assuming the case in which the front side 1a is selected as the deposition surface of the laser beam. However, the orientation of the wafer 1 is not limited to this.

[0025] After the wafer 1 and the frame 7 are placed on the holding surface 2a of the clamping table 2, the polyester film 9 is provided on the back 1b (or the front 1a) (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.

[0026] 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.

[0027] The polyester film 9 is then heated to a state in which it is drawn in by the vacuum source 2b, thereby performing 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 blower 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.

[0028] Another method can be used to heat the polyester film 9. For example, any element heated to a predetermined temperature can be pressed onto the polyester film 9 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.

[0029] 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 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 the heating roller 6 to press the polyester film 9, 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 against the polyester film 9 held on the clamping table 2.

[0030] 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.

[0031] 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.

[0032] 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 circumference of the inner opening 7a of the ring frame 7) and the outer circumference of the ring frame 7 are arranged and 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 polyester film 9 is surrounded by the circular cutting track 9a. Subsequently, a remaining circumferential section of the polyester film 9 outside the circular cutting track 9a is removed. This means that an unwanted circumferential section of the polyester film 9, including an outermost circumferential section outside the outer circumference of the ring frame 7, can be removed.

[0033] 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 is formed from 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 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.

[0034] 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.

[0035] 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.

[0036] 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 in practice, 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.

[0037] 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 a laser beam to form several modified layers along the multiple intersecting division lines 3 within the wafer 1, thereby dividing the wafer 1 into individual component chips. In this preferred embodiment, the division step is performed using a Fig. 8A shown laser processing device 12 was carried out. Fig. 8A is a schematic perspective view illustrating the division step. Fig. 8B is a schematic sectional view illustrating the division step. As in Fig. As shown in Figure 8A, the laser processing device 12 comprises a laser processing unit 14 for applying a laser beam 16 to 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 the laser beam 16 with a transmission wavelength suitable for the wafer 1 (which has a wavelength that is transmissible to 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., movable in a feed direction. The laser beam 16 generated by the laser oscillator in the laser processing unit 14 is applied to the wafer 1 held on the clamping table.The laser processing unit 14 further comprises a processing head 14a with a mechanism for positioning a focal point 14b of the laser beam 16 at a predetermined vertical position within the wafer 1.

[0038] During laser processing 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 device 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. The focal point 14b of the laser beam 16 is then positioned at a predetermined vertical position. Finally, the laser beam 16 is applied within the wafer by the laser processing unit 14.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. In particular, the focal point 14b of the laser beam 16 is positioned within the wafer 1, and the laser beam 16 is applied to the wafer 1 along the predefined division lines 3. Consequently, the modified layer 3a is formed within the wafer 1. Note that in . Fig. Figure 8A shows the modified layer 3a formed within wafer 1, indicated by dashed lines. Accordingly, a division groove 3a is formed in wafer 1 along the predefined division line 3 by the laser beam 16. The division groove 3a has a depth from the front face 1a to the back face 1b of 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: 1064 nm Repetition frequency: 50 kHz Average power consumption: 1 W Feed rate: 200 mm / s

[0039] After forming the modified layer 3a within the wafer 1 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 laser processing along the next parting line 3 extending in the first direction. Laser processing is then performed similarly along all other parting lines 3 extending in the first direction. Thus, several similar modified layers 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 laser processing similarly along all parting lines 3 extending in the second direction perpendicular to the first.Thus, several similar modified layers 3a are formed along all division lines 3 extending in the second direction.

[0040] When the laser beam 16 is focused by the laser processing unit 14 within the wafer 1 to form the modified layer 3a, leakage light from the laser beam 16 reaches the polyester film 9 beneath the wafer 1. For example, if an adhesive tape is used in the frame unit 11 instead of the polyester film 9, when the leakage light from the laser beam 16 is applied to an adhesive layer of the adhesive tape, the adhesive layer of the adhesive tape melts, causing part of the adhesive layer to adhere to the back 1b of the wafer 1. In this case, the portion of the adhesive layer remains on the back of each of the component chips formed by parting the wafer 1. Consequently, a reduction in the quality of each component chip occurs. In comparison, in the wafer processing method according to the present embodiment, the polyester film 9 is used without an adhesive layer in the frame unit 11.Accordingly, even if the leakage light of the laser beam 16 reaches the polyester film 9, the adhesive layer is not attached to the back 1b of the wafer 1. Thus, the quality of each component chip formed from the wafer 1 is advantageously maintained.

[0041] Next, the polyester film 9 is expanded radially outward in one direction, dividing the wafer 1 into individual component chips. After performing the division step, a pick-up step is carried out to pick up each component chip from the polyester film 9. Expansion of the polyester film 9 is achieved using a [missing information - likely a specific feature or process] located in a lower section of [missing information - likely a specific feature or process]. 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 onto the receiving device 18. As 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 via 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.

[0042] 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.

[0043] Furthermore, a lifting mechanism 34 is provided for lifting each component chip carried on the polyester film 9 within the drum 20. The lifting mechanism 34 has a cooling section 34a at its upper end, which contains 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.

[0044] During the expansion of the polyester film 9, each air cylinder 30 in the receiving 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 by the laser processing device 12, is positioned on the drum 20 and the frame support table 26 in the receiving device 18 in a state where the front face 1a of the wafer 1 of the frame unit 11 is 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 several modified layers 3a have already been formed within the wafer 1 along the division lines 3.

[0045] 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 showing the expanded polyester film 9. When the polyester film 9 is expanded, a force is applied to the wafer 1 in a radial outward direction, and the wafer 1 is split with the modified layers 3a as a starting point, forming individual device chips 1c. As the polyester film 9 expands further, the spacing between adjacent device chips 1c supported on the polyester film 9 is increased as shown in Figure 10B. Fig. Figure 10B is shown enlarged. Accordingly, each component chip 1c can be easily accommodated.

[0046] In the wafer processing method according to the present embodiment, a pickup step of picking up the component chips 1c from the polyester film 9 is carried out after the wafer 1 has been divided into individual component chips 1c. In the pickup step, a target of the component chips 1c is selected and the lifting mechanism 34 is then used as shown in 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 section 34a is then activated to reduce its temperature, and the lifting mechanism 34 causes the cooling section 34a to come into contact with an area in the polyester film 9 corresponding to the component chip 1c, thus cooling that area. The lifting mechanism 34 is then activated to lift the target component chip 1c from the side of 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 action is performed similarly for all other component chips 1c.Subsequently, each captured component chip 1c is mounted for actual use on a specified wiring substrate or the like. Note that when the area in the polyester film 9 is cooled by the cooling section 34a, the polyester film 9 shrinks, and a large stress occurs at an interface between the polyester film 9 and the component chips, thus facilitating separation of the polyester film 9. Accordingly, a load applied to the component chip when peeling it from the polyester film 9 is reduced.

[0047] In the case of forming the frame unit 11 using an adhesive strip, the leakage light of the laser beam 16 applied to the wafer 1 reaches the adhesive strip during the division step, 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.

[0048] 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. For example, the polyester film usable in the present invention can be made from any other materials (polyesters) such as polytrimethylene terephthalate, polybutylene 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 a 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 of the ring frame (7) and providing a polyester film (9) on a back or front (1a) of the wafer (1) and on a back 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) to form a frame unit in a state in which the wafer (1) and the front of the ring frame (7) are exposed; a division step of positioning a focal point of a laser beam within the wafer (1), wherein the laser beam has a transmission wavelength for the wafer (1), and of applying the laser beam to the wafer (1) along each division line (3), thereby forming a modified layer in the wafer (1) along each division line (3) to divide the wafer (1) into the individual component chips (1c), after performing the interconnection step; and a pickup step of cooling the polyester film (9) in each of the several separate areas corresponding to a respective component chip (1c), pushing up each component chip (1c) through the polyester film (9) and then picking 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 comprises a step of widening the polyester film (9) in order to increase the distance between 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. [9] Wafer processing method according to one of the preceding claims, wherein the joining step comprises a step of supplying hot air to the polyester film (9), whereby thermocompression joining is carried out. [10] Wafer processing method according to one of claims 1-8, wherein the joining step comprises a step of pressing and heating the polyester film (9) by a heat roller (6), whereby thermocompression joining is carried out.

Images