Wafer processing methods

Abstract

A wafer processing method for processing a wafer (W) having a device surface (602) where a plurality of devices (601) are formed respectively in a plurality of regions separated by a plurality of intersecting dividing lines, and a peripheral edge surface (603) surrounding the device surface (602) formed on a front side (W1) of the wafer (W), the wafer processing method comprising: a tape attachment step of attaching a ring adhesive tape (611) having a ring-shaped adhesive layer (612) on a peripheral surface thereof to the front surface (W1) of the wafer (W) in the state where the front surface (W1) of the wafer (W) is completely covered with the ring adhesive tape (611) and the ring-shaped adhesive layer (612) is arranged to coincide with the peripheral edge surface (603) of the wafer (W); a layer change forming step of holding the wafer (W) on a holding table in the state where the ring adhesive tape (611) attached to the front side (W1) of the wafer (W) comes into contact with the holding table, and then applying a laser beam having a transmission wavelength from the back side (W2) of the wafer (W) along the dividing lines to the wafer (W), thereby forming a plurality of changed layers (641) within the wafer (W) along the dividing lines after performing the tape attachment step; a ring adhesive tape peeling step for applying a protective tape (651) to the back side (W2) of the wafer (W) and peeling the ring adhesive tape (611) from the front side (W1) of the wafer (W) after performing the layer change forming step; and after performing the ring adhesive tape peeling step, a dividing step of applying an external force to the wafer (W) to divide the wafer (W) along the dividing lines where the altered layers (641) are respectively formed as dividing start points, thereby obtaining a plurality of individual device chips (661).

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a wafer processing method for dividing a wafer having a microstructure on the front surface thereof, and more particularly to a wafer processing method for dividing a MEMS wafer or a CMOS wafer. State of the art

[0002] A wafer having a plurality of MEMS (Micro-Electro-Mechanical Systems) devices formed on the front surface thereof is divided along a plurality of intersecting division lines to separate these MEMS devices, thereby obtaining a plurality of individual device chips. When such a MEMS wafer is diced by a knife, there is a possibility that cutting water will scatter on the microstructure of the MEMS devices, resulting in damage to the microstructure. To address this problem, a method for dividing a MEMS wafer has been proposed in which a protective tape is attached to the front surface of the MEMS wafer, and then a laser beam is applied to the MEMS wafer from the back surface thereof (see, for example, Japanese Patent Laid-Open Publication No. JP 2006-140341 A).

[0003] In the case where a wafer having a plurality of semiconductor imaging devices, such as CMOS (Complementary Metal Oxide Semiconductor) devices formed on the front surface thereof, is cut into individual chips by a knife, there is a possibility that a waste or the like may adhere to the front surface of each device, leading to device failure. To address this problem, a cutting method using a protective tape attached to the front surface of such a CMOS wafer is also employed.

[0004] JP 2011- 23 659 A relates to a wafer processing method.

[0005] US 2011 / 0 308 739 A1 relates to a method for removing a wafer from a substrate. SUMMARY OF THE INVENTION

[0006] However, in the case where the protective tape is applied to the front side of the MEMS wafer where the MEMS devices are formed, a problem arises because the device structures of the MEMS may be damaged by the adhesive force of an adhesive layer formed on the protective tape upon peeling the protective tape from the MEMS wafer. Furthermore, a problem also arises during peeling of the protective tape from the CMOS wafer because the adhesive layer may adhere to the semiconductor imaging devices, leading to device failure.

[0007] It is therefore an object of the present invention to provide a wafer processing method which can divide a wafer into individual device chips without damaging or contaminating the front side of the wafer.

[0008] According to one aspect of the present invention, there is provided a wafer processing method for processing a wafer having a device surface where a plurality of devices are respectively formed in a plurality of regions separated by a plurality of intersecting dividing lines and a peripheral edge surface surrounding the device surface formed on a front surface of the wafer, the wafer processing method comprising a tape attaching step of attaching a ring-shaped adhesive tape having a ring-shaped adhesive layer on only one peripheral surface thereof to the front surface of the wafer in the state where the front surface of the wafer is completely covered with the ring-shaped adhesive tape and the ring-shaped adhesive layer is arranged to correspond to the peripheral edge surface of the wafer;A layer-alteration forming step of holding the wafer on a holding table in the state where the ring adhesive tape attached to the front side of the wafer comes into contact with the holding table, and then applying a laser beam having a transmission wavelength from the back side of the wafer along the dividing lines to the wafer, thereby forming a plurality of altered layers within the wafer along the dividing lines after performing the tape attachment step; A ring adhesive tape peeling step of applying a protective tape to the back side of the wafer and peeling the ring adhesive tape from the front side of the wafer after performing the layer-alteration forming step;and after performing the ring adhesive tape peeling step, a dividing step of applying an external force to the wafer to divide the wafer along the dividing lines where the altered layers are respectively formed as dividing starting points, thereby obtaining a plurality of individual device chips.;

[0009] In this embodiment, the device surface where the plurality of devices are formed is protected by the annular adhesive tape, so that modified layers can be formed within the wafer without damaging the device surface. The annular adhesive layer of the annular adhesive tape is arranged to coincide only with the peripheral edge surface formed on the front side of the wafer, so that the annular adhesive layer does not adhere to the device surface formed on the front side of the wafer. Accordingly, when peeling the annular adhesive tape from the front side of the wafer, there is no possibility of the device surface being damaged or contaminated by the annular adhesive tape.

[0010] Preferably, the wafer processing method of the present invention further comprises a grinding and polishing step of holding the wafer on a second holding table in a state where the ring adhesive tape attached to the front side of the wafer comes into contact with the second holding table, then grinding the back side of the wafer using abrasives, and then polishing the back side of the wafer by using polishing agents after performing the tape attaching step and before performing the layer change forming step.

[0011] Preferably, the protective tape attached to the back surface of the wafer in the ring adhesive tape peeling step is formed of an expandable member; and the wafer processing method further includes an expanding step of expanding the protective tape to increase the pitch of the device chips after performing the dividing step.

[0012] According to the present invention, the ring adhesive tape is attached to the front side of the wafer in the state where the ring-shaped adhesive layer formed on the peripheral surface of the ring adhesive tape is arranged to coincide with the peripheral edge surface of the wafer, so that it is possible to prevent damage or staining of the device surface of the wafer.

[0013] The above and other objects, features and advantages of the present invention and the manner of carrying them out will become more apparent and the invention itself best understood by studying the following description and the appended claims with reference to the accompanying drawings which show some preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a ring adhesive tape and a wafer; Fig. 2 is a perspective view of a grinding device; Fig. 3 is a perspective view of a laser processing apparatus; Fig. 4 is a perspective view of a stretching device; Fig. 5A to 5E are sectional side views illustrating the flow of a wafer processing method according to a first preferred embodiment of the present invention; and Fig. 6A to 6F are cross-sectional side views illustrating the flow of a wafer processing method according to a second preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] A wafer processing method according to a first preferred embodiment of the present invention will now be described with reference to the accompanying drawings. Division of a wafer using the wafer processing method according to the first preferred embodiment is achieved through a tape attachment step, a grinding and polishing step using a grinder and a polishing device, a layer variation forming step using a laser processing device, a ring adhesive tape peeling step using a tape attachment / peeling device, and a division step using a stretching device. In the tape attachment step, a ring adhesive tape is attached to the front surface of a wafer on which a plurality of devices are formed.The ring adhesive tape has an adhesive layer on only one peripheral surface thereof so that the adhesive layer is prevented from adhering to a device surface formed as a central surface of the wafer.

[0015] In the grinding and polishing step, the back surface of the wafer is ground to reduce the thickness of the wafer to a predetermined thickness and then polished. In the layer variation forming step, a laser beam is applied to the wafer from the back surface thereof to continuously form a varied layer within the wafer along each dividing line. In the ring adhesive tape peeling step, a protective tape is attached to the back surface of the wafer, and the ring adhesive tape is peeled off from the front surface of the wafer. In the dividing step, an external force is applied to the wafer to thereby divide the wafer along the varied layers as dividing starting points to thereby obtain individual device chips. The wafer processing method according to the present embodiment will now be described in further detail.

[0016] The ring adhesive tape to be attached to the wafer in the tape attaching step will now be described with reference to Fig. 1. Attaching the ring adhesive tape in the tape attaching step can be performed manually by an operator or by using a tape attaching device not shown. As shown in Fig. 1, a plurality of intersecting division lines are formed on a front surface W1 of a substantially circular wafer W, thereby forming a plurality of rectangular regions where a plurality of devices 601 are respectively formed. These devices 601 are formed in a central surface of the wafer W. The front surface W1 of the wafer W includes a device surface 602 where the plurality of devices 601 are formed, and a peripheral edge surface 603 surrounding the device surface 602. The outer periphery of the wafer W is formed with a notch 604 to indicate the crystal orientation of the wafer W.

[0017] In this preferred embodiment, the wafer W is an MEMS wafer having MEMS devices formed on the front surface thereof. However, the wafer W is not limited to such MEMS wafers, but may also be a CMOS wafer having CMOS devices as semiconductor imaging devices formed on the front surface thereof. Further, the wafer W may be a silicon wafer configured by forming devices such as ICs and LSIs on a silicon substrate, or an optical device wafer configured by forming optical devices such as LEDs (Light Emitting Diodes) on an inorganic material substrate made of ceramic, glass, or sapphire.

[0018] A ring adhesive tape has a circular shape and has an outer diameter substantially identical to that of the wafer W. The ring adhesive tape 611 is formed of polyolefin or the like. An annular adhesive layer 612 is formed on one side of the ring adhesive tape 611 on its peripheral surface along the outer circumference. The annular adhesive layer 612 is formed by applying an acrylic resin containing a UV (ultraviolet) curable component. The annular adhesive layer 612 has a width that lies within the peripheral edge surface 603 of the wafer W to which the ring adhesive tape 611 is to be applied. Accordingly, the ring adhesive tape 611 is applied to the front side W1 of the wafer W in such a manner that the annular adhesive layer 612 adheres only to the peripheral edge surface 603.That is, the device surface 602 is protected by the ring adhesive tape 611 without adhesion of the ring-shaped adhesive layer 612 to the device surface 602. After performing the tape attachment step in which the ring adhesive tape 611 is attached to the front surface W1 of the wafer W as mentioned above, the wafer W is transferred to a grinding apparatus 100 shown in FIG. Fig. 2 is shown.

[0019] While the annular adhesive tape 611 has substantially the same size as the wafer W in this preferred embodiment, the configuration of the annular adhesive tape 611 is not limited to the above configuration. That is, it is appropriate that the annular adhesive tape 611 has a size to completely cover the front surface W1 of the wafer W, and that the annular adhesive layer 612 is formed to adhere only to the peripheral edge surface 603 of the wafer W. Further, the annular adhesive layer 612 may be formed of a liquid resin curable by external stimulation. For example, a thermosetting resin curable by heat may be used. The external stimulation mentioned above includes not only ultraviolet radiation and heat, but also, for example, radiation, electron beams, electric fields, and chemical reactions.

[0020] A grinding apparatus 100 for reducing the thickness of the wafer and a polishing apparatus (not shown) for polishing the wafer in the grinding and polishing step will now be described with reference to Fig. 2. The polishing apparatus is substantially similar in structure to the grinding apparatus 100, and only one difference will be described below. The grinding apparatus and polishing apparatus that can be used in the present invention are not limited in structure to that used in the present embodiment. It is important to note that the grinding apparatus can have any structure capable of reducing the thickness of the wafer, and the polishing apparatus can have any structure capable of polishing the wafer.

[0021] As in Fig. 2, the grinding apparatus 100 is configured to grind the wafer W by relatively rotating a chuck table 102 holding the wafer W thereon and a grinding wheel 131. The grinding apparatus 100 includes a box-like base 101. An operation panel 111 for inputting operator commands to the grinding apparatus 100 is provided on the upper surface of the front end portion of the base 111. The upper surface of the base 101 is formed with a recess 112 extending in the Y direction in a portion on the rear side of the operation panel 111. A column 113 for supporting a grinding unit 103 is formed at a rear end of the base 101 so as to extend vertically at the rear side of the recess 112.The chuck table 102 is supported on a moving plate 121 so as to be movable in the Y direction, and a pair of front and rear bellows-shaped waterproof covers 122 are connected to the front and rear ends of the moving plate 121. The entire chuck table 102, the moving plate 121, and the waterproof covers 122 are provided in the recess 112. A ball screw-like moving mechanism (not shown) for moving the chuck table 102 in the Y direction is provided under the waterproof covers 122. The chuck table 102 is movable on both sides in the Y direction between a loading position where the wafer W is received and a grinding position where the wafer W held on the chuck table 102 faces the grinding unit 103.

[0022] The chuck table 102 has a circular shape and is rotatably provided on the upper surface of the moving plate 121. The upper surface of the chuck table 102 is formed as a holding surface 123 for holding the wafer W under suction. The holding surface 123 is formed of a porous ceramic material. The wafer W is held under suction on the holding surface 123 of the chuck table 102 in the state where the ring adhesive tape 611 attached to the front side W1 of the wafer W is arranged downward.

[0023] A grinding unit moving mechanism 104 for vertically moving the grinding unit 103 is provided on the front surface of the column 113. The grinding unit moving mechanism 104 includes a pair of parallel guide rods 141 extending vertically in the Z direction and a motor-driven Z-axis table 142 movably mounted on the guide rods 141 so as to be movable in the Z-axis direction. A nut portion (not shown) is formed on the rear surface of the Z-axis table 142, and a ball screw 143 is screw-engaged with this nut portion. A servo motor 144 is connected to one end of the ball screw 143. Accordingly, the ball screw 143 is rotatably driven by the servo motor 144.

[0024] The grinding unit 103 is supported by a support member 145 on the front surface of the Z-axis table 142. The grinding unit 103 includes a cylindrical spindle housing 132, a spindle 134 rotatably received in the spindle housing 132, and a grinding wheel 131 fixed to the lower end of the spindle 134. A plurality of grinding elements 133 are attached to the lower surface of the grinding wheel 131. Each grinding element 133 is formed of a diamond grinding element formed by bonding diamond abrasive particles with a bonding agent such as a metal adhesive or a resin adhesive. The grinding elements 133 are arranged in a ring shape and rotate at high speed around the Z-axis by driving the spindle 134.The grinding surface (lower surface) of each grinding member 133 is brought into contact with the back surface W2 (upper surface) of the wafer W held on the chuck table 102 in the state where the grinding wheel 133 and the chuck table 102 are rotated in a mutually parallel state, whereby the back surface W2 of the wafer W is ground to reduce the thickness of the wafer W to a predetermined thickness.

[0025] Subsequently, the wafer W, which has been ground by the grinding apparatus 100 as explained above, is transferred to the polishing apparatus (not shown). This polishing apparatus is configured to perform, for example, dry polishing or CMP (Chemical Mechanical Polishing). Dry polishing can be performed using a polishing tool provided by a felt polishing agent obtained by dissolving polishing particles in a felt and fixing the polishing particles with a suitable binder. This polishing apparatus polishes the back surface W2 of the wafer W, which has been previously ground, to thereby suppress scattering of a laser beam applied to the wafer W from the back surface thereof in the subsequent layer variation formation step.

[0026] After polishing the back surface W2 of the wafer W as described above, the wafer W is mounted on a support belt (saw belt) 632, the peripheral portion of which is preliminarily attached to a ring frame 631 in the state where the ring adhesive belt 611 attached to the front surface W1 of the wafer W is oriented downward (see Fig. 3). The wafer W attached to the support belt 632 is formed into a Fig. 3. The laser processing apparatus 200 for forming the modified layers within the wafer W in the layer modification forming step will now be described with reference to Fig. 3. The laser processing apparatus that can be used in the present invention is not limited to the Fig. 3, but it is essential that the laser processing device has any configuration that is capable of forming the modified layers within the wafer.

[0027] As in Fig. 3, the laser processing apparatus 200 is configured to process the wafer W by relatively moving a laser processing unit 203 for applying a laser beam to the wafer W and a chuck table 202 for holding the wafer W. The laser processing apparatus 200 includes a box-like bed portion 201. On the upper surface of the bed portion 201, a chuck table moving mechanism 204 is provided for feeding the chuck table 202 in the X direction and moving the chuck table 202 in the Y direction. A column portion 211 is provided on the upper surface of the bed portion 201 at its rear end so as to extend vertically on the rear side of the chuck table moving mechanism 204. An arm portion 212 protrudes from the front surface of the column portion 211, and the laser processing unit 203 is fixed to the arm portion 212 so as to face the chuck table 202.

[0028] The chuck table moving mechanism 204 includes a pair of parallel guide rails 241 provided on the upper surface of the bed portion 201 to extend in the X direction, and a motor-driven X-axis table 242 movably mounted on the guide rails 241 in the X direction. The chuck table moving mechanism 204 further includes a pair of parallel guide rails 243 provided on the upper surface of the X-axis table 242 to extend in the Y-axis direction, and a motor-driven Y-axis table 244 movably mounted on the guide rails 243.

[0029] The chuck table 202 is provided on the upper surface of the Y-axis table 244. Although not shown, a nut portion is formed on the lower surface of the X-axis table 242, and a nut portion is provided on the lower surface of the Y-axis table 244. A ball screw 245 is threadably engaged with the nut portion of the X-axis table 242, and a ball screw 246 is threadably engaged with the nut portion of the Y-axis table 244. A servo motor 247 is connected to one end of the ball screw 245, and a servo motor 248 is connected to one end of the ball screw 246. Accordingly, the X-axis table 242 is moved along the guide rails 241 in the X-axis direction by operating the actuator 247, and the Y-axis table 244 is moved along the guide rails 243 in the Y-axis direction by operating the actuator 248, so that the chuck table 202 is moved in the X-axis direction and Y-axis direction.

[0030] The chuck table 202 has a circular shape and is rotatably supported by a θ-table 221 on the upper surface of the Y-axis table 244. The upper surface of the chuck table 202 is formed as a holding surface 222 for holding the wafer W under suction. The holding surface 222 is formed of a porous ceramic material. Four clamps 223 are provided at identical intervals around the chuck table 202 in such a shape that each clamp 223 is supported by a pair of radially extending support arms. These four clamps 223 are driven by an actuator to hold the ring frame 631, which holds the wafer W via the support belt 623.

[0031] The laser processing unit 203 includes a laser head 231 provided at the front end of the arm portion 212. Although not shown, an optical system of the laser processing unit 203 is provided in the arm portion 212 on the laser head 231. The laser head 231 includes a focusing lens for focusing a laser beam oscillated by an oscillator (not shown) to laser process the wafer W held on the chuck table 202. The laser beam has a transmission wavelength to the wafer W, and the focal point of the laser beam is set within the wafer W by the optical system.

[0032] By operating the laser beam applied to the wafer W by the laser head 231, a modified layer 641 (see Fig. 5C) as a division starting point within the wafer W along each division line. Each altered layer 641 means a region that is different from its surrounding region in density, refractive index, strength, or other physical properties in the wafer W due to the application of the laser beam, resulting in a reduction in strength compared to the surrounding region. Examples of each altered layer 641 include a melted and re-hardened region, a cracked region, a fractured region, and a region with an altered refractive index. These regions may exist in a mixed state.

[0033] By performing the layer alteration forming step using the laser processing apparatus 200, the Y-axis table 244 is moved so that a laser beam output of the laser head 231 is aligned with a predetermined one of the dividing lines of the wafer W. Subsequently, the laser beam from the laser head 231 is applied to the wafer W, and the X-axis table 242 is moved to thereby form the altered layer 641 within the wafer W along the predetermined dividing line. This laser processing is performed similarly along all the dividing lines to form a plurality of altered layers 641 along all the other dividing lines. Subsequently, the wafer W is transported to a tape applying / peeling device (not shown) to be used in performing the ring adhesive tape peeling step.

[0034] By performing the ring adhesive tape peeling step using the tape attaching / peeling device, a protective tape 651 having an expandability is attached to the back surface W2 of the wafer W, and the ring adhesive tape 611 is peeled off from the front surface W1 of the wafer W together with the support tape 632 (see Fig. 5D). By such a tape attachment / peeling process, the front side W1 of the wafer W is exposed, and the back side W2 of the wafer W, which is to be held in the subsequent dividing step, is protected by the protective tape 651.

[0035] The annular adhesive layer 612 of the annular adhesive tape 611 is attached only to the peripheral edge surface 603 of the wafer W. Accordingly, by peeling the annular adhesive tape 611 from the front side W1 of the wafer W, there is no possibility that the device surface 602 may be damaged or contaminated by the annular adhesive layer 612. While the tape application process for applying the protective tape 651 to the back side W2 of the wafer W and the tape removal process for removing the annular adhesive tape 611 from the front side W1 of the wafer W are performed by the tape application / removal device in the present embodiment, the tape application process and the tape removal process may be performed separately by individual devices. After performing the annular adhesive tape removal step as described above, the wafer W is transferred to a stretching device 300, which is in Fig. 4, is transported in the state where the front side W1 where the devices 601 are formed is oriented upward.

[0036] The stretching device 300 for stretching the protective tape 651 to thereby divide the wafer W in the dividing step will now be described with reference to Fig. 4. The stretching device that can be used in the present invention is not limited to the configuration shown in Fig. 4, but it is essential that the expansion device may have any configuration capable of dividing the wafer along the altered layers as division starting points.

[0037] As in Fig. As shown in Figure 4, the protective tape 651 is preliminarily fixed at its peripheral portion to a ring frame 652. The stretching device 300 is configured to move a ring table 302, which holds the ring frame 651, relative to a stretching drum 303 to thereby stretch the protective tape 651. The stretching device 300 has a substantially circular base 301, and the stretching drum 303, which has a cylindrical shape, is provided on the upper surface of the base 301 at its central portion. Four moving mechanisms 304 are provided on the upper surface of the base 301 so as to surround the cylindrical surface of the stretching drum 303.

[0038] Each moving mechanism 304 includes an air cylinder 341 and a piston rod 342 extending upward from the air cylinder 341. The ring table 302 is connected to the upper end of each piston rod 342. When the ring frame 652 is placed on the ring table 302, the wafer W is placed just above the expansion drum 303. Four clamps 321 for clamping the ring frame 652 are provided at identical intervals on the outer circumference of the ring table 302. Further, a lifting jig 500 for lifting each device chip under suction after dividing the wafer W is arranged above the expansion drum 303.

[0039] The outer diameter of the expansion drum 303 is smaller than the inner diameter of the ring frame 652, and the inner diameter of the expansion drum 303 is larger than the outer diameter of the wafer W. Accordingly, the upper end of the expansion drum 303 is disposed between the outer periphery of the wafer W and the inner periphery of the ring frame 652. Since the protective tape 651 is attached to the back side W2 of the wafer W, the upper end of the expansion drum 303 is configured to abut against the protective tape 651 in an annular area formed between the outer periphery of the wafer W and the inner periphery of the ring frame 652.

[0040] Then, performing the dividing step using this stretching device 300, the moving mechanisms 304 are operated to lower the ring table 302 holding the ring frame 652. As a result, the stretching drum 303 is relatively raised with respect to the ring table 302, so that the protective tape 651 is pushed upward by the upper end of the stretching drum 303 and is thereby radially expanded. When the protective tape 651 is stretched, an external force is applied to the altered layers 641 within the wafer W. As a result, the wafer W is divided along the dividing lines where the altered layers 641 are formed as division starting points, thereby forming a plurality of individual device chips 661 (see Fig. 5E). Subsequently, the protective tape 651 is further extended to increase the distance between the device chips 661, which are separated from each other. Each device chip 661 is then peeled off the protective tape 651 and lifted under suction by the lifting receptacle 500.

[0041] The flow of the wafer processing method according to the first preferred embodiment will now be described with reference to Fig. 5A to 5E. The steps described in Fig. 5A to 5E are merely illustrative and the steps of the wafer processing method according to the present invention are not limited to those shown in Fig. 5A to 5E. First, the tape application step shown in Fig. 5A is shown. As shown in Fig. As shown in Fig. 5A, the ring adhesive tape 611 is attached to the front side W1 of the wafer W where the device surface 602 is formed. The ring adhesive layer 612 is preliminarily formed on the ring adhesive tape 611 on its peripheral surface corresponding to the peripheral wall surface 603 of the wafer W. Accordingly, the ring-shaped adhesive layer 612 adheres only to the peripheral edge surface 603 of the wafer W, so that no adhesive adheres to the device surface 602 of the wafer W. Furthermore, the device surface 602 of the wafer W is protected by the ring adhesive tape 611 in its central surface where the ring adhesive layer 612 is not formed. This tape attachment step can be performed manually by the operator or by using a tape attachment device not shown.

[0042] The Fig. The grinding and polishing step shown in Figure 5B is then carried out. As shown in Fig. As shown in Figure 5B, the ring adhesive tape 611 is attached to the front side W1 of the wafer W held on the chuck table 102. The grinding elements 133 are rotated and brought into contact with the back side W2 of the wafer W, thereby grinding the back side W2 of the wafer W. After the thickness of the wafer W is reduced to the predetermined thickness by this grinding process, the back side W2 of the wafer W is polished using the polishing device not shown. By grinding the back side W2 of the wafer W to reduce the thickness of the wafer W and then polishing the back side W2 of the wafer W, the wafer W is processed to be suitable for the formation of the modified layers 641. Subsequently, the ring adhesive tape 611 attached to the front side W1 of the wafer W is attached to the support table 632 supported on the ring frame 631 (see Fig. 5C).

[0043] The shift change training step, which is Fig. 5C is then executed. As shown in Fig. As shown in Fig. 5C, the support tape 632, which is attached to the front surface W1 of the wafer W by the ring adhesive tape 611, is held on the chuck table 202. Further, the laser beam output of the laser head 231 is aligned with a predetermined one of the dividing lines of the wafer W, and the focal point of the laser beam is set within the wafer W. Subsequently, the laser beam is applied from the laser beam output of the laser head 231, and the chuck table 202 holding the wafer W is moved in the X direction to thereby move the modified layer 641, which has a predetermined thickness within the wafer W, along the predetermined dividing line. Since the back surface W2 of the wafer W is polished, scattering of the laser beam applied to the back surface W2 of the wafer W can be suppressed.Subsequently, the chuck table 202 is moved in the Y direction to similarly form the modified layers 641 within the wafer W along all other division lines extending in a first direction. Subsequently, the chuck table 202 is rotated 90° to similarly form the modified layers 641 within the wafer W along all other division lines extending in a second direction perpendicular to the first direction.

[0044] The ring adhesive tape removal step, which Fig. 5D is then executed. As shown in Fig. 5D, the protective tape 651 is supported by the ring frame 652 attached to the back surface W2 of the wafer W, and the ring adhesive tape 611 is peeled off from the front surface W1 of the wafer W together with the support tape 632. Since the ring-shaped adhesive layer 612 of the ring adhesive tape 611 does not adhere to the device surface 602 on the front surface W1 of the wafer W, there is no possibility that the devices 601 are damaged by the adhesive forces of the ring-shaped adhesive layer 612 or that adhesive remains on the devices 601.

[0045] The division step, which is Fig. 5E is then executed. As shown in Fig. As shown in Fig. 5E, the ring frame 652 supporting the support tape 651 is held on the ring table 302 and fixed by the clamps 321. Subsequently, the expansion drum 303 is relatively raised with respect to the ring table 302 to thereby expand the protective tape 651, so that an external force is applied to the altered layers 641 formed inside the wafer W. As a result, the wafer W is divided along the altered layers 641 as the division starting points to thereby obtain the individual device chips 661. After such division of the wafer W, the protective tape 651 is further expanded to increase the distance between the device chips 661 to facilitate peeling off each device chip 661 from the protective tape 651. In such a state where the pitch of the device chips 661 has been increased, each device chip 661 is peeled off from the protective tape 651 and lifted under suction by the lifting receptacle 500.

[0046] According to the first preferred embodiment of the present invention, as described above, the device surface 602 is protected by the annular adhesive tape 611. Accordingly, the modified layers 641 can be formed within the wafer W without damaging the device surface 602. That is, the annular adhesive layer 612 of the annular adhesive tape 611 is arranged to coincide only with the peripheral edge surface 603 formed on the front surface W1 of the wafer W. Accordingly, the annular adhesive layer 612 does not adhere to the device surface 602 formed on the front surface W1 of the wafer W. As a result, when the annular adhesive tape 611 is peeled off from the front surface W1 of the wafer W, there is no possibility that the device structure of the MEMS may be damaged by the adhesive force of the annular adhesive layer 612.

[0047] A wafer processing method according to a second preferred embodiment of the present invention will now be described. Division of the wafer using the wafer processing method according to the second preferred embodiment is achieved through a tape attachment step, a grinding and polishing step using a grinder and a polishing device, a layer variation forming step using a laser processing device, a ring adhesive tape peeling step using a tape attachment / peeling device, a division step using a breaking device, and an expanding step using an expanding device.The second preferred embodiment is different from the first preferred embodiment in the point that the dividing step is carried out using a breaking device, and the wafer divided by the dividing step undergoes the expanding step.

[0048] The flow of the wafer processing method according to the second preferred embodiment will now be described with reference to Fig. 6A to 6F. The steps described in Fig. 6A to 6F are merely illustrative and the steps of the wafer processing method according to the present invention are not limited to those shown in Fig. 6A to 6F. The steps shown in Fig. 6A to 6D are the same as in Fig. 5A to 5D. Accordingly, the description of the steps described in Fig. 6A to 6D are omitted here. Furthermore, when the dividing step is performed using a breaking device, the second preferred embodiment is not suitable for dividing a MEMS wafer, which is more susceptible to damage. Accordingly, a CMOS wafer is used here instead of the MEMS wafer in the second preferred embodiment.

[0049] As in Fig. As shown in Fig. 6E, the wafer E attached to the protective tape 651 is transported to the breaking device 400 in the state where the front side W1 on which the devices 601 are formed is facing upward. The breaking device 400 is configured to press a pressing blade 403 against the wafer held on the ring table 402 to thereby divide the wafer W along each changed layer 641 as a division starting point. The ring table 402 is movable in the X direction by a moving mechanism not shown and also rotatable around the Z axis direction by a rotating mechanism not shown. The ring frame 652, which supports the wafer W through the protective tape 651, is held on the ring table 402 and held by four clamps 421 provided on the ring table 402.

[0050] A pair of parallel support beds 405 for supporting a support plate 671 are provided inside the ring table 402.

[0051] The support plate 671 acts to protect the front surface W1 of the wafer W. The outer peripheral portion of the support plate 671 is supported by the ring table 402. The pair of parallel support beds 405 extend in the Y direction, and an imaging means (not shown) is provided between the pair of parallel support beds 405. This imaging means functions to image the front surface W1 of the wafer W through the support plate 671 between the pair of parallel support beds 405. The pressing blade 403 is provided above the pair of parallel support beds 405 and acts to press the wafer W and the support plate 671 downward. The pressing blade 403 extends in the Y direction and is vertically movable by a pressing mechanism (not shown).

[0052] The dividing step using the aforementioned breaking device 400 is carried out in the following manner. First, the wafer W is placed on the pair of parallel support beds 405 by the support plate 671, and the ring frame 652 holding the wafer W by the protective tape 651 is firmly held on the ring table 402 by the clamps 421. The support plate 671 is formed of a material that transmits visible light, so that the front surface W1 of the wafer W is imaged by the support plate 671 through the imaging means disposed below the support plate 671. A predetermined one of the dividing lines formed on the front surface W1 of the wafer W is located between the pair of parallel support beds 405 directly below the pressing blade 403 according to an image obtained by the imaging means.Subsequently, the pressing blade 403 is lowered to press the wafer W downward along this predetermined dividing line where the modified layer 641 is formed as the dividing starting point, thereby dividing the wafer W along the predetermined dividing line. Subsequently, this dividing operation is performed similarly along all the other dividing lines of the wafer W by moving the ring table 402 in the X direction and rotating the ring table 402 around the Z axis. As a result, the wafer W is divided into individual device chips 661.

[0053] The expansion step, which in Fig. 6F is then carried out using the stretching device 300 shown in Fig. 4 is shown. As shown in Fig.As shown in Fig. 6F, the ring frame 652 is firmly held on the ring table 302 by the clamps 321 in the state where the front side W1 of the wafer W is oriented upward. Subsequently, the expansion drum 303 is relatively lifted with respect to the ring table 302 to thereby expand the protective tape 651. As a result, the pitch of the individual device chips 661 is increased. In such a state where the pitch of the device chips 661 has been increased, each device chip 661 is peeled off from the protective tape 651 and lifted under suction by the lifting jig 500.

[0054] According to the second embodiment of the present invention, as described above, the modified layers 641 can be formed within the wafer W without damaging the device surface 602, as in the first preferred embodiment. Further, the annular adhesive layer 612 of the annular adhesive tape 611 is arranged to coincide only with the peripheral edge surface 603 formed on the front surface W1 of the wafer W. Accordingly, the annular adhesive layer 612 does not adhere to the device surface 602 formed on the front surface W1 of the wafer W. As a result, during peeling of the annular adhesive tape 611 from the front surface W1 of the wafer W, there is no possibility of the adhesive of the annular adhesive layer 612 adhering to the semiconductor image devices to cause device failure.

[0055] The present invention is not limited to the above embodiments, but any changes may be made. That is, the configuration of the present invention, such as size and shape, is not limited to the embodiments shown in the accompanying figures, but the configuration may be appropriately changed within the range where the effect of the present invention is apparent. Furthermore, any changes may be made without departing from the scope of the object of the present invention.

[0056] For example, the grinding and polishing step performed in the first and second preferred embodiments is not essential to the present invention. That is, the grinding and polishing step may be omitted provided that the modified layers 641 can be formed within the wafer W. Furthermore, only one of the grinding and polishing steps may be performed in the grinding and polishing step.

[0057] In the first preferred embodiment, the layer change forming step is performed by the laser processing device, the grinding and polishing step is performed by the grinding device and the polishing device, the ring adhesive tape peeling step is performed by the tape attaching / peeling device, and the dividing step is performed by the stretching device. However, all or some of these steps may be performed by a single device. Similarly, in the second preferred embodiment, the layer change forming step is performed by the laser processing device, the grinding and polishing step is performed by the grinding device and the polishing device, the ring adhesive tape peeling step is performed by the tape attaching / peeling device, the dividing step is performed by the breaking device, and the stretching step is performed by the stretching device. However, all or some of these steps may be performed by a single device.

[0058] As described above, the present invention can achieve the effect of dividing the wafer into individual device chips without causing damage or contamination on the front side of the wafer. The present invention is particularly suitable as a wafer processing method for dividing a MEMS wafer or a CMOS wafer.

Claims

[1] A wafer processing method for processing a wafer (W) having a device surface (602) where a plurality of devices (601) are formed respectively in a plurality of regions separated by a plurality of intersecting division lines, and a peripheral edge surface (603) surrounding the device surface (602) formed on a front surface (W1) of the wafer (W), the wafer processing method comprising: a tape attachment step of attaching a ring adhesive tape (611) having a ring-shaped adhesive layer (612) on a peripheral surface thereof to the front surface (W1) of the wafer (W) in the state where the front surface (W1) of the wafer (W) is completely covered with the ring adhesive tape (611) and the ring-shaped adhesive layer (612) is arranged to coincide with the peripheral edge surface (603) of the wafer (W); a layer change forming step of holding the wafer (W) on a holding table in the state where the ring adhesive tape (611) attached to the front side (W1) of the wafer (W) comes into contact with the holding table, and then applying a laser beam having a transmission wavelength from the back side (W2) of the wafer (W) along the dividing lines to the wafer (W), thereby forming a plurality of changed layers (641) within the wafer (W) along the dividing lines after performing the tape attachment step; a ring adhesive tape peeling step for applying a protective tape (651) to the back side (W2) of the wafer (W) and peeling the ring adhesive tape (611) from the front side (W1) of the wafer (W) after performing the layer change forming step; and after performing the ring adhesive tape peeling step, a dividing step of applying an external force to the wafer (W) to divide the wafer (W) along the dividing lines where the altered layers (641) are respectively formed as dividing start points, thereby obtaining a plurality of individual device chips (661). [2] The wafer processing method according to claim 1, further comprising a grinding and polishing step of holding the wafer (W) on a second holding table in the state where the ring adhesive tape (611) attached to the front surface (W1) of the wafer (W) comes into contact with the second holding table, then grinding the back surface (W2) of the wafer (W) using abrasives, and then polishing the back surface (W2) of the wafer (W) using polishing agents, after performing the tape attaching step and before performing the layer change forming step. [3] The wafer processing method according to claim 1, wherein the protective tape (651) attached to the back surface (W2) of the wafer (W) in the ring adhesive tape peeling step is formed of an expandable member; and the wafer processing method further comprises an expanding step of expanding the protective tape (651) to increase the pitch of the device chips (661) after performing the dividing step.

Images