Support plate and method for forming support plates

Abstract

A support plate (11) to which a front surface (25a) of a wafer (25) having a device region (31) in which a plurality of devices (29) are formed and a peripheral excess region (33) surrounding the device region (31) on the front surface is adhered, the support plate (11) comprising: a base plate (13) in which a recess (15) is formed in a front surface region corresponding to the device region (31) of the wafer (25) to be adhered to the support plate, and an annular groove (17) is formed in a region corresponding to the circumferential excess region (33) of the wafer, an upper surface and a side surface of the annular groove (17) being open; and a soft element (19) which is packed into the recess (15) of the base plate (13), wherein the wafer is adapted to be adhered to a front surface of the support plate with an adhesive (23) therebetween by injecting the adhesive into the annular groove (17).

Description

BACKGROUND OF THE INVENTIONTechnical field

[0001] The present invention relates to a support plate that supports a wafer, a method of forming a support plate, and a method of processing a wafer using a support plate. Description of the state of the art

[0002] A semiconductor wafer, on which a large number of devices such as ICs and LSIs are formed on the front side, with the individual devices separated by multiple planned dividing lines (streets) formed in a grid pattern, is machined to a predetermined thickness by grinding the back side with a grinder. Subsequently, the planned dividing lines are cut by a cutter (division saw), dividing the semiconductor wafer into individual devices. The devices obtained by the division are widely used in various types of electronic devices, such as mobile phones and personal computers.

[0003] The grinding apparatus for grinding the back surface of a wafer includes a chuck table that holds the wafer and a grinding unit on which a grinding wheel with an abrasive is rotatably mounted for grinding the wafer held by the chuck table. The grinding apparatus can grind the wafer to a desired thickness with high precision. To grind the back surface of the wafer, the front surface side, on which a large number of devices are formed, must be held under suction by the chuck table. Therefore, a protective tape is generally adhered to the front surface of the wafer to prevent scratching of the wafer (see, for example, JP H05-198542 A).

[0004] In recent years, electronic devices have shown a trend toward smaller sizes and thinner thicknesses, and semiconductor devices embedded therein have also shown a trend toward smaller sizes and thinner thicknesses. However, when the back surface of a wafer is ground to reduce the thickness of the wafer to, for example, 100 µm or less, and further to 50 µm or less, the rigidity decreases significantly, making subsequent handling very difficult. In addition, the wafer may bend, and there is also a possibility of the wafer itself breaking due to the bending. To solve such a problem, a wafer support system (WSS) is used.In the WSS, the front surface of a wafer is bonded to a rigid protective member using an adhesive beforehand, and the back surface of the wafer is then ground to a predetermined thickness to reduce the thickness of the wafer (see, for example, JP 2004 - 207 606 A).

[0005] US 2013 / 0 230 966 A1, DE 10 2013 219 271 A1 and US 2013 / 0 023 107 A1 disclose further prior art. DESCRIPTION OF THE INVENTION

[0006] However, it is difficult to remove the wafer from the protective tape or the protective element of the WSS without damaging it. Specifically, in recent years, there has been a trend toward larger wafer diameters and smaller final thicknesses, making it difficult to remove the wafer from the protective element without damaging it. Furthermore, there is the problem that an adhesive or bonding agent remains on the device surfaces after the wafer is removed from the protective element.

[0007] Accordingly, it is an object of the present invention to provide a support plate which allows easy removal of a wafer therefrom, the surfaces of the devices being free from the residue of an adhesive or bonding agent.

[0008] The present invention is defined by the support plate according to the features of independent claim 1, the method for forming a support plate according to the features of independent claim 2 and the method for processing a wafer according to the features of independent claim 3.

[0009] According to one aspect of the present invention, there is provided a support plate to which a front surface of a wafer is adhered, having a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region on the front surface, the support plate comprising: a base plate in which a recess is formed in a front surface region corresponding to the device region of the wafer to be adhered to the support plate, and an annular groove is formed in a region corresponding to the peripheral excess region of the wafer; and a soft member packed in the recess of the base plate, the wafer being adapted to be adhered to a front surface of the support plate with an adhesive therebetween by injecting the adhesive into the annular groove.

[0010] According to another aspect of the present invention, a method for forming a support plate to which a front surface of a wafer is adhered is provided. The support plate has a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region on the front surface. The support plate includes a recess corresponding to the device surface of the wafer, and a soft member is packed in the recess.The method includes a recess forming step of forming the recess by grinding a front surface portion of a base plate corresponding to the device portion of the wafer to be adhered to the support plate, an annular groove forming step before or after performing the recess forming step of forming an annular groove with a cutting blade in a portion of the base plate corresponding to the circumferential excess portion of the wafer to be adhered to the support plate, and a soft member packing step at least after performing the recess forming step of packing the soft member into the recess.

[0011] According to yet another aspect of the present invention, there is provided a method for processing a wafer having a device region in which a plurality of devices are formed and a peripheral excess region surrounding the device region on a front surface thereof. The method includes a support plate preparation step of preparing a support plate including a base plate in which a recess is formed in a front surface region corresponding to the device region of the wafer to be adhered to the support plate and an annular groove is formed in a region corresponding to the peripheral excess region of the wafer, and a soft member packed in the recess of the base plate, and an adhesive injection step of injecting an adhesive into the annular groove of the support plate.The method further comprises an adhering step after the adhesive injection step is performed for adhering the wafer to the support plate with the adhesive therebetween in such a manner that the setup area of the wafer is adjacent to the soft member, a processing step after the adhering step is performed for holding the wafer with the support plate therebetween and performing processing on the wafer, and an adhesive removing step after the processing step is performed for cutting a cutting blade into an area corresponding to the annular groove of the support plate and removing the adhesive.

[0012] To the support plate of the present invention, only the peripheral excess portion of the wafer is adhered with the adhesive injected into the annular groove therebetween. Therefore, no adhesive or adhesive remains on the front surfaces of the devices. Since the wafer is adhered to the support plate by a small amount of adhesive applied to the periphery of the wafer, removing the wafer from the support plate is easy. Moreover, when the peripheral portion of the wafer is adhered to the support plate with the adhesive therebetween, the device surface of the wafer is adjacent to the soft member of the support plate, thus preventing the devices from being scratched.

[0013] The above and other objects, features and advantages of the present invention and the mode for carrying them out, as well as the invention itself, will be best understood by studying the following description and appended claims with reference to the accompanying drawings which show some preferred embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a sectional view of a support plate of a first embodiment; Fig. 1B is a sectional view of a support plate of a second embodiment; Fig. 2 is a perspective view showing a deepening training step; Fig. 3 is a partial side sectional view showing a ring groove forming step; Fig. 4 is a sectional view showing a soft element packing step; Fig. 5 is a sectional view showing an adhesive injection step; Fig. 6 is a perspective view of a semiconductor wafer; Fig. 7 is a sectional view showing a bonding step; Fig. 8 is a perspective view showing a grinding step as an example of a machining step; Fig. 9A is a partial side sectional view showing a first embodiment of an adhesive removing step; Fig. 9B is a partial side sectional view showing a second embodiment of the adhesive removing step; and Fig. 10 is a partial side sectional view showing a third embodiment of the adhesive removing step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1A is a sectional view of a support plate 11 of a first embodiment of the present invention. The support plate 11 has a base plate 13 in which a recess 15 is formed in a front surface portion that is in contact with a device portion 31 of a wafer 25 (see Fig. 6) to be bonded to the support plate 11, and an annular groove 17 is formed in a region corresponding to a circumferential excess region 33 of the wafer 25. The support plate 11 further includes a soft element 19 packed into the recess 15 of the base plate 13.

[0015] The base plate 13 is formed from a silicon wafer, a glass wafer, or the like. The upper surface and one side surface of the annular groove 17 are opened. The soft member 19 is formed from, for example, foam rubber or rubber. When the soft member 19 is flat, it is preferable that a surface of the soft member 19 be flush with a surface of the base plate 13. However, when the surface of the soft member 19 packed into the recess 15 of the base plate 13 does not have such high flatness and a planarization step for planarizing the surface of the soft member 19 is performed, it is preferable to form the soft member 19 with a height higher than the surface of the base plate 13 by h1. h1 is, for example, about 2 µm to 20 µm.

[0016] Fig. 1B is a sectional view of a support plate 11A of a second embodiment. In the present embodiment, an annular groove opening only upward is used as an annular groove 21 formed in a region corresponding to the peripheral excess portion 33 of the wafer 25. It is preferable that the surface of the soft member 19 packed in the recess 15 of the base plate 13 be flush with the front surface of the base plate 13. However, in the case where the planarization step described above is performed, the soft member 19 is formed so that its surface is higher than the surface of the base plate 13 by 2 μm to 20 μm.

[0017] Subsequently, an in-depth training step is carried out with reference to Fig. 2. In Fig. In FIG. 2, reference numeral 2 denotes a grinding unit of a grinding device. The grinding unit includes a spindle 6 rotatably received in a spindle housing 4, a wheel mount 8 mounted on the tip of the spindle 6, and a grinding wheel 10 attachably / detachably mounted on the wheel mount 8. The grinding wheel 10 is formed of a ring gear base 12 and a plurality of grinding means 14 mounted on the peripheral portion of the lower end of the wheel base 12 in an annular manner.

[0018] In the recess forming step, the base plate 13 is held under suction by a chuck table 16 of the grinding apparatus, and the grinding wheel 10 is rotated in a direction indicated by an arrow B at, for example, 6000 rpm, while the chuck table 16 is rotated in a direction indicated by an arrow A at, for example, 300 rpm. Furthermore, an unillustrated grinding unit feeding mechanism is driven to bring the abrasives 14 into contact with the base plate 13. Subsequently, the grinding feed of the grinding wheel 10 is performed downward by a predetermined amount at a predetermined grinding feed rate. As a result, in the base plate 13, the portion corresponding to the device portion 31 of the wafer 25 is removed by grinding, and the recess 15 having a circular shape is formed.In addition, the area corresponding to the peripheral excess area 33 of the wafer 25 is left.

[0019] After or before the recess forming step is performed, an annular groove forming step for forming an annular groove with a cutting blade in the area of the base plate 13 corresponding to the circumferential excess area 33 of the wafer 25 to be bonded to the support plate 11 is performed. As shown in Fig. As shown in Figure 3, the annular groove forming step is performed by a cutting unit 18 of a cutting device. The cutting unit 18 includes a spindle 20 that is rotationally driven and a cutting blade 22 attached to a tip portion of the spindle 20. Preferably, the cutting blade 22 is a disc blade, the entire circumference of which is formed as a cutting edge.

[0020] In the annular groove forming step, the base plate 13 in which the recess 15 is formed is held by suction by a chuck table 24 of the cutting device. Subsequently, the cutting blade 22, rotating at a high speed in a direction of arrow R1, is caused to cut into the peripheral part of the base plate 13 to a predetermined depth while the chuck table 24 is rotated at a low speed in a direction of arrow R2. Accordingly, as shown in Fig. 4, an annular groove 17, whose upper surface and one side surface are open, is formed on the peripheral part of the base plate 13. This annular groove 17 may be formed by a grinding wheel instead of the cutting blade 22.

[0021] At least after the recess forming step has been carried out, a soft member packing step for packing the soft member 19 into the recess 15 of the base plate 13 is carried out as shown in Fig. 4. As the soft member 19, for example, a member that has high close contact performance and adhesive force with respect to a wafer but no stickiness is preferable. For example, an elastic member such as rubber or foam rubber can be used. After the soft member 19 is packed into the recess 15 of the base plate 13, the front surface of the soft member 19 can be cut to be planarized, for example, by a single-point cutting tool. In this case, the front surface of the soft member 19 is set to be higher than the front surface of the base plate 13 by h1, as shown in Fig. 1A shown.

[0022] Next, a method for processing a wafer using the support plate 11 shown in Fig. 1A, with reference to Fig. 5 to 10. First, an adhesive injection step is carried out for injecting an adhesive 23 into the annular groove 17 of the support plate 11. In this adhesive injection step, as shown in Fig. 5, the support plate 11 is held by suction using a chuck table (not shown). Subsequently, the adhesive 23 is supplied from an adhesive supply nozzle 26 to the annular groove 17 while slowly rotating the support plate 11, injecting the adhesive 23 into the entire circumference of the annular groove 17. The adhesive 23 may be continuously injected into the entire circumference of the annular groove 17 or intermittently. Furthermore, an arcuate adhesive, previously formed in a size corresponding to the annular groove, may be disposed on the annular groove.

[0023] Subsequently, the semiconductor wafer (from here on often referred to simply as wafer) 25, which is to be adhered to the support plate 11, is placed with reference to Fig. 6. The semiconductor wafer 25 is formed of, for example, a silicon wafer having a thickness of 700 μm and a plurality of streets (planned division lines) 27 formed in a lattice shape on a front surface 25a. Furthermore, devices 29, such as ICs and LSIs, are formed in the respective regions delimited by the plurality of streets 27. The wafer 25 configured in this manner has, on its front surface 25a, the device region 31 in which the devices 29 are formed and the peripheral excess region 33 surrounding the device region 31. Furthermore, a chamfered part 25e having a circular arc shape is formed on the outer periphery of the wafer 25.

[0024] After the adhesive injection step, which is Fig. 5 is shown, is carried out as in Fig. 7, an adhesion step for adhering the wafer 25 to the support plate 11 by the adhesive 23 disposed in the annular groove 17 of the support plate 11 is performed in such a manner that the device region 31 of the wafer 25 is adjacent to the soft member 19. The wafer 25 is adhered to the support plate 11 only at the peripheral part.

[0025] After the bonding step is performed, a processing step is performed for holding the wafer 25 with the support plate 11 therebetween and for performing processing on the wafer 25. The processing step includes a grinding step such as that described in Fig. 8. The grinding step is described with reference to Fig. 8 described. In Fig. 8, a grinding unit 28 of a grinding device includes a spindle 30 that is rotationally driven, a wheel holder 32 attached to the tip of the spindle 30, and a grinding wheel 34 attachably / detachably mounted on the wheel holder 32 by a plurality of screws 35. The grinding wheel 34 is formed of an annular wheel base 36 and a plurality of abrasives 38 attached to the peripheral part of the lower end of the wheel base 36 in an annular manner.

[0026] In the grinding step, the support plate 11 is held by suction with a chuck table 40 of the grinding apparatus, with a back surface 25b of the wafer 25 exposed. Then, the grinding wheel 34 is rotated in a direction indicated by an arrow b at, for example, 6000 rpm, while the chuck table 40 is rotated at, for example, 300 rpm in a direction indicated by an arrow a. Furthermore, a grinding unit feeding mechanism (not shown) is driven to bring the abrasives 38 of the grinding wheel 34 into contact with the back surface 25b of the wafer 25. Subsequently, the grinding feed of the grinding wheel 34 is performed downward by a predetermined amount at a predetermined grinding feed rate. By measuring the thickness of the wafer 25 by a thickness gauge of a contact system or a non-contact system, the wafer 25 is ground to a predetermined thickness, specifically, for example, 100 μm.

[0027] The machining step is not limited to the grinding step, as in Fig. 8, but may also include, for example, a laser processing step in which the support plate 11 is held by suction by a chuck table of a laser processing apparatus, and a modified layer is formed inside the wafer 25 by irradiating the wafer 25 with a laser beam having such a wavelength as to be transmissible through the wafer 25 from the back surface 25b side of the wafer 25, etc.

[0028] After the grinding step, which is Fig. 8 is shown, is carried out as in Fig. 9A, an adhesive removal step is performed. In this step, the cutting blade 22, rotating at a high speed in a direction of arrow R1, is caused to cut into the area corresponding to the annular groove 17 of the support plate 11, and the chuck table 24 is rotated at a low speed in a direction of arrow R2 to remove the adhesive 23.

[0029] This adhesive removal step can be carried out using a cutting unit 18A such as that shown in Fig. 9B. The cutting unit 18A includes a spindle 20A extending along the vertical direction and the cutting blade 22 attached to the lower end part of the spindle 20A. In the adhesive removing step of the present embodiment, the cutting blade 22, which rotates at a high speed in a direction of an arrow R3, is moved in a direction of an arrow A, whereby the cutting blade 22 is caused to cut into the area from the lateral side corresponding to the annular groove 17 of the support plate 11. Moreover, the chuck table 24 is rotated at a low speed in a direction of an arrow R2 to remove the adhesive 23.

[0030] Fig. Fig. 10 shows another embodiment of the adhesive removal step. In the present embodiment, the adhesive 23, which is inserted into the annular groove 21 of the support plate 11A of the second embodiment shown in Fig. 1B is injected. More specifically, a cutting blade 22A having a small thickness is caused to cut into the area corresponding to the annular groove 21 of the support plate 11A while rotating it at a high speed in a direction of an arrow R1 and the chuck table 24 is rotated at a low speed in a direction of an arrow R2, to remove the adhesive 23 in the annular groove 21.

[0031] In the embodiments described in Fig. 9A, Fig. 9B and Fig.10, the adhesive removal step is performed by the cutting blade. However, the adhesive removal step is not limited to this, and the adhesive may be removed using a grinding wheel or a laser beam.

[0032] The present invention is not limited to the details of the preferred embodiments described above. The scope of the invention is defined by the accompanying claims.

Claims

[1] A support plate (11) to which a front surface (25a) of a wafer (25) having a device region (31) in which a plurality of devices (29) are formed and a peripheral excess region (33) surrounding the device region (31) on the front surface is adhered, the support plate (11) comprising: a base plate (13) in which a recess (15) is formed in a front surface region corresponding to the device region (31) of the wafer (25) to be adhered to the support plate, and an annular groove (17) is formed in a region corresponding to the circumferential excess region (33) of the wafer, an upper surface and a side surface of the annular groove (17) being open; and a soft element (19) which is packed into the recess (15) of the base plate (13), wherein the wafer is adapted to be adhered to a front surface of the support plate with an adhesive (23) therebetween by injecting the adhesive into the annular groove (17). [2] A method for forming a support plate (11) to which a front surface (25a) of a wafer (25) is adhered, said support plate having a device region (31) in which a plurality of devices (29) are formed and a peripheral excess region (33) surrounding the device region (31) on the front surface (25a), wherein the support plate (11) has a recess (15) corresponding to the device region of the wafer, a soft member (19) is packed in the recess (15), and the method comprises: a recess forming step for forming the recess (15) by grinding a front surface portion of a base plate (13) corresponding to the device portion of the wafer (25) to be bonded to the support plate (11); an annular groove forming step before or after performing the recess forming step for forming an annular groove (17) by a cutting blade (22) in a region of the base plate (13) corresponding to the circumferential excess region (33) of the wafer (25) to be adhered to the support plate (11), wherein an upper surface and a side surface of the annular groove (17) are opened; and a soft element packing step at least after performing the recess forming step for packing the soft element (19) into the recess (15). [3] A method of processing a wafer (25) having a device region (31) in which a plurality of devices (29) are formed and a peripheral excess region (33) surrounding the device region (31) on a front surface (25a) thereof, the method comprising: a support plate preparation step for preparing a support plate (11) having a base plate (13) in which a recess (15) is formed in a front surface region corresponding to the device region (31) of the wafer (25) to be adhered to the support plate, and an annular groove (17, 21) is formed in a region corresponding to the circumferential excess region (33) of the wafer, and a soft member (19) packed in the recess (15) of the base plate (13); an adhesive injection step for injecting an adhesive (23) into the annular groove (17, 21) of the support plate (11); an adhering step after the adhesive injection step has been carried out for adhering the wafer (25) to the support plate (11) with the adhesive (23) therebetween in such a manner that the device region (31) of the wafer is adjacent to the soft member (19); a processing step after the bonding step has been performed for holding the wafer (25) with the support plate (11) therebetween and performing processing on the wafer; and an adhesive removing step after the machining step is performed, for causing a cutting blade (22) to cut into a region corresponding to the annular groove (17, 21) of the support plate and removing the adhesive (23).

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