JP2011054808A - Method of processing wafer, and wafer processed by the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of processing a wafer, capable of reducing chippings caused in an annular projecting part, and efficiently discharging a treatment liquid such as an etchant or a resist liquid to the outside of the wafer. <P>SOLUTION: The method of processing a wafer includes: a holding step of holding a front surface side of the wafer with a protective member arranged thereon by using a holding means including a holding surface and a rotary shaft vertical to the holding surface; and a grinding step of bringing a grinding wheel into contact with the back surface of the wafer held by the holding means rotated and driven while rotating the grinding wheel to grind the back surface of the wafer corresponding to a device region of the wafer, to form a circular recessed part on the back surface, and of forming an annular projecting part surrounding the circular recessed part, wherein, in the grinding step, the grinding wheel is fed in a direction coming close to the wafer by relatively moving the grinding wheel and the holding means, and is moved in the central direction of the wafer at the same time, whereby a tapered surface tilting from the upper surface inner peripheral side of the annular projecting part toward the wafer center direction of the circular recessed part is formed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wafer processing method that is easy to handle even if processed thinly, and a wafer processed by the processing method.

  In a semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets arranged in a lattice pattern on the surface of a substantially wafer-shaped semiconductor wafer, and ICs, LSIs, etc. are partitioned in these partitioned regions. Form the device. Then, the semiconductor wafer is cut into individual semiconductor chips (devices) by cutting the semiconductor wafer along a street with a cutting device.

  The divided wafer is formed to have a predetermined thickness by grinding or polishing the back surface before cutting along the street. In recent years, in order to achieve weight reduction, size reduction, and thickness reduction of electrical equipment, it is required that the thickness of the wafer be made thinner, for example, about 50 μm. The thinned wafer is appropriately etched about several μm in order to remove the grinding distortion generated by grinding.

  Such thin wafers are difficult to handle and may be damaged during transportation. In order to solve this problem, the present applicant has proposed a wafer processing method that facilitates handling of a thinned wafer in Japanese Patent Application Laid-Open No. 2007-19461.

  In this method, a circular recess is formed on the back surface of the wafer by grinding the back surface of the wafer corresponding to the device region on which the device is formed, and thinning the device region to a predetermined thickness. Wafer handling is facilitated by forming an annular convex portion (annular reinforcing portion) by leaving the surplus region.

  On the other hand, Japanese Patent Laid-Open No. 2009-21462 discloses a wafer in which a rear surface of a wafer is ground to form a circular concave portion and an annular convex portion surrounding the circular concave portion is formed, and then a rewiring layer is formed in the circular concave portion. A processing method is disclosed.

JP 2004-319885 A JP 2007-19461 A JP 2009-21462 A

  However, when the side surface of the annular convex portion surrounding the circular concave portion is perpendicular to the grinding surface of the wafer, there is a problem that the outer peripheral edge of the annular convex portion is very easily lost during handling such as conveyance.

  In particular, if the inner peripheral portion of the annular convex portion is chipped, when the etching is performed later, the annular convex portion is greatly eroded because it becomes easier to etch, and as a result, the annular convex portion becomes the reinforcing portion. Can no longer serve as.

  In addition, when a rewiring layer is formed in a circular concave portion of a wafer in which the side surface of the annular convex portion surrounding the circular concave portion is perpendicular to the grinding surface of the wafer, the resist solution used in photolithography is discharged out of the circular concave portion. There is a problem that it is difficult to be done.

  The present invention has been made in view of these points, and the object of the present invention is to reduce chipping generated in the annular convex portion and to efficiently remove a processing solution such as an etching solution or a resist solution outside the circular concave portion. It is to provide a method of processing a wafer that can be discharged.

  According to the present invention, there is provided a wafer processing method for processing a wafer provided with a device region in which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region, the protective member being provided on the surface side of the wafer. A protective member disposing step for disposing; a retaining step for retaining the surface side of the wafer on which the protective member is disposed by a retaining means having a retaining surface and a rotating shaft perpendicular to the retaining surface; and a grinding wheel. The back surface of the wafer corresponding to the device area of the wafer is ground by abutting against the back surface of the wafer held by the holding means that is rotated while being rotated to form a circular recess on the back surface. A grinding step for forming a surrounding annular convex portion, and in the grinding step, the grinding wheel and the holding means are moved relative to each other so that the grinding wheel approaches the wafer. A wafer having a tapered surface inclined from the inner peripheral surface of the upper surface of the annular convex portion toward the wafer central direction of the circular concave portion by moving the wafer toward the central direction of the wafer simultaneously with the cutting and feeding. A processing method is provided.

  Preferably, the wafer processing method further includes a finish grinding step of grinding the circular recess using a finishing grinding wheel, and an etching step of etching the circular recess to remove grinding distortion.

  According to the present invention, since the tapered surface is formed on the inner peripheral side of the annular convex portion, the annular convex portion is not easily chipped. Further, during etching after grinding, the etching solution supplied into the circular concave portion is easily discharged from the circular concave portion by the taper surface, and in the case of forming a rewiring layer on the circular concave portion, etc., from the inside of the circular concave portion of the resist solution. Can be easily discharged.

  Furthermore, when a wafer with circular recesses formed by backside grinding is divided into individual chips with a cutting device, a dicing tape is attached to the backside to facilitate handling of each chip after division. However, in the present invention, since the tapered surface is formed on the annular convex portion, it is possible to prevent bubbles from being generated between the annular convex portion and the circular concave portion when the dicing tape is attached.

1 is an external perspective view of a grinding apparatus suitable for carrying out the wafer processing method of the present invention. It is a front side perspective view of a semiconductor wafer. It is a back surface side perspective view of a semiconductor wafer in the state where a protective tape was stuck on the surface. It is a flowchart which shows the processing method of the wafer of this invention. It is a perspective view of the circular recessed part grinding step implemented by the rough grinding unit. It is explanatory drawing of the circular recessed part grinding step implemented by the rough grinding unit. It is a partially broken sectional view of the semiconductor wafer explaining the formation method of a taper surface. It is sectional drawing of the semiconductor wafer in which the circular recessed part grinding step which has a taper surface on the internal peripheral surface of a cyclic | annular convex part was implemented. It is a perspective view of the finish grinding step performed by a finish grinding unit. It is a partially broken sectional view of a semiconductor wafer explaining a finish grinding step. It is sectional drawing of the semiconductor wafer in which the finish grinding step was implemented. It is explanatory drawing of an etching step.

  Hereinafter, a wafer processing method according to an embodiment of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a grinding apparatus suitable for carrying out the wafer processing method of the embodiment of the present invention. The grinding apparatus includes a device housing 2 having a substantially rectangular parallelepiped shape. A vertical support plate 4 is adjacent to the upper right end of the device housing 2.

  Two pairs of guide rails 6 and 8 extending in the vertical direction are provided on the inner surface of the vertical support plate 4. A rough grinding unit 10 is mounted on one guide rail 6 so as to be movable in the vertical direction, and a finish grinding unit 12 is mounted on the other guide rail 8 so as to be movable in the vertical direction.

  The rough grinding unit 10 includes a unit housing 14, a grinding wheel 18 attached to a wheel mount 16 rotatably attached to the lower end of the unit housing 14, and a wheel mount 16 attached to the lower end of the unit housing 14 counterclockwise. An electric motor 20 that rotates in the rotating direction and a moving base 22 on which the unit housing 14 is mounted are configured.

  The grinding wheel 18 includes an annular grinding wheel base 18a and a grinding wheel 18b for rough grinding mounted on the lower surface of the grinding wheel base 18a. A pair of guided rails 24 are formed on the moving base 22, and these guided rails 24 are movably fitted to guide rails 6 provided on the vertical support plate 4, so that the rough grinding unit 10 can be moved. Is supported so as to be movable in the vertical direction (Z-axis direction).

  A grinding feed mechanism 26 moves the moving base 22 of the rough grinding unit 10 along the guide rail 6 and feeds the grinding wheel 18 by grinding. The grinding feed mechanism 26 is arranged on the vertical support plate 4 in a vertical direction parallel to the guide rail 6 and rotatably supported, a pulse motor 30 that rotationally drives the ball screw 28, and a moving base 22. It comprises a nut (not shown) that is mounted and screwed onto the ball screw 28.

  By rotating the ball screw 28 forward or backward by the pulse motor 30, the rough grinding unit 10 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later). Although not particularly shown, the rough grinding unit 10 is configured to be movable in the Y-axis direction by a Y-axis moving mechanism.

  The finish grinding unit 12 is configured in the same manner as the rough grinding unit 10, and includes a unit housing 32, a grinding wheel 36 attached to a wheel mount 34 rotatably attached to the lower end of the unit housing 32, and a unit housing 32. An electric motor 38 that is mounted on the upper end and drives the wheel mount 34 in a counterclockwise direction, and a moving base 40 on which the unit housing 32 is mounted. The grinding wheel 36 includes an annular grindstone base 36a and a grinding wheel 36b for finish grinding mounted on the lower surface of the grindstone base 36a.

  A pair of guided rails 42 is formed on the movable base 40, and these guided rails 42 are movably fitted to guide rails 8 provided on the vertical support plate 4, so that the finish grinding unit 12 can be moved. Is supported so as to be movable in the vertical direction.

  Reference numeral 44 denotes a grinding feed mechanism that moves the moving base 40 of the finish grinding unit 12 along the guide rail 8 and feeds the grinding wheel 36 by grinding. The grinding feed mechanism 44 includes a ball screw 46 that is vertically supported on the vertical support plate 4 in parallel with the guide rail 8, a pulse motor 48 that rotationally drives the ball screw 46, and a moving base 40. And a nut (not shown) that engages with the ball screw 46.

  By driving the ball screw 46 forward or backward by the pulse motor 48, the finish grinding unit 12 is moved in the vertical direction (perpendicular to the holding surface of the chuck table described later).

  The grinding apparatus includes a turntable 50 disposed so as to be substantially flush with the upper surface of the apparatus housing 2 on the front side of the vertical support plate 4. The turntable 50 is formed in a relatively large-diameter disk shape, and is rotated in a direction indicated by an arrow 51 by a rotation driving mechanism (not shown).

  On the turntable 50, three chuck tables 52 are arranged so as to be rotatable in a horizontal plane, spaced from each other by 120 degrees in the circumferential direction. The chuck table 52 includes a disk-shaped frame body 54 and a suction chuck 56 formed in a disk shape by a porous ceramic material. The chuck table 52 includes suction means (not shown) for a wafer placed on the holding surface of the suction chuck 56. Holds by suction when activated.

  The chuck table 52 configured as described above is rotated in a direction indicated by an arrow 53 by a rotation driving mechanism (not shown). The three chuck tables 52 arranged on the turntable 50 are rotated in accordance with the rotation of the turntable 50, so that the wafer loading / unloading area A, rough grinding area B, finish grinding area C, and wafer loading / unloading are performed. The region A is sequentially moved.

  The grinding device is disposed on one side with respect to the wafer carry-in / out region A, and is disposed on the other side with respect to the first cassette 58 for stocking the wafer before grinding, and the wafer carry-in / out region A, A second cassette 60 for stocking the wafer after grinding is provided.

  Between the first cassette 58 and the wafer loading / unloading area A, a temporary placing table 62 for placing the wafer unloaded from the first cassette 58 is disposed. A spinner cleaning means 68 is disposed between the wafer loading / unloading area A and the second cassette 60.

  The wafer transfer means 70 is composed of a holding arm 72 and a multi-joint link mechanism 74 that moves the holding arm 72. The wafer transport means 70 carries out the wafer stored in the first cassette 58 to the temporary placement table 60 and spinner cleaning means. The wafer cleaned at 68 is transported to the second cassette 60.

  The wafer carry-in means 76 carries the wafer that has been placed on the temporary placement table 62 and before grinding to the chuck table 52 that is positioned in the wafer carry-in / out area A. The wafer carry-out means 78 carries the wafer after grinding mounted on the chuck table 52 positioned in the wafer carry-in / out area A to the spinner cleaning means 68.

  A semiconductor wafer 11 shown in FIG. 2 is accommodated in the first cassette 58. The semiconductor wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm, and a plurality of streets 13 are formed in a lattice shape on the surface 11a, and an IC, a plurality of areas partitioned by the plurality of streets 13, A device 15 such as an LSI is formed.

  The semiconductor wafer 11 configured as described above includes a device region 17 in which the device 15 is formed, and an outer peripheral surplus region 19 that surrounds the device region 17. In addition, the width | variety of the outer periphery surplus area | region 19 is set to about 2-3 mm. A notch 21 is formed on the outer periphery of the semiconductor wafer 11 as a mark indicating the crystal orientation of the silicon wafer.

  A protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by a protective tape attaching process. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and as shown in FIG. 3, the back surface 11b is exposed, and the plurality of semiconductor wafers 11 are placed in the first cassette 58 with the back surface 11b facing upward. It is stored.

  Referring to FIG. 4, a flowchart of the wafer processing method according to the embodiment of the present invention is shown. Since a plurality of devices 15 are formed on the surface 11 a of the wafer 11, a protective member is disposed on the surface side of the wafer 11 in step S <b> 10 before the wafer 11 is ground. Specifically, for example, as shown in FIG. 3, a protective tape 23 is attached to the surface 11 a of the wafer 11.

  Next, in step S11, the surface side of the wafer 11, that is, the protective tape 23 side is held by holding means such as a chuck table 52 having a holding surface and a rotation axis perpendicular to the holding surface. That is, the wafer 11 is loaded into the chuck table 52 positioned in the wafer loading / unloading area A by the wafer loading means 76, and the suction tape 56 of the chuck table 52 sucks and holds the protective tape 23 side of the wafer 11.

  When the wafer 11 is held by the chuck table 52 in this way, the turntable 50 is rotated 120 degrees counterclockwise and positioned in the rough grinding region B. Then, the grinding step of step S12 using the rough grinding unit 10 is performed.

  That is, as shown in FIGS. 5 and 6, while rotating the chuck table 52 in the direction shown by the arrow 53 at 300 rpm, for example, the grinding wheel 18b is rotated in the direction shown by the arrow 55 at 6000 rpm, for example, and the grinding feed mechanism 26 Is driven to bring the grinding wheel 18 of the grinding wheel 18 into contact with the back surface corresponding to the device region 17 of the wafer 11.

  Then, the grinding wheel 11 is ground by a predetermined amount at a predetermined grinding feed speed, and simultaneously moved in the center direction of the wafer 11. That is, the back surface of the wafer 11 corresponding to the device region 17 is ground while moving the grinding wheel 18 in the direction of arrow A in FIG.

  As a result, as shown in FIGS. 7B and 8, a region corresponding to the device region 17 is ground and removed to form a circular recess 80 having a predetermined thickness (for example, 30 μm) on the back surface of the wafer 11. At the same time, a region corresponding to the outer peripheral surplus region 19 remains, and an annular convex portion (annular reinforcing portion) 82 is formed. Further, an annular tapered surface 86 is formed which is inclined from the inner peripheral side of the upper surface 82 a of the annular convex portion 82 toward the wafer center of the circular concave portion 80.

  Here, the relationship between the wafer 11 held on the chuck table 52 and the grinding wheel 18b constituting the grinding wheel 18 will be described with reference to FIG. The rotation center P1 of the chuck table 52 and the rotation center P2 of the grinding wheel 18b are eccentric, and the outer diameter of the grinding wheel 18b is smaller than the diameter of the boundary line 84 between the device region 17 and the outer peripheral surplus region 19 of the wafer 11, and the boundary line The grinding wheel 18b, which is set to a size larger than the radius of 84 and arranged in an annular shape, is set so as to pass through the rotation center P1 of the chuck table 52.

  Then, the grinding wheel 18 b is ground and fed in the vertical direction and is simultaneously moved in the center direction of the wafer 11 as indicated by an arrow 57. Specifically, it is preferable to move the grinding wheel 18 in the horizontal direction at, for example, 10 μm / second while grinding and feeding in the vertical direction at, for example, 5 μm / second.

  When the rough grinding of the wafer 11 is completed, the process proceeds to step S13 and finish grinding is performed using the finish grinding wheel 36b. That is, as shown in FIG. 10 (A), the finish grinding wheel 36b is positioned on the outermost periphery of the circular recess 80, and the chucking wheel 52 is rotated in the direction indicated by the arrow 53 in FIG. The grinding wheel 36 is ground by a predetermined amount at a predetermined grinding feed speed while being rotated in the direction indicated by 55 at, for example, 6000 rpm. As a result, as shown in FIG. 10B, a circular recess 80a having a predetermined depth is formed on the inner peripheral side of the tapered surface 86, and grinding distortion remains.

  Next, the process proceeds to step S14, where an etching solution is supplied from the etching solution supply means 90 into the circular recess 80a of the wafer 11 held by the chuck table 88 as shown in FIG. Remove.

  After the etching is completed, it is necessary to discharge the etching solution from the circular concave portion 80a. However, as shown in a partially enlarged view of FIG. 12, a tapered surface 86 is formed between the annular convex portion 82 and the circular concave portion 80a. Therefore, the etching solution can be easily discharged from the circular recess 80a as indicated by the arrow 92.

  As an option, when it is necessary to form a rewiring layer on the bottom surface of the circular recess 80a of the wafer 11, the rewiring layer is formed by photolithography used in the semiconductor manufacturing process. Since the tapered surface 86 is formed, it can be easily discharged from the circular recess 80a.

  According to the wafer processing method of the present embodiment, since the annular tapered surface 86 is formed on the inner peripheral side of the annular convex portion 82 of the wafer 11, the annular convex portion 82 is not easily chipped. Further, when the wafer 11 thus ground is divided into individual chips by a cutting device, a dicing tape attached to an annular frame is pasted on the back surface in order to facilitate handling of each chip after division. However, since the tapered surface 86 is formed between the annular convex portion 82 and the circular concave portion 80a, bubbles are generated between the annular convex portion 82 and the circular concave portion 80a when the dicing tape is attached. Is prevented.

2 Grinding device 10 Coarse grinding unit 11 Semiconductor wafer 12 Finish grinding unit 17 Device area 18 Grinding wheel 18b Grinding wheel 19 Outer peripheral area 23 Protective tape 36 Finish grinding wheel 52 Chuck table 80, 80a Circular recess 82 Annular convex part (annular reinforcing part) )
86 Annular taper surface

Claims (3)

A wafer processing method for processing a wafer having a device region in which a plurality of devices are formed and a peripheral surplus region surrounding the device region on a surface thereof,
A protective member disposing step of disposing a protective member on the front surface side of the wafer;
A holding step of holding the surface side of the wafer on which the protective member is disposed by a holding means having a holding surface and a rotation axis perpendicular to the holding surface;
A grinding wheel is rotated while being driven, and is brought into contact with the back surface of the wafer held by the holding means to grind the back surface of the wafer corresponding to the device region of the wafer to form a circular recess on the back surface, A grinding step for forming an annular convex portion surrounding the circular concave portion,
In the grinding step, the grinding wheel and the holding means are relatively moved so that the grinding wheel is ground and fed in a direction approaching the wafer, and at the same time, the grinding stone is moved in the center direction of the wafer, so A method of processing a wafer, comprising forming a tapered surface inclined from the inner peripheral side of the upper surface toward the wafer center of the circular recess. A finishing grinding step of grinding the circular recess using a finishing grinding wheel;
Etching step to remove grinding distortion by etching the circular recess that has been ground, and
The wafer processing method according to claim 1, further comprising:   A wafer processed by the wafer processing method according to claim 1.

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