JP2011071377A - Method of processing wafer - Google Patents

Abstract

Provided is a wafer processing method capable of reducing chipping generated in an annular convex portion and efficiently discharging a processing solution such as an etching solution or a resist solution out of the wafer.
A method of processing a wafer 11 having a device region and an outer peripheral surplus region surrounding the device region on a surface, wherein a region corresponding to the device region of the wafer 11 is ground and a circular recess 56 is formed on a back surface. And a wafer grinding step for forming an annular convex portion 58 surrounding the circular concave portion 56, a first surface and a second surface orthogonal to the rotation shaft 86, and an inclination on the outer periphery of the first surface While rotating the cutting blade 88 formed with the tapered surface 89, the taper surface 89 is positioned on the inner peripheral edge of the annular convex portion, and the cutting blade 88 and the holding means are moved relative to each other to cut the cutting blade 88 into the annular convex portion. And an annular convex cutting step for forming an inclined surface following the tapered surface 89 of the cutting blade on the inner peripheral edge of the annular convex.
[Selection] Figure 9

Description

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

  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 wafer to be divided is formed to have a predetermined thickness by grinding or polishing the back surface before cutting along the street (see, for example, JP-A-2004-319885). 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 for processing a wafer that can be discharged.

  According to the present invention, there is provided a wafer processing method for processing a wafer having a device region in which a plurality of devices are formed and an outer peripheral surplus region surrounding the device region on a surface, and a protective member is provided on the surface side of the wafer. A front surface side of the wafer on which the protective member is disposed by a first retaining means comprising a protective member disposing step, a first retaining surface and a first rotating shaft perpendicular to the first retaining surface; A first holding step for holding, and a grinding wheel having an annular grinding wheel having a grinding surface facing the back surface of the wafer is held by the first holding means while rotating around a second rotating shaft perpendicular to the grinding surface. An annular convex portion that contacts the back surface of the wafer and rotates the first holding means to grind the region corresponding to the device region of the wafer to form a circular concave portion on the back surface and surround the circular concave portion A wafer grinding step to be formed, and a second holding means having a second holding surface and a third rotating shaft perpendicular to the second holding surface to hold the surface side of the wafer on which the wafer grinding step has been performed. 2 holding step and a first surface and a second surface orthogonal to the fourth rotation axis, and at least the outer periphery of the first surface is inclined from the first surface toward the second surface The cutting blade on which the tapered surface is formed is positioned on the inner peripheral edge of the annular convex portion while rotating the cutting blade on the fourth rotation shaft, and the cutting blade and the first rotating member are rotated while the second holding means is rotated. 2. An annular convex portion that forms an inclined surface that follows the tapered surface of the cutting blade at the inner peripheral edge of the annular convex portion by moving the cutting blade into the annular convex portion by moving the holding means relative to each other. And a cutting step. Method for processing Eha is provided.

  According to the present invention, since the inclined surface is formed on the inner peripheral side of the annular convex portion, the annular convex portion is not easily chipped. In addition, during etching after grinding, the etching solution supplied into the circular concave portion by the inclined surface can be easily discharged out of the circular concave portion, and in the case of forming a rewiring layer on the circular concave portion, the resist solution can be discharged from the circular concave portion. 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 inclined 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.

It is a surface 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. 1 is a perspective view of a grinding apparatus suitable for carrying out the wafer processing method of the present invention. It is a perspective view of a wafer grinding step performed by a grinding unit. It is explanatory drawing of the wafer grinding step implemented by a grinding unit. It is sectional drawing for demonstrating the wafer grinding step of this invention. It is a perspective view of the cutting device suitable for implementing the cyclic | annular convex part cutting step of this invention. FIG. 8A shows a first embodiment of a cutting blade suitable for use in the annular convex cutting step, and FIG. 8B shows a second embodiment of the cutting blade. It is explanatory drawing which shows a cyclic | annular convex part cutting step. It is sectional drawing of the semiconductor wafer by which the inclined surface was formed in the internal peripheral surface of a cyclic | annular convex part. 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, a front side perspective view of a semiconductor wafer 11 is shown. The semiconductor wafer 11 is made of, for example, a silicon wafer having a thickness of 700 μm. A plurality of streets (division lines) 13 are formed in a lattice shape on the surface 11 a and a plurality of sections partitioned by the plurality of streets 13. A device 15 such as an IC or LSI is formed in this area.

  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.

  When grinding the back surface of the semiconductor wafer 11, the surface 11a side of the semiconductor wafer 11 is sucked and held by the chuck table of the grinding device, so that the surface 11a needs to be protected. Therefore, for example, the protective tape 23 is attached to the surface 11a of the semiconductor wafer 11 by the protective member disposing step. Therefore, the front surface 11a of the semiconductor wafer 11 is protected by the protective tape 23, and the back surface 11b is exposed as shown in FIG.

  Referring to FIG. 3, a perspective view of a grinding apparatus 2 suitable for grinding the back surface 11b of the semiconductor wafer 11 is shown. Reference numeral 4 denotes a base (housing) of the grinding apparatus 2, and a column 6 is erected on the rear side of the base 4. A pair of guide rails 8 extending in the vertical direction is fixed to the column 6.

  A grinding unit (grinding means) 10 is mounted along the pair of guide rails 8 so as to be movable in the vertical direction. The grinding unit 10 includes a base 12 and a support portion 14 that holds the base 12, and the support portion 14 is attached to a moving base 16 that moves in the vertical direction along the pair of guide rails 8. .

  The grinding unit 10 includes a spindle 18 rotatably accommodated in a base 12, a mounter 20 fixed to the tip of the spindle 18, and a plurality of grinding wheels that are screwed to the mounter 20 and arranged in an annular shape. A wheel 22 and a servomotor 26 that rotationally drives the spindle 18 are included.

  The grinding apparatus 2 includes a grinding unit moving mechanism 32 including a ball screw 28 that moves the grinding unit 10 in the vertical direction along the pair of guide rails 8 and a pulse motor 30. When the pulse motor 30 is driven, the ball screw 28 rotates and the moving base 16 is moved in the vertical direction.

  A recess 4a is formed on the upper surface of the base 4, and a chuck table mechanism 34 is disposed in the recess 4a. The chuck table mechanism 34 has a chuck table 36 and is moved in the Y-axis direction between a wafer attachment / detachment position A shown in FIG. 3 and a grinding position B facing the grinding unit 10 by a moving mechanism (not shown). 38 and 40 are bellows. On the front side of the base 4, an operation panel 42 on which an operator of the grinding apparatus 2 inputs grinding conditions and the like is disposed.

  A wafer processing method in which a circular recess is formed on the back surface corresponding to the device region 17 of the semiconductor wafer 11 and the annular protrusion is left in the outer peripheral surplus region 19 by the grinding apparatus 2 configured as described above will be described below. .

  As shown in FIG. 4, a grinding wheel 22 is detachably attached to a mounter 20 fixed to the tip of the spindle 18. The grinding wheel 22 includes a wheel base 24 and a plurality of grinding wheels 25 arranged annularly on the outer periphery of the lower surface of the wheel base 24.

  The wafer 11 on which the protective tape 23 shown in FIG. 2 is adhered is sucked and held with the protective tape 23 down on the chuck table 36 positioned at the wafer attachment / detachment position A shown in FIG. Next, the chuck table 36 is moved in the Y-axis direction and positioned at the grinding position B.

  4 and 5, while rotating the chuck table 36 in the direction indicated by the arrow 37 at 300 rpm, for example, the grinding wheel 25 is rotated in the direction indicated by the arrow 53 at 6000 rpm, for example, and the grinding unit moving mechanism 32 is driven to bring the grinding wheel 25 of the grinding wheel 22 into contact with the back surface of the wafer 11. Then, the grinding wheel 22 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, on the back surface of the semiconductor wafer 11, as shown in FIGS. 4 and 6B, a region corresponding to the device region 17 is ground and removed to form a circular recess 56 having a predetermined thickness (for example, 30 μm). At the same time, the region corresponding to the outer peripheral surplus region 19 is left, and the annular convex portion 58 is formed.

  Referring to FIG. 7, there is shown a perspective view of a cutting device 62 suitable for carrying out the annular convex cutting step of the present invention. On the front side of the cutting device 62, operating means 64 is provided for an operator to input instructions to the device such as machining conditions. In the upper part of the apparatus, there is provided display means 66 such as a CRT on which a guide screen for the operator and an image taken by an imaging means described later are displayed.

  A plurality of wafers 11 in which a circular concave portion 56 and an annular convex portion 58 surrounding the circular concave portion 56 are formed on the back surface of the wafer 11 by the wafer grinding step are accommodated in a wafer cassette 68. The wafer cassette 68 is placed on a cassette elevator 69 that can move up and down.

  Behind the wafer cassette 68 is a loading / unloading means 70 for unloading the wafer 11 from the wafer cassette 68 and loading a wafer having an inclined surface on the inner periphery of the annular convex portion into the wafer cassette 68 by the annular convex portion cutting step. It is installed.

  Between the wafer cassette 68 and the loading / unloading means 70, a temporary placement area 72, which is an area on which a wafer to be loaded / unloaded is temporarily placed, is provided. In the temporary placement area 72, the wafer 11 is placed. Positioning means 74 for positioning at a fixed position is provided.

  In the vicinity of the temporary placement area 72, a transport means 76 having a turning arm that sucks and transports the wafer 11 is arranged. The wafer 11 carried to the temporary placement area 72 is sucked by the transport means 76. It is conveyed onto the chuck table 78 and sucked and held on the chuck table 78. Reference numeral 79 denotes a clamp.

  The chuck table 78 is configured to be rotatable and reciprocally movable in the X-axis direction. Above the movement path of the chuck table 78 in the X-axis direction, an alignment unit 80 that detects an area to be cut of the wafer 11 is provided. It is arranged.

  The alignment unit 80 includes an imaging unit 82 that images the surface of the wafer 11 and can detect a region to be cut by processing such as pattern matching based on an image acquired by imaging. The image acquired by the imaging unit 82 is displayed on the display unit 66.

  A cutting means (cutting unit) 84 for cutting the wafer 11 held on the chuck table 78 is disposed on the left side of the alignment means 80. The cutting unit 84 is configured integrally with the alignment means 80, and both move in conjunction with each other in the Y-axis direction and the Z-axis direction.

  The cutting unit 84 is configured by mounting a cutting blade 88 on the tip of a spindle 86 that is rotationally driven, and is movable in the Y-axis direction and the Z-axis direction. The cutting blade 88 is located on the extended line of the image pickup means 82 in the X-axis direction.

  Reference numeral 85 denotes transport means for transporting the wafer 11 that has been cut to the cleaning device 87. The cleaning device 87 cleans the wafer 11 and blows air from an air nozzle to dry the wafer 11.

  Referring to FIG. 8A, there is shown a cutting blade 88 of the first embodiment suitable for carrying out the annular convex cutting step of the present invention. The cutting blade 88 has a first surface 88a and a second surface 88b orthogonal to a spindle (rotation axis) 86, and the outer periphery of the first surface 88a is directed from the first surface 88a to the second surface 88b. An inclined taper surface 89 is formed.

  FIG. 8B shows a cutting blade 88A of the second embodiment suitable for carrying out the annular convex cutting step. The cutting blade 88A has a first surface 88a and a second surface 88b orthogonal to the spindle (rotation axis) 86, and the thickness direction center of the cutting blade 88A is formed on the outer periphery of the first surface 88a and the second surface 88b. Tapered surfaces 89a and 89b that are inclined toward each other are formed.

  Next, with reference to FIG. 9, the cyclic | annular convex part cutting step using the cutting blade 88 of 1st Embodiment is demonstrated. In the annular convex portion cutting step, the taper surface 89 is positioned on the inner peripheral edge of the annular convex portion 58 while the cutting blade 88 having the tapered surface 89 formed on the outer periphery of the first surface 88 a is rotated by the spindle 86.

  Then, while rotating the chuck table 78 at a low speed, the cutting blade 88 is moved in the direction of arrow A and cut into the annular convex portion 58. As a result, as shown in FIG. 10, an annular inclined surface 59 that follows the tapered surface 89 of the cutting blade 88 is formed on the inner peripheral edge of the annular convex portion 58.

  When the annular convex cutting step is completed, the etching liquid is supplied from the etching liquid supply means 92 into the circular concave portion 56 of the semiconductor wafer 11 sucked and held by the chuck table 90 of the etching apparatus as shown in FIG. Remove the grinding distortion of the bottom of the.

  After the etching is completed, it is necessary to discharge the etching solution from the circular concave portion 56. However, as shown in a partially enlarged view of FIG. 11, an annular inclined surface 59 is formed between the circular convex portion 58 and the circular concave portion 56. Therefore, the etching solution can be easily discharged from the circular recess 56 as indicated by the arrow 94.

  As an option, when it is necessary to form a rewiring layer on the bottom surface of the circular recess 56 of the wafer 11, the rewiring layer is formed by photolithography used in the semiconductor manufacturing process. Since the inclined surface 59 is formed, it can be easily discharged from the circular recess 56.

  According to the wafer processing method of the present embodiment, since the annular inclined surface 59 is formed on the inner peripheral side of the annular convex portion 58 of the wafer 11, the annular convex portion 58 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 an annular inclined surface 59 is formed between the annular convex portion 58 and the circular concave portion 56, bubbles are generated between the annular convex portion 58 and the circular concave portion 56 when the dicing tape is attached. It is prevented.

2 grinding device 10 grinding unit 11 semiconductor wafer 17 device region 18 spindle 19 outer peripheral surplus region 22 grinding wheel 25 grinding wheel 36 chuck table 56 circular concave portion 58 annular convex portion 59 annular inclined surface 62 cutting device 78 chuck table 88 cutting blade 88a first Surface 88b Second surface 89, 89a, 89b Tapered surface

Claims (1)

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 first holding step of holding the surface side of the wafer on which the protective member is disposed by a first holding means having a first holding surface and a first rotating shaft perpendicular to the first holding surface;
A grinding wheel having an annular grinding wheel having a grinding surface facing the back surface of the wafer is annularly contacted with the back surface of the wafer held by the first holding means while being rotated by a second rotating shaft perpendicular to the grinding surface. And rotating the first holding means to grind a region corresponding to the device region of the wafer to form a circular concave portion on the back surface and to form an annular convex portion surrounding the circular concave portion,
A second holding step of holding the wafer surface on which the wafer grinding step has been carried out by a second holding means comprising a second holding surface and a third rotating shaft perpendicular to the second holding surface;
A tapered surface that has a first surface and a second surface orthogonal to the fourth rotation axis and is inclined from the first surface toward the second surface is formed at least on the outer periphery of the first surface. The cutting blade is rotated on the fourth rotating shaft, the tapered surface is positioned on the inner peripheral edge of the annular convex portion, and the cutting blade and the second holding means are rotated while the second holding means is rotated. An annular convex cutting step for forming an inclined surface following the tapered surface of the cutting blade on the inner peripheral edge of the annular convex by cutting the cutting blade into the annular convex by being relatively moved,
A wafer processing method characterized by comprising:

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