JP5441587B2 - Wafer processing method - Google Patents

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 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 wafer is held in contact with the back surface of the wafer held by the holding means rotated while being rotated, and the back surface of the wafer corresponding to the device region of the wafer is ground to form a circular recess on the back surface, and the outer peripheral surplus region was and a grinding step to leave an annular protrusion surrounding the circular recess, the grinding step, planting the grinding grindstone and said holding means and a are relatively moved the grinding grindstone A vertical direction grinding step for grinding and feeding in a direction approaching C, and a horizontal direction moving step for relatively moving the grinding wheel and the holding means to move the grinding wheel a predetermined distance toward the center of the wafer, by the multiple該鉛straight direction grinding step with repeated a plurality of times to carried out in the same processing conditions by a vertical grinding step and said horizontal moving step and the same the grinding grindstone, top inner circumference side of the annular convex portion A method for processing a wafer is provided in which an annular inclined surface that is inclined stepwise toward the wafer center direction of the circular recess is formed.

  According to the present invention, since the stepped inclined surface is formed on the inner peripheral side of the annular convex portion, the annular convex portion is not easily chipped. In addition, when etching after grinding, the etching solution supplied into the circular recess is easily discharged to the outside of the circular recess by the stepped inclined surface, and the resist solution is circular in the case of forming a rewiring layer on the circular recess. Ejection from the inside of the recess becomes easy.

  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 stepped 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. It is a perspective view of the grinding step performed by a grinding unit. It is explanatory drawing of the grinding step implemented by the grinding unit. It is sectional drawing for demonstrating the grinding step of this invention. It is sectional drawing of the semiconductor wafer in which the grinding step which has a step-like inclined surface on the internal peripheral surface of a cyclic | annular convex part 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, 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.

  Next, with reference to FIG. 3 thru | or FIG. 5, the grinding step of this embodiment is demonstrated in detail. Referring to FIG. 3, a perspective view of the circular recess grinding step is shown. Reference numeral 10 denotes a grinding unit of a grinding apparatus, and a spindle 12 is rotatably accommodated in a spindle housing 14.

  A mounter 16 is fixed to the tip of the spindle 12, and a grinding wheel 18 is detachably attached to the mounter 16. The grinding wheel 18 includes an annular grinding wheel base 18a and a plurality of grinding wheels 18b mounted on the lower surface of the grinding wheel base 18a.

  In the grinding step, the side of the protective tape 23 attached to the surface of the semiconductor wafer 11 is sucked and held by the chuck table 20 of the grinding device. Then, while rotating the chuck table 20 in the direction indicated by the arrow 22 at 300 rpm, for example, the grinding wheel 18b is rotated in the direction indicated by the arrow 24 at 6000 rpm, for example, and the grinding feed mechanism (not shown) is driven to grind the grinding wheel 18. The grindstone 18b is brought into contact with the back surface corresponding to the device region 17 of the wafer 11 as shown in FIG.

  When the grinding wheel 18 is ground and fed downward by a predetermined grinding feed rate, a circular recess 28 is formed on the back surface of the wafer 11 as shown in FIG. After the circular recess 28 having a predetermined depth is formed, the grinding unit 10 is moved slightly horizontally in the direction of the arrow 26, that is, toward the center of the wafer 11, so that the grinding wheel 18b is formed into an annular convex portion as shown in FIG. Positioned away from the inner circumferential surface of 30. When grinding is continued at this position, a deep circular recess 28 is formed as shown in FIG.

  By alternately repeating the vertical grinding step shown in FIG. 5B and the horizontal movement step shown in FIG. 5C a plurality of times, the region corresponding to the device region 17 is removed by grinding as shown in FIG. Thus, a circular concave portion 28 having a predetermined thickness (for example, 30 μm) is formed, and a region corresponding to the outer peripheral surplus region 19 is left to form an annular convex portion (annular reinforcing portion) 30.

  Further, as shown in a partially enlarged view of FIG. 6, an annular inclined surface 34 that is inclined stepwise from the inner peripheral side of the upper surface 30 a of the annular convex portion 30 toward the wafer center of the circular concave portion 28 is formed. The annular inclined surface 34 has a plurality of steps 36.

  Here, the relationship between the wafer 11 held on the chuck table 20 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 20 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 32 between the device region 17 and the outer peripheral surplus region 19 of the wafer 11, and the boundary line The above-described grinding is performed by setting the grinding wheel 18b, which is set to a size larger than the radius of 32, so as to pass through the rotation center P1 of the chuck table 20 in an annular manner.

  When the grinding is completed, the etching solution is supplied from the etching solution supply means 42 into the circular recess 30 of the semiconductor wafer 11 sucked and held by the chuck table 40 of the etching apparatus as shown in FIG. Remove distortion.

  After the etching is completed, it is necessary to discharge the etching solution from the circular recess 28. However, as shown in the partially enlarged view of FIG. 7, a step-like annular inclined surface 34 is formed between the annular protrusion 30 and the circular recess 28. Therefore, the etching solution can be easily discharged from the circular recess 28 as shown by the arrow 44.

  As an option, when it is necessary to form a rewiring layer on the bottom surface of the circular recess 28 of the wafer 11, the rewiring layer is formed by photolithography used in the semiconductor manufacturing process. Since the step-like inclined surface 34 is formed, it can be easily discharged from the circular recess 28.

  According to the wafer processing method of the present embodiment, since the step-like annular inclined surface 34 is formed on the inner peripheral side of the annular convex portion 30 of the wafer 11, the annular convex portion 30 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 a step-like annular inclined surface 34 is formed between the annular convex portion 30 and the circular concave portion 28, air bubbles are formed between the annular convex portion 30 and the circular concave portion 28a when the dicing tape is attached. Is prevented from occurring.

DESCRIPTION OF SYMBOLS 10 Grinding unit 11 Semiconductor wafer 12 Spindle 17 Device area | region 18 Grinding wheel 18b Grinding wheel 19 Outer periphery excess area | region 20 Chuck table 23 Protection tape 28 Circular recessed part 30 Circular convex part 34 Stair-shaped annular inclined 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 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;
To form a circular recess in the back surface of the back surface of the wafer which is brought into contact with the rear surface of the wafer held by said holding means is rotated while rotating the grinding wheel corresponding to the device region of the wafer is ground, the A grinding step for leaving an outer peripheral surplus region as an annular convex portion surrounding the circular concave portion,
The grinding step includes moving the grinding wheel and the holding means relative to each other to move the grinding wheel in a direction approaching the wafer and moving the grinding wheel and the holding means relative to each other. A horizontal movement step of moving the grinding wheel by a predetermined distance toward the center of the wafer,
該鉛multiple該鉛straight direction grinding step with a straight direction grinding step and the said horizontal movement step is repeated a plurality of times by the same the grinding wheels by performing the same processing conditions, the upper surface within the periphery of the annular convex portion A method of processing a wafer, comprising forming an annular inclined surface inclined stepwise from the side toward the wafer center direction of the circular recess.

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