JP2014220444A - Sheet and method for processing wafer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet capable of reducing the risk of breaking a wafer when removing an outer peripheral protrusion, and a method for processing wafer using the same.SOLUTION: A sheet is stuck on a back side of a wafer in which the center of the back side is ground so that a recess can be formed and so that an outer peripheral protrusion surrounding the recess can be formed. The sheet comprises a base material, and a paste layer that has a size corresponding to the size of the recess arranged on the base material and that has a thickness corresponding to the depth of the recess.

Description

  The present invention relates to a sheet that is attached to a wafer having a recess and an outer peripheral protrusion that surrounds the recess on the back surface, and a wafer processing method using the sheet.

  In the 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 semiconductor wafer having a substantially disk shape, and devices such as IC and LSI are divided into these partitioned regions. Form. 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 the back surface before cutting along the street. In recent years, in order to achieve a reduction in weight and size of electrical equipment, it has been required to make the wafer thinner, for example, about 50 μm.

  Such thinly formed wafers are not as elastic as paper and are difficult to handle and may be damaged during transportation. Therefore, a grinding method in which only the back surface corresponding to the device region of the wafer is ground and a reinforcing annular convex portion is formed on the back surface of the wafer corresponding to the outer peripheral surplus region surrounding the device region is disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-173487. Proposed in the gazette.

  As a method of dividing the wafer having the annular convex portion formed on the outer periphery of the back surface along the street (scheduled line), there is a method in which the annular convex portion is removed and then the wafer is cut with a cutting blade from the front side of the wafer. It has been proposed (see JP 2007-19379 A).

  In Japanese Patent Application Laid-Open No. 2007-17379, as a method of removing the annular convex portion, a method of removing the annular convex portion by grinding, and after cutting the interface between the circular concave portion and the annular convex portion with a cutting blade into a circular shape, A method for removing the portion is disclosed.

  Recently, in the removal of the annular convex portion by grinding, the bottom of the circular concave portion is scratched, or, for example, after the circular concave portion is formed at the center of the back surface of the wafer and the annular convex portion surrounding the circular concave portion is formed. In a wafer in which a metal film is formed in a circular recess, it has been found that a grinding wheel entrains the metal film during grinding of the annular protrusion and causes grinding failure.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. 2011-61137 has a circular concave portion formed on the back surface and an annular convex portion surrounding the circular concave portion, and a boundary portion between the circular concave portion and the annular convex portion. An annular convex portion for removing the annular convex portion from the wafer unit comprising a wafer formed with a dividing groove, an adhesive tape attached to the back surface of the wafer, and an annular frame to which an outer peripheral portion of the adhesive tape is attached. A removal device is disclosed.

JP 2007-173487 A JP 2007-19379 A JP 2011-61137 A

  In the annular convex part removal device disclosed in Patent Document 3, the annular convex part is not easily peeled off from the adhesive tape during the removal of the annular convex part, and the damaged debris adheres to the upper surface of the wafer or is damaged on the upper surface of the wafer. It may be scratched.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a sheet that can reduce the risk of damaging the wafer when the outer peripheral convex portion is removed, and the processing of the wafer using the sheet. Is to provide a method.

  According to the first aspect of the present invention, a sheet is affixed to the back surface of a wafer in which the center of the back surface is ground to form a concave portion and an outer peripheral convex portion surrounding the concave portion is formed. And a glue layer having a size corresponding to the size of the concave portion disposed on the substrate and having a thickness corresponding to the depth of the concave portion.

  According to a second aspect of the present invention, there is provided a wafer processing method using the sheet according to the first aspect, wherein the center of the back surface is ground to form a concave portion and an outer peripheral convex portion surrounding the concave portion is formed. Positioning the adhesive layer of the sheet in the concave portion of the wafer and attaching the back side of the wafer on the sheet; and after performing the wafer attaching step, the concave portion of the wafer and the outer peripheral convex portion A laser beam irradiation step for irradiating a wafer with a laser beam along the boundary to form a dividing groove or a dividing starting point along the boundary, and removing the outer peripheral convex portion from the wafer after performing the laser beam irradiation step. And a step of processing the wafer.

  The sheet of the present invention has a size corresponding to the size of the concave portion of the wafer and a paste layer having a thickness corresponding to the depth of the concave portion disposed on the substrate. When the wafer is attached to the sheet, only the concave portion of the wafer is attached to the sheet by the adhesive layer, and the outer peripheral convex portion is not attached to the sheet. Therefore, when the outer peripheral convex portion is removed from the wafer, the risk of the outer peripheral convex portion being damaged can be reduced.

It is a surface side perspective view of a semiconductor wafer. It is a back surface side perspective view of a wafer which has a circular concave part and an annular convex part which surrounds the circular concave part on the back surface. It is a perspective view of a sheet concerning an embodiment of the present invention. It is a perspective view which shows a wafer sticking step. 5A is a perspective view of the wafer unit, and FIG. 5B is a cross-sectional view thereof. It is a perspective view which shows a laser beam irradiation step. FIG. 7A is a cross-sectional view showing the laser beam irradiation step, and FIG. 7B is a cross-sectional view showing the removal step. It is sectional drawing which shows a dicing step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a front side perspective view of a semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11. On the surface 11 a of the semiconductor wafer 11, devices 15 such as ICs and LSIs are formed in each region partitioned by a plurality of division lines (streets) 13 formed in a lattice pattern.

  The wafer 11 has a device region 17 in which a plurality of devices 15 are formed on the surface 11 a and an outer peripheral surplus region 19 that surrounds the device region 17. Reference numeral 11 b denotes the back surface of the wafer 11.

  Referring to FIG. 2, a rear perspective view of the wafer 11 to which the sheet of the present invention is attached is shown. In the wafer 11 shown in FIG. 1, the back surface 11 b of the wafer 11 corresponding to the device region 17 is ground to form a circular recess 21 having a thickness of about 50 μm, and the outer peripheral side of the circular recess 21 is not ground. An annular convex portion 23 that remains and includes the outer peripheral surplus region 19 is formed. The annular convex part 23 acts as a reinforcing part, and its thickness is 700 μm, for example.

  Referring to FIG. 3, a perspective view of the seat 10 according to the embodiment of the present invention is shown. The sheet 10 includes a base material 12 formed from polyolefin, polyethylene terephthalate, polyvinyl chloride, or the like, and a rubber-based or acrylic paste layer (adhesive layer) 14 formed on the base material 12.

  The glue layer 14 has a diameter slightly smaller than the diameter of the circular recess 21 of the wafer 11 shown in FIG. 2 and has a thickness substantially the same as the depth of the circular recess 21, that is, about 650 μm in this embodiment. ing. In other words, the glue layer 14 has a size corresponding to the size of the circular recess 21 and a thickness corresponding to the depth of the circular recess 21.

  Next, a wafer processing method according to an embodiment of the present invention in which the annular protrusion 23 is removed from the wafer 11 using such a sheet 10 will be described with reference to FIGS. Referring to FIG. 4, there is shown a perspective view of a wafer attaching step in which the adhesive layer 14 of the sheet 10 is positioned in the circular recess 21 of the wafer 11 and the back surface 11 b side of the wafer 11 is attached on the sheet 10.

  Since the adhesive layer 14 of the sheet 10 has a size corresponding to the circular concave portion 21 formed on the back surface 11b of the wafer 11 and a thickness corresponding to the depth of the circular concave portion 21, the wafer bonding step is performed. Only the 11 circular recesses 21 are attached to the adhesive layer 14 of the sheet 10, and the annular protrusions 23 are not attached to the adhesive layer 14 and abut against the base material 12 of the sheet 10.

  In carrying out the wafer processing method of the present embodiment, the sheet 10 in which the circular recess 21 of the wafer 11 is adhered to the adhesive layer 14 is bonded to the annular frame F with the base material 12 interposed therebetween. The outer periphery of the sheet 10 is cut into a circle to form the wafer unit 16.

  After the wafer unit 16 is formed, as shown in FIGS. 6 and 7A, the wafer 11 is sucked and held via the sheet 10 by the chuck table 18 of the laser processing apparatus. Then, a laser beam having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer 11 is irradiated from the condenser (laser processing head) 20 to the boundary 25 between the circular concave portion 21 and the annular convex portion 23, and the chuck table 18 is applied. By rotating slowly in the direction of the arrow R1, a dividing groove 27 is formed over the entire circumference at the boundary 25 between the circular concave portion 21 and the annular convex portion 23 of the wafer 11.

  The dividing groove 27 may be formed at a depth at which the wafer 11 is completely cut, or may be formed at a depth at which the wafer 11 is cut incompletely, and may be a starting point for cutting in a subsequent removal step. As an alternative embodiment, a laser beam having a wavelength (for example, 1064 nm) having transparency to the wafer 11 is irradiated from the laser processing head 20, and a wafer at a boundary 25 portion between the circular concave portion 21 and the annular convex portion 23 of the wafer 11. A circular modified layer may be continuously formed inside, and this modified layer may be a starting point for separation in a subsequent removal step.

  After performing the laser beam irradiation step, as shown in FIG. 7B, a removal step of removing the annular convex portion 23 from the wafer 11 is performed. When this removal step is carried out, the device region 17 remains adhered to the sheet 10 with the adhesive layer 14.

  When a partially cut groove or modified layer is formed on the wafer 11 instead of the divided groove 27 that completely cuts the wafer 11 and the partially cut groove or modified layer is used as the dividing starting point, an external force is applied to the wafer 11. Is applied to divide the wafer 11 into the device region 17 and the outer peripheral surplus region 23 from the separation starting point, and then remove the annular protrusion 23 from the wafer 11.

  After performing the removal step, the device region 17 of the wafer 11 is diced, and a dicing step is performed to divide the device region 17 into individual devices 15. In the dicing step, the device region 17 is sucked and held via the sheet 10 by the chuck table 22 of the cutting apparatus. In FIG. 8, reference numeral 24 denotes a cutting unit, which includes a spindle 26 that is rotationally driven and a cutting blade 28 that is attached to the tip of the spindle 26.

  In the dicing step, the cutting blade 28 is cut to the glue layer 14 through the division line 13 extending in the first direction while rotating at high speed, and the chuck table 22 is processed and fed in the processing feed direction (perpendicular to the paper surface). The dividing line 13 extending in the first direction is cut.

  While the cutting unit 24 is indexed and fed, the division lines 13 extending in the first direction are cut one after another. Next, after rotating the chuck table 22 by 90 degrees, all the planned dividing lines extending in the second direction orthogonal to the first direction are cut to divide the device region 17 of the wafer 11 into the individual devices 15. To do.

  In the wafer processing method according to the above-described embodiment, the wafer 11 has only the circular concave portion 21 of the wafer 11 adhered to the sheet 10 by the adhesive layer 14 formed on the sheet 10, and the annular convex portion 23 is not adhered. When removing the annular projection 23 from the wafer 11, the risk of damage to the annular projection can be reduced.

  In the embodiment described above, the wafer 11 has been described as having the circular recess 21 on the back surface, but the recess is not necessarily limited to the circular recess 21 and may be a recess having another shape. In this case, the glue layer 14 formed on the sheet 10 is formed in a shape and size suitable for the recess.

DESCRIPTION OF SYMBOLS 10 Sheet | seat 11 Semiconductor wafer 12 Base material 14 Adhesive layer 16 Wafer unit 17 Device area | region 19 Outer peripheral area | region 21 Circular recessed part 23 Annular convex part 25 Boundary 27 Dividing groove

Claims (2)

The sheet is pasted on the back surface of the wafer where the center of the back surface is ground to form a recess and the outer peripheral convex portion surrounding the recess is formed,
A substrate;
A paste layer having a size corresponding to the size of the recess disposed on the substrate and having a thickness corresponding to the depth of the recess;
A sheet characterized by comprising: A wafer processing method using the sheet according to claim 1,
The adhesive layer of the sheet is positioned in the concave portion of the wafer in which the center of the back surface is ground to form the concave portion and the outer peripheral convex portion surrounding the concave portion is formed, and the rear surface side of the wafer is stuck on the sheet Wafer sticking step,
A laser beam irradiation step of irradiating the wafer with a laser beam along a boundary between the concave portion of the wafer and the outer peripheral convex portion after forming the wafer, and forming a dividing groove or a dividing starting point along the boundary;
After the laser beam irradiation step is performed, a removal step of removing the outer peripheral convex portion from the wafer;
A wafer processing method characterized by comprising:

Images