JP6086754B2 - Wafer processing method - Google Patents

Description

  The present invention relates to a wafer processing method in which a back surface corresponding to a device region is circularly ground and an annular convex portion surrounding a concave portion remains.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 1, a wafer processing method is known in which a recess formed by grinding a back surface corresponding to a device region into a circular shape and an annular protrusion that surrounds the recess are formed. .

  When such a processing method is carried out, a grinding strain is generated on the wafer. However, if this grinding strain remains on the wafer, the bending strength of the wafer becomes low, and handling is difficult. In addition, damage may occur in subsequent processes.

JP 2007-019461 A

  As a technique for eliminating the grinding distortion, it is conceivable to form a concave portion and an annular convex portion by grinding and then polish the concave portion with a polishing pad to remove the grinding strain.

  However, even if the recess is polished for the purpose of removing the grinding strain, it is difficult to remove the grinding strain at the boundary between the recess and the annular projection, and the single polishing pad does not remove the recess. Since it is difficult to reliably polish the boundary portion while polishing, grinding distortion may remain in the boundary portion only by polishing the recess.

  Then, there is a possibility that the wafer may be damaged at the time of handling or in the subsequent process due to the grinding distortion remaining in the boundary portion.

  The present invention has been made in view of the above problems, and the object of the present invention is to handle a wafer in which the back surface corresponding to the device region is circularly ground and the annular convex portion surrounding the concave portion remains. It is an object of the present invention to provide a method for processing a wafer that can reduce the risk of the wafer being damaged at any time or in subsequent steps.

According to the first aspect of the present invention, there is provided a wafer processing method having a concave portion and an annular convex portion surrounding the concave portion on the back surface of the wafer, the front surface side of the wafer being held by the holding means. A holding step that exposes the wafer, and after performing the holding step, the outer peripheral edge of the first polishing pad having a diameter smaller than the diameter of the wafer is rotated between the annular protrusion and the recess while rotating the holding means that holds the wafer. same time when polishing the concave portion at a first polishing pad by rotating the first polishing pad positioned to polish the by pressing the polishing member on the outer periphery boundary is brought into contact with the polishing member to the border of the wafer including the boundary And a polishing step.

  According to the present invention, for a wafer having a recess and an annular protrusion, the recess is polished, and the polishing of the boundary portion is performed by bringing the polishing member into contact with the boundary portion between the recess and the annular protrusion. To be implemented.

  Thereby, it is possible to prevent the grinding distortion from remaining in the boundary portion, and it is possible to reduce the possibility that the wafer is damaged at the time of handling or in a subsequent process.

It is a perspective view shown about the semiconductor wafer which is a process target. It is a perspective view of the grinding unit for implementing a grinding step. It is side surface sectional drawing explaining a holding | maintenance step. It is side surface sectional drawing explaining a grinding | polishing step. It is a perspective view explaining a grinding | polishing step. It is a top view explaining a grinding | polishing step.

  Hereinafter, embodiments 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 W to be processed (hereinafter also simply referred to as “wafer W”) is shown. On the surface of the wafer W, the first division planned line (street) S1 and the second division planned line S2 are formed orthogonally, and a plurality of sections divided by the first division planned line S1 and the second division planned line S2. A device D such as an LSI is formed in each region.

  A region where the device D is formed on the surface Wa of the wafer W is a device region 17. An outer peripheral surplus region 19 where the device D is not formed is formed so as to cover the outer periphery of the device region 17.

  Embodiments of the present invention for processing such a wafer W will be described in the following order. As shown in FIG. 2, in this embodiment, before carrying out the division starting point forming step described in detail later, the back surface Wb of the wafer W is ground to form a circular recess Wc and surround the circular recess Wc. A grinding step for forming the annular convex portion Wd is performed.

  FIG. 2 shows a grinding unit 11 for performing a grinding step. The spindle 18 is rotatably accommodated in a housing 12, the mounter 13 is fixed to the tip of the spindle 18, and the mounter 13 is screwed. A grinding wheel 21 having a plurality of grinding wheels 22 arranged in an annular shape and a servo motor (not shown) for rotating the spindle 18 are configured.

  A chuck table 25 is disposed below the grinding unit 11, and the wafer W is sucked and held on the chuck table 25. In the previous stage of the suction and holding, a protective tape attaching step for attaching the protective tape 10 (FIG. 1) to the surface Wa of the wafer W is performed in order to protect the device D (FIG. 1). Then, the wafer W is held on the chuck table 25 so that the protective tape 10 is on the lower side.

  Next, while rotating the chuck table 25 in the direction indicated by the arrow 27 at, for example, 300 rpm, the grinding wheel 21 is rotated in the direction indicated by the arrow 26, for example, at 6000 rpm, and the grinding wheel 22 of the grinding wheel 21 contacts the back surface of the wafer W. Let Then, the grinding wheel 21 is ground and fed downward by a predetermined amount at a predetermined grinding feed speed.

  As a result, as shown in FIG. 2, the back surface of the device region 17 (see FIG. 1) corresponding to the region where the device D is formed is ground and removed on the back surface of the wafer W to a predetermined thickness (for example, 30 μm). While the circular recessed part Wc is formed, the area | region corresponding to the outer periphery surplus area | region 19 (refer FIG. 1) in which the device D is not formed remains, and the cyclic | annular convex part (ring-shaped reinforcement part) Wd is formed.

  In order to remove the grinding distortion remaining on the wafer W ground as described above, the processing described below is performed. First, as shown in FIG. 3, a holding step is performed in which the front surface Wa side of the wafer W is held by the chuck table 42 and the back surface Wb side of the wafer W is exposed.

  The holding surface 44 of the chuck table 42 of this embodiment is connected to a suction source (not shown) so that the surface Wa side of the wafer W is sucked and held.

  Further, since the surface Wa of the wafer W is protected by the protective tape 10, the wafer W is held by the holding surface 44 via the protective tape 10.

  After performing the holding step, as shown in FIGS. 4 to 6, the first polishing pad 50 having a diameter smaller than the diameter of the wafer W while rotating the chuck table 42 holding the wafer W in the direction of the arrow R1. The outer peripheral edge 52 is positioned at the boundary We between the annular convex portion Wd and the concave portion Wc, and the first polishing pad 50 is rotated in the direction of the arrow R2 to polish the concave portion Wc with the first polishing pad 50 and includes the boundary We. A polishing step is performed in which the polishing member 60 is pressed against the outer peripheral portion Wf of the wafer W to bring the polishing member 60 into contact with the boundary We and polish the boundary We.

  In the present embodiment, the grinding step is performed using a polishing apparatus 70 including two spindles 51 and 61 that are rotationally driven.

  A mount 53 is provided at the lower end of the spindle 51, and the first polishing pad 50 is fixed to the lower portion of the mount 53.

  As shown in FIG. 6, the first polishing pad 50 is configured such that the outline in plan view is circular, and the diameter D1 formed by the outer peripheral edge 52 is smaller than the diameter Dw of the wafer W. Composed.

  Further, the rotation axis center 50c of the first polishing pad 50 is arranged such that the outer peripheral edge 52 of the first polishing pad 50 is positioned at the boundary We between the annular convex portion Wd and the concave portion Wc.

  Then, while rotating the first polishing pad 50 in the direction of the arrow R2, the surface of the recess Wc is polished by pressing the first polishing pad 50 against the recess Wc.

  For example, the first polishing pad 50 may be composed of urethane impregnated with abrasive grains, and polishing may be performed while supplying pure water. In addition, it is conceivable that the first polishing pad 50 is composed of a pad-shaped member made of urethane or nonwoven fabric, and polishing is performed by supplying a grinding liquid (slurry) containing loose abrasive grains. .

  By the polishing by the first polishing pad 50 as described above, the grinding distortion generated in the concave portion Wc of the wafer W is removed.

  A mount 63 is provided at the lower end of the other spindle 61, and the polishing member 60 is fixed to the lower portion of the mount 63.

  As shown in FIG. 6, the polishing member 60 is configured such that the outline in plan view is circular, and the diameter D2 formed by the outer peripheral edge 62 is configured to be smaller than the diameter Dw of the wafer W. The

  Further, the rotation axis center 60c of the grinding device 2 is arranged such that the outer peripheral edge 62 of the polishing member 60 straddles the boundary We between the annular convex portion Wd and the concave portion Wc.

  Then, while rotating the polishing member 60 in the direction of the arrow R3, the portion of the boundary We is polished by pressing the polishing member 60 against the boundary We.

  For example, the polishing member 60 may be made of urethane impregnated with abrasive grains, and polishing may be performed while supplying pure water. In addition to this, it is conceivable that the polishing member 60 is composed of a pad-like member made of urethane or nonwoven fabric, and polishing is performed by supplying a grinding liquid (slurry) containing free abrasive grains.

  In the present embodiment, the polishing member 60 is made of urethane, so that the polishing member 60 is deformed so as to follow the shape of the annular protrusion Wd, and the boundary Wel is wrapped in the state where the annular protrusion Wd is wrapped from above. The polishing member 60 is pressed against the surface.

  By the polishing by the polishing member 60 as described above, the grinding distortion generated at the boundary We of the wafer W is removed.

  In this embodiment, the polishing member 60 is attached to the spindle 61 and rotated. However, the polishing may be performed by simply pressing the polishing member 60 against the boundary We without rotating. The shape of the polishing member 60 may be a cylindrical shape as in the first polishing pad 50, or may be a cubic shape, and the shape is not particularly limited. Further, the polishing member 60 may be exactly the same as the first polishing pad 50.

  Further, in the present embodiment, the first polishing pad 50 and the polishing member 60 are arranged adjacent to each other, and two polishing means are arranged side by side, so that both the recess Wc and the boundary We of the wafer W are simultaneously applied. Polishing is performed. As a result, it is possible to shorten the time required for removing the grinding strain. Note that these two polishing means may be provided in separate apparatuses, and the recess Wc and the boundary We may be polished stepwise.

The present invention can be implemented as described above.
That is, the wafer W has a recess Wc on the back surface Wb of the wafer W and an annular protrusion Wd surrounding the recess Wc, and the front surface Wa side of the wafer W is held by a chuck table 42 as a holding means. The first polishing pad 50 having a diameter smaller than the diameter of the wafer W while rotating the chuck table 42 holding the wafer W after performing the holding step for exposing the back surface Wb side of the wafer W and the holding step. The outer peripheral edge 52 is positioned on the boundary We between the annular convex part Wd and the concave part Wc, the first polishing pad 50 polishes the concave part Wc, and the outer peripheral part Wf of the wafer W including the boundary Wel is polished. A polishing step is performed in which the member 60 is pressed to bring the polishing member 60 into contact with the boundary We and polish the boundary We.

  As a result, for the wafer W on which the concave portion Wc and the annular convex portion Wd are formed, the concave portion Wc is polished, and the polishing member 60 is brought into contact with the boundary We between the concave portion Wc and the annular convex portion Wd. Polishing of the boundary We is performed.

  Further, residual grinding distortion can be prevented also at the boundary We part, and the possibility that the wafer W may be damaged during handling or in a subsequent process can be reduced.

2 Grinding device 42 Chuck table 50 First polishing pad 52 Outer peripheral edge 60 Polishing member 70 Polishing device W Wafer Wa Front surface Wb Back surface Wc Recessed portion Wd Annular convex portion We Boundary Wf Outer peripheral portion

Claims (1)

A wafer processing method having a concave portion and an annular convex portion surrounding the concave portion on the back surface of the wafer,
A holding step of holding the front side of the wafer with a holding means to expose the back side of the wafer;
After carrying out the holding step, while rotating the holding means holding the wafer, the outer peripheral edge of the first polishing pad having a diameter smaller than the diameter of the wafer is set at the boundary between the annular convex portion and the concave portion. to rotate said first polishing pad positioned simultaneously when polishing the concave portion at said first polishing pad, and pressing the polishing member on the outer peripheral portion of the wafer including the boundary of the polishing member to the boundary those A polishing step for contacting and polishing the boundary;
For processing a wafer comprising:

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