JP2012043824A - Wafer processing method and protection member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wafer processing method which inhibits deterioration in processing quality of a wafer though bumps are formed and enables planarization.SOLUTION: The processing method of cutting or polishing a rear face of a wafer whose front face has a bump-formed region on which a plurality of bumps are formed and a peripheral bump-unformed region surrounding the bump formed region, comprises: a preparation step of preparing a protection member having a circular concave part housing the plurality of bumps and having a depth substantially same as a height of the bump, and an annular convex part formed corresponding to the peripheral bump-unformed region so as to surround the circular concave part; a bump protection step of protecting the bumps on the wafer by housing the plurality of bumps in the circular concave part of the protection member while pasting the annular convex part of the protection member to the peripheral bump-unformed region; and a processing step of processing the rear face of the wafer by cutting means or polishing means by holding the wafer with a chuck table on the protection member side on which the protection member is pasted.

Description

  The present invention relates to a wafer processing method for grinding or polishing the back surface of a wafer having a plurality of bumps formed on the surface, and a protective member used in the processing method.

  In the manufacturing process of semiconductor devices, grid-like division lines called streets are formed on the surface of a wafer made of silicon or a compound semiconductor, and devices such as ICs and LSIs are formed in each area partitioned by the division lines. The These wafers are ground and polished on the back surface and thinned to a predetermined thickness, and then divided by a cutting device or the like along the streets to manufacture individual semiconductor devices.

  In order to protect a device formed on the surface of the wafer during grinding or polishing, a protective tape as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-307620 is attached to the surface of the wafer. The wafer is held by a chuck table of a grinding or polishing apparatus via a protective tape, and the exposed back surface of the wafer is ground and polished.

  In recent years, as a technology for realizing lighter, thinner, and smaller semiconductor devices, flip chips have been formed by forming a plurality of metal protrusions called bumps on the device surface, and directly bonding these bumps against the electrodes formed on the wiring board. A mounting technique called bonding has been put into practical use (see, for example, JP-A-2001-237278).

JP-A-11-307620 JP 2001-237278 A

  When a protective tape is attached to the surface of the wafer on which the bumps are formed, the wafer is supported by the protective tape via the bumps. However, since no device is normally formed on the outer periphery of the wafer, bumps are not formed on the outer periphery of the wafer.

  As a result, the outer peripheral portion of the wafer on which no bump is formed is not supported by the protective tape. If the back surface of the wafer is ground or polished in this state, there is a problem that processing quality deteriorates such as a lack of the outer peripheral portion of the wafer, or flattening is difficult.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wafer processing method that prevents deterioration of processing quality even in a wafer on which bumps are formed and enables flattening. It is to be.

  According to the first aspect of the present invention, there is provided a wafer processing method for grinding or polishing a back surface of a wafer having a bump forming region in which a plurality of bumps are formed and an outer peripheral bump non-forming region surrounding the bump forming region on the surface. A circular recess that accommodates the plurality of bumps having substantially the same depth as the height of the bump, and an annular protrusion that is formed so as to surround the circular recess corresponding to the peripheral bump non-formation region. A preparatory step for preparing a protection member having a plurality of bumps, and accommodating the plurality of bumps in the circular recesses of the protection member, and attaching the annular projections of the protection members to the peripheral bump-unformed region on the wafer surface. A bump protection step for protecting the bumps of the wafer by attaching the protective member side of the wafer to which the protective member is adhered to a chuck table and grinding the back surface of the wafer by grinding means or polishing. The wafer processing method, characterized by comprising a processing step of processing by means is provided.

  According to the second aspect of the present invention, when a back surface of a wafer having a bump forming region on which a plurality of bumps are formed and an outer peripheral bump non-forming region surrounding the bump forming region on the surface is ground or polished, the wafer is attached to the wafer. A protective member that is attached and holds the wafer and protects the bump, the circular recess having a depth substantially the same as the height of the bump and accommodating the plurality of bumps, and surrounding the circular recess, There is provided a protective member comprising an annular convex portion corresponding to the peripheral bump non-formation region.

  Preferably, a resin coating is applied on the bottom surface of the circular recess of the protective member.

  According to the wafer processing method of the present invention, the outer peripheral bump unformed region where the bump is not formed in a state where the plurality of bumps are accommodated in the circular concave portion is supported by the annular convex portion of the protective member. Therefore, when grinding or polishing the wafer, it is possible to prevent deterioration of processing quality such as lack of the outer peripheral portion of the wafer, and to flatten the entire back surface of the wafer.

It is a perspective view of a semiconductor wafer suitable for processing by the processing method of the present invention. 2A is a perspective view of the protective member, and FIG. 2B is a cross-sectional view of the protective member. It is a perspective view which shows the protection member manufacturing method. It is explanatory drawing of a protection member manufacturing method. It is a partial cross section side view which shows a bump protection step. It is a perspective view of the grinding device suitable for implementing the processing method of the present invention. It is a partial cross section side view which shows a grinding step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a semiconductor wafer 11 suitable for processing by the processing method of the present invention is shown. The semiconductor wafer 11 has a front surface 11 a and a back surface 11 b, and a plurality of streets 13 are formed orthogonally on the front surface 11 a, and devices 15 are formed in each region partitioned by the streets 13.

  As shown in the enlarged view of FIG. 1, a plurality of protruding bumps 17 are formed on the four sides of each device 15. Since the bumps 17 are formed on the four sides of each device 15, the semiconductor wafer 11 has a bump formation region 19 where the bumps 17 are formed and an outer peripheral bump non-formation region 21 surrounding the bump formation region 19. Yes.

  Referring to FIG. 2A, a perspective view of the protective member 2 used in the wafer processing method of the present invention is shown. FIG. 2B is a longitudinal sectional view of the protection member 2. The protective member 2 has a diameter corresponding to the diameter of the bump forming region 19 of the semiconductor wafer 11 shown in FIG. 1 and a circular recess 4 having a depth substantially equal to the height of the bump 17 and the circular recess 4. An annular convex portion 6 corresponding to the outer peripheral bump unformed region 21 of the surrounding wafer 11 is provided.

  The depth of the recess 4 is 50 μm to 300 μm depending on the height of the bump 17. Preferably, a resin coating 8 for protecting the bumps 17 is applied on the bottom surface of the recess 4. As a material of the protection member 2, a silicon wafer sliced from a silicon ingot, resin, glass or the like is suitable.

  Next, with reference to FIG.3 and FIG.4, the manufacturing method of the protection member 2 which uses the silicon wafer 3 is demonstrated. In this manufacturing method, the protective member 2 is manufactured by the grinding unit 10 of the grinding apparatus.

  The grinding unit 10 has a spindle 14 rotatably accommodated in a spindle housing 12, and the spindle 14 is driven by a motor (not shown). A wheel mount 16 is fixed to the tip of the spindle 14, and a grinding wheel 18 having a plurality of grinding wheels 20 arranged in an annular shape with respect to the wheel mount 16 is detachably mounted.

  As shown in FIG. 3, while rotating the chuck table 22 in the direction indicated by the arrow 25 at 300 rpm, for example, the grinding wheel 20 is rotated in the direction indicated by the arrow 23 at, for example, 6000 rpm, and the grinding unit feed mechanism is driven to perform grinding. The grinding wheel 20 of the wheel 18 is brought into contact with the back surface of the wafer 3. Then, the grinding wheel 18 is ground by a predetermined amount at a predetermined grinding feed speed.

  As a result, a circular recess 4 is formed in the wafer 3 and an annular protrusion 6 surrounding the circular recess 4 is formed, so that the protection member 2 can be manufactured. By grinding while measuring the thickness of the circular recess 4 with a thickness measurement gauge (not shown), the circular recess 4 having a desired depth can be obtained.

  The relationship between the wafer 3 and the grinding wheel 18 when the protective member 2 is formed by grinding will be described with reference to FIG. The silicon wafer 3 has the same diameter as the semiconductor wafer 11 shown in FIG.

  The center of rotation P1 of the chuck table 22 and the center of rotation P2 of the grinding wheel 20 arranged annularly are eccentric, and the grinding wheel 20 passes through the center of rotation P1 of the wafer 3 and is ground on the grinding wheel 18. The outer peripheral edge of the grindstone 20 is set to an outer diameter passing through the outer periphery 24 of the bump forming region 19 of the wafer 11, and the grindstone 20 disposed in an annular shape is set so as to pass through the rotation center P <b> 1 of the chuck table 22. Yes.

  When the protection member 2 having the circular recess 4 having a desired depth is completed, a relatively soft resin coating 8 that protects the bump 17 when the bump 17 of the wafer 11 contacts the bottom surface of the circular recess 4 of the protection member 2. Form.

  When the preparation step of the protection member 2 is completed, the bumps 17 of the wafer 11 are accommodated in the circular recesses 4 of the protection member 2 as shown in FIG. The forming region 21 is bonded with an adhesive.

  The bumps 17 are in contact with the resin coating 8 formed on the bottom surface of the circular recess 4 of the protective member 2 and the wafer 11 is supported by the protective member 2 via the bumps 17, but the resin coating 8 is made of a relatively soft resin. Since it is formed, the bump 17 can be protected without being damaged.

  After the protective member 2 is adhered to the outer peripheral bump non-formation region 21 of the wafer 11 and the bumps 17 of the wafer 11 are accommodated and protected in the circular recesses 4 as described above, a grinding device 32 as shown in FIG. 6 is used. Then, a grinding step for grinding the back surface 11b of the wafer 11 is performed.

  In FIG. 6, 34 is a base (housing) of the grinding device 32, and a column 36 is erected on the rear side of the base 34. A pair of guide rails 38 extending in the vertical direction are fixed to the column 36.

  A grinding unit (grinding means) 40 is mounted along the pair of guide rails 38 so as to be movable in the vertical direction. The grinding unit 40 includes a spindle housing 42 and a support portion 44 that supports the spindle housing 42, and the support portion 44 is attached to a moving base 46 that moves up and down along a pair of guide rails 38. Yes.

  The grinding unit 40 includes a spindle 48 rotatably accommodated in a spindle housing 42, a wheel mount 50 fixed to the tip of the spindle 48, and a plurality of grinding wheels that are screwed to the wheel mount 50 and arranged in an annular shape. A grinding wheel 52 having an electric power source 54 and an electric motor 56 for rotating the spindle 48 are included.

  The grinding device 32 includes a grinding unit feed mechanism 62 including a ball screw 58 and a pulse motor 60 that move the grinding unit 40 in the vertical direction along a pair of guide rails 38. When the pulse motor 60 is driven, the ball screw 58 rotates and the moving base 46 is moved in the vertical direction.

  A recess 34a is formed on the upper surface of the base 34, and a chuck table mechanism 64 is disposed in the recess 34a. The chuck table mechanism 64 has a chuck table 66 and is moved in the Y-axis direction between a wafer attaching / detaching position A and a grinding position B facing the grinding unit 40 by a moving mechanism (not shown). 68 and 70 are bellows. On the front side of the base 34, an operation panel 72 is provided for an operator of the grinding device 32 to input grinding conditions and the like.

  A grinding step performed using such a grinding apparatus 32 will be described below. On the chuck table 66 positioned at the wafer attaching / detaching position A shown in FIG. 6, the wafer 11 having the protective member 2 adhered to the surface thereof as shown in FIG. Next, the chuck table 66 is moved to the grinding position B by moving in the Y-axis direction.

  While the chuck table 66 is rotated at, for example, 300 rpm, the grinding wheel 52 is rotated in the same direction as the chuck table 66 at, for example, 6000 rpm, as shown in FIG. The feed mechanism 52 is operated to bring the grinding wheel 54 into contact with the back surface 2 b of the wafer 2.

  Then, the grinding wheel 50 is ground by a predetermined amount at a predetermined grinding feed speed, and the wafer 2 is ground. While measuring the thickness of the wafer 2 with a contact-type thickness measurement gauge (not shown), the wafer 2 is finished to a desired thickness, for example, 50 μm.

  In the grinding method of the above-described embodiment, the outer peripheral bump unformed region 21 of the wafer 11 where the bumps 17 are not formed is supported by the annular convex portion 6 of the protective member 2, and the bump forming region 19 where the plurality of bumps 17 are formed. Is accommodated in the circular recess 4 of the protective member 2 to protect the bumps 17.

  Since the peripheral bump non-formation region 21 is supported by the annular convex portion 6 and the bump 17 is supported by the circular concave portion 4 through the resin coating 8, the wafer 11 having the bump 17 can be uniformly supported. As a result, the back surface 11b of the wafer 11 can be ground uniformly, and deterioration of processing quality such as chipping of the outer peripheral portion of the wafer 11 can be prevented.

  In the above-described embodiment, an example in which the present invention is applied to a wafer grinding method has been described. However, the present invention is not limited to this, and a polishing method for polishing the back surface 11b of the wafer 11 using a polishing pad. It can be similarly applied to.

2 Protective member 4 Circular concave portion 6 Annular convex portion 8 Resin coating 10 Grinding unit 11 Semiconductor wafer 15 Device 17 Bump 19 Bump formation region 21 No peripheral bump formation region 32 Grinding device 40 Grinding unit 52 Grinding wheel 54 Grinding wheel 66 Chuck table

Claims (3)

A wafer processing method for grinding or polishing a back surface of a wafer having a bump forming region on which a plurality of bumps are formed and a peripheral bump non-forming region surrounding the bump forming region on the surface,
A circular concave portion accommodating the plurality of bumps having substantially the same depth as the height of the bump, and an annular convex portion formed so as to surround the circular concave portion corresponding to the peripheral bump non-formation region, A preparation step of preparing a protective member having;
Bump protection that protects the bumps of the wafer by accommodating the plurality of bumps in the circular recesses of the protection member and affixing the annular projections of the protection members to the peripheral bump-unformed region on the wafer surface Steps,
A processing step of holding the protective member side of the wafer to which the protective member is adhered with a chuck table and processing the back surface of the wafer with a grinding means or a polishing means;
A wafer processing method characterized by comprising: When a back surface of a wafer having a bump forming area on which a plurality of bumps are formed and a peripheral bump non-forming area surrounding the bump forming area is ground or polished, the wafer is affixed to the wafer to hold the wafer. A protective member for protecting the bump,
A circular recess capable of accommodating the plurality of bumps having a depth substantially the same as the height of the bumps;
An annular convex portion surrounding the circular concave portion and corresponding to the peripheral bump unformed region;
A protective member comprising:   The protective member according to claim 2, wherein a resin coating is provided on a bottom surface of the circular recess.

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