TWI779109B - Grinding method of workpiece - Google Patents

Abstract

[Problem] In the grinding method of forming a ring-shaped reinforcing part on the back surface of the workpiece, it is necessary to prevent the formation of scratches on the back surface or the occurrence of cracks in the workpiece due to the entanglement of the abrasive grains that fall out during grinding. [Solution] The grinding method of the workpiece of the present invention is to use the grinding stone (42b) to grind the back surface (Wb) of the workpiece (W) having the element region (Wa1) and the peripheral remaining region (Wa2) on the surface (Wa). ) method, comprising: a protection step of covering the surface (Wa) of a workpiece (W) with a protection member (T1); The holding surface (30a) of the suction cup platform (30) that the rotating shaft (33) rotates, the step of holding the protective member (T1) side; and utilizing the rotating shaft (40) that is orthogonal to the holding surface (30a) to rotate The grinding whetstone (42b) grinds the back surface (Wb) of the workpiece corresponding to the element area (Wa1) while supplying grinding water to form a circular concave portion (Wb1) and an annular reinforcing portion surrounding the circular concave portion (Wb1). (Wb2) The grinding step, in which the discharge of the grinding water including the dropped abrasive grains is promoted by the inclination of the workpiece (W).

Description

Grinding method of workpiece

The present invention relates to a method of grinding a plate-shaped workpiece such as a semiconductor wafer with a grinding whetstone.

A workpiece with a plurality of components such as ICs or LSIs formed on the surface is ground to a predetermined thickness on the back, and is divided into individual component wafers by a dicing device or other dividing device and used in various electronic devices. The grinding device that grinds the back of the workpiece is equipped with: a suction cup table that holds the workpiece to which a surface protection member made of resin or the like is attached; a grinding machine that rotatably supports and grinds the workpiece held on the suction cup table The grinding unit of the grinding stone; and the grinding water supply means for supplying grinding water to the grinding grinding stone through the flow path formed in the shaft center of the spindle constituting the grinding unit can efficiently grind the workpiece.

In recent years, in order to achieve weight reduction and miniaturization of element wafers, thinner workpieces are required in wafer grinding methods. However, a thinner wafer as described above has lower rigidity, is difficult to handle, and may be damaged during wafer transfer or the like. Therefore, there is a grinding method that, for example, grinds the workpiece to be thinner to 100 μm or less. In addition, only the area on the back surface of the workpiece corresponding to the area where the device is formed is thinned, and the corresponding surface remains on the back surface. The ring-shaped reinforcing part surrounding the remaining area of the outer periphery of the element area makes it easier to handle the thinned workpiece (see, for example, Patent Document 1). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2007-19461

(Problem to be solved by the invention)

However, in the above-mentioned grinding method, since the annular reinforcing portion is formed on the back surface of the workpiece, the annular reinforcing portion forms an embankment during grinding, and the grinding water including the abrasive grains falling off from the grinding stone will Stuck in the circular recess of the workpiece. Then, the dropped abrasive grains remaining in the circular concave portion of the workpiece are drawn into the grinding stone being ground and adhere to the grinding surface of the front end of the grinding stone. If grinding is continued with the grinding stone in the state where the dropped abrasive grains are attached to the grinding surface at the tip, scratches will be formed on the ground surface of the workpiece or the workpiece will be broken.

Therefore, the object of the present invention is to provide a circular concave portion formed in a region corresponding to the device region on the back surface of the grinding workpiece, and to form a ring-shaped reinforcing portion in a region corresponding to the back surface of the wafer surrounding the remaining region of the outer periphery of the device region. Among the grinding methods, the grinding method of the workpiece can prevent the formation of scratches on the back surface of the workpiece or the occurrence of cracks in the workpiece. (means to solve the problem)

According to the present invention, there is provided a grinding method of a workpiece, which is to use a grinding whetstone to grind a workpiece having an element region in which a plurality of elements are formed on the surface, and a back surface of the workpiece having a remaining area around the periphery of the element region. A grinding method comprising: a surface protection step of covering the surface of a workpiece with a protective member; and a holding step of, after the surface protection step is carried out, grinding the surface at an angle of 45 degrees to 180 degrees relative to the vertical direction. The holding surface of the suction table that rotates on the inclined rotation axis holds the protection member side of the workpiece; and the grinding step uses the grinding stone that rotates on the rotation axis perpendicular to the holding surface to grind the corresponding element The back surface of the workpiece in the area is ground while supplying grinding water to form a circular concave portion and a ring-shaped reinforcing portion that surrounds the circular concave portion corresponding to the remaining area of the outer periphery. In this grinding step, the The inclination promotes the discharge of the grinding water including the abrasive grains dropped from the grinding stone.

It is preferable that the said protective member is comprised from an adhesive tape.

Preferably, in the above-mentioned grinding step, the discharge position of the grinding water containing the abrasive grains dropped from the grinding stone is the lowest point of the suction cup platform whose rotation axis is inclined, so that the rotation track of the grinding stone and the grinding stone The grinding stone is positioned in such a way that the discharge positions of the water do not overlap. (Effect of Invention)

According to the present invention, in the grinding step, the inclination of the workpiece promotes the discharge of the grinding water including the abrasive grains that have fallen off from the grinding stone, so that during grinding, the grinding stone is less likely to be involved in the falling abrasive grains, and Prevents scratches from being formed on the back of the workpiece or breakage of the workpiece.

In the grinding step, the discharge position of the grinding water including the abrasive grains dropped from the grinding stone is the lowest point of the sucker platform whose rotation axis is inclined. The grinding stones are positioned in such a way that they do not overlap, whereby the discharge of the grinding water including the abrasive grains falling off from the grinding stones can be performed more efficiently.

The workpiece W shown in FIG. 1 is, for example, a circular plate-shaped semiconductor wafer that uses silicon as a base material. On its surface Wa, there are: an element region Wa1 and an outer peripheral remaining region Wa2 surrounding the element region Wa1. . The remaining outer peripheral area Wa2 is an area outside of the imaginary line L1 shown by the two-dot chain line on the surface Wa of the workpiece W in FIG. 1 . The element region Wa1 is partitioned into a grid by a plurality of dividing lines S crossing at right angles, and devices D such as ICs are formed in each of the regions partitioned into the grid. The back surface Wb of the workpiece W becomes a ground surface to be ground. Wherein, besides silicon, the workpiece W may also be composed of gallium arsenide, sapphire, gallium nitride, or silicon carbide.

The steps for grinding the workpiece W shown in FIG. 1 to a predetermined thickness by implementing the grinding method of the present invention will be described below.

(1) Surface protection step When the workpiece W is ground, the surface Wa of the workpiece W is attached with, for example, a circular protective member T1 having substantially the same diameter as the workpiece W, and the element region Wa1 And the remaining outer periphery area Wa2 is formed in the state covered and protected by the protection member T1. The protective member T1 is, for example, an adhesive tape provided with a base material layer and an adhesive layer, but it is not limited to this, and a rigid hard plate such as a glass substrate may be attached to the surface Wa with an adhesive to form a protective member. After the liquid resin is applied to the surface Wa, the resin may be cured by heating or irradiating with ultraviolet light, thereby forming a protective member covering the surface Wa of the object W to be processed.

(2) Holding step The workpiece W whose surface Wa is covered with the protective member T1 is transported to the grinding device 2 shown in FIG. 2 . The grinding device 2 includes: a chuck table 3 for sucking and holding the workpiece W; and a grinding unit 4 for grinding the workpiece W with a rotating grinding stone 42b. The chuck table 3 is, for example, circular in shape, made of a porous member, etc., and includes a holding portion 30 for sucking and holding the workpiece W, and a frame 31 for supporting the holding portion 30 . The holding part 30 is connected to an unillustrated suction source formed by a vacuum generator, a compressor, etc. through a pipe, a rotary joint, etc., and the suction generated by the unillustrated suction source is transmitted to the holding surface. 30a, whereby the suction cup platform 3 sucks and holds the workpiece W on the holding surface 30a.

The sucker platform 3 can reciprocate in the Y-axis direction by a Y-axis direction feeding means not shown in the figure. In addition, one end of a rotating shaft 33 is connected to the bottom surface side of the chuck table 3 , and a motor 34 is connected to the other end of the rotating shaft 33 . The rotation axis 33 is inclined at an angle of 45° to 180° relative to the vertical direction (Z-axis direction), and the suction cup platform 3 is also inclined at the same angle as the rotation axis 33 with respect to the vertical direction. The motor 34 rotates the rotating shaft 33 , whereby the suction cup platform 3 also rotates around the axis of the rotating shaft 33 inclined at a predetermined angle.

The grinding unit 4 is equipped with: a rotating shaft 40; a motor not shown that rotates the rotating shaft 40; a circular frame 41 connected to the lower end of the rotating shaft 40; Grinding wheel 42 below. Next, the grinding wheel 42 is provided with a wheel base 42a and a plurality of substantially rectangular parallelepiped grinding stones 42b annularly arranged on the outer peripheral portion of the bottom surface of the wheel base 42a. The grinding whetstone 42b is formed by bonding diamond grains or the like with resin bonding or metal bonding, for example. The grinding stones 42b arranged in a ring shape are, for example, formed such that the diameter of the outermost periphery is larger than the radius of the element region Wa1 of the workpiece W and smaller than the diameter of the element region Wa1, and the diameter of the innermost periphery is smaller than that of the element region Wa1. radius.

In addition, the rotating shaft 40 is the same as the rotating shaft 33 of the chuck table 3, and is inclined at an angle of 45° to 180° relative to the vertical direction (Z-axis direction). The inclination angle is the same angle, inclining in the vertical direction. That is, for example, if the rotation axis 33 of the suction cup platform 3 is inclined at 45 degrees relative to the vertical direction, the rotation axis 40 is also inclined at 45 degrees relative to the vertical direction, and the grinding whetstone 42b is surrounded on one side and is orthogonal to the holding surface 30a of the suction cup platform 3. The back surface Wb of the workpiece W is ground while the axis of the rotary shaft 40 is rotated. The grinding unit 4 inclined at a predetermined angle in the vertical direction is moved in a direction (axial direction of the rotating shaft 40 ) away from or close to the holding surface 30a of the inclined chuck table 3 by a grinding feeding means not shown. .

Inside the rotating shaft 40 , a flow path 43 serving as a passage of grinding water is formed penetrating in the axial direction of the rotating shaft 40 . The flow path 43 passes through the frame 41, and an opening is formed on the lower end thereof so that grinding water can be sprayed toward the grinding stone 42b from the bottom surface of the wheel base 42a. Further, a grinding water supply means 44 for supplying grinding water such as pure water to the flow channel 43 communicates with the upper end side of the flow channel 43 .

As shown in FIG. 2 , in the holding step, first, the workpiece W with the protective member T1 attached to the surface Wa is held, for example, in a state where the rotating shaft 33 is inclined at an angle of 45 degrees with respect to the vertical direction. The center of the surface 30a substantially coincides with the center of the workpiece W, and the back surface Wb is exposed, and is placed on the holding surface 30a. Then, the suction force generated by the suction source (not shown) is transmitted to the holding surface 30a, thereby forming a state where the chuck table 3 sucks and holds the protection member T1 side of the workpiece W by the holding surface 30a.

(3) Grinding step Next, the chuck table 3 holding the workpiece W is moved in the Y-axis direction under the grinding unit 4 which is inclined at an angle of 45 degrees relative to the vertical direction, and the grinding wheel equipped in the grinding unit 4 is carried out. 42 Alignment with workpiece W. In this alignment system, for example, at the inner peripheral edge of the remaining area Wa2 on the outer periphery of the workpiece W, that is, the back surface Wb, the imaginary line L1 overlaps with a part of the outermost periphery of the orbit of the grinding stone 42b, and the rotation of the grinding stone 42b The orbit is performed so as to pass through the rotation center of the workpiece W. As shown in FIG. In addition, in this grinding step, the discharge position of the grinding water including the abrasive grains falling off from the grinding whetstone 42b described later is the lowest point shown in FIGS. Therefore, in order not to overlap the rotation locus of the grinding stone 42b shown by the dotted line in FIG. 3 and the discharge position of the grinding water, as shown in FIG. The position is positioned at a predetermined position on the -Y direction side opposite to the center. The positioning of the grinding whetstone 42b is not limited to the example in this embodiment, and the grinding whetstone 42b may be positioned at a predetermined position on the back surface Wb of the workpiece W that draws any rotation trajectory shown by a dotted chain line in FIG. 3 . so that the discharge position of the grinding water containing the dropped abrasive grains does not overlap with the rotation track of the grinding stone 42b.

As shown in FIG. 2 , after the grinding stone 42 b is aligned with the workpiece W, the rotating shaft 40 is driven to rotate by a motor (not shown), and the grinding stone 42 b is rotated. In addition, the grinding unit 4 is ground and fed toward the direction of the arrow E shown in FIG. 2 close to the holding surface 30a of the chuck table 3, and the rotating grinding stone 42b abuts against the back surface Wb of the workpiece W, thereby grinding the back surface Wb. grinding. In addition, during the grinding process, as the chuck table 3 rotates around the axis of the rotation shaft 33 inclined at an angle of 45 degrees relative to the vertical direction, the workpiece W held on the chuck table 3 also rotates.

During grinding, for example, the center of rotation of the workpiece W is always located inside the outermost circumference of the orbit of rotation of the grinding stone 42b and outside the inner circumference of the orbit of rotation, and the grinding stone 42b rotates. In addition, the outermost periphery of the orbit of the grinding stone 42b does not contact the outer peripheral region of the back surface Wb corresponding to the remaining outer peripheral region Wa2 of the workpiece W, that is, does not protrude outward beyond the imaginary line L1. , the grinding whetstone 42b is rotated. Therefore, the grinding whetstone 42b grinds the central area of the back surface Wb corresponding to the element region Wa1 of the workpiece W into a circular concave shape, and as shown in FIG. . Also, on the back surface Wb of the workpiece W, an annular reinforcing portion Wb2 corresponding to the remaining outer peripheral region Wa2 and surrounding the circular concave portion Wb1 is formed so as to protrude in the +Z direction.

During the grinding process, the grinding water M is supplied to the contact portion of the grinding stone 42b and the workpiece W through the flow path 43 in the rotating shaft 40, and the contact portion of the grinding stone 42b and the back surface Wb of the workpiece W is Allow to cool/wash. The washing water that has reached the contact part flows out from the gap between the grinding stones 42b together with the grinding chips and the abrasive grains falling off from the grinding stones 42b by the centrifugal force generated by the rotation of the suction cup platform 3 . Next, in the grinding method of the present invention, due to the inclination of the workpiece W sucked and held on the chuck platform 3 inclined at 45 degrees relative to the vertical direction, the grinding water M including the abrasive grains falling off from the grinding stone 42b is It flows over the circular recess Wb1 toward the discharge position shown in FIG. 4 . Next, the grinding water M is accelerated by the inclination of the workpiece W, and is discharged out of the workpiece W at the discharge position over the annular reinforcing portion Wb2. In addition, since the discharge position of the grinding water M does not overlap with the rotation locus of the grinding stone 42b, the discharge of the grinding water M including abrasive grains dropped from the grinding stone 42b is not hindered. After grinding the workpiece W to a desired thickness while supplying the grinding water M, the grinding unit 4 separates the workpiece W to complete the grinding.

As mentioned above, in the grinding method of the present invention, it is provided with: the surface protection step of covering the surface Wa of the workpiece W with the protection member T1; The holding surface 30a of the chuck table 3 that rotates the rotating shaft 33 inclined at an angle of 30a, the holding step of holding the protection member T1 side of the workpiece W; and the grinding using the rotating shaft 40 that is perpendicular to the holding surface 30a The whetstone 42b grinds the back surface Wb of the workpiece W corresponding to the element region Wa1 while supplying the grinding water M to form the circular concave portion Wb1 and the grinding of the annular reinforcing portion Wb2 corresponding to the remaining peripheral region Wa2 and surrounding the circular concave portion Wb1 Therefore, in the grinding step, the inclination of the workpiece W promotes the discharge of the grinding water M containing the abrasive grains that have fallen off from the grinding stone 42b. Therefore, during the grinding, the grinding stone 42b is involved in the falling abrasive grains. It is possible to prevent scratches from being formed on the back surface Wb of the workpiece W or breakage of the workpiece W from occurring.

In addition, in the grinding step, the discharge position of the grinding water M containing the abrasive grains dropped by the grinding stone 42b is the lowest point of the chuck table 3 where the rotating shaft 33 is inclined, so it is formed as the rotation track of the grinding stone 42b. By positioning the grinding stone 42b so as not to overlap with the discharge position of the grinding water M, the grinding water M including the abrasive grains dropped from the grinding stone 42b is more efficiently discharged.

However, the grinding method of the present invention is not limited to the above-mentioned embodiments. In addition, the respective configurations of the grinding device 2 shown in the accompanying drawings are not limited thereto, and the effects of the present invention can be exerted. Appropriate changes. For example, instead of passing through the rotating shaft 40 of the grinding unit 4, grinding water may be supplied from the outside to the contact portion between the grinding stone 42b and the workpiece W by using a spray nozzle. The supply of grinding water to the contact part of the object W.

W‧‧‧Workpiece Wa‧‧‧Surface of Workpiece Wa1‧‧‧Component Area Wa2‧‧‧Residual Perimeter Area S‧‧‧Separation Schedule D‧‧‧Component Wb‧‧‧Backside of Workpiece Wb1‧‧‧circular recess Wb2‧‧‧annular reinforcing part L1‧‧‧imaginary line M‧‧‧grinding water T1‧‧‧protective member 2‧‧‧grinding device 3‧‧‧suction cup platform 30‧‧‧holding Part 30a‧‧‧holding surface 31‧‧‧frame 33‧‧‧rotating shaft 34‧‧‧motor 4‧‧‧grinding unit 40‧‧‧rotating shaft 41‧‧‧frame 42‧‧‧grinding wheel 42a‧ ‧‧wheel base 42b‧‧‧grinding whetstone 43‧‧‧flow path 44‧‧‧grinding water supply means

Fig. 1 is a perspective view showing an example of a workpiece and a protection member protecting the surface of the workpiece. Fig. 2 is a cross-sectional view showing a state in which a workpiece held on a chuck table is ground with a grinding stone. Fig. 3 is a schematic perspective view illustrating a state where the rotation track of the grinding stone and the discharge position of the grinding water do not overlap. Fig. 4 is a cross-sectional view showing a state in which grinding water is discharged from the back surface of a ground workpiece.

2‧‧‧Grinding device

3‧‧‧Suction cup platform

4‧‧‧Grinding unit

30‧‧‧Maintenance Department

30a‧‧‧Retaining surface

31‧‧‧frame

33‧‧‧rotation axis

34‧‧‧Motor

40‧‧‧rotation axis

41‧‧‧Frame

42‧‧‧Grinding wheel

42a‧‧‧wheel abutment

42b‧‧‧grinding whetstone

43‧‧‧flow path

44‧‧‧Development of water supply means

L1‧‧‧imaginary line

M‧‧‧Grinding water

T1‧‧‧protective components

W‧‧‧processed object

Wa‧‧‧surface of workpiece

Wa1‧‧‧component area

Wa2‧‧‧outer peripheral area

Wb‧‧‧back side of workpiece

Wb1‧‧‧circular recess

Wb2‧‧‧ring reinforcement part

Claims (2)

A grinding method of a workpiece, which is a grinding method of grinding a workpiece having an element region formed with a plurality of elements on the surface and a back surface of the workpiece surrounding the remaining peripheral region of the element region with a grinding whetstone, which is It is equipped with: a surface protection step, which is to cover the surface of the workpiece with a protective member; and a holding step, which is carried out after the surface protection step is carried out on a rotation axis inclined at an angle of 45 degrees to 90 degrees relative to the vertical direction. The holding surface of the rotating suction cup platform holds the protection member side of the workpiece; and the grinding step uses a grinding stone that rotates with a rotation axis perpendicular to the holding surface to grind the workpiece corresponding to the component area Grinding while supplying grinding water to form a circular concave portion and an annular reinforcing portion surrounding the circular concave portion corresponding to the remaining area of the outer periphery. The discharge position of the water is the lowest point of the sucker platform whose rotation axis is inclined, so the rotation track of the grinding stone passes through the rotation center of the workpiece, and the rotation track of the grinding stone is different from the discharge position of the grinding water. The grinding stones are positioned so as to overlap each other, and the discharge of the grinding water including the abrasive grains dropped from the grinding stones is promoted by the inclination of the workpiece and the positioning of the grinding stones. For the grinding method of the processed object in item 1 of the scope of the patent application, its In the present invention, the aforementioned protective member is an adhesive tape.

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