JP2013008814A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a chamfered outer peripheral edge from being chipped when grinding a wafer of a bonded wafer.SOLUTION: An outer peripheral edge 13 of a surface 10a of a wafer 10 is removed to a depth not reaching a back surface 10b, and a residual portion 14 is left on the side of the back surface 10b (outer peripheral removal step). Then, a bonded wafer 1 is formed by sticking the surface 10a of the wafer 10 onto a support wafer 20 (bonded wafer formation step), then the residual portion 14 is removed with a cutting blade 37 (residual portion removal step), and thereafter, the back surface 10b of the wafer is ground or polished and thinned to a prescribed thickness (thinning step). By performing thinning in the state without a chamfered outer peripheral edge 14, chipping of the outer peripheral edge 14 is prevented.

Description

  The present invention relates to a wafer processing method for grinding a back surface of a wafer in a bonded wafer in which a wafer is bonded onto a support wafer such as an SOI (Silicon on Insulator) wafer.

  The above-mentioned SOI wafer, which is a kind of semiconductor device substrate structure, has an insulating film provided on the bottom of a semiconductor wafer such as silicon. As a manufacturing method, a support wafer, which is another wafer, is directly bonded to one side of the semiconductor wafer. There is known a wafer bonding method in which bonding is performed by grinding and the semiconductor wafer side is ground (Patent Document 1).

  In general, in a semiconductor device manufacturing process, a back surface side of a semiconductor wafer on which a large number of devices having electronic circuits are formed is ground and thinned, and then divided into each device. In recent years, along with the reduction in size and weight of electronic devices, semiconductor wafers are sometimes processed extremely thin, for example, with a thickness of 100 μm or less. In such cases, a technology to process a wafer by bonding a support wafer to a semiconductor wafer before grinding in order to improve the handling of thin semiconductor wafers after grinding or to prevent warping or damage during processing. Is known (Patent Document 2).

Japanese Patent Laid-Open No. 5-21763 JP 2004-111434 A

  By the way, in order to prevent so-called chipping in which the outer peripheral edge is chipped during the transfer between processes, the wafer such as the semiconductor wafer or the support wafer is subjected to chamfering processing so that the outer peripheral edge has a semicircular arc shape. Has been. For this reason, in a bonded wafer in which a support wafer is bonded to a semiconductor wafer, a gap is formed between the outer peripheral edges of both wafers, resulting in an unbonded region that is not bonded to each other.

  If the semiconductor wafer is ground and thinned in this state, the outer peripheral edge becomes thinner than the inner main body part and sharply sharpens like a knife edge, and the outer peripheral edge is missing in combination with not being bonded to the support wafer. The phenomenon occurred. In particular, in the bonded wafer in which the wafers are bonded by direct bonding like the above-mentioned SOI wafer, the non-bonded region that is in contact but not actually bonded becomes large, so that the outer peripheral edge is easily chipped. . If the outer peripheral edge is chipped, the main body portion is damaged, and the chipped waste accumulates in the grinding device and clogs the drainage port, resulting in the occurrence of overflow or frequent cleaning.

  The present invention has been made in view of the above circumstances, and a main technical problem thereof is a wafer processing method capable of preventing the outer peripheral edge of the wafer from being chipped when the wafer of a bonded wafer is ground. It is to provide.

  The wafer processing method of the present invention includes an outer peripheral edge removing step that removes the outer peripheral edge of the wafer surface to a depth that does not reach the back surface and leaves a remaining portion on the back surface side, and after performing the outer peripheral edge removing step, the wafer surface A bonded wafer forming step of forming a bonded wafer in which the side of the wafer is bonded to the support wafer and exposing the back side of the wafer; and after performing the bonded wafer forming step, the remaining portion is removed from the back side of the wafer with a cutting blade. It is characterized by comprising a remaining portion removing step to be removed, and a thinning step in which after the remaining portion removing step is performed, the back surface of the wafer is ground or polished to thin it to a predetermined thickness.

  According to the present invention, by performing the remaining portion removal step, the outer peripheral edge of the wafer is removed over the entire thickness direction, and then the thinning step for grinding or polishing the wafer is performed. A wafer having no outer peripheral edge is ground or polished. Therefore, the outer peripheral edge of the wafer is prevented from being lost during the thinning step.

  The wafer obtained by the present invention may be used in a state where the support wafer is bonded, or may be used in a state where the support wafer is peeled off to become only the wafer. When the support wafer is peeled off and used in a state where only the wafer is used, a wafer-only state is obtained by providing a peeling step for peeling the wafer from the support wafer after performing the thinning step. be able to.

  ADVANTAGE OF THE INVENTION According to this invention, when grinding the wafer of a bonded wafer, there exists an effect that the processing method of the wafer which can prevent that the outer periphery of a wafer is missing is provided.

It is the (a) perspective view and (b) sectional view of the wafer which are ground by the processing method concerning one embodiment of the present invention. It is (a) perspective view and (b) sectional drawing of the support wafer used with the processing method. It is a side view which shows the outer periphery removal step of the processing method. FIG. 4 is a plan view of FIG. 3. FIG. 4 is a view taken in the direction of arrow V in FIG. 3. It is a side view of the wafer after performing an outer periphery removal step. It is a side view which shows the bonded wafer formation step of the processing method which concerns on one Embodiment. It is a side view which shows the remaining part removal step of the processing method. It is a top view of FIG. FIG. 9 is a view on arrow X in FIG. 8. It is a side view which shows the thinning step of the processing method which concerns on one Embodiment. It is a top view of FIG. It is a side view which shows the peeling step of the processing method which concerns on one Embodiment. It is a side view of the wafer which shows another form of the remaining part left on the outer periphery of a wafer in a remaining part removal step. It is a side view which shows the state which is implementing the remaining part removal step to the wafer of FIG. It is an expanded sectional view which shows the remaining part removed in the wafer of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a wafer processed by the processing method of one embodiment and a support wafer used in the processing method will be described.

(1) Wafer FIG. 1A is a perspective view of a disk-shaped wafer 10 that is thinned by backside grinding by the processing method of one embodiment, and FIG. 1B is a cross-sectional view of the wafer 10. is there. The wafer 10 is a substrate wafer for an electronic device made of a semiconductor material such as silicon or gallium arsenide, and has a thickness of about 500 to 700 μm, for example. On the surface 10 a of the wafer 10, grid-like division planned lines 11 are set, and devices 12 having electronic circuits such as IC and LSI are formed in a large number of rectangular areas surrounded by the division planned lines 11. ing. As shown in FIG. 1B, the outer peripheral edge 13 of the wafer 10 is chamfered so as to have a semicircular cross section from the front surface 10a side to the back surface 10b side.

(2) Support wafer FIG. 2A is a perspective view of the support wafer 20, and FIG. 2B is a side view of the support wafer 20. It is. The support wafer 20 is a disk-shaped wafer having a diameter and thickness that are substantially the same as those of the wafer 10. The support wafer 20 is made of a material having a predetermined rigidity that can be easily handled. For example, the support wafer 20 is made of the same semiconductor material as that of the wafer 10 or glass. As shown in FIG. 2B, the outer peripheral edge 23 of the support wafer 20 is chamfered so as to have a semicircular cross section from the front surface 20 a side to the back surface 20 b side, similarly to the wafer 10.

(3) Processing Method Next, a method for thinning the wafer 10 according to an embodiment will be described.
First, the outer peripheral edge 13 of the wafer 10 that has been chamfered is removed to a depth that does not reach the back surface 10b from the front surface 10a side, and the remaining portion of the outer peripheral edge 13 is left on the back surface 10b side (outer peripheral edge removal step). In order to perform the outer peripheral edge removing step, as shown in FIGS. 3 to 5, a cutting apparatus including a rotatable disk-shaped holding table 31 that holds the wafer 10 and a cutting means 35 is used.

  The holding table 31 is of a negative pressure chuck type in which a workpiece is adsorbed and held by a negative pressure action by air suction on a horizontal holding surface 32 formed porous by a porous material. The holding surface 32 has a circular shape having the same diameter as that of the wafer 10, and the holding table 31 is rotated by a rotation driving mechanism (not shown) around a rotating shaft 33 that is coaxial with the holding surface 32 and extends in the vertical direction. The wafer 10 is placed concentrically on the holding surface 32 with the back surface 10b aligned with the holding surface 32 and exposed on the front surface 10a side, and is attracted and held on the holding surface 32 by a negative pressure action. The wafer 10 is rotated by the rotation of the holding table 31.

  The cutting means 35 has a cutting blade 37 fixed to the tip of a horizontal spindle shaft 36 that is rotationally driven by a motor (not shown). The spindle shaft 36 is disposed above the holding table 31 so as to be movable up and down. ing. Further, the cutting blade 37 is set to cut in a state along the tangential direction of the wafer 10 with respect to the outer peripheral edge 13 of the wafer 10 as shown in FIG. In FIG. 4, illustration of the device 12 formed on the surface 10a of the wafer 10 is omitted.

  In the outer peripheral edge removing step, the spindle shaft 36 is lowered from the state where the holding table 31 is rotated in one direction at a predetermined speed, and the rotating cutting blade 37 is moved to the outer peripheral edge 13 of the wafer 10 to a certain depth (from the surface 10a side). For example, the surface 10a side of the outer peripheral edge 13 is cut into an annular shape over the entire circumference by cutting the wafer 10 and rotating the wafer 10 one or more times. In order to cut the surface 10a side of the outer peripheral edge 13 in an annular shape over the entire periphery, a cutting blade 37 that rotates by lowering the spindle shaft 36 first is cut into the outer peripheral edge 13 of the wafer 10 while the holding table 31 is stopped. After that, the procedure of rotating the holding table 31 may be taken.

  4 and 5 indicates the rotation direction of the holding table 31, that is, the rotation direction of the wafer 10, and the rotation direction of the cutting blade 37 is the rotation of the wafer 10 as indicated by the arrow A in FIG. A down cut direction that is forward with respect to the direction is desirable. However, it may be in the opposite direction to the down cut, that is, the up cut direction facing the rotation direction of the wafer 10.

  As shown in FIG. 6, the wafer 10 on which the outer peripheral edge removing step is performed has an annular remaining portion 14 on the back surface 10 b side of the outer peripheral edge 13. Since the rotation axis of the cutting blade 37 is horizontal, the cutting surface by the cutting blade 37 has a stepped shape with the inner corner being a right angle, and the lower side of the horizontal cutting surface 14 a is the remaining portion 14.

  When the outer peripheral edge removal step is completed, the wafer 10 is unloaded from the holding table 31, and then the front surface 10a side of the wafer 10 is attached concentrically on the support wafer 20 as shown in FIG. The bonded wafer 1 with the exposed side 10b is formed (bonded wafer forming step).

  In affixing the wafer 10 on the support wafer 20, wax, UV curable adhesive, or thermosetting adhesive may be used, but the above-described direct bonding method may be employed. This direct bonding is performed by a method in which the bonding surfaces are directly bonded in a dust-free state, and heat treatment is performed at a predetermined temperature in order to enhance the bonding strength.

  Next, after performing the bonded wafer forming step, the remaining portion 14 is removed from the back surface 10b side of the wafer 10 with a cutting blade (residual portion removing step). In order to perform the remaining part removing step, the cutting device used in the outer peripheral edge removing step is used.

  That is, as shown in FIGS. 8 to 10, the support wafer 20 side is placed on the holding surface 32 of the holding table 31, the bonded wafer 1 is sucked and held, and the back surface 10 a side of the wafer 10 is exposed. Then, the holding table 31 is rotated while the cutting blade 37 of the rotated cutting means 35 is cut above the remaining portion 14, and the remaining portion 14 is cut and removed. In this case, the rotation direction of the cutting blade 37 with respect to the wafer 10 is preferably an up-cut direction facing the rotation direction C of the wafer 10 as indicated by an arrow B in FIG.

  When the remaining portion removing step is completed, the bonded wafer 1 from which the remaining portion 14 has been removed is unloaded from the holding table 31 of the cutting apparatus, and the back surface 10b of the wafer 10 is ground using the grinding apparatus shown in FIG. Thinning to thickness (thinning step).

  The grinding apparatus includes a rotatable holding table 41 that holds the wafer 10 and a grinding means 45. The holding table 41 has the same configuration as the holding table 31 of the above-described cutting apparatus, and is negatively held by adsorbing and holding a workpiece by a negative pressure action by air suction on a horizontal holding surface 42 formed porous by a porous material. It is a pressure chuck type, and is rotated around a rotation shaft 43 by a rotation drive mechanism (not shown).

  The grinding means 45 has a disk-like grinding tool 48 having a number of grinding wheels 48b fixed to the lower surface of a flange 47 at the tip of a spindle shaft 46 that extends in the vertical direction and is rotated by a motor (not shown). The spindle shaft 46 is disposed above the holding table 41 so as to be vertically movable.

  The grinding tool 48 has a large number of grindstones 48 b arranged in an annular manner and fixed to the outer peripheral portion of the lower surface of a disc-shaped grinding wheel 48 a that is detachably fixed to the flange 47. As the grindstone 48b, a material suitable for the material of the wafer 10 is used. For example, a diamond grindstone formed by solidifying diamond abrasive grains with a binder such as metal bond or resin bond is used. The grinding tool 48 is rotationally driven integrally with the spindle shaft 46.

  In the thinning step, the bonded wafer 1 is concentric with the holding surface 42 with the support wafer 20 side of the bonded wafer 1 aligned with the holding surface 42 of the holding table 41 and the back surface 10b of the wafer 10 exposed upward. And is attracted to and held on the holding surface 42 by a negative pressure action. Then, the spindle shaft 52 is lowered from the state in which the holding table 41 is rotated in one direction at a predetermined speed, and the grindstone 48b of the rotating grinding tool 48 is pressed against the back surface 10b of the wafer 10 with a predetermined load. Grind. In this case, as shown in FIG. 12, the outer diameter of grinding by the grinding tool 48 (the outermost diameter of the rotation trajectory of the grinding wheel 48 b) is approximately the same as or slightly larger than the diameter of the wafer 10. The position is set to a position where the cutting edge, which is the lower surface of the grindstone 48b, passes through the rotation center of the rotating wafer 10. By pressing the grindstone 48b of the grinding tool 48 against the back surface 10b of the wafer 10 while rotating the wafer 10 by the rotation of the holding table 41, the entire back surface 10b is ground.

  When the back surface 10b is ground and the wafer 10 is thinned to the target thickness, the thinning step is finished, and the bonded wafer 1 is unloaded from the holding table 41. Then, as shown in FIG. 13, the support wafer 20 is peeled from the thinned wafer 10 (peeling step). Thereby, the wafer 10 having a target thickness is obtained. In the thinning step, only the back surface 10b of the wafer 10 is ground, but the back surface 10b may be polished after grinding as necessary. When polishing is included, the support wafer 20 is peeled off after polishing.

(4) Effects of One Embodiment According to the above embodiment, the outer peripheral edge removing step of removing a part of the thickness of the outer peripheral edge 13 from the front surface 10a side of the wafer 10 and leaving the remaining portion 14 on the back surface 10b side. After the execution, a bonded wafer forming step of attaching the front surface 10a side of the wafer 10 onto the support wafer 20 is performed, and then a remaining portion removing step of removing the remaining portion 14 from the back surface 10a side of the wafer 10 is performed. The outer peripheral edge 13 of the wafer 10 that has been chamfered can be reliably removed over the entire thickness direction without damaging the support wafer 20.

  Then, by removing the outer peripheral edge 13 in this manner, an unbonded region where the outer peripheral edge 13 is not bonded to the support wafer 20 does not occur. Therefore, in the thinning step of grinding the back surface 10b of the wafer 10, the wafer 10 without the chamfered outer peripheral edge 13 is ground, and as a result, the outer peripheral edge 13 of the wafer 10 is missing during the thinning step. Is prevented.

(5) Other Embodiments In the outer peripheral edge removing step of the above embodiment, the surface 10a side of the outer peripheral edge 13 of the wafer 10 is removed by the cutting blade 37 of the cutting means. For example, a technique other than cutting with the blade 37, such as etching, grinding with a grinding wheel or a cup wheel, may be employed.

  Moreover, in the said embodiment, although the remaining part 14 which remains in the outer periphery 13 at the outer periphery removal step is formed in the level | step difference shape in which an inner corner becomes a right angle, as shown in FIG. The outer peripheral edge 13 may be deleted so as to form an inclined surface 15a that approaches the back surface 10b as it goes, and the lower portion of the inclined surface 15a may be the remaining portion 15.

  In this case, as shown in FIG. 15, the bonded wafer 1 is configured by sticking the front surface 10 a continuous with the inclined surface 15 a to the support wafer 20, and the remaining portion 15 is backed by the cutting blade 37 of the cutting means in the remaining portion removing step. 10b is removed by cutting. When the remaining portion 15 is cut, the removal region of the remaining portion 15 is controlled so that the remaining portion 15 is removed as much as possible within a range where the cutting edge of the cutting blade 37 does not contact the support wafer 20 as shown in FIG. .

DESCRIPTION OF SYMBOLS 1 ... Bonded wafer 10 ... Wafer 10a ... Wafer surface 10b ... Wafer back surface 13 ... Outer peripheral edge 14 ... Remaining part 20 ... Support wafer 37 ... Cutting blade

Claims (2)

A wafer processing method,
An outer peripheral edge removing step for removing the outer peripheral edge of the wafer surface to a depth not reaching the back surface and leaving a remaining portion on the back surface side;
After performing the outer peripheral edge removing step, a bonded wafer forming step of forming a bonded wafer in which the wafer side is attached to the support wafer and the back surface side of the wafer is exposed, and
After performing the bonded wafer forming step, a remaining part removing step of removing the remaining part from the wafer back side with a cutting blade;
After performing the remaining portion removing step, a thinning step of grinding or polishing the back surface of the wafer to thin it to a predetermined thickness;
A method for processing a wafer, comprising:   The wafer processing method according to claim 1, further comprising a peeling step of peeling the wafer from the support wafer after performing the thinning step.

Images