U.S. patent application number 11/174520 was filed with the patent office on 2006-01-12 for grinding wheel, grinding apparatus and grinding method.
This patent application is currently assigned to Tokyo Seimitsu Co., Ltd.. Invention is credited to Ichiro Katayama.
Application Number | 20060009134 11/174520 |
Document ID | / |
Family ID | 35541990 |
Filed Date | 2006-01-12 |
United States Patent
Application |
20060009134 |
Kind Code |
A1 |
Katayama; Ichiro |
January 12, 2006 |
Grinding wheel, grinding apparatus and grinding method
Abstract
The present invention provides the grinding wheel, the grinding
apparatus and the grinding method of the present invention so that
increase in the size of the grinding apparatus can be suppressed,
and the back surface grinding of the wafer and the grinding of the
peripheral edge part of the wafer are performed at the same time,
whereby the peripheral edge part of the extremely thin wafer is
prevented from being sharpened, and cracking and chipping of the
wafer peripheral edge part can be prevented.
Inventors: |
Katayama; Ichiro;
(Tsuchiura-shi, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASHINGTON
DC
20004-2128
US
|
Assignee: |
Tokyo Seimitsu Co., Ltd.
Tokyo
JP
Tosei Engineering Corp.
Tsuchiura-shi
JP
|
Family ID: |
35541990 |
Appl. No.: |
11/174520 |
Filed: |
July 6, 2005 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24D 7/18 20130101; B24B
9/065 20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 1/00 20060101
B24B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2004 |
JP |
2004-203308 |
Claims
1. A grinding wheel, comprising: a cup-shaped grindstone; and a
small-diameter grindstone provided at a center part of an inside of
the cup-shaped grindstone.
2. The grinding wheel according to claim 1, wherein the
small-diameter grindstone is a grindstone in a cylindrical shape or
a truncated cone shape.
3. The grinding wheel according to claim 1, wherein the
small-diameter grindstone has an entire shape formed into a
truncated cone shape, and a clearance groove is formed at a
mid-portion of an inclined side surface of the truncated cone.
4. The grinding wheel according to claim 1 wherein the
small-diameter grindstone is integrally formed at a base of the
cup-shaped grindstone.
5. The grinding wheel according to claim 2 wherein the
small-diameter grindstone is integrally formed at a base of the
cup-shaped grindstone.
6. The grinding wheel according to claim 3 wherein the
small-diameter grindstone is integrally formed at a base of the
cup-shaped grindstone.
7. The grinding wheel according to claim 1 wherein the
small-diameter grindstone is detachably provided at a base of the
cup-shaped grindstone.
8. The grinding wheel according to claim 2 wherein the
small-diameter grindstone is detachably provided at a base of the
cup-shaped grindstone.
9. The grinding wheel according to claim 3 wherein the
small-diameter grindstone is detachably provided at a base of the
cup-shaped grindstone.
10. The grinding wheel according to claim 1 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
11. The grinding wheel according to claim 2 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
12. The grinding wheel according to claim 3 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
13. The grinding wheel according to claim 4 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
14. The grinding wheel according to claim 5 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
15. The grinding wheel according to claim 6 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
16. The grinding wheel according to claim 7 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
17. The grinding wheel according to claim 8 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
18. The grinding wheel according to claim 9 wherein the
small-diameter grindstone is a composite grindstone with a rough
grinding grindstone and a fine grinding grindstone being
stacked.
19. A grinding apparatus which grinds one surface of the wafer,
comprising: a chuck table which rotates with a wafer placed
thereon; a hollow spindle which is provided eccentrically with
respect to an axis of rotation of the chuck table and mounted with
a cup-shaped grindstone on a tip end of the hollow spindle; a small
spindle which is provided by being inserted through the hollow
spindle and mounted with a smaller-diameter grindstone than the
cup-shaped grindstone on a tip end of the small spindle; a
cup-shaped grindstone driving motor which rotationally drives the
hollow spindle; a small-diameter grindstone driving motor which
rotationally drives the small spindle; and a cut-in driving device
which brings the hollow spindle and the small spindle, and the
chuck table relatively closer to and away from each other in the
rotational axis direction of the chuck table.
20. The grinding apparatus according to claim 19, further
comprising a transverse driving device which brings an axis of the
hollow spindle and an axis of the small spindle, and a rotational
axis of the chuck table relatively closer to and away from each
other.
21. A grinding method for grinding one surface of a wafer placed on
a rotating chuck table, comprising the step of: grinding one
surface of the wafer with the cup-shaped grindstone and grinding a
circumferential side surface of the wafer with the small-diameter
grindstone with using the grinding wheel according to claim 1.
22. A grinding method, comprising the steps of: mounting a
cup-shaped grindstone at the hollow spindle and a smaller-diameter
grindstone than the cup-shaped grindstone to the small spindle;
independently setting a number of rotations of the cup-shaped
grindstone and a number of rotations of the small-diameter
grindstone respectively; and grinding one surface of the wafer with
the cup-shaped grindstone and grinding a circumferential side
surface of the wafer with the small-diameter grindstone with using
the grinding apparatus according to claim 19.
23. A grinding method, comprising the steps of: mounting a
cup-shaped grindstone at the hollow spindle and a smaller-diameter
grindstone than the cup-shaped grindstone to the small spindle;
independently setting a number of rotations of the cup-shaped
grindstone and a number of rotations of the small-diameter
grindstone respectively; and grinding one surface of the wafer with
the cup-shaped grindstone and grinding a circumferential side
surface of the wafer with the small-diameter grindstone with using
the grinding apparatus according to claim 20.
24. The grinding method according to claim 21, further comprising
the steps of: bringing the cup-shaped grindstone and the
small-diameter grindstone, and the chuck table relatively close to
each other in a rotational axis direction of the chuck table; and
grinding the one surface and the circumferential side surface of
the wafer while bringing a rotational axis of the rotating
cup-shaped grindstone and small-diameter grindstone, and the
rotational axis of the chuck table relatively close to each other,
or while bringing the rotational axis of the cup-shaped grindstone
and the small-diameter grindstone, and the rotational axis of the
chuck table relatively close to and away from each other.
25. The grinding method according to claim 22, further comprising
the steps of: bringing the cup-shaped grindstone and the
small-diameter grindstone, and the chuck table relatively close to
each other in a rotational axis direction of the chuck table; and
grinding the one surface and the circumferential side surface of
the wafer while bringing a rotational axis of the rotating
cup-shaped grindstone and small-diameter grindstone, and the
rotational axis of the chuck table relatively close to each other,
or while bringing the rotational axis of the cup-shaped grindstone
and the small-diameter grindstone, and the rotational axis of the
chuck table relatively close to and away from each other.
26. The grinding method according to claim 23, further comprising
the steps of: bringing the cup-shaped grindstone and the
small-diameter grindstone, and the chuck table relatively close to
each other in a rotational axis direction of the chuck table; and
grinding the one surface and the circumferential side surface of
the wafer while bringing a rotational axis of the rotating
cup-shaped grindstone and small-diameter grindstone, and the
rotational axis of the chuck table relatively close to each other,
or while bringing the rotational axis of the cup-shaped grindstone
and the small-diameter grindstone, and the rotational axis of the
chuck table relatively close to and away from each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a grinding wheel, a
grinding apparatus and a grinding method, and more particularly, to
a grinding wheel, a grinding device and a grinding method to obtain
a thin wafer by grinding one surface of a semiconductor wafer or
the like.
[0003] 2. Description of the Related Art
[0004] A wafer of silicone or the like which becomes a material of
a semiconductor device, an electronic component and the like is
sliced with a sliding device such as an inner peripheral blade and
a wire saw from an ingot state, and thereafter, chamfering work is
performed for an outer peripheral part as shown in FIG. 9A to
prevent occurrence of a cracking, chipping and the like at an
peripheral edge of the wafer in the forming process of a
semiconductor device, an electronic component and the like. In FIG.
9A, reference character W designates a wafer, and reference
character S designates a protection sheet for the wafer
surface.
[0005] Recently, however, in order to manufacture extremely thin
semiconductor chips incorporated into a smart card and a thin IC
card, a back surface side of the wafer, which has a semiconductor
device or an electronic component is formed on its front surface
side, is ground to be an extremely thin wafer, and this extremely
thin wafer is diced to manufacture individual extremely thin
chips.
[0006] However, since in this extremely thinning work, the wafer is
thinned to a half of the thickness of the wafer before the work,
there arises the problem that the outer peripheral part of the
wafer, which is worked to be extremely thin, is in a sharp shape
due to chamfering of the outer peripheral part previously
performed, and is easy to break.
[0007] In order to solve the problem, there is provided a method
for cutting the peripheral edge part of the wafer vertically or by
inclining the peripheral edge toward the center before grinding of
the back surface of the wafer is performed, and thereafter,
performing the back surface grinding (for example, see Japanese
patent Application Laid Open No. 2003-273053).
[0008] A method for performing grinding by inclining the peripheral
edge part of the wafer toward the center before performing the back
surface grinding of the wafer, and thereafter performing the back
surface grinding, or a method for performing the back surface
grinding and chamfering grinding at the same time by providing a
general chamfering grindstone applied to a thin wafer on the
opposite side from a back surface grindstone with the axis of the
wafer therebetween is proposed (for example, see embodiment 1, and
embodiment 2 in Japanese Patent Application Laid Open No.
08-037169).
[0009] Further, a method for performing the back surface grinding
and chamfering grinding at the same time by providing an inclined
cylindrical chamfering grindstone at the opposite side from the
back surface grinding grindstone with the axis of the wafer
therebetween (for example, see Japanese Patent Application Laid
Open No. 11-033887).
SUMMARY OF THE INVENTION
[0010] However, in the method disclosed in the aforementioned
Japanese Patent Application Laid Open No. 2003-273053, cutting of
the peripheral edge part of the wafer and the back surface grinding
have to be worked by using the separate apparatuses in the separate
process steps, and there exists the problem of increasing the
number of working process steps and increasing time and cost.
[0011] In the method disclosed in embodiment 1 in the
aforementioned Japanese Patent Application Laid Open No. 08-037169,
work can be performed with one apparatus, but inclination grinding
of the peripheral edge part of the wafer and the back surface
grinding are performed in the separate process steps, and
therefore, there exists the problem of increasing the number of
working process steps and increasing time and cost as in the
Japanese patent Application Laid Open No. 2003-273053.
[0012] In the method disclosed in the embodiment 2 of the
aforementioned Japanese Patent Application Laid Open No. 08-037169
and the method disclosed in the aforementioned Japanese Patent
Application Laid Open No. 11-033887, the back surface grinding and
chamfering grinding can be performed at the same time, but in both
of them, the chamfering grindstones are provided at the opposite
sides from the back surface grinding grindstones with the axes of
the wafers therebetween, and therefore, there exists the problem of
increasing the size of the apparatus, increasing the manufacturing
cost of the apparatus and enlarging the footprint.
[0013] The present invention is made in view of the above
circumstances, and it is an object of the present invention to
provide a grinding wheel, a grinding apparatus and a grinding
method which restrain increase in the size of the apparatus and are
capable of preventing an peripheral edge part of an extremely thin
wafer from being sharpened, and preventing cracking and chipping of
the wafer peripheral part by performing the back surface grinding
of the wafer and grinding of the peripheral edge part of the wafer
at the same time.
[0014] In order to attain the above-described object, a grinding
wheel of the present invention is characterized by comprising a
cup-shaped grindstone, and a small-diameter grindstone provided at
a center part of an inside of the cup-shaped grindstone. The
small-diameter grindstone is a grindstone in a cylindrical shape or
a truncated cone shape.
[0015] According to the grinding wheel of the present invention,
one surface of the wafer is ground with the cup-shaped grindstone,
and the peripheral edge part of the wafer can be ground with the
small-diameter grindstone at the same time. Therefore, increase in
the size of the grinding apparatus can be restrained, and the back
surface grinding of the wafer and grinding of the peripheral edge
part of the wafer are performed at the same time, whereby the
peripheral edge part of the extremely thin wafer can be prevented
from being sharpened, and cracking and chipping of the wafer
peripheral edge part can be prevented.
[0016] The grinding wheel of the present invention is characterized
in that the small-diameter grindstone has an entire shape formed
into a truncated cone shape, and a clearance groove is formed at a
mid-portion of an inclined side surface of the truncated cone.
According to this, grinding of the peripheral edge part of the
wafer is finished before the final grinding of the back surface
grinding of the wafer, the small-diameter grindstone is moved away
from the peripheral edge part of the wafer at the time of the final
grinding of the wafer back surface grinding, and chipping of the
wafer peripheral edge part can be restrained.
[0017] The grinding wheel of the present invention is characterized
in that the small-diameter grindstone is integrally formed at a
base of the cup-shaped grindstone, or detachably provided at a base
of the cup-shaped grindstone. When the small-diameter grindstone is
integrally formed at the base of the cup-shaped grindstone, the
positional relationship of the cup-shaped grindstone and the
small-diameter grindstone is determined by the manufacturing
accuracy of the grindstone, and adjustment is not required. When
the small-diameter grindstone is detachably provided at the base of
the cup-shaped grindstone, only the small-diameter grindstone can
be easily replaced when the small-diameter grindstone is worn.
[0018] The grinding wheel of the present invention is characterized
in that the small-diameter grindstone is a composite grindstone
with a rough grinding grindstone and a fine grinding grindstone
being stacked. Thus, the peripheral edge part of the wafer is
roughly ground with the rough grinding grindstone of the
small-diameter grindstone, and subsequently, the peripheral edge
part of the wafer can be finely ground with the fine grinding
grindstone. Therefore, the peripheral edge part of the wafer can be
smoothly finished by one work.
[0019] A grinding apparatus of the present invention is, in a
grinding apparatus which grinds one surface of the wafer,
characterized by comprising a chuck table which rotates with a
wafer placed thereon, a hollow spindle which is provided
eccentrically with respect to an axis of rotation of the chuck
table and mounted with a cup-shaped grindstone on a tip end of the
hollow spindle, a small spindle which is provided by being inserted
through the hollow spindle and mounted with a smaller-diameter
grindstone than the cup-shaped grindstone on a tip end of the small
spindle, a cup-shaped grindstone driving motor which rotationally
drives the hollow spindle, a small-diameter grindstone driving
motor which rotationally drives the small spindle, and a cut-in
driving device which brings the hollow spindle and the small
spindle, and the chuck table relatively closer to and away from
each other in the rotational axis direction of the chuck table.
[0020] In addition to the above described construction, the
grinding apparatus of the present invention is characterized by
further comprising a transverse driving device which brings an axis
of the hollow spindle and an axis of the small spindle, and a
rotational axis of the chuck table relatively closer to and away
from each other.
[0021] According to the grinding apparatus of the present
invention, the hollow spindle and the small spindle provided by
being inserted through the hollow spindle are included, and
therefore, by mounting the cup-shaped grindstone to the hollow
spindle and by mounting the smaller-diameter grindstone than the
cup-shaped grindstone at the small spindle, the one surface of the
wafer is ground with the cup-shaped grindstone and the peripheral
edge part of the wafer can be ground with the small-diameter
grindstone at the same time.
[0022] Therefore, increase in the size of the grinding apparatus is
suppressed, the back surface grinding of the wafer and grinding of
the peripheral edge part of the wafer are performed at the same
time, whereby the peripheral edge part of the extremely thin wafer
is prevented from being sharpened, and cracking and chipping of the
wafer peripheral edge part can be prevented.
[0023] A grinding method of the present invention is characterized
by comprising the step of grinding one surface of the wafer with
the cup-shaped grindstone and grinding a circumferential side
surface of the wafer with the small-diameter grindstone with using
a grinding wheel comprising a cup-shaped grindstone, and a
small-diameter grindstone provided at a center portion of the
inside of the cup-shaped grindstone.
[0024] According to the grinding method of the present invention,
the back surface grinding of the wafer and grinding of the
peripheral edge part of the wafer are performed at the same time,
whereby the peripheral edge part of the extremely thin wafer is
prevented from being sharpened, and cracking and chipping of the
wafer peripheral edge part can be prevented.
[0025] A grinding method of the present invention is characterized
by comprising the steps of mounting a cup-shaped grindstone at the
hollow spindle and a smaller-diameter grindstone than the
cup-shaped grindstone is mounted to the small spindle,
independently setting a number of rotations of the cup-shaped
grindstone and a number of rotations of the small-diameter
grindstone respectively, and grinding one surface of the wafer with
the cup-shaped grindstone and grinding a circumferential side
surface of the wafer with the small-diameter grindstone with using
the grinding apparatus of the above described present
invention.
[0026] According to the grinding method described above, the number
of rotations of the cup-shaped grindstone and the number of
rotations of the small-diameter grindstone are respectively set
independently, and therefore, grinding of one surface of the wafer
and grinding of the peripheral edge part of the wafer can be
performed at the optimal numbers of rotations of the grindstone for
the respective grindings.
[0027] The grinding method of the present invention is
characterized by further comprising the steps of bringing the
cup-shaped grindstone and the small-diameter grindstone, and the
chuck table relatively close to each other in a rotational axis
direction of the chuck table, and grinding the one surface and the
circumferential side surface of the wafer while bringing a
rotational axis of the rotating cup-shaped grindstone and
small-diameter grindstone, and the rotational axis of the chuck
table relatively close to each other, or while bringing the
rotational axis of the cup-shaped grindstone and the small-diameter
grindstone, and the rotational axis of the chuck table relatively
close to and away from the rotational axis of the chuck table.
[0028] According to this grinding method of the present invention,
the small-diameter grindstone can be moved along the initial
chamfered shape of the peripheral edge part of the wafer, and edge
grinding of the wafer can be performed with a small cut-in.
Therefore, edge grinding can be favorably performed for the
peripheral edge part of the extremely thin wafer.
[0029] As explained above, according to the grinding wheel, the
grinding apparatus and the grinding method of the present
invention, increase in the size of the grinding apparatus can be
suppressed, and the back surface grinding of the wafer and the
grinding of the peripheral edge part of the wafer are performed at
the same time, whereby the peripheral edge part of the extremely
thin wafer is prevented from being sharpened, and cracking and
chipping of the wafer peripheral edge part can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a perspective view showing a grinding wheel
according to an embodiment of the present invention;
[0031] FIG. 2 is a sectional view showing the grinding wheel
according to the embodiment of the present invention;
[0032] FIG. 3 is a sectional view showing a grinding wheel
according to another embodiment of the present invention;
[0033] FIG. 4 is a sectional view showing a modified example of a
grinding wheel according to another embodiment of the present
invention;
[0034] FIG. 5 is a side view showing a grinding apparatus according
to the embodiment of the present invention;
[0035] FIG. 6 is a sectional side view showing a grinding method
according to the embodiment of the present invention;
[0036] FIG. 7 is a schematic view showing the grinding method
according to the embodiment of the present invention;
[0037] FIG. 8 is a schematic view showing a grinding method
according to another embodiment of the present invention; and
[0038] FIGS. 9A and 9B are sectional views showing a wafer for
which conventional back surface grinding is performed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] A preferred embodiment of a grinding wheel, a grinding
apparatus and a grinding method according to the present invention
will be explained in detail with reference to the attached drawings
hereinafter. In each of the drawings, the same members are given
the same reference numerals or characters.
[0040] FIG. 1 is a perspective view showing a grinding wheel
according to an embodiment of the present invention. The grinding
wheel 10 is constructed by a segment type cut-shaped grinding wheel
11 in which a plurality of grindstone chips 11B are formed on an
end surface of a base 11A, and a small-diameter grindstone 12
formed at a center part of the cup-shaped grindstone 11.
[0041] FIG. 2 is a sectional view when the grindstone chips 11B of
the grinding wheel 10 are faced downward. As shown in FIG. 2, the
small-diameter grindstone 12 is a cylindrical grindstone, and its
undersurface is provided to project from the undersurfaces of the
grindstone chips 11B.
[0042] The small-diameter grindstone 12 may be formed integrally at
the base 11A of -the cup-shaped grind stone 11, or the
small-diameter grindstone 12 may be formed at a small-diameter
grindstone base 13A which will be described later and may be
detachably mounted to the base 11A of the cup-shaped grindstone 11
with a screw or the like. The cup-shaped grindstone 11 is a segment
type, but it is not limited to the segment type, and it may be in
the ring shape in which the grindstone parts are connected.
[0043] When the small-diameter grindstone 12 is made detachable, it
is preferable because only the small-diameter grindstone 12 can be
replaced when the small-diameter grindstone 12 is worn. When the
cup-shaped grind stone 11 is of a segment type, supply of the grind
water to the grinding point and discharge of the grinding powder
are favorably performed.
[0044] When the grinding wheel 10 is used for back surface grinding
of the silicon (Si) wafer of a semiconductor, the diamond abrasive
grain of the grain size of #800 to #1500 is used for the abrasive
grain of the grindstone chip 11B, and a metal bond or a resin bond
is used as a bonding agent. The diamond abrasive grain of the grain
size of #2000 to #3000 is used for the abrasive grain of the
small-diameter grindstone 12, and a metal bond or a resin bond is
used for the binder. Considering the required worked surface
roughness and working speed, a fine grindstone of a resin bond is
more suitable than a rough grindstone of the metal bond.
[0045] When the diameter of the wafer W for which the back surface
grinding work is performed is 200 mm, the outer diameter of the
cup-shaped grindstone 11 is preferably about 250 mm, and when the
diameter of the wafer W is 300 mm, the outer diameter of the
cup-shaped grindstone 11 is preferably about 350 mm. In both cases,
the outer diameter of the small-diameter grindstone 12 is about 30
mm to 50 mm.
[0046] FIG. 3 is a sectional side view showing another embodiment
of the grinding wheel according to the present invention. In this
other embodiment, a small-diameter grindstone 13 is provided at a
center part of the cup-shaped grindstone 11. The small-diameter
grindstone 13 is formed into a truncated cone at a small-diameter
grindstone base 13A, and is screwed onto the center part of the
base 11A of the cup-shaped grindstone 11 and is detachably
provided.
[0047] The small-diameter grindstone 13 in the truncated cone shape
is not limited to a detachable type, and it may be formed
integrally at the base 11A. When the small-diameter grindstone 13
is made a detachable type, it is preferable because only the
small-diameter grindstone 13 can be replaced when the
small-diameter grindstone 13 is worn.
[0048] The small-diameter grindstone 13 formed into the truncated
cone shape is constructed by a stacked structure of a rough
grinding grindstone 13B on a tip end side of the truncated cone and
a fine grinding grindstone 13C on a base side of the truncated
cone. In the grinding wheel of the present invention, the
small-diameter grindstone 13 in the truncated cone shape is not
limited to the stacked structure of the rough grinding grindstone
13B and the fine grinding grindstone 13C. It may be constructed by
only the rough grinding grindstone 13B, or only the fine grinding
grindstone 13C in accordance with the use purpose.
[0049] FIG. 4 shows a modified example of the aforementioned
embodiment shown in FIG. 3. In this modified example, a clearance
groove 13D is formed on the inclined side surface of the
small-diameter grindstone 13 formed into the truncated cone shape.
The position of the clearance groove 13D is at such a position as
the extension surface of the undersurface of the grindstone chip
11B of the cup-shaped grindstone 11 slightly lies on the lower side
of the clearance groove 13D.
[0050] When a wafer is ground by using the grinding wheel of this
modified example, setting can be made so that the peripheral edge
of the wafer is ground with the small-diameter grindstone 13 prior
to the grinding of the wafer back surface by the grindstone chip
11B of the cup-shaped grindstone 11, and the peripheral edge of the
wafer goes into the clearance groove 13D just before the wafer has
the final thickness. Therefore, at the time of the final grinding
of the wafer back surface, grinding of the peripheral edge part of
the wafer is completed, and the back surface grinding can be
performed in the state without contact with the small-diameter
grindstone 13. Therefore, chipping of the peripheral edge part of a
thin wafer can be suppressed.
[0051] FIG. 5 is a side view showing a grinding apparatus according
to the embodiment of the present invention. A grinding apparatus 20
has a Y table 22 supported movably in the Y-direction in the
drawing by a guide not shown on a machine base 21, a .theta.-table
23 which is mounted to the Y-table 22 and rotates around an axis
(WC) in a Z-direction orthogonal to the Y-direction, and a chuck
table 24 which is mounted to the .theta. table 23 and fixes the
wafer W by suction. The Y table 22 is fed horizontally in the
Y-direction in the drawing at the time of grinding by a transverse
driving device 25 constructed by a motor 25A and a ball screw
25B.
[0052] A column 26 fixed on the machine base 21 is provided with a
grindstone table 27 which is guided by a guide not shown and for
which cut-in feed in the Z-direction in the drawing is performed by
a cut-in driving device 28 constructed by a motor 28A and a ball
screw not shown.
[0053] The grindstone table 27 is in a horseshoe shape, a hollow
spindle 31 and a cup-shaped grindstone driving motor 32 are mounted
to a lower side of the horseshoe shape, and the hollow spindle 31
and the cup-shaped grindstone driving motor 32 are connected by a
belt 33 via pulleys respectively provided at them. A hollow
cup-shaped grindstone 15 is mounted to a tip end of the hollow
spindle 31, and is rotationally driven around an axis (SC) by the
cup-shaped grindstone driving motor 32.
[0054] A small spindle 34 which penetrates through the hollow
spindle 31 and the hollow cup-shaped grindstone 15, and a
small-diameter grindstone driving motor 35 are mounted on an upper
side of the horseshoe shape of the grindstone table 27, and the
small spindle 34 and the small-diameter grindstone driving motor 35
are connected by a belt 36 via pulleys respectively provided at
them. A small-diameter grindstone 16 is mounted to a tip end of the
small spindle 34, and is rotationally driven around the axis (SC)
by the small-diameter grindstone driving motor 35.
[0055] The grinding apparatus 20 of the present invention is
provided with the hollow spindle 31 and the small spindle 34
penetrating through the hollow spindle 31, and they are
respectively rotated by the independent driving devices. Therefore,
optimal rotation can be given to the hollow cup-shaped grindstone
15 mounted to the hollow spindle 31 and the small-diameter
grindstone 16 mounted to the small spindle 34.
[0056] It is the basic form that the axis of the hollow spindle 31
and the axis of the small spindle 34 are concentric, but it is
possible to take the structure in which the axis of the hollow
spindle 31 and the axis of the small spindle 34 are eccentric by a
predetermined amount.
[0057] In the case where the numbers of rotations of the cup-shaped
grindstone 15 and the small-diameter grindstone 16 may be the same,
rotation control of the cup-shaped grindstone driving motor 32 and
the small-diameter grindstone driving motor 35 may be performed so
that the number of rotations of the hollow spindle 31 and the
number of rotations of the small spindle 34 become the same, or
grinding work may be performed with only the hollow spindle 31 by
mounting the grinding wheel 10 shown in the aforementioned FIGS. 1
and 2 to the hollow spindle 31 without using the small spindle
34.
[0058] The structure in which cut-in feed in the Z-direction of the
hollow spindle 31 and the small spindle 34 is performed together is
adopted, but the structure capable of performing the cut-in feed in
the Z-direction independently for each of the hollow spindle 31 and
the small spindle 34 may be adopted.
[0059] Further, the structure in which the cut-in feed in the
Z-direction is performed for the grindstone and the transverse feed
in the Y-direction is performed for the wafer W is adopted, but the
present invention is not limited to this structure, and the
structure in which the cut-in feed in the Z-direction is performed
for the wafer W and the transverse feed in the Y-direction is
performed for the grindstone may be adopted, or the structure in
which the cut-in feed in the Z-direction and the transverse feed in
the Y-direction are performed for the grindstone, or the structure
in which the cut-in feed in the Z-direction and the transverse feed
in the Y-direction are performed for the wafer W may be
adopted.
[0060] FIGS. 6 and 7 schematically shows a back surface grinding
method of the wafer W using the grinding wheel 10 shown in the
aforementioned FIGS. 1 and 2. As shown in FIG. 6, the wafer W has a
protection sheet S attached on the main surface side on which the
circuit pattern is formed, fixed by suction onto a chuck table 24
with the back surface up, and is rotated around the axis WC. The
grinding wheel 10 is disposed to oppose to the back surface of the
wafer W, and is rotated around the axis SC.
[0061] When the back surface of the wafer W is ground, the
aforementioned Y-table 22 mounted with the chuck table 24 performs
transverse feed for the wafer W in the Y-direction to position the
wafer W at the position just before the peripheral edge part of the
wafer W contacts the small-diameter grindstone 12. In this case,
the portion slightly inward from the outermost peripheral portion
of the grindstone chip 11B of the cup-shaped grindstone 11 is at
the position passing through the center of the wafer W placed
concentrically with the axis WC.
[0062] Next, the grinding wheel 10 lowers to grind the back surface
of the wafer W with the grindstone chips 11B of the cup-shaped
grindstone 11. When the grinding wheel 10 further lowers to grind
to reduce the half thickness of the wafer W, the back surface and
the peripheral edge part of the wafer W are ground at the same time
while transverse feed of the wafer W is performed in the
Y-direction so that the side surface of the small-diameter
grindstone 12 cuts in the peripheral edge part of the wafer W.
[0063] The grinding work is thus continued, and just before the
thickness of the wafer W reaches a predetermined value, the wafer W
is fed in the reverse direction so that the peripheral edge part of
the wafer W is slightly separated from the small-diameter
grindstone 12, and the back surface of the wafer W is finally
ground with the grindstone chips 11B of the cup-shaped grindstone
11 in the state in which the small-diameter grindstone 12 does not
touch the peripheral edge part of the wafer W.
[0064] Moving away the small-diameter grindstone 12 at the time of
final grinding of the back surface of the wafer W is for the
purpose of suppressing chipping of the peripheral edge part of the
thinned wafer W. When the thickness of the wafer W reaches the
predetermined value in this manner, the grinding wheel 10 releases
upward and the work is finished.
[0065] Since the wafer W thinned in this manner by the back surface
grinding has the peripheral edge part ground by the small-diameter
grindstone 12, the peripheral edge part is not in the sharpened
shape as shown in FIGS. 6 and 7, and thus, the wafer W is worked
into the shape which is strong against cracking and chipping.
[0066] FIG. 7 schematically shows the state in which the back
surface of the wafer W is ground by the cut-in feed in the
Z-direction of the aforementioned small-diameter grindstone 12 and
the transverse feed in the Y-direction of the wafer W, and shows
the final position of the back surface grinding. In FIG. 7, the
relative movement locus of the small-diameter grindstone 12 with
respect to the wafer W is shown to be easily understood. Namely,
the relative movement locus of the small-diameter grindstone 12
with respect to the wafer W becomes the locus shown by the arrow
written outside the small-diameter grindstone 12 in FIG. 7.
[0067] Since transverse feed in the Y-direction is performed for
the small-diameter grindstone 12 as described above, the transverse
feed in the Y-direction of the grindstone chips 11B of the
cup-shaped grindstone 11 is performed at the same time, and it is
necessary to have a sufficient transverse feed rate for the
grindstone chip 11B not to deviate from the center of the wafer
W.
[0068] In the aforementioned embodiment, the peripheral edge part
of the wafer W is ground with the side surface of the
small-diameter grindstone 12, but the present invention is not
limited to this. The peripheral edge part of the wafer W can be
ground by using both of the end surface of the small-diameter
grindstone 12 or both of the end surface and the side surface.
[0069] FIG. 8 schematically shows the state in which the back
surface of the wafer W is ground by using a grinding wheel 10A
having the small-diameter grindstone 13 in a truncated cone shape
shown in the aforementioned FIG. 3. In this case, the wafer W is
thinned by only the cut-in feed in the Z-direction of the grinding
wheel 10A without performing the transverse feed in the Y-direction
of the wafer W. In this embodiment, the peripheral edge part of the
wafer W is worked into the strong shape against cracking and
chipping without being formed into the sharpened shape.
[0070] In the aforementioned embodiment, the explanation is made
with the back surface grinding of the wafer W and the peripheral
edge grinding performed at the same time, but the small-diameter
grindstone 12 is sufficiently projected with respect to the
grindstone chip 11B of the cup-shaped grindstone 11, the peripheral
edge grinding of the wafer W is completed first, and then the back
surface grinding of the wafer W can be performed. In this case,
working time becomes longer as compared with the case where the
back surface grinding of the wafer W and the peripheral edge
grinding are performed at the same time.
[0071] As explained thus far, according to the present invention,
the back surface grinding and the peripheral edge grinding of the
wafer W can be performed at the same time while avoiding increase
in the size of the grinding apparatus, the peripheral edge part of
the extremely thin wafer is prevented from being into the sharpened
shape, and the thin wafer W in which cracking and chipping of the
peripheral edge part hardly occur can be obtained.
* * * * *