Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-03-10
2002-08-27
Everhart, Caridad (Department: 2825)
Abrading
Abrading process
Glass or stone abrading
C451S011000, C451S044000, C451S065000
Reexamination Certificate
active
06439969
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a wafer, an apparatus and a method of chamfering a wafer, particularly a semiconductor wafer. The apparatus and method of chamfering a semiconductor wafer, includes chamfering a notch groove of the semiconductor wafer using a disc shape grindstone so as to form an edge of the wafer into a concave-shape in a pseudo manner.
2. Description of the Related Art
In a conventional apparatus and process for manufacturing a semiconductor device, a notch groove is formed by cutting a portion of the periphery of a semiconductor wafer into a V-shape or a circular-arc shape in order to easily align the orientation of crystal of the semiconductor wafer. The V-shape notch groove is widely employed due to enabling a limited area of the wafer to efficiently be used and having excellent locating accuracy.
In such a process for manufacturing the semiconductor device, the periphery of the semiconductor wafer sometimes comes in contact with a portion of an apparatus for use in the manufacturing process. Such a contact causes dust and a crack to occur. In order to prevent such a contact, the periphery of the semiconductor wafer is chamfered in general.
A conventional method of chamfering the notch groove is shown in
FIGS. 15 and 16
.
In
FIGS. 15 and 16
, the reference numeral
1
represents a wafer;
3
, notch groove;
10
, a formed grindstone
10
;
11
, a grindstone shaft.
The phrase “formed grindstone” means a grindstone having a grinding surface a cross-section which is substantially the same as the ground portion of the wafer
1
after grinding operation, as shown in FIG.
15
. At this time, the formed grindstone
10
is formed into a hand-drum shape.
As shown in
FIG. 15
, the formed grindstone
10
is a rotatable grindstone having a bus line
10
a
and rotates around grindstone shaft
11
. The bus line
10
a
of the formed grindstone
10
is formed into a concave shape corresponding to a convex bus line of the wafer. The notch groove
3
formed into a substantially V-shape in preprocess comprises straight portions
3
a
, a groove bottom
3
b
, and orifices
3
c
as shown in FIG.
16
. The notch groove
3
is chamfered by the formed grindstone
10
as shown in
FIG. 16 . A
curvature radius r (a diameter d) in the center of the formed grindstone
10
is smaller than that of a groove bottom
3
b
of the notch groove
3
.
The chamfering process is performed by chamfering the notch groove
3
as drawing such a tool locus
13
shown in
FIG. 16
by the formed grindstone
10
while the grindstone shaft
11
is being maintained to be in parallel with the center line of the wafer
1
.
The notch grooves of the wafer before/after chamfering is performed are shown respectively in
FIGS. 17 and 18
. A surface
3
f
of the wafer
1
shown in
FIG. 17
is chamfered by formed grindstone
10
so as to form chamferings C
1
, C
2
and C
3
as shown in FIG.
18
.
Since the straight portion
3
a
of the notch groove
3
is brought into contact with a locating pin having a diameter of about 3 mm and the groove bottom
3
b
has a small curvature radius, the diameter d of the formed grindstone
10
is about 2 mm. Therefore, the grindstone is rotated at about 100,000 rpm to realize required grinding speed.
Further, since the diameter of the grindstone is small, a metal-bond diamond grindstone is employed as the grindstone to prevent abrasion of the grindstone. The metal-bond grindstone, however, has a maximum surface roughness Rmax of 1 &mgr;m which causes the wafer to sustain damage of about 10 &mgr;m in the form of a crack layer and polishing such as buffing, which is performed as a following process, takes about 10 minutes.
Moreover, in order to subject the mirror-surface polishing/finishing process into the chamfered portion of the notch groove similar to the chamfered portion of the peripheral side surface of the disc shape wafer, surface roughness of the chamfered portion of the notch groove must be improved, that is grinding must be performed to realize surface roughness of about 0.1 &mgr;m. A resinoid-bond grindstone is used so that the notch groove is chamfered to realize the surface roughness of about 0.1 &mgr;m. However, the use of the resinoid-bond grindstone excessively causes abrasion of the grindstone and considerable deformation of the shape of the grindstone. Accordingly,the shape of the chamfered portion deteriorates.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a wafer, an apparatus and a method of chamfering a notch groove of a wafer, in which the wafer is chamfered so as to have satisfied surface roughness of the formed notch groove and reduced abrasion of the grindstone.
According to a first aspect of the present invention, there is provided a method of chamfering a notch groove of a wafer formed into a disc shape, comprising the steps of:
using a wafer having a notch groove surface, means for holding the wafer, a grindstone frame incorporating a grindstone formed into a disc shape and structured such that a leading end of a radial-directional cross section of an peripheral side surface obtained by cutting with a plane including a grindstone axis has a curvature radius smaller than a minimum curvature radius of the notch groove and moving means which is capable of relatively moving the wafer and the grindstone along the notch groove of the wafer on a plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on a plane intersecting the parallel plane;
(1) making the central line of the wafer and the central line of the grindstone to intersect each other;
(2) causing the grindstone to act on the notch groove such that a locus of a tool is drawn on a plane which is in parallel with the principal plane of the wafer to relatively move the grindstone and the wafer along the notch groove to perform chamfering along the notch groove;
(3) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with a chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove in a portion except for the chamfered portion;
(4) causing the grindstone to act on the notch groove on a plane which is in parallel with the plane which is in parallel with the principal plane of the wafer and which is different from the plane such that a locus of a tool is drawn to relatively move the grindstone and the wafer along the notch groove to furthermore performing chamfering along the notch groove;
(5) relatively moving the grindstone and the wafer on a plane intersecting the plane in accordance with the chamfered shape of the notch groove to allow the grindstone and the wafer to correspond to the notch groove in a portion except for the chamfered portion; and
(6) similarly chamfering the notch groove into a polygonal shape.
According to a second aspect of the present invention, there is provided a method of chamfering a notch groove of a wafer formed into a disc shape, comprising the steps of:
using a wafer having a notch groove surface, means for holding the wafer, a grindstone frame incorporating a grindstone formed into a disc shape and structured such that a leading end of a radial-directional cross section of an peripheral side surface obtained by cutting with a plane including a grindstone axis has a curvature radius smaller than a minimum curvature radius of the notch groove and moving means which is capable of relatively moving the wafer and the grindstone along the notch groove of the wafer on a plane which is in parallel with the principal plane of the wafer and relatively moving substantially along the chamfering shape of the wafer on a plane intersecting the parallel plane;
(1) making the central line of the wafer and the central line of the grindstone to intersect each other;
(2) causing the grindstone to act on the notch groove such that a locus of a tool is drawn on a plane which is in parallel with the principal plane of th
Kaga Muneaki
Koma Kikuo
Murai Shirou
Takata Michihiro
Everhart Caridad
Malsawma Lex H.
Nippei Toyama Corporation
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