Severing by tearing or breaking – Breaking or tearing apparatus – Combined with preliminary weakener or with nonbreaking cutter
Reexamination Certificate
2000-08-08
2003-02-04
Goodman, Charles (Department: 3724)
Severing by tearing or breaking
Breaking or tearing apparatus
Combined with preliminary weakener or with nonbreaking cutter
C225S101000, C125S023010
Reexamination Certificate
active
06513694
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor wafer cleaving method and apparatus by which semiconductor wafers are cleaved along scribing marks.
BACKGROUND ARTS
Since priorly, various types of semiconductor chips have been obtained by cutting off a plurality of element areas formed and arrayed on a semiconductor wafer at boundary positions. Recently, the cutting of semiconductor wafers is carried out by, for example, cleaving the wafers along scribing marks with the scribing marks provided at boundary positions of the element formed areas at the end edge on the surface of the semiconductor wafers.
FIG.
11
and
FIG. 12
show a conventionally general method for cleaving semiconductor wafers. The cleaving method is called a “three-point bending method.” First, a plurality of scribing marks
2
are arrayed and formed at the end edge on the surface of a semiconductor wafer
1
(These scribing marks
2
are provided at the boundary positions of the element formed areas on a semiconductor wafer
1
). Next, a pair of fulcrum members
4
a
and
4
b
are disposed in parallel to the scribing marks
2
with each of the scribing marks
2
placed therebetween on the surface
3
where the scribing marks are formed. Also, on the rear side
5
opposite the scribing mark formed surface, a fulcrum member
6
is disposed so as to become parallel to each of the scribing marks
2
, at the position opposed to the above scribing marks
2
. After that, a tensile force is given to the scribing marks
2
by causing fulcrum forces P
2
, P
1
, and F
1
to operate thereon from these fulcrum members
4
a
,
4
b
and
6
, whereby the semiconductor wafer
1
is cleaved at the plane ZOY from the position of the scribing marks
2
.
The relationship between a shearing force and a bending moment in carrying out a cleaving by the “three-point bending method” is expressed as shown in FIG.
13
. As shown in
FIG. 13
, the positive or negative polarity of the shearing force is reversed at the lower fulcrum member
6
used as the boundary. In fact, the operating point of a fulcrum force F
1
acting from the fulcrum member
6
on the semiconductor wafer
1
has a definite width although being slight. Therefore, the shearing stress does not become zero in the entirety of the operating area of the fulcrum force F
1
. As shown in
FIG. 12
, a portion of a minute cubic volume dva of one-sided half of the scribing mark is taken for instance, wherein a shearing stress &tgr; parallel to the plane ZOY to be cleaved, and a bending tensile stress &sgr;
ax
perpendicular to the plane ZOY to be cleaved are produced.
If the shearing stress and bending tensile force are expressed in terms of Mohr's stress circle, they will become as shown in FIG.
14
. That is, the direction of action of the ruling maximum main stress &sgr;
a1
of cleavage produced on the cleavage plane of the scribing mark is not a direction &sgr;
ax
perpendicular to the vertical cleavage plane (plane ZOY) ideal to the semiconductor wafer
1
, but has an angle &agr;
1
from the direction &sgr;
ax
, (which can be easily calculated by Mohr's stress circle). Therefore, as in the cleavage plane of a cleavage state illustrated in
FIG. 15
, an oblique cleaved portion
7
a
is produced at the portion at the lower side of the scribing mark
2
on the cleavage plane
7
of the semiconductor wafer
1
, whereby such a problem arises, by which an expected cleavage plane could not reliably be obtained.
In addition, as shown in
FIG. 16
, when actually carrying out a cleaving work, the fulcrum member
6
does not become parallel to the scribing marks
2
, whereby a possibility exists, that the fulcrum member
6
is disposed so as to cross the extension line of the scribing marks
2
. In such cases, a problem arises, by which a cleavage plane
7
bent as shown in
FIG. 17
would be produced.
The present invention was developed in order to solve the above shortcomings and problems, and it is therefore an object of the invention to make the shearing stress zero in the vicinity of the scribing marks, and to make the direction of the maximum main stress produced in the scribing mark perpendicular to the ideal vertical cleavage direction. That is, the invention is to provide a semiconductor wafer cleaving method and apparatus which enables an ideal mirror-finished cleavage plane by operating only the bending tensile stress onto scribing marks.
DISCLOSURE OF THE INVENTION
The invention is constructed as described below. That is, a first aspect of a semiconductor wafer cleaving method according to the invention is constructed so that the lower side of a semiconductor wafer, which has a scribing mark inscribed on the surface, is supported by fulcrum members in parallel to the above scribing mark at least two or more positions between which the scribing mark is placed, and similarly, the upper side of the semiconductor wafer is supported by fulcrum members in parallel to the above scribing mark in at least two or more positions, between which the scribing mark is placed, different from the positions where the scribing mark is supported so as to be placed at the innermost side on the lower side, a fulcrum force, which makes zero the shearing force of a semiconductor wafer between the fulcrum members supporting the innermost side with the scribing mark placed therebetween, is given from the respective fulcrum members at both upper side and lower side to the semiconductor wafer to cause pure bending tensile stress to operate onto the scribing mark, and the semiconductor wafer is cleaved at the scribing mark.
Further, a second aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first aspect of the semiconductor wafer cleaving method, the fulcrum members at both upper side and lower side of the semiconductor wafer are placed left-right symmetrically, centering around a scribing mark, and a left-right symmetrical pair of fulcrum members which support at the innermost side the plane where the scribing mark is formed, are disposed outside the corresponding left-right symmetrical pair of fulcrum members which support at the innermost side the opposite back side.
Further, a third aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first or second aspect of the semiconductor wafer cleaving method, one side of the upper side fulcrum members and the lower side fulcrum members of the semiconductor wafer are caused to move in a direction of applying a fulcrum force when applying a fulcrum force from the respective fulcrum members to the semiconductor wafer, the moving side fulcrum members are supported via a slide mechanism which self-adjusts the hypothetical plane connecting the fulcrum tip ends of the above moving side fulcrum members in parallel to the plane in which a fulcrum force of the semiconductor wafer is applied, and the slide mechanism causes the moving side fulcrum members while maintaining the parallel of the above hypothetical plane of the moving side fulcrum members with respect to the plane in which a fulcrum force of the semiconductor wafer is applied, whereby a fulcrum force is applied to the semiconductor wafer.
Also, a fourth aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first, second or third construction of the semiconductor wafer cleaving method, a fulcrum force of a fixed load is applied from the upper side fulcrum members and the lower side fulcrum members of a semiconductor wafer.
Moreover, a fifth aspect of the semiconductor wafer cleaving method according to the invention is constructed so that, in addition to the first, second or third construction of the semiconductor wafer cleaving method, a fulcrum force applied from the above fulcrum members to a semiconductor wafer is a distributional load, the force of which is increased in the direction a crack generated along the scribing mark develops.
Further, a sixth aspect of the semicond
Suzuki Kenji
Xu Jie
Goodman Charles
Lacasse & Associates, L.L.C.
The Furukawa Electric Co. Ltd.
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