Stone working – Sawing – Rotary
Reexamination Certificate
2002-01-31
2003-08-19
Rachuba, M. (Department: 3723)
Stone working
Sawing
Rotary
C125S002000, C451S041000, C451S011000, C451S005000, C083S425200
Reexamination Certificate
active
06606985
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of cutting a workpiece such as a semiconductor wafer using a cutting apparatus having two cutting blades equipped therewith.
2. Related Arts
Referring to
FIG. 5
, a semiconductor wafer W has a plurality of cross streets S to define a lattice pattern thereon, each square area having a circuit pattern formed thereon. The semiconductor wafer W can be diced into a plurality of square chips C.
Referring to
FIG. 6
, such a semiconductor wafer W is attached to a holder frame F by using a piece of adhesive sheet T, and the wafer-and-frame combination is fixedly supported by a chuck table
11
. Then, a cutting means
20
is lowered in the Z-axial direction until its cutting blade
24
has reached the surface of the semiconductor wafer W, and the chuck table
11
is moved in the X-axial direction while the cutting blade
24
is rotated at an increased speed. Every time the cutting in the X-axial direction has been finished, the cutting means
20
is moved the street-to-street distance in the Y-axial direction for indexing, and then, the cutting in the X-axial direction is repeated.
Referring to
FIGS. 7 and 8
, the cutting means
20
comprises a housing
22
, a rotary shaft
23
rotatably supported by the housing
22
, the rotary shaft
23
having a blade mount
23
a
integrally connected to its end, a fastening nut
27
to be mated with the male threads
23
b
formed on the blade mount
23
a
, and a cutting blade
24
to be fixed to the mount
23
a
by fastening with the nut
27
. The cutting blade
24
comprises an annular hub
24
a
and a cutting edge
24
b
integrally connected to the annular hub
24
a
. As seen from
FIG. 6
, the cutting bade
24
is covered by a blade casing
26
, and a pair of coolant supply nozzles
25
are so positioned that cooling water may flush to the place at which the cutting is being effected.
Some cutting apparatuses, as for instance, disclosed in Japanese Patent 11-26402(A) use two cutting means such as shown in
FIGS. 6
,
7
and
8
. Referring to
FIG. 9
, the first cutting blade
24
is fixed to the end of the first rotary axis
26
whereas the second cutting blade
61
is fixed to the end of the second rotary axis
60
. These rotary axes
26
and
60
are aligned in line so that the first and second cutting blades
24
and
61
confront each other. With this arrangement the two cutting blades
24
and
61
can be used simultaneously in cutting the semiconductor wafer W. The efficiency with which the workpiece can be cut is increased substantially thanks to simultaneous use of two cutting blades, permitting two streets to be cut simultaneously.
According to the cutting method disclosed in Japanese Patent 11-26402(A), at the outset the cutting edge
24
b
of the first cutting blade
24
is aligned with one of the outermost opposite streets of a circular workpiece whereas the cutting edge
61
b
of the second cutting blade
61
is aligned with the other outermost street, as shown in FIG.
10
. These cutting blades
24
and
61
are moved stepwise toward each other by the street-to-street distance L
2
every time two streets have been cut.
The first and second cutting means
20
and
21
are constructed as shown in
FIGS. 6
,
7
and
8
. Therefore, these cutting means cannot be put close to each other, leaving a minimum distance L
1
(equal to the total thickness of their hub projections
24
a
and
61
a
), which is larger than the street-to-street distance L
2
in the intermediate zone D of the workpiece W. As a matter of fact, the minimum edge-to-edge distance L
1
is 5 times as large as the street-to-street distance L
2
, thus preventing the simultaneous cutting of two streets in the intermediate zone D. Therefore, one of the first and second cutting blades
24
and
61
is used in the intermediate zone, and accordingly, the cutting efficiency is lowered.
Referring to
FIG. 11
, the first cutting edge
24
b
is aligned with the outermost street of the side zone E of the workpiece W whereas the second cutting edge
61
b
is aligned with the center street of the intermediate zone D of the workpiece W. The cutting of two lines or streets S is repeated every time these cutting edges
24
b
and
61
b
have been moved the street-to-street distance in the −Y-axial direction for indexing. The workpiece such as a semiconductor wafer is a circle, and therefore, the X-axial stroke of the first cutting edge
61
b
in the intermediate zone D is much longer than that of the second cutting edge
24
b
. The X-axial stroke of the second cutting edge
24
b
must be extended beyond the circle to be equal to the longer stroke of the first cutting edge
61
b
. This will cause the second cutting edge
24
b
to run a significant length of useless stroke, and accordingly the cutting efficiency will be lowered.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a method of cutting a workpiece at an increased efficiency or a dual-cutting method devoid of useless strokes of cutting blades across a workpiece.
To attain this object, a method of cutting a workpiece with the aid of a cutting apparatus comprising: at least a first cutting means whose first rotary shaft has a first cutting blade fixed to its end; a second cutting means whose second rotary shaft has a second cutting blade fixed to its end; each first and second cutting blades has a circular cutting edge on its periphery; guide means for holding the first and second cutting means with their center axes aligned in line, and for supporting movably the first and second cutting blades in the confronting relation, thereby permitting them to be fed for indexing; and a chuck table adapted to be moved in the cutting direction perpendicular to the indexing direction, thereby making the first and second cutting edges cut a plurality of parallel lines separated at a predetermined interval in the workpiece while the chuck table is being fed in the cutting direction, is improved in that the method comprises:
the first step of: separating one of the first and second cutting means from the other at such an edge-to-edge distance that the first and second cutting edges may be separated two or more integer “n” times the line-to-line distance; putting one of the first and second cutting means in alignment with the particular center line at the center of the intermediate zone of the workpiece, allowing the other cutting means to remain the edge-to-edge distance apart; and cutting the workpiece with the first and second cutting blades simultaneously; and cutting 2
n
lines every two lines longitudinally every time the first and second cutting means have been fed the line-to-line distance laterally; and
the second step, which is subsequent or antecedent to the first step, of: allotting one of the first and second cutting edge to one of the opposite sides of the intermediate zone and the other cutting edge to the other side to cut two lines longitudinally in the opposite side zones every time the first and second cutting means have been fed the line-to-line distance laterally so that the first and second cutting edges may be brought close to each other or apart from each other.
The workpiece may be a semiconductor wafer having cross streets drawn to draw a lattice pattern on its surface, the workpiece being diced into square chips by cutting crosswise.
Other objects and advantages of the present invention will be understood from the following description of a preferred embodiment, which is illustrated in accompanying drawings.
REFERENCES:
patent: 4688540 (1987-08-01), Ono
patent: 5842461 (1998-12-01), Azuma
patent: 6102023 (2000-08-01), Ishiwata et al.
patent: 6119675 (2000-09-01), Akram et al.
patent: 6250192 (2001-06-01), Akram et al.
patent: 6422227 (2002-07-01), Kobayashi et al.
patent: 6427676 (2002-08-01), Akram et al.
patent: 2001/0023973 (2001-09-01), Akram et al.
patent: 2002/0184982 (2002-12-01), Smith et al.
patent: 11-026402 (1999-01-01), None
patent: 2001-230221 (2001-08-01), None
Disco Corporation
Rachuba M.
Rader & Fishman & Grauer, PLLC
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