Cutting – With control means responsive to replaceable or selectable... – Arithmetically determined program
Reexamination Certificate
2001-04-18
2003-05-13
Rachuba, M. (Department: 3723)
Cutting
With control means responsive to replaceable or selectable...
Arithmetically determined program
C083S076700, C125S013010, C125S023020
Reexamination Certificate
active
06561066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cutting apparatus for cutting a workpiece such as a semiconductor wafer with precision.
2. Related Art
FIG. 7
shows a semiconductor wafer cutting apparatus. It comprises a holder means
15
for holding a workpiece to be cut, a cutting means
23
including a rotary blade
24
for cutting the workpiece held by the holder means
15
, an alignment means
36
having an imaging means
37
equipped therewith, and other associated parts. As seen from the drawing, a semiconductor wafer W is attached to a holder frame F using a piece of adhesive sheet T, and the wafer-bearing holder frame F is held on the holder means
15
. The holder means
15
is driven in the X-axial direction to be just below the alignment means
36
, allowing the alignment means
36
to detect a selected street along which the semiconductor wafer W is to be cut, and then, the holder means
15
is further driven in the X-axial direction while the cutting means
23
is lowered, thus allowing the rotary blade
24
to cut the semiconductor wafer W along the selected street.
The alignment means
36
and the cutting means
23
are integrally connected to each other, so that these parts may be moved as a whole in the Y- and Z-axial directions. The alignment means
36
is equipped with the imaging means
37
, e.g., comprising a CCD camera. As shown in
FIG. 8
, the imaging means
37
has an imaging screen
38
in which a hairline
39
is drawn as a reference line in the X-axial direction.
Before cutting the semiconductor wafer along a selected street, it is necessary that the rotary blade
24
be set in alignment with the hairline
39
in the X-axial direction, as shown in FIG.
9
. The imaging means
37
is moved in the Y-axial direction to scan an image of the selected street along which the semiconductor wafer W is to be cut, and a required adjustment is made until the selected street is found in alignment with the hairline
39
, which means that the rotary blade
24
is put in alignment with the selected street.
After establishing the alignment of the rotary blade
24
with the selected street to be cut, the holder means
15
is driven in the X-axial direction while the cutting means
23
is lowered in the Z-axial direction, thus allowing the rotary blade
24
to cut the semiconductor wafer W along the selected street.
Every time the cutting means
23
is moved by a street-to-street interval in the Y-axial direction, the cutting operation is resumed. Finally the semiconductor wafer W is cut along all streets in the X-axial direction. Then, the wafer-holding table
15
is rotated 90 degrees to repeat the cutting operation of the semiconductor wafer. Thus, the semiconductor wafer W is cut crosswise into squares.
Required precise cutting can be attained provided that the rotary blade
24
is aligned exactly with the hairline
39
in terms of their Y-coordinate. Such alignment, however, cannot be attained, for instance, if a new rotary blade is used in place of the old one; rotary blades cannot be exactly the same, but they are somewhat different from each other to the extent of causing misalignment between the new rotary blade and the hairline in terms of their Y-coordinate.
As seen from FIGS.
10
(A) and
10
(B), the rotary blade
24
is press-fitted on a rotary spindle
50
, and then a screw nut
51
is applied to a threaded-end
52
of the rotary spindle
50
to tighten the rotary blade
24
with the screw nut
51
, sandwiching the rotary blade
24
between a mount flange
53
and the screw nut
51
. The position of the rotary blade
24
on the spindle
50
will minutely vary according to a degree of fastening or tightening with the screw nut
51
and the like, and it is very difficult to fasten a new rotary blade
24
as tightly as in another or old one, in case of, e.g., changing the rotary blade. Therefore, the new rotary blade
24
would usually be spaced apart more or less from the hairline
39
.
Conventionally, in replacing the rotary blade with a new one, a dummy wafer is held by the holder means
15
, and then the new rotary blade is used to cut a straight groove
54
on the dummy wafer. The imaging means
37
is used to scan an image of the straight groove
54
. If the image of the straight groove
54
is not found in alignment with the hairline
39
(see FIG.
11
), an adjusting screw is rotated until the image of the straight groove
54
has been put in alignment with the hairline
39
(see FIG.
12
). This is tedious, time-consuming work.
Assuming that the rotary blade
24
happens to be broken while cutting a semiconductor wafer, the broken rotary blade
24
must be removed from the rotary spindle
50
to be replaced with a new one, following a series of actions beginning with the changing of the broken rotary blade for a dummy wafer and ending with the aligning of the straight groove made on the dummy wafer with the hairline.
Subsequent to the alignment effected on the dummy wafer relative to the hairline
39
, the dummy wafer must be removed from the holder means
15
to put the unfinished semiconductor wafer in place of the dummy wafer, and again an image of the unfinished cut along the selected street is scanned for alignment with the new rotary blade before resuming the cutting of the semiconductor wafer. This is a significant cause of lowering the workability and productivity.
SUMMARY OF THE INVENTION
One object of the present invention is to enable the changing of rotary blades in a cutting machine without requiring such tedious, time-consuming work as described above.
To attain this object, the present invention provides a cutting apparatus comprising at least a holder means for holding a workpiece to be cut and a cutting means including a rotary blade for cutting the workpiece held by the holder means, where the holder means and the cutting means are adapted to be driven relative to each other in a cutting direction, an indexing direction and a blade-thrusting direction, which apparatus further comprises a marking member positioned at such a place that the rotary blade can make a mark of cutting position (alignment marks) in an indexing direction on the marking member in order to align the rotary blade with a cutting line on the workpiece.
The marking member may be of an abrasion-resistant material.
The abrasion-resistant material may be a hard urethane.
The cutting apparatus may further comprise an alignment means having an imaging means for scanning a cutting area of the workpiece held on the holder means in order to align the cutting area and the rotary blade with each other with respect to the indexing direction, the imaging means having an imaging screen with a hairline drawn as a reference line for the alignment on the screen, wherein the mark of cutting position made on the marking member is scanned by the imaging means and imaged on the screen, while the mark of cutting position is aligned with the hairline on the screen, whereby the alignment of the cutting area with the blade is attained.
Thanks to the marking member the quick and easy alignment of the rotary blade relative to the hairline is permitted without using a dummy wafer. If the marking member is made of an abrasion-resistant material, marks made on the marking member become invisible in a while, thus permitting the marking member to be used repeatedly.
Further, even when a rotary blade is broken during the cutting operation, the broken blade can be readily changed without putting an operator to such a bother as in the conventional cutting machine.
REFERENCES:
patent: 3684939 (1972-08-01), Perry
patent: 4085494 (1978-04-01), Sybertz et al.
patent: 6421456 (2002-07-01), Son et al.
patent: 6-2173147 (1987-07-01), None
patent: 5-29410 (1993-02-01), None
patent: 5-326700 (1993-10-01), None
patent: 6-270038 (1994-09-01), None
Disco Corporation
Rachuba M.
Wenderoth , Lind & Ponack, L.L.P.
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