Television – Special applications – Manufacturing
Reexamination Certificate
1998-10-30
2002-02-19
Britton, Howard (Department: 2613)
Television
Special applications
Manufacturing
C348S092000
Reexamination Certificate
active
06348943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a blade position detection apparatus for wafer dicing machine used in the dicing of a material piece, such as a semiconductor wafer or a ceramic piece, and more particularly, to a digital non-contact blade position detection apparatus for use on a wafer dicing machine for blade position detection that can be used to correct the blade position of the cutting blade due to wear to the cutting blade.
2. Description of Related Art
In a wafer dicing machine, a rotating circular blade is used to cut a fabricated wafer apart into separate chips. After a long time of use, however, the cutting edge of the blade can be worn out, thus affecting the cutting depth into the wafer. As a result, the wafer would not be cut properly. A solution to this problem is to constantly measure the radius of the blade to accordingly correct the blade position. This solution, however, is inaccurate and can cause damage to the blade or the platform on which the wafer is fixed. Another solution is disclosed in European Patent No. 0532933A1 entitled “Blade Position Detection Apparatus”. This patent is briefly described in the flowing with reference to
FIGS. 4-6
.
As shown in
FIG. 4
, the apparatus of European Patent No. 0532933A1 includes a pair of prisms
2
,
3
, a first lens system
5
, a second lens system
6
, a light source
4
, a light sensor
7
, and an analog control circuit
8
. The blade
1
of the wafer dicing machine is interdisposed in the optical path
11
between the two prisms
2
,
3
. In operation, the light source
4
generates a light beam which is then successively guided through the first lens system
5
, the first prism
2
, the second prism
3
, and the second lens system
6
to the light sensor
7
. If the blade
1
is unworn, it will block out a certain amount of the fight beam transmitting from the first prism
2
to the second prim
3
; and when the blade
1
is worn out, it will allow an increased amount of the light beam to pass therethrough to the second prism
3
if positioned at the same vertical position. Accordingly, the correction in position for the blade
1
can be obtained by first adjusting the blade
1
to a vertical position that allows the light sensor
7
to receive a predetermined fixed amount of light beam and then using the Z-as displacement detector
10
to measure the vertical displacement. The measured data can be then used to adjust the blade
1
to the suitable cutting position.
FIGS. 5A and 5B
are two graphs used to explain the operation of the conventional blade position detection apparatus of
FIG. 4
, wherein
FIG. 5A
shows the V versus Z relationship, where V is the magnitude of the electrical voltage signal generated by the fight sensor
7
in response to the received light beam, and Z is the vertical displacement of the blade
1
; and
FIG. 5B
shows the &Dgr;V/&Dgr;Z versus Z relationship, where &Dgr;V/&Dgr;Z is the rate of change of V with respect to Z. When the blade
1
is located at positions away from Za, the light beam
11
(shown here in cross section) between the prisms
2
,
3
is entirely unblocked by the blade
1
, thus allowing V to be at its maximum magnitude V
0
; and at the position Zc, the blade
1
blocks nearly half of the light beam
11
, thus making V to be reduced in half to V
0
/2; and at the position Zb, the light beam
11
is entirely blocked by the blade
1
, thus reducing V to 0. The voltage V
0
/2 is selected as the threshold voltage for the error signal used in blade position correction
One drawback to the foregoing apparatus of
FIG. 4
, however, is that, due to its analog method of processing the light signal, the precision of the blade position detection can be easily affected by external factors such as contamination to the optical components, changes in ambient temperature and humidity, and varieties in component characteristics. As illustrated in
FIGS. 6A and 6B
, alien particles reside in the optical path
11
between the first and second prisms
2
,
3
, they would block part of the light beam transmitting along the optical path
11
, and as a result, would causes a shift in the threshold V
0
/2 and a shift in the &Dgr;V/&Dgr;Z versus Z curve toward Za. As a consequence, the precision of the blade position detection would be adversely affected. Besides, ambient scattering light intruding into the system can also adversely affect the precision of the blade position detection. Still moreover, the blade position detection by the foregoing apparatus of
FIG. 4
is quite slow in response.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a digital non-contact blade position detection apparatus, which can perform the blade position detection digitally.
it is another objective of the present invention to provide a digital non-contact blade position detection apparatus, which can help enhance the resolving power of the blade position detection to the submicron level.
It is still another objective of the present invention to provide a digital non-contact blade position detection apparatus, which can perform the blade position detection by positing the blade always at a fixed position
It is yet another objective of the present invention to provide a digital non-contact blade position detection apparatus, which can perform the blade position detection without being affected by ailed particles intruding into the optical system.
It is still yet another objective of the present invention to provide a digital non-contact blade position detection apparatus, which can perform the blade position detection with quick response and high precision.
In accordance with the foregoing and other objectives of the present invention, a new digital non-contact blade position detection apparatus is provided. The apparatus of the invention includes the following constituent elements:
a light source for generating a light beam;
a light converging optical unit for converting the light beam from the light source to a preset converging point;
light diverting means for diverting the beam light from the light converging optical unit to a preset optical path in which the blade is interdisposed, with the blade being interdisposed between a pair of prims at a first predetermined distance from the converging point of the light beam passing through the light converging optical unit;
a light diverging optical unit, disposed at a second predetermined distance from the position where the blade is disposed, for diverging the diverted light beam from the second prism;
a CCD position detector, disposed at a third predetermined distance from the light diverging optical unit, for detecting a displacament of a diffractive part of the light beam passing through the optical path between the first and second prisms that is partly blocked out by the blade;
an analog-to-digital converter for converting the analog displacement signal from the CCD position detector into digital data; and
computer means, king the digital data from the analog-to-digital converter as inputs, for determining accordingly the required correction in the position of the blade due to wear to the blade.
The foregoing apparatus of the invention has the benefits of performing the blade position detection in a digital manner, enhancing the resolving power of the blade position detection to the submicron level; allowing the detection to be unaffected by alien particles; and performing the blade position detection with quick response and high precision.
REFERENCES:
patent: 4757550 (1988-07-01), Uga
patent: 5276497 (1994-01-01), Oono
patent: 5642159 (1997-06-01), Oba
patent: 5886787 (1999-03-01), Hercher
patent: 6191429 (2001-02-01), Suwa
Huang Chien-Rong
Lai Chih-Yi
Lin Chien-Hsing
Liu Chun-Hung
Britton Howard
Diep Nhon T
Industrial Technology Research Institute
Smith , Gambrell & Russell, LLP
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