Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
2000-03-28
2001-09-04
Everhart, Caridad (Department: 2825)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C438S064000, C438S118000, C438S127000, C257S432000
Reexamination Certificate
active
06285064
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to image sensing integrated circuits, and more particularly, to a method for chip scale packaging using an adhesive matrix.
2. Background Information
Currently, prior art chip scale packaging for optical image sensor devices require that a wafer be completely coated with an optically clear adhesive and subsequently covered with a transparent covering material. Typically, the optically clear adhesive can be an epoxy and the transparent material is glass.
However, nearly all image sensors require the application of micro lenses to increase the optical fill factor to meet performance objectives. As seen in
FIG. 1
, a typical chip scale package for an imaging sensor is shown. The packaging technique includes a wafer
101
having the image sensor chips formed thereon. Micro lenses
103
are formed atop of the wafer
101
to cover each pixel (picture element) individually. After pads have been extended into the scribe lines, an adhesive layer
105
is then applied, typically using some type of homogenous spin coating technique. Finally, a cover glass
107
is applied to the adhesive. The adhesive
105
serves to secure the cover glass
107
to the wafer
101
. Typically, the adhesive
105
is an epoxy.
Next, the backside of the wafer
101
is ground down to make the wafer thinner. Next a wafer sawing operation is used to expose the extended image sensor electrical leads though the back side of the thinned wafer. The exposed leads are then extended to form electrical contacts with traditional deposition and etching processes. Finally, a die cutting machine is used to cut the wafer
101
into individual image sensors.
However, this prior art method of chip scale packaging is problematical for image sensors because the refractive index of the micro lens material is very similar to the adhesive
105
. Thus, the adhesive
105
tends to counteract the optical effect of the micro lenses
103
.
SUMMARY OF THE INVENTION
The present invention is a chip scale packaging method for optical image sensor integrated circuits. Micro lenses are placed on top of a wafer having the image sensors formed thereon. An adhesive matrix such as epoxy is placed atop of the wafer. The matrix has openings that align with the image-sensing array of the integrated circuit on top of the wafer. A cover glass is then placed over the matrix and the adhesive is activated to secure the cover glass to the wafer. Because the adhesive has openings above the micro lenses, no distortion is caused by the adhesive.
REFERENCES:
patent: 5225935 (1993-07-01), Watanabe et al.
patent: 09159806 (1997-06-01), None
Blakely , Sokoloff, Taylor & Zafman LLP
Everhart Caridad
OmniVision Technologies Inc.
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