Backside illumination of CMOS image sensor

Details Backside illumination of CMOS image sensor Backside illumination of CMOS image sensor

2000-01-14

2002-08-06

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Making device or circuit responsive to nonelectrical signal

Responsive to electromagnetic radiation

C438S458000, C438S460000

Reexamination Certificate

active

06429036

ABSTRACT:

This invention relates to image sensors, and more particularly to the manufacturing of CMOS image sensors capable of backside illumination.
BACKGROUND
Typically, a CMOS image sensor is illuminated from the front (or top) side of the silicon die. Because of processing features (metalization, polysilicon, diffusions, etc.), the pixel area is partially obscured, resulting in a loss of photons reaching the sensitive area and a reduction in the area in which photons are effectively collected. This results .in a reduction of the overall sensitivity of the sensor. If photons were collected from the backside of the pixel area, these obstacles could be overcome.,
However, backside illumination can be difficult because of the thickness of the bulk silicon and the packaging technology that allow the backside to be exposed to the illumination source. The thickness of a typical silicon wafer needs to be thinned considerably in order to absorb the photons in the sensitive area. Prior approaches utilized methods for thinning the die after they have been scribed from a wafer and then packaging the die in specialized packages. The specialized packages provide support to the thin die while providing unobstructed ports for illumination from the backside. However, this approach is both costly and time consuming.
SUMMARY
A CMOS image sensor is fabricated and packaged to allow the light sensitive area of the die to be illuminated from either the front side or the back side, or both. The implementation is achieved using wafer level processing that facilitates photon collection at both surfaces. This approach permits processing at the wafer level to allow the deposition of color filter arrays (CFA) on either surface. The silicon is thinned and the bump contacts and interconnect lines are relocated away from the image area of the die. The die is covered with an optically transparent material to provide additional support.


REFERENCES:
patent: 5753537 (1988-05-01), Dekker et al.

Affiliated with

Also associated with

Rating

Backside illumination of CMOS image sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Backside illumination of CMOS image sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Backside illumination of CMOS image sensor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2892379