Sunday, November 16, 2008

Fortnightly Patent Review

I spotted just two noteworthy applications in the last two weeks flow of more than 40 image sensor-related applications:

Micron application US20080265295 talks about making a deep red pixel in Bayer pattern, while green and blue pixels are shallower. This might be a useful idea for old simple 3T pixels, but Micron is going to apply it to 4T design. The problem with it is that essentially Micron has to optimize two different pixels in the same sensor, including dark current, image lag, full well, etc. All these are long and hard optimizations, requiring many trade-offs. Having two different pixels to optimize certainly does not help in this.

Application US20080265348 was filed by Philips in May 2005, right before the image sensor group was acquired by DALSA. It contains quite a detailed description of manufacturing steps of backside illuminated imager. It appears that Philips experimented with CMOS BSI well before the acquisition.

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