Tuesday, May 27, 2008

Omnivision Demos 1.4um BSI Sensor

Yahoo: Omnivision officially announces that it has developed 8MP backside illuminated (BSI) sensor with 1.4um pixels in 0.11um process. OmniVision is currently demonstrating its 8MP OmniBSI sensor, and expects to start sampling its first products based on this technology before the end of June. There is now word on MP start.

This approach is said to allow 1.4um BSI pixel to surpasses all the performance metrics of 1.4um, and even most 1.75um, conventional pixels. It has increased sensitivity per unit area, improved QE and reduced cross talk and photo response non-uniformity and larger CRA. The later enables thinner camera modules with larger aperture lens.

"Moving FSI pixel architectures down to 1.4 micron and below, under current design rules, poses some real challenges because metal lines and transistors are driving the aperture of the pixel close to the wavelength of light, its physical limit," said Howard Rhodes, Vice President of Process Engineering at OmniVision. "To overcome this with traditional FSI pixel technology would require a migration to 65 nm copper process technologies, which would significantly increase the complexity and cost of manufacturing. Because it allows for more than three layers of metal, BSI achieves significant manufacturing benefits without moving to smaller process nodes. This means routing can be simplified and die sizes can be smaller than in FSI sensors, without the need to move to smaller process nodes with all their associated complexities and additional costs."

"Although backside illumination concepts have been studied for over 20 years, up until now nobody has been able to successfully develop the process for commercial, high volume CMOS sensor manufacturing," said Dr. Ken Chen, Senior Director, Mainstream Technology Marketing, TSMC. "Combining OmniVision's imaging expertise with TSMC's experience in process development, we have delivered a truly advanced technology that defines the future of digital imaging."

Thus Omnivision becomes the first company moving BSI concept into consumer space. This is really great achievement, not only for Omnivision, but for whole the industry! With Samsung showing BSI on its roadmap, I believe other companies will follow the same path eventually. The next big step would be moving BSI into MP.

As a side note, we can see a technology divirgence in 1.4um pixel generation with Kodak pursuing hole-based photodiode and RGB-W color filter, Omnivision taking BSI path and Aptina and Samsung following conventional technology (albeit Samsung has BSI on its horizon too). It would be interesting to see these approaches competing once they all reach MP stage.

Update: EETimes article downplays Omnivision's innovation. The article says that BSI technology has been around for decades and Omnivision just applied it to consumer imagers. But just looking on the number of analysts commenting on that and interpreting the scarce details, the overall impression is quite opposite: the announcement is taken very seriously by everybody.


  1. Taking backside illumination to the consumer thru mass production is a big step. It sounds like the congratulations are due to TSMC.

    Meanwhile, the EE Times article suggests the first backside illumination patent was filed by Micron. In fact, it was filed by us at Photobit a few years prior to Photobit being acquired by Micron.


  2. And of course, I was referring to backside illumination in a CMOS image sensor...CCD backside illumination has been around for a very long time.

  3. Yes, backside illumination looks like the next big thing in consumer imaging, if mass production difficulties are really overcomed. It also might put Omnivision into the image quality leaders ahead of Micron and Sony.


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