[Interview] OmniVision on Backside-illuminated CMOS Sensors (1)
OmniVision Technology Inc is one of the key players who changed the image sensor market, which had been dominated by Japanese companies until 2004 or so.
The company expanded its share of the market, aided by the diffusion of camera-equipped mobile phones. Aptina Imaging Corp, the image-sensor spin-off from Micron Technology Inc, lost its momentum as the business of Motorola Inc, its main customer, slumped. On the other hand, OmniVision maintained the largest share by shipping more products to EMS/ODM firms that have plants in China.
OmniVision is the company that announced a plan to commercialize backside-illuminated (BSI) CMOS sensors for the first time in the industry. But Sony commercialized a BSI CMOS earlier than OmniVision, which plans to ship its production model in the summer of 2009.
In this way, OmniVision is gaining footholds in terms of not only quantity but also quality. However, for those who do not have business relations with the company, it is a very private company being reluctant to disclose information to the media.
Nikkei Electronics, with the help of a public relations firm, interviewed James He, COO of OmniVision, and its marketing director. Though they did not reveal details of their technologies, we could see part of their development policies.
In this article, we will provide the content of the interview and the characteristics of the product released at a later date.
Q: Why did you decide to adopt the backside-illumination (BSI) technology?
As is widely known, the BSI technology is not a new technology. But nobody had ever applied the technology to a sensor with a pixel pitch as small as 1.4μm and mass-produced it.
There is a physical limit in designing image sensors, diffraction of light. We had to challenge BSI sooner or later. Plus, it is impossible to enhance the performance of a 1.4μm-pitch CMOS sensor, which the market is demanding, without the BSI technology. So, from now on, we will use the BSI technology for all of our products with a pitch of 1.4μm and below.
At first, we were, of course, not sure whether we could lower the cost of a BSI image sensor to the level that meets demands of mobile phones. But we started the development about four years ago, believing that the cost problem can be solved as the production volume increases.
Q: I guess there were many pixel defects at first?
No. We got a feeling that we could make it from the first.
Q: TSMC (Taiwan Semiconductor Manufacturing Co Ltd), which has a close relationship with OmniVision, will manufacture your BSI image sensors. Which company suggested commercializing the sensor?
We did. TSMC and OmniVision cooperated in developing the process technologies. We developed technologies to make a very thin wafer so that light shines on photo diodes from the back and to properly handle the thin wafer. The number of masks only slightly increased compared with that of existing CMOS sensors.
Q: How many process engineers does OmniVision have?
I can only tell you that we have enough number of process engineers in our headquarters (Santa Clara, the US).
Q: How have you been keeping a good relationship with TSMC? There are many Chinese and Taiwanese executive officers at OmniVision. So, communication in Pekingese is the key?
No. We use English in all meetings. Engineers at TSMC are very good at English. I have never found it difficult to communicate in English.
Q: OmniVision is using TSMC's old plants. But that does not necessarily help create a good relationship.
Mutual trust cannot be built in a day. I think our relationship started in 1996.
Q: Did TSMC believe the potential of CMOS sensor that long ago? For example, CCDs were once replacing CMOS sensors in camera-equipped mobile phones.
Not to change the subject, but Kyocera Corp developed the first camera-equipped mobile phone, whose camera module was externally connected. It was embedded with our CMOS sensor.
Moreover, "EyeToy" of Sony Computer Entertainment Inc employed our CMOS sensor and a USB bridge chip we designed. We expanded the CMOS sensor market by designing camera systems too.
In February 2009, we released the "CameraCube," a small camera module whose lens is added in a semiconductor packaging process. This product represents our know how in system design. (It is manufactured by VisEra Technologies Co of Taiwan, a company spun out of TSMC.)