Over the last few years, CMOS sensors have improved in leaps and bounds. On that front, Fujifilm and Panasonic announced a new development in CMOS technology at the 2013 International Image Sensor Workshop, held June 15 in Utah (U.S.).
FUJIFILM and Panasonic have developed organic CMOS image sensor technology that uses an organic photoelectric conversion layer with a photoelectric conversion property at the light receiving section of an image sensor to achieve performance beyond that of conventional image sensors.
The industry has put forth continuous efforts to explore image sensor technologies for increasing their number of pixels. This has dramatically improved sensor resolutions, but, in order to further boost image quality, it is necessary to expand the dynamic range, enhance sensitivity and prevent crosstalk or color mixing between pixels. Panasonic took advantage of its semiconductor device technology to boost image quality for its high-performance image sensors. Fujifilm, on the other hand, has developed highly reliable organic photoelectric conversion layer with high absorption coefficient to be used on a sensor's light receiving section instead of silicon photodiode in its effort to build a new image sensor technology.
In the latest collaboration, Fujifilm and Panasonic have combined Fujifilm's organic photoelectric conversion layer technology with Panasonic's semiconductor device technology to jointly develop an organic CMOS image sensor that outperforms conventional image sensors. The new organic CMOS image sensor offers the industry's highest dynamic range of 88dB, advanced sensitivity 1.2 times more sensitive than conventional sensors and broader range of incident angle to enable the production of more sensitive and compact cameras with better image quality.
The two companies will promote the application of this organic CMOS image sensor technology to a wide range of products including security cameras, in-vehicle cameras, mobile device and digital cameras.
Overview
A conventional image sensor consists of a silicon photodiode for capturing light, metal interconnect, color filter and on-chip micro-lens. The newly-developed organic CMOS image sensor technology uses organic photoelectric conversion layer with high absorption coefficient instead of the silicon photodiode, reducing the thickness of the light receiving section down to 0.5µ, a fraction of the thickness of a silicon photodiode. This structure provides the following benefits:
- Industry's highest dynamic range of 88dB to prevent highlight clipping and produce a texture-rich image even in low light
- Higher fill factor than conventional sensors giving improved sensitivity.
The transistors and metal interconnects in each pixel, fabricated using Panasonic's semiconductor device technology, are coated with photoelectric conversion layer, developed using Fujifilm's organic material technology. The area of the light receiving section becomes limited in conventional image sensors because of the existence of metal interconnects and the need to form light shield film to prevent light incidence into areas other than the photodiode in each pixel. However, the organic CMOS image sensor technology coats the sensor with organic film, which can harvest all the light received on the sensor. - Offering high reliability for broad range of applications.
Fujifilm has developed a process technology to produce inorganic films for protecting the organic film. It prevents the entry of moisture and oxygen into the organic film to safeguard it against performance degradation. The sensor technology has cleared reliability tests involving the application of stress such as temperature, humidity, electrical voltage and light, paving the way for the use of the organic CMOS image sensor in a wide range of applications.
