Fujifilm and Panasonic develop organic CMOS image sensor

During the recent years sensor resolutions have been dramatically improved, it was now necessary to expand the dynamic range, enhance sensitivity and prevent cross-talk or color mixing between pixels to further boost image quality, the companies said. The sensor features an organic photoelectric conversion layer at the light receiving section of an image sensor. Panasonic took advantage of its semiconductor device technology to improve image quality of 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.

The new organic CMOS sensor is the result of a combination of Fujifilm’s organic photoelectric conversion layer technology with Panasonic’s semiconductor device technology. According to the manufacturers, it offers the industry’s highest dynamic range of 88dB, advanced sensitivity 1.2 times more sensitive than conventional sensors and a broader range of incident angle to enable the production of more sensitive and compact cameras with better image quality. The two companies want to promote the application of this organic CMOS image sensor technology to a wide range of products including security cameras, in-vehicle cameras, mobile devices and digital cameras.

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, on the other hand, replaces the silicon photodiode by an organic photoelectric conversion layer with high absorption coefficient, reducing the thickness of the light receiving section down to 0.5 microns, only a fraction of the thickness of a silicon photodiode. Compared with conventional image sensors, Panasonic’s semiconductor device technology has improved the signal saturation value by a factor of four.

The transistors and metal interconnects in each pixel are coated with photoelectric conversion layer, developed by Fujifilm. While the light receiving section of conventional sensors is limited by metal interconnects and the need to form a light shield film that prevents light incidence into other areas, the organic CMOS image sensor can harvest all the light received on the sensor. As a result, sensitivity is 1.2 times higher than that of conventional sensors.

Since the thickness of the organic film with high absorption coefficient has been reduced to just 0.5 microns, the new sensor allows for greater flexibility in lens designs, enabling the reduction of overall camera size.

Fujifilm has developed a process technology to produce inorganic films for protecting the organic film against the entry of moisture and oxygen. According to the manufacturers, 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.