Process enables integrating color sensors at CMOS level

December 03, 2018 // By Christoph Hammerschmidt
The production of color sensors has been significantly simplified by a new process that also allows the integration of sensor functions, including special lens arrangements at the semiconductor level, in standard CMOS technology. Due to their very low overall height, the integrated sensors offer a wide range of applications. They can be used, for example, in mobile devices and for colour control of LED luminaires.

Color sensors are required for many applications. One of the most important is color control in displays and LEDs. To date, components with complex nanoplastic structures are used for this purpose. They filter the incident light in such a way that only defined parts of the color spectrum reach the detector surface. The angle of incidence of the light is decisive for functional color filtering. In order to avoid light from unwanted angles and thus color errors, the sensors are combined with macroscopic elements to improve filter accuracy. The disadvantage is that they significantly increase the overall size of the structure. In the joint development project FOWINA, the Fraunhofer Institutes for Integrated Circuits (IIS) and for Silicate Research (ISC) have developed an all-in-one solution that combines many functions in a minimum of space.

The color sensor chip integrates color filter structures, angle filters for controlling the incidence of light, evaluation electronics for signal processing, and photodiodes for converting light into electricity. Due to their very compact design, the new color sensors allow an ultra-flat design, so that they can be used in many products such as cameras or mobile phones. In addition to the high degree of integration, which combines as many functions as possible in a small area, the scientists also succeeded in simplifying production. The sensors can thus be manufactured and sold much more cost-effectively than with previous processes.

The Fraunhofer IIS (Erlangen, Germany) is developing the sensor chip including the nanoplasmic color filters. These can be produced cost-effectively in the CMOS process together with photodiodes and evaluation electronics using a single technology on a common silicon chip. The Fraunhofer ISC (Würzburg, Germany) has developed arrays of microstructures that act as angle filter elements for the sensors. The scientists used two-photon polymerization for this purpose. With this modern technology, microstructures of any shape and structured surfaces can be produced. To accelerate the manufacturing process, the Fraunhofer ISC uses

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