CMOS imagers made in Europe
Image sensors transform the light captured by Earth observation and planetary exploration missions into a digital signal that, when processed, recreates the image. Recently, the focus has been on providing a complementary metal-oxide semiconductor (CMOS) solution for these applications. Both the European Space Agency (ESA) and the European Commission have identified a need for the development of space-qualified CMOS image sensors (CIS) using solely European manufacturing sources. EU-funded researchers have launched the EUROCIS (Platform for European CMOS imagers) project to meet this need. Until recently, image sensors were based on charge coupled device technologies that are available in Europe. The researchers established a CIS design that matches the demanding requirements for space applications and withstands harsh operating conditions. Key to success was backside passivation using laser annealing. Numerous experiments were performed using a test vehicle, which consisted of photodiodes of different sizes, to define the optimum conditions for enhanced chemical stability of silicon substrate wafers. The researchers also evaluated the application of post-processing coatings to reduce reflection and maximise transmission on silicon surfaces. Components were fabricated and sample CISs were built and tested to validate the new design. The test set up included electrical and optical ground support equipment. The first supplied the sensor with power and read the analogue output, while the latter provided optical stimulus from various sources, depending on the parameters to be measured. Vibration tests were also performed. By exploiting their state-of-the-art infrastructure and accumulated know-how, the EUROCIS project partners have strengthened their offering of innovative concepts through prototyping and small-scale production. Additional high-end applications of the newly designed CIS in medical imaging and security are expected to follow.
Keywords
Imaging systems, space industry, complementary metal-oxide semiconductor, image sensor