Leti-SNRS Full-Frame Curved Sensor Paper

Leti-SNRS curved sensor paper "Curved detectors developments and characterization: application to astronomical instruments" by Simona Lombardo, Thibault Behaghel, Bertrand Chambion, Wilfried Jahn, Emmanuel Hugot, Eduard Muslimov, Melanie Roulet, Marc Ferrari, Christophe Gaschet, Stephane Caplet, and David Henry is available on-line. This work was first announced a year ago.

"We describe here the first concave curved CMOS detector developed within a collaboration between CNRS-LAM and CEA-LETI. This fully-functional detector 20 Mpix (CMOSIS CMV20000) has been curved down to a radius of Rc =150 mm over a size of 24x32 mm2. We present here the methodology adopted for its characterization and describe in detail all the results obtained. We also discuss the main components of noise, such as the readout noise, the fixed pattern noise and the dark current. Finally we provide a comparison with the flat version of the same sensor in order to establish the impact of the curving process on the main characteristics of the sensor.

The curving process of these sensors consists of two steps: firstly the sensors are thinned with a grinding equipment to increase their mechanical flexibility, then they are glued onto a curved substrate. The required shape of the CMOS is, hence, due to the shape of the substrate. The sensors are then wire bonded keeping the packaging identical to the original one before curving. The final product is, therefore, a plug-and-play commercial component ready to be used or tested (figure 1B)."

"The PRNU factor of the concave sensor shows an increase of 0.8% with respect to the flat sensor one. The difference between the two is not significant. However more investigations are required as it might be due to the curving process and it could explain the appearance of a strong 2D pattern for higher illumination levels."