Micro Hard-X Ray Camera: From Caliste 64 to Caliste 256

Caliste project aims at hybridizing 1 cm² Cd(Zn)Te detectors with low noise front-end electronics, in a single component standing in a 1 times 1times 2 cm³ volume. The micro-camera is a spectroscopic imager for X and gamma rays detection, with time-tagging capability. Hybridization consists in stacking full custom ASICs perpendicular to the detection surface. The first prototype Caliste 64 integrates a detector of 8 times 8 pixels of 1 mm pitch. Fabrication and characterizations of nine cameras units validate the design and the hybridization concept. Spectroscopic tests result in a mean energy resolution of ~0.7 keV FWHM at 14 keV and ~0.85 keV FWHM at 60 keV using 1 mm-thick Al Schottky CdTe detectors biased at -400 V and cooled down to -15degC. The new prototype called Caliste 256 integrates 16 times 16 pixels of 580 mum pitch in the same volume as Caliste 64. Electrical tests with the first sample fabricated without detector result in a mean equivalent noise charge of 64 e^- rms (9.6 mus, no leakage current). Caliste devices are 4-side buttable and can be used as elementary detection units of a large hard X-ray focal plane, as for the 64 cm² high energy detector of the Simbol-X astronomical space mission.