High Density 3D Interconnections for High Performance CdTe Based X-Rays Detectors

Résumé fourni par la source

The X-Spectro-imaging camera under development consists of three blocks assembled in a compact 3D module. The top level is a monolithic pixelated cadmium telluride (CdTe) crystal to detect the X-rays. Underneath is a mosaic of$2 \times 2$finely pixelated analog ASICs (D2R2) to amplify, filter and locate the detectors charges induced by the interactions of photons with CdTe. The lowest layers concern post-treatment signal such as Analog to Digital converter, power supply filter, etc. The main challenge is the resulting high density of interconnections because each ASIC of the matrix contains 32×32 pixels and the pitch between two pixels is 250 μm. Furthermore, spectrometric grade CdTe detectors are sensitive devices for which elevated temperature process is not recommended. This is a soft and fragile material that requires extra care during handling. During this study, a prototype of the front-end layers of a module have been designed and several test vehicles have been produced. The objective is to develop and demonstrate 2D and 3D connections such as CdTe crystal onto ASIC mosaic by using electrically conductive dots, from D2R2 ASICs mosaic to the external part of the module with a Redistribution Layer deposition, and from ASIC mosaic level to the lower level with metallic inserts. Performance on test vehicles is demonstrated through measurements results.

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