Development of edgeless TSV X-ray detectors

Abstract

We report about the activity and progress on the development of TSV edgeless detectors at DESY. One part of the development is Through Silicon Via (TSV) technology for the Medipix3RX readout chip (ROC). TSV technology is a concept of connecting readout chips to readout electronics. Instead of wire-bonding which introduces a large dead area, TSV enables connection through the ROC itself. By replacing wire-bonding with TSV, the dead space between detector modules will be reduced from around 7 mm to only 1.6 mm. The thickness of the wafer will be 200 μ m, with a via diameter of 60 μ m. Inside of the via, a 5 μ m thick copper layer will be used as a conducting layer. On the back side of the chip a Redistribution Layer (RDL) will be deposited. For the RDL structure, 5 μ m thick copper with 40 μ m wide conductive lines will be used. Bump bonding of the sensor plus ROC assembly to ceramic readout board will be optimized in terms of material and bonding temperature. The second part of the project is the development of the edgeless sensor units using active edge sensor technology. Active edge sensors have been simulated with Synopsys TCAD for different polarities including p-on-n, p-on-p, n-on-p and n-on-n with p-spray or p-stop for different thicknesses from 150 μ m to 500 μ m. Results show that the bending of the electric field close to the active edge is leading to image distortion on the sensor edge. In addition, the current design of active-edge sensors shows very poor radiation hardness. We are currently working on the development of a radiation hard active-edge sensor with optimized imaging quality. The final goal of this development is to make Large Area Medipix Detector (LAMBDA) with TSV edgeless units.