1. Edgeless Medipix sensors for medical X-ray imaging applications Marten Bosma BND School in Rathen, 2009-Sep-14

2. Medipix Originated from the hybrid pixel technology developments for vertex detection at the LHC experiments. Collaboration of more than 20 institutes. Grown to a product in X-ray diffraction. Aim for an X-ray imaging device with Medipix. Marten Bosma, BND School in Rathen, 2009-Sep-14 Single photon counter Pixel size: 55 x 55 μm 2 Active area per chip ≈ 14 x 14 mm 2 (256 x 256 pixel matrix) I/O periphery (wire bonded) Pixelated 300 μm silicon sensor (256 x 256 pixels) Medipix2 readout ASIC Detector bias voltage 14 mm

3. Use of Medipix in medical applications High-Z (HiDRaLoN) Colour X-ray imaging (Medipix 3) Large surface areas (ReLAXD) { 0.5 cm  Medipix is a SPC →: Ultra-low noise Large Dynamic range Therefore, low contrast detectability. → potential dose reduction! MedipiX-ray Imaging Marten Bosma, BND School in Rathen, 2009-Sep-14

4. Large Surface Area TSV’s + BGAEdgeless Assemblies Edgeless Sensors Deep Reactive Ion Etching (DRIE) instead of conventional dicing Narrow n + or p + Stop Ring (SR) instead of wide Guard Ring Conventional structureEdgeless structure “Edgeless” Marten Bosma, BND School in Rathen, 2009-Sep-14 Quad Sensor with Guard Ring Medipix ASIC PCB ‘Edgeless’ Quad Sensor Medipix ASIC PCB  Ball-Grid-ArrayThrough-Silicon-VIa

5. Technologies:  Edgeless sensor technology(Canberra)  Through-Silicon-Via and Ball-Grid-Array(IMEC)  1 Gbit/s ethernet data transmission(Nikhef)  CO 2 -cooling (Nikhef)  Product development (PANalytical) Marten Bosma 5 Large Area X-ray Detector (RELAXD) SenterNovem Eureka project

6. Gap AA-Edge SR: 75 µm Different types of structures Each structure type is characterised by its Stop Ring (SR) width and the gap in between the Active Area (AA) edge and the trench (i.e. edge of the structure). We are interested in the influence of both on the leakage current density in the AA. Circular diodeRectangular test diodePixel detectorCircular detector Marten Bosma, BND School in Rathen, 2009-Sep-14

7. Leakage Current We want to have a high SNR in the Active Area. By biasing the Stop Ring at the same potential as the Active Area, it is possible to eliminate leakage currents from the Stop Ring to the Active Area and at the same time prevent the edge leakage current from reaching the Active Area. Generation current → Electron-hole pair generation. Number is proportional to the area and depletion thickness → proportional to number of intrinsic carriers. Diffusion current → Pair generation outside depletion region, which drift into depleted volume before recombination. Surface Current → Current flowing around edges, caused by possible damage and contamination Reduction of edge leakage current : The depletion layer width increases with the square root of the applied potential → leakage current characteristic can be determined by studying the current as a function of the voltage. Three types: Marten Bosma, BND School in Rathen, 2009-Sep-14

8. Concerns Light tightness → structure fully enclosed by probe station. Guarding → use of triax cables. Avoidance of ground loops → can cause a shift in the measured voltage or fluctuating currents Settling time (we took 60 s) Probing needles → the thicker the needle, the higher the measured current (we used two 407-A needles). Temperature and humidity changes → stable clean room (~ 50 % hum.) and possible chuck temperature control. Averaging → in each configuration, the leakage current characteristic has been measured five times. Accuracy → in terms of ±(% of reading + fraction of range) Voltage: ±(0.015% + 3 mV) Current: ±(0.05%) In order to allow the structure to settle, the actual measurement of I leak was done 120 seconds after applying V bias Marten Bosma, BND School in Rathen, 2009-Sep-14