First results on DEPFET Active Pixel Sensors fabricated in a CMOS foundry—a promising approach for new detector development and scientific instrumentation

Abstract

A: DEPFET Active Pixel Sensors (APS) have been introduced as focal plane detectors for X-ray astronomy already in 1996. Fabricated on high resistivity, fully depleted silicon and back-illuminated they can provide high quantum efficiency and low noise operation even at very high read rates. In 2009 a new type of DEPFET APS, the DSSC (DEPFET Sensor with Signal Compression) was developed, which is dedicated to high-speed X-ray imaging at the European X-ray free electron laser facility (EuXFEL) in Hamburg. In order to resolve the enormous contrasts occurring in Free Electron Laser (FEL) experiments, this new DSSC-DEPFET sensor has the capability of nonlinear amplification, that is, high gain for low intensities in order to obtain singlephoton detection capability, and reduced gain for high intensities to achieve high dynamic range for several thousand photons per pixel and frame. We call this property "signal compression".Starting in 2015, we have been fabricating DEPFET sensors in an industrial scale CMOS foundry maintaining the outstanding proven DEPFET properties and adding new capabilities due to the industrial-scale CMOS process. We will highlight these additional features and describe the progress achieved so far. In a first attempt on double-sided polished 725 µm thick 200 mm high resistivity float zone silicon wafers all relevant device related properties have been measured, such as leakage current, depletion voltage, transistor characteristics, noise and energy resolution for X-rays and the nonlinear response. The smaller feature size provided by the new technology allows for an advanced design and significant improvements in device performance. A brief summary of the present status will be given as well as an outlook on next steps and future perspectives.

The MiniSDD-Based 1-Mpixel Camera of the DSSC Project for the European XFEL

“…The sensors used for the second camera are the first DEPFET devices produced with a modified commercial CMOS process [18]. A prototype ladder using large format sensors and the complete readout chain has already been assembled and is currently under test.…”

“…A short outlook on the second generation of the DSSC camera and other possible future developments is given in section VIII. In the second camera the use of non-linear DEPFET sensors [16], [17], [18], instead of the MiniSDDs will enable lower noise and higher dynamic range. Fig.…”

A color x-ray camera for 2–6 keV using a mass produced back illuminated complementary metal oxide semiconductor sensor

“…The advent of time-resolved spectroscopy at synchrotron and x-ray free electron laser (XFEL) facilities has greatly expanded the need for this class of detectors. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Similar needs are also present in laser-plasma physics, where entire spectra for fluorescence, x-ray band thermal emission, or inelastic scattering must often be collected in few-pulse or even truly single-pulse experiments. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] While there is an impressive effort aimed at either improvement of existing state-of-the-art technology or de novo development of new ideas for truly advanced highperformance detectors, [1][2][3][4][5][6][7][8][9][10][11][12][13]…”

Qualification and Integration Aspects of the DSSC Mega-Pixel X-Ray Imager

“…A weight of 12.8 kg provides a pressure of 2.6 kg/cm 2 to the H70E-contact areas and 6.4 kg/cm 2 to the B/C/B-pad contact areas. The pressure to the B/C/B sheet between MB and heat spreader amounts to the desired 400 g/cm 2 . The curing process in the production run was performed at 125 • C for 73 min.…”

“…T HE DEPFET sensor with signal compression (DSSC) X-ray imager for experiments at the European X-ray free-electron laser (XFEL) Facility is being developed [1]. The DEPFET sensor is a symbiosis of DEPFET and silicon (Si)-drift detector (SDD) type drift rings [2]. For fast signalcharge collection, the pixel has a hexagonal shape with two drift rings and a side length of 136 μm.…”