From: Dennis Doering Date: Fri, 10 Jan 2014 12:07:21 +0000 (+0100) Subject: Jahresbericht X-Git-Url: https://jspc29.x-matter.uni-frankfurt.de/git/?a=commitdiff_plain;h=046c806ba91b58f2a057b4c66a898536de17c091;p=radhard.git Jahresbericht --- diff --git a/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex b/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex index 1c35719..574402e 100644 --- a/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex +++ b/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex @@ -39,10 +39,13 @@ \hbox{ } %\section{Introduction} -\textbf{So far CMOS active pixel sensors (MAPS) matched the requirements of CBM in terms of spatial resolution and material budget. During several years, their radiation tolerance has been adapted to the needs of this experiment. In 2012, the radiation tolerance of a sensor, produced in an \mbox{0.18 $\upmu \rm m$} CMOS process was tested. It could be demonstrated that this sensor provides the radiation tolerance required for CBM at SIS-100. \newline} -In a first step, the tolerance of MAPS to non-ionizing radiation was improved by more than one order of magnitude. This was reached by partially depleting the active volume of the sensors \cite{DevMi26paper,DevMi26paper2}. Still, the tolerance of the sensors to ionizing radiation remained to be improved. This was done by migrating a simple imager sensor from the established \mbox{0.35 $\upmu \rm m$} process to an \mbox{0.18 $\upmu \rm m$} process. It was hoped that this would allow for exploiting the known higher intrinsic radiation tolerance of deep sub-micron CMOS processes. Besides providing benefits in terms of radiation tolerance, the \mbox{0.18 $\upmu \rm m$} process comes with additional features which are expected to allow for a better time resolution of the device.\newline -To explore the new technology, three different prototypes named MIMOSA-32 (V1-3) were designed by the PICSEL group of the IPHC and tested in the laboratory and at the CERN-SPS.\newline -Each flavor of MIMOSA-32 is composed of arrays of 32 different pixels with various parameters, which were put to study selected pixel parameters in a systematic way. +\textbf{In 2013, we studied in detail the noise performance of sensors, produced in an \mbox{0.18 $\upmu \rm m$} CMOS process.\newline} +So far CMOS active pixel sensors (MAPS) matched the requirements of CBM in terms of spatial resolution and material budget. During several years, their radiation tolerance has been adapted to the needs of this experiment. The radiation tolerance of a sensor, produced in an \mbox{0.18 $\upmu \rm m$} CMOS process could be demonstrated that this sensor provides the radiation tolerance required for CBM at SIS-100. + + +The tolerance of MAPS to non-ionizing radiation was improved by more than one order of magnitude. This was reached by partially depleting the active volume of the sensors \cite{DevMi26paper,DevMi26paper2}. Still, the tolerance of the sensors to ionizing radiation remained to be improved. This was done by migrating a simple imager sensor from the established \mbox{0.35 $\upmu \rm m$} process to an \mbox{0.18 $\upmu \rm m$} process. It was hoped that this would allow for exploiting the known higher intrinsic radiation tolerance of deep sub-micron CMOS processes. Besides providing benefits in terms of radiation tolerance, the \mbox{0.18 $\upmu \rm m$} process comes with additional features which are expected to allow for a better time resolution of the device.\newline +To explore the new technology, three different prototypes were designed by the PICSEL group of the IPHC and tested in the laboratory and at the CERN-SPS.\newline +Each flavor is composed of arrays of 32 different pixels with various parameters, which were put to study selected pixel parameters in a systematic way. The aim of this study is the noise performance in dependence of the transistor layout. Increasing the surface of the transistor gate seems to reduce the relative impact of the RTS and is therefore found to be beneficial. This holds also for the gate of the reset transistor, which was enlarged in \mbox{Pixel D}. After this modification, the median noise was reduced from \mbox{$19.8~\rm e$} \mbox{(Pixel A)} to \mbox{$16.2~\rm e$} \mbox{(Pixel D)}. Note that, while enlarging the transistor size reduces the RTS, cooling seems not to show a positive impact. This is in contrast to our observations on RTS-noise originating from the pixel \mbox{diodes \cite{RTS}}. We conclude MAPS manufactured in an \mbox{0.18 $\mu \rm m$} CMOS process combined with a high-resistivity epitaxial layer provide the radiation tolerance required by the micro-vertex-detector of CBM at SIS-100. Moreover, there are first evidences that the technology might also match the higher needs of CBM at SIS-300. While this conclusion appears robust for simple imagers, it remains to be confirmed for the more complex sensors with integrated data processing circuits. \newline