From: Dennis Doering Date: Fri, 10 Jan 2014 13:56:09 +0000 (+0100) Subject: Jahresbericht2 X-Git-Url: https://jspc29.x-matter.uni-frankfurt.de/git/?a=commitdiff_plain;h=5f966e6a22689135bfb85acc64dda3e3bebb6688;p=radhard.git Jahresbericht2 --- diff --git a/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex b/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex index 574402e..e6a051f 100644 --- a/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex +++ b/Jahresbericht2013/Doering-Mi34-GSIbericht2013.tex @@ -24,7 +24,9 @@ \author[2]{J. Baudot} \author[1]{M. Deveaux} \author[2]{M. Goffe} +\author[1]{B. Linnik} \author[2]{S. Senyukov} +\author[1]{S. Strohauer} \author[1]{J. Stroth} \author[2]{M. Winter} %\affil{Institut f\"ur Kernphysik, Goethe University Frankfurt, Germany and IPHC Strasbourg, France} @@ -40,43 +42,39 @@ %\section{Introduction} \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. +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. However, it was found that this new sensors have a quite substantial high noise. In 2013, the origin of this noise was studied to understand the effect and provide strategies to suppress the noise and improve the performance. +To explore the new noise issue, three different prototypes named MIMOSA-32, MIMOSA-32ter and MIMOSA-34 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. Therefore the matrices MIMOSA-32ter-P2, MIMOSA-32ter-P6, MIMOSA-32ter-P5 and MIMOSA-34-P17 were studied. In the following, the pixels are named Pixel A-D accordingly (table \ref{tab:Mi32-1-f-noise-table}). As a reference, the matrix MIMOSA-18AHR-A2, produced in an \mbox{0.35 $\upmu \rm m$} CMOS process is supplemented (Pixel R).\newline +The pixels in $0.18 \mum$-process have in comparison to the reference pixel R a higher noise. In particular the 99\%-noise, which represents the noise value that >99\% of the pixel have a lower noise, is increased. \newline +In more detail, it was observed that decreasing the the surface of the source follower transistor, the gain improves by $10\%$, however the noise increases by $8\%$. Therefore the smaller transistor surface is not beneficial for the noise performance. The origin of this effect was identified as an 1/f-noise as it was already described in \cite{RTS0.18,RTS0.182}. 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{PaperRTS}}. +We conclude that the lower feature size of the $0.18 \mum$-process under study cannot be fully exploited to reduce the capacitive noise of the pixels. This is as the smaller transistors show an RTS-1/f noise, which dominates the capacitive noise. Knowing this effect, it should be possible to reduce the noise of the above presented sensors by means of optimizing the layout of the few relevant transistors.\newline + + +\bibliographystyle{plain} +\bibliography{Lit} -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 -\begin{table}[tbp] +\begin{table} \centering -\begin{tabular}{|l|c|cc|ccc|c|} +\begin{tabular}{|c|c|ccc|c|} \hline -Matrix& &Width &Length &Noise & Gain & Noise & Noise \\ - & &$[\mu m]$ &$[\mu m]$ &$ADU$ & $[e/ADU]$ & $[e]$& $99\%<[e]$\\ +Pixel& Width &Noise & Gain & Noise & Noise \\ + &$[\mu m]$ &$ADU$ & $[e/ADU]$ & $[e]$& $99\%<[e]$\\ \hline %ELT & & 1.85 & 12.1 & 22.4\\ -Mi-32ter-P2& A & 1.5 & 0.2 & 1.81 & 11.1 & 19.8 & 41\\ -Mi-32ter-P6& B & 0.9 & 0.2 & 1.97 & 10.5 & 20.5 & 55\\ -Mi-32ter-P5& C & 0.5 & 0.2 & 2.09 & 10.1 & 21.3 & 63\\ -Mi-34-P17 & D & 1.5 & 0.2 & 2.83 & 5.8 & 16.2 & 38\\ -Mi-18AHR-A2 ($0.35~\upmu \rm m$)&R & - & 0.35 & 1.71 & 6.0 & 10.7 & 18\\ -\hline -Difference A$\rightarrow$C & & & & +15\% & +10\% & +8\% & +54\%\\ + A & 1.5 & 1.81 & 11.1 & 19.8 & 41\\ + B & 0.9 & 1.97 & 10.5 & 20.5 & 55\\ + C & 0.5 & 2.09 & 10.1 & 21.3 & 63\\ + D & 1.5 & 2.83 & 5.8 & 16.2 & 38\\ +R & - & 1.71 & 6.0 & 10.7 & 18\\ \hline + + \end{tabular} -\caption{Noise and gain in dependence of the source follower gate size. The uncertainties of the absolute measurements are 5\% for the gain and 10\% for the median noise. The diode size of all pixels listed is $11~\rm \upmu m^2$. The width of the gate of all reset transistors is $0.25~\rm \upmu m$ and the length is $0.20~\rm \upmu m$ (pixel A-C) and $0.30~\rm \upmu m$ (pixel D). The source follower transistor of pixel R has an enclosed layout. Note, the gain includes the gain of the external readout chain. Therefore, only the gain of pixels of the same chip can be compared.} +\caption{Noise and gain in dependence of the source follower gate size.} \label{tab:Mi32-1-f-noise-table} \end{table} -%\section{The results of the annealing study} -%\section{Outlook} - -\bibliographystyle{plain} -\bibliography{Lit} - - - \end{document} diff --git a/Jahresbericht2013/Lit.bib b/Jahresbericht2013/Lit.bib index b324540..7f4b055 100644 --- a/Jahresbericht2013/Lit.bib +++ b/Jahresbericht2013/Lit.bib @@ -63,4 +63,13 @@ booktitle={Electron Devices Meeting, 2006. IEDM '06. International}, title={Random Telegraph Signal in CMOS Image Sensor Pixels}, year={2006}, pages={1-4}, -doi={10.1109/IEDM.2006.346973},} \ No newline at end of file +doi={10.1109/IEDM.2006.346973},} +@INPROCEEDINGS{PaperRTS, +author={Deveaux, M. and Amar-Youcef, S. and Budenbender, A. and Doering, D. and Frohlich, I. and Muntz, C. and Stroth, J. and Wagner, F. M.}, +booktitle={Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE}, +title={Random Telegraph Signal in Monolithic Active Pixel Sensors}, +year={2008}, +pages={3098-3105}, +doi={10.1109/NSSMIC.2008.4775010}, +ISSN={1095-7863}, +} \ No newline at end of file