21st International Workshop on Radiation Imaging Detectors

Development and characterization of CMOS Sensors for Electron Microscopy

8 Jul 2019, 16:35

1m

Poster general Poster Exhibition 1: Posters ID 1 - 80, chair: Christer Frojdh

Speaker

Horacio Mateos (KIT - Karlsruhe Institute of Technology (DE))

Description

In this work, we show the design and characterization of an image sensor with 64x64 pixels and its associated hardware and software needed to use the chip. The aim of the chip is to be used as a sensor for TEM electron microscopy. First measurements were done using X-Rays to characterize the chip and to test the whole system (ASIC, Software, and Hardware).
The here described sensor was developed in 180nm AMS HV-technology [1]. Pixel sensors are based on deep n-well in p-substrate diodes. Signals generated by particles are collected by the deep n-wells. Pixel electronics is placed inside the n-wells. The pixel electronics contains a charge sensitive amplifier and a correlated double sampling circuit. Pixel matrix is readout in rolling shutter mode. The signals are passed to 128 readout channels at the chip periphery. Each channel contains an amplifier and an 8-bit digital-to-analog converter (D/A converter). The digital values of the pixels’ signals are sent outside the chip, in serial mode, via 8 Low Voltage Differential Signals (LVDS). The output of the chip is received by a Nexys Video FPGA, which is the link between the Chip and the PC. This FPGA allows the user to configure the Chip using the Qt interface designed for this purpose. The interface also allows the user to store the incoming data and watch online the chip readout.
The chip has been illuminated by X-Ray source for 30 minutes. A Seyfert ISO-DEBYEFLEX 3003 X-Ray tube was used, with seven different targets in order to have an X-Ray of specific energy on the range $6,4KeV$ to $25,3KeV$.
Depending on the energy of the X-Ray, the peak of the Gaussian (on the histogram) moves to higher bin output values. Plotting the mean value of each Gaussian vs. the energy shows a linear behavior in the energy range used, with a conversion factor of $253.82\frac{eV}{bit}$ (where "bit" is the 8-bit value of the output).
The chip was tested for radiation tolerance, reaching $50Mrad$ without showing signs of malfunctioning but with an increase of noise (from $82e^{-}$ to $239e^{-}$), and a change in the conversion factor, from $250.28\frac{eV}{bit}$ to $328.18\frac{eV}{bit}$.

[1] Ehrler, F., Blanco, R., Leys, R., Perić, I.; “High-voltage CMOS detectors”; Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment; 2015; 650. 10.1016/j.nima.2015.09.004.

Presentation materials

Poster_HPixel_iWoRiD_Mateos.pdf