Fabrication and characterization of a novel x-ray silicon detector

Kyung-Wook Shin; Karim S. Karim

doi:10.1117/12.2007900

19 March 2013 Fabrication and characterization of a novel x-ray silicon detector

Kyung-Wook Shin, Karim S. Karim

Proceedings Volume 8668, Medical Imaging 2013: Physics of Medical Imaging; 86683S (2013) https://doi.org/10.1117/12.2007900
Event: SPIE Medical Imaging, 2013, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

Protein crystallography is a key method for protein structure investigation in modern medicine and X-ray diffraction detectors are key to performance. We introduced a silicon detector, based on an active-pixel readout of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs) for protein crystallography. In this work, we present the fabrication process of the detector array, performance of the first fabricated TFT arrays, and the performance of the TFTs in terms of fieldeffect mobility, gate material quality, and stability under long stress using a Fe-55 (50 μCi)gamma ray source (6 to 10 keV photon energies). Device fabrication was performed in an in-house facility, Giga-to-Nano microfabrication facility, at the University of Waterloo, and involved plasma enhanced chemical vapor deposition (PECVD) and wet and dry etch techniques with a simple two mask process. The TFT test results promise higher effective field effect mobility of 16.49 cm²/V·s due to the presence of silicon substrate contacting the a-Si:H channel layer along with a compromise in leakage current, yielding a 10⁴ ON/OFF ratio. Meanwhile, the threshold voltage shift is manageable by applying a negative voltage of a duration less than 1/10 of the duty cycle. From the detector leakage test, the leakage current through the TFT gate was acceptable range while the photo-generated current needs to be suppressed with positive voltage bias at the gate electrode. Thus, minimizing the negative gate bias in readout operation is crucial. Finally, TFT readout current under the same Fe-55 X-ray source shows that optimal operation range can be determined when bulk bias is higher than TFT operation bias.

Citation Download Citation

Kyung-Wook Shin and Karim S. Karim "Fabrication and characterization of a novel x-ray silicon detector", Proc. SPIE 8668, Medical Imaging 2013: Physics of Medical Imaging, 86683S (19 March 2013); https://doi.org/10.1117/12.2007900

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