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High Resolution, High Fill Factor A-SI:H Sensor Arrays for Optical Imaging

Published online by Cambridge University Press:  15 February 2011

J.T. Rahn ,
F. Lemmi ,
P. Mei ,
J.P. Lu ,
J.B. Boyce ,
R.A. Street ,
R.B. Apte ,
S.E. Ready ,
K.F. van Schuylenbergh  and
P. Nylen
...Show all authors
J.T. Rahn
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
F. Lemmi
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
P. Mei
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
J.P. Lu
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
J.B. Boyce
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
R.A. Street
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
R.B. Apte
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
S.E. Ready
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
K.F. van Schuylenbergh
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
P. Nylen
Affiliation:
Dept. of Physics, University of Stockholm, Sweeden
J. Ho
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
R.T. Fulks
Affiliation:
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA 94304
R.L. Weisfield
Affiliation:
dpiX, 3406 Hillview Ave., Palo Alto, CA 94304
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Abstract

Amorphous silicon large area sensor arrays are in production for x-ray medical imaging. The most common pixel design works very well for many applications but is limited in spatial resolution because the available sensor area (the fill factor) vanishes in small pixels. One solution is a 3-dimensional structure in which the sensor is placed above the active matrix addressing. However, such high fill factor designs have previously introduce cross talk between pixels.

We present data for a design in which the a-Si:H p-i-n photodiode sensor layer has a continuous i-layer and top p+-layer, and a patterned n+-layer contact to the pixel. Arrays of 64 μm and 75μm pitch have been fabricated and are the highest resolution a-Si:H arrays reported to date. The resolution matches the pixel size, and sensitivity has been improved by the high fill factor. Comparison is made between arrays with standard TFTs and TFTs with self-aligned source and drain contacts. Data line capacitance is improved by use of the self-aligned contacts.

Measurements are included on the contact to bias capacitance. The high fill factor design greatly suppresses lateral leakage currents, while retaining ease of processing. Provided illumination levels remain below saturation, the resolution matches expectation for the pixel size.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 809
Copyright
Copyright © Materials Research Society 1999

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