Image sensor or LCD including switching pin diodes

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THIS INVENTION Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views.
FIGS.
3(a) to 3(c) illustrate a method of making an improved PIN diode structure according to an embodiment of this invention.
It is noted that herein a "PIN" diode will be referred to as such regardless of whether the positive (p+) or negative (n+) layer is on the bottom of the intrinsic layer.
A PIN diode is known to include a p+ layer (e.
g.
boron doped), an intrinsic layer, and a n+ layer (e.
g.
phosphorus doped), wherein the intrinsic layer is sandwiched between the p+ and n+ layers.
Referring first to FIG.
3(c), the structure includes switching PIN diode 21 and PIN photodiode 23 on substrate 25.
When PIN photodiode 23 is provided, the PIN diode structure is useful in imagers, such as X-ray imagers where the photodiode allows a signal to be output that is indicative of the amount of light or X-rays received by the sensor in a given pixel.
In the case of X-ray imaging, X-ray signals are converted into light signals by so called conversion materials such as CsI.
However, even when photodiode 23 is not provided, arrays of switching PIN diodes 21 are useful in LCD addressing applications as well as other known imaging applications.
Each PIN diode structure 21 and 23 shown in FIG.
3(c) includes substantially transparent substrate 25 upon which are provided bottom PIN diode electrodes 27 and 29 (e.
g.
of Mo, Cr, Ta, Ti, or the like), passivating or insulating layer 31 (e.
g.
of silicon nitride, silicon oxide, an acrylic such as FujiClear, BCB, a polyimide, or the like) in which contact holes or vias 33 are formed where the PIN diodes are to be located, negative (n+) a-Si(amorphous silicon) layer 35, intrinsic (i) a-Si layer 37, positive (p+) a-Si layer 39, and overlying top electrode layer 41 (e.
g.
formed of ITO or some other transparent conductor).
After the FIG.
3(c) structure is formed, the entire structure may be covered with a passivation layer such as silicon nitride, silicon oxide, a polyimide, an acrylic, FujiClear, BCB, or the like in order to provided a good base onto which other imager materials or LCD materials may be deposited or otherwise provided