PHOTODIODE ARRAYS: Amorphous-silicon approach beats the temperature challenge
D. Jason Palmer, Laser Focus World, November 1, 2007
Excerpts from the article:
Electronic devices on flexible substrates are a hot area of research, but there are as many problems associated with their manufacture as there are potential applications for them. But a team of researchers at the Palo Alto Research Center in California has made it a slightly less hot area of research, showing amorphous-silicon-based photodiode arrays at process temperatures much lower than the typical 210°C. Better yet, they use inkjet-printing of the etch masks for the backplane, a promising result for large-scale arrays on the cheap.
...The digital-lithography part of the process is probably the most promising aspect of the work. “This type of digital lithography has attracted a lot of attention from academia and industry for reducing manufacturing cost for conventional electronics, displays, and sensor applications,” says Yongtaek Hong of the Advanced Flexible Device and Electronics Laboratory at Seoul National University.
TseNga Ng, the lead author of the studies, agrees. “The development of the a-Si:H sensor materials at low temperature enables fabrication of flexible sensor arrays within the temperature constraints of plastic substrates, minimizes film cracking, and will lead to low-cost roll-to-roll processing of large-area electronics,” says Ng.
Besides making it cheap, the digital-lithography approach makes minute control of the manufacturing possible...
However, device operational stability is key for the low-temperature versions of devices. While the prototype looks like a clear winner for maximum manufacturing flexibility, Hong warns that commercial applications will have to wait until the devices have been put to longer-term tests.
While the research came out of a collaboration with Varian Medical Systems (Palo Alto, CA), the likely first application the team will pursue is border control...
The group is interested in extending the approach using its expertise with organic semiconductors, to make even more cost cuts in large-area sensor-array applications...As Hong says, the team continues to be “the leading group in the field.”
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