This Small Business Innovation Research Phase I project will demonstrate printing of fully formed thin film transistors on plastic substrates for use as high performance backplanes in flexible displays. No company has developed a cost-effective process for forming high performance thin film electronic devices on plastic substrates. This missing capability has prevented the development of flexible displays as well as a large number of other flexible electronic innovations. In the proposed approach, high performance electronics are first formed on a "mother" semiconductor wafer using conventional wafer processing techniques, specific wet etching chemistries are used for undercutting the devices in such a way that they become lift-able in an ultra-thin and flexible format from the mother wafer, and are "transfer printed" onto a plastic sheet using a silicone rubber transfer "stamp". The proposed work will focus on developing the processes and materials necessary to meet the demanding registration and yield requirements of large area array printing necessary for display manufacturing. In addition the team will identify, analyze and resolve key issues yielding circuit defects. A fully printed 400 mm by 300 mm plastic substrate with thousands of circuit elements will be produced with yields exceeding 99%.
The key feature of this approach is the fact that all the demanding fabrication process steps necessary to fabricate high performance electronic systems are performed on the "mother" substrate and not on the final plastic substrate. As a result, the inherent mechanical or chemical instabilities of the final receiving plastic substrate do not limit the choice of semiconductor manufacturing processes for fabricating the devices. The ability to manufacture flexible display backplanes to the demanding standards of the display industry will open up a broad market of opportunity in flexible electronics far beyond displays, including configurable X-ray sensors, RFID tags, and wearable electronics and sensors. In displays, backplanes using the proposed technology would be utilized by all TFT-LCD manufacturers, OLED manufacturers, and other specialty display manufacturers.
