SBIR-STTR Award

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

This Small Business Innovation Research (SBIR) Phase II project focuses on fabrication of flexible display backplanes using transfer printed electronics. The display industry has been successful at fabricating amorphous silicon (a-Si) thin film transistor (TFT) backplanes on rigid glass. However, a-Si TFT manufacturing does not easily translate to flexible substrates due to handling issues and the high temperature process of a-Si deposition. In transfer printing, a novel elastomeric stamp is used to pick-up specially designed circuits from the parent wafer and transfers the circuits to the desired target substrate. The parent wafer is fabricated using a standard silicon IC foundry and the single crystal silicon transistors have much better performance than the a-Si counterparts. The SBIR Phase I project demonstrated chip transfer printing process yields of 99.9% and chip placement accuracies better than +/- 5 ìm. Phase II objectives include design, fabrication and characterization of flexible backplane prototypes and further optimization of transfer printing by increasing throughput and demonstrating rework methods. The anticipated result is a manufacturing approach to flexible electronics that is cost competitive, low temperature and well suited to handle flexible substrates. The competitive advantage of the proposed 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. If successful the inherent mechanical or chemical instabilities of the receiving plastic substrate do not limit the choice of semiconductor manufacturing processes for fabricating 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 biosensors. In displays, backplanes using the proposed technology will be utilized by all major display manufacturers and many specialty manufacturers.