Low-temperature monocrystalline TFT process targets OLEDs

November 28, 2017 // By Julien Happich
Solar-Tectic LLC has patented a novel thin-film transistor (TFT) technology which the company claims has potential to replace low temperature polysilicon (LTPS), a standard process currently used in the display industry for the manufacture of OLEDs' TFT backplanes.

LTPS is a process central to the manufacture of thin-film transistors (TFTs) used in AMOLED displays (Active Matrix Organic Light Emitting Diodes), LCD (liquid crystal) displays, and micro-LED technologies. The new process, dubbed "LT1CS" or "Low temperature single crystal silicon", exhibits single crystal-like silicon qualities, arising from the highly oriented c-axis aligned or "textured" silicon crystals. It is well known that oriented or aligned crystalline thin-films perform much better than polycrystalline thin-films on many levels. In addition, Solar-Tectic claims the new "LT1CS" process can be used to produce films with large grains or crystals which also enhance performance in the backplane of displays.

Electron mobility in textured, aligned thin silicon films would be higher than in IGZO (indium gallium zinc oxide) which is another contender to replace LTPS, and uniformity in the LT1CS technology would also be better. Currently IGZO performance is lower than LTPS with regard to both electron mobility and uniformity. IGZO also consists of indium and gallium which are rare-earth elements, which could drive costs up.

The company's LT1CS technology leverages III-V materials like GaN and could potentially be used in the emerging micro-LED (µLED) field, combining III-V materials with silicon thin-film transistors.

Another benefit of the patented LT1CS TFT process is that it is a low temperature process which can be applied to soda-lime glass. This would be a cheaper substrate than the quartz substrate required for today's high-temperature TFT film growth. The new process is detailed in a paper titled "Textured (111) crystalline silicon thin film growth on flexible glass by e-beam evaporation".

Solar-Tectic LLC - www.solartecticllc.com