Breakthrough in TFT materials for LCD and OLED displays

January 12, 2018 // By Julien Happich
Solar-Tectic LLC ("ST") and Blue Wave Semiconductors announced they were granted a patent by the US patent office on a material and process breakthrough that dramatically improve the performance of thin-film transistors (TFTs) used in almost all displays on the market today, including LCDs, LEDs and OLEDs.

Specifically, the patent (U.S. No. 9,856,578) is for making crystalline films on glass at low temperature with a high degree of crystal orientation or "texture". The particular material demonstrated, which has been reported in the Materials Letters back in 2013 under the title "Extremely highly textured MgO [111] crystalline films on soda-lime glass by E-beam", is magnesium oxide. The insulating material is not only highly transparent, but also has very high thermal conductivity, high thermal stability, and a high melting point.

More importantly, it has an unusual (111) orientation which can enhance the preferred orientations of silicon and germanium.

Silicon is used in almost all TFTs made today in a process called LTPS (low temperature polysilicon) and the new MgO material could enhance the LTPS process (as well as common a-Si TFT process) because of its high (111) texture which, by inducing texture in the silicon without chemical degradation, can increase electron mobility.

This is due to the resulting aligned crystals along the c-axis. The electrical performance and homogeneity of semiconductor layers can also be enhanced by the highly crystalline and oriented MgO film. The thin-film can be grown in a wide range of thicknesses, and deposited on a variety of technical glasses, including soda-lime or alkali-free glass, at temperatures as low as around 450°C or lower. The MgO film, when deposited on soda-lime glass, serves as a diffusion barrier preventing impurities such as Na from contaminating the silicon layer along with enhancing the crystallography along the (111) plane.

Last month Solar-Tectic LLC announced an entirely new low temperature process for making TFTs, which can replace LTPS and IGZO-CAAC, and this MgO material is an essential part of that technology.

Solar-Tectic LLC and Blue Wave Semiconductors, Inc. also recently received a patent for a new ceramic glass technology for use with displays

Solar-Tectic LLC - www.solartecticllc.com

Blue Wave Semiconductors - www.bluewavesemi.com