IGZO AMeTFT

Amorphous Metal Thin Film Transistor technology (AMeTFT) implements innovations in materials and device structure currently in mass production in VLSI to multiply the mobility of any thin film transistor. FinFET gate structure and materials revitalized Moore’s Law for the 21st Century.

Amorphyx applied the foundational concepts of FinFET to revitalize TFT performance - and transition TFT backplanes to flexible substrates. AMeTFT leverages the ultra-smooth surface of amorphous gate metals in uniquely enabling a thin gate insulator for increasing the gate electric field strength. A high-k dielectric oxide is used as the gate insulator to ensure the ability to withstand electric field strengths 5-7 times larger than IGZO or silicon-based TFT gate structures can support. This higher gate electric field dramatically expands the conduction channel in the semiconductor, increasing transconductance and electron mobility.

One of the unique features of IGZO AMeTFT operation is the use of very high gate electric field strength to substantially increase IGZO surface potential (Øs). (See image at right.) This transitions the relationship between carrier density and surface potential from linear to exponential, resulting in the exponential increase in transcendence and field effect mobility with V(GS) unique to IGZO AMeTFT.

The work of Andrew Flewitt’s group at University of Cambridge on the relationships between amorphous metal oxide semiconductor materials science and TFT device physics leads the global academic community. One of the limits on the performance of amorphous metal oxide TFTs in the display industry to date is the relative lack of understanding of these relationships.

This high gate electric field strength puts the IGZO into bulk accumulation mode, maximizing I(DS, sat) and field effect mobility while creating a system incorporating gate insulator, IGZO and etch stop layer for controlling operating stress, field effect mobility, subthreshold swing, and threshold voltage.

Amorphyx has developed fabrication process flows for IGZO AMeTFT incorporating sputtered amorphous metal gate with both reactive sputter and ALD high-k oxide gate insulators. The AMeTFT process flow has been developed to utilize existing deposition equipment, etchants, and photolithography processing.

In addition, amorphous metals are inherently flexible and strong. They are as elastic as the polymer substrates used in flexible displays and electronics while being stronger than steel. Amorphous metals are sputtered at room temperature - ideal for deposition on polymers.