The Development of Polysilicon Dielectrics and Thin Film Transistors and Sensors by Using High-K Materials(I)

The high-k Nd2O3, Er2O3 as gate dielectrics applied in thin film transistors have been fabricated successively in our study. Furthermore, we would like to develop high performance high-k thin film transistors and sensors. At first stage, high quality high-k dielectrics as Sm2O3 與 Dy2O3 are developed combined with rapid thermal annealing. Furthermore, the characteristics of high-k thin film transistors can be improved by using Ti doped high-k or varying different argon to oxygen gas ratios (Ar/O). Besides, the fluorine implantations are also used to apply in high-k thin film transistors for improvements. On the other hand, using the metal-induced lateral re-crystallization (MILC) combined with High-k dielectrics can obtain high performance thin film transistors. Finally, it’s expected to integrate those process technologies to develop extended gate thin film transistor and sensor. So far, only a few papers have been reported of ion sensor using thin film as the semiconductor layer. Therefore, we try to utilize the high-k dielectric layer as sensing membrane layer to realize the extended gate ion sensitive field effect transistor for display and sensor applications. This is a two-year plan. The focus of the first year is to develop high quality high-k gate dielectrics and thin-film transistors. At first, high-k dielectrics (Sm2O3, Dy2O3) doping with Ti (titanium) and combine with post rapid thermal annealing to passivate the trap states in the high-k dielectrics and the interfaces between the gate dielectrics and the polysilicon to improve the electrical characteristics of the high-k dielectrics. Since high-k materials with higher dielectrics constant and lower leakage current and better thermal stability can be used as gate dielectrics of the poly-Si thin film transistors after proper RTA densification. Furthermore, the characteristics of high-k gate dielectrics can be improved by doped Ti or optimum argon to oxygen gas flow ratio, and proper fluorine implantation, which can improve the dangling bonds and strain bonds in the interface between the high-k dielectrics and polysilicon for performance improvements. The second year of the plan is to use Pd and Au to fabricate the MILC thin-film transistors, which can induce larger polycrystalline grains along channel direction due to faster growth rates the incorporated fluorine ions can pile up at interface to passivate dangling bonds and effectively reduce leakage current to improve the characteristics and reliability of the poly-Si TFTs. Finally, it’s expected to integrate those process technologies to develop extended gate thin film transistor and sensor. Therefore, we try to utilize the developed high-k dielectric layer as sensing membrane layer to realize the extended gate ion sensitive field effect transistor for display and sensor applications.

Project ID:PB9907-12672
External Project ID:NSC99-2221-E182-060