The Performance of the Gate Electrode Using Co Thin Films Selectively Deposited on SAMs Patterns for a-Si TFT

Abstract

AbstractSelective deposition of Co thin films has been developed to produce Co pattern for TFT gate electrode on glass. We have been carried out by the selective growth of Co films with combination of micro-contact printing and metal organic chemical vapor deposition (MOCVD) at low temperature below 100°C. In the first step octadecyltrichlorosilane(OTS) layer with polydimethylsiloxane(PDMS) stamps was pre-patterned on glass. The patterned OTS area created a hydrophobic surface on glass which can prohibit nucleation and growth of Co films. In the second step a MOCVD Co selective deposition examined the difference of incubation time between OTS coated glass and pure glass.We optimized Co selective deposition through working pressure, deposition temperature, and gas flow rate ratio. Root mean square (rms) of Co films deposited on glass is 2nm enough to use gate electrode.OTS pattern was decomposed by UV treatment in the range of 280 and 350nm and then trilayer(n+Si/a-Si/SiNx) was continuously created on the sample which was selectively organized Co gate electrode on glass. We fabricated thin film transistor (TFT) of inverse staggered type using selectively deposited Co gate pattern. Reflectance was used to evaluate incubation time for Co deposition time and AFM was employed to confirm selectivity of Co thin film. The subthreshold slope and on/off current ratio was 0.88 V/decade and 6x106, respectively. The electron field-effect mobility at saturation was 0.35 cm2/Vs for Vd = 9V.