K.-S. Sun’s scientific contributions

The hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) with copper as source and drain electrode has been fabricated to obtain its transfer characteristics and stressed with positive and negative bias to investigate the instability variation comparing to conventional MoW-Al based TFT device. The results show that there is no copper diffusion into active layer of a-Si:H TFT, even during the thermal process. In addition, a 15-inch XGA a-Si:H TFT LCD display utilizing Cu as gate electrodes has been developed.

AMOLED driven by a-Si:H TFTs array matrix is getting attractive. Both higher field-effect mobility and stable device characteristics are crucial points for this technology application. PECVD a-SiNx:H is a common used material as the gate insulator layer in a-Si:H TFT-LCD fields, and its composition makes a great impact on a-Si:H TFTs performance. Our results suggest that the field-effect mobility and stability of a-Si:H TFTs could be further improved by adopting N-rich a-SiNx:H, which will be more suitable for AMOLED application. In addition, the obvious dependence between threshold voltage shift after bias stress test and the refractive index of a-SiN x:H was found in our study. The results confirm the N-rich a-SiN x:H (lower R.I) incorporated into a-Si:H TFTs demonstrate less threshold voltage shift after bias stress test.

Quantitative adhesion testing of copper films on glass substrate is investigated by microindentation measurement. The object of adhesion testing is to evaluate the adhesion of soft films on hard substrates by Vicker hardness testing. Experimental result shows interposing a transparent dielectric layer (SiNx) between copper films and glass substrates promotes adhesion abruptly. Furthermore, the effect of sputtering parameters and precleaning plasma treatment on adhesion is discussed by Taguchi method analysis.