C.-Y. Wu’s scientific contributions

The high stability of a-Si:H TFTs device is studied with different deposited conditions of SiNx films by PECVD. The process parameters of N2, NH3 gas flow rate, RF power, and pressures of hydrogenated amorphous silicon nitride are taken into account and analyzed by Taguchi experimental design method. The NH3 gas flow rate and RF power are two major factors on the average threshold voltage and the a-SiN x:H film's structure. The hydrogen contents in SiNx films were measured by FTIR using the related Si-H/N-H bonds ratio in a-SiN x:H films. After the 330,000 sec gate bias stress is applied, the threshold voltages (Vth) shift less than 10%. This result indicates that the highly stable a-Si:H TFTs device can be fabricated with optimum gate SiNx insulator.

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.