IMPORTANCE OF FIRST LAYER THICKNESS ON TFT CHARACTERISTICS USING A-SI-H DEPOSITED BY 2-STEP PROCESS

In order to increase the throughput during thin film transistor-liquid crystal display manufacture, we investigated a 2-step deposition proc ess for hydrogenated amorphous silicon. The first hydrogenated amorpho us silicon layer of an inverted staggered type thin film transistor wa s deposited at a lower deposition rate to improve the interface with t he gate insulator layer and the second hydrogenated amorphous silicon layer was deposited at a higher rate to improve the throughput, It was found that the mobility values of thin film transistors increased wit h increasing first layer thickness and reached a saturation value afte r a certain first layer thickness. When the first hydrogenated amorpho us silicon layer quality was improved by decreasing its deposition rat e, a thicker first layer hydrogenated amorphous silicon was needed to reach a mobility saturation.