Method for making a thin film transistor using a concentric inlet feeding system

Claim 1

A process for forming an improved amorphous silicon thin-film transistor comprising an insulating substrate, a first layer formed from a film of non-doped amorphous silicon semiconductive material deposited on the surface of the substrate, a second layer formed from a film of n-type impurity doped amorphous silicon material, a third layer formed from a film of amorphous silicon insulating material, a gate electrode formed from a metallic thin film, a source electrode formed from a metallic thin film and a drain electrode formed from a metallic thin film, the gate electrode being separated from the first layer by the third layer, the second layer being situated between the first layer and the source electrode and between the first layer and the drain electrode, said process comprising the steps of: (a) maintaining the substrate at an elevated temperature in an evacuated film-forming space; (b) introducing a gaseous starting material for formation of a deposited film via a first gas transportation conduit into the evacuated film-forming space wherein the gaseous starting material is capable of being a constituent for a film, but essentially incapable of contributing to film formation when the gaseous starting material is in an original state; (c) introducing a gaseous halogenic oxidizing agent via a second gas transportation conduit, wherein the first and second gas transportation conduits are concentric and terminate adjacent to the substrate forming a reaction space, the gaseous halogenic oxidizing agent having an oxidizing property on the gaseous starting material in the reaction space to effect chemical contact therebetween and to thereby cause a chemical reaction in the absence of a plasma in the reaction space, to generate a plurality of precursors containing excited precursors, wherein at least one of the precursors form the film constituting at least one of the first, second and third layers; and (d) maintaining the distance between the outlet of the first and second concentric gas transportation conduits and the surface of the substrate from 5 millimeters to 15 centimeters.