Thin film transistor formed by an etching process with high anisotropy

A process for forming a thin film transistor formed on a substrate, said process comprising the steps of:

• (a) providing a transistor element on a substrate that is capable of supporting a thin film transistor, said transistor element including at least a gate electrode, a gate insulating layer, a semiconductor layer and source and drain electrodes;
• (b) depositing a passivation layer to cover the transistor element;
• (c) forming an interlayer insulator on the passivation layer and patterning said interlayer insulator to form first openings for contact holes;
• (d) patterning the passivation layer by an anisotropic etching process so as to form second openings, said anisotropic etching process having an etch selectivity for the passivation layer to drain electrode that is greater than or equal to 5:1 using an etchant gas comprising fluorine without oxygen (O);
• (e) removing etching residues formed by step (d) by a dry etching process including an oxygen (O2) gas;
• and
• (f) forming a pixel electrode and a contact electrode by depositing and patterning an electrical conductive layer, wherein the electrical conductive layer is deposited on an inner wall of the contact hole and the inner wall is formed by the first and second openings tapered smoothly and continuously.

A display device with an improved aperture ratio of a pixel, said display device including arrayed thin film transistors on a substrate, said thin film transistor comprising:

• a transistor element including a gate electrode, a gate insulating layer, a semiconductor layer, and source and drain electrodes;
• a passivation layer having first openings for contact holes formed on said transistor element;
• and
• an interlayer insulator having second openings for the contact holes extending over said passivation layer, said first and second openings are self-aligned with each other over the substrate, and wherein an electrical conductive layer is deposited on an inner wall of the contact hole, said inner wall is formed by the first and second openings tapered smoothly and continuously by an anisotropic etching process.