Method of making tapered poly profile for TFT device manufacturing

The method of forming a thin film transistor integrated circuit with a tapered polysilicon profile comprising:

• depositing a layer of polysilicon over the surface of a semiconductor substrate;
• implanting ions into said polysilicon layer whereby the upper half of said polysilicon layer is damaged by the presence of said ions within said layer;
• anisotropically etching said polysilicon layer;
• isotropically etching said damaged portion of said polysilicon layer whereby said polysilicon layer is uniformly tapered;
• depositing a layer of gate oxide over the surface of said uniformly tapered polysilicon layer;
• forming a thin film transistor body overlying said gate oxide layer wherein said forming said thin film transistor body comprises the steps of:
• depositing a layer of amorphous silicon over the surface of said gate oxide layer;
• crystallizing said amorphous silicon layer to yield uniform grain sizes;
• covering said crystallized amorphous silicon layer overlying said uniformly tapered polysilicon layer with a photoresist mask wherein said covered portion of said crystallized amorphous silicon layer forms the channel of said thin film transistor body;
• and
• implanting ions into said crystallized amorphous silicon layer not covered by said photoresist mask to form source/drain regions within said amorphous silicon layer to complete formation of said thin film transistor body;
• depositing an insulating layer over said thin film transistor body and said semiconductor substrate;
• opening contacts through said insulating layer to source/drain regions within said thin film transistor body;
• and
• filling said contact openings with a conductive material to complete said contacts in the formation of said thin film transistor integrated circuit.