Method of removing a catalyst substance from the channel region of a TFT after crystallization

A method of manufacturing an insulated gate thin film transistor comprising the steps of:

• disposing a catalyst substance adjacent to a silicon semiconductor film on a glass substrate, said catalyst capable of promoting a crystallization of said silicon semiconductor film;
• thermally annealing said semiconductor film provided with said catalyst substance;
• after said annealing, directly etching a surface of said semiconductor film including a channel forming region of the film, by using an etchant which contains a hydrofluoric acid;
• forming source and drain regions in said semiconductor film with said channel forming region therebetween;
• forming a gate insulating layer on said upper surface after said etching;
• and
• forming a gate electrode adjacent to said gate insulating layer,
• wherein after said etching, at least said channel forming region of said semiconductor film contains said catalyst substance at a concentration of not higher than 1.times.10.sup.20 atoms/cm.sup.3.

A method of manufacturing an insulated gate thin film transistor comprising the steps of:

• disposing a catalyst substance adjacent to a silicon semiconductor film on a glass substrate, said catalyst capable of promoting a crystallization of said silicon semiconductor film;
• thermally annealing said semiconductor film provided with said catalyst substance;
• and
• after said annealing, directly etching a surface of said semiconductor film over at least a channel forming region of the film by using a plasma which contains chlorine or fluorine;
• forming source and drain regions in said semiconductor film with said channel forming region therebetween;
• forming a gate insulating layer on said upper surface after said etching;
• and
• forming a gate electrode adjacent to said gate insulating layer,
• wherein after said etching, at least said channel forming region of said semiconductor film contains said catalyst substance at a concentration of not higher than 1.times.10.sup.20 atoms/cm.sup.3.

A method of manufacturing an insulated gate thin film transistor comprising the steps of:

• disposing a catalyst substance adjacent to a silicon semiconductor film on a glass substrate, said catalyst capable of promoting a crystallization of said silicon semiconductor film;
• crystallizing said semiconductor film provided with said catalyst substance;
• and
• directly removing an excess amount of said catalyst substance from said semiconductor film over at least a channel forming region of the film, leaving said catalyst substance diffused in said channel forming region at a concentration of not higher than 1.times.10.sup.20 atoms/cm.sup.3 ;
• forming source and drain regions in said semiconductor film with said channel forming region therebetween;
• forming a gate insulating layer on said semiconductor film after said removing step;
• and
• forming a gate electrode adjacent to said gate insulating layer.

A method of manufacturing an insulated gate thin film transistor comprising the steps of:

• disposing a catalyst substance adjacent to a silicon semiconductor film on a glass substrate, said catalyst capable of promoting a crystallization of said silicon semiconductor film;
• annealing said semiconductor film provided with said catalyst substance to crystallize said film;
• after said annealing, directly etching said catalyst substance over at least a channel forming region of the film in order to expose a clean surface of said semiconductor film;
• forming source and drain regions in said semiconductor film with said channel forming region therebetween;
• forming a gate insulating layer on said film after said etching;
• and
• forming a gate electrode adjacent to said gate insulating layer,
• wherein after said etching, at least said channel forming region of said semiconductor film contains said catalyst substance at a concentration of not higher than 1.times.10.sup.20 atoms/cm.sup.3.