Method of fabricating a bottom-gate-type thin film transistor using a heat relaxation layer during laser crystallization
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorShunpei Yamazaki
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Abstract
Provided is a constitution for forming a polysilicon film having uniform crystallinity. To construct a structure of a bottom-gate-type TFT, a heat relaxation layer is formed to cover a gate electrode. The heat conductivity of the heat relaxation layer is lower than that of the gate electrode, and it acts to inhibit heat propagation to the gate electrode. In the step of laser crystallization of an amorphous silicon film into a polysilicon film, the heat relaxation layer prevents local temperature gradation in the film owing to the heat-absorbing effect of the underlying gate electrode. The polysilicon film formed has extremely excellent uniformity and crystallinity.
Claims26
A method for producing a semiconductor device, which comprises:
- forming a gate electrode over a substrate having an insulating surface,
- forming a heat relaxation layer to cover said gate electrode,
- forming a gate-insulating layer over said heat relaxation layer,
- forming an amorphous silicon film over said gate-insulating layer, and
- exposing said amorphous silicon film to light, to thereby crystallize said film into a polysilicon film;
- wherein heat conductivity of said heat relaxation layer is lower than that of said gate electrode, and
- wherein said heat relaxation layer comprises a material selected from the group consisting of titanium, chromium, tantalum silicide, molybdenum silicide and tungsten silicide.
A method for producing a semiconductor device, which comprises:
- forming a gate electrode over a substrate having an insulating surface,
- forming a heat relaxation layer to cover said gate electrode,
- forming a gate-insulating layer over said heat relaxation layer,
- forming a semiconductor film comprising amorphous silicon over said gate-insulating layer,
- providing said semiconductor film with a crystallization-promoting element,
- heating said semiconductor film to thereby crystallize said semiconductor film into a semiconductor film comprising polysilicon, and
- irradiating said semiconductor film with a light, to thereby improve the crystallinity of said semiconductor film comprising polysilicon,
- wherein heat conductivity and the electric conductivity of said heat relaxation layer are lower than those of said gate electrode, and
- wherein said heat relaxation layer comprises a material selected from the group consisting of titanium, chromium, tantalum silicide, molybdenum silicide and tungsten silicide.
Dependencies are inferred from the claim text.