Thin film transistor and liquid crystal display unit
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsKazufumi Ogawa, Kazuyasu Adachi
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Abstract
A bottom-gate type thin-film transistor free from alignment shift of the gate electrode and from damage caused by injection of impurities. The crystal grains of a polycrystalline silicon thin-film are anisotropically grown to form a prescribed angle relative to the gate length direction. The angle between the gate length direction and the longitudinal direction of the grains is adjusted according to use of the liquid crystal display unit. The bottom-gate transistor includes an undercoat insulating layer containing impurities on the substrate. Impurities are diffused from the undercoat layer to the semiconductor layer by laser-annealing the amorphous silicon.
Claims32
A thin-film transistor (TFT) comprising, as an active area, a polycrystalline semiconductor thin film formed by crystallizing an amorphous semiconductor material deposited on a substrate with laser annealing technique which conducts scanning in a direction at right angle to the longitudinal direction with a beam having a strip or rectangular shape, and having an energy density distribution in a shorter side direction, and uniform in the longitudinal direction;
- wherein:
- the crystal grains of said semiconductor thin film have been anisotropically grown into a long ellipsoid having a longer diameter of from 3 to 5 microns and a shorter diameter of from 0.5 to 2 microns, of which the longitudinal growth direction forms a certain angle relative to the gate length direction connecting a source electrode and a drain electrode of each TFT in the substrate plane.
A thin-film transistor (TFT) which is a thin-film transistor of at least any one of the pixel section and the peripheral driving circuit section of a liquid crystal display unit having, as an active area, a polycrystalline semiconductor thin film formed by crystallizing an amorphous semiconductor material deposited on a substrate by a laser annealing technique which conducts scanning in a direction at right angle to the longitudinal direction with a beam having a strip or rectangular shape, and having an energy density distribution in a shorter side direction, and uniform in the longitudinal direction, wherein:
- the crystal grains of said semiconductor thin film have been anisotropically grown into a long ellipsoid having a longer diameter of from 3 to 5 microns and a shorter diameter of from 0.5 to 2 microns, of which the longitudinal growth direction forms a certain angle relative to the gate length direction connecting a source electrode and a drain electrode of each TFT in the substrate plane.
Dependencies are inferred from the claim text.