Thin-film transistor device manufacturing method, thin-film transistor device, and display device

1. A thin-film transistor device manufacturing method, comprising:

providing a substrate;

forming a plurality of gate electrodes above the substrate;

forming a silicon nitride layer on the plurality of gate electrodes;

forming a silicon oxide layer on the silicon nitride layer;

forming an amorphous silicon layer on the silicon oxide layer;

crystallizing the amorphous silicon layer using laser light emitted from a predetermined laser of 405 nm to 488 nm in wavelength while moving the predetermined laser in a given direction relative to the substrate, to produce a crystalline silicon layer; and

forming a source electrode and a drain electrode on the crystalline silicon layer in a region that corresponds to each of the plurality of gate electrodes,

wherein a film thickness of the silicon oxide layer, a film thickness of the silicon nitride layer, and a film thickness of the amorphous silicon layer satisfy X and Y that are in ranges defined by Expressions 1 to 6:

Y≧ 0.264+14.444 ×ΔA′   Expression 1

X≦ 0.729−67.777×Δ A′   Expression 2

Y≦− 0.388 X+ 0.584−21.124 ×ΔA′   Expression 3

Y≦ 0.427−28.519 ×ΔA′   Expression 4

X≧ 0.344+32.963 ×ΔA′   Expression 5

Y≧− 0.388 X+ 0.457+21.412 ×ΔA′,   Expression 6

where X is a value obtained by dividing an optical film thickness of the amorphous silicon layer by the wavelength of the laser light, the optical film thickness of the amorphous silicon layer being a result of multiplying the film thickness of the amorphous silicon layer by a refractive index of the amorphous silicon layer,

Y is a value obtained by dividing a silicon oxide layer converted optical film thickness by the wavelength of the laser light, the silicon oxide layer converted optical film thickness being a value obtained by dividing a sum of an optical film thickness of the silicon oxide layer and an optical film thickness of the silicon nitride layer by a refractive index of the silicon oxide layer, the optical film thickness of the silicon oxide layer being a result of multiplying the film thickness of the silicon oxide layer by the refractive index of the silicon oxide layer, and the optical film thickness of the silicon nitride layer being a result of multiplying the film thickness of the silicon nitride layer by a refractive index of the silicon nitride layer, and

ΔA′ is a value calculated according to an expression (A G /d G )×(ρ Si ×c Si )/(ρ G ×c G ), where ρ Si and c Si are respectively a density and a specific heat of the amorphous silicon layer, d G , ρ G , and c G are respectively a film thickness, a density, and a specific heat of the gate electrode, and A G is a maximum absorptance of the gate electrode when the amorphous silicon layer located above the gate electrode and the amorphous silicon layer not located above the gate electrode have an equal light absorptance for the laser light.

2. The thin-film transistor device manufacturing method according to claim 1 ,

wherein, in said crystallizing of the amorphous silicon layer, the predetermined laser emits the laser light in an oscillation mode that is a continuous wave mode or a quasi-continuous wave mode.

3. The thin-film transistor device manufacturing method according to claim 1 ,

wherein the predetermined laser includes a solid-state laser device.

4. The thin-film transistor device manufacturing method according to claim 1 ,

wherein the predetermined laser includes a laser device that uses a semiconductor laser element.

5. The thin-film transistor device manufacturing method according to claim 1 ,

wherein, in said crystallizing of the amorphous silicon layer, a variation in irradiation energy density of the laser light on the amorphous silicon layer is less than approximately 5%.

6. The thin-film transistor device manufacturing method according to claim 1 ,

wherein, in said forming of the silicon nitride layer and said forming of the silicon oxide layer, the silicon nitride layer and the silicon oxide layer are formed with the respective film thicknesses so that a capacitance of a series capacitor composed of the silicon nitride layer and the silicon oxide layer is equal to a capacitance of a silicon oxide single layer of 100 nm to 140 nm in film thickness.

7. The thin-film transistor device manufacturing method according to claim 1 ,

wherein the film thickness of the silicon oxide layer, the film thickness of the silicon nitride layer, and the film thickness of the amorphous silicon layer satisfy X and Y that are in ranges defined by Expressions 7 and 8:

0.442 ≦X≦ 0.559  Expression 7

0.310 ≦Y≦ 0.341.  Expression 8

8. The thin-film transistor device manufacturing method according to claim 6 ,

wherein the wavelength of the predetermined laser is 445 nm to 455 nm.

9. The thin-film transistor device manufacturing method according to claim 6 ,

wherein the film thickness of the amorphous silicon layer is in a range of 40 nm to 45 nm.

10. The thin-film transistor device manufacturing method according to claim 1 ,

wherein said forming of the plurality of gate electrodes includes:

forming an undercoat layer made of silicon oxide, on the substrate; and

forming the plurality of gate electrodes on the undercoat layer.

11. A thin-film transistor device comprising:

a substrate;

a plurality of gate electrodes formed above said substrate;

a silicon nitride layer formed on said plurality of gate electrodes;

a silicon oxide layer formed on said silicon nitride layer;

a crystalline silicon layer formed on said silicon oxide layer; and

a source electrode and a drain electrode formed on said crystalline silicon layer in a region that corresponds to each of said plurality of gate electrodes,

wherein said crystalline silicon layer is produced by forming an amorphous silicon layer on said silicon oxide layer and then crystallizing the amorphous silicon layer using laser light emitted from a predetermined laser of 405 nm to 488 nm in wavelength while moving the predetermined laser in a given direction relative to said substrate, and

a film thickness of said silicon oxide layer, a film thickness of said silicon nitride layer, and a film thickness of the amorphous silicon layer satisfy X and Y that are in ranges defined by Expressions 1 to 6:

Y≧ 0.264+14.444 ×ΔA′   Expression 1

X≦ 0.729−67.777×Δ A′   Expression 2

Y≦− 0.388 X+ 0.584−21.124 ×ΔA′   Expression 3

Y≦ 0.427−28.519 ×ΔA′   Expression 4

X≧ 0.344+32.963 ×ΔA′   Expression 5

Y≧− 0.388 X+ 0.457+21.412 ×ΔA′,   Expression 6

where X is a value obtained by dividing an optical film thickness of the amorphous silicon layer by the wavelength of the laser light, the optical film thickness of the amorphous silicon layer being a result of multiplying the film thickness of the amorphous silicon layer by a refractive index of the amorphous silicon layer,

Y is a value obtained by dividing a silicon oxide layer converted optical film thickness by the wavelength of the laser light, the silicon oxide layer converted optical film thickness being a value obtained by dividing a sum of an optical film thickness of said silicon oxide layer and an optical film thickness of said silicon nitride layer by a refractive index of said silicon oxide layer, the optical film thickness of said silicon oxide layer being a result of multiplying the film thickness of said silicon oxide layer by the refractive index of said silicon oxide layer, and the optical film thickness of said silicon nitride layer being a result of multiplying the film thickness of said silicon nitride layer by a refractive index of said silicon nitride layer, and

ΔA′ is a value calculated according to an expression (A G /d G )×(ρ Si ×c Si )/(ρ G ×c G ), where ρ Si and c Si are respectively a density and a specific heat of the amorphous silicon layer, d G , ρ G , and c G are respectively a film thickness, a density, and a specific heat of said gate electrode, and A G is a maximum absorptance of said gate electrode when the amorphous silicon layer located above said gate electrode and the amorphous silicon layer not located above said gate electrode have an equal light absorptance for the laser light.

12. A display device comprising a liquid crystal panel or an EL panel, said display device comprising

the thin-film transistor device according to claim 11 ,

wherein said thin-film transistor device drives said liquid crystal panel or said EL panel.

13. The display device according to claim 12 ,

wherein said EL panel is an organic EL panel.

14. A thin-film transistor device manufacturing method, comprising:

providing a substrate;

forming a plurality of gate electrodes above the substrate;

forming a silicon nitride layer on the plurality of gate electrodes;

forming a silicon oxide layer on the silicon nitride layer;

forming an amorphous silicon layer on the silicon oxide layer;

crystallizing the amorphous silicon layer using laser light emitted from a predetermined laser of 405 nm to 488 nm in wavelength while moving the predetermined laser in a given direction relative to the substrate, to produce a crystalline silicon layer; and

forming a source electrode and a drain electrode on the crystalline silicon layer in a region that corresponds to each of the plurality of gate electrodes,

wherein said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the amorphous silicon layer are performed so that, in said crystallizing of the amorphous silicon layer, when the amorphous silicon layer is irradiated with the laser light, a maximum reached temperature of the amorphous silicon layer in a region not located above the gate electrode is higher than a maximum reached temperature of the amorphous silicon layer in a region located above the gate electrode and also the amorphous silicon layer in the region located above the gate electrode has a substantially uniform maximum reached temperature, the region not located above the gate electrode being upstream in the direction of the relative movement of the predetermined laser.

15. The thin-film transistor device manufacturing method according to claim 14 ,

wherein in said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the amorphous silicon layer, the gate electrode, the silicon nitride layer, the silicon oxide layer, and the amorphous silicon layer are formed with respective film thicknesses so that, in said crystallizing of the amorphous silicon layer, when the amorphous silicon layer is irradiated with the laser light, the maximum reached temperature of the amorphous silicon layer in the region not located above the gate electrode is higher than the maximum reached temperature of the amorphous silicon layer in the region located above the gate electrode and also the amorphous silicon layer in the region located above the gate electrode has the substantially uniform maximum reached temperature, the region not located above the gate electrode being upstream in the direction of the relative movement of the predetermined laser.

16. A thin-film transistor device manufacturing method, comprising:

providing a substrate;

forming a gate electrode above the substrate;

forming a silicon nitride layer on the gate electrode;

forming a silicon oxide layer on the silicon nitride layer;

forming a semiconductor material layer that includes a semiconductor material, on the silicon oxide layer;

crystallizing the semiconductor material by irradiating the semiconductor material layer with predetermined laser light of 405 nm to 488 nm in wavelength, to produce a semiconductor layer; and

forming a source electrode and a drain electrode on the semiconductor layer in a second region that does not correspond to the gate electrode, the second region being different from a first region that corresponds to the gate electrode,

wherein said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the semiconductor material layer are performed so that a heating value of the semiconductor material layer in the second region per unit volume is higher than a heating value of the semiconductor material layer in the first region per unit volume, and

in said crystallizing of the semiconductor material, heat generated in the semiconductor material layer in the first region by the irradiation with the predetermined laser light and transmitted to and absorbed by the gate electrode is accumulated in the gate electrode without being diffused into the semiconductor material layer in the second region, and a part having a uniform temperature distribution is formed in the semiconductor material layer in the first region generating the heat, to crystallize the semiconductor material.

17. The thin-film transistor device manufacturing method according to claim 16 ,

wherein in said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the semiconductor material layer, the gate electrode, the silicon nitride layer, the silicon oxide layer, and the semiconductor material layer are formed with respective film thicknesses so that the heating value of the semiconductor material layer in the second region per unit volume is higher than the heating value of the semiconductor material layer in the first region per unit volume.

18. The thin-film transistor device manufacturing method according to claim 16 ,

wherein the second region of the semiconductor material layer is a region upstream and downstream of the first region of the semiconductor material layer, in a direction in which the predetermined laser light is moved relative to the substrate in said crystallizing of the semiconductor material.

19. The thin-film transistor device manufacturing method according to claim 16 ,

wherein said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the semiconductor material layer are performed so that, in said crystallizing of the semiconductor material, a difference between the heating value of the semiconductor material layer in the second region per unit volume and the heating value of the semiconductor material layer in the first region per unit volume is equal to or more than a heating value of the gate electrode per unit volume.

20. The thin-film transistor device manufacturing method according to claim 16 ,

wherein said forming of the plurality of gate electrodes, said forming of the silicon nitride layer, said forming of the silicon oxide layer, and said forming of the semiconductor material layer are performed so that, in said crystallizing of the semiconductor material, the part having the uniform temperature distribution is formed in the semiconductor material layer in the first region at a ratio of 0.8 to 1.0 in size to the first region.