CRYSTALLIZATION METHOD, THIN FILM TRANSISTOR MANUFACTURING METHOD, THIN FILM TRANSISTOR, DISPLAY, AND SEMICONDUCTOR DEVICE

Abstract

According to a crystallization method, in the crystallization by irradiating a non-single semiconductor thin film of 40 to 100 nm provided on an insulation substrate with a laser light, a light intensity distribution having an inverse peak pattern is formed on the surface of the substrate, a light intensity gradient of the light intensity distribution is controlled, a crystal grain array is formed in which each crystal grain is aligned having a longer shape in a crystal growth direction than in a width direction and having a preferential crystal orientation (100) in a grain length direction, and a TFT is formed in which a source region and a drain region are formed so that current flows across a plurality of crystal grains of the crystal grain array in the crystal growth direction.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a structural block diagram schematically showing a crystallization device used for the crystallization method of the invention;

FIG. 2A is a schematic plan view showing crystallized grain array formed by the crystallization device shown in FIG. 1;

FIG. 2B is a schematic cross-sectional view showing a thin film transistor including the crystallized grain array shown in FIG. 2A;

FIG. 3A is a schematic plan view of a phase shifter;

FIG. 3B is a schematic lateral side view of the phase shifter;

FIG. 3C is a vertical cross-sectional view of a substrate to be processed;

FIG. 3D is a light intensity distribution map of laser light phase-modulated by the phase shifter;

FIG. 4 is a property view showing a relation between a distance from a crystallization start point of a crystal grain and the average grain width when the film thickness of an amorphous silicon film is varied;

FIG. 5A is a property view showing a relation between the half period of the light intensity distribution and the grain length of crystallized grain array when the film thickness of an amorphous silicon film is 100 nm;

FIG. 5B is a property view showing a relation between the half period of the light intensity distribution and the average grain width at a growth end point when the film thickness of the amorphous silicon film is 100 nm;

FIG. 6A is a property view showing a relation between the half period of the light intensity distribution and the grain length of crystallized grain array when the film thickness of the amorphous silicon film is 50 nm;

FIG. 6B is a property view showing a relation between the half period of the light intensity distribution and the average grain width at a growth end point when the film thickness of the amorphous silicon film is 50 nm;

FIG. 7 is a schematic view showing in a table, a relation between a light intensity gradient and a relative light intensity at which a lateral direction growth starts when the film thickness of the amorphous silicon film is 100 nm;

FIG. 8 is a schematic view showing in a table, a relation between a light intensity gradient and a relative light intensity at which a lateral direction growth starts when the film thickness of the amorphous silicon film is 50 nm;

FIG. 9A is a schematic view for use in explaining a change of the light intensity distribution when a cap film is made of a light absorptive material (reference condition);

FIG. 9B is a schematic view for use in explaining a change of the light intensity distribution when light intensity gradient is softer than that of the reference condition (experiment condition 1);

FIG. 9C is a schematic view for use in explaining a change of the light intensity distribution when the cap film is made of a translucent material (experiment condition 2);

FIG. 10 is an inverse pole figure showing in a table, a relation between the half period of V shaped light intensity distribution and the crystal orientation in a grain length direction of crystallized grain array when the film thickness of the amorphous silicon film is 50 nm;

FIG. 11 is an inverse pole figure showing an example of the crystal orientation in the longitudinal direction of the crystallized grain array;

FIGS. 12A, 12B, 12C, and 12D are cross-sectional views of the substrates showing the respective processes in manufacturing a bottom gate TFT according to the method of manufacturing a thin film transistor of the invention;

FIGS. 13A, 13B, and 13C are cross-sectional views of the substrates showing the respective processes in manufacturing a top gate TFT according to the method of manufacturing a thin film transistor of the invention;

FIG. 14 is a schematic view showing in a table, a relation between a crystal surface in a crystallization region in which a channel region of the TFT is formed and the mobility of the TFT; and

FIG. 15 is a schematic perspective view showing a display.

Claims

1. A crystallization method comprising: (i) directly or indirectly forming a non-single crystal semiconductor thin film on a substrate;(ii) forming an insulating film on the non-single crystal semiconductor thin film;(iii) irradiating the substrate with a laser light having a light intensity distribution of a plurality of inverse peak patterns continuous on an irradiation region of the insulating film;(iv) forming a crystal grain array, in which each crystal grain crystallized in a longer shape in a crystal growth direction than in a width direction is aligned adjacently in the width direction, on the non-single crystal semiconductor thin film; and(v) changing a period T of the light intensity distribution and controlling a light intensity gradient G.

2. A crystallization method comprising: (a) directly or indirectly forming a non-single crystal semiconductor thin film on a substrate;(b) forming an insulating film on the non-single crystal semiconductor thin film;(c) irradiating the substrate with a laser light under such a condition that a light intensity distribution of the laser light has a plurality of inverse peak patterns continuous on an irradiation surface of the insulating film and, when a relative light intensity of the maximum value in the light intensity distribution of the laser light is defined as 1, a light intensity gradient G is selected in the range of 0.02 μm−1 to 0.25 μm−1; and(d) forming a crystal grain array, in which each crystal grain crystallized in a longer shape in a crystal growth direction than in a width direction is aligned adjacently in the width direction, on the non-single crystal semiconductor thin film.

3. The method according to claim 2, wherein when the relative light intensity of the maximum value in the light intensity distribution is 1, the relative light intensity of the minimum value is in the range of 0.4 to 0.8.

4. The method according to claim 2, wherein the period T of the light intensity distribution is in the range of 4 μm to 80 μm.

5. A method of manufacturing a thin film transistor, comprising: (a) directly or indirectly forming a non-single crystal semiconductor thin film on a substrate;(b) forming an insulating film on the non-single crystal semiconductor thin film;(c) irradiating the substrate with a laser light under such a condition that a light intensity distribution of the laser light has a plurality of inverse peak patterns continuous on an irradiation surface of the insulating film and, when a relative light intensity of the maximum value in the light intensity distribution of the laser light is defined as 1, a light intensity gradient G is selected in the range of 0.02 μm−1 to 0.25 μm−1;(d) forming a crystal grain array, in which each crystal grain crystallized in a longer shape in a crystal growth direction than in a width direction is aligned adjacently in the width direction, on the non-single crystal semiconductor thin film, and(e) forming a circuit so that current flows in the crystal growth direction of the crystal grains.

6. A thin film transistor manufactured according to the method as claimed in claim 5.

7. A display comprising: the crystal grains manufactured according to the method as claimed in claim 1, which are previously formed at a predetermined position to form a pixel switching transistor; anda thin film transistor for the pixel switching transistor which is formed so that current flows in the crystal growth direction of the crystal grains.

8. A crystallization method comprising: (a) directly or indirectly forming a non-single crystal semiconductor thin film on a substrate and selecting a film thickness of the non-single crystal semiconductor thin film in the range of 40 nm to 70 nm;(b) forming a light absorptive insulating film which absorbs part of a laser light for crystallization on the non-single crystal semiconductor thin film;(c) irradiating the substrate with a laser light to crystallize an irradiation region of the non-single crystal semiconductor thin film, under such a condition that a light intensity distribution of the laser light has a plurality of inverse peak patterns continuous on an irradiation surface of the insulating film and, when a relative light intensity of the maximum value in the light intensity distribution of the laser light is defined as 1, a light intensity gradient G is selected in the range of 0.02 μm−1 to 0.04 μm−1; and(d) preferentially determining at (100) a surface orientation in a crystal growth direction on the irradiation region of the non-single crystal semiconductor thin film.

9. A crystallization method comprising: (a) directly or indirectly forming a non-single crystal semiconductor thin film on a substrate and selecting a film thickness of the non-single crystal semiconductor thin film in the range of 40 nm to 100 nm;(b) forming a translucent insulating film which does not absorb a laser light for crystallization on the non-single crystal semiconductor thin film;(c) irradiating the substrate with a laser light to crystallize an irradiation region of the non-single crystal semiconductor thin film, under such a condition that a light intensity distribution of the laser light has a plurality of inverse peak patterns continuous on an irradiation surface of the insulating film and, when a relative light intensity of the maximum value in the light intensity distribution of the laser light is defined as 1, a light intensity gradient G is selected in the range of 0.02 μm−1 to 0.25 μm−1; and(d) preferentially determining at (100) a surface orientation in the irradiation region of the non-single crystal semiconductor thin film.

10. A thin film transistor comprising: a substrate;a non-single crystal semiconductor thin film directly or indirectly formed on the substrate;a crystal grain which is grown in a lateral direction from a crystal seed provided on the semiconductor thin film and crystallized in a longer shape in a crystal growth direction than in a width direction;a crystal grain array in which the crystal grains are aligned adjacently in the width direction; anda source region and a drain region formed so that current flows across a plurality of the crystal grains of the crystal grain array in a crystal growth direction,wherein a crystal surface in the current flowing direction is preferentially determined at (100) in a channel region provided between the source region and the drain region.

11. A semiconductor device comprising: a substrate;a non-single crystal semiconductor thin film directly or indirectly formed on the substrate; anda crystal grain array of crystallized grains grown from crystal seeds provided on the semiconductor thin film in a lateral direction,wherein in the crystal grain array, each grain in a longer shape in a crystal growth direction than in a width direction is adjacently aligned in the width direction and a surface orientation in the crystal growth direction is preferentially determined at (100).

12. The semiconductor device according to claim 11, wherein the crystal grain has a grain length in the range of 2 μm to 15 μm and an average grain width in the range of 0.2 μm to 0.8 μm.

13. A display comprising: a substrate;a non-single crystal semiconductor thin film directly or indirectly formed on the substrate;a crystal grain which is grown in a lateral direction from a crystal seed provided on a predetermined pixel switching circuit in the non-single crystal semiconductor thin film and crystallized in a longer shape in a crystal growth direction than in a width direction;a crystal grain array in which the crystal grains are aligned adjacently in the width direction and a crystal orientation in the growth direction is preferential determined at (100); anda thin film transistor including a source region and a drain region which are formed so that current flows across a plurality of the crystal grains of the crystal grain array in the crystal growth direction.