Silicon thin film, group of silicon single crystal grains and formation process thereof, and semiconductor device, flash memory cell and fabrication process thereof

A process of forming a group of silicon single crystal grains comprising:

• a step (a) of irradiating a pulsed rectangular ultraviolet beam on an amorphous or polycrystalline silicon layer formed on a base body, to thereby form a silicon thin film composed of a group of silicon single crystal grains which are each approximately rectangular-shaped and which are arranged in a grid pattern on said base body, a selected orientation of said silicon single crystal grains to the surface of said body being approximately the <100> direction;
• and
• a step (b) of separating adjacent ones of said silicon single crystal grains to each other;
• wherein the moved amount of an ultraviolet beam irradiating position in a period from completion of an irradiation pulse of said rectangular ultraviolet beam to starting of the next irradiation pulse of said rectangular ultraviolet beam being in a range of 4 μm to 20 μm, and a ratio of said moved amount to a width of said rectangular ultraviolet beam measured in the movement direction thereof being in a range of 0.1 to 5%.

A process of fabricating a semiconductor device, comprising the steps of:

• irradiating a pulsed rectangular ultraviolet beam on an amorphous or polycrystalline silicon layer formed on a base body, to form a silicon thin film composed of a group of silicon single crystal grains on said base body;
• and
• forming a source/drain region and a channel region in said silicon thin film or said silicon single crystal grains;
• wherein the moved amount of an ultraviolet beam irradiating position in a period from completion of an irradiation pulse of said rectangular ultraviolet beam to starting of the next irradiation pulse of said rectangular ultraviolet beam being in a range of 4 μm to 20 μm, and a ratio of said moved amount to a width of said rectangular ultraviolet beam measured in the movement direction thereof being in a range of 0.1 to 5%, whereby forming a silicon thin film composed of a group of silicon single crystal grains which are each approximately rectangular-shaped and which are arranged in a grid pattern on said base body, a selected orientation of said silicon single crystal grains to the surface of said base body being approximately the <100> direction.

A process of fabricating a flash memory cell, comprising:

• a step (a) of irradiating a pulsed rectangular ultraviolet beam on an amorphous or polycrystalline silicon layer formed on a tunnel oxide film, to form a silicon thin film composed of a croup of silicon single crystal grains which are each approximately rectangular-shaped and which are arranged in a grid pattern on said tunnel oxide film, a selected orientation of said silicon single crystal grains to the surface of said tunnel oxide film is approximately the <100> direction;
• and
• a step (b) of separating adjacent ones of said silicon single crystal grains to each other, whereby forming a floating gate composed of said group of silicon single crystal grains;
• wherein the moved amount of an ultraviolet beam irradiating position in a period from completion of an irradiation pulse of said rectangular ultraviolet beam to starting of the next irradiation pulse of said rectangular ultraviolet beam being in a range of 4 μm to 20 μm, and a ratio of said moved amount to a width of said rectangular ultraviolet beam measured in the movement direction thereof being in a range of 0.1 to 5%.