Crystal silicon film forming method, thin-film transistor and display device using the crystal silicon film

A crystal silicon film forming method comprising:

• forming a metal film above an insulating substrate including glass, the metal film being made of a refractory metal or alloy both of which including Mo or MoW;
• forming an insulating film on the metal film;
• and
• forming a crystal silicon film on the insulating film, the silicon film being made of polycrystal Si,
• wherein in the forming of an insulating film, the insulating film is formed from a SiO2 film of a predetermined film thickness range,
• the forming of a crystal silicon film includes:
• forming an amorphous silicon film made of a-Si on the insulating film, within a predetermined film thickness range;
• and
• forming the crystal silicon film from the amorphous silicon film by irradiating a light of a green laser on the amorphous silicon film such that:
• a first light component is absorbed by the amorphous silicon film when the light of the green laser is irradiated on the amorphous silicon film;
• a first reflected light component is reflected off the metal film when the light of the green laser passes through the amorphous silicon film and the insulating film;
• and
• a second light component is absorbed by the amorphous silicon film when the light of the green laser passes through the amorphous silicon film and multiple beam interference occurs between the light and a second reflected light component that is reflected off an interface of the amorphous silicon film and the insulating film, and
• the predetermined film thickness range of the SiO2 film and the predetermined film thickness range of the amorphous silicon film correspond to a region satisfying any one of Expression 1 to Expression 4, when a film thickness of the SiO2 film is denoted as d(SiO2) nm and a film thickness of the amorphous silicon film is denoted as d(a-Si) nm:
• d(a-Si)≧25 nm, and
• d(SiO2)≧80 nm, and
• d(a-Si)≦(−0.0015×(d(SiO2))2+0.1929×d(SiO2)+30.105) nm;
• Expression 1
• (a-Si film thickness upper limit)
• d(a-Si)≦75 nm, where d(SiO2)≦170 nm, and
• d(a-Si)≦(−0.0001×(d(SiO2))3+0.0969×(d(SiO2))2−22.395×(d(SiO2))+1769.8) nm, where d(SiO2)≧170 nm
• (a-Si film thickness lower limit)
• d(a-Si)≧−0.007×(d(SiO2))3+0.2932×(d(SiO2))2−38.913×(d(SiO2))+1797.2 nm, where 120 nm≦d(SiO2)≦163 nm, and
• d(a-Si)≧−0.0438×(d(SiO2))2−16.494×(d(SiO2))+1574.8 nm, where 163 nm≦d(SiO2)≦200 nm, and
• d(a-Si)≧−0.12×(d(SiO2))+52 nm, where 200 nm≦d(SiO2);
• Expression 2
• d(SiO2)≧80 nm, and
• d(a-Si)≦0.002×(d(SiO2))2+0.2489×d(SiO2)+57.966 nm, and
• d(a-Si)≧0.0005×(d(SiO2))2−0.1681×d(SiO2)+67.03 nm;
• and Expression 3
• d(a-Si)≦75 nm, and
• d(a-Si)≦0.0087×(d(SiO2))2−4.421×d(SiO2)+628.38 nm, and
• d(a-Si)≧0.0031×(d(SiO2))2−1.5578×d(SiO2)+255.6 nm. Expression 4

A crystal silicon film forming method comprising:

• forming a metal film above an insulating substrate including glass, the metal film being made of a refractory metal or alloy both of which including Mo or MoW;
• forming an insulating film on the metal film;
• and
• forming a crystal silicon film on the insulating film, the silicon film being made of polycrystal Si,
• wherein in the forming of an insulating film, the insulating film is formed from a SiO2 film and a SiN film that are of a predetermined film thickness range,
• the forming of a crystal silicon film includes:
• forming an amorphous silicon film made of a-Si on the insulating film, within a predetermined film thickness range;
• and
• forming the crystal silicon film from the amorphous silicon film by irradiating a light of a green laser on the amorphous silicon film such that:
• a first light component is absorbed by the amorphous silicon film when the light of the green laser is irradiated on the amorphous silicon film;
• a first reflected light component is reflected off the metal film when the light of the green laser passes through the amorphous silicon film and the insulating film;
• and
• a second light component is absorbed by the amorphous silicon film when the light of the green laser passes through the amorphous silicon film and multiple beam interference occurs between the light and a second reflected light component that is reflected off an interface of the amorphous silicon film and the insulating film, and
• the predetermined film thickness range of the SiO2 film, the predetermined film thickness range of the SiN film, and the predetermined film thickness range of the amorphous silicon film correspond to a region satisfying one of Expression 5 and Expression 6, when a film thickness of the SiO2 film is denoted as d(SiO2) nm and a film thickness of the amorphous silicon film is denoted as d(a-Si) nm:
• d(a-Si)≧25 nm, and d(a-Si)≦45 nm, and
• d(SiO2)≧55 nm, and d(SiO2)<120 nm, and
• d(SiN)≧30 nm, and d(SiN)≦90 nm;
• Expression 5
• d(a-Si)≧25 nm, and d(a-Si)≦45 nm, and
• d(SiO2)>120 nm, and d(SiO2)≦150 nm, and
• d(SiN)≧30 nm, and d(SiN)≦90 nm. Expression 6