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(12) United States Patent ao) Patent No.: Us 7,675,060 B2
Yamazaki et al. (45) Date of Patent: Mar. 9,2010
FOREIGN PATENT DOCUMENTS
0 085 406 8/1983
J. M. Green et al., "Method to Purify Semiconductor Wafers," IBM Technical Disclosure Bulletin, vol. 16, No. 5, Oct. 1973, pp. 16121613.
(Continued) Primary Examiner—Ori Nadav
(74) Attorney, Agent, or Firm—Eric J. Robinson; Robinson Intellectual Property Law Office, PC.
Disclosed is a technique of improving the heat resistance of the aluminum gate electrode in bottom-gate-type TFT of which the active layer is made of a crystalline silicon film. A pattern of a laminate of a titanium film 102 and an aluminum film 103 is formed on a glass substrate 101. The pattern is to give a gate electrode 100. Then, the titanium film 102 is side-etched. Next, the layered substrate is heated to thereby intentionally form hillocks and whiskers on the surface of the aluminum pattern 103. Next, the aluminum pattern 103 acting as an anode is subjected to anodic oxidation to form an oxide film 105 thereon. The anodic oxidation extends to the lower edge of the aluminum pattern 103, at which the titanium layer was side-etched. Next, a gate-insulating film 106 and an amorphous silicon film are formed. A mask is formed over the pattern, which is to give the gate electrode, and then a nickel acetate solution is applied to the layered structure. Thus, nickel is kept in contact with the surface of the structure. Next, this is heated to induce crystal growth in the silicon film from the region contacted with nickel to the masked region. In the bottom-gate-type TFT thus produced, the active layer is made of a crystalline silicon film. In this process, since the anodic oxide film is formed as in FIG. 1(C), aluminum does neither melt to flow away nor diffuse away. Thus, the heat resistance of the aluminum electrode formed is improved.
31 Claims, 15 Drawing Sheets
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* cited by examiner