US 7449377

Patent Overview — US 7,449,377 B2

Title: Method of fabricating poly silicon layer
Assignee: Chunghwa Picture Tubes, Ltd. (original and current assignee per the source listing)
Inventors: Chiung-Wei Lin, Sheng-Chi Lee, Yi-Liang Chen, Rui-Cheng Huang, Te-Hua Teng
Application No.: US 11/308,961
Priority/filing date: 2006-05-30
Publication date (grant): 2008-11-11
Status (as listed): Expired – Fee Related; adjusted expiration 2026-07-14
Other version: US 2007/0281404 A1
Source: https://patents.google.com/patent/US7449377/en

Purpose. The patent is directed to a method of fabricating a polysilicon layer "for preventing metal contamination," and to a polysilicon layer "having comparatively larger grains size." It is described in the context of thin film transistors (TFTs), including low-temperature poly silicon (LTPS) TFTs, where the polysilicon layer serves as the channel layer.

Plain-language scope. A substrate (glass or quartz) is provided, and an amorphous silicon layer is formed on it (e.g., CVD or plasma enhanced CVD). A patterned metal layer is formed on the amorphous silicon layer using a metal such as nickel, cobalt, copper, tantalum, iron, or platinum, for example by sputtering, with patterning by photolithography and etching. A pulsed rapid thermal annealing (PRTA) process is then performed, operating between 550° C and 900° C, to form a metal silicide between the patterned metal layer and the amorphous silicon layer. The patterned metal layer and the metal silicide conduct thermal energy to the amorphous silicon layer, converting it into a polysilicon layer. Finally, the patterned metal layer is removed, for example by etching. Described results include spherical grains, grain size larger than 4000 angstrom, and surface roughness smaller than 10 angstrom. The specification contrasts this with conventional metal induced lateral crystallization (MILC), stating the metal silicide "may not migrate laterally," thereby avoiding lateral-crystallization-region metal contamination.

What the excerpt does not establish. The supplied text is an excerpt; it omits much of the specification and all claims, so claim scope, claim count, and dependency are not established. The excerpt mentions FIG. 1A–1F, FIG. 2, and FIG. 3 but does not include them. Specific PRTA values given (5 seconds at 900° C, 70° C/second heating, 35° C/second cooling) are described for an embodiment only. Legal status is expressly an assumption, not a legal conclusion. No litigation, ownership transfer, validity, or prior-art analysis is addressed here.