| 摘要 |
A method is disclosed to form a large-grain, lightly p-doped polysilicon film suitable for use as a channel region in thin film transistors. The film is preferably deposited lightly in situ doped with boron atoms by an LPCVD method at temperatures sufficiently low that the film is amorphous as deposited. After deposition, such a film contains an advantageous balance of boron, which promotes crystallization, and hydrogen, which retards crystallization. The film is then preferably crystallized by a low-temperature anneal at, for example, about 560 degrees for about twelve hours. Alternatively, crystallization may occur during an oxidation step performed, for example at about 825 degrees for about sixty seconds. The oxidation step forms a gate oxide for a thin film transistor device, for example a tunneling oxide for a SONOS memory thin film transistor device.
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