Low-Temperature Gate Insulator for Poly-Si Thin Film Transistors by Combination of Photo-Oxidation and Plasma Enhanced Chemical Vapor Deposition Using Tetraethylorthosilicate and O2 Gases

Yukihiko NAKATA  Tetsuya OKAMOTO  Toshimasa HAMADA  Takashi ITOGA  Yutaka ISHII 

Publication
IEICE TRANSACTIONS on Electronics  Vol.E85-C  No.11  pp.1849-1853
Publication Date: 2002/11/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Electronic Displays)
Category: Active Matrix Displays
Keyword: 
oxidation,  poly-Si,  TFT,  gate insulator,  SiO2, 

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Summary: 
We report, in this paper, on a combined process of photo-oxidation and PECVD using TEOS and O2 gases to produce an SiO2 gate insulator for poly-Si TFTs. Light of 172 nm-wavelength from a Xe excimer lamp generates active oxygen radicals efficiently and selectively without producing ozone. These oxygen radicals efficiently oxidize silicon. In contrast to plasma oxidation, photo-oxidation offers the ability to produce gate oxides without ion bombardment. Oxide-silicon interfaces with interface trap densities of 2-3 1010 cm-2 eV-1 were obtained by photo-oxidation at 200-300. A stack structure was produced using 4.3-nm-thick photo-oxide topped with a 40-nm-thick PECVD oxide film deposited at 300. This stack structure without annealing exhibited excellent interface behavior and the same J-E characteristics as a 100-nm-thick PECVD film annealed at 600.