Intellectual Property Office
Non-Confidential Disclosures
A Method of Depositing High Quality Silicon Dioxide Dielectric Thin Films Using Tetramethylsilane
PSU Inv. Disc. No. 97-1779
Field of the Invention:
Low temperature deposition of high quality silicon dioxide (SiO2) with a benign precursor which also is easily metered with conventional mass flow controllers (MFCs).
Inventors:
D.M. Reber and S.J. Fonash
Background:
Low temperature chemical vapor deposited SiO2 thin films are routinely used as passivation and dielectric layers in integrated circuit (IC) microelectronics and in large area electronics such as displays and solar photovoltaic cells. In many of these areas there is heightened demand for reducing the oxide film deposition temperature while assuring uniformity, homogeneity and overall dielectric quality. Furthermore, high quality oxides deposited at temperatures below 200 °C would be highly valued by the optical coatings industry and they could help bring into fruition microelectronics on plastic substrates. Although both tetraethylorthosilicate (TEOS, Si(OC2H5)4) liquid and silane gas based oxides can be deposited at low temperatures with high quality, they are not without drawbacks. For example, quality PETEOS SiO2 films are difficult to achieve at temperatures below 250 °C. Also, TEOS has a low vapor pressure of ~ 2 Torr (25 °C and 1 atm.). Thus, metering with conventional mass flow controllers is not possible and the heating of all delivery lines and chamber surfaces is required to prevent TEOS condensation. Silane, conversely, is easily metered but it is a toxic and pyrophoric gas which constitutes an explosion hazard at high SiH4 concentrations. These limitations add to the cost and complexity of TEOS and silane silicon dioxide deposition equipment.
Invention description:
The inventors have found a means and method of depositing a thin, high-quality SiO2 film at temperatures below 250 °C utilizing tetramethylsilane (TMS, Si (CH3)4) as an alternative precursor source. Tetramethylsilane is found to be a superior source gas because it is non-toxic, non-pyrophoric and because its high vapor pressure ~ 580 Torr allows for conventional MFC use. Furthermore, uniform high quality films can be deposited at higher rates with TMS then similar high quality films deposited with silane or TEOS. The TMS oxides display excellent electrical properties such as breakdown fields of 7-10 MV/cm and leakage current densities of ~ 10-9 A/cm2 at fields up to 3.5 MV/cm.
Contact:
Richard M. Weyer
Sr. Technology Licensing Officer
Intellectual Property Office
113 Technology Center
The Pennsylvania State Univ.
University Park, PA 16802-7000
Phone: (814) 865-6279
Fax: (814) 865-3591
E-mail: rmw4@psu.edu
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