LOW-TEMPERATURE, ATMOSPHERIC-PRESSURE CVD USING HEXAMETHYLDISILOXANE AND OZONE

Hexamethyldisiloxane (HMDSO), a new organic silicon source, was studied for use in depositing high quality non-doped silicon dioxide for very large scale integrated device fabrication. The high vapor pressure, 20 mm Hg at 13-degrees-C, makes it easier to use than other conventional sources, such as tetraethyorthosilicate (TEOS). A deposition rate of 0.1-mu-m/min at 400-degrees-C with 2-6% ozone was obtained making it suitable for production oxide applications. Step coverage was found to be excellent and varied from conformal to 'flow-shaped with a 40 degree step angle. The deposition rate obtained on thermal oxide was poor relative to bare silicon, but this can be overcome through the use of a two-step deposition method or a surface modification pre-treatment. Film quality improved with increasing deposition temperature as indicated by a decrease in the HF etch rate and film shrinkage. The stress of the as-deposited film was moderate at less-than-or-equal-to 2 x 10(9) dyn/cm2 (tensile), when deposited at 0.1-mu-m/min at 400-degrees-C using 4% ozone. These deposition conditions also yielded an excellent crack limit of 2-mu-m. The deposition rate, etch rate, and film shrinkage did not show the same strong dependence on ozone concentration encountered with TEOS/O3 chemistry. The excellent film properties along with the greater ease of use afforded by the higher vapor pressure indicate that HMDSO/O3 is a superior chemistry for the deposition of both interlevel and intermetal dielectrics.