WATER-INDUCED ROOM-TEMPERATURE OXIDATION OF SI-H AND -SI-SI- BONDS INSILICON-OXIDE

Hydrogenated amorphous silicon oxide (a-SiOx:H) films have been fabric ated by plasma-enhanced chemical vapor deposition at temperature rangi ng from 15 to 150 degrees C. It is found that once these films are tak en out from the reaction chamber and immersed into water or exposed to the atmosphere, the Si-H and -Si-Si- bonds in the films start to oxid ize. After immersing the films into deionized water, many small gas bu bbles are formed upon the films' surface and these bubbles were collec ted into sealed tubes and identified as hydrogen gas (H-2(g) using gas chromatography technique. By using infrared absorption spectroscopy a nd monitoring these oxidation processes at various times, it is clear that at room temperature water (H2O) molecules react with Si-H bonds a nd -Si-Si- bonds and form more chemically stabilized Si-O-Si, Si-O-H, H-O-H bonds, and H-2(g). Study of the Si-H decreasing rates reveals th at second-order reaction occurs at the initial stage of oxidation, whi ch is consistent with two adjacent Si-H bonds oxidizing together with one attacking H2O molecule. A model of porous structure, which is prob ably inherent at low temperature deposition, is proposed to explain wh y H2O molecules can percolate through the films and eventually fully o xidize these films. (C) 1996 American Institute of Physics.