NMR CHARACTERIZATION OF DOPED SIO2-FILMS USED IN INTEGRATED-CIRCUITS

Phosphorus-doped silicon dioxide dielectric films, prepared by plasma- enhanced chemical-vapor deposition at low temperature (400 degrees C), play a critical role in the reliability of very large scale integrati on devices. The phosphorus in the phosphosilicate glass (PSG) neutrali zes the effect of mobile ion species and improves the glass flow, resu lting in better gap filling and improved planarization. To extract the maximum contribution from this and other doped films (boron and germa nium doped) in advanced sub-0.5 mu m complimentary metal-oxide-semicon ductor technologies, it is necessary to understand dopant incorporatio n and the effects of variation in the exposure to water, dopant concen tration, and high-temperature annealing. An analysis of PSG by H-1, Si -29 and P-31 solid-state nuclear magnetic resonance establishes the ch emistry of the phosphorus dopant incorporation and the effect of moist ure on the glass structures. Exposure to water results in a depolymeri zation of the PSG structures and a concurrent decrease in the crosslin k density of the glass network. Similar concentrations of silanols are observed in both doped and undoped samples of SiO2. An increase in si lanol concentration is found in P-doped glass after exposure to moistu re in air. The level of exposure to water will determine the extent of structural changes in the dielectric film. Variations in this exposur e can be expected to produce variability in the glass flow and other p roperties of the dielectric. (C) 1995 American Institute of Physics.