CORRELATION OF STRESS BEHAVIOR WITH HYDROGEN-RELATED IMPURITIES IN PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITED SILICON DIOXIDE FILMS

The presence of undesirable hydrogen-related impurities and the result ing stress instability in chemical vapor deposited silicon dioxide fil ms are important issues. In this work, the bonding nature and stress b ehavior of relatively low-temperature deposited silicon dioxide films deposited at high rates were investigated. Films were deposited at 100 0 Angstrom/min and at a substrate temperature in the 250-350 degrees C range. A considerable change in stress was observed in these films up on annealing in the 250-400 degrees C temperature range. Both as-depos ited and annealed films were then stored in a cleanroom environment fo r long periods of time, and their stress was monitored intermittently. In parallel, Fourier transform infrared studies were performed on an identical set of as-deposited and annealed films to investigate change s in the bonding nature of the films during aging. Thus, film stress a nd their bonding nature were studied concurrently over an extended per iod of time. Si-H and silanol (Si-OH) were identified as impurities re sponsible for the observed stress instability of the deposited films. Initial concentrations of these impurities have been observed to vary depending on the deposition conditions. Also, depending on the concent rations of these impurities, both reversible and irreversible bond rec onstruction were observed in the films upon annealing. Concomittantly, reversible and irreversible changes in stress were observed in anneal ed films, the amount of change depending on the impurity type and cont ent. Impurities responsible for reversible and irreversible bond recon struction were identified. Good correlation between film stress and bo nding was observed. (C) 1997 American Institute of Physics.