Bond strain, chemical induction, and OH incorporation in low-temperature (350-100 degrees C) plasma deposited silicon dioxide films

New device concepts are being considered with very demanding requirements f or low-temperature processing. In this article, infrared transmission and e llipsometry is used to compare silicon oxide films formed by plasma chemica l vapor deposition using SiH4 N2O, and either He or H-2 dilution, gas betwe en 350 and 100 degrees C. The Si-O asymmetric stretching mode is affected b y bond strain and chemical induction, and monitoring the Si-O peak position gives insight into the effect of process conditions on local bond structur e. Hydrogen is expected to affect surface processes during growth, for inst ance, to enable the removal of surface SiOH bonds through H-mediated abstra ction, leading to improved bonding structure at low temperature. We find th at exposing the surface to hydrogen atoms during grow ih helps eliminate is olated SiOH bonds, leading to Si-Si bond formation. However, an increase in associated SiOH bonding groups, stabilized by hydrogen bonding, is also ob served. The density of associated SiOH groups is larger at low temperature where the rate of water desorption is reduced, suggesting that the associat ed OH is formed by physisorbed water produced during OH removal. Films depo sited with hydrogen dilution show somewhat improved electrical performance at <200 degrees C, but further work is required to produce high quality fil ms at very low temperatures. (C) 2000 American Vacuum Society.