Stress and microstructure in tungsten sputtered thin films
Tungsten films, 0.05--1 ..mu..m thick, were deposited on silicon wafers by rf magnetron sputtering. Induced film stresses were investigated as a function of substrate temperature and background pressure in connection with microstructural observations and limited compositional analysis. Homologous substrate temperatures /ital T//sub /ital s////ital T//sub /ital m//, where /ital T//sub /ital m// is the melting point of tungsten (3683 K), ranged from 0.08 to 0.15. Argon pressures investigated ranged from 1 to 7 Pa. This corresponds to the low-temperature part of Thornton's microstructure model, within zones I and T. Two regions were distinguished for increasing values of the homologous temperature and/or decreasing values of argon pressure: (i) The first region, observed for low substrate temperature and high argon pressure, was a voided zone I microstructure with small grain size (200--400 A). Film stresses increased from zero towards tensile values as voids disappeared. (ii) The second region, observed for higher values of /ital T//sub /ital s////ital T//sub /ital m// and/or low /ital p//sub Ar/, was a denser zone T structure, with a bimodal grain distribution (/lt/3000 A). After reaching a maximum tensile value sigma=2/times/10/sup 3/ MPa, corresponding to the transition from zone I to zone T microstructure, the stress decreased abruptly to a constant value sigma=/minus/2.7/times/10/sup 3/ MPa. All stress values were found to be quite independent of thickness in the range from 0.05 to 1 ..mu..m. Even though ..beta.. metastable phase is usually observed for zone I deposits, a quasipure ..cap alpha.. film was obtained at low temperature and high pressure (within zone I) under especially clean conditions. Independent of phase composition (..cap alpha.. or ..beta.. phase) the voided zone I was observed to be highly reactive in air.
- Research Organization:
- Laboratoire de Microstructures et de Microelectronique L2M-C.N.R.S., 196 avenue H. Ravera, 92220 Bagneux, France(FR); Centre National d'Etudes des telecommunications C.N.E.T., 196 avenue H. Ravera, 92220 Bagneux, France
- OSTI ID:
- 6096210
- Journal Information:
- J. Vac. Sci. Technol., A; (United States), Vol. 7:4
- Country of Publication:
- United States
- Language:
- English
Similar Records
Characterization of electron-beam deposited tungsten films on sapphire and silicon
Characterization of electron-beam deposited tungsten films on sapphire and silicon