J. Phys. IV France
Volume 05, Numéro C5, Juin 1995
Proceedings of the Tenth European Conference on Chemical Vapour Deposition
Page(s) C5-887 - C5-893
Proceedings of the Tenth European Conference on Chemical Vapour Deposition

J. Phys. IV France 05 (1995) C5-887-C5-893

DOI: 10.1051/jphyscol:19955105

Influence of the Doping Gas on the Axial Uniformity of the Growth Rate and the Electrical Properties of LPCVD In-Situ Doped Polysilicon Layers

D. Briand1, M. Sarret1, P. Duverneuil2, T. Mohammed-Brahim1 and K. Kis-Sion1

1  Groupe de Microélectronique et Visualisation, URA 1648 du CNRS, Université de Rennes 1, Campus de Beaulieu, Bât. 11B, 35042 Rennes cedex, France
2  Laboratoire de Génie Chimique, URA 192 du CNRS, ENSIG/INPT, 18 Chemin de la Loge, 31078 Toulouse cedex, France

We report in-situ doping of polysilicon grown on glass substrates by a LPCVD process. The growth rate, the resistivity and the dopant concentration of boron in-situ doped polysilicon layers are studied as a function of the deposition pressure and the dopant gas to silane mole ratio. A dependence of the axial uniformity on pressure and B2H6/SiH4 mole ratio is put forward, and this effect appears to be very strong especially at high pressure. It is explained by a lowering of the diborane concentration in the gas mixture along the load, because of a different threshold for the thermal decomposition of diborane and silane. It is also put forward that a critical concentration of boron exists above which the growth rate is increasing. Improvements of the horizontal homogeneity are obtained by varying the total gas flow rate.

© EDP Sciences 1995