Low Pressure Chemical Vapor Deposition of Tungsten and Aluminum for VLSI Applications

This paper reviews the current status of LPCVD tungsten and aluminum for VLSI applications. Using deposition chemistries based on tungsten hexafluoride and tri-isobutyl aluminum, W and A1 deposits are characterized with respect to their electrical, mechanical, structural, chemical, and optical properties. Although results of this study prove these two LPCVD processes to be compatible with current VLSI fabrication, certain problems must still be resolved for complete commercial acceptance. These problems include, in the case of selective LPCVD tungsten, the occurrence of leakage current across N⁺/P-Tub junctions, and, in the case of LPCVD aluminum, the relatively poor electromigration resistance (compared to Al-Cu) and excess surface roughness.