As-Deposited Low-Strain LPCVD (Low-Pressure, Chemical-Vapor-Deposition) Polysilicon

摘要

As-deposited polysilicon films with very low residual strain (lower than 5 x 10 sup -5 ) are obtained by a low-pressure, chemical-vapor-deposition (LPCVD) process. Straight polysilicon bridges 300 mu m long, 1.2 mu m thick, and 2 to 20 mu m wide, made using this process. No buckling has been observed in any of the nearly one thousand bridges of this type made in two separate process runs. In addition, no problems of sticking between the bridges and the substrate were encountered with these structures. The polysilicon films from which the beams were fabricated were deposited by pyrolyzing silane at 605/degree/C on a phosphosilicate-glass (PSG) layer (8 wt % P). The PSG layer serves as a sacrificial layer to be subsequently etched away to free the bridge. Our research is aimed at obtaining an understanding of these relationships through consideration of the role of interfacial stresses and the kinetics of initial crystalline nucleation. The technique for producing these low-strain films is significant, however, because no high-temperature annealing steps are required to produce them. 4 refs., 4 figs. (ERA citation 13:054323)