AVS 47th International Symposium
    Semiconductors Monday Sessions
       Session SC2+EL+SS-MoM

Paper SC2+EL+SS-MoM5
Relaxation of SiGe Films on Silicon-on-Insulator Substrates Utilizing Borosilicate Glass

Monday, October 2, 2000, 9:40 am, Room 312

Session: Dissimilar Materials
Presenter: E.M. Rehder, University of Wisconsin, Madison
Authors: E.M. Rehder, University of Wisconsin, Madison
D.E. Savage, University of Wisconsin, Madison
P. Moran, University of Wisconsin, Madison
T.S. Kuan, SUNY at Albany
M.G. Lagally, University of Wisconsin, Madison
T.F. Kuech, University of Wisconsin, Madison
Correspondent: Click to Email
We have grown epitaxial silicon germanium (SiGe) alloy films and studied the relaxation effects of thin silicon-on-insulator (SOI) substrates. Bond and etchback SOI (BESOI) wafers having a top Si layer of 15nm were fabricated. The insulators in these structures were either SiO@sub 2@, using commercial wafers, or chemical vapor deposited borosilicate glass as the insulator. Si@sub 0.82@Ge@sub 0.18@ films were grown on these substrates by ultra high vacuum chemical vapor deposition at temperatures of 550, 630, and 670°C. Films were grown up to 175nm in thickness, which is beyond the equilibrium critical thickness. The low growth temperatures nonetheless result in metastable strained films. Any observed relaxation during growth was then enabled by the SOI. The relaxation following growth was studied by high-resolution double and triple crystal x-ray diffraction and cross sectional transmission electron microscopy. The growth layers on substrates using the SiO@sub 2@ insulator as well as those grown directly on Si substrates are identical and fully strained. However, SOI substrates utilizing a borosilicate glass with 50% B@sub 2@O@sub 3@ content yielded films in which the film strain was reduced by 30%. Post-growth annealing at temperatures from 700 to 1050°C were employed to promote relaxation. When annealed at 950°C the film on the Si substrate remained largely unrelaxed, while the film on the SiO@sub 2@-SOI substrate relaxed to 50%. Lower temperatures resulted in no relaxation, while annealing at 1050°C allows interdiffusion to occur resulting in additional relaxation. Cross-sectional TEM images of these samples reveal a complex dislocation structure in both the film and substrate. The relationship between the oxide viscosities at these temperatures and the image forces affecting dislocation formation and motion will be discussed.