The effect of stress on the dielectric properties of barium strontium titanate thin films

Barium strontium titanate thin films are being developed as capacitors in d ynamic random access memories. These films, grown on silicon substrates, ar e under tensile residual stress. By a converse electrostrictive effect, the in-plane tensile stress reduces the capacitance in the thickness direction of the film. We measured the substrate curvature change upon the removal o f the film, and found the magnitude of the residual stress to be 610 MPa. I n a separate experiment, we applied a force to vary the stress in a film on a substrate, and simultaneously recorded the capacitance change of the fil m. The measurements quantify the effect of stress on thin film capacitance. The stress free capacitance was found to be 23% higher than the capacitanc e under residual stress. (C) 1999 American Institute of Physics. [S0003-695 1(99)02340-2].