Characterizing the spatial uniformity of thin-film stress, modulus, and strength via novel experimental techniques

Abstract

Controlling thin-film stress magnitudes and nonuniformities is a persistent and pervasive challenge for applications ranging from the semiconductor industry to nanotechnology. Consequently, the ability to measure the intensity and spatial distribution of film stress accurately is essential for fabrication process optimization. In addition to intrinsic stress, thin-film properties such as the fracture strength and biaxial modulus are also important. However, these properties are typically different from bulk values and are more difficult to measure. But such data can be obtained from experimental measurements using the pressure bulge tool and the membrane resonance tool. This paper describes novel extensions of both methods to characterize global thin-film properties. Arrays of freestanding membrane windows are fabricated across a silicon substrate (or mask). Individual membranes are tested to provide a discrete assessment of the thin-film properties, which allows for the determination of gradients in the film across the substrate.