Spherical deformation of compliant substrates with semiconductor device islands

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Abstract
This article explores, through experiments and finite element analysis, the ability to plastically deform thin-film semiconductor structures on deformable substrates to spherical cap shapes without cracking the semiconductor layers. The major challenge involves contending with the large strain due to extreme deformation that will crack uniform stiff layers, such as silicon or silicon nitride. By patterning amorphous silicon and silicon nitride layers into islands, such problems can be avoided despite average strains in the substrate in excess of 5%. The strain in the device islands after deformation is a function of the island structure, size, and substrate material properties. Although the substrate is plastically expanded to a spherical dome, device islands can experience either tension or compression depending on the structure.