Thermomechanical criteria for overlay alignment in flexible thin-film electronic circuits

A simple mechanical model for a deposited film / substrate couple is presented to describe how film deposition at elevated temperature induces change in the substrate’s in-plane dimensions at room temperature. The model provides a quantitative guideline for reducing, or completely eliminating, this elongation, by tailoring the tensile built-in stress in the deposited film. The dimensional stability so achieved is necessary for accurate overlay alignment of photomasks during the fabrication of thin-film electronic circuits