Low Temperature Curing of Polyimide Wafer Coatings

Polyimide films are commonly used on wafers as passivation layers, stress buffer layers, dry etch masks, structural layers, and re-distribution layers for chip scale packaging and wafer level packaging. These films are cured in convection or diffusion ovens at high enough temperatures (350-400°C) to assure adequate mechanical and electrical properties. These high temperatures can change the electrical properties of the devices. If the cure temperature of these films were lowered there could be a reduction in the film (and wafer) stress as well as a lower thermal budget for the devices. However, curing polyimide films at lower temperatures than 250°C has not been found to provide the mechanical, chemical, and dielectric properties required for the final device operation parameters or mechanical and dielectri