Patent ID: 7067223
Filing Date: 2006-06-27
Classification: G03F

Abstract:
1. A method for making a phase shift mask with feature sizes smaller than a wavelength of an incident light beam, the method comprising the steps of: applying a first phase shift layer to a substantially transparent mask substrate, the first phase shift layer selected from alkali metal titanyl phosphates, the first phase shift layer having a refractive index that is nonlinear with the intensity of the incident light beam, wherein the refractive index of the first phase shift layer changes with the intensity of the incident light beam on the phase shift mask, applying photoresist to the first phase shift layer on the mask substrate, developing the photoresist to provide a mask pattern, etching the first phase shift layer according to the mask pattern to form a patterned first phase shift layer, and stripping the photoresist from the mask substrate to provide the phase shift mask, which exhibits a transmission that is dependent at least in part on an intensity of the incident light beam on the first phase shift layer.