Patent ID: 8476004

Claim:
A method for forming photoresist patterns comprising: providing a substrate; forming a bi-layered photoresist on the substrate, the bi-layered photoresist comprising a first photoresist layer and a second photoresist layer positioned between the first photoresist layer and the substrate, the first photoresist layer having a first refractive index, the second photoresist layer having a second refractive index, and the second refractive index is larger than the first refractive index, wherein a thickness of the second photoresist layer is decided according to a formula (1): (4π n f /λ f ) d *cos θ t =(2 m+ 1)π (1) wherein n f is the second refractive index of the second photoresist layer, λ f is a wavelength of an incident light, d is the thickness of the second photoresist layer, θ t is an incident angle of the incident light, and m is a node of the incident light; and performing a photolithography to pattern the bi-layered photoresist.