A method of forming a masking element is provided. The method includes forming a photoresist material having a polymer backbone over a substrate, where the polymer backbone includes a linking group that links a first polymer segment to a second polymer segment, each of the first and the second polymer segments having an ultraviolet (UV) curable group. The method includes exposing the photoresist material under a first UV radiation to break the link between the first polymer segment and the second polymer segment. The method includes exposing the photoresist material under a second UV radiation different from the first UV radiation to form a patterned resist layer. And the method includes developing the patterned resist layer to form a masking element.