Patent ID: 7700247

Claim:
A method for measuring a dimension on a substrate, the method comprising the steps of: providing a target pattern on a substrate, said target pattern corresponding to a nominal pattern, said nominal pattern comprising an array of features characterized by a primary pitch of period P in a primary direction, said nominal pattern further characterized by a characteristic dimension defined along a direction substantially orthogonal to said primary direction, wherein said target pattern has a substrate characteristic dimension corresponding to said characteristic dimension of said nominal pattern; illuminating said target pattern along said primary direction with radiation characterized by at least one wavelength, so as to produce diffracted radiation from said target pattern, wherein said diffracted radiation has one zero order of said diffracted radiation and one or more none-zero orders of said diffracted radiation and said at least one wavelength is chosen relative to said primary pitch P such that said zero-order of said diffracted radiation is spatially separated from said one or more none-zero orders of said diffracted radiation along said substantially orthogonal direction to said primary direction; providing a relationship for determining a dimension of interest along said primary direction in said target pattern as a function of a measurable quantity of said one or more none-zero orders of said diffracted radiation along said substantially orthogonal direction to said primary direction, said measurable quantity of said one or more none-zero orders occurring in response to said substrate characteristic dimension in said target pattern; detecting said zero order of said diffracted radiation and said measurable quantity of said one or more none-zero orders of said diffracted radiation along said substantially orthogonal direction to said primary direction, wherein said zero order of said diffracted radiation is detected separately from said none-zero orders of said diffracted radiation; and determining said dimension of interest in accordance with said relationship, based on said detected measurable quantity of said one or more none-zero orders of said diffracted radiation.