Spectroscopic Beam Profile Overlay Metrology

摘要

A spectroscopic beam profile metrology system simultaneously detects measurement signals over a large wavelength range and a large range of angles of incidence (AOI). In one aspect, a multiple wavelength illumination beam is reshaped to a narrow line shaped beam of light that is projected onto an overlay metrology target such that the direction of the line shaped beam is aligned with the direction of extent of a grating structure of the overlay metrology target. Collected light is dispersed across a detector according to AOI in one direction and according to wavelength in another direction. The measured signal at each detector pixel is associated with a particular AOI and wavelength. The collected light includes first order diffracted light, zero order diffracted light, or a combination thereof. In some embodiments, first order diffracted light and zero order diffracted light are detected over separate areas of the detector.

主权项

1. A metrology system comprising:
a multiple wavelength illumination source configured to provide a beam of illumination light having multiple wavelengths and a two-dimensional beam intensity cross-section; a beam shaping element configured to reshape the beam of illumination light such that the reshaped beam of illumination light has a beam intensity cross-section that is approximately one dimensional and is characterized by a length dimension. a high numerical aperture (NA) objective configured to receive the reshaped beam of illumination light and illuminate an overlay metrology target with the reshaped beam of illumination light over a range of angles of incidence such that the length dimension of the reshaped beam of illumination light is projected onto the overlay metrology target in a first direction that is parallel with a direction of extent of a grating structure of the overlay metrology target, the high NA objective further configured to collect light from the overlay metrology target in response to the illumination; and a first two dimensional detector configured to detect the collected light according to angle of incidence along a first dimension of the first two dimensional detector and according to wavelength along a second dimension of the first two dimensional detector.