Patent ID: 6608313
Filing Date: 2003-08-19
Classification: B82Y,G21K,H01J

Abstract:
In a charged-particle-beam (CPB) microlithography method in which a charged-particle illumination beam, propagating from a beam source and having a respective propagation axis, is passed through an illumination-optical system that includes a lens, a deflector, and an aperture-angle-limiting aperture, a method for aligning the propagation axis of the illumination beam with a center of the aperture-angle-limiting aperture, the method comprising:(a) providing a projection-optical system that forms an image of the aperture-angle-limiting aperture at an imaging plane; (b) providing an alignment-measurement aperture situated at the imaging plane, and a beam detector situated downstream of the alignment-measurement aperture; (c) providing a scanning deflector upstream of the alignment-measurement aperture, the scanning deflector being configured to impart a deflection in two dimensions to an imaging beam formed of a portion of the illumination beam passing through the aperture-angle-limiting aperture and having a propagation axis, the deflection being transverse to the propagation axis of the imaging beam; (d) energizing the scanning deflector so as to cause the imaging beam to be deflected in the two dimensions over the alignment-measurement aperture, while using the beam detector to obtain an image of beam intensity of the imaging beam passing through the alignment-measurement aperture, as distributed over the two dimensions; (e) in the image of beam intensity, identifying a point of maximum intensity corresponding to the propagation axis of the imaging beam; and (f) based on the two-dimensional image obtained in step (d), energizing the deflector in the illumination-optical system as required to align the propagation axis of the imaging beam with a center of the aperture-angle-limiting aperture.