Sub-micron device fabrication using multiple aperture filter

Claim 1

Method for fabrication of a device of feature size corresponding with design rule of a maximum of 0.5 μm, comprising at least one lithographic delineation step comprising illuminating a plurality of imaging regions of a mask by an electronically scanning beam of charged particles so that imaging information is imposed on such beam by two types of mask imaging regions, differing with regard to degree of scatter imposed on such beam, so as to produce a projected image on a device in fabrication by use of a lens system including a projection lens, said particles emanating from a particle source and being accelerated to a velocity resulting in a deBroglie wavelength, λ, of a value sufficient to satisfy design rule requirements, the transmission path for patterned radiation including a "back focal plane filter", defined as positioned on the back focal plane or on some equivalent conjugate plane of such lens system, said filter including an aperture defining the pass portion of said filter, characterized in that such beam during electronic scanning is maintained substantially on axis with regard to such projection lens by corresponding variation of the shape of such lens, in which the filter includes at least two apertures of size and separation to maintain desired image contrast and in that the delineation step entails image projection through at least two such apertures.