International Business Machines Corporation

Raymond E Tibbetts

Janusz S Wilczynski

Alan Edward Rosenbluth

Douglas S Goodman

Frederick Hayes Dill

Bunsen Fan

David F Witman

An optical system having a plurality of substantially planar reflecting surfaces and a plurality of curved reflecting surfaces providing an optical projection system which can scan a mask object onto an image plane by having the mask and copy substrate substantially fixed in position relative to each other and either simultaneously moving the mask and copy substrate in the same direction or maintaining the mask and image plane substantially stationary and fixed with respect to each other while scanning the optical system. The optical system uses one wavelength of an electromagnetic radiation to align the mask to the copy substrate and another wavelength of electromagnetic radiation to form the image of the mask on the copy substrate. The apparatus can be used as a laser ablation optical tool to laser ablate the image of a mask onto the copy substrate, as an inspection tool, as a photolithographic and for other related applications. The projection lens is a modified Dyson type lens.

Optical projection system

A coherent laser beam having a possibly non-uniform spatial intensity distribution is transformed into an incoherent light beam having a substantially uniform spatial intensity distribution by homogenizing the laser beam with a light tunnel (a transparent light passageway having flat internally reflective side surfaces). It has been determined that when the cross-section of the tunnel is a polygon (as preferred) and the sides of the tunnel are all parallel to the axis of the tunnel (as preferred), the laser light at the exit of the light tunnel (or alternatively at any image plane with respect thereto) will have a substantially uniform intensity distribution and will be incoherent only when the aspect ratio of the tunnel (length divided by width) equals or exceeds the contangent of the input beam divergence angle .theta. and when

Laser beam homogenizer

A unit magnification optical system having micron resolution capability over a broad frequency spectrum. A spherical concave mirror is used to provide unit magnification at high numerical aperture with respect to object and image planes which are both located at or in the proximity of the center of curvature of the mirror, or the optical equivalent thereof. A first refractory element optically close to the object and image planes corrects longitudinal chromatic aberration of the principal rays while a second refractory element optically close to the mirror corrects residual longitudinal chromatic aberration of the marginal rays. In the preferred embodiment, a double prism arrangement located between the first refractory element and the center of curvature of the mirror optically reflects the object and image planes to parallel opposed positions having a common axis perpendicular to the axis of the mirror. The system may be used for either step-and-repeat or scanning exposure operations in fabricating microcircuits.

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Mahopac, NY, United States of America

Raymond E Tibbetts