Abstract: An attenuating phase-shifting optical lithographic mask is fabricated, in a specific embodiment of the invention, by first depositing a uniformly thick molybdenum silicide layer on a top planar surface of quartz. The molybdenum silicide layer has a thickness sufficient for acting as an attenuating (partially transparent) layer in a phase-shifting mask. A uniformly thick chromium layer is deposited on the molybdenum silicide layer. The chromium layer has a thickness sufficient for acting as an opaque layer in the phase-shifting mask. Next, the chromium layer is patterned by dry or wet etching, while the chromium is selectively masked with a patterned resist layer. Then the molybdenum silicide is patterned by dry or wet etching, using the patterned chromium layer as a protective layer, whereby a composite layer of molybdenum silicide and chromium is formed having mutually separated composite stripes. Any remaining resist is removed.

Abstract: A phase-shifting optical lithographic mask is made by a method that produces a set of phase shifting features (11) located in phase-shifting areas and a set of reinforced alignment marks (13, 33) located in alignment areas of the mask. Both of these sets are located on a single slab of quartz (10). The method involves a lift-off step that results in the self-alignment of the alignment marks with respect to the phase-shifting features. All of the phase-shifting features together with all of the alignment marks are patterned during a single step, and all of them comprise a bottom layer (11) of common material and common thickness so as to be partially transparent to optical radiation used in an optical lithographic system. Typically the bottom layer is essentially chromium oxynitride.

Abstract: In order to print an isolated feature having a width W in a photoresist layer using an optical radiation imaging system whose lateral magnification is equal to m, a phase-shifting mask is used having a corresponding isolated feature. In one embodiment this corresponding isolated feature has a central square portion having a refractive index n.sub.1 and a thickness t.sub.1, and a peripheral (rim) square-ring phase-shifting portion having a width B, as well as a refractive index n.sub.2 and a thickness t.sub.2, such that the phase-shift .phi.=2.pi.(n.sub.2 t.sub.2 -n.sub.1 t.sub.1)/.lambda. of the central portion relative to the peripheral portion is equal to .pi. radian or odd multiple integral thereof. The width C of the central portion advantageously is selected such that mC/W is equal to at least 1.2, and preferably greater than 1.5, rather than unity.

Abstract: A phase-shifting lithographic mask is fabricated, in one embodiment, by using a resist layer that is negative tone with respect to a (patterned) electron beam and is positive tone with respect to a (flood) mid-ultraviolet beam, with the tone of the electron beam predominating over that of the mid-ultraviolet beam. The resist layer is spun on a body comprising a patterned metallic layer located on a (transparent) quartz slab. The body is subjected from below to a flood mid-ultraviolet beam and from above to a patterned electron beam whose edges are located somewhere in the midst of the patterned opaque layer but are not coincident with any edges of the patterned opaque layer. Thus, a subsequent development of the resist layer removes those regions and only those regions of the resist layer upon which the ultraviolet beam was incident--i.e., not in the shadows cast by the patterned opaque layer--in the absence of incidence of the patterned electron beam.

Abstract: A phase-shifting lithographic mask is made by a procedure involving only a single patterned electron, ion, or photon beam bombardment of a resist layer. The bombardment is arranged to produce three kinds of regions in the resist: no dosage, low dosage, and high dosage. These three regions in the resist are then utilized--in conjunction with an ordinary wet development step followed by either a silylation or an optical flooding technique, and thereafter by another ordinary wet development step--to pattern the resist layer and thereby to enable forming, by dry or wet etching, an underlying double layer consisting of a patterned opaque layer and a patterned transparent phase-shifting layer, the phase-shifting layer being located on, or being part of, a transparent substrate.

Abstract: Phase-shifting (two-optical-level) masks are manufactured by a self-aligned technique in which after first-level trenches in the mask have been formed, second-level trenches therein are formed by patterning an electron resist overlying the mask in such a manner that the edges of the patterned resist can be located anywhere within the first-level trenches, whereby the need for precise alignment of the resist patterning for the second-level trenches is avoided.

Abstract: In order to reduce alignment errors arising in the fabrication of semiconductor integrated circuits using electron beam lithography, enhanced registration marks--(i.e., registration marks that are more easily and accurately detectable by the electron beam)--are formed at the edges of oxide layers, located at the surface of a silicon body, by means of forming metal silicide layers having edges coincident with the edges of the oxide layers. Advantageously, the enhancing of the registgration marks by forming the metal silicide is performed subsequent to any high temperature processing steps, whereby the integrity of the marks is maintained.