Abstract: This invention involves an optical system in which optical radiation containing a wavelength .lambda. is directed onto a patterned mask, in order to form an image feature on a photoresist layer located on the image plane of the system. The patterned mask has a main object feature, which has the form of the image feature. The object feature has a portion whose width is everywhere less than (1.5).lambda./NA, where NA is the numerical aperture of the image side of the system. An assist feature whose width is everywhere less than (0.5).lambda./NA is located on the mask in a neighborhood of the portion of the main object feature. Advantageously, the optical radiation is directed through an annular aperture ("off-axis illumination") in an opaque screen and through a collimating lens onto the mask. In one exemplary situation, the assist feature is located outside the main object feature and has a distance of closest approach to the main object feature that is everywhere equal to less than .lambda./NA.

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 having two or more self-aligned phase-shifting regions is fabricated by a sequence of etchings of the phase-shifting mask using a protective resist layer having three or more regions that have been subjected to mutually different doses (including possibly zero) of actinic radiation-such as electron beam, ion beam, or photon beam radiation. A self-aligned opaque region can be supplied by carbonization of remaining resist material.

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.