Next generation lithography (NGL) concept application in x-ray lithography

The term Next Generation Lithography (NGL) is defined as a Departure from the Classical Concept of Replication Fidelity, thus widening the term Post Optical Lithography. It addresses the necessity to form mask features different from those to be produced in the resist. The term NGL is used to address the x- ray, e-beam projection and direct-write lithographies. It is also applicable to the advanced optical lithography employing the optical proximity correction (OPC) as a part of reticle enhancement techniques (RET) based on auxiliary features, phase shifters, complementary mask and multiple exposures. Following the basic concept of NGL and applying it to proximity x-ray lithography, we are developing a technique to form features on a wafer substantially smaller than those on the mask. This is achieved by exposure and development process and lithographic bias optimization, thus providing local demagnification-by-bias. Analysis shows that features as small as 25 nm can be formed at 10 - 15 micrometer mask/wafer gaps. This approach not only solves difficulties of 1X mask generation, but also offers an advantage of relaxed mask CD control.