Two-exposure phase shift photolithography with improved inter-feature separation

Abstract

A method of double-exposure photolithography of a semiconductor wafer in the manufacture of integrated circuits is disclosed. The two exposures of the same positive photoresist layer are carried out using a binary photomask (25) having chrome regions (22) that define non-critical dimension features (6c) and also serve as protection for phase shift exposure of critical dimension features (6g). The phase shift photomask (23) includes apertures 200, 20π that expose the sides of the critical dimension feature (6g) with opposite phase light. The phase shift photomask (23) also includes an additional aperture (30) for double exposure of a region exposed by the binary photomask, for example as between a non-critical dimension feature (6c) and the end of a critical dimension feature (6g). According to another disclosed feature, orthogonal overlapping chrome regions (34, 36), each of critical dimension width (w34, w36), are provided on the binary and phase shift photomasks (35, 33), to define a feature by way of their intersection.

Dependencies are inferred from the claim text.