Phase shift mask used in photolithography for integrated circuit fabrication comprises support coated in part with a pattern and having uncoated ion-implanted and non-ion-implanted regions

Phase shift mask comprises a support (1) transparent to light radiation, a pattern (2) coating that absorbs light radiation, and an uncoated part of the support comprising regions (5, 6) having different chemical compositions and providing optically different paths for two light beams, resulting in a phase shift of 180 degrees between the beams after passage through the support. Preferred Features: The chemical composition of regions (5) of the support (1) is that of the support modified by an implanted chemical species, and the chemical composition of regions (6) of the support (1) is the same as that of the support. The support is preferably SiO2 and the introduced chemical species is Ti or N. An Independent claim is given for a process for fabricating a phase-shift mask for photolithography. L'invention concerne un masque de lithographie à décalage de phase, comprenant un support (1) transparent à une lumière d'insolation et recouvert d'un motif (2) en matériau absorbant la lumière d'insolation, le motif (2) laissant découverte au moins une partie du support transparent. La partie du support transparent comprend des zones (5, 6) présentant aux deux faisceaux lumineux des compositions chimiques différentes fournissant aux faisceaux des chemins optiques différents d'où il résulte, après traversée du support, un décalage de phase de 180degre.