1. A method for fabricating integrated circuit devices comprising a plurality of layers, the method comprising: producing a group of one or more multi-layer masks (MLMs) for a first subset of the plurality of layers, each MLM including a plurality of different images for different layers; producing a first group of one or more production-ready masks for a second subset of the plurality of layers, each production-ready mask including a plurality of similar images; performing a pilot production using a combination of the MLMs and the production-ready masks; after the pilot production, producing a second group of one or more production-ready masks for the first subset of the plurality of layers; and fabricating the integrated circuit devices using the first and second groups of production-ready masks.