Method and apparatus for analyzing a group of photolithographic masks

A method for analyzing a group of at least two photolithographic masks, comprising:

• recording a first aerial image of a first one of the two photolithographic masks;
• recording a second aerial image of a second one of the two photolithographic masks;
• digitizing the first and second aerial images;
• storing the first aerial images in a data structure;
• storing the second aerial images in a data structure;
• modifying the data of the first aerial image by using a photoresist simulation after recording, and
• generating a combination image by modifying the data of the second aerial image by using the photoresist simulation, taking into consideration the modified data of the first aerial image;
• wherein modifying the data of the first and second aerial images comprises subjecting the data of each of the first and the second aerial images to folding with a Gaussian function in a first step during photoresist simulation and to a threshold function in a second step, so that the modified data correspond to a photoresist image on the layer of the wafer.

Apparatus for analyzing a group of at least two masks for photolithography, wherein each of the masks comprises a substructure of a total structure, which is to be introduced in a layer of a wafer in the lithographic process by introducing the substructures in sequence in the layer of the wafer, said apparatus comprising:

• a device for recording aerial images of the masks;
• and an evaluating unit;
• wherein said device for recording aerial images of the masks records, digitizes and stores in a data structure a first aerial image of a first one of the at least two masks and records, digitizes and stores in a data structure a second aerial image of a second one of the at least two masks, and the first and second aerial images are recorded with different illumination settings, and
• the evaluating unit generates a combination image from the data of the aerial images of the masks by adding the data of the first and second aerial images pixel by pixel, and represents and/or evaluates said combination image, and
• wherein the evaluating unit comprises a photoresist simulator that modifies the data of the combination image by photoresist simulation,
• wherein the data of the combination image are subjected to folding with a Gaussian function in a first step and to a threshold function in a second step, so that the modified data correspond to a developed photoresist image on the layer of the wafer.