Photomask structure with an etch stop layer that enables repairs of detected defects therein and extreme ultraviolet(EUV) photolithograpy methods using the photomask structure

A method comprising:

• providing a photomask structure comprising:
• a multilayer stack on a substrate, the multilayer stack comprising:
• multiple first pairs of layers;
• and,
• a second pair of layers that is different from the first pairs of layers,
• wherein the second pair of layers is stacked between two first pairs of layers,
• wherein each pair of the first pairs of layers and the second pair of layers comprises a first layer and a second layer on the first layer, the first layer having a higher atomic number than the second layer,
• wherein the first layer of all of the first pairs of layers comprises a first material, and,
• wherein the first layer in the second pair of layers comprises a different material than the first material;
• a protective layer on the multilayer stack;
• and
• a light absorber layer on the protective layer;
• forming multiple openings that extend vertically through the light absorber layer to the protective layer;
• inspecting the photomask structure to detect any defects adjacent to exposed surfaces in the openings;
• and,
• in response to a defect being detected adjacent an exposed surface in an opening, removing the defect by extending the opening to the first layer of the second pair of layers.

A method comprising:

• providing a photomask structure comprising:
• a multilayer stack on a substrate, the multilayer stack comprising:
• multiple first pairs of layers;
• and,
• a second pair of layers that is different from the first pairs of layers,
• wherein the second pairs of layers is stacked between two first pairs of layers,
• wherein each pair of the first pairs of layers and the second pairs of layers comprises a first layer and a second layer on the first layer, the first layer having a higher atomic number than the second layer,
• wherein the first layer of all of the first pairs of layers comprises a first material, and
• wherein the first layer of the second pair of layers comprises a different material than the first material;
• a protective layer on the multilayer stack;
• and
• a light absorber layer on the protective layer;
• forming multiple openings that extend vertically through the light absorber layer to the protective layer;
• inspecting the photomask structure to detect any defects adjacent to exposed surfaces of the openings;
• and,
• in response to a defect being detected adjacent any exposed surface in any opening, removing the defect by extending all the openings to the first layer of the second pair of layers.