TECHNICAL FIELD

The disclosure relates to photolithography and more particularly to photomasks and methods of manufacturing photomasks for photolithography.

BACKGROUND

As the semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, and lower costs, challenges from both fabrication and design issues become greater. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of processing and manufacturing ICs.

Photolithography operations are one of the key operations in the semiconductor manufacturing process. Photolithography techniques include ultraviolet lithography, deep ultraviolet lithography, and extreme ultraviolet lithography (EUVL). The photomask is an important component in photolithography operations. It is critical to fabricate and maintain photomasks free of resolvable defects. However, photomask fabrication techniques typically include electron beam lithography and etching operations. Electron beam lithography can generate particles during resist coating, development, and stripping operations. Etching operations can generate particles and etching residues. Particles and etching residues can cause defects in imaging when the mask is used if the particles and residues are not completely removed during a cleaning operation. In addition etched sidewalls of photomask patterns may also be sources of particles.

