As the demand for smaller semiconductor features continues to increase, so too does the demand for optical-based semiconductor inspections systems capable of imaging such small features. One semiconductor processing technique developed to achieve the increased fabrication demands includes extreme ultraviolet (EUV) lithography. EUV lithographic integrated circuit (IC) fabrication involves the use of a reticle carrying a pattern mask to expose an integrated circuit into silicon wafers using EUV light, generate by a EUV source, such as discharge produced plasma source or a laser produced plasma source. In order to accommodate the corresponding demands on inspection technologies improved EUV spectral purity filters are required. Past EUV spectral purity filters include gas stream based filters, multi-layered structures disposed on mesh-like grids, pellicles disposed on mesh-like grids, and diffractive grating based filters. Each of these types of EUV spectral purity filters carries along with it a number of disadvantages, such as chemical contamination, difficulty of implementation, and lack of transmission efficiency. It is therefore desirable to produce a spectral purity filter which overcomes the deficiencies identified in previous spectral purity filters.
USPTO Backgrounds
USPTO Backgrounds