Inspection system with enhanced contrast

#The present invention relates generally to an inspection system and an inspection method. More particularly, the present invention relates to an inspection system for and a method of inspecting a pattern on a reticle or photomask for defects and errors.

#Semiconductor fabrication techniques often utilize a mask or reticle. Radiation is provided through or reflected off the mask or reticle to form an image on a semiconductor wafer. The wafer is positioned to receive the radiation transmitted through or reflected off the mask or reticle. The image on the wafer corresponds to the pattern on the mask or reticle. The radiation can be light, such as ultraviolet light, vacuum ultraviolet (VUV) light, extreme ultraviolet light (EUV) and deep ultraviolet light. The radiation can also be x-ray radiation, e-beam radiation, etc.

#One advanced form of lithography is extreme ultraviolet (EUV) light lithography. A conventional EUV system (e.g., an optical reduction camera or stepper) utilizes an EUV radiation source, a first EUV lens assembly (e.g., a condenser lens), an EUV reticle, and a second EUV lens assembly (e.g., an objective lens). EUV radiation can be created at the EUV radiation source and projected onto the EUV reticle. The EUV reticle is typically a resonant-reflective medium including a pattern of absorbing material.

#The present invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements, and:

#FIG. 1 is a general schematic block diagram of an inspection system for inspecting a mask or reticle in accordance with an exemplary embodiment;

#FIG. 2 is a more detailed schematic cross-sectional view of the reticle illustrated in FIG. 1;

#With reference to FIG. 1, an inspection system 10 is configured to analyze the lithographic pattern (e.g., the absorber or reflector pattern) associated with a mask or reticle 18. Mask or reticle 18 can be any tool for use in integrated circuit (IC) lithographic equipment. System 10 advantageously achieves a higher contrast of an advanced lithographic pattern than possible with conventional inspection tools.

#System 10 can detect defects or errors associated with reticle 18. For example, system 10 can be utilized to determine if defects manifested in a variety of forms including foreign matter, dust, scratches, bubbles, striations, steps, or other improper structures are provided on reticle 18. In addition, system 10 allows mask or reticle 18 to be inspected to determine that the appropriate absorber pattern or reflective pattern has been provided on reticle 18. System 10 can ensure that critical dimensions on reticle 18 are within tolerances.

#Reticle 18 is preferably a lithographic tool for use in extreme ultraviolet (EUV) light lithography, wherein radiation having wavelengths less than 70 nm is utilized (most preferably, between 5 and 14 nm). For example, radiation or ultraviolet light at a wavelength of 13 nm can be reflected off reticle 18 to a semiconductor wafer coated with a photoresist. Alternatively, reticle 18 can be employed at other locations with respect to the EUV or advanced lithographic system.