Ultra-Thin Uncooled Integrable-on-Chip Detector to Measure Wide Infrared Radiation Residue in Lithography Exposure and Metrology Inspection Tools

In modern nano-scale lithography, an essential role of the source, the illumination, and projection lenses is to deliver the precise amount of energy at a specific wavelength to the photoresist deposited on a wafer surface during exposure. Unfortunately, the source of the most advanced lithography processes may produce unwanted infrared components passing through the illumination and projection lenses and reaching the wafer surface. These infrared residues can cause local heating resulting in deformation of the optical elements and the exposed wafer, thus causing deterioration of the image quality. Some infrared spectrum components are in the band from 2 µm to 12 µm. An infrared detector that can measure only these spectral components of the exposure beam, without being affected by the much more powerful exposure spectral component, is helpful for optics diagnostic purposes and improving imaging quality. In this paper, an ultra-thin uncooled integrable-on-chip linear array infrared detector to measure the band of 2-12 µm infrared radiation is designed and fabricated based on the photovoltaic multiple junction heterostructure from VIGO Photonics, made of a HgCdTe narrow bandgap semiconductor. Features such as zero bias, low noise, and fast response, together with a wide active window, make the detector unique for use in the mid-infrared band. Besides lithography applications, the new detector can be useful in testing, inspection, and equipment using infrared sources such as: He-Ne lasers (0.6 to 4 µm), STEAM lasers (2 to 200 µm), CO2 lasers (5 to 11 µm), InGaAsP lasers (0.8 to 3 µm), and PbSnTe (3 to 20 µm) and PbSnSe (7 to 40 µm) lasers.