Ultraviolet-induced densification in fused silica is investigated using birefringence measurements to detect compaction-induced strain. This technique is capable of measuring compaction in the 10 parts per billion range in cm-sized specimens. A universal relation describing ultraviolet-induced compaction is discovered in which, using the total energy absorbed from two-photon absorption as the dose parameter, density changes equal a material dependent constant times the dose parameter to a power of about 0.65. This dose dependence is consistent with past compaction studies using electron beam and gamma radiation. Moreover, the density change per ionization “event” is found to be consistent for all radiation types. By comparing density measurements to refractive index change measurements found with interferometry, polarizability changes from ultraviolet-induced densification are extracted and compared with previous results using other radiation sources and inelastic densification methods.
Novel RET-Pixelated Phase Mask (PPM) is proposed as a novel Resolution Enhancement Technique (RET). PPM is made of pixels of various phases with lateral dimensions significantly smaller than the illuminating radiation wavelength. Such PPM with a singular choice of pixel dimensions acts as a mask with variable phase and transmission due to radiation scattering and attenuation on pixel features with the effective intensity and phase modulated by the pixel layout. Key properties of the pixelated phase masks, the steps for their practical realization, and the benefits to random logic products discussed. Wafer patterning performance and comparative functional yield results obtained for a 65nm node microprocessor patterned with PPM, as well as current PPM limitations are also presented.
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