Removal of sub-100 nm particles from substrates such as wafers and photo masks is an essential requirement in semiconductor, microelectronics, and nanotechnology applications. The proposed laser-induced plasma (LIP) based approach is an effective technique for removal of sub-100 nm particles, as the minimum tolerable particle on the substrates shrinks to sub-100 nm levels with each technological node. In the current study, our progress in sub-100 nm particle removal is reviewed, and the results of the kinetic theory simulations conducted to understand the dynamics of the gas molecule-nanoparticle interactions excited by the shock front are discussed. It is shown from the simulations and experiments that particles as small as sub-100 nm can be successfully detached. To explain possible mechanisms for the nanoparticle detachment in nanoscale, the concepts of rolling resistance moment and rocking motion are utilized as novel detachment mechanisms. The pressure experiments illustrate that the peak pressure levels achieved with the LIP shock wave fields are below damage thresholds of most substrate materials. The potential of the proposed approach as a practical noncontact, dry, fast, and damage-free method for removal of sub-100 nm particles is discussed.
Mitigation of pit-type defects proves to be a major hurdle facing the production of a defect-free mask blank for EUV lithography. Recent efforts have been directed toward substrate smoothing methods during deposition. The angle of incidence of the substrate is known to have a significant effect on the growth of defects during deposition. It has been shown that shadowing effects for bump-type defects are reduced when depositing Mo/Si films at near-normal incidence, resulting in a Gaussian growth profile in which the height and volume of the defect are minimized. Conversely, operating at off-normal incidence reduces shadowing of pit-type defects. When altering the angle of incidence of the substrate, the target angle must be changed to maintain uniformity. The resulting mask blank must also meet surface roughness specifications post-deposition while maintaining a low defect density. In this study, various substrate angle and target angle combinations were investigated within the Veeco Nexus Low Defect Density tool at SEMATECH to find optimum in situ pit smoothing conditions using ion beam deposition on both quartz and low thermal expansion material (LTEM) substrates. The possible substrate-target angle combinations are limited by the design of the current deposition tool; therefore, a phase space has been mapped out to determine uniform and non-uniform regions. Other deposition parameters including operating pressure and working gas composition were also explored. After deposition, EUV reflectrometry measurements were taken to evaluate uniformity in the wavelength; surface roughness, change in pit depth, change in full width at half maximum, and pit smoothing power were determined using atomic force microscopy (AFM); transmission electron microscopy (TEM) was used to study the effect of film disruption through the multilayer; and the printability of smoothed pits will be measure actinically using SEMATECH's AIT tool.Preliminary results show that positive values for substrate angles in the uniform region tend to give a high surface roughness after multilayer deposition; however, the combinations with negative substrate angles show promising results. Substrate angles with lower values resulted in better smoothing than the higher substrate angles. AFM results confirmed that pit smoothing power at lower substrate angles is greater than under the standard deposition conditions employed by the tool. Lower chamber pressure was proven to increase the smoothing power of pit-type defects during deposition. Preliminary TEM cross-section data confirmed the smoothing results obtained by AFM analysis. The use of Ne and Xe as working gases is also under review. Extensive AFM analysis, TEM cross-sections, and printability data will be presented.
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