After the introduction of the ATHENA TM alignment sensor, advanced applications of the sensor data are becoming increasingly important to meet the tightening overlay specifications for future technology nodes. As part of the total overlay budget, the effects of different alignment strategies on overlay performance need to be investigated. Keeping in mind that such strategies are simple and easy to use, two developments are addressed in this paper: advanced alignment recipes and advanced mark designs.An alignment recipe defines which signals from the sensor are used to calculate the aligned position. By making advanced use of the available data, wafer alignment can be made more accurate and more robust to processing effects. It is shown that the new Smooth Color Dynamic alignment recipes exhibit good overlay performance on STI, Cu dual damascene and W-CMP / Al-PVD layers. Since Smooth Color Dynamic also takes away the choice of a particular color in the alignment recipe, it is the preferred alignment recipe for all product layers.The optimum design of an alignment mark depends on the process characteristics. As the process characteristics may vary over time, the optimum mark design can change accordingly. To cover a larger process range, multiple alignment mark designs are combined in a new multi-grating mark: the Versatile Scribeline Primary Mark (VSPM). By measuring all gratings during regular production, the optimum grating of a VSPM can be selected and aligned with a Smooth Color Dynamic alignment recipe. For CMP layers a further overlay improvement can be achieved if all gratings have comparable phase depths. By combining alignment signals from different gratings in a predictive alignment recipe, wafer-to-wafer variations due to CMP effects can be reduced.
Laser-ablation studies of highly-oriented thin films of the electon-doped infinite-layer copper-oxide compounds Sr 1 La CuO 2 are reported. We observe significant variations in film properties with substrate or buffer layer material. X-ray diffraction, atomic force microscopy (AFM), Rutherford back-scattering (RBS), and electrical resistivity were used to characterize the films. Films were deposited on strontium titanate (001) or on buffer layers of -phase copper oxides (Ln 2 CuO 4 with Ln = Pr, Nd, Sm), Sr 3 FeNb 2 O 9 , and La 1 8 Y 0 2 CuO 4 on SrTiO 3 (001). The in-plane lattice constants of such buffer layers ( = 0 390-0 400 nm) should provide the bond tension required for electron doping. Extremely flat, epitaxial buffer layers with X-ray rocking curves as narrow as 0.08 were obtained from stoichiometric targets of Ln 2 CuO 4 ; the other buffer layers yielded poor epitaxy. A linear dependence of infinite-layer -axis plane spacing on substrate or buffer-layer in-plane -axis lattice constant is observed.
We report laser-ablation studies of highly-oriented thin films of the electon-doped infinite-layer copper-oxide compounds Sri_,LaCuO2. The primary synthesis variables were substrate or buffer layer material, temperature, laser fluence, target-substrate distance, and oxygen pressure. The films were characterized by x-ray diffraction, atomic force microscopy (AFM), Rutherford back-scattering (RBS), and electrical resistivity. Films were deposited on strontium titanate (001) or on buffer layers ofT'-phase copper oxides, Ln2CuO4 (Ln = Pr, Sm) on SrTiO3 (001).The in-plane lattice constants of such T'-phase materials (a = 0.391-0.396 nm) could provide a structure more amenable to electron doping than strontium titanate (a = 0.390 nm). Extremely fiat buffer layers were obtained from stoichiometric targets of Sm2CuO4 and Pr2CuO4. However, ablation from stoichiometric infinite-layer targets onto buffer layers resulted in mixtures of infinite-layer and chain/ladder phases. Non-stoichiometric deposition was confirmed by RBS analysis. We thus utilized non-stoichiornetric targets to obtain single-phased infinite-layer films. The x-ray rocking curves of highly-oriented epitaxial infinite-layer films exhibited full-widths at half maximum as narrow as 0.05° . Infinite-layer films grown on T'-phase buffer layers exhibited lattice constants closer to those of the bulk superconductor than films grown directly on SrTiO3.
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