Step-and-repeat projection

Deep-UV source brightness is another issue, because the power output of a 1-kW mercury-xenon lamp in the 200-250-nm range is only 30-40 mW. For this reason, excimer lasers (such as KrCl and KrF), which can deliver several watts of power at the required wavelengths, are being considered as alternatives (7). In fact, a deep-UV step-and-repeat projection system with an all-quartz lens and a KrF excimer laser with an output at 248 nm has been reported (8). Even the laser-based systems require resists with a sensitivity of 30-70 mj/cm2. 

Bouwer, G. Bouwhuis, H. Van Heek, and S. Wittkoek, The sihcon repeater, Philips Tech. Rev. 37(11/12), 330 333 S. Wittkoek, Optical aspects of the silicon repeater, Philips Tech. Rev. 41, 268 (1983/84) H. Binder and M. Lacomhat, Step and repeat projection printing for VLSI circuit fahrication, IEEE Trans. Electron Dev. ED-26(4), 698 704 (1979) J. Wilcyncski, Optical step and repeat camera with dark field automatic alignment, J. Vac. Sci. Technol. 16,1929 1933 (1979). 

Pol et al. 10) developed an excimer laser-based DUV projection system by modifying a commercial step-and-repeat exposure tool (GCA model 4800 DSW). This system is equipped with a KrF (248 nm) excimer laser, an all-... 

For the next generation of submicrometer ground rules, a fourfold reduction in alignment and other errors will be necessary. Almost every type of mask aligner—contact/proximity, projection scanner, and step and repeat—is used for some of the lithography steps in the fabrication of state of the art integrated circuitry today. For a detailed description of mask alignment equipment we refer to the literature [2, 3]. 

Whereas in a micro plant only the most important process steps and some of the recycle loops are tested, in the miniplant the complete process with all recycle loops is executed and processed continuously for several weeks. For environmental and economic reasons, solvents and unconverted reactants are recycled. Here, it is especially important to find out if small impurities below the detection limit will possibly accumulate or form deposits. To minimize the up-scaling risk for the final production plant, often a pilot plant is the next scale-up step. Now the final product is produced and often first samples are sent to customers. Every step in this scale-up procedure is followed by an evaluation step defined in a number of evaluation studies, which assist in the decision as to whether the project has to be terminated, repeated or further processed. 

Figure 6.34. a) Two-dimensional crystal. Each circle represents a growth unit of KosseVs repeatable step, b) and (c) Projection of a three-dimensional crystal along a PBC. Each circle represents a PBC. An F-face results when neighbouring PBCs are linked together by strong bonds, otherwise an S-face develops... 

Repeat from steps 1 to 6 for other assessment tools like quiz, lab, and mini project. 

If X is not detected as an outlier then it is projected onto an affine subspace which is computed using a Weighted PCA algorithm. The outlier detection and affine subspace projection steps are repeated until the algorithm converges. 

The prediction step for PLS is also slightly different than for PCR. It is also done on a rank-by-rank basis using pairs of special and concentration factors. For each component, the projection of the unknown spectrum onto the first spectral factor is scaled by a response coefficient to become a corresponding projection on the first concentration factor. This yields the contribution to the total concentration for that component that is captured by the first pair of spectral and concentration factors. We then repeat the process for the second pair of factors, adding its concentration contribution to the contribution from the first pair of factors. We continue summing the contributions from each successive factor pair until all of the factors in the basis space have been used. 

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