This paper investigates the CD correction methods to obtain better across-wafer CD uniformity (CDU) after etching for logic devices which have various types of patterns. CD optimization methods are evaluated for contact holes with a diameter of 46 nm after etching. CD optimization methods with PEB temperature and exposure-dose mapping on a wafer at a lithography step are examined in detail. Simulation study using a full physical resist model is done to analyze the detailed effects of each optimization method. The results of the simulation show that better optical and chemical image gives better CD controllability through pitches for etching CD correction. Simulation results also show that the pitch with a middle CD sensitivity makes the CD correction sensitivity difference minimum through pitches. From the simulation, the sensitivity behaviors are found to be relatively similar for both of PEB temperature and dose control. Rather than sensitivity behavior differences between the two CD control methods, the intra-wafer spatial resolution of the CD control methods is found to be an important factor for the strategy of CD optimization. Finally, by contact-layer CD optimization, across-wafer CDUs are improved by more than 50%. The variation in the electric resistance of contacts is also improved by more than 20%. As a result, the proposed method is found to be effective for CDU improvement of through-pitch contact-hole patterning for advanced logic device.
Shewanella species are widely distributed in sea, brackish, and fresh water areas, growing psychrophilically or mesophilically, and piezophilically or piezo-sensitively. Here, membrane-bound 5'-nucleotidases (NTases) from deep-sea Shewanella violacea and brackish water Shewanella amazonensis were examined from the aspect of NaCl tolerance to gain an insight into protein stability against salt. Both NTases were single polypeptides with molecular masses of ~59 kDa, as determined on mass spectroscopy. They similarly required 10 mM MgCl for their activities, and they exhibited the same pH dependency and substrate specificity for 5'-nucleotides. However, S. violacea 5'-nucleotidase (SVNTase) was active enough in the presence of 2.5 M NaCl, whereas S. amazonensis 5'-nucleotidase (SANTase) exhibited significantly reduced activity with the same concentration of the salt. Although SVNTase and SANTase exhibited high sequence identity (69.7%), differences in the ratio of acidic to basic amino acid residues and the number of potential salt bridges maybe being responsible for the difference in the protein stability against salt. 5'-Nucleotidases from these Shewanella species will provide useful information regarding NaCl tolerance, which may be fundamental for understanding bacterial adaptation to growth environments.
Cytochrome c' (SACP) from mesophilic Shewanella amazonensis, growing optimally at 37 °C, was thermally more stable than cytochrome c' (AVCP) from mesophilic Allochromatium vinosum, growing optimally at 25 °C. In contrast, SACP was less stable than cytochrome c' (PHCP) from thermophilic Hydrogenophilus thermoluteolus, growing optimally at 52 °C. Although only 28% of the SACP amino acid sequence was identical to those of AVCP and PHCP, the latter two being 55% identical, the overall main chain structures of the three cytochromes c' were similar, and SACP exhibited thermal stability intermediate between those of AVCP and PHCP. For these three proteins, the higher the stability is, the lesser the number of Gly residues in the putative α-helical regions is. Cytochromes c' including the present three are suitable for examining the protein stabilization mechanisms, because they are structurally similar and available from environments with a wide range of temperatures.
We investigated the magnetic interaction between antiferromagnetic, magnetoelectric Cr2O3 film and ferromagnetic La0.7Sr0.3MnO3 film, which shows colossal magneto-resistance. Magnetic properties and structural analyses revealed that a decrease in the thickness of La0.7Sr0.3MnO3 films gives rise to a change in magnetic anisotropy from perpendicular to in-plane. The exchange interaction between Cr2O3 and La0.7Sr0.3MnO3 also changed depending on the magnetic properties of La0.7Sr0.3MnO3. This suggests that the crystallographical control and the selection of a suitable thickness of La0.7Sr0.3MnO3 are important to obtain an exchange interaction in the magnetic hetero system using colossal magneto-resistance material.
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