A colony of Wistar rats with a hereditary defect in L-ascorbic acid-synthesizing ability was established. This rat, like primates and guinea pigs, lacks L-gulonolactone oxidase (EC 1.1.3.8) which catalyzes the last step of L-ascorbic acid biosynthesis. When L-ascorbic acid was added to their drinking water, the rats grew almost normally and were fertile. These mutant rats should be useful not only for nutritional and pharmacological studies on vitamin C, but also for genetic studies on the lack of this enzyme.

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200-mm and 300-mm device wafers were successfully thinned down to less than 10-µm. A 200-nm non-crystalline layer remaining after the high-rate Back Grind process was partially removed down to 50-nm by Ultra Poligrind process, or was completely removed with either Chemical Mechanical Planarization or Dry Polish. For FRAM device wafers thinned down to 9-µm, switching charge showed no change by the thinning process. CMOS logic device wafers thinned to 7-µm indicated neither change in I on current nor junction leakage current. Thinning such wafers to <10-µm will allow for lower aspect ratio less than 4 of Through-Silicon-Via (TSV) in a via-last process.

Many observations of stress-induced voids beneath vias in wide Cu lines have been performed to analyze stress migration phenomena. Most of the voids that caused fatal failures of circuits accompanied grain boundaries in the lower lines. Finite element method calculations were performed to obtain the stress distribution around a via sandwiched between wide upper and lower lines. Based on these results, a void growth model for the Cu stress migration phenomena has been proposed by applying the Hull and Rimmer theory. This model takes two diffusion paths, such as a grain boundary and a barrier/Cu interface, into consideration. Compared with experimental results, the proposed model successfully explained the mean time to failure dependence on the temperature and geometrical parameters of Cu interconnects.