The stripping method of high-dose ion-implanted resist layers was studied on the basis of the chemical structure of carbonized layers formed by ion implantation and that of residues remaining on the wafer surface after O2 plasma ashing. The chemical structure of the carbonized layer was observed with solid NMR and that of residues was analyzed with XPS. A decrease in the etching rate of the high-dose ion-implanted resist was caused by carbonization of polymers of the resist. Residues were mainly formed during O2 plasma ashing by chemical reaction between oxygen and implanted species, i.e., the main component of residues was oxide of the implanted species. On the basis of these results, to remove the high dose ion implanted resist without damage, we developed a two-step ashing process which was composed of H2 RIE and downstream ashing, and achieved the purpose.
We report atomic resolution imaging of Cu-planar precipitates in aged Al-Cu alloys, known as Guinier-Preston (GP) zones, by high-angle annular detector dark-field scanning transmission electron microscopy. Single layered GP-I zones as small as 2 nm in length were resolved among densely populated GP-I zones, whereas double layered GP zones were clearly identified. The images of GP-II zones showed not only the commonly accepted structure, in which single Cu layers are separated by three Al layers, but also a variant, in which double Cu layers are separated by a single Al layer.
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