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The perovskites PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 were synthesized at high temperatures (1000°C) and high pressures (4 – 6 GPa). The crystal and magnetic structures were determined using powder neutron diffraction. Quenched PbFeO2F has the cubic perovskite-type, Pm3m, structure in which the Pb ion shifts from ideal A-site along the directions, which is in good accordance with a previous report. The magnetic structure is antiferromagnetic G-type with propagation vector k = (1/2 1/2 1/2) and an Fe3+ ordered moment of 3.83 μB at 283K. The Néel temperature is 655(5) K. Annealed PbFeO2F has a tetragonal perovskite-type structure at room temperature and transforms reversibly from tetragonal to cubic at approximately 470 K. A superlattice with dimensions a × a × 5c is observed both in electron and x-ray diffraction. The solid solution 0.5PbFeO2F-0.5PbTiO3 belongs to the non-centrosymmetric space group P4mm. The magnetic structure is G-type antiferromagnetic and shows a weak ferromagnetic moment at 4 K. Consequently, 0.5PbFeO2F-0.5PbTiO3 is simultaneously ferroelectric and a weak ferromagnet at low temperature. The Néel temperature is 450 K but the temperature dependence of the ordered Fe moment is anomalous.

A novel fabrication technique for submicrometer trench isolation is proposed. This features a phosphorus-doped polysilicon field shield filled into the trench and a thick isolation oxide formed on polysilicon by impurity-enhanced oxidation (IEO). Due to the oxide entirely covering the trench shoulder by a self-aligned process, the proposed structure has notable merits: (i) the anomalous hump current in Id-Vg subthreshold characteristics is suppressed even in a narrow-channel transistor and (ii) the proposed structure provides less susceptibility to crystal defect generation. These can facilitate fabrication of controllable devices. In addition, a deeply implanted channel stopper yields a low parasitic capacitance for fast device operation and excellent isolation performance characteristics such as low field penetration and low punch-through current. These are attributed to the effect of the electric field shield.

Highly selective etching of Si3N4 to SiOC film has been studied, using dual frequency superimposed (DFS) rf capacitively coupled plasma, which controlled the self-bias voltage (-V dc) independently of electron density (N e). The SiOC etch rate was effectively suppressed by fluorocarbon polymer deposition, which was controlled by the additive H2 gas flow rate ratio and carbon-to-silicon ratio of the SiOC film, without reduction in Si3N4 etching rate. Infinitely highly selective etching could be realized with a H2 gas flow rate ratio of above 50%. Stringent V dc control was required for line-and-space pattern etching in order to suppress the erosion of the SiOC pattern edge, even when a highly selective etching condition was used. The V dc range that was available for selective etching of Si3N4 to SiOC was as small as 150 V, which was approximately 50 V lower than that for selective etching of SiOC to Si3N. However, a much lower -V dc, such as 100 V, caused excess deposition and taper etching. It was also found that lower N e, which was controlled by a 100 MHz rf power, was required to suppress the excess deposition.

A dual-frequency superimposed (DFS) 100 MHz and 3.2 MHz rf capacitive-coupled plasma etch process for sub-90 nm devices has been developed. The electron density of DFS reactive ion etching (RIE) plasma at 40 mTorr was controlled from 4.0×1010 to 3.6×1011 cm-3 by adjusting the 100 MHz rf power, and the self-bias voltage (-V dc) was controlled from 20 to 760 V by adjusting the superimposed 3.2 MHz rf power. DFS RIE demonstrated independent control of electron density and self-bias voltage in a wide range. In the damascene etch process of SiOC film using Si3N4 as an etch mask, it was found that mask edge erosion is dependent on ion energy regardless of the selectivity of SiOC to Si3N4. DFS RIE offers the most suitable process for damascene etching of SiOC, which requires precise ion energy control.