Yuan-Bin Chen

New Dielectric Material System of La(Mg1/2Ti1/2)O3-CaTiO3 at Microwave Frequencies

The dielectric characteristics and microstructures of xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics with B2O3 additive (0.25 wt%) prepared by the conventional solid-state method were investigated. Doping with B2O3 (0.25 wt%) effectively improves the densification and the dielectric characteristics of xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics. xLa(Mg1/2Ti1/2)O3–(1-x)CaTiO3 ceramics can be sintered at 1400°C because of the liquid phase effect of B2O3 addition observed by scanning electron microscopy. At 1450°C, 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 ceramics with 0.25 wt% B2O3 additive have a dielectric constant (er) of 43, a Q×f value of 24470 (at 8 GHz) and a temperature coefficient of resonant frequency (τf) of -8.94 ppm/°C. As the content of La(Mg1/2Ti1/2)O3 increases, the highest Q×f value of 38000 (GHz) for x=0.7 is achieved at the sintering temperature of 1475°C.

Microwave Dielectric Properties and Microstructures of 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 Ceramics with B2O3 Addition

La(Mg1/2Ti1/2)O3-based ceramics are prepared with a conventional solid-state route. With 50 mol % CaTiO3 addition, 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 ceramics with 0.25 wt % B2O3er value of ~ 42.92–43.38, Q ×f values of ~24000 (at 7 GHz) and τf values of ~-8.9 ppm/°C. However, the sintering temperature remains above 1400°C. Doping with B2O3 (up to 1 wt %) can effectively promote the densification and improve the dielectric properties of 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 ceramics. The effects of a B2O3 additive on the microstructures, phase formation and microwave dielectric properties of La(Mg1/2Ti1/2)O3–CaTiO3 ceramics system are investigated. The Q ×f value of B2O3–doped 0.5La(Mg1/2Ti1/2)O3–0.5CaTiO3 ceramics can be improved to 28000 (at 8 GHz) at 1400°C due to the liquid-phase effect. The microwave dielectric properties are found to strongly correlate with the sintering temperature as well as the amount of B2O3 added.

Improvement of thin-gate oxide integrity using photo-enhanced low-temperature nitridation

Abstract A photo-enhanced low-temperature nitridation process to improve the integrity of thin-gate oxide is described. With the aid of mercury UV light energy, the gate oxide can be nitrided thermally at 600°C. Measurements were made on a polycrystalline silicon (poly-Si)-gate MOS capacitor. Interface-state generation and charge-to-breakdown under high-field stress are significantly improved. The ability to resist r.f. (radio frequency) radiation damage in a plasma ambient is also improved. These results show that photo-enhanced low-temperature-nitrided thin-gate oxides are approaching high-temperature nitrided oxides in quality, and may be suitable as gate dielectrics in device applications.

Microwave Dielectric Properties and Microstructure of 0.85MgTiO3–0.15Ca0.6La0.8/3TiO3 Dielectric Ceramics with Added Sintering Aids

The effects of additive sintering aids on the microstructures and microwave dielectric properties of 0.85MgTiO3–0.15Ca0.6La0.8/3TiO3 ceramics were investigated. CuO was selected as a liquid phase sintering aid to lower the sintering temperature of 0.85MgTiO3–0.15Ca0.6La0.8/3TiO3 ceramics. With added CuO, the densification temperature of 0.85MgTiO3–0.15Ca0.6La0.8/3TiO3 can be effectively reduced from 1450 to 1160–1300°C. Low-level doping of CuO (0.5–5 wt %) significantly improves the density and dielectric properties of 0.85MgTiO3–0.15Ca0.6La0.8/3TiO3 ceramics. The quality factor Q×f was strongly dependent upon the amount of additives. Q×f values of 60000 and 20000 GHz could be obtained at 1160–1300°C with 0.5 and 5 wt % CuO added, respectively. Over all ranges of addition, the relative dielectric constants differed significantly and ranged from 23.2 to 26.1. The temperature coefficient varied from 0 to -3.7 ppm/°C.