We demonstrate significantly improved thermal stability of the amorphous phase for hafnium-based gate dielectrics through the controlled addition of Al2O3. The (HfO2)x(Al2O3)1−x films, deposited using atomic layer deposition, exhibit excellent control over a wide range of composition by a suitable choice of the ratio between the Al and Hf precursor pulses. By this method, extremely predictable hafnium aluminate compositions are obtained, with Hf cation fractions ranging from 20% up to 100%, as measured by medium energy ion scattering. Using x-ray diffraction, we show that (HfO2)x(Al2O3)1−x films with Hf:Al∼3:1 (25% Al) remain amorphous up to 900 °C, while films with Hf:Al∼1:3 (75% Al) remain amorphous after a 1050 °C spike anneal.

We report the effects of annealing on the morphology and crystallization kinetics for the high-gate dielectric replacement candidate hafnium oxide (HfO 2 ). HfO 2 films were grown by atomic layer deposition ͑ALD͒ on thermal and chemical SiO 2 underlayers. High-sensitivity x-ray diffractometry shows that the as-deposited ALD HfO 2 films on thermal oxide are polycrystalline, containing both monoclinic and either tetragonal or orthorhombic phases with an average grain size of ϳ8.0 nm. Transmission electron microscopy shows a columnar grain structure. The monoclinic phase predominates as the annealing temperature and time increase, with the grain size reaching ϳ11.0 nm after annealing at 900°C for 24 h. The crystallized fraction of the film has a strong dependence on annealing temperature but not annealing time, indicating thermally activated grain growth. As-deposited ALD HfO 2 films on chemical oxide underlayers are amorphous, but show strong signatures of ordering at a subnanometer level in Z-contrast scanning transmission electron microscopy and fluctuation electron microscopy. These films show the same crystallization kinetics as the films on thermal oxide upon annealing.

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This paper reports a silicon MEMS vaporizing liquid microthruster (VLM) with an internal p-diffused microheater. The device fabrication and testing have been briefly described. The VLM consisting of two micromachined, bonded silicon chips produces thrusts in the range of 5 µN to 120 µN with a heater power of 1 W to 2.4 W at a water flow rate of 1.6 µl s −1 using an exit nozzle of throat size 30 µm × 30 µm. A maximum thrust of 120 µN was produced with a heater power of 2 W at a water flow rate of 0.7 µl s −1 with exit nozzle of throat size 50 µm × 50 µm. The measurement has been carried out using a sensitive cantilever and a laser based lamp-and-scale arrangement. The internal microheater is expected to yield a higher efficiency compared with the external microheater.

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