H ion implantation into crystalline Si is known to result in the precipitation of planar defects in the form of platelets. Hydrogen-platelet formation is critical to the process that allows controlled cleavage of Si along the plane of the platelets and subsequent transfer and integration of thinly sliced Si with other substrates. Here we show that H-platelet formation is controlled by the depth of the radiation-induced damage and then develop a model that considers the influence of stress to correctly predict platelet orientation and the depth at which platelet nucleation density is a maximum.
HfO 2 films have been grown with two atomic layer deposition (ALD) chemistries: (a) tetrakis(ethylmethylamino)hafnium (TEMAHf)+O3 and (b) HfCl4+H2O. The resulting films were studied as a function of ALD cycle number on Si(100) surfaces prepared with chemical oxide, HF last, and NH3 annealing. TEMAHf+O3 growth is independent of surface preparation, while HfCl4+H2O shows a surface dependence. Rutherford backscattering shows that HfCl4+H2O coverage per cycle is l3% of a monolayer on chemical oxide while TEMAHf+O3 coverage per cycle is 23% of a monolayer independent of surface. Low energy ion scattering, x-ray reflectivity, and x-ray photoelectron spectroscopy were used to understand film continuity, density, and chemical bonding. TEMAHf+O3 ALD shows continuous films, density >9g∕cm3, and bulk Hf–O bonding after 15 cycles [physical thickness (Tphys)=1.2±0.2nm] even on H-terminated Si(100). Conversely, on H-terminated Si(100), HfCl4+H2O requires 50 cycles (Tphys∼3nm) for continuous films and bulk Hf–O bonding. TEMAHf+O3 ALD was implemented in HfO2∕TiN transistor gate stacks, over the range 1.2nm⩽Tphys⩽3.3nm. Electrical results are consistent with material analysis suggesting that at Tphys=1.2nm HfO2 properties begin to deviate from thick film properties. At Tphys=1.2nm, electrical thickness scaling slows, gate current density begins to deviate from scaling trendlines, and no hard dielectric breakdown occurs. Most importantly, n-channel transistors show improvement in peak and high field electron mobility as Tphys scales from 3.3 to 1.2nm. This improvement may be attributed to reduced charge trapping and Coulomb scattering in thinner films. Scaled HfO2 enables 1nm equivalent oxide thickness and 82% of universal SiO2 mobility.
Work on silicon crystal quality improvement and defect control has been carried out on lab-scale seeded growth ingots allowing wafers with controlled grain orientations. Both <111> and <100> monocrystalline-like ingots were produced using a combination of quartz rod dipping and a modulated conductive heat extraction system, made in-house, in a directional solidification system. Two mono-like wafer morphology types have been produced. Their structural and electrical properties are presented in detail.
Direct measurements of the mosaic twist in GaN films have been carried out using grazing incidence in-plane x-ray diffraction (GIIXD) on a commercially-available diffractometer in the laboratory. The GaN 11.0 in-plane diffraction was measured to obtain the twist mosaic directly, while the GaN 00.2 surface-symmetric rocking curve was used to measure the tilt mosaic. For GaN growth temperatures between 1002°C and 1062°C, the tilt mosaic decreased monotonically with increased temperature, while the twist mosaic showed a minimum at 1022°C, a temperature previously selected empirically as giving the best device yield and optimum optical domain size. A substantial fall in twist and tilt mosaic was observed on annealing of the nucleation layers, the lowest twist mosaic occurring at an annealing temperature of 1002°C, where it was almost equal to the tilt mosaic. A weak minimum in the tilt mosaic variation was seen at an annealing temperature of 1023°C.
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