Joseph M. Karasinski

Molecular-beam-deposited yttrium-oxide dielectrics in aluminum-gated metal–oxide–semiconductor field-effect transistors: Effective electron mobility

We report on high effective mobilities in yttrium-oxide-based n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) with aluminum gates. The yttrium oxide was grown in ultrahigh vacuum using a reactive atomic-beam-deposition system. Medium-energy ion-scattering studies indicate an oxide with an approximate composition of Y2O3 on top of a thin layer of interfacial SiO2. The thickness of this interfacial oxide as well as the effective mobility are found to be dependent on the postgrowth anneal conditions. Optimum conditions result in mobilities approaching that of SiO2-based MOSFETs at higher fields with peak mobilities at approximately 210 cm2/V s.

Ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on surface-nitrided Ge

We have studied ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on Ge grown by ultrahigh vacuum-reactive atomic-beam deposition and ultraviolet ozone oxidation. Al/sub 2/O/sub 3/-Ge gate stack had a t/sub eq//spl sim/23 /spl Aring/, and three orders of magnitude lower leakage current compared to SiO/sub 2/. HfO/sub 2/-Ge allowed even greater scaling, achieving t/sub eq//spl sim/11 /spl Aring/ and six orders of magnitude lower leakage current compared to SiO/sub 2/. We have carried out a detailed study of cleaning conditions for the Ge wafer, dielectric deposition condition, and anneal conditions and their effect on the electrical properties of metal-gated dielectric-Ge capacitors. We show that surface nitridation is important in reducing hysteresis, interfacial layer formation and leakage current. However, surface nitridation also introduces positive trapped charges and/or dipoles at the interface, resulting in significant flatband voltage shifts, which are mitigated by post-deposition anneals.

Hall mobility in hafnium oxide based MOSFETs: charge effects

The Hall effect is used to measure the electron mobility in HfO/sub 2/ based n-channel field effect transistors with poly-Si gates. Large deviations between measured Hall and drift mobilities are explained by the presence of high concentrations of nonfixed charge (up to 4/spl times/10/sup 12/ cm/sup -2/). Simulated mobility curves show that the observed concentrations of fixed and nonfixed charge can estimate the measured mobility significantly better than if only the fixed charge concentration is used.

Ultrathin

We have studied ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on Ge grown by ultrahigh vacuum-reactive atomic-beam deposition and ultraviolet ozone oxidation. Al/sub 2/O/sub 3/-Ge gate stack had a t/sub eq//spl sim/23 /spl Aring/, and three orders of magnitude lower leakage current compared to SiO/sub 2/. HfO/sub 2/-Ge allowed even greater scaling, achieving t/sub eq//spl sim/11 /spl Aring/ and six orders of magnitude lower leakage current compared to SiO/sub 2/. We have carried out a detailed study of cleaning conditions for the Ge wafer, dielectric deposition condition, and anneal conditions and their effect on the electrical properties of metal-gated dielectric-Ge capacitors. We show that surface nitridation is important in reducing hysteresis, interfacial layer formation and leakage current. However, surface nitridation also introduces positive trapped charges and/or dipoles at the interface, resulting in significant flatband voltage shifts, which are mitigated by post-deposition anneals.

hbox Al_2hbox O_3

We report on the physical and electrical properties of AlN as grown by reactive-atomic-beam deposition under various growth and anneal conditions. The physical characterization shows that AlN grown on hydrogen terminated (HF-last) Si has a thin layer of Si3N4 at the interface while growth of AlN on SiO2 or Al2O3 suffers from nucleation problems. The AlN on HF-last Si, grown and annealed at 650 °C, shows high interfacial quality and four to five orders of magnitude lower leakage current as compared to SiO2. In contrast, poor interfacial properties and leakage current are reported for the AlN grown on SiO2 or Al2O3. The relative permittivity of the AlN is found to be close to 18 and the equivalent thickness of the interfacial layer is approximately 6 A. The effective electron mobility in Al-gated N-channel metal-oxide-silicon field-effect transistors with a 22 A thick AlN layer peaks at ∼130 cm2/V s. The relatively low mobility is attributed to a combination of high concentration of fixed charge (>5×1012 cm...

and

We have studied ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on Ge grown by ultrahigh vacuum-reactive atomic-beam deposition and ultraviolet ozone oxidation. Al/sub 2/O/sub 3/-Ge gate stack had a t/sub eq//spl sim/23 /spl Aring/, and three orders of magnitude lower leakage current compared to SiO/sub 2/. HfO/sub 2/-Ge allowed even greater scaling, achieving t/sub eq//spl sim/11 /spl Aring/ and six orders of magnitude lower leakage current compared to SiO/sub 2/. We have carried out a detailed study of cleaning conditions for the Ge wafer, dielectric deposition condition, and anneal conditions and their effect on the electrical properties of metal-gated dielectric-Ge capacitors. We show that surface nitridation is important in reducing hysteresis, interfacial layer formation and leakage current. However, surface nitridation also introduces positive trapped charges and/or dipoles at the interface, resulting in significant flatband voltage shifts, which are mitigated by post-deposition anneals.

hboxHfO_2

We demonstrate that Si layers overgrown on GaN/sapphire substrate structures can be transferred onto host substrates by using the technique of laser-induced metallization of GaN at the GaN/sapphire interface via the reaction GaN=Ga+1/2N2. This may allow the grafting of films of Si onto substrates such as glass or plastic for microelectronic applications. We examine the debonding mechanism and propose that it occurs due to pressures of the order of a few thousand atmospheres generated with the release of nitrogen from the GaN metallization reaction.