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Atomic layer deposition (ALD) is used in applications where inorganic material layers with uniform thickness down to the nanometer range are required. For such thicknesses, the growth mode, defining how the material is arranged on the surface during the growth, is of critical importance. In this work, the growth mode of the zirconium tetrachloride/water and the trimethyl aluminum/water ALD process on hydrogen-terminated silicon was investigated by combining information on the total amount of material deposited with information on the surface fraction of the material. The total amount of material deposited was measured by Rutherford backscattering, x-ray fluorescence, and inductively coupled plasma–optical emission spectroscopy, and the surface fractions by low-energy ion scattering. Growth mode modeling was made assuming two-dimensional growth or random deposition (RD), with a “shower model” of RD recently developed for ALD. Experimental surface fractions of the ALD-grown zirconium oxide and aluminum oxide films were lower than the surface fractions calculated assuming RD, suggesting the occurrence of island growth. Island growth was confirmed with transmission electron microscopy (TEM) measurements, from which the island size and number of islands per unit surface area could also be estimated. The conclusion of island growth for the aluminum oxide deposition on hydrogen-terminated silicon contradicts earlier observations. In this work, physical aluminum oxide islands were observed in TEM after 15 ALD reaction cycles. Earlier, thicker aluminum oxide layers have been analyzed, where islands have not been observed because they have already coalesced to form a continuous film. The unreactivity of hydrogen-terminated silicon surface towards the ALD reactants, except for reactive defect areas, is proposed as the origin of island growth. Consequently, island growth can be regarded as “undesired surface-selective ALD.” [ABSTRACT FROM AUTHOR]

In this paper, the deep levels found by Deep-Level Transient Spectroscopy in Si-O superlattices (SLs) on n-type silicon are reported. Samples have been grown with one, two or five silicon-oxygen layers, separated by 3 nm of silicon. A Cr Schottky barrier (SB) is thermally evaporated on top of the SL. Similar as for p-type silicon, no deep levels have been found for a bias pulse in depletion, while a broad distribution of electron traps shows up when pulsing into forward bias. At the same time, these bands are absent in a zero SL reference sample. Similar as for the p-type results, the trap filling of the electron states exhibits a logarithmic capture. The possible origin of this slow filling will be discussed. [ABSTRACT FROM AUTHOR]

The presence of deep levels in a silicon-oxygen (Si-O) superlattice (SL) deposited on p-type silicon substrates has been investigated by deep-level transient spectroscopy (DLTS) on thermally evaporated Cr Schottky barriers (SBs). The SLs have been fabricated with different thicknesses of the silicon interlayers, formed by chemical vapor deposition. It is shown that a broad band of hole traps is present near the surface of the SB, which is associated with the SL. In addition, the activation energy corresponding with the peak maximum shifts to higher values with respect to the valence band and gives rise to a higher trap concentration with increasing silicon interlayer thickness. It is proposed that these states are associated with the structural defects found in similar SL structures, that is, with the epitaxial quality and not with the SiO bonds in the atomic layers. The change in the DLT-spectra with silicon thickness could be related with the transformation of the structural defects from small self-interstitial clusters to stacking faults. [ABSTRACT FROM AUTHOR]

Abstract: Band engineered Si/O superlattices are promising channel materials for ultimately scaled complementary metal oxide semiconductor devices. Theoretical calculations have indicated that insertion of O monolayers into Si lattice creates anisotropy in the Si band structure with an enhanced carrier mobility in the channel direction. However, the experimental demonstration of such superlattices is not straightforward, as it requires processes for the deposition of a monolayer of O on Si, and to continue the Si epitaxy thereon. In this work, we investigate processes for the fabrication of Si/O superlattices using the chemical vapor deposition technique. Ozone is used for the O deposition with control of the deposited O content at the monolayer level. The SiH4 based Si deposition is performed at low temperatures (500°C–550°C) in order to obtain a confined O monolayer in the Si superlattice. Si deposited on O layer of 1.2 O monolayers is completely amorphous. This indicates that this O layer is extremely uniform as it prevents any epitaxial ordering with the substrate. Reducing the O content to 0.9 O monolayers in combination with a slower Si deposition favors epitaxial ordering of Si on O/Si. Finally a defect free Si epitaxy is demonstrated on the O monolayer. Such ordering of epitaxial Si on the O layer provides a promising outlook for the growth of superlattices. [Copyright &y& Elsevier]

We report on a novel Au-free CMOS process-compatible process for AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors. The process starts from a 150-mm GaN-on-Si substrate with an embedded \Si3\N4\/ \Al2\O3 bilayer gate dielectric, encapsulated by a high-temperature low-pressure chemical vapor deposited nitride layer. Power devices with a 20-mm gate width reach a maximum output current of 8 A, a breakdown voltage of 750 V, and a specific on-resistance Ron, sp of 2.9 \m\Omega\cdot\cm^2. The off-state drain leakage at 600 V is 7 \mu\A. We show robust gate dielectrics with a large gate bias swing. [ABSTRACT FROM PUBLISHER]

A route is presented for activation of hydrogen-terminated Si(100) prior to atomic layer deposition. It is based on our discovery from in situ infrared spectroscopy that organometallic precursors can effectively initiate oxide growth. Narrow nuclear resonance profiling and Rutherford backscattering spectrometry show that surface functionalization by pre-exposure to 10[sup;8] Langmuir trimethylaluminum at 300 ?C leads to enhanced nucleation and to nearly linear growth kinetics of the high-permittivity gate dielectrics aluminum oxide and hafnium oxide. [ABSTRACT FROM AUTHOR]

The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O 3 ) or oxygen (O 2 ) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH 4 ) at 500 °C. After O 3 exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH 4 reactants, allowing more time for surface diffusion. After O 2 exposure, the O atoms are present in the form of SiO x clusters. Regions of hydrogen-terminated Si remain present between the SiO x clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness. [ABSTRACT FROM AUTHOR]