Long range enhancement of boron diffusivity by phosphorus diffusion

The effect of electron and ion beam irradiation on the Si_{L vv} Auger spectra of SiO₂, Si₃N₄ and Si-oxynitride films was measured by the relative intensity of the 92 eV signal, characteristic for the formation of “free” silicon during irradiation. While in Si-oxynitride (O/N = 0.37) the beam effects were almost negligible, some damage was found in Si₃N₄, but SiO₂ appeared to be extremely sensitive for electron and ion beam irradiation. By low energy electron loss spectroscopy (ELS) of ion bombarded SiO₂ and Si₃N₄ films new electron states due to broken Si-O and Si-N bonds could be determined within the band gap of the insulators. The measured energy losses were interpreted by means of electron energy level schemes of the amorphous films.     

The impact of ultra thin silicon nitride buffer layer on GaN growth on Si (1 1 1) by RF-MBE

Ultra thin films of pure silicon nitride were grown on a Si (1 1 1) surface by exposing the surface to radio-frequency (RF) nitrogen plasma with a high content of nitrogen atoms. The effect of annealing of silicon nitride surface was investigated with core-level photoelectron spectroscopy. The Si 2p photoelectron spectra reveals a characteristic series of components for the Si species, not only in stoichiometric Si₃N₄ (Si⁴⁺) but also in the intermediate nitridation states with one (Si¹⁺) or three (Si³⁺) nitrogen nearest neighbors. The Si 2p core-level shifts for the Si¹⁺, Si³⁺, and Si⁴⁺ components are determined to be 0.64, 2.20, and 3.05 eV, respectively. In annealed sample it has been observed that the Si⁴⁺ component in the Si 2p spectra is significantly improved, which clearly indicates the crystalline nature of silicon nitride. The high resolution X-ray diffraction (HRXRD), scanning electron microscopy (SEM) and photoluminescence (PL) studies showed a significant improvement of the crystalline qualities and enhancement of the optical properties of GaN grown on the stoichiometric Si₃N₄ by molecular beam epitaxy (MBE).     

Electron and ion beam effects in auger electron spectroscopy on insulating materials

Some insulating films—like SiO₂, P-doped SiO₂, B-doped SiO₂, K-silica glasses, SiaN₄, and alumina—are of primary interest in silicon device technology. In this work the main problems concerning the electron and ion beam interactions with these materials when performing Auger analyses are outlined. A few examples of radiation effects are provided. Among these, electron stimulated desorption as well as ion beam induced adsorption and oxide reduction are treated in some detail. General trends in avoiding charging problems with Auger Electron Spectroscopy are provided.     

High‐mobility solution‐processed zinc oxide thin films on silicon nitride

A high effective electron mobility of 33 cm² V^–1 s^–1 was achieved in solution‐processed undoped zinc oxide (ZnO) thin films. The introduction of silicon nitride (Si₃N₄) as growth substrate resulted in a mobility improvement by a factor of 2.5 with respect to the commonly used silicon oxide (SiO₂). The solution‐processed ZnO thin films grown on Si₃N₄, prepared by low‐pressure chemical vapor deposition, revealed bigger grain sizes, lower strain and better crystalline quality in comparison to the films grown on thermal SiO₂. These results show that the nucleation and growth mechanisms of solution‐processed films are substrate dependent and affect the final film structure accordingly. The substantial difference in electron mobilities suggests that, in addition to the grain morphology and crystalline structure effects, defect chemistry is a contributing factor that also depends on the particular substrate. In this respect, interface trap densities measured in high‐κ HfO₂/ZnO MOSCAPs were about ten times lower in those fabricated on Si₃N₄ substrates. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

     

Enhancement of the electron-stimulated desorption from amorphous aluminum oxide films on silicon during an increase in the substrate temperature

The effect of high-temperature electron-stimulated desorption (ESD) from 20-nm-thick Al₂O₃ films deposited onto silicon wafers is studied. The ESD effect is found to be significantly enhanced upon heating. The films are found to decompose during ion beam irradiation of a heated substrate resulting in pure Al appearance. This process is accompanied by the formation of islands and almost pure silicon surface regions at a certain critical irradiation dose. Outside the irradiation zone, a 20-nm-thick Al₂O₃ film remains continuous even upon heating to 700°C and holding for 90 min. The effect of the primary electron beam energy on ESD from a 20-nm-thick Al₂O₃ film on silicon is investigated, and the parameters at which ESD takes place or absent are determined.     

Low-temperature fabrication of silicon nitride films by ArF excimer laser irradiation

The low-temperature fabrication of silicon nitride films by ArF excimer laser irradiation has been studied. Two fabrication methods are presented. One is photoenhanced direct nitridation of a silicon surface with NH₃ for very thin gate insulators, and the other is photo-enhanced deposition of silicon nitride films with Si₂H₆ and NH₃ gases for stable passivation films. The ArF excimer laser irradiation dissociates the NH3 gas producing NH and NH₂ radicals which proved effective in instigating the nitridation reaction. The quality of both films has been much improved and the growth temperature has been lowered by using laser irradiation. These photo-enhanced processes seem to be promising ULSI techniques because they do not depend on high temperatures and are free from possible reactor contamination.     

AES analysis of nitridation of Si(100) by 2–10 keV N+2 ion beams

Ion beam nitridation of Si(100) as a function of N⁺₂ ion energy in the range of 2–10 keV has been investigated by in-situ Auger electron spectroscopy (AES) analysis and Ar⁺ depth profiling. The AES measurements show that the nitride films formed by 4–10 keV N⁺₂ ion bombardment are relatively uniform and have a composition of near stoichiometric silicon nitride (Si₃N₄), but that formed by 2 keV N⁺₂ ion bombardment is N-rich on the film surface. Formation of the surface N-rich film by 2 keV N⁺₂ ion bombardment can be attributed to radiation-enhanced diffusion of interstitial N atoms and a lower self-sputtering yield. AES depth profile measurements indicate that the thicknesses of nitride films appear to increase with ion energy in the range from 2 to 10 keV and the rate of increase of film thickness is most rapid in the 4–10 keV range. The nitridation reaction process which differs from that of low-energy (< 1 keV) N⁺₂ ion bombardment is explained in terms of ion implantation, physical sputtering, chemical reaction and radiation-enhanced diffusion of interstitial N atoms.     

Capturing properties of a threefold coordinated silicon atom in silicon nitride: Positive correlation energy model

The electronic structure and capturing properties of threefold coordinated silicon atoms (≡Si·) and the Si-Si bond in silicon nitride (Si₃N₄) were studied using the ab initio density functional theory. The results show that the previously proposed negative correlation energy (NCE) model is not applicable to Si₃N₄. The NCE model was proposed for interpreting the absence of the ESR signal for threefold coordinated silicon defects and suggested that an electron can transfer between two silicon defects. We proposed that the absence of this ESR signal is due to the creation of neutral diamagnetic Si-Si defects in Si₃N₄. This model offers the most fundamental theory for explaining the hole localization (memory) effect in silicon nitride.     

Improving the tribological performances of graphite-like carbon films on Si3N4 and SiC by using Si interlayers

Si interlayers were used to obtain the excellent tribological performances of graphite-like carbon (GLC) film on silicon nitride (Si₃N₄) and silicon carbide (SiC). The microstructure and mechanical characteristics of the as-prepared GLC films with Si interlayers were investigated by scanning electron microscopy, Raman spectroscopy, nanoindention and scratch test. The tribological behaviors of GLC-coated and uncoated Si₃N₄ and SiC were comparatively studied by a ball-on-disc tribo-meter in both dry and water environments. Results showed that the Si interlayers were dense and bonded well with both the substrates and GLC layers. The as-prepared GLC films exhibited excellent tribological performances in both dry and water environments. More importantly, the stably mild wear without any delamination was obtained in water by using Si interlayer. The mechanisms of friction reduction and anti-wear performances of GLC films on the two ceramics with Si interlayers under different environmental conditions were discussed, as well as the corresponding models were deduced.     

Ti-Si-N复合膜的界面相研究

为了揭示Ti_Si_N复合膜中Si₃N₄界面相的存在方式及其对薄膜力学 性能的影响 ，采用x射线衍射仪、高分辨透射电子显微镜、俄歇电子能谱仪和显微硬度仪对比研究了磁 控溅射Ti_Si_N复合膜和TiN/Si₃N₄多层膜的微结构和力学性能. 实 验结果表明 ，Ti_Si_N复合膜均形成了Si₃N₄界面相包裹TiN纳米晶粒的微结构. 其中低Si 含量的Ti_Si_N复合膜中Si₃N₄界面相的厚度小于1nm，且以晶体态 存在，薄膜 呈现高硬度. 而高Si含量的Ti_Si_N复合膜中的Si₃N₄界面相以非晶 态存在，薄 膜的硬度也相应降低. 显然，Ti_Si_N复合膜中Si₃N₄界面相以晶体 态形式存在 是薄膜获得高硬度的重要微结构特征，其强化机制可能与多层膜的超硬效应是相同的. 关键词： Ti－Si－N复合膜 界面相 微结构 超硬效应     

Deposition of silicon oxynitride films by ion beam sputtering at room temperature

Silicon oxynitride films, possessing various compounds of SiO₂ and Si₃N₄, were deposited by ion beam sputtering at room temperature. This technique can easily and precisely control the refractive index and composition of the silicon oxynitride film. Properties of these films, such as the refractive index, the extinction coefficient, the surface roughness, and so on were measured in this study.     

Infrared and auger spectra of dysprosium silicate films

Dysprosium silicate films, Dy _x Si _y O _z , have been investigated using infrared (IR) and Auger spectroscopy. The films have been formed by oxidizing dysprosium metal films on 5.2-nm-thick silicon dioxide films at a temperature of 600°C. It is shown that the composition of the Dy _x Si _y O _z dysprosium silicate films is close to that of dysprosium pyrosilicate, Dy₂Si₂O₇, and irregular in thickness. On going from the film outer surface to the silicon substrate, the amount of dysprosium decreases and that of silicon bound to oxygen increases. Silicon dioxide, SiO₂, predominates in the layer composition near the silicon substrate. The dielectric leakage current density in the accumulation mode is one order of magnitude lower in the Dy _x Si _y O _z films than in the SiO₂ films of the same equivalent thickness due to the larger physical thickness of the former.     

n-type conductivity in Si-doped amorphous AlN: an ab initio investigation

We report the electronic structure and topology of a heavily Si-doped amorphous aluminium nitride (Al_37.5Si_12.5N₅₀) using ab initio simulations. The amorphous Al_37.5Si_12.5N₅₀ system is found to be structurally similar to pure amorphous aluminium nitride. It has an average coordination number of about 3.9 and exhibits a small amount of Si–Si homopolar bonds. The formation of Si–Al bonds is not very favourable. Electronic structure calculations reveal that the Si doping has a negligible effect on the band gap width but causes delocalization of the valence band tail states and a shift of the Fermi level towards the conduction band. Thus, amorphous Al_37.5Si_12.5N₅₀ alloys show n-type conductivity.     

Electrical characteristics of metal-dielectric-semiconductor structures with silicon nitride prepared by reactive cathode atomization

The effect of the technology of preparation of silicon nitride in a low temperature gas discharge plasma upon the volt-ampere and volt-farad characteristics of metal-dielectricsemiconductor (MDS) structures (Al-Si₃N₄-Si-Al) is studied. It is shown that by using a heterogeneous Si₃N₄ formation reaction with ionic purification of the silicon surface, it is possible to obtain MDS structures with lower and more stable surface charge in comparison to similar structures in which the Si₃N₄ is grown by other methods (for example, gas transport reaction methods). The conductivity of the Si₃N₄ film is described approximately by the well known Frankel model, and its value is close to that of Si₃N₄ films prepared by other methods.     

Thermal stability and electronic structures of N-doped SiSb films for high temperature applications of phase-change memory

Undoped and N-doped Si_10.5Sb_89.5 films were deposited by magnetron sputtering. The X-ray diffraction spectra indicated that all of the films crystallized into crystalline Sb with a rhombohedral structure after annealing at 280°C for 3 min. X-ray photoelectron spectroscopy analysis indicated that the incorporated nitrogen combined with Si to form silicon nitride in the SiSb films. The changes in electrical resistance and thermal stability of the undoped and N-doped Si_10.5Sb_89.5 films were investigated. The crystallization temperature increased from ∼225°C to ∼250°C when 13 at.% nitrogen was added into the Si_10.5Sb_89.5 film and increased further with increasing nitrogen content. The thermal stability of the amorphous film was enhanced by nitrogen doping. The maximum temperature for 10-year retention of amorphous state of a pure Si_10.5Sb_89.5 film is ∼140°C and the temperature of N-doped Si_10.5Sb_89.5 films is even higher, which may be helpful to improve the data retention and performance of phase-change memory in high temperature applications.     

A new generation of CMOS-compatible high frequency micro-inductors with ferromagnetic cores: Theory,fabrication and characterisation

A new generation of CMOS-compatible micro-inductor prototypes with magnetic cores were realized, characterised as well as theoretically modelled in a frequency range up to 4 GHz, a frequency range where, e.g., mobile communication and global positioning systems (GPS) are operated. The micro-inductor's electrical magnitudes like inductance (L) and quality factor (Q) were theoretically described by means of an equivalent circuit model taking the frequency behaviour of the magnetic film core, expressed by the Landau-Lifschitz and Maxwell equations, into account. Six inch targets were used to deposit metallic layers (Al₉₉Si_0.5Cu_0.5), diffusion barriers (Si₃N₄), insulating layers (SiO₂) and magnetic films (Fe₃₉Co₃₀Ta₈N₂₃) by DC or reactive r.-f.-magnetron sputtering. All film materials were patterned by NUV-lithography (Near Ultra Violet), plasma beam milling and reactive ion etching to form the micro-inductors on 4-inch silicon wafers. The inductor windings are arranged in a way that they possess a low resistance and generate a quasi closed flux at the end of the cores to minimise eddy current losses in the silicon substrate. In order to diminish demagnetising effects in an efficient working core the magnetic films were patterned into micro squares with lateral dimensions of 20 and 100 μm with 100 nm in thickness. More magnetic volume and a higher micro-inductor cross-section was achieved by producing 100 nm magnetic double layers separated by a 800 nm thick Si₃N₄ inter-layer. To guarantee a sufficiently high cut-off frequency of the magnetic films, they were annealed in a static magnetic field at a temperature of 400 °C for uniaxial anisotropy induction. This represents a temperature treatment where aluminium CMOS processes take place. As a result of patterning, the magnetic film material exhibited a remarkable increase of the cut-off frequency from 2 GHz in laterally extended films up to 3.2 GHz which could be also observed in the measured frequency dependent inductance and quality factor. This was accompanied by an acceptable decrease of the initial permeability that still enabled initial inductances between 1 and 2 nH to be attained.     

Heteroepitaxial GaN films on silicon substrates with porous buffer layers

New complex buffer layers based on a porous material have been developed for epitaxial growth of GaN films on Si substrates. The characteristics of gallium nitride heteroepitaxial layers grown on silicon substrates with new buffer layers by metal-organic vapor phase epitaxy are investigated. It is shown that the porous buffer layers improve the electric homogeneity and increase the photoluminescence intensity of epitaxial GaN films on Si substrates to the values comparable with those for reference GaN films on Al₂O₃ substrates. It is found that a fianite layer in a complex buffer is a barrier for silicon diffusion from the substrate into a GaN film.     

Electronic structure of silicon nitride according to ab initio quantum-chemical calculations and experimental data

Charge transfer ΔQ = 0.35e at the Si-N bond in silicon nitride is determined experimentally using photoelectron spectroscopy, and the ionic formula of silicon nitride Si₃^+1.4N₄^−1.05 is derived. The electronic structure of α-Si₃N₄ is studied ab initio using the density functional method. The results of calculations (partial density of states) are compared with experimental data on X-ray emission spectroscopy of amorphous Si₃N₄. The electronic structure of the valence band of amorphous Si₃N₄ is studied using synchrotron radiation at different excitation energies. The electron and hole effective masses m _e ^* ≈ m _h ^* ≈ 0.5m _e are estimated theoretically. The calculated values correspond to experimental results on injection of electrons and holes into silicon nitride.     

辉光放电等离子体辅助XeCl准分子激光溅射沉积碳氮薄膜

利用直流辉光放电等离子体辅助的脉冲激光沉积技术在Si衬底上生长了碳氮薄膜.通过扫描电子显微镜、X射线衍射、X射线光电子能谱、俄歇电子能谱等多种手段,对薄膜的形貌、成分、晶体结构、价键状态等特性进行了分析和确定.结果表明,沉积薄膜为含有非晶SiN和晶态氮化碳颗粒结构,晶态成分呈多晶态,主要为α-C₃N₄相、β-C₃N₄相,晶粒大小为40—60nm.碳氮之间主要以C-N非极性共价键形式相结合. 关键词： 脉冲激光沉积 直流辉光放电 碳氮薄膜