Depth profiles of refractive index in thermally grown and LPCVD oxide films on silicon

Thin and thick silicon oxide films are grown by thermal oxidation of silicon in dry oxygen or by LPCVD from a mixture of monosilane with oxygen or nitrous oxide. Depth profiles of refractive index are determined in these films by monochromatic ellipsometry, with the measurements interpreted by solving an inverse problem within a multilayer model. The differences between the depth profiles are found to be consistent with well-known mechanisms of film growth under the process conditions applied.     

Recombination of self-trapped excitons in silicon nanocrystals grown in silicon oxide

The kinetics of photoluminescence (PL) and steady-state PL from silicon nanocrystals formed in the SiO₂ matrix by silicon ion implantation were studied experimentally for the first time in the temperature range from liquid-helium to room temperature. A dramatic increase in the photoluminescence decay time, accompanied by PL intensity quenching, is observed below 70 K. The results obtained indicate that the silicon nanocrystal PL arises from radiative recombination of excitons self-trapped at the silicon nanocrystal-SiO₂ interface.     

Topography induced preferential crystallization of thermally grown silicon dioxide films

We have investigated the crystallization of the oxide layer that grows on a deposited silicon film in a high temperature furnace. The growth of large SiO₂ crystal grains can be controlled by interfacial stress or surface topography. When the Si film is deposited on topographically patterned surfaces, the SiO₂ grains are nucleated along the edges and extremities of the relief structure. A competition in which faster growing grains terminate slower growing grains results in an average growth direction perpendicular to the edges. Single crystal grains of α-cristobalite up to hundreds of microns in length can be grown in this fashion.     

Effects of nitric oxide annealing of thermally grown silicondioxide characteristics

The effects of nitric oxide (NO) annealing on conventional thermal oxides are reported in this letter. The oxide thickness increase, resulting from NO annealing, is found to be only a few angstroms (<0.5 nm) and independent on the initial oxide thickness. Furthermore, both the electrical and physical characteristics are improved. This technique is expected to achieve sub-5 nm high quality ultrathin dielectric films for the applications in EEPROM's and ULSI     

A quantitative model for the conduction in oxides thermally grown from polycrystalline silicon

Oxides thermally grown from polycrystalline silicon are known to conduct much higher currents than oxides grown on monocrystalline material, which has led to their application in floating-gate electrically erasable programmable READ-only memories (EEPROM) devices (so-called textured devices) for the purpose of electrical programming and erasing of the memory device. This increased conductivity has been previously explained qualitatively by field enhancement due to the surface roughness of the polysilicon-polyoxide interfaces, but a quantitative model that could explain and predict the true injection current behavior was never proposed. In this paper, a new model is introduced, which is able to explain all of the experimental observations of conduction in polyoxides, including trapping phenomena. The new model is verified by comparison with two types of capacitor measurements. Since electron trapping in the oxide is included in the model it can also be used to investigate the degradation behavior of the textured-type floating-gate EEPROM cells. In all cases it is found that the nonuniformity of the polyoxide current strongly influences its behavior and that more specifically for EEPROM devices this nonuniformity puts severe limits on the number of program ERASE cycles that are possible.     

Electron and hole mobilities in inversion layers on thermally oxidized silicon surfaces

Extensive measurements of electron and hole mobilities in inversion layers on thermally oxidized silicon surfaces were performed using the field effect conductance technique. It was found that both electron and hole mobilities are practically constant and approximately equal to one half of their respective bulk values up to a surface field of about 1.5 × 10⁵volts/cm, corresponding to about 10¹²electronic charges/cm²induced in the silicon. At higher fields the inversion layer mobilities begin to decrease slightly. The temperature dependence of inversion layer mobilities follows a T^-1.5rule at the upper range of the interval -196 to 200°C, indicating a scattering mechanism similar to lattice scattering. This observation is further supported by the lack of a significant effect of an order-of-magnitude variation in the bulk impurity concentration (10¹⁵- 10¹⁶cm³) on the inversion layer mobilities. No significant effect of structural and geometrical parameters (such as channel length and shape, oxide type and thickness, and surface charge density) was found on the inversion layer mobilities.     

Structural characterization of oxide layers thermally grown on 3C-SiC films

The oxidation of 3C-SiC films deposited on off-oriented Si(001) substrates by reactive magnetron sputtering has been studied. The oxidation was carried out using dry conditions at a temperature of 1200°C. The composition of the oxide layer was investigated by Auger electron spectroscopy (AES). The oxide layer was found to contain no C except for the region very close to the interface, and the stoichiometry was found to be close to that of SiO₂. Cross-sectional transmis-sion electron microscopy (XTEM) showed the oxide layer to be completely amorphous, dense, and homogeneous with a uniform thickness. High-resolution XTEM imaging showed an atomically sharp SiO₂/SiC interface.     

Standardized terminology for oxide charges associated with thermally oxidized silicon

Standarized terminology for oxide charges associated with the thermally oxidized silicon system is presented. This terminology is recommended by a committee established by the Electronics Division of the Electrochemical Society and the IEEE Semiconductor Interface Specialists Conference. All engineers and scientists concerned with oxide charges in silicon semiconductor applications are urged to adopt this terminology.     

Electron-microscopic imaging of single-walled carbon nanotubes grown on silicon and silicon oxide substrates

Direct imaging of single-walled carbon nanotubes (SWNTs) suspended on pillar-patterned Si or SiO2 substrates is investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The suspended nanotubes are successfully observed by direct TEM imaging and it is seen that they have either individual or bundles of SWNTs. Low energy (< or =2 keV) SEM produces high contrast images of suspended SWNTs. On the contrary, when SWNTs contact a SiO2 substrate, they are imaged using electron-beam induced current. The image brightness depends on the length of SWNTs.     

Erbium impurity atoms in silicon

It is shown using ¹⁶⁹Er(¹⁶⁹Tm) Mössbauer emission spectroscopy that the photoluminescent centers in crystalline erbium-doped silicon are [Er-O] clusters and that the local symmetry of the Er³⁺ ions in these clusters is similar to that in Er₂O₃. The photoluminescent centers in amorphous hydrogenated erbium-doped silicon are clusters, whose local structure also corresponds to erbium oxide.     

Copper impurity levels in silicon

This paper presents a new model of copper impurity levels in silicon, and suggests a new method to analyze the parameters of multilevel impurities using Hall data. On the assumption that the energy levels of copper do not depend on the conduction type of silicon and the concentration of copper, an impurity level model which can explain all the Hall data of many different copper-doped silicon samples is proposed using a computer-aided numerical analysis. Experimental data and analysis indicate that copper exists in silicon in the form of four independent species, viz. substitutional species (Cu_I), interstitial species (Cu_IV) and two copper-associated species Cu^II and Cu^III. The usual species Cu^I has three acceptor levels and a donor level below the intrinsic level. Cu^II has two levels, an acceptor and a donor level respectively, below the donor level of Cu^I. Cu^III produces an acceptor level at a slightly distant position from the conduction band edge. That the intersitial species Cu^IV behaves as a shallow donor is well-known, but its behavior is predominant only in samples diffused at temperatures below 900°C because of the precipitation of its species. Not only the energy levels of copper, but also the degeneracy ratios associated with these levels have been simultaneously determined, and it has been indicated that the degeneracy ratios have an important effect on the temperature dependence of the carrier concentration.     

利用ICPCVD方法在GaN上沉积氧化硅薄膜的特性

使用感应耦合等离子体化学气相沉积(Inductively coupled plasma chemical vapor deposition,ICPCVD)方法在GaN上沉积SiOx薄膜,生长参数中采用不同RF功率,研究RF功率对薄膜物理性能和电学性能的影响.结果发现,随着RF功率增大,薄膜应力增大,表面粗糙度减小,薄膜致密度增大.选择最优的RF功率参数,制作了SiOx/nGaN金属-绝缘体-半导体(metal-insulator-semiconductor,MIS)器件,结果得到薄膜漏电流密度在外加偏压为90V时小于1×10-7A/cm2,SiOx/n-GaN界面态密度为2.4×1010eV-1cm-2.表明利用ICPCVD低温沉积的SiOx-GaN界面态密度低,薄膜绝缘性能良好.     

Ultrathin gate oxide grown on nitrogen-implanted silicon for deepsubmicron CMOS transistors

Nitrogen implantation on the silicon substrate was performed before the gate oxidation at a fixed energy of 30 keV and with the split dose of 1.0×10¹⁴/cm² and 2.0×10¹⁴ /cm². Initial O₂ injection method was applied for gate oxidation. The method is composed of an O₂ injection/N₂ anneal/main oxidation, and the control process is composed of a N₂ anneal/main oxidation. CMOS transistors with gate oxide thickness of 2 nm and channel length of 0.13 μm have been fabricated by use of the method. Compared to the control process, the initial O₂ injection process increases the amount of nitrogen piled up at the Si/SiO₂ interface and suppresses the growth of gate oxide effectively. Using this method, the oxidation retarding effect of nitrogen was enhanced. Driving currents, hot carrier reliability, and time-zero dielectric breakdown (TZDB) characteristics were improved     

IR luminescence in thermally treated silicon

Near-edge IR luminescence with peak emission at E = 1.084 eV has been studied in n- and p-type silicon samples with different contents of interstitial oxygen under excitation with a Nd: YAG laser diode. Thermal treatments of the samples demonstrated that the luminescence nearly completely disappears upon thermal treatments at T = 1050°C and is partly restored in two stages in subsequent thermal treatments in the temperature range 550–800°C. The temperature intervals of luminescence quenching and restoration (500–600 and 700–800°C) correlate with the temperature ranges of dissolution for shallow oxygen precipitates (1000°C) and the generation of oxygen-containing thermal defects, the so-called thermal donors of types I and II. The data obtained suggest that the electronic states related to thermal donors are traps for nonequilibrium carriers and the emptying of these traps contributes to the near-edge emission.     

Planar junctions in silicon on oxide grown using lateral epitaxy by seeded solidification

Current-voltage characteristics of large planar junctions fabricated in silicon on oxide have been studied. These junctions have slightly higher reverse leakage currents and slightly lower breakdown voltages than similar junctions fabricated in bulk silicon. The electrical properties of the junctions are dependent on the regrowth parameters of the silicon films. Fairly uniform junction properties are obtained over the entire sample.     

高场生长晶体的电子探针分析

高场晶体生长现象分为阳极晶体生长和阴极晶体生长两类[1,2 ] ,近来还有人利用这种现象制出了含有碳纳米管的金属纤维[3] 。在试制一种新阴极的过程中[4 ] ,观察到阴极晶体生长现象[5] 。为了解生长物的组份 ,尝试使用安装于一台国产扫描电子显微镜 (ＳＥＭ)上的能谱探针 (ＥＤＳ) [6] ,其困难来源于接收角 (ｔａｋｅ ｏｆｆａｎｇｌｅ)的确定。我们发展了一种可以称为“物镜电流焦距法”的方法 ,改进了常规的几何测量法 ,该法方便、快速而且准确。1　样品制备使用ＳＥＭ中的发夹式热发射钨 (Ｗ )灯丝作为基底 ,在电子发射尖端附近蒸镀一定…     

Electron and hole traps in SiO2 films thermally grown onSi substrates in ultra-dry oxygen

The densities of electron and hole traps in SiO₂ films, thermally grown on Si substrates in ultra-dry oxygen, were compared with those in SiO₂ films grown in pyrogenic steam (wet-oxide films). The results show that ultra-dry-oxide films have an undetectable density of electron traps that is less that 10¹¹/cm² , and little interface-states generation during carrier injection. However, hole traps in ultra-dry-oxide films are high, (2.6±0.1)×10¹²/cm² compared with (1.3±0.2)×10¹²/cm² in wet-oxide films, and these increase by a factor of two with post-oxidation anneal in ultra-dry Ar. The results of electron spin resonance measurements of E' centers in SiO₂ films are consistent with the results of electrical measurements. These suggest that there is a tradeoff correlation between the density of electron traps and hole traps, with respect to the amount of water- or hydrogen-related defects in SiO₂     

Characterization of silicon oxide films grown at room temperature by point-to-plane corona discharge

Oxide films grown on silicon in dry oxygen ambient at room temperature by negative point-to-plane corona discharge are investigated. A significant oxidation rate is observed at room temperature using this technique. Electrical properties of these room termperature grown oxides are examined. The capacitance-voltage measurements on the MOS structures fabricated from these oxides indicate a negative flat-band voltage of −1.5 V. Interface state density distribution in the range of 10¹⁰−10¹³ cm⁻²(eV)⁻¹ is observed with a value of 2×10¹⁰ cm⁻²(eV)⁻¹ at 0.17 eV above the valence band edge. Electrical conduction through the oxide is greater for negative values of applied gate bias voltages and the magnitude of conduction through the oxide decreases with decreasing current density during the corona discharge. Oxides grown at room temperature by this technique may find selective application in low temperature device processing.     

Detection of hydrogen impurity in silicon radiation detectors

The behavior of silicon particle detectors irradiated with 2.5-MeV electrons during subsequent annealing is studied. Annealing at 100–250°C was found to result in the formation of two types of traps with the levels E _c ?0.32 eV and E_v+0.29 eV. Increasing the annealing temperature to 300°C makes both traps disappear. On the basis of data obtained, it was concluded that these traps are related to hydrogen-containing complexes. The presence of hydrogen in a crystal results in a decrease in the annealing temperature for vacancy-oxygen (VO) complexes and complexes consisting of carbon and oxygen interstitials (C_iO_i). The reason for this phenomenon is the passivation of these complexes by hydrogen, which results in the formation of electrically active VOH centers {with the level E _c ?0.32 eV} in an intermediate stage of this process. It is assumed that hydrogen penetrates the structures under investigation in one of the stages of their fabrication.