Low temperature plasma enhanced chemical vapor deposition of silicon oxide films using disilane and nitrous oxide

Silicon oxide films have been deposited between room temperature and 300°C using disilane and nitrous oxide by plasma enhanced chemical vapor deposition. Film deposition was investigated as a function of the gas flow ratio of nitrous oxide to disilane, the substrate temperature, the total gas flow rate, the radio frequency discharge power, and the process pressure. The stoichiometric SiO₂ films were obtained when the gas ratio of nitrous oxide to disilane was in the range of 50-150. The deposition was found to be nearly temperature independent indicating the mass transport limited regime.     

A study of aluminum oxide thin films prepared by atmospheric-pressure chemical vapor deposition from trimethylaluminum + oxygen and/or nitrous oxide

A significant improvement in the deposition rate of thin films of aluminum oxide, using trimethylaluminum and oxygen at a substrate temperature of 570° C, is demonstrated. Hard, transparent, strongly adherent films of refractive index 1.62–1.63 were consistently achieved with controlled growth rates from 15 Å/sec to 94 Å/sec, depending upon the Al mole fraction. Systematic analysis of the growth rate data offers insight into the complicated kinetics of the deposition process. In comparison, the films produced from the trimethylaluminum and nitrous oxide system were of inferior quality.     

Plasma deposition of aluminum oxide films

A plasma deposition technique for amorphous aluminum oxide films is discussed. A 450 kHz or 13.56 MHz power supply was used to generate the plasma and the deposition of the film was achieved at low plasma power using trimethyl-aluminum and carbon dioxide reactant sources. It has been found that for the low frequency plasma the growth is strongly dependent upon TMA concentration, indicating that the growth process is mass transport limited. On the other hand using the 13.56 MHz discharge results in a surface controlled growth rate. An increase in the deposition temperature up to 300° C makes the films more dense and lowers their etching rate. FTIR and ESCA measurements showed that oxidation is only completed with high CO₂ concentrations and a deposition temperature above 250° C. The dielectric films were found to have a dielectric constant in the range 7.3=2-9 and a refractive index between 1.5–1.8 depending upon deposition conditions.     

Chemical vapor deposition of AlxOyNz films

A chemical vapor deposition process for depositing dielectric films of aluminum oxynitride is described. AlCl₃, CO₂ and NH₃ were employed as the reactive gases in a nitrogen carrier. Films were grown from the mixed gases at 770 and 900°C in a resistively heated fused silica enclosure. The composition of the films could be varied over the entire range of the pseudobinary AlN-Al₂O₃ system by controlling the NH₃/CO₂ gas ratio with an appropriate flow of gaseous AlCl₃. Growth rate and index of refraction for the films were obtained using ellipsometric techniques. The film compositions reported were determined by electron microprobe analysis. Film structure, evaluated using transmission electron microscopy, and the electrical properties of the dielectric films have been correlated and are discussed separately in a companion paper entitled, “Some Properties of CVD Films of Al_xO_yN_z on Silicon”.     

氧化物薄膜晶体管刻蚀阻挡层PECVD沉积条件研究

为实现氧化物TFT(Indium Gallium Zinc Oxide Thin Film Transistor,IGZO TFT)特性的最优化,采用I-V数据和SEM(Scanning Electron Microscope)图片研究蚀阻挡层(Etch-Stop Layer,ESL)沉积条件与氧化物TFT特性的关系。通过调整沉积温度、正负极板间距、压力和功率,分析了PECVD沉积ESL SiO2的成膜规律,并对所得到的TFT进行了特性分析。发现ESL膜层致密性过差时,后期高温工艺会造成水汽进入IGZO半导体膜层,从而引起TFT特性恶化。而采用高温、高压力等方法取得高致密性的ESL膜层由于高强度等离子体对IGZO本体的还原反应也会致使TFT特性劣化。结果表明,在保证膜层致密性前提下,等离子体对IGZO本体伤害最小的ESL沉积条件才是最优化的ESL沉积条件。     

ArF excimer laser induced CVD of aluminum oxide films

The authors have demonstrated photochemical deposition of aluminum oxides from Trimethylaluminum (TMA) and N₂O by using a pulsed ArF excimer laser (193 nm). Both TMA and N₂O are efficiently photodissociated by the 193 nm light. The films are grown on Si and InP wafers contained in a low pressure flowing cell with a heated substrate. The incident laser beam is focused and parallel to the substrate surface. Typical deposition rates are 80–150 A/min. Stripes of aluminum oxide 30 mm wide are uniformly grown on 7.5 cm Si-wafers. The film composition and purity have been investigated using Auger and Infra-red spectroscopy analysis. Surprising results are the relatively low concentration of carbon. Refractive index and thickness have been determined by an ellipsometer. Typical values for the films are 1.54–1.62. Metal-oxide-semiconductor capacitors have been fabricated and characterized. The C-V curves for n-InP/aluminum oxide have clockwise hysteresis, and minimum loop width is less than 0.5 V. The surface state densities are 1 × 10¹¹ cm^-2 eV⁻¹ at the mid band gap.     

Optoelectronic properties of expanding thermal plasma deposited textured zinc oxide: Effect of aluminum doping

Aluminum-doped zinc oxide films exhibiting a rough surface morphology are deposited on glass substrates utilizing expanding thermal plasma. Spectroscopic ellipsometry is used to evaluate optical and electronic film properties. The presence of aluminum donors in doped films is confirmed by a shift in the zinc oxide bandgap energy from 3.32 to 3.65 eV. In combination with transmission reflection measurements in the visible and NIR ranges, charge carrier densities, optical mobilities, and film resistivities have been obtained from the free carrier absorption. Film resistivities are consistent with direct measurements, values as low as 6.0×10⁻⁴ ω cm have been obtained. The interdependence of electrical conductivity, film composition, and film morphology is addressed.     

High Quality Carbon Nanotubes on Conductive Substrates Grown at Low Temperatures

For carbon nanotubes (CNTs) to be exploited in electronic applications, the growth of high quality material on conductive substrates at low temperatures (<450 °C) is required. CNT quality is known to be strongly degraded when growth is conducted on metallic surfaces, particularly at low temperatures using conventional chemical vapor deposition (CVD). Here, the production of high quality vertically‐aligned CNTs at low substrate temperatures (350–440 °C) on conductive TiN thin film using photo‐thermal CVD is demonstrated by confining the energy required for growth to just the catalyst using an array of optical lamps and by optimizing the thickness of the TiN under‐layer. The thickness of the TiN plays a crucial role in determining various properties including diameter, material quality, number of shells, and metallicity. The highest structural quality with a visible Raman D‐ to G‐band intensity ratio as low as 0.13 is achieved for 100 nm TiN thickness grown at 420 °C; a record low value for low temperature CVD grown CNTs. Electrical measurements of high density CNT arrays show the resistivity to be 1.25 × 10^‐2 Ω cm representing some of the lowest values reported. Finally, broader aspects of using this approach as a scalable technology for carbon nanomaterial production are also discussed.     

铝膜沉积温度对铝诱导结晶化多晶硅薄膜性能的影响

以超白玻璃为衬底,采用热丝化学气相沉积法沉积初始非晶硅膜,经自然氧化形成二氧化硅层,最后利用磁控溅射 法在不同衬底温度下沉积铝膜,制备了glass/Si/SiO/Al叠层结构并对其进行铝诱导晶化形成多晶硅薄膜.用X射线衍射,光学显微镜和拉曼光谱对样品进行了分析.结果表明,铝诱导晶化制备的多晶硅薄膜的晶粒大小随着铝膜沉积...     

Electron microscopy and energy loss study of low temperature plasma deposited oxide on a CZ grown Si substrate

Transmission electron microscopy (TEM) and computer-controlled parallel electron energy loss spectroscopy (PEELS) are used to obtain the structure of and compositional profile across a thin oxide film deposited by remote plasma enhanced chemical vapor deposition at 300°C. The film, believed to be stoichio-metrically correct SiO₂ as determined by Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS), was found to be oxygen rich with a composition non-uniformity across it. The existence of an abundance of oxygen was supported by capacitance-voltage measurements and etch rate studies. The non-uniformity was observed in TEM images. These results show what a powerful characterization technique computer-controlled PEELS can be. In addition, this is the first time that PEELS profiling was used to help interpret TEM images.     

Electrical properties of silicon dioxide films fabricated at 700°C. II: Low pressure hydride deposition

We have investigated the effects of different annealing treatments on silicon dioxide films produced from the reaction of dichlorosilane and nitrous oxide at 700° C. The electrical quality of these LPCVD films was evaluated by measuring oxide charge and interface trap densities on metal oxide semiconductor (MOS) capacitors. These densities were measured before and after avalanche injection of electron currents into the oxide films. The results of these studies were as follows. (1) The LPCVD oxide films required a post deposition anneal at 1000° C to produce as-grown charge densities similar to those of a standarddry thermal oxide grown and annealed at 1000° C. (2) Post-injection charge densities of LPCVD films given a post deposition anneal at 1000°C were an order of magnitude greater than those of the standard dry thermal oxide. (3) Different annealing treatments produced a series of dominant electron trapping centers in the oxide bulk₁₇ with capture cross sections ranging from 10⁻¹⁴ cm² to 10⁻¹⁷ cm². (4) The electron traps in the LPCVD oxides films were similar to those previously observed in standardwet thermal oxides grown and annealed above 1000° C.     

低温高速率沉积非晶硅薄膜及太阳电池

采用射频等离子体增强化学气相沉积(RF-PECVD)技术,保持沉积温度在125℃制备非晶硅薄膜材料及太阳电池。在85 Pa的低压下以及400～667 Pa的高压下,改变Si H4浓度和辉光功率等沉积参数,对本征a-Si材料的性能进行优化。结果表明,在高压下,合适的Si H4浓度和压力功率比可以使a-Si材料的光电特性得到优化,并且薄膜的沉积速率得到一定程度的提高。采用低压低速和高压高速的沉积条件,在125℃的低温条件下制备出效率为6.7%的单结a-Si电池,高压下本征层a-Si材料的沉积速率由0.06～0.08 nm/s提高到0.17～0.19 nm/s。     

Cleaning and passivation of the Si(100) surface by low temperature remote hydrogen plasma treatment for Si epitaxy

This paper presents the results of a study of the hydrogen-passivated Si(100) surface prepared by a remote hydrogen plasma treatment which serves the dual purpose of cleaning and passivating the Si(100) surface prior to low temperature Si epitaxy by Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD). The remote hydrogen plasma treatment was optimized for the purposes of cleaning and passivation, respectively. To achieve a clean, defect-free substrate surface, the remote hydrogen plasma process was first optimized using Transmission Electron Microscopy (TEM) and Auger Electron Spectroscopy (AES). For hydrogen passivation, the substrate temperature was varied from room temperature to 250° C in order to investigate the degree of passivation as a function of substrate temperature by examining the amount of oxygen readsorbed on the substrate surface after air exposure. Low temperature Si expitaxy was subsequently performed on the air-exposed substrates without further cleaning to evaluate the effectiveness of the hydrogen passivation. It was found that better Si surface passivation is achieved at lower substrate temperatures as evidenced by the fact that less oxygen is observed on the surface using AES and Secondary Ion Mass Spectroscopy (SIMS) analyses. The amount of readsorbed oxygen on the H-passivated Si surface after a two hour air exposure was found to be as low as 0.1 monolayer from SIMS analysis. Using Reflection High Energy Electron Diffraction (RHEED) analysis, different surface reconstructions ((3 × 1) and (1 × 1)) were observed for H-passivated Si surfaces passivated at various temperatures, which was correlated to the results of AES and SIMS analyses. Epitaxial growth of Si films at 305° C was achieved on the air-exposed Si substrates, indicating a chemically inert Si surface as a result of hydrogen passivation. A novel electron-beam-induced-oxygen-adsorptiom phenomena was observed on the Hpassivated Si surface. Scanning Auger Microscopy (SAM) analysis was performed to study the reaction kinetics as well as the nature of Si—H bonds on the H-passivated Si surface. Preliminary results show that there is a two-step mechanism involved, and oxygen adsorption on the H-passivated Si surface due to electron beam irradiation may be due to the formation of O-H groups rather than the creation of Si—O bonds.     

Growth of high-quality 1.93-eV AIGaAs using metalorganic chemical vapor deposition

High-quality Al_xGa_1-xAs with a bandgap of 1.93 eV has been grown using metalorganic chemical vapor deposition (MOCVD). Levels exceeding 10₁₈ cm_-3 can be obtained for Se, Si and Zn dopants. In particular, incorporation of the re-type dopants at this bandgap is not appreciably less efficient than in lower-bandgap Al_xGa_1-xAs. The best material, as measured by photoluminescence intensity, is obtained using high V/III ratios (40 forp-type material and as high as 60 forn- type and low growth rates (300 Å/min). Purification of the arsine in situ with an Al/Ga/In eutectic bubbler to remove trace water and oxygen impurities is found to be essential for the growth of high-quality material, as indicated by photoluminescence intensity measurements. Solar cells fabricated from such material exhibit efficiencies as high as 12.1% under one-sun, airmass zero (AMO) conditions, with an open-circuit voltage of 1.38 V, short-circuit current density of 14.1 mA/cm², and fill factor of 0.84.     

MCVD工艺沉积温度对有源光纤掺杂浓度的影响研究

以掺镱双包层光纤为例,主要介绍了用MCVD工艺及溶液掺杂法制备掺稀土离子有源光纤,通过对低温沉积疏松芯层时温度控制对最终研制的有源光纤镱离子掺杂浓度的影响研究,得出沉积温度对有源光纤掺杂浓度影响的规律,为目前国内普遍采用的MCVD工艺结合溶液掺杂技术制备掺稀土离子有源光纤提供了参考.     

Epitaxial garnet films by organometallic chemical vapor deposition

Epitaxial films of Y₃Fe₅O₁₂, Eu₃Fe₅O₁₂, (Eu, Y)₃Fe₅O₁₂, and Er₃Fe₅O₁₂ l-2μm thick have been chemically vapor deposited on <111> GGG and <100> SmGG garnet substrates from 1000°C to 1200°C in an oxygen atmosphere from metal organic source compounds. These source compounds which are used here for the first time in chemical vapor deposition are tris 2, 2, 6, 6, tetramethyl 3, 5 heptanedionate complexes, (thd or M(thd)₃) of the metals used. In the reactor, the individual compounds are volatilized in a helium carrier in separate source containers. The vapors are then combined, and premixed without reaction at about 300°C with a large excess of 0₂ and passed with high velocity, ∿500 cm/sec, onto an r.f. heated substrate. The growth rate under these conditions is 0.4 - 0.8μm/hr. X-ray double diffraction, glancing angle X-ray and microprobe analyses were employed to characterize the crystallinity and stoichiometry, respectively, of the resulting garnet films. They were single crystal and exhibited a lattice constant dependent upon the rare earth to Fe ratio. The Eu containing films were not pseudomorphic probably due to the large lattice mismatch between substrate and film in most cases. The erbium iron garnet films were apparently close to pseudomorphic as determined by measured film and substrate lattice constants.     

VLP／CVD低温硅外延

研究了VLP／CVD低温硅外延生长技术,利用自制的VLP／CVD设备,在低温条件下,成功地研制出晶格结构完好的硅同质结外延材料。扩展电阻、X射线衍射谱和电化学分布研究表明,在低温下（T＜800℃）应用VLP／CVD技术,可以生长结构完好的硅外延材料,且材料生长界面的杂质浓度分布更陡峭。     

Metalorganic chemical vapor deposition and characterization of ZnO materials

Zinc oxide is attracting growing interest for potential applications in electronics, optoelectronics, photonics, and chemical and biochemical sensing, among other applications. We report herein our efforts in the growth and characterization of p- and n-type ZnO materials by metalorganic chemical vapor deposition (MOCVD), focusing on recent nitrogen-doped films grown using diethyl zinc as the zinc precursor and nitric oxide (NO) as the dopant. Characterization results, including resistivity, Hall measurements, photoluminescence, and SIMS, are reported and discussed. Electrical behavior was observed to be dependent on illumination, atmosphere, and heat treatment, especially for p-type material.     

Heterogeneous Solid Carbon Source‐Assisted Growth of High‐Quality Graphene via CVD at Low Temperatures

Polycyclic aromatic hydrocarbons (PAH) have been widely used as solid carbon sources for the synthesis of graphene at low temperatures. The inevitable formation of structural defects, however, has significantly limited the quality of the synthesized graphene. This article describes a low‐temperature chemical vapor deposition method that effectively mitigates defect formation in graphene by heterogeneous solid carbon sources containing a mixture of aromatic and aliphatic carbon on a Cu substrate. The addition of small amount of aliphatic carbon sources to the PAH significantly decreases the defect density of graphene synthesized at 400 ≤ T ≤ 600 °C by incorporating small aliphatic carbon fragments into defect sites. The carrier mobility of graphene grown using this heterogeneous solid carbon source is more than five times that of graphene synthesized using only PAH. Two mechanisms are also proposed by which vacancies can be generated during graphene growth using PAH sources on Cu, defect generation due to the disordered packing and the geometric limitation of PAH molecules. This low‐temperature method of synthesizing graphene reduces the degree of defect density using heterogeneous solid carbon sources promises to provide wide utility in electronics applications.     

Cross-sectional TEM characterization of low temperature (750-800°C) epitaxial silicon by very low pressure (6 mTorr) chemical vapor deposition with and without plasma enhancement

Cross-sectional transmission electron microscopy (XTEM) and high resolution transmission electron microscopy (HRTEM) were used to characterize epitaxial silicon grown by chemical vapor deposition at 750–800° C. Optimum conditions for pre-deposition argon plasma sputter cleaning were found to be -100 V dc substrate bias and 2.5 W rf power for 13 minutes at 4 m Torr and 750–800° C. No dislocations were observed by XTEM in films deposited subsequent to this plasma exposure. Analysis of the epitaxial layer/substrate interface by HRTEM indicates complete lattice registration despite the presence of a discontinuous array of defects or microprecipitates. The strain field associated with these defects is approximately 13Å in width. Annealing the epitaxial layers at 1150° C inN ₂ for 4 hours led to the generation of additional defects believed to be associated with carbon and oxygen clustering. Preliminary results indicate that neither temporary (30 seconds) growth interruptions nor low power (2.5 W) plasma enhancement of thedeposition process lead to the generation of defects observable by XTEM.