β-SiC/Si heterojunction bipolar transistors with high currentgain

The combination of single-crystalline β-SiC and Si permits the fabrication of a heterojunction bipolar transistor (HBT) in which the conventional poly-Si or single-crystalline Si emitter is replaced with a single-crystalline SiC emitter, a technique compatible with existing Si technology. A common-emitter current gain of 800 is attained with this device. The value of the ideality factor n of the base current is 1.1, which suggests that diffusion current is dominant. The large number of misfit dislocations at the SiC/Si heterojunction are ineffective as recombination centers and do not deteriorate the characteristics of the HBT     

Epitaxial growth of silicon from SiH4 in the temperature range 800–1150°C

Results on the deposition of silicon from SiH₄ are reported for a temperature range 800–1150°C. Deposition was carried out at atmospheric pressure and at reduced pressures in the range 0·2-1 Torr where it was possible to maintain an h.f. glow discharge in the reactor tube. Using the h.f. discharge good quality epitaxial growth was achieved at 800°C for both undoped and heavily doped n-type layers. The main advantage of using the discharge is thought to be the marked cleanup it gives to the substrate prior to deposition taking place.     

已烷对甲基氟远红外激光器的影响

观察了在不同气压比例下C_6H_(14)对CH_3F496微米激光振荡的影响。最佳气压比是CH_3F:C_6H_(14)=1:2,与纯CH_3F相比较,远红外激光输出功率增加了53％。     

Kinetics of chemical vapor deposition of WSix films from WF6 and SiH2Cl2: Effect of added H2, SiH4, and Si2H6

This paper describes reaction kinetics of chemical vapor deposition of WSi_x films from WF₆ and SiH₂Cl₂, focusing on the effect of added H₂, SiH₄, and Si₂H₆ as an active reaction initiator. Our studies indicate that the temperature at which film formation is extinguished, T_ex, can be lowered by introducing H₂ instead of the standard Ar carrier gas. For a SiH₂Cl₂/WF₆ pressure ratio of 20, H₂ addition changed the deposition mode from selective W deposition to blanket WSi_x deposition. The added H₂ also improved the step-coverage profile for substrate temperatures below 600 °C. Measured step coverage profiles indicate that the activation energy of deposition species was 147 kJ/mol. Adding either SiH₄ or Si₂H₆ can assist the film-forming reactions to achieve acceptable Si/W atomic composition ratios. Under these conditions, the residual fluorine concentration remained at acceptably low levels that are typical of conventional WF₆/SiH₂Cl₂ CVD processes.     

Epitaxial growth of LaAlO3 on Si(0 0 1) using interface engineering

In this work, the potentiality of molecular beam epitaxy techniques to prepare epitaxial lanthanum aluminate (LaAlO₃) films on Si(0 0 1) is explored. We first demonstrate that the direct growth of LaAlO₃ on Si(0 0 1) is impossible : amorphous layers are obtained at temperatures below 600 °C whereas crystalline layers can be grown at higher temperatures but interfacial reactions leading to silicate formation occur. An interface engineering strategy is then developed to avoid these reactions. SrO and SrTiO₃ have been studied as buffer for the subsequent growth of LaAlO₃. Only partial LaAlO₃ epitaxy is obtained on SrO whereas high quality layers are achieved on SrTiO₃. However both SrO and SrTiO₃ appear to be unstable with respect of Si at the growth temperature of LaAlO₃ (700 °C). This leads to the formation of relatively thick amorphous interfacial layers. Despite their instability at high temperature, these processes could be used for the fabrication of twins-free LaAlO₃ templates on Si, and for the fabrication of complex oxide/Si heterostructures for various applications.     

Optimization of WSi2 by SiH4 CVD: impact on oxide quality

The deposition of WSi₂ on transistor gate in SiH₄/WF₆ ambient produces strong variations into the active oxide layer, introducing a significant fluorine concentration into the dielectric. This phenomenon is here shown to have different effects on p-well and n-well structures and to strongly depend on thermal budget. Different amorphization implants after deposition may also be implemented to avoid cracks formations but they will be shown to interact with fluorine into the dielectric and strongly impact reliability performances.     

Comparison of etching characteristics of SiO2 with ArF photoresist in C4F6 and C4F8 based dual-frequency superimposed capacitively coupled plasmas

In this study, we compared the C₄F₆ and C₄F₈ based plasma etching characteristics of silicon dioxide and ArF photoresist (PR) in a dual-frequency superimposed capacitively coupled plasma (DFS-CCP) etcher under different high- and low-frequency combinations (f_HF/f_LF), while varying the process parameters such as the dc self-bias voltage (V_dc), O₂ flow, and CH₂F₂ flow rate in the C₄F₈/CH₂F₂/O₂/Ar and C₄F₆/CH₂F₂/O₂/Ar plasmas. The silicon oxide etch rates increased significantly in both chemistries with increasing f_HF and O₂ flow rate. The silicon oxide etch rates were higher in the C₄F₈/CH₂F₂/O₂/Ar than in the C₄F₆/CH₂F₂/O₂/Ar plasmas, but the PR etch rate was much higher in the C₄F₆/CH₂F₂/O₂/Ar than in the C₄F₈/CH₂F₂/O₂/Ar plasmas under the present experimental conditions. The slower oxide etch rate in the C₄F₆ based plasmas was attributed to the thicker steady-state fluorocarbon layer on the silicon oxide surface, while the faster PR etch rate in the C₄F₈ based plasmas was ascribed to the higher F radical density in the plasma.     

Reactive ion etching of III-V compounds using C2H6/H2

Reactive ion etching of InP, GaInAs and GaAs using a mixture of ethane and hydrogen, C₂H₆/H₂, is demonstrated for the first time. It has been found that by choosing optimum etching parameters one can obtain excellent vertical sidewalls as well as very smooth surfaces, keeping the etching rate at a convenient value of 20-60 nm/min     

Influence of SiH4 on the WNx-PECVD process

Silane was added to an existing WN_x PECVD process in different flow ratios to the WF₆, to obtain higher thermal stability of the barrier in comparison to the WN_x. The deposition rate rises drastically with increased SiH₄/WF₆ ratios. The ternary compositions were investigated with regard to the sheet resistance and thickness. The X-ray diffraction (XRD) measurements of selected layers with low electrical resistivities in the as-deposited state show a broad amorphous peak like the WN_x barrier, indicating an amorphous structure. After characterising the as-deposited state of these samples, thermal treatments of the layers were performed at temperature of 600 °C for 1 h in vacuum.     

激光诱导SiH4等离子体反应碎片的产生机制

Using the technique of optical emission spectroscopy,time-dependence of fragment in SiH₄ laser plasma is measured.After analyzing the evolution and reaction progress of fragments,we proposed that si.H and si⁺ were the first reaction products,but Si₂ SiH and Si²⁺ the second ones.This conclusion is further verified by the experimental results of Si390.6nm and SiH412.8nm emission lines in various conditions.     

Frequency-stabilized DFB laser module using 1.53159 μmabsorption line of C2H2

A frequency-stabilized distributed-feedback (DFB) laser module using the vibrational-rotational absorption of acetylene molecules is discussed. The size of this device is about 4.5 cm long, 2 cm wide, and 2 cm high. Frequency stability to within 0.5 MHz peak/peak fluctuation was achieved at the 1.53159 μm wavelength     

肖特基型β-Ga2O3日盲紫外光电探测器

本文制备并研究了肖特基型β-Ga₂O₃日盲紫外光电探测器.结果表明：通过脉冲激光沉积外延生长的β-Ga₂O₃的（-201）晶面 X射线衍射峰半高宽仅为36 arcsec,表现出了高的晶体质量;光暗条件下的I-V曲线显示所制备的器件具有明显的肖特基整流特性,在-5V偏压下暗电流保持在0.1nA量级,正向导通电压为1.5V;光电流谱显示器件在240nm处存在显著的峰值响应,并在260nm左右呈现陡峭的截止边,日盲紫外的带内带外抑制比达到1000.同时,也研究了不同掺杂对Ga₂O₃晶体质量的影响.     

NH3/SiH4流量比对多晶硅/氮化硅复合层电池光电性能的影响研究

SiN薄膜因为具有良好的减反射性质和钝化作用, 越来越广泛地应用于晶硅太阳电池的制造工艺中。用等离子体化学气相沉积(PECVD)法, 通过改变流量比、气体总量及基底温度等工艺参数沉积SiN薄膜, 研究了流量比对在多晶硅太阳电池上所沉积的氮化硅薄膜性能的影响。实践表明, NH3/SiH4气体流量比为11.5∶1时电池材料具有最佳的光电性能。     

Picosecond optical parametric amplification in β-BaB2O4

In this paper, a detailed theoretical study using a computer simulation and a system experiment centering large signal optical parametric amplification in type I β-BaB₂O₄ are presented. Pumped by 354.7 mm 30 ps laser pulses, the experimental results agree with the theoretical analysis and the computer simulation. A tunable wavelength of 420-2800 nm, a linewidth less than 0.5 nm, and a peak power of 51 MW have been obtained. The highest one-BBO-OPA energy conversion efficiency has been up to 61%     

火焰中OH基激光激发的荧光光谱

给出了火焰中OH基A~2∑~+-X~2∏紫外跃迁激光激发荧光光谱。对得到的0-0,1-0,2-1带可分辨的线逐一进行了标定。对乙炔/空气火焰中OH相对浓度在不同燃烧区的分布进行了测量。     

The degradation of TDDB characteristics of Si02/Si3N4/Si02 stacked films caused by surfaceroughness of Si3N4 films [DRAMs]

The effect of surface roughness of Si₃N₄ films on time-dependent dielectric breakdown (TDDB) characteristics of SiO₂/Si₃N₄/SiO₂ (ONO) stacked films was investigated. The surface roughness of Si₃N ₄ films-was found to become higher with increasing deposition temperature and to cause the degradation of TDDB characteristics of ONO films in DRAMs. A local thinning of ONO films, evaluated from the TDDB characteristics, agreed with the surface roughness measured by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). Dependence of time to breakdown of ONO films on the deposition conditions was interpreted by electric field intensification due to the surface roughness of Si₃N₄ films     

微波等离子体化学气相沉积法制备C3N4薄膜的研究

本文采用微波等离子体化学气相沉积法（ＭＰＣＶＤ）,高纯Ｎ２（９９．９９９％）和ＣＨ４（９９．９％）作反应气体,在多晶Ｐｔ（９９．９９％）基片上沉积Ｃ３Ｎ４薄膜。Ｘ－射线能谱（ＥＤＸ）分析结果表明Ｎ／Ｃ原子比为１．０～１．４,接近Ｃ３Ｎ４的化学比;Ｘ射线衍射谱说明薄膜主要由β和α－Ｃ３Ｎ４组成;ＦＴ－ＩＲ谱和Ｒａｍａｎ谱支持Ｃ－Ｎ键的存在。     

Extended range of second harmonic generation in β-BaB2O4

Cooling a β-barium metaborate crystal to 89 K extends second harmonic generation to 203.1 nm and greatly increases it efficiency     

High quality silicon nitride deposited by Ar/N2/H2/SiH4 high-density and low energy plasma at low temperature

The high-quality PECVD silicon nitride has been deposited by high-density and low-ion-energy plasma at 400 °C and the effect of the process parameters, such as silane and nitrogen flow rate, pressure, on its structure and electrical properties has been investigated. The experimental results show that silane flow rate is the most sensitive parameter for determining deposition rate and N/Si atomic ratio of silicon nitride in the range of process parameters employed. The change of nitrogen flow rate leaded to slightly change in deposition rate, however, it effects significantly on the refractive index or densification of silicon nitride. With the addition of hydrogen gas in plasma, the hysteresis of C-V characteristics of MIS structure decreases from 0.4 to 0.1 V. The moderate increment of ion energy makes further reduction in the hysteresis of C-V characteristics of MIS from 0.1 V to below 0.05 V. The interface trap density of 6.2×10¹⁰ (ev⁻¹ cm^-2), deduced from the high frequency and quasistatic C-V characteristics of the MIS structure, is about the same as that of LPECVD silicon nitride deposited at the range of 750-850 °C. The stoichiometric silicon nitride of excellence electric and structural properties is obtained by Ar/N₂/H₂/SiH₄ high-density and low ion energy plasma.     

Influence of the annealing temperature on the IR properties of SiO2 films grown from SiH4 + O2

Dispersion analysis was performed on low pressure chemically vapor deposited (LPCVD) SiO₂ films grown from SiH₄ + O₂ at 425 °C. The transmission spectra were analyzed using four Lorentz oscillators within the range 900–1400 cm⁻¹. It was found that the distribution of the SiOSi angles is a superposition of two Gaussians; one corresponding to bridges located in the bulk of the film and one corresponding to bridges located close to the boundaries of the film namely the interfaces of the films and the grain boundaries. The ratio between the bulk like SiOSi bridges over the boundary bridges was found equal to 0.61:1 indicating that films grown from SiH₄ + O₂ contain a higher number of boundary SiOSi bridges relative to those located in the bulk of the film. After annealing for 30 min at temperatures in the range from 550 to 950 °C, films were found to have a lower thickness. The calculated ratio of the two distributions after annealing have shown a clear reduction in the concentration of the boundary bridges as the temperature of annealing increases, in advance of the bridges located in the bulk of the film. For the film annealed at 950 °C for 30 min the ratio was found equal to 4.0:1 which is the same to that of thermally grown films at the same temperature.