UHV/CVD生长本征硅外延层的研究

在微波双极型晶体管中,收集区的厚度是影响其截止频率的一个重要因素。普通的常压外延难以生长出杂质浓度变化陡峭的薄外延层。文章利用自行研制的超高真空化学气相淀积(UHV/CVD)系统SGE500,在N型(掺As)重掺杂衬底上进行了薄本征硅外延层生长规律的研究;并采用扩展电阻(SPR)、原子力显微镜(AFM)、双晶衍射(DCXRD)等方法,对外延层的质量进行了评价。采用该外延材料制作的锗硅异质结双极型晶体管(SiGe HBT)器件击穿特性良好。     

Atomic scale KMC simulation of {100} oriented CVD diamond film growth under low substrate temperature—Part I simulation of CVD diamond film growth under Joe—Badgwell—Hauge model

The growth of {100} oriented CVD( Chemical Vapor Deposition) diamond film under Joe-Badgwell-Hauge(J-B-H) model is simulated at atomic scale by using revised KMC(Kinetic Monte Carlo)method.The results show that:(1) under Joe‘s model,the growth mechanism from single carbon species is suitable for the growth of {100} oriented CVD diamond film in low temperature;(2) the deposition rate and surface roughness(Rq) under Joe‘s model are influenced intensively by temperature(Ts) and not evident bymass fraction Wc1 of atom chlorine;(3) the surface roughness increases with the deposition rate.i.e.the film quality becomes worse with elevated temperature,in agreement with Grujicic‘s prediction;(4) the simulation results cannot make sure the role of single carbon insertion.     

沉积参数对ZnS体材料红外透过率的影响

采用低压化学气相沉积法系统研究了Ｈ２Ｓ／Ｚｎ流量比、沉积温度、沉积速率及衬底材料对ＺｎＳ体材料红外透过率的影响规律，在本实验研究的条件下认为采用低的Ｈ２Ｓ／Ｚｎ流量比及低的沉积速率，适宜的沉积温度可以提高ＺｎＳ的透过率。同时高沉积温度及高Ｈ２Ｓ／Ｚｎ流量比可减少ＺｎＳ对波长６．２μｍ光的吸收。在优化的工艺下获得了高红外透过率的ＺｎＳ体材料。     

Properties of Pt/C catalyst modified by chemical vapor deposition of Cr as a cathode of phosphoric acid fuel cell

Cr-modified Pt/C catalysts were prepared by the chemical vapour deposition (CVD) of Cr on Pt/C, and their performance as a cathode of phosphoric acid fuel cell (PAFC) was compared with the case of catalysts containing Cr added by impregnation (IMP).The catalyst prepared by CVD showed a higher activity for oxygen reduction reaction (ORR) than one prepared by IMP. There was an optimum amount of Cr that yielded the maximum mass activity of the catalyst because the gain in the intrinsic activity due to the promotional effect of Cr was counterbalanced by the loss of exposed Pt surface area as a result of the Cr introduction. Nevertheless, the activity increase at the optimum amount of Cr was greater for the CVD catalyst than for the IMP catalyst. Also, the optimum amount of Cr to yield the maximum activity was smaller for the former catalyst [Cr/Pt]_CVD = 0.6, than for the latter, [Cr/Pt]_IMP = 1.0.The enhancement of the Pt catalyst activity by Cr addition is attributed to two factors: changes in the surface Pt-Pt spacing and the electronic modification of the Pt surface. The formation of a Pt-Cr alloy, as confirmed by X-ray diffraction, decreased the lattice parameter of Pt, which was beneficial to the catalyst activity for ORR. X-ray photoelectron spectroscopy results showed that the binding energies of Pt electrons were shifted to higher energies due to Cr modification. Accordingly, the electron density of Pt was lowered and the Pt-O bond became weak on the Cr-modified catalysts, which was also beneficial to the catalyst activity for ORR.The promotion of oxygen reduction on Cr-modified catalysts was confirmed by measuring the cyclic voltammograms of the catalysts. All the above changes were made more effectively for catalysts prepared by CVD than for those prepared by IMP because the former method allowed Cr to interact more closely with the Pt surface than the latter, which was demonstrated by the characterization of catalysts in this study.     

热丝辅助等离子体化学气相法生长c－BN薄膜

用热丝辅助射频等离子体化学气相沉积法（ＰＣＶＤ）合成：ｃ－ＢＮ薄膜获得成功。实验结果表明，灯丝温度、反应气压、衬底温度、灯丝与衬底距离对薄膜质量有重要影响。     

Dependence of electrical properties of polycrystalline cvd si films on grain size and impurity doping concentrationa,b

The electrical properties of sets of simultaneously grown p-type polycrystalline Si films, deposited by SiH₄ pyrolysis on polycrystalline high-purity alumina substrates and B-doped during growth, were determined by Hall-effect measurements in the temperature range 77-420K as functions both of impurity doping concentration N (~10^l5 to ~10²⁰cm⁻³) and average grain size (≈1 to ≈125μm) in the film. Room temperature data showed rapidly increasing resistivities and rapidly decreasing free-carrier concentrations for doping below a critical concentration N_m and distinct mobility minima at that concentration, with the value of N_m being larger the smaller the average grain size. Measurements as a function of sample temperature showed the intergrain barrier height E_b, decreasing from a maximum value of ~0.4eV at the critical concentration to very small values (~0.01eV) for concentrations above 10¹⁹cm⁻³, with a functional dependence close to E_b ∝l/N^1/2 and E_b for any given concentration being larger the smaller the average grain size. Results are interpreted in terms of the grain-boundary trapping model. Trapped carrier densities in the grain boundaries were calculated to range from ~5×l0¹¹cm⁻² at N≈N_m to ~5×l0¹²cm⁻² for N>10¹⁹cm⁻³, the density being higher the smaller the grain size, and evidence was found for an energy distribution of traps in the Si bandgap, rather than a fixed density at a single discrete energy level. The observed relationship between N_m and average grain size nearly coincides with that of the model for films with ~lμm grain size but sharply departs from it for larger grain sizes, indicating probable applicability of the model for grain sizes up to that range. ^aThis work was supported by the U.S. Department of Energythrough its San Francisco Operations Office under Contract DE-AC03-79ET23045 and monitored by the Solar Energy Research Institute, Golden, CO. bThese results were first described at the 22nd Electronic Materials Conference, Ithaca, NY, June 21–27, 1980, Paper No. M4.     

Growth of SiGe film by using a single-wafer rapid thermal processing UHV/CVD system

Ultra-high-vacuum chemical vapor deposition (UHV/CVD) system displays excellent performance for the growth of high-quality SiGe film. Investigations have shown that have shown that SiGe film grown by this system has high quality. A 10-finger SiGe hetero-junction bipolar transistor (HBT) device displayed good electrical performance. The current gain was about 500, and the f_T was 5.4 GHz with f_max 7.5 GHz under V_CB=3 V, I_C=10 mA. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24–27, 2003.     

RF-500型CVD镀膜机计算机控制系统

针对RF-500型CVD镀膜机传统的电气控制缺点,开发了基于PC-PLC的RF-500型CVD镀膜机计算机控制系统.介绍了RF-500型CVD镀膜机的结构以及工作原理;并对该控制系统的硬件结构和软件功能进行了描述.对该控制系统的控制效果进行了大量的实验研究,研究结果表明:基片温度控制精度达到±1℃、工作(反应)气体的流量控制精度达到10mL、可以进行精确的开关量控制.     

利用化学气相沉积法在SiO2小球基底上制备纳米碳管的研究

利用匀胶机将经过超声混合的二氧化硅小球的酒精溶液旋涂在洗净的硅片上,获得了具有曲面的纳米碳管生长基底.利用以二茂铁和二甲苯作为反应前驱体的化学气相沉积法在该基底上实现了碳管在二氧化硅与硅之间的选择性生长,并在不同的沉积温度条件下,可以分别获得球状和束状碳管产物.通过扫描电镜观察分析经过退火处理的原始基底的表面形貌,讨论了碳管产物与反应温度之间的关系.     

钢渗铬层上金刚石薄膜的表面、界面结构及附着性

在钢渗铬层表面用化学气相沉积(CVD))法制备了金刚石薄膜.使用扫描电镜(SEM)、透射电镜(TEM)和压痕法研究了金刚石膜的表面、界面结构及附着力.用拉曼光谱分析了金刚石膜的纯度及非金刚石碳相.甲烷含量超过0.6%(体积分数)后,金刚石膜为球形纳米晶,形核密度＞107cm-2.用甲烷含量为0.6%(体积分数)沉积的金刚石膜表面的残余压应力为1.22 Gpa,而膜背面的残余压应力更高,达2.61 Gpa.压痕显示在19.6 N载荷下膜发生开裂.TEM观察发现,膜/基界面为微观非平面,有利于提高金刚石膜的附着力.