The effect of Ar flow rate in the growth of SiGe:H thin films by PECVD

In this article, by investigating the influence of Ar flow rate on deposition rate and structural properties of hydrogenated silicon germanium (SiGe:H) films, we showed that the addition of Ar in the diluted gas efficiently improve the deposition rate and crystallinity due to an enhanced dissociation of source gases and bombardment on growth surface. The hydrogen content and SE results suggest that the defect density and void volume fraction increases with increasing Ar flow rate, which is attributed to the injection of higher energy Ar⁺ ions into the film led to a displacement of the atoms and an increased possibility of argon being trapped with the films. The optoelectronic properties are investigated by absorption coefficient and dark conductivity measurements and a reasonable explanation is presented.     

Growth of n-type ZnO thin films by using mixture gas of hydrogen and argon

High-quality oxide semiconductor ZnO thin films were prepared on single-crystal sapphire and LaAlOZnO薄膜 氩氢混合气体 薄膜生长 异质结构 薄膜物理学ZnO, PLD, heterostructureProject supported by the National Natural Science Foundation of China (Grant No 19974001) and the National Key Basic Research Special Foundation of China (Grant No NKBRSF G1999064604 and G2000036505).2005-05-309/3/2005 12:00:00 AMHigh-quality oxide semiconductor ZnO thin films were prepared on single-crystal sapphire and baAlO3 substrates by pulsed laser deposition （PLD） in the mixture gas of hydrogen and argon. Low resistivity n-type ZnO thin films with smoother surface were achieved by deposition at 600℃ in 1Pa of the mixture gas. in addition, ferromagnetism was observed in Co-doped ZnO thin films and rectification Ⅰ - Ⅴ curves were found in p-GaN/n-ZnO and p-CdTe/n-ZnO heterostructure junctions. The results indicated that using mixture gas of hydrogen and argon in PLD technique was a flexible method for depositing high-quality n-type oxide semiconductor films, especially for the multilayer thin film devices.     

沉积温度对微晶硅薄膜结构特性的影响

采用PECVD技术，在玻璃衬底上沉积μc-Si:H薄膜. 用拉曼光谱、SEM和UV分光光度计对不同沉积温度下沉积的薄膜的结构特性进行分析. 研究发现：沉积温度较低时，随着沉积温度的升高，薄膜的晶化率增加；当沉积温度超过某一温度值时，随着温度的进一步升高，薄膜的晶化率降低. 这时，表面反应由表面扩散限制转变为流量控制. 该温度值随着硅烷含量的降低而降低. 关键词： 氢化微晶硅薄膜 拉曼散射谱 晶化率 UV分光光度计     

直流磁控溅射沉积含He钛膜的研究

研究了用He/Ar混合溅射气体的直流磁控溅射制备钛膜中，He的掺入现象.分析结果表明，大量的He原子（He/Ti原子比高达56%）被均匀地引入到Ti膜中，其He含量可由混合溅射气体的He分量精确控制.通过调节溅射参数，可实现样品中He的低损伤引入.研究还发现，溅射沉积的含氦Ti膜具有较高的He成泡剂量和高的固He能力，这可能是溅射沉积形成了纳米晶Ti膜所致.纳米晶Ti膜较粗晶材料具有很高浓度的He捕陷中心，使He泡密度增大而泡尺寸减小.随He引入量的增加，Ti膜的晶粒尺寸减小，He引起的晶体点阵参数和X射线衍射峰宽度增大，晶体的无序程度增加.Helium trapping in the Ti films deposited by DC magnetron sputtering with a He/Ar mixture was studied. He atoms with a surprisingly high concentration (He/Ti atomic ratio is as high as 56%)incorporate evenly in deposited film. The trapped amount of He can be controlled by the helium partial amount. The introduction of the helium with no extra damage(or very low damage) can be realized by choosing suitable deposition conditions. It was also found that because of the formation of nanophase Ti film a relative high He flux for bubble formation is needed and the amount of the retain He in sputtering Ti films is much higher than that in the coarse grain Ti films. The nanophase Ti film can accommodate larger concentration of trapped sites to He, which results in a high density and small size of the He bubbles. With the increasing He irradiation flux, the grain size of Ti film decreases and the lattice spacing and width of the X ray diffraction peak increase due to the He introduction, and the film tends to amorphous phase.     

氦气对MPCVD沉积金刚石的影响

为了确定添加氦气对微波等离子体化学气相沉积(MPCVD)金刚石膜的影响,采用发射光谱法(OES)在线诊断了CH₄-H₂-He等离子体的发射光谱特性,研究了He对等离子体内基团空间分布的影响;并利用扫描电子显微镜(SEM)和拉曼(Raman)光谱对不同He体积分数下沉积出的金刚石膜进行了表征。结果表明：随着He体积分数的增加,等离子体内H_α, H_β, H_γ, CH和C₂基团的谱线强度均呈上升趋势,其中H_α基团的谱线强度增加最大。光谱空间诊断发现He的加入导致等离子体中各基团的空间分布均匀性变差,造成沉积出的金刚石膜厚度极不均匀。沉积速率测试表明,He的加入导致碳源基团相对浓度增加,有利于提高薄膜的沉积速率,当He体积分数由0 vol.%增加至4.7 vol.%时,沉积速率提高了24%。SEM测试结果表明,随着He体积分数的增加,金刚石膜表面形貌由(111)晶面取向向晶面取向混杂转变,孪晶生长明显。高He(4.7 vol.%)体积分数下由于C₂基团的相对浓度较高,导致二次形核密度增加。此外,由于基片台受到等离子体的刻蚀和溅射作用,导致薄膜沉积过程中引入了金属杂质原子。二次形核和杂质原子的存在使得孪晶大量的产生,薄膜呈现出压应力。     

Optical,electrical and structural properties of amorphous SiCN:H films prepared by rf glow-discharge decomposition

Amorphous quaternary alloy (a-SiCN:H) films composed of silicon, carbon, nitrogen and hydrogen have been prepared by the rf glow-discharge decomposition in a gas mixture of methane, silane, nitrogen and helium. Effects of nitrogen addition on the optical, electrical, structural and optoelectronic properties of the films have been investigated. Optical bandgap remains almost constant for a wide range of nitrogen addition. Dark and photoconductivity becomes greater by the nitrogen addition than those of undoped a-SiC:H films. Incorporation of a small amount of nitrogen in the film is likely to reduce the structural disorder and/or the density of defects, and some nitrogen atoms seem to work as a dopant. On the other hand, large incorporation deteriorates these properties. The nitrogen addition effect appears more remarkably in the films prepared under the low flow rate ratio of methane to silane.     

Surface passivation of crystalline silicon by sputter deposited hydrogenated amorphous silicon

This letter shows that intrinsic hydrogenated amorphous silicon (a‐Si:H) films deposited by RF magnetron sputtering can provide outstanding passivation of crystalline silicon surfaces, similar to that achieved by plasma enhanced chemical vapour deposition (PECVD). By using a 2% hydrogen and 98% argon gas mixture as the plasma source, 1.5 Ω cm n‐type FZ silicon wafers coated with sputtered a‐Si:H films achieved an effective lifetime of 3.5 ms, comparable to the 3 ms achieved by PECVD (RF and microwave dual‐mode). This is despite the fact that Fourier transform infrared spectroscopy measurements show that sputtering and PECVD deposited films have very different chemical bonding configurations. We have found that film thickness and deposition temperature have a significant impact on the passivation results. Self‐annealing and hydrogen plasma treatment during deposition are likely driving forces for the observed changes in surface passivation. These experimental results open the way for the application of sputtered a‐Si:H to silicon heterojunction solar cells. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

The excellent physical and chemical properties of cubic boron nitride(c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon(100) substrates by radio frequency(RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of H_2 gas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed.     

磁控溅射制备氧化硅薄膜生长速率

氧化硅薄膜是半导体工业中常见的薄膜材料,通常采用化学气相沉积方法制备。但是这种制备方法存在缺欠。采用磁控溅射的方法首先在石英衬底上制备了氧化硅薄膜。研究了射频功率、氧气含量和溅射压强对氧化硅薄膜沉积速率的影响。发现沉积速率随着射频功率的增加而增加;随着氧气含量的增加,先减小后增大;当溅射压强在0.4~0.8 Pa之间变化时,沉积速率变化很小,当溅射压强超过0.8 Pa时沉积速率迅速下降。讨论了不同生长条件下造成氧化硅薄膜生长速率变化的原因。     

氢稀释对高速生长纳米晶硅薄膜晶化特性的影响

以SiH₄与H₂为气源,采用射频等离子体增强化学气相沉积技术,在较高的压强(230Pa)下,研究氢稀释率对纳米晶硅薄膜的生长速率和晶化特性的影响. 实验表明,薄膜的晶化率,晶粒尺寸随着氢稀释率的提高而增加,当氢稀释率为99%,薄膜的晶化率接近70%. 而沉积速率却随着氢稀释率的减小而增加,当氢稀释率从99%减小到95%时,薄膜的沉积速率由0.3nm/s 增加至0.8nm/s. 关键词： 纳米晶硅薄膜 氢稀释 晶化率 硅烷     

Influence of the Plasma Kinetics on the Si/C Ratio of a-SixC1-x: H Thin Films Deposited by Reactive Magnetron Sputtering of a Si Target in Ar + CH4 Gas Mixtures

Possible sources of silicon and carbon atoms built-in amorphous hydrogenated silicon carbide thin films grown by reactive magnetron sputtering (RMS) in argon/methane gas mixtures are evaluated. It is found out that the plasma decomposition of methane molecules plays an essential role in providing of growing film surface by active hydrocarbon fragments, thus influencing significantly the film stoichiometry even though the methane partial pressure in the sputtering gas mixture is only 1.5–4.7%.     

Effects of hydrogen on photoluminescence properties of a-SiNx:H films prepared by VHF-PECVD

Luminescent hydrogenated amorphous silicon nitride films were prepared with different hydrogen flow rate in very high frequency plasma enhanced chemical vapor deposition system. Very bright orange-red light emissions can be clearly observed with the naked eye in a bright room for the films grown at the hydrogen flow rate of 30 sccm. The photoluminescence intensity of the film grown at the hydrogen flow rate of 30 sccm is found to be four times higher than that of the film without hydrogen dilution. However, with further increasing the hydrogen flow rate from 30 to 90 sccm, the photoluminescence intensity of the film rapidly decreases. Fourier-transform infrared absorption spectra indicate that the introduction of hydrogen concentration bonded to silicon and nitrogen is of a key role to enhance the photoluminescence intensity of the films. Based on the measurements of structural and bonding configurations, the improved photoluminescence intensity is attributed to the well hydrogen passivation of nonradiative defect states related to N and Si at proper hydrogen flow rate.     

Distribution of Excited Atoms and Ions in a Plasma Generated at the Surface of Ferroelectric Ceramic

The distribution of excited atoms and ions in a plasma generated at the surface of ferroelectric ceramic has been studied. For all studied spectral lines of He I, Ar I, Ar II and hydrogen a decrease of the total line intensity with the increasing distance from the ceramic surface has been found. The shapes of these distributions are characteristic of the specific spectral lines. The distributions for He I lines depend strong on the concentration of argon in the helium — argon mixture. The effect of overpopulation of some excited Ar II ion levels in an argon discharge observed already in a previous work has been found also in the case of a helium — argon plasma.     

氢化非晶硅叠层薄膜对单晶硅表面钝化研究

采用等离子体增强化学气相沉积法生长的单层本征氢化非晶硅薄膜对单晶硅片进行钝化,结果表明增加氢稀释比有利于减少薄膜中的缺陷,增强钝化效果,过量的氢稀释比会导致非晶硅在硅片表面的外延晶化生长,降低钝化效果。退火导致非晶硅晶化程度增加,降低了钝化效果,同时退火提升了薄膜的质量,改变了H键合方式,增强了钝化效果。因此,单层氢化非晶硅只有在合适的氢稀释比和退火温度才可以获得最佳钝化效果。为了提高非晶硅薄膜对硅片的钝化效果,采用具有高低氢稀释比的叠层本征非晶硅薄膜对硅片进行钝化。因此将高氢稀释比沉积的非晶硅薄膜叠层生长于低氢稀释比的薄膜之上,避免非晶硅在硅片表面的外延生长。在退火过程中,高氢稀释比薄膜中的氢扩散到低氢稀释比薄膜中,有效地钝化了非晶硅中和单晶硅表面的悬挂键,改善了非晶硅/硅片的界面质量,叠层钝化后硅片的少子寿命为7.36 ms,隐含开路电压为732 mV。     

The influence of substrate emissivity on plasma enhanced CVD of diamond-like carbon films

In a planar capacitively coupled RF reactor we deposited diamond-like carbon (DLC) films from the mixture of methane and argon. The self biased electrode was in a poor thermal contact with walls of the reactor, neither water cooled nor electrical heated by a special external circuit. The heating of the electrode was caused mainly by the ion bombardment. We measured the temperatures of a self biased electrode and silicon substrates placed on it with Raytek Thermalert pyrometer in the temperature range 0–500°C. The temperatures were continuously increasing even during the longest deposition time of 120 min and differed for the electrode and the silicons of different specific resistances correlated to their emissivities. Ellipsometric and reflectance measurements of films deposited on two different silicon substrates of different emissivities were carried out. We discussed appropriate models for a film optical characterisation and found that apart a transient layer the studied films were homogeneous. Their deposition rate depended significantly on the silicon emissivities because of the different temperatures. The influence of the silicon substrate emissivity on the mechanical properties of DLC films was studied by means of Vickers microhardness tester. Dedicated to Prof. Jan Janča on the occasion of his 60th birthday. The present work was supported by the Grant Agency of the Czech Republic, contract 106/96/K245.     

氢稀释对FTS沉积a-Si:H薄膜结构特性的影响

采用对靶磁控反应溅射技术,以氢气作为反应气体在不同的氢稀释比条件下制备了氢化非晶硅薄膜.利用台阶仪、傅里叶红外透射光谱、Raman谱和紫外-可见光透射谱测量研究了不同氢稀释比对氢化非晶硅薄膜生长速率和结构特性的影响.分析结果发现,利用对靶磁控溅射技术能够实现低温快速沉积高质量氢化非晶硅薄膜的制备.随着氢稀释比不断增加,薄膜沉积速率呈现先减小后增大的趋势.傅里叶红外透射光谱表明,氢化非晶硅薄膜中氢含量先增大后变小.而Raman谱和紫外-可见光透射谱分析发现,氢稀释比的增加使氢化非晶硅薄膜有序度和光学带隙均先增大后减小.可见,此技术通过改变氢稀释比R能够实现氢化非晶硅薄膜结构的有效控制.     

氮流量在高氢氛围中对富硅氮化硅薄膜材料结构及其发光特性的影响

采用等离子体增强化学气相沉积技术,以N₂掺入到SiH₄和H₂的沉积方式,分别在玻璃和N型单晶硅片(100)衬底上制备富硅氮化硅薄膜。通过紫外-可见光吸收光谱、傅里叶变换红外吸收光谱(FTIR光谱)、拉曼光谱和光致发光谱(PL谱)分别表征掺氮硅薄膜材料的带隙、结构及其发光特性的变化。结果表明：在氢气的氛围中,随着氮气流量的增加,氢原子能够对薄膜缺陷起到抑制作用,并使较低的SiH₄/N₂流量比下呈现富硅态,但却不利于硅团簇的形成。随着氮原子的掺入,Si—N键的含量增大,带隙增大,薄膜内微结构的无序度也增大,薄膜出现了硅与氮缺陷相关的缺陷态发光;随着氮原子进一步增加,出现了带尾态发光,进一步讨论了发光与结构之间的关联。这些结果有助于采用PECVD制备富硅氮化硅对材料发光与结构特性的优化。     

Formation of surface stabilized Si nanocrystal by pulsed laser ablation in hydrogen gas

We prepared silicon nanocrystallites by pulsed laser ablation (PLA) of a Si target in hydrogen background gas. A mixture of hydrogen and helium was used as a background gas and the hydrogen partial pressure was varied. The deposited nanocrystal-film system shows a hierarchical structure composed of surface hydrogenated silicon nanocrystallites as the primary structure and aggregates of the nanocrystallites as the secondary structure. The size of the primary particles was not sensitive to the hydrogen partial pressure, while the porosity of the secondary structure constituted by the aggregation of the primary particles increased with increasing hydrogen partial pressure. This indicates that the surface is stabilized and that aggregation of the primary structure is depressed by surface hydrogenation. The optical gap energy of the deposits shifted to higher energy with increasing hydrogen partial pressure due to the formation of well-isolated nanocrystallites by surface stabilization. These results indicate that PLA in hydrogen gas is a promising technique to prepare surface stabilized and controlled silicon nanocrystallites.     

离子束反应溅射沉积SiO2薄膜的光学特性

 主要研究采用离子束反应溅射（RIBS）制备SiO2薄膜的折射率、消光系数、化学计量比与氧气在氩氧混合工作气体中含量及其沉积速率的关系。研究结果表明：RIBS制备的SiO2薄膜在0.63 μm处折射率n= 1.48,消光系数小于10-5;随着沉积速率的增加,薄膜的折射率和消光系数随之变大,当沉积速率超过0.3 nm/s,即使是在纯氧环境溅射,折射率值也不低于1.5;通过对红外透射光谱的主吸收峰位置研究得到沉积的SiO2薄膜为缺氧型,化学计量比不超过1.8,且红外吸收峰位置和SiO2折射率存在对应关系,因此在不加热衬底情况下使用RIBS制备SiO2薄膜时,会限制沉积速率的提高。     

Transport and stability studies on high band gap a-Si:H films prepared by argon dilution

Device quality hydrogenated amorphous silicon films (a-Si:H) are deposited at a high deposition rate (4–5 Å/s) using a mixture of argon and hydrogen-diluted silane. The films exhibit good opto-electronic properties and show less degradation upon light soaking. Light-induced changes in conductivity could be annealed at much lower temperature. The presence of Ar^* and atomic hydrogen in plasma replaces the weak Si-Si bonds, which are responsible for light-induced degradation by strong Si-Si bonds. This results in the improved stability of the films.