Growth and microstructure properties of microcrystalline silicon films deposited using jet-ICPCVD

Microcrystalline silicon films were deposited at a high rate and low temperature using jet-type inductively coupled plasma chemical vapor deposition(jet-ICPCVD).An investigation into the deposition rate and microstructure properties of the deposited films showed that a high deposition rate of over 20 nm/s can be achieved while maintaining reasonable material quality.The deposition rate can be controlled by regulating the generation rate and transport of film growth precursors.The film with high crystallinity deposited at low temperature could principally result from hydrogen-induced chemical annealing.     

Stress control of silicon nitride films deposited by plasma enhanced chemical vapor deposition

Stress controllable silicon nitride(Si Nx) films deposited by plasma enhanced chemical vapor deposition(PECVD) are reported. Low stress Si Nx films were deposited in both high frequency(HF) mode and dual frequency(HF/LF) mode. By optimizing process parameters, stress free(-0.27 MPa) Si Nx films were obtained with the deposition rate of 45.5 nm/min and the refractive index of 2.06. Furthermore, at HF/LF mode, the stress is significantly influenced by LF ratio and LF power, and can be controlled to be 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited Si Nx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuit(IC), micro-electro-mechanical systems(MEMS) and bio-MEMS.     

Cadmium sulfide thin films growth by chemical bath deposition

Cadmium sulfide (CdS) thin films have been prepared by a simple technique such as chemical bath deposition (CBD).A set of samples CdS were deposited on glass substrates by varying the bath temperature from 55 to 75 ℃ at fixed deposition time (25 min) in order to investigate the effect of deposition temperature on CdS films physical properties.The determination of growth activation energy suggests that at low temperature CdS film growth is governed by the release of Cd2+ ions in the solution.The structural characterization indicated that the CdS films structure is cubic or hexagonal with preferential orientation along the direction (111) or (002),respectively.The optical characterization indicated that the films have a fairly high transparency,which varies between 55％ and 80％ in the visible range of the optical spectrum,the refractive index varies from 1.85 to 2.5 and the optical gap value of which can reach 2.2 eV.It can be suggested that these properties make these films perfectly suitable for their use as window film in thin films based solar cells.     

Influence of deposition rate on the structural,optical and electrical properties of electron beam evaporated SnO2 thin films for transparent conducting electrode applications

The role of deposition rate in the structural,optical and electrical properties of SnO2 thin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz.50,75,and 100 W.The structural characterization of the films is done by X-ray diffraction (XRD) technique.The surface morphology of the films is studied by scanning electron microscopy (SEM).Rutherford back scattering (RBS) measurements revealed the thickness of the films ranging from 200 nm to 400 and also a change in the concentration of oxygen vacancies which is found to be the maximum in the film deposited at the lowest deposition rate.Optical absorption spectrum is recorded using the UV-V is spectroscopy and the films are found to be transparent in nature.A shift in the absorption edge is observed and is attributed to a different level of allowed energy states in conduction band minimum.The Hall effect and electrical measurements show a variation in the carrier concentrations,mobility and resistivity of the films.In order to explore a better compromise in electrical and optical properties for transparent electrode applications,skin depths calculations are also done to find the optimized values of carrier concentration and mobility.     

Investigation of AlN Thin Films as Buried Insulator in SOI Structure

Self-heating effects in silicon-on-insulator (SOI) devices limit the applicability of SOI materials in electronics in cases where high power dissipation is expected. AlN film as a potential candidate for buried insulator material in SOI-structures is investigated. Ion-beam-enhanced deposition (IBED) is used to manufacture large area AlN films. SIMS measurements indicate the formation of AlN films. The characterization of the films reveals that the quality of the films strongly depends on the evaporation rate of Al. For the film with high quality deposited at 0.05nm/s, it has higher component of N, excellent dielectric property and a smoother surface with roughness RMS value of 0.13nm, and can be bonded directly at room temperature by the smart-cut process. SOI structure with the AlN film as buried insulator has formed successfully for the first time, which is confirmed by XTEM micrograph.     

Structural and optical properties of ZnO films prepared by ion beam sputtering

Based on the ion beam sputtering deposition technology,ZnO thin films are deposited on the glass substrate.The four-factor and three-level L 9(34)orthogonal experiment is used to obtain the best technological parameters of the deposited ZnO thin films,which are the discharge voltage of 3.5 kV,the oxygen current capacity of 8 sccm,the coil current of 8 A and the distance between target and substrate of 140 mm.The purity of the deposited ZnO thin film is 85.77%,and it has good crystallization in orientation.The experimental results show that research and development of the ion beam sputtering source are advanced,and the ion beam sputtering deposition technology can be used to deposit the orientation preferred thin films with good performance.     

Optical Constants and Structure of ZnO Films by Radio Frequency Magnetron Sputtering

ZnO films are deposited on glass slides by radio frequency（RF） magnetron sputtering under different powers. The polycrystal structures and surface morphologies of the film are investigated. The optical transmission spectra for the ZnO films are measured within the range from 300 nm to 800 nm. The optical constants and thickness of the films are determined using a nonlinear programming method suggested by Birgin et al. The band gap of the film increases with reducing the nano-size of the film grains. The packing density of the films can be improved by reducing the RF power.     

Influence of monomer concentration on optical properties of electrochemically synthesized polypyrrole thin films

Polypyrrole(PPy) thin films were deposited on stainless steel and ITO coated glass substrate at a constant deposition potential of 0.8 V versus saturated calomel electrode(SCE) by using the electrochemical polymerization method.The PPythin filmswere deposited at room temperatureat variousmonomer concentrations ranging from 0.1 M to 0.3 M pyrrole.The structural and optical properties of the polypyrrole thin films were investigated using an X-ray diffractometer(XRD),FTIR spectroscopy,scanning electron microscopy(SEM),and ultraviolet– visible(UV–vis) spectroscopy.The XRD results show that polypyrrole thin films have a semi crystalline structure.Higher monomer concentration results in a slight increase of crystallinity.The polypyrrole thin films deposited at higher monomer concentration exhibit high visible absorbance.The refractive indexes of the polypyrrole thin films are found to be in the range of 1 to 1.3 and vary with monomer concentration as well as wavelength.The extinction coefficient decreases slightly with monomer concentration.The electrochemically synthesized polypyrrole thin film shows optical band gap energy of 2.14 eV.     

Properties of ITO：Zr films deposited by co-sputtering

ITO：Zr films were deposited on glass substrate by co-sputtering with an ITO target and a Zirconium target. Substrate temperature and oxygen flow rate have important influences on the properties of ITO：Zr films. ITO：Zr films show better crystalline structure and lower surface roughness. Better optical-electrical properties of the films can be achieved at low substrate temperature. The certain oxygen flow rates worsen the electrical properties but can enhance the optical properties of ITO：Zr films. The variation in optical band gap can be explained on the basis of Burstin-Moss effect.     

Stress Controlled Silicon Nitride Thin Film Deposited by Plasma Enhanced Chemical Vapour Deposition

SiN, films are deposited on silicon wafers through plasma enhanced chemical vapor deposition （PECVD）. The relationship between the film stress and deposition factors is investigated. It is found that low stress films would be obtained by adjusting the ratio of low frequency（LF） power to high frequency（HF） power pulse time or the chamber pressure. The best of the two methods to control stress in the film is changing the percentage of LF power pulse time. The low stress condition is achieved when the percentage of low frequency power pulse time in total time（LF and HF pulse time） is close to 40%, The low stress cantilever of tunable vertical cavity surface emitting laser is obtained by using this deposition condition,     

Diamond-like carbon protective films for organic photoconductors

The deposition of a protective film to increase the hardness of an organic photoconductor (OPC) surface is an effective method of lengthening the lifetime of the OPC. In this work, diamond-like carbon (DLC) protective films were deposited onto OPC samples by the electron cyclotron resonance (ECR)-microwave plasma chemical vapor deposition (MPCVD) method with low substrate temperature. The DLC films were deposited with optimized deposition conditions and exhibited high transmissivity and high electrical resistivity. The films caused a remarkable increase in the hardness of the OPC surface, by a factor of 2.5∼5.4. The acceptance voltage, dark decay rate, photodischarge rate, and contrast potential of the OPC protected by DLC film were improved. These results show DLC is a suitable protective film for OPC.     

激光沉积红外窗口高性能类金刚石膜技术

类金刚石(DLC)膜具有宽光谱高透射率、高硬度、高热传导及高稳定性等优点,是红外窗口增透保护膜的优选,但现有方法制备的类金刚石膜难以满足高马赫数或海上盐雾等恶劣条件下的应用。激光法相比其他制备方法具有诸多优点,介绍了激光法制备DLC膜的原理及特点,并分析了实现工程应用的难题及关键技术。采用激光沉积法制备出综合性能优异的类金刚石膜,纳米硬度高达44 GPa、内应力仅0.8 GPa、临界刮擦载荷附着力为59.1 mN。正面镀DLC膜,背面镀普通增透膜的硫化锌、硅、锗等红外窗口的平均透射率达82%~91%。实现了150 mm基片的激光法大尺寸均匀薄膜,膜厚不均匀性≤±2%。制备的DLC膜红外窗口通过军标环境适应性试验,并已实现工程化应用。     

Atmospheric pressure chemical vapor deposition of blanket tungsten films on silicon substrates for integrated circuit applications

Atmospheric pressure chemical vapor deposition (APCVD) of tungsten films using WF₆/H₂ chemistry has been studied. A statistical design of experiments approach and a surface response methodology were used to determine the most important process parameters and to obtain the best quality film possible in the parameter range studied. It was found that the deposition rate depends strongly on WF₆ flow rate, temperature, and the interaction between hydrogen flow rate and temperature. The resistivity was found to have a strong dependence on WF₆ and H₂ flow rates and temperature. An activation energy of 0.4 eV was calculated for the reaction rate limited growth regime. Empirical equations for predicting the deposition rate and resistivity were obtained. The resistivity decreases with both increasing film thickness and grain size. The films grown in the studied process parameter range indicate that (110) is the preferred orientation for films deposited with low WF₆/H₂ flow rate ratios at all deposition temperatures (350–450°C), whereas, the (222) orientation dominates at high WF₆/H₂ flow ratios and high deposition temperatures. Also, the grain size is larger for (222) oriented films than for (110) oriented films. The results of this study suggest that high-quality, thin film tungsten can be deposited using APCVD.     

Structural characteristics of as-deposited and crystallized mixed-phase silicon films

In this work, we report on the structural characteristics of as-deposited and crystallized mixed-phase silicon films prepared by thermal decomposition of silane in a low pressure chemical vapor deposition reactor. Mixed-phase films consist of crystallites embedded in an amorphous matrix. The size of these crystallites depends upon the surface diffusion length, a parameter quantitatively expressing the potential of adsorbed silicon atoms for surface diffusion. The density of the pre-existing crystallites can be related to the maximum density of critical nuclei, which develops during the deposition of the film. Both variables were quantitatively related to the deposition temperature and rate via physical models reflecting the experimental observations. Values for the parameters associated with these models were extracted by fitting the experimental data to the theoretical equations. Our theoretical analysis is the first to relate quantitatively the structural characteristics of as-deposited mixed-phase films to the prevailing deposition conditions. Mixed-phase films can crystallize in a much shorter time than as-deposited amorphous films, due to the combination of the growth of the pre-existing crystallites and the higher nucleation rate of new crystallites within the amorphous matrix of the mixed-phase film. The crystallization time and final grain size of crystallized mixed-phase films were found to decrease with increasing density of pre-existing crystallites. However, we showed that if composite films are deposited, consisting of a mixed-phase layer and an amorphous layer, the grain size after crystallization could be comparable to that of crystallized as-deposited amorphous films, with the crystallization time of such composite films about threefold shorter. The structure of both as-deposited and crystallized single and composite mixed-phase films was found to be identical for films deposited on both oxidized silicon and Corning Code 1735 glass substrates.     

离子束溅射宽带吸收薄膜设计与制备技术研究

Si薄膜在可见光和近红外波段具有一定的吸收特性,可用于宽带吸收薄膜的制备。采用离子束溅射技术,在熔融石英基底上制备了不同沉积工艺参数的Si薄膜,基于透、反射光谱和椭偏光谱的全光谱数值拟合法,计算了Si薄膜的光学常数,并研究了氧气、氮气流量对其光学特性的影响。选择Si和Ta2O5作为高折射率材料、SiO2作为低折射率,设计了吸收率为2%和10%的宽带（1 000~1 400 nm）吸收薄膜。采用离子束溅射沉积技术,在熔融石英基底上制备了宽带吸收薄膜,对于A=2%的宽带吸收光谱,在1 064、1 200、1 319 nm的吸收率分别为2.12%、2.15%和2.22%;对于A=10%的宽带吸收光谱,在1 064、1 200、1 319 nm的吸收率分别为9.71%、8.35%和9.07%。研究结果对于吸收测量仪、光谱测试仪等仪器的定标具有重要的作用。     

Influence of AIN protective film thickness on the hardness and electrophotographic properties of organic photoconductors

The deposition of a protective film to increase the hardness of an organic photoconductor (OPC) surface is an effective method to lengthen the lifetime of the OPC. In this work, A1N protective films were deposited onto OPC samples by rf reactive magnetron sputtering with low substrate temperature. The A1N films were deposited with optimized sputtering conditions and exhibited very high transmissivity in the visible wavelength range 300-800 nm. The films caused a remarkable increase in the hardness of the OPC surface, by between 32 and 62%. The acceptance voltage, dark decay rate, photodischarge rate, difference between the residual potential and the acceptance voltage of the OPC protected by A1N film were improved. These results show A1N is a suitable protective film for OPC.     

生长功率对HgCdTe薄膜微观结构以及表面形貌影响

实验采用射频磁控溅射生长了HgCdTe薄膜,并利用台阶仪、XRD、原子力显微镜等现代分析手段对HgCdTe薄膜的生长速率、物相、表面形貌进行了研究。实验结果表明,随着溅射功率增大,其生长速率成线性增大,当溅射功率低于30w时,薄膜XRD衍射图谱上没有出现任何特征衍射峰,只是在2θ=23°附近出现衍射波包,材料具有明显的非晶态特征,当溅射功率高于30w时,XRD表现为多晶结构;AFM和SEM分析表明生长速率对HgCdTe薄膜表面粗糙度、形貌、形成机理等有直接影响,随着生长速率提高,薄膜表面粗糙度逐渐增大,且薄膜逐渐形成“迷津”结构。     

Effect of power variation on microstructure and surface morphology of HgCdTe films deposited by RF magnetron sputtering

Mercury cadmium telluride films were grown by the RF magnetron sputtering technique at different sputtering powers.In experiment,X-ray diffraction (XRD) and atomic force microscopy (AFM) have been used to characterize the microstructure of HgCdTe films.The experimental results showed that when the growth power increased,the growth rate of HgCdTe films increased; when the growth power was less than 30 W,the HgCdTe film deposited by RF magnetron sputtering was amorphous; when the growth power was more than 30 W,the films exhibited polycrystalline structure.Films deposited at different growth rates were found to have characteristically different formations and surface morphologies; as observed through AFM,the surface morphology is composed of longitudinal islands forming a maze-like pattern in the high deposition rate.AFM analysis also illustrated that a significant reduction in the areal density of large islands and characteristically smoother films was achieved using a low deposition rate.