Effect of deposition conditions on the physical properties of Sn_xS_y thin films prepared by the spray pyrolysis technique

Tin sulfide thin films（Sn_xS_y） with an atomic ratio of y/x = 0.5 have been deposited on a glass substrate by spray pyrolysis.The effects of deposition parameters,such as spray solution rate（R）,substrate temperature （T_s） and film thickness（t）,on the structural,optical,thermo-electrical and photoconductivity related properties of the films have been studied.The precursor solution was prepared by dissolving tin chloride（SnCl₄,5H₂O） and thiourea in propanol,and Sn_xS_y thin film was prepared with a mole ratio of y/x = 0.5.The prepared films were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and UV-vis spectroscopy. It is indicated that the XRD patterns of Sn_xS_y films have amorphous and polycrystalline structures and the size of the grains has been changed from 7 to 16 nm.The optical gap of Sn_xS_y thin films is determined to be about 2.41 to 3.08 eV by a plot of the variation of（αhv）² versus hv related to the change of deposition conditions.The thermoelectric and photo-conductivity measurement results for the films show that these properties are depend considerably on the deposition parameters.     

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,     

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.     

BP Learning Algorithm Based on DFP and Trust Region Method

The Back propagation （BP） algorithm is one of the most widely used learning algorithms of Neural network （NN）. The traditional BP learning algorithm has some defects, such as slow convergence rate and poor stabilization. In this paper, a new learning algorithm based on Davidon-fletcher-powell （DFP） and Trust Region method is proposed to solve these problems. Compare with other learning algorithms, DFP has advantages, such as higher searching efficiency, super-linear convergence rate and lower computation cost. On the other hand, trust region method make the new learning algorithm hold global convergence, stability, and high accuracy, especially in large residuals problems. Simulation results on XOR problem and non-linear system recognition show that this new method work well in improving the convergence rate and accuracy.     

衬底温度对In掺杂CdO薄膜的结构和性能的影响

Transparent indium-doped cadmium oxide（In-CdO） thin films were deposited on quartz glass substrates by pulsed laser deposition（PLD） from an ablating Cd-In metallic target.The effect of substrate temperature on the structural,optical and electrical properties of In-doped CdO thin films were studied in detail.The optical transmittance of In doped CdO films are obviously influenced by the substrate temperature.All films exhibit a transmittance higher than 75%in the visible region.More significantly,In-doping leads to an evident widening of optical band gap from 2.56 to 2.91 eV;and the increase in optical band gap is found to depend on the deposition temperature.It is also seen that the electrical properties of these films strongly depend on the substrate temperature. The In-CdO thin film grown at 300℃has low resistivity(1.15×10^-4Ω·cm),high carrier concentration(5.35×10²⁰ cm^-3),and high mobility（101.43 cm²/（V·s））.     

Effect of Electron Drag on Performances of Carbon Nanotubes as Flow Sensors

Experimentally, the electron drag effect on carbon nanotube surface in flowing liquids was investigated. It was found that electric current could be generated in metallic carbon nanotubes immersed in the liquids. Carbon nanotubes were synthesized on Si substrate by hot filament chemical vapor deposition. The experimental results showed that the flow--induced current on the surface of carbon nanotube films was closely depended on the flow rate, concentration, properties and temperature of liquids. The flow--induced current was increased with the increasing of flow rate, concentration and temperature of liquids. The obtained results were discussed in detail.     

Theoretical investigation of some parameters into the behavior of quantum dot solar cells

The main goal of this paper is to determine the accurate values of two parameters namely the surface generation–recombination rate and the average total number of electrons density generated in the i-region. These values will enhance the performance of quantum dot solar cells(QDSCs). In order to determine these values, this paper concentrates on the optical generation lifetime, the recombination lifetime, and the effective density state in QDs. Furthermore, these parameters are studied in relation with the average total number of electrons density. The values of the surface generation–recombination rate are found to be negative, which implies that the generation process is dominant in the absorption quantum dot region. Consequently, induced photocurrent density relation with device parameters is determined. The results ensure that QDSCs can have higher response photocurrent and then improve the power conversion efficiency. Moreover, the peak value of the average total number of electrons density is achieved at the UV range and is extended to the visible range, which is adequate for space and ground solar applications.     

立式MOCVD反应室感应加热温度场的有限元分析*

The temperature field in the vertical metalorganic chemical vapor deposition （MOCVD） reactor chamber used for the growth of GaN materials is studied using the finite element analysis method （FEM）. The effects of the relative position between the coils and the middle section of the susceptor, the radius of the coil, and the height of the susceptor on heating condition are analyzed. All simulation results indicate that the highest heating efficiency can be obtained under the conditions that the coil distributes symmetrically in the middle section of the susceptor and the ratio of the height of the susceptor to that of the coil is three-quarters. Furthermore, the heating efficiency is inversely proportional to the radius of the coil.     

Electroless Cu deposition process on TiN for ULSI interconnect fabrication via Pd/Sn colloid activation

In this study, (100)-orientation silicon wafer coated with TiN barrier is catalyzed by a Pd/Sn colloid, which serves as an activator for electroless copper deposition. After activation, electroless deposition of Cu occurs on the catalytic surface. The coverage of the Cu deposit reaches 100% and the adsorptive amount of Pd is greatly increased by the conditioning process. The correlation between deposition rate, resistivity, morphology, crystal structure, and composition of the deposit when varying the temperature of the plating bath is discussed. The deposition rate of Cu is monitored by both the electrochemical method and the profilometer (α-step), while the other properties of the deposit are measured by four-point probe, scanning electron microscopy (SEM), x-ray diffraction (XRD), and Auger electron microscopy (AES). Deposition at 70°C is favorable due to the higher deposition rate, lower resistivity, less impurities, and more preferred orientation in the crystal structure than that at lower temperature. Problems regarding adhesion and high resistivity can be greatly mitigated via 400°C thermal annealing. The resistivity of Cu can be reduced to 2.2 μΩcm. Moreover, trenches of 1 μm and 0.25 μm on patterned wafer have been successfully filled by electroless deposition of Cu with the aid of surfactant C12.     

Surface and optical properties of silicon nitride deposited by inductively coupled plasma-chemical vapor deposition

The surface and optical properties of silicon nitride samples with different compositions were investigated.The samples were deposited on InP by inductively coupled plasma chemical vapor deposition using different NH3 flow rates.Atomic force microscopy measurements show that the surface roughness is increased for the samples with both low and high NH3 flow rates.By optimization,when the NH3 flow rate is 6 sccm,a smooth surface with RMS roughness of 0.74 nm over a 5 × 5μm2 area has been achieved.X-ray photoelectron spectroscopy measurements reveal the Si/N ratio of the samples as a function ofNH3 flow rate.It is found that amorphous silicon is dominant in the samples with low NH3 flow rates,which is also proved in Raman measurements.The bonding energies of the Si and N atoms have been extracted and analyzed.Results show that the bonding states of Si atoms transfer from Si0 to Si+4 as the NH3 flow rate increases.     

YMnO_3薄膜的铁电性能及其应用

对金属 -铁电体 -半导体场效应晶体管器件而言 ,具有六方晶系结构的稀土锰酸盐 ( Re Mn O3)是性能优良的薄膜材料 ,它们的介电常数低 ,仅仅只有单一的极化轴 ,没有挥发性的元素 Pb、Bi等。本文作者对 Re Mn O3材料的结构特征、制备方法及其铁电性能等进行了介绍 ,并指出存在的困难及其发展方向。     

传统PECVD高品质氢化非晶硅的淀积率

根据 Winer模型 ,联合 Winer模型和 Street的氢化学势理论 ,分别研究了传统 PECVD( CPECVD)高品质氢化非晶硅 ( HQ a-Si:H)的淀积率上限 rdup和淀积率 rd 与 a-Si:H缺陷密度 ND 的关系。得到的结论是 :( 1 )rdup=1 .6nm/s(目前实验上 rd 已接近 1 .0 nm/s)。( 2 )对每一优化淀积温度 ( Ts=2 0 0～ 30 0°C) ,存在一相应的优化淀积率 rdop,当 rd相似文献   

Copper chemical vapor deposition from Cu(hexafluoroacetylacetonate)trimethylvinylsilane

Copper chemical vapor deposition using Cu-hexafluoroacetylacetonate (hfac) trimethylvinylsilane (TMVS) as precursor was performed in a cold-wall low pressure chemical vapor deposition (CVD) reactor. The design and operation of the reactor are described. Copper deposition on thermal SiO₂, W, and CoSi₂ substrate surfaces was investigated over the temperature range of 160–300°C and pressure range of 10–1000 mTorr. The activation energies of Cu CVD were determined to be 13.33 and 11.54 kcal/mole for the W and CoSi₂ substrates, respectively. The dependence of film resistivity, grain size, and growth rate on deposition pressure and temperature were also investigated. The film uniformity was found to be better than ten percent over a 4-inch diameter substrate. Experimental results also show that selective deposition can be achieved at a pressure of 10 mTorr within the temperature range of 160–200°C. In addition, hydrofluoric acid dipping was found to modify the SiO₂ surface and influence the copper deposition on it.     

深亚微米CMOS布线工艺中等离子对薄栅氧损伤的预防研究

A comparison is made of several plasma-induced damage(PID) measurement techniques.A novel PID mechanism using high-density plasma(HDP) inter-metal dielectric(IMD) deposition is proposed.The results of a design of experiment(DOE) on Ar pre-clean minimizing PID are presented.For HDP oxide deposition,the plasma damage is minimal,assuring minimal exposure time of the metal line to the plasma using a maximal deposition to sputter ratio.This process induces less PID than classic SOG processing.Ar pre-clean induces minimal plasma damage using minimal process time,high ion energy and high plasma power.For metal etching,an HDP etch is compared to a reactive ion etch,and the impact of the individual process steps are identified by specialized antenna structures.The measurement results of charge pumping,breakdown voltage and gate oxide leakage correlate very well.On metal etching,the reactive ion etching induces less plasma damage than HDP etching.For both reactors, PID is induced only in the metal over-etch step.     

Modeling of low-pressure chemical vapor deposition

A simple mathematical model is established for low-pressure chemical vapor deposition (LPCVD) reactors which takes into account the interaction between diffusion and convection. The classical method of separation of variables can be applied to solve the partial differential equations describing the process, in view of the fact that in practice the deposition rate is small.     

非晶硅薄膜的LF-PECVD制备及椭偏表征

以SiH4为先驱气体,采用低频等离子体增强化学气相沉积（LF-PECVD）方法在Si衬底上制备了氢化非晶硅（a-Si∶H）薄膜。在薄膜沉积过程中,工艺参数将会影响非晶硅薄膜的沉积速率和光学性能。通过反射式椭圆偏振光谱仪（SE）研究了SiH4气体流量、工作压强和衬底温度等条件对氢化非晶硅沉积速率和光学性质的影响。实验结果表明,氢化非晶硅沉积速率随着SiH4流量、工作压强和衬底温度的改变而规律地变化。相比于SiH4流量和工作压强,衬底温度对折射率、吸收系数和折射率的影响更大。各工艺条件下所制备的非晶硅薄膜光学禁带宽度在1.61～1.77eV。     

应用高压高功率的微晶硅薄膜高速沉积

应用高压高功率(hphP)甚高频等离子增强化学气相沉积(VHF-PECVD)法对微晶硅(μc-Si:H)进行高速沉积,确定了hphP VHF-PECVD法沉积μc-Si:H的最优条件参数,在此参数下对hphP和低压低功率(IplP)两组样品沉积速率、光电导、暗电导及光敏性等性能参数进行测试,得到了1.58 nm的较高沉...     

变温LPCVD沉积氮化硅薄膜的均匀性优化

以低压化学气相沉积(LPCVD)热壁立式炉为实验平台,由二氯硅烷和氨通过LPCVD工艺合成氮化硅薄膜,利用降温成膜提高氮化硅薄膜的膜厚均匀度.基于气体碰撞理论建立了氮化硅薄膜沉积速率与反应气体浓度的关系式.分析比较了LPCVD炉内不同升温速率沉积氮化硅薄膜的表面性能.发现在变温沉积阶段,选择合适的降温速率是实现薄膜沉积...     

SiOF and SiO2 deposition in a HDP reactor: tool characterization and film analysis

A high density plasma chemical vapour deposition (HDP CVD) system based on electron cyclotron resonance (ECR) plasma excitation for deposition of inter metal dielectric (IMD) is presented. With the system deposition of SiO₂ and SiOF has been performed. The influence of pressure, Ar content in the flow, total flow, bias voltage, microwave power on gap fill capability and growth rate has been investigated. A figure of merit, the product of gap filling capability and growth rate is defined. In addition measurements of the uniformity of the composition over the wafer of the deposited SiO₂ and SiOF layers were performed. The dielectric constant of the layers was measured on SiOF films with different composition. The stability of these SiOF films was also analysed. This was done by treating the films with moisture and measuring composition before and after this treatment.