铝诱导晶化法制备多晶硅薄膜

多晶硅薄膜在微电子和能源科学领域有着广泛的应用.本文介绍了利用铝诱导晶化非晶硅制备多晶硅薄膜的方法,叙述了铝诱导晶化法制备多晶硅薄膜的一般过程,着重讨论了铝诱导晶化非晶硅的机理和在制备过程中各种参数对多晶硅薄膜质量的影响.     

铝诱导晶化法制备多晶硅薄膜

多晶硅薄膜在微电子和能源科学领域有着广泛的应用.本文介绍了利用铝诱导晶化非晶硅制备多晶硅薄膜的方法,叙述了铝诱导晶化法制备多晶硅薄膜的一般过程,着重讨论了铝诱导晶化非晶硅的机理和在制备过程中各种参数对多晶硅薄膜质量的影响.     

铝诱导晶化法制备多晶硅薄膜

多晶硅薄膜在微电子和能源科学领域有着广泛的应用。本文介绍了利用铝诱导晶化非晶硅制备多晶硅薄膜的方法,叙述了铝诱导晶化法制备多晶硅薄膜的一般过程,着重讨论了铝诱导晶化非晶硅的机理和在制备过程中各种参数对多晶硅薄膜质量的影响。     

铝诱导多晶硅薄膜籽晶层的电学性质

利用磁控溅射系统在玻璃衬底上制备出具有玻璃∕铝∕非晶硅的多层膜结构样品,然后在管式退火炉中以一定的温度退火,使非晶硅晶化形成多晶硅薄膜籽晶层。扫描电子显微镜(SEM)及光学显微镜测试表明,铝诱导结晶后样品中的铝层已被完全置换为连续并且厚度均匀的多晶硅层,多晶硅晶粒的平均尺寸为23μm。喇曼光谱测试和X射线衍射(XRD)分析表明,多晶硅薄膜籽晶层具有良好的结晶质量,并且具有高度的(111)择优取向。霍尔测试结果表明,铝诱导多晶硅薄膜籽晶层属于高浓度p型掺杂,掺杂浓度达到了1018/cm3。分析认为铝在非晶硅晶化过程中不仅扮演了诱导金属的角色,还起到了掺杂的作用。     

PECVD制备纳米晶多晶硅薄膜

以Si(100)为衬底,采用磁控溅射和射频等离子体增强化学气相沉积系统制备了Si(100)/Al膜/非晶Si膜结构的样品。对该样品进行Al诱导真空退火以制备多晶硅薄膜,采用X射线衍射仪(XRD)和AFM分析薄膜微结构及表面形貌。实验结果表明,在经过500℃、550℃Al诱导退火后,形成了择优取向为〈111〉晶向的多晶硅薄膜。AFM给出了550℃退火后薄膜表面形貌,为100～200nm大小的圆丘状硅晶粒,密集排列在薄膜表面;并对Al诱导真空退火晶化的机理进行了分析。     

镀铜玻璃衬底上柱状多晶硅薄膜的制备

采用热丝化学气相沉积方法在镀铜玻璃衬底上制备了柱状多晶硅薄膜.使用XRD、Raman光谱、扫描电子显微镜(SEM)和原子力显微镜(AFM)等测试手段研究了灯丝与衬底间距(5～10 mm)、灯丝温度(1 800～1 500℃)以及对应的衬底温度(在320～200℃变化)对多晶硅薄膜的微观形貌、结晶性及晶体学生长方向的影响规律.研究结果表明:在镀铜玻璃衬底上金属诱导生长的多晶硅薄膜具有较高的晶化率,较低的晶化温度,同时铜过渡层影响多晶硅薄膜的晶体学生长方向.     

连续氩氪离子激光晶化非晶硅薄膜的研究

为了研究连续激光晶化非晶硅薄膜中激光功率密度对晶化效果的影响,利用磁控溅射法制备非晶硅薄膜,采用连续氩氪混合离子激光器对薄膜进行退火晶化,用显微喇曼光谱测试技术和场发射扫描电子显微镜研究了薄膜在5ms固定时间下不同激光功率密度对晶化效果的影响,并对比了普通玻璃片和石英玻璃两种衬底上薄膜晶化过程的差异。结果表明,在一定激光功率密度范围内(0kW/cm2~27.1kW/cm2),当激光功率密度大于15.1kW/cm2时,普通玻璃衬底沉积的非晶硅薄膜开始实现晶化;随着激光功率密度的增大,晶化效果先逐渐变好,之后变差;激光功率密度增大到24.9kW/cm2时,薄膜表面呈现大面积散落的苹果状多晶硅颗粒,晶粒截面尺寸高达478nm ;激光功率密度存在一个中间值,使得晶化效果达到最佳;石英衬底上沉积的非晶硅薄膜则呈现与前者不同的结晶生长过程,当激光功率密度为19.7kW/cm2时,薄膜表面呈现大晶粒尺寸的球形多晶硅颗粒,并且晶粒尺寸随着激光功率密度的增大而增大,在 27.1kW/cm2处晶粒尺寸达到最大5.38m。研究结果对用连续激光晶化法制备多晶硅薄膜的研究具有积极意义。     

玻璃衬底多晶硅薄膜太阳电池

玻璃衬底多晶硅薄膜太阳电池因具有成本低廉、转换效率高以及性能稳定等优点引起了人们的广泛关注。详细阐述了玻璃衬底多晶硅薄膜太阳电池的两种典型结构、基本制备流程及其关键工艺对太阳电池性能的影响,还介绍了玻璃衬底制备多晶硅薄膜的直接制备技术、固相晶化技术、液相晶化技术和籽晶层技术以及玻璃衬底多晶硅薄膜太阳电池的研究现状。由于薄膜太阳电池性能的好坏直接取决于薄膜的质量,所以关键工艺中的快速热退火和氢钝化能显著提高电池性能。然而,至今各种制备方法都不够成熟,不能规模化制备多晶硅薄膜,因此改进和发展现有多晶硅薄膜的制备技术是今后玻璃衬底多晶硅薄膜太阳电池研究的核心课题。     

低温沉积硅薄膜微结构的Raman分析

用Raman散射谱研究了以SiH4/H2为气源,用等离子体增强化学气相沉积技术,低温制备的一系列硅薄膜的微结构特征.结果表明:在常规气压和常规功率下,衬底温度在200～500 ℃之间,存在结晶最佳点,400 ℃结晶效果相对最好;在高压高功率下沉积和常压常功率下沉积相比,高压高功率更有利于薄膜晶化;低温短时的高气压高功率沉积,玻璃衬底与铝覆盖的玻璃衬底相比,玻璃上的硅薄膜晶粒尺寸更大,而铝覆盖的玻璃衬底上的硅薄膜的晶化率更高.     

准分子激光诱导非晶硅晶化制备多晶硅薄膜晶体管

讨论了用准分子激光诱导非晶硅晶化法制备多晶硅薄膜晶体管的结构与工艺优化问题。用 Xe Cl准分子激光器对 PECVD法生长的非晶硅薄膜进行了诱导晶化处理 ,成功制备了多晶硅薄膜晶体管 ,获得最大场效应迁移率为 1 4.5cm2 /V· s,亚阈值斜率为 1 .9V/dec,开关电流比为 1 .0× 1 0 6的器件性能。     

Understanding the Effects of Stress on the Crystallization of Amorphous Silicon

This paper presents the results of a systematic study on the effects of stress on aluminum-induced crystallization (AIC) of plasma-enhanced chemical-vapor-deposited (PECVD) amorphous silicon (a-Si:H). To decouple the impact of stress on the AIC of a-Si:H from other factors that may affect crystallization, such as a-Si:H and aluminum deposition conditions, identical thin film structures [Al (200 nm)/a-Si:H (200 nm)] were deposited on the front surface of all samples. On the back surfaces, various amorphous silicon films were deposited to adjust the curvature of the samples and, therefore, the stress in the a-Si:H film on the front surface. It was found that tensile stress in a-Si:H can retard the AIC of a-Si:H.     

The effects of hydrogen on aluminum-induced crystallization of sputtered hydrogenated amorphous silicon

The effects of hydrogen on aluminum-induced crystallization (AIC) of sputtered hydrogenated amorphous silicon (a-Si:H) were investigated by controlling the hydrogen content of a-SiH films. Nonhydrogenated (a-Si) and hydrogenated (a-Si:H) samples were deposited by sputtering and plasma-enhanced chemical vapor deposition (PECVD). All aluminum films were deposited by sputtering. Hydrogen was introduced into the sputter-deposited a-Si films during the deposition. After deposition, the samples were annealed at temperatures from 200°C to 400°C for different periods of time. X-ray diffraction (XRD) patterns were used to confirm the presence and degree of crystallization in the a-Si:H films. For nonhydrogenated films, crystallization initiates at a temperature of 350°C. The crystallization of sputter-deposited a-Si:H initiates at 225°C when 14% hydrogen is present in the film. As the hydrogen content is decreased, the crystallization temperature increases. On the other hand, the crystallization initiation temperature for PECVD a-Si:H containing 11at.%H is 200°C. Further study revealed that the crystallization initiation temperature is a function, not only of the total atomic percent hydrogen in the film, but also a function of the way in which the hydrogen is bonded in the film. Models are developed for crystallization initiation temperature dependence on hydrogen concentration in a-Si:H thin films.     

Dependence of thin film transistor characteristics on thedeposition conditions of silicon nitride and amorphous silicon

The systematic relation between thin film transistors' (TFT's) characteristics and the deposition conditions of amorphous silicon nitride (a-SiN) films and hydrogenated amorphous silicon (a-Si:H) films is investigated. It is observed that field effect mobility μ_FE and threshold voltage V_th of the TFT's strongly depend on the deposition conditions of these films. The maximum μ_FE of 0.88 cm²/V·s is obtained for the TFT of which a-SiN film is deposited at a pressure of 85 Pa. This phenomenon is due to the variation of the interface states density between a-Si:H film and a-SiN film     

Novel polycrystalline silicon thin film transistors prepared by deposition from Si2H6 and subsequent annealing by NH3 plasma

This work investigated the channel layer of polycrystalline silicon (poly-Si) thin film transistors (TFTs) prepared by amorphous silicon (a-Si) films deposited using Si₂H₆ gas. The recrystallization of channel layers, source/drain, gate electrodes and post implant anneal were performed at the same time. Due to the larger grain size, the device has higher field effect mobility than SiH₄ deposited devices. These devices were also subsequently passivated by NH₃ plasma. The NH₃ plasma significantly improves the n-channel devices; however, the improvement of p-channel devices is limited. Especially, the threshold voltage of n-channel devices is significantly shifted toward the negative gate voltage than the shift magnitude of p-channel devices. To investigate the band gap width and Fermi level by determining the leakage activation energy, it is found that the channel film is changed slightly from p-type to n-type. These results may be attributed to the donor effect by NH₃ plasma passivation.     

A high-performance polycrystalline silicon thin film transistorwith a silicon nitride gate insulator

We have fabricated a high performance polycrystalline silicon (poly-Si) thin film transistor (TFT) with a silicon-nitride (SiN_x ) gate insulator using three stacked layers: very thin laser of hydrogenated amorphous silicon (a-Si:H), SiN_x and laser annealed poly-Si. After patterning thin a-Si:H/SiN_x layers, gate, and source/drain regions were ion-doped and then Ni layer was deposited. This structure was annealed at 250°C to form a NiSi silicide phase. The low resistive Ni silicides were introduced as gate/source/drain electrodes in order to reduce the process steps. The poly-Si with a grain size of 250 nm and low resistance n⁺ poly-Si for ohmic contact were introduced to achieve a high performance TFT. The fabricated poly-Si TFT exhibited a field effect mobility of 262 cm²/Vs and a threshold voltage of 1 V     

High efficiency polycrystalline silicon solar cells using lowtemperature PECVD process

Conventionally directionally solidified (DS) and silicon film (SF) polycrystalline silicon solar cells are fabricated using gettering and low temperature plasma enhanced chemical vapor deposition (PECVD) passivation. Thin layer (~10 nm) of PECVD SiO₂ is used to passivate the emitter of the solar cell, while direct hydrogen rf plasma and PECVD silicon nitride (Si₃N₄) are implemented to provide emitter and bulk passivation. It is found in this work that hydrogen rf plasma can significantly improve the solar cell blue and long wavelength responses when it is performed through a thin layer of PECVD Si₃N₄. High efficiency DS and SF polycrystalline silicon solar cells have been achieved using a simple solar cell process with uniform emitter, Al/POCl₃ gettering, hydrogen rf plasma/PECVD Si₃N₄ and PECVD SiO₂ passivation. On the other hand, a comprehensive experimental study of the characteristics of the PECVD Si₃N₄ layer and its role in improving the efficiency of polycrystalline silicon solar cells is carried out in this paper. For the polycrystalline silicon used in this investigation, it is found that the PECVD Si₃N₄ layer doesn't provide a sufficient cap for the out diffusion of hydrogen at temperatures higher than 500°C. Low temperature (⩽400°C) annealing of the PECVD Si₃N ₄ provides efficient hydrogen bulk passivation, while higher temperature annealing relaxes the deposition induced stress and improves mainly the short wavelength (blue) response of the solar cells     

Silicon nitride thin-film deposition by LPCVD with in situ HF vaporcleaning and its application to stacked DRAM capacitor fabrication

Silicon nitride film deposited by LPCVD with newly developed in situ HF vapor cleaning has been studied and applied to fabricate dielectric films for stacked DRAM capacitors. Using this method, an oxide-free surface of underlaid poly-Si can be obtained. Silicon nitride film deposited on this surface has been verified by FTIR measurement to have the stoichiometrically proper composition of Si₃N₄ . However, the film was found to be selectively deposited on poly-Si electrodes. This selective deposition degrades the reliability of the stacked capacitor, because the silicon nitride can not completely cover the periphery of poly-Si electrodes on SiO₂. We propose a simple process that avoids the problem making it possible to apply silicon nitride film to stacked-capacitor fabrication. Stacked capacitors fabricated by this process exhibit very low leakage current and high electrical reliability even for ultra-thin silicon nitride films less than 5 nm thick     

金属诱导法低温多晶硅薄膜的制备与研究

利用金属诱导晶化（Metal Induced Crystallization,MIC）的方法研究了a-Si/Ni的低温晶化,MIC晶化温度能降低到440℃.采用XRD、Raman、SEM、XPS等分析手段研究了Ni-MIC多晶硅薄膜的特性,对薄膜结构和组成进行了分析,对晶化过程的机理进行了讨论.     

Modeling the growth of PECVD silicon nitride films for solar cellapplications using neural networks

Silicon nitride films grown by plasma-enhanced chemical vapor deposition (PECVD) are useful for a variety of applications, including anti-reflection coatings in solar cells, passivation layers, dielectric layers in metal/insulator structures, and diffusion masks, PECVD nitride films are known to contain hydrogen, and defect passivation by hydrogenation enhances efficiency in polycrystalline silicon solar cells. PECVD systems are controlled by many operating variables, including RF power, pressure, gas flow rate, reactant composition, and substrate temperature. The wide variety of processing conditions, as well as the complex nature of particle dynamics within a plasma, makes tailoring Si₃N₄ film properties very challenging, since it is difficult to determine the exact relationship between desired film properties and controllable deposition conditions. In this study, silicon nitride PECVD modeling using neural networks has been investigated. The deposition of Si₃N₄ was characterized via a central composite experimental design, and data from this experiment was used to train optimized feed-forward neural networks using the back-propagation algorithm. From these neural process models, the effect of deposition conditions on film properties has been studied. It was found that the process parameters critical to increasing hydrogenation and therefore enhancing carrier lifetime in polysilicon solar cells are temperature, silane, and ammonia flow rate. The deposition experiments were carried out in a Plasma Therm 700 series PECVD system