非晶硅薄膜晶化过程的研究

多晶硅薄膜具有较高的电迁移率和稳定的光电性能,是制备微电子器件、薄膜晶体管、大面积平板液晶显示的优质材料.多晶硅薄膜被公认为是制备高效、低耗、最理想的薄膜太阳能电池的材料.因此,如何制备多晶硅薄膜是一个非常有意义的研究课题.固相法是制备多晶硅薄膜的一种常用方法,它是在高温退火的条件下,使非晶硅薄膜通过固相相变而成为多晶硅薄膜.本文采用固相法,利用X-ray衍射及拉曼光谱,对用不同方法制备的非晶硅薄膜的晶化过程进行了系统地研究.     

铝诱导晶化真空蒸镀多晶硅薄膜的研究

采用真空蒸镀的方法在玻璃衬底上沉积1层非晶硅薄膜,再通过铝诱导晶化的方法制备出晶粒分布较均匀、晶粒尺寸0.5～5μm、晶化率达到89%的多晶硅薄膜。研究了衬底距离、衬底温度、退火温度对薄膜表面形貌、晶粒尺寸和分布及晶化率的影响。结果表明适中的衬底距离下得到的薄膜晶粒分布均匀,表面平整度好,薄膜厚度较大。薄膜的晶化率随着衬底温度和退火温度的提高而增大;随着退火温度的进一步提高,薄膜的晶化率达到最大值然后降低。     

100μm大晶粒多晶硅薄膜的铝诱导法制备

以Corning Eagle 2000玻璃为衬底,用磁控溅射法制备了glass/a-Si/Si O2/Al叠层结构,于Ar气保护下退火,制备了具有很强的(111)择优取向,最大晶粒尺寸达100μm的铝诱导晶化多晶硅薄膜。研究结果表明,非晶硅的氧化时间越长,所制备的多晶硅晶粒尺寸越大,当氧化时间达约47h后,再延长氧化时间对薄膜性能的影响不明显。还发现退火温度越高,晶粒越小,但是反应速率越快。     

以SiCl4/H2为气源低温制备pc-Si薄膜的稳恒光电导特性

研究了以SiCl4/H2为气源、用等离子体增强化学气相沉积方法, 在低于300℃温度下所制备的pc-Si薄膜在长时间的光照下电导率的变化情况.实验结果表明,所制备的多晶硅薄膜具有类稳恒光电导效应,而且薄膜的稳恒光电导特性依赖于薄膜的晶化率和晶粒尺寸,随晶化率的增加和晶粒尺寸的增大而增大.     

磷含量对真空蒸镀磷掺杂多晶硅薄膜的影响

采用真空蒸镀的方法制备磷掺杂多晶硅薄膜,研究了磷含量对多晶硅薄膜的表面形貌、组织结构、晶粒尺寸及晶化率的影响。结果表明:随着磷掺杂分数的增加,多晶硅薄膜的晶粒尺寸和晶化率表现出先增加后降低的趋势,当磷掺杂分数为1%时,薄膜晶粒尺寸达到最大值,为0.55μm,晶化率为96.82%,且晶粒的均匀性最佳。     

铝诱导晶化法低温制备多晶硅薄膜

为了满足在普通玻璃衬底上制备多晶硅薄膜晶体管有源矩阵液晶显示器,低温（＜６００℃）制备高质量多晶硅薄膜已成为研究热点．本文研究了一种低温制备多晶硅薄膜的新工艺：金属诱导非晶硅薄膜低温晶化法．在非晶硅薄膜上蒸镀金属铝薄膜,并光刻形成铝膜图形,而后于氮气保护中退火．利用光学显微镜和拉曼光谱等测试方法,研究了Ａｌ诱导下非晶硅薄膜的晶化过程,结果表明;在５６０℃退火６ｈ后;铝膜下的非晶硅已完全晶化,确定了所制备的是多晶硅薄膜．初步探讨了非晶硅薄膜金属诱导横向晶化机理．     

金属镍诱导p型多晶硅薄膜的光电性能研究

利用电子束蒸镀方法及重掺杂p型硅为蒸发源在K8玻璃衬底上沉积非晶硅薄膜,采用镍诱导晶化法在氮气氛围下进行退火处理制备出p型多晶硅薄膜.研究了不同温度热处理条件对p型多晶硅薄膜的光电性能的影响,通过霍尔测量、拉曼光谱、原子力显微镜、紫外-可见光吸收光谱等测试手段对薄膜进行分析.结果表明,随着晶化温度的提高晶化程度先增强后...     

多晶硅薄膜的铝诱导晶化法制备及其晶粒的择优取向特性

采用铝诱导非晶硅薄膜晶化技术制备了多晶硅薄膜,并研究了多晶硅的成核和生长特性。非晶硅薄膜采用等离子体增强化学气相沉积法制备,其表面沉积铝薄膜后经不同温度的氮氛围退火处理。结果表明,退火后的硅薄膜层与铝层发生置换,所生长的多晶硅颗粒的平均尺寸约为150nm。X射线衍射分析结果揭示,薄膜的晶向显著依赖于退火温度,较低温度下,铝诱导晶化速率较慢,薄膜的优化晶向与非晶硅薄膜中团簇的初始原子排列趋势紧密相关。而较高温度下,铝诱导晶化促使多晶硅(111)择优成核及随后的固相生长。     

锗掺杂真空蒸镀基板距离对多晶硅薄膜的影响

在真空蒸镀多晶硅薄膜中掺入杂质可改善膜的微结构及电特性,目前有关基板距离对所得膜层的影响研究不多。采用真空蒸镀掺杂锗的方法制备出多晶硅薄膜;通过扫描电镜、X射线衍射仪、拉曼光谱仪等研究了基板距离对掺锗多晶硅薄膜的组织、形貌、晶粒尺寸及晶化率的影响。结果表明:随着基板距离的增大,薄膜的晶粒尺寸和晶化率均呈现出先增大后减小的相似趋势;当基板距离为90 mm时,晶粒尺寸显著增大,最大达到0.8μm左右,多晶硅薄膜晶粒形貌、结构性能最好,且具有较高的结晶度,薄膜的晶化率最高可达到85.10%。     

铝诱导非晶硅薄膜低温晶化及结构研究

介绍了一种非晶硅薄膜低温晶化的新工艺－金属诱导非晶硅薄膜低温晶化。在非晶硅膜上蒸镀金属铝薄膜,而后于氮气保护中退火,实现了非晶硅薄膜的低温（＜600℃）晶化。利用X射线衍射、光学显微镜及透射电等测试方法,研究了不同退火工艺对非晶硅薄膜低温晶化的影响,确定了所制备的是多晶硅薄膜。     

Nanocrystalline silicon films formed under the impact of pulsed excimer laser radiation on polyimide substrates

Polycrystalline silicon films on polyimide substrates were obtained by a method based on the crystallization of amorphous films under the impact of nanosecond pulses of excimer laser radiation. Characteristics of the film structure were studied by methods of Raman scattering and high-resolution electron microscopy. For the laser crystallization regimes employed, nanocrystalline silicon films with an average grain size of 5 nm were obtained. The results are of interest for the development of large-scale microelectronic devices (active thin-film transistor matrices) on cheap flexible substrates.     

Dependence of transport parameters on thickness in polycrystalline CdS thin films

Polycrystalline CdS thin films of different thickness heavily doped with indium were deposited onto glass substrates by vacuum evaporation of CdS and indium. The films were characterized by Hall measurements and scanning electron microscopy observations. The variations in conductivity, carrier concentration and mobility with the film thickness are similar to the dependence of the grain size on the thickness. The deduced dependences of the electrical parameters on the grain size show the trends characteristic of polycrystalline semiconductor which are explained by the boundary carrier trapping theory. Thus, the polycrystalline origin of the thickness dependence of the electrical parameters in heavily doped CdS films is concluded.     

In-situ diagnostics for preparation of laser crystallized silicon films on glass for solar cells

Polycrystalline silicon thin film solar cells require coarse grained silicon layers on a glass substrate. The preparation starts with a layer of amorphous silicon some hundred nanometers thick. By laser crystallization it is converted into a seed layer consisting of grains several ten μm in size. We report on in situ diagnostics by time resolved reflection and transmission (TRRT) measurements during the preparation process. Joint diagnostics by different lasers and the comparison with optical and electron micrographs of the resulting films give unique information about the crystallization processes. Even if different processes occur in hydrogenated or hydrogen free amorphous silicon films during the heating induced by different irradiation parameters the results of crystallization are quite similar.     

Microstructure and lattice bending in polycrystalline laser-crystallized silicon thin films for photovoltaic applications

Grain size, grain boundary population, orientation distribution and lattice defects of polycrystalline silicon thin films are investigated by electron backscatter diffraction (EBSD). The silicon thin films are produced by a combination of diode laser melt-mediated crystallization of an amorphous silicon seed layer and epitaxial thickening of the seed layer by solid phase epitaxy (SPE). The combined laser-SPE process delivers grains exceeding several 10 μm of width and far larger than 100 μm in length. Strong lattice rotations between 10 and 50° from one side of the grain to the other are observed within the larger grains of the film. The misorientation axes are well aligned with the direction of movement of the laser. The intragranular misorientation is associated both with geometrically necessary dislocations and low angle boundaries, which can serve as recombination centres for electron-hole pairs. Since the lateral grain size is up to two orders of magnitude larger than the film thickness, the high dislocation density could become an important factor reducing the solar cell performance.     

非晶态Se薄膜晶化过程中微裂纹产生的研究

薄膜在热处理过程中存微晶结构的变化。利用光学显微镜对非晶态Ｓｅ薄膜在晶化过程中微裂纹的产生做了详细的分析和研究，利用位形坐标解释了非晶薄膜室温下的转为的原因。并对三层结构的ＳｉＯ／Ｓｅ／ＳｉＯ的晶化做了进一步研究，结果表明微裂纹产生与晶化过程中砂揶重新排序，原子迁移导致晶界的产生和体积收缩产生的应力有关，裂纹的产生还同薄膜与衬底间的热失配有关。     

Energy equilibrium of cleavage front transmission across a high-angle grain boundary in a free-standing silicon thin film

In this article, the crack growth driving force and the resistance to cleavage cracking associated with crack front transmission across a high-angle grain boundary in a silicon thin film are analyzed, and a closed-form solution of grain boundary toughness is obtained. It is noticed that the fracture resistance of the grain boundary is a function of the film thickness. This size effect is attributed to the nonuniform nature of cleavage front advance.     

The fabrication and application of ZnO:Al thin films in low-frequency inductively coupled plasma fabricated silicon solar cell

A home-made radio frequency magnetron sputtering is used to systematically study the structural, electrical, and optical properties of aluminum doped zinc oxide (ZnO:Al) thin films. The intensity of the (002) peak exhibits a remarkable enhancement with increasing film thickness. Upon optimization, we achieved low resistivity of 4.2 × 10^− 4 Ω cm and high transmittance of ~ 88% for ZnO:Al films. Based on the present experimental data, the carrier transport mechanism is discussed. It is found that the grain boundary scattering needs to be considered because the mean free path of free carrier is comparable to the grain size. The 80 nm-ZnO:Al thin films are then deposited onto low-frequency inductively coupled plasma fabricated silicon solar cells to assess the effect of ZnO:Al thin films on the performance of the solar cells. Optimized ZnO:Al thin films are identified as transparent and conductive oxide thin film layers.     

Crystallization of amorphous silicon thin films: The effect of rapid thermal processing pretreatment

In the present work, the effect of low temperature short-time rapid thermal processing (RTP) pretreatment on the average grain size and the crystallinity of the polycrystalline silicon thin films, fabricated by subsequent solid phase crystallization (SPC) of amorphous silicon (a-Si) thin films grown by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at high temperature has been studied. The average grain size and the crystallinity results were estimated using X-ray diffraction (XRD) and Raman spectroscopy, respectively. It was found that RTP at 800 °C for 60 s resulted in slightly larger average grain size and higher crystallinity than those without the RTP pretreatment after SPC at 800 °C for 5, 10 and 22 h. The results suggest that the low-temperature short-time RTP pretreatment can promote the crystallization process of the as-deposited a-Si thin films during the following SPC and then improve their crystallinity. Finally, the mechanism is also discussed in detail in the paper.