纳米金属银、铜辅助化学刻蚀制绒金刚线切割多晶硅的研究

以金刚线切割多晶硅为原料,研究不同纳米金属催化剂(银、铜)辅助化学刻蚀对纳米结构引入及多晶硅片表面制绒效果的影响。研究结果表明:不同纳米金属物种诱导刻蚀对硅片表面形貌结构的影响巨大,相比于纳米银辅助刻蚀形成的硅纳米线阵列结构而言,纳米铜辅助刻蚀形成的倒金字塔结构在各方面的性能均比较突出,大面积微尺度的倒金字塔阵列结构可以更完美地融合表面低反射率和钝化不佳之间的矛盾,且硅片表面切割纹去除效果明显。当金属铜辅助化学刻蚀制绒15 min时,倒金字塔结构最规则、均匀,且在300~1 100 nm波段范围内,反射率由原片的41.8%降低至5.8%。同时倒金字塔形貌具有优越的减反效果和去除切割纹能力,使得制绒金刚线切割多晶硅片有望用来制备高效率的太阳能电池。     

Mechanical Strength of Silicon Wafers Cut by Loose Abrasive Slurry and Fixed Abrasive Diamond Wire Sawing

This paper reports on the mechanical strength of polycrystalline silicon wafers cut by loose abrasive slurry and fixed abrasive diamond wire sawing processes. Four line bending and biaxial flexure tests are used to evaluate the fracture strength of the wafers. Fracture strength of the wafers depends on the location, size, and orientation of microcracks in the silicon wafer and the distribution and magnitude of applied stresses. Measurement of microcracks at the wafer edge and center shows that edge cracks are typically larger than center cracks. Fixed abrasive diamond wire sawn wafers are found to have a higher crack density but smaller average crack length. Wafer fracture in four line bending is found to be primarily due to the propagation of edge cracks while center cracks are found to be the primary cause of wafer failure in biaxial flexure tests. Fracture mechanics based analyses demonstrate that crack orientation plays a significant role in four line bending, but not in biaxial flexure. Correlations of the wafer fracture strength and critical crack length agree well with microcrack measurements. The fracture strength of diamond cut wafers is found to be comparable or superior to the strength of slurry cut wafers.     

金刚石线锯切割多晶硅片表面制绒工艺研

晶体硅片的制绒技术是太阳能电池制造工艺中的关键步骤。本研究以工业中酸制绒方法为基础, 研究了腐蚀时间、浓度对绒面结构以及反射率的影响。此外, 还采用金属催化化学腐蚀法进行制绒, 选用氢氟酸和硝酸银作为腐蚀液。而且对两种制绒方法效果进行了对比。研究获得的最优绒面结构及反射率结果的实验条件为: 氢氟酸浓度4.6 mol/L、硝酸银浓度0.02 mol/L, 室温下反应90 min, 得到的平均反射率为8%, 远低于目前多晶硅片制绒生产标准。     

Fixed Abrasive Diamond Wire Saw Slicing of Single-Crystal Silicon Carbide Wafers

This article investigates the slicing of single-crystal silicon carbide (SiC) with a fixed abrasive diamond wire. A spool-to-spool rocking motion diamond wire saw machine using a 0.22 mm nominal diameter diamond wire with 20 µm average size diamond grit was used. The effect of wire downfeed speed on wafer surface roughness and subsurface damage was first investigated. The surface marks generated by loose diamond grit and stagnation of the wire during the change of the wire-cutting direction were studied. The use of scanning acoustic microscopy (SAcM) as a nondestructive evaluation method to identify the subsurface damage was explored. Effects of using a new diamond wire on cutting forces and surface roughness were also investigated. Scanning electron microscopy has been used to examine the machined surfaces and wire wear. This study demonstrated the feasibility of fixed abrasive diamond wire cutting of SiC wafers and the usage of a SAcM to examine the subsurface damage.     

Fracture Strength of Photovoltaic Silicon Wafers Evaluated Using a Controlled Flaw Method

Propagation of pre‐existing micro cracks and their associated residual contact stresses, generated from the wafer sawing process, is the leading cause for photovoltaic (PV) silicon wafer/cell breakage during handling and processing. In the current work, the impact of a single micro crack on the fracture strength of PV silicon wafer is investigated based on a controlled flaw method. Radial/median cracks with controllable scales are introduced through microindentation at the center of a PV silicon sample to simulate micro cracks resulting from wafer sawing, handling, or thermal processing. Results indicate that the fracture strength of PV silicon wafer decreases linearly with the increasing of the microindentation load (radial crack scale). In addition, it is found that the impurity carbon plays an important role in the contact cracking‐fracture process. The fracture strength increased ≈21% when the substitutional carbon concentration is increased from 1.2 × 10¹⁸ to 6.4 × 10¹⁸ cm^?3.     

多晶硅扩散氧化层对太阳电池性能的影响

重点研究了多晶硅扩散氧化层对电池性能的影响,并对大规模生产多晶硅扩散工艺进行了优化研究。采用少子寿命测试仪分析了扩散前后的硅片少子寿命,发现当扩散氧化时的干氧流量控制在2800sccm,扩散后的方块电阻控制在60～70Ω/□时,扩散后硅片少子寿命最高达到了10.45μs,与扩散前的硅片少子寿命相比延长了5倍多;此时的太阳电池并联电阻和短路电流分别高达40.4Ω和8522mA,光电转换效率也由16.69%(干氧流量2000sccm)提高到了16.83%。此外,主要针对扩散氧化层对片内方阻均匀性及少子寿命的影响做了解释。     

Lock-in and Heterodyne Carrierographic Imaging Characterization of Industrial Multicrystalline Silicon Solar Cells

A novel non-destructive, non-contact laser-induced near-infrared imaging technique using an InGaAs camera and based on dynamic carrierography (a spectrally gated modulated photoluminescence modality) was used in direct lock-in (LICG) and heterodyne (HDCG) modes to characterize industrial multicrystalline silicon solar cells. The image amplitude depends on the free-photocarrier diffusion-wave density, the spatial resolution is a function of modulation frequency, and the contrast is due to the spatial distribution of important parameters influencing the efficiency of the solar cell, such as base recombination lifetime. High-spatial-resolution and high-frequency carrierographic images have been obtained using a HDCG method. The relationship between the LICG amplitude and the solar cell terminal photovoltage under an external load was investigated. The influence of surface recombination velocities and damage of the solar cell p?Cn junction was studied. A correlation between the solar cell efficiency and the surface-integrated LICG amplitude from the entire solar cell is presented.     

太阳能级硅切割废料的回收技术

太阳能级硅棒在切割生产硅晶片过程中会产生大量的切割废料。概述了废料中切割液和碳化硅回收技术的进展,重点介绍和分析了价值更高的硅与碳化硅微粉分离回收技术的特点及现状,并比较各种方法的优缺点,同时结合自身的课题研究,提出了新的解决思路。分析认为先通过离心、浮选等方法对切割废料初步提纯后再经高温热处理或合金化等方法将其进一步分离,是较有前景的回收技术。     

太阳能多晶硅锭中夹杂的物相与分布特性

多晶硅锭中经常出现硬质夹杂颗粒,严重影响线切割硅片的表面质量,严重时造成硅片切割生产中断线.我们采用光学显微镜、扫描电镜特征X射线能谱仪、X射线衍射仪等手段对定向凝固多晶硅锭中的夹杂进行了分析.采用溶解硅基体后沉淀萃取的方法取得硅锭不同部位的夹杂.分析结果表明,硅锭中夹杂的物相主要有两种:β-SiC和β-Si3N4,SiC的数量较多;二者形貌有显著区别:前者呈不规则块状,而后者则呈平直杆状.硅锭的顶表面附近夹杂高度富集,但内部仍偶有大于100微米的较大的碳化硅夹杂颗粒出现.     

钢丝钳断裂分析

采用外观和金相检验方法对断裂的钢丝钳进行了分析。结果表明：该钢丝钳的断裂由锻造工艺、热处理工艺和焊接工艺不合理导致的。提出了改进措施。     

太阳能电池硅片线锯砂浆中硅屑的回收技术研究

多线切割是当前硅太阳能电池片生产的主要工艺.在线切割过程中约有1/2的晶体硅成为锯屑进入到切割砂浆.砂浆中的各种污染物并未进入高纯硅屑晶体内部,因此可以期望通过物理分离、清洗等技术来提取获得高纯硅粉,而不需要通过高耗能的高温化学或相变过程.综述了硅片线切割过程、硅屑形成及废砂浆特性,评述了从线切割废砂浆中回收高纯硅粉的研究现状和进展,包括本研究组近期的研究结果.     

线材拉拔断裂原因分析

归纳了线材拉拔断裂的常见原因,总结了线材失效分析的步骤,并将线材拉拔断裂分为两大类：一是断裂源起源于外表面（包括线纹、折叠、钢坯上裂纹、皮下气泡和非金属夹杂物等）;二是断裂源产生于内部（包括中心夹杂物、中心缩孔、中心马氏体和中心网状碳化物等）,并举例进行了说明。     

Analysis of Enhanced Photocarrier Radiometry Signals for Ion-Implanted and Annealed Silicon Wafers

It is experimentally observed that the photocarrier radiometry (PCR) signals of silicon wafers are greatly enhanced by ion implantation and thermal annealing. A two-layer theoretical model is employed to analyze the experimental observation in detail. Theoretical simulations indicate that the increased optical-to-electronic quantum efficiency of the implanted layer could be the main photoluminescence mechanism contributing to the PCR signal enhancement. The decreased surface recombination velocity induced by surface electric field and the change of electronic transport properties of the implanted layer also contribute to the signal enhancement.     

77MnA盘条断裂原因分析

通过宏观观察,夹杂物评级和显微组织观察,分析了77MnA盘条拉拔过程中断裂的原因.实验结果表明:马氏体的出现和基体为索氏体、屈氏体和少量的贝氏体的混合组织是断裂的主要原因;基体组织为混合组织和马氏体的出现是由于轧件出精轧机组进斯太尔摩控制冷却线时冷却温度过低造成的;同一直径钢丝心部的马氏体含量相对边部的马氏体含量多表明存在C、Mn、Cr元素的偏析,并提出改进措施.     

非晶硅太阳电池窗口层材料掺硼非晶金刚石的研究

以固态掺杂方式利用过滤阴极真空电弧技术制备掺硼非晶金刚石薄膜, 获得性能优良的宽带隙p型半导体材料, 再利用等离子增强化学气相沉积技术制备p-i-n结构非晶硅太阳电池的本征层和n型层, 最终制成以掺硼非晶金刚石薄膜为窗口层的非晶硅太阳电池. 利用Lambda950紫外-可见光分光光度计表征薄膜的光学带隙, 并测试电池开路电压、短路电流、填充因子以及转化效率等参数, 再分析电池的光谱响应特性. 实验表明, 掺硼非晶金刚石薄膜的光学带隙(～2.0eV)比p型非晶硅更宽, 以掺硼非晶金刚石薄膜用作非晶硅太阳电池的窗口层, 能够改善电池的光谱响应特征, 并提高转化效率达10%以上.     

冷坩埚原理及其在多晶硅制备中的应用

综述了冷坩埚技术的原理、特点与技术要求,重点介绍了电磁冷坩埚技术的工艺性能与影响因素,总结了各因素对冷坩埚性能的影响规律,最后概述了冷坩埚技术在多晶硅提纯与成型制备中的优势和应用,并展望了其未来的发展.     

船用钢丝绳断裂失效分析

目的 了解某船用?76mm锚泊定位镀锌钢丝绳累计使用寿命较短、多处出现单丝断裂现象的原因。方法 采用宏观分析、硬度测试、力学性能试验、断口分析、化学成分分析、扫描电镜显微组织观察等方法对该钢丝绳的断裂原因进行分析。结果 拉伸试验断口为杯锥状断口,其放射区面积较纤维区更大,表明材料塑性差,硬脆性大,断口中包含有夹杂,这些因素会导致钢丝发生断裂;试样心部的显微硬度最高,钢丝断裂是从钢丝心部开始产生之后,裂纹向四周开始扩散直至整根钢丝断裂,纤维区硬脆性最大,断裂源位于纤维区。结论 钢丝绳断裂为韧性断裂。实际工况下,钢丝绳断口为劈裂状断口,符合韧性断裂的滑移分离特征,其主要原因是钢丝的屈服强度不能适应工作应力要求从而发生断裂。观察断口发现,断口的放射区面积占比较大,纤维区面积占比小,表明材料塑性差,硬脆性大,断口中包含夹杂,钢丝绳易在此处发生断裂。试样心部的显微硬度最高,距离心部越远,显微硬度越低,可知钢丝绳断裂源是由心部产生的,断裂源位于纤维区。     

金刚石串珠绳张力传感器和性能指标分析

介绍了金刚石串珠绳张力传感器的工作原理,并进行了传感器的标定.通过对传感器的性能指标分析,该传感器达到了设计要求,其主要性能指标:测量范围0～3000 N;准确度＜0.5%F·S;非线性度＜0.2%F·S;迟滞＜0.01%F·S;重复性＜0.05%F·S.该张力传感器能够准确、可靠地测量出串珠绳张力,根据串珠绳张力状态来控制金刚石绳锯机的工作过程,有利于提高绳锯机的工作效率.该传感器具有良好的防水密封性能和抗振动性能,保证了在水下安全稳定地工作.