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longigroup 高效单晶硅片技术与设备应用现状及发展前景 High efficiency mono wafer technology and its equipment application and future developing trend 隆基绿能科技股份有限公司 单晶研究室 周锐 LONGi Green Energy Technology CO.， Ltd Monocrystalline Silicon Lab of R&D Presenter: Rui Zhou longigroup Page 2 ONTENTS 目录 C 一、前言概述 Introduction 二、高效硅片技术 研发 High-efficiency wafer technology research 三 、设备及系统应用 Equipment and system application 四、 结语 Conclusion longigroup Page 3 前言 概述 Introduction longigroup Page 4 随着光伏行业的不断发展，高效产品逐渐成为未来市场需求的主流，这对前段的晶体生长及切片生产也提出了更高的要求，提升硅片品质逐渐成为硅片生产企业面对的最重要的技术课题。 With the development of PV industry， high efficiency production would be the domestic demand of future market， it also improve the requirements to the crystalline growing and wafer slicing process， so how to improve the wafer quality has become the most essential technical subjects for wafer manufacturers. 与此同时，硅片生产成本依旧是提升企业市场竞争力的最重要手段之一，除了传统的技术改进之外，通过提升电池效率也可以带来较大的系统成本下降。 At the same time， wafer production cost still be the most important way to promote the market competitiveness, except for the traditional way of technology improvements, improve the cell efficiency could also reduce the system cost sharply. 一、前言概述 Introduction longigroup Page 5 一、前言概述 Introduction 在长期的发展中，硅片生产企业在传统的热场设计、工艺改进等方面投入了大量的精力，用于提升硅片质量，降低加工成本，其提升空间已经越来越有限。相比之下，在装备系统方面，虽然也取得了巨大的进步，但是可以提升的空间依然巨大，会成为未来提升硅片品质、降低生产成本的极其重要的途径。 In the long-term development, wafer manufacturers made lots of efforts on hot-zone design and process innovation to improve the wafer quality and reduce the cost, however, the space has become more and more limited. In comparison, though we have made lots of progress on the equipment and system development, there are still rooms for developing, so it would be the main approach to reduce the cost and improve quality. longigroup Page 6 高效硅片技术研发 High-efficiency wafer technology research longigroup Page 7 二、高效硅片技术研发 High-efficiency wafer technology research 2.1电池对硅片品质的需求 The requirement of cell for the wafer 电池对于硅片品质的常规需求 Common requirement of cell for the wafer 由于太阳能属于低密度能源，需要大面积收集，而其中的土地、铝框、玻璃是刚性成本，难以降低，因此只有 提升电池的转化效率 ，才能摊薄这些成本，真正实现“平价上网”。 高品质单晶硅材料将 有效降低低效电池比例，降低光衰减，直接提升电池转化效率的特性 。 For solar energy is low density， it needs large area， and the rigid cost like land, aluminum lash， glass is hard to reduce， so only way to dilute these costs is improving the transfer efficiency, then realizing grid parity. High quality monocrystalline silicon material could reduce the proportion of low efficiency cell and LID， promote cell efficiency directly. 地表太阳辐照能量密度 1000W / m2标准日照条件 Energy density of solar irradiation on the earth surface 1000W / m2 Under standard sunshine condition longigroup Page 8 2.1电池对硅片品质的需求 The requirement of cell for the wafer 新的电池技术对于硅片品质的 需求 New technology wafer to the wafer quality 随着太阳能光伏行业的发展，一些新的电池技术大大提升了太阳能电池的转换效率。与此同时，这些新技术也对硅片品质提出了更高的要求。 With the development of PV industry, some new cell technology greatly improve the cell efficiency. Meanwhile, these technologies also raise its requirement to the wafer 要求硅片具有更高的寿命和更低的 LID； require wafer with high lifetime and lower LID PERC技术 PERC technology 要求硅片具有更高的寿命，更低的缺陷及施主浓度； require longer lifetime, lower defect and donor concentration. HIT（ IBC）等 N型电池技术 HIT(IBC) and other N-type cell technology 需要硅片具有更低的应力及更好的切割清洗质量； require the wafer with lower stress and better slicing and cleaning quality. 电池薄型化的需求 Thinner cell 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 9 2.2品质的改善方向 The way to improve the quality 针对现有普通电池及一些新技术对于硅片品质的需求，硅片品质最重要的改善方向可以分为五个部分： Aiming at those requirements of comment and new cells， wafer quality would be improved from five points： 提高少子寿命 High minority lifetime 降低氧碳含量 Low content of O & C 降低金属杂质含量 Low metal impurities 减少缺陷 Less dislocation 采用合适的电阻率 Reasonable resistivity 高品质单晶硅材料： High quality mono-silicon material 提升电池转化效率 Promoting cell efficiency 降低光衰 Reducing LID 无低效片 No low efficiency wafer 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 10 2.3 低效问题 Low efficiency problems 拉晶端 品质问题 Quality problem 同心圆 Dark ring 黑边 /黑角 Black edge 整面发黑 Black coating 黑心片 Black center wafer 目前比较常见的低效问题可以分为四大类： 针对这些问题，我们通过对其产生机理的研究，对工艺技术进行改进。同时，不断探究新的检测方法和手段，加强监控，从而达到减少甚至消除这些品质问题的目的。 The current common low efficiency problems contain four types： In terms of these problems， we modify the process technology through mechanism research. Meanwhile， we constantly find the new testing method， and supervised the control so that remove these problems. 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 11 2.3.1同心圆现象研究 /Research on dark rings 同心圆产生的 机理 1 Mechanism of dark ring 1 空位 -氧缺陷环 vacancy-oxygen defect ring 在 拉晶 过程中在 一定的 VG比下 ， 间隙 富集区与空位富集区之间 的会出现一个环状 区域 ， 如果氧含量提升到一定水平 ， 会形成空位 -氧 缺陷 环 。 At specific VG ratio, The annular section that formed in the pulling process between interval enrich area and vacancy enrich area，if the oxygen content reached to certain level，it would form vacancy-oxygen defect ring。 空位氧缺陷环位置 的氧在晶体冷却过程中会形成热施主 。 影响 少子寿命与电阻率 ， 再加上其他因素的影响 ， 在 PL扫描下会呈现 同心圆的现 象 。 The oxygen in vacancy-oxygen defect ring area would form thermal donor in the process of crystalline cooling. It would influence the minority lifetime and resistivity， and there would be a dark ring through PL scanning 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 12 2.3.1同心圆现象研究 /Research on dark rings 同心圆产生的 机理 1 Mechanism of dark ring 这种在少子寿命扫描中也呈现严重的环状低寿命的硅片做成电池后就会出现严重的低效 ， 对应区域在 EL扫描下就会呈现同心圆现象 。 这种同心圆是有害的 。 The oxygen in OSF area would form thermal donor in the process of crystalline cooling. It would influence the minority lifetime ， and there would be a dark ring through PL scanning. This kind of dark ring is harmful. 二、高效硅片技术研发 High-efficiency wafer technology research 这种严重同心圆的硅片在少子寿命扫描过程中也会呈现明显的环状低寿命区域 。 The lifetime in the dark ring is extremely low when testing . longigroup Page 13 2.3.1同心圆现象研究 /Research on dark rings 同心圆产生的 机理 2 Mechanism of dark ring 2 二、高效硅片技术研发 High-efficiency wafer technology research 在直拉单晶生长中 ， 由于生长界面是不是平坦的 ， 在同一片硅片的不同的环状区域生长的时间也是不同的 ，生长时间的差异会造成这些环状区域的掺杂剂浓度等存在差异 ， 也会有条纹状的形貌出现 ， 一般称之为生长 条纹 ， 这种现象在使用一些分凝系数很小的掺杂剂时尤为明显 ， 比如 P， Ga。 Because the growing interface during the pulling is not flat, the growth time in different ring area in one wafer is diverse which would cause difference on dopant concentration and some other factors. The difference will cause annular stripe. That is so called growth striation. this phenomenon would be more obvious when using some little segregation coefficient dopant such as P,Ga longigroup Page 14 2.3.1同心圆现象研究 /Research on dark rings 同心圆产生的 机理 2 Mechanism of dark ring 这种生长条纹在 PL下也会呈现 轻微 同心圆现象 ， 这种同心圆在少子寿命扫描时并不会出现环状的低寿命区域 ， 做电池后也不会出现低效 ， EL扫描下也是正常的 。 也就是说 ， 这种同心圆是无害的 。 The growth striation would appear slight dark ring in PL scanning but no annular low lifetime area under minority lifetime scanning, and it would not cause low efficiency cell, and appear normal under EL scanning. That is to say, this kind of dark ring is harmless. 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 15 2.3.1同心圆现象研究 /Research on dark rings 0.40.470.540.610.680.750.82Oi/（E+18）退火前 (原片） 1050 退火后 硅片中心 Wafer centre 边缘 edge 从右图可以看出 ， 同心圆与硅片本身氧含量分布的不均匀性也有关系 。 亮环所在位置氧含量明显偏高 。 We can see from the picture that dark rings is influenced by the wafer original oxygen inhomogeneity distribution 同心圆产生的影响因素 -氧含量的不均匀性 Influence factor of dark ring inhomogeneity of oxygen content 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 16 2.3.2 黑心片现象研究 /Research of black center wafer 氧含量 （ ppma） 10 15 18 21 PL图像 P型 N型 当氧含量高到一定程度后 ， 再加上一些其他的影响因素 ， PL扫描下发黑的区域会扩大为整个中心区域 ，同心圆会转化为黑心片 。 When the oxygen content reach to a level， dark ring would become to black center wafer. Coupled with other factors， the dark area in the PL scanning would expand into whole centre area， dark ring would become black center. 注：左侧 PL图像只代表程度变化趋势，不代表特定图样； The left PL imager only represent the trend, no special provision. 黑心现象的产生 Cause of black center 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 17 2.3.2 黑心片现象研究 /Research of black center wafer 选取高氧样片，模拟客户电池工艺热处理后，发现红心处氧含量明显偏高，这进一步说明了黑心现象与氧含量偏高的关系。 Simulating the heat treatment process of the customers cell, and we found that the red center has higher oxygen content . It could further prove that dark ring is closely related to the high oxygen content. 氧含量分布与黑心的关系 Relation of oxygen content distribution and black center 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 18 2.3.2 黑心片现象研究 /Research of black center wafer 原生片氧 Original wafer OC/ppma 原生片碳 Original wafer CC/ppma 中心 寿命 Central lifetime/ s 退火后寿命扫描 图 after annealing 15.2 4.4 1.9 15.0 1.1 11.2 可以看到在氧含量较低时 ， 碳含量高的硅片也会产生红心 ， 并且寿命较低 。 We can see when the oxygen content relatively low， but the carbon content high would also cause red center， and also low lifetime. 选取碳含量为 4.4ppma与 1.1ppma的尾部硅片 （ 电阻率 1.1 cm） 进行退火处理并进行少子寿命扫描 。 Do annealing treatment and lifetime scanning to tail wafer with carbon content of 4.4ppma and 1.1ppma（ Resistivity 1.1 .cm） . 碳含量与黑心的关系 /Relationship of carbon content and black center 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 19 2.3.2 黑心片现象研究 /Research of black center wafer 020406080100120140160原生片 6501h 6501h+8501h LIFETIME少子寿命/s 21ppma17.6ppma15.8ppma12.0ppma7.6ppma 随着热处理温度升高 、 时间延长 ，少子寿命在不断下降； The higher heat treatment temperature and time lasting，the lower lifetime； 氧含量越高 ， 少子寿命下降越严重 。 少子寿命降低与氧沉淀形成有关 。 The higher OC, the lower lifetime, it is conclude that reduction of lifetime is related to oxygen precipitation. 降低同心圆、黑心低效的关键手段是降低单晶硅材料氧含量。 To conclude， the main method to reduce dark rings and black center is reduce the oxygen content of mono-silicon material. 热历史与黑心的关系 /Relationship of heat history and black center 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 20 2.3.3 硅片黑边研究 /Research of black edges of wafer PL图 EL图 WT-2010 寿命图 黑边表现为由硅片或者电池边缘呈暗区，在黑边区域少子寿命相对偏低。 Black edges are represented by the black area in the edge of wafer . The lifetime of the black area is relatively low. 改善措施 /targeted improvement： 1、选择高纯热场配件，提高热场 纯度（不仅仅是 N型）； Selecting high-purity hot zone accessories, and improving the purity of thermal field; 2、提高硅棒加工环境洁净度，增加硅棒及硅片包装质量。 Improving the environment cleanliness of silicon rod processing, and increasing the packaging quality. 黑边 产生原因 Causes 拉晶过程中热场纯度不够 The purity of hot zone is not enough during pulling 外界环境中金属杂质在硅棒端或硅片端边缘的污染 Contamination of metal impurities a in external Environment 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 21 2.3.4 整面发黑研究 Research on overall wafer black coating 整面发黑 产生原因 Causes 电阻率与电池工艺不匹配、unlatching of resistivity and cell process 硅片自身少子寿命低 Low lifetime wafer PL图 EL图 WT-2010 寿命图 整面发黑 表现为由硅片或者电池 PL及 EL扫描整面呈暗区。 overall wafer black coating reflect in the PL and EL dark area in wafer or cell 改善措施 /targeted improvement： 1、加强现场管控，避免混片； Improve the site control， avoiding the mix. 2、规范质量管控，避免寿命不合格硅片流出。 Standarding the quality control， avoiding some disqualification wafer outflow. 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 22 2.3.5 低效片检测方法 Testing method of low efficiency wafer 生产预防： Product prevention 原生硅片 Original wafer 问题追溯： Problem trace 低效电池片 Low efficiency cell 表面处理后直接检测 testing after surface treatment 模拟电池进行退火处理 annealing treatment 进行剥离处理，露出硅片本体 Stripping treatment 氧碳寿命电阻率Oxygen and carbon lifetime and resistivity testing 缺陷检查 Defect testing 微缺陷 BMD检测 Micro defect BMD testing 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 23 2.4光致衰减问题 /LID problem -0.26% -0.65% -1.46% -1.57% -0.18% -0.94% -1.36% -1.42% -1.8%-1.0%-0.2%18 16 13.8 11 8 13.6 12.4 9.8 5.7 5 :1.8 cm :2.1 cm 氧 /ppma LID相对减少量Baseline Baseline 光衰的产生和硼氧复合体有关 ， 如下图所示相同电阻率下选取不同氧含量硅片制成 P型普通电池 ， 可以发现随着氧含量降低 ， 光衰减有明显降低 。 The cause of LID is related with the B-O complex. Selecting P-type normal cell with different oxygen content wafer, we can see the along with the oxygen content reducing, LID is lower. 影响光衰的因素 -氧含量 Factor of LID-oxygen content 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 24 除了 B-O复合体，还存在 LeTID等衰减机制，主要存在于多晶中，在单晶中也存在，具体见如下文献： except for the B-O compound， there are also LeTID and defect mechanism which mainly exist in multi and also mono， we can see the following documents: C. Fahrland et al, Sponge LID-a new degradation mechanism? in: Proceedings of the 40th IEEE Photovoltaic Specialist Conference, 2014, pp. 0135 0139. F.Kersten et al, Degradation of multicrystalline silicon solar cells and modules after illumination at elevated temperature, Sol. Energy Mater.Sol.Cells 142 (2015) 83 86. Cu杂质也是引起 LID的另一种杂质，在 N型片，掺 Ga单晶均有发现与 Cu有关的 LID。具体 见如下文献： Cu could also contribute to the LID. We have found LID related to Cu in both N type water and water doped by Ga. J. Lindroos et al, Preventing light-induced degradation in multicrystalline silicon, J. Appl. Phys. 115 (2014) 154902. T.Buonassisi et al, Interactions between metals and different grain boundary types and their impact on multicrystalline silicon device performance, 4th World Conference on Photovoltaic Energy Conversion, IEEE, 2006, pp. 944 947. 影响光衰的因素 -金属杂质含量 Factor of LID-metal impurity content 2.4光致衰减问题 /LID problem 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 25 降光衰基本措施 Measure to reduce LID 降低硼浓度 Reducing boron concentration 降低氧杂质 Reducing oxygen impurities 降低金属杂质含量 Reducing metal impurities 1.提高电阻率，但目前一般要求掺硼电阻率 1-3 cm； 2.采用掺镓，但镓的分凝系数 0.008远小于硼 0.8； 3.采用掺磷 N型掺杂，而目前 P型单晶还属于主流产品； 1. Increase the resistivity, the general requirements of boron resistivity is 1-3 cm; 2. Adopting doped gallium of N-type, but gallium segregated coefficient 0.008 is far less than boron 0.8; 3. Using N type doping, and the P type mono crystal is also belong to the mainstream products; 1.优化热场设计； 2.优化拉晶工艺； 1. Optimizing the hot zone design; 2. Optimizing the crystal pulling process; 降低光衰基本措施 Basic measure to reduce LID 1.提升原料品质，改善清洗工艺； 2.提升热场纯度，隔绝外部污染源； 1.Improving the raw materials quality and clean process； 2.Improving the hot zone purity and isolating the pollution source 2.4光致衰减问题 /LID problem 二、高效硅片技术研发 High-efficiency wafer technology research longigroup Page 26 2.5 高效电池研发与验证 High efficiency cell research and verification 高效硅片研发的关键途径 Key approach of high efficiency wafer reserve 降低碳含量 Reduce carbon content 降低氧
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