MACE纳米刻蚀与退火处理协同强化工业硅中杂质酸浸脱除研究

The hydrometallurgical purification of industrial silicon with low produce cost, simple operation, appropriate for the large scale production, and other many advantages, has been widely used for producing low-cost solar grade polysilicon (SoG-Si) in the metallurgical process. However, the traditional hydrometallurgy purification technology confronts the deep impurity removal of MG-Si with the challenge. This project presents a novel hydrometallurgical purification industrial silicon method, which combines the metal-assisted chemical etching (MACE), high temperature activation and the acid leaching purification techniques, is designed to achieve deep removal of impurity in industrial silicon for producing low-cost and high-quality SoG-Si. Those nano-scale channels induced by MACE and the high temperature activation treatment would respectively improve the contact and reactivity of metal impurity and non-metal impurity with leaching agent. The coordination mechanism of the intensified impurity removal is discussed through studying the effect of channel structure, annealing temperature and mode and acid-leaching condition on the impurity form and dissolution behavior. The ultimate goal is to provide a theoretical basis for producing high purity polycrystalline silicon through metallurgical process with advantages of high efficient, short and low energy consumption innovative technology, which will be of significant interest to improve the product competitiveness of metallurgical polysilicon.

工业硅的湿法酸浸除杂因其具备成本低、操作简单及适合规模化应用等特点而被广泛用于冶金法提纯制备太阳能级多晶硅生产。然而，传统湿法酸浸处理在硅中杂质的深度去除方面仍然面临挑战。本项目中创新性地将纳米刻蚀技术、退火活化处理与传统湿法酸浸相结合，通过可控地纳米孔道引入及退火活化处理来强化酸浸过程中浸出剂与硅中包裹金属夹杂及固溶非金属杂质的接触和反应活性，最终实现工业硅中杂质深度脱除的目的。深入系统地研究不同多孔结构、不同退火温度、退火方式及酸浸条件对工业硅中各主要杂质形态及溶出行为的影响规律，探明多孔结构引入及退火活化处理在湿法酸浸强化除杂过程中的协同作用机理，为构建一种短流程、低能耗的冶金法高纯多晶硅制备新方案提供理论指导，为提升冶金法多晶硅的产品竞争力奠定基础。

冶金法制备太阳能级多晶硅技术在降低成本、减少能耗等方面表现出巨大潜力。然而，传统湿法酸浸处理在硅中杂质的深度去除方面仍然面临挑战。本项目将纳米金属辅助刻蚀技术（MACE）、退火活化处理与传统湿法酸浸相结合，通过可控地纳米孔道引入及退火活化处理来强化酸浸过程中浸出剂与硅中包裹金属夹杂及固溶非金属杂质的接触和反应活性，最终实现工业硅中杂质深度脱除的目的。.本项目对工业硅中杂质赋存状态、不同刻蚀体系对工业硅中杂质去除的影响规律、两步金属辅助刻蚀法对杂质深度脱除以及大颗粒工业硅粉金属铜辅助辅助刻蚀以协同退火酸浸除杂研究等工作开展了系统研究。获得的主要研究结论为：两步金属辅助刻蚀技术好于一步金属辅助刻蚀技术好于常规氢氟酸酸洗。相比氢氟酸酸洗，经过两步金属辅助浸出后的工业硅纯度可以从99.55%提高到99.99%以上。金属纳米颗粒辅助刻蚀方法比其他方法在孔道生长速率、孔道形貌结构调控方面均表现更加出色，通过选取合适的氧化剂和浓度，可以高效地获得孔径在50~300 nm之间，孔深在约0~60μm范围内可调的多孔工业硅粉。对两步金属辅助刻蚀技术中沉积和刻蚀两大过程各因素对工业硅中杂质去除和多孔结构的影响进行了系统探究。得出优化后沉积条件为[HF]:4.6M，[AgNO3]:10mM，沉积时间:60s，优化后的刻蚀条件为：[HF]:4.6M，[H2O2]:0.0075M，刻蚀温度：25℃，刻蚀时间:2h,添加25%乙醇。实验中最高的杂质去除率分别为：Fe:99.7%; Al:96.83%，Ca:98%，Ti:94.35%，B:78.55%，P:81.33%。铜辅助化学刻蚀（CuACE）杂质溶出速度优于氢氟酸-过氧化氢体系优于氢氟酸酸洗，以大颗粒工业硅为原料，经过铜辅助刻蚀后，主要金属杂质含量可以从6759ppmw降低到193.41ppmw。铜辅助浸出过程形成的微孔道有助于杂质的去除，特别是对于难溶金属杂质Ca和Al的去除。刻蚀后的多孔硅粉在较优的快速热退火温度（900℃）退火30min协同酸浸条件下，非金属杂质B和P的去除率分别可以由26%提高到67%，65%提高到74%。