单晶硅片制绒不均匀性对PECVD的影响-杜俊霖-中国科学院.pdf

杜俊霖 Ph.D. Research Center for New Energy Technology The purpose of texturization Pre clean SDR TEX 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 1 Dissolve the contaminatio n on the raw wafer Reflectivity: 35.4% Remove the saw damage caused by diamond wire Reflectivity: 37.6% Form pyramid morpholog y made of (111) Reflectivity: 12.1% The process of texturization 1min Rfl: 37.0% 2min Rfl: 31.3% 3min Rfl: 24.5% 4min Rfl: 15.7% 6min Rfl: 13.5% 8min Rfl: 12.1% (100) (111) 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 2 The optimal time of texturization Secondary reflection Primary reflection 70.5° （ 100） （ 111） Primary reflection Optimal TEX time 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 3  • Wafer thickness is reduced. • Plane (100) is multiplied. • Pyramid shape is destroyed. The distribution of pyramid sizes Image obtained by 3D laser microscope Distribution of pyramid sizes 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 4 Various size distributions 4.08μm, R 12.3% 3.16μm, R 12.2% 2.14μm, R 12.1% 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 5 Nonuniform texturization Side view of wafer carrier Light and dark areas 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 6 PL image and lifetime map PL image after PECVD Lifetime: 526μs, VOC: 726mV Sample: SDR+TEX+SC1(3min)+HF Lifetime map of the same sample Flow of solution and N2 bubbles 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 7 Support bars SDR 10min+TEX+SC1 PECVD: 87μs/660mV PL images for different SDR times SDR 0min+TEX+SC1 PECVD:1059μs/734mV SDR 5min+TEX+SC1 PECVD: 416μs/710mV 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 8 Infrared absorption spectrum The residue of additive on the textured wafer increases while applying SDR. A possible explanation could be that the wafer with a rough surface reacts violently with KOH, releasing a large amount of H2, which hindering the absorption of additive to the wafer surface. Si+2KOH+H2O = K2SiO3+2H2↑ 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 9 Replacing NH3 with KOH • SDR 10min+TEX+SC1’ 3min • SC1’: KOH+H2O2 • PECVD: 445μs/724mV • SDR 10min+TEX+SC1 3min • SC1: NH3+H2O2 • PECVD: 238μs/699mV 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 10 The effect of basicity in cleaning 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 11 SDR10min+TEX+SC2 SC2: HCl+H2O2 PECVD: 69μs/652mV SDR10min+TEX+SC1’ SC1’: KOH+ H2O2 PECVD: 445μs/724mV SDR10min+TEX+SC1 SC1: NH3+ H2O2 PECVD: 238μs/699mV Conclusions 1. The reflectivity reaches the lowest point at a right texturization time. 2. Both large and small pyramid sizes lead to similar reflectivities. 3. Nonuniform flow leads to nonuniform distribution of pyramid size. 4. Wafer with SDR absorbs greater amount of additive than rough wafer. 5. Enhancing the basicity of solution increases cleaning efficiency. 14th China SoG Silicon and PV Power Conference, Xi’an, 2018 Page 12