刻蚀液中HF和H2O2的摩尔分数对Ag辅助化学刻蚀Si形貌的影响
收稿日期: 2012-12-12
修回日期: 2013-05-18
网络出版日期: 2013-08-11
基金资助
国家自然科学基金项目51171118,辽宁省自然科学基金项目20212339和沈阳市科技基金项目F10--205-1-60资助
EFFECT OF MOLE FRACTION OF HF AND H2O2 ON MORPHOLOGY OF POROUS SILICON FORMED BY Ag ASSISTED CHEMICAL ETCHING
Received date: 2012-12-12
Revised date: 2013-05-18
Online published: 2013-08-11
采用扫描电镜和紫外-可见分光光度计研究了Ag粒子在小团聚条件下辅助化学刻蚀Si过程中,刻蚀剂HF和氧化剂H2O2的体积比对刻蚀孔隙结构和刻蚀速度的影响.结果表明,HF和H2O2的体积比对刻蚀Si中的孔隙生长速度和形貌有明显的影响,HF和H2O2的摩尔分数ρ=[HF]/([HF]+[H2O2])过低或过高均不利于孔隙的生长.当60%<ρ<80%时, Si可获得快速刻蚀, 刻蚀速度为1050—1260 nm/min. 此时,孔隙密度高, 孔径较大且相互连通, 沿垂直Si表面生长.所获得的Si表面对200—1000 nm波段太阳光的平均反射率可降至5.9%.此外, 孔隙生长速度和形貌也与Ag颗粒的尺寸和形态密切相关.
贺春林 , 杨雪飞 , 马国峰 , 王建明 , 赵栋梁 , 才庆魁 . 刻蚀液中HF和H2O2的摩尔分数对Ag辅助化学刻蚀Si形貌的影响[J]. 金属学报, 2013 , 49(8) : 989 -995 . DOI: 10.3724/SP.J.1037.2012.00734
The research of silicon solar cells mainly focuses on reducing cost and improving conversion efficiency, and one of the effective methods of improving photoelectric conversion efficiency of solar cells is to decrease the reflection of incident sunlight onto the light-receiving surface. The porous Si layer can work for the antireflection of Si surfaces, which can be prepared by noble metal assisted chemical etching. In this work, the effects of HF, H2O2 and their volume ratio on morphology and growth of pores on single-crystalline Si surface by using Ag (with a small cluster) metal assisted etching were investigated in order to produce a highly efficient antireflecting structure. The metal particles were deposited onto Si wafer by electroless deposition from a metal salt solution including HF. The surface and cross-sectional morphologies of the porous Si surfaces were observed with field-emission scanning electron microscope. The reflectivity of the etched Si surface was measured with a UV-Vis spectrophotometer equipped with an integrating sphere accessory. The experimental results show that the growth rate and morphology of the pores formed on the Ag metallized Si surfaces are strongly dependent on the volume ratio of HF and H2O2. It is not beneficial for the pore growth when mole fraction ρ=[HF]/([HF]+[H2O2]) is too low or too high, and the etching goes well only whenρ is between 60%—80%; in this case, the pore growth rate is up to 1050—1260 nm/min, and the pores grow straightly and vertically with a relatively large pore density, pore size and connected pore net. The Si surface exhibits an average reflectivity as little as 5.9% in the wave range of 200—1000 nm, showing that a satisfactory antireflection is obtained. Additionally, the growth rate and morphology of the pores also depend on the size and morphology of catalyst Ag particles.
Key words： Silicon; Ag assisted chemical etching; antireflection
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