不同沉积速率下微晶硅薄膜的生长行为研究
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摘要
鉴于微晶硅薄膜在沉积过程中先经历一个非晶过渡层才开始晶化的生长特点,试图通过降低薄膜的沉积速率来延长沉积原子在薄膜生长表面的扩散时间,以达到促进晶粒生长的目的。研究结果表明,反应气体气流量的减小可以有效降低薄膜的沉积速率;随着沉积速率的降低,薄膜的表面粗糙度明显减小,且其平均晶粒尺寸有所增大,通过HRTEM甚至能观察到尺寸在10nm以上的晶粒,说明沉积速率的降低对沉积粒子在薄膜生长表面的扩散过程有较大影响;另外,薄膜的少子寿命随着沉积速率的降低逐渐增大,这与薄膜结晶程度和平均晶粒尺寸的变化趋势一致,可见微观结构对电学性能起着决定作用。
In view of the growth characteristics of microcrystalline silicon thin films which first undergo amorphous transition layer before crystallization,in this paper,it was attempted to prolong the diffusion time of deposited atoms on the growth surface of thin films by reducing the deposition rate of thin films,in order to promote grain growth.The results show that the deposition rate decreased with the decrease of gas flow.And as the deposition rate decreased,surface roughness decreased obviously and the average grain size improved.Grains which were bigger than 10 nm could be observed in HRTEM photos,which indicated that the decrease of the deposition rate had a great effect on the diffusion of deposited particles on growth surface.At the same time,the change rule of minority carrier lifetime agreed with the change rules of the crystallinity and average grain size,which showed a decisive effect of the microstructure on electrical properties.
In view of the growth characteristics of microcrystalline silicon thin films which first undergo amorphous transition layer before crystallization,in this paper,it was attempted to prolong the diffusion time of deposited atoms on the growth surface of thin films by reducing the deposition rate of thin films,in order to promote grain growth.The results show that the deposition rate decreased with the decrease of gas flow.And as the deposition rate decreased,surface roughness decreased obviously and the average grain size improved.Grains which were bigger than 10 nm could be observed in HRTEM photos,which indicated that the decrease of the deposition rate had a great effect on the diffusion of deposited particles on growth surface.At the same time,the change rule of minority carrier lifetime agreed with the change rules of the crystallinity and average grain size,which showed a decisive effect of the microstructure on electrical properties.
引文
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[2] Lu Yuanyuan,Li Hejun,Yang Guanjun et al.The influence of RF power on the solid phase crystallization of a-Si thin films[J].Journal of Functional Materials,2015,46(3):3033-3040(in Chinese).鲁媛媛,李贺军,杨冠军,等.射频功率对非晶硅膜固相晶化效果的影响[J].功能材料,2015,46(3):3033-3040.
[3] Li Z L,Letha A J,Wei J F et al.Structural analysis of polycrystalline silicon thin films produced by two different ICPCVD approaches[J].Materials Science in Semiconductor Processing,2018,75(3):51-57.
[4] Matsuda A,Takai M,Nishimoto T et al.Control of plasma chemistry for preparing highly stabilized amorphous silicon at high growth rate[J].Solar Energy Materials and Solar Cells,2003,78(1-4):3-26.
[5] Lee Y J,Kwon J D,Kim D H et al.Structural characterization of wavelength-dependent Raman scattering and laser-induced crystallization of silicon thin films[J].Thin Solid Films,2013,542(2):388-392.
[6] Geng X,Zhu F,Hou G.The effect of doped layers on the characteristics ofμc-Si solar cells[C].Germany:19th European Photovoltaic Solar Energy Conference and Exhibition,2004:57-60.
[7] Zhang Y K,Hao H L,Wu Z K,et al.Effect of the hydrogen dilution on the film structure and photoluminescence of nc-Si:H thin films[J].Micronanoelectronic Technology,2014,51(11):717-723.
[8] Qiu Y,Kunz O,Fejfar A,et al.On the effects of hydrogenation of thin film polycrystalline silicon:a key factor to improve heterojunction solar cells[J].Solar Energy Materials and Solar Cells,2014,122(3):31-39.
[9] Lu Yuanyuan,Li Hejun,Yang Guanjun.Influence of hydrogen dilution on two-phase structure and electrical properties of hydrogenated silicon thin films[J].Journal of Inorganic Materials,2015,30(5):474-478(in Chinese).鲁媛媛,李贺军,杨冠军.氢稀释比对氢化硅薄膜两相结构和电学性能的影响[J].无机材料学报,2015,30(5):474-478.
[10] Catena A,Mcjunkin T,Agnello S,et al.Surface morphology and grain analysis of successively industrially grown amorphous hydrogenated carbon films(a-C∶H)on silicon[J].Applied Surface Science,2015,347(8):657-667.
[11] Ohdaira K,Abe Y,Fukuda M,et al.Poly-Si films with long carrier lifetime prepared by rapid thermal annealing of Cat-CVD amorphous silicon thin films[J].Thin Solid Films,2008,516(5):600-603.
[12] Robertson J.Deposition mechanism of hydrogenated amorphous silicon[J].Journal of Applied Physics,2000,87(5):2608-2617.
[13] Takai M,Nishimoto T,Kondo M,et al.Chemical-reaction dependence of plasma parameter in reactive silane plasma[J].Science and Technology of Advanced Materials,2001,2(3-4):495-503.