纳米尺度多晶硅微结构刻蚀研究

Study of the Nanometer Scale Polysilicon Micro Structure Etching

以HBr作为刻蚀气体,采用ICP金属刻蚀系统对气体流量、刻蚀压力、离子源功率、偏压功率等工艺参数与刻蚀速率、刻蚀选择比和侧壁垂直度的对应关系进行了大量工艺实验。借助理论分析和工艺条件的优化,开发出一套可满足制备侧壁垂直度的纳米尺度多晶硅密排线结构的优化刻蚀工艺技术。实验结果表明:当采用900 W的离子源功率、11 W的偏压功率、25 cm3/min流量的HBr气体和3 mTorr(1 mTorr=0.133 3 Pa)刻蚀压力的工艺条件时,多晶硅与二氧化硅的刻蚀选择比大于100∶1;在保持离子源功率、偏压功率、气体流量不变的条件下,单纯提高反应腔工艺压力则会大幅提高上述选择比值,同时损失多晶硅和二氧化硅的刻蚀均匀性;HBr气体流量的变化在上述功率及反应腔工艺压力的工艺范围内,对多晶硅与二氧化硅的刻蚀选择比和多晶硅刻蚀的形貌特征均无显著影响。采用上述优化的刻蚀工艺条件,配合纳米电子束光刻技术成功得到多晶硅纳米尺度微结构,其最小线宽为40 nm。

Numerous process experiments for the effect of the gas flow rate,etching pressure,ion source power,bias power and other process parameters on the etching rate,etching selective ratio and slide wall verticality were carried out by ICP metal etching system with HBr as the etching gas.The optimized etching process technology for the fabrication of the densely line structure of the nanometer scale poly silicon satisfying the slide wall verticality was developed by theoretical analysis and optimization of the process conditions.The experimental results show that the optimized process conditions for the nanometer scale poly silicon micro structure are 900 W ion source power,11 W bias power and 25 cm3/min flow rate for the HBr and 3.0 mTorr（1 mTorr=0.133 3 Pa）reactor pressure,resulting in greater than 100∶1 of the etching selective ratio for the poly silicon to silicon oxide.The etching selective ratio increases greatly with the increase of the process pressure for the reactor while the ion source power,bias power and gas flow rate are unchanged,however the etching uniformity of the poly silicon and silicon oxide will be reduced.With the same power and reactor process pressure,the change of the flow rate of HBr can sligh-tly affect the etching selective ratio for the poly silicon to silicon oxide and the etching profile of the poly silicon.The nanometer scale poly silicon micro structure with the minimum line width of 40 nm was successfully obtained with the above optimized etching process conditions and nano electron beam lithography technology.