高数值孔径光刻中衬底反射率的控制

Control of substrate reflectivity in hyper numerical aperture lithography

高数值孔径(N4)光刻中,需要控制衬底反射率以减小薄膜干涉对光刻性能的影响。采用薄膜光学方法研究了高NA光刻中底层抗反膜(BARC)对衬底反射率的控制。针对硅基底对单层和双层BARC进行优化以探索满足高NA光刻要求的BARC材料光学参数容限。结果表明,当NA超过0.8时,单层BARC无法控制衬底反射率而有必要采用双层BARC。横电(TE)比横磁(TM)偏振光的衬底反射率更难以控制。NA越大,单层BARC折射系数的优化值越大。双层BARC中的顶层膜应采用低吸收率材料而底层膜应采用高吸收率材料。本研究可为高NA光刻中的BARC材料研制及衬底反射率控制提供理论依据。

Substrate reflectivity needs to be controled to reduce the impact of thin-film interference on lithography performance in hyper numerical aperture （NA） lithography. Based on thin film optics method, the control of substrate reflectivity with bottom antireflection coating （BARC） was investigated for hyper- NA lithography. Single-layer and dual-layer BARC on a silicon substrate were optimized to investigate the margins of BARC＇s optical parameters which meet the requirements of hyper-NA lithography. It is found that single-layer BARC fails to control substrate reflectivity when NA is more than 0.8 and dual-layer BARCs become essential. The substrate reflectivity of TE wave is more uncontrollable as compared to TM wave. The optimized values of refractive index for single-layer BARC grow as the NA increases. In a dual- BARC structure, the top layer should be low absorptive while the bottom one should be high absorptive. It provides theory base for the research of BARC materials and the control of substrate reflectivity in hyPer-NA lithography.