双束聚焦离子束/扫描电子显微镜中位点选择性掺杂对比原理,Ultramicroscopy

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双束聚焦离子束/扫描电子显微镜中位点选择性掺杂对比原理
Ultramicroscopy ( IF 2.1 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.ultramic.2020.112947
Augustus K W Chee ₁

Affiliation

在扫描电子显微镜 (SEM) 中使用二次电子 (SE) 信号的掺杂对比度可以满足国际半导体路线图 (ITRS) 对下一代集成电路和器件的定量掺杂分析的要求，但前提是采用位点选择性标本制备程序。在这项研究中，通过 30 kV Ga+ 聚焦离子束 (FIB) 将沟槽侧壁切割成硅 pn 结样品，并在双束 FIB/SEM 中使用连续较低的电压进行铣削，在此研究中进行了位点特定的掺杂分析。尽管在表面沉积保护性铂金带可有效控制最终研磨电压低时的“遮蔽”效应，与受到相同离子束能量的解理表面相比，侧壁的掺杂对比度显着降低，这归因于受先前铣削步骤影响的材料，以及铣削和成像的不同几何形状。考虑到离子注入的深度和浓度以及非晶化损伤作为最终研磨电压的线性函数，研究了支持掺杂对比机制的新原理。贴片场受到抑制，但非晶-晶体界面处的体掺杂相关表面带弯场对于掺杂对比度至关重要。一般来说，随着铣削电压的降低，掺杂对比度增加，虽然它只能达到新鲜切割样品可获得的一半，但仍然可用，

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Principles of site-selective doping contrast in the dual-beam focused ion beam/scanning electron microscope

Doping contrast using the secondary electron (SE) signal in the scanning electron microscope (SEM) can satisfy the International Roadmap for Semiconductors (ITRS) requisites for quantitative dopant profiling of next-generation integrated circuits and devices, but only if adopting a site-selective specimen preparation procedure. In this study, site-specific dopant profiling was performed on the trench side-wall cut by a 30-kV Ga+ focused ion beam (FIB) into silicon p-n junction specimens and milled using successively lower voltages in the dual-beam FIB/SEM. Although depositing the protective platinum strap on the surface effectively controls 'curtaining' effects at low final milling voltages, significantly reduced doping contrast from the side-wall compared to that from a cleaved surface subjected to the same ion-beam energy is ascribed to the material affected by a previous milling step, as well as the dissimilar geometries of milling and imaging. New principles underpinning the doping contrast mechanism were surveyed taking into account the depth and concentration of ion implantation and amorphization damage as a linear function of the final milling voltage. Patch fields are suppressed, but the bulk doping-dependent surface band-bending fields at the amorphous-crystalline interface is crucial for doping contrast. In general, as the milling voltage decreases the doping contrast increases, which although reaches up to only half that attainable from a freshly-cleaved specimen, is usable, and demonstrates the feasibility of site-specific dopant profiling in situ in the SEM.

更新日期：2020-06-01

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