Development of a compact low energy reactive gas ion gun for ultra high resolution depth profiling

在本研究中，利用所开发的紧凑型FLIG对GaAs/AlAs超晶格样品进行了离子能量范围为100 ~ 500eV的AES深度谱分析。在150eV以上的能量区，实际刻蚀速率可达1.5nm/min以上。在Al-LVV深度剖面前缘溅射能量分别为100,150,200和300eV时，获得了1.3,1.6,1.8和2.0nm（84-16%）的高深度分辨率。在能量为100eV时，MRI计算的最佳拟合要求前后边缘的表面粗糙度分别为0.4和1.2nm，导致前缘（Δz_1=1.3nm）深度分辨率显著提高，但后边缘（Δz_1=2.7nm）深度分辨率明显下降。虽然这种趋势与O_2^+离子溅射ABS深度剖面的情况非常相似，但可能是由于O_2^+离子轰击在AlAs层中形成的al -氧化物的溅射率很低，因此在测量过程中无法观察到任何氧气吸附在试样表面的痕迹。为了研究这种现象的起源，我们进行了动态蒙特卡罗模拟。

In the present study, AES depth profiling of GaAs/AlAs super lattice sample using the developed compact FLIG was performed with the ion energy ranging from 100 to 500eV. The practical etching rate of more than 1.5nm/min was attained in the energy region over 150eV. The high depth resolutions of 1.3,1.6,1.8 and 2.0nm (84-16%) were obtained with the sputtering energies of 100,150,200 and 300eV at the leading edge of Al-LVV depth profiles, respectively.At the energy of 100eV, the best fit of the MRI calculation required different surface roughness of 0.4 and 1.2nm at the leading and trailing edges, leading to the remarkable improvement of the depth resolution at the leading edge (Δz_1=1.3nm) but followed by considerable deterioration at the trailing edge (Δz_1=2.7nm). Although this tendency is quite similar to the case of the ABS depth profiling with O_2^+ ion sputtering, probably due to the low sputtering yield of Al-oxides formed in AlAs layers by O_2^+ ion bombardment, any trace of oxygen adsorption onto a specimen surface could not be observed during the measurement. To investigate the origin of this phenomenon, we performed dynamic Monte-Carlo simulation.