Vandalon V, Kessels W M M Erwin
Department of Applied Physics , Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven , The Netherlands.
Langmuir. 2019 Aug 13;35(32):10374-10382. doi: 10.1021/acs.langmuir.9b01600. Epub 2019 Jul 30.
The initial growth during the atomic-layer deposition (ALD) of AlO using trimethylaluminum (TMA) and water was studied on two starting surfaces: SiO and -H-terminated Si(111) [H/Si(111)]. In situ spectroscopy ellipsometry (SE) showed virtually immediate growth of AlO on both surfaces, although for H/Si(111) a reduced growth-per-cycle was observed in the initial 20 cycles. The underlying surface chemistry during the initial cycles of ALD was monitored with in situ broadband sum-frequency generation (BB-SFG) spectroscopy. For the SiO surface, the -CH surface groups were followed revealing that only the first TMA half-cycle deviates from the steady-growth regime. The reaction cross section of the initial TMA half-cycle (σ = 2.0 ± 0.2 × 10 cm) was a factor of 3 lower than the cross section of the TMA half-cycle during the steady-growth regime of ALD (σ = 6.5 ± 0.6 × 10 cm). All HO half-cycles, including the first, showed steady-growth behavior with a corresponding reaction cross section (σ = 4.0 ± 0.4 × 10 cm). Therefore, only the first ALD cycle was affected by initial growth effects on the SiO starting surface, in line with the SE data. For the H/Si(111) surface, the Si-H groups were monitored with BB-SFG spectroscopy, revealing a reaction cross section of σ = 3.1 ± 0.3 × 10 cm for the first TMA half-cycle on H/Si(111); a factor two lower than that during the steady regime of AlO. These results demonstrate that the chemistry during the initial growth regime of AlO ALD on SiO and H/Si(111) shows subtle but measurable differences compared to the steady-growth regime.
使用三甲基铝（TMA）和水在原子层沉积（ALD）AlO过程中的初始生长情况在两种起始表面上进行了研究：SiO和氢终止的Si(111) [H/Si(111)]。原位光谱椭偏仪（SE）显示在两种表面上AlO几乎立即开始生长，尽管对于H/Si(111)，在最初的20个循环中观察到每个循环的生长有所减少。原子层沉积初始循环期间的底层表面化学情况通过原位宽带和频产生（BB-SFG）光谱进行监测。对于SiO表面，跟踪-CH表面基团发现只有第一个TMA半循环偏离稳定生长状态。初始TMA半循环的反应截面（σ = 2.0 ± 0.2 × 10 cm）比原子层沉积稳定生长状态下TMA半循环的截面（σ = 6.5 ± 0.6 × 10 cm）低3倍。所有的HO半循环，包括第一个，都显示出稳定生长行为，对应的反应截面为（σ = 4.0 ± 0.4 × 10 cm）。因此，只有第一个原子层沉积循环受SiO起始表面上的初始生长效应影响，这与SE数据一致。对于H/Si(111)表面，用BB-SFG光谱监测Si-H基团，发现在H/Si(111)上第一个TMA半循环的反应截面为σ = 3.1 ± 0.3 × 10 cm；比AlO稳定状态下低两倍。这些结果表明，与稳定生长状态相比，在SiO和H/Si(111)上AlO原子层沉积初始生长状态期间的化学情况显示出细微但可测量的差异。
