Thermal atomic layer etching of amorphous and crystalline Al2O3 films
Thermal atomic layer etching of amorphous and crystalline Al2O3 films
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非晶和结晶 Al2O3 薄膜的热原子层蚀刻
DOI：
10.1116/6.0000995
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发表时间：
2021
影响因子：
2.9
通讯作者：
S. George
中科院分区：
文献类型：
--
作者：
J. Murdzek;A. Rajashekhar;Raghuveer S. Makala;S. George
热原子层蚀刻（ALE）可以实现连续的，自我限制的表面反应。热ALE的一种机制是基于氟化和配体交换反应。对于金属氧化物ALE，氟化将金属氧化物转化为金属氟化物。然后，配体交换反应通过形成挥发性产物来去除金属氟化物。以前的研究已经证明了非晶Al2O3薄膜的热ALE。然而，以前的研究没有探讨过非晶Al2O3薄膜和结晶Al2O3薄膜的热ALE之间的差异。本研究探讨了非晶Al2O3薄膜和结晶Al2O3薄膜的热ALE。采用HF、SF4或XeF2作为氟化反应物。采用三甲基铝（TMA）或二甲基氯化铝（DMAC）作为金属前体进行配体交换。椭偏光谱测量结果表明，非晶Al2O3薄膜的腐蚀速率远高于晶体Al2O3薄膜。在300℃的高温下使用HF和TMA，以0.78 A/cycle的蚀刻速率去除非晶Al2O3薄膜。对于晶体Al2O3薄膜，在去除约10a薄膜后停止刻蚀之前，最初观察到的刻蚀速率为0.06 A/循环。含HF和DMAC的热ALE结果相似。在300℃下，非晶Al2O3薄膜和结晶Al2O3薄膜的腐蚀速率分别为0.60和0.03 A/循环。其他氟化剂，如SF4或XeF2，也与TMA或DMAC一起用于Al2O3 ALE。这些用于氟化和配体交换的反应物能够在300°C下蚀刻无定形Al2O3薄膜。然而，他们不能在300°C时蚀刻超过初始10-20 A表面层的Al2O3晶体薄膜。研究还考察了退火温度对300°C下HF和TMA作为反应物的每循环蚀刻速率的影响。在≥880°C的温度下，以0.78 A/cycle的刻蚀速率刻蚀非晶Al2O3薄膜，直至非晶Al2O3薄膜结晶。利用非晶态Al2O3与晶态Al2O3热ALE的差异，可以获得晶态Al2O3存在下非晶态Al2O3的选择性热ALE。
Thermal atomic layer etching (ALE) can be achieved with sequential, self-limiting surface reactions. One mechanism for thermal ALE is based on fluorination and ligand-exchange reactions. For metal oxide ALE, fluorination converts the metal oxide to a metal fluoride. The ligand-exchange reaction then removes the metal fluoride by forming volatile products. Previous studies have demonstrated the thermal ALE of amorphous Al2O3 films. However, no previous investigations have explored the differences between the thermal ALE of amorphous and crystalline Al2O3 films. This study explored the thermal ALE of amorphous and crystalline Al2O3 films. HF, SF4, or XeF2 were used as the fluorination reactants. Trimethylaluminum (TMA) or dimethylaluminum chloride (DMAC) were used as the metal precursors for ligand-exchange. Spectroscopic ellipsometry measurements revealed that the amorphous Al2O3 films had much higher etch rates than the crystalline Al2O3 films. When using HF and TMA at 300 °C, the amorphous Al2O3 film was removed at an etch rate of 0.78 A/cycle. For the crystalline Al2O3 film, an etch rate of 0.06 A/cycle was initially observed prior to the stoppage of etching after removing about 10 A of the film. Thermal ALE with HF and DMAC resulted in similar results. Etch rates of 0.60 and 0.03 A/cycle were measured for amorphous and crystalline Al2O3 films at 300 °C, respectively. Other fluorination agents, such as SF4 or XeF2, were also used together with TMA or DMAC for Al2O3 ALE. These reactants for fluorination and ligand-exchange were able to etch amorphous Al2O3 films at 300 °C. However, they were unable to etch crystalline Al2O3 film at 300 °C beyond the initial 10–20 A surface layer. The investigations also examined the effect of annealing temperature on the etch rate per cycle using HF and TMA as the reactants at 300 °C. Amorphous Al2O3 films were etched at approximately the same etch rate of 0.78 A/cycle until the crystallization of amorphous Al2O3 films at ≥ 880 °C. The differences between amorphous and crystalline Al2O3 thermal ALE could be used to obtain selective thermal ALE of amorphous Al2O3 in the presence of crystalline Al2O3.