Isotropic plasma atomic layer etching of Al2O3 using a fluorine containing plasma and Al(CH3)3

Abstract

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Reaction Mechanisms during Atomic Layer Deposition of AlF3 Using Al(CH3)3 and SF6 Plasma

“…The ALE process using TMA and SF 6 plasma developed in the same reactor showed an etch rate of approximately 3 Å at 250 °C and 2 Å at 200 °C, while no etching was observed for temperatures below 150 °C, which indicates a strong dependence on the temperature and corroborates the observed transition from AlF 3 ALD to Al 2 O 3 ALE. 55 In addition, it was confirmed that an SF 6 plasma can be used for fluorination of Al 2 O 3 , similar to the use of HF for thermal ALE. Al 2 O 3 films (∼10 nm thick) were exposed to SF 6 plasma and subsequently analyzed by spectroscopic ellipsometry (SE; see Figure S1).…”

“…Interestingly, the chemistry based on fluorination and TMA dosing can also be used for ALE of Al 2 O 3 at higher substrate temperatures, which was demonstrated using an SF 6 plasma as the reactant in our previous work . The transition between AlF 3 ALD and Al 2 O 3 ALE is governed by the substrate temperature and is believed to depend on the desorption temperature of AlF x (CH 3 ) 2– x species .…”

“…As discussed in the Experimental Section, the actual sample temperature during the experiments on the wafer coupons deviates from the sample temperature during infrared spectroscopy experiments. In our previous work, ALE was already observed at a substrate temperature of 155 °C by employing a high TMA dose of 0.5 s . This indicates that, besides the temperature, the TMA dose has an influence on the competition between deposition and etching.…”

“…Interestingly, the chemistry based on fluorination and TMA dosing can also be used for ALE of Al 2 O 3 at higher substrate temperatures, 48 which was demonstrated using an SF 6 plasma as the reactant in our previous work. 55 The transition between AlF 3 ALD and Al 2 O 3 ALE is governed by the substrate temperature and is believed to depend on the desorption temperature of AlF x (CH 3 ) 2−x species. 47 At low sample temperatures, AlF x (CH 3 ) 2−x species remain adsorbed to the surface, leading to growth, while at higher temperatures, they desorb from the surface; hence, etching is obtained.…”

“…Recently, we presented an ALD process for AlF 3 as well as an ALE process for Al 2 O 3 , , using SF 6 plasma as an alternative, easy-to-handle, and readily available co-reactant. SF 6 is a stable and nontoxic gas, which is widely used in the industry.…”