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<p>Inhibitor-free area selective atomic layer deposition (AS-ALD) of SiO<sub>2</sub> thin films was studied using a dual-chamber system designed to alternate surface cleaning and deposition without air exposure. In the cleaning chamber, NF<sub>3</sub> and NH<sub>3</sub> were reacted in a remote plasma to form an ammonium fluoride-based etchant, which enabled selective etching of SiO<sub>2</sub> over SiN. This step allowed pre-cleaning to remove native oxides and post-cleaning to restore the non-growth SiN surface. However, when only NF<sub>3</sub> and NH<sub>3</sub> were used, excessive residual fluorine remained on the surface. During repeated cleaning and deposition cycles, this fluorine increased the etch rate of the ALD SiO<sub>2</sub>, preventing accurate thickness control. To solve this problem, O<sub>2</sub> was added. Oxygen reacted with hydrogen from NH<sub>3</sub> to form H<sub>2</sub>O, which reduced surface fluorine and stabilized thickness control through multiple cycles. In the ALD chamber, SiO<sub>2</sub> thin films were deposited at 200&#xa0;℃ using diisopropylamino silane (DIPAS) and O<sub>3</sub>. Owing to its inherent chemo-selective adsorption characteristic, DIPAS exhibited shorter incubation cycles on SiO<sub>2</sub> than on SiN, enabling preferential nucleation. As a result, the ALD SiO<sub>2</sub> could be deposited more effectively on SiO<sub>2</sub> surfaces, while repeated post-cleaning maintained selectivity on SiN. By continuing this cycle, thickness differences between SiO<sub>2</sub> and SiN regions were steadily accumulated. Selective growth on patterned wafers was confirmed by <i>in situ</i> ellipsometry, residual gas analysis, high-resolution transmission electron microscopy, and atomic force microscopy.</p>

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Inhibitor-free area selective atomic layer deposition of SiO2 thin films by in situ surface cleaning using isotropic SiO2 selective removal

  • 期刊论文

  • 发表日期：

    2025年9月26日

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  • Min Su Kim,
  • Hyun Gu Kim,
  • So Myeong Shin,
  • Byungchul Cho,
  • Juhwan Park,
  • Min Kim

摘要

Inhibitor-free area selective atomic layer deposition (AS-ALD) of SiO2 thin films was studied using a dual-chamber system designed to alternate surface cleaning and deposition without air exposure. In the cleaning chamber, NF3 and NH3 were reacted in a remote plasma to form an ammonium fluoride-based etchant, which enabled selective etching of SiO2 over SiN. This step allowed pre-cleaning to remove native oxides and post-cleaning to restore the non-growth SiN surface. However, when only NF3 and NH3 were used, excessive residual fluorine remained on the surface. During repeated cleaning and deposition cycles, this fluorine increased the etch rate of the ALD SiO2, preventing accurate thickness control. To solve this problem, O2 was added. Oxygen reacted with hydrogen from NH3 to form H2O, which reduced surface fluorine and stabilized thickness control through multiple cycles. In the ALD chamber, SiO2 thin films were deposited at 200 ℃ using diisopropylamino silane (DIPAS) and O3. Owing to its inherent chemo-selective adsorption characteristic, DIPAS exhibited shorter incubation cycles on SiO2 than on SiN, enabling preferential nucleation. As a result, the ALD SiO2 could be deposited more effectively on SiO2 surfaces, while repeated post-cleaning maintained selectivity on SiN. By continuing this cycle, thickness differences between SiO2 and SiN regions were steadily accumulated. Selective growth on patterned wafers was confirmed by in situ ellipsometry, residual gas analysis, high-resolution transmission electron microscopy, and atomic force microscopy.