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A study from Georgia Techinvestigates the mechanisms behind area-selective atomic layer deposition (AS-ALD) of titanium dioxide (TiO2) and hafnium dioxide (HfO2) on poly(methyl methacrylate) (PMMA) and silicon (Si) substrates, emphasizing their effects on feature sizes and film thickness. The researchers found that TiO2 exhibits highly selective deposition on Si compared to PMMA, though the PMMA sidewalls inhibit deposition, resulting in smaller feature dimensions than the original patterns. In contrast, HfO2, while less selective, combines selective deposition with a lift-off mechanism, allowing for smaller feature sizes but limiting the possible thickness before full coverage occurs.
The study highlights that TiO2's truly area-selective deposition mechanism causes significant sidewall inhibition, restricting the achievable feature size to larger dimensions. However, HfO2's combination of selective deposition and lift-off results in less sidewall inhibition, enabling the formation of much smaller features. The research further suggests that the choice of deposition material and the mechanism it employs critically influences the minimum feature sizes that can be achieved in semiconductor fabrication, with practical implications for future device miniaturization.
The findings underscore that the AS-ALD mechanism—whether a pure area-selective process or a combination with lift-off—directly affects the precision and scalability of nanofabrication. TiO2's area-selective mechanism is more effective for creating precise patterns but is limited by sidewall effects, while HfO2 offers greater flexibility in feature size at the cost of potential thickness limitations due to less selective deposition behavior. Potentially the research provides valuable insights for optimizing deposition techniques in advanced semiconductor manufacturing.
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