Predictive Evaluation of Atomic Layer Deposition Characteristics for Deposition of Al₂O₃ thin films

Atomic Layer Deposition (ALD) is the new variant of chemical vapor deposition process where the reactants are supplied sequentially as a timed pulse. The pulse of reactant precursor is usually separated by purging using inert gas pulse or a sufficient wait time. The chemisorption of precursors is self-limiting and reactive site dependent and thus provides very precise thickness control over intricate surfaces with high conformality and depth to width aspect ratios of features over 1000. These aspects of atomically controlled thickness due to self-limiting reaction mechanisms with high conformality and ease of operation has made ALD one of the most prospective deposition technique for semiconductor and synthetic biological applications.

This paper evaluates parametric interactions of the Vecco Savannah thermal ALD system for deposition of Al₂O₃ thin films. Trimethyl Aluminum (TMA) and Water (H₂O) are the precursors used for depositing high-K dielectric layers on Si/SiO₂ substrates. The high-quality pin hole free deposition of Al₂O₃ is carried out by varying the pulse time for TMA and H₂O from 0.01 sec to 0.02 sec. Temperature is changed from 100 to 200 ⁰C. The effect of Ozone pulse is also evaluated. The response characteristics of thickness is measured by spectroscopic ellipsometry. Sampling evaluation of thickness is also carried out using AFM and SEM microscopy for surface consistency. The number of cycles is kept constant at 100, as it is known to have a direct relationship with the thickness of Al₂O₃ thin film deposition. JMP is used for Design of Experiment (DoE) of ALD. It was identified that, the interaction of temperature of H₂O pulse is dominant than the two parameters independently. The Ozone pulse too has a significant impact.