The authors present a new method to determine film thicknesses and sticking coefficients (SC) of precursor molecules for atomic layer deposition (ALD) in high aspect ratio three dimensional (3D) geometries as they appear in microelectromechanical system manufacturing. The method combines a specifically designed experimental test structure with the theoretical predictions from a novel 3D Monte Carlo process simulation for large structures. The authors exemplify our method using Al2O3 and SiO2 ALD processes. SCs for trimethylaluminium and bis-diethyl aminosilane (BDEAS) are extracted. The SC for BDEAS is determined for the first time.
In this paper, the authors present the temperature dependent sticking coefficient (SC) of bis-diethyl aminosilane (BDEAS) and trimethylaluminum (TMA) in atomic layer deposition. SiO2 from BDEAS and ozone at substrate temperatures between 200 and 350 °C as well as Al2O3 from TMA and water deposited at substrate temperatures between 150 and 300 °C was deposited on our likewise in this journal published cavity test structures. The SC of BDEAS shows an Arrhenius dependence while for TMA no temperature dependent SC could be resolved. The activation energy for BDEAS which is extracted from a linear fit to the Arrhenius diagram is compared to the value gained by density functional theory calculations from the literature. Furthermore, the different growth behavior of BDEAS and TMA under substrate temperature considerations is identified with different deposition regimes as proposed in the literature.
We present a new simulation method predicting thicknesses of thin films obtained by atomic layer deposition in high aspect ratio 3D geometries as they appear in MEMS manufacturing. The method features a Monte-Carlo computation of film deposition in free molecular flow, as well as in the Knudsen and diffusive gas regime, applicable for large structures. We compare our approach to analytic and simulation results from the literature. The capability of the method is demonstrated by a comparison to experimental film thicknesses in a large 3D structure. Finally, the feasability to extract process parameters, i.e. sticking coefficients is shown.
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