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.

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We investigated chlorine trifluoride ͑ClF 3 ͒ etching of silicon with a patterned oxide mask layer prepared by e-beam lithography. The mask apertures varied from 0.1 m to 300 m. This enables to adjust the flow rate of ClF 3 molecules into the etched cavity leading to a strong variation of the ClF 3 abundance at the silicon surface. A crucial dependence of the etch rate on the aperture area was observed revealing a maximum of the etch rate for a specific ClF 3 abundance. A physical description of the etch process is developed in order to distinguish between different mechanisms within the etching process. At low ClF 3 abundance the etch rate is limited due to a lack of ClF 3 . For high abundance the etch rate is assumed to be hampered by a diffusion like transport of ClF 3 molecules through a fluorosilyl layer formed on the silicon surface. It can be shown that the etch rate of silicon with ClF 3 is not limited by the chemical reaction at high ClF 3 abundance. Additionally, we observed a change in etching behavior from isotropic to anisotropic with a strong correlation to the etching regime.