Reaction mechanisms for atomic layer deposition of aluminum oxide on semiconductor substrates

Abstract

In this work, we have studied the TMA/H2O (TMA = Al(CH3)3) atomic layer deposition (ALD) of Al2O3 on hydroxyl (OH) and thiol (SH) terminated semiconductor substrates. Total reflection x-ray fluorescence reveals a complex growth-per-cycle evolution during the early ALD reaction cycles. OH and SH terminated surfaces demonstrate growth inhibition from the second reaction cycle on. Theoretical calculations, based on density functional theory, are performed on cluster models to investigate the first TMA/H2O reaction cycle. Based on the theoretical results, we discuss possible mechanisms for the growth inhibition from the second reaction cycle on. In addition, our calculations show that AlCH3 groups are hydrolyzed by a H2O molecule adsorbed on a neighboring Al atom, independent of the type of backbonds (Si-O, Ge-O, or Ge-S) of AlCH3. The coordination of Al remains four-fold after the first TMA/H2O reaction cycle.

Computational Fluid Dynamics simulation of the ALD of alumina from TMA and H2O in a commercial reactor

“…As experimental investigations are tedious at such different time and length scales, physical based modelling has emerged as a way to study the fundamentals of those mechanisms. A wide number of density functional theory (DFT) calculations (Elliott and Greer, 2004;Widjaja and Musgrave, 2002;Weckman and Laasonen, 2015;Delabie et al, 2012) has been published to study the surface reaction energetics during the reactant exposure steps of the ALD process of alumina from TMA and H 2 O. These investigations consider the nature of the surface phenomena, and the different reaction states that the reactant molecules undergo during the process.…”

Reaction factorization for the dynamic analysis of atomic layer deposition kinetics

“…Widjaja and Musgrave (2002) However, because the first of these surface species will be found in only minute quantities on the surface and because we do not consider the second species, our water-exposure mechanism will be based on the more closely related work of Delabie et al (2012). In the cited reference, the authors examine water adsorption and (1-2) and (1-4) H-transfer reactions associated with monomethyl surface species during the water exposure.…”

Time‐scale analysis of atomic layer deposition processes: Predicting the transition from mass‐transfer to kinetically limited regimes

“…Again, partition function definitions and other reaction details are found in [12] which is based on the mechanisms and reaction energies of [1] and [2]. One difference, however, that we do point out between (3) and (18) is the addition of the [S] 3 /[Ŝ] 3 term which accounts for the steric hindrance resulting from the TMA Me groups.…”

“…We also would like to determine the ALD analog to (1). The objective of this manuscript is to establish a criterion to distinguish these regimes based on analyzing the relative timescales of these processes, and to demonstrate the effectiveness of this criterion on the ALD of alumina from trimethyaluminum and water precursors [11].…”