Surface reaction kinetics in atomic layer deposition: An analytical model and experiments

Abstract

Atomic layer deposition (ALD) surface reactions are comprised of several elementary surface interactions (such as physisorption, desorption, and chemisorption) occurring at the substrate. Since ALD processes are often far from thermodynamic equilibrium, the surface saturation behavior is controlled by the kinetics of these involved interactions. In this article, we present a first-order kinetic model for ALD reaction, to simulate the cumulative effect of precursor exposure (tA), post-precursor purge (tP1), reactant exposure (tB), post-reactant purge (tP2), and substrate temperature (Tsub) on the resulting growth per cycle (GPC) in an ABAB… pulsed ALD process. Furthermore, to simulate the effect of inadequate reactor purges (tP1, and/or tP2) and undesired non-ALD side reactions, reaction pathways to account excess GPC are also taken into consideration. From our model calculations, we simulate GPC vs Tsub trends observed in ALD growth experiments and demonstrate that the process temperature window (ΔTALD) for a constant GPC depends upon the deposition cycle parameters tA, tP1, tB, and tP2. The modeled GPC vs Tsub trends are discussed and compared with SiNx, ZrN, and ZnO PEALD growth experiments.

On the dynamics in chemical vapor deposition of InN

“…5. Such trend has previously been seen by Muneshwar and Cadien 42 and suggests that the surface dynamics, producing chemisorbed species, is of very high importance for the film deposition. In addition, 8 sec is adequate for the purge time in our case as the growth rate becomes saturated (Fig.…”

“…According to the work by Muneshwar and Cadien, an ALD precursor pulse results in physiosorbed species, able to diffuse on the surface before being chemisorbed. 42 With a long purge, all physiosorbed surface species should either chemisorb or desorb from the surface, leaving only chemisorbed In-species for nitridation. The growth rate per ALD cycle increases with increasing purge time; 0.1 s purge renders 0.22 Å/cycle, 2 s purge renders 0.31 Å/cycle and 8 s purge gives 0.41 Å/cycle as shown in Fig.…”

AlN PEALD with TMA and forming gas: study of plasma reaction mechanisms

“…Comparing the size of the TMA molecules 40,41 to the lm thickness increase aer TMA dose, the surface coverage of TMA molecules aer absorption is less than 100%, which can be explained by the steric hindrance effect. 39 The ttings of the Plasma_add effect and the Plasma_remove effect are shown in Fig. 12(c) and (d), respectively.…”

“…The effect of precursor exposure was studied with a first-order kinetic model by Muneshwar and Cadien. 39 According to the first-order kinetic model, this TMA_absorption effect on the film thickness change in a single cycle is modeled with exponential decay: TMA abs = A 0 × {1 − exp[− B 0 × ( t − C 0 )]} …”

On the dynamics in chemical vapor deposition of InN

“…According to the work by Muneshwar and Cadien, an ALD precursor pulse results in physiosorbed species, able to diffuse on the surface before being chemisorbed. 45 With a long purge, all physiosorbed surface species should either chemisorb or desorb from the surface, leaving only chemisorbed In-species for nitridation. The SEM image shown in Fig.…”