2026-08-14 –, Room 4
A precise material deposition is nowadays a key component of any microchip production. A prominent deposition technique offering the required level of control is area-selective atomic layer deposition. To improve this technique the chemical reactions of the adsorbates at the substrate surface are modeled. Here, the presented random sequential adsorption approach targets to model the adsorption and packing of the first adsorbate layer. Implementation of the key assumptions as well as first results are part of this contribution.
The scientific background
The continuous shrinking of building blocks in modern microchip production has led to steady improvements in material deposition processes. As atomic layer deposition (ALD) offers nearly atomic control over the thickness of the deposited material it has become a common tool within the lithography process. Within ALD, so-called precursors and co-reactants are alternately offered to a surface where they react and result in the desired material deposition. Current research is focusing on improving ALD by constraining the material deposition to a certain area, the so-called growth surface, while preventing deposition on other parts of the surface, the so-called non-growth surface. Consequently, this deposition technique is called area-selective ALD (AS-ALD). The most promising strategy to AS-ALD is to use small molecules, which selectively adsorb only on the non-growth surface and block all other incoming molecules. As material deposition is inhibited by these molecules on the non-growth surface, they are usually termed small molecule inhibitors (SMI). To understand the chemistry of SMIs different modelling approaches spanning density functional theory, molecular dynamics, kinetic Monte-Carlo or random sequential adsorption are used.
The modeling approach
The presented random sequential adsorption (RSA) approach targets to derive realistic SMI packing layers on the non-growth surface. This approach assumes that SMIs are only weakly interacting with each other and their behavior therefore best described by a random adsorption. The adsorption takes place on a grid representing all adsorption sites of the modeled surface. In addition to adsorption events, the present implementation also includes diffusion, rotation and conformer changes of the adsorbates. Here, the implementation follows a simplified kinetic Monte-Carlo as time evolution and chemically motivated rate constants are ignored while the common cycle of generating a list of possible events, selecting the event to execute and updating the event list is maintained. Convenience functions to run and evaluate thousands of RSA runs are provided to easily judge the packing and inhibition efficiency of studied SMIs.
I'm a staff scientist in the theoretical chemistry group at Leipzig University. My research is focusing on modeling chemical reactions within the (area-selective) atomic layer deposition.