Tool for micro-diagnostics of atmospheric pressure proximity plasmas for spatial atomic layer deposition (ToMicro APPs)

Atomic layer deposition (ALD) is a technique that is able to provide self-limited monolayer deposition of high-quality films with superior 2D and 3D thickness control. Recently, ALD has become more attractive to the large-area electronics industry with the introduction of atmospheric pressure spatial ALD (sALD), co-pioneered by TNO. This concept is based on the spatial separation of the half-reactions, instead of temporal, combined with gas-bearing technology. The reactor has separate zones exposing the precursors one by one to a substrate that moves underneath the reactant inlets at close proximity (~100 μm distance). Between and around the reaction zones, shields of inert gas separate the precursor flows and also act as gas bearings, thus facilitating virtually frictionless movement of a substrate in the reactor chamber. More improvement to the process concept is offered by the introduction of plasma in the ALD cycle, which makes it possible to deliver additional reactivity to the substrate with additional advantages in process speed, lower temperature and improved material quality. With the new micro-diagnostics implemented in an atmospheric pressure plasma-enhanced (AP-PE) sALD reactor we target the following R&D questions to be answered: -Which are the primary active species in the plasma/gas phase? -Is any material re-deposited from the plasma, or other sources? -How can radical recombination be limited? What is the growth rate in the reactor? The main goal of this project is the design of an optical diagnostics tool for a laboratory Atmospheric Pressure Plasma-Enhanced spatial ALD (APPE sALD) reactor. All classical design steps from exploration to proposed solutions will be described in detail as well as background theory and technical criteria to select the appropriate diagnostics to answer the R&D questions. The design is divided into two blocks: 1) a diagnostic to probe the plasma itself, including our motivation to select Optical Emission Spectroscopy (OES) as the best method to implement, and 2) a real-time, in-situ monitoring layer diagnostic, i.e. Spectroscopic Ellipsometry.