In-situ Diagnostics for Plasma Enhanced ALD and CVD

Plasma process in industry has largely relayed on empirical data gathered from ex-situ measurements such as etch or deposition rate, composition, comformality, selectivity, critical dimensions, etc.  Empirical evidence derived from experiment and observation has helped wafer process from nodes to nodes for decades without raising significant issues. However, in the fast-moving pace to sub-nanometer nodes, such trial-and-error method has found itself inefficient and incompetent for timely, cost-effectively, and accurately delivering the desired process result. This is because the surfaces being processed change dynamically at the atomical scale such as during plasma enhanced atomic layer deposition and etch. Ex-situ measurements would not be able to gain the insight of real-time surface reactions and reaction products formation because it is destructive regarding surface-gas phase equilibrium.

For the ultimate sake of designing a process from first principles, in-situ plasma and surface diagnostics are the minimum requirements to rightfully “observe” the real-time and dynamic evolution of the surfaces modified by a plasma and gas molecule adsorption. Only by in-situ, surface chemistry can be measured and monitored without distributing the reaction, preserving the integrity of reaction and identifying transient intermediates.

In this talk, we will give some practical examples to demonstrate how in-situ plasma and surface diagnostics play a critical role in plasma process development, focusing on PEALD and PECVD. An integrated plasma-surface interaction measurement system has been built with in-situ plasma diagnostics to quantitatively access the species and their energy states of process radicals and ions along with in-situ metrologies to monitor surface reactions at each process steps dynamically. The in-situ measurement is also interplayed with first principles and micro kinetics simulations to elucidate how the type and energy of radical and ion species reacts with different surfaces sites, which in turn, generates thin films of different properties.