Plasma based process control of reactive sputtering

• Applicants: Professor Dr. Ralf-Peter Brinkmann; Professor Dr.-Ing. Jan Lunze; Professor Dr. Julian Schulze
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 417888799

Reactive sputtering is frequently used to deposit thin films in low temperature plasmas as the basis for a variety of high-tech products. Despite its enormous societal impact many fundamental mechanisms such as the electron heating, plasma-surface interactions, and transport phenomena are not understood in such plasmas. Consequently, there is also a lack of insights into the non-linear and non-local effects of global control parameters such as the neutral gas pressure, gas flows, powers, magnetic fields, etc. on the characteristics of deposited thin films. This leads to massive limitations of process optimization and control. Due to a lack of understanding of and access to the energy distribution functions of different particle species, that determine the film properties, as well as to the surface characteristics themselves current concepts of process control are based on controlling secondary parameters such as gas glows and powers, which do not determine the film characteristics uniquely, as well as greybox-models. In this sense plasma sputter processes are a representative example of a variety of other plasma processes that suffer from the same problems.In this project, a plasma based concept, i.e. based on plasma parameters and scientific understanding, to control reactive sputtering to deposit Al2O3-films in a capacitive radio frequency (RF) magnetron plasma will be developed and tested for the first time. A fundamental understanding of the effects of global control parameters on energy distribution functions of different particle species, that determine the film characteristics, as well as of the film characteristics themselves will be developed based on a synergistic combination of experimental and theoretical methods. The discharge will be characterized experimentally by a variety of plasma and surface diagnostics as well as numerically by kinetic simulations. Based on this fundamental understanding capable plasma parameters suitable for process control will be identified. These parameters must be measurable within seconds by non-invasive diagnostics and must be uniquely correlated to energy distributions and surface characteristics. They will be described theoretically by fast reduced global models that can predict causes of parasitic process drifts and procedures to compensate them. These plasma parameters and models will be used for process control in the frame of a control loop that is developed in parallel. This plasma based control loop will result in a significant improvement of the control of the characteristics of deposited thin films. The goal is to control plasma characteristics such as the energy per deposited particle to correlate film and plasma characteristics and to ultimately control the film characteristics. If successful, this principle of plasma based process control can be transferred to other plasma processes. Moreover, important fundamental insights into the physics of such plasmas are expected.

• DFG Programme: Research Grants