Christopher Metting, AccuStrata, Inc., Rockville, MD
Multiple challenges associated with thin film deposition accuracy, and especially the challenge of real-time control of chemical composition for compound films and alloys, spread over the entire contemporary thin film vacuum coating industry. These challenges especially affect the new-generation thin film applications such as wide band semiconductors and superconductors, solar thin films, Extreme UV and X-Ray coatings and others. The limitations associated with current process control capabilities result in increased product cost, due to the inherent waste of energy, material and labor, and delay the commercialization and manufacturing scale up of many important recent innovations.
A novel in situ PVD process control system for the manufacturing of high-precision thin films, based on simultaneous atomic absorption and optical emission spectrometry in the vicinity of the substrate (AtOMS), is presented. By simultaneous monitoring the atomic concentration of up to 4 chemical elements in the deposition region together with the optical emission of a variety of particles and radicals, the method provides for accurate deposition control of extremely thin films, compound thin films and complex multilayer structures with controlled interface layers as well as metal alloys and other opaque films. It provides real time deposition rate and film composition measurements that can be utilized for dynamic feedback process control. The fiber optics design of the system allows flexibility and reconfigurability for fast and seamless installation in almost all legacy PVD equipment.
We present our most recent experimental results from in situ monitoring of variety of thin films such as Si, Mo, Al, In, Cu, Au, B and compound thin films (MoSi_x, AlSi_x, ITO) deposited by a variety of PVD processes (epitaxial growth, magnetron sputtering and E-beam evaporation). Results for the achieved accuracy, stability and repeatability under various equipment configurations and monitored materials in manufacturing environment are also presented.
The results validate the applicability and practicality of combined atomic absorption/ optical emission spectroscopy in the deposition of compound thin films and provide a path forward for use in manufacturing of new generation thin film processes such as deposition of compound materials, high entropy alloys, pre-engineered interfaces and others.