Thin film deposition by Physical Vapor Deposition or PVD is a proven technique for a diverse range of applications including multi-layer x-ray optics, coatings of aerospace, automotive and machine tool components, depositing solar materials or thin films in electronic, semiconductor and medical device production. The AtOMS (Atomic Optical Monitoring System) from Accustrata uses Atomic Absorption Spectroscopy or AAS and Optical Emission Spectroscopy (OES) to address the need for in-situ, real time monitoring of the deposition process to ensure film quality and yield.
In PVD, metals, alloys, compound semiconductors or other materials are vaporized, resulting in a cloud of atoms, which are precisely deposited onto a substrate to create a thin film. The layer can be as thin as a few Angstroms. AAS is a real time optical metrology technique to monitor this process as it happens.
To achieve this unique capability, a probe beam of light at a wavelength, specific to the element it needs to monitor is passed through the plasma. Specific hollow cathode light sources are used that uniquely match the wavelength to the element under study. The vaporized atoms absorb the probe light proportionally to their atomic concentration. By monitoring this absorption, Atoms provides a unique method of process monitoring. Software is used to calculate the atomic concentration of the individual elements of interest and correlates the film deposition rate, thickness and chemical composition.
HCL light sources can be selected to monitor over 60 elements and some HCLs can emit lines to monitor 2 elements, and with two such lamps 4 elements can be measured simultaneously. This provides for monitoring the chemical composition of the growing film in real time. In addition, the unique, fiber optic-based approach supports multi-sensor capabilities for mapping of the entire area of the substrate to control uniformity.
In many applications, Atomic Spectroscopy has proven to be the best choice compared to more traditional monitoring techniques. It can be applied to non-transparent films such as metals and alloys, extremely thin films and complex multi-layers, as well as films deposited on curved or moving substrates.