Method and apparatus for thickness control and reproducibility of dielectric film deposition

Abstract

The invention embodies a method and apparatus for controlling the thickness of a dielectric film formed by physical vapor deposition (PVD). The method compensates for the continuously varying electrical load conditions inherent in dielectric deposition via PVD. The method can be implemented through three different stages. Initially, the system power supply can be configured to operate in either constant current or constant voltage mode, herein referred to as constant supply parameter mode. Next, a gas composition which minimizes excursions in system impedance under these conditions is empirically determined. Finally, a test deposition can be performed using the constant parameter power supply mode and the gas mixture. This deposition is performed while tracking and summing the energy delivered to the system. The thickness of the deposited film is subsequently measured, and from these data a thickness-per-unit-energy relationship is determined. Depositions of predictable film thickness are then reproducibly performed under these established conditions. In practice, a given deposition is terminated at a value of total energy as determined by the established thickness per unit energy value and the required film thickness. The method is much more reliable than the current art technique of deposition at constant power for a fixed time.