Computer simulation of magnetron sputtering — Experience from the industry

Abstract

Development of new PVD processes and corresponding magnetron cathodes to meet the ever growing customer requirements is increasingly costly when done only by experimental iterations. Examples of such customer requirements are: (1) high thickness uniformity over the substrate, (2) feature coverage in semiconductor wafer processing, (3) growing substrate size for flat panel displays, (4) high target utilization for optical and magnetic data storage applications, and (5) high rate reactive sputtering with uniform chemical composition in architecture glass coating. Computer simulations help to reduce development time and cost in these cases. A brief overview of well established simulation methods is given, including methods of computing resulting target erosion, feature size models, and models of sputtered material transport to the substrate in inert and reactive gases. Advances in development of the Direct Simulation Monte Carlo (DSMC) method used for neutral transport and in models of reactive sputtering are reviewed. Finally, self-consistent plasma simulation methods are discussed, namely Particle in Cell, fluid and hybrid models. Limitations and challenges of various simulation methods for industrial magnetron processes are summarized and discussed. Examples of successful deployment of the models for the technologies mentioned are given. An efficient 3D test-electron Monte Carlo model of magnetron plasma based on movement of energetic electrons is presented. Simulations are compared with experiments for an industrial magnetron equipped with rotating magnet set and 300 mm diameter target. Asymmetries in ionization due to interaction of drifting electrons with the magnetic field pattern are discussed. Simulation of current–voltage characteristics is presented and importance of electron loss to anode, walls and recapturing on target is underlined.