Characterization of the ion angle distribution function in low-pressure plasmas using a micro-electromechanical system

In recent years, micro-electromechanical systems (MEMSs) have found broad applications in various sensors. However, aside from quartz crystal microbalances, they have not yet been utilized in plasma analysis. Building on previous work with piezoelectric MEMS, the functionality of a MEMS-based sensor system capable of measuring the ion angular distribution function on the wafer holder surface is demonstrated. To enable this functionality, an array of high aspect ratio holes was added to the tiltable silicon plate of a piezoelectric MEMS. These holes allow for the filtering of incoming ions based on their angle perpendicular to the surface of the tiltable element. An algorithm was developed to fit the width and mean of the ion angular distribution function (IADF) based on the RMS ion current for various MEMS amplitudes. Compared to previously used methods for measuring the IADF, the MEMS presented in this paper represents a significant miniaturization. This work is the first to successfully characterize the angular distribution function of ions using a MEMS.