RESEARCH AND DESIGN SENSOR TO MEASURE THIN FILM THICKNESS

Abstract

This paper presents research, design of capacitive coplanar sensors for measuring thin film thicknesses applied
in industry. The sensor structure consists of two flat, thin rectangular electrodes of mili-meter size mounted in fixed
positions on a printed circuit board base, one of which acts as the emitter and the other electrode is placed parallel
on the same plane as the receiver electrode. A thin non-conductive film thickness is placed against the sensing
electrode. The proposed sensor can measure thin film thicknesses from 10µm to 50µm. When the thin film is placed
close to the sensor, the thin film will change the dielectric in the capacitor sensor, thereby changing the
capacitance value of the capacitor, this helps us to determine the thickness of the thin film.
The sensor's operation was investigated by finite element method (FEM) using Ansoft Maxwell simulation
software. Simulation results show the change in capacitance when there is appearance and change in thickness of thin
film. Based on this simulation result, the size of the electrodes and the placement distance of the thin film to the
electrode of the sensor were found to design the sensor with the required sensitivity. In this study, the dimensions of
the sensor were found with the following parameters: width of electrodes plate (a = 5 mm), thickness of electrode
plate (h = 0.2mm), electrodes gap distance (d = 0.1mm) and the coating thickness of the electrode (t = 0.01mm). The
sensor can have industrial applications in manufacturing of thin film resistors and capacitors, thin film transistors, thin
film piezoelectricity, oxide thin films and in a number of other similar applications.