Effect of surface roughness on small particle adhesion forces evaluated by atomic force microscopy

One of the issues in semiconductor device manufacturing is particle contamination on wafers. To improve the production yield of devices, it is necessary to reduce the number of particles. One approach to avoiding particle contamination caused by scattering in semiconductor processing apparatuses is by improving the adhesion forces between particles and surfaces of apparatus components. Such forces depend on the roughness of the surface where particles are attached. There are models to explain dependency of adhesion forces on the surface roughness. However, variations of the adhesion forces caused by surface roughness have not been sufficiently investigated in experiments. In this research, dependency between the adhesion forces of small particles and the surface roughness was evaluated by atomic force microscopy. It was found that reducing surface roughness to a nanometer scale increases the mean values and reduces the coefficients of variations of adhesion forces between particles and practical surfaces in apparatuses.