Pad conditioning in chemical mechanical polishing

As circuits become increasingly complex and device sizes shrink, the demands placed on manufacturing processes increases. For successful manufacture of such circuits, high levels of wafer planarity are required. Chemical mechanical polishing (CMP) is a manufacturing process used to achieve global planarity. Studies have shown that the degree of planarity achieved is influenced by the pad properties. During polishing, the properties of the pad can deteriorate causing reduced polish rates and reduced planarity. It has been shown that this is caused by plastic deformation of the pad material, leading to glazed areas on the surface. Conditioning is used to regenerate the pad surface by breaking up these areas, but in doing so induces pad wear. As some areas of the pad will experience a higher degree of glazing, varying conditioning densities are necessary to counter this effect. The conditioning profile dictates the travel of the conditioning arm over the pad and hence the conditioning density experienced at each point. The aim of such a profile is to aid planarity by creating a uniform and constant removal rate over the whole wafer. The variations in pad properties between new and worn-out pads and the effect of conditioning in changing the pad properties will be examined. By examining correlations between conditioning densities experienced and pad properties over the radius of the pad, it is hoped to further understand the effect of conditioning on the process. Such understanding is vital in improving process reliability and yields in semiconductor manufacture.