INVESTIGATION OF PAD-WAFER CONTACT PRESSURE IN CHEMICAL MECHANICAL POLISHING WITH FINITE ELEMENT ANALYSIS

摘要

Chemical mechanical polishing (CMP) has become an essential process technology for the fabrication of sub-half micron devices. The goal of CMP is to preferentially remove "raised" material in order to reduce height differences across the wafer surface. The material removal rate of a CMP process is dependent on the contact pressure between the wafer and the pad. For a patterned wafer, the pattern density and layout affect the pressure. This study applies finite element analysis (FEA) to investigate the effect that the pattern has on the contact pressure. In the first phase of a multipart study, single fixed-pitch lines and fixed-pitch squares are investigated. The study reveals: 1) an uneven pressure distribution over the contact area, 2) the pressure variation along with the pattern density and 3) the changes of the contact area with different pad materials. The FEA approach provides an alternative method to broaden the understanding of the CMP process mechanism.