Endpoint detection for CMP

Abstract

In spite of dramatic advances in oxide chemical mechanical polishing (CMP) process performance in recent years, there has been relatively little published data on semiconductor production line worthy endpoint detection (EPD) systems for interlevel dielectric (ILD) planarization.1 In contrast, numerous EPD methods have been successfully developed for metal polishing, most notably friction sensing via motor current monitoring. However, these methods have so far not been proven to be 100% reliable. Semiconductor manufacturers have been searching for a viable method of either monitoring the dielectric removal rate or the planarization of the surface during the polish process, and for improved metal endpoint detection systems. A coustic methods have been patented, but to date no commercially viable acoustic based EPD system exists. A great deal of effort has been expended developing optical methods, and some success has been reported for STI structures. In this paper, we discuss many of the approaches that have been published. We categorize these approaches as being either global or local methods. We further categorize the methods as being either a direct or indirect assessment of events taking place at the surface of the wafer.