END-POINT DETECTION FOR CMP

In spite of dramatic advances in oxide chemical mechanical polishing ( CMP) process performance in recent years, there has been relatively li ttle published data on semiconductor production line worthy endpoint d etection (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 m onitoring. However, these methods have so far not been proven to be 10 0% reliable. Semiconductor manufacturers have been searching for a via ble method of either monitoring the dielectric removal rate or the pla narization of the surface during the polish process, and for improved metal endpoint detection systems. Acoustic 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, a nd some success has been reported for STI structures. In this paper, w e discuss many of the approaches that have been published. We categori ze these approaches as being either global or local methods. We furthe r categorize the methods as being either a director indirect assessmen t of events taking place at the surface of the wafer.