Abstract

An in-situ thickness monitoring/endpoint detection method and apparatus for chemical-mechanical polishing (CMP) of a dielectric layer on a top surface of a semiconductor wafer is disclosed. The apparatus comprises center and guard electrodes and associated electronic circuitry, including a high frequency, low voltage signal generating means, for converting a current which is inversely proportional to the dielectric layer thickness into a corresponding analog voltage. A position detection device triggers an analog-to-digital converter to convert the analog voltage into a digital signal while the wafer is located within a detection region as the wafer is being polished. A control means gathers the digital signals corresponding to the thickness data for processing and CMP device control.