OPTICAL ENDPOINT DETECTION SYSTEM FOR ROTATIONAL CHEMICAL MECHANICAL POLISHING

摘要

An apparatus is provided for use with a tool for polishing thin films on a semiconductor wafer surface that detects an endpoint of a polishing process. In one embodiment, the apparatus includes a polish pad having a through-hole, a light source, a fiber optic cable assembly, a light sensor, and a computer. The fiber optic cable propagates the light through the through-hole to illuminate the wafer surface during the polishing process. The light sensor receives reflected light from the surface through the fiber optic cable and generates data corresponding to the spectrum of the reflected light. The computer receives the reflected spectral data and generates an endpoint signal as a function of the reflected spectral data. The light source, fiber optic cable assembly and light sensor are disposed within a platen of a chemical mechanical polishing machine. The computer is located external to the platen. A wireless link is used to communicate the reflected spectral data to the computer. Alternatively, the light source and light sensor are disposed external to the platen and a rotary union is included to allow the fiber optic cable assembly to be used in a rotary chemical mechanical polishing machine. A through-cylinder is used to provide a protected passage through the platen for the fiber optic cable as the fiber optic cable extends into the through-hole in the polishing pad.