Monitoring of electric potential of semiconductor wafer

Abstract

AbstractThe International Technology Roadmap for Semiconductors (ITRS) forecasts increasing number of issues with electrostatic discharge (ESD) related phenomena and the need for improved wafer electrostatic charge control in semiconductor wafer processing. This means that wafer metrology should encompass charge measurements as a routine operation. The ability to make wafer potential measurements in‐line, either before and after the wafer processing can help with detection and prevention of the ESD events and with minimizing wafer charging issues during loading/unloading operations. One of the instruments utilized in such measurements is an electrostatic voltmeter (ESVM). In this paper the authors would like to introduce and discuss novel designs of the ESVMs. A new, non‐contacting probe allows for the measurement of surface voltages with DC stability and millivolt sensitivity. Another design features a specially designed probe that permits contact with the wafer surface without transfer of the electric charge to/from the surface under test. Results of performance evaluation along with feasibility studies of the sensors are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)