APPLICATION OF LASER-INDUCED PHOTOCHARGE VOLTAGE SPECTROSCOPY IN SEMICONDUCTOR TESTING

A system for evaluating the surface electrical properties of semicondu ctor wafers and devices using Laser-induced Photocharge Voltage (PV) m easurements is proposed. The optically induced electric charge is meas ured capacitively, thus PV measurements do not require the fabrication of metal contacts. The Photocharge voltage is a function of the elect rical properties of the surface of the semiconductor sample, hence die spatial variation of PV can be utilized to evaluate the surface condi tions of the sample. Similar to many optical characterization methods, the proposed technique is completely contactless and it can be used a s an in-line nondestructive characterization of semiconductor wafers d uring the various stages of integrated circuits fabrication. Experimen tal results and a qualitative explanation of the Photocharge effect ar e presented. The design of an automatic testing probe to be used for s emiconductor wafer characterization in a computer-feedback system for a integrated circuit (IC) processing is also presented. The high spati al resolution of the laser beam coupled with the development of a capa citive testing probe using fiber optics will yield a high spatial reso lution of approximately 10 nm, which is well beyond any resolution cur rently obtainable by any electrical testing procedure in the IC manufa cturing environment.