SUMMARY

This thesis addresses the use of a vibrating Kelvin probe to monitor the potential on the front surface of a silicon wafer while shining visible light on the rear surface. A change in the front surface potential between an excited state, in which incident light was present, and an unexcited state, whereby no light was present, was found to be dependent on both the wavelength and intensity of the light. The voltage output of the Kelvin probe sensor can be attributed to physical mechanisms occurring inside the silicon wafer. Proof of this concept was achieved by monitoring the front surface potential of the wafer while light was pulsed on the rear surface. A vibrating Kelvin probe sensor equipped with a voltage feedback-biasing probe tip was used to monitor the potential difference between the probe tip and the silicon wafer. When the wafer was exposed to light, the output voltage decreased from an unexcited value to a saturated excited value. When the light was removed, the output voltage increased and returned to the unexcited value. Once this was observed, a number of experiments were performed in which the light’s wavelength and intensity were systematically increased. The repeatable outcomes of the experiments verified that the front surface potential of the silicon wafer was dependent on both the wavelength and intensity of the incident light. A predictive model was created to determine properties of the silicon wafer, given the geometry of the measuring system and the wavelength and intensity of the incident light. This system can be used to create a novel, non-vibrating Kelvin probe sensor. Without vibration, the method of signal generation is the changing surface potential of the silicon wafer due to pulsed incident light. The sensor is sensitive to any process that alters the work function of the surface of the silicon wafer, such as adsorption, surface defects, and stress.