Quality monitor and monitoring technique employing optically stimulated electron emmission

An apparatus for performing quality inspections on a test surface based on optically stimulated emission of electrons comprising:

• (a) a light source for producing and directing ultraviolet light onto the test surface;
• (b) means for detecting a current of photoelectrons emitted from the test surface and generating a signal indicative of the photoelectron current, said means for detecting including a collector for collecting the photoelectron current and means for positively biasing said collector with respect to the test surface, wherein the collector comprises a window transparent to the ultraviolet light directed by said light source, a metal layer coated on the window which is partially transparent to the ultraviolet light directed by said light source;
• and
• (c) means for indicating a condition of quality based on the generated signal indicative of photoelectron current.

A method of performing quality inspection on a test surface based on optically stimulated emission of electrons comprising the steps of:

• directing ultraviolet light on the test surface;
• positively biasing a collector with respect to the test surface to collect the photoelectrons emitted from the test surface, whereby a certain charge is removed from the test surface;
• measuring the current of photoelectrons emitted from the test surface;
• correlating the measured photoelectron current with a condition of quality;
• and
• negatively biasing the collector with respect to the test surface until an amount of charge equal to the certain amount of charge transferred during the measurement step is replaced to the test surface.

A method of performing quality inspection on an insulator test surface comprising the sequential steps of:

• bombarding the insulator test surface with ultraviolet radiation in the presence of an electric field to remove negative charges from the insulator test surface;
• exposing the insulator test surface to an ion field until the insulator test surface no longer exhibits a net charge status;
• directing ultraviolet light on the test surfaces;
• measuring a current of photoelectrons emitted from the test surface;
• and
• correlating the measured photoelectron current with a condition of quality.