Apparatus for inspection of semiconductor wafers and masks using a low energy electron microscope with two illuminating beams

An apparatus for imaging insulating or partially insulating substrates to find and characterize manufacturing defects, comprising:

• a) means for exposing said substrate to a first set of electrons traveling along a first path, said first set of electrons having an energy selected to maintain surface voltage present on said substrate at a predetermined level and causing a fourth set of electrons to leave said substrate;
• b) means for exposing said substrate to a second set of electrons traveling along a second path, said second set of electrons having an energy selected to cause a third set of electrons to leave said substrate;
• and
• c) means for detecting at least one of said third set or fourth set of electrons, thereby imaging a portion of said substrate,
• wherein the first and second paths have an end section which is common to both the paths such that the first and second sets of electrons both flood same said portion of said substrate.

An apparatus for imaging insulating a partially insulating substrates to find and characterize manufacturing defects a substrate, comprising:

• a) a first beam traveling along a first path and exposing substrate to a first set of electrons, said first set of electrons having an energy selected to maintain surface voltage present on said substrate at a predetermined level and to cause a fourth set of electrons to leave said substrate;
• b) a second beam traveling along a second path and exposing said substrate to a second set of electrons, said second set of electrons having an energy selected to cause a third set of electrons to leave said substrate;
• and
• d) a sensor detecting at least one of said third set or fourth set of electrons, thereby imaging a portion of said substrate,
• wherein the first and second paths have an end section which is common to both the paths such that the first and second sets of electrons both flood same said portion of said substrate.