Patent ID: 7193222

Claim:
A secondary electron detector, especially in a scanning electron microscope, comprising: a detector chamber adapted to be coupled with a vacuum pump to produce a vacuum inside the detector chamber, the detector chamber comprising an interior and a plurality of walls separating the interior from a surrounding environment; at least one source of bias voltage; and a sensor located in said detector chamber and having an active surface, wherein one of said walls of said detector chamber is near to the active surface of the sensor and is closed by an electrically conductive grid, said electrically conductive grid including a plurality of orifices having a high resistance to a transmission of gas and a low resistance to a transmission of electrons, said electrically conductive grid connected with the at least one source of bias voltage, said orifices defining electron microlenses inside and in front of said orifices, said electron microlenses being created by an electrical field protruding through said orifices, said electrical field originating from a conductive coating inside of the detector chamber, and the conductive coating adapted to be connected to a voltage source.