Patent ID: 8957390
Filing Date: 2015-02-17
Classification: H01J

Abstract:
1. A gun arrangement configured for generating a primary electron beam for a wafer imaging system, comprising: a controller configured for switching between normal operation and cleaning operation; a field emitter having an emitter tip adapted for providing electrons and emitting an electron beam along an optical axis, wherein the field emitter is selected from the group consisting of: a cold field emitter and a thermally assisted cold field emitter, and wherein the emitter is electrically connected to the controller; and an extractor electrode adapted for extracting the electron beam from the emitter tip electrode; a suppressor electrode arranged, with respect to the optical axis, radially outside the emitter, wherein at least one of the suppressor electrode and the extractor electrode is electrically connected to the controller such that the suppressor electrode is at a first potential relative to the extractor electrode during normal operation and at a second, negative potential relative to the extractor electrode during cleaning operation; and at least one auxiliary emitter electrode arranged, with respect to the optical axis, radially outside the suppressor electrode, and provided as a thermal electron emitter for thermally emitting electrons towards the optical axis.