Patent ID: 8461526
Filing Date: 2013-06-11
Classification: H01J

Abstract:
1. An electron beam column comprising: a first vacuum chamber having an opening which is positioned along an optical axis so as to pass a primary electron beam that travels down the column; an electron source positioned within the first vacuum chamber, the electron source including a cathode configured to emit electrons, and an anode configured to accelerate the emitted electrons through an opening of the anode; a beam-limiting aperture configured to pass a limited angular range of the emitted electrons; a magnetic immersion lens positioned outside of the first vacuum chamber which is configured to immerse the electron source in a magnetic field so as to focus the emitted electrons into the primary electron beam; a second vacuum chamber with an opening which is aligned with the opening in the first vacuum chamber so as to receive the primary electron beam from the electron gun; an o-ring around the opening in the second vacuum chamber; a movable bar comprising a thinner portion, a thicker portion, and selectable apertures in the thinner portion, wherein the movable bar is arranged such that the thicker portion contacts the o-ring when in a closed valve position; an objective lens configured to focus the primary electron beam onto a beam spot on a substrate surface so as to produce scattered electrons from the beam spot; and controllable deflectors configured to scan the beam spot over an area of the substrate surface.