Adjustment of particle beam landing angle
AssigneeInternational Business Machines Corporation
InventorsMaris A. Sturans, Rodney A. Kendall
Life of this patent
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Abstract
The invention relates to a method and apparatus for measuring The landing angle of a particle beam is adjusted by scanning the beam over two cylindrical beam target surfaces that are positioned close to the system axis. The output of a beam detector is differentiated and displayed on an oscilloscope. The relevant lens current is adjusted until one side of the scan indicates that the focal plane of the beam is at the center of the beam target. The angle of the beam is then adjusted with the relevant deflector until both sides of the scan are the same, indicating that the beam is accurately vertical.
Claims10
An apparatus for adjusting landing angle on a workpiece of a particle beam travelling along a beam direction substantially parallel to a system axis and substantially perpendicular to said workpiece, comprising:
- a detector disposed to intercept said beam;
- electronic means for processing beam current intercepted by said detector;
- and
- at least one pair of first and second beam target members disposed on a top surface of at least one support plate on opposite sides of said system axis, each of said beam target members having a flat support surface abutting said top surface, a cylindrical surface convex toward said system axis having a target length of said cylindrical surface, and having a radius of curvature lying in a radial plane extending along said target length and being substantially perpendicular to said system axis.
A method for adjusting a landing angle on a workpiece of a particle beam travelling along a beam direction substantially parallel to a system axis and substantially perpendicular to said workpiece, comprising:
- a) sweeping said beam in a first adjustment plane across first and second beam target members disposed on a top surface of at least one support plate on opposite sides of said system axis, each of said beam target members having a flat support surface abutting said top surface, a cylindrical surface convex toward said system axis having a target length of said cylindrical surface, and having a radius of curvature lying in a radial plane extending along said target length and being substantially perpendicular to said system axis;
- b) detecting said beam in a detector disposed to intercept said beam;
- c) processing a signal from said detector in electronic means for processing beam current intercepted by said detector to generate first and second differentiated beam signals;
- and
- d) adjusting a focal plane of said beam until it intercepts one of said first and second beam target members, whereby a corresponding differentiated beam signal from said detector adopts a characteristic shape;
- and
- e) adjusting said beam direction until both said first and second differentiated beam signals adopt said characteristic shape.
Dependencies are inferred from the claim text.