Variable curvilinear axis deflection means for particle optical lenses
AssigneeInternational Business Machines Corporation
InventorPaul F. Petric
Life of this patent
Estimating the term…
Abstract
An improved particle lens has an axis which is shifted to follow the central ray as it is deflected through the lens creating, in effect, a variable curvilinear optical axis for the lens. The variable curvilinear optical axis is created for the lens so that the axis varies proportionally to the magnitude of the beam deflection. The optical axis of the lens is shifted by applying a uniform field to the lens to cancel the first term of the radial field with a function that is dependent on the position along the z-axis. This function is the trajectory of the central ray of the electron beam.
Claims16
A curvilinear axis correction system for particle optical lenses comprising:
- a lens having field generating means disposed about a system axis and extending a lens length along said system axis for producing a focussing field to focus a particle beam;
- and
- axis-shifting means for producing a set of compensation fields within said lens, each of said set of compensation fields being substantially uniform in a plane perpendicular to said system axis and which set of compensation fields varies in magnitude as a function of position along said system axis, said function of position being dependent on a trajectory of a central ray of said particle beam and each of said set of compensation fields having a magnitude sufficient to cancel a radial component of said focussing field, whereby a variable axis of said focussing field is substantially coincident with said trajectory of a central ray of said particle beam.
A particle beam system having a system axis and comprising:
- beam generating means for generating a beam of particles and directing said beam along said system axis;
- deflection means disposed about said system axis for deflecting said beam in a plane containing said system axis;
- a set of lenses for generating a magnetic field to focus said beam on a target, said lenses having field generating means disposed about said system axis and extending a lens length along said system axis for producing a focussing field to focus said beam;
- a set of axis-shifting means, disposed within at least one of said set of lenses, for shifting a variable axis of said lens by generating a set of compensation fields within said lens, each of said set of compensation fields being substantially uniform in a plane perpendicular to said system axis and which set of compensation fields varies in magnitude as a function of position along said system axis, said function of position being dependent on a trajectory of a central ray of said beam and each of said set of compensation fields having a magnitude sufficient to cancel a radial component of said focussing field, whereby a field axis of said focussing field is substantially coincident with said trajectory of a central ray of said beam;
- and
- control means for applying electrical signals to said deflection means, said compensation means and to said at least one lens.
Dependencies are inferred from the claim text.