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US 6,605,398 B2Granted
Methods and apparatus for controlling beam blur in charged-particle-beam microlithography
AssigneeNikon Corporation
InventorShohei Suzuki
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AssigneeNikon Corporation
InventorShohei Suzuki
Estimating the term…
Charged-particle-beam (CPB) microlithography methods and apparatus are disclosed with which large single-shot image-transfer regions (subfields) can be exposed using maximal beam current. Beam current is changed over a selected range to determine a suitable range of beam-spread angles that include the maximum permissible values for average blur, Δblur, and distortion. Assuming that that range of beam-spread half-angles is between α1 and α2, then the beam current for which α1=α2 is designated as a cutoff beam current. The beam-spread half-angle at that beam current is the optimal beam-spread half-angle. The ratio between the distribution half-angle and the cutoff half-angle is varied, and a determination is made of the distribution half-angle and cutoff half-angle that will accommodate the greatest beam current. Thus, a maximum beam current can be used while maintaining blur and distortion of the projected subfield image within specified values set for them.
In a method for forming a projected image of a pattern, defined by a reticle, on a sensitive substrate situated on a projected-image plane using a charged particle beam passing through a charged-particle-beam (CPB) optical system, a method for controlling blur of the projected image as formed by the charged particle beam on the substrate, the method comprising:
A charged-particle-beam (CPB) exposure apparatus, comprising:
In a method for forming a projected image of a pattern, defined by a reticle, on a sensitive substrate situated on a projected-image plane using a charged particle beam passing through a charged-particle-beam (CPB) optical system, a method for determining an optimum beam-cutoff half-angle of the charged particle beam, the method comprising:
A method for producing a microelectronic device, comprising transfer-exposing a pattern, defined by a reticle, onto a sensitive layer on a surface of a wafer using a charged particle beam passing through a charged-particle-beam (CPB) exposure apparatus, the CPB exposure apparatus comprising (i) a CPB-optical system including an illumination-optical system situated upstream of the reticle and (ii) a projection-optical system situated between the reticle and the wafer, the CPB-optical system being configured to control blur, of a projected image as formed by the charged particle beam on the wafer, by configuring the charged particle beam to have, at a projected-image plane, a distribution half-angle and a cutoff half-angle such that, at maximum lateral deflection of the beam within the projected subfield, total blur, Δblur, and distortion (all as caused by geometrical aberrations and by Coulomb Effects) within the projected subfield that are all no greater than respective threshold values.
Dependencies are inferred from the claim text.