US 6,441,384 B1 · Charged particle beam exposure device exhibiting reduced image blur

Abstract

Charged-particle-beam microlithography apparatus and methods are disclosed that reduce spherical aberrations and other aberrations of the beam without increasing blurring from Coulomb effects or space-charge effects. The beam semi-angle of the beam as incident on the reticle and/or substrate is limited to a range greater than zero but less than an upper limit, so as to remove paraxial portions of the beam. Also, the substrate can be moved as required along the optical axis to place the substrate at the optimal image plane where beam spreading from spherical aberration is minimal. The beam semi-angle is preferably limited by passage of the beam through an annular aperture placed axially upstream of the substrate. A preferred range for beam semi-angle at the reticle is 1.5 to 3 mrad. Alternatively, at least six deflectors are disposed on the reticle side of a scattering aperture located in the projection-optical system, and at least three deflectors are disposed on the substrate side of the scattering aperture to simultaneously correct, respectively, deflection-induced image-plane inclination, deflection coma, deflection astigmatism, deflection chromatic aberration, deflection-induced secondary distortion (x and y directions), axial propagation of the beam through the scattering aperture, incidence of the beam at a target position on the substrate, and zero angle of incidence of the beam on the substrate.

Claims21

Dependent claims

A charged-particle-beam microlithography apparatus, comprising on an optical axis:

(a) an illumination-optical system configured and situated so as to direct a charged particle beam from a source to a reticle and illuminate a region of the reticle with the charged particle beam;
(b) a projection-optical system configured and situated relative to the reticle so as to direct the charged particle beam, passing through the illuminated region of the reticle, to a substrate so as to form an image of the illuminated region on a corresponding exposure region on the substrate, the image having an optimal image plane;
(c) a beam-semi-angle-limiting device situated upstream of the substrate, the beam-semi-angle-limiting device being configured to configure the charged particle beam such that, as the beam is incident on the substrate, the beam has a beam semi-angle that is greater than a lower limit but not zero, and less than an upper limit greater than the lower limit, the beam-semi-angle-limiting device comprising an aperture plate that defines an annular aperture, the aperture plate being situated within a region in which the charged particle beam is collimated;
and
(d) a mechanism for imparting a displacement of the optimal image plane and the substrate relative to each other along the optical axis as required to achieve a reduction of blurring of the charged particle beam incident on the substrate.

2 more elements

In a method for performing microlithographic projection-transfer of a pattern, defined by a reticle, onto a sensitive surface of a substrate by directing a charged particle beam along an optical axis from a source to a reticle to illuminate a region of the reticle with the charged particle beam, and directing the charged particle beam that passes through the illuminated region of the reticle to the sensitive surface of the substrate so as to imprint an image of the illuminated region on a corresponding exposure region on the sensitive surface, an improvement for reducing beam blurring at the sensitive surface caused by any one or more of spherical aberrations, Coulomb effects, and space-charge effects, the improvement comprising:

(a) at a location at which the charged particle beam is collimated, blocking paraxial portions of the beam smaller than a first diameter;
(b) at the location, blocking off-axis portions of the beam greater than a second diameter that is larger than the first diameter, so as to allow passage to the sensitive surface of portions of the charged particle beam having a beam semi-angle that is greater than a lower limit greater than zero, and less than an upper limit greater than the lower limit;
and
(c) displacing the substrate and an optimal image plane relative to each other along the optical axis as required to reduce blur of the charged particle beam as incident on the substrate.

1 more element

Dependencies are inferred from the claim text.

Charged particle beam exposure device exhibiting reduced image blur

Life of this patent

Charged particle beam exposure device exhibiting reduced image blur

Life of this patent

Abstract

Claims21