Abstract: Exposure methods are disclosed for use in charged-particle-beam microlithography and that yield decreased blur and variation in blur within individual exposure fields (subfields) of a pattern. Blur at a location on the optical axis increases monotonically with increased shift in the focal point of a subfield image on the substrate. In contrast, blur at a subfield edge exhibits comparatively little change over a limited range in focal-point shift, and exhibits sharply increased change as the shift in focal point exceeds a threshold. Variation in blur within individual subfields decreases monotonically with increased shift in the focal point. Consequently, by changing the focal point during exposure, within a range in which maximum blur within the subfield is within an acceptable range, ?blur is decreased more than conventionally, thereby increasing the uniformity of blur within the projected subfield.

Abstract: Charged-particle-beam (CPB) optical systems (especially projection-lens systems for use in CPB microlithography apparatus) are disclosed that exhibit excellent control of geometric aberration and the Coulomb effect while exhibiting low combined aberration and blur. As the column length of the projection-lens system is increased, geometric aberration is reduced but the Coulomb effect increases, which degrades overall optical characteristics. Conversely, as the column length is decreased, the Coulomb effect is reduced but geometric aberration increases, which degrades overall optical characteristics. Hence, the projection-lens system, exhibiting a magnification of 1/M and having a column length (distance in mm between reticle and wafer) of 250×M0.63±10% (wherein 0<M; e.g., 0<M<4 or 4<M) exhibits blur and geometric distortion of about 70 nm or less and about 4 nm or less, respectively.

Abstract: Magnetic lenses and coils for magnetic lenses, charged-particle-beam (CPB) optical systems and pattern-transfer apparatus comprising such magnetic lenses, and manufacturing methods for such lenses, systems, and apparatus are disclosed. In the coils for magnetic lenses, the number of coil turns per unit length is adjusted so that the axial magnetic field at the ends of the coils more closely approximates an ideal magnetic field. In another example, a coil for a magnetic lens comprises two or more subcoils. The currents in the subcoils or the products of current and coil turns for respective subcoils are adjusted to approximate a selected magnetic field, such as to correct or at least reduce magnetic field “droop” at the ends of the coil. Magnetic lenses including such coils and a yoke are provided as well as CPB pattern-transfer apparatus using these magnetic lenses.

Abstract: Electron-beam sources are disclosed that exhibit substantially reduced spherical aberration compared to conventional sources. In a beam produced by the cathode of such a source, axially propagating electrons are subjected to a lens action by voltage applied to a Wehnelt electrode and an extraction electrode. The cathode includes a peripheral portion that is “drawn back” (displaced along the axis of the source away from the beam-propagation direction) relative to a center portion of the cathode. With such a cathode, the percentage of dimensions of the crossover involved in spherical aberration of the crossover is reduced. This improves the uniformity of beam current at a lithographic substrate and minimizes location-dependency of the aperture angle. Since the Wehnelt voltage can be reduced, positional changes in the electrical field at the cathode surface are reduced, and the distribution of electrons in the beam propagating from the cathode surface is made more uniform than conventionally.

Abstract: Methods and devices are disclosed for aligning a beam-propagation axis with the center of an aperture, especially an aperture configured to limit the aperture angle of the charged particle beam. In an exemplary method, an alignment-measurement aperture is provided at an imaging plane of a charged-particle-beam (CPB) optical system, and a beam detector is downstream of the alignment-measurement aperture. A scanning deflector is energized to cause the beam to be scanned in two dimensions, transverse to an optical axis, over the aperture. Meanwhile, the beam detector obtains an image of beam intensity in the two dimensions. In the image a maximum-intensity point is identified, corresponding to the propagation axis. Based on the two-dimensional image, the beam is deflected as required to align the propagation axis with the aperture center.

Abstract: Charged-particle-beam (CPB) microlithography apparatus and methods are disclosed that produce reduced blur resulting from the Coulomb effect, without having to reduce exposure current, exposure accuracy, or throughput. An exemplary apparatus is configured to expose regions (“exposure units” or “subfields”) each having a maximal lateral dimension of at least 1 mm. The beam half-angle (half width at half maximum of the distribution of beam intensity) is 1 mrad or less.

Abstract: Exposure methods are disclosed for use in charged-particle-beam microlithography and that yield decreased blur and variation in blur within individual exposure fields (subfields) of a pattern. Blur at a location on the optical axis increases monotonically with increased shift in the focal point of a subfield image on the substrate. In contrast, blur at a subfield edge exhibits comparatively little change over a limited range in focal-point shift, and exhibits sharply increased change as the shift in focal point exceeds a threshold. Variation in blur within individual subfields decreases monotonically with increased shift in the focal point. Consequently, by changing the focal point during exposure, within a range in which maximum blur within the subfield is within an acceptable range, &Dgr;blur is decreased more than conventionally, thereby increasing the uniformity of blur within the projected subfield.

Abstract: Charged-particle-beam (CPB) microlithography apparatus and methods are disclosed that produce reduced blur resulting from the Coulomb effect, without having to reduce exposure current, exposure accuracy, or throughput. An exemplary apparatus is configured to expose regions (“exposure units” or “subfields”) each having a maximal lateral dimension of at least 1 mm. The beam half-angle (half width at half maximum of the distribution of beam intensity) is 1 mrad or less.

Abstract: Magnetic lenses and coils for magnetic lenses, charged-particle-beam (CPB) optical systems and pattern-transfer apparatus comprising such magnetic lenses, and manufacturing methods for such lenses, systems, and apparatus are disclosed. In the coils for magnetic lenses, the number of coil turns per unit length is adjusted so that the axial magnetic field at the ends of the coils more closely approximates an ideal magnetic field. In another example, a coil for a magnetic lens comprises two or more subcoils. The currents in the subcoils or the products of current and coil turns for respective subcoils are adjusted to approximate a selected magnetic field, such as to correct or at least reduce magnetic field “droop” at the ends of the coil. Magnetic lenses including such coils and a yoke are provided as well as CPB pattern-transfer apparatus using these magnetic lenses.

Abstract: Electron-beam sources are disclosed that exhibit substantially reduced spherical aberration compared to conventional sources. In a beam produced by the cathode of such a source, axially propagating electrons are subjected to a lens action by voltage applied to a Wehnelt electrode and an extraction electrode. The cathode includes a peripheral portion that is “drawn back” (displaced along the axis of the source away from the beam-propagation direction) relative to a center portion of the cathode. With such a cathode, the percentage of dimensions of the crossover involved in spherical aberration of the crossover is reduced. This improves the uniformity of beam current at a lithographic substrate and minimizes location-dependency of the aperture angle. Since the Wehnelt voltage can be reduced, positional changes in the electrical field at the cathode surface are reduced, and the distribution of electrons in the beam propagating from the cathode surface is made more uniform than conventionally.

Abstract: Charged-particle-beam (CPB) optical systems (especially projection-lens systems for use in CPB microlithography apparatus) are disclosed that exhibit excellent control of geometric aberration and the Coulomb effect while exhibiting low combined aberration and blur. As the column length of the projection-lens system is increased, geometric aberration is reduced but the Coulomb effect increases, which degrades overall optical characteristics. Conversely, as the column length is decreased, the Coulomb effect is reduced but geometric aberration increases, which degrades overall optical characteristics. Hence, the projection-lens system, exhibiting a magnification of 1/M and having a column length (distance in mm between reticle and wafer) of 250×M0.63±110% (wherein 0<M; e.g., 0<M<4 or 4<M) exhibits blur and geometric distortion of about 70 nm or less and about 4 nm or less, respectively.

Abstract: Methods and devices are disclosed for aligning a beam-propagation axis with the center of an aperture, especially an aperture configured to limit the aperture angle of the charged particle beam. In an exemplary method, an alignment-measurement aperture is provided at an imaging plane of a charged-particle-beam (CPB) optical system, and a beam detector is downstream of the alignment-measurement aperture. A scanning deflector is energized to cause the beam to be scanned in two dimensions, transverse to an optical axis, over the aperture. Meanwhile, the beam detector obtains an image of beam intensity in the two dimensions. In the image a maximum-intensity point is identified, corresponding to the propagation axis. Based on the two-dimensional image, the beam is deflected as required to align the propagation axis with the aperture center.

Abstract: Apparatus and methods are disclosed for projecting a mask pattern, divided into multiple mask subfields, onto a substrate at high resolution using a charged-particle beam (CPB). At least some of the mask subfields comprise "minimum-linewidth regions". To expose each mask subfield, a CPB (e.g., electron beam) is directed onto the mask subfield. The image of the mask subfield is projected by lens systems onto a respective transfer subfield on the substrate. Deflectors deflect the CPB to the selected mask subfield and to the corresponding transfer subfield on the substrate. A memory stores data concerning the locations of minimum-linewidth regions in the selected mask subfields and the corresponding amount of deflection of the beam for each corresponding mask subfield.

Abstract: Charged-particle-beam optical systems are disclosed that are usable in projection-exposure apparatus employing a charged particle beam for projecting an image of an object (e.g., region of a lithographic mask) onto a sample (e.g., semiconductor wafer). Such an optical system comprises a deflection system for deflecting a trajectory of the charged particle beam such that a second-order derivative of the deflected trajectory is substantially constant in an object-side region extending from an object point to a crossover image point, and substantially constant in an image-side region extending from the crossover image point to an image point.

Abstract: Charged-particle-beam optical systems are disclosed exhibiting reduced aberrations. Such a system comprises a symmetric magnetic doublet type projection lens system and deflectors. An imaginary Z-axis is superimposed on the optical axis with an origin at an image-crossover point. Excitation of the deflectors and lenses is controlled by a controller so that the ratio of G.sub.1 (Z) to G.sub.2 (-M.multidot.Z) is substantially equal to the ratio of (-M) to 1 (i.e., G.sub.1 (Z):G.sub.2 (-M.multidot.Z)=(-M):1), and the deflection trajectory of the charged-particle beam intersects with the optical axis at a crossover Z.sub.c, where M is the magnification of the lens system, G.sub.1 (Z) is the distribution of the deflective magnetic field formed on the object side of the crossover, and G.sub.2 (Z) is the distribution of the deflective magnetic field formed on the image side of the crossover.

Abstract: The imaging characteristics of focal-point position, image rotation, and magnification of a projection system of a charged-particle-beam image-transfer apparatus are corrected by correction lenses positioned between a first projection lens and a second projection lens. The driving currents of the correction lenses are determined by solving a system of three linear equations with three unknowns, whose coefficients are the correction amounts for the three imaging characteristics of the projection system produced by the three correction lenses when they are driven by the unit Ampere-turn, and the target correction amounts for the three imaging characteristics. More correction lenses can be employed than imaging characteristics to be corrected, with Ampere-turn values selected from among those that satisfy the corresponding equations. Also, the driving currents of one or more projection lenses can be varied to allow the projection lenses to operate as correction lenses.

Abstract: A thin slab that is free of internal cracks is formed by reducing a continuously cast strand having a liquid core. The placement of the reduction rolls is controlled to effect a suitable amount of reduction. The methods effectively reduce bulging strain, as well as strain associated with reduction of the strand. As a result, total accumulated strain is reduced and a thin slab free of internal cracks can be manufactured at high speeds. The apparatus includes reduction blocks which are capable of shifting the rotation angle of an upper roller segment frame. Misalignment strain is reduced and the thickness of the strand can be changed without stopping the manufacturing operation.

Abstract: A charged particle beam transfer device exhibiting a low level of aberration is disclosed. The device comprises a first deflector for deflecting a charged particle beam, that has passed through a subfield on a reticle, such that the beam passes through the optical axis, or at least the center, of a projection lens. To such end, the first deflector deflects the beam a first angle of deflection relative to an optical axis of the device. The device also comprises a second deflector to deflect the beam, after having passed through the projection lens, at a second angle of deflection that is opposite the first angle of deflection. Thus, the beam is guided to a region on a substrate surface corresponding to the particular subfield on the reticle.