Nikon Corporation

Other

Shintaro Kawata

Mamoru Nakasuji

Teruaki Okino

Keitaro Hara

Kazuaki Suzuki

Kazuya Okamoto

Shinichi Takahashi

Noriyuki Hirayanagi

Shohei Suzuki

Koichi Kamijo

Apparatus and methods are disclosed pertaining to microlithography performed using a charged particle beam. In an exemplary apparatus, the projection-optical system includes a first projection lens situated downstream of a pattern-defining reticle and a second projection lens situated downstream of the first projection lens. Between the first and second projection lenses is a back focal plane of the first projection lens, at which focal plane a beam crossover is formed. The projection-optical system includes a cutoff-plate assembly, including at least one aperture-defining cutoff plate, located between the reticle and the back focal plane. The respective aperture in each cutoff plate is wider than an aperture in a scattering aperture conventionally located at the back focal plane. If the cutoff-plate assembly includes multiple cutoff plates, the aperture defined in the cutoff plate closer to the reticle is wider than the aperture defined in the more downstream cutoff plate. At least one of the cutoff plates defines an aperture that is laterally extended in a beam-deflection direction in the projection-optical system.

Apparatus and methods for blocking highly scattered charged particles in a patterned beam in a charged-particle-beam microlithography system

Methods are provided for complementarily dividing, on a divided stencil reticle as used in charged-particle-beam (CPB) microlithography, certain pattern elements into complementary pattern-element portions, and for exposing the pattern-element portions without significantly reducing throughput. For example, a large-area pattern element, having length and width equal to or greater than a division criterion L, is complementarily divided into linear pattern-element portions each having a width<L, and length&gE;L. Each pattern-element portion can have respective overlap regions along edges at which the portions as projected are conjoined on a lithographic substrate. The pattern-element portions are defined on at most two complementary reticles (or reticle portions) thereby imposing less adverse effect on throughput than conventionally. In other embodiments, pattern elements are divided into complementary pattern-element portions based on profile and shape of certain blocking regions versus non-blocking regions of the pattern element. The pattern elements are divided so as to reduce size errors that otherwise would be excessive at corners of the pattern elements when projected onto a substrate. I.e., whenever the size error exceeds a predetermined tolerance, then the pattern element is complementarily divided.

Stencil reticles for use in charged-particle-beam microlithography, and pattern-determination methods for such reticles

Disclosed are reticle assemblies for use in electron-beam microlithography. An exemplary reticle assembly includes a scattering-stencil reticle portion and a scattering-membrane reticle portion that define respective portions of the overall pattern defined by the reticle assembly. The reticle portions desirably are mounted to a reticle frame to provide strength and rigidity to the assembly. By combining both types of reticles in a single reticle assembly, the shortcomings of each are minimized compared to a single reticle type by which the entire pattern is defined. Because fabrication processes for the two reticle types are different, the reticle types can be fabricated separately and then bonded to the reticle frame to form the reticle assembly. Also disclosed are electron-beam microlithography apparatus and methods that include use of such reticle assemblies. Compared to conventional reticle assemblies as well as conventional apparatus and methods using them, reticle assemblies as disclosed herein can reduce the need to stitch together complementary pattern portions and reduce chromatic aberrations.

Scattering-reticle assemblies for electron-beam microlithography including a scattering-stencil reticle portion and a scattering-membrane reticle portion

Charged-particle-beam (CPB) apparatus and methods are disclosed that achieve efficient correction of imaging conditions such as shape-astigmatic aberrations, etc., caused by differences in the distribution of pattern elements within respective subfields of the reticle. Indices based on the pattern-element distributions within subfields are stored, together with corresponding optical-correction data for the subfields. As the subfields are exposed, respective data are recalled and the exposure is performed with optical corrections made according to the data. The indices are determined beforehand from pattern data at time of reticle manufacture. The tabulated data are rewritable with changes in apparatus parameters such as beam-current density and beam-divergence angle. Intermediate data can be determined by interpolation of tabulated data.

Charged-particle-beam microlithography apparatus and methods including optical corrections made during subfield exposures

Methods are provided for performing axial alignment of the optical system in a charged-particle-beam (e.g., electron-beam) microlithographic exposure apparatus employing an illumination beam and a scattering-type reticle. The microlithographic exposure apparatus projects and forms an image of a patterned beam that has passed through a reticle onto a substrate (e.g., semiconductor wafer). The reticle can be a scattering-stencil mask in which feature-defining cutouts are formed in a membrane that transmits an illumination beam while scattering the beam. A contrast aperture is disposed at the beam-convergence plane of the projection lens, i.e., at the Fourier plane of the reticle surface. Axial alignment is performed using an adjustment reticle having a &ldquo;white subfield&rdquo; (in a scattering-stencil reticle, a cutout area covering the entire subfield) and a &ldquo;black subfield&rdquo; (in a scattering-stencil reticle, a subfield consisting entirely of a reticle membrane lacking any cutouts).

Beam-adjustment methods and apparatus for charged-particle-beam microlithography

Reticles are provided for use in charged-particle-beam (CPB) microlithography, especially electron-beam microlithography. The reticle is configured as a segmented reticle of which the overall reticle size is reduced without compromising projection or stitching accuracy. A representative reticle includes a membrane that defines a pattern to be projection-transferred to a sensitive substrate, and support. struts that divide the membrane into multiple rectangular regions. Each rectangular region includes multiple subfields arranged longitudinally with intervening non-patterned regions. The width of the non-patterned regions is within the range of 1 &mgr;m to 50 &mgr;m.

Reticles for charged-particle beam microlithography

Methods are disclosed for reducing distortions, differences in focal point-positions, and astigmatic blurring of a pattern defined on a reticle and projected onto a sensitive substrate using a charged particle beam. The methods reduce variations in the distribution of beam current as projected onto the substrate. To such end, a charged particle beam passing through pattern features as defined on the reticle is projected onto a region on the substrate. The reticle is provided with multiple &ldquo;micro features&rdquo; each having a size less than the resolution limit of the projection-optical system. The micro features can be provided on a portion of the reticle having a low feature density.

Charged-particle-beam projection-exposure methods exhibiting more uniform beam-current density

This invention provides the charged particle beam transfer method, which can control adverse effect of distortion or blur that arises from the space charge effect due to the non-uniform pattern density to a minimum. A pattern formed on reticle is raster or step-and-repeat scanned with a charged particle beam and is illuminated in consecutive order, and a pattern image of a sub-field, which is illuminated, is to be formed on a certain position of a radiation sensitive substrate. On the radiation sensitive substrate whole pattern is projected through stitching the said pattern image. The pattern is to be divided into plural areas A and B which differ in pattern density one another, and the above-described scan boundary is made to coincide with the boundary of these plural areas.

Charged particle beam transfer method

Charged-particle-beam (CPB) projection-exposure apparatus are disclosed for inspecting a reticle and/or a substrate without having to remove the reticle and/or substrate from a vacuum chamber in which projection-exposure occurs. The CPB projection-exposure apparatus comprises a microscope for inspecting the reticle or substrate inside the vacuum chamber. For inspection, the reticle or mask is moved from a projection-exposure position to an inspection position within a field of view of the microscope without having to open the vacuum chamber.

Charged-particle-beam projection-exposure apparatus with integrated

Charged-particle-beam (CPB) lithography apparatus are disclosed that provide high accuracy in forming, by projection exposure using a charged particle beam, a pattern on a sensitive substrate at high throughput. The apparatus comprise a cathode having a work function of 2.65 eV or less within a space-charge limitation region. The temperature of the cathode is controlled within a range of 1,200 to 1,400.degree. C.

Charged-particle-beam (CPB) lithography apparatus, evaluation method,

Electron-beam projection-exposure apparatus are disclosed that allow a mask pattern to be transferred to a sensitized substrate without defects. An apparatus includes an electron-beam scanner, housed in a vacuum chamber, that scans an electron beam over the mask. As the mask is scanned, an emitted-electron detector senses electrons emitted from the mask at a point of contamination. The contamination is then removed from the mask by a mask-cleaning system, after which the mask is used for exposing a sensitized substrate. The scanner as well as the mask-cleaning system are housed in the same vacuum chamber where projection-exposure of the substrate are performed. Thus, the mask is not exposed to the external environment during inspection, cleaning, and projection-exposure, and inspection, cleaning and projection-exposure of the mask are performed more rapidly than conventionally. The mask-cleaning system, which can utilize a laser beam or a locally delivered reactive gas, cleans the mask at only the points of contamination, rather than the entire mask. Thus, cleaning time is shortened.

Electron-beam-projection-exposure apparatus with integrated mask

An electron-beam exposure system includes: (1) a stage for supporting a wafer, (2) a planar electron-beam source that emits multiple electron beamlets toward the stage, (3) an electric-field generator for forming an electric field to accelerate the electrons in the electron beamlets, (4) a magnetic-field generator for forming a magnetic flux in the space between the planar electron-beam source and the wafer stage. The magnetic filed generator is structured and arranged such that the magnetic flux formed thereby is (1) substantially evenly distributed within a plane perpendicular to the optical axis, and (2) of increasing flux density, ranging from a first density in the vicinity of the planar electron-beam source, to a second density (greater than the first density) in the vicinity of the wafer stage. The electrons in the electron beamlets follow the lines of magnetic flux such that the beamlet width is decreased at the stage compared to the beamlet width at the planar electron-beam source. The electron beamlets are preferably individually switchable, on and off, by word lines and bit lines on the planar electron-beam source. To form a desired pattern on a wafer surface, the stage is moved through a small area, while the electron beamlets are modulated as needed to write the desired pattern.

High-throughput direct-write electron-beam exposure system and method

Methods are disclosed for manufacturing masks for charged-particle-beam (CPB) or X-ray transfer. The masks have substantially no pattern defects. In a representative method for making stencil masks, the mask is defined using multiple subfields each having a respective pattern of voids. The subfields are separated from each other by boundary regions lacking any pattern features. The boundary regions include supports to provide the mask with physical and thermal stability. The supports are formed by an etching step in which relatively large amounts of substrate are removed. In the methods, the mask pattern is formed, inspected, and 'repaired' as required before performing the etching step that forms the supports. Thus, the forming, inspection, and repair steps can be performed before the mask is made too delicate.

Manufacturing method for mask for charged-particle-beam transfer or mask

Charged-particle beam masks are disclosed that comprise a plurality of mask subfields separated by a plurality of boundary regions. The subfields are formed in a scattering layer deposited on a membrane. The membrane is supported by a support structure provided in proximity to the boundary regions. In one embodiment, the support structure comprises a plurality of support beams, parallel to each other, and preferably formed by anisotropically etching a silicon wafer. A boron-doped layer of the silicon wafer forms the membrane.

Growing community of inventors

Moriya, Japan

Shintaro Kawata