Nikon Corporation

Teruaki Okino

Mamoru Nakasuji

Noriyuki Hirayanagi

Shintaro Kawata

Kazuaki Suzuki

Tomoharu Fujiwara

Shinichi Kojima

Kazuya Okamoto

Shohei Suzuki

Koichi Kamijo

Kenji Morita

Reticles and apparatus for performing charged-particle-beam microlithography, and associated methods, are disclosed, in which the pattern to be transferred to a sensitive substrate is divided according to any of various schemes serving to improve throughput and pattern-transfer accuracy. The methods and apparatus are especially useful whenever a divided stencil reticle is used that includes complementary pattern portions.

Divided reticles for charged-particle-beam microlithography apparatus, and methods for using same

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 disclosed for correcting proximity effects as affected by varying magnitudes of beam blur occurring at different respective locations in an image of a reticle subfield as projected onto the sensitive surface of a substrate. Local resizings of pattern-element profiles as defined on the reticle are made taking into consideration not only proximity effects arising from Coulomb interactions but also different magnitudes of beam blur occurring at different respective locations in a projected subfield. Beam blur is imparted by the projection-optical system and is a function of the magnitude of beam deflection, the location of pattern element(s) within the area of the exposed subfield, and the exposure-energy profile on the surface of the substrate being exposed. A resist-development energy threshold is established such that the edges of pattern elements as transferred to the wafer in response to the exposure-energy profile will be at their desired locations according to design specifications. The corresponding elements as defined on the reticle are adjusted accordingly so that their linewidths as projected will be within design specifications.

Charged-particle-beam microlithography apparatus and methods including proximity-effect correction

Methods and apparatus are disclosed for performing charged-particle-beam (CPB) microlithography, in which methods and apparatus certain position-measurement marks are detected by appropriate deflections of a charged particle beam. The deflections are performed using a primary deflector and a mark-scanning deflector. For example, the beam is deflected by the primary deflector to illuminate a position-measurement mark on the reticle and a corresponding position-measurement mark on the substrate. The position-measurement mark on the substrate is scanned by minute deflections of the beam as performed by the mark-scanning deflector. Meanwhile, charged particles backscattered from the position-measurement mark on the substrate (as the mark is being scanned) are captured and detected by a detector. The marks are detected at timing moments during normal operation of the primary deflector. Thus, during detection of the marks, the resulting positional determinations are less affected by extraneous variables such as changes in temperature and/or hysteresis of the primary deflector.

Mark-detection methods and charged-particle-beam microlithography methods and apparatus comprising same

In the context of charged-particle-beam (CPB) microlithography methods and systems, methods are disclosed for detecting the incidence orthogonality of a patterned beam on the lithographic substrate. In an embodiment, the position of reticle-fiducial-mark images, as formed on the substrate stage at a position Z are detected at two lateral positions of a corresponding reticle fiducial mark. A distance L between the images is determined. Then, the substrate stage is moved to a position Z at which the position of reticle-fiducial-mark images are detected at two lateral positions of the corresponding reticle fiducial mark. A distance L between the images is determined. The incidence-orthogonality error &Dgr;&thgr; is calculated by substitution into &Dgr;&thgr;&equals;(L &minus;L )/2&Dgr;H. The projection-optical system of the CPB microlithography apparatus is adjusted so that &Dgr;&thgr;&equals;0.

Methods for detecting incidence orthogonality of a patterned beam in charged-particle-beam (CPB) microlithography, and CPB microlithography systems that perform same

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 and apparatus are provided for performing charged-particle-beam microlithography at improved accuracy. A pattern is formed on a substrate (wafer) by repeated shot exposure of respective areas on a wafer substrate mounted on a wafer stage. Exposure of the wafer is made while the wafer stage is undergoing continuous motion and the charged particle beam making the exposure is being deflected continuously. As the magnitude of the beam deflection changes according to the motion of the stage, correction data for deflecting the beam are updated appropriately so as to correct deflection aberrations continuously.

Methods for charged-particle-beam microlithography including correction of deflection aberrations, and device-manufacturing methods comprising same

Methods are disclosed for reducing effects of thermal expansion of a sensitive substrate arising during microlithographic exposure of the substrate using a charged particle beam. Thermal expansion ordinarily causes lateral shift of exposure position of dies (chips) on the substrate which tends to reduce the positional accuracy with which images of the dies are formed on the substrate. Generally, regions of the substrate where entire dies are formed are exposed first, followed by regions (especially peripheral regions) exposed with only portions of dies. In addition, the substrate can be mounted on a wafer chuck configured to circulate a heat-transfer gas in contact with the substrate to remove heat from the substrate. In addition, the wafer chuck can be maintained at a constant temperature by circulating a liquid coolant through a conduit in the body of the wafer chuck.

Charged-particle-beam microlithography methods including chip-exposure sequences for reducing thermally induced lateral shift of exposure position on the substrate

Charged-particle-beam microlithography apparatus and methods are disclosed that achieve correction of positioning errors of one or both the reticle stage and wafer stage using a deflector. The deflector is situated in one or both lenses of the projection-optical system of the apparatus. The deflector preferably is electrostatic for rapid responsiveness, and desirably is configured also to correct distortions corresponding to the positioning errors.

Charged-particle-beam microlithography apparatus and methods including correction of stage-positioning errors using a deflector

Methods and apparatus are disclosed for reducing thermal deformation of &ldquo;upstream&rdquo; marks (as used for alignment and/or calibration) situated on a reticle or on a reticle plane (e.g., on the reticle stage), thereby facilitating more accurate transfer of the reticle pattern to a sensitized substrate (e.g., semiconductor wafer) using a charged particle beam (e.g., electron beam). The charged particle beam illuminates an upstream mark situated on the reticle or on a reticle plane and projects an image of the illuminated upstream mark onto a corresponding &ldquo;downstream&rdquo; mark situated on a substrate plane. A shield is situated upstream of the upstream mark and serves to block downstream passage of the charged particle beam except to illuminate the upstream mark or a portion of the upstream mark. The upstream mark can be situated on the reticle or on a mark member situated in the reticle plane.

Charged-particle-beam microlithography methods exhibiting reduced thermal deformation of mark-defining member

Charged-particle-beam pattern-transfer methods and apparatus are disclosed. Circuit patterns on a mask are divided into a plurality of fields, each field including respective connection ends. Fields that are to be adjacent as transferred to a substrate include a common portion of the circuit pattern in their respective connection ends. The common portions are projected onto the substrate to substantially overlap. The connection ends are illuminated by an image of a shaping aperture image that is illuminated with a charged-particle beam. The shaping-aperture image can be scanned across the fields so that wafer areas corresponding to the connection ends are exposed during exposure of the connecting adjacent fields and so that the dose received by the wafer is substantially uniform. The shaping-aperture image can be vibrated in a direction perpendicular to a scanning direction to illuminate connection ends. The vibration provides uniform dose on the wafer in areas corresponding to the connection ends. With such methods, circuit patterns are connected, even if the patterns from the fields are slightly offset.

Pattern-transfer method and apparatus

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

An exposure method using a charged particle beam is used to improve the accuracy of stitching the patterns according to the divided pattern transfer. The exposure method according to the present invention comprises dividing the pattern into a plurality of subfields arranged in stripes; forming the subfields (,L) and (,R) laid around the boundary in the adjacent stripes (,L) and (,R), exposing the subfields (,L) and (,R) by half the exposure time amount, and overlapping the images of the patterns of the subfields (,L) and (,R) at substantially the same position on the wafer.

Charged particle beam exposure method utilizing partial exposure stitch area

Charged-particle-beam microlithography apparatus and methods exhibiting reduced thermal deformation of mark-defining member

Methods are disclosed for transferring a pattern from a mask to a sensitive substrate. The mask is illuminated substantially orthogonally with a charged particle beam propagating along an optical axis. An image of the charged particle beam that has passed through the mask is projection-exposed onto the substrate. At multiple locations displaced from each other in the optical-axis direction, a size measurement is obtained on a transverse profile of the beam as incident on at least one of the mask and substrate. From the size measurements, a respective parallelism of the beam incident to the mask and/or substrate is determined. From these determinations, the parallelism of the beam relative to the mask and/or substrate is adjusted as required.

Growing community of inventors

Kamakura, Japan

Teruaki Okino