Nikon Corporation

Koichi Kamijo

Kazuya Okamoto

Atsushi Yamada

Shinichi Kojima

Mamoru Nakasuji

Teruaki Okino

Shinichi Takahashi

Katsushi Nakano

Shintaro Kawata

Hiroyasu Simizu

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

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 are disclosed for quantifying blur, of a beam of an optical medium, exhibited by an optical system through which the beam of the optical medium passes. An embodiment of the method includes the step of determining, in an image plane of the optical system, respective destination positions of a number (N) of rays of the optical medium originating according to a probability distribution from respective points in an object plane of the optical system. The destination positions are projected onto an axis in a direction, in the image plane, in which blur is to be quantified. Respective coordinates of each of the destination positions on the axis are determined and the determined coordinates are ranked. Blur is calculated from a profile of the ranked coordinates.

Methods and apparatus for determining blur of an optical system

Methods are disclosed for determining a reticle pattern to be defined on a reticle used for charged-particle-beam microlithography performed using a high beam-acceleration voltage. The pattern is determined so as to define pattern elements, destined for transfer-exposure to respective edges of chips, on the reticle in a manner serving to reduce proximity effects in such elements when imprinted on the substrate, whether or not the elements are in peripherally situated chips (located at or near a wafer perimeter) or in chips located centrally on the substrate. On the reticle the profile of such an element is reconfigured as required to reduce proximity effects caused by proximal pattern elements in neighboring chips. To reduce variations in the imprinted profile of such an element in peripherally located chips versus centrally located chips on the substrate, portions of neighboring chips that straddle the substrate edge are imprinted nevertheless. This ensures that the edges of each entire chip imprinted on the substrate experiences the same proximity effect that is offset by the pattern defined by the reticle, regardless of whether the imprinted entire chips are located peripherally or centrally on the substrate.

Methods for determining a pattern on a microlithography reticle to minimize proximity effects in pattern elements in chips located on substrate periphery

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&times;M &plusmn;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.

Charged-particle-beam projection-lens system exhibiting reduced blur and geometric distortion, and microlithography apparatus including same

Charged-particle-beam (CPB) optical components (e.g., electromagnetic lenses and deflectors) are disclosed that exhibit very low to no image displacement or loss of focus accompanying changes in temperature of the optical components during use. An optical component includes a unit of ferrite (typically in a ferrite stack). The ferrite is configured to exhibit substantially no permeability change with a change in temperature relative to normal operating temperature, thereby maintaining image displacement caused by permeability changes to below a predetermined threshold. As the ferrite temperature T rises to T&prime;, the saturation magnetic flux density B of the ferrite decreases while the initial permeability &mgr; increases. Thus, the initial magnetization curves of the ferrite intersect at a particular magnetic field intensity H, which exhibits substantially no change from T to T&prime;. With H being the particular magnetic field intensity, the ferrite is selected so that the magnetic field intensity acting on the ferrite during operation is near H .

Charged-particle-beam optical components and systems including ferrite exhibiting reduced image displacement from temperature fluctuations

Methods are disclosed for calculating exposure energy on a sensitive substrate as realized whenever the substrate is exposed with a reticle pattern. The reticle pattern is divided into regions each defining one or more respective pattern elements. The respective pattern element(s) in the various regions are represented by a respective representative figure having an aspect ratio that reflects the aspect ratio of the pattern elements in the region. The representative figure also has an area equal to the collective area(s) of the respective pattern element(s) in the region, and a centroid located at the centroid of the pattern element(s) in the region. If (1) the direction of one side of the representative figure is in the X-axis direction, (2) the direction of a perpendicular side of the representative figure is in the Y-direction, (3) the sum of the moment of inertia of the actual respective pattern element(s) around an axis parallel to the X-axis and passing through the centroid is I , and (4) the sum of the moment of inertia of the actual pattern element(s) around an axis parallel to the Y-axis and passing through the centroid is I , then the ratio between the length of the sides in the X-axis direction and the length of the sides in the Y-axis direction is (I ) :(I ) .

Proximity effect correction methods

Charged-particle-beam microlithography apparatus are disclosed that exhibit minimal deflection aberrations while providing large-magnitude deflections of the charged particle beam using a relatively small excitation current. The apparatus comprises multiple deflectors. A representative deflector comprises a toroidal deflector coil having a semi-angle of 72&deg; and a toroidal saddle deflector coil having a semi-angle of 36&deg;. By adjusting the dimensions and number of windings of each coil, and the excitation current applied to each coil, magnetic-field components associated with cos&lsqb;3&phgr;&rsqb; and with cos&lsqb;5&phgr;&rsqb;, which are higher-order components in the deflection field, are minimized. As a result, four-fold aberrations are minimized and deflection sensitivity is increased.

Apparatus and methods for charged-particle-beam microlithography exhibiting reduced four-fold aberrations

Methods are disclosed for calculating cumulative exposure energy from a microlithography reticle, especially a reticle used for charged-particle-beam (CPB) microlithography. The methods provide an accuracy of results at least as high as conventional methods, but the subject methods can be performed using substantially less calculation time, even for complex patterns. The pattern features contained within a region and/or one or more size parameters of the region are evaluated according to specified rules. The region also is subdivided according to the specified rules. Subdivision produces subregions that also are evaluated according to the rules to determine whether to subdivide further or to cease further subdivision. The result is a branching structure for the region, containing multiple levels of subregions arranged in an hierarchical manner. As a result, e.g., a subregion distant from a cumulative-energy evaluation point (and that has little effect on the distribution position of elements therein) can be left relatively large, whereas a subregion near the evaluation point has a relatively large effect on the distribution position of the elements therein and hence is relatively small. From the branching structure, cumulative energy is calculated from the constituent subregions.

Methods for calculating cumulative dose of exposure energy from regions of a microlithography reticle for use in correcting proximity effects

Astigmatism-correction devices are disclosed for use in a charged-particle-beam (CPB) microlithography apparatus and methods and that do not produce higher-order aberrations when correcting deflection aberrations. The CPB microlithography apparatus includes a projection-optical system that includes first and second projection lenses and associated deflectors. The astigmatism-correction device can include a first coil array associated with the first projection lens upstream of an aperture, and a second astigmatism-correction device associated with the second projection lens downstream of the aperture. In each coil array, the nominal half-angle of the constituent coils is 30&deg;. With such a configuration, higher-order aberrations that otherwise would be produced by the deflectors are reduced nearly to zero, making it possible to use large electrical currents in the deflectors. Specifically, deflection-astigmatism aberrations and hybrid deflection-astigmatic distortions otherwise produced by the deflectors are eliminated.

Astigmatism-correction device and charged-particle-beam microlithography apparatus and methods comprising same

Devices and methods are disclosed for reducing or eliminating deflection aberrations in charged-particle-beam (CPB) optical systems and CPB microlithography apparatus including such systems. The devices and methods also reduce the number of adjustment iterations required to make adjustments to compensators employed for correcting aberrations. In an imaging-optical system, an astigmatism compensator is used to eliminate linear aberrations generated by deflection of the beam. A four-fold-aberration compensator is used that eliminates the non-linear aberrations that are generated by beam deflection. The four-fold-aberration compensator is configured to generate a magnetic-field component proportional to cos&lsqb;5&thgr;&rsqb;. Using such a compensator, linear aberrations generated whenever four-fold aberrations are eliminated are made smaller than when four-fold aberrations are eliminated by generating a magnetic-field component proportional to cos&lsqb;3&thgr;&rsqb;, as in the past. Therefore, the number of adjustment iterations is decreased.

Devices for reducing deflection aberrations in charged-particle-beam optical systems and microlithography apparatus comprising same, and related methods

A mask is irradiated by an optical illumination system. An electron beam passing through the pattern on the mask is formed into an image on a wafer by two lenses, and a pattern on a mask is projected onto the wafer in reduced manner. The semi-angles and ratio of ampere-turn values of the deflecting coils of at least one of deflectors constituting the deflector are then set in such a manner that a 3&thgr; component, 5&thgr; component and 7&thgr; component of a magnetic field generated by the deflector are substantially zero. As a result, four-fold aberrations generated at the deflector can be reduced.

Charged particle beam exposure apparatus and semiconductor device manufacturing method

A pattern to be transferred to a wafer or other substrate is defined by a mask and divided into a plurality of sub-fields. The sub-fields include pattern lines having interconnection patterns for interconnecting patterns from the sub-fields on the wafer The interconnection patterns comprise one or more sections that transmit an incident charged-particle beam or light flux. The widths of the transmitting sections are selected to be less than or equal to the resolution limit of the optical system (CPB or light optical system) that images the sub-fields onto the wafer. In one embodiment, the widths of the transmitting sections monotonically increase or decrease at the ends towards the edges of the sub-fields. In another embodiment, the interconnection pattern is a square-spiral pattern formed of transmitting and absorbing segments. These interconnection patterns allow lines from connecting sub-field patterns to be connected with a reduced area of double-exposure even if the patterns are projected with an offset.

Growing community of inventors

Kumagaya, Japan

Koichi Kamijo