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Kehan Tian

Kehan Tian, Hopewell Junction, NY US

Patent application numberDescriptionPublished
20110096313Constrained Optimization Of Lithographic Source Intensities Under Contingent Requirements - A method for illuminating a mask to project a desired image pattern into a photoactive material is described. The method includes receiving an image pattern. Determining a relationship between source pixels in a set of source pixels to desired intensities at one or more points in the image pattern is performed. Linear constraints are imposed on a set of intensity values based on one or more contingent intensity condition. The contingent intensity conditions include integer variables specifying contingent constraints. The method includes determining values of the set of intensity values in accordance with the linear constraints, using a constrained optimization algorithm. The set of intensity values represents intensities of a set of source pixels. The set of intensity values are output. Apparatus and computer readable storage media are also described.04-28-2011
20110231803Wavefront engineering of mask data for semiconductor device design - Optical wave data for a semiconductor device design is divided into regions. First wavefront engineering is performed on the wave data of each region, accounting for just the wave data of each region and not accounting for the wave data of neighboring regions of each region. The optical wave data of each region is normalized based on results of the first wavefront engineering. Second wavefront engineering is performed on the wave data of each region, based at least on the wave data of each region as has been normalized. The second wavefront engineering takes into account the wave data of each region and a guard band around each region that includes the wave data of the neighboring regions of each region. The second wavefront engineering can be sequentially performed by organizing the regions into groups, and sequentially performing the second wavefront engineering on the regions of each group in parallel.09-22-2011

Kehan Tian US

Patent application numberDescriptionPublished
20100283982High Contrast Lithographic Masks - A structure and a method for an equi-brightness optimization. The method may include projecting a plurality of bright patterns having a plurality of bright points and a plurality of dark patterns having a plurality of dark points on a substrate, generating a plurality of joint eigenvectors of the plurality of bright points and a plurality of dark points, selecting a predetermined number of joint eigenvectors to project the plurality of bright patterns, generating a plurality of natural sampling points from the plurality of bright points, wherein the plurality of natural sampling points has a substantially equal intensity, and obtaining a representation of an aperture from the plurality of natural sampling points, wherein an image of the representation of the aperture has a substantially uniform intensity.11-11-2010

Kehan Tian, Poughkeepsie, NY US

Patent application numberDescriptionPublished
20090021718Method, Computer Program, Apparatus and System Providing Printing for an Illumination Mask for Three-Dimensional Images - A method able to provide illumination source parameters for illumination of a lithographic mask in order to project a three-dimensional image into a resist system. Source intensities of incident beams are determined using a near linear program and responsive to an allowed range of variation. Computer program, apparatus and system are detailed and variations are described.01-22-2009
20090185740CALCULATING IMAGE INTENSITY OF MASK BY DECOMPOSING MANHATTAN POLYGON BASED ON PARALLEL EDGE - A method, system, computer program product and table lookup system for calculating image intensity for a mask used in integrated circuit processing are disclosed. A method may comprise: decomposing a Manhattan polygon of the mask into decomposed areas based on parallel edges of the Manhattan polygon along only one dimension; determining a convolution of each decomposed area based on a table lookup; determining a sum of coherent systems contribution of the Manhattan polygon based on the convolutions of the decomposed areas; and outputting the determined sum of coherent system contribution for analyzing the mask.07-23-2009
20100003605 SYSTEM AND METHOD FOR PROJECTION LITHOGRAPHY WITH IMMERSED IMAGE-ALIGNED DIFFRACTIVE ELEMENT - A novel system and method and computer program product for exposing a photoresist film with patterns of finer resolution than can physically be projected onto the film in an ordinary image formed at the same wavelength. A hologram structure containing a set of resolvable spatial frequencies is first formed above the photoresist film. If necessary the photoresist is then sensitized. An illuminating wavefront containing a second set of resolvable spatial frequencies is projected through the hologram, forming a new set of transmitted spatial frequencies that expose the photoresist. The transmitted spatial frequencies include sum frequencies of higher frequency than is present in the hologram or illuminating wavefront, increasing the resolution of the exposing pattern. These high spatial frequency transmitted waves can be evanescent, or they can propagate at a steeper obliquity in a higher index medium than is possible in a projected image. A further method is described for designing lithographic masks to fabricate the hologram and to project the illuminating wavefront. In other embodiments, a simple personalization based on Talbot fringes and plasmonic interference is performed.01-07-2010
20100153901Determining manufacturability of lithographic mask by reducing target edge pairs used in determining a manufacturing penalty of the lithographic mask - The manufacturability of a lithographic mask employed in fabricating instances of a semiconductor device is determined. Target edge pairs are selected from mask layout data of the lithographic mask to determine a manufacturing penalty in making the lithographic mask. The mask layout data includes polygons, where each polygon has edges, and where each target edge pair is defined by two of the edges of one or more of the polygons. The number of the target edge pairs is reduced to decrease computational volume in determining the manufacturing penalty in making the lithographic mask. The manufacturability of the lithographic mask, including the manufacturing penalty in making the lithographic mask, is determined based on the target edge pairs as reduced in number. The manufacturability of the lithographic mask is output. The manufacturability of the lithographic mask is dependent on the manufacturing penalty in making the lithographic mask.06-17-2010
20100153902DETERMINING MANUFACTURABILITY OF LITHOGRAPHIC MASK BY SELECTING TARGET EDGE PAIRS USED IN DETERMINING A MANUFACTURING PENALTY OF THE LITHOGRAPHIC MASK - The manufacturability of a lithographic mask employed in fabricating instances of a semiconductor device is determined. Target edges are selected from mask layout data of the lithographic mask. The mask layout data includes polygons distributed over cells, where each polygon has edges. The cells include a center cell, two vertical cells above and below the center cell, and two horizontal cells to the left and right of the center cell. Target edge pairs are selected for determining a manufacturing penalty in making the lithographic mask, in a manner that decreases the computational volume in determining the manufacturing penalty. The manufacturability of the lithographic mask, including the manufacturing penalty in making the lithographic mask, is determined based on the target edge pairs selected. The manufacturability of the lithographic mask is output. The manufacturability of the lithographic mask is dependent on the manufacturing penalty in making the lithographic mask.06-17-2010
20100153903DETERMINING MANUFACTURABILITY OF LITHOGRAPHIC MASK USING CONTINUOUS DERIVATIVES CHARACTERIZING THE MANUFACTURABILITY ON A CONTINUOUS SCALE - The manufacturability of a lithographic mask employed in fabricating instances of a semiconductor device is determined. Target edge pairs are selected from mask layout data of the lithographic mask, for determining a manufacturing penalty in making the lithographic mask. The mask layout data includes polygons, where each polygon has a number of edges. Each target edge pair is defined by two of the edges of one or more of the polygons. The manufacturability of the lithographic mask, including the manufacturing penalty in making the lithographic mask, is determined. Determining the manufacturing penalty is based on the target edge pairs as selected. Determining the manufacturability of the lithographic mask uses continuous derivatives characterizing the manufacturability of the lithographic mask on a continuous scale. The manufacturability of the lithographic mask is output. The manufacturability of the lithographic mask is dependent on the manufacturing penalty in making the lithographic mask.06-17-2010
20120008134METHOD TO MATCH EXPOSURE TOOLS USING A PROGRAMMABLE ILLUMINATOR - Programmable illuminators in exposure tools are employed to increase the degree of freedom in tool matching. A tool matching methodology is provided that utilizes the fine adjustment of the individual source pixel intensity based on a linear programming (LP) problem subjected to user-specific constraints to minimize the difference of the lithographic wafer data between two tools. The lithographic data can be critical dimension differences from multiple targets and multiple process conditions. This LP problem can be modified to include a binary variable for matching sources using multi-scan exposure. The method can be applied to scenarios that the reference tool is a physical tool or a virtual ideal tool. In addition, this method can match different lithography systems, each including a tool and a mask.01-12-2012
20120017194METHOD FOR FAST ESTIMATION OF LITHOGRAPHIC BINDING PATTERNS IN AN INTEGRATED CIRCUIT LAYOUT - The present invention provides a lithographic difficulty metric that is a function of an energy ratio factor that includes a ratio of hard-to-print energy to easy-to-print energy of the diffraction orders along an angular coordinate θ01-19-2012

Patent applications by Kehan Tian, Poughkeepsie, NY US

Kehan Tian, Fishkill, NY US

Patent application numberDescriptionPublished
20120036487FRACTURING CONTINUOUS PHOTOLITHOGRAPHY MASKS - A method, system, and computer usable program product for fracturing a continuous mask usable in photolithography are provided in the illustrative embodiments. A first origin point is selected from a set of points on an edge in the continuous mask. A first end point is identified on the edge such that a separation metric between the first origin point and the first end point is at least equal to a threshold value. Several alternatives are determined for fracturing using the first origin point and the first end point. A cost associated with each of the several alternatives is computed and one of the alternatives is selected as a preferred fracturing. Several pairs of origin points and end points are formed from the set of points. Each pair has a cost of a preferred fracturing between the pair. The continuous mask is fractured using a subset of the several pairs.02-09-2012