Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70691—Handling of masks or workpieces
  • G03F7/70791—Large workpieces, e.g. glass substrates for flat panel displays or solar panels
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70216—Mask projection systems
  • G03F7/70283—Mask effects on the imaging process
  • G03F7/70291—Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
  • G03F7/70508—Data handling in all parts of the microlithographic apparatus, e.g. handling pattern data for addressable masks or data transfer to or from different components within the exposure apparatus
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70691—Handling of masks or workpieces
  • G03F7/70783—Handling stress or warp of chucks, masks or workpieces, e.g. to compensate for imaging errors or considerations related to warpage of masks or workpieces due to their own weight

Definitions

• the present invention relates to an in-line virtual masking method for exposing a pattern in a maskless lithography system using micromirrors . More specifically, the present invention relates to an in-line virtual masking method for exposing a pattern onto a large sized substrate, such as a flat panel display, in a maskless lithography system using micromirrors, which is applicable to mass production.
• a pattern is generated with light beams selectively reflected from micromirrors of a micromirror array to a surface of the substrate translating along with time.
• the binary reflection information for the micromirrors of the micromirror array corresponding to each of substrate translations serves as a partial mask
• a full set of the binary reflection information for the micromirrors of the micromirror array corresponding to a sum of all substrate translations serves as a complete mask. Therefore, the pattern generation and transfer in the maskless lithography system using micromirrors can be virtual masking, or mask emulating, i.e., generating a virtual mask proper to the pattern per each of the substrate translations, and transferring the virtual masks to a micromirror controller in accordance with the substrate translation.
• the pattern is generated on the substrate while correcting errors due to substrate deformations, such as sagging, expansion, contraction, and so on of the large sized substrate and errors associated with large sized stage controls, such as a translating velocity errors, i.e., errors in translation directions and translation time.
• a pattern correction method related to stage control, using alignment marks and CCD cameras and using physical correcting parts for positioning or aligning an exposure location of an exposing apparatus is disclosed in above laid open patent No. 2006-0045355, and an aligning method using alignment marks and CCD cameras for exposure of the large sized flat display substrates using a plurality of micromirror devices is disclosed in above laid open patent 2006-0109724.
• an object of the present invention is to provide an in-line virtual masking method for generation and transfer of a pattern in a maskless lithography system using micromirrors suitable for mass production of large sized flat display substrates.
• Another object of the present invention is to provide an in-line virtual masking method in which pattern regions, a cell of image (COI) array reference coordinate system, an Instantaneous Cell Intensity (ICI) in the COI, an overlay intensity basis (0IB) , and an occupancy limit are in-line controlled so that binary reflection information for the micromirrors is in-line determined to transfer a unit translation virtual mask to a micromirror controller in accordance with substrate translation for generation of a pattern enabling in-line compensation for errors due intensity distribution or variation of the light beams reflected from micromirrors and errors due to inaccurate control of physical components such as substrate deformation and inaccurate control of substrate .
• COI cell of image
• ICI Instantaneous Cell Intensity
• Another object of the present invention is to insert a finish virtual mask calculated upon pre-tested pattern finish information suitably selected according to a result of the comparison of the user specified portions of an input pattern to that of the virtual pattern generated by superposition of the OIBs upon the binary reflection information, simultaneously with in-line virtual masking described above, in order to prevent or to reduce chemically caused errors, such as stains.
• Another object of the present invention is to provide a virtual masking method in which a COI array reference coordinate system is set according to information on substrate alignment, and an overlay intensity base of COI is corrected according to information on substrate translation and determining binary reflection according to the correction, for enabling in-line compensation of a substrate translation error without using a physical correction parts.
• Still further object of the present invention is to provide a virtual masking method in which binary reflection for micromirrors is determined by using a base of an overlay intensity basis in constructing a COI unit mask for fast, accurate, and precise generation of a pattern so that a center of the pattern is conserved the most accurately without shifting of the pattern with respect to a substrate which is an object of exposure even when the pattern has a large size, and complicate shape and structure with a wide variety.
• an in-line virtual masking method for maskless lithography in a maskless lithography process using micromirrors applicable to a maskless lithography system with an in-line virtual masking system including an exposure hosting computer connection unit for receiving inputs required for exposure of a pattern and generating and transferring an exposure virtual mask for the pattern, and a micromirror controller connection unit for constructing binary reflection information for the micromirrors upon the exposure virtual mask transferred from the exposure hosting computer connection unit and transferring the binary reflection information to a micromirror controller, includes the steps of (a) constructing pattern region on the exposure hosting computer connection unit for the in-line virtual masking system, (b) comparing an occupancy of the pattern per unit base of an overlay intensity basis to a reflection definitive occupancy limit for each cell of image (COI), and determining binary reflection information for each of the micromirrors corresponding to each COI to generate a COI unit virtual mask for each
• the generating the virtual mask for each cell of image in the step (b) includes the step of setting a COI array reference coordinate system for the micromirror array, transforming the pattern region to the COI array reference coordinate system, and determining the binary reflection on the COI array reference coordinate system.
• the generating the virtual mask for each cell of image in the step (b) includes the step of setting instantaneous cell intensity (ICI) the beam reflected from the micromirror and incident on the substrate in the COI higher than an effective intensity as a function of a COI center, and integrating the function with reference to a virtual translation time period of the COI center corresponding to the substrate translation to generate an overlay intensity basis (0IB) for extracting a base of the 0IB, or taking a boundary of the ICI as the 0IB if overlay of the beams for unit translation of the substrate is small enough to disregard.
• ICI instantaneous cell intensity
• the generating the virtual mask for each cell of image in the step (b) includes the step of setting the occupancy limit for the micromirror according to the effective intensity.
• the step of making in-line transfer in the step (d) includes the step of taking the translation unit virtual mask as the exposure virtual mask as it is or the translation unit virtual mask is subjected to lossless compression to generate the exposure virtual mask if the quantity of pattern or virtual masking data is very small, or fast exposure is not necessary.
• the step of making in-line construction of the binary reflection information in the step (e) includes the step of making in-line construction of the binary reflection information for the micromirrors after a compressed exposure virtual mask is subjected to lossless decompression if the exposure virtual mask is compressed, or as it is if the exposure virtual mask is not compressed.
• the step of constructing a pattern region in the step (a) includes the step of mapping the pattern in conformity with a substrate shape and correcting an error caused by a change of the substrate shape.
• the step of determining binary reflection information includes the step of correcting an error caused by substrate alignment by setting the COI array reference coordinate system taking the substrate alignment in addition to the translation of the substrate.
• the setting of ICI in the COI higher than an effective intensity as a function of the COI center minimizes an exposure error caused by the effective intensity and distribution of each mirror or change of the intensity along with a time by setting the ICIs in the COI different from each other in conformity with the intensity distribution of each COI for every substrate translation.
• the generating the 0IB includes the step of correcting an error caused by a substrate translation time period by integrating the ICIs in the COIs different from one another for every substrate translation with respect to the virtual translation time period of the center of the COI corresponding to the substrate translation different from one another to generate the 0IB.
• the extraction of a base of the 0IB includes the step of correcting an error caused by a substrate translation direction by extracting the bases of the OIBs different from one another for substrate translation directions different from one another for every substrate translation.
• the step of setting the occupancy limit for the micromirrors according to the effective intensity includes the step of correcting an error caused by intensity deviation by setting the occupancy limit for the micromirrors different form each other according to an effective intensity deviation for each mirror and change along with time corresponding to each COI for every substrate translation.
• the step of generating a translation unit virtual mask in the step (c) includes the step of multiplying the COI unit virtual mask generated in the step
• the step of generating the translation unit virtual mask includes the step of generating a time unit virtual pattern by superposition of the translation unit virtual patterns corresponding to virtual translation of the COI array as the virtual translation of the COI array is progressed following the substrate translation starting from an initial stage of exposure.
• the generating a translation unit virtual mask in the step (c) includes the step of making logical production of the finish virtual mask of tested pattern finish information to the translation unit virtual mask for preventing or reducing errors caused by chemical, such as stains, from taking place for every substrate translation or every substrate translation of orders the user designates.
• the making logical production of the finish virtual mask includes the step of comparing a time unit virtual pattern to an input pattern for a specific portion the user designates if necessary, and selecting and calculating a finish virtual mask having a suitable and excellent function as a result of the comparison according to the pattern finish information already tested.
• the step of comparing a time unit virtual pattern to an input pattern, and selecting and calculating a finish virtual mask includes the step of updating the time unit virtual pattern so that accurate prediction of a result of the exposure is possible progressed by updating the time unit virtual pattern by calculating the finish virtual mask.
• the step of making in-line transfer of the exposure virtual mask to the micromirror controller connection unit in the step (d) includes the step of making in-line provision of the finally updated virtual pattern to the exposure hosting computer at the time of final substrate translation of the exposure, enabling to predict a result of exposure at the moment an exposure of a substrate is finished, and to accumulate the results for utilizing the result in process improvement in the future.
• the present invention has following advantageous effects.
• the use of the overlay intensity basis unique to the present invention permits the most accurate determination of the binary reflection for the micromirrors .
• the use of the overlay intensity basis, the occupancy limit, the costruction of the pattern region, the COI array reference coordinate system unique to the present invention permits real time correction of physical errors caused by beam intensity distribution or an error thereof, a shape and translation of a substrate, and so on.
• the systematic in-line generation of the virtual mask according to a concept of the virtual mask unique to the present invention permits an easy real time pattern finish for preventing or reducing errors chemically caused, such as stains and the like.
• the use of the overlay intensity basis unique to the present invention permits in-line generation of a virtual pattern only with superposition without complicate operation.
• the in-line virtual masking unique to the present invention permits in-line correction of a physical error or an error caused by a chemical reaction which is liable to take place in the exposure, thereby enabling real time mask lithography suitable for mass production of the substrates .
• the in-line correction method for a physical error or an error caused by a chemical reaction by the inline virtual masking method unique to the present invention is a method for compensate for an error without using a physical or mechanical correction member.
• FIG. 1 illustrates a block diagram of a maskless lithography system using micromirrors applicable to an inline virtual masking method in accordance with a preferred embodiment of the present invention
• FIG. 2 illustrates a flow chart showing the steps of an in-line virtual masking method in accordance with a preferred embodiment of the present invention
• FIG. 3 illustrates a pattern mapping in a case of deformation of a substrate in accordance with a preferred embodiment of the present invention, wherein FIG. 3(A) illustrates the substrate and the pattern both without deformation, and 3 (B) illustrates the pattern mapped to compensate for the deformation of the substrate;
• FIG. 4 illustrates setting of a COI array reference coordinate system for substrate alignment in accordance with a preferred embodiment of the present invention, wherein FIG. 4 (A) illustrates the substrate without an alignment error and the COI array reference coordinate system, and 4 (B) illustrates the COI array reference coordinate system set to compensate for the alignment error of a substrate;
• FIG. 5 illustrates examples of ICI of the beam reflected from micromirrors defined in the present invention incident on a substrate in COI higher than an effective intensity
• FIGS. 5(A) and 5 (B) illustrate ICIs of top and side of a COI having a uniform square intensity respectively
• FIGS. 5(C) and 5 (D) illustrate ICIs of top and side of a COI having a uniform circular Gauss intensity respectively
• FIG. 6 illustrate examples of COIs each having ICI higher than an effective intensity defined in the present invention and OIBs of the present invention, wherein FIG. 6A illustrates translations along with time of COIs each having a uniform square intensity, and COIs each having a circular Gauss intensity
• FIGS. 6A illustrates translations along with time of COIs each having a uniform square intensity
• FIG. 6B, 6C, and 6D illustrate top and side of a three dimensional 0IB of a COI having a uniform square intensity respectively
• FIGS. 6E, and 6F illustrate top and side of an 0IB of a COI having a circular Gauss intensity
• FIG. 7 illustrates extraction of a base of 0IB for a direction of substrate translation in accordance with a preferred embodiment of the present invention, wherein FIGS. 7 (A) and 7 (B) illustrate bases of OIBs of COIs having a uniform square intensity and a circular Gauss intensity extracted to compensate for a translating direction error of the substrate, respectively;
• FIG. 8 illustrates setting of occupancy limits for intensity changes in accordance with a preferred embodiment of the present invention, wherein FIG. 8(A) illustrates a result of setting of a general reflection definitive occupancy limit under a normal intensity, and FIG. 8 (B) illustrates a result of setting of a reflection definitive occupancy limit to compensate for the intensity change,-
• FIG. 9 illustrates binary reflection in accordance with preferred embodiments of the present invention for describing prevention of translating of a pattern to maintain a center of the pattern accurately by determining binary reflection for micromirrors with reference to an occupancy of the pattern per unit base of an overlay intensity basis, wherein FIG. 9(A) illustrates locations of the pattern and the COI, FIG. 9 (B) illustrates determination of the binary reflection with reference to the COI in accordance with a preferred embodiment of the present invention, and FIG. 9(C) illustrates determination of the binary reflection with reference to a base of the overlay- intensity basis in accordance with a preferred embodiment of the present invention;
• FIG. 10 illustrates an initial window of an inline virtual masking system for embodying the present invention.
• FIG. 11 illustrates results by an in-line virtual masking system, wherein FIG. H(A) illustrates a virtually exposed virtual pattern, FIG. H(B) illustrates a virtually developed virtual pattern, FIG. H(C) illustrates a partially enlarged virtually developed virtual pattern, and FIG. H(D) illustrates an optical microscopic photograph showing a result of actual exposure and development of a pattern exposed onto a semiconductor substrate by an in-line virtual masking system of the present invention.
• FIG. 1 illustrates a maskless lithography system using micromirrors applicable to an in-line virtual masking method for maskless lithography in accordance with a preferred embodiment of the present invention, schematically. As shown in FIG. 1, the system has four parts at large.
• the maskless lithography system using micromirrors includes an emissive device 10 for emission of a light, such as a UV (Ultraviolet) beam, a laser beam, or so on, an exposing device 20 for selective reflection of the beam from the emissive device 10 to a substrate for forming a pattern, an exposure process control and monitoring device 30 for controlling and monitoring entire exposure process, and an X-Y stage device 40 for translating the substrate on an X-Y plane.
• a light such as a UV (Ultraviolet) beam, a laser beam, or so on
• an exposing device 20 for selective reflection of the beam from the emissive device 10 to a substrate for forming a pattern
• an exposure process control and monitoring device 30 for controlling and monitoring entire exposure process
• an X-Y stage device 40 for translating the substrate on an X-Y plane.
• the emissive device 10 controls and measures an intensity and a intensity distribution of a light source, and exchanges information on the control and measurement with an exposure hosting computer 31 in the exposure process control and monitoring device 30.
• the exposure device 20 includes a micromirror array 21, a micromirror controller 22, and a light converging unit 24.
• the micromirror array has 1024x768 micromirrors for selective reflection of a beam from the emissive device 10 to the substrate through the light converging unit 24 in response to a mirror beam reflection control signal from the micromirror controller 22.
• the micromirror controller 22 provides the mirror beam reflection control signal to the micromirror array 21 according to a binary reflection which is provided thereto from a micromirror controller connection unit 34 in an inline virtual masking system 32 which will be described later.
• the light converging unit 24 adjusts a shape or size of the beam selectively reflected at the micromirror array 21 and directs the beam to a predetermined region of the substrate 43 having a photoresist film coated thereon.
• the exposure process control and monitoring device 30 includes an exposure hosing computer 31 for controlling and monitoring entire exposing process including the emissive device 10 and the X-Y stage device 40, and an in-line virtual masking system 32 having an exposure hosting computer connection unit 33 for receiving a data from the exposure hosing computer 31 and in-line generation of a compressed exposure virtual mask, and a micromirror controller connection unit 34 for decompressing the compressed exposure in-line virtual mask received from the exposure hosting computer connection unit 33, and reconstructing and providing micromirror binary reflection to the micromirror controller 22.
• the X-Y stage device 40 controls or measures alignment of the substrate 42, or translation of the substrate 42 or the X-Y stage 41, exchanges information on the control and measurement with the exposure hosting computer 31, and includes an X-Y stage 41 movable on an X-Y plane, and a substrate 42 fixedly secured to the X-Y stage 41 having a photoresist film coated thereon.
• the in-line virtual masking method for maskless lithography includes the following steps, and will be described with reference to FIGS. 2 which is a representative drawing and 1, 3 to 11.
• an input data required for performing the in-line virtual masking method of the present invention is prepared, tested, measured, or detected to the purpose and by necessity, partly at an initial stage of exposure and partly during the exposing process, and provided by an exposing device user through the exposure hosting computer 31.
• User designated input data provided at the initial stage of the exposure are input patterns, tested pattern finish information, an effective intensity and distribution thereof for each micromirror at the initial stage of the exposure, the occupancy limit taking photoresist film properties and the effective intensity for each micromirror at the initial stage of the exposure and distribution thereof into account, a shape of the substrate and an alignment thereof at the initial stage of the exposure, and other exposure conditions.
• the user provided input data provided during the exposure as required is substrate alignment and translation information, and intensity information for each mirror.
• the in-line virtual masking method for maskless lithography of the present invention is carried out as follows according to a flow shown in FIG. 2 with an in-line virtual masking system including the exposure hosting computer connection unit 33 and the micromirror controller connection unit 34 upon reception of the input data from the exposure hosting computer 31.
• the pattern region is constructed.
• the substrate shape has no deformation (for an example, sagging, expansion, contraction, distortion, and so on)
• a DXF (Drawing Exchange Format) or other CAD (Computer Aided Design) format pattern data is parsed to construct the pattern region as it is without mapping, and if the substrate shape has deformation, the substrate is mapped in conformity with the deformation of the substrate to compensate for the deformation of the substrate, so that the pattern exposed thus is the same with an original input pattern when the deformed substrate is restored to an original state, later.
• DXF Digital Exchange Format
• CAD Computer Aided Design
• Equation 1 A method for mapping a pattern in conformity with a substrate is described in an example 1 below in detail.
• the example 1 is a case when the deformation of the substrate shape is expressed with a transformation of a coordinate system like an equation 1 as shown in FIG. 3. [Equation 1]
• FIG. 3(A) illustrates an ideal pattern and a substrate without deformation, and a point P on the pattern
• FIG. 3 (B) illustrates a substrate deformed as expressed in equation 1, a pattern mapped in conformity with the deformation of the substrate, and a point P on FIG. 3(A) mapped to a point P' in FIG. 3 (B) in conformity with the deformation of the substrate.
• Coordinates of P and P' in equation 2 and 3 are coordinates on a (Z 1 , Z 2 ) coordinate system. If the deformation of the substrate is non-linear, the pattern is mapped by using a Generalized Curvilinear Coordinate as the substrate reference coordinate system, of which method is disclosed in a reference document of Numerical Grid generation: Foundations and Applications, J. F. Thompson et. al., Elsevier, 1985, ISBN 0-444-00985-X, of which detailed description will be omitted, and is hereby incorporated by- reference as if fully set forth herein.
• the COI array reference coordinate system is set according to the substrate alignment information provided from the exposure hosting computer 31 at the initial stage of the exposure, or during the exposing process.
• An example 2 below describes a method for transformation of a coordinate system to compensate for an alignment error of the substrate taking rotation of the micromirror array or a COI array from an absolute coordinate system to a COI array reference coordinate system into account in detail.
• the example 2 is for a case when there is the alignment error of the substrate as much as an angle ⁇ E as shown in FIG. 4.
• FIG. 4(A) illustrates a substrate without a substrate alignment error, and a COI array rotated by an angle ⁇ with respect to a direction of translation of the substrate, and a vector P indicating an origin of a COI array reference coordinate system on the absolute coordinate system
• FIG. 4 (B) illustrates a substrate with an substrate alignment error of an angle ⁇ E
• a COI array and a COI array reference coordinate system both rotated by an angle ⁇ * ⁇ + ⁇ E which is a corrected angle with respect to a direction of translation of the substrate to compensate for the substrate alignment error and having the origin the vector P in FIG. 4(A) indicates translated to (z O i*,z 2 o*).
• coordinate system transformation is expressed as an equation 4, which compensates for an alignment error of the substrate taking rotation of the micromirror array or the COI array from the absolute coordinate system to the COI array reference coordinate system into account. [Equation 4]
• Z 1 and z 2 are absolute coordinate systems
• Z 1 * and Z 2 * are COI array reference coordinate systems
• J'..[x,y,a( ⁇ ), ⁇ ( ⁇ )] which is the ICI in the COI higher than the effective intensity reflected at the mirror incident on the substrate is set for each COI as functions of a COI center [ ⁇ ( ⁇ ), ⁇ ( ⁇ )] which is a function of time ⁇ and a rotation angle ⁇ of the COI array.
• Example 3 The ICI in the COI having a square uniform intensity (sizel) in FIG. 5(A) is expressed as an equation 5 below and shown as FIG. 5 (B) .
• ⁇ , and ⁇ denote x, and y coordinates of an initial COI respectively
• W denote 1/2 of a length of one side of the square COI
• ⁇ denotes an integer index of (int) [ ⁇ 45-180 ( ⁇ - ⁇ ) / ⁇ /90]
• u denotes a unit step function.
• the ⁇ is an expression limited to a first quadrant, and can be expressed similarly for the other quadrants.
• Example 4 The ICI in the COI having a circular Gauss intensity distribution in FIG. 5 (C) is expressed as an equation 6 below and shown as FIG. 5 (D) .
• Equation 6 Equation 6
• I c denotes an intensity of the COI center
• ⁇ denotes an radius of an effective beam fixed by an effective intensity of a light incident on the substrate.
• the ICI is integrated with respect to the translation time period of the substrate to generate the OIB [overlay intensity basis, Z 1 *(x,y) ] on an i th and a j th COIs corresponding to a k th translation of the substrate.
• Examples 5 and 6 below describe above in detail in a case the shape deformation and the alignment error of the substrate are small enough to be disregarded, and the substrate translates in -x direction during a beam reflection shifting time period of the micromirrors .
• Example 5 In a case the COI has a square uniform intensity (sizel) as shown in FIG. 5(A) or the square in a solid line translates to a location of a square in a dashed line as shown in FIG. 6(A), the 0IB is expressed with ⁇ 's, a maximum overlay intensity I 0 , a rotation angle ⁇ of the COI array, and a translating pitch S, and defined as an equation 8.
• the translating pitch S is 1.2 ⁇
• the rotation angle ⁇ is 18°
• FIG. 6(C) shows a side of the 0IB
• FIG. 6 (D) shows a top of the 0IB.
• Equation 8
• ⁇ 1 tan "1 (I 0 /S)
• ⁇ 2 tan "1 (I 0 /Ssin ⁇ )
• ⁇ 3 tan ⁇ 1 (I 0 /Scos ⁇ )
• the 0IB is defined as an equation 9.
• the translating pitch S is l.O ⁇
• FIG. 6(E) shows a side of the OIB
• FIG. 6 (F) shows a top of the 0IB.
• the base of the OIB is extracted in the substrate translation direction, for detail description of which examples 7 and 8 are illustrated in FIG. 7.
• the example 7 shown in FIG. 7(A) is a case of COI having the square uniform intensity (size 1) shown in 5(A) described in the example 3
• the example 8 shown in FIG. 7 (B) is a case of the COI having the circular Gauss intensity distribution shown in FIG.
• the base may be extracted by rotating the OIB described in the example 6 and shown in FIGS. 6(E) and 6(F) by an angle ⁇ x as it is, or rotating the base by the angle ⁇ x after extracting the base of the OIB at first.
• regions each having a intensity higher than the effective intensity or the base of the ICI obtained in the 123 step in FIG. 2 may be taken as the base of the OIB.
• the occupancy limit is set higher or lower on the COI having a changed intensity to enable to compensate for the intensity change. It is required to construct a reference of the higher or lower setting of the occupancy limit to compensate for the intensity change experimentally before the exposure process according to kinds of the beam, the intensity distribution, kinds of the photoresist film, the beam reflection shifting time period of the micromirrors, kinds of the substrate, and pattern characteristics.
• FIGS. 8(A) and 8 (B) illustrate the base (blue square) of the 0IB and a pattern (green) for a unit translation of the substrate or the virtual translation of the COI, respectively.
• FIG. 8(A) illustrates overlay intensities of the pattern in numerals and a profile of the pattern in a red line, which is appeared as a result of determination of the binary reflection of beam at each mirror (reflected beams are violet) when an average non-dimensional intensity is 1.0 and the user designated occupancy limit is set to 0,55, and FIG.
• FIG. 8 (B) illustrates overlay intensities of the pattern in numerals and a profile of the pattern in a red line, which is appeared as a result of determination of the binary reflection of beam at each mirror (reflected beams are violet) when an average non-dimensional intensity is 0.7 and the user designated occupancy limit is set to 0,35.
• an overlay exposure intensity of an accurate pattern is calculated by using a location of an OIB profile and superposition of the beam reflection.
• the overlay intensities of patterns each of which is a multiplication of the average dimensionless intensity to a number of reflection times of the beam are compared.
• FIG. 8(A) and 8 (B) denotes a value having the intensity multiplied to the number of reflection.
• 3 in FIG. 8(A) denotes a value having the intensity 1.0 multiplied to the number of reflection 3
• 3.5 in FIG. 8 (B) denotes a value having the intensity 0.7 multiplied to the number of reflection 5. It is verified by the results shown in FIG. 8(A) and 8 (B) that the overlay intensity can be maintained similar at a boundary of the pattern by making the occupancy limit the lower as the intensity becomes the lower. However, as described before, it is required that the relation between the intensity and the occupancy limit before the exposure is constructed experimentally, and is optimized before each of the steps. 7.
• an occupancy of the pattern per unit base of the 0IB is compared to the user designated occupancy limit to determine binary reflection of the beam for each micromirror such that the beam is reflected if the occupancy of the pattern per unit base of the OIB is the same or greater than the user designated occupancy limit, and the beam is not reflected if smaller, and a data of the binary reflection information for each micromirror is converted into a binary data, to generate a COI unit virtual mask C* which corresponds to i(th) and j (th) COI in a (k)th unit translation of the substrate.
• a COI unit virtual mask is the binary reflection itself of the beam for each micromirror.
• the selection of the reflect TRUEl brings about a result the same with one in which the beam passes through an opened part of a physical mask and is incident on the substrate, and if the selection of the no reflect FALSE2 brings about a result the same with one in which the beam hits the physical mask to fail to pass through the physical mask.
• the COI array reference coordinate system i.e., in a case the OIB base is on the COI array reference coordinate system
• the binary reflection is determined.
• Q "'Q N ' N Q j C y I y ⁇ x,y) is generated by overlay of the translation unit N ' N> virtual pattern QQC * I]j(x,y) corresponding to (n ⁇ ) th virtual
• the translation unit virtual mask is taken as the exposure virtual mask as it is .
• lossless decompression of the compressed exposure virtual mask received from the exposure hosting computer connection unit 33 is made by RLE (Run-length encoding) , or Parallel difference coding described before, for constructing in-line binary reflection of the micromirrors .
• RLE Un-length encoding
• Parallel difference coding described before
• the data on micromirror binary reflection in-line constructed in the 131 step is in- line transferred to the micromirror controller 22.
• the occupancy of the pattern per unit base of the OIB is compared to the user designated occupancy limit, to reflect the beam when the occupancy of the pattern per unit base of the OIB is the same with or greater than the user designated occupancy limit, and not to reflect the beam when smaller, thereby determining the binary reflection for each micromirror, preventing the pattern from displacing, to maintain a center of the pattern, exactly.
• occupancy based pattern generation method for maskless lithography discloses a method for determining the binary reflection for each micromirror by comparing the occupancy of the pattern for COI to the user designated occupancy limit.
• FIGS. 9(A) to 9(C) are embodiments of the method, wherein FIG. 9(A) illustrates an initial location (red square) of the COI and the pattern (green) of the COI for the unit translation of the substrate or the virtual translation of the COI, and COIs (yellow) which reflect beams according to the user designated occupancy limit (0.55 presently).
• FIG. 9(A) illustrates an initial location (red square) of the COI and the pattern (green) of the COI for the unit translation of the substrate or the virtual translation of the COI, and COIs (yellow) which reflect beams according to the user designated occupancy limit (0.55 presently).
• FIG. 9(A) illustrates an initial location (red square) of the COI and the pattern (green) of the COI for the unit translation of the substrate or the virtual translation of the COI
• COIs (yellow) which reflect beams according to the user designated occupancy limit (0.55 presently).
• FIG. 9 (B) illustrates overlay intensities of the pattern in numerals, and a profile of the pattern in red lines, which pattern is generated as a result of comparing the occupancy of the pattern for the COI to the user designated occupancy limit (0.55 presently), and determining binary reflection of each micromirror of the registered patent filed by the inventors.
• FIG. 9(C) illustrates overlay intensities of the pattern in numerals, and a profile of the pattern in a red line, which pattern is generated as a result of comparing the occupancy of the pattern per unit base of the 0IB to the user designated occupancy limit (0.55 presently, too), and determining binary reflection of each micromirror (reflected beams are violet) of the present invention.
• the object of the in-line virtual masking method for maskless lithography of the present invention is implemented with a prototype lithography system.
• the system is implemented with the in-line virtual masking system described with reference to FIG. 1.
• the system includes the exposure hosting computer connection unit 33, the micromirror controller connection unit 34, a signal interchange module (not shown) for making real time communication with the emission control unit, the stage control unit, and so on of the exposure hosting computer, and a graphic user interface GUI for enabling the in-line virtual masking system operator to observe system operation.
• FIG. 10 illustrates a main window of a GUI for the exposure hosting computer connection unit of the prototype in-line virtual masking system.
• the main window of the GUI has an exposure control window, a management toolbar, and pattern region, virtual mask and virtual pattern generation process display window on an upper side of a left side, a lower side of the left side, and on a right side, respectively.
• Conditions the system operator can select and apply are kinds of beam and size, pattern correction for the intensity, the substrate alignment, and the substrate translation, generation of the virtual pattern, kinds of the finish masks and calculation thereof, application of each intensity distribution, resolution, a number, and arrangement of the micromirrors , CAD data flip/mirror change, and so on.
• the in-line virtual masking system of the present invention enables in-line correction of a physical error and/or chemical reaction error which are liable to take place in the exposure .
• FIG. 11 (A) illustrates a final virtual pattern generated by the in-line virtual masking method of the present invention
• FIG. 11 (B) illustrates a pattern virtually developed from a virtual pattern according to the appropriate photoresist film retranslating ratio corresponding to the occupancy limit for maintaining a pattern width the patent No. 655165 filed by the inventors titled "Occupancy based pattern generation method for maskless lithography”
• FIG. 11 (C) illustrates an enlarged view of a portion of the pattern in FIG. 11 (B)
• FIG. 11 (C) illustrates an enlarged view of a portion of the pattern in FIG. 11 (B)
• FIG. 11 (D) illustrates an optical microscopic photograph of a pattern exposed onto a semiconductor substrate by the in- line virtual masking method of the present invention and developed for 15 seconds, actually.
• the developed virtual pattern in the FIG. 11 (B) and the developed actual pattern are compared to find that it is possible to determine that the actual pattern in FIG. 11 (D) is developed slightly excessively because an actual development time period used in the experiment is slightly longer than a proper development time period. Therefore, upon reviewing the results illustrated in FIGS. H(A)-Il(D), it can be known that the in-line virtual masking method has improved over the registered patent of the inventors in view of effectiveness and accuracy.
• the present invention is applicable to an in-line virtual masking method for a maskless lithography system which is applicable to mass production in which a pattern is exposed onto a large sized substrate by using the micromirrors.

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• 2007
  • 2007-05-14 KR KR1020070046450A patent/KR100868242B1/ko active IP Right Grant
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