Showing papers on "Proximity effect (electron beam lithography) published in 2000"

Correcting method for correcting exposure data used for a charged particle beam exposure system

Abstract: A charged particle beam exposure system which draws a pattern on an object to be exposed by a plurality of charged particle beams emitted from a plurality of element electron optical systems includes (a) a storage device storing (i) a standard dose data for controlling the irradiation of charged particle beams to an object to be exposed, (ii) plural pieces of proximity effect correction data for correcting the irradiation of the charged particle beams for each incidence position with respect to the object to be exposed, in order to reduce the influence of a proximity effect, and (iii) calibration data for correcting variations in the irradiation dose among the plurality of the charged particle beams emitted from the plurality of element electron optical systems, and (b) a controller for controlling the irradiation of each of the charged particle beams, based on the standard dose data, the proximity effect correction data, and the calibration data.

Method of electron-beam exposure and mask and electron-beam exposure system used therein

Abstract: An electron-beam exposure method of segmented mask-pattern transfer type wherein a prescribed pattern is segmented into a plurality of divisions so as to form a segmented pattern in every division and exposure is made through every division one after another, so that the projection of the whole of the prescribed pattern is accomplished. The method includes the steps of carrying out the exposure through every division and transcribing a segmented pattern thereon one after another. The method also includes the steps of carrying out the correction exposure for every projection region of the segmented patterns one after another with a defocused beam of the inverse pattern of the respective segmented patterns, and thereby the proximity effect caused by the pattern exposure is corrected.

Using a dummy frame pattern to improve CD control of VSB E-beam exposure system and the proximity effect of laser beam exposure system and Gaussian E-beam exposure system

Abstract: A new method is provided for E-beam exposure. A new method is provided for variable shaped E-beam (VSB) and Gaussian laser and E-beam exposure systems. The conventional main pattern is, under the method of the invention involving VSB, surrounded on all sides by a dummy frame whereby the dummy frame limits the beam size of the exposure shots that are adjacent to the main pattern. All patterns that are created in this manner are therefore composites using the same exposure shot. This improves the CD uniformity of the pattern by reducing the shot linearity error for VSB exposure systems. For Gaussian beam exposure systems, the exposure shots are at times located exactly over the exposed figure. Typically, gray level is used to simulate the small figure, this however induces proximity effects. The method of the invention therefore also improves the proximity effect of the Gaussian beam exposure systems.

Charged particle beam exposure method

Abstract: PROBLEM TO BE SOLVED: To improve dimensional accuracy of a completed pattern, without increasing the calculation time significantly, and further reduce the number of shots. SOLUTION: A designed pattern width is changed, so as to have half the width of an exposure intensity distribution obtained by the surface integral of the forward scattered terms of a fundamental exposure intensity distribution function over an subject pattern equal to the designed dimension, and a correction exposure amount Qcp is determined so as to have Qcp times that of the sum of the exposure intensity to give the half width and the exposure intensity obtained from the back scattered terms of the fundamental exposure intensity distribution function equal to the threshold of the pattern development of correct the proximity effect. The exposure intensity from the back scattered terms is obtained by a pattern area density method. The plane, on which the pattern to be exposed is arranged, is divided into meshes which are smaller than a block pattern exposure shot, and those among the meshes to which exposure intensities are insufficient applied are respectively conduct supplementary exposure.

Automatic dose optimization system for resist cross-sectional profile in a electron beam lithography

Abstract: An automatic dose optimization system for electron beam lithography is newly developed to get a specified resist cross-sectional profiles. The system takes into account not only the proximity effect but also resist development process. It is experimentally demonstrated that the newly proposed method is superior to the conventional method to fabricate saw teeth like blazed grating pattern for optical diffraction devices.

Electron Beam Lithography Simulation on Homogeneous and Multilayer Substrates

Abstract: A fast simulator for electron beam lithography, called SELID, is presented and applied in the case of homogeneous and multilayer substrates. For exposure simulation, an analytical solution based on the Boltzmann transport equation is used instead of the Monte Carlo. All important phenomena (forward scattering, backscattering, generation of secondary electrons) have been taken into account for a wide range of e-beam energies. The case of substrates consisting of more than one layer (multilayer) is considered in depth as it is of great importance in e-beam patterning. Results of simulation are compared with experimental ones in the case of single pixel exposures. Additionally, simulation results are compared with experimental ones for isolated and dense patterns in the sub-half-micron range, on conventional positive resist on homogeneous and multilayer substrates. By using SELID, forecast of resist profile with considerable accuracy for a wide range of resists, substrates and energies is possible. Additionally, proximity effect parameters are extracted easily for use in any proximity correction package.

Dose and shape modification proximity effect correction for forward-scattering range scale features in electron beam lithography

Abstract: We propose a dose and shape modification proximity effect correction (PEC) for forward-scattering range scale features in electron beam lithography (EBL). An existing dose modification PEC provides good results for the features of size larger than 2/spl alpha/ or 3/spl alpha/ (/spl alpha/ is forward-scattering range parameter). For the forward-scattering range scale features, exposure contrast has too small a value to delineate the features. To delineate the forward-scattering range scale features, the exposure contrast should be increased by using shape modification. In the case of existing dose and shape modification PECs or Hybrid PECs, additional computation time-consuming back-scatter correction is required, or those PECs with large features make additional back-scatter correction unnecessary. Accordingly, for forward-scattering range scale features, we propose a dose and shape modification PEC in which the additional computation time-consuming back-scatter correction is unnecessary.

Electron beam writing method

Abstract: An electron beam lithography apparatus includes (a) an electron beam source emitting an electron beam, (b) a wafer stage on which a wafer is to be mounted and which is horizontally movable, (c) a horizontally movable mask located above the wafer stage, the electron beam passing through the mask and reaching the wafer, the mask having areas in each of which a divisional pattern is formed, the divisional pattern being obtained by dividing a pattern to be written, in accordance with an area density, and (d) a controller which controls a speed of at least one of the mask and the wafer stage for each of the areas in accordance with the area density. The electron beam lithography apparatus can make it possible to compensate for the proximity effect in each of the areas of the mask, ensuring to write a minute pattern with high accuracy.

Method for correcting an optical proximity effect in an interconnect pattern by shortening the legs of cutout patterns to avoid linewidth reduction

Abstract: A method for correcting an optical proximity effect in an exposure process includes the step of extracting corner portions of a mask interconnect pattern, providing a default “L”-shaped cutout correction pattern on the inner corner of the extracted corner portion, extracting a “]”-shaped pattern including a pair of corner portions in proximity, adjusting the distance of the opposing ends of the default cutout correction patterns in the “]”-shaped pattern to have a specified space. The method prevents the width of the straight portion of the “]”-shaped pattern of the resultant interconnect from being made smaller than the design width.

Charged-particle beam exposure method, reticle and manufacturing method of device

Abstract: PROBLEM TO BE SOLVED: To provide a charged-particle beam exposure method or the like, by which a high pattern dimensional accuracy can be attained and the cost can be held down at a low value. SOLUTION: A design pattern to be formed on an induction substrate is set (S21), and the correction of a pattern shape for correcting the proximity effect is calculated regarding the design pattern (S22). A reticle pattern data is prepared, referring to the result of the calculation of the correction of the pattern shape (S23). An actually used reticle is prepared on the basis of the reticle pattern data (S24). A variable shaped beam type electron-beam drawing device is used in this case, and dose adjustment is executed. COPYRIGHT: (C)2002,JPO

Manufacture of optical proximity effect correction mask

Abstract: PROBLEM TO BE SOLVED: To manufacture an optical proximity effect mask capable of highly precisely correcting optical proximity effect without lowering the throughput by adding the exposure correction data of at masked electron beam plotting that are decided based on the correction amount of the optical proximity effect in a photolithography process to mask pattern data SOLUTION: Relation between the correction value of mask dimension and the dimensional error of a resist pattern in the photolithography process is obtained with respect to the designed mask patterns having the various kinds of dimension by the simulation of an optical image or an exposure experiment result Then, the correction value of the mask dimension required for minimizing the dimensional error is decided Based on the correction value, the ideal corrected pattern 6 obtained by correcting the dimension of the designed pattern of a mask is formed Besides, the mask pattern data is constituted of mask shape data and the exposure correction data of a mask electronic beam plotting device decided based on the correction amount of the optical proximity effect Then, the mask is exposed by changing exposure according to the exposure correction data

High Resolution Resists for Next Generation Lithography: The Nanocomposite Approach

Abstract: The SIA roadmap predicts mass production of sub-100 nm resolution circuits by 2006. This not only imposes major constraints on next generation lithographic tools but also requires that new resists capable of accommodating such a high resolution be synthesized and developed concurrently. Except for ion beam lithography, DUV, X-ray, and in particular electron beam lithography suffer significantly from proximity effects, leading to severe degradation of resolution in classical resists. We report a new class of resists based on organic/inorganic nanocomposites having a structure that reduces the proximity effects. Synthetic routes are described for a ZEP520®nano-SiO2 resist where 47nm wide lines have been written with a 40 nm diameter, 20 keV electron beam at no sensitivity cost. Other resist systems based on polyhedral oligosilsesquioxane copolymerized with MMA, TBMA, MMA and a proprietary PAG are also presented. These nanocomposite resists suitable for DUV and electron beam lithography show enhancement in both contrast and RIE resistance in oxygen. Tentative mechanisms responsible for proximity effect reduction are also discussed.

Electron beam lithography

Abstract: PROBLEM TO BE SOLVED: To provide an aperture for correcting the nonuniformity of the pattern line width due to the difference of back scattering electrons between a corner part and central part of an electron beam lithography area. SOLUTION: Lithography opening patterns 23-27 are formed on a second aperture 4 for the electron beam lithography. L-shaped auxiliary exposure opening patterns 28 for correcting the proximity effect are provided adjacently to corner parts of the lithography opening patterns 23, 27 at the outermost sides of the second aperture 4 and have widths allowing an electron quantity below a resolution limit of said resist to pass through.

Method for suppressing optical proximity effect bias within a wafer

Abstract: A method for suppressing the optical proximity effect bias within a wafer by compensating the optical proximity effect within the wafer includes the steps of: Firstly, performing a first exposure step with a first exposure parameter setup to transfer a pattern from a photomask to a first die of the wafer. Secondly, performing a second exposure step with a second exposure parameter setup to transfer the pattern from the photomask to a second die of the wafer, wherein the first and second exposure parameter setups are adjusted according to the local optical proximity effect bias of the dies within the wafer. The exposure parameter setup can be numerical aperture setup, partial coherence setup, exposure energy setup, exposure time setup, exposure light intensity setup, or best focus setup. The light source used in the exposure steps can be an I-line, G-line, KrF laser, ArF laser, X-ray, or e-beam.

Method of reducing optical proximity effect

Abstract: A method of reducing the optical proximity effect of an exposed etch pattern occurred during a conventional photolithography process, wherein a primary pattern according to the present invention is first divided into a plurality of sub-patterns. Each of the sub-patterns formed on a photomask is then exposed under a light source to be sequentially transferred onto a corresponding photoresist layer during a photolithography process. Subsequently, the operating parameters of a stepper used in the photolithography process such as numerical perture, coherence, intensity of energy, and intensity of light are set according to the charts as shown in FIG. 5A, 5B, 6A, 6B, and 6C to obtain desirable critical dimensions, thereby reduces the optical proximity effect. Therefore, an etch pattern with different line pitches can be successfully transferred onto a photoresist layer with each critical dimension of the different line pitches accurately met according to the present invention.

Evaluation of fine pattern definition with electron-beam direct writing lithography

Abstract: Electron beam (e-beam) lithography is one of the potential candidates for defining fine patterns smaller than 100 nm. To increase throughput, variably shaped beams with vector scan and cell projection techniques have been proposed on the e- beam system. In order to achieve high pattern fidelity in the e-beam lithography special care must be taken with respect to effects, that could result from shot-to-shot, subfield-to- subfield, and stripe boundaries. The key considerations on the pattern fidelity are dimension control and edge roughness. In this paper, methods to enhance pattern fidelity are proposed and discussed. A Leica's WEPRINT 200 system (Leica Microsystems Lithography GmbH), which exerts exposure while continuously moving the stage technique to increase throughput, is used for evaluating the effectiveness of these methods. For the dimension uniformity, the important task is to master shot butting, subfield and stripe stitching and counteract the proximity effects. By employing beam sizing for proximity effect correction and double-pass exposure to suppress stitching error, the dimension variation is largely eliminated. Several factors including accelerating voltage, beam size, proximity effect, beam blur due to Coulomb interaction, and process controllability are found to affect the CD accuracy. To improve the CD accuracy, pattern-bias compensation and proximity effect correction methods are employed in 0.1 micrometer range and below. Good results on dimension accuracy are obtained by properly considering the intra- and inter-proximity effects. Finally, the performance comparison between these methods is discussed.

Correcting method of exposure pattern, exposure method, exposure system, photomask and semiconductor device

Abstract: The present invention provides a correcting method of exposure pattern, an exposure method, a exposure system, a photomask and a semiconductor device, which can simplify an operation required for correcting an optical proximity effect of a light shielding film pattern and data processing. A serif pattern ( 37 ) relative to a light shielding film pattern ( 35 ) constituting a layout-designed exposure pattern ( 1 ) is prepared, and the light shielding film pattern ( 35 ) and the serif pattern ( 37 ) is graphically computed so as to correct the light shielding film pattern ( 35 ). An optical proximity effect in exposure is corrected by using the light shielding film pattern ( 35 ), and thereby, it is possible to simplify operational processing required for making an optical proximity effect correction with respect to the light shielding film pattern ( 35 ), and to considerably shorten a processing time for making the optical proximity effect correction.

Investigation of proximity effect correction in electron projection lithography (EPL)

Abstract: An electron projection lithography (EPL) system which projects reticle patterns onto a wafer will be applied to sub 100 nm lithography. Requirements for line width accuracy are very strict as feature sizes are less than 100 nm. For electron beam lithography, proximity effect corrections have always been an important issue for accurate feature width control. In this paper characteristics of several correction methods are examined, and appropriate correction methods for 100 kV EPL are introduced. Employing the shape correction method burdens the reticle pattern preparation system much more than other methods. Therefore a calculation method suitable for 100 kV EPL where the backscatter radius is very wide ((beta) b approximately equals 30 micrometer) and the forward scatter radius is narrow ((beta) f approximately equals 7 nm) has been developed. The calculation of deposition energy by the backscattered electron beam is carried out with a coarse grid but wide range. The calculation of the combined effect of the electron scattering blurs from the features is carried out only within a narrow range. The correction calculation is carried out using both of these results. Using this method, accurate and fast calculations can be achieved. Employing the GHOST correction method increases total exposure cost. The practical GHOST correction methods may also be improved. An additional correction method named shape correction with GHOST is also shown.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High precision mask fabrication for deep X-ray lithography

Abstract: Deep X-ray lithography with synchrotron radiation represents the primary process step of the LIGA technique, by means of which high volume production of micro-mechanical, micro-optical and micro-fluidic components becomes possible. We report on a new approach where the direct patterning of an intermediate mask has been performed by an upgraded Leica ZBA23 shaped beam electron writer with an acceleration voltage of 40 kV. Optimised development and exposure processes as well as the use of particularly performed proximity correction methods allowed to produce feature sizes down to 0.4 μm. Taking CD-values of the final gold absorber structure as a target, an optimised parameter set has been found to manufacture periodic lines-and-spaces structures of 1.5 μm width with an accuracy of 0.18 μm per edge which were written into 2 μm thick PMMA resist. Additionally, new intermediate mask membrane materials have been investigated. Special PECVD deposition processes have been developed in order to produce thin mask membranes made from silicon nitride, silicon carbide, and diamond. We produced a fully operational LIGA working mask with a thickness of 4.5 μm on the basis of a diamond membrane with a 30% thickness uniformity over a process diameter of 60 mm. Finally, thorough investigations have been performed in order to determine the accuracy of structure transfer in the X-ray lithography process to the final LIGA mask. Taking all the structure accuracy limiting aspects into account, we found a runout per edge of 0.15 μm using the BESSY I radiation spectrum as a reference. These data fit very precisely into experimentally obtained results.

Formation of mask pattern and device and mask as well as exposure method

Abstract: PROBLEM TO BE SOLVED: To form an optimum mask pattern corresponding to adjacent conditions by uniformly reducing the size of all exposure patterns in such a manner that the exposure patterns to resist attain optimum exposure in the densest state. SOLUTION: The respective exposure patterns of the photomask pattern are uniformly reduced from a designed pattern by taking a proximity effect into consideration in such a manner that the resist patterns transferred by exposure of the patterns attain the size defined by a design rule even in the region where the exposure patterns are densest (Fig.a). When the arrangement state of the adjacent patterns existing within the predetermined prescribed adjacent condition range coincide with the assigned adjacent conditions, the optimization processing of the pattern shape is executed by expansion toward the direction where the proximity effect hardly appears in correspondence to the adjacent conditions. Namely, the patterns formed at the points where the exposure patterns are coarse are expanded by a prescribed rate in the direction where the proximity effect appears among the directions where the adjacent patterns do not exist (Fig. b).

Method of correcting proximity effect, electron-beam projection exposure device and manufacturing method thereof

Abstract: PROBLEM TO BE SOLVED: To provide a method or the like for correcting the proximity effect which facilitates the manufacture of a reticle for correction exposure and easily conducting correction of the exposure works. SOLUTION: There is a method, in which the complete inversion pattern of an actual pattern for the so-called primary pattern is used for the primary pattern as the pattern of the reticle for secondary exposure. Pattern CAD data prepared for the actual pattern at a time when the reticle is manufactured are used as they are in this case, the inversion pattern can be manufactured simply when a resist in the case of the processing of a reticle pattern is inverted to a negative or positive state, and the number of processes is omitted and the reticle can be prepared efficiently. COPYRIGHT: (C)2002,JPO

A new correction method for dry etch loading effect in photomask fabrication

Abstract: The wet etching process in photomask fabrication could not meet requirements for small features for high density devices having optical proximity correction (OPC) features. Therefore, a dry etching process should be employed in mask making. However, there are some critical issues in dry etching process: one of the most important issues is critical dimension (CD) variation across the mask due to the loading effect during dry etching. CD errors caused by dry etch process are known to be originated from non-uniformity of plasma, non-vertical resist profile, and loading effect due to the various pattern densities. In case of loading effect, we are concerned about only macro-loading effect rather than micro-loading effect because the aspect ratio in the photomask is very small compared to that in the wafer. After dry etch, the patterns surrounded with large chrome area have large CDs because of the lower etch rate. We found that the macro-loading effect was about 5-10nm. And the effective range of the loading effect is amount to more than 10mm. In order to improve the CD variation caused from loading effect, we should optimize process conditions based on plasma uniformity, etch selectivity, resist profile, etc. However, it is a time consuming job. In this paper, we present a new method to improve loading effect, which is used for correcting e-beam proximity effect. Once we know the degree of loading effect, we can compensate it by allocating various doses at necessary locations.

Method for charged particle beam exposure

Abstract: PROBLEM TO BE SOLVED: To execute correction of the proximity effect, which is in accord with the theory and can be easily realized, by a method wherein an exposure intensity distribution function which includes the out-of-focussing of an electron beam as a variable, is used as the exposure intensity distribution function. SOLUTION: An exposure pattern to respond to each manufacturing process of an LSI is decided based on data, which is one on the LSI to be manufactured and is created by a CAD tool or the like, and this exposure pattern is divided into a plurality of shots, a pattern for performing a partial one-shot exposure is extracted. Then, first, uncorrected exposure data are prepared, then a correction of the proximity effect is applied for the uncorrected exposure data using the variation the pattern size variations of an electron beam due to Coulomb force, aberrations and the like, that is, a double Gaussian or triple Gaussian exposure intensity distribution function including the out-of-focussing of beam δof the electron beam as a variable and an electron beam exposure is performed based on the finished corrected exposure data.

Electron beam exposing device and method

Abstract: PROBLEM TO BE SOLVED: To enhance the degree of resolution in a critical resolution region by decreasing the proximity effect caused by the forward scattering of an electron beam. SOLUTION: An electron beam exposure device is contracted the electron beam B emitted from a source of electron beams by a first aperture 3a and radiates it into the pattern of a second aperture 3 and the radiated pattern is exposed and transferred to a resist R of a wafer W by the projection optical system 5 in an electron beam path A. In this case, a first incident angle changing deflector 6a and a second incident angle changing deflector 6b, with which an electron beam B can be made incident with a prescribed tilt angle θi on the surface of the resist R, are provided in the electron beam path A in this electron beam exposing device.

Dose latitude dependency on resist contrast in e-beam mask lithography

Abstract: In mask-making process with e-beam lithography, the process capability is usually affected by exposure profile, resist contrast and development process. Dose latitude depends significantly on these three parameters. In this work, dose latitude between different resist contrasts has been experimentally studied as a function of linewidth, dose, beam size and over development magnitude using commercial PBS and ZEP 7000 resist on a photomask with 10 keV exposure. It has been found that ZEP 7000 resist with high contrast shows lower dose latitude, more sensitivity to the variation of linewidth, dose and beam size except for over development magnitude due to its relatively longer development time.

Inspection of mask pattern

Abstract: PROBLEM TO BE SOLVED: To provide a method capable of carrying out exact inspection even when the pattern formed on a mask of a system to correct a proximity effect by making the size of the pattern different from a design value is inspected for good or not. SOLUTION: There is an extremely large pattern part 5 in a part of a pattern part 4 of the ordinary size. Pattern formation is so executed that the proximity effect at the time of transfer by an electron beam may be corrected at the large pattern part 5, and as a result, the actual pattern 2 is made thinner than the pattern 1 complying with the design value. When, therefore, the inspection of the pattern is carried out by comparing the design size of the pattern and the actually measured pattern detected from the actual pattern edge position, this portion is detected as a defect. The portion, however, is a direction where the pattern is made finer in the direction of correcting the proximity effect and coincides with the direction of the actual pattern 2 and, therefore, the decision of this portion as the defect is averted.

Device and method for electron beam lithography

Abstract: PROBLEM TO BE SOLVED: To obtain an electron beam lithography method and an electron beam lithography device which can practice the correction of an proximity effect with a simple construction in a short time. SOLUTION: When a field is lithographed, pattern area data of adjacent fields are successively read out of a control CPU 11. The respective data are sent to a characteristic value calculation circuit 25 in a proximity effect correction circuit 24 together with the pattern data of a specific field. The characteristic values of the patterns of the respective fields are calculated by the calculation circuit 25 and stored in a characteristic value memory 26. The correction value of a shot time in the field is calculated by a correction value calculation circuit 27 in accordance with the respective characteristic values and stored in a correction value memory 28. The correction value is supplied to a shot time control unit 18 and the shot time of a pattern shot in the field is adjusted so as to correct a proximity effect.

Electron beam exposure system and electron beam exposure method

Abstract: PROBLEM TO BE SOLVED: To enable correction adjustment of the proximity effect of scattered electrons without causing the throughput of an electron beam exposure system to lower and to realize the superior dimensional accuracy of the aligner. SOLUTION: This system is a scatter angle limiting system of an electron beam exposure system, having a mask having a scattered region and limiting apertures for controlling the quantity of passage of scattered electrons which scattered penetratingly in this mask. In this case, the electron beam exposure system is provided with the first limiting aperture 3a, which is fixed at the crossover positions of the scattered electrons or in the vicinities of the crossover positions and has an aperture provided in its central part and closed strip-shaped apertures encircling this aperture, and the second limiting aperture 3b, which is movable on the optical axis of a projection optical system and has an aperture provided in its central part and closed strip-shaped apertures encircling this aperture.

Projection exposure method

Abstract: PROBLEM TO BE SOLVED: To reduce the scattering of the line width of a resist pattern by using a Cr mask for a line and space in a memory cell and a half tone phase shift mask for its peripheral part SOLUTION: A Cr mask 1 is used for a line and space part in a memory cell where the pitch of a resist pattern is narrow, and a half tone phase shift mask 2 is used for the other peripheral parts where the pitch of the resist pattern is wide In this manner, by using the half tone phase shift mask for the parts where the pattern pitch is wide, the thin-line of the line width of a pattern at the peripheral part where the pitch of the pattern caused by the light proximity effect is wide can be suppressed, thus reducing the scattering of the line width of the pattern