Showing papers on "Proximity effect (electron beam lithography) published in 2005"

Electron beam writing method and lithography mask manufacturing method

Abstract: A writing pattern to be a correcting object is divided by a rough mesh for a Foggy effect correction and a fine mesh for a proximity effect correction, a rate of an area occupied by the pattern to be written for each of the meshes is obtained, a stored energy based on a Foggy effect and a proximity effect in execution of exposure in a state in which a correction for a calculating object mesh is not carried out at all is calculated, an dose in the fine mesh for a proximity effect correction is obtained by a first calculation in such a manner that an influence of the Foggy effect and the proximity effect is reduced and a pattern and a dimension which can disregard the influence of the Foggy effect and the proximity effect are coincident with each other by the stored energy which is calculated, are calculation is carried out in such a manner that the pattern and the dimension which can disregard the influence of the Foggy effect and the proximity effect are coincident with each other with the influence of the Foggy effect and the proximity effect fixed, and the recalculation is repeated until desirable precision in a dimension is reached.

Method for reducing the fogging effect

Abstract: Method for reducing the fogging effect in an electron beam lithography system wherein the exposure is controlled in order to obtain resulting pattern after processing which are conform to design data. A model for the fogging effect is fitted by individually changing at least the basic input parameters of the control function, the function type is chosen in accordance to the Kernel type used in the proximity corrector. The proximity effect is considered as well and an optimised set of parameters is obtained in order to gain a common control function for the proximity and fogging effect. The pattern writing with an e-beam lithographic system is controlled by the single combined proximity effect control function and the fogging effect control function in only one data-processing step using the same algorithms as are implemented in a standard proximity corrector.

Dimension measuring SEM system, method of evaluating shape of circuit pattern and a system for carrying out the method

Abstract: The present invention relates to a dimension measuring SEM system and a circuit pattern evaluating system capable of achieving accurate, minute OPC evaluation, the importance of which increase with the progressive miniaturization of design pattern of a circuit pattern for a semiconductor device, and a circuit pattern evaluating method. Design data and measured data on an image of a resist pattern formed by photolithography are superposed for the minute evaluation of differences between a design pattern defined by the design data and the image of the resist pattern, and one- or two-dimensional geometrical features representing differences between the design pattern and the resist pattern are calculated. In some cases, the shape of the resist pattern differs greatly from the design pattern due to OPE effect (optical proximity effect). To superpose the design data and the measured data on the resist pattern stably and accurately, an exposure simulator calculates a simulated pattern on the basis of photomask data on a photomask for an exposure process and exposure conditions and superposes the simulated pattern and the image of the resist pattern.

On proximity effect in electron beam induced deposition

Abstract: Beam induced deposition is versatile technique to fabricate nano-structure. In this paper, the proximity effect in electron beam induced deposition was studied, and the beam scan sequence which minimizes the effect was suggested.

Experimental optimization of the electron-beam proximity effect forward scattering parameter

Abstract: The electron-beam forward scattering parameter α characterizes the width of the incident beam plus an additional radius due to scattering of primary electrons in the resist. These “forward scattering” effects can be included in proximity-effect correction algorithms by using the point-spread energy function generated by a Monte Carlo simulation. Alternatively, correction algorithms may use a superposition of Gaussian functions to fit Monte Carlo simulations or to fit experimental data. Long-range (β>10μm) effects due to electrons backscattered from the substrate are well characterized by simulations; however, forward scattering effects are difficult to model or measure. Experimental methods of measuring α include the exposure of dot arrays, line arrays, or so-called “doughnut” patterns over a large range of doses. Proximity parameters are then inferred indirectly through fitting line and dot widths. We have instead used a simpler and faster technique based on the method of [Dubonos et al., Microelectron. ...

A new long range proximity effect in chemically amplified photoresist processes: chemical flare

Abstract: Anomalous linewidth variations of tens of nanometers have been observed for certain chemically amplified resist processes, a phenomenon we call chemical flare These variations are highly undesirable, since they fall outside the scope of normal OPC corrective action Experimental data is presented which clarifies the magnitude and range of chemical flare for two different 193nm resist processes We observed that very weak background exposure, less than half the dose required to clear the resist, can have profound effects when chemical flare is strong A TARC coating was found to completely eliminate chemical flare In the absence of a first principles understanding of this phenomenon, we demonstrate simple screening tests for assessing resist processes

A novel contact hole shrink process for the 65-nm-node and beyond

Abstract: Patterning of sub-100nm contacts for sub-90-nm-node devices is one of the primary challenges of photolithography today. The challenge involves achieving the desired resolution while maintaining manufacturable process windows. Increases in numerical aperture and reductions in target CDs will continue to shrink process windows and increase mask error factor resulting in larger CD variation. Several techniques such as RELACS, SAFIER, and resist reflow have been developed to improve the resolution of darkfield patterns such as contacts and trenches. These techniques are all post-develop processes applied to the patterned resist. Reflow is a fast process with low cost of ownership, but has two major disadvantages of high temperature sensitivity and large proximity bias. SAFIER and RELACS both have much slower throughput and higher cost of ownership than reflow. SAFIER also is sensitive to temperature and has large proximity bias. In this paper, a novel process is described that reduces the diameter of contact holes in resist up to 25nm without proximity effects. This process uniformly swells the resist film resulting in a shrink of patterned holes or trenches. Results are shown for 248nm and 193nm single layer resists, and a 193nm bilayer resist. This process has the potential to be high throughput with low cost of ownership similar to reflow techniques but without the proximity effects and thermal sensitivity observed with reflow.

A flexible and efficient approach to E‐beam proximity effect correction—PYRAMID

Abstract: Electron scattering in the resist causes blurring of the written circuit features in electron-beam (E-beam) lithography, which is referred to as the proximity effect. As the feature size in a circuit pattern is continuously reduced in an effort to increase circuit density, the proximity effect has become too prominent to be ignored any more. Without a proper correction of the proximity effect, the pattern density and feature shapes that can be fabricated would be significantly limited especially for nanoscale circuit patterns. A hierarchical approach, named PYRAMID, was proposed in order to develop a flexible and efficient method for proximity effect correction. It distinguishes itself from other methods in that it takes a two-level approach to exposure estimation and modification of shape and/or dose of circuit features. The hierarchical approach of PYRAMID, which exploits the shape of a typical point spread function (PSF) of the E-beam lithographic process, attempts to reduce the computational requirement without degrading correction accuracy substantially. Through experiments and simulation, it has been demonstrated that PYRAMID has a potential to be a practical E-beam proximity effect correction method. Currently, PYRAMID is being extended for grayscale lithography and nonrectangular features.

Forming method of micropattern

Abstract: PROBLEM TO BE SOLVED: To reduce a misalignment of finished dimension of a resist pattern caused by optical proximity effect SOLUTION: When a photomask having a transparent portion and an optical shielding portion for performing exposure on a resist 7 is formed, a process wherein a region in which a line portion 13a and a contact portion 13b of a pattern of the photomask are adjacent is extracted, and a first mask 11 constituted of the line portion 13a and a second mask 12 constituted of the contact portion 13b are formed, a process wherein exposure is performed on the resist 7 under a first lighting condition by using the first mask 11, and a process wherein exposure is performed on the resist 7 under a second lighting condition by using the second mask 12 are involved As a result, an increase of dimension of the line portion 13a is restrained which is caused by optical proximity effect due to large pattern dimension of the contact portion 13b COPYRIGHT: (C)2005,JPO&NCIPI

Adjusting method for exposure device, pattern forming method, and exposure device

Abstract: PROBLEM TO BE SOLVED: To provide an adjusting method for an exposure device, a pattern forming method, and an exposure device capable of reducing the difference in optical proximity effect between exposure devices, and carrying out stable pattern formation. SOLUTION: An L/S pattern with a pitch P2 is formed which is subjected to deformation of the shape due to optical proximity effect in an exposure device A which is a reference device used in the creation of the OPE rule. Then, in an exposure device B, the same L/S pattern is formed using the same mask, and the coherence factor of the exposure device B is adjusted to achieve the condition that the dimensional difference becomes minimum between the line width PB in that L/S pattern and the line width PA in the L/S pattern formed in the exposure device A. At that time, a relay lens 11 is moved along the optical axis in parallel. Alternatively, the diameter of a lighting stop aperture 20 is changed to adjust the coherence factor. COPYRIGHT: (C)2006,JPO&NCIPI

Lithography evaluating method, lithography process and program

Abstract: PROBLEM TO BE SOLVED: To provide a lithography evaluating method capable of accurately evaluating a proximity effect even when a substrate is not composed of a uniform material. SOLUTION: The lithography evaluating method includes the step (step S1) of preparing the substrate comprising a silicon substrate 1 and a wiring structure containing a silicon oxide film 12 on a silicon substrate 11, and Cu wiring layers 13, 14 in the silicon oxide film 12; the step (step S2) of sorting the substrate into a plurality of areas to be evaluated; and the step (step S3) of comparing the number of the wiring layers with the number of critical wiring layers in each area to be evaluated, to evaluate the proximity effect in each area to be evaluated. COPYRIGHT: (C)2005,JPO&NCIPI

An efficient method to improve the proximity effect for electron beam optical disc mastering

Abstract: For the next-generation optical disc, electron beam mastering has been considered as a high-potential technique to fabricate a high-density optical disc. However, for electron beam mastering, the proximity effect caused by electron backscattering is an important problem. In this study, the influence of the proximity effect on the linewidth (full width at half magnitude, FWHM) and thickness of the residual resist is discussed. Some methods are presented to solve the proximity effect for optical disc mastering, i.e., by raising the electron beam voltage and depositing thin film material with low atomic number on a silicon substrate. In the study, thin film materials such as Al, Ni, SiO2, and Si3N4 are deposited on a silicon wafer to explore the proximity effect. The preliminary experimental results show that raising the electron beam voltage and depositing SiO2 or Si3N4 thin film on a silicon substrate can efficiently solve this problem. Later, the resist with a nano-pattern is transferred into a metal Ni–Co (nickel–cobalt) mould by electroplating. The technique of the Ni–Co electroplating process with hardness at least Vicker hardness (Hv) 650 and residual stress below 1.5 kg mm−2 is developed. Then, with the Ni–Co mould, a modified LIGA process is applied to produce a high-density optical disc. The Ni–Co mould serves as the master for the hot embossing process to replicate the nano-pattern onto the PMMA sheet. Since the feature size is down to the nanometre range, the study presents an innovative demoulding mechanism to demould the master from the PMMA sheet without damaging the nanometre patterns.

Method for estimating pattern shape in charged particle beam exposure transfer, and method for determining reticle pattern used in charged particle beam exposure transfer

Abstract: PROBLEM TO BE SOLVED: To provide a method for estimating the pattern shape in a charged particle beam exposure transfer by decreasing the number of repeated calculations of a proximity effect and a blur to be able to shorten the computation time for proximity effect correction. SOLUTION: An average backward scattering amount is computed for one whole chip for the exposure of each sub-field. When a backward scattering amount in the vicinity of some pattern equals to the average backward scattering amount, the threshold value is determined so that a pattern deformation amount by the proximity effect correction is zero to correct the proximity effect with the use of the threshold value. COPYRIGHT: (C)2005,JPO&NCIPI

Through-process window resist modelling strategies for the 65 nm node

Abstract: Ensuring robust patterning after OPC is becoming more and more difficult due to the continuous reduction of layout dimensions and diminishing process windows associated with each successive lithographic generation. Lithographers must guarantee high imaging fidelity throughout the entire range of normal process variations. As a result, post-OPC verification methods have become indispensable tools for avoiding pattern printing issues. The majority of these methods are primarily based on lithographic simulations of pattern printing behaviour across dose and focus variations. The models used for these simulations are compact optical models combined with one single resist model. Even if very predictive resist models exist, they have often a large number of parameters to fit and suffer from long computing times to execute the simulations. Simplified resist models are thus needed to enhance run-time computing during simulation. The objective of this study is to test the predictability of such resist models across the process window. Two different resist models will be considered in this study. The first resist model is a pure variable threshold resist model. The second resist modelling approach is a simplified physical model which uses Gaussian convolutions and a constant threshold to model resist printing behaviour. The study concentrates on poly layer patterning for the 65 nm node. Examples of specific simulations obtained with the two different techniques are compared against experimental results.

Electron beam lithography with negative Calixarene resists on dense materials: Taking advantage of proximity effects to increase pattern density

Abstract: A high-resolution negative Calixarene resist has been used to pattern 2-nm-thick TiO2 films on 50-nm-thick Pt layers by electron beam lithography, in order to carry out site controlled growth of Pb(Zr,Ti)O3 structures. Single dot structures have been written in a 60-nm-thick Calixarene layer at e-beam acceleration voltages of 10 kV (100 pA) and 20 kV (200 pA). The necessary dose for complete dot development ranged from 5 to 25mC∕cm2. Due to the high density Pt layer, the dot-size depended very much on the volume of backscattered electrons. The minimum dot size (70 nm) was found to lie in the range of the resist film thickness. Proximity effects have been studied. At smaller beam energies, a reversed proximity effect has been observed, in the sense that the dot size decreased due to proximity. An irradiation model is proposed based on exposure from bottom to top, and taking into account a competition between cross-linking and bond-scission.

Electron-beam lithography simulation for EUV mask applications

Abstract: Extreme-ultraviolet-(EUV) mask fabrication using electron-beam lithography has to eliminate the proximity effect defects, for the accurate representation of the patterned features. One special characteristic of EUV masks is that they contain a multilayer stack of repeated Si/Mo thin layers. This has to be considered explicitly in the simulation of electron-beam energy dissipation calculation using Monte Carlo methods. In a first approximation to the problem of electron scattering in a multi-layer substrate, the continuous slowing down approximation utilizing the Rutherford differential cross section is used in order to describe the electron inelastic energy loss mechanism and determine the amount of deposited backscattered energy, in the resist film on top of the multi-layer substrate. Three-dimensional modeling is used and in this first attempt to describe the process, no secondary electron generation or other excitation processes are considered. The effect of the number of layers and their relative thickness in terms of incident electron energy is investigated.

Photomask for forming contact pattern to improve profile of edge part in main pattern

Abstract: PURPOSE: A photomask for forming contact patterns is provided to correct proximity effect by unifying the light strength on both of the center and the edge part of the main pattern, and thus to improve the profile of the edge part of the main pattern. CONSTITUTION: The photomask for forming contact pattern comprises main patterns(540) to define light exposure area where transfer of pattern to a semiconductor substrate is occurred, and at least one auxiliary pattern(500), which is aligned on the extended center lines of the main patterns and has a width as much as the transfer of pattern to the semiconductor substrate is not occurred.

Fabrication of identical sub-100 nm closely spaced parallel lines using electron beam lithography

Abstract: The electron proximity effect makes it difficult to fabricate uniform patterns at nanometer scale. A simple scheme to correct the effect is presented and applied to fabricate 100 parallel lines spaced at 250 and 500 nm on a photoresist mask using electron beam lithography. The width of each line is less than 100 nm and nearly identical. Two rectangles adjacent to the first and the last lines were exposed with a dosage below the threshold that the electron beam resist requires for development. The linewidths are more uniform with this proximity effect correction than without it. This technique has been used to fabricate ion-damaged high temperature superconducting Josephson junction arrays.

Optimization of distributed implementation of grayscale electron-beam proximity effect correction on a temporally heterogeneous cluster

Abstract: Grayscale electron-beam lithography is one of the techniques used in transferring circuit patterns with multi-level structures onto substrates. The proximity effect caused by electron scattering imposes a severe limitation on the ultimate spatial resolution attainable by e-beam lithography. Therefore, proximity effect correction is essential particularly for fine-feature, high-density circuit patterns. One difficulty is that it is extremely time-consuming due to the intensive computation required in the correction procedure and a large size of circuit data to be processed. Hence, it is an ideal candidate for distributed computing where the otherwise-unused CPU cycles of a number of computers on a network (cluster) can be efficiently utilized. In this paper, optimization of the distributed grayscale proximity effect correction procedure previously developed is addressed for minimizing the correction time. Also, a different circuit partitioning approach (localized partitioning) is considered.

Methods of proximity effect correction in electron beam lithography

Abstract: Proximity effect is one of the most important limitations to the resolution of electron beam lithography.The mechanism of proximity effect was introduced.Some correction methods of proximity effect such as GHOST,pattern area density map and shape modification were described in detail,including its principle,correction procedure and efficiency.The advantages and shortages of these methods were also given.

Low energy electron beam proximity projection lithography

Abstract: The low energy electron beam proximity projection lithography (LEEPL) system consists of three properties: low energy electron beam, a parallel beam, and proximity projection. The low energy electrons increase the effective resist sensitivity and greatly minimize the proximity effect. Over a 20 µm depth of focus is achieved by the parallel beam on the proximity projection. The subdeflection system of the LEEPL system is useful in correcting the mask distortion and chip distortion on the wafer by a correction data map corresponding to the field, because of the space (>30 µm) between the wafer and the mask. The overlay accuracy of the machine itself is less than 14 nm and that of mix and match is less than 25 nm. This implies that the overlay between the LEEPL system and an ArF scanner in both the x and y directions are obtained. This machine shows the 48 nm CH resist patterns as the ultimate resolution. The cost of ownership (CoO) of the LEEPL system for a 65 nm node device will be approximately less than $25/wafer/layer and the value is lower than that of an ArF scanner.

Mask for electron beam exposure, and method and device for electron beam exposure

Abstract: PROBLEM TO BE SOLVED: To provide a proximity effect correction mask required for correcting proximity effect occurring on the periphery of an adjoining pattern drawn by using a partial collective exposure mask precisely by a partial collective exposure method, to provide a proximity effect correction method employing that mask, and to provide an electron beam exposure device performing proximity effect correction. SOLUTION: In the method for the electron beam exposure, exposure is repeated on the periphery of an adjoining pattern drawn by using a partial collective exposure mask by using an electron beam exposure mask having proximity effect correction openings arranged such that the size of the openings varies periodically at a predetermined ratio in the order of arrangement. Repeated exposure on the periphery of the pattern may be performed using a part of the electron beam exposure mask. COPYRIGHT: (C)2007,JPO&INPIT

Mask pattern determining method

Abstract: PROBLEM TO BE SOLVED: To provide a mask pattern determining method, capable of highly precisely and reliably judging an optical proximity effect compensated pattern to exposure a circuit pattern having the desired electrical characteristics. SOLUTION: The method includes steps of performing optical simulation to determine a plurality of candidate patterns to be a candidate of the optical proximity effect compensated pattern; producing a mask having the plurality of candidate patterns; forming a plurality of circuit patterns on a wafer by using the mask; measuring the electrical characteristics of each circuit pattern; and determining a candidate pattern, corresponding to the circuit pattern having the desired electrical characteristics as the optical proximity effect compensated pattern. COPYRIGHT: (C)2006,JPO&NCIPI

Method of exposure and mask

Abstract: PROBLEM TO BE SOLVED: To provide a method of exposing which can control a pattern line width by correcting a proximity effect by making a dose in a small region on a substrate to be transferred uniform even when a pattern array on a master and a pattern array on the substrate to be transferred are different. SOLUTION: In the method of exposure, first, a mask is formed. A device pattern small region and a proximity effect correcting pattern small region are formed on the mask. When the device pattern small region is formed, a size is corrected by assuming that the amount of the exudation of the dose from the adjacent subfield is maximum. The proximity effect correcting pattern small region is obtained by forming a dose supplementing pattern on the outer periphery of the small region. Here, a plurality of types of the proximity effect correcting pattern small regions which correspond to the pattern array of the periphery are formed. Then, the device pattern small region is exposed/transferred on a wafer. When the proximity effect correction is needed, the suitable proximity effect correcting pattern small region is superposed on the device pattern small region and exposed. COPYRIGHT: (C)2005,JPO&NCIPI

Comparison of different approaches for the correction of residual mask proximity effects

Abstract: Linearity- and proximity effects do exist on actual masks even if manufactured with current state-of-the-art processes. The impact of these short-range mask effects on the results of the optical lithography for features sizes relevant in the 90nm-node is investigated. For this purpose, an approach is chosen which employs mask process simulations in combination with simulations of optical lithography. Two mask models are deduced and verified from measurement data of an existing mask process. The lithographic results are simulated using parameters of current optical- and process models. Both mask models are used to evaluate the impact of the mask proximity effects on the printing results of optical lithography for critical pattern geometries. The differences in the mask proximity characteristics lead to additional pattern-dependent CD-offtargets after wafer lithography. Additionally, a mask-process dependent sensitivity of the CD-offtarget on the presence of optical sub-resolution assist features is observed. Based on these simulation results, the efficiencies of two techniques for the correction of the mask proximity signatures are evaluated. The application of mask sub-resolution features is compared with model-based data correction on mask level. Mask sub-resolution assist features reduce the influence of the mask process significantly and provide an enhanced stability against mask process fluctuations. Data correction yields even better correction results at the cost of an increased complexity due to the susceptibility to changes of the mask processes characteristics.

Electron projection lithography method

Abstract: PROBLEM TO BE SOLVED: To provide an electron projection lithography method which appropriately corrects variations in the optimum dose caused by the proximity effect and has improved line width control. SOLUTION: A reference bias is determined on condition that the dose (reference dose, reference dose level) on the surface of a sensitive substrate, which is assumed to be able to obtain a predetermined line width with no mask bias correction, has a margin, which is an indicator of variations in the line width caused by unexpected variations in the dose, of 5 nm/μC/cm 2 or less. On the basis of the reference bias, the amount of mask bias for each element of a pattern is calculated, and correction is made to give dimensional change (reshaping) to each element. COPYRIGHT: (C)2005,JPO&NCIPI

Analysis of various blur effects on mask CD distortion

Abstract: Implementation of high resolution E-beam tools is an attractive candidate for next generation lithography. To understand the forward scattering blur and proximity in 100kV E-beam tool, we studied E-beam acceleration voltage effects on dose sensitivity and iso-dense CD bias. We measured and analyzed the dose sensitivity (nm/%dose) near the design CD using various local density patterns. Proximity effects due to backscattering were much larger in 100keV exposure and caused the degraded dose sensitivity. We made a simple model and analyzed each contribution from a resist process, forward scattering and backscattering. We concluded that backscattering was the major reason of decreasing ILS(Image Log Slope) and the difference of forward scattering blur between 50 and 100 keV was negligible. Backscattering contribution compared to that of forward scattering was two times larger in the 100keV exposure, which can make accurate CD control difficult.

Method for forming pattern, method for manufacturing semiconductor device, phase shift mask, and method for designing phase shift mask

Abstract: PROBLEM TO BE SOLVED: To improve a dimensional precisision as a whole semiconductor device by reducing the influences of a proximity effect due to optical interference, and reducing the influences of aberration of a projection lens such as including coma aberration. SOLUTION: In the method for forming the pattern, a plurality of gate patterns 204 parallel to one another are formed on a resist 200 in a predetermined circuit block region 102 by exposure through a phase shift mask having apertures with two kinds of inverted phases. When the spacing between adjacent gate patterns 204 exceeds a preliminarily determined maximum allowable pitch, a virtual pattern 208 is laid between the adjacent gate patterns 204, the virtual pattern being parallel to the gate patterns 204 and at a distance smaller than the maximum allowable pitch; and phases in different types are alternately assigned between each gate pattern 204 and the virtual pattern 208 laid parallel to each other, in the arrangement direction of the patterns. COPYRIGHT: (C)2006,JPO&NCIPI

Method for generating mask pattern data/mask inspection data, and method for manufacturing/inspecting photomask

Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing/inspecting a photomask by which the defect detection sensitivity can be enhanced. SOLUTION: The method includes steps of: preparing design data of a semiconductor device; preparing lithography conditions relating to the lithography process for transferring a mask pattern formed in a photomask onto a wafer and wafer process conditions relating to processing the wafer using the pattern transferred onto the wafer; preparing a first proximity correction rule or a first proximity correction model to correct the proximity effect relating to the lithography conditions and the wafer process conditions; creating mask pattern data based on the design data and the first proximity correction rule or the first proximity correction model; and creating mask inspection data corresponding to the mask pattern data. COPYRIGHT: (C)2006,JPO&NCIPI