Showing papers on "Proximity effect (electron beam lithography) published in 1981"
TL;DR: In this article, a new method for computing proximity effect corrections for submicron electron-beam lithography is introduced based on a fast algorithm for shape partitioning to gain better control for resultant exposure intensity distribution across each shape in the pattern.
Abstract: A new method for computing proximity effect corrections for submicron electron‐beam lithography is introduced It is based on a fast algorithm for shape partitioning to gain better control for resultant exposure intensity distribution across each shape in the pattern By careful investigation of the intrashape and the intershape proximity effects the program supplies a means of controlling the submicron pattern delineation Values for the parameters of the double Gaussian function used in the calculation of the dose variation factors are given for a variety of exposure conditions Results of the application of the program to delineation of submicrometer patterns in PMMA and AZ 1350 resist on silicon substrate are presented
37 citations
TL;DR: In this article, thin film silicon is found to be a desirable interlayer material for e-beam lithography with multilayer resist systems, and lines as narrow as 200 nm in 2 μm of Hunt positive resist were holographically produced.
Abstract: Thin film silicon is found to be a desirable interlayer material for e‐beam lithography with multilayer resist systems. It is easily etched in CF4 plasma (Si/PMMA: 30/1) yet resists O2 reactive ion etch (Si/HPR: 1/300). It is sufficiently conductive to avoid charging effects, both during lithography and SEM inspection. High optical contrast aids in inspection. Monte Carlo calculations show that a 2.5 μm bottom layer of polymer can substantially alleviate the proximity effect, even with an 80 nm Si interlayer. Pattern transfer with less than 100 nm linewidth loss is demonstrated. Lines as narrow as 200 nm in 2 μm of Hunt positive resist were holographically produced.
24 citations
TL;DR: In this paper, an experimental and theoretical study on a correction method of the proximity effect which contains the consideration of the three-dimensional profile of a resist is presented. But the work is limited to two-dimensional exposure intensity distribution (EID).
Abstract: Electron‐beam fabrication offers several important advantages for lithography, including a capability of geometries smaller than one micrometer, a high adaptability to automation and the ability to write directly on a Si wafer without the need for a mask. However, for submicron patterns, a proximity effect is observed by the behavior of incident electrons in a resist. In electron‐beam lithography the exposure intensity distribution (hereafter EID) is an essential physical quantity for implementing a proximity effect correction. There are many correction methods and several methods have been tried to correct for practical devices. However, the variation of the EID along the distance into the resist from the surface is neglected, and only a two‐dimensional EID is presented in those articles. The present paper describes experimental and theoretical study on a correction method of the proximity effect which contains the consideration of the three‐dimensional profile of a resist. It has been found from a Monte Carlo simulation that a cross‐sectional profile can be controlled by an additional exposure at the vicinity of a pattern edge. With this method, for example, an undercut resist pattern, which is suitable for a lift‐off process, can be obtained, avoiding as a whole the overdose on a pattern. A 0.5 μm line and space pattern with 1 μm thickness PMMA has been easily obtained, namely, when under‐developed, the wall profile of the resist becomes rather steep, and when properly developed, the profile becomes undercut.
20 citations
TL;DR: A variably shaped electron beam exposure system (EB55) with a high exposure rate was developed for direct beam lithography of 0.5 μm patterns in this article, where the column design facilitates a shortened distance between the object and its image plane.
Abstract: A variably shaped electron beam exposure system (EB55) with a high exposure rate is developed for direct beam lithography of 0.5 μm patterns. The electron beam column consists of seven magnetic lenses. The projection lens is specially designed to minimize deflection aberations and beam landing angle deviation on the wafer. The column design facilitates a shortened distance between the object and its image plane. Accelerating voltage is 30 kV due to decreased Coulomb interaction and proximity effect. In a shaped beam system, the electron gun should have a wide emission angle, high brightness, and large crossover size. A square rod type LaB6 cathode is developed for this purpose. The shaped beam is vector scanned by electrostatic deflection plates and electromagnetic coils. The scanning area is 2.6 mm square and the maximum beam size is 5.10 μm square. The size change unit is 0.02 μm. A beam current density higher than 10 A/cm2 is obtained with a small beam covergence angle. A shape edge slope smaller than ...
17 citations
TL;DR: A new concept, the dose compensation curve, is described for use in a proximity effect correction algorithm which automatically corrects the exposure dose factor in the electron‐beam data base for vector scan machines.
Abstract: A new concept, the dose compensation curve, is described for use in a proximity effect correction algorithm. The dose compensation curve links dose compensation factors, developed resist images, and calculated values of energy density at pattern boundaries. An experimentally measured dose compensation curve agrees very well with theoretical predictions. This technique has been successfully implemented in a fast promixity‐effect correction algorithm which automatically corrects the exposure dose factor in the electron‐beam data base for vector scan machines.
15 citations
TL;DR: In this article, an electron beam lithography system designed for making structures with dimensions in the range 100 to 1000 A is described, where the beam diameter is 10 A and the maximum beam energy is 100 keV.
Abstract: An electron beam lithography system designed for making structures with dimensions in the range 100 to 1000 A is described. The beam diameter is 10 A and the maximum beam energy is 100 keV. The system is calibrated for resist exposure by measuring the beam size and current after magnifying it with projector lenses. The beam is deflected electromagnetically under computer control and vector scanning is used during lithography. The system has been used to make fine lines and grids with linewidths in the range 150 to 500 A. Relatively dense structures with large ratios of resist thickness to linewidth have been demonstrated on both thick and thin electron‐transparent, silicon substrates with the system operated at 50 keV. Results have been obtained on both single layer crosslinked resists and double layers of crosslinked resists and PMMA. It is concluded that finer lines and more densely packed structures over larger areas can be obtained on solid substrates using 100 keV beam energy.
15 citations
TL;DR: In this article, a new method for computing proximity effect corrections for submicrometer electron beam lithography is introduced, based on a two-parameter resist development model and the restatement of the proximity effect problem as a linear programming problem.
Abstract: A new method for computing proximity‐effect corrections for submicrometer electron beam lithography is introduced. It is based on a two‐parameter resist development model and the restatement of the proximity‐effect problem as a linear programming problem. Example solutions in several relevant physical regimes are presented.
11 citations
TL;DR: This work has evolved a scheme which separates the center from the edges of designed shapes and investigates tradeoffs between the CPU time it takes to process these designs and the dose correction of the resultant shapes.
Abstract: Future device technologies will call for the use of very dense and pseudorandom logic patterns. Microfabrication techniques will have to cope with a large number of different designs which are essentially nonrepetitive (e.g., logic). Electron beam technology will also have to be concerned with the large amounts of CPU time it will take to process these designs, especially when considering correction for the scattering of electrons in the resist and substrate (the proximity effect). Proximity correction is divided into the partitioning of design shapes and the dose correction of the resultant shapes. For partitioning, we have evolved a scheme which separates the center from the edges of designed shapes. The centers are given a fixed dose increase of electron exposure to ensure their development and the edges are sent to the proximity correction routine. This will save CPU time for a design which has an abundance of large shape patterns. We have also investigated tradeoffs between the CPU time it takes to s...
5 citations
01 Feb 1981
TL;DR: In this paper, an experimental and theoretical investigation of the more important parameters which affect the developed profile shape in electron-beam lithography is described, based on a Monte Carlo method of simulating electron scattering in the substrate to calculate the energy dissipation in the electron resist layer for a scanned electron beam.
Abstract: An experimental and theoretical investigation of the more important parameters which affect the developed profile shape in electron-beam lithography is described. The theoretical approach is based on a Monte Carlo method of simulating electron scattering in the substrate to calculate the energy dissipation in the electron resist layer for a scanned electron beam. The current distribution in the beam is taken into account with a separate convolution procedure. The developed profile shape is obtained with a threshold solubility model which predicts a threshold energy density of 6.58 × 10 21 eV/cm 3 . A development simulation using the string method is used to predict the profile shape when the development process becomes a significant factor at a resist thickness of about 0.7μm. Finally the proximity effect is investigated by means of adjacent line experiments and compared with the predictions of the threshold solubility model.
4 citations
Patent•
24 Apr 1981
TL;DR: In this article, the half-width of the electron beam at least in the scanning direction is set to be smaller than the scanning pitch, and the halfwidth A2 in the direction to be a smaller ellipse than the scan pitch B. This enables the pattern edge perpendicular to the scanning directions to be almost straight as well as the proximity effect to be reduced by the difference between the half width A2 and scanning pitch B, so that a desired resist pattern is obtained.
Abstract: PURPOSE:To permit a simple electron beam lithography to reduce the proximity effect and to obtain a desired resist pattern by setting the half-width of an electron beam spot in the scanning direction so as to be smaller than the scanning pitch. CONSTITUTION:When lithography is performed by scanning with a spotlike electron beam, the half-width of the electron beam spot at least in the scanning direction is set to be smaller than the scanning pitch, preferably, the half-width is set to be 2/5-3/5 of the scanning pitch. This permits the proximity effect to be greatly reduced, and thus any pattern, large or small, to be obtained more close to a desired geometry and dimension. Moreover, it is effective to set the half-width A1 in the direction perpendicular to the scanning direction so as to be almost equal to the scanning pitch B, and the half-width A2 in the scanning direction to be a smaller ellipse than the scanning pitch B. This permits the pattern edge perpendicular to the scanning direction to be almost straight as well as the proximity effect to be reduced by the difference between the half-width A2 and the scanning pitch B, so that a desired resist pattern is obtained.
4 citations
TL;DR: In this paper, a mask stencil problem is overcome by distributing the pattern to be printed on two complementary masks, and the double dose deposited in the central position of the shape modifies the development process so that the proximity effect can be corrected.
Abstract: Electron beam proximity printing employs shadow projection for submicron lithography. The pattern mask has physical holes for the transmitted electrons. The mask stencil problem (ring shaped apertures would fall out of these masks) is overcome by distributing the pattern to be printed on two complementary masks. The use of two complementary masks provides means to correct the proximity effect, known to impede micron resolution in electron beam lithography. To that end, for a shape in the first complementary mask a smaller correction shape in the second is introduced. The double dose deposited in the central position of the shape modifies the development process so that the proximity effect can be corrected. Experiments are reported which demonstrate the feasibility of this proximity correction method.
TL;DR: In this article, the Weibull probability density functions are used to approximate the lateral energy dissipation profiles determined by Monte Carlo calculations of 20-keV electrons in polymethylmethacrylate (PMMA), and their application to simple line and square patterns of electron-beam exposure are also discussed.
Abstract: Monte Carlo calculations have been used extensively to study the energy dissipation of electrons penetrating into solid materials both in the direction of the initial electron trajectory and lateral to it. Knowing the lateral energy dissipation is important for the prediction of proximity effects in electron‐beam lithography and limiting resolution in scanning electron microscopy. The Weibull probability density functions are shown to approximate the lateral energy dissipation profiles determined by Monte Carlo calculations of 20‐keV electrons in polymethylmethacrylate (PMMA), and their application to simple line and square patterns of electron‐beam exposure are also discussed.