Showing papers on "Electron-beam lithography published in 1979"
TL;DR: In this paper, a simulator is described which produces line-edge profiles at various key stages in integrated circuit processing, including the positive resist model of Dill and the string development model of Jewett.
Abstract: A simulator is described which produces line-edge profiles at various key stages in integrated circuit processing. Optical models are included for contact and projection lithography. The effects of multiple wavelengths, defocus, and partially coherent sources may be simulated in projection lithography. The positive resist model of Dill is used with the string development model of Jewett to obtain resist line-edge profiles. The string model is generalized to surface reaction rate limited etching of any layer. The application of the simulator to projection lithography is illustrated with a number of examples including monochromatic and multiwavelength exposure, the effect of a post-exposure anneal, plasma descum, and defocus.
229 citations
TL;DR: In this article, three corrections techniques are discussed: shape-dimension adjustment, region compensation, and self-consistent technique to compensate for proximity effects in regions between shapes, which leads to computational complexities and impracticalities.
Abstract: Electron lithography at micrometer dimensions suffers from a seemingly fatal problem due to proximity effects. Three corrections techniques are discussed. The self‐consistent technique computes the incident electron exposure such that identical average specific fragmentation occurs in each written shape of the pattern. A unique solution, that depends only on the form and on the magnitude of proximity function, is obtained. The unaddressed‐region compensation technique attempts to compensate for proximity effects in regions between shapes; this, however, leads to computational complexities and impracticalities. The shape‐dimension adjustment technique attempts to compute dimension of exposed shapes such that the shapes developed in the resist will have the designed dimension. A set of nonlinear (and impractical) equations are obtained in this case. The implementation of these techniques and the experimental results obtained therefrom are the subject of the two succeeding papers.
146 citations
TL;DR: In this paper, a Monte Carlo simulation of electron scattering in the resist and substrate of a target in electron lithography was used to obtain the spatial distribution of energy deposition in resist, and analytical approximations were subsequently obtained by a least square fit of Gaussian functions to the forward and backward scattered components of these distributions.
Abstract: A Monte Carlo simulation of electron scattering in the resist and substrate of a target in electron lithography was used to obtain the spatial distribution of energy deposition in the resist. Analytical approximations were subsequently obtained by a least‐squares fit of Gaussian functions to the forward‐ and backward‐scattered components of these distributions. The parameters in the analytical functions were deduced and a compendium of values are tabulated for a variety of resist thicknesses, incident electron energies, and substrates. The parameters were found to agree with other parameters that can be physically correlated with electron‐scattering processes and with available experimental data. These approximations and parameters provide quantitative guidelines for understanding and compensating of electron‐scattering and proximity effects in electron‐beam lithography.
98 citations
IBM1
TL;DR: A spectrum of shaped-beam systems which combine projection and scanning techniques has been developed for various lithographic applications as mentioned in this paper, which has increased the efficiency of serial exposure by several orders of magnitude over the basic SEM approach.
Abstract: Recent advances in scanning-electron-beam lithography techniques have increased the efficiency of serial exposure by several orders of magnitude over the basic SEM approach. A spectrum of shaped-beam systems which combine projection and scanning techniques has been developed for various lithographic applications. The first generation of electron-beam production systems at IBM have demonstrated the feasibility of the shaped-beam technique under manufacturing conditions. More advanced shaping techniques such as VSS and Character Projection provide the means to make a high-resolution lithography for VLSI technically and economically feasible.
86 citations
25 Jun 1979
TL;DR: This paper discusses electron beam lithography and the devices and circuits that have been fabricated with this technology.
Abstract: Electron beam lithography is a rapidly maturing technology that has opened the realm of submicron design to the semiconductor device and circuit designer. This improved pattern resolution has already yielded devices and circuits exhibiting higher density, higher operating frequency, and lower operating power than has been possible with other lithography methods. This paper discusses electron beam lithography and the devices and circuits that have been fabricated with this technology.
55 citations
TL;DR: A high-resolution electron beam has been used to generate metal structures 8 nm wide and 10 nm high using contamination resist and dense metal patterns with 25 nm linewidths on 50 nm centers using PMMA resist as mentioned in this paper.
Abstract: A high‐resolution electron beam has been used to generate metal structures 8 nm wide and 10 nm high using ’’contamination’’ resist and dense metal patterns with 25 nm linewidths on 50‐nm centers using PMMA resist. These resist materials together with standard deposition techniques and ion beam milling have been used to prepare a variety of structures on the order of nanometers in dimension. Present metal structure dimensions are limited by electron backscattering events in the substrate, the microstructure of the metallic thin film, and unknowns in the contamination resist process itself. The processing techniques are discussed as well as the preparation of substrates which are almost transparent to the electron beam.
52 citations
TL;DR: A multielectrode probe structure is described in which several thin-film metal electrodes are defined on the outer surface of a glass micropipette using electron-beam lithography, resulting in electrode recording characteristics which are extremely well matched.
Abstract: A multielectrode probe structure is described in which several thin-film metal electrodes are defined on the outer surface of a glass micropipette using electron-beam lithography. Electrode geometries are controlled to within one micron, resulting in electrode recording characteristics which are extremely well matched. Recording sites are 5 , um wide rings spaced 100 , um apart in depth. Analysis and characterization show the structure to be capable of accurately recording tissue potentials with a minimum of tissue damage. Use of these probes in current source-density (CSD) analysis of extraceliular current flow is described.
42 citations
TL;DR: In this article, the importance of mutual repulsion of beam electrons is investigated for conditions relevant to electron beam lithography and a Monte Carlo calculation has been performed which evaluates the spot size for a given beam current and column geometry.
Abstract: The importance of mutual repulsion of beam electrons is investigated for conditions relevant to electron beam lithography. A Monte Carlo calculation has been performed which evaluates the spot size for a given beam current and column geometry. The results show that the beam broadening due to mutual repulsion significantly limits the current density obtainable. Experimental results are presented, and the agreement with theory is excellent. For a column 21.5 cm long operating with a 3 mrad aperture semi‐angle, the spot size was measured as .14 μm at 100 nA, and .30 μm at 1 μA of beam current. The theory predicts that an optimum spot size exists that is proportional to the 1/4 power of the lens spherical aberration coefficient, and to the 3/4 power of the beam current.
39 citations
Patent•
10 Dec 1979
TL;DR: In this article, the energy absorbed by the resist from the electrons, substantially greater at the perimeter of each shape in the pattern rather than at the interior of those shapes, is compensated for by making the energy that is absorbed by resist from electrons more concentrated in the perimeter rather than the interior.
Abstract: In the process of constructing microelectronic circuits on a semiconductor chip, electron-beam lithography is utilized to fabricate high resolution resist patterns. The resolution however, is limited by proximity effects which are due to scattering of the electron-beam as it passes through the resist. In the disclosed method, those proximity effects are compensated for by making the energy that is absorbed by the resist from the electrons, substantially greater at the perimeter of each shape in the pattern than at the interior of those shapes.
34 citations
IBM1
TL;DR: In this paper, the fabrication of 1 µm minimum linewidth FET polysilicon-gate devices and circuits was discussed using vector-scan electron-beam technology and processing.
Abstract: This paper discusses the fabrication of 1 µm minimum linewidth FET polysilicon-gate devices and circuits. These were designed for the tight dimensional ground rules (resolution, linewidth control, and overlay) achievable using direct wafer write scanning electron-beam lithography with individual chip registration. The present work focuses on vector-scan electron-beam technology and processing, while other papers in this series discuss other aspects of the work. Different types of 1 µm MOSFET chips were written on 57 mm Si wafers using a totally automated electron-beam system which performs table stepping, registration to fiducial marks, and pattern writing in a vector scan mode (on an individual shape basis) with control of exposure dose for individual shapes. The pattern data were prepared by batch processing which includes proximity correction as well as sorting of shapes to achieve data compaction and minimal distance between shapes. A novel two-layer positive resist system has been developed to achieve reproducible liftoff profiles over topography and better linewidth control. The final results presented here demonstrate that there are no fundamental barriers to the extension of this work to small dimensions.
32 citations
TL;DR: In this paper, the authors explored intra line and inter line proximity effects and their dependence on beam voltage via computer simulation of electron scattering, energy deposition, and subsequent development in electron beam lithography processes.
Abstract: Intra line and inter line proximity effects and their dependence on beam voltage are explored via computer simulation of electron scattering, energy deposition, and subsequent development in electron‐beam lithography processes. For thin resist films (?1 μm) on silicon substrates,the simulation predicts that smaller linewidths and gaps can be achieved without proximity correction at 10 kV, compared to 20 kV. Experimental confirmation of the predictions is presented.
TL;DR: In this paper, a Monte Carlo simulation for electron scattering trajectories was used to obtain the spatial distributions of absorbed energy in a resist layer, constituting the modeled proximity effect, are in good agreement with experimental results.
Abstract: The dependence of the proximity effect, which deforms electron‐beam exposed patterns, on the substrate material has been investigated theoretically and experimentally. Substrates examined are Si, SiO2, Cr, Mo, Au and their double layers, which are used in LSI fabrication process with a direct writing technique. The proximity effect is approximated as the sum of absorbed energy distributions in a resist layer, which are calculated separately with respect to electron re‐incidence number (Ns) from substrate into resist. A Monte Carlo simulation for electron scattering trajectories was used to obtain the spatial distributions of absorbed energy in a resist. The incident beam extent influence was examined. A new evaluation technique was used to obtain the exposed intensity distributions. The absorbed energy distributions, constituting the modeled proximity effect, are in good agreement with experimental results. The absorbed energy distribution for Ns=0 with a Gaussian incident beam is approximated by the func...
TL;DR: In this paper, the importance of electron scattering on pattern fidelity in electron-beam lithography was examined using computer simulation of the exposure and development of resist images, and it was found that electron scattering can be treated in terms of an effective Gaussian halfwidth which is the quadrature sum of the incident Gaussian halfwidth and the characteristic width for forward-scattered electrons.
Abstract: The importance of electron‐scattering on pattern fidelity in electron‐beam lithography is examined using computer simulation of the exposure and development of resist images. It is found that electron scattering can be treated in terms of an effective Gaussian half‐width which is the quadrature sum of the incident Gaussian half‐width and the characteristic width for forward‐scattered electrons. Linewidth control is improved by reducing the effective half‐width; this is accomplished by using higher beam energies, thinner resists and smaller spot sizes. Developer simulation shows that using 2 pixels per minimum linewidth with a spot size equal to half the pixel size gives better developed images than the more conventional writing strategy which uses four pixels per minimum linewidth and a spot size equal to the pixel size.
TL;DR: In this article, a mathematical formulation for the correction of proximity effects in electron beam lithography has been developed, which involves an efficient evaluation of the proximity interaction between every pair of shapes in the pattern.
Abstract: Mathematical formulations for the correction of proximity effects in electron beam lithography have been developed in the preceding paper. The implementation of these techniques to practical electron lithographic patterns involves (1) an efficient evaluation of the proximity interaction between every pair of shapes in the pattern. This interaction can be computed explicitly in limited cases; an algorithm for general cases is described. (2) The solution of the linear equations that yield the corrections to proximity effect. This is accomplished via a series of algorithms that involve dissecting the data into overlapping zones of different types. Pattern data manipulation is reduced by an algorithm involving generation of additional data, tagging, and sorting.
TL;DR: In this paper, the influence of electron scattering on the resolution of electron beam lithography has been studied and two different Monte-Carlo approaches were used to study the spatial extent of energy dissipation in a thin film of electron sensitive polymer film coated on various thicknesses of silicon substrates.
Abstract: The influence of electron scattering on the resolution of electron‐beam lithography has been studied. Theoretically, we have used two different Monte‐Carlo approaches to study the spatial extent of energy dissipation in a thin film of electron sensitive polymer film coated on various thicknesses of silicon substrates. The two Monte‐Carlo approaches are the conventional continuous‐slowing‐down approximation approach and the direct simulation approach in which individual inelastic scattering is taken into account. Experimentally, we have exposed lithographic patterns on the structures mentioned above. Agreement between both Monte‐Carlo approaches and experiment is satisfactory. Results show that higher resolution in electron beam lithography can be achieved by using thin electron sensitive resist layers and thin substrates. Improvement in proximity effect is also obtained for thin structures.
Patent•
19 Apr 1979
TL;DR: In this article, a halogen atom is selected from the group comprising fluorine, bromine and iodine atoms in a molecule for a lower layer resist in a multi-layer resist process applying an electron beam lithography.
Abstract: PURPOSE:To prevent the charging up of a lower layer resist, and to enable the processing of a resist pattern at a low temp. by using a material contg. a halogen atom selected from the group comprising fluorine, bromine and iodine atoms in a molecule for a lower layer resist in a multi-layer resist process applying an electron beam lithography. CONSTITUTION:In the method for forming a resist pattern according to the multi-layer resist process applying the electron beam lithography, the material which contains at least one kind of halogen selected from the group comprising the fluorine, the bromine and the iodine atoms in the molecule is used for the lower layer resist. The useful halogen contg. material is exemplified by, for example, an acrylic polymer or a styrene polymer, etc. which is substd. for the halogen atom. Said halogen contg. material is applied on the substrate by a technique such as a spin coating method, followed by baking the obtd. layer to form the lower layer resist. Thus, the charging up of the lower layer resist is prevented, and the processing of the resist pattern at the low temp. is permitted.
IBM1
TL;DR: An n-channel single-level polysilicon, 25 nm gate-oxide technology, using electron-beam lithography with a minimum feature size of 1 µm, has been implemented for MOSFET logic applications as mentioned in this paper.
Abstract: An n-channel single-level polysilicon, 25 nm gate-oxide technology, using electron-beam lithography with a minimum feature size of 1 µm, has been implemented for MOSFET logic applications. The six-mask process employs semirecessed oxide isolation and makes extensive use of ion implantation, resist liftoff techniques, and reactive ion etching. A description of the process is given, with particular emphasis on topographical considerations. Implementation of a field etchback after source/drain implant to eliminate a low thick-oxide parasitic-device threshold is also discussed.
Patent•
IBM1
TL;DR: Sub-100A line width patterns are formed on a member by electron beam conversion and fixing of a resist that arrives at the reaction zone point by surface migration into a resist pattern of a precise thickness and width while the member rests on an electron backscattering control support as discussed by the authors.
Abstract: Sub-100A line width patterns are formed on a member by electron beam conversion and fixing of a resist that arrives at the reaction zone point by surface migration into a resist pattern of a precise thickness and width while the member rests on an electron backscattering control support. The resist is for example a contamination film from a vacuum pump oil used in evacuating the apparatus used to perform the process, e.g. silicone oil.
TL;DR: In this article, a theoretical and experimental investigation of the developed profile shape in thick resist layers is described, where the profiles that are exposed by a single line scan at various incident doses and by two adjacent scans with increasing separations between the scans are compared with a threshold solubility model and a development model.
Abstract: A theoretical and experimental investigation of the developed profile shape in thick resist layers is described. The profiles that are exposed by a single line scan at various incident doses and by two adjacent scans with increasing separations between the scans are compared with a threshold solubility model and a development model. Near the neck of the profiles, the predictions of the theoretical models are in good agreement with experiments. In the resist substrate interface regions, the development model is satisfactory but the threshold solubility model is found to be inadequate. A proximity effect correction method is also described in which the edge of the exposed pattern is monitored to obtain accurate pattern fidelity. Experimental results using this method of correction are presented.
TL;DR: The lithographic characteristics of homopolymers and copolymers of substituted styrenes have been determined by electron lithography and compared to polystyrene, which is used as a standard for high contrast among negative resists as discussed by the authors.
Abstract: The lithographic characteristics of homopolymers and copolymers of substituted styrenes have been determined by electron lithography and compared to polystyrene, which is used as a standard for high contrast among negative resists. Homopolymers, as well as copolymers with glycidyl methacrylate, can be almost equal in contrast to the standard. They are more sensitive than it by at least an order of magnitude. For the homopolymers, the order of contrast among the styrene‐substituents is hydrogen?methyl≳chloro∠chloromethy. For copolymers, the order is hydrogen≳chloromethyl≳methyl≳chloro. γ‐values, although a familiar index of contrast and an adequate one when comparing families of materials with similar molecular weight distributions, ignore material variations that are significant in thick relief lithography. Preliminary, patterned exposures of three of these substituted styrenes are compared; poly(3‐chlorostyrene), poly(vinylbenzyl chloride‐co‐glycidyl methacrylate). The limiting feature for each was a 2 μm gap of 0.7 μm final thickness. Better resolution is obtained with different features.
Patent•
09 Nov 1979TL;DR: In this article, an x-ray target made of tungsten is utilized and the apparatus operated to generate the Tungsten M-line, this line being at a wavelength which will be absorbed by the resist normally used in lithography.
Abstract: In order to obtain shorter exposure time and to obtain a longer life in x-ray lithography apparatus, an x-ray target made of tungsten is utilized and the apparatus operated to generate the tungsten M-line, this line being at a wavelength which will be absorbed by the resist normally used in lithography. To develop the resist, which was initially designed for use in an electron beam lithography, a developing method is used in which a initial short development with a high concentration is first carried out followed by a longer, full development with a concentration which is approximately the lowest at which complete development will take place.
TL;DR: Experimental and theoretical study was carried out on cross sectional profiles of resist patterns for line and area exposures using an electron beam exposure system and a new model based on the Spencer and Fano theory for electron energy loss was performed.
Abstract: Experimental and theoretical study was carried out on cross sectional profiles of resist patterns for line and area exposures. Experimental work was performed using an electron beam exposure system, where a PMMA film of 6000 A thickness was used as an electron resist and the incident electron energy was 20 keV. The electron‐beam probe size was measured from a line spectrum of the secondary electron signal when the probe was scanned over a fine gold wire. The diameter of the probe was 5500 A. The developer was a 1:1 solution of MIBK and IPA. The time evolution of the cross sectional profile was obtained from the SEM observation at various development times. Theoretical evaluation of the time evolution was conducted by a combination of Monte Carlo calculation of electron scattering and a well‐known equation for the solubility rate. Monte Carlo calculation was performed with a new model based on the Spencer and Fano theory for electron energy loss. For assumed parameters in the solubility rate equation a reasonable agreement between experiment and theory was obtained in the results of the time evolution of the cross sectional profiles. Also a difference between the Monte Carlo results through use of new and old models is discussed for a typical case of an exposure pattern.
TL;DR: In this article, a new lithographic technique is described which makes it possible to increase the height-to-width (aspect) ratio of electron-beam-exposed patterns in the resist layer, without significantly increasing proximity effects.
Abstract: A new lithographic technique will be described in this paper which makes it possible to increase the height‐to‐width (aspect) ratio of electron‐beam‐exposed patterns in the resist layer, without significantly increasing proximity effects. The technique consists of applying two resist layers on the substrate, separated by a thin metal film. The pattern is electron‐beam exposed on the top resist layer, and after development, a thin (2000–3000 A) gold or other x‐ray absorbing material is used to form an in situ x‐ray mask to expose a much thicker bottom resist layer in an x‐ray exposure system. It is shown that with this technique, lines of 0.25‐μm wide with vertical walls, can be obtained in 2‐μm‐thick PMMA resist or an aspect ratio of eight can be easily achieved. It is also shown that the in situ mask can be registered to a previous level on the workpiece with accuracy better than 0.1 μm.
TL;DR: Computing algorithms have been proposed to handle arbitrarily shaped pattern data to remove overlapping, which causes multiple exposure, to invert polarity of mask patterns that produce negative exposure patterns, and to partition patterns into subfields whose domains are limited by the scanning angle of the electron-beam equipments.
Abstract: A data processing system called Automatic Masking-Data generation for Electron-beam exposure System (AMDES) for drawing submicrometer patterns of integrated circuits has been developed. Electron-beam exposure data are generated based on the mask pattern design data. Distortion of patterns due to electron-beam deflection is compensated for by analyzing the inverse-mapping of the distortion function. Furthermore, a method of compensating for distortion due to the proximity effect is proposed. This method applies to multiple integral of the exposure intensity distribution (EID) function around the characteristic length neighborhood of the representative point. Computing algorithms have also been proposed to handle arbitrarily shaped pattern data to remove overlapping, which causes multiple exposure, to invert polarity of mask patterns that produce negative exposure patterns, and to partition patterns into subfields whose domains are limited by the scanning angle of the electron-beam equipments. By using this system with 1-µm design rule, a highly integrated resist pattern was produced by directly exposing an electron beam onto the wafer.
TL;DR: In this article, a Monte Carlo simulation for electron-beam lithography is presented, where the three-dimensional spatial distribution of the absorbed energy density in a resist was calculated for a 0.8-µm thick poly-methyl methacrylate film on a silicon substrate irradiated by 20-keV electrons.
Abstract: We have developed a computer simulation program based on the Monte Carlo calculation for electron-beam lithography, which can take account of pattern geometry. The three-dimensional spatial distribution of the absorbed energy density in a resist was calculated for a 0.8-µm thick poly-methyl methacrylate film on a silicon substrate irradiated by 20-keV electrons. The pattern geometries investigated here are composed of the two adjacent elements of a 20-µm square and a 1.5×10 µm2 rectangle, where the proximity effect cannot be disregarded. Some exposure experiments under the same conditions were conducted using an electron beam exposure system in the dose range 0.72×10-4 to 5.43×10-4 C/cm2. The plane profiles of the developed resist-pattern agree well with those predicted by the simulation. Though the accuracy of the simulation decreases at low doses, there is a prospect of improvement by introducing the energy-loss formula proposed by Spencer and Fano instead of Bethe's formula used here.
TL;DR: In this article, different combinations of beam-line windows, mask membranes, and thicknesses of absorber assuming the use of PMMA resist are taken into account, and the influence of electrons produced in the substrate and backscattered into the resist is also numerically estimated.
Abstract: Depending on the electron energy of a storage ring, exposure time and contrast due to the mask absorber are calculated. Different combinations of beam-line windows, mask membranes, and thicknesses of absorber assuming the use of PMMA resist are taken into account. The influence of electrons produced in the substrate and backscattered into the resist is also numerically estimated. From these evaluations it is concluded that the optimum electron energy of a storage ring for X-ray lithography is 0.9 GeV at a magnetic field of 1.5 T in the deflection magnets.
TL;DR: In this paper, an n-channel single-level polysilicon, 25 nm gate-oxide technology, using electron-beam lithography with a minimum feature size of 1 /spl mu/m, has been implemented for MOSFET logic applications.
Abstract: For pt. IV see ibid., vol.SC14, no.2, p.268 (1979). An n-channel single-level polysilicon, 25 nm gate-oxide technology, using electron-beam lithography with a minimum feature size of 1 /spl mu/m, has been implemented for MOSFET logic applications. The six-mask process employs semirecessed oxide isolation and makes extensive use of ion implantation, resist liftoff techniques, and reactive ion etching. A description of the process is given, with particular emphasis on topographical considerations. Implementation of a field etchback after source/drain implant to eliminate a low thick-oxide parasitic-device threshold is also discussed.
TL;DR: A novel two-layer positive resist system has been developed to achieve reproducible liftoff profiles over topography and better linewidth control and the final results presented here demonstrate that there are no fundamental barriers to the extension of this work to small dimensions.
Abstract: For pt.V see ibid., vol.SC14, no.2, p.275 (1979). The authors discuss the fabrication of 1 /spl mu/m minimum linewidth FET polysilicon-gate devices and circuits, with emphasis on vector-scan electron-beam technology and processing. Different types of 1 /spl mu/m MOSFET chips were written on 57 mm Si wafers using a totally automated electron-beam system. The pattern data were prepared by batch processing which includes proximity correction as well as sorting of shapes to achieve data compaction and minimal distance between shapes. A novel two-layer positive resist system has been developed to achieve reproducible liftoff profiles over topography and better linewidth control. The final results presented here demonstrate that there are no fundamental barriers to the extension of this work to small dimensions.
TL;DR: In this paper, the authors described an exposure technique that further improves resolution so that 1 μm minimum features can be resolved in 05 μm of x-ray resist using O2 partial pressure in the space separating the mask and the wafer.
Abstract: A previous paper described the formulation of a negative x‐ray resist with markedly improved adhesion that was capable of producing 2 μm minimum features in 05 μm final resist thickness This work describes an exposure technique that further improves resolution so that 1 μm minimum features can be resolved in 05 μm of x‐ray resist The technique utilizes the fact that resist exposure is strongly influenced by the partial pressure of oxygen in the space separating the mask and the wafer The interaction of x‐ray photons and oxygen partial pressure produces an ideal exposure and developing profile for the resist The result is greatly improved adhesion and high resolution of the resist feature This technique may also be applicable to other resist types that are affected by the presence of O2 during exposure Some experimental results show straighter edges and square corners as well as improved surface quality Feature size control is ±01 μm for a 2 μm feature with a ±10% variation in exposure dose about the 50% exposure setting
TL;DR: In this paper, a process for fabricating x-ray lithography masks with structures as small as 0.1 μm is described, where the patterns are made by electron-beam lithography in PMMA resist laid on 1.5μm-thick polyimide membrane.
Abstract: A process for fabricating x‐ray lithography masks having structures as small as 0.1 μm is described in detail. The patterns are made by electron‐beam lithography in PMMA resist laid on 1‐μm‐thick polyimide membrane. The fact we use a very thin substrate strongly reduces the influence of electron backscattering on the resolution. That way it is possible to transfer 0.1 μm lines and spaces in 0.25‐μm‐thick PMMA resist. Gold absorber patterns are formed using electroplating, this technique being able to reproduce the smallest details of the lithography. On the other hand it allows high‐aspect ratios because electroplated gold may be as high as the resist layer. Examples of 0.25 μm lines with 0.05 μm spaces in 0.25‐μm‐thick gold and 0.2 μm spatial period gratings in 0.15‐μm‐thick gold are given.