Simulating the effects of pattern density gradients on electron-beam projection lithography pattern transfer distortions (original) (raw)
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Mask membrane distortions due to pattern transfer for electron-beam lithography (SCALPEL) masks
Microelectronic Engineering, 1999
in order to successfully employ Scattering with Angular Limitation Projection Electron-Beam Lithography (SCALPEL) to produce integrated circuits with features below 0.13 ~tm, mask membrane distortions (which lead to pattern placement errors) must not exceed the error budget. When designing a mask, finite element (FE) models are created to identify sources of distortion and quantify the resulting errors. Distortions arise during fabrication, mounting, and in situ exposure of the mask. The focus of this study was to determine the mask membrane distortions induced during the pattern transfer process for a large format SCALPEL mask. Three cases were investigated: the IBM Talon pattern, 100% removal of the scatterer layer, and 50% removal of the scatterer layer. The IBM Talon pattern was chosen to quantify typical pattern specific-distortions while the other two cases, 100% and 50% removal of the scatterer layer, were investigated to determine distortions corresponding to worst case situations.
J. Vac. Sci. Technol. B, 2002
Electron projection lithography ͑EPL͒ is one of the leading candidates for the sub-65 nm lithography node. The development of a low-distortion mask is critical to the success of EPL. This article proposes and analyzes two new EPL mask formats described as a ''corrugated-continuous membrane mask'' and a ''carbon-continuous membrane mask.'' Novel process flows for the manufacture of these masks have been developed at Team Nanotec GmbH. Resonant frequency stress measurements of the ultrathin membrane bilayers were completed and subsequently used in the finite element simulation of the mask fabrication and pattern transfer. The new mask types have the benefits of the lower distortions of a typical continuous membrane mask, but maintain the advantage of the higher throughput stencil format because of the ultrathin films. In addition, the proposed masks remove the need for pattern splitting typically used with complementary systems.
Simulating the mechanical response of electron-beam projection lithography masks
J. Vac. Sci. Technol. B, 2000
This article describes the results of distortion simulations for Motorola's 200 mm electron-beam projection lithography ͑EPL͒ mask due to the fabrication process, pattern transfer, and mounting. Finite element models have been created as predictive tools, which incorporate the orthotropic elastic material properties of single crystal silicon. Both membrane-flow and wafer-flow processes have been simulated, identifying the significant advantage of the former. Modeling results for parametric studies of the fabrication process and the effects of mounting under gravitational loading are presented. The predictive studies illustrate that the metal layer ͑Cr/TaSiN͒ stress most strongly influences the image placement error. It is also shown that common mounting techniques for e-beam writing and exposure are essential for minimizing pattern placement errors.
Assessment of image placement errors induced in electron projection lithography masks by chucking
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2004
Electron projection lithography (EPL) is under active development, with potential applications at the sub 65nm nodes. In order to meet the stringent error budgets in this regime, image placement (IP) errors induced by chucking the mask during e-beam patterning, metrology, and exposure must be characterized and minimized. The focus of this study is to assess the distortions induced in200-mm-diam EPL stencil masks by chucking during e-beam patterning and EPL exposure. High-throughput test masks (with 3.39mm square membrane windows) were evaluated, to assess IP errors throughout a typical mask process flow. Finite element structural models were developed to simulate the response of the test mask during each processing step. Finally, the results of the analysis were used to identify and characterize the sources of IP errors.
Stress and image-placement distortions of 200mm low-energy electron projection lithography masks
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2004
Low-energy electron projection lithography (LEEPL) is a candidate for next generation lithography and thus the 1× LEEPL mask requires a stringent local image placement (IP) error budget. Applying a doping method with silicon-on-insulator substrates, 700-nm-thick membranes were investigated for stress control and in-plane distortion (IPD), which are the main contributors to local IP errors. Stress control results show that at a dopant concentration of 6.74×1019∕cm3, the membrane stress in a 10mm test structure is 8.4MPa. Also stress variation is excellent at 0.3MPa across a 200mm complementary stencil mask on support strut-type LEEPL mask. The IPD results indicate that small membrane window size, low void fraction, as well as low membrane stress is the proper strategy to allow a stencil mask with dense stencil patterns to meet required IPD. Additionally, the local IP errors of large scale integrated 90nm hole pattern were demonstrated.
Modeling mask fabrication and pattern transfer distortions for EPL stencil masks
Microelectronic Engineering, 2001
Electron-beam stencil lithography, a next-generation lithography technology planned for the sub-100 nm nodes, requires the manufacture of a low distortion mask. Fabrication and pattern transfer processes were modeled for the 4-inch format mask using finite element simulations. A comparison of pattern transfer distortions between the wafer flow and the membrane flow process was conducted. Sensitivity to the stress level of the membrane layers was also investigated. In-plane and out-of-plane distortions were reported for each step in the fabrication process, utilizing the IBM Falcon pattern format.
J. Vac. Sci. Technol. B, 2001
The mounting standard based upon a proposed four-pad electrostatic chuck for the 200 mm PREVAIL and SCALPEL® masks was assessed to support the electron-beam projection lithography ͑EPL͒ mask standardization process. Using numerical simulations, comparative studies were performed to investigate the mask response during fabrication, pattern transfer, and mounting, employing the IBM Falcon/Nighteagle layout as a pattern-specific design for both EPL masks. The results indicated that consistent mounting schemes in the e-beam writer and exposure tool minimized the in-plane distortion ͑IPD͒. The proposed chucking configuration appeared to be robust for both EPL technologies for controlling IPD. With additional support enhancement beneath the major strut across the center of the grillage area of the mask, the IPD can be reduced to negligible values.
Electron beam lithography simulation for high resolution and high-density patterns
Vacuum, 2001
A fast simulator for electron beam lithography, called SELID2+, is applied for the simulation and prediction of the resist pro"le of high-resolution patterns in the case of homogeneous and multilayer substrates. For exposure simulation, an analytical solution based on the Boltzmann transport equation (where all important scattering phenomena have been taken into account) for a wide range of e-beam energies is used. 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. By combining the energy deposition data from simulation with analytical functions describing the resist development (for the conventional positive-resist PMMA), complete simulation of dense layouts in the sub-quarter-micron range has been carried out. Additionally, the simulation results are compared with experimental ones for dense patterns in the sub-quarter-micron region. By using SELID2+, forecast of resist pro"le with considerable accuracy for a wide range of resists, substrates and energies is possible, reducing in that way the cost of process development. Additionally, proximity e!ect parameters are extracted easily for use in any proximity correction package.
Predicting in-plane distortion from electron-beam lithography on x-ray mask membranes
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 1996
To produce x-ray masks useable for 0.25 μm lithography and beyond, all sources of mask distortion must be minimized. In order to facilitate the fabrication of high-quality masks, the phenomenon of changes in resist stress during e-beam exposure has been studied. Finite element modeling was employed to determine the effects of various geometric and material properties on final image quality. Additionally, writing patterns and multipass exposure were also studied. The results indicate that the stress relief phenomenon can be controlled in a well-designed system.
E-beam lithography experimental results and simulation for the 45-nm node
2004
E-Beam Lithography is still the driving technology for semiconductor manufacturing of critical levels at the 45nm node. Mask costs, yields and representation of the mask on wafer are important factors to consider. Mask-less E-beam lithography is being considered, but major manufacturing is still done by scanner technology. Therefore the same emphasis on modeling applied in the 1990's on the wafer is now being applied to mask technologies to drive down costs, improve yields and to develop viable mask to wafer transfer patterns.