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2011
Doctoral Thesis
Titel
The waveguide electromagnetic field solver and its extension and application to lithography simulation
Alternative
Die Wellenleiterlösungsmethode für elektromagnetische Felder und ihre Erweiterung und Anwendung auf die Lithographiesimulation
Abstract
As semiconductor lithography marches towards the era of sub 45nm feature size, many novel technologies are proposed to prolong the lifetime of photolithography, such as advanced resolution enhancement techniques (RETs), extreme ultraviolet (EUV) lithography, and double patterning/exposure techniques. The increasingly stringent process conditions, the immaturity of facilities, processes, and materials, and the dramatically rising expenses in cost and time for all the promising novel lithography technologies have put indispensable demands on the physical modeling and simulation of the lithography process. In particular, the interaction of light with sub-wavelength features on the lithographic masks and wafers is found to have more and more pronounced impact on the lithographic performance. T his impact cannot be simply ignored as it is in many current simulations. Therefore, rigorous electromagnetic field (EMF) solvers become indispensable for the simulation of novel lithography technologies. However, the choice of the EMF solvers is greatly limited due to the requirement on its speed, accuracy, efficiency, and flexibility. In this thesis, the Fraunhofer IISB developed Waveguide Method is presented as the rigorous EMF solver for the simulation of novel lithography technologies. New modeling approaches, extensions, and optimizations are proposed and developed to enhance the performance of the Waveguide Method, and to enable new applications such as rigorous exposure simulation in double patterning/exposure techniques. An important new model, namely the Waveguide decomposit ion method (WDM), reduces the computational complexity of the diffraction of a 3D mask to that of several 2D masks. WDM is demonstrated to have superior simulation speedup with sufficient accuracy. It allows rapid simulation of large 3D mask areas (> 10 mm×10 mm at a wavelength of 193 nm, or > 50l × 50l) and extremely fast computation of standard sized masks (< 1 mm × 1 mm at a wavelength of 193 nm, or < 5l × 5l). The speedup of WDM can be further scaled up by distributed computation with excellent parallelization efficiency. Another important and originative model, namely WaferWaveguide, tailors theWaveguide Method for the rigorous EMF simulation of topographic (non-planar) wafers in many emerging double patterning/exposure techniques. A flexib le layer-based description approach is developed to model diverse wafer topographies. Extensions and optimizations to reduce the computation load and to enable dynamic exposure simulation in case of bleachable resists are developed and featured. A parallelization of the Wafer-Waveguide Method is also presented to speed up the computation. Applications employing the proposed Waveguide Method, WDM, and WaferWaveguide are exemplified. The rigorous EMF effects in advanced phase-shift masks are demonstrated. EUV mask induced aberrations and the resulting imaging artifacts are investigated. The printability of EUV multilayer defects is analyzed with respect to the defect parameters and other process conditions. Several emerging double patterning / exposure techniques are explored. The impact of wafer topography on the final lithographic performance is evaluated. The simulation results can be used to instruct the control of critical parameters in these processes to avoid detrimental wafer topography effects. An example exploiting simulations to predict the best process condition in a double exposure scheme is also given.
ThesisNote
Erlangen-Nürnberg, Univ., Diss., 2011
Verlagsort
Erlangen-Nürnberg