Enhanced model for the efficient 2D and 3D simulation of defective EUV masks

Predictive simulation of EUV (extreme ultraviolet) lithography is important for a better understanding of the technology because the capabilities for experimental studies are still limited. One of the most critical and important issues in EUV lithography modeling is the description of the mask including multilayer defects. Such defects can have a significant impact on the lithographic process. An earlier presented model for the simulation of defective EUV masks, developed at Fraunhofer IISB, is the basis for the new enhanced simulation model. The basic model is a combination of a rigorous electromagnetic field (EMF) computation, based on a finite-difference time-domain (FDTD) algorithm, and an analytical thin film computation. This approach leads to significant reduced computation time and memory requirements compared to other methods, such as fully rigorous EMF simulations. The model can be applied to two and three dimensional defects and masks. This contribution reports on the enhancement of the basic model, including new simulation results. The higher efficiency of the new simulation model is based on the assumption that only certain discrete mask illumination angles, the multiples of the discrete diffraction orders of the mask near field, are allowed. This approach allows for an decrease of computation time and memory requirements in half, compared to the computations of the predecessor-model allowing arbitrary angles. Comparisons of the two models, based on the reflected mask near fields, and the aerial images of typical mask structures in combination with a defective multilayer and various defect parameters, are presented. Furthermore, the alternative wave guide method, also applied to the computation of EUV mask near fields, is presented. First comparisons of the enhanced simulation model and the wave guide method are performed.

[1]  Iwao Nishiyama,et al.  Quantifying EUV imaging tolerances for the 70-, 50-, 35-nm modes through rigorous aerial image simulations , 2001, SPIE Advanced Lithography.

[2]  Thomas Schmoeller,et al.  Modification of boundaries conditions in the FDTD algorithm for EUV mask modeling , 2002, Photomask Japan.

[3]  Thomas Schmoeller,et al.  Rigorous simulation of defective EUV multilayer masks , 2003, SPIE Photomask Technology.

[4]  Andreas Erdmann,et al.  Rigorous diffraction analysis for future mask technology , 2000, Advanced Lithography.

[5]  Andreas Erdmann.  Process optimization using lithography simulation , 2004, International Conference on Micro- and Nano-Electronics.

[6]  Tsuneo Terasawa,et al.  Simulation of Multilayer Defects in Extreme Ultraviolet Masks , 2001 .

[7]  Andrew R. Neureuther,et al.  Extreme ultraviolet mask defect simulation , 1999 .

[8]  Thomas V. Pistor,et al.  Calculating aerial images from EUV masks , 1999, Advanced Lithography.

[9]  Konstantinos Adam,et al.  Rigorous simulation of mask corner effects in extreme ultraviolet lithography , 1998 .

[10]  Yunfei Deng,et al.  Extreme ultraviolet mask defect simulation: Low-profile defects , 2000 .

[11]  Ronald L. Gordon,et al.  Mask topography simulation for EUV lithography , 1999, Advanced Lithography.

[12]  Hsuen-Li Chen,et al.  Simulation on a new reflection type attenuated phase-shifting mask for extreme ultraviolet lithography , 1999, Advanced Lithography.

[13]  Mumit Khan,et al.  Imaging properties of the extreme ultraviolet mask , 1998 .

[14]  Andreas Erdmann,et al.  Rigorous simulation of alignment for microlithography , 2003 .

[15]  Iwao Nishiyama,et al.  Impact of the EUV mask phase response on the asymmetry of Bossung curves as predicted by rigorous EUV mask simulations , 2001, SPIE Advanced Lithography.

[16]  A. Taflove.  The Finite-Difference Time-Domain Method , 1995 .

[17]  Patrick Schiavone,et al.  Rigorous electromagnetic simulation of EUV masks: influence of the absorber properties , 2001 .

[18]  Franco Cerrina,et al.  Image formation in extreme ultraviolet lithography and numerical aperture effects , 1999 .

[19]  Andreas Erdmann,et al.  Simulation of extreme ultraviolet masks with defective multilayers , 2003, Photomask Japan.

[20]  Peter Evanschitzky,et al.  The impact of EUV mask defects on lithographic process performance , 2004, European Mask and Lithography Conference.

[21]  Andreas Erdmann,et al.  Simulation of optical lithography , 1999, Other Conferences.

[22]  Fadi Issam Baida,et al.  Critical size of multi-resonant optical tunnel structures. Application to nonradiative effects , 1993 .

[23]  Mumit Khan,et al.  Modeling Image Formation in Layered Structures: Application to X-ray Lithography , 1998 .

[24]  Thomas Schmoeller,et al.  Efficient simulation of light diffraction from three-dimensional EUV masks using field decomposition techniques , 2003, SPIE Advanced Lithography.