Source and mask optimization (SMO) should be applied in extreme ultraviolet lithography (EUVL) for 7-3 nm technology node. Ineluctable wavefront error (WFE) coming from projection optics or 3D mask effect is considered as a single field point effect instead of full field aware in traditional SMO flow. For getting more qualified SMO, a model of full-field wavefront error aware source and mask optimization (FFSMO) is invented. This method focuses on the tradeoff of lithographic imaging at different typical field point as a multi-objective problem. A new multi-objective cost function is established to improve the uniformity of pattern fidelity at different field point. Simulation results show that the proposed FFSMO method has better imaging uniformity at different field points than non-wavefront error aware SMO (SMO-Ideal) or single field point aware SMO (SMO-F2). For line and space pattern at 7nm node, the standard deviation of pattern error (PAE) reduced from 185.0 to 79.2 comparing with the single field point aware SMO. It is demonstrated that the effectiveness of this FFSMO model in terms of balancing and improving imaging uniformity and PW across full exposure field. For contact hole pattern, the standard deviation of pattern error (PAE) reduced from 233.7 to 75.6 comparing with the single field point aware SMO.
Source and mask optimization (SMO) technology is an increasingly important resolution enhancement technology (RET) that can optimize the source and mask. Various SMO methods have made great progress in terms of computational efficiency and pattern fidelity. Besides, process window (PW) is also an important indicator to evaluate the performance of lithography imaging. PW consists of exposure latitude (EL) and depth of focus (DOF). However, currently, there are few SMO methods that can directly improve EL. In this paper, we propose an EL aware SMO (ELASMO) method by innovating a new penalty function for improving the exposure latitude. Compared to the conventional SMO, the proposed ELASMO can significantly enhance aerial image contrast and enlarge the exposure latitude from 5% to 11% under the premise of ensuring imaging fidelity. ELASMO achieves high-fidelity lithography in a larger process window.
Source optimization (SO) is an extensively used resolution enhancement technology which can improve the imaging performance of optical lithography. To improve the computational efficiency of traditional SO, compressive sensing (CS) has been involved. In the CS-SO theory, the source pattern needs to be presentation as sparsely as possible by sparse basis, because the sparsity of source pattern can significantly improve the recovery performance of CS-SO. Therefore, the selection of the sparse basis can affect the performance of CS-SO. Discrete Fourier transform (DFT) basis, especially its variant discrete cosine transform (DCT) basis has been widely used in CS. Furthermore, some overcomplete bases have also been used in many fields. In this paper we present a comparison of sparse-based full chip SO with spatial basis, DCT basis, DFT basis, overcomplete DCT (ODCT) basis, overcomplete DFT (ODFT) basis and haar wavelet basis. The full chip SO problem is formulated as a cost function of multi-objective adaptive optimization, and then a soft threshold iterative (IST) algorithm is used to obtain the optimized source pattern. The simulation results show that the sparse-based method can effectively improve the imaging performance. Exactly, in terms of imaging fidelity, spatial, DCT, DFT, ODCT, and haar wavelet bases are similar, and better than the ODFT basis. However, in terms of optimizing speed, the spatial and DCT basis can converge to an acceptable SO solution at a faster speed than other bases.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.