Mask optimization for arbitrary patterns with 2D-TCC resolution enhancement technique

Kawashima, Miyoko; Yamazoe, Kenji; Sekine, Yoshiyuki; Hakko, Manabu; Ohta, Masakatsu; Honda, Tokuyuki

doi:10.1117/12.771943

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…In (6), 0 (x, y) represents the light intensity distribution of the light transmitted from a point source on the source plane to the objective plane. It is also the Fourier transformation of an effective light source S [31]. The Fourier transformation of the pupil function is the impulse response in the imaging system.…”

Section: Projection Lithograph Modelmentioning

confidence: 99%

Placement of Sub-Resolution Assist Features Based on a Genetic Algorithm

Kan

Huang

et al. 2019

IEEE Access

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Resolution enhancement techniques compatible with an ArF (193 nm) immersion optical lithography system may constitute an effective means of minimizing the size of technology nodes of the dynamic random access memory. This paper investigated one such technique, namely mask optimization (MO), and applied sub-resolution assist features (SRAFs) in the MO to improve the aerial image quality of a target pattern that had undergone optical proximity correction (OPC). This paper first developed an optical model based on the Hopkins model to create an interference map, which was then used to create a cutlevel map. The cut-level map was instrumental in predicting potential SRAF sites and randomly generating SRAFs that would serve as the initial population for a genetic algorithm (GA). Chromosomes were defined as a section map and encoded genes were used to define SRAF and target pattern. Using a GA to identify SRAF geometric measurements and placement was revealed to increase the process window and improve the image performance of the target pattern. This paper used 1D and 2D line/space (L/S) images as the baseline to test the convergence of the proposed method. 2D images were also used to test improvements in aerial image performance. The results indicated that the 1D L/S pattern converged at the 100th iteration. Furthermore, the depths of the focus of the 2D L/S array and 2D contact hole patterns were successfully increased by 113 and 21 nm, respectively. The proposed SRAF method, which integrated the GA and interference map, was able to ensure the diversity of potential SRAF solutions. Moreover, it was able to restrict the SRAF solutions to rectangular structures through the application of mask rules, thereby reducing the cost and improving the feasibility of photomasks. INDEX TERMS Sub-resolution assist feature (SRAF), interference map, genetic algorithm (GA), mask optimization, depth of focus (DOF).

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Section: Projection Lithograph Modelmentioning

confidence: 99%

Placement of Sub-Resolution Assist Features Based on a Genetic Algorithm

Kan

Huang

et al. 2019

IEEE Access

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“…In the first step, kernel Φ is calculated by using optical conditions of exposure tools such as source shape, NA, aberrations, and defocus. The details of this calculation method are shown in the references [5][6][7][8]. The second step is the calculation of coherence map ) , ( y x Ψ from the kernel Φ and lithography target layout w , Φ • = Ψ w (1) Here • shows the convolution operation.…”

mentioning

confidence: 99%

Novel fine-tuned model-based SRAF generation method using coherence map

et al. 2010

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We have developed the comprehensive sub-resolution assist features (SRAFs) generation method based upon the modulation of the coherence map. The method has broken through the trade-off relation between processing time and accuracy of the SRAF generation. We have applied this method to a real device layout and the average of Process Variation band width (PV band width) has improved to 40% without any processing time loss. １．INTRODUCTIONAs Integrated Circuit(IC) pattern shrinks, the mask layout used in optical lithography differs from the corresponding IC design layout owing to the optical proximity effect correction (OPC). In order to satisfy the robustness to the process variations such as exposure dose variation and focus variation, recent mask layout includes not only the modified IC design patterns (OPCed patterns) but also the sub-resolution assist features (SRAFs). Establishment of the technology for the "holistic" optimization of this SRAF layout has been a hot issue for lithography engineers for a long time. However, as is well known, such an optimization is generally a difficult problem because the goal should be a "holistic" one. This means that it should be verified that the optimized mask layouts are robust against not only a single process variation but against a number of them in order to gain the maximum process yield. In addition, Issues specific to mask layout pattern and extremely low k1 lithography conditions should be considered in order to fix all hot-spot and warm-spot patterns.Recently, several novel techniques have been developed for the generation of the model-based SRAF at the final stage of the lithography. The local search heuristics to generate the model-based SRAF such as genetic algorithm (GA) [1], the optimal gradient method[2], inverse lithography technology (ILT)[3][4] can greatly improve the generation of the model-based SRAF, but these approaches have not been widely applied due to the intractable computer run-times. The coherence map technology that includes 2D-TCC method [5][6], interference map technology (IMT) [7], and SRAF guidance map technology(SGM) [8] is a novel promising method of optimizing SRAFs with drastically shorter turnaround time (TAT). They described a mask optimization algorithm using a "coherence map" that shows the optimum degree to be placed in a mask layout as to robustness against a specific process variation such as image contrast, or exposure latitude (EL). This intelligent method can actually increase the process robustness to some extent, but there are still some challenging problems to be solved in order to increase the robustness to the ultimate level for huge numbers of IC random layouts with an easy conscience. For example, our extensive studies of various mask designs have clarified that the acquired mask layouts optimized in order to increase a single process variation such as EL "frequently" result in poor robustness against the unconsidered process variations such as focus variations. For instance, in some contact hole patterns, the positions...

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