Lithography
The simulation of the lithography process using dissipative particle dynamics is described. A simulation model for the development process is constructed and the dissolution process simulation is performed to obtain an isolated line pattern. From a series
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Lithography Hiroshi Morita
29.1 Introduction The line widths of lithography patterns have become increasingly smaller, reaching values less than 20 nm [1]. As the pattern width decreases, the pattern size becomes closer to the gyration radius of the resist polymer. Thus it is more difficult to develop the resist polymer [2]. Line edge roughness (LER) is a problem related to the resist polymer that is difficult to solve. The problem involves the roughness at the side wall of a pattern being transferred to the circuit pattern, resulting in inhomogeneous electric resistance of a circuit. LER must therefore be reduced. LER is derived from the interfacial structure after the resist polymer dissolves, and one of the essences of LER is the control of the dissolution of the resist polymer without the problem of photoirradiation. To understand and control the dissolution process of resist polymer, as a virtual experiment, a coarse-grained simulation is conducted for the lithography process. Chapter 20 described an application study of the evaporation process conducting coarse-grained simulation and demonstrated that the coarse-grained model is applicable to the simulation of solvent evaporation. Furthermore, as previously mentioned, the pattern width has recently become smaller than 20 nm, which is within the applicable range of coarse-grained simulation. This chapter introduces the application of dissipative particle dynamics (DPD) simulation to the lithography process. Traditional lithography is done in the following way: coating of resist film, baking, photoexposure, development, rinsing, and etching. Although the processes of exposure, development, and rinsing are repeated several times in recently developed double and triple patterning methods, the basic procedure of lithography
H. Morita () National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan e-mail: [email protected] © Springer Science+Business Media Singapore 2016 Japan Association for Chemical Innovation, Computer Simulation of Polymeric Materials, DOI 10.1007/978-981-10-0815-3_29
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is not so different from the described method. Because it is difficult for us to simulate all the procedures of lithography, in this simulation, the process related to LER, that is, the development process, is simulated here [3–7]. Once the coarse-grained simulation is performed, the dynamics of each chain, which cannot be observed in experiments, can be obtained. In this chapter, the development process is simulated using the DPD method on COGNAC. The development process is the dissolution process of resist polymer. The chapter focuses on the model simulation of the dissolution of polymers. Here the simulations described in [3] are realized. Owing to the size limitation of User Definable Format (UDF) files, the system size, which is directly related to the total number of particles, must be smaller than that in [3]. Note that the effect of using a smaller system may affect the results, and these results must be treated carefully. If
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