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Currently, the most widely used photoresists in optical lithography are organic-based resists. The major limitations of such resists include the photon accumulation severely affects the quality of photolithography patterns and the size of the pattern is constrained by the diffraction limit. Phase-change lithography, which uses semiconductor-based resists such as chalcogenide Ge2Sb2Te5 films, was developed to overcome these limitations. Here, instead of chalcogenide, we propose a metallic resist composed of Mg58Cu29Y13 alloy films, which exhibits a considerable difference in etching rate between amorphous and crystalline states. Furthermore, the heat distribution in Mg58Cu29Y13 thin film is better and can be more easily controlled than that in Ge2Sb2Te5 during exposure. We succeeded in fabricating both continuous and discrete patterns on Mg58Cu29Y13 thin films via laser irradiation and wet etching. Our results demonstrate that a metallic resist of Mg58Cu29Y13 is suitable for phase change lithography, and this type of resist has potential due to its outstanding characteristics.

Several techniques such as the electron beam technology and ion beam technology are employed to obtain the high resolution nanopatterns. However, these techniques cause some problems, for example, the vacuum installation, high voltage power supply and low throughput, which consequently make these techniques more expensive. On the other hand, the organic resists used for lithography are important to control the shape and size of the patterns. The reactivity of the resist is dominated by the total irradiation amounts of a beam, that is, the number of electrons or ions or photons absorbed by the resist. As a result, the precision control of the shape and size for nanopatterns become difficult due to their intrinsic accumulation effect of the absorption in the resists.

Maskless phase-change lithographic technology is developed as a photoresist of phase-change materials. The controllable growth behavior of the crystallization region on an amorphous thin film of Ge 2 Sb 2 Te 5 (GST) irradiated by a laser beam is investigated; the GST thin film is deposited on a silicon substrate by the sputtering method. The results of a series of the experiments and the simulations all show that the width of a crystalline pattern is not only closely related to laser power and pulse duration, but also is apparently affected by the interactive area between the focused laser spot and thin film. The width maintains a nonlinear growth with the enhancement of the laser power until the thin film approaches melting, whereas it gradually reaches a constant value due to the local thermal equilibrium. This equilibrium makes the width irrelevant to the moving velocity with certain constraints when the laser works in continuous-wave mode. Within a defocus range of 15 μ m , the widths of the crystalline patterns are obtained in a broad range from 690 nm to 8.13 μ m under a 0.4-NA objective lens. By adjusting the defocus amount, some crystalline square patterns with expected widths in a wide range are fabricated, and the mean percentage error between the expected and fabricated widths is only 1.495%.