Detailed illuminator design for full-field ArF lithography system with a method based on the fly's eye

Abstract

Lithography is the key technology to semiconductor manufacture. With the rapid improvement of projection lens and resolution enhancement technique (RET), the essence of the illuminator can never be overestimated in the lithography system. However, due to various and complex components and the fact that fewer design methods were proposed in the papers compared with those of the projection lens, a detailed design method for the illuminator is needed. This paper introduces the detailed design process for the illuminator in a NA 0.75 lithography system on 90nm node. The exposure field at the reticle plane is 104mm×42mm. The illuminator mainly consists of three parts: the beam shaping unit, the uniformizer and the relay lens. In order to construct the matching relationship among the various components in the illuminator, a design method based on the fly's eye, which is the core and starting point, has been proposed. This method has been successfully used in small field lithography system. With this method, the matching relationship in the illuminator can be determined easily, and the illumination NA and size are guaranteed simultaneously. Furthermore, the detailed design for some key issues in the illuminator is given: the diffractive optical element (DOE), zoom lens and axicon are used together to generate different sources in the entrance pupil of the projection lens; the condenser design; and 1X relay with two cylinder lenses to achieve trapezoid intensity distribution in the scan direction. A demonstration simulation result is given, and the uniformity of the non-scan and scan direction reached 1.2% and 1.7% respectively under all illumination modes. The result showed good performance and the requirements of the lithography tools have been met.

Generation of trapezoidal illumination for the step-and-scan lithographic system

“…Therefore, they should be strictly controlled [17]. Usually, the nonuniformity of the nonscan and scan directions reached 1.2% and 1.7%, respectively, under all illumination patterns [18]. As shown in Fig.…”