Fabricate large area and defect free periodic structures with advance achromatic laser interference lithography

摘要

Laser interference lithography (LIL) is a great way to produce micro and nano scale periodic structures. The principle of LIL is that two or more coherent laser beams overlap with each other and form a standing wave in the space which can be recorded by the photoresist. However, due to the principle of LIL, exposure result is very sensitive to the light source, especially in large area exposure. Regular defects occurs in large area exposure result when the laser source has multiple longitudinal mode or mode hopping. Therefore, this paper design and build up an advanced achromatic interference lithography system to solve this problem. Due to the principle of achromatic interference lithography, the exposure result is no longer relative to the wavelength of the laser source, and the pitch of the periodic structures is half of the grating pitch. As a result, achromatic interference lithography is able to eliminate the regular defects caused by the unstable laser source. But traditional achromatic interference lithography system is not very efficient due to transmission lost and only first order light is used. This paper build up an advanced achromatic interference lithography system with two reflective blazed gratings. Because of the principle of the reflective blazed grating, we can improve the efficiency of our achromatic interference lithography system. In this paper, 20 mm~2 of large area periodic structures with 420nm pitch and 130 nm linewidth have been successfully fabricated without any defects.