Design an asymmetrical three-beam laser interference lithography for fabricating micro- and nano-structures

Multi-beam laser interference lithography (LIL) has become one of the most important techniques and shown significant advantages in the fabrication of micro- and nano-structures. Controlling inten-sity ratio of optical distributions is a key issue in LIL for fabricating micro- and nano-structures. This paper presents an asymmetrical three-beam LIL system which effectively improves the intensity ratio of optical distributions. Comparing with the symmetrical three-beam interference, the asymmetrical three-beam LIL achieved the high intensity ratio of optical distribution when producing the similar interference pattern. In addition, this system also avoids modulation patterns in multi-beam LIL sys-tems and reduces the difficulty of actual LIL processing. A fast Fourier Transform (FFT) analysis used to study the pattern distributions of the asymmetrical three-beam interference from frequency spectra which shows that the pattern with a high-intensity array can be obtained by adjusting the parameter settings of incident laser beams. The asymmetrical three-beam LIL system was verified through fab-ricating patterns. The experimental results are in good agreement with the theoretical analyses.