A DMD based UV lithography method with improved dynamical modulation range for the fabrication of curved microstructures

For the fabrication of curved microstructures, the fabrication fidelity is greatly affected by the nonlinear relationship between the gray levels of the digital micromirror device (DMD) and the exposure dose in DMD gray-scale lithography. In this study, a method is proposed for the high fidelity fabrication of curved microstructures using DMD based dynamical ultraviolet lithography. A target curved microstructure is mapped into multiple discretized exposure profiles to control DMD mirrors. By extracting the same rows in all the discretized exposure profiles and arranging all the extracted rows in sequence, binary frame images to be exposed are constructed and then combined into a dynamical digital mask. With the proposed method, the nonlinear modulation of the DMD in gray-scale lithography is replaced with a linear binary modulation; thus, the dynamical modulation range of the DMD has been improved. We demonstrate the effectiveness of the method by theoretically simulating and experimentally fabricating a curved microlens array, compared with DMD gray-scale lithography. The experimental results show that the fabrication deviation in the edge region of the fabricated curved microlens array has been effectively decreased. This method may have great potential for the precision and low-cost industrial production of curved microstructures.