Research And Implementation Of Gap Measurement System For Surface Plasmon Lithography Device Based On FPGA

Lithography is an important step in the manufacturing process of ICs and micronano devices.With the advancement of science and technology,research fields such as microelectronics and micro-nano optics have increasingly higher requirements for lithography resolution.The lithography resolution of conventional optical lithography is limited by the optical diffraction limit.Surface Plasmon(SP)lithography,which has emerged in recent years,is a new type of nano-processing technology.Utilizing the short-wavelength characteristics of surface plasmon and the enhanced amplification characteristics of evanescent waves,it can achieve nano-level lithography resolution through ultraviolet long-wavelength light sources.However,the high-frequency information of surface plasmon that can be used for lithography only exists in the nearfield region,which limits the working distance of SP lithography.Therefore,a highprecision gap measurement system is required to ensure accurate measurement and control of the working distance between the mask and the substrate.In this paper,the research on the gap measurement requirements in SP lithography is carried out.Through the analysis of the mask-substrate GPG film structure,the masksubstrate gap measurement method based on white light interferometry technology is adopted.In order to solve the problem of insufficient speed of gap demodulation,FPGA hardware logic with parallel processing capability was used to improve processing efficiency.The main contents of this article include:(1)Firstly,through research and comparison of several lithography techniques,the principle and prospect of SP lithography were analyzed,and the requirements of SP lithography for the working distance between the mask and the substrate were analyzed.Then for the precise positioning system in the lithography device,the commonly used positioning technologies were analyzed and compared.At the same time,combined with the special requirements of the SP lithography scene for the gap measurement system,the overall scheme for gap measurement based on white light interferometry was adopted.(2)Secondly,the theoretical basis and characteristics of different demodulation algorithms for white light interferometry were analyzed.And the achievability of different processing platforms was analyzed.The realization scheme of demodulation by cross-correlation algorithm on FPGA hardware logic was determined,and Xilinx ZYNQ-7000 series chip XC7Z020CLG400 was selected as the main controller.The onchip ARM of this chip is used for initial configuration,drive management and interactive display.The programmable logic is used to implement data processing and gap demodulation of white light spectrum.The system operates in a distributed parallel structure,which greatly improves the measurement speed and realizes the real-time measurement of the mask-substrate gap.(3)Finally,a gap measurement precision testing platform based on laser interferometer was designed and built.Test experiments show that the repeat measurement accuracy of the gap measurement is about 4.5nm,which meets the design requirements of the gap measurement system.In addition,this paper also analyzed the operating performance of the system,the processing time is about 23.2ms,power consumption is about 2.101 W.The system has good measurement accuracy and realtime performance,and has good practicality.