Lift-off Method And The Performance Analysis Of The Single-layer Subwavelength Metallic Gratings

With the development of the micro-nano fabrication technology, the linewidth of the subwavelength metallic gratings is decreasing, and the application of the subwavelength metallic gratings is expanded from the far-infrared spectrum to the near-infrared spectrum and the visible spectrum. Based on the application of the multi-directions single-layer subwavelength gratings to the sensor models for the polarizer angle testing, the angle of the skylight polarized light can be detected and which can be used as direction determination method. This novel navigation method with less susceptible to the disturbance and no accumulation errors is becoming a research hotspot in the field of navigation methods. This paper is aiming to fabricate the metallic gratings by the micro-nano fabrication processes for testing the angle of the polarized light, and the fabricated metallic gratings is performed by the polarization navigation sensor made by our research group.The transmission characteristics of the TM and TE polarized light were discussed through the Effective Bragg Cavity Model. With the help of the Finite Different Time Domain (FDTD) method, the influence of the addition of the polymer layer in the subwavelength metallic gratings was proposed, and the variation tendency of the transmission enhancement along with the change of the metal layer thickness and the incident wavelength was discussed. It was prove that the addition of the polymer layer was the main reason that the s-polarization transmittance enhanced via the subwavelength metallic gratings.A fabrication process of the single-layer subwavelength metallic gratings based on the nanoimprint lithography and the lift-off process was designed. The influence of different wafer cleaning methods to the resist spinning was discussed. The etching parameters of the ICP process is also under discussion to determine better etching parameters to obtain a vertical sidewall of the lift-off resist. The interval ultrasonic was proposed to improve the efficiency of the lift-off process as well as remained the integrity of the gratings structure. According to above methods, a multi-direction metallic gratings was successfully fabricated on the glass substrate and was tested by the polarization navigation sensor. The original angle error was within ±1.2°, and through the error compensation algorithm, the final angle error reduced to ±0.45°.However, the error mentioned above was not better enough for the polarized light anger determination. From the perspective of the fabrication processes, this paper proposed an improved method by SiO2 addition to enhance the transmission performance of the metallic gratings from 40% to around 70%. The multi-direction gratings fabricated by the improved process also tested by the sensor and the original angle error is within ±0.7° which was less than the previous process result. The final error after the error compensation processing was within 0.25°, which was proved that the proposed process was available to improve the performance of the polarized light angle testing.