A new fabrication method for enhancing the yield of linear micromirror arrays assisted by temporary anchors

Abstract

As one of the most common spatial light modulators, the linear micromirror array (MMA) based on the microelectromechanical system (MEMS) process is utilized in many fields nowadays. However, two crucial challenges exist to fabricate such devices: adhesion of silicon microstructures caused by anodic bonding and destruction of the suspended silicon film due to residual stress. To solve these issues, an innovative processing method assisted by temporary anchors is proposed. It effectively reduces the span of silicon microstructures and improves the Euler buckling limit of the silicon film. Importantly, these temporary anchors are strategically placed within the primary etching areas, requiring no additional processing steps for easy removal. As a result, we successfully achieve wafer-level, high-yield manufacturing of linear MMAs with filling factor as high as of 95.1%. Compared to the original MMA, this enhanced version now boasts a total of 60 linear micromirror elements, each featuring a length-to-width ratio of 52.6, and the entire optical aperture measures 5 mm × 6 mm. The linear MMA exhibits optical deflection angle of 20.4° at 110 Vdc while maintaining exceptional deflection flatness and uniformity. This study offers a viable approach for design and fabrication of thin-film MEMS devices with high yields, and the proposed MMA holds promise as a replacement of the digital micromirror device (DMD, by TI Corp.) in such fields as spectral imaging and optical communication.