Synthesis of anodic oxide thin films on Si{100}wafers and their characterization in TMAH for MEMS

Akarapu, A and Pal, Prem (2015) Synthesis of anodic oxide thin films on Si{100}wafers and their characterization in TMAH for MEMS. ECS Journal of Solid State Science and Technology, 4 (2). Q1-Q7. ISSN 2162-8769

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Abstract

Silicon dioxide thin films are most widely used for different applications in microelectromechanical system (MEMS) fabrication such as etch mask, structural and sacrificial layers. Anodic oxidation method offers several advantages over other techniques, such as room temperature deposition, low cost, simple experiment setup, etc. In the present work, anodic oxidation of silicon is employed to grow oxide thin films at wafer-scale at room temperature. As-grown oxide films are characterized using ellipsometry, scanning electron microscope (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, optical microscope and 3D measuring laser microscope. Thickness uniformity and refractive index are measured using ellipsometry. FTIR spectra are used to conform the absence of hydroxyl and water absorption in the films. In order to exploit the application of anodic oxide in MEMS, the etch rates and the corner undercutting are studied in different concentration TMAH solutions at various temperatures. The as-grown oxide thin films with a thickness of about 155 nm are successfully demonstrated for the realization of various shapes freestanding MEMS structures such as rectangular cantilever beams, diaphragms, etc. using TMAH solution. Furthermore, as-grown oxide is used as mask to fabricate cavities with different shape and sizes in silicon substrate using wet anisotropic etching.

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