Hybrid surface-/bulk-micromachining processes for scanning micro-optical components.

摘要

This dissertation discusses the design and fabrication of micro-optical scanners that have high-quality optical-surface properties and are capable of previously unattainable high scanning rates.; A first project investigates methods of creating scanning rectangular diffraction gratings using well-established fabrication methods of silicon surface-micromachining in a foundry process. We then introduce new methods to form an actuated blazed grating, a diffraction grating having a triangular surface profile that provides improved diffraction efficiency and wavelength resolution when compared to the rectangular grating. The measured diffraction efficiency of 60% in the blazed grating is four times that of the rectangular grating at an incident wavelength of 632.8 nm. Wavelength resolution for the high-order blazed grating is not limited by the linewidth of the fabrication process in contrast to the case of first-order rectangular gratings. Thus, the wavelength resolution of the blazed grating holds a fivefold increase from that of a comparably sized rectangular grating made in a minimum 2 μm-linewidth process.; In the second case (that of the large-angle low-frequency scanner), the micromirror should have relatively large-force actuators and soft torsional hinges. The softer hinges provide lower restoring forces, thus allowing larger-angle scanning for a fixed amount of actuator force. As dynamic-surface deformations and overall mass are lesser issues for this scanner, its design is easier with only static-surface deformations to consider. A low tensile stress (under 100 MPa tensile) polysilicon-mirror surface supported by a very wide (and thus very stiff) single-crystal silicon support rib is sufficient to ensure minimal static-surface deformations.; The research described here targets designs and fabrication technologies that can create optical MEMS scanners with high-quality optical surfaces that do not deform nor degrade during operation. We have pushed the limits by creating optical scanners to scan at previously unattainable speeds (as high as 81 kHz). In this work, we have developed a fabrication process that produces robust scanners and brought the technology to a level suitable for transfer to industry. (Abstract shortened by UMI.)