Growth of Self-Aligned Oxide Photonic Devices on Silicon

Functional oxides play a significant role in the emergence and growth of novel plasmonic and quantum photonics devices. The ability to precisely engineer micro/nano structures with smooth surfaces of these oxides is a critically important technical enabler for device applications. However, using reactive ion etching (RIE) tools, to pattern oxides remains a formidable challenge as many of the cations do not form volatile species easily. At the University of Oklahoma, we have developed a reproducible technique for epitaxial growth of yttria-stabilized zirconia (YSZ) on silicon substrates with native oxides on their surface with a rocking curve full width at half maximum (FWHM) of 0.68 degrees on silicon (100) [1]. This establishes a solid foundation for the epitaxial growth of diverse functional oxide materials, including dielectric, ferroelectric, magnetic, conducting, and electro-optic materials, over large areas (up to 4 inches).<br/>To circumvent the problem of patterning these oxide films with smooth and vertical side walls, we have used the highly directional nature of pulsed laser deposition (PLD), which allows for self-aligned growth of functional oxide materials on pre-patterned silicon wafers. Reactive ion etching (RIE) of silicon [2] is utilized to achieve the required device dimensions. PLD deposition of oxides onto the patterned substrates gave non-conformal growth with negligible deposition on the sidewalls. High temperature deposition gave rougher surfaces than room temperature due to crystallization induced non uniformities. Furthermore, the non-conformality of the deposition may depend on the sidewall undercut and nature of the oxide. By combining electron beam lithography and RIE with PLD, we demonstrate the capability to fabricate high aspect ratio optoelectronic device structures and will report on their performance. This technology facilitates the seamless integration of state-of-the-art silicon electronics with oxides for optoelectronic devices.<br/><br/>1. Dubbink, David, Gertjan Koster, and Guus Rijnders. "Growth mechanism of epitaxial YSZ on Si by Pulsed Laser Deposition." <i>Scientific Reports</i> 8.1 (2018): 5774.<br/><br/>2. Wu, Banqiu, Ajay Kumar, and Sharma Pamarthy. "High aspect ratio silicon etch: A review." <i>Journal of applied physics</i> 108.5 (2010).