RF Waveguide Pattern Engineering to Mitigate Bonding Surface Nonuniformities in CMOS Compatible Fabrication Processes

Heterogeneously integrating silicon photonic devices and circuits with other optical materials (III/V semiconductors, LiNbO3, and so on) is a promising approach toward bolstering the capabilities of silicon photonics and improving the manufacturability of other photonic platforms. An approach to heterogeneous integration is to directly bond an optical material to the surface oxide of a silicon photonic circuit or device, which requires locally and globally smooth bonding surfaces to facilitate sufficient bonding quality. However, embedded silicon photonic metal structures, such as RF waveguides for high-speed photonic devices and electrical interconnects, can impact the surface topography during planarization, resulting in nonideal bonding surfaces. In this article, we discuss and demonstrate a method of patterning the ground planes of RF waveguides to achieve a more uniform distribution of embedded metal density, in turn, providing more constant planarization rates. This provides a more uniform bonding surface which is a requirement for the high-volume manufacturing of these technologies.