The breadth of circuit fabrication opportunities enabled by metal-oxide thin-film transistors (MO-TFTs) is unprecedented. Large-area deposition techniques and high electron mobility are behind their adoption in the display industry, and substrate agnosticism and low process temperatures enabled the present wave of flexible electronics research. Reports of circuits involving complementaryMO-TFTs, oxide-organic hybrid combinations, and even MO-TFTs integrated onto Si LSI back end of line interconnects demonstrate this technology’s utility in 2D and 3D monolithic heterogeneous integration (HI). In addition to a brief literature review focused on functional HI between MO-TFTs and a variety of dissimilar active devices, we share progress toward integrating MO-TFTs with compound semiconductor devices, namely GaN HEMTs. A monolithically integrated cascode topology was used to couple a HEMT’s >200 V breakdown characteristic with the gate driving characteristic of an IGZO TFT, effectively shifting the HEMT threshold voltage from -3 V to +1 V.
It has long been recognized in the design of micromirror-based optical systems that balancing static flatness of the mirror surface through structural design with the system’s mechanical dynamic response is challenging. Although a variety of mass reduction approaches have been presented in the literature to address this performance trade, there has been little quantifiable comparison reported. In this work, different mass reduction approaches, some unique to the work, are quantifiably compared with solid plate thinning in both curvature and mass using commercial finite element simulation of a specific square silicon-on-insulator–based micromirror geometry. Other important considerations for micromirror surfaces, including surface profile and smoothness, are also discussed. Fabrication of one of these geometries, a two-dimensional tessellated square pattern, was performed in the presence of a 400-μm-tall central post structure using a simple single mask process. Limited experimental curvature measurements of fabricated samples are shown to correspond well with properly characterized simulation results and indicate ∼67% improvement in radius of curvature in comparison to a solid plate design of equivalent mass.