Integrated photonics optimized to leverage low loss, nonlinear-optical processes and optoelectronic integration requires robust optical cladding materials and associated fabrication process flows. We develop low-loss silicon dioxide (SiO₂) claddings with tantalum pentoxide (Ta₂O₅, tantala) integrated photonics to realize robust, high intrinsic quality factor (Qᵢ) microresonators and photonic-crystal resonators (PhCRs) for soliton microcomb generation. Specifically, we introduce a full-wafer, low-temperature process compatible with two tantala-based films: pure tantala and an amorphous metal-oxide mixture of titanium dioxide (TiO₂, titania) and tantala. Combining tantala with titania enhances the film's resistance to damage from the SiO₂ cladding deposition process, offering access to high Qᵢ above 4 × 10⁶ in fully cladded microresonators. Our platform supports low-loss edge couplers, group-velocity dispersion engineering by waveguide geometry, access to nanophotonic structures particularly to control phase-matching, and high dimensional tolerance in devices across an entire wafer. Using the platform, we explore the generation of high-efficiency, dark-soliton microcombs with repetition frequency from 50 GHz to 500 GHz, which supports applications such as photonic artificial intelligence acceleration, electronic signaling, and optical data communication.