Engineering High Kinetic Inductance Metal Nitride Films via PEALD for Fluxonium Qubit Superinductors

 Fluxonium qubits are a promising candidate for noise-protected quantum computation, utilizing superinductors to achieve high coherence and anharmonicity. The realization of these superinductors relies on high kinetic inductance (HKI) superconducting materials, such as disordered metal nitrides (e.g., TiN, NbN). However, engineering these films presents a significant challenge: a critical trade-off between maximizing kinetic inductance (L_k), which scales with normal-state resistivity, and maintaining robust superconductivity (e.g., T_c) and low microwave loss. To address this challenge, we investigate Plasma-Enhanced Atomic Layer Deposition (PEALD) for the synthesis of metal nitride thin films. PEALD offers atomic-level precision in controlling film thickness, composition, and uniformity, which are critical parameters for meticulously tuning the disorder and optimizing the L_k-T_c balance. We have fabricated a series of metal nitride films, varying key PEALD process conditions. The structural, chemical, and morphological properties of these films are characterized using XRD, XPS, and TEM. Low-temperature electrical transport measurements (PPMS) are underway to evaluate their superconducting properties (T_c, ρ_n) and estimate L_k. This ongoing study aims to establish a clear process-property relationship for PEALD-grown HKI films, paving the way for optimized superinductors in advanced fluxonium circuits.