Geometry and process optimization for ultra-high RPM plating

Various embodiments herein relate to methods and apparatus for electroplating metal onto substrates. The apparatus used to practice electroplating may be designed to have a geometric configuration that makes it difficult for air to travel and become trapped under the substrate. By using such apparatus, electroplating can occur at higher rates of substrate rotation than would otherwise be acceptable. The higher rate of substrate rotation allows electroplating to occur at higher limiting currents, which in turn increases throughput. The disclosed embodiments are particularly useful in the context of electrolytes that otherwise exhibit a relatively low limiting current (e.g., electrolytes having a low concentration of metal ions), though the embodiments are not so limited.