A dry etch fabrication technology for high‐speed AlInAs/InGaAs heterojunction bipolar transistors (HBTs) utilizing low‐damage electron cyclotron resonance (ECR) CH4/H2/Ar plasma etching is detailed. Small‐area (2×4 to 3×9 μm2) devices demonstrated current gains up to 160, unity gain cutoff frequency ( fT) of 57 GHz and a maximum oscillation frequency ( fmax) of 35 GHz. The dry etch process uses triple self‐alignment of the emitter and base metals and the base mesa, minimizing the base‐collector capacitance (CBC). These results represent the first report of a truly scalable process for In‐based HBTs and demonstrate the ability of ECR plasma etching to provide smooth, degradation‐free etching of III–V semiconductors.