Optimized emitter-base interface cleaning for advanced Heterojunction Bipolar Transistors

International audience; A B S T R A C THeterojunction Bipolar Transistors needed for high-frequency applications require precise dopant control. Insitu doped epitaxies used during device fabrication rely on surface preparation to obtain an optimized dopingprofile. Defects due to imperfect cleaning relates to high emitter resistance and low-frequency noise.Base epitaxy is followed by the fabrication of thin L-shaped oxide spacers and in-situ arsenic-doped emitterepitaxy by Low Pressure Chemical Vapor Deposition. A cleaning step between spacers formation and emitterepitaxy is mandatory to remove residual contamination. Hydrofluoric acid (HF) wet cleaning, in-situ remoteplasma cleaning (SiconiTM) and thermal treatments have been tested. A minimum etching budget is sought forlimiting spacer consumption while adequately cleaning the interface.Time Of Flight-Secondary Ion Mass Spectroscopy (TOF-SIMS) and High-Resolution Transmission ElectronMicroscopy (HR-TEM) are used to characterize the interface and measure levels of arsenic, oxygen, fluorineand carbon. Emitter resistance and base-emitter breakdown voltage measurements are used to show the impacton electrical figures of merit. Siconi targeting 10 Å of thermal oxide removal followed by a thermal treatment(800 ◦C, 60 s) in the deposition chamber results the best process among the tested ones.