A Fabrication Process of Self-Aligned Tantalum-Silicide Gate Gallium-Arsenide Metal-Semiconductor Field Effect Transistors with Tantalum-Silicide Cap-Annealing Technique

The tantalum silicide ( TaSix ) was investigated for the application of self-aligned gate (SAG) GaAs metal-semiconductor field-effect transistors (MESFET). TaSix film was deposited by sputtering with substrate bias from -100 V to +75 V. The optimal condition of substrate bias voltage is +50 V for MESFET process according to AES, XRD, and resistivity analysis. The Si+ implantation at 80 keV with dose 4×1013 cm-2 through thin TaSix film was adopted for the channel doping. For the gate patterning, reactive ion etching (RIE) of TaSix was performed in CF4+O2 (15% O2) mixture at total pressure 40 mTorr with RF power 60 W. A 2 µ m×50 µ m TaSix SAG GaAs MESFET was then successfully fabricated. In this process, the TaSix film was used for the gate material, encapsulating layer, and film for through implantation. This new method simplifies the fabrication process of self-aligned GaAs MESFET.