Lateral Profile of Doping Concentration Extracted From the C‐V Characteristics in Self‐Aligned Top‐Gate Coplanar InGaZnO Thin‐Film Transistors

ABSTRACT Self‐aligned top‐gate (SATG) amorphous InGaZnO (a‐IGZO) thin‐film transistors (TFTs) are strong candidates for low‐power display backplanes and back‐end‐of‐line (BEOL)‐integrated circuits. Their scaling, however, is limited by short‐channel effects (SCEs), such as threshold‐voltage (V T ) roll‐off and drain‐induced barrier lowering (DIBL), which are strongly influenced by the lateral effective doping profile, N D (y), formed by oxygen‐vacancy/hydrogen‐related donor diffusion from the source/drain (S/D) extensions. Conventional transfer length method (TLM) approaches provide only indirect, lumped estimates and often lose accuracy in low‐doping regions. Here, we propose a capacitance–voltage (C–V)‐based extraction technique that directly reconstructs N D (y) and key profile parameters—including overlap length (L OV ), gradient length (L Grad ), and base doping concentration (N D,Base )—from measured gate capacitances (C GG /C GS /C GD ). Using L‐split SATG a‐IGZO TFTs with channel lengths ranging from 4.5 to 40 µm, we validate the extracted profiles by directly comparing them with those obtained from a TLM‐based extraction and demonstrate the quantitative prediction of V T (V ON ) roll‐off across different channel lengths. The results reveal that S/D dopant overlap increases the channel‐center doping N D,ch in short channels, thereby accelerating V T roll‐off and enhancing DIBL. This C–V‐based lateral profiling framework provides practical diagnostics and design guidelines for suppressing SCEs in future low‐power, high‐reliability oxide electronics.