Effect of ammonia (NH3) plasma treatment on silicon nitride (SiNx) gate dielectric for organic thin film transistor with soluble organic semiconductor

The effect of an ammonia plasma treatment on silicon nitride (SiNx) gate dielectrics for organic thin film transistors (OTFTs) with soluble organic semiconductors (OSCs) was studied. Our OTFTs were fabricated by using the soluble derivatives of Poly(bi-thiophene) as the p-type polymer semiconductor material and SiNx thin films with nitrogen oxygen (N2O) and ammonia (NH3) plasma treatments as the gate dielectric. To improve the performance and stability of the OTFT devices, we studied the basic mechanism of the plasma treatment on the SiNx gate dielectric and the gold (Au) electrode surface. The SiNx-OTFTs with a NH3 plasma treatment yielded the improved results in terms of a higher field-effect mobility (μfe) of 0.06 cm2 V−1 S−1 with a lower interface charge trap density of 4.45 × 10−11 (cm2 eV)−1 and a lower contact resistance of 0.384 MΩ-cm. The repulsive force of the soluble OSC solvent was reduced at the edge of the source-drain (S-D) electrode due to the difference between the surface energies of the channel region and Au S-D electrodes.