Conductive Carbon as a Novel Front-End Electrode Material for a Trench DRAM

We report on the electronic properties and application of conductive carbon as a novel front-end material. Conductive carbon is attractive due to its metallic properties, high thermal stability, compatibility to Si-based dielectrics, and the availability of a low-cost batch deposition process. Here, we utilize carbon instead of a polysilicon top electrode in a deep trench capacitor with SiON node dielectric. A capacitance gain of 10% is observed due to suppression of electronic depletion. Furthermore, the midgap work function of 4.4 eV leads to a reduction of leakage currents due to a higher tunneling barrier. This allows electric thinning of the dielectric for a total capacitance gain of 20%, compared to a polysilicon electrode, while maintaining excellent electronic reliability characteristics.