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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.

A high performance surrounding gate transistor (SGT) enabling sufficient static and dynamic retention time of future DRAM cells is presented. For the first time, we demonstrate a fully depleted SGT, that shows no reduction of the retention time due to the transient bipolar effect. This effect potentially prevents DRAM application of fully depleted SGTs and is therefore investigated in detail. Based on experimental results, the impact of the proposed SGT on the scalability and performance of future DRAMs is discussed.

One of the key enablers in scaling DRAM trench capacitors to sub-100 nm ground rules is a viable collar integration concept. We report, for the first time, the successful implementation of a buried collar concept, which leaves ample space for the connection from the array device to the inner electrode. The new collar integration scheme is fully compatible with a number of capacitance enhancement techniques including surface enlargement by trench widening, HSG deposition as well as the utilization of high-k node dielectrics such as Al/sub 2/O/sub 3/. These capacitance enhancement techniques are required to maintain a capacitance in excess of 30 fF/cell. In addition, a metal fill of the deep trench is necessary to maintain a low series resistance of the inner electrode, which is also demonstrated for the first time. The successful integration of these key enablers in deep trenches is presented.