A review of high dielectric materials for DRAM capacitors

There has been growing interest in the use of materials with the perovskite structure as a dielectric for capacitors in dynamic random access memory chips. The heightened activity in this field is exemplified by the nearly exponential increase in the number of patents issued during the past 5 years. At the present time, a fully functional DRAM with a capacitor incorporating these high-dielectric constant materials has not been demonstrated. All existing DRAMs use silicon dioxide and/or silicon nitride as the capacitor dielectric. This paper will describe the potential advantages of incorporating high-dielectric materials into the storage capacitor of a DRAM and review the requirements of the high-dielectric layer when used in a simple stack capacitor structure suitable for the GBit generation of DRAM. Recent advances in this technology are reviewed and the major issues, which could be potential show-stoppers and still need to be resolved, are described.