Hiang C. Chan

Trapping, conduction, and dielectric breakdown in Si/sub 3/N/sub 4/ films on as-deposition rugged polysilicon

Rugged polysilicon stacked capacitors recently emerged as the storage structures of choice for the manufacture of advanced DRAMs. The authors present the charge-trapping characteristics of such capacitors showing a capacitance increase of more than 50%. It is observed that electron trapping is dominant on rugged structures, whereas hole trapping is observed on smooth structures. Conduction and breakdown properties are also reported. Measurements show that rugged polysilicon capacitors provide the low leakage current, the sharp breakdown distributions, and the trapping characteristics needed for advanced DRAM applications.<<ETX>>

Ultrathin oxide-nitride dielectrics for rugged stacked DRAM capacitors

Ultrathin dielectric materials that provide high capacitance values are needed for 64- and 256-Mb stacked DRAMs. It is shown that capacitance values as high as 12.3 fF/ mu m/sup 2/ can be obtained with ultrathin nitride-based layers deposited on rugged polysilicon storage electrodes. These films present the reliability and low leakage current levels required for 3.3-V applications. The nitride thickness, however, cannot be scaled much below 6 nm to avoid the oxidation-punchthrough mechanisms that appear when too-thin films are unable to withstand the reoxidation step.<<ETX>>

Oxide‐nitride storage dielectrics on smooth and rough polycrystalline silicon layers

We demonstrate that for the same capacitance value, 9.5‐nm‐thick oxide‐nitride storage dielectrics deposited on rough polycrystalline silicon exhibit a lower leakage current and a higher lifetime than 5.9 nm layers on smooth polycrystalline silicon. Leakage current reduction of more than two orders of magnitude and a lifetime increase of more than three orders of magnitude are reported. These improvements are explained by the nitride bulk‐limited type of conduction. Our data show that textured storage capacitors have all the properties required for efficient fabrication of 64 megabit dynamic random access memories.

Electrical properties of oxide‐nitride dielectric films incorporating passivation oxide on polycrystalline silicon for advanced dynamic random access memory stacked capacitors

We demonstrate that electron trapping in oxide/nitride (ON) dielectric films with a passivation oxide on rugged polycrystalline silicon is lower than in those without passivation oxide. The leakage current at high field through the Si3N4 films incorporating a passivation oxide is smaller than through Si3N4 films without passivation oxide. The deposited passivation oxide allows the formation of thinner Si3N4 films and also reduces the leakage current through Si3N4 films at high field. Our results show that oxide‐nitride layers on deposited passivation oxides have the low leakage current, tight dielectric breakdown distribution, and trapping characteristics suitable for advanced dynamic random access memory (DRAM) stacked capacitors.

Influence of silicon nitride deposition conditions on the electrical properties of oxide‐nitride (ON) dielectrics on smooth and as‐deposited rugged polycrystalline silicon

The effect of Si3N4 deposition conditions on the electrical properties of ON dielectric films on smooth and as‐deposited rugged polycrystalline silicon is investigated. The results show that the leakage current, dielectric breakdown strengths, and the charge trapping characteristics of ON dielectric films are influenced by the Si3N4 deposition conditions. Larger capacitance increases on rugged electrodes, lower leakage currents, higher breakdown fields, and lower electron trapping rates are observed for ON dielectric films fabricated with low NH3: SiH2Cl2 gas ratio and deposited at higher temperature. These films are also expected to have a thicker bottom oxide due to the poor oxidation resistant characteristic of the thin nitride layer deposited at high temperature.

Leakage current and reliability of thin nitride films on as‐deposited rugged polycrystalline silicon

The leakage current and reliability characteristics of thin oxide/nitride (ON) storage dielectrics on as‐deposited rugged polycrystalline silicon layers are discussed. Rugged capacitors showing capacitance improvements as high as 53% exhibit only a slight increase in leakage current when compared to smooth structures. Even though these capacitors have a shorter lifetime at high electric fields, time‐dependent dielectric breakdown data at various fields show that their field acceleration coefficient is larger. However, lifetime extrapolations to low operating fields might be inaccurate if the field enhancement at the electrode asperities is not taken into account for the rugged capacitors.