Reliability and Characterization of Composite Oxide/Nitride Dielectrics for Multi‐Megabit Dynamic Random Access Memory Stacked Capacitors

Abstract

The reliability and electrical properties of planar and 3D interpoly oxide/nitride films stacked on multi-megabit dynamic random access memory (DRAM) array topography are reported to determine their thinning and capacitance limits. A compromise between reliability, leakage current, and storage capacity is proposed for oxidized low-pressure chemical vapor deposited nitride layers with different nitride thicknesses, oxidation conditions, and top/bottom polysilicon doping levels. Capacitance, leakage current, and time-dependent dielectric breakdown measurements show that thinner nitride layers with longer oxidation times provide the maximum lifetime and capacitance. However, the nitride thinning is limited when leakage current by Poole-Frenkel or Fowler-Nordheim emission occurs. For 5 V operated high-density DRAMs, nitride layers as thin as 7 nm, giving a capacitance of 6 fF/~m 2 present the optimum conditions. For 3.3 V operations, films as thin as 4-5 nm, giving a capacitance of 9 fF/~m 2, can be expected.

Preparation of Thin Dielectric Film for Nonvolatile Memory by Thermal Oxidation of Si-Rich LPCVD Nitride

“…As shown in the figure, remarkable oxygen and nitrogen tails are found due to the ion recoil as a result of 1 keV Cs ϩ ion sputtering. Although the SIMS spectra may not reflect the real distribution of atoms and bonds in these samples, 6,17 it still provides useful information for the comparative study concern. The bulk nitrogen concentration is as high as 70 atom % ͑sample B͒.…”

“…Oxide-nitride-oxide ͑ONO͒ structure was considered as a good structure and has been used as dielectric in electrically erasable programmable read only memory ͑EEPROM͒ devices. [6][7] In comparison to thermal oxide, the ONO structure has lower leakage current, higher effective dielectric permittivity, and higher reliability. [8][9][10][11] However, these characteristics are still not good enough for the crucial constraints of 1 Gbit flash memory application.…”

Ultrathin Silicon Nitride Films Fabricated by Single‐Wafer Processing Using an SiH2Cl2 ‐ NH 3 ‐ H 2 System and In Situ H 2 Cleaning

“…9 is 1.4 decade/(MV cm'), which is identical with the maximum values for the conventional stacked capacitors reported by Ohji et aV and Fazan et at. 7 In order to discuss whether it is possible to use the oxidized nitride film formed by the single-wafer process in the next generation DRAMs, we extrapolate the intrinsic lifetime at the operational electric field and the capacitor area of the device from the experimental TDDB data, based on the following two assumptions:…”

Study of Excess Silicon at Si3 N 4 / Thermal SiO2 Interface Using EELS and Ellipsometric Measurements

“…The ONO structures are used in DRAM as the dielectric in the three-dimensional stacked and trench memory capacitors instead of thermal SiO 2 and as the interpoly dielectric for multilevel metallization in complementary metal oxide semiconductors (CMOS) technology. 1,2 In floating gate EEPROM, the ONO structure is used as the dielectric between the floating gate and the control gate. This layer reduces the electronic discharge from the floating gate.…”