Reliability of 10 nm Stacked Insulator on Polycrystalline Silicon in Planar and Trench Capacitors

Abstract

The reliability of three types of stacked insulating films (ONO, ON, NO) with thicknesses of 10 nm and below deposited on highly doped polysilicon are compared. It is shown that the doping process of the underlaying polysilicon plays an important role in the dielectric breakdown behavior. Evaluation of I-E characteristics from voltage ramp measurements demonstrates the influence of top and bottom oxide thickness. Under NO double layers generally a native oxide is found. This leads to similar reliability results as found for triple layers. Real double layers (ON) without any potential barrier at the top electrode show significantly shorter lifetimes at positive gate voltage. Hence the native oxide between bottom electrode and nitride is not negligible. Extrapolations of the data measured by the constant voltage method on planar and trench capacitors indicate that the investigated ultrathin multilayer films on polysilicon show promise as dielectrics in storage capacitors of future DRAMs.

Charge transport in thin interpoly nitride/oxide stacked films

“…[12][13][14][15][16] A transport analysis of experimental data allows us to point out the role of each single layer dielectric in the multilayer structure conduction mechanism. In particular, we claim that the electrical transport through the analyzed multilayer structures can be described in terms of conduction mechanisms of isolated single-layer dielectrics.…”

“…Experimental data, reported in the literature, have shown that silicon nitride is more conductive than silicon dioxide for a given electric field, 12,13 the current-field characteristic of the nitride/oxide dual-layer film with an oxide cathode ͑called hereafter ON͒ is very similar to that of a single oxide film, 13,14 the nitride/ oxide dual-layer film with a nitride cathode ͑called hereafter NO͒ is less conductive than the ON case for a given electric field, 13,14 and finally, the tri-layer ONO current-field characteristics are similar to the NO structure 13,15 and are strongly influenced by the thickness of the anode side oxide. 15,16 The electrode-limited conduction mechanisms of SiO 2 are presently well known. 17 Nitride bulk charge transport has been widely studied in the past.…”

“…1͑c͒ and 1͑d͔͒, based on MNOS and SONOS theories. Transport models, invoking a dominant electron conduction for both gate polarities, 14,16 have been proposed, as well as hole flow models for nitride conduction ͑where the anodic oxide reduced hole tunneling from the poly-silicon to the nitride͒. 6,9,11,25,26 A quantitative current conduction model, based on electron ͑hole͒ Fowler-Nordheim current through the cathodic ͑anodic͒ SiO 2 and hole Poole-Frenkel current in the Si 3 N 4 is proposed in Refs.…”

Bimodal lifetime distributions of dielectrics for integrated circuits

“…The change of the slope of the intrinsic distribution does not affect the reliability of the product since the specified lifetime of the product is always in a region of decreasing failure rate for large area capacitors and moreover it is some decades below the intrinsic dielectric lifetime. Distributions measured at different voltages are fitted very well applying equation (5).…”

Thickness and polarity dependence of intrinsic breakdown of ultra-thin reoxidized-nitride for DRAM technology applications

“…Much of these published reliability results were obtained from planar structures with the bottom-oxide grown on doped poly-Si, which is known to have microstructure and morphology problems (43. The films reported previously were much thicker (8.0-10.0 nm) than the data presented in this work (4)(5)(6)(7). For the first time, this paper describes extensive results for intrinsic breakdown characteristics of reoxidized nitride (NO) dielectric films using deep-trench capacitors with the oxide equivalent thickness (T,) down to 3.9 nm.…”