Anindya Dasgupta

Si0.85Ge0.15 oxynitridation in nitric oxide/nitrous oxide ambient

Low temperature, nitric oxide (NO)/nitrous oxide (N2O) aided, sub-35 A Si0.85Ge0.15 oxynitrides have been grown at 550 and 650 °C, while the oxynitridation feed gases have been preheated to 900 and 1000 °C, respectively, before entering the reaction zone. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy (SIMS) data suggest that NO-assisted oxynitridation incorporates more nitrogen than the N2O-assisted one, while there is minimal Ge segregation towards the dielectric/substrate interface in both oxynitridation processes. Moreover, SIMS results suggest that nitrogen is distributed throughout the film in contrast to high temperature Si oxynitridation, where nitrogen incorporation takes place near the dielectric/substrate interface. Z-contrast imaging with scanning transmission electron microscopy shows that the oxynitride grown in NO at 650 °C has a sharp interface with the bulk Si0.85Ge0.15, while the roughness of the dielectric/Si0.85Ge0.15 substrate interface is less than 2 A. These re...

Two-step processes for bimodal N concentration profiles in ultra-thin silicon oxynitrides

The presence of nitrogen in the dielectric films is known to impart highly desirable properties in the ultra-large-scale-integration era; the position, amount and concentration profiles of nitrogen are of great interest. In this work, we have studied two-step processes leading to bimodal nitrogen concentration profiles, with one nitrogen peak near the Si ydielectric interface and the other at the dielectric surface. Secondary Ion Mass Spectroscopy and Angled Resolved X-Ray Photoelectron Spectroscopy studies suggest that an ammonia nitridation step (at 1000 8C and 1 atm) following silicon oxynitridation in N O (or possibly following 2 oxidation in O ) at the same conditions results in a bimodal nitrogen profile when short nitridation times are used; increasing the 2 duration of the nitridation step is found to completely nitridate the initially grown oxynitride (or oxide). Post nitridation of NOgrown oxynitrides that are not found to result in bimodal N concentration profiles at the conditions studied. The experimental findings are in agreement with theoretical predictions of preliminary modeling studies. The engineering of desired bimodal nitrogen concentration profiles in nano-dielectric materials of interest becomes, therefore, possible through two-step processes. 2003 Elsevier Science B.V. All rights reserved.

Growth kinetics of thermal silicon oxynitridation in nitric oxide ambient

The chemical kinetics and process-structure relationships of silicon oxynitride films grown in nitric oxide (NO) ambient at 900–1000 °C are studied in flow reactor systems. Residual gas analyses at the reactor exit suggest that no detectable gas phase decomposition of NO takes place at these conditions. Two regions, one nitrogen-depleted (near the top dielectric surface) and one nitrogen-rich (near the dielectric/substrate interface), are considered within the dielectric film, based on reported secondary ion mass spectrometric and angled resolved x-ray photoelectron spectroscopic data. Nitrogen removal reactions are accounted for in the nitrogen-rich layer, while nitrogen incorporation reactions are considered at the dielectric/substrate interface. The diffusion-reaction growth rate model makes use of literature values for the solid-state diffusivities, reaction rate constants, and fraction of the nitrogen-rich layer. The model predictions are found to be in good agreement with all trends of the experimen...

Process-Structure Relationships of Nitrided Oxides and Oxynitrides

The presence of nitrogen in the dielectric films is known to impart highly desirable properties in the ultra-large-scale-integration era; the position, amount and concentration profiles of nitrogen are therefore of great interest. In this work, we investigate two-step processes leading to bimodal nitrogen profiles, with one nitrogen peak near the Si/dielectric interface and the other near the dielectric surface. At 1000°C and 1 atm, a nitridation step with NH 3 following either an oxidation (in O 2 ) or oxynitridation (in N 2 O) step is found to result in a bimodal nitrogen concentration profile for short nitridation times. Increasing the duration of the nitridation step with NH 3 is found to completely nitridate the entire film. Secondary Ion Mass, Angle Resolved X-Ray Photoelectron, and Fourier Transform Infrared Spectroscopic studies are shown to support these observations. Therefore, based on such process-property-structure relationships, the engineering of desired nitrogen concentration profiles in nano-dielectric materials of interest becomes possible. Such knowledge may have significant implications on micro- and nano-electronic applications of silicon oxynitrides.