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Control over the Growth of Thin SiO(2)

IP.com Disclosure Number: IPCOM000080861D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Cahill, JG: AUTHOR [+3]

Abstract

In the growth of thin films of SiO(2), HCl is added to the oxidant used during the formation of SiO(2) in such a way, that greater control over the oxide growth is maintained than if the HCl had been added at the beginning of the oxidation process.

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Control over the Growth of Thin SiO(2)

In the growth of thin films of SiO(2), HCl is added to the oxidant used during the formation of SiO(2) in such a way, that greater control over the oxide growth is maintained than if the HCl had been added at the beginning of the oxidation process.

The manufacture of MIOS (metal-insulator-silicon) oxide-silicon) memory devices (in field-effect transistor (FET) configuration) requires high precision, regarding the control of the thickness of the oxide layer immediately adjacent to the silicon. Depending upon the required device performance, the oxide layer is generally grown to a thickness of under 50 angstroms with a required control of the order of +/- 1 to 2%. It is also well known that the electrical performance of these devices requires the lowest possible flatband voltage, consistent with the type and doping level of the silicon and counterelectrode conductor. Deviations from the ideal flatband voltage values have been established to arise from the presence of sodium ions within the oxide layer.

Among the various procedures used to control this problem, i.e., the limitation of the concentration of sodium ions below a certain level, the addition of chlorinated compounds to the oxidizing environment, and in particular the use of pure gaseous HCl, has been found most useful. The addition of HCl results also in improved breakdown properties of the dielectric film. It was also observed that the addition of the HCl yielded a relatively thicker oxide for a particular time and temperature of exposure, as compared to that obtained with oxygen or oxygen and nitrogen alone for the same time and temperature. The reason for this difference is explained by reference to Fig. 1 attached.

The variation of oxide thickness with time for oxygen alone is indicated in curve 1. The growth of oxide from an initial thickness d(o) (approx. 10 angstroms) consists of a rapid initial process followed by a...