This review discusses within a unified framework various phenomena occurring in thermally grown SiO2 films on silicon with hydrogen as the most important contaminant or additive. The possible sources of hydrogen are (i) H20 in the oxidizing ambient, deliberately i~ntroduced or resulting from permeation through hot furnace tubes, (ii) hydrogen in the room ambient oxide film on silicon, and (iii) deliberate or unintentional H2 or H20 in the ambient of postoxidation heat-treatments. The "critical oxide thickness," which separates the linear oxidation regime from the parabolic one, is a very sensitive indicator of H20 present in the oxidizing ambient. There is plenty of evidence, both direct and indirect, of hydrogen in SiO2 films. In particular, infrared spectroscopy shows that OH and Sill groups are present whose concentration and distribution depend strongly on preparation conditions. These groups can be H-bonded to an oxygen; this feature and the presence of Sill distinguishes SiO2 films from fused SiO2 which is another form of noncrystalline SIO2. The H-bonded OH groups in grown SiO2 films may be preferentially aligned along structural channels and responsible for various transport processes characterized by ~.,0.3 eV activation energy. Hydrogen greatly affects the properties of the Si/SiO2 interface, particularly its behavior under negative bias stress and irradiation. In fact, practically all properties of Si/SiO2 interface structures depend so strongly on hydrogen that its proper control and the understanding of its complicated role are probably the most important problems associated with these structures. This is particularly true for silicon-based chemical sensors whose operation is basically determined by hydrogen in the SiO2 film. Various aspects of the hydrogen in Si/SiO2 interface structures are similar to the role of hydrogen in SisN4 and SiH~ polymer films as well as in passivating films on metals.It has been known for many years that hydrogen, often in the form of water, greatly affects the oxidation of silicon and the interface properties of Si/SiO2 structures. Various observations on negative bias instability, irradiation behavior, and dielectric properties have corroborated the evidence that hydrogen plays a major role in Si/SiO2 interface structures. Also, it is very likely that hydrogen essentially determines the operation of some devices, particularly solidstate chemical sensors involving the Si/SiO2 interface, such as ion-sensitive field-effect transistors (ISFET).This paper discusses within a unified framework various phenomena occurring in SiO2 films on silicon, with hydrogen as the most important contaminant or additive. Thermally grown SiO2 films will be emphasized since thermal rather than anodic oxidation is the technologically important process. It will be shown that practically all properties of Si/SiO2 interface structures depend very strongly on hydrogen and that the precise control of hydrogen in the various processing steps is probably the most important problem of MOS technology. ...
Analysis of thickness vs. time data for oxides thermally grown on Si in dry oxygen reveals that deviations from the widely used linear parabolic rate law exist in the thick oxide regime as well as in the better‐known initial “fast” growth regime. We suggest two rate laws that eliminate these deviations without resorting to a special oxidation mechanism in either regime. One of these rate laws is phenomenological, and one is based on a physical model in which the oxygen flux through the growing oxide is considered to have two components. One component reflects the usual diffusion of oxygen, and is thickness dependent; another one is thickness independent and is attributed to transport through structural channels.
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