Properties of SiO2 on Si after Exposure to 3:1 H 2 + N 2 and NH 3

An annealing study was performed on nonstoichiometric amorphous SiO= (x < 2) films fabricated by plasmaenhanced chemical vapor deposition (PECVD) at 300~ using Sill4 and N20 chemistry. After deposition, these layers contain hydrogen and nitrogen impurities, which were found to play a major role in the explanation of the properties of annealed films. Fourier transform infrared absorption spectra of plasma enhanced vapor deposited oxide layers annealed at elevated temperatures show approximately the same features as the spectra of thermal oxide films. This similarity demonstrates the ability of PECVD oxides to form a regular network of Si-O tetrahedrals. From distinct deviations in these spectra, the participation of Si-N bonds located within the Si-O network is concluded. The participation of Si-N bonds is also confirmed by the estimation of the activation energies in wet chemical etching studies using ammonium hydroxide water solution. The mechanical stress of the PECVD oxides clearly depends on the deposition conditions and their thermal history. With increasing annealing temperature the intrinsic stress increases until a maximum film stress value is reached between 700 and 800~ Above this temperature the intrinsic stress is continuously reduced until the total stress approaches the value of the thermal film stress. This is explained mainly by hydrogen desorption, Si-N bond formation, and SiO2 bond rearrangement processes. Depending on deposition conditions and postannealing steps, it is possible to design layers with a predefined stress.

Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

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Thermal Annealing Effects on the Mechanical Properties of Plasma‐Enhanced Chemical Vapor Deposited Silicon Oxide Films

Schliwinski

Schnakenberg

Windbracke

et al. 1992

“…This has been shown in a detailed study of a deposition process of a-SiOxNy :H, which was published recently, 22 and by a nitridation study of thermally grown oxides. 23 We did not observe any -H, -OH, or -NH~, related absorption bands in the spectra. This, of course, has to be expected since no hydrogen is involved in the growth process.…”

Section: T H I C K N E S S U N I F O R M I T I E S --I N General Tmentioning

confidence: 55%

Growth Rate and Characterization of Silicon Oxide Films Grown in N 2 O Atmosphere in a Rapid Thermal Processor

Lange

Bernt

Hartmannsgruber

et al. 1994

A rapid thermal oxidation process of silicon in N20 ambient was investigated using a commercially available reactor with a fixed wafer position and a gas flow parallel to the wafer surface. For such a configuration, thickness uniformities in the 2% range were obtained for the first time. The oxidation rate as a function of process temperature and time was investigated. A retardation in the N20 oxidation rate as compared to the oxidation in O2 ambient is explained by the formation of a nitrided interracial layer. A comparison of experimental results with an oxidation model calculation shows that this interface can affect either the oxidant diffusivity through the oxide or the reaction rate at the silicon surface. Infrared spectra of nitrided oxide films reveal a regular arrangement in the Si-O network, similar to that of high quality thermally grown oxides. A vibrational contribution to that spectrum from a Si-ON subnetwork is displayed. The accumulated charge to breakdown on metal-oxide-semiconductor capacitors as a function of the injected current density revealed different slopes for oxides either thermally grown or grown in N20. Hence, the projected lifetime for devices with N20 grown oxide under low operating fields is extended by one order of magnitude in comparison with th e thermal oxide.

“…In order to meet the needs of ultra large scale integration, SiO2 films are usually annealed prior to their use as the gate dielectric material in insulated gate field effect transistors (IGFETs). It was observed that annealing effectively reduces the insulator fixed charge density, the interface state density, the bulk electron traps, and even improves electrical strength (1)(2)(3). Thermal annealing is usually performed in a pure and/or a mixture ambient of Ar, N2, or H2.…”

mentioning

confidence: 99%

Charge Trapping and Interface State Generation by Avalanche Hot‐Electron Injection in Rapid Thermal NH 3 Annealed and Reoxidized SiO2 Films

Liu

Chen

Cheng

et al. 1990

Using rapid thermal processing (RTP), SiO2 films with a thickness of 35 nm were annealed in NH3 and subsequently reoxidized. The properties of charge trapping and interface state generation of these films were investigated by an avalanche hot-electron injection technique. Experimental results indicate that by reoxidation, both the density of NH3 annealing induced traps and their capture cross section can be reduced; the hardness of the interface against hot-electron bombardment is improved while the low oxide fixed charge and interface state density as well as the high breakdown field are also preserved. A correlation between the interface state generation and the history of thermal nitridation is observed. Results also show that rapid thermal NH3 annealing induced traps must be water related and have a much smaller capture cross section than that of the conventionally nitrided oxide. It is proposed that hydrogen dissolved from NH3 during nitridation introduces defects in the form of unsaturated Si--O bonds which may be responsible for the high density of electron traps while the interface-incorporated nitrogen will help to increase the resistance to the hot-electron injection induced damage. An oxygen deficiency model can be used to explain the origin of these traps as well as the generation of interface states and the mechanism of reoxidation.