Oxynitride layer, silicon

Germann R, Salemink HWM, Beyeler R, Bona GL, Horst F, Massaiek I, Of ein BJ (2000) Silicon oxynitride layers for optical waveguide applications. J Electrochem Soc 147 2237-2241... 

Silicon oxynitrides (SiOxNy) are thin films that are basically a mixture of silicon oxide and silicon nitride, produced in a CVD-process by adding nitrous oxide (N20) to the gases used for silicon nitride deposition. By changing the oxide-to-ni-tride ratio, the properties of these films can be modified towards improved thermal and moisture stability and lower stress compared to pure silicon oxide or silicon nitride thin films [32]. At low oxygen concentrations (0/(0+ N) <0.3), oxynitride layers have good diffusion barrier characteristics [33] and oxidation resistance. 

Lanthanum oxide thin film was grown on Si substrates by the metall-organic chemical vapor deposition (MOCVD) method (400-650°C) [27]. Thin silicon oxynitride layer on the Si substrate functions well to suppress the interfacial reaction between lanthanum oxide and Si and results in the increase in the dielectric constant of deposited lanthanum oxide. The formed oxynitride layer is also effective in decreasing the leakage current. 

Aroutiounian, V. M., Martirosyan, Kh. and Soukiassian, P. Almost zero reflectance of a silicon oxynitride/porous silicon double layer antireflection coating for sihcon photovoltaic cells , (2006a) J. Phys. DiAppl. Phys. 39,1623-5. 

Silicon oxynitride (SiO cN),) films exhibit properties that fall somewhere between those of Si02 and those of Si3N4 films and have diverse applications in microelectronics. The oxynitride layers can be obtained if nitrogen oxide (N2O) is involved in the reaction of silane with ammonia [108, 109, 117-119], when silicon nitride is deposited onto an oxidized silicon substrate (silicon dioxide nitrification is incomplete at 800°C [100, 107]), or upon addition of gaseous oxygen during the CVD of silicon nitride [64, 100, 104, 120]. 

Figure 7-8. Cross-section of CVD SijN4 oxidized for 48 h at 1400°C showing the amorphous silicon oxynitride layer. The Si02 layer has been thinned. (Ogbuji, 1994).

Figure 7-9. Schematic diagram of the Si3N4 oxidation model in which a continuously varying oxygen and nitrogen content of the silicon oxynitride layer is proposed. (Adapted from Ogbuji and Jayne, 1993.)...

Studies on the oxidation behavior of dense SiCNO ceramic materials revealed the formation of a dense and continuous oxide layer with a sharp oxide/ceramic interface and parabolic kinetics from 800 °C to 1400 °C (Chollon, 2000). The parabolic constants and the activation energies were found to be similar with the values obtained for SiC and SijN. These results may be explained if oxidation of SiCNO PDCs is attributed to an oxidation mechanism involving the formation of an intermediate silicon oxynitride layer, which is also found for silicon nitride ceramics (Chollon, 2010). 

This model goes a long way towards explaining most experimental results reported in the literature for ISFETs with oxide or nitride surfaces. Unfortunately, the properties of these materials prepared in different laboratories are very different. It is known that silicon nitride (really silicon oxynitride SisNztOx) forms an oxygen-rich layer at the surface, whose thickness depends on the deposition conditions. This passivation layer forms rapidly (in a matter of hours) and is very stable, even under continuous exposure to aqueous electrolyte. The hydration of this layer seems to fit the requirements and predicted behavior of the Sandifer model. Consequently, ISFETs that have been exposed to aqueous solution for more than one hour show no adsorption effects which would be expected from the SBT model. 

The hydration layer model more or less fits the behavior of all oxides and of silicon oxynitride. The latter has a great advantage over other pH-sensitive layers because it is an excellent passivation material itself that can be prepared virtually pinhole-free. On the other hand, even thermally grown Si02 has pinholes and cracks that form a leakage path. It is that leakage path that apparently served as a... 

Finally, we will consider PECVD silicon oxynitrides, and their unique characteristics. When oxygen is added to a PECVD nitride film, there are indications that it may improve its crack resistance as a final passivation layer.13 Also, there may be advantages in terms of its electrical characteristics as an interlayer dielectric. Therefore, the nature of films grown when N20 is added to a SiH4, NH3 and He gas mixture in a high frequency (13.56 MHz), cold-wall, parallel-plate reactor have been studied. 

The topics of subsequent sections are the different materials used for thin films, specifically, silicon oxide (Section 5.5.3), silicon nitride (Section 5.5.4), poly-silicon (Section 5.5.5), and other materials, such as metals and silicon oxynitride, as well as novel thin film materials that may appear in future sensor designs (Section 5.5.6). In these sections, we adhere to the following structure first, the basic deposition process is briefly described, followed by the common function of the layer in sensor design. Subsequently, we discuss in detail the important material properties. 

The hard mask approach employs ultrathin resist films, typically < 100 nm, as the imaging layer, which are coated over inorganic hard mask substrates such as silicon oxynitride, silicon nitride, amorphous carbon, etc. 

SILICON NITRIDE, OXYNITRIDE, AND CARBON NITRIDE LAYERS... 

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