Silicon oxide formation, chemical vapor

Narushima T, Goto T, Yokoyama Y, Takeuchi Y, IguchiY, Hirai T, Active-to-passive transition and bubble formation for high-temperature oxidation of chemically vapor-deposited silicon carbide in CO-CO2 atmosphere , J Am Ceram Soc, 1994 77(4) 1079-1082. 

A schematic view of the cold cathode fabrication process is shown in Fig. 10.18. The cold cathode is fabricated by low pressure chemical vapor deposition (LPCVD) of 1.5 pm of non-doped polysilicon on a silicon wafer or a metallized glass substrate. The topmost micrometer of polysilicon is then anodized (10 mA cnT2, 30 s) in ethanoic HF under illumination. This results in a porous layer with inclusions of larger silicon crystallites, due to faster pore formation along grain boundaries. After anodization the porous layer is oxidized (700 °C, 60 min) and a semi-transparent (10 nm) gold film is deposited as a top electrode. 

In the processing of integrated circuits, silicon dioxide (SiOa) can be used as a mask during ion implantation or diffusion of impurity into silicon, for passivation, for protection of the device surface, as interlayers for multilevel metallization, or as the active insulating material — the gate oxide film in metal-oxide-semiconductor (MOS) devices [1, 2], At the present time, several methods have been developed for the formation of Si02 layers, including thermal and chemical oxidation, anodization in electrolyte solutions, and various chemical vapor deposition (CVD) techniques [2, 3],... 

Figure 1 shows the surface imaging system using photogenerated add-catalyzed SiOj formation by the chemical vapor deposition (CVD) method. Upon irradiation with UV light the surface of polymers having imino sulfonate units becomes hydrophilic because of the formation of sulfonic add. Water sorption firom the atmosphere occurs at the top surface of the irradiated films. When the irradiated surface is exposed to the vapor of alkoxysUanes, a silicon oxide network is formed at the near surface of Ae polymers. No silicon oxide network is formed at unirradiated areas... 

Table 1 summarizes some microstructural and electrochemical properties of porous Si anode materials, as pertaining to the second approach mentioned above, collected from the literature published since 2005. Several synthesis methods have been identified for preparing the porous Si anode materials (column 1, Table 1). One of the two most adopted methods is known as the metal-assisted chemical etching (MACE denoted as E in Table 1). The fundamental principle of this method can be found in the handbook chapter Porous Silicon Formation by Metal Nanoparticle Assisted Etching. Figure 2 shows an example of the MACE-derived porous Si particle. The other most adopted method is magnesiothermic reduction (denoted as M in Table 1). In this method (see handbook chapter Porous Silicon Formation by Porous Silica Reduction ), porous Si oxide materials are reduced by magnesium vapor under high-temperature thermal treatment. The porous Si oxide precursors may be synthesized via the conventional sol-gel processes. Porous Si particles with unique pore structures, such as hollow interior and ordered mesoporosity, may be obtained from Si oxides having the same pore structures which are achieved by using proper templates.

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