Silicon dioxide film formation

Figure 7. A viscous flow model for silicon dioxide film formation.

The properties of silicon dioxide films also depend upon all plasma deposition parameters. Temperature is the critical parameter (240), although the compressive stress level varies with rf frequency (237, 240). Film topography can be varied during deposition by altering ion bombardment conditions (242, 243). In particular, the incorporation of Ar in the deposition atmosphere enhances sputtering and thus promotes conformal step coverage during film formation (243). 

Figure 9. Formation of micropillars from a solid precursor (schematic). (1) A175 nm thick thermal silicon dioxide film is grown on a silicon wafer. (2) A photoresist is applied by spin coating. (3) The oxide film Is selectively exposed, and then (4) selectively plasma etched with CHFs. (5) The photoresist is stripped, and (6) the silicon water is plasma etched with CI2/BCI3. (7) The residual oxide film is removed with a HF etch, and the silicon miaopillars as-formed are ready for use. Courtesy of Dr. A. Perez, Cornell University, Ithaca, NY.

Beta SiC (PSiC) has good chemical resistance, particularly to oxidation owing to the formation of a thin adherent and protective film of silicon dioxide on the surface. Its characteristics are summarized in Table 9.6. 

Since positron annihilation spectroscopy is highly sensitive to atomic defects in solid materials, positron annihilation experiments have been carried out extensively on silicon (Si) and silicon dioxide (Si02), both of which are extremely important for the microelectronic device industry. While several reviews are available [1], those reviews are mainly focused on positron (not positronium) annihilation behavior because positronium (Ps) formation dose not occur in bulk crystalline Si. Recent positron annihilation experimental studies revealed that Ps formation occurs in some Si-based thin films, such as porous Si and hydrogenated amorphous Si furthermore, Ps formation is dominant in high-purity amorphous Si02 thin films. In this chapter, Ps annihilation characteristics in Si and Si02 thin films will be discussed from the experimental point of view. 

Bertrand and Fleischer (38) have studied the chemical deposition of silicon dioxide on Indium phosphide. They found that on unoxldlzed, etched surfaces, oxide coverage was "always patchy". If the InP had a monolayer of chemisorbed oxygen, an approximately 60A-thlck oxide film could be formed at room temperature through the formation of Sl-O-P bonds at the Interface. 

A possible mechanism of formation of a sidewall passivation film in the case of silicon etching in a HCI/O2/BCI3 plasma is shown in Fig. 18 [77]. SiCf Hv-type byproducts are sputtered away by ion bombardment from the bottom of the trench. A portion of the sputtered flux strikes and sticks on the sidewalls on the trench. Oxygenation of the byproducts on the sidewalls results in a silicon dioxide type of film that resists etching. The sidewalls do not receive any appreciable ion bombardment and hence, depending on conditions, a rather thick inhibitor film may be formed. 

The commercial importance of this reaction is that water-resistant coatings are obtained from aqueous solutions of the monomers. But the linear polymers obtained from bifunctional monomers are relatively soft. Hard coatings are produced by copolymerization with multifunctional zwitterions. The hardness of these coatings can be increased by film formation in the presence of latices or colloidal silicon dioxide. 

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],... 

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