Fluorine, atomic, etchant

Etchant species (for example, fluorine atoms) diffuse to the surface of the material and adsorb onto a surface site. It has been suggested (20) that free radicals have fairly large sticking coefficients compared with relatively inert molecules such as CF4, so adsorption occurs easily. In addition, it is generally assumed (20) that a free radical will chemisorb and react with a solid surface. Further, surface diffusion of the adsorbed species or of the product molecule can occur. 

CO2 laser) etch Si0 2 on Si(lll), both processes occurring via SiF formation [974a]. Fluorine atoms (generated by ArF laser photolysis of COFj) also form a very effective etchant for polycrystalline silica deposited on Si0 2 [1273a]. Finally, COFj and fluorine atoms are both generated in a CF -NO plasma [1775]. 

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