Specific Plasma-Chemical Etching Processes

Saturates like CF4, CCU, CF3CI, COF4, SFe, and NF3. The saturates are chemically not very active and unable themselves either to etch or to form a surface film. They dissociate in plasma through collisions with electrons, producing chemically aggressive etchants and unsaturates. 

Etchants like atoms F, Cl, Br, and O (applied for resist) and molecules such as F2, CI2, and Br2. Etchants are obviously the major players in etching processes they are very aggressive, reacting with substrates and producing volatile products. 

Oxidants like O, O2, and so forth. The oxidants added to feed gas are able to react with unsaturates, converting them into etchants and volatile products. 

Reductants like H, H2, and others. The reductants added to the feed gas are able to react with etchants and neutralize those producing passive volatile products. 

Non-reactive gases like N2, Ar, He, and so forth. The non-reactive additives are sometimes used to control electrical properties of etching discharges and thermal properties of a substrate. 

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Positive ions are obvionsly major players in plasma-chemical processes. Their exothermic reactions with neutrals usually have no activation energy, which makes their contribution significant in many specific plasma-chemical processes, particularly in plasma catalysis. In addition to high chemical activity, the ions can have significant kinetic eneigy, which determines their contribntion, for example, in reactive ion etching. 

Grigoryev, Y.N., Gorobchuk, A.G. Specific Features of Intensification of Silicon Etching in GE4/O2 Plasma. Russian Microelectronics 36, 321-332 (2007) Grigoryev, Y.N., Gorobchuk, A.G. Simulation of the polymerization process on a silicon surface under plasma-chemical etching in CF4,/H2- Journal of Surface Investigation X-ray, Synchrotron and Neutron Techniques 9, 184-189 (2015)... 

Like the literature of plasma-assisted etching, the literature on the PECVD of specific materials is considerable. Because film properties are ultimately determined by chemical reaction mechanisms, reactor design, and film structure (Figure 5), the determination of the exact relationships between properties and processing is difficult. At present, the fundamental understanding of such relationships is limited, and thus, empirical efforts have been the norm. In this chapter, the more widely studied film materials deposited by PECVD will be briefly discussed. More extensive information on these and other films can be found in a number of review articles (9-14, 32, 50, 200-203) and references therein. 

The chemical, electrochemical, and photoelectrochemical etching processes by which microelectronic components are made are controlled by electrochemical potentials of surfaces in contact with electrolytes. They are therefore dependent on the specific crystal face exposed to the solution, on the doping levels, on the solution s redox potential, on the specific interfacial chemistry, on ion adsorption, and on transport to and from the interface. Better understanding of these processes will make it possible to manufacture more precisely defined microelectronic devices. It is important to realize that in dry (plasma) processes many of the controlling elements are identical to those in wet processes. 

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