Gaseous etchants

The method of molecular dynamics (MD), described earlier in this book, is a powerful approach for simulating the dynamics and predicting the rates of chemical reactions. In the MD approach most commonly used, the potential of interaction is specified between atoms participating in the reaction, and the time evolution of their positions is obtained by solving Hamilton s equations for the classical motions of the nuclei. Because MD simulations of etching reactions must include a significant number of atoms from the substrate as well as the gaseous etchant species, the calculations become computationally intensive, and the time scale of the simulation is limited to the... 

Solid + gaseous etchant volatile products Si(s) + 2Xep2(g) Sip4(g) + 2Xe(g)... 

Chlorine ttifluoride is utilized in the processing of nuclear fuels to convert uranium to gaseous uranium hexafluoride. Chlorine ttifluoride has also been used as a low temperature etchant for single-crystalline siHcon (122,123). 

The major use of C1F3 is in the nuclear industry which converts unclean spent fuel reprocessing, uranium metal into gaseous uranium hexafluoride. Other applications are low temperature etchant for single crystalline silicon [63,64], It is also used as a fluorinating reagent and in the synthesis of GIF and conversion of metals to metal fluorides such as tantalum and niobium metals to tantalum pentafluoride and niobium pentafluoride, respectively. 

As the name implies, the species that do the etching in this technique are gaseous plasmas generated within an evacuated chamber to which is introduced the etchant precursor gas(es) and which is subjected to high-frequency electric power via external electrodes. These plasmas comprise ionic and neutral fragments. For a precursor etchant gas such as carbon tetrafluoride (CF4), species including C, CF" ", CF, C, F, CF, CF2, and CF3 have been detected in the generated plasma. ... 

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