The characterization of octafluorocyclobutane-based plasma discharges for the selective etching and processing of silicon dioxide and low-K dielectric thin films

Utilizing IRDLAS, and Langmuir probe measurements; we were able to demonstrate that C₂F₄ and CF₂ are the main dissociation products in a C₄F₈ plasma discharge. Under conditions of energetic ion bombardment, C₂F₄ and CF₂ are consumed at the wafer surface. Increases in ion energy increase the rate of consumption of C₂F₄ and CF₂, resulting in increased SiO₂ etch rates.; The addition of Ar to the C₄F₈ discharge increased the ion flux in the discharge. The increased ion flux reduced the thickness of the fluorocarbon film, thus enhancing etch rates. During these experiments we were able to monitor SiF2 using UV-Vis absorption. From these experiments we determined that SiF₂ is an important etch product of the SiO ₂ etching process, due to its presence in high concentrations in the discharge.; By using IRDLAS and XPS we were able to correlate changes in the surface chemistry during etching with changes in the neutral radical densities as a function of Ar addition to the discharge. The results of these experiments provided further evidence the ion energy, ion flux, and neutral radical flux all have important roles in the selective etch mechanism. Using the results from a parametric study we performed, we found that the roles of the ion energy, ion flux, and neutral radical flux are valid over a wide range of parameters. Additionally, by performing these studies on two different reactor platforms, we determined that our findings are not reactor dependent.; We have shown that fluorocarbon plasmas can be used to modify the pore surface of porous silica. This modification process allowed us to decrease the dielectric constant of the porous silica film by the replacement of hydroxyl groups on the pore surface with fluorine. The plasma modified films allowed us greater control of the etch process, as was shown by the comparison of patterned plasma modified and as prepared EISA porous silica films.; We have shown that hydroxyl radicals on the pore surface inhibit etching. We speculate that the hydroxyl radicals scavenge fluorine from the fluorocarbon layer, thereby rendering the film F-deficient. Due to this process surfaces with high hydroxyl concentrations required high ion energy to break through this layer and etch the underlying substrate. Conversely, pore surfaces where a fraction of the hydroxyl radicals have been replaced by fluorine enhance etching. We speculate both the reduction in the hydroxyl radicals and addition of fluorine allows the formation of a F-rich fluorocarbon layer. Due to the high surface area of the porous films, an increased amount of C₂F ₄ and CF₂ were consumed, compared with SiO₂ , thus the enhancement of the etch rate.