Patterning of fluorine-, hydrogen-, and carbon-containing SiO2-like low dielectric constant materials in high-density fluorocarbon plasmas:: Comparison with SiO2

Successful pattern transfer of 0.36-0.62 mu m features into fluorinated silicon dioxide, hydrogen silsesquioxane (HSQ), and methyl silsesquioxane (MSQ) has been demonstrated in a transformer coupled plasma (TCP) source using fluorocarbon feedgas chemistries. These films have a lower dielectric constant than conventional SiO2. It is this property that makes them attractive for implementation in future integrated circuit technology. The etching of these novel dielectrics was compared to conventional SiO2. We have observed that the different chemical makeup of these SiO2-like dielectrics does not affect the etching when weakly polymerizing gases are used, such as CF4. In this case, the etch rate is primarily dependent on the ion energy. For more polymerizing chemistries, like CHF3 or C3F6/H-2 gas mixtures, x-ray photoelectron spectroscopy analysis showed that an increasing steady state fluorocarbon film thickness limits the ion and neutral flux at the interface of the various dielectrics. It is suggested that, as the fluorocarbon film thickness increases, the etching becomes more dependent on neutral species from the gas phase. In this case, hydrogen and carbon impurities in HSQ and MSQ, respectively, limit the etch rate. On the other hand, fluorine in the fluorinated SiO2 film enhances the etch rate as compared with the etch rate of conventional SiO2. In line with these observations, we conclude that fluorine from the gas phase is most likely the controlling etchant as the fluorocarbon film increases beyond the ion penetration depth. (C) 1999 American Vacuum Society. [S0734-2101(99)01903-X].