다층배선 절연용 저유전율 비정질 불화탄소박막의 증착과 특성평가
Fabrication and characterization of amorphous fluorinted carbon film with low dielectric constant for intermetallic dielectric material
반도체 다층배선 저유전율 불화탄소박막;
- 원문 URL
Fluorinated amorphous carbon thin films (a-C:F) for the use of low dielectric constant intermetallic layer dielectrics are deposited by plasma enhanced chemical vapor deposition with C_(4)F_(8) and Si_(2)H_(6)/He gas mixture as precursors. CF_(4) had been conventional carbon and fluorine source for many years, but CF_(4) has 4 times fluorine against carbon. To reduce the ratio of carbon to fluorine, C_(4)F_(8) was chosen. During the growing amorphous fluorinated carbon film, the carrier gas of Si_(2)H_(6)/He gas is not only just carrying the precursor to the silicon wafer but also capturing the excessive fluorine ion from carbon fluorine source that is C_(4)F_(8). Because the decomposed fluorine ions from C_(4)F_(8) by heat or plasma are so reactive that they can easily attack the film. Therefore the choosing the carrier gas is as important as the choosing the precursor itself. The Si_(2)H_(6)/He gas was chosen to fulfill the required role of capturing the excessive fluorine ions. To characterize and improve film properties, we changed various conditions such as deposition temperature, RF power, etc., and we measured the thickness and refractive indexes and FT-IR before and after annealing. We also performed XPS measurement and EDS measurement for analyzing the element components, and SEM and AFM for surface morphology. At low temperature the film properties are very poor although the growth rate was very high. On the other hand, the growth rate was low at high temperature. The growth rate increases as deposition pressure. The dielectric constants of samples were in the range of 1.5∼6. Relatively good result was come from 125C temperature condition sample. The growth rate and energy gap change were mostly affected by temperature change not ambient pressure change, however, the FT-IR result shows there is no large difference between various temperature samples except 200C. The SEM and AFM results shows good smoothness of sample, and XPS and EDS results shows that there are no oxygen in the sample which can degrade the sample severely. The films were hydrophobic.