Low dielectric constant (low-k) films have been widely used as insulating materials in ultra-large-scale integrated circuits. Low-k films receive heavy damage during the plasma processes of etching or ashing, resulting in an increase in their dielectric constant. In order to realize damage-free plasma processes for low-k films, it is essential to determine the influence of radiation, radicals, and ions emitted in the plasma process on the characteristics of low-k films. We have developed a technique to evaluate the influence of radiation, radicals, ions, and their synergies on films in real plasma processes and have named it pallet for plasma evaluation (PAPE). Using the PAPE, plasma-induced damage on porous SiOCH films were investigated in dual-frequency capacitively coupled H2∕N2 plasmas. The damage was characterized by ellipsometry, Fourier-transform infrared spectroscopy, and thermal desorption spectroscopy. On the basis of the results, the damage mechanisms associated with vacuum ultraviolet (VUV) and UV radiation, radicals, and ions were clarified. The damage was caused not only by ions and radicals but also by VUV and UV radiation emitted by the plasmas. Moreover, it was found that the synergy between the radiation and the radicals enhanced the damage.

The fluctuations in etch rates caused by changes in chamber conditions were studied. Excess deposition of C-F polymer on the chamber wall increased CF x density while H was consumed by the polymer and/or was deactivated on the conductive surface of Si electrodes. The change in radical densities had a clear relationship with the SiN etch rate. The etch rate was accurately predicted by statistical analysis using equipment engineering system (EES) data and optical emission spectroscopy (OES) signals which were extracted by considering both the physical model and the results of statistical analysis.

In reactive-ion etching (RIE) of silicon oxide (SiO2) or silicon nitride (SiN) by fluorocarbon (FC) or hydrofluorocarbon (HFC) plasmas, fluorinated carbon layers may be formed on the etched surfaces and affect their etching rates. In this study, the properties of SiO2 and SiN etching by FC or HFC plasmas are examined in light of the formation mechanism of such carbon layers by molecular dynamics (MD) simulation. Furthermore, in this study, the electronegativity effect of fluorine (F) is taken into account in the interatomic potential functions for C–F and Si–F bonds and MD simulations here show SiO2 and SiN sputtering yields are closer to those obtained from ion beam experiments. It has been found from MD simulations that the SiN sputtering yield during etching by HFC ions is higher than that by FC ions owning to the fact that hydrogen in the HFC ion beam tends to impede the formation of a fluorocarbon layer on SiN and therefore energetic fluorine ions/atoms are more readily available to etch SiN underneath the polymer layer.

Articles you may be interested inEffects of plasma and vacuum-ultraviolet exposure on the mechanical properties of low-k porous organosilicate glass J. Appl. Phys. 116, 044103 (2014); 10.1063/1.4891501Plasma damage effects on low-k porous organosilicate glass Plasma-induced damage to porous SiOCH ͑p-SiOCH͒ films during organic resist film ashing using dual-frequency capacitively coupled O 2 plasmas was investigated using the pallet for plasma evaluation method developed by our group. The damage was characterized by ellipsometry and Fourier-transform infrared spectroscopy. Individual and synergetic damage associated with vacuum ultraviolet ͑VUV͒ and UV radiation, radicals, and ions in the O 2 plasma were clarified. It was found that the damage was caused not only by radicals but also by synergetic reactions of radicals with VUV and UV radiation emitted by the plasmas. It is noteworthy that the damage induced by plasma exposure without ion bombardment was larger than the damage with ion bombardment. These results differed from those obtained using an H 2 / N 2 plasma for resist ashing. Finally, the mechanism of damage to p-SiOCH caused by O 2 and H 2 / N 2 plasma ashing of organic resist films is discussed. These results are very important in understanding the mechanism of plasma-induced damage to p-SiOCH films.

An organic low-dielectric constant (low-k) film, polyallylene (PAr), is a prospective candidate for low-k interlayer films for ultra large-scale integrated circuits (ULSIs). PAr films are caused the property changes such as increases of the dielectric constant during plasma etching and ashing. In a previous study, we have developed a novel technique called pallet for plasma evaluation (PAPE) for separately evaluating the property changes caused by radiation, radicals, and ions in process plasmas and clarified the mechanism of plasma-induced property changes on low-k porous SiOCH films. In this study, using the PAPE technique, we investigated the changes on the surface of a PAr film due to radiation, radicals, radiation with radicals, and ions in dual-frequency capacitively coupled H2/N2 plasmas. The property changes were characterized by ellipsometry and X-ray photoelectron spectroscopy. The property changes on the PAr films due to radiation and radicals were considerably smaller compared to those on the low-k porous SiOCH films.