Influence of network bond percolation on the thermal, mechanical, electrical and optical properties of high and low-k a-SiC:H thin films

As demand for lower power and higher performance nano-electronic products increases, the semiconductor industry must adopt insulating materials with progressively lower dielectric constants (i.e. low-k) in order to minimize capacitive related power losses in integrated circuits. However in addition to a lower dielectric constant, low-k materials typically exhibit many other reduced material properties that have limited the ability of the semiconductor industry to implement them. In this article, we demonstrate that the reduced material properties exhibited by low-k materials can be understood based on bond constraint and percolation theory. Using a-SiC:H as a case study material, we utilize nuclear reaction analysis, Rutherford backscattering, nuclear magnetic resonance and transmission Fourier transform infra-red spectroscopy measurements to determine the average coordination (〈r〉) for these materials. Correlations of 〈r〉 to Young's modulus, hardness, thermal conductivity, resistivity, refractive index, intrinsic stress, mass density and porosity show that an extremely wide range in material properties (in some cases several orders of magnitude) can be achieved through reducing 〈r〉 via the controlled incorporation of terminal SiHx and CHx groups. We also demonstrate that the critical point at 〈r〉 ≤ 2.4 predicted by constraint theory exists in this material system and places limitations on the range of properties that can be achieved for future low-k a-SiC:H materials.