Chemical mechanical polishing of low dielectric constant oxide films deposited using flowfill chemical vapor deposition technology

In this work, the properties and chemical mechanical polishing (CMP) characteristics of thin films of a new low dielectric constant (low-kappa) oxide deposited using Flowfill chemical vapor deposition (CVD) technology are presented. This oxide film consists of silicon dioxide network with methyl groups incorporated and has a dielectric constant kappa as low as similar to 2.7. The film properties were studied using Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry, Rutherford backscattering, atomic force microscopy, and capacitance-voltage measurements. The refractive index, as low as 1.38, was measured using spectroscopic ellipsometry. The surface was found to be more hydrophobic compared to conventional CVD oxide. The stretching mode of the Si-O bond peak in the FTIR spectrum shifts to lower wavenumber, which corresponds to lower Si-O bonding energy, with increase in the methyl concentration inside the film. The CMP removal rate decreases as the methyl concentration in the film increases. An atomically smooth surface with root mean square surface roughness <1 nm over an area 2 x 2 mu m was obtained after CMP. Our results suggest that the incorporation of methyl groups results in a reduction in the CMP removal rate. We speculate that the diffusion of water into the film is probably the CMP removal rate-limiting step. (C) 2000 The Electrochemical Society. S0013-1651(00)03-018-4. All rights reserved.