Chemical Mechanical Polishing of Low Dielectric Constant Oxide Films Deposited Using Flowfill Chemical Vapor Deposition Technology

Abstract

In this work, the properties and chemical mechanical polishing (CMP) characteristics of thin films of a new low dielectric constant (low-) 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 as low as ϳ2.7. 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 ϫ 2 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.

Dependency of the Underlying Surface Condition on Dielectric Film Removal at Wafer Edge

“…Dielectric films consisting of a plasma CVD SiO 2 (P-SiO: cap and base layers) and a low-k film (middle layer in between the cap and base film) were then formed in a Trikon Planar 200 System. 2 The base SiO 2 (50 nm) and the cap SiO 2 (300 nm) were deposited using SiH 4 and N 2 O gas at 400 • C. The low-k film (300 nm) was deposited using a carbon-based organic source (CH 3 SiH 3 ) and H 2 O 2 1,2 at 5 • C as a middle layer between the base and the cap film. The low-k film was degasified at 400 • C with N 2 for 3 min in a vacuum chamber.…”

“…[1][2][3][4][5] The rise in the number and variation of processing tools and processing steps in high-volume manufacturing increases the risk of cross-contamination with subsequent loss of yield and device performance. Of particular concern is the wafer back side and its edge, which can be sites for contamination due to handling and accidental processing.…”

“…Ultra large scale integrated (ULSI) semiconductor fabrication is facing an increasing number of processing steps, increasing complexity of device technologies, process integration flows, and incorporation of new material (for example; low dielectric constant (low-k) film). [1][2][3][4][5] The rise in the number and variation of processing tools and processing steps in high-volume manufacturing increases the risk of cross-contamination with subsequent loss of yield and device performance. Of particular concern is the wafer back side and its edge, which can be sites for contamination due to handling and accidental processing.…”

Mechanistic Understanding of Low κ Organosilicate Glass Film Planarization

“…% C as measured by XPS) was considered to be a representative measure of film hydrophobicity. Cui et al and Matz et al 14,15 took this one step further by analyzing the nature of the carbon bonding. The total carbon can be resolved into two key regions in the FTIR spectra: 16 the Si-CH 3 stretch at 1259 cm −1 and CH x stretch at ∼2900 cm −1 .…”

“…The ratio of hydrophobic to hydrophilic content in the OSG film is typically tracked by the FTIR peak area ratio Si(CH 3 ) x /SiO x ; sometimes more generally expressed as Si-CH 3 /SiO . Cui et al 15 observed that CMP removal rate decreases with increase in Si(CH 3 ) x /SiO x peak ratio. However, Cui et al did not comment on the mechanical strength of their two unique flowable CVD films.…”