Abstract
A serious concern for borophosphosilicate (BPSG) interlayer is still about film stability in terms of dopant out-diffusion and defect formation. The thermal and compositional instabilities of the PECVD BPSG depend on dopant concentration in the film and on stoichiometry of SiOx matrix. This study addresses the diffusivity of boron and phosphorus through the BPSG and the low temperature oxide (LTO) films. Phosphorus significantly diffuses out of the BPSG film during high temperature densification. The significant boron out-gassing happens in the as-deposited film even at room temperature. This effect depends on the BPSG film composition and whether the LTO film is present or not. The effect is explained based on the change in the charge state in the silicon-oxide interface. The dopant out-diffusion is restricted from the oxygen-rich BPSG film. In addition, the effect of the undoped cap layer on the BPSG is discussed.
Published Version
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