Loading...

Retardation of Ta silicidation by bias sputtering in Cu/Ta/Si(111) thin films

Moshfegh, A. Z ; Sharif University of Technology | 2001

890 Viewed
  1. Type of Document: Article
  2. DOI: 10.1088/0022-3727/34/14/304
  3. Publisher: 2001
  4. Abstract:
  5. In this investigation, we have studied the effect of negative bias voltage on the properties of a sputtered Ta layer deposited at high Ar pressure (13.3 Pa) which is used as a diffusion barrier in a Cu/Ta/Si structure focusing on its silicidation process. According to Rutherford backscattering spectrometry, the Cu(85 nm)/Ta(100 nm, unbiased)/Si(111) structure was found to be stable up to 300°C in a N2 environment for 30 min. At a temperature of 450°C, TaSi2 was formed at the Ta/Si(111) interface, and the Ta diffusion barrier completely failed. By applying various negative bias voltages ranging from 0 to -150 V, an optimum bias voltage of Vb = -50 V for the sputtered Ta layer was found from scanning electron microscopy and four-point-probe resistivity measurements. In addition, the normalized ion flux (ni), defined as the ratio of Ar+ ion flux to Ta flux, was determined to be 7.5 for optimum experimental conditions. As a result, the biased Ta layer was used as a diffusion barrier between Cu and Si; it showed a low resistivity of 99 μΩ cm, a density of about 14.1 g cm-3 with a good surface morphology and a contribution of bcc-Ta phase structure of about 65%. The Cu(50 nm)/Ta(50 nm, biased)/Si(111) structure was demonstrated to be thermally stable under perfect conditions up to 500°C and TaSi2 formation in an N2 environment for 30 min was retarded up to 700°C
  6. Keywords:
  8. Source: Journal of Physics D: Applied Physics ; Volume 34, Issue 14 , 2001 , Pages 2103-2108 ; 00223727 (ISSN)
  9. URL: https://iopscience.iop.org/article/10.1088/0022-3727/34/14/304/meta