Engineering the Al-Ti/p-SiC Ohmic contact for improved performance

J. Y. Lin, S. E. Mohney, M. Smalley, J. Crofton, J. Crofton, J. R. Williams, T. Isaacs-Smith

Research output: Contribution to journalArticle

Abstract

The influence of composition on Al-Ti ohmic contacts to 4H p-SiC was studied. When NA was 7 × 1018 cm-3, contacts with 70 wt.% or more Al became ohmic when annealed at 1000°C for 2 min, whereas when there was 60 wt.% or less Al, the contacts did not become ohmic even when annealed under more severe conditions (longer times and/or higher temperatures). Spiking of the contact metallization always accompanied ohmic behavior and could be correlated with Al-Ti compositions that contain both an Al-rich liquid and solid TiAl3 at 1000°C prior to reaction with SiC or evaporative loss of Al. For the 70 wt.% contacts, a specific contact resistance of 1.5 × 10-4 Ω•cm2 was measured along with spiking of the metallization into the SiC with a room-mean-square interfacial roughness of 150 Å and a maximum spiking depth of 1200 Å. Although still a concern, this spiking was less severe than observed for the 90 wt.% composition. A conductive CrB2 cap layer was next demonstrated to retard evaporation of Al during annealing of the Al-Ti contacts with 70 wt.% Al. The cap allowed use of thinner contact layers, reducing the depth of spiking and improving the surface morphology and edge definition of the ohmic contacts, with a one order of magnitude penalty in the specific contact resistance.

Original languageEnglish (US)
Pages (from-to)H7.3.1-H7.3.6
JournalMaterials Research Society Symposium-Proceedings
Volume640
StatePublished - 2001

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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    Lin, J. Y., Mohney, S. E., Smalley, M., Crofton, J., Crofton, J., Williams, J. R., & Isaacs-Smith, T. (2001). Engineering the Al-Ti/p-SiC Ohmic contact for improved performance. Materials Research Society Symposium-Proceedings, 640, H7.3.1-H7.3.6.