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 language | English (US) |
---|---|
Pages (from-to) | H7.3.1-H7.3.6 |
Journal | Materials Research Society Symposium - Proceedings |
Volume | 640 |
State | Published - 2001 |
Event | Silicon Carbide- Materials, Processing and Devices - Boston, MA, United States Duration: Nov 27 2000 → Nov 29 2000 |
All Science Journal Classification (ASJC) codes
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering