IntelliJ IDEA runs on JRE 6, and so does its SBT plugin.

If you need to use a more recent version of Java (and you should):

• Open the Preferences panel
• Go to the SBT section
• Tick the Use alternative JRE option
• Click the arrow on the right of the field to check if the IDE suggests the desired JRE
  • If so, choose it.
  • Otherwise, look for the path by yourself.
    It’s /Library/Java/JavaVirtualMachines/jdk1.7.0_09.jdk/Contents/Home on my Mac.