I don't think Judges can be impeached under present system. Supreme and other Federal Courts Judges appointed for life by President, subject to Senate approval.
I actually had a post on my blog why not to have a possibility to impeach judges in light of how certain judges keep on abusing and outstepping their constitutionally defined power and hand one absurd verdict after another ("gay marriage" as a Constitutional Right, 10 commandement and other Jewish and Christian symbols removals from public places, Tossing out death Penalty case because one of the Jurors brought Bible, Terri Schiavo, etc.). Other possible solutions is to have Judicial term Limits for Federal Judges instead of life-time appointments.
This is very delicate issue, but something definitely must be done to institute more checks and balances in judiciary system.
http://sergeywatch.blogspot.com/2005/03/if-president-can-be-impeached-why-not.html
My understanding of the constitution is that federal and supreme court judges can be impeached and removed from the bench by congress.
They serve in "good behavior." Of course they can be impeached.