The Chelmsford star is now one win away from securing his third ranking title of his career after a gutsy performance saw him clinch a 6-2 victory at the Tempodrom arena in Berlin.
Carter, who lost in the final of the world championship last year, got off to a good start winning the first frame after coming back from 43-0 down against the Australian.
A scrappy second frame was won by Carter before Robertson got off the mark to trail the match at 2-1.
But unfortunately for the Australian that was to be his only joy for a long period as Carter took the next three frames to put him on the brink of the final with a healthy 5-1 advantage.
Robertson pulled a frame back with a break of 90 but there was to be no epic comeback as Carter managed to get over the winning line in the next frame after the Australian missed missed the pink with two reds left on the table.
Having won the Welsh Open and Shanghai Masters in 2009 and 2010 respectively, Carter will hope to add the German Masters title to his trophy cabinet on Sunday when he takes on either Barry Hawkins or Marco Fu.
After the game, a thrilled Carter told World Snooker: “It feels great, it was a scrappy match and not the best performance, but I’m delighted.
“The crowd were magnificent, it’s such a buzz to play in front of all those people. I hope I can do the business tomorrow (Sunday). It wasn’t a free flowing game today which was probably to my advantage. I stuck to my task and won comfortably in the end.”