Holder Michael van Gerwen threw a 170 checkout to seal a 5-2 victory over Scotsman Robert Thornton in the PDC World Championship quarter-finals.
The Dutchman was coasting after winning the opening three sets, but the 2012 UK champion fought back to 3-2.
Van Gerwen, 25, took the next two tight sets to reach his third successive semi-final at Alexandra Palace.
He will face 2011 finalist Gary Anderson, who beat fellow Scot Peter Wright 5-1, in the last four.
Van Gerwen's average of 105.26 was his highest ever in the PDC World Championship and he also hit 13 maximums, but he was pushed all the way by Thornton.
The defending champion said: "The 170 was a big relief and it couldn't come at a better time."