Yet after all their intricacy, it was an ugly goal that brought United level, when Scholes' low shot took a deflection off Huddlestone to leave Alnwick stranded.
But the strike that put United was top quality - and a double blow for Spurs as it involved two of their former players.
Carrick picked out Berbatov with a sublime pass and the Bulgarian took one touch to control before placing the ball into the bottom corner.
Spurs made a change at half-time, bringing on Giovani for the disappointing Luka Modric.
But while there was a little more threat from Redknapp's side there was no real cutting edge.
Gareth Bale shot wide from a tight angle and David Bentley, who later made way for Jermain Defoe, also struck a shot off target.
The former Blackburn winger's well-struck volley that whistled into the side netting was the closest his side came to an equaliser.
Ronaldo forced another good save from Alnwick but chances dried up as the tempo of the matched slowed.
Spurs tried to inject some pace into their play but never looked like getting an equaliser, despite applying some pressure at the end.
The Londoners had one handball appeal and one appeal for a foul turned down by the referee as United held on.
United will clinch an unprecedented quadruple if they win the Carling Cup, the FA Cup, the Premier League and the Champions League.
However, boss Sir Alex Ferguson will be concerned after Da Silva and Welbeck became the latest additions to a lengthy injury list while Ronaldo, who was suffering from a stomach bug, was withdrawn early.
Manchester United manager Sir Alex Ferguson:
"Give them a start - it always helps, doesn't it?
"But they recovered well, they played excellent stuff in the first half and the goalkeeper's made two or three very good saves, we hit the crossbar.
"Dimitar Berbatov's goal was fantastic but it was also a marvellous pass from Michael Carrick."
Tottenham boss Harry Redknapp:
"I thought we did well. It is tough to come here - you have to be careful, if you open up you can get beaten by four, five or six goals.
"We started well, but a bad two-minute spell cost us. In the second half neither keeper had an awful lot to do.
"But I thought we were always in the game and I could see us nicking a goal and earning a replay."
Man Utd: Foster, O'Shea, Neville, Vidic, Fabio Da Silva (Eckersley 53), Welbeck (Fletcher 86), Carrick, Scholes, Ronaldo (Tosic 72), Berbatov, Tevez.
Subs Not Used: Kuszczak, Giggs, Possebon, Chester.
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