The Dutchman's strike was enough for Bayern to dump United out of the Champions League on away goals.
Robben admitted he had to keep his cool to score the crucial goal as he expected to be picked out by his team-mate.
The Dutchman told German TV: "When we were behind 3-0 I thought it was going to be a very difficult evening. But 3-0 was the same as 2-0. We had to score a goal.
"The goal from Olic gave us faith that we could still advance. We have to be honest. They were the better team at the start, with the atmosphere.
"I saw that Franck (Ribery) saw me at the corner. I knew the ball would come across to me. I tried to stay calm.
"You can use force or technique. I tried to use technique. It worked out."