The 2,000 full-time employees of the yogurt company Chobani were handed quite the surprise on Tuesday: an ownership stake that could make some of them millionaires. Hamdi Ulukaya, the Turkish immigrant who founded Chobani in 2005, told workers at the company’s plant here in upstate New York that he would be giving them shares worth up to 10 percent of the company when it goes public or is sold. The goal, he said, is to pass along the wealth they have helped build in the decade since the company started. Chobani is now widely considered to be worth several billion dollars.“I’ve built something I never thought would be such a success, but I cannot think of Chobani being built without all these people,” Mr. Ulukaya said in an interview in his Manhattan office that was granted on the condition that no details of the program would be disclosed before the announcement. “Now they’ll be working to build the company even more and building their future at the same time,” he said.