A method and apparatus for immersion lithography is described. The method includes positioning a semiconductor substrate under an optical immersion head assembly, providing an immersion liquid between the substrate and the optical immersion head assembly, and supplying a tensio-active gaseous substance along the perimeter of the contact area of the immersion liquid and the substrate. The immersion liquid contacts at least an area of the substrate. The tensio-active gaseous substance is chosen such that, when at least partially mixed with the immersion liquid, the mixture has a lower surface tension than the immersion liquid, thereby creating a surface tension gradient pulling the immersion liquid from the perimeter towards an inside portion of the contact area.