Patent ID: 8813764

Claim:
An apparatus for physically confining a liquid meniscus over a semiconductor wafer, comprising: a first and a second chemical head disposed to cover at least a portion of a top and an underside surface of the semiconductor wafer, each of the first and the second chemical heads comprising: an angled inlet conduit at a leading edge to deliver liquid chemistry into a pocket of meniscus in a single phase, the pocket of meniscus defined over the portion of the top and the underside surface of the semiconductor wafer covered by the first and the second chemical heads so as to contain the liquid chemistry applied to the surface of the semiconductor wafer as a meniscus; an inner return conduit located within the pocket of meniscus at a trailing edge of the first and the second chemical heads so as to remove the liquid chemistry from the surface of the semiconductor wafer in a single phase; and a step formed along at least a portion of an outer periphery of the pocket of meniscus at the leading edge of the first and the second chemical heads so as to substantially confine the meniscus of the liquid chemistry within the pocket of meniscus, the step having a height that is sufficient to preserve confinement characteristic of the meniscus, wherein the inlet conduit is spaced apart from the step and wherein the first chemical head and the second chemical head are misaligned such that a wall of the step adjoining the pocket in the second chemical head disposed on the underside of the semiconductor wafer when present, is extended outward in relation to a wall of the step adjoining the pocket in the first chemical head disposed on the top of the semiconductor wafer.