Patent ID: 8051863

Claim:
Apparatus for monitoring meniscus processing of a wafer surface to maintain stability of a meniscus, the processing being in response to a recipe, the apparatus comprising: a proximity head configured with a fluid emitter surface to supply and collect fluid for defining the meniscus extending across a gap between the fluid emitter surface and the wafer surface, meniscus stability being characterized by a continuous configuration of the meniscus, meniscus instability being characterized by a discontinuous configuration of the meniscus; a carrier configured to mount the wafer for movement relative to the head for the meniscus processing, during the movement a desired orientation of the wafer surface and the fluid emitter surface relative to each other being changeable to an undesired relative orientation; a meniscus monitor system mounted on the head and comprising a first meniscus monitor configured to direct a first monitor beam across the gap to a first location of the meniscus, the meniscus monitor system further comprising a second meniscus monitor configured to direct a second monitor beam across the gap to a second location of the meniscus and separately from the first beam, each of the meniscus monitors configured to separately receive a return of the respective monitor beam for generating a separate orientation monitor signal representing the relative orientation of the wafer surface and the fluid emitter surface at the respective meniscus location during processing in response to a current recipe; and a processor configured to respond to the orientation monitor signals and to the current recipe for generating meniscus monitor signals to allow maintaining the meniscus stability.