US Patent 7226339 Spectrum based endpointing for chemical mechanical polishing

Methods and apparatus for providing a flushing system for flushing a top surface of an optical head. The flushing system includes a source of gas configured to provide a flow of gas, a delivery nozzle, a delivery line that connects the source of gas to the delivery nozzle, a vacuum source configured to provide a vacuum, a vacuum nozzle, and a vacuum line that connects the vacuum source to the vacuum nozzle. The source of gas and the delivery nozzle are configured to direct a flow of gas across the top surface of the optical head. The vacuum nozzle and vacuum sources are configured so that the flow if gas is laminar.