Patent ID: 7156951

Claim:
A multiple zone gas distribution apparatus for controlling temperature across a workpiece during processing, the apparatus comprising: a chuck having a top face configured to hold a workpiece during processing, the chuck top face defining inner and outer zones between the top face of the chuck and the workpiece into which zone coolant gas may be admitted; inner and outer zone feed lines adapted to feed the coolant gas to the inner and outer zones of the chuck; a pressure and flow control system adapted to supply zone coolant gas to the feed lines with separate pressure for the inner and outer zones controlled to control the temperature across the workpiece; and inner and outer zone bleed lines connected to the respective inner and outer zone feed lines respectively between the pressure and flow control system and the chuck, the inner zone bleed line having a connecting line in fluid connection with the outer zone bleed line and a fixed orifice adapted to continuously bleed the pressure of the inner zone to the outer zone bleed line during processing of the workpiece, the inner zone bleed line having an evacuation valve which is adapted to bypass the fixed orifice for immediate inner zone evacuation, and the outer zone bleed line having an evacuation valve for pressure release, which is located upstream of the inner zone connecting line.