A high-pressure processing system for processing a layer on a substrate, the system comprising: a first chamber; a support to hold the substrate in the first chamber; a second chamber adjacent the first chamber; a foreline to remove gas from the second chamber; a vacuum processing system configured to lower a pressure within the second chamber to near vacuum; a valve assembly between the first chamber and the second chamber to isolate the pressure within the first chamber from the pressure within the second chamber; a gas delivery system configured to introduce one or more gases into the first chamber and to increase the pressure within the first chamber to at least 7600 Torr (10 atmospheres) while the gas is in the first chamber and while the first chamber is isolated from the second chamber, the gas delivery system including: a first gas delivery module to deliver a first gas at a first pressure that is at least 7600 Torr (10 atmospheres); and a second gas delivery module to deliver the first gas or a second gas of different composition at a second pressure that is less than the first pressure but greater than 760 Torr (1 atmosphere); a controller configured to operate the gas delivery system and the valve assembly; a first exhaust system comprising an exhaust line to remove gas from the first chamber; and a common housing surrounding both the first gas delivery module and the second gas delivery module; and a second exhaust system configured to remove gas from the common housing. a first chamber; a support to hold the substrate in the first chamber; a second chamber adjacent the first chamber; a foreline to remove gas from the second chamber; a vacuum processing system configured to lower a pressure within the second chamber to near vacuum; a valve assembly between the first chamber and the second chamber to isolate the pressure within the first chamber from the pressure within the second chamber; a gas delivery system configured to introduce one or more gases into the first chamber and to increase the pressure within the first chamber to at least 7600 Torr (10 atmospheres) while the gas is in the first chamber and while the first chamber is isolated from the second chamber, the gas delivery system including: a first gas delivery module to deliver a first gas at a first pressure that is at least 7600 Torr (10 atmospheres); and a second gas delivery module to deliver the first gas or a second gas of different composition at a second pressure that is less than the first pressure but greater than 760 Torr (1 atmosphere); a first gas delivery module to deliver a first gas at a first pressure that is at least 7600 Torr (10 atmospheres); and a second gas delivery module to deliver the first gas or a second gas of different composition at a second pressure that is less than the first pressure but greater than 760 Torr (1 atmosphere); a controller configured to operate the gas delivery system and the valve assembly; a first exhaust system comprising an exhaust line to remove gas from the first chamber; and a common housing surrounding both the first gas delivery module and the second gas delivery module; and a second exhaust system configured to remove gas from the common housing.