The DPC consists of three sections – an inlet subassembly, a pressure control/flow metering subassembly, and an outlet subassembly. Pressurized helium gas is fed into the inlet subassembly. A pneumatic valve is then opened and the gas flow is split to two channels.

In the pressure control section, Baratron® Capacitance Manometers measure pressure for each of the two zones. These pressures are compared to the pressure set points and an appropriate signal adjusts the position of the solenoid control valve to bring actual pressures into agreement with the set points. At the same time, mass flow is monitored on each channel by MKS Mass-Flo® meters calibrated for helium, which is the typical gas used for backside wafer cooling.

Downstream of the pressure control section, the outlet subassembly directs flow to the electrostatic chuck and provides a controlled “bleed” to vacuum through fixed orifices. 

The purpose of the bleed is to insure that the pressure control system is not “dead-ended”. Since leak past the wafer is typically very low, the controlled bleed provides additional pressure relief for faster response to set point. Two different orifice sizes are used depending on the Full Scale range of the flow sensors. A smaller orifice size is used on units with 10 and 20 sccm FS flow sensors, and a larger orifice size is used on units with 50 and 100 sccm FS flow sensors.

Both analog and DeviceNet™ versions of the DPC are available. For the analog version, power is supplied at ±15 VDC. The pressure set point and readout signals are 0-10 VDC and the flow sensor readout signal is 0-5 VDC. Ten-position gain and integral (P&I) term rotary switches provide a wide dynamic range for tuning pressure control performance. P&I switches are provided for each channel for independent tuning.

The digital DPC features digital control electronics and DeviceNet-compliant communication. The DPC DeviceNet profile for each channel basically adds an S-Analog Sensor object for mass flow sensing to the Process Control Valve object. Each channel has its own distinct MAC ID that is user-settable by two switches per DeviceNet specification. To optimize pressure control performance, users may adjust gain, integral and differential (P, I, D) constants for each channel using the DeviceNet communications protocol.