Patent ID: 6712132
Filing Date: 2004-03-30
Classification: H01L

Abstract:
A piezoelectric wafer clamping system comprising:a plurality of piezoelectric stack assemblies adapted for providing a vertical clamping force to a semiconductor wafer; a annular wafer clamp member coupled to each one of said plurality of piezoelectric stack assemblies, said annular wafer clamp being positionable to abut a top surface of a semiconductor wafer; a wafer support assembly adapted for supporting a semiconductor wafer during processing; and a control assembly adapted for regulating a clamping force applied by said plurality of piezoelectric stack assemblies and the positioning of said wafer support assembly based upon a plurality of control input signals; each one of said plurality of piezoelectric stack assemblies further comprises: a stack housing, said stack housing having a substantially circular top wall, said stack housing having a perimeter wall extending downwardly from said top wall, said stack housing having a flange portion extending from a lower edge of said perimeter wall, said flange portion being adapted for coupling said stack housing to a wall of a processing chamber; a piezoelectric stack positioned within said stack housing, said piezoelectric stack having a first end and a second end, said first end abutting an interior surface of a top wall of said stack housing; a diaphragm member positioned substantially within an interior area defined by said perimeter wall, said diaphragm member being positioned adjacent said lower edge of said perimeter wall, said diaphragm member resiliently sealing said interior area; said second end of said piezoelectric stack abutting a medial portion of said diaphragm member; a stem member having a diaphragm end and a clamp end, said diaphragm end abutting said medial portion of said diaphragm member, said stem member being substantially aligned with said piezoelectric stack such that a vertical throw of said piezoelectric stack moves said stem member, said clamp end of said stem member abutting said annular wafer clamp member for transferring a clamping force generated by said piezoelectric stack through said diaphragm member and said stem member to said annular wafer clamp member; said stack housing further comprises: an annular groove positioned on a lower surface of said flange portion, said annular groove preferably being positioned substantially adjacent to said diaphragm member; an o-ring member, said o-ring member being positioned substantially in said annular groove, said o-ring member providing an environmental barrier between an interior of the processing chamber and an external environment; said stack housing further comprises: a plurality of apertures extending through said flange portion; a plurality of connecting members, each one of said connecting members being positionable through an associated one of said apertures for coupling said stack housing to the processing chamber; said annular wafer clamp member further comprises: a base portion positionable to control a vertical spacing between said semiconductor wafer and said wafer support assembly, a lip portion extending from said base portion such that a bottom surface of said lip portion is coplanar with a bottom surface of said base portion, said lip portion being for engaging a perimeter edge portion of a semiconductor wafer such that a clamping force is transferable to the semiconductor wafer; said annular wafer clamp member further comprises: a plurality of protrusions extending from said lip portion, said plurality of protrusions being positioned such that a top surface of said protrusions is coplanar with a bottom surface of said lip portion, said plurality of protrusions preferably being positioned in a substantially uniformly spaced relationship around an interior edge of said lip portion, said protrusions providing additional contact surfaces for said wafer clamping member with respect to the semiconductor wafer; said wafer support assembly further comprises: a heatsink adapted for providing a thermal sink for cooling the semiconductor wafer; a vertical adjustment assembly for controlling a height of said wafer support assembly; and a bellows assembly for providing an environmental barrier between an interior of a processing chamber and an external environment; said heatsink further comprises: an metal disk having a substantially circular depression centered on a top surface of said metal disk, said metal disk having a cooling channel routed through an interior portion of said metal disk, said cooling channel having an input portion and an output portion each extending from said metal disk; a via positioned at a focus of said depression, said via extending through said metal disk for conducting a barrier gas through said metal disk, said barrier gas providing a heat transfer buffer between a semiconductor wafer and said metal disk; said vertical adjustment assembly further comprises: a vertical adjustment shaft coupled to a bottom surface of said heatsink, said vertical adjustment shaft having an aperture extending from a lower portion radially into said vertical adjustment shaft, said vertical adjustment shaft having a bore extending from a top edge downwardly to said aperture, said bore and aperture being for providing a gas to form a gas barrier for said heatsink; a stepper motor operationally coupled to said vertical adjustment shaft such that the position of said vertical adjustment shaft is controlled by said stepper motor; said bellows assembly further comprises: a upper flange member coupled to a bottom surface of said heatsink; a lower flange member coupled to a lower interior surface of a process chamber; a bellows member extending between said upper and lower flange members, said bellows member providing an environmental barrier between an interior of said process chamber and an external environment; said vertical adjustment assembly being extending through said upper and lower flanges and said bellows member; said upper flange member further comprises: an annular groove positioned on a upper surface of said upper flange member, said annular groove preferably being positioned substantially adjacent to said bellows member; an o-ring member, said o-ring member being positioned substantially in said annular groove, said o-ring member providing an environmental barrier between an interior of the processing chamber and an external environment; a plurality of apertures extending through said upper flange member; a plurality of connecting members, each one of said connecting members being positionable through an associated one of said apertures for coupling said upper flange member to said heatsink; said lower flange member further comprises: an annular groove positioned on a lower surface of said lower flange member, said annular groove preferably being positioned substantially adjacent to said bellows member; an o-ring member, said o-ring member being positioned substantially in said annular groove, said o-ring member providing an environmental barrier between an interior of the processing chamber and an external environment; a plurality of apertures extending through said lower flange member; a plurality of connecting members, each one of said connecting members being positionable through an associated one of said apertures for coupling said lower flange member to a lower interior surface of the processing chamber; said control assembly further comprises: a temperature sensor adapted for monitoring the temperature of the semiconductor wafer, said temperature sensor providing a first process monitoring input signal; a pressure transducer adapted for monitoring a back-pressure associated with a barrier gas buffering the semiconductor wafer from the heatsink, said pressure transducer providing a second process monitoring input signal; a mass flow controller adapted for controlling the rate of flow of the barrier gas, said mass flow controller providing a third process monitoring input signal; a stepper motor controller for controlling the positioning of a vertical adjustment assembly whereby the vertical position of said wafer support assembly is controlled; a piezoelectric controller, said piezoelectric controller using said first, second, and third process monitoring inputs and a set of external input signals associated with a process chamber, said piezoelectric controller being operationally coupled to said stepper motor controller and said mass flow controller such that said piezoelectric controller controlling the operation of said stepper motor controller and said mass flow controller.