Workpiece holder for vacuum processing

An electric heating apparatus for heating a workpiece to a selected temperature when the workpiece abuts a workpiece supporting surface of a substrate, the heating apparatus comprising:

• a first bifilar heating element configured as a spiral disposed entirely on the workpiece supporting surface of the substrate, the first bifilar heating element having an electric resistance that varies as a function of temperature in a known manner;
• a second bifilar heating element configured as a spiral interleaved with the first bifilar heating element on the workpiece supporting surface of the substrate, the first and second bifilar heating elements mutually electrically insulated from each other;
• a circuit for measuring the electrical resistance of the first bifilar heating element;
• a controller for controlling an electric current to a selected one of the bifilar heating elements responsive to the measured resistance;
• and
• an electric power supply for applying a voltage between the first and second bifilar heating elements for electrostatically clamping the workpiece to the workpiece supporting surface of the substrate.

Apparatus for supporting a workpiece, the apparatus comprising:

• a substrate having a workpiece supporting surface;
• and
• two or more mutually electrically insulated bifilar conductors configured as interleaved spirals disposed on the workpiece supporting surface, each of the bifilar conductors having a respective electrode at each of two ends thereof;
• a first electric power supply connected to each of the two electrodes of one of the bifilar conductors, whereby an electric current from the first power supply passed through that bifilar conductor serves to heat the substrate;
• and
• a second electric power supply connected to at least two of the at least two bifilar conductors so as to create an electric potential therebetween, the electric potential for clamping the workpiece to the substrate.