An electrostatic chuck is provided having a plurality of small electrostatic structures for holding an
electrically conductive workpiece forming a plate of a
capacitor. Each electrostatic structure includes a first thermally conductive single-
crystal dielectric sheet, and a first
electrode in sheet form sandwiched between the first
dielectric sheet and a second
dielectric surface. The workpiece, typically a conductive or semiconductive
wafer, is juxtaposed to the first dielectric sheet of each electrostatic structure and forms a second
electrode. The second dielectric sheet, if thick, is used as a thermally conducting base plate which can be attached to a low
pressure reactor. If the second dielectric is a
thin sheet, then it is mounted to a thermally conductive
metal base plate through which heat can be controllably conducted. The
resultant electrostatic structure may be brazed to the
metal base plate if the
thermal expansion characteristics of the two elements are sufficiently matched. The first thermally conductive dielectric sheet is preferably formed of
sapphire (Al2O3), which is sufficiently thermally conductive to allow for rapid
heat transfer between the base plate and the workpiece. The first electrodes of different electrostatic structures are held at different electrical potentials (typically of several thousand volts difference) and a charge is maintained by this
potential difference between selected electrostatic structures.