An electrostatic chuck includes a pedestal having a metallic upper surface, and a layer of a porous dielectric material formed on said upper surface of the pedestal. The dielectric layer is impregnated with a plasma-resistant sealant. ...http://www.google.de/patents/US5792562?utm_source=gb-gplus-sharePatent US5792562 - Electrostatic chuck with polymeric impregnation and method of making
