Combined Contactless Electrostatic and Vacuum Wafer Chuck
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A combined vacuum and electrostatic wafer chuck is described which can electrostatically attract non-conductive workpieces and/or workpieces which are not electrically contacted. This is done by electrically subdividing the chuck surface so that adjacent areas on the chuck surface can be charged oppositely and will attract insulating and/or non-charged workpieces. In a vacuum environment it is not possible to use a regular vacuum chuck to hold a wafer flat. Under such conditions an electrostatic chuck may be used. Since an electrostatic chuck can only hold a wafer flat, but not flatten it, a combined electrostatic and vacuum chuck may be used to flatten the wafer before the voltage is applied. A disadvantage of this type of chuck is that an electrical contact to the wafer is necessary for the electrostatic chucking.