Electrostatic Damage in Semiconductor Manufacturing Through the Inappropriate Use of Grounding

Until now, the first rule of static discharge control has been to ground all conductors wherever possible. This is a process known as equipotential bonding. While this most often is a successful ESD mitigation strategy, this article identifies occasions where grounding is potentially detrimental to device security. In cases where charge can be generated on insulating or isolated conductive structures of an ESD sensitive item, such as by handling or processing, grounding a conductive part can create a strong internal electric field that can damage the item. Equipotential grounding of an object will protect it from ESD damage from other objects in its environment but such grounding will increase its sensitivity to internal discharge and possible damage. Such internal fields may not be detectable during normal ESD audits, which may give a “clean bill of health” to conditions that expose sensitive items to electrostatic risk. Examples of situations where the use of equipotential bonding can be detrimental to the electrostatic safety of sensitive items during manufacture and handling are given.