Abstract: A metal code process for a read-only memory (ROM) combines the alignment dip back process (to reduce the polyoxide thickness over the gate electrode and to protect the field oxide) with a double charge implant approach to provide the function of a depletion mode ROM cell. The alignment dip back process also avoids leakage current problems. A stable depletion mode device character is achieved by implant step energies greater than 150 keV.

Abstract: The invention provides a vacuum pencil having an abutment pin which limits the distance the tip of the vacuum pencil can extend past the edge of a wafer thus reducing scratches on the device sides of adjacent wafers. The vacuum pencil has a relatively flat tip connected to a body. The tip has a flat top side for engaging a wafer. The top side of the tip has channels for delivering a vacuum to seal against the wafer against the tip. The top side of the tip also has an pin mounted between the channels and the body. A passage for delivering a vacuum runs through the body and the channel is connected to the channel in the tip. The pin can be a pentagon shaped pin which is about 1 mm high.