Abstract: An interlock controller device is used in an ion implantation machine to prevent an overdose ions from being implanted into a semiconductor wafer due to fluctuations in the power supply to the ion beam used to scan the wafer. The device stores a pre-selected count corresponding to the number of times the wafer should be scanned at a particular ion beam current in order to achieve a desired implantation dose, and decrements the count each time the wafer is scanned. When the count is decremented to zero, the device turns off the current to the ion beam, thereby terminating ion implantation, even though scanning of the wafer is continued.

Abstract: The present invention provides a wafer holder shield in a physical vapor deposition chamber for use in a metal deposition process without the arcing problem. The shield is constructed in a configuration of a toroid wherein the toroid has a rectangular cross-section and a flat bottom surface. The toroid further has a cavity at the center adapted for receiving a wafer when the shield is placed on a wafer holder. The flat bottom surface of the wafer holder shield has an inner end adjacent to an inner periphery of the toroid that is supported by the wafer holder. The flat bottom surface further has an outer end adjacent to an outer periphery of the toroid suspended over and spaced apart from a chamber shield for the deposition chamber at a distance sufficient to prevent bridge formation between the wafer holder shield and the chamber shield by metal particles generated in the deposition chamber.