Method of making a semiconductor wafer having a depletable multiple-region semiconductor material

Abstract

Semiconductor devices are known comprising a multiple p-n junction RESURF semiconductor material ( ) that provides a voltage-sustaining space-charge zone when depleted from a blocking junction ( ). Charge balance is important in the alternating p-type ( ) and n-type ( ) regions which together provide the voltage-sustaining space-charge zone. The invention provides a low-cost yet reliable way of manufacturing such a material ( ), and also devices with such a material ( ). A p-type silicon body ( ) having an acceptor doping concentration (Na) for the p-type regions ( ) of the material is subjected to irradiation with collimated beams ( ) of thermal neutrons ( ) at window areas ( ) in a mask ( ) so as to form the n-type regions ( ) by transmutation of silicon atoms into phosphorus. A well-defined and controllable phosphorus doping concentration to balance the low acceptor concentration of the p-type regions ( ) is achievable in this manner, even when the acceptor concentration is of boron. The silicon body ( ) so formed with the alternating p-type and n-type regions ( ) is sliced and/or polished transverse ( ) to the p-n junctions ( ) between the p-type and n-type regions ( ) so as to form a wafer for device manufacture. The invention is particularly advantageous for the manufacture of high voltage MOSFETs having a low on-resistance.