GB1378667A - Ion implantation - Google Patents

Abstract

1378667 Automatic control of ion implantation WESTERN ELECTRIC CO Inc 24 Aug 1972 [24 Aug 1971] 39378/72 Heading G3N [Also in Division H 1] In a method of ion implantation, the ion current arriving at a sample is measured and used to control the exposure. Relative movement of the sample and the ion beam is determined by a program and is servo-controlled. As shown, a sample 10 on a movable holder 11 is exposed to an ion beam 12. The ion current charges a capacitor 18 until a voltage sensor 17 is triggered to supply a stepping pulse to a counter and displacement command generator 14, and reset the capacitor 18 by discharge to earth. A program stored in generator 14 supplies signals to circuits 13 for controlling the movement of the holder 11 in a plane perpendicular to the beam 12. The actual position of the holder, measured by a laser or otherwise, is compared with the programmed position in a comparator 21 to produce movement correction signals if necessary. The correction signals may be produced by a bridge circuit. Continuous variations in implantation density may be obtained by controlling the speed and acceleration of the holder 11 in conjunction with the use of a mask 31.