The electrical behaviour of abrupt ion implanted and diffused P+N junctions

Abstract

Results are reported of measurements of the properties of diodes formed by ion implantation, and for comparison boron diffused P⁺N diodes of similar area close by on the same chip. The four group III acceptor impurities were implanted separately to a dose of 5 × 10¹⁵ ions/cm² at room temperature into similar samples of suitably masked silicon. Boron ions were also implanted at liquid nitrogen temperature and 450°C. Annealing was limited to a maximum temperatare of 550 °C.

Measurements have been made of sheet resistance, forward and reverse I-V characteristics (from 10^?9 amps/cm²), reverse breakdown voltage, noise, minority carrier storage time and junction series resistance.

The bulk properties of boron implanted diodes were found to be reproducible. The introduction of recombination centres by implantation is the major factor influencing variation in these properties between one implantation condition and another. Changes in surface oxide conditions probably affect reverse leakage currents and breakdown voltages.

The properties of boron implanted diodes are considered suitable for applications such as the MOSFET, and are superior to those of the AI, Ga and In implanted diodes.