Some Observations on High Energy Nitrogen Implantations in Silicon
There is an increasing interest in the buried layers produced by the high energy implantation of dopants into silicon. The published results have been principally concerned with the profiles of the implanted atoms and less with the electrical properties of the buried layers.
This paper reports on some physical and electrical measurements made on 3 MeV nitrogen implanted layers in silicon for range of ion doses, and annealing temperatures. The work has concentrated on the crystal perfection and the electrical properties of the buried layer and the region above it. The crystal perfection was observed by the electron channelling patterns formed when the specimen is examined in a scanning microscope. The type and electrical activity of the layers were measured by thermal probe, four point probe, and capacitance-voltage methods. I/V measurements were made on shallow diffused and implanted diodes and resistors in the region above the buried layer.
Simple p-n-p structures were made by etching deep mesas through the buried implanted layer. The I/V characteristics are those of a pair of back to back p-n diodes confirming the presence of the n layer.
The results show that the buried layer is n type and that approximately 1% of the number of implanted ions are electrically active after a 900 °C anneal. The depth of the buried layer agrees reasonably well with the L.S.S. theory and the p layer above the buried layer is crystalline after implantation and before annealing even for the heavy ion dose (1016 ions/cm2).
KeywordsBreakdown Voltage Crystal Perfection Thermal Probe Nitrogen Implantation Thyristor Switching
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