Systematics of positive secondary ion mass spectrometry relative sensitivity factors for Si and SiO2 measured using oxygen and argon ion bombardment

Abstract

We have measured normalized positive ion yields of more than 20 elements implanted into SiO2 and compare them with positive ion yields of the same elements sputtered from Si by oxygen and argon ion bombardment. All measurements were made using similar instruments and similar primary ion beam conditions; thus, we compare secondary ion emission from an unoxygenated matrix (Si using argon ion bombardment), from a partially oxygenated matrix (Si using oxygen ion bombardment), and from a fully oxygenated matrix (SiO2). Plots of the logarithm of secondary ion yield or secondary ion mass spectrometry relative sensitivity factor (RSF) versus ionization potential of the sputtered impurity elements exhibit primary linear trends for these three conditions, the slopes of which decrease with increasing oxygenation. A trend line of opposite slope for impurity elements that have ionization potential greater than about 10.5 eV is observed in each case. This latter trend moves to lower values of yield (higher RSF) with increasing oxygenation, perhaps as the result of competition from electronegative elements with oxygen in forming element–Si bonds. These observed changes are primarily the result of increasing the oxygen content in the surface of the Si.