On the effect of an oxygen beam in sputter depth profiling

Abstract

Experiments of depth resolution measurements on silicon with secondary ion mass spectrometry reveal that oxygen primary particles provide always a smaller decay length (better depth resolution) compared with other primary particles for the same penetration depth of the particle. This deviation from the classical collisional mixing model can be explained by a model which does take the incorporation of the primary particle during sputtering into account. For oxygen particles the incorporation is so high that it leads to a different matrix composition at the surface compared with the bulk of the Si sample and it results in a target swelling at the surface. It is now important to realize that the displacements of the atoms are only important relative to the position of the Si atoms in the expanded lattice and that movements with respect to the incorporated oxygen atoms does not matter. The model presented quantifies this effect and gives an accurate estimate of the reduction of the decay lengths. The model predicts a similar behavior for all primary particles with low matrix sputter yield and high incorporation of the primary particle.

Cluster SIMS using metal cluster complex ions

“…As shown in Fig. 6b, oxygen flooding causes successive surface swelling by oxygen incorporation, resulting in the improvement in the depth resolution by the buffer effect [28][29][30]. However, in the case of lower beam energy Ir 4 (CO) 7 + bombardment, the implanted carbon most likely forms a carbon layer on the sample surface, thereby suppressing oxygen incorporation and subsequent swelling by the growth of SiO 2 [17].…”

“…Hence, it can be seen that the increase in oxygen partial pressure resulted in further improvement of the depth resolution. The improvement of the depth resolution is attributed to the reduction of atomic mixing by buffer effect of surface oxide layer [28][29][30], since the silicon surface is fully oxidized successively in the case of high oxygen partial pressure. Fig.…”

On the migration behavior of metal impurities in Si during secondary ion mass spectrometry profiling using low-energy oxygen ions

“…Among these processes, segregation, collisional-mixing, and electric-field-driven effects are the most dominant. [4][5][6][7][8] For instance, the dramatic profile broadening observed for ion-implanted Cu and Ag under bombardment conditions for which a stoichiometric oxide is formed has been attributed mainly to their migration towards the interface between the SiO 2 layer and the underlying Si substrate. This behavior has been explained in terms of bombardment-induced Gibbsian segregation, whereby the impurities migrated to the SiO 2 /Si interface ͑a site of lower chemical potential͒ because of the difference between the heat of their oxide formation and Si.…”

“…8,15 If the sputter-depth profiling analysis produces as little as 1 V of surface charge on a 5000 Å thick SiO 2 film, a field gradient of 2ϫ10 4 negative oxygen ions or under electron flooding ͑for positive oxygen ions͒, under conditions where surface oxide still forms, may suppress migration of Na and reduce segregation of some metals in Si. The electric-field-driven migration of Cu and Na has also been shown to be more pronounced in n-type than p-type Si.…”

Improved Step-Graded-Channel Heterostructure Field-Effect Transistor

“…On the other hand, as for surface roughness, AFM measurements showed that root-meansquare surface roughness increased from 0.3 nm to over 1 nm with pressure. As a consequence, the improvement of the depth resolution is attributed to the reduction of atomic mixing by the buffer effect of the surface oxide layer, [18][19][20] since the silicon surface is always fully oxidized in the case of high oxygen partial pressure. Figure 3(b) shows the beam energy dependence of the decay length at the incident angle of 45 .…”