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Abstract: Roughness development is one of the most often addressed issues in the secondary ion mass spectrometry (SIMS) ultra-shallow depth profiling. The effect of oxygen flooding pressure on the roughness development has been investigated under the bombardment of 500eV O2 + beam with simultaneous sample rotation. Oxygen flooding had two competing effects on the surface roughening, i.e., enhancement of initiating roughening and suppression of roughening development, which were suggested to be described by the onset depth z on and transient width w tr of surface roughening. Both z on and w tr decreased as oxygen flooding pressure increased. As the result, surface roughening was most pronounced at the intermediate pressure from 4.4E−5Pa to 5.8E−5Pa. The surface roughening is negligible while without flooding or with flooding at the saturated pressure. No flooding is preferable for depth profiling ultra-shallow B implantation because of the better B profile shape and short analysis time. [Copyright &y& Elsevier]

Following the increasingly stringent requirements in the characterization of sub-micron IC devices, an understanding of the various factors affecting ultra shallow depth profiling in secondary ion mass spectrometry (SIMS) has become crucial. Achieving high depth resolution (of the order of 1 nm) is critical in the semiconductor industry today, and various methods have been developed to optimize depth resolution. In this paper, we will discuss ultra shallow SIMS depth profiling using B and Ge delta-doped Si samples using low energy 0.5 keV O2+ primary beams. The relationship between depth resolution of the delta layers and surface topography measured by atomic force microscopy (AFM) is studied. The effect of oxygen flooding and sample rotation, used to suppress surface roughening is also investigated. Oxygen flooding was found to effectively suppress roughening and gives the best depth resolution for B, but sample rotation gives the best resolution for Ge. Possible mechanisms for this are discussed. [Copyright &y& Elsevier]

SIMS depth profiles obtained from a B implanted Si sample capped with a thin HfO2 film revealed the presence of several artifacts that make it problematic to determine the distribution and concentration of elements in the underlying Si substrate. The distribution of the B implant, normalized to 30Si+, was much broader than expected. Variations in the intensities of several matrix species under the HfO2 film were also observed. AFM measurements from the sputtered crater bottoms suggested that sputter-induced surface roughness is present under the high-k/Si interface. The roughness is partially responsible for reducing the sputter rate, which in turn lowers matrix ion intensities. The sputter rate variation can be corrected using the ratio of intensity loss of different matrix species. Use of the variation in the SiO+ intensity to correct the depth scale of the normalized B profile provided the best agreement with the original B implant-only sample. Rotating the sample while profiling improves the shape of the normalized B profile but some sputter rate correction was still necessary. The presence of 10% Hf (atomic) in the Si leads to slight reduction in the SiO+ intensity but the sputter rate does not need correcting. Under these conditions, point-by-point normalization of the B profile to a matrix species cancels out the ion yield variations. At Hf concentrations >10% the combination of ion yield and sputter rate variations complicates the depth profiles. [Copyright &y& Elsevier]

In secondary ion mass spectrometry depth profiling, a more accurate junction depth can be acquired by sputtering from the backside of the wafer [J. Vac. Sci. Technol. B 16 (1) (1998) 298]. This technique takes advantage of the better depth resolution of the leading edge as compared to the trailing edge [Nucl. Instrum. Meth. B 47 (1990) 223]. By using silicon-on-insulator (SOI) wafers, we have developed a backside depth profiling technique for studying ultra shallow implants. The abrupt interface of the SOI wafer and the large selectivity in chemical etching result in smooth after-etched surfaces, which facilitate high resolution SIMS profiling. The true dopant distribution of B 1 keV implants was studied by performing front and backside depth profiling using SOI substrates. The 7.5 and 0.5 keV O2+ primary ions were used at oblique incidence in a Cameca IMS-6f, with and without oxygen flooding and sample rotation. The effectiveness of backside SIMS profiling of the ultra shallow dopant implants using SOI substrates is evaluated. [Copyright &y& Elsevier]