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A B-buried layer with a dose of 1×1014 atoms/cm2 was introduced into p-doped Si at a depth of 2.2 μm to enhance copper diffusion via its inherent gettering effect. Copper was then introduced into silicon either via a low-energy implantation followed by a thermal anneal, or through the thermal drive in of physical vapor deposited (PVD) copper film. Secondary ion mass spectrometry depth profiling of both annealed samples later indicated that while substantial amounts of copper was gettered by the B layer in the former sample, no copper was gettered by the B-buried layer in the latter sample. Further analysis with an x-ray diffraction technique showed that copper silicide, Cu3Si was formed in the latter sample. It is thus surmised that the formation of this silicide layer impeded the diffusion of copper towards the B-buried layer. This work investigates the cause of CuSix formation and the underlying reasons for the lower mobility of Cu in PVD Cu film samples.

The scaling of the junction depth, which can help to suppress the short channel effect, has become essential for the emerging nanoscale IC technology. The 2000 National Roadmap for semiconductors indicates that for complementary metal-oxide semiconductors with 0.13 µm and 0.09 µm gate lengths, junction depths of 43 nm and 35 nm are required, respectively. It will be of utmost importance to obtain accurate dopant profiles of the electrically activated junctions. In SIMS depth profiling, dopant profiles are broadened by sputter-induced roughening and a primary-energy-dependent ion mixing effect; shallow profiles are obscured by surface transient effects. Crater bottom roughening usually can be removed by oxygen flooding 1,2 or sample rotation 3,4 techniques; ion mixing can be minimized by lowering the primary ion energy and optimizing the incidence angle. For implanted profiles, the knock-on effects when sputtering from a high concentration to lower concentration region will significantly degrade the depth resolution.Backside SIMS depth profiling using primary ion energies >3 keV has been shown to improve the implanted trailing edge profile and avoid surface transient effects.5 -8 However, sample thinning from the backside, either by etching or polishing, requires that the surface be kept flat and smooth in order to achieve high depth resolution. We have developed an ultrashallow backside profiling technique