Wee Kiong Choi

Thermal reaction of nickel and Si0.75Ge0.25 alloy

The interfacial reactions and chemical phase formation between nickel and ultrahigh vacuum chemical vapor deposited Si0.75Ge0.25 alloy have been studied within the temperature range of 300–900 °C for forming low resistive and uniform silicide films for future application in SiGe based metal–oxide–semiconductor field effect transistor devices. The silicided films were characterized by the x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, transmission electron microscopy, and micro-Raman microscopy techniques. Smooth and uniform nickel monogermanosilicide NiSi0.75Ge0.25 films have been observed for samples annealed at around 400–500 °C. For annealing temperatures of 500 °C and above, Ge-rich Si1−zGez grains where z>0.25 were found among Ge deficient Niy(SiwGe1−w)1−y grains where w 0.25 were found among Ge deficient Niy(SiwGe1−w)1−y grains where w<0.25 and the Niy(Si1−wGew)1−y phase is thermally stable up to an annealing temperature of 800 °C. We found that the Ni/SiGe reaction is mainly diffusion controlled with Ge and Ni as the dominant diffusi...

Stability and composition of Ni–germanosilicided Si1−xGex films

The stability and composition of the Ni–germanosilicided films formed on relaxed Si1−xGex alloy has been studied in the temperature range of 400–900 °C. During the solid phase thermal reaction between Ni and Si1−xGex, a nickel–germanosilicide Niy(Si1−wGew)1−y ternary phase (w⩽x and y≈0.5) and a Ge-rich Si1−zGez phase (z>x) have been found. In the lower annealing temperature range of 500 °C, the Ge composition in the nickel–germanosilicide phase is similar to that of the Si0.75Ge0.25 substrate. At the same time, germination of Si1−zGez (z>x) takes place within the germanosilicide film. At higher annealing temperatures, Ni thermodynamically prefers to react with Si compared to Ge, and as a result, Ge segregates out from the germanosilicide grains to enrich Ge in the formed Si1−zGez (z>x) grains in between the germanosilicide grains. On the other hand, the size of the germanosilicide grains increases almost linearly with annealing temperature while that for the Si1−zGez grains remains almost constant up to a...

Monitoring oxide quality using the spread of the dC/dV peak in scanning capacitance microscopy measurements

This article proposes a method for evaluating the quality of the overlying oxide on samples used in scanning capacitance microscopy (SCM) dopant profile extraction. The method can also be used generally as a convenient in-process method for monitoring oxide quality directly after the oxidation process without prior metallization of the oxide-semiconductor sample. The spread of the differential capacitance characteristic (dC/dV versus V plot), characterized using its full width at half maximum (FWHM), was found to be strongly dependent on the interface trap density as a consequence of the stretch-out effect of interface traps on the capacitance-voltage ( C-V) curve. Results show that the FWHM of the dC/dV characteristic is a sensitive monitor of oxide quality (in terms of interface trap density) as it is not complicated by localized oxide charging effects as in the case of the SCM probe tip voltage corresponding to maximum dC/dV. The magnitude of the dC/dV peak, at any given surface potential, was also found to be independent of the interface traps and only dependent on the substrate dopant concentration, which makes SCM dopant profile extraction possible.