Lateral Silicide Growth Research Articles

Formation of self-aligned TiSi2 for very large scale integrated contacts and interconnects

In this paper, we present the results of a study on self-aligned TiSi2 formation. TiSi2 was formed by a rapid thermal anneal (RTA) of a sputtered Ti film on crystalline Si and on phosphorus doped poly-Si at a temperature from 600 to 1100 °C. A film resistivity of 16 μΩ cm has been achieved after an RTA at 800 °C for 10 s. Auger electron spectroscopy analysis indicated that a stoichiometric TiSi2 below a surface TiNxOy layer was formed by RTA in N2. The Si consumption during RTA in N2 was less than in Ar ambient due to the TiNxOy formation. In addition, RTA in N2 resulted in less lateral silicide growth than in Ar. Ti film started to react with the underlying SiO2 layer at 600 °C for 30 s and titanium oxide and titanium silicide were observed after RTA at 800 °C for 30 s. The TiSi2 formation on POCl3 doped poly-Si and moderately doped crystalline Si exhibited the same characteristics as on bare Si. Secondary ion mass spectroscopy analysis indicated that As+ and B+ did not pile up at the TiSi2/Si interface. From the measurements of lateral silicide growth lengths after stripping the ‘‘unreacted Ti’’ on oxide, a process window of RTA temperature and time for forming self-aligned silicide was determined. Good I–V characteristics of silicided diodes and salicide metal–oxide semiconductor field-effect transistors have been obtained.

Silicon Transport in Lateral Silicide Growth of CrSi2

AbstractSilicide formation and growth are studied in three geometries: conventional planar thin films, lateral diffusion couples formed by depositing metal layers on Si islands, and device geometry couples formed by depositing metal on oxide-patterned Si substrates. The influence of impurities is studied by implanting arsenic and krypton into conventional and device geometry structures.Here we present growth kinetics of CrSi2 where the presence of impurities has a strong influence. Si transport dominates in disilicide formation and leads to erosion of contacts around the periphery of oxide windows. Implantation of arsenic suppresses CrSi 2 formation; with krypton implantation, the growth kinetics shifts from linear to square-root in character. We attribute these results to impurity segregation at interfaces or grain boundaries.

Selective tungsten silicide formation by ion-beam mixing and rapid thermal annealing

Smooth layers of tungsten silicide have been formed on silicon substrates by deposition of a tungsten film, As+ ion implantation through the film to produce ion-beam mixing, and rapid thermal annealing. This process has been used to form tungsten silicide selectively in patterned openings etched in the SiO2 film on oxidized Si wafers, without lateral silicide growth. Rapid thermal annealing results in the activation of the As implanted in the Si substrate, without significant redistribution, to form shallow n+-p junctions with good electrical properties.

Ion-Beam Modification of Silicided Ti/Si Contacts

ABSTRACTIon-beam mixing studies were performed with arsenic implantation up to a dose of 1015/ cm2 through Ti on n+-Si contacts. Lateral silicide growth of many microns over the contact edges was observed for furnace annealed samples. The lateral growth is greatly enhanced by ion-beam mixing and can be suppressed with silicon nitride capping or using rapid thermal annealing (RTA) with a flash-lamp system. For RTA annealed samples. the implanted arsenic profile measured by RBS showed no snowplowing during the silicide growth process. Hligh contact resistivity was measured in the high-temperature annealed samples. This observation is consistent with the lower dopant concentration at the silicide/Si interface, due to silicide growth consuming the n+-Si layer.

Modeling a heterogeneous metal/semiconductor interface: Ce on Si(111)

High-resolution synchrotron radiation photoemission studies of Ce deposited onto cleaved Si(111)-2\ifmmode\times\else\texttimes\fi{}1 reveal heterogeneous growth which involves clustering, Ce/Si reaction to form silicide patches, lateral silicide growth, and finally Ce overlayer formation with surface segregated Si. Core-level line-shape analysis reveals three distinct Si local bonding configurations. The relative interface concentration of each Si species has been determined as a function of overlayer thickness, and a model for this interface is presented and discussed.

Lateral growth of titanium silicide over a silicon dioxide layer

If a silicon dioxide step on a single crystal of silicon covered with titanium is annealed, then, following vertical growth on the silicon part, lateral growth of titanium silicide takes place over the oxide layer. In the temperature range 750–950 °C this lateral growth of Ti–silicide was found to be a linear function of the square root of the annealing time. The activation energy of the lateral growth was found to be 1.89 eV. During lateral growth the Ti–silicide forms a deep spike in the silicon crystal at the SiO2 step.