Silicidation in Ni-Si System
Silicide formation induced by thermal annealing in Ni/Si thin film system has been investigated using glancing incidence X-ray diffraction. Silicide formation takes place at 600degC with Ni2Si, NiSi and NiSi2 phases co-existing with Ni. Complete conversion of intermediate silicide phases to the final NiSi2 phase takes place at 900degC. A comparison of the experimental results in terms of annealing temperature, Ni thickness, and dopant impurities with Ni-Si phases is presented. Nickel silicide (NiSi) is emerging to be the choice material for contact application in semiconductor device processing for sub_65 nm technology node and beyond. The focus of present work is to facilitate better understanding of the influence of thermal budget on nickel silicide solid-state reaction. Requirements for low temperature anneal and improving within wafer sheet resistance uniformity pose challenges for conventional lamp-based rapid thermal processing (RTP) due to lamp response effects on temperature controllability. Evolution of the nickel-rich silicide phase as a function of temperature is recorded using X-ray diffraction (XRD) techniques. It is postulated that lowering the Ni2Si/Si interface energy favors the delay of the agglomeration of the NiSi.
A thermally robust Ni-FUSI process using in 65 nm CMOS technology
The interest in the low resistivity fully silicided (FUSI) gate increased significantly because of promising in use as contact to the source, drain, and gate for sub−65 nm/45 nm CMOS devices. NiSi is potentially an attractive material due to its capability to maintain low resistivity even for channel length down to 100 nm. The Formation of thermally stable silicide gates is important for improving the devices fabrication processes. In order to obtain a thermally stable Ni-FUSI gate electrode, we introduced a two-step annealing process associated with properly tuned thickness of the initial Ni film and additional of implantation of BF2 during the poly-gate formation to push the transformation of NiSi2 to higher temperatures at about 900°C and retard agglomeration. A mixed-phase of nickel silicide layer was commonly observed during phase transformation. For the first time, we established an effective way to identify the phase transformations by some nondestructive techniques such as X-ray diffraction, sheet resistance measurement and AFM analysis. The correlations between its electrical and morphological changes during Ni–Si phase transformation were presented. Furthermore, the effect with addition amount of BF2 impurities into NiSi was investigated. F-incorporation demonstrated some improvements in both morphology and phase stability of the NiSi films at high processing temperatures.
Epitaxial growth of the nickel disilicide phase
Abstract The nickel disilicide (NiSi 2 ) phase which forms epitaxially on silicon single-crystal substrates in many ways exhibits an interesting behavior. A regular network of the silicon-rich phase was observed to originate at or near the Si-silicide interface using the Berg-Barrett X-ray topographic technique. The regularity, the thickness and the density of the network increase as the epitaxial layer increases in thickness. For (100)-oriented silicon substrates the network runs along two perpendicular 〈110〉 directions; for (111)-oriented silicon substrates the network runs along 〈112〉 directions. Large voids on the surface of the epitaxial layer and fracturing of the layer along the edges of the network for thick epitaxial layers were also observed. The results are explained in terms of the corrugated morphology of the NiSi 2 -Si structure.