Phase formation and thermal stability of ultrathin nickel-silicides on Si(100)

Abstract

The solid-state reaction and agglomeration of thin nickel-silicide films was investigated from sputter deposited nickel films ͑1-10 nm͒ on silicon-on-insulator ͑100͒ substrates. For typical anneals at a ramp rate of 3°C / s, 5-10 nm Ni films react with silicon and form NiSi, which agglomerates at 550-650°C, whereas films with a thickness of 3.7 nm of less were found to form an epitaxylike nickel-silicide layer. The resulting films show an increased thermal stability with a low electrical resistivity up to 800°C. © 2010 American Institute of Physics. ͓doi:10.1063/1.3384997͔Nickel-silicides are currently used as contacting materials in state-of-the-art microelectronic devices.1,2 Feature size has shrunk to a few tens of nanometers, and for nickel monosilicide ͑NiSi͒ layers, this results in a particularly severe tendency to agglomerate, 3 leading to a large increase in the electrical resistance of the contact, and an increased mobility of the nickel as it starts to move on the defects, both resulting in a low yield. Since the agglomeration of thin films is driven by a minimization of interface energy, it is expected that thinner films will agglomerate faster ͑i.e., have a lower agglomeration temperature͒. 4 In this letter, we show that this holds true only for films with a thickness of at least 5 nm ͑as-deposited thickness of the nickel layer͒, while for thinner layers the resulting nickel-silicide layer is much more resistant to agglomeration.Nickel films with a thickness between 1 and 10 nm were sputter deposited onto lightly p-doped ͑ =14-22 ⍀ cm͒, Radio Corporation of America ͑RCA͒ cleaned, and HF dipped silicon-on-insulator substrates, with a top layer of 117 nm of Si ͑100͒. The deposition chamber was first evacuated to 10 −4 Pa during deposition, the samples were mounted on a rotating carousel to ensure a uniform deposition thickness. An argon pressure of 0.5 Pa and a sputtering power of 100 W were used, resulting in a deposition rate of 0.04 nm/s. After deposition, the samples were annealed in a high-purity He atmosphere, from 100 to 850°C at a rate of 3°C / s, and the surface roughness ͑using laser light scattering, recording the intensity of nonspecular reflection of the laser light͒, and the sheet resistance ͑using a four point probe͒ were recorded in situ. The thickness of both the as-deposited and annealed films was determined using x-ray reflectivity and cross section transmission electron microscopy, resulting in the reported thicknesses with a precision of Ϯ0.2 nm.An overview of the in situ sheet-resistance is shown in Fig. 1. All of the samples with more than 3.7 nm of nickel ͑6, 8, and 10 nm are shown͒, exhibit a sheet resistance qualitatively similar to what was previously reported 5 for 10 nm layers of nickel on Si ͑100͒; a complex phase sequence of high-resistive metal rich nickel-silicides at low temperatures, and the formation of the low-resistive NiSi phase at 400-450°C. This layer then agglomerates at 550-650°C, leading to the observed increase in sheet resistance. In contrast, for the thinn...

Structural changes during the reaction of Ni thin films with (100) silicon substrates

“…7 and 8). Previous studies have shown complete consumption of thin nickel films in contact with an Si substrate to form nickel silicides after rapid thermal annealing to 850°C [33][34][35]. During the in situ annealing experiments presented in this study, the formation of NiSi 2 crystallizing in the CaF 2 structure occurred at 280°C for the thinner film and 500°C for the thicker film.…”

Flexible and Transparent Conducting ZZO/Ag/ZZO Multilayer Grown by Sputtering at Room Temperature

“…A low deposition rate was obtained by adjusting an argon (Ar) pressure and a sputtering power for depositing the ultrathin films. 18,19) Finally, the top ZZO film with a thickness of 40 nm was sputtered onto the Ag film under the process conditions identical to those of the bottom ZZO film. The physical thicknesses of ZZO films and complete multilayers were measured by a surface profilometer.…”

Texture in thin film silicides and germanides: A review

“…This idea of simultaneously measuring pole figures for different 2h angles was introduced in the field of metallurgy in the 1980s, 32 but was only recently adopted in the field of thin silicide/germanide films. [33][34][35][36] Technical and mathematical details on using linear or area detectors for pole figure measurements can be found in Refs. 37 and 38.…”

“…41 Nonetheless, EBSD has been successfully applied to a few thin film silicide and germanide materials over the past years. 36,[41][42][43][44][45][46] …”