Characterization of silver films deposited by radio frequency magnetron sputtering

Abstract

Silver thin films have been deposited on various substrates at floating potentials by radio frequency magnetron sputtering of a silver target in pure argon plasma using load-locked sputtering equipment. Under the experimental conditions investigated, the deposition rate of silver films was about 70 nm/min so that metal films as thin as 200 nm could be deposited within easily controllable deposition durations. Film surfaces and cross sections were examined by scanning electron microscopy. The morphology was fully dense. The crystallographic structure was investigated by x-ray diffraction. The grains were preferentially oriented with the (111) lattice planes parallel to the film surface and without preferred azimuthal orientation. The films analyzed by Rutherford backscattering spectroscopy were free of detectable impurities. The residual stresses were determined to be tensile from the measurements of the curvature radius of silicon substrates. The calculated value of the thermal stress showed that the intrinsic stress in the films was compressive. The effective Knoop hardness of 2-μm-thick silver films deposited on glass substrates was in the range 1600–1800 MPa, i.e., three times higher than the hardness of the bulk metal. Pure silver films exhibited an electrical resistivity of 1.5–2 μΩ cm, nearly equal to the bulk resistivity.

Heat shrink formation of a corrugated thin film thermoelectric generator

“…This resistivity is higher than typically observed for these metals in bulk form (20 nO m and 190 nO m for Ag and Ni, respectively) [26][27][28]. The large resistivity of the films in the flat configuration is attributed to the vacuum deposition process and thin film nature, which has previously been shown to increase the resistivity of metals compared to their bulk counterpart [29,30].…”

Silicon shadow mask fabrication for patterned metal deposition with microscale dimensions using a novel corner compensation scheme

“…For example, similar heaters deposited under like conditions showed resistance variations of less than 0.5 , and the change in resistance per unit temperature difference for similar aluminum heaters, ∼25 m wide and ∼1 mm in length varied by only ∼0.2%. Interestingly, silver heaters (deposited using e-beam evaporation) exhibited measured resistances that were up to ∼25% different than predicted values using bulk resistivity data for the calculation [30,31]. These differences were attributed to the fact that the electrical resistivity of thin silver films can significantly depend on deposition conditions such as temperature [30], argon pressure [31] and thickness [32].…”

“…Interestingly, silver heaters (deposited using e-beam evaporation) exhibited measured resistances that were up to ∼25% different than predicted values using bulk resistivity data for the calculation [30,31]. These differences were attributed to the fact that the electrical resistivity of thin silver films can significantly depend on deposition conditions such as temperature [30], argon pressure [31] and thickness [32]. Nonetheless, these resistance measurements provided confidence that the metal deposition through the shadow mask provided robust and continuous lines as well as repeatable results.…”

Smooth Ag Film Deposited Using e-beam Evaporated Ge as an Intermediate Layer for Applications in Nanoscale Devices and Optical Superlens

“…The RMS surface roughness improves by a factor of ~10 for the optically thin Ag film and ~1.5x for the optically thick Ag film with the introduction of evaporated Ge layer. It is postulated that the Ge acts as a wetting layer for the evaporated Ag film thus directly minimizing the commonly seen 3D-island (Volmer-Weber growth) cluster formation of Ag [5][6][7].…”