In-situ Spectroscopic Ellipsometry of the Cu Deposition Process from Supercritical Fluids: Evidence of an Abnormal Surface Layer Formation

Abstract

In this paper, we report in-situ spectroscopic ellipsometry of Cu deposition from supercritical carbon dioxide fluids. The motivations of this work were 1) to perform a detailed observation of Cu growth with precision optical metrology, 2) to study substrate dependence on Cu growth, particularly for Ru and TiN substrates in the present case, and 3) to demonstrate the possibility and usefulness of ellipsometry for diagnosing supercritical fluid processing. The Cu deposition was carried out through hydrogen reduction of a Cu-diketonate precursor at 160-180 C. During growth, a very large deviation of ellipsometric parameters (É and Á) from a single-layer model prediction was observed; this deviation was much larger than that expected from island formation which has been frequently reported in in-situ ellipsometric observation of the vapor growth of thin films. From model analyses, it was found that an abnormal dielectric layer having a high refractive index and a thickness of 10-50 nm is present on the growing Cu surface. The refractive index of this layer was ð1:5{2Þ þ ð0:2{0:3Þi; and from this, we concluded that this layer is the condensed precursor. The condensed layer develops prior to Cu nucleation. As for the substrate dependence on Cu growth, both layers develop faster on Ru than on TiN. This corresponds to the fact that chemisorption occurs more easily on Ru. The deposition kinetics under the presence of the condensed layer are also discussed.

Fast Imaging Ellipsometer Using a LiNbO3 Electrooptic Crystal

“…In the future, we plan to apply this IE to the in-situ measurement and study of the optical properties and/or thickness distribution of a metal film while depositing on a substrates in a supercritical fluid. 33) Unlike other existing thin film deposition processes such as physical vapor deposition (PVD) and chemical vapor deposition (CVD) whose mechanisms are known clearly, the deposition process in the supercritical fluid is not understood completely yet; therefore, it must to be investigated in more detail by using such techniques as fast imaging ellipsometry. The IE developed at our laboratory is expected to provide both temporal and spatial instrumentations and much information to further clarify the mechanism of this deposition process.…”

Synthesis of Cu or Cu2O-polyimide nanocomposites using Cu powders and their optical properties

“…For high refractive index film applications of PI-nanoparticle nanocomposites, most research has focused on TiO 2 nanoparticles because of their high refractive index [21][22][23]. However, cuprous oxide is another material with a high refractive index of 2.93 at a wavelength of 633 nm [25].…”

Correction of large birefringent effect of windows for in situ ellipsometry measurements

“…During measurement, samples are usually kept inside a chamber and surrounded with particular environmental conditions, such as a vacuum [2], high pressure and high temperature [3], and liquid [1]. The materials of the entrance and exit optical windows attached to the chamber are selected to endure these environments as well as exhibit very small intrinsic birefringence.…”

“…Approaches with large window effect have been reported [3,9]. The correction method mentioned in [3] needed measurement of windows' birefringence under a given condition in advance by changing the incident polarization state with a rotating quarterwave plate installed before the entrance window. In this measurement, authors performed corrections, assuming that the stress-induced birefringences of both windows were the same.…”