Thickness Of Thin Metal Films Research Articles

EDDY CURRENT METHOD FOR STUDYING INHOMOGENEITIES AND DEFECTS IN THIN METAL FILMS

The variety of structure and specific properties associated with the small thickness of thin metal films lead to the fact that their physical characteristics differ significantly from the characteristics of the same materials in the bulk state. To determine the characteristics of thin metal films, the development of new non-destructive research methods is relevant. The article substantiates the advantages of the eddy current testing method for studying the surface of thin metal films of various metals. The design of a subminiature eddy current transducer designed to study the electrical conductivity, thickness and degree of damage of thin metal films is presented, and a hardware and software complex is designed that allows the control of the developed transducer. The study of metal films made it possible to show the inhomogeneity of the distribution of the substance over the surface of the substrate. The dependence of the signal amplitude of the developed transducer on the film thicknesswas also determined. To verify the results obtained, studies of the light transmittance of the films were carried out using the photometric method. Comparison of the measurement results obtained by the two methods showed a high degree of agreement betweenthe two developed methods for studying films.

An optical method for determination of the mass thickness of thin gold films with arbitrary morphology

The mass thickness of thin metal films is an important parameter determining the film structure, however a robust routine method for its determination is still missing. In this work, we have developed a simple optical method for determining the mass thickness of gold films with arbitrary morphology on transparent substrates in the range 1–20 nm. The method is based on film spectrophotometry in the far-UV range when the light attenuation is due to interaction with core electrons and thus the influence of the film morphology is negligible. The calibration was performed at a wavelength of 200 nm for gold films of known thickness and a good agreement with the Beer–Lambert law was obtained. The feasibility of the method was demonstrated with gold films of various morphologies produced on quartz substrates by pulsed laser deposition.

Cracking behavior of thin gold strip deposited on polycarbonate plate under Cyclic and stepwisely-increased tension

Thin metal films deposited on polymers have been attracting much attention in flexible electronics. Various combinations of film and polymer substrate are expected to be developed. In this paper, deformation and fracture of thin metal film on polymer substrate was briefly analysed and the influencing factors were summarized. After that, focusing on the shape and thickness of thin metal film on polymer substrate, cracking behavior of small rounded-rectangular thin gold films called “strips” with a thickness less than one micrometer was observed under cyclic and stepwisely-increased trapezoidal tensions. The strips were deposited on a polycarbonate plate specimen, and wide and narrow strips with different thickness were prepared for the tests. The cracking behaviour was successfully observed and the increasing rate of crack number with the load or strain was examined. Since most cracks were initiated from the small defects, the crack initiation behavior was correlated with the distribution of defects.

A facility for measuring the thickness of thin metal films

A facility is described for measuring the thickness of a thin metal film. A measurement method is proposed that is based on the dependence of the phase velocity of harmonic antisymmetric Lamb waves that propagate along the film on the film thickness. A continuous method for excitation of acoustic waves has been applied to velocity measurements. It makes it possible to eliminate the effect of dispersion of the Lamb-wave velocity on the measurement accuracy.

SPR phase detection for measuring the thickness of thin metal films

In this paper, a novel method to determine the thickness of thin metal film is put forward which uses Surface Plasmon Resonance (SPR) phase detection method. The relations between the metal film thickness and the phases of the transverse magnetic (TM) and transverse electric (TE) polarization of the reflected light are shown in the simulation results. By recording the interference patterns which contain the information of the phase differences in the experiments, the values of thickness are calculated. Both of the theoretical analysis and experimental results indicate that the approach presented is feasible and reliable. Thus, it is possible to use the method of phase detection to determine the thickness of thin metal films within 100nm in SPR prism couplers directly with nanometer resolution.

Surface erosion induced by heavy ion backscattering analysis

Material removal induced by HIBS (Heavy Ion Backscattering Spectrometry) analysis has been investigated. For this purpose the thickness of thin metal films deposited on graphite was measured as a function of fluence of the Si and Ti projectile ion beam. Steady state erosion rates are in fair agreement with surface sputtering rates calculated by SRIM. For some layers however, the first few monolayers are removed at a much faster rate. A comparison with standard He RBS is made and consequences for the applicability of HIBS are discussed.

Determination of thickness and optical constants of thin metal films with an extended ATR spectrum

An extended attenuated total reflection (ATR) spectrum, which consists of a surface plasmon resonance (SPR) dip and a total internal reflection (TIR) step, is used to determine the optical constant and the thickness of a thin metal film at a given frequency in the conventional Kretschmann configuration. Previous research has shown that two sets of solutions for the optical constant and thickness can be obtained from a SPR dip, and ambiguity should be removed by carrying out another angular scan process or employing a more complicated structure. However, we find that the true solution can be simply selected by a new parameter that denotes the TIR step change. Our method can avoid not only the troubles caused by the double-scan techniques but also the increased difficulties due to the existence of an additional polymer film in a single-scan method.

Industrial applications of spectroscopic ellipsometry

In this work we develop the concept of the ‘typical’ industrial ellipsometry user, discussing his/her needs and skills, compared to the scholarly user. Following this, we will give examples of industrial problems where spectroscopic ellipsometry (SE) was used to obtain the end result. Included will be an example of designing material with chosen optical constants, an example of measuring the thickness of thin metal films, and methods development for measuring a polymer/bio film on a glass substrate.

Investigation on the optical properties of side-polished fiber contacted with planar waveguide including a thin metal film

We investigate the characteristics of an asymmetric directional coupler made of side-polished fiber and multimode planar waveguide incorporating a thin metal film. The influence of the metal film thickness and the refractive index of the superstrate on the spectral and polarization properties of the coupler is measured and explained based on the weakly coupled model. It is shown that the coupler behaves like a band-rejection filter or a polarizer, depending on the device parameters. The application possibilities of the sensors to measure the thickness of thin metal film and the refractive index of the liquid are also observed.

Improved SPR technique for determination of the thickness and optical constants of thin metal films

A novel method with single-wavelength light is developed to determine the optical constants and the thickness of a thin metal film. It bases on a new geometry that consists of a coupling prism, a transparent coating layer directly deposited onto the prism base, a thin metal film to be detected, and the air. The attenuated total reflection technique is employed in our configuration to excite two different kinds of surface plasmon waves simultaneously. As a result, the reflection curve shows two obvious surface plasmon resonant dips. Using the Chen's et al. (Opt. Soc. Am. 71 189, 1981) method, we can obtain two sets of e(ω) and thickness of the thin metal film through one resonant dip (surface plasmon), then the real value can be determined through the other resonant dip (modified long-range surface plasmon). Compared to conventional double wavelength method and the double-medium technique (Yang et al. Appl. Opt. 27 11, 1988), the present single-scan method avoids both the ambiguity of different conditions caused by two-scan technique, and the dispersion problem with different light wavelength.

Features of low-frequency nondestructive photothermal testing of the thickness of thin metallic films on glass

Features of low-frequency nondestructive photothermal testing of the thickness of thin metallic films on glass

Spectroscopic ellipsometry measurements of thin metal films

Optical methods are used to determine the thickness of thin metal films, with emphasis on spectroscopic ellipsometry and transmission. We discuss the conditions where this is possible and how to determine the optical constants for the material. The determination of the thickness of each of two metals in a bimetallic stack is discussed. Finally, by measuring thickness with these methods and measuring weight gain, we determine the density of platinum deposited by evaporation and deposited by a simple sputter deposition method. Explicitly, one of the results is that the determined optical constants depend on the deposition method. This implies that, with only a few exceptions, one must determine the optical constants of the material of interest, and that it is inappropriate to use values from another source such as a handbook or from another investigator. The resulting optical constants in this work suggest that the microstructure of the platinum films from the two different methods will not be the same, and x-ray diffraction and sheet resistance measurements verify that this is the case. Specifically, the significantly lower extinction coefficient of the sputter-deposited films correlates with a higher sheet resistance. Copyright © 2000 John Wiley & Sons, Ltd.

Spectroscopic ellipsometry measurements of thin metal films

Optical methods are used to determine the thickness of thin metal films, with emphasis on spectroscopic ellipsometry and transmission. We discuss the conditions where this is possible and how to determine the optical constants for the material. The determination of the thickness of each of two metals in a bimetallic stack is discussed. Finally, by measuring thickness with these methods and measuring weight gain, we determine the density of platinum deposited by evaporation and deposited by a simple sputter deposition method. Explicitly, one of the results is that the determined optical constants depend on the deposition method. This implies that, with only a few exceptions, one must determine the optical constants of the material of interest, and that it is inappropriate to use values from another source such as a handbook or from another investigator. The resulting optical constants in this work suggest that the microstructure of the platinum films from the two different methods will not be the same, and x-ray diffraction and sheet resistance measurements verify that this is the case. Specifically, the significantly lower extinction coefficient of the sputter-deposited films correlates with a higher sheet resistance.

Determining thickness of thin metal films with spectroscopic ellipsometry for applications in magnetic random-access memory

Metal thicknesses can be determined using optical methods such as spectroscopic ellipsometry when the thickness of the film is small enough that the light penetrates to the bottom of the film. In order to use ellipsometry, it is necessary to determine the optical constants of the film material accurately. In this work, we describe the determination of the optical constants and thicknesses of single metal layers of NiFe, Cu, Co, Ta, FeMn deposited with two different deposition methods. The thicknesses range from about 6 to about 20 nm thick. We have also investigated the ex situ measurement of multiple metal layers, and discuss the conditions where the thicknesses of the individual layers can be determined and the conditions where they cannot be distinguished from each other.

Angular dependence of the secondary electron emission crystal current: Effects of surface modification

The variation of the angle between the incident electron beam and sample surface contributes in two ways to the secondary electron emission from single crystals. These contributions are a monotonically varying background due to the changing number of secondaries produced near the surface, and an oscillatory component previously explained as a bulk effect related to Kikuchi patterns. This work shows that for emission from a Au(111) surface, the background can be described well by a simple model based on the semiempirical theory of Kanaya and Kawakatsu. It also provides additional support for the explanation of the oscillations as a bulk effect by showing that the oscillation amplitude remains essentially unchanged either by surface sputtering or by the deposition of a thin lead layer. The presence of these oscillations requires some care in the use of the secondary electron crystal current as a measure of the thickness of thin metal films.

Excitation of nonlinear surface electromagnetic waves in the prism-metal film-nematic liquid crystal system

The excitation of nonlinear p-polarized surface electromagnetic waves (SEW) in prism-metal film-nematic liquid crystal (NLC) attenuated total reflection (ATR) systems (Kretschmann ATR system) has been investigated both theoretically and experimentally. The third-order optical nonlinearity of the NLC (the only nonlinear medium in our system) has been estimated by measuring the dependence of the reflectance minimum on the incident radiation intensity. The nonlinear optical method of determination of the thickness of thin metal films, used in the Kretschmann system, has been suggested. The hysteresis loops in the outgoing intensity versus input intensity curves were obtained experimentally when the light field increases and decreases consecutively.

A new simple method of determining the effective mass of an electron or the thickness of thin metal films

A simple method of determining the effective mass m* of free electrons in thin metal films (or the film thickness) only from the measured transmission of light in the range of the plasma reflection is discussed. The method is verified for gold films with thicknesses ranging from 7-40 nm. It was stated that the effective mass in this material does not depend on the film thickness and equals (1.0+or-0.03) me. On the other hand, knowing the value of m*, the absolute film thickness can be obtained directly with a high accuracy within an error of a few angstroms, which is better than by the alpha -step or the Tolansky method.

Detection of thermal waves through optical reflectance

We show that thermal wave detection and analysis can be performed, in a noncontact and highly sensitive manner, through the dependence of sample optical reflectance on temperature. Applications to the study of microelectronic materials are illustrated by an example of measuring the thickness of thin metal films.

Rapid and accurate measurement of the thickness of thin films by an x-ray fluorescence technique using a new background subtraction method

A simple apparatus for measuring the thickness of thin metal films is described in which a new background correction method is applied to the X-ray fluorescence technique. This method provides film thickness measurements that are almost independent of the nature and the thickness of substrates with a low mean atomic number Z. Several test measurements were performed on gold and copper monolayers and on Au/Cu double layers. An improvement in the accuracy and in the minimum detectable limit was found.

Microprobe technique for determining the thickness of thin metal films in multilayered structures

The microprobe technique applies to metal or alloy film composites in which the chemical composition is uniform. Film thicknesses of such structures are determined on the basis of characteristic X-ray intensities detected for each layer. Composite standards with layers arranged in the same sequence as in the samples are required to minimize or eliminate backscattering and secondary fluorescence effects. The absorption correction, however, is built into the method. The technique was developed using Cu/Ni composites in which Cu was used as a tracer element at various depths in a Ni matrix. It was then applied to Al/SiO 2 structures with several thickness ratios ranging from 1.0 to 2.0. Routine analyses achieved an accuracy of ±5%. To determine thickness the ionization curves had to be expressed analytically as a function of depth and accelerating potential, and an expression was derived for the detected intensity. The X-ray intensity of each layer, from the surface down, was processed through a computer program so that thickness information determined for the first layer was input information for the second, and so on. The technique can also be used to determine a contaminant density in any of the layers.