Estimation Of Film Thickness Research Articles

Study on Estimation of Metal Film Thickness by Attenuated Total Reflection

The estimation of thin film thickness by attenuated total reflection (ATR) was proposed. This technique is caused by be fitted curve evaluated from Fresnel's formula to experimental values of reflectivity in the resonance dip due to surface plasmon. The equation for the thickness, d spr, estimated from ATR and the minimum, R min, of the resonance dip in reflectivity due to surface plasmon resonance is represented by d spr=D+√E(R min-F). The values obtained by this method were compared with those obtained by the surface roughness tester made by the Rank Tayler Hobson Company. From this comparison, the experimental formula d srt=Gd spr+H was proposed, and G and H were obtained as 0.69 and 6.7 respectively for an Ag film, 0.86 and -1.45 respectively for an Au film, and 0.67 and 8.98 respectively for a Cu film, all ranging from about 30 nm to 70 nm in thickness.

Endpoint prediction for polysilicon plasma etch via optical emission interferometry

In semiconductor manufacturing, the completion or “endpoint” of a plasma etch is typically controlled as a timed process, or monitored by use of optical emission spectroscopy. As etch process requirements and complexity increase (sequences of discrete recipe changes during the etch), consistency in timing changes is becoming an important issue. Newly developed full wafer interferometry sensors enable real-time monitoring of the entire wafer surface during an etch. In this article, endpoint prediction (or film thickness estimation) for etching polysilicon is considered. For the etch of a specific film structure, the interferometric signal is cyclical with a known number of cycles. Similar to the phase angle of a cosine function, data points of an interferometric curve can be associated with a linear phase function. If the phase at endpoint is known, in situ film thickness can be obtained by determining the phase of the incoming signal in real-time. Simulations show that the proposed film thickness estimation algorithm has good accuracy in the face of etch rate drift and variation in film structure. We also find that estimation is more robust if shorter wavelength signals are used. Finally, experimental data verifies that remaining film thickness can be estimated within reasonable accuracy, and endpoint effectively predicted for blanket and patterned films. These methods provide the critical information needed to make control decisions (e.g., when to switch to a more selective chemistry) based on reaching a desired known film thickness.

Nondestructive measurement of interfacial SiO2 films formed during deposition and annealing of Ta2O5

It is demonstrated that infrared absorption spectroscopy of the transverse optic and longitudinal optic vibrational modes of the asymmetric bridging oxygen stretch in amorphous SiO2 may be used to conveniently estimate film thickness in sandwiched structures. Measurements have been made on the SiO2 film formed at the substrate/dielectric interface during deposition of Ta2O5 on Si substrates and the evolution of its thickness during subsequent annealing. The accuracy of the film thickness determined is compared with electron microscopy observations.

Relationship between tribological performance of liquid crystals and their molecular structure

The tribological behaviour of nematic and smectic liquid crystals was observed using a two-roller friction tester under the conditions of 735 N load and 220 rpm rotational speed. Each liquid crystal has two typical structures: a flexible structure (alkyl chain) and a rigid structure (cyanophenyl group). Structural features of the liquid crystals were (1) alkyl cyanobiphenyl (CB), (2) alkoxyl cyanobiphenyl (ECB) and (3) alkyl cyanophenyl cyclohexane (CPC). The frictional coefficient of the test samples was lower and the estimated film thickness was larger than those of synthetic oils. The friction coefficient was not affected by the carbon number of the alkyl chain, but was closely dependent on the molecular structure of the rigid part of the liquid crystal module. The frictional coefficient of CB which has a biphenyl group was 0.035, but CPC had a higher friction coefficient of 0.045. The molecular orientation of the rigid group was observed under shearing conditions. It is concluded that the flat structure of the biphenyl group plays an important role on the tribological behaviour.

Polymer Film Thickness Determination with a High-Precision Scanning Reflectometer

A fiber-optic-based optical low coherence reflectometer (OLCR) is used to measure the thickness of polyester films. The measurements are made on both stationary and moving films to show the feasibility of this technique in a process environment. Autocorrelation is used to extract useful data from raw reflectometry data, and a statistical analysis of the data from both moving and stationary films is done to help demonstrate the application of this method. Although the reflectometer is not optimally configured for process analysis, a reliable estimate of polymer film thickness is shown in less than one minute measurement time for the moving films.

The Effects of Collimator Life Time on the Ti and Tin Film Growth Rates and Conformalities in Sputter Deposition Processes: Experiments and Simulations

AbstractExperimental and simulation studies were conducted in an attempt to understand the effects of collimator life time on the Ti and TiN film growth rates and conformalities in sputter deposition processes. The Ti and TiN films were deposited with and without collimation. The hexagonal cells of the collimator used in this study have a 1:1 aspect ratio. A Monte Carlo based simulator was used to calculate the angular distributions of species exiting from a collimator cell and the percentage decrease in the rate of film growth as a function of the collimator life time. Then, a low pressure deposition process simulator, EVOLVE, was used to predict the conformalities of deposited films in contacts or vias, assuming that the films were uniformly deposited on the side-walls of collimator cells. We conclude that the loss in growth rate is largely due to the shrinkage in the cross sectional area of the collimator cell inlets. We arrive at this conclusion after comparing an estimated film thickness on the collimator side-walls with experimental measurements. With extended collimator usage, the predicted and experimental film profiles in contacts or vias show increasing bottom coverage and decreasing side-wall coverages.

The Effects of Collimator Life Time on the Ti and Tin Film Growth Rates and Conformalities in Sputter Deposition Processes: Experiments and Simulations

ABSTRACTExperimental and simulation studies were conducted in an attempt to understand the effects of collimator life time on the Ti and TiN film growth rates and conformalities in sputter deposition processes. The Ti and TiN films were deposited with and without collimation. The hexagonal cells of the collimator used in this study have a 1:1 aspect ratio. A Monte Carlo based simulator was used to calculate the angular distributions of species exiting from a collimator cell and the percentage decrease in the rate of film growth as a function of the collimator life time. Then, a low pressure deposition process simulator, EVOLVE, was used to predict the conformalities of deposited films in contacts or vias, assuming that the films were uniformly deposited on the side-walls of collimator cells. We conclude that the loss in growth rate is largely due to the shrinkage in the cross sectional area of the collimator cell inlets. We arrive at this conclusion after comparing an estimated film thickness on the collimator side-walls with experimental measurements. With extended collimator usage, the predicted and experimental film profiles in contacts or vias show increasing bottom coverage and decreasing side-wall coverages.

Optical determination of the film thicknesses in multilayer thin film structures

An optical method for determining the layer thicknesses in a multilayer thin film structure is developed and its performance in terms of accuracy and resolving power is characterized. The effects of layer thicknesses, their indices of refraction, light absorption, measurement wavelength range, thickness non-uniformity and unintentional transition layers are characterized. The measurement procedure is applied to oxide, sulphide and fluoride thin film multilayer structures, up to nine individual layers thick, deposited on a glass substrate using atomic layer deposition. In most cases the method is found reliable and error estimates of film thickness vary between 1 and 50 nm depending on the thin film structure in the sample.

The Use of a Scanning Tunneling Microscope to Estimate Film Thickness and Conductivity of an Electrochemically Produced Poly‐1‐aminoanthracene Film

An electronically conductive poly‐1‐aminoanthracene (PAA) film was prepared electrochemically on Pt, Au, and C substrates by cycling the potential between −0.40 and +0.80 V in solutions. Adding pyridine to the solution resulted in a marked increase in the growth rate of the polymer film, as indicated by a large increase of faradaic current. A new scanning tunneling microscopy (STM) approach is also presented to determine film thickness and film conductivity through measuring the tip current vs. tip displacement. In this approach, the tip excursion between its initial contact with the polymer film and its contact with the Pt substrate is a measure of film thickness. A comparison of the STM current‐displacement behavior in the poly‐1‐aminoanthracene film to that of a polypyrrole film relates to film conductivity. The PAA film was about an order of magnitude less conductive than polypyrrole.

Lubrication in Cold Strip Rolling in the ‘Mixed’ Regime

Lubrication in metal rolling in the mixed lubrication regime has been considered. An inlet analysis has been used to calculate the film thickness and area of contact ratio in the bite, taking into account the effect of roughness on the pressure build-up and the effect of the bulk deformation on the crushing of asperities. The film thickness with rough contact is most strongly dependent on the variables which determine the film thickness with smooth contacts, that is, roiling speed, oil properties and inlet geometry, but the effect of yield stress, strip thickness, roughness geometry and inlet tension are also examined. In a separate calculation hydrodynamic theory has been used to estimate film thickness under the ‘contact’ areas. These two calculations have been combined with recent measurements of oil properties to estimate friction-slip relations when rolling thin aluminium foil. These calculations provide quantitative information on friction conditions to help model the rolling process and to estimate the strip surface quality.

An Empirical Test Of A Thin-Film Analysis Routine On Bisrcacu Oxide Superconductor Precursors

Until quite recently, electron microprobe analysis techniques were limited to samples of “infinite” thickness, that is, to samples thick enough such that the entire excitation volume was contained within the material of interest. Thin film analysis was not possible with available matrix correction programs, which were based on the assumption of samples of “infinite” thickness. Now however, algorithms are available that permit analysis of thin samples.We have obtained one of the more versatile and sophisticated of these programs. In order to investigate the accuracy of this routine we have analyzed several BiSrCaCuO thin films at 15 kV and repeated the analysis at 30 kV. These films were thick enough such that at 15 kV conventional ZAF data reduction yielded acceptable totals (98-101 %) with minimal substrate x rays observed. At 30 kV, however abundant substrate x rays were observed and ZAF yielded very low totals. X-ray intensity ratios from 30 kV runs were used to estimate film thickness and matrix corrections were applied using the Waldo algorithm.

Estimation of film thickness from the background signal in x-ray photoemission spectroscopy

A nondestructive estimation of the thickness of a uniform overlayer has been investigated using x-ray photoemission spectroscopy (XPS), which is an application of Tougaard’s formalism. It has been shown that it is possible to estimate the thickness of an overlayer existing on a semi-infinite underlayer, by measuring the ratios of the peak area to the background signal on the high binding energy side of a photoelectron peak produced by an element existing in an underlayer before and after removing the overlayer. Especially when the inelastic mean free path of a photoelectron in an overlayer and an underlayer can be approximated equal, the relation between those ratios and the overlayer thickness is expressed in a very simple mathematical form. This method has been applied to various thickness of a-Si:H overlayers on SiNx formed by plasma chemical vapor deposition (CVD) method. A good linear correlation has been obtained between the thickness estimated by this method and that estimated from the deposition time, and thus the validity of this method has been shown.

Observation of the initial droplet formation mechanism in dropwise condensation using a microscope. Film growth hypothesis as suggested by three experiments.

Initial droplet formation in dropwise condensation is one of the important mechanisms for nucleation in the phase change phenomenon. Film fracture hypothesis has been proposed by other researchers and they have estimated film thickness. But they could not observe the initial droplet formation. Here three experimental studies based on microscopic observations were performed. The authors observed that dropwise condensation nuclei were grown from a very thin film. Film thickness was from 0.1 μm to 0.3 μm and critical droplet size was from 0.8 μm to 1.3 μm. Critical droplet size densities of 1.4-2.8 × 107 sites/cm2 were found.

X-Ray Diffraction Study of a Thin GaAs Film on Si(100)

ABSTRACTA 900A single crystalline GaAs film deposited by molecular beam epitaxy (MBE) on a silicon crystal cut 4.1° from (001) surface was characterized with X-ray diffraction measurements of the mosaic spread, particle size and strain distribution, and lattice parameter. The GaAs film had a larger mosaic spread in the direction of the steps of the silicon surface and coherent particle sizes of about 900 Å compared to the estimated film thickness of approximately 1000 Å. Superlattice reflections gave an ordered domain size of about 330 Å. There is a residual strain gradient in the film which is nearly linear with the lattice constant differing by about 0.044 Å between the surface of the film and its interface with the silicon substrate. Lattice parameter measurements indicate a small expansion of 0.13% perpendicular to the plane of the film.

Elastohydrodynamic Film Thickness in Concentrated Contacts: Part 2: Correlation of Experimental Results with Elastohydrodynamic Theory

The existence of a coherent film of lubricant between highly loaded machine elements has been recognized for many years. Over this period of time measurements of film thickness have gone hand in hand with theoretical analyses in the field now known as elastohydrodynamic lubrication. The experimental techniques of capacitance, electrical resistance and X-ray measurement have been supplemented by the use of optical interferometry while the analytical expressions obtained with the use of elegant simplifications have been superseded by those developed from extensive and comprehensive computational procedures. These developments in experimental techniques have yielded a substantial number of measurements of both minimum and central film thickness. Likewise, the advent of the digital computer has allowed the derivation of a large number of solutions to the problem of elastohydrodynamic lubrication of concentrated contacts. All these results, covering a wide range of geometrical conditions, are to be found in the literature, yet little attempt appears to have been made to assemble a representative set of experimental data to permit a detailed evaluation of the theoretical formulae for elliptical contacts. The second part of this paper therefore considers the correlation between a number of experimental studies covering a wide range of operating conditions and geometries, and the predictions of recent elastohydrodynamic theory. Some of the important aspects of each set of experimental results are then considered and examples are provided which illustrate the following points: 1. Good estimates of lubricant film thickness may be obtained from the theoretical expressions recently derived, even when the dimensionless parameters involved are outside the ranges considered in the derivation of the formulae. 2. The discrepancies which exist between theoretical predictions and some of the measured film thicknesses are nevertheless quite large, even when the dimensionless parameters are within their usual limits. On the whole there is good agreement between experiment and theory, while the general trend of the results indicates that theoretical predictions may underestimate the minimum film thickness by about 10 per cent and the central film thickness by about 25 per cent. This measure of agreement is quite remarkable when the extreme difficulty of interpreting the magnitudes of effective and very thin mean film thicknesses between machined components in various forms of experimental equipment is considered.

Seizure initiation mechanism in cold metalworking processes. (2nd report Estimation of oil film thickness in extrusion-type friction test.

An oil film thickness at the tool-work interface was estimated theoretically in an extrusion-type friction test, to examine the effects of oil film thickness on seizure initiation. It has been presumed that a lubricant oil is trapped between the tool and the workmetal when the workmetal is filling up a die chamber. The trapped oil film thickness calculated could be varied in a range less than about 2 μm by changing the viscosity grade and the applied thickness of the mineral oil. Furthermore, it has been presumed that the trapped oil film thickness reduces with the punch stroke owing to the surface expansion of the workmetal and the contact pressure distribution. The oil film thickness calculated decreased toward the die exit, where it was less than 0.4μm. The ratio of the oil film thickness at the die inlet to that at the die exit could be varied in a range from 3.7 to 5.5.

The anomalous refractive index in the ellipsometric evaluation of an inhomogeneous film

Abstract When the refractive index of a surface film is a function n(x) of x, where x is the coordinate normal to the film surface, the values of the film thickness d and the film index n determined ellipsometrically by assuming that the film is homogeneous can be significantly different from the real thickness d and the mean index 〈n〉 = 1 d ∫ 0 d n(x) d x respectively. In this work the relative differences e d = ( d −d) d and e n = ( n −〈n〉) 〈n〉 were computed as functions of the film thickness d for SiO2 films on silicon substrates. Three types of refractive index profile n(x) were assumed. It is shown that ed and en can become quite large when the optical path length difference between the light reflected at the air-film interface and that reflected at the film-substrate interface approaches mλ(m = 1, 2, 3, …). A method is proposed by which a better estimate of film thickness can be obtained from a single observation of Δ and Ψ. This method is useful when en is small.

Photoelectron emission from aluminum and nickel measured in air

Photoelectron emission from Al and Ni has been performed under atmospheric condtions. Measurements of photoemission current Ip as a function of oxide thickness yield attenuation lengths of 28 Å for Al2O3/Al and 71 Å for NiO/Ni for λ=2500 Å (∼5 eV). Photoemission from Al2O3/Al originates at the metal and is only attenuated by the oxide unless the oxide is bombarded with Ar+. After ion bombardment the oxide also emits electrons. Photoemission from NiO/Ni originates from the oxide for λ=2500 Å. Estimates of oxide film thickness can be made for very thin films (0∼200 Å) by very simple photoemission measurments in air.

ChemInform Abstract: AN ELLIPSOMETRIC STUDY OF ANODIC PASSIVATION OF NICKEL IN BORATE BUFFER SOLUTION

Ellipsometrische und elektrochemische Messungen der anodischen Passivierung und der Filme sekundärer Passivierungsvorgänge an Ni in boratgepufferter Lösung mit pH 8,42 werden durchgeführt.

An ellipsometric study of anodic passivation of nickel in borate buffer solution

Ellipsometric and electrochemical measurements of the anodic passivation and secondary passivation films on nickel in borate buffer solution at pH 8·42 were made. The reference bare surface, obtained by cathodic reduction of electropolished nickel, gives the optical constants N 3 = 1·65−3·81 i for nickel. In the passivity region, where a little dissolution of nickel occurs, the surface film has the optical constants N 2 = 2·7−0·25 i and the film thickness as estimated by ellipsometry increases linearly with rise of the potential, from 4 to 13 Å, which is in fairly good agreement with the coulometrically estimated film thickness. In the oxygen evolution region, secondary passivation occurs with an abrupt increase in both optical constants and thickness of the surface film. The anodic passivation of nickel is compared with that of iron in terms of thickness of the surface film as a function of potential.