Thin Film Thickness Monitor Research Articles

Affordable Open-Source Quartz Microbalance Platform for Measuring the Layer Thickness.

The layer thickness measurement process is an indispensable companion of vacuum sputtering and evaporation. Thus, quartz crystal microbalance is a well-known and reliable method for monitoring film thickness. However, most commercial devices use very simple signal processing methods, offering only a readout of the frequency change value and an approximate sputtering rate. Here, we show our concept of instrument, to better control the process parameters and for easy replication. The project uses open-source data and its own ideas, fulfilling all the requirements of a measuring system and contributing to the open-source movement due to the added value and the replacement of obsolete technologies with contemporary ones. The device provides an easy way to expand existing sputtering machines with a proper controller based on our work. The device described in the paper can be easily used in need, being a proven project of a fast, inexpensive, and reliable thin-film thickness monitor.

On-line thin film thickness monitor by pulsed laser photoacoustics

On-line thickness monitor of thin film deposition by thermal evaporation is demonstrated using femtosecond pump-probe photoacoustics. A Ti:sapphire femtosecond laser (wavelength 800 nm, pulse width ~110 fs, pulse energy ~1.3 nJ) is split into a pump and a probe beams. The pump beam is used to instantaneously heat the illuminated area of an aluminum thin film during its deposition on a silicon substrate, whereas the probe beam is used to investigate the change in the transient thermoreflectance ΔR/R. The thermal expansion, by the laser heating, creates stress in the aluminum surface region that generates an acoustic wave of ultrasonic frequency. The travel time of the optically-induced acoustic wave normal to the surface of the thin film is measured to evaluate the thickness of the aluminum in the range of ~32 to 388 nm during the film deposition.

Photometric calibration of an in situ broadband optical thickness monitoring of thin films in a large vacuum chamber.

To improve the in situ monitoring of thin films at the Laboratoire des Matériaux Avancés, a broadband optical monitoring of the coated thin films was developed and installed in the biggest ion-beam sputtering machine in the world. Due to the configuration of the coating machine and the chamber strain under vacuum, a standard calibration procedure is impossible and a double-beam optical system is not suitable. A novel theoretical and practical solution to calibrate the measurements was found and is described in this paper. Some relevant results achieved thanks to this technique are discussed as well.

基于AVR单片机的高精度光学测厚系统设计

The thin film thickness system is analyzed in detail,and the film thickness measuring system is discussed on the whole.The key parts of hardware circuit is studied in film thickness instrument of thickness measuring system,and the software flow of the film thickness instrument is designed discretely.The AVR microcontroller as the core processor for data acquisition and processing,the on-line optical thin film thickness measurement and monitoring system is designed and manufactured.By contrast experiment with the actual film thickness,it is verified that the thin film measuring system has high precision,high stability and high reliability.It can be applied to practical industrial production.

Thickness and density evaluation for nanostructured thin films by glancing angle deposition

Thickness evaluation is a particular challenge encountered in the fabrication of nanosculptured thin films fabricated by glancing angle deposition (GLAD). In this article, we deduce equations which allow for accurate in situ thickness monitoring of GLAD thin films deposited onto substrates tilted with respect to the direction of incoming vapor. Universal equations are derived for the general case of Gaussian vapor flux distribution, off-axis sensors, variable substrate tilt, and nonunity sticking coefficient. The mathematical description leads to an incidence angle dependence of thickness and density, allowing for quantitative prediction of porosity in samples with different morphologies and thickness calibrations. In addition, variation of sticking probability with the incidence angle creates a nonmonotonic variation of the film thickness and porosity with the substrate tilt. We discuss the implications of the substrate type, sensor type, and source geometry in a precise quantitative determination of the thickness of thin films fabricated on tilted substrates. Our equations can be particularized for the case of films fabricated at normal incidence.

In situ laser reflectometry measurements of pyrolytic ZnO film growth

In situ thin film thickness monitoring and profilometering was implemented for a spray pyrolysis deposition technique, based on measuring the reflection of a laser beam from the film–substrate system; the interference pattern obtained during film deposition was used to calculate the film thickness. Recording in situ the reflection pattern for points separated 0.5 cm along the film allowed the film profile to be obtained. The growth of pyrolitic ZnO film on glass was studied by this method. It was found that the in situ measured thickness is in good agreement with that measured by ex situ profilometering or scanning electron microscopy (SEM). SEM micrographs of the films showed that the surface is formed by elongated-shaped particles, which become rounded and larger in size as the film becomes thicker. This fact was correlated with an increment of the diffuse component of the optical spectral reflectance and transmittance and with the trend of the surface roughness factor, obtained in situ.

Cheap control unit for quartz crystal thin film monitor

This paper presents a cheap thin film thickness monitor control unit for piezoelectric crystal heads. The output of the unit is a TTL compatible crystal frequency signal.

An optical fibre thin film thickness monitor

A simple and easily calibrated thin film thickness monitor involving optical fibre components is described. Film thickness was determined by monitoring the return power via a 2*2 directional coupler arrangement. This optical fibre monitor was used to calibrate a conventional quartz crystal microbalance.

Molecular beam deposition of Dy1Ba2Cu3O7−δ(001) high‐temperature superconductor thin films

Epitaxial Dy1Ba2Cu3O7−δ(001) high‐temperature superconductor thin films on LaAlO3 substrates have been prepared by coevaporation of Dy, BaF2, and Cu and postannealing. The vapors in desired ratio were evaporated from effusion cells in a miniature molecular beam deposition system. The films show critical transition temperature (Tc,0) of 89.5±0.5 K. During process development it was found that single phase Dy1+xBa2−xCu3Oy(001) thin films can be grown (x=0 to 0.3). Their electrical properties were useful in calibration of quartz crystal thin film thickness monitor (FTM) for determination of relationships between the actual vapor arrival rate (flux) and FTM reading.

Simple and inexpensive single-oscillation quartz crystal thin-film thickness monitor and growth-rate meter

Commercially available quartz crystal thin-film thickness monitors have limitations due to: (i) their inability to indicate the absolute frequency of oscillation of the mass measuring crystal; and (ii) the instability of the variable frequency LC oscillator, if any, incorporated in the circuit. Recently it has been suggested that it is economical and simple to use a digital frequency meter for the direct measurement of the frequency shift due to film deposition of the measuring crystal. Such an arrangement gives better results than commercial film thickness monitors. A single oscillation quartz crystal monitor and growth rate meter has been designed using this idea and locally available electronic components. In this instrument a quartz crystal wafer having one pair of gold electrodes is used, while the shift in resonance frequency measured by a digital frequency meter is used for the estimation of thickness of thin films. To measure the rate of growth of the film the resonance frequency signal from the crystal is suitably processed to produce a DC signal, which may be recorded on an x-y/x-t recorder to obtain the rate of growth during the deposition of the film.

Recent trends in thin film thickness monitoring

Recent trends in thin film thickness monitoring

High-precision low-cost quartz-crystal thin-film monitor with temperature control

An accurate thin-film thickness monitor capable of a resolution of at least 0.01 nm is described. The errors arising from the temperature dependence of the crystal resonant frequency are minimized by heating a closely matched reference crystal until their temperatures are equalized; and by subtracting their frequencies of oscillations. These functions are performed by simple electronic devices.

Improved quartz crystal microbalance technique

The importance of using the most pertinent mathematical description of the mass load versus frequency relation for quartz crystal thin-film thickness monitors is reviewed. The different usable crystal load ranges of the so-called frequency- and period-measurement techniques in comparison with the Z-Match technique are calculated for most of the commonly used deposition materials. A new thin-film thickness monitoring procedure is described, which takes the influence of the acoustic film properties on the mass load versus frequency slope into consideration without need for the explicit knowledge of the acoustic impedance ratio z of the deposited film and the quartz crystal. It is shown how the effective z value in the composite resonator built by the quartz crystal and the deposited foreign layer can be derived from a measurement of a quasiharmonic overtone resonance frequency in addition to the commonly practiced exclusive measurement of the fundamental resonance frequency. The presently established relation between the mass load or the deposited film thickness and the corresponding resonance frequency of the loaded crystal is enhanced by a more rigorous one-dimensional composite resonator description. The introduced so-called series resonance relation is of significance for the accurate determination of the specific acoustic impedance ratio z of the deposited film and the crystal. Furthermore, the deviations of the frequency spectra of plano-convex shaped crystals from that of the one-dimensional (infinite plate) geometry are investigated and taken into account. The achieved accuracy in the z determination from the first and third quasiharmonic frequencies justifies the applicability of the two-frequency or auto slope accommodation technique introduced in this paper.

Thin film thickness monitoring using a doubly oscillating quartz crystal and measurement of growth rate

A single quartz crystal wafer of 5 MHz frequency and 20 mm*20 mm size, with two pairs of circular gold electrodes deposited on it, was used to measure the rate of growth and the thickness of thin films during deposition. This arrangement may be called a doubly oscillating quartz crystal monitor (DQM). The main limitations in the use of this arrangement arises from the coupling between the two electrode system. The coupling was minimised by depositing the gold electrodes at a suitable distance of about 4.2 mm. Further, the thin film whose thickness is to be measured was deposited on one side of one electrode pair while the other pair was kept covered from deposition. The resonance frequencies of the two electrode system were then processed in a conventional manner and the beat frequency was measured by a digital frequency meter. The latter's output was analysed in a frequency-to-voltage converter and the resulting output voltage plotted on a X-Y recorder or X-t chart recorder was proportional to the rate of growth of thin films during deposition.

An optical thin film thickness monitor

A modified technique for optical monitoring of the quarter-wave stacks of dielectric materials, utilising the principle of wavelength modulation and phase sensitive detection, is suggested. The accuracy and the sensitivity of the method is very high and can be used for making the coating process self-controlled and programmable.

Thickness monitoring of optical thin films. (GB)

Thickness monitoring of optical thin films. (GB)

A thickness monitor using the frequency demodulation technique

A new approach is presented for designing a thin film thickness monitor using the frequency demodulation technique. The monitor permits film thicknesses to be measured to an accuracy of +or-1%. Provision is made for automatic termination of deposition and for measurement of rate control.

Application of OTDR for thickness monitoring of optical thin films

Application of OTDR for thickness monitoring of optical thin films

Thickness monitoring of optical thin films

A simple experiment set up to measure the spectral values of u is described. It is shown th is described. It is shown that the monitoring of ; values offers an adv values offers an advantage over the conventional monitoring of R or T values in control and monitoring of transparent optical films on transparent substrates. A method is proposed to derive the optical constants of the transparent films (refractive index and thickness of the film simultaneously) from the measured ; values in the region values in the region of transparency.

Thin film thickness monitor shutter

This article describes a simple electronic dual-activated shutter which is designed to interface with the Sloan digital thickness monitor model DTM-200 or a set of double-pole double-throw switches which can be operated manually.