Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
  • G01B7/06—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness
  • G01B7/063—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators
  • G01B7/066—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring thickness using piezoelectric resonators for measuring thickness of coating

Definitions

• the present invention relates to a measuring device for real-time thin film thickness measurement using QTF (Quartz Tuning Fork) sensors that operate based on the piezoelectric effect of quartz crystals.
• QTF Quadrature Tuning Fork
• Thin film coating methods are one of the important subjects of engineering areas known as advanced technologies.
• Today, thin film coating is successfully applied in high-film magnets, power cables, rotating machines, water treatment systems, superconductor technology, magnetic recording media, military technologies, space and aerospace, electronic semiconductor devices, light-emitting diodes such as LEDs, optical coatings such as anti- reflective coatings, hard coatings such as incision tools, energy production such as solar cells, energy storage such as thin film batteries, health care such as medical implants.
• the coating thickness is quite thin, and its control is very critical. For example, the construction of selective permeable or selectively suppressive optical filters can be achieved with coatings made at the thickness level equivalent to the wavelength. Therefore, thin film coating applications are a technology that significantly contributes to the country's economy (Mbam et al., 2019)
• the properties of the materials at the quantum level emerge, and the structural, optical, and electrical properties of the materials change as the thin film thickness changes.
• microstructure plays a very important role in conductivity behavior in addition to stoichiometry.
• the presence and density of the microstructure in question control conductivity through grain boundaries closely related to the size and direction of the crystallite. Therefore, these two parameters can be affected by film thickness (Bouderbala et al., 2008).
• film thickness (Bouderbala et al., 2008).
• surface plasmons can be formed and this feature is used in sensor technologies.
• the coating thickness values given are critical for the emergence of the feature in question. Apart from these values, no surface plasmons are formed.
• the material surface of the device plays an important role in adapting the in-vivo response by controlling the body's biological response. Therefore, the surface of biomaterials has become one of the most intense research topics.
• a nano-functionalized surface has promising biological properties, and clinical applications of biomaterials can be improved by producing a nanostructured surface. Therefore, thin film coating studies are also carried out to improve the biocompatibility, blood compatibility, biodegradability, corrosion resistance, mechanical and antibacterial properties of biomaterials used in the human body (Alias et al., 2019, Rahmati et al., 2016, Yang et al., 2002, Shi et al., 2009, Sommerdijk et al., 2007).
• thin film coating thickness plays an important role in the development of materials with new and unique properties.
• Methods are available to monitor and measure the thin film thickness in the state of the art. However, in most methods, measurements are not performed simultaneously, but after the coating process is completed. Spectroscopic, microscopic, and quartz-based methods are the most commonly used methods for monitoring the rate and thickness of thin film accumulation today.
• Spectroscopic methods are mass spectroscopy (MS), electron pulse emission spectroscopy (EIES), x-ray photoelectron spectroscopy (XPS), x-ray reflectance (XRR), and x-ray fluorescence (XRF), alpha particle energy loss (APEL), atomic absorption spectroscopy (AAS), spectroscopic ellipsometry (SE), laser reflectometry (LR), optical fiber sensor (OFS), surface plasmonic resonance spectroscopy (SPR), multi -wavelength pyrometric interferometry (MWPI).
• MS mass spectroscopy
• EIES electron pulse emission spectroscopy
• XPS x-ray photoelectron spectroscopy
• XRR x-ray reflectance
• XRF x-ray fluorescence
• APEL alpha particle energy loss
• AAS atomic absorption spectroscopy
• SE spectroscopic ellipsometry
• SE laser reflectometry
• LR optical fiber sensor
• SPR
• the deposition velocity measurement with MS and EIES methods which are among the spectroscopic methods, is based on real-time measurement of particle density in the steam flow near the substrates. Both of these methods are highly sensitive and material specific.
• the life span of the EIES sensor is equivalent to hundreds of QCMs. It is also useful for applications with large material accumulation. EIES can be used to produce special alloys from pure elements using separate evaporation sources. (Buzea et al. 2005).
• the basic working principle of AAS which is another spectroscopic method, is based on the selective absorption of photons by free atoms and does not impose restrictions on the working pressure. The method may be used for spraying, thermal evaporation, or molecular beam epitaxy.
• AAS By using multiple units sensitive to a given element, it is sensitive to absolute material specificity and can monitor multiple sources simultaneously and independently. At low deposition speeds, the system shows very high accuracy for many elements. Unlike previous accumulation control methods that sampled steam flow at a single point away from the substrate, AAS achieves significantly more accurate accumulation rate control and sampled steam flow along a finite length in front of the substrate. Advantages of AAS include absolute material specificity, high precision, long-term stability, no operating pressure limits, optical detection, and easy access to the sensor. AAS is the only material-specific deposition control method that can operate in high gas-pressure environments (Buzea et al. 2005).
• SE spectroscopic ellipsometry
• SE is a very precise optical method that can be used to monitor thickness during thin film deposition.
• SE is based on the change in the polarization state of light reflected obliquely from a thin film sample.
• the SE can measure any type of material on almost any type of substrate as long as a specular reflection is produced.
• SE is applied for monitoring the thickness of thin metal films and multilayers, and the thickness information of thin metal films can be obtained with reasonable accuracy from ellipsometry measurements using the optical constants of the films. This method is very repeatable and highly sensitive (Buzea et al. 2005).
• XPS X-ray photons with specific energy are used to irradiate the surface and cause electron emission with characteristic kinetic energies from the atoms on the surface. Thickness can be deduced from angle-resolved XPS by comparing relative peak densities over a range of angles between the sample and detector (Buzea et al., 2005).
• the basic principle of XRR is based on the reflection of an X-ray beam by a sample and the measurement of the intensity of the X-rays reflected at certain angles. The data measured afterward are matched to the simulated curves and the film thickness is determined from the fringe gap in the reflectometry curve. Both high k (dielectric constant) and low k are used routinely for dielectrics, metals, epitaxial, and amorphous films. Since the XRR method effectively provides a measure of the density difference, it is not limited to the degree of crystallinity of the materials being investigated (Buzea et al. 2005).
• the thickness is determined as the fluorescent X-ray passes through the sample. Some of the X-rays are absorbed or reflected, and the thickness is measured by quantification of this fraction. When the sample is thick enough to absorb all X-rays on the side farthest from the detector, the fraction change stops and the maximum thickness that the XRF can determine is reached. The thickness determined by the XRF varies from 10 to 1000 nm.
• OFSs are used for on-site monitoring of the deposition rate of thin films.
• the sensor contains a layer of silicon wafer, the diameter of which is the same as that of optical fiber.
• the accumulation of a film on the silicon sheet is measured optically using the principles of the Fabry-Perot interferometer theory.
• fiber optic sensors have advantages such as being lightweight, having immunity to electromagnetic interference (EMI), small size, high sensitivity, wide bandwidth, high temperature, and the ability to operate remotely (Rahman et al., 2009).
• LR is used to monitor the growth rate of epitaxial thin films from Fabry -Perot oscillations at reflected light intensity (Buzea et al. 2005).
• SPR Surface plasmon resonance
• SPs surface plasmons
• Said measurements may be performed in several different configurations including scanning angle (angle shift), wavelength shift, and imaging.
• scanning angle SPR measurement the reflectivity of a p-polarized beam of light (usually a HeNe laser) is measured as a function of the angle of incidence from a prism/Au film assembly. At a certain angle of arrival, a minimum in reflectivity is observed due to the formation of surface plasmons at the metal/dielectric interface.
• the position of this minimum is called the SPR angle and is sensitive to the thickness and refractive index of any material adsorbed on the metal surface.
• the amount of adsorbed material can be determined by following the shifts in the SPR angle. (Frutos et al., 1999).
• MWPI is an optical method for in-situ film thickness and temperature determination at the same time.
• the thermal emission of the substrate is reflected and broken at the interfaces of the growing film, causing interference effects.
• Pyrometric interferometry exemplifies a series of spreading spectral lines and analyzes them with complex fitting algorithms and monitors film thickness using this effect.
• MWPI requires only one access port. Observation angle can be selected between 0° and 60° and there is no pressure limitation. Since it is a passive measurement, it is resistant to rotation, vibration, and substrate misalignment errors (Buzea et al. 2005).
• the microscopic methods are optical microscopy, scanning, transmission electron microscopy (SEM and TEM), and atomic force microscopy (AFM).
• An optical microscope is a type of microscope that uses visible light (400-700 nm) and a lens system to magnify images of samples.
• a sample is usually mounted on a motorized stage and illuminated by a diffuse light source.
• the image of the specimen is projected through a concentrator lens system into an imaging system, such as an eye, film, or charge-coupled device.
• an imaging system such as an eye, film, or charge-coupled device.
• the SEM is a type of electron microscope that provides information about the thickness of thin films with a significantly high magnification ratio of up to 50,000 times by obtaining surface images of the samples from the scattering angles of the secondary electrons scattered from the sample by scanning the sample surface with a high-energy electron beam in a raster scanning model.
• TEM is a type of high-resolution microscope that can process images by passing through the material or diffraction as a result of the interaction of highly high-energy electrons with very thin thickness material ( ⁇ 100 nm).
• the resolution limit is below 400 nm for optical microscopes, 2 nm for scanning electron microscopes (SEM), and 1 nm for transmission electron microscopes (TEM) (Canh et al., 2010). As can be seen, in optical and electron microscopes, TEM is capable of imaging a sample of a significantly higher resolution.
• AFM is the most versatile and powerful microscopy technology for examining samples at the nanoscale.
• the AFM consists of a flexible lever and a pointed end that is used to scan the surface attached to it. By measuring the contact hardness between the AFM tip and a thin film sample, the film thickness can be extracted, provided that the elastic properties of the film and sample are known (Crozier et al., 2016).
• Quartz crystal thickness monitors typically include a piezo-electric quartz crystal sandwiched between a pair of electrodes, a monitor for speed and thickness measurement, and a controller to automate the process.
• the electrodes When the electrodes are connected to an oscillator and an AC voltage is applied, the quartz crystal begins to oscillate at the resonance frequency due to the piezoelectric effect. As the material settles on the crystal, the oscillation frequency changes and this change is related to the amount of mass added. If a solid layer is deposited evenly on the QCM, the resonance frequency will decrease in proportion to the mass of the adsorbed layer according to the Sauerbrey equation.
• QCM deposition controllers calculate the thickness of the material deposited on the quartz crystal with equations that correlate the change in crystal frequency.
• MS which is one of the methods used in the state of the art, is extremely sensitive, but does not have the necessary long-term stability and has not achieved significant commercial success. Since mass spectrometers form and manipulate gas phase ions, they only operate in a high vacuum system. The main disadvantage of MS and EIES is the requirement of a high vacuum environment, as they use a heated filament sensor as a source of electrons. These methods cannot be used in the case of copper oxide-based superconductors, where oxygen is used to obtain appropriate stoichiometry, or for many thin film growth procedures that require a gas medium, such as in spraying systems (Buzea et al., 2005).
• SE may not be accurate in measuring very thin films or thin films with very rough surfaces. The thin metallic film growth can only be monitored for a thickness of less than about 50 nm. (Buzea et al. 2005).
• APEL APEL
• the disadvantages of APEL are the presence of a complementary step in the fabrication process implantation of the substrate before deposition and the contamination of the radioactivity. Furthermore, if a large number of alpha emitters are used, the accumulated film is susceptible to damage and functional integrity should be checked after irradiation, and this method is not suitable for the deposition of thinner layers than 10 nm (Buzea et al., 2005).
• OFS orthogonal frequency division multiple access
• MWPI is very sensitive to the optical constant values of thin films and cannot be used for thin films whose optical constant varies significantly during film growth.
• the film must be at least partially permeable at the observed wavelength. If the substrate temperature is not high enough to radiate sufficient density, the temperature and thickness cannot be determined at the same time. Transparency of the substrates results in two serious limitations in pyrometric measurements. These are low substrate emission and optical interference from other hot elements in the room. Ensuring substrate opacity is a key element in addressing many of the sensor disadvantages.
• An opaque substrate prevents radiation from a filament heater from being delivered to the pyrometer. It also prevents the light from other radiation sources in the chamber from scattering from the back of the substrate to the pyrometer.
• the substrate opacity ensures that the emission of the substrate is high enough to provide a measurable signal.
• errors due to image area coverage and misalignment of the optics and image window limit the success of pyrometers such as thickness and temperature sensors.
• Simultaneous application of two substrate monitoring channels may make it possible to measure temperature, growth composition, and deposition rate during growth. (Buzea et al. 2005).
• a limitation of SEM is that its samples must be electrically conductive in order to transmit the charge formed on the surface from the incoming electron beam. This problem can be overcome with a coating of thin, conductive coatings, typically gold or platinum. (Zhang et al 2013).
• the only quartz-based method that allows measuring the thin film coating thickness in real-time is QCM.
• QTF and QCM are different from each other and there is no method or device for measuring thin film thickness in real-time with QTF.
• One of the disadvantages of QCM is the temperature, which can affect the frequency shift and therefore cause errors in the thickness measurement.
• the fundamental frequency of the crystal can vary considerably with temperature. The temperature during evaporation is affected by the radiant heat of the evaporation source. Also, there is heat directly released by the condensation of steam on the crystal. The heat of condensation can significantly affect the local temperature.
• the QCM is highly affected by the ambient forces (this ambient force in thin film coating methods; temperature). This exhibits negative behavior in terms of the accuracy of the thin film coating thickness measurement.
• the water-cooled holders used to reduce the effect of temperature add additional cost to the measurement system and make the instrument unwieldy.
• QCM monitors have disadvantages such as shifting oscillator frequencies, non-linearity in pulse-analog frequency counter, short sensor life (although periodic sampling methods can expand the crystal range), common limitations in physical vapor deposition methods, sensitivity due to stress changes, and requiring geometric and adhesion coefficient calibration. (Buzea et al., 2005; Groth et al., 1968; Eckertova., 1977).
• the patent document TR2016/05031 which is in the state of the art, discloses a portable measuring device especially for measuring mass change, which uses the QTF (Quartz Tuning Fork-quartz sound fork) sensor, wherein the sensor can be inserted and removed, and measurements can be taken.
• QTF Quadrature Tuning Fork-quartz sound fork
• the object of the present invention is to realize a measuring device for real-time thin film thickness measurement using QTF (Quartz Tuning Fork) sensors based on the piezoelectric effect of quartz crystals.
• QTF Quadrat Tuning Fork
• Another object of the invention is to realize a measuring device for real-time thin film coating thickness measurement by means of a quartz tuning fork (QTF) transducer, which enables measurements to be taken from multiple regions within the coating devices in thickness measurement.
• QTF quartz tuning fork
• Another aim of the invention is to realize a measuring device that can take measurements from multiple locations at a low cost and has a high Q factor, i.e., a more stable measurement.
• the other object of the invention is to realize a measuring device for measuring the thickness of thin film coatings made with QTF, a mass-sensitive sensor, during coating.
• Figure 1 A schematic view of a measuring device for real-time thin film thickness measurement of the invention.
• Figure 2 A schematic view of another embodiment of a measuring device for real-time thin film thickness measurement of the invention.
• a measuring device of the invention for real-time measurement of coating thickness using QTF (1) comprising;
• At least one microcontroller with at least one analog-digital converter (ADC) (4) on it which enables real-time coating thickness measurement by the DDS circuits (2) to provide a signal to more than one QTF sensor (3).
• ADC analog-digital converter
• 5 different circuits are used in the measuring device (1) as a DDS circuit (2), and signals are provided to five different QTF sensors (3). It performs real-time thickness measurement through the analog-digital converter (4) on the microcontroller (5).
• the DDS circuit (2), the QTF sensor (3), the analog-digital converter (4), and the microcontroller (5) can be located hardware on a body.
• a measuring device (1) of the invention which allows real-time measurement of the coating thickness by using QTF, includes at least one analog data distributor (DMUX) (6).
• DMUX analog data distributor
• a single circuit is used as the DDS circuit (2) in the measuring device (1) and the signal is provided to five different QTF sensors (3) using the analog data distributor (6).
• the DDS circuit (2) contains the frequency information increased step by step by the microcontroller (5).
• DDS circuit (2) synthesizes the signal according to the loaded frequency information in the form of a sinus function.
• the analog data distributor (6) decides which QTF sensor (3) synthesized signal will be applied. It performs real-time thickness measurement by processing the signal received from the QTF sensor (3) through an analog-digital converter (4) on the microcontroller (5).
• the analogdigital converter (4) is configured for fast reading and provides the measured amplitude value against the frequency of the QTF sensor (3) to the microcontroller (5) by performing the signal sampling process.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Analysing Materials By The Use Of Radiation (AREA)

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• 2022
  • 2022-12-07 TR TR2022/018799A patent/TR2022018799A2/tr unknown
• 2023
  • 2023-05-17 EP EP23901223.0A patent/EP4630752A1/en active Pending
  • 2023-05-17 WO PCT/TR2023/050453 patent/WO2024123275A1/en not_active Ceased

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