Abstracts 2015

The use of terahertz sensors: out of the lab and into the factory

Introduction

Over the last few years very rapid development has occurred in the application of terahertz sensor technology in the industrial environment.  Areas that have been explored by terahertz methods include

•         Cancer diagnosis

•         Teeth analysis

•         Pharmaceutical products

•         Art studies

To name but a few in this presentation I very recent progress in two areas.  The first the application in NDT and examining recent progress in the determination on using a sensor for non-contact paint layer on automobiles.  The second area is testing advanced semiconductor package for failure analysis (FA).  The former uses the optical properties of terahertz waves to follow the build-up of complex coatings on cars during the manufacture process. The later uses the electrical properties of a terahertz pulse in which a very fast electrical pulse is injected into an advance package (for example flip chips, package-on-package (PoP) when the pulse encounters deflects within the packaging electrical reflections are obtained this allows for precise determination of the failure point within the package.

Thin Film analysis

Terahertz instruments offer three key advantages over industry standard ultrasound technology: i) the terahertz method is inherently non-contact, enabling a greater degree of automation. ii) The instrument can measure moderately curved surfaces, where the ultrasound probe cannot make good contact. iii) The on-site calibration process is substantially faster than required for ultrasound, which requires that samples are sent off-site for time-consuming and expensive calibration procedures.  Ultimately, this technology is intended for in-line integrated robotic deployment on a car production line, providing real-time feedback to painting robots.  We developed a demonstrator to measure paint structures on cars consisting of four layers: electrocoat, primer, basecoat and clearcoat, for solid, partially metallic (mica) and heavily metallic (aluminum) basecoats, on horizontal and vertical panels, of varying curvature. Unlike earlier proof of concept demonstrations of thickness measurements, with artificial coatings exhibiting strong contrasts, we find that typical car paints are very closely matched in refractive index. In real world films, we cannot use simple mathematical descriptions where the refractive index is assumed real and frequency-independent: hence a more physical model is required.

Semiconductor package analysis

Over the past few years we have developed for advanced semiconductor packaging testing.  The terahertz pulses are generated by irradiating GaAs antennas and the terahertz pulses are detected with photoconductive receivers. In contrast to optical measurements electrical case the pulses are coupled into and out-of waveguide which is then coupled into the device-under-test.  The system has a rise time of less than 8 picoseconds and a frequency content that extends beyond 100 GHz.  Using two properties of the technology the very fast electrical properties is able to determine failures within advance semiconductor packaging to within 10 μm.  This compares with conventional methods of about 500 μm.  This is a considerable improvement on the current state-of-art instruments. 

 

Characterizing Electromagnetic Properties of Materials at 110GHz and Beyond
Giovanni D'Amore,Shelley Begley, Suren Singh, Keyisght Technologies

Characterizing electromagnetic properties of materials is important to many industries.  Over the years measurement techniques have evolved to meet industry needs.  In recent years, the frequency of interest has increased into the mm-wave range and above.  Quasi optical or free-space techniques using a network analyzer have been developed to meet this need.  These measurements are often used for design and test of radome, low observables, and absorbing materials, but this non-contacting technique is useful for other materials as well.  This talk will cover system components and calibration.

 

Test & Measurement for mm-Wave Communications

The availability of wide frequency bandwidth at mm-waves has generated considerable interest in using these bands in communication networks. This talk will discuss both test equipment and measurement techniques for mm-wave communication systems. Schottky diode heterodyne up and down converters can be used to characterize key parameters of mixers and transceivers such as noise and EVM. A variety of additional components such as filters, low-noise amplifiers and compact receivers are used to tailor the converters to a particular measurement. The talk will conclude with a discussion of Schottky diode demodulators used in ultra-wideband optical based communications systems.

 

Terahertz measuring technology offers a number of advantages over alternative non-destructive testing methods. Harnessing terahertz technology for industrial quality control and security applications is the object of several projects at Fraunhofer IPM. This involves the development of powerful components and complete customized systems for special applications. We report on our current system developments for volume inspections, multi-layer thickness measurements and material characterization.

 

From atoms to amplifiers: on-wafer and material characterization at cryogenic temperatures and terahertz frequencies
 
For DC and RF applications, cryogenic measurements of developing materials and semiconductor devices often reveal key physical characteristics which impact device performance including defects, trap states or leakage mechanisms. For certain applications, such as radio astronomy, operation and characterization of components in these extreme cryogenic environments is critical. As applications and integrated circuit design push toward operation at THz frequencies, cryogenic testing of new materials and devices will require novel approaches to sourcing, delivery and measurement at these frequencies. This presentation will focus on the development and applications of two cryogenic platforms for complementary aspects of THz frequency characterization; the first is a cryogenically-compatible on-wafer probing solution for device characterization, and the second is a variable-temperature, magneto-optical spectrometer for bulk and thin film materials.

 

Measurement challenges for Amplifier Characterization in the millimeter wave range
Phase Error sensitivity for Millimeter Wave Imaging Systems

This presentation will cover two topics :

1.)        Amplifier characterization and the challenge to perform compression point measurements in the millimeter wave range

Amplifier characterization in the millimeter wave range requires calibrated power sweeps for measuring the compression point.  How to achieve accurate power levels at the DUT input will be discussed.

2.)        Millimeter Wave Imaging systems for security applications

The image quality of digital-beamforming multistatic imaging systems corresponds to the ability to compensate for systematic and random errors. The different error sources and the phase error sensitivity of the R&S imaging system  will be analyzed and possible solutions for correction and compensation will be discussed.

Slides

 

Material Measurements for THz Space Antennas

Space antennas have seen significant developments in the recent years and among these, two facts are irrefutable: satellite applications are becoming more demanding, requiring more complex antennas, and the frequencies utilised are getting higher.
The State-of-the-art in telecommunications systems is slowly moving into Q/V bands, making use of large bandwidths and future space science missions rely on high performance instruments working in the (sub)mm-wave and Terahertz domains. The consequences of such trends are that the tolerances in antenna design and manufacture become more stringent and the accurate knowledge of material proprieties early in the design phase is key.

Even if space qualified materials can be considered as a subset of the materials industry offers to antenna designers (mostly due to the stringent thermal and outgassing requirements), we still make use of a very large collection of materials: nearly all space antennas contain dielectrics, films and RF transparent materials and reflector based antenna solutions make use of metallic and carbon fibre based composite reflective surfaces. In addition, coatings and paints which have a thermal function or to provide a better RF reflectivity to their surfaces, are also commonly used.

This talk will present an overview of the work being developed in ESA/ESTEC in the frame of Material RF Characterization at high frequencies, having as background the Agency's future missions carrying high frequency and (sub)mm-wave/terahertz payloads.

 

Pharmaceutical manufacturing involves different powder processing techniques and it is key to control the process to ensure the quality of the manufactured material and patient's safety. Quantities of interest normally involve moisture content, density and uniformity of powder mixtures. The purpose of this talk will be to provide an overview of common pharmaceutical manufacturing processes for both oral and inhaled products and the opportunities for electrical measurements from low frequency to THz frequency regime. The talk will provide examples of different innovative measurement solutions developed at AstraZeneca R&D.

 

Fundamental to the advancement of technology are substrate materials.  In order to choose the correct materials, it is critical to understand both how to characterize and the factors that influence key properties.  DuPont has a rich history developing innovative advanced materials.  This presentation will focus on the advanced materials utilized in electronics and communications applications.  In addition, a perspective will be provided with respect to the challenges in characterizing materials as applications advance from the GHz to THz regime.

Slides

 

Toward Dielectric Spectroscopy at Terahertz Frequencies.

Applications that make use of electromagnetic signal beyond microwaves are becoming the game-changing ingredients in a large variety of markets. These applications require an understanding of material properties when exposed to such mm-wave and THz signal frequencies. Examples span from substrate measurement for semiconductor devices, aquametry in paper or pharma industry, characterisation of radome materials or magnetic resonance spectroscopy.

Accurate permittivity measurements are necessary to provide scientists and engineers with valuable information to properly incorporate dielectric materials into their applications.

A material may have several dielectric mechanisms or polarization effects that contribute to its overall permittivity. In particular, atomic and electronic mechanisms affecting the permittivity are relatively weak, and usually constant over the low frequency side of the microwave region. As frequency increases toward THz these mechanisms start to play a role, thus leading to frequency dependences.

Several solutions are currently used at THz based on principles scaled up from microwave frequencies, but those show mitigated success for Terahertz spectroscopy. The key difficulties reside in the measurements of both low and high loss samples, low and high permittivity samples, as well as accurate sample preparation and repeatable measurement set-ups.

This talk will demonstrate the advantages of a novel concept called Material Characterization Kit (MCK) introduced by SWISSto12. Interest in temperature dependent dielectric spectroscopy as well as a benchmark to other techniques will also be discussed.

 

In this talk I will discuss how Metamaterials and other advanced materials are enabling valuable technologies in the millimeter wave and terahertz industries.  Metamaterials provide access to parts of the electromagnetic spectrum otherwise unobtainable by conventional materials.   This is particularly useful in the THz and millimeter wave regimes, where there is a general lack of devices such as sources, detectors, and modulators. THz and millimeter wave Metamaterials, such as imaging and active modulators, have been designed and experimentally demonstrated.  These structures can be used to create devices with great potential in the fields of security and defense, bio-medical imaging, communications, and material characterization.  The application of these devices into the realm of industry is still in its infancy, but has a promising future.

Slides

 

The growing maturity of THz technology is paving the road towards industrial applications. One field where the technology could be a real differentiator is quality control of automatized processes.  Recently, THz spectroscopy has been used to explore this topic on e.g. paper sheets, paint layers, pharmaceutical tablets, etc. Common methods employed to obtain the material parameters are typically based on time-domain peak subtraction or inversion of the transfer function. These methods assume low absorption and zero to little dispersion of single layered materials and are therefore only applicable in simple situations. Industrial quality control often deals with more complex structures and requires accuracy standards which these methods typically cannot fulfill.
In this talk I first present a novel THz material analysis approach based on (i) a stratified dispersive model, (ii) an appropriate measurement configuration, (iii) a time-domain fitting procedure, which together allow for high precision material parameter determination. In the second part, this analysis approach is applied on solventborne and waterborne paint layers studied in situ as a function of drying. For the first time, we obtain the optical and geometrical properties of wet paints during drying, which provides the dynamic behavior of the dry top layer and wet bottom layer thicknesses. From the temporal thickness evolutions we deduce the rates of external evaporation and internal particle and solvent diffusion of the drying colloidal dispersion, which compare well to the existing drying theory. For all paints, the results demonstrate stratification only when the drying process is evaporation controlled, whereas outside this regime the coating dries as a single layer. Eventually, I show that such a profound understanding of the material properties is key to the application of THz technology in the field of industrial quality control.

 

Schmid & Partner Engineering AG (SPEAG) recently developed open coaxial probes for fast, precise, non­destructive, and facile measurements of liquids, solids, and semi­solids for the 10 MHz – 67 GHz frequency range. The next improvement of the Dielectric Assessment Kit (DAK) is the extension of the probes to measure dielectric properties of thin layers of solid samples by offering a turn-key solution for the electronic industry. By combining two open coaxial probes and placing the sample in-between a unique measurement system is created. Dielectric and magnetic material properties can be assessed at the same time at the frequency of the application, up to 67 GHz. We will discuss the potentials and limitations to increase frequency range further toward THz.

 

A system for contactless measurements of water content in thin paper layers

A system for remote measurement of water content in thin paper layers is presented. The system is a prototype of a sensor developed for applications in paper production and offset printing industries. The water content is calculated from a measurement of the absorption of a signal transmitted through the paper at mm-wavelengths where water presents substantial attenuation. A voltage controlled oscillator (VCO) generates the probing signal at around 16 GHz, this signal is then multiplied to an RF frequency of about 200 GHz by an in-house developed X12 frequency multiplier. A compact optical system, consisting of two mirrors focuses the RF on the surface of the paper and, after transmission through the paper, to a receiving horn antenna. The measured signal from the receiving antenna is then detected by a zero-bias Schottky detector and compared to a reference copy of the RF signal, not transmitted through the paper.

This measurement approach has certain advantages in comparison to other sensor technologies currently in use, as for example microwave and infra-red. The method is insensitive to vibrations in the paper and its structure. The sensor is convenient to cross scan the paper and map the water content with a spatial resolution of about 4 cm2.

The performance of the sensor was tested in several occasions at the V-TAB offset-print production facilities in Sweden and was later on installed on a drier machine in a paper production process. The sensor was benchmarked to a commercial microwave resonator sensor and proved to deliver high quality data. The data delivered by both sensors agree well to laboratory moisture measurements of samples of the paper. The sensor demonstrates a resolution of 0.16% for average moisture content of 5 % and 0.06% for moisture content of 40%.