Életünk további fejlődése elképzelhetetlen a félvezető-technológia nélkül. A 75 éves tranzisztor apropóján futólag áttekintjük azt az utat, amelyet a szilíciumtranzisztorok integrálásával a mai napig megtettünk, kitekintést adva a jövőben várható korlátlan lehetőségekre is. Az integrált áramkörök életünk valamennyi területén eszközeink alapvető alkatrészei, az ipari táplálékláncbeli szerepük, hozzáférhetőségük globálpolitikai jelentőségű, ahogy napjaink fejleményei bizonyítják.

Due to their complex electro-thermal characteristics microhotplates used in environmental gas sensors require careful design to exhibit uniform temperature and low power dissipation during the expected long time operation. The layout design becomes more complex if the multiple operational parameters required by the battery operation and the driver and readout logic are considered. In this paper, we describe a simple analytical filament design procedure to determine the dimensions of the annular metal filament exhibiting uniform surface temperature without additional heat distribution layer. The presented method operates with the cumulative thermal losses towards the ambient and heat conduction via the membrane. Moreover, it handles the operation requirements like the targeted temperature in the atmospheric environment, supply voltage range, current density, filament layer thickness and its coverage ratio. The efficacy of the method is demonstrated by electrical and thermal characterisation of the manufactured devices having 150 µm diameter active area. The microheater achieves the targeted 500 °C operation temperature with 1.4–1.55 V supply. The temperature non-uniformity along the filament was measured by Spectral pyrometry and was found to decrease from ± 3.5% to ± 1% when the temperature was raised from 530 to 830 °C.

Ion implantation has been a key technology for the controlled surface modification of materials in microelectronics and generally, for tribology, biocompatibility, corrosion resistance and many more. To form shallow junctions in Ge is a challenging task. In this work the formation and accumulation of shallow damage profiles was studied by in-situ spectroscopic ellipsometry (SE) for the accurate tracking and evaluation of void and damage fractions in crystalline Ge during implantation of 200-keV Sb ions with a total fluence up to 1E16 cm-2 and an ion flux of 2.1E12 cm-2 s-1. The consecutive stages of damage accumulation were identified using optical multi-layer models with quantitative parameters of the thickness of modified layers as well as the volume fractions of amorphized material and voids. The effective size of damaged zones formed from ion tracks initiated by individual bombarding ions can be estimated by numerical simulation compared with the dynamics of damage profiles measured by ion beam analysis and ellipsometry. According to our observations, the formation of initial partial disorder was followed by complete amorphization and void formation occurring at the fluence of about 1E15 cm-2, leading to a high volume fraction of voids and a modified layer thickness of approx. 200 nm by the end of the irradiation process. This agrees with the results of numerical simulations and complementary scanning electron microscopy (SEM) measurements. In addition, we found a quasi-periodic time dependent behavior of amorphization and void formation represented by alternating accelerations and decelerations of different reorganization processes, respectively.

One of the most dangerous threats to everyday life and industrial activity is the possible explosion of earth gas, which can occur in various conditions, but usually occurs due to an excess of explosive gases in an enclosed environment. In order to protect people at their home and workplace, several types of gas sensors have been developed. Nevertheless, one of the most useful devices for explosive and combustive gases detection is the catalytic gas sensor. This type of sensors has shown a good performance in detecting of flammable gases with concentration close to the lower explosion limit (LEL). In order to meet the growing need for portable devices further evolution of these gas sensors is required to make them smaller and reduce the power consumption. To achieve this goal it is essential to reduce the 120 to 150 mW power dissipation of the Pt-coil based sensors (pellistors). Low Power Thermocatalytic Sensors manufactured with SOI (silicon on insulator) technology can be functional at temperatures below 600 ℃ with the power consumption in a range of 20–50 mW. The current aim of researches is the elaboration of novel sensor processing and development of nanostructured catalyst layer which is stable and effective at high temperatures and compatible with microelectronic silicon MEMS technology.

Micro-catalytic gas sensors are essential devices for detection of combustive gases up to lower explosion limit (LEL). Micro-catalytic gas sensors capable to detect hydrocarbons below 50 mW power consumption at 550 degrees C operation temperature were developed by using a novel gas sensing material technique. Experiments were aiming at deposition of controlled volume and structure of the catalyst. Constant current method in a Wheatstone-bridge configuration was applied in functional tests of developed Al2O3 catalysts. (C) 2019 Elsevier Ltd. All rights reserved.

Introduction Catalytic gas sensors are essential devices for detection of combustive gases near lower explosion limit (LEL). As the minimum power dissipation of Pt coil based sensors (pellistors) are 120 - 150 mW [1] intensive research is devoted to reduce it to be better compatible with portable devices while preserving sensitivity and stability. The reported microheater structures can operate up to 600 oC at a cost of 20-50 mW power consumption [2]. Nowadays the research activity is focused on development of stablenanostructured catalyst layer effective at low temperature, whereas compatible with MEMS thick film technology. Gas Sensitive Catalytic Materials The approach of fabrication gas sensitive material for coil and silicon membrane sensors is different. In first case the catalyst is bulky and forms bead or cylinder with diameter 400-500µm. In MEMS structures the catalyst is deposited on a microhotplate with a characteristic diameter of 100µm, de facto forming 2D surface. In the present work nanodespersed Al2O3 and ZrO2 ceramic carriers were prepared as presented on figs.5 and 6, respectively. Each material was divided into two equal parts - an active catalytic layer from one part and a comparative element from the second part were made exhibiting equal surface area. .In order to impregnate the catalyst support with the catalyst metal, salts of palladium chloride (PdCl2) and platinum acid (H2PtCl6) were used. Having annealed at high temperature metal clusters were formed in the catalyst support. Finally the active and reference materials were mixed with an organic binder to make the paste suitable for drop-coating deposition to MEMS silicone microheater. SOI Based MEMS Microheater Uniform and reproducible crystalline Si filaments were formed from SOI (silicon on insulator) wafers, because the buried oxide provides uniform thickness of the device layer and guarantees identical geometry. Cantilevers are suspended on stress compensated SiO2-Si3N4 membrane to increase their mechanical stability and eliminate their bending out of the original plane (fig. 1-4). Thereby the reduced stress provides longer lifetime. The higher resistivity of device silicon ensures higher filament resistance at the same temperature compared to its thin film metal reference, therefore the cross section of the current routes should be increased to achieve the sufficient resistance. A plausible advantage of the single crystalline filament material and the design is the minimized degradation effect of electromigration, thereby the lifetime of the heater is expected to achieve 6000-8000 hours. Moreover, the heated area of filament can be completely covered with catalyst or passive material, similarly to the coil-type filament devices.The opened side chip design facilitates catalyst deposition. Results and Conclusions Significant issues arise when the design of thermocatalytic sensors are transferred from the volumetric to the microplanar approach. First of all, the catalytic gas-sensitive layer must provide chemical activities:3∙10-6÷10-5mW/μm3. The solution of the problem is to choose classical materials alreadybeen used for many years in coil types pellistors - catalysts of platinum group metals on Al2O3 or ZrO2 ceramic carriers. The stability and behavior of these materials at high working temperatures has been already tested over tens of years in real working conditions (mains, gas line pipes, leakage alarm systems and etc.). The decrease in the quantity of the catalytic material deposited on the microheater leads to insufficient catalytic activity of the sensor as a whole. An increase in the operating temperature can correct the situation, but it is limited by the long-term stability of the microheater and the transformation of the crystallographic phase of the ceramic catalyst carrier. The critical temperature is around 550 °C. The Pt-Pd mixed-catalysts can be applied in the microplanar structure if uniform hotplate temperature is provided and the active and the reference sensing layers are deposited such as to minimize imbalance between the two elements. Acknowledgement This research was sponsored by the Sponsored by the National Research, Development and Innovation Office Foundation, Hungary, funding No. 2017-2.3.4-TeT-RU-2017-00006, and the Ministry of Science and Higher Education of the Russian Federation founding with unique identifier RFMEFI58718X0053. References [1] Karpova, E., Mironov, S., Suchkov, A., Karelin, A., Karpov, E.E., Karpov, E.F. Increase of catalytic sensors stability (2014) Sensors and Actuators, B: Chemical, 197, pp. 358-363. [2] Bíró, F., Dücső, C., Radnóczi, G.Z., Baji, Z., Takács, M., Bársony, I. ALD nano-catalyst for micro-calorimetric detection of hydrocarbons (2017) Sensors and Actuators, B: Chemical, 247, pp. 617-625. Figure 1

This work analyses the role of phase changes in TiO2/Pt/TiO2 layer stacks for micro-heater application regarding their stability and reliable operation. The polycrystalline Pt layer wrapped in a TiO2 adhesion layer underwent a continuous recrystallisation in a self-heating operation causing a drift in the resistance (R) versus temperature (T) performance. Simultaneously, the TiO2 adhesion layer also deteriorates at high temperature by phase changes from amorphous to anatase and rutile crystallite formation, which not only influences the Pt diffusion in different migration phenomena, but also reduces the cross section of the Pt heater wire. Thorough scanning electron microscopy, energy dispersive spectroscopy, cross-sectional transmission electron microscopy (XTEM) and electron beam diffraction analysis of the structures operated at increasing temperature revealed the elemental structural processes leading to the instabilities and the accelerated degradation, resulting in rapid breakdown of the heater wire. Owing to stability and reliability criteria, the conditions for safe operation of these layer structures could be determined.

We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO2) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies.

This work established the correlation between the location of temperature gradients and the positions where breakdown is observed on different Pt filament layouts in cantilever and full membrane type micro-hotplates. Focusing on practical aspects like in real operation, self-heating was applied to investigate the limitations of high temperature application and to reveal the fatal failure mechanisms. Besides electromigration, another phenomenon playing dominant role in the breakdown of the filaments, the temperature gradient driven thermomigration of Pt was identified. This limits the local allowable temperature gradient to <0.4°C/μm for operation temperature above 700°C.

Explosion alarm in atmospheric condition requires detection of hydrocarbons at the level of volume percent concentration range. This is best achieved by the combustion type detection, contrary to the available sensitive conductive type sensors, which would be driven to saturation by concentration close to LEL. Therefore, for catalytic gas sensing a micro-heater system was prepared with an integrated thin film porous Anodic Aluminium Oxide (porous AAO) on the heated area which offers simultaneously large surface support material and better thermal control. Uniformly distributed Pt catalyst was selectively deposited in the porous AAO by atomic layer deposition (ALD). The device was tested and characterized by detection of methane and propane concentrations between 20 and 100% of their Lower Explosion Limit (LEL), and provided readings of > 30 mV for 20% LEL (> 5 vol%) of both methane and propane. The combination of porous alumina with ALD deposited Pt exhibited catalytic activity for both gases. As the temperature of the micro-heater is limited to ca. 700 degrees C, during methane detection the sensor can be operated in the reaction kinetic controlled regime, whereas for propane measurement the temperature range of the ideal mass transport control can be set. The sensitivity loss was analysed in terms of possible ways for optimization. (C) 2017 Elsevier B.V. All rights reserved.

Various deposition techniques were tested to form Pt catalyst on nano-structured materials characterized by 50-200 nm dimensions. Different layer structures applied in gas sensing were sensitized by Pt sputtering and droplet deposition of Pt nano-particles formed from H2[PtCl6] solutions. Besides, atomic layer deposition (ALD) of Pt was also investigated. The layers to be coated were disordered piles of WO3 nano-rods and sol-gel deposited WO3 nano-crystals as well as electrochemically formed alumina with high aspect ratio perpendicular pores. Distribution of Pt particles inside these layers was analyzed by scanning (SEM) and transmission electron microscopy (TEM). Demonstration of functionality is also provided.

Highly conductive and uniform Ga doped ZnO (GZO) films were prepared by atomic layer deposition (ALD) as transparent conductive layers for InGaN/GaN LEDs. The optimal Ga doping concentration was found to be 3 at%. Even for 4" wafers, the TCO layer shows excellent homogeneity of film resistivity (0.8 %) according to Eddy current and spectroscopic ellipsometry mapping. This makes ALD a favourable technique over concurrent methods like MBE and PLD where the up-scaling is problematic. In agreement with previous studies, it was found that by an annealing treatment the quality of the GZO/p-GaN interface can be improved, although it causes the degradation of TCO conductivity. Therefore, a two-step ALD deposition technique was proposed and demonstrated: a "buffer layer" deposited and annealed first was followed by a second deposition step to maintain the high conductivity of the top layer. (C) 2016 Elsevier B.V. All rights reserved.

The paper presents a detailed study of a reliable method developed for aluminum fusion wafer bonding assisted by the electrostatic force evolving during the anodic bonding process. The IC-compatible procedure described allows the parallel formation of electrical and mechanical contacts, facilitating a reliable packaging of electromechanical systems with backside electrical contacts. This fusion bonding method supports the fabrication of complex microelectromechanical systems (MEMS) and micro-opto-electromechanical systems (MOEMS) structures with enhanced temperature stability, which is crucial in mechanical sensor applications such as pressure or force sensors. Due to the applied electrical potential of -1000 V the Al metal layers are compressed by electrostatic force, and at the bonding temperature of 450 degrees C intermetallic diffusion causes aluminum ions to migrate between metal layers.

A new treatment of some oncological diseases is brachytherapy that means the insertion of low level radiation isotopes into the organ to be healed. This cure has much less intensive side effects than traditional radiation therapy, while it is just as much effective. The problem is to determine how to position the 50-90 capsules in such a way that the tissue to be healed obtains at least a given level of dose, while the surrounding other organs absorb a dose less than a prescribed level. The related nonlinear optimization problem is of moderate dimensional (120-270). The resulting global optimization problem is very redundant, and it shows several forms of symmetries as well. The first test results obtained for an artificial model are reported.

Tungsten oxide nano-rods were prepared by acidic precipitation from sodium tungstate solution and sensitized with gold nanoparticles prepared by Turkevich method from tetrachloroauric acid trihydrate. In order to prevent aggregation the gold nanoparticles of 18nm characteristic size were stabilized by methoxy-polyethylene glycol (mPEG-SH) and mixed with hexagonal WO3. Suspension drops of doped and non-doped WO3 were deposited on micro-hotplates with interdigitated gold electrodes to measure sensing layer conductivity. Sensor responses of pure and doped WO3 were measured for NH3 and H2S in synthetic air up to 100ppm at the operation temperature of 140-200°C. The presence of gold nanoparticles significantly increased the sensitivity for H2S, whereas for NH3 the response was not affected. Test results are compared in terms of sensitivity, response time and operating temperature.

In this work recently produced and commercially available glazed ceramic object with metallic lustre decoration was studied by using a spectroscopic ellipsometer with rotating compensator. The thickness and metal content of the surface lustre layers are determined by ion beam analytical techniques, i.e., Rutherford backscattering spectrometry and external beam particle-induced X-ray emission and the results were utilized in the construction of multilayer optical models for the evaluation and interpretation of the spectroellipsometric measurements.

This work describes the results of a systematic investigation of micro-hotplates capable of operating up to 600°C both in static and dynamic modes. The goal of development is to form a reduced power consumption micro-pellistor for portable devices. For the selection of optimum device geometry and the membrane layer structure, alternatives FEM analysis was applied. The materials considered were Si3N4, SiO2, TiO2/Pt, Al2O3 and their combination in various multilayer structures. To reduce the chip size DRIE was selected for the release of the membrane. Experimental characterization of the hotplates was carried out by various techniques; the average hotplate temperature was deduced from the resistance of the applied Pt heater and verified by micro-melting point measurements. Buckling of the membranes was tested by means of optical methods and the cumulative stress of the multilayer structure was quantified by Makyoh-topography. Pulsed mode cyclic heating revealed the dynamic properties and also served for accelerated stability tests. For demonstration, micro-heaters with heat dissipation up to 23°C/mW and t90%<3ms were constructed. The hotplates were coated with Pt catalyst to form a combustive type gas sensor operated at elevated temperature.

In the past half century the IC technology could produce an unprecedented growth and penetration into all segments of our daily life due to the achieved extreme productivity and reliability by using well established and continuously refined processing platforms. This uninterrupted trend continued also with the advent of the More than Moore-type MEMS technology allowing the combination of the signal processing capability of the mature IC technology with the exploitation of mechanical, thermal, optical properties of the materials used in IC technology in different sensing and actuation purposes. Mass producibility by monolithic integration required here also the development of appropriate unified set of techniques for the various applications, i.e. sort of standardised platforms to explore. In this paper we focus on the development of bulk micromachined membrane platforms, being exploited in such applications. At the same time this summary also offers a "case study", a retrospective review of the development of integrable sensors from pressure measurement to nanopore-type, label-free biosensing at the Institute of Technical Physics & Materials Science-MFA, Budapest. (C) 2014 The Authors. Published by Elsevier Ltd.