R. Kunze

A discrete one component wave model and its application to SAW resonator filters

A one component acoustic bulk wave model is presented for the description of SAW devices using plane waves or waveguide modes. No equivalent circuit components are used, and the calculations always remain on the level of acoustic waves. As fundamental elements the transfer matrix and the source vector of one electrode region are derived. Using these elements, the particle displacements in an array consisting of striplike electrodes can be calculated as a function of all single capacitor voltages taking into account the boundary conditions including the amplitudes of foreign waves meeting the array. After determining the waveguide mode velocities and profiles the model is applied to transversely coupled waveguide resonator filters resulting in the admittance matrix which is needed to calculate the filter insertion loss. Two filter examples are investigated, and a sufficiently good agreement of the theoretical and experimental results is found. The resonance splitting due to cascading of two (or more) single resonator filters can be increased by a coupling inductor yielding a smaller insertion loss under matched conditions at a given bandwidth.<<ETX>>

Detection and characterization of carbon contamination on EUV multilayer mirrors

In this paper, we detect and characterize the carbon contamination layers that are formed during the illumination of extreme ultraviolet (EUV) multilayer mirrors. The EUV induced carbon layers were characterized ex situ using spectroscopic ellipsometry (SE) and laser generated surface acoustic waves (LG-SAW). We show that both LG-SAW and SE are very sensitive for measuring carbon layers, even in the presence of the highly heterogeneous structure of the multilayer. SE has better overall sensitivity, with a detection limit of 0.2 nm, while LG-SAW has an estimated detection limit of 2 nm. In addition, SE reveals that the optical properties of the EUV induced carbon contamination layer are consistent with the presence of a hydrogenated, polymeric like carbon. On the other hand, LG-SAW reveals that the EUV induced carbon contamination layer has a low Youngs modulus (<100 GPa), which means that the layer is mechanically soft. We compare the limits of detection and quantification of the two techniques and discuss their prospective for monitoring carbon contamination build up on EUV optics.

Monitoring blood coagulation with QCM and SH- SAW sensors

Investigations concerning a coagulation sensor based on shear horizontal surface acoustic waves (SH-SAW) are described. As a first step, experimental work was focused on a simpler system: a quartz crystal micro balance (QCM) also called thickness shear mode resonator (TSM). In the literature the suitability of such devices for the characterization of coagulation process is already described. Coagulation tests like Quick and activated partial thromboplastin time (aPTT) have been performed at a resonance frequency of 9 MHz. In a further step, smaller changes in resonant frequency with smaller concentration of fibrinogen could be shown with plasma dilution tests. While performing measurements with different sample volumes the coagulation process was still detectable with five microlitres of blood plasma. A special measurement cylinder was designed and tested to separate the sample from environmental influences. Performing all these tests with plasma or whole blood samples leads to similar results. For determination of the coagulation time, the steepest decrease of resonance frequency vs. time was found as a reproducible value. Measurements have been done at the overtones of the TSM in order to study whether the hemostasis is still measurable at frequencies common to SAW devices. The coagulation process could be measured up to 243 MHz (overtone 27) although the decay length decreases with higher frequencies. Tests using SAW devices with SH-SAW resonator filters (36°rotYX-LiTaO3 substrate) have been done at 168 MHz. The electrolytic character of the plasma caused damage to the electrode structure which could be avoided at later tests. Afterwards the blood coagulation process was successfully measured with SH-SAW. Finally a specially adapted SH-SAW sensor was designed, constructed and tested. Compared to TSM resonators vibrating on the fundamental mode, sensitivity was greatly increased.

Investigation of SAW-induced acoustomigration effects in Cu- and Al-based metallizations

Surface acoustic wave (SAW) filter devices are successfully used for a variety of applications in telecommunication at low power levels. Shrinking sizes, raising frequencies and higher power levels lead now to new requirements regarding the device power capability since the metal electrodes tend to fatigue under high load due to acoustomigration effects. A lot of work was done to study the influence of several Al alloys and layered systems on the power durability usually by loading an existent layout with high power. By contrast, we have started our comparative investigations with in-situ experiments on different test metallizations, in order to gain a deeper insight into the acoustomigration phenomena and the basic mechanisms. These observations gave the experimental counterpart to the theoretical work on modeling the SAW stress fields. First results show clear differences in the migration behavior of Cu-based and Al-based metallization systems, with a significant higher power durability for the Cu systems.

3F-1 Thrombelastography Using Acoustic Sensors

The purpose of the present paper is to show that thrombelastography can be carried out by means of a quartz crystal microbalance (QCM) also known as a thickness shear mode resonator (TSM). A 9 MHz AT cut quartz was taken for the characterization of whole blood samples from healthy donors. To initiate fibrinolysis effects a special agent was used. The coagulation process was measured by monitoring the resonant frequency of the TSM. This frequency is affected by viscosity changes taking place during the coagulation process. The experimental setup was improved by covers made of PMMA (polymethyl methacrylate) and PDMS (polydimethylsiloxane). These covers seal the electrode in the TSM which is in contact with the coagulating blood sample. The use of such covers allows deleterious environmental effects such as evaporation and drying of the sample to be avoided. The ability of TSM to produce thrombelastograms was successfully demonstrated. The use of such devices allows state of the art measurement setups to be greatly simplified. No complicated mechanical or moving parts must be produced nor is an optical detection unit needed. In addition, direct monitoring of the viscosity results in additional findings at the end of fibrinolysis curves

Investigation of acoustomigration effects in Al-based metallizations

In contrast to other investigations on power durability where the over-all time-to-failure (TTF) of commercial filter devices is measured for comparison of different metallizations we extrapolate the TTF values in a steady-state of acoustomigration. The filters were driven in a cw-mode at their center frequency at constant power level and fixed ambient temperature. Within short terms the frequency characteristic was regularly probed to track the shift of center frequency in order to secure constant loading conditions. The TTF value calculated from the slope of a middle-term linear frequency shift over time was taken as a measure of power durability. The electrical measurements were assisted by scanning electron (SEM) and ion (FIB) microscopic techniques to investigate the structural changes in the metallization layer at different states of degradation. In addition, we have used for the first time very thin (thickness in the nm scale) protective layers for electrode cladding. The influence of these layers on the device characteristics was studied as well as their power capability enhancement.

Saw resonators for temperature stable oscillators

A double two-port resonator by means of which the compensation of the TCF1 as well as the TCF2 is possible is presented. The double resonator is composed of two coupled two-port single SAW resonators. The propagation directions are characterized by opposite and equal signs of TCF1 and TCF2, respectively. The coupling is realized by cascading and using a coupling inductance. In order to explain the TC compensation qualitatively a simple coupled spring resonator is treated analytically. An example of a double two-port resonator is studied by means of model calculations and experiments. 35.5° rotY quartz is used as a wafer material. The propagation angles (angle between the propagation direction and the X axis) of the single resonators are chosen to be larger and smaller, respectively, than the angle in vicinity of 45° whose TCF1 is zero. The frequency whose temperature stability is studied is defined as frequency belonging to a fixed phase. This phase is kept constant within the entire temperature range. The frequency and |S21| are calculated and measured as functions of temperature. Not only the theoretical but also the experimental results express the temperature shift of frequency from −30°C until 70°C to be essentially smaller than that in the case TCF1= 0 in vicinity of 45°.

High precision characterization of SAW materials and devices

Three original methods, developed and used for the characterization of SAW materials and devices, are presented: an electric scanning force microscope, a laser induced SAW pulse propagation method, and an optical glass fibre interferometer. The electric scanning force microscope enables to map dielectric and piezoelectric properties in nanoscale. Two examples of its use in developing SAW thin film solutions are shown: PZT layers on Si and laser deposited LiNbO/sub 3/ layers on sapphire. The laser induced SAW pulse technique is shown to be a useful method to evaluate the mechanical properties of thin coatings in SAW preparation techniques and to determine unknown material constants of new substrate materials. The optical interferometer has been developed in such a way that the SAW velocity can be determined with an accuracy of 10/sup -5/ within transducer and reflector grating structures. This property has been used to determine the key parameters of potential materials for SAW waveguide resonator filters.

Investigation of Al/Ti metallization performance in terms of acoustomigration stability

Due to their excellent properties SAW-based filters expand into applications with higher frequencies, up to the GHz range. Because of increasing operating frequencies and shrinking sizes, these filters were confronted with increasing requirements regarding their aging stability and their power durability, as well. The latter addresses to an improved acoustomigration (AM) stability, what can be achieved by alloying addition of e.g. Ti, Cu, Mg etc. to a usual Al metallisation or by using multilayer stacks. A different method is be to employ Al-based intermetallic phases, such as Al3Ti, which may have an increased AM stability starting from layered systems. This phase can be established by a special heat treatment of Al/Ti multilayers. The power performance of such a metallization was evaluated in this paper in comparison to conventional Al electrodes. The devices were loaded at about 130 MHz with an SAW input power of several Watts to investigate and to compare the damage behavior of each metallization system. During this SAW loading the electrical behavior (e.g. peak frequency shift of the admittance curves) of interdigital test transducers was measured as an indicator of acoustomigration. Additionally, observations by means of scanning probe microscopy were used to correlate the electrical behavior with the degradation of the electrode microstructure.

Ellipsometric and surface acoustic wave sensing of carbon contamination on EUV optics

Carbon contamination layers, deposited on extreme ultraviolet (EUV) multilayer mirrors during illumination were characterized ex situ using spectroscopic ellipsometry (SE), laser generated surface acoustic waves (LG-SAW), and by their EUV reflectance loss. We show SE is more sensitive to the deposition of carbon layers than the EUV reflectance loss, even in the presence of the highly heterogeneous structure of the multilayer. SE has better overall sensitivity, with a detection limit of 0.2 nm, while LG-SAW has an approximate detection limit < 5 nm.