Christof Metzmacher

Materials for bulk acoustic wave (BAW) resonators and filters

Abstract Thin film bulk acoustic wave (BAW) resonators and filters are appropriate for mobile communication systems operating at high frequencies between 1–10 GHz. The resonance frequency is mainly determined by the thickness of the piezoelectric layer. Piezoelectric films used for this application are, therefore, several 100 nm in thickness (up to approx. 2 μm) depending on frequency. Piezoelectric thin film materials used for bulk acoustic wave devices include AlN, ZnO thin films for small bandwidth applications and also PZT films for wide bandwidth applications. Within Philips piezoelectric AlN and PbZr x Ti 1− x O 3 (PZT) layers are investigated with respect to their potential for RF micro-electronic applications. High quality AlN films with strong c -axis orientation are achieved by optimum sputter deposition conditions and by applying suited nucleation layers. Electromechanical coupling factors k of 0.25±0.03, which are close to the bulk data, have been found in highly c-axis oriented AlN thin films. The relationship between sputter deposition conditions, AlN films structure on the one hand and electromechanical coupling factor k and relevant electrical parameters on the other hand will be discussed. A one-dimensional physical model is used to describe the bulk acoustic wave resonators electrical impedance data accurately. Thin PZT films are grown via sol–gel processing. These films show high electromechanical coupling factor k of 0.3–0.6 and are therefore attractive for wide bandwidth filter applications.

Narrow band bulk acoustic wave filters

Bulk acoustic wave (BAW) filters are competing successfully in the range of 800 MHz to 10 GHz with SAW filters. USPCS and UMTS filters require a bandwidth of 60 MHz at approximately 2 GHz (fractional BW /spl Delta/f/f/spl ap/3%). This can be realized by optimum design and high quality piezoelectric AlN which allows figure of merit, k/sup 2/Q, values of up to 100. On the other hand, relatively narrow band solidly mounted BAW filters can also be made. We present a narrow band filter with approximately 8 MHz bandwidth at a center frequency of approximately 1.2 GHz (fractional BW /spl Delta/f/f/spl ap/0.5%). The resonators required for narrow band filters can be designed to have extremely good temperature characteristics (down to -2 ppm/K) and high Q (>1000), which makes such devices interesting for new applications.

Ferroelectric thin films for integrated passive components

Abstract Miniaturisation and integration of passive components play an important role in todays components market. It can be achieved by applying thin-film technologies for capacitors, resistors and inductors; high component densities have been realised with ‘Passive Only Networks’. The dielectric materials used for integrated thin-film capacitors ranging from Si3N4, Ta2O5, TiO2 to earth alkaline as well as lead perovskite layers are reviewed. The capacitor performances including temperature stability, insulation resistance, breakdown fields and endurance are discussed as a function of material composition.

EUV sources for the alpha-tools

In this paper, we report on the recent progress of the Philips Extreme UV source. The Philips source concept is based on a discharge plasma ignited in a Sn vapor plume that is ablated by a laser pulse. Using rotating electrodes covered with a regenerating tin surface, the problems of electrode erosion and power scaling are fundamentally solved. Most of the work of the past year has been dedicated to develop a lamp system which is operating very reliably and stable under full scanner remote control. Topics addressed were the development of the scanner interface, a dose control system, thermo-mechanical design, positional stability of the source, tin handling, and many more. The resulting EUV source-the Philips NovaTin(R) source-can operate at more than 10kW electrical input power and delivers 200W in-band EUV into 2π continuously. The source is very small, so nearly 100% of the EUV radiation can be collected within etendue limits. The lamp system is fully automated and can operate unattended under full scanner remote control. 500 Million shots of continuous operation without interruption have been realized, electrode lifetime is at least 2 Billion shots. Three sources are currently being prepared, two of them will be integrated into the first EUV Alpha Demonstration tools of ASML. The debris problem was reduced to a level which is well acceptable for scanner operation. First, a considerable reduction of the Sn emission of the source has been realized. The debris mitigation system is based on a two-step concept using a foil trap based stage and a chemical cleaning stage. Both steps were improved considerably. A collector lifetime of 1 Billion shots is achieved, after this operating time a cleaning would be applied. The cleaning step has been verified to work with tolerable Sn residues. From the experimental results, a total collector lifetime of more than 10 Billion shots can be expected.

Compact extreme ultraviolet reflectometer for the characterization of grazing incidence optics based on a gas discharge light source

A grazing incidence reflectometer operating in the extreme ultraviolet (EUV) spectral range around 13.5 nm is presented which is making use of a compact xenon pinch plasma light source. The apparatus allows for measuring the absolute reflectivity of a sample for grazing incidence angle in the range from typically 5° to 35° by comparing the EUV diode signal for the reflected light and a reference diode with an accuracy of better than 2%. Design criteria for proper matching of diode apertures and distances with respect to the spatially extended plasma source are presented. The absolute accuracy has been checked by investigating a ruthenium sample with low roughness, which has a reflectivity in the EUV close to the theoretical limit. Comparison to measurements at the EUV-reflectometer of the Physikalisch Technische Bundesanstalt in Berlin at a synchrotron source confirm the absolute accuracy of better than 2% for the reflectivity for the angle interval of interest.

Filter system with bulk wave resonator having a reflection layer composition that varies with the layer thickness

The invention relates to a filter device equipped with at least one bulk acoustic wave resonator, which comprises a resonator unit and a reflection unit. The resonator unit comprises a first (3) and a second electrode (5) together with a textured piezoelectric layer (4) between the first (3) and second (5) electrodes.