Franz-Josef Schmückle

Coplanar passive elements on Si substrate for frequencies up to 110 GHz

This paper provides both modeling and design information on coplanar passive elements on a silicon substrate. The influence of substrate resistivity on coplanar waveguide (CPW) loss is discussed, and elements of a cell library for coplanar monolithic microwave integrated circuits (MMICs) on high-resistivity substrates are presented. The elements include discontinuities, junctions, and spiral inductors. The models are based on field-theoretical simulations and verified by S-parameter measurements up to 110 GHz.

Fabrication of application specific integrated passive devices using wafer level packaging technologies

Integrated passives have become increasingly popular in the last years. Especially wafer level packaging technologies offer an interesting variety of different possibilities for the implementation of integrated passive components. In this context particularly the fabrication of integrated passive devices (IPDs) represents a promising solution regarding the reduction of size and assembly costs of electronic systems in package (SiP). These IPDs combine different passive components (R, L, C) in one subcomponent to be assembled in one step by standard technologies like SMD or flip chip. In this paper the wafer level thin film fabrication of such IPDs (WL-IPDs) will be discussed. After a brief overview of the different possibilities for the realization of IPDs using wafer level packaging technologies two fabricated WL-IPDs will be presented. Design, technological realization as well as results from the electrical characterization will be discussed.

26 GHz coplanar SiGe MMICs

First results on coplanar MMICs with SiGe HBTs are presented. The circuits are fabricated on high-resistivity Si substrates using a double-mesa HBT process. In the Ka-band, an oscillator output power of 1 dBm and 4.4 dB gain for a one-stage amplifier are achieved. This demonstrates the potential of SiGe transistors for applications in the higher microwave range.

Modelling of passive elements for coplanar SiGe MMIC's

As the first step in the development of coplanar SiGe MMICs, modelling and experimental results on passive components are presented. The investigations demonstrate that parasitic effects induced by passivation of high-resistivity silicon substrates play an important role. Efficient CAD tools are developed and verified by comparison with measurements.<<ETX>>

Evaluation of Micro Structured Glass Layers as Dielectric-and Passivation Material for Wafer Level Integrated Thin Film Capacitors and Resistors

This work describes the integration of thin micro-structured glass layers into copper / benzocyclobutene (Cu/BCB) thin film multi layer. The glass, which is deposited by a low temperature PVD-PIAD process (physical vapor deposition with plasma ion assisted deposition) using special synthesized targets, was evaluated to act as local dielectric and passivation material for integrated capacitors and resistors. Metal-insulator-metal (MIM) capacitors and micro strip resonators were realized to determine the breakdown voltage as well as the dielectric constant of the material. Furthermore the glass material was used as passivation for integrated nickel-chromium (NiCr) resistors, which were evaluated regarding their maximum applicable current density, temperature coefficient of resistance as well as long-term stability. The first chapters of this paper describe the glass deposition and structuring as well as the integration of these processes into the Cu/BCB redistribution process of Fraunhofer IZM. Afterwards the fabrication of the test structures and the results from their characterization are discussed in detail.

Crosstalk Corrections for Coplanar-Waveguide Scattering-Parameter Calibrations

We study crosstalk and crosstalk corrections in coplanar-waveguide vector-network-analyzer calibrations. We show that while crosstalk corrections can improve measurement accuracy, the effectiveness of the corrections depends on a number of factors, including the length of the access lines, transverse dimensions, the separation between the crosstalk standards, and the substrate configuration.

Flip-Chip Interconnects for 250 GHz Modules

With the increasing availability of MMICs at frequencies beyond 100 GHz low-loss interconnects for module fabrication in this frequency range become essential. This letter presents results on a flip-chip mounting approach exhibiting a bandwidth of more than 250 GHz, supporting both coplanar and stripline transitions. The interconnects are realized with 10 μm-diameter AuSn microbumps. S-parameter measurements show an insertion loss of less than 1.0 dB per interconnect and a return loss better than 10 dB up to 250 GHz. The experimental results are in good agreement with 3-D EM simulations.

A 30-GHz Waveguide-to-Microstrip-Transition

Waveguide-to-microstrip transitions are essential elements for mm-wave transmitters and receivers. This paper presents an optimized transition with a relatively simple geometry and a minimum of compensation structures in order to mitigate sensitivity to fabrication tolerances. Almost 5 GHz bandwidth is achieved around 30 GHz, with an insertion loss of less than 0.25 dB. The transition can be implemented with a hermetic sealing.

Multifinger Indium Phosphide Double-Heterostructure Transistor Circuit Technology With Integrated Diamond Heat Sink Layer

The RF power output of scaled subterahertz and terahertz indium phosphide double-heterostructure bipolar transistors (InP DHBTs) is limited by the thermal device resistance, which increases with the geometrical frequency scaling of these devices. We present a diamond thin-film heat sink process aimed at the efficient removal of the heat generated in submicrometer InP HBTs. The thin-film diamond is integrated in a wafer bond process. Vertical connections are facilitated by plasma-processed contact holes through the diamond layer, metallized with electroplated gold. The process is suitable for monolithic circuit integration, amenable to the realization of high-power analog circuits in the millimeter-wave region and beyond. The thermal resistance of double-finger transistors with a 0.8-μm emitter width could be reduced to 0.7 K/mW, while reaching the gain cutoff frequencies of fT = 360 GHz and fmax = 350 GHz. An integrated two-stage power amplifier with four-way power combining fabricated in this technology exhibited 20-dBm power output at 90 GHz with a bandwidth of 10 GHz.

Coplanar High Gain Millimeter Wave Amplifier Module

A 58 GHz amplifier module with more than 55 dB gain has been developed in coplanar technology. The signal distortion could be minimized by using a low number of substrates and high performance interconnection and packaging technologies. Flip chip bonding of the MMICs allowed the minimization of the parasitic inductance and capacitance of the chip interconnection. By two local cavities, realized as substrate integrated packages (SIP) on one thin film substrate, a miniaturized solution to reduce cross talk inside the package was used resulting in an isolation of more than 80 dB. The coupling of the coplanar mode to other parasitic modes could be suppressed by a special coplanar feed-through for the SIP. A direct coaxial to coplanar transition allowed the realization of a pure coplanar signal path between the coaxial connectors at the module input and output.