A successful wafer-scale device layering process for fabricating three-dimensional integrated circuits (3D ICs) using Benzocyclobutene (BCB) is described. In the reported embodiment of the method, a sub-micron thick “donor” device layer is transplanted onto a fully fabricated “host” wafer with BCB as the intervening medium. Experimental results, including RIE study and planarization of BCB processed through the 3D fabrication procedure are reported. We conclude with an approach to alleviate BCB and fabrication induced wafer bowing, which leads to poor wafer to wafer alignment in 3D integration.

Metal-insulator-metal (MIM) capacitors were fabricated in a coplanar waveguide type using the Al2O3 thin film. The Al2O3 film was grown by atomic layer deposition(ALD) using Methyl-Pyrolidine-Tri-Methyl-Aluminum (MPTMA) and H2O on Ti. The capacitance per unit area of the fabricated MIM capacitor was 0.229 μF/cm2. And it had lower voltage coefficient of capacitance (VCC) and lower leakage current than that of Al2O3 MIM capacitor prepared by Al oxidation and Si3N4 MIM capacitor prepared by PECVD respectively. The fabricated Al2O3 MIM capacitors prepared by ALD exhibited low VCC, low leakage current, small frequency-dependent capacitance reduction, low temperature coefficient of capacitance (TCC) and good reliability. The characteristics of the device were suitable for RF ICs and DRAM.

The damage of finger electrodes of surface acoustic wave (SAW) structures due to material transport (acoustomigration) forming voids and hillocks is strongly associated with the SAW stress field, the temperature and properties of the fingers material and their configuration. By application of Cu thin films a significant higher performance of SAW structures with respect to power durability, reliability and lifetime is obtained. In the present paper Cu finger electrodes of a special power SAW test structure were fabricated in trenches of STX quartz substrates using the copper damascene technique. In comparison with conventional finger electrodes located on the substrate surface, such an embedded structure enables some new features regarding their acoustical and acoustomigration behavior. So high power SAW load cannot cause fatal failures by shorts between adjacent fingers. This fact is specially important for SAW devices in the GHz range. The trench structuring into the substrate was carried out by reactive ion (RIE) or ion beam etching (IBE) technique using a metallic hard mask. Etched trenches were filled with a conductive Ta-Si-N / Cu-layer system by magnetron sputtering in a cluster tool, and structured by a chemical-mechanical polishing (CMP) process. Subsequently, after cleaning an insulating Ta-based barrier (system Ta-Si-O / Ta-Si-N) layer was deposited on the wafer surface. This covering layer also acts as a protective coating. Such a metallization system enables sufficient bonding properties using Al-wires. First results of electrical measurements show that travelling SAW could be excited in quartz substrates.

Dense and highly textured BaLa4Ti4O15 (BLT) ceramics was fabricated by templated grain growth method. Plate-like BLT particles prepared via a molten salt synthesis using NaCl flux were mixed with B LT powders obtained by the conventional solid state method. X-ray diffraction and scanning electron microscope studies of the textured ceramics showed plate-like BLT grains aligned parallel to the casting direction. Large anisotropy was found in the dielectric properties.

Polycrystalline Al2O3 substrates have been proposed and tested for high temperature micro devices packaging intended for operation at temperatures up to 500°C. The dielectric properties of this material, including dielectric constant and effective volume conductivity, at elevated temperatures are of interest, especially for RF packaging applications. This article reports temperature dependent dielectric properties of polycrystalline 96% Al2O3 substrates from room temperature to 550°C measured by the AC impedance method at 120 Hz, 1 kHz, 10 kHz, 100 kHz, and 1 MHz. We observed negative temperature coefficients of volume electrical conductivity of 96% Al2O3 at 1 k, 10 k, and 100 kHz between room temperature and 50°C. The dielectric constant of the material increases significantly with temperature at frequencies below 10 kHz. The physical mechanisms of these dielectric behaviors of 96% Al2O3 at elevated temperatures are discussed.

A significant degradation of current gain of InP/InGaAs/InP double heterojunction bipolar transistors was observed after passivation. The amount of degradation depended on the degree of surface exposure of the p-type InGaAs base layer according to the epi-structure and device structure. The deposition conditions such as deposition temperature, kinds of materials (silicon oxide, silicon nitride and aluminum oxide) and film thickness were not major variables to affect the device performance. The gain reduction was prevented by the BOE treatment before the passivation. A possible explanation of this behavior is that unstable non-stoichiometric surface states produced by excess In, Ga, or As after mesa etching are eliminated by BOE treatment and reduce the surface recombination sites.

Microwave dielectrics with high Q and low εr are expected for millimeterwave applications. In this paper the preparation and properties of some candidates for microwave dielectrics such as forsterite, willemite, alumina, corundum-type compounds, green phase of Y2BaCuO5 are presented. High purity forsterite has low εr of 7.0 high Q·f of 270000 GHz and τf of -65ppm/°C. Willemite also has low εr of 6.5, and high Q·f of 160000 GHz. Alumina has ultra high Q·f of 680000GHz with εr of 10.05, and τf of -60 ppm/°C. Mg4(Nb2-x Tax)O9 which belongs to corundum group has εr of 11.5, Q·f of 350000 GHz, and τf of -70ppm/°C. Y2Ba(Cu1/4Zn3/4)O5 which belongs to green phase group has εr of 15.4, Q·f of 220000 GHz. The τf’s of these materials, which are an important property for millimeterwave applications, have been adjusted to zero ppm/°C by the addition of rutile, or adjustment of solid solution composition.

AC-coupled interconnects (ACCI) is a very exciting technology for achieving high-density chip-to-package interconnects while simultaneously providing a simple, mechanically robust interface. The technology combines the stress-relieving ‘underfill’ layer with the dielectric medium for capacitive coupling. For good AC coupling, it is desirable for the underfill material to have a permittivity around 20 at operating frequencies. However, there is a lack of microwave frequency data for high permittivity ceramic-polymer composite systems in the literature. This paper describes the development and microwave frequency characterization of high K nanocomposite underfill. For composite thick film preparation, 200 nm BaTiO3 nano-sized powder and photosensitive epoxy were used. The thermal behavior of composites was evaluated by DSC (differential scanning calorimetry). Dielectric properties were evaluated as a function of ceramic loading and curing temperature. The microwave dielectric properties were measured from 45 MHz up to 26.5 GHz to extract the capacitance and quality factor of the capacitor over the frequencies of interest using floating plate capacitors and T-resonator CPW structures. The permittivity was found to be ∼ 18 up to 14 GHz and the total Q factor of the capacitors was found to be 2 at 26.5 GHz for BaTiO3 (30 vol%)-epoxy composite. Dielectric loss was found to be 0.3 at 3 GHz, which would satisfactorily allow signaling well into the muti-gigabits range. The high K nanocomposite shows higher permittivity compared to materials currently used (air, K=1 or SiO2, K∼3.9) in capacitively coupled interconnects for chip-to-package communications.

Ferrites have magnetic properties suitable for electronic applications, especially in the microwave range (circulators and isolators). Hexagonal ferrite, such as barium ferrite (BaFe12O19 or BaM), which have a large resistivity and high permeability at high frequencies are of great interest for microwave device applications.

This contribution deals with BaM films, 1 to 36 microns thick, which were deposited under optimized conditions by RF magnetron sputtering. The films were then crystallized using a 800°C thermal annealing. Isolators were then realized using patterning of coplanar wave guides with standard lift-off technique. The slots and the central width were 300 μm wide, gold was used for the conductor lines. We evaluated the influence of various parameters on the device performances: the magnetic film thickness, the positioning of the magnetic film (CPW deposited onto the magnetic film or directly on the substrate) and the CPW metallic thickness. As standard design, the CPW were deposited on the top of the magnetic film. For the first design, transmission coefficients showed a non reciprocal effect, which reaches 7 dB per cm of line length at 50 GHz for a 26.5 μm thick BaM film. Both the insertion losses and the non-reciprocal effect measured increased with the magnetic film thickness with a saturation effect. In the second design where the CPW is deposited directly on the substrate, the BaM film was selectively wet etched prior to the metal deposition everywhere except between the conductors. In that case we measured that the non reciprocal effect reached high values for lower BaM thicknesses than in comparison to design # 1 and that the insertion losses also decreased. Moreover for the design # 2, also in relation with the localization of the BaM between the conductors, the non reciprocal effect improved with increasing conductor thickness as the interaction between the field lines created by the conductors and the magnetic film is then favored.

High power durable electrodes have been successfully grown on 38.5° rotated Y-X LiTaO3 piezoelectric substrates featuring epitaxial Al films with a pseudo-homoepitaxial Ti intermediate layer. We found that a two-step process sequence in the deposition temperature of an intermediate layer could make it possible for an Al/Ti structure to grow epitaxially on low-cut-angle Y-X LiTaO3. Specified epitaxial relationship was Al(111)<011>//Ti(001)<100>//LiTaO3(001)<100>. Duplexers with epitaxial Al electrodes had a breakdown power above 6 W and more than ten times longer lifetime in contrast to filters with polycrystalline electrodes of which the breakdown power is 3.4 W. Epitaxial electrodes with extremely less grain boundary can improve power durability because self-diffusion of Al atoms occurs mainly in the grain boundary of the film. Material variation of epitaxial electrodes will be discussed as well.

The on-chip magnetic inductors with patterned permalloy (Ni80Fe20) cores are fabricated on Si-substrates with different resistivities and thicknesses as well as on thin membranes. With the patterned permalloy cores, the on-chip magnetic inductors achieve high self-resonant frequencies over 25GHz in thin membranes. To distinguish the influence from the permalloy core patterns and substrate losses on the inductance and quality factor, multiple solenoids in series and parallel are designed to investigate the resistive, capacitive, and magnetic coupling losses.

This paper shows the potentialities of merging the MEMS and micromachining with SiGe technologies in order to speed up the performances of next generation of front end in term of flexibility, reconfigurability and adaptability. MEMS technologies are presented based on Benzo-Cyclo-Butene (BCB) materials and Bulk Acoustic Wave (BAW) materials. Special attention is paid to ensure a full compatibility between IC and MEMS. We have shown that very innovative functions could be considered by using this MEMSIC concept.

Microwave device engineers continually seek materials advances to improve performance of magnetic components at reduced size and cost. Wherever possible, microstrip or stripline device configurations are adopted in preference to bulky waveguide structures. In radar and communications applications, the nonreciprocal propagation properties of ferrites are essential for realizing phase shifters, circulators, isolators, and power limiters. The introduction of superconductor circuits has led to the development of very low-loss phase shifters and circulators. Recent demonstrations of tuning reciprocal rf permeability by varying the state of magnetization at very low magnetic fields has led to the development of high-speed, high-Q tunable filters. In this paper, design issues of four classes of microwave device are reviewed from the standpoint of their ferrite material requirements: (1) low-loss microstrip phase shifters (2) microstrip tunable resonators, (3) self-biased microstrip circulators with normal or in-plane uniaxial anisotropy, and (4) high-power quasi-optical circulators.

We have conducted low-temperature flip-chip bonding for both optical interconnect and microwave applications. Flip-chip bonding of vertical-cavity surface-emitting laser (VCSEL) arrays was performed on a fused silica substrate that provides propagation paths of laser beams and also supports a polymeric waveguide. To avoid thermal damage of the polymeric waveguide during the flip-chip bonding, indium bumps were used and the bonding condition of the flip-chip was determined as a heating temperature of 150 °C and a pressure of 500 gf. Experimentally, a thin silver (Ag) layer coated on the indium bump was very effective to enhance the adhesion strength between the indium bump and the VCSEL chip pads. In addition, the microwave characteristic of coplanar waveguide (CPW) package was slightly improved by the Ag coating.

The growth of the wireless industry over the past ten years has created a need for good quality passive components, and in particular high Q factor inductors. There has been a large amount of work aimed at improving the quality factors of inductors on both silicon and ceramic/insulating substrates. KAIST and other research groups have explored a MEMS technique, releasing the inductor coil to create an air gap between the coil and underpass, on silicon [1]. Typically the inductor coil has been separated by a 50 to 100μm air gap and has required special processing such as a dual exposure photoresist mold [1]. In the present work, suspended inductor coils have been fabricated and characterized on an alumina ceramic substrate [2]. The gap used was only 1μm and this was enough to increase the self-resonance frequency by up to 4GHz after release. The inductor coils were created in 6–10μm thick electroplated gold and the underpass in an aluminum layer. A sacrificial LPCVD oxide layer was used as the released dielectric. In the present study a range of inductance from 1 to 30nH was explored before and after release. The Q factors achieved in this work range from 40 to 70 in the 2 to 10 GHz range, which are some of the best Q factors reported for planar inductors (see Table I). In addition, since the architecture allowed the use of three metal layers, released transformers were also fabricated. They showed promising high frequency performance, which also will be presented. Minimum insertion loss better then –2dB was achieved between 10–12 GHz. The above described process is simple, precise, and manufacturable with the ability to extend the useful range of inductors to higher frequencies (1–10 GHz).

We have developed a hydrofluoric acid (HF) resistant, composite shallow trench isolation (STI) process for MOSFETs utilizing silicon nitride as isolation material for on-chip integration of micro-electro-mechanical (MEMS) resonators and CMOS devices. Peripheral leakage currents in silicon nitride isolated MOSFETs are suppressed by employing an independently controlled polysilicon side-gate, surrounding the active area of the devices. Electrostatic control of the threshold voltage at the device periphery alleviates the need for edge implants, resulting in increased thermal budget. Compatibility with HF release processes and high temperature anneal cycles allows integration of MEMS components in close proximity to CMOS devices for system-on-chip applications. nMOSFET devices fabricated using this composite STI process show excellent device characteristics.