Joachim N. Burghartz

75-GHz f/sub T/ SiGe-base heterojunction bipolar transistors

The fabrication of silicon heterojunction bipolar transistors which have a record unity-current-gain cutoff frequency (f/sub T/) of 75 GHz for a collector-base bias of 1 V, an intrinsic base sheet resistance (R/sub bi/) of 17 k Omega / Square Operator , and an emitter width of 0.9 mu m is discussed. This performance level, which represents an increase by almost a factor of 2 in the speed of a Si bipolar transistor, was achieved in a poly-emitter bipolar process by using SiGe for the base material. The germanium was graded in the 45-nm base to create a drift field of approximately 20 kV/cm, resulting in an intrinsic transit time of only 1.9 ps.<<ETX>>

Microwave inductors and capacitors in standard multilevel interconnect silicon technology

Spiral inductors and metal-to-metal capacitors for microwave applications, which are integrated on a silicon substrate by using standard 0.8 /spl mu/m BiCMOS technology, are described. Optimization of the inductors has been achieved by tailoring the vertical and lateral dimensions and by shunting several interconnect metal layers together. Lumped element models of inductors and capacitors provide detailed understanding of the important geometry and technological parameters on the device characteristics. The high quality factors of nearly 10 for the inductors are among the best results in silicon, particularly when using standard silicon technology.

RF circuit design aspects of spiral inductors on silicon

In this experiment, the substrate silicon is removed using micromachining techniques, and the remaining thin-film structure is bonded onto a quartz substrate. The micromachined inductor has Q/sub MAX//spl ap/60 at 6 GHz. The lower resistivity and the greater conductor thickness of copper (Cu) compared to the aluminum (Al) process leads to a 3-4/spl times/ increased Q/sub MAX/ over the entire range of feasible inductance values.

Contact Resistance and Megahertz Operation of Aggressively Scaled Organic Transistors

Bottom-gate, top-contact organic thin-film transistors (TFTs) with excellent static characteristics (on/off ratio: 10(7) ; intrinsic mobility: 3 cm(2) (V s)(-1) ) and fast unipolar ring oscillators (signal delay as short as 230 ns per stage) are fabricated. The significant contribution of the transfer length to the relation between channel length, contact length, contact resistance, effective mobility, and cutoff frequency of the TFTs is theoretically and experimentally analyzed.

Spiral inductors and transmission lines in silicon technology using copper-damascene interconnects and low-loss substrates

Spiral inductors and different types of transmission lines are fabricated by using copper (Cu)-damascene interconnects and high-resistivity silicon (HRS) or sapphire substrates. The fabrication process is compatible with the concepts of silicon device fabrication. Spiral inductors with 1.4-nH inductance have quality factors (Q) of 30 at 5.2 GHz and 40 at 5.8 GHz for the HRS and the sapphire substrates, respectively. 80-nH inductors have Qs as high as 13. The transmission-line losses are near 4 dB/cm at 10 GHz for microstrips, inverted microstrips, and coplanar lines, which are sufficiently small for maximum line lengths within typical silicon-chip areas. This paper shows that inductors with high Qs for lumped-element designs in the 1-10-GHz range and transmission lines with low losses for distributed-element designs beyond 10 GHz can be made available with the proposed adjustments to commercial silicon technology.

Multilevel-spiral inductors using VLSI interconnect technology

A multilevel-spiral (MLS) inductor structure for implementation in VLSI interconnect technology is presented. Inductances of 8.8 and 32 nH and maximum quality-factors (Q) of /spl sim/6.8 and 3.0, respectively, are achieved in a four-level metal BiCMOS technology, with four turns at each of the two or four stacked spiral coils and with an area of 226/spl times/226 /spl mu/m/sup 2/. The comparison of the MLS inductors to different single-level-spiral (SLS) control devices shows that a MLS inductor provides the same inductance at /spl sim/50% dc resistance, but the maximum Q is typically measured at a lower frequency and the self-resonance frequency is reduced due to a high inter-wire capacitance.

Integrated RF and microwave components in BiCMOS technology

This paper presents and discusses an approach to exploit conventional BiCMOS technology for monolithic integration of RF & microwave systems. Several components, which are important elements of RF and microwave circuit design and which are not available in current BiCMOS, are described and characterized. The results for integrated spiral inductors in particular show that obvious limitations in comparison to compound semiconductor technology or hybrid configurations can be overcome to a large extent by utilizing the structural design options given with VLSI silicon integration technology.

Bridging the gap between optical fibers and silicon photonic integrated circuits

We present a rigorous approach for designing a highly efficient coupling between single mode optical fibers and silicon nanophotonic waveguides based on diffractive gratings. The structures are fabricated on standard SOI wafers in a cost-effective CMOS process flow. The measured coupling efficiency reaches -1.08 dB and a record value of -0.62 dB in the 1550 nm telecommunication window using a uniform and a nonuniform grating, respectively, with a 1 dB-bandwidth larger than 40 nm.

Progress in RF inductors on silicon-understanding substrate losses

The recent progress in the integration of inductors on silicon substrates is reviewed first. The substrate losses, which present the main difference to the well-established inductor integration on quasi-ideal GaAs or printed circuit boards, are then investigated through specific experiments to support the inductor optimization and modeling. Metal ground shield structures, that potentially isolate the spiral inductor coil from the lossy silicon, are evaluated as well.

Integrated RF components in a SiGe bipolar technology

Several components for the design of monolithic RF transceivers on silicon substrates are presented and discussed. They are integrated in a manufacturable analog SiGe bipolar technology without any significant process alterations. Spiral inductors have inductance values in the range of /spl sim/0.15-80 nH with typical maximum quality-factors (Q/sub max/) of 3-20. The Q/sub max/s are highest if the doping concentration under the inductors is kept minimum. It is shown that the inductor area is an important parameter toward optimization of Q/sub max/ at a given frequency. The inductors can be represented in circuit design by a simple lumped-element model. MOS capacitors have Qs of /spl sim/20/f (GHz)/C(pF), metal-insulator-metal (MIM) capacitors reach Qs of /spl sim/80/f (GHz)/C(pF), and varactors with a 40% tuning range have Qs of /spl sim/70/f (GHz)/C(pF). Those devices can he modeled by using lumped elements as well. The accuracy of the modeling is verified by comparing the simulated and the measured high-frequency characteristics of a fully integrated, passive-element bandpass filter.