Xiao Huo

Silicon-based high-Q inductors incorporating electroplated copper and low-K BCB dielectric

We have fabricated high-Q copper inductors using low-K benzocyclobutene (BCB) dielectric as an interface layer on standard CMOS silicon substrate. Metal ohmic loss and substrate loss, the two major factors that degrade the Q-factors of on-chip inductors, are suppressed by the employment of electroplated copper and the BCB dielectric, respectively. The inductors exhibit Q-factors as high as 25 at 2 GHz. The dependence of inductors high-frequency performance on inductors parameters, such as BCB and copper thickness, has been investigated in detail. The inductor fabrication process is low-cost and low-temperature, making it suitable for post-IC process for high-performance RFICs and MMICs.

A Physical Model for On-Chip Spiral Inductors With Accurate Substrate Modeling

A physical-based analytical model for on-chip inductors is developed. A ladder structure is used to model the skin and proximity effects in metal lines. The substrate electric and substrate magnetic losses are accurately modeled by RC and RL ladder structures, respectively. The effective inductance reduction due to the eddy current in the lossy silicon substrate at high frequency is modeled by a negative mutual inductance between the inductor and the substrate. All the model parameters can be calculated from the layout and process parameters. On-chip inductors with different geometries and substrate resistivities were fabricated for the verifications. The measured results are in very good agreement with the proposed model. This generic model can be applied to various substrate resistivities; thus, it is suitable for different technologies. This model can facilitate the design and optimization of on-chip inductors for RF IC applications

Radio-frequency transmission properties of carbon nanotubes in a field-effect transistor configuration

In this letter, the radio-frequency (RF) transmission properties of single-walled carbon nanotubes (CNTs) have been characterized up to the frequency of 12 GHz in a carbon nanotube field-effect transistor (CNFET) configuration using a two-port S-parameter method for the first time. The RF characteristics of the CNTs were measured from the drain to the source of the CNFET. A resistance, inductance, and capacitance model has been proposed, and the element values have been extracted. Without the effect of the parasitics, the RF signal transmission in the CNTs presents no degeneration even at 12 GHz. The capacitive contact between CNTs and metal electrodes is reported

Radio-frequency characterization for the single-walled carbon nanotubes

Carbon nanotube (CNT) has a potential to be used as nanoscale transmission lines and as high-performance passive components in nanoelectronics. In this letter, we discuss single-walled carbon nanotubes (SWNTs) that were grown using a chemical-vapor deposition technique. Both the dc and ac two-terminal resistances were measured and analyzed. The transmission properties of the SWNTs were shown by comparing the S parameters of a device with CNTs with those of a device without a CNT. The radio-frequency characterization of the CNTs was carried out using the network analyzer to frequency of 20GHz.

High frequency S parameters characterization of back-gate carbon nanotube field-effect transistors

High frequency S parameters characterization up to 10 GHz for back-gate carbon nanotube field-effect transistors (CNFETs) was carried for the first time. The high frequency transmission properties of back-gate CNFETs were compared and analyzed at different gate bias voltages using a lumped element model.

High-Q copper inductors on standard silicon substrate with a low-k BCB dielectric layer

High-Q Cu inductors using low-k benzocyclobutene (BCB) dielectric as an interface layer have been fabricated on a standard CMOS-grade silicon substrate. Metal ohmic loss and substrate loss, the two major factors that degrade the Q-factors of on-chip inductors, are suppressed by the employment of electroplated copper and the BCB dielectric, respectively. Quality-factor as high as 25 was obtained for a 1-nH inductor at 2 GHz. The inductor fabrication process is low-cost and low-temperature, making it suitable for post-IC process for high-performance RFICs and MMICs.

On-Chip Microwave Filters on Standard Silicon Substrate Incorporating a Low-k BCB Dielectric Layer

A low-loss, low-pass microstrip transmission line based microwave filter using 6-¿m low-k dielectric, Benzocyclobutene (BCB), as an interface layer has been fabricated on a standard CMOS grade silicon substrate. Standard 50-Ohm microstrip lines were fabricated and exhibit lower loss compared with the microtrip line on silicon without the BCB layer. The filter has a cut-off frequency at 10 GHz with an insertion loss of 1.1 dB. Simulation and measurement results of the filter are provided. Full-wave analysis of a 10 GHz bandpass filter is shown as well.

Silicon-on-Organic Integration of a 2.4–GHz VCO Using High-Q Copper Inductors and Solder-Bumped Flip Chip Technology

High-Q copper inductors were fabricated on low-cost and low-loss bismaleimide triazine (BT) and glass substrate using electroplating process. A differential LC voltage-controlled oscillator (VCO) circuit was designed using these high-Q inductors at 2.4 GHz. Flip chip and multichip module (MCM) technologies were applied to assemble the active chips on BT and glass substrate. The inductors exhibited Q-factor as high as 25 at 2.4 GHz. VCOs with copper inductors on BT and glass substrate had phase noise of -108 dBc/Hz at 600 kHz offset for a 2.4-GHz carrier, which is 6-dB improvement compared with the one with on-chip Al inductors. There was almost no substrate loss for inductors on BT and glass substrates. The effect of fabrication defects and solder joint resistance were also investigated. This technique can be extended to other building blocks, thus realizing integration of the whole RF system.

High frequency characterization for the single-walled carbon nanotubes using S-parameter

Metallic carbon nanotube (CNT) is a potential material for nano-scale transmission lines as well as high performance passive components in nano-scale systems. Single-walled carbon nanotubes (SWCNTs) were grown using CVD technique. Ti and Au were used for metal nodes. The characterization and analysis for metallic SWCNTs at GHz range are carried out in this paper. The S parameters of CNTs measured using network analyzer are reported for the first time.

Accurate modeling of lossy silicon substrate for on-chip inductors and transformers design

A physical based lumped element model is developed for lossy silicon substrates, considering both electric loss and eddy current loss induced by the substrate. A simplified ladder structure is used to accurately model the skin effect of the high conductivity silicon substrate. Good agreement with a full wave solver is obtained for inductors on different resistivity silicon substrates.