Electrical Parasitics Research Articles

Design optimization of one-turn helix: A novel compliant off-chip interconnect

As the rapid advances in integrated circuit (IC) design and fabrication continue to challenge and push the electronic packaging technology, in terms of fine pitch, high performance, low cost, and good reliability, compliant interconnects show great potential for next-generation packaging. One-turn helix (OTH) interconnect, a compliant chip-to-next level substrate or off-chip interconnect, is proposed in this work, and this interconnect can facilitate wafer-level probing as well as wafer-level packaging without the need for an underfill. The interconnect has high mechanical compliance in the three orthogonal directions, and can accommodate the differential displacement induced by the coefficient of thermal expansion (CTE) mismatch between the silicon die and an organic substrate. The fabrication of the helix interconnect is similar to the standard IC fabrication, and the wafer-level packaging makes it cost effective. In this paper, we report the fabrication of an area array of helix interconnects on a silicon wafer. Also, we have studied the effect of interconnect geometry parameters on its mechanical compliance and electrical parasitics. Thinner and narrower arcuate beams with larger radius and taller post are found to have better mechanical compliance. However, it is found that structures with excellent mechanical compliance cannot have good electrical performance. Therefore, a trade off is needed for the design of OTH interconnect. An optimization technique using response surface methodology has been applied to select the optimal structure parameters. The optimal compliant OTH interconnect will have a total standoff height of about 100 /spl mu/m, a radius of about 35 /spl mu/m and a cross section area of about 430 /spl mu/m/sup 2/.

Modeling the Electrical Parasitics for Large I/O Ball Grid Array Packages for RF Applications

This publication describes a computer program that can rapidly generate RF models of the electrical parasitics for either two layer low cost BGA packages or for multi-layer high performance BGA packages. The user enters simple dimensional information for the geometry's of the package from the package drawings. There are two files generated as outputs of the program. One file is a table containing all of the leads with each of the lead's parasitics listed along with the input data and some of the calculated dimensions. The other file generated -is a “SPICE deck.” This file contains all the leads' parasitics in the form of a circuit topology that can be used as input for a SPICE simulation. The Package Parasitic Model Program is helpful in integrated circuit package design and analysis by delivering a complete model of package parasitics within a few minutes. Also presented in this paper is a technique of measuring large I/O BGA packages to 2 GHz and a comparison of sample measurements to simulated models generated by the program.

High performance selectively oxidized VCSELs and arrays for parallel high-speed optical interconnects

High-bandwidth single-mode selectively oxidized vertical-cavity surface-emitting laser (VCSEL) arrays operate at 980 nm or 850 nm emission wavelength for substrate or epitaxial side emission. Coplanar feeding lines and polyimide passivation are used to reduce electrical parasitics in top-emitting GaAs and bottom-emitting InGaAs VCSELs. To enhance fundamental single-mode emission for larger devices of reduced series resistance a surface relief transverse mode filter is employed. Fabricated VCSELs are applied in various interconnect schemes. InGaAs quantum-well based VCSELs at 935 nm emission wavelength are investigated for use in perfluorinated graded-index plastic-optical fiber (GI-POF) links. We obtain a 7 Gb/s pseudo random bit sequence (PRBS) nonreturn-to-zero (NRZ) data transmission over 80 m long 155 /spl mu/m diameter GI-POF. We investigate data transmission over standard 1300 nm, 9 /spl mu/m core diameter single-mode fiber with selectively oxidized single-mode GaAs and InGaAs VCSELs. We achieve biased 3 Gb/s and bias-free 1 Gb/s pseudo-random data transmission over 4.3 km at 830 nm emission wavelength where a simple fiber mode filter is used to suppress intermodal dispersion caused by the second order fiber mode. For the first time, we demonstrate 12.5 Gb/s data rate transmission of PRBS signals over 100 m graded-index multimode fiber or 1 km single-mode fiber using high performance single-mode GaAs VCSELs of 12.3 GHz modulation bandwidth emitting at /spl lambda/=850 nm.

Parasitic extraction methodology for insulated gate bipolar transistors

This paper presents a methodology for extraction of the electrical package parasitics of insulated gate bipolar transistor power modules using simple electrical measurements. Non-idealities of device performance in zero-voltage and zero-current switching are exploited to obtain the parasitic collector and emitter inductance. Simple impedance measurements are performed to extract gate inductance and resistance. The extraction methodology is validated by comparing two-dimensional numerical simulation results including package parasitics with measured data. A close match between the two indicates the robustness of the extraction procedure.

Matching network for microwave applications of semiconductor laser diodes (LDs): Consideration of the effects of electrical parasitics and LD carrier-dependent impedance

A complete semiconductor laser transmitter model consisting of a matching circuit, an electrical parasitic circuit, and a nonlinear intrinsic laser is introduced. The model is based on the transmission-line laser modeling method, which is very efficient and flexible. The effect of electrical parasitics on the modulation response of the laser and the associated improvements owing to matching are also reported. It has been found that the dependency of laser impedance on the carrier density is negligible. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 197–200, 2000.

Micro-Optical Platform for All-Optical Demultiplexing Switch Array

As it is free from electrical parasitics, the use of the all-optical switch array is an attractive approach for achieving very high-speed signal processing for optical communication and interconnection beyond the Gbit/s range. However, two incident beams and one outgoing beam for each switch may require a complex geometry, thus the module assembly procedure remains a serious obstacle for its realization. The present work reports the design, test fabrication, and characterization of an optical platform dedicated to all-optical demultiplexing at 1.55 µm, using asymmetric Fabry-Perot saturable absorber switches as active devices, and off-axis binary Fresnel zone lenses as the focusing optics. Two different platform configurations were fabricated by a substrate stacking technique achieving spot sizes of 13 µm and 22.5 µm at the switch plane, with reasonable overlap between the pump and signal beams. The influence of wavelength variation, fabrication tolerance and throughput are discussed.

Integrated semiconductor laser-transmitter model for microwave-optoelectronic simulation based on transmission-line modelling

The transmission-line laser model is a powerful and flexible method to model various types of laser devices. An integrated laser transmitter model comprising the intrinsic laser, an electrical parasitics network and a passive matching network is proposed for microwave-optoelectronic simulation in the time domain. Transmission-line matrix stub lines and link lines are used to model the matching network and electrical parasitics. The passive matching network is based on monolithically integrated lumped elements. The effect of electrical parasitics has been taken into account when designing the matching network. Simulation results are in good agreement with those of commercial software. A microwave application of the integrated laser transmitter model is demonstrated in harmonic generation through gain switching.

Integrated microwave-optoelectronic simulation of semiconductor laser transmitters

By combining an electrical parasitics model and a laser equivalent circuit model in a microwave circuit simulator, nonlinear laser transmitter operations are simulated. Harmonic generation through gain switching a laser is used as an example of nonlinear operation to experimentally verify the utility of the simulation approach. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14: 313–315, 1997.

Relative figures of merit for chip-to-MCM substrate interconnection methods

Functional performance of an electronic system is proportional to the functional throughput rate, which is defined as the product of the function density (gates/cm/sup 2/) and the clock rate. Various chip-to-module assembly methods for high-density substrates can provide a functional throughput rate approaching that of the integrated circuit (IC). Results of a comparative study for the performance of simultaneously switching off-chip drivers in various multichip module (MCM) scenarios are reported for CMOS and emitter-coupled-logic (ECL) technologies. Flip-chip technology can provide up to twelvefold improvement in performance over tab automated bonding (TAB) for a CMOS system, and about sevenfold improvement for an ECL system. However, when the delay in the critical path is dominated by on-chip circuits, speed improvement by MCM becomes negligible. Electrical parasitics of the chip-to-substrate interconnections also create undershoot in the switching signal, which reduces the noise margin. It is concluded that the advantages of high-density multichip packaging, in decreasing order of importance, are density of integration, reduction in the switching noise, shorter off-chip delays, and reduction in power dissipation. >

Experimental determination of gain compression factors of a DFB laser in the presence of TM light injection

Compared to direct current modulation, an optical modulation scheme of laser diodes exhibits no rolling off characteristics due to the electrical parasitics existing in the laser diodes. In particular, in the TM light injection scheme, no injection locking phenomena take place. A number of applications of TM light injection have been reported. In relation to these, determining the gain compression factors of laser diodes in the presence of TM light injection is essential. A new technique for determining these factors is presented. The technique is shown to be viable for measuring the gain compression of distributed feedback (DFB) lasers. >

High-speed, low-threshold InGaAsP semi-insulating buried crescent lasers with 22 GHz bandwidth

The authors have fabricated high-speed, low-threshold 1.3 mu m InGaAsP semi-insulating buried crescent lasers with a CW 3 dB modulation bandwidth of 22 GHz and a threshold current as low as 6.5 mA at room temperature. This is the highest 3 dB modulation bandwidth ever reported for the planar-type semiconductor laser. These results were achieved by implementing a submicron photolithographic process in the channel etching to reduce the cavity width and a polyimide dielectric layer under the bonding pad area to minimize the electrical parasitics.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Short pulse generation using multisegment mode-locked semiconductor lasers

Mode-locked semiconductor lasers which incorporate multiple contacting segments are found to give improved performance over single-segment designs. The functions of gain, saturable absorption, gain modulation, repetition rate tuning, wavelength tuning, and electrical pulse generation can be integrated on a single semiconductor chip. The optimization of the performance of mode-locked lasers in terms of material parameters, waveguiding parameters, electrical parasitics, and segment length is discussed experimentally and theoretically. >

Characterization of the dynamics of semiconductor lasers using optical modulation

An optical modulation technique for measuring the intrinsic frequency response of semiconductor lasers is described. This technique, which uses an RF-modulated pump laser to create an optical modulation signal to inject into a DC-biased probed laser, offers significant advantages over previous methods such as being affected by electrical parasitics of either the laser to be characterized or the photodetector. The method allows extremely accurate measurements of many important dynamic parameters, including the nonlinear gain coefficients, the amount of spontaneous emission into the guided modes, and the differential carrier lifetime at lasing threshold.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Simultaneous measurement of spontaneous emission rate, nonlinear gain coefficient, and carrier lifetime in semiconductor lasers using a parasitic-free optical modulation technique

An optical modulation technique is used to determine three important parameters for 1.3 μm InGaAsP diode lasers: the rate of spontaneous emission into the guided modes, the nonlinear gain coefficient, and the carrier lifetime at threshold. These results are unaffected by electrical parasitics, and are essential to understanding the noise and modulation properties of diode lasers.

Gain-switched picosecond pulse (&amp;gt;10 ps) generation from 1.3 mu m InGaAsP laser diodes

Fabry-Perot-type laser diodes with high injection efficiency were found to be suitable for ultrashort pulse generation. By decreasing cavity length, the shortest pulsewidth of 6.7 ps at a repetition rate of 100 MHz was achieved under a gain switching scheme. A systematic investigation of bias-level-dependence of pulsewidth, peak output power, as well as the effect of cavity-length shortening was performed. Suppression of facet reflection of a laser diode with a normal cavity length was effective in reducing the pulsewidth (from 16.6 to 10.2 ps). It was found that the optimum condition both for minimizing pulsewidth and for maximizing peak output power can be obtained by selecting the DC bias level. The rate equation analysis also indicated that the gain compression factor may not influence the multimode lasers as much under the gain switching condition as single-mode lasers. The influence of electrical parasitics of the lasers is briefly discussed. >

Performance of the Coolidge Solar Thermal Electric Power Plant

Energy performance and equipment evaluation results are presented for the grid-connected Coolidge solar thermal-electric power plant. Performance was determined for each of the major subsystems—line-focus collector array, thermal energy storage and 200 kW, organic Rankine cycle engine and generator. Day-long collector array efficiency was about 32, 26, and 9 percent in June, September, and December, respectively. Energy conversion efficiency was about 20 percent; electrical parasitics reduced this by 12 percent. Operation and maintenance required about 90 h/mo, only 20 percent requiring special skills or training. Operating supplies and repair services cost about $6300 per year. Major equipment problem catagories were fluid leakage and electric motor and electronic component failures. The presented operating data provide a basis for improved design and analysis.

Spice simulation of laser diode modules

For simulating laser diode modules, a subcircuit has been implemented in the SPICE network simulation program. In addition to the properties of the laser chip and electrical package parasitics, incoherent optical reflections from the end of the fibre pigtail are included. Numerical results are compared to measurements on DFB and FP lasers.

Frequency response of an InGaAsP vapor phase regrown buried heterostructure laser with 18 GHz bandwidth

The frequency response of a 1.3-μm InGaAsP vapor phase regrown buried heterostructure laser with an 18-GHz cw bandwidth is analyzed in detail. The intrinsic bandwidth of the device is shown to be 22 GHz and the 3-dB RC roll-off frequency due to electrical parasitics is found to be 10 GHz.

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers, The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.

High-speed modulation of semiconductor lasers

An overview is given of the direct modulation performance of high-speed semiconductor lasers. The high-speed response characteristics are described using a cascaded two-port model of the laser. This model separates the electrical parasitics from the intrinsic laser and enables these subsections to be considered separately. The presentation concentrates on the small-signal intensity modulation and frequency modulation responses, and the large-signal switching transients and chirping. Device-dependent limitations on high-speed performance are explored and circuit modeling techniques are briefly reviewed.