This article provides a practical introduction to the design trade-offs of the currently available 3D IC technology options. It begins with an overview of techniques, such as wire bonding, microbumps, through vias, and contactless interconnection, comparing them in terms of vertical density and practical limits to their use. We then present a high-level discussion of the pros and cons of 3D technologies, with an analysis relating the number of transistors on a chip to the vertical interconnect density using estimates based on Rent's rule. Next, we provide a more detailed design example of inductively coupled interconnects, with measured results of a system fabricated in a 0.35-/spl mu/m technology and an analysis of misalignment and crosstalk tolerances. Lastly, we present a case study of a fast Fourier transform (FFT) placed and routed in a 0.18-/spl mu/m through-via silicon-on-insulator (SOI) technology, comparing the 3D design to a traditional 2D approach in terms of wire length and critical-path delay.

Demystifying 3D ICs: the pros and cons of going vertical

IEEE International Solid-State Circuits Conference

Within-die parameter variation poses a major challenge to high-performance microprocessor design, negatively impacting a processor's frequency and leakage power. Addressing this problem, this paper proposes a microarchitecture-aware model for process variation-including both random and systematic effects. The model is specified using a small number of highly intuitive parameters. Using the variation model, this paper also proposes a framework to model timing errors caused by parameter variation. The model yields the failure rate of microarchitectural blocks as a function of clock frequency and the amount of variation. With the combination of the variation model and the error model, we have VARIUS, a comprehensive model that is capable of producing detailed statistics of timing errors as a function of different process parameters and operating conditions. We propose possible applications of VARIUS to microarchitectural research.

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VARIUS: A Model of Process Variation and Resulting Timing Errors for Microarchitects

Inductive-peaking-based bandwidth extension techniques for CMOS amplifiers in wireless and wireline applications are presented. To overcome the conventional limits on bandwidth extension ratios, these techniques augment inductive peaking using capacitive splitting and magnetic coupling. It is shown that a critical design constraint for optimum bandwidth extension is the ratio of the drain capacitance of the driver transistor to the load capacitance. This, in turn, recommends the use of different techniques for different capacitance ratios. Prototype wideband amplifiers in 0.18-mum CMOS are presented that achieve a measured bandwidth extension ratio up to 4.1 and simultaneously maintain high gain (>12 dB) in a single stage. Even higher enhancement ratios are shown through the introduction of a modified series-peaking technique combined with staggering techniques. Ultra-wideband low-noise amplifiers in 0.18-mum CMOS are presented that exhibit bandwidth extension ratios up to 4.9

Bandwidth Extension Techniques for CMOS Amplifiers

This paper describes a 6.25-Gb/s 14-mW transceiver in 90-nm CMOS for chip-to-chip applications. The transceiver employs a number of features for reducing power consumption, including a shared LC-PLL clock multiplier, an inductor-loaded resonant clock distribution network, a low- and programmable-swing voltage-mode transmitter, software-controlled clock and data recovery (CDR) and adaptive equalization within the receiver, and a novel PLL-based phase rotator for the CDR. The design can operate with channel attenuation of -15 dB or greater at a bit-error rate of 10-15 or less, while consuming less than 2.25 mW/Gb/s per transceiver.

A 14-mW 6.25-Gb/s Transceiver in 90-nm CMOS

In sub 1 V CMOS designs, especially around 0.5 V CMOS designs, the on-state drain current of MOSFET's shows positive temperature dependence, being different from the negative temperature dependence in the conventional voltage designs. Together with the low threshold voltage less than 0.2 V in the low-voltage CMOS, a possibility of temperature instability increases. The paper describes possible temperature instabilities in the low-voltage regime by using circuit simulation environments incorporating temperature change in time and experiments using MOSFET's and 32-bit adder circuit in quarter micron CMOS technology with low threshold voltage of 0.25 V.

Design impact of positive temperature dependence of drain current in sub 1 V CMOS VLSIs

A low-power high-speed chip-to-chip interface scheme is described having a density of 625pins/mm/sup 2/. The interface utilizes capacitively coupled contactless minipads, return-to-half-V/sub 00/ signaling and sense amplifying F/F. The measured test chip fabricated in 0.35/spl mu/m CMOS delivers up to 1.27Gb/s/pin at 3mW/pin.

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1.27Gb/s/pin 3mW/pin wireless superconnect (WSC) interface scheme

This paper describes a low-power write scheme which reduces SRAM power by 90% by using seven-transistor sense-amplifying memory cells. By reducing the bitline swing to V/sub DD//6 and amplifying the voltage swing by a sense-amplifier structure in a memory cell, the charging and discharging component of the power of the bit/data lines is reduced. A 64-kb test chip has been fabricated and correct read/write operation has been verified. It is also shown that the scheme can also have the capability of leakage power reduction with small modifications. Achievable leakage power reduction is estimated to be two orders of magnitude from SPICE simulation results.

90% write power-saving SRAM using sense-amplifying memory cell

A 1.2V 40Gbit/s 4:1 MUX and 1:4 DEMUX are implemented in a in 90nm digital-compatible standard CMOS technology. The MUX and DEMUX operate from a 1.2V supply and draw 110mA and 52mA, respectively. Experimental results show a clear eye opening of 300mV/sub pp/ for the MUX and that of 540mV/sub pp/ for the DEMUX at 40Gbit/s.

40Gb/s 4:1 MUX/1:4 DEMUX in 90nm standard CMOS

The introduction of the IEEE802.15.6 standard (15.6) for wireless-body-area networks signals the advent of new medical applications, where various wireless nodes in, on or around a human body monitor vital signs. Radio communication often dominates the power consumption in the nodes, thus low-power transceivers are desired. Most state-of-the-art low-power transceivers support only proprietary modes with OOK or FSK modulations, and have poor sensitivity or low data rate [1,2]. In this work, a 15.6-compliant transceiver with enhanced performance is proposed. First, the data-rate is extended to 4.5Mb/s to cover multi-channel EEG applications. Second, while a best-in-class energy efficiency of 0.33nJ/b is achieved in the high-speed mode, a dedicated low-power mode reduces the RX power further in low-data-rate operation. Third, a sensitivity 5 to 10dB better than the 15.6 specification is targeted to accommodate extra path loss due to shadowing effects from human bodies.

Kouichi Kanda

Papers

Design impact of positive temperature dependence of drain current in sub 1 V CMOS VLSIs

1.27Gb/s/pin 3mW/pin wireless superconnect (WSC) interface scheme

90% write power-saving SRAM using sense-amplifying memory cell

40Gb/s 4:1 MUX/1:4 DEMUX in 90nm standard CMOS

9.7 A 0.33nJ/b IEEE802.15.6/proprietary-MICS/ISM-band transceiver with scalable data-rate from 11kb/s to 4.5Mb/s for medical applications