International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

The discovery of graphene has ignited intensive interest in two-dimensional layered materials (2DLMs). These 2DLMs represent a new class of nearly ideal 2D material systems for exploring fundamental chemistry and physics at the limit of single-atom thickness, and have the potential to open up totally new technological opportunities beyond the reach of existing materials. In general, there are a wide range of 2DLMs in which the atomic layers are weakly bonded together by van der Waals interactions and can be isolated into single or few-layer nanosheets. The van der Waals interactions between neighboring atomic layers could allow much more flexible integration of distinct materials to nearly arbitrarily combine and control different properties at the atomic scale. The transition metal dichalcogenides (TMDs) (e.g., MoS2, WSe2) represent a large family of layered materials, many of which exhibit tunable band gaps that can undergo a transition from an indirect band gap in bulk crystals to a direct band gap in monolayer nanosheets. These 2D-TMDs have thus emerged as an exciting class of atomically thin semiconductors for a new generation of electronic and optoelectronic devices. Recent studies have shown exciting potential of these atomically thin semiconductors, including the demonstration of atomically thin transistors, a new design of vertical transistors, as well as new types of optoelectronic devices such as tunable photovoltaic devices and light emitting devices. In parallel, there have also been considerable efforts in developing diverse synthetic approaches for the rational growth of various forms of 2D materials with precisely controlled chemical composition, physical dimension, and heterostructure interface. Here we review the recent efforts, progress, opportunities and challenges in exploring the layered TMDs as a new class of atomically thin semiconductors.

Two-dimensional transition metal dichalcogenides as atomically thin semiconductors: opportunities and challenges

Molybdenum disulfide holds great potential for advanced flexible electronic devices. Here, using a transferred gate technique, the authors fabricate molybdenum disulfide-based transistors with optimized device geometry and contact, improving device speed and demonstrating gigahertz circuits with voltage gain.

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Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics

Printed circuit board

This paper provides evidence that, as a result of constant-field scaling, the peak f T (approx. 0.3 mA/μm), peak f MAX (approx. 0.2 mA/μm), and optimum noise figure NF MIN (approx. 0.15 mA/pm) current densities of Si and SOI n-channel MOSFETs are largely unchanged over technology nodes and foundries. It is demonstrated that the characteristic current densities also remain invariant for the most common circuit topologies such as MOSFET cascodes, MOS-SiGe HBT cascodes, current-mode logic (CML) gates, and nMOS transimpedance amplifiers (TIAs) with active pMOSFET loads. As a consequence, it is proposed that constant current-density biasing schemes be applied to MOSFET analog/mixed-signal/RF and high-speed digital circuit design. This will alleviate the problem of ever-diminishing effective gate voltages as CMOS is scaled below 90 nm, and will reduce the impact of statistical process variation, temperature and bias current variation on circuit performance. The second half of the paper illustrates that constant current-density biasing allows for the porting of SiGe BiCMOS cascode operational amplifiers, low-noise CMOS TIAs, and MOS-CML and BiCMOS-CML logic gates and output drivers between technology nodes and foundries, and even from bulk CMOS to SOI processes, with little or no redesign. Examples are provided of several record-setting circuits such as: 1) SiGe BiCMOS operational amplifiers with up to 37-GHz unity gain bandwidth; 2) a 2.5-V SiGe BiCMOS high-speed logic chip set consisting of 49-GHz retimer, 40-GHz TIAs, 80-GHz output driver with pre-emphasis and output swing control; and 3) 1-V 90-nm bulk and SOI CMOS TIAs with over 26-GHz bandwidth, less than 8-dB noise figure and operating at data rates up to 38.8 Gb/s. Such building blocks are required for the next generation of low-power 40-80 Gb/s wireline transceivers.

The invariance of characteristic current densities in nanoscale MOSFETs and its impact on algorithmic design methodologies and design porting of Si(Ge) (Bi)CMOS high-speed building blocks

A differentially tuned VCO is fully integrated in a standard microprocessor 0.12 /spl mu/m SOI CMOS. A phase noise of -101.8dBc/Hz at 1MHz offset is measured with 7.5mW at 1.5V. The VCO tuning range is 9.8% from 40GHz to 44GHz. The output power is up to -6dBm after a single-stage buffer amplifier with 6mW at 1.5V.

A 44GHz differentially tuned VCO with 4GHz tuning range in 0.12 /spl mu/m SOI CMOS

A complementary LC-VCO is integrated in a 65nm SOI process and is statistically characterized on a 300mm wafer. Average center frequency is 67.9GHz and frequency tuning range is 6.14GHz or 9.05%. It achieves a phase noise of -106dBc/Hz at 10MHz offset and consumes 5.37mW from a 1.2V supply. The VCO yield is 94.7% for 70GHz operation.

A 70GHz Manufacturable Complementary LC-VCO with 6.14GHz Tuning Range in 65nm SOI CMOS

SOI CMOS technology offers low parasitic junction capacitance, and therefore provides speed and power enhancements to digital applications compared to bulk CMOS. It is also emerging as a good candidate for high-performance SoC, with integratable RF circuits that operate beyond 30-GHz already demonstrated at the 130-nm technology node. The digital aspects of the base 90-nm SOI technology were previously reported. This paper presents the RF performance of this technology, and shows that the capabilities of CMOS technology are expanding into the millimeter-wave regime.

A 243-GHz F/sub t/ and 208-GHz F/sub max/, 90-nm SOI CMOS SoC technology with low-power millimeter-wave digital and RF circuit capability

This paper reports a thin wafer handling technology that is compatible to CMOS processing conditions to enable 3D integration and assembly with high throughput at low cost. Using pulsed ultraviolet (UV) radiation from excimer lasers, device wafers as thin as 50µm can be released from the temporary mechanical handler wafer in less than 1min. Bonding, adhesive, debonding and post debond clean processes were demonstrated. CMOS circuit test vehicles were shown to be compatible with this temporary bonding and debonding processes.

CMOS compatible thin wafer processing using temporary mechanical wafer, adhesive and laser release of thin chips/wafers for 3D integration

This paper describes the design and technology optimization of power-efficient monolithic VCOs with wide tuning range. Four 5-GHz LC-tank VCOs were fabricated in a 0.12-/spl mu/m SOI CMOS technology that was not enhanced for RF applications. High and regular resistivity substrates were used, as were single-layer and multiple-layer copper inductors. Using a new figure-of-merit (FOM/sub T/) that encompasses power dissipation, phase noise and tuning range, our best VCO has an FOM/sub T/ of -189 dBc/Hz. The measured frequency tuning range is 22 % and the phase noise is 126 dBc/Hz at 1 MHz offset for 4.5-GHz. Oscillation was achieved at 5.4-GHz at a minimum power consumption of 500 /spl mu/W.

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Robert Trzcinski

Papers

A 44GHz differentially tuned VCO with 4GHz tuning range in 0.12 /spl mu/m SOI CMOS

A 70GHz Manufacturable Complementary LC-VCO with 6.14GHz Tuning Range in 65nm SOI CMOS

A 243-GHz F/sub t/ and 208-GHz F/sub max/, 90-nm SOI CMOS SoC technology with low-power millimeter-wave digital and RF circuit capability

CMOS compatible thin wafer processing using temporary mechanical wafer, adhesive and laser release of thin chips/wafers for 3D integration

A power-optimized widely-tunable 5-GHz monolithic VCO in a digital SOI CMOS technology. On high resistivity substrate