Scalability of strained-Si nMOSFETs down to 25 nm gate length

Strained-Si nMOSFETs with a standard polysilicon gate process were fabricated down to 25 nm gate length with well-behaved characteristics and small difference in short channel effects. The performance enhancement degrades linearly as the gate length becomes shorter, due to not only the parasitic resistance but also heavy halo implant. Thus the key integration issues are how to manage threshold difference and As diffusion without excess doping. With comparable doping and well controlled parasitic resistance, up to 45% improvement in drive current is predicted for sub-50 nm gate length strained-Si nMOSFETs on the Si/sub 0.8/Ge/sub 0.2/ substrate. In this work approximately 45% enhancement is in fact demonstrated for 35 nm gate length devices, through advanced channel engineering and implementation of metal gates.     

Scaled GaAs MESFET's with gate length down to 100 nm

Fully ion-implanted GaAs depletion MESFET's with gate lengths from 1 µm down to 0.1 µm and with closely spaced source and drain contacts have been fabricated with electron-beam lithography. Gate-length dependence of transconductance, capacitance, output conductance, and threshold voltage is presented. Maximum transconductance obtained was 370 mS/mm for 0.1-µm gate length. The experimental data indicate that shallow implants do indeed result in better devices, but further vertical scaling of the devices is mandatory.     

On the time-dependent degradation of LDD n-MOSFETs under hot-carrier stress

A unified model for hot-carrier-induced degradation in LDD n-MOSFETs is presented. A novel oxide spacer charge pumping method enables interface trap generation in the spacer and overlap/channel regions to be distinctly separated. An excellent correlation between trap generation in the spacer region and linear drain current degradation at high gate voltage is observed. Moreover, trap generation in the overlap/channel region is found to correlate well with linear drain current degradation at low gate voltage. The results point unambiguously to a two-mechanism degradation model involving drain resistance increase by trap generation in the spacer region, and carrier mobility reduction by trap generation in the overlap/channel region. The combined effect of a time-independent lateral electron temperature profile and a finite density of interface trap precursors within the LDD region leads to a self-limiting degradation behavior. This insight forms the basis of a time-dependent trap generation model, which indicates the existence of a single degradation curve. The fact that the degradation curves at different stress drain voltages fall onto a time-scaled version of the single degradation curve provides strong support for the model. This also offers a straightforward and yet accurate means by which the hot-carrier lifetime corresponding to a specific failure criterion may be extracted. Finally, a power-law relationship between hot-carrier lifetime and substrate current is also observed for the LDD devices, thus preserving the physical essence based on which earlier lifetime models for conventional drain devices are established.     

Performance of 30 nm Gate Length InAlAs-InGaAs MODFETs: Comparison of Conventional and Asymmetric Coupled-Well Transport Channel Configurations

This paper presents simulation results highlighting the effects of variations in the transverse potential profile of the transport channel, on the electrical characteristics of Modulation Doped Field-Effect Transistors (MODFETs). In particular, the I-V and f_T-V_g characteristics of 30 nm gate length InAlAs-InGaAs MODFETs, having conventional quantum well channels, are in good agreement with our simulations. The simulation further predicts improvement in performance when asymmeteric coupled quantum wells are used as the electron transport channels. Energy bands, 2-D electron distributions, and various I-V characteristics are compared for conventional quantum well and asymmeteric coupled quantum well channels. Both quantum well and quantum wire configurations are enhanced by the incorporation of asymmetric coupled quantum well channel.     

Gate-voltage-dependent effective channel length and series resistance of LDD MOSFET's

A measurement algorithm to extract the effective channel length and source-drain series resistance of MOSFET's is presented. This extraction algorithm is applicable to both conventional and LDD MOSFET's. It is shown that the effective channel length and the source-drain series resistance of an LDD device are gate-voltage dependent. The effective channel length of an LDD device is not necessarily the metallurgical junction separation between the source and drain as it is commonly seen in a conventional device. A more generalized interpretation of effective channel length is introduced to understand the physical meaning of this gate-voltage dependence. The result also indicates that the effective channel length and source-drain resistance are two inseparable device parameters regardless of LDD or conventional FET's.     

Extraction of metallurgical effective channel length in LDD MOSFET's

A new extraction method of metallurgical effective channel length (L/sub met/) in LDD MOSFET's is proposed. This method is based on the clear device physics. First, the carrier density modulation effect is overcome by "paired V/sub TH/" method. Second, the effect of charge sharing is eliminated by extrapolating L/sub eff/ found by "paired V/sub TH/" method to that at zero depletion width between the lightly doped region and the substrate. Both simulation and experimental results demonstrate the accuracy and usefulness of our approach. For example, the device simulation result shows that the extracted L/sub met/ has only 60 /spl Aring/ error compared with the physical dimension defined by the distance between the source and drain n/sup -/ metallurgical junctions. Proposed method is accurate, reliable enough to be used for the routine monitoring in manufacturing environment.<>     

Power scalability to 6 W of 770 nm source based on seeded fibreamplifier and PPKTP

A 6 W average power at 772 nm is achieved by using a fibre integrated optical modulator for seeding of a 10 W erbium fibre amplifier followed by 64% efficient second-harmonic generation in PPKTP. The source benefits from a compact, efficient, fibre-based format and high overall efficiency     

On the accuracy of channel length characterization of LDD MOSFET's

A comprehensive investigation into the various mechanisms that limit the accuracy of channel length extraction techniques for lightly doped drain (LDD) MOSFET's is presented. Analytic equations are derived to quantify the sensitivity of the extraction techniques to the geometry effect, and bias dependence of the n^-source and drain resistance. The analytic approach is supplemented and verified by exercising channel length extraction algorithms on current-voltage characteristics obtained from rigorous numerical simulations of a variety of LDD MOSFET's. The analyses clearly show that low gate overdrives and consistent threshold voltage measurements are required to accurately extract the metallurgical channel length. The analytic equations can be used to project the limitations of channel length extraction methods for future submicrometer LDD MOSFET's.     

Design and Characteristics of the Lightly Doped Drain-Source (LDD) Insulated Gate Field-Effect Transistor

The LDD structure, where narrow, self-aligned n/sup -/ regions are introduced between the channel and the n/sup +/ source-drain diffusions of an IGFET to spread the high field at the drain pinchoff region and thus reduce the maximum field intensity, is analyzed. The design is shown, including optimization of then- dimensions and concentrations and the boron channel doping profile and an evaluation of the effect of the series resistance of the n- regions on device transconductance. Characteristics of experimental devices are presented and compared to those of conventional IGFET's. It is shown that significant improvements in breakdown voltages, hot-electron effects, and short-channel threshold effects can be achieved allowing operation at higher voltage, e.g., 8.5 versus 5 V, with shorter source-drain spacings, e.g., 1.2 versus 1.5 /spl mu/m. Alternatively, a shorter channel length could be used for a given supply voltage. Performance projections are shown which predict 1.7 X basic device/circuit speed enhancement over conventional structures. Due to the higher voltages and higher frequency operation, the higher performance results in an increase in power which must be considered in a practical design.     

Improvement of performance deviation and productivity of MOSFETs with gate length below 30 nm by flash lamp annealing

The impact of new flash lamp annealing (FLA) technology, which both minimizes diffusion to yield a shallow junction and realizes low sheet resistivity, is investigated based on MOSFET fabrication and computer simulations. Productivity can be improved since FLA makes it possible to employ higher acceleration energy ion implantation and higher throughput. The MOSFET performance can be improved and its deviation suppressed by using FLA. In analyzing MOSFETs with gate length (L) of 20 nm by computer simulations, it was clarified that in contrast to spike annealing, the shallow junction realized by applying FLA to pMOSFET fabrication enabled the suppression of |I/sub off/| with a low channel surface dopant concentration. This provided a higher mobility value and a higher drive current. FLA is promising for improving the performance and productivity of sub-30-nm gate-length MOSFETs.     

A new extraction algorithm for the metallurgical channel length ofconventional and LDD MOSFETs

A new extraction algorithm for the metallurgical channel length of conventional and LDD MOSFETs is presented, which is based on the well-known resistance method with a special technique to eliminate the uncertainty of the channel length and to reduce the influence of the parasitic source/drain resistance on threshold-voltage determination. In particular, the metallurgical channel length is determined from a wide range of gate-voltage-dependent effective channel lengths at an adequate gate overdrive. The 2-D numerical analysis clearly show that adequate gate overdrive is strongly dependent on the dopant concentration in the source/drain region. Therefore, an analytic equation is derived to determine the adequate gate overdrive for various source/drain and channel doping. It shows that higher and lower gate overdrives are needed to accurately determine the metallurgical channel length of conventional and LDD MOSFET devices, respectively. It is the first time that we can give a correct gate overdrive to extract L_met not only for conventional devices but also for LDD MOS devices. Besides, the parasitic source/drain resistance can also be extracted using our new extraction algorithm     

具有应变沟道及EOT 1.2nm高性能栅长22nm CMOS器件

深入研究了亚30nm CMOS关键工艺技术，特别是提出了一种新的低成本的提高空穴迁移率的技术--Ge预非晶化S/D延伸区诱生沟道应变技术，它使栅长90nm pMOS空穴有效迁移率在0.6MV/cm电场下提高32%. 而且空穴有效迁移率的改善，随器件特征尺寸缩小而增强. 利用零阶劳厄线衍射的大角度会聚束电子衍射分析表明，在沟道区相应的压应变为-3.6%. 在集成技术优化的基础上，研制成功了高性能栅长22nm应变沟道CMOS器件及栅长27nm CMOS 32分频器电路（其中分别嵌入了57级/201级环形振荡器）, EOT为1.2nm,具有Ni自对准硅化物.     

3—6nm超薄SiO_2栅介质的特性

采用栅氧化前硅表面在 H2 SO4/ H2 O2 中形成化学氧化层方法和氮气稀释氧化制备出 3.2、 4和 6 nm的 Si O2超薄栅介质 ,并研究了其特性 .实验结果表明 ,恒流应力下 3.2和 4nm栅介质发生软击穿现象 .随着栅介质减薄 ,永久击穿电场强度增加 ,但恒流应力下软击穿电荷下降 .软击穿后栅介质低场漏电流无规则增大 .研究还表明 ,用软击穿电荷分布计算超薄栅介质有效缺陷密度比用永久击穿场强分布计算的要大 .在探讨软击穿和永久击穿机理的基础上解释了实验结果     

Two-dimensional numerical simulation of Schottky barrier MOSFETwith channel length to 10 nm

We present simulation results of a silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET), which has a structure similar to that of a conventional MOSFET, but the source and drain regions are now entirely replaced by metals. By using abrupt metal/silicon Schottky junctions, short-channel effects are avoided. Based on a few commonly used physical assumptions, we have calculated the transistor characteristics, and we find that this new three-terminal transistor can offer gain and impedance isolation, desirable for logic circuit applications     

A study of the effects of tunneling currents and reliability of sub-2 nm gate oxides on scaled n-MOSFETs

This work examined various components of direct gate tunneling currents and analyzed reliability of ultrathin gate oxides (1.4–2 nm) in scaled n-metal-oxide-semiconductor field effective transistor (MOSFETs). Direct gate tunneling current components were studied both experimentally and theoretically. In addition to gate tunneling currents, oxide reliability was investigated as well. Constant voltage stressing was applied to the gate oxides. The oxide breakdown behaviors were observed and their effects on device performance were studied. The ultrathin oxides in scaled n-MOSFETs used in this study showed distinct breakdown behavior and strong location dependence. No “soft” breakdown was seen for 1.5 nm oxide with small area, implying the importance of using small and more realistic MOS devices for ultrathin oxide reliability study instead of using large area devices. Higher frequency of oxide breakdowns in the source/drain extension to the gate overlap region was then observed in the channel region. Possible explanations to the observed breakdown behaviors were proposed based on the quantum mechanical effects and point-contact model for electron conduction in the oxide during the breakdown. It was concluded that the source/drain extension to the gate overlap regions have strong effects on the device performance in terms of both gate tunneling currents and oxide reliability.     

亚0.1μm高K栅介质MOSFETs的特性

用二维模拟软件ISE研究了典型的70nm高K介质MOSFETs的短沟性能.结果表明,由于FIBL效应,随着栅介质介电常数的增大,阈值电区减小,而漏电流和亚阈值摆幅增大,导致器件短沟性能退化.这种退化可以通过改变侧墙材料来抑制.     

Leakage Current through the Gate Dielectric in Transistors with Channel Lengths of up to 100 nm

Semiconductors - The temperature dependence of the leakage current through a gate dielectric in a metal?oxide?semiconductor transistor with a design rule of 90 nm formed on a...     

105 nm Gate length pMOSFETs with high-K and metal gate fabricated in a Si process line on 200 mm GeOI wafers

We report on the fabrication and electrical characterization of deep sub-micron (gate length down to 105 nm) GeOI pMOSFETs. The Ge layer obtained by hetero-epitaxy on Si wafers has been transferred using the Smart Cut^TM process to fabricate 200 mm GeOI wafers with Ge thickness down to 60–80 nm. A full Si MOS compatible pMOSFET process was implemented with HfO₂/TiN gate stack. The electrical characterization of the fabricated devices and the systematic analysis of the measured performances (I_ON, I_OFF, transconductance, low field mobility, S, DIBL) demonstrate the potential of pMOSFET on GeOI for advanced technological nodes. The dependence of these parameters have been analyzed with respect to the gate length, showing very good transport properties (μ_h ～ 250 cm²/V/s, I_ON = 436 μA/μm for L_G = 105 nm), and OFF current densities comparable or better than those reported in the literature.     

Estimating oxide thickness of tunnel oxides down to 1.4 nm usingconventional capacitance-voltage measurements on MOS capacitors

High-frequency capacitance-voltage (C-V) measurements have been made on ultrathin oxide metal-oxide-semiconductor (MOS) capacitors. The sensitivity of extracted oxide thickness to series resistance and gate leakage is demonstrated. Guidelines are outlined for reliable and accurate estimation of oxide thickness from C-V measurements for oxides down to 1.4 nm     

Use of the polysilicon gate layer for local interconnect in a CMOStechnology incorporating LDD structures

In conventional single-level polysilicon technologies, the polysilicon gate layer can be used as an interconnect layer through buried contacts between polysilicon and one type of junction (usually n ⁺) in the underlying substrate. The formation and characteristics of buried contacts between n⁺ and p⁺ junctions and a single polysilicon gate layer are discussed. In addition, it is shown that the obstacles posed by the inclusion of oxide-sidewall spacers (common in present-day VLSI CMOS technologies) are surmountable with respect to the formation of useful buried contacts and the resultant local interconnect level that they provide