基于MOCVD再生长n_+ GaN欧姆接触工艺f_T/f_(max)>150/210 GHz的AlGaN/GaN HFETs器件研究（英文）

基于SiC衬底AlGaN/GaN异质结材料研制具有高电流增益截止频率(fT)和最大振荡频率(fmax)的AlGaN/GaN异质结场效应晶体管(HFETs).基于MOCVD外延n+GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(Lsd)缩小至600 nm.此外,采用自对准工艺制备了60 nm T型栅.由于器件尺寸的缩小,在Vgs=2 V下,器件最大饱和电流(Ids)达到2.0 A/mm,该值为AlGaN/GaN HFETs器件直流测试下的最高值,器件峰值跨导达到608 mS/mm.小信号测试表明,器件fT和fmax最高值分别达到152 GHz和219 GHz.     

f_T为350 GHz的InAlN/GaN HFET高频器件研究（英文）

采用再生长n~+GaN非合金欧姆接触工艺研制了具有高电流增益截止频率(f_T)的InAlN/GaN异质结场效应晶体管(HFETs),器件尺寸得到有效缩小,源漏间距减小至600 nm.通过优化干法刻蚀和n~+GaN外延工艺,欧姆接触总电阻值达到0.16Ω·mm,该值为目前金属有机化学气相沉积(MOCVD)方法制备的最低值.采用自对准电子束曝光工艺实现34 nm直栅.器件尺寸的缩小以及欧姆接触的改善,器件电学特性,尤其是射频特性得到大幅提升.器件的开态电阻(R_(on))仅为0.41Ω·mm,栅压1 V下,漏源饱和电流达到2.14 A/mm.此外,器件的电流增益截止频率(f_T)达到350 GHz,该值为目前GaN基HFET器件国内报道最高值.     

基于MOCVD再生长n+ GaN 欧姆接触工艺fT/fmax＞150/210 GHz的AlGaN/GaN HFETs器件研究

基于SiC衬底AlGaN/GaN异质结材料研制具有高电流增益截止频率(fT)和最大振荡频率(fmax)的AlGaN/GaN异质结场效应晶体管(HFETs).基于MOCVD外延n+ GaN 欧姆接触工艺实现了器件尺寸的缩小, 有效源漏间距(Lsd)缩小至600 nm.此外, 采用自对准工艺制备了60 nm T型栅.由于器件尺寸的缩小, 在Vgs=2 V下, 器件最大饱和电流(Ids)达到2.0 A/mm, 该值为AlGaN/GaN HFETs器件直流测试下的最高值, 器件峰值跨导达到608 mS/mm.小信号测试表明, 器件fT和fmax最高值分别达到152 GHz和219 GHz.     

电流增益截止频率为236GHz的InAIN/GaN高频HEMT

研制了高电流增益截止频率(fT)的InAlN/GaN高电子迁移率晶体管(HEMT).采用金属有机化学气相沉积(MOCVD)再生长n+GaN非合金欧姆接触工艺将器件源漏间距缩小至600 nm,降低了源、漏寄生电阻,有利于改善器件的寄生效应;使用低压化学气相沉积(LPCVD)生长SiN作为栅下介质,降低了InAlN/GaN HEMT栅漏电;利用电子束光刻实现了栅长为50 nm的T型栅.此外,还讨论了寄生效应对器件fT的影响.测试结果表明,器件的栅漏电为3.8 μA/mm,饱和电流密度为2.5 A/mm,fT达到236 GHz.延时分析表明,器件的寄生延时为0.13 ps,在总延时中所占的比例为19％,优于合金欧姆接触工艺的结果.     

超薄势垒InAlN/GaN HFET器件高频特性分析

采用二次外延重掺杂n+ GaN实现非合金欧姆接触,并通过优化干法刻蚀和金属有机化学气相沉积(MOCVD)外延工艺,有效降低了欧姆接触电阻.将非合金欧姆接触工艺应用于InAlN/GaN异质结场效应晶体管(HFET)器件制备,器件的有效源漏间距缩小至600 nm.同时,结合40 nm T型栅工艺,制备了高电流截止频率(fT)和最大振荡频率(fmax)的InAlN/GaN HFET器件.结果显示减小欧姆接触电阻和栅长后,器件的电学特性,尤其是射频特性得到大幅提升.栅偏压为0V时,器件最大漏源饱和电流密度达到1.88 A/mm;直流峰值跨导达到681 mS/mm.根据射频小信号测试结果外推得到器件的fT和fmax同为217 GHz.     

基于60 nm T型栅fT & fmax为170 & 210 GHz 的InAlN/GaN HFETs 器件

基于蓝宝石衬底InAlN/GaN异质结材料研制具有高电流增益截止频率(fT)和最大振荡频率(fmax)的InAlN/GaN异质结场效应晶体管 (HFETs)。基于再生长n GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(Lsd)缩小至600 nm。此外,采用自对准栅工艺制备60 nm T型栅。由于器件尺寸的缩小,在Vgs= 1 V下,器件最大饱和电流(Ids)达到1.89 A/mm,峰值跨导达到462 mS/mm。根据小信号测试结果,外推得到器件的fT和fmax分别为170 GHz和210 GHz,该频率特性为国内InAlN/GaN HFETs器件频率的最高值。     

基于再生长欧姆接触工艺的220 GHz InAlN/GaN场效应晶体管（英文）

在蓝宝石衬底上研制了具有高电流增益截止频率(f_T)的InAlN/GaN异质结场效应晶体管(HFETs).基于MOCVD外延n+-GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(Lsd)缩小至600 nm.此外,采用自对准工艺制备了50 nm直栅.由于器件尺寸的缩小,Vgs=1 V下器件最大饱和电流(I_(ds))达到2.11 A/mm,峰值跨导达到609 mS/mm.根据小信号测试结果,外推得到器件的fT和最大振荡频率(fmax)分别为220 GHz和48 GHz.据我们所知,该f_T值是目前国内InAlN/GaN HFETs器件报道的最高结果.     

基于60nmT型栅f_T&f_(max)为170&210 GHz的InAlN/GaN HFETs器件（英文）

基于蓝宝石衬底InAlN/GaN异质结材料研制具有高电流增益截止频率(f_T)和最大振荡频率(f_(max))的InAlN/GaN异质结场效应晶体管(HFETs).基于再生长n+GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(Lsd)缩小至600nm.此外,采用自对准栅工艺制备60nmT型栅.由于器件尺寸的缩小,在Vgs=1V时,器件最大饱和电流(Ids)达到1.89A/mm,峰值跨导达到462mS/mm.根据小信号测试结果,外推得到器件的f_T和f_(max)分别为170GHz和210GHz,该频率特性为国内InAlN/GaNHFETs器件频率的最高值.     

大电流密度高性能AlGaN/GaN HEMT器件研制

在SiC衬底上制备得到了表面钝化氮化硅(SiN)的AlGaN/Ga N高电子迁移率场效应晶体管(HEMTs)。采用高电子浓度的AlGaN/GaN异质结材料、90 nm T型栅、100 nm SiN表面钝化、低欧姆接触以及较短漏源间距等方法来提升器件性能。在Vgs=4 V时器件的最大漏源饱和电流密度为1.72 A/mm,最大跨导为305 m S/mm,此结果为国内报道的AlGaN/GaN HEMT器件最大漏源饱和电流密度。此外,栅长为90 nm T型栅器件的电流增益截止频率(fT)为109GHz,最大振荡频率(fmax)为144 GHz。     

基于再生长欧姆接触工艺的220 GHz InAlN/GaN 场效应晶体管

本文在蓝宝石衬底上研制了具有高电流增益截止频率(f_T)的InAlN/GaN异质结场效应晶体管 (HFETs)。基于MOCVD外延n -GaN欧姆接触工艺实现了器件尺寸的缩小,有效源漏间距(L_sd)缩小至600 nm。此外,采用自对准工艺制备了50 nm直栅。由于器件尺寸的缩小,V_gs= 1 V下器件最大饱和电流(I_ds)达到2.11 A/mm,峰值跨导达到609 mS/mm。小信号测试表明,器件f_T达到220 GHz、最大振荡频率(f_max)达到48 GHz。据我们所知,该f_T值是目前国内InAlN/GaN HFETs器件报道的最高结果。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.