Analysis of issues in gate recess etching in the InAlAs/InGaAs HEMT manufacturing process

We have developed an InAlAs/InGaAs metamorphic high electron mobility transistor device fabrication process where the gate length can be tuned within the range of 0.13 μm–0.16 μm to suit the intended application. The core processes are a two-step electron-beam lithography process using a three-layer resist and gate recess etching process using citric acid. An electron-beam lithography process was developed to fabricate a T-shaped gate electrode with a fine gate foot and a relatively large gate head. This was realized through the use of three-layered resist and two-step electron beam exposure and development. Citric acid-based gate recess etching is a wet etching, so it is very important to secure etching uniformity and process reproducibility. The device layout was designed by considering the electrochemical reaction involved in recess etching, and a reproducible gate recess etching process was developed by finding optimized etching conditions. Using the developed gate electrode process technology, we were able to successfully manufacture various monolithic microwave integrated circuits, including low noise amplifiers that can be used in the 28 GHz to 94 GHz frequency range.     

栅槽横向宽度对InAlAs/InGaAs HEMTsDC及RF特性的影响

我们制造出了栅长为88 nm的InP基InAlAs/InGaAs 高电子迁移率器件(HEMTs),该器件的频率特性为ft = 100 GHz, fmax = 185 GHz。本文对横向栅槽宽度分别为300 nm, 412 nm, 1070 nm的器件进行了实验。借助能带图的方式,定性分析了横向栅宽的增加会因为表面态和碰撞电离的作用,使得器件直流特性表现出kink效应,并得到减小横向栅槽宽度能减弱kink效应的结论,文中还讨论了横向栅槽宽度通过改变器件寄生电容及其源漏电阻,从而对频率特性产生影响。这些分析对制造出更高性能的HEMT器件有比较重要的意义。     

栅长90nm的晶格匹配InAlAs／InGaAs／InP HEMT

文章报道了90nm栅长的晶格匹配InP基HEMT器件。栅图形是通过80kV的电子束直写的,并采用了优化的三层胶工艺。器件做在匹配的InAlAs／InGaAs／InP HEMT材料上。当Vds=1．0V时,两指75μm栅宽器件的本征峰值跨导达到720ms／mm,最大电流密度为500mA／mm,器件的阂值电压为．0．8V,截止频率达到127GHz,最大振荡频率达到152GHz。     

Ordering in InGaAs/InAlAs layers

The structure of InCaAs/InAlAs layers lattice matched to an InP substrate, grown on either (100) or on (110) with a 4° tilt toward [111] at 500 and 300°C has been investigated by transmission electron microscopy. High perfection resulted for the layers grown on [001] oriented substrates whereas growth on the near [110] substrates resulted in compositional nonuniformities, macrosteps formation, and ordering of the group III elements. This difference in structural perfection between the two sets of samples was also reflected in differences in electrical properties.     

GaAs基InAlAs/InGaAsMHEMT直流特性研究

报道了用 MBE技术生长的 Ga As基 In Al As/In Ga As改变结构高电子迁移率晶体管 (MHEMT)的制作过程和器件的直流性能。对于栅长为 0 .8μm的器件 ,最大非本征跨导和饱和电流密度分别为 3 5 0 m S/mm和1 90 m A/mm。源漏击穿电压和栅反向击穿电压分别为 4V和 7.5 V。这些直流特性超过了相同的材料和工艺条件下 Ga As基 PHEMT的水平 ,与 In P基 In Al As/In Ga As HEMT的性能相当     

Fabrication of a 120 nm gate-length lattice-matched InGaAs/InAlAs InP-based HEMT

A new PMMA/PMGI/ZEP520/PMGI four-layer resistor electron beam lithography technology is successfully developed and used to fabricate a 120 nm gate-length lattice-matched In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48) As InP-based HEMT,of which the material structure is successfully designed and optimized by our group.A 980 nm ultra-wide T-gate head,which is nearly as wide as 8 times the gatefoot(120 nm),is successfully obtained,and the excellent T-gate profile greatly reduces the parasitic resistance and capaci...     

High-power InAlAs/InGaAs Schottky barrier photodiodes for analog microwave signal transmission

The design,manufacturing and DC and microwave characterization of high-power Schottky barrier In Al As/In Ga As back-illuminated mesa structure photodiodes are presented.The photodiodes with 10 and 15μm mesa diameters operate at≥40 and 28 GHz,respectively,have the output RF power as high as 58 m W at a frequency of 20 GHz,the DC responsivity of up to 1.08 A/W depending on the absorbing layer thickness,and a photodiode dark current as low as 0.04 n A.We show that these photodiodes provide an advantage in the amplitude-to-phase conversion factor which makes them suitable for use in highspeed analog transmission lines with stringent requirements for phase noise.     

太赫兹InP基InAlAs/InGaAs PHEMTs的研制

研制了一种T型栅长为90 nm的InP基In0.52Al0.48As/In0.65Ga0.35As赝配高电子迁移率晶体管(PHEMTs).该器件的总栅宽为2×25 μm,展现了极好的DC直流和RF射频特性,其最大饱和电流密度和最大有效跨导分别为894 mA/mm和1640 mS/mm.采用LRM+ (Line-Reflect-Reflect -Match)校准方法实现系统在1~110 GHz全频段内一次性校准,减小了传统的分段测试多次校准带来的误差, 且测试数据的连续性较好.在国内完成了器件的1~110 GHz全频段在片测试,基于1~110 GHz在片测试的S参数外推获得的截止频率ft和最大振荡频率fmax分别为252 GHz和394 GHz.与传统的测试到40 GHz外推相比,本文外推获得的fmax更加准确.这些结果的获得是由于栅长的缩短,寄生效应的减小以及1~110 GHz全频段在片测试的实现.器件的欧姆接触电阻率减小为0.035 Ω·mm.     

采用InGaAs或InAlAs缓冲层的高In组分InGaAs探测器结构材料特性

利用气态源分子束外延在InP衬底上生长了具有InxGa1-xAs或InxAl1-xAs连续递变缓冲层的高In组分In0.78Ga0.22As探测器结构.通过原子力显微镜、X射线衍射、透射电子显微镜和光致发光对它们的特性进行了表征和比较.结果表明,具有InxGa1-xAs或InxAl1-xAs缓冲层的结构都能获得较平整的...     

88 nm栅长fmax＝201 GHz InP基In0.53Ga0.47As/In0.52Al0.48As HEMT器件

我们成功研制了栅长88 nm, 栅宽2 50 μm, 源漏间距为2.4 μm 的InP基In0.53Ga0.47As/In0.52Al0.48As高电子迁移率器件(HEMT)。栅是使用PMMA/Al/UVⅢ,通过优化电子束曝光时间及其显影时间的方式制作的。这些器件有比较好的直流及其射频特性：峰值跨导、最大源漏饱和电流密度、开启电压、ft和fmax 分别为765 mS/mm, 591 mA/mm, -0.5 V, 150 GHz 和201 GHz。这些器件将非常适合于毫米波段集成电路。     

InGaAs/InAlAs光电导太赫兹发射天线的制备与表征

光电导天线作为太赫兹时域光谱仪产生与探测太赫兹辐射的关键部件，具有重要的科研与工业价值。本文采用分子束外延(MBE)方法制备InGaAs/InAlAs超晶格作为1 550 nm光电导天线的光吸收材料，使用原子力显微镜、光致发光、高分辨X射线衍射等方式验证了材料的高生长质量；通过优化制备条件得到了侧面平整的台面结构光电导天线。制备的光电导太赫兹发射天线在太赫兹时域光谱系统中实现了4.5 THz的频谱宽度，动态范围为45 dB。     

InAlAs/InGaAs PHEMTs的设计及其110GHz全频段小信号建模

90-nm T-shaped gate InP-based In_0.52Al_0.48As/In_0.6Ga_0.4As pseudomorphic high electron mobility transistors were designed and fabricated with a gate-width of 2×30 μm,a source-drain space of 2.5 μm,and a source-gate space of 0.75 μm.DC,RF and small-signal model characterizations were demonstrated.The maximum saturation current density was measured to be 755 mA/mm biased at V_gs=0.6 V and V_ds=1.5 V.The maximum extrinsic transconductance was measured to be 1006 mS/mm biased at V_ds=—0.1V and V_ds=1.5 V.The extrapolated current gain cutoff frequency and maximum oscillation frequency based on S-parameters measured from 0.5 to 110 GHz were 180 and 264 GHz,respectively.The inflection point（the stability factor k=1）where the slope from-10 dB/decade（MSG） to-20 dB/decade（MAG） was measured to be 83 GHz.The smallsignal model of this device was also established,and the S-parameters of the model are consistent with those measured from 0.5-110 GHz.     

有效跨导为1052 mS/mm的高性能InP基In0.52Al0.48As/In0.53Ga0.47As HEMTs

我们成功研制了栅长为0.15 μm、栅宽为2?50 μm、源漏间距为2 μm 的InP 基In_0.52Al_0.48As/In_0.53Ga_0.47As高电子迁移率器件。室温下,当器件V_DS为1.7 V,V_GS为0.1 V时,其有效跨导达到了1052 mS/mm。传输线方法(TLM)测试显示器件的接触电阻为0.032 Ω.mm,器件欧姆接触电阻率为1.03?10_-7Ω.cm_-2. 正是良好的欧姆接触及其短的源漏间距减小了源电阻,进而使得有效跨导比较大。器件还有比较好的射频特性：当V_DS＝1.5 V, V_GS ＝0.1 V 时,f_T和f_max分别为151 GHz,303 GHz。文章报道的HEMT器件非常适合毫米波段集成电路的研制。     

Optical effect in InAlAs/InGaAs/InP MODFET

Analytical results have been presented for an optically illuminated InAlAs/InGaAs/InP MODFET with an opaque gate. Partial depletion of the active region is considered. The excess carriers due to photo generation are obtained by solving the continuity equation. The energy levels are modified due to the generation of carriers. The surface recombination effect has also been taken into account. The results of I-V characteristics have been compared under dark conditions, since under illumination experimental results are not available. The offset voltage, sheet concentration, I-V, and transconductance have been presented and the effect of illumination discussed     

InP衬底上InAlAs异变缓冲层和高铟组分InGaAs的生长温度优化

利用气态源分子束外延技术在InP衬底上生长了包含InAlAs异变缓冲层的In0.83Ga0.17As外延层.使用不同生长温度方案生长的高铟InGaAs和InAlAs异变缓冲层的特性分别通过高分辨X射线衍射倒易空间图、原子力显微镜、光致发光和霍尔等测量手段进行了表征.结果表明, InAlAs异变缓冲层的生长温度越低, X射线衍射倒易空间图 (004) 反射面沿Qx方向的衍射峰半峰宽就越宽, 外延层和衬底之间的倾角就越大, 同时样品表面粗糙度越高.这意味着材料的缺陷增加, 弛豫不充分.对于生长在具有相同生长温度的InAlAs异变缓冲层上的In0.83Ga0.17As外延层, 采用较高的生长温度时, X射线衍射倒易空间图 (004) 反射面沿Qx方向的衍射峰半峰宽较小, 77K下有更强的光致发光, 但是表面粗糙度会有所增加.这说明生长温度提高后, 材料中的缺陷得到抑制.     

InAlAs/InGaAs/InP基PHEMTs小信号建模及低噪声应用

利用改进的小信号模型对采用100nmInAlAs/InGaAs/InP工艺设计实现的PHEMTs器件进行建模, 并设计实现了一款W波段单片低噪声放大器进行信号模型的验证。为了进一步改善信号模型低频S参数拟合差的精度, 该小信号模型考虑了栅源和栅漏二极管微分电阻, 在等效电路拓扑中分别用Rfs和Rfd表示.为了验证模型的可行性, 基于该信号模型研制了W波段低噪声放大器单片.在片测试结果表明:最大小信号增益为14.4dB@92.5GHz, 3dB带宽为25GHz@85-110GHz.而且, 该放大器也表现出了良好的噪声特性, 在88GHz处噪声系数为4.1dB, 相关增益为13.8dB.与同频段其他芯片相比, 该放大器单片具有宽3dB带宽和高的单级增益.     

An 88 nm gate-length In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As InP-based HEMT with f_(max) of 201 GHz

正An 88 nm gate-length In_(0.53)Ga_(0.47)As/In_(0.52)Al_(0.48)As InP-based high electron mobility transistor (HEMT) was successfully fabricated with a gate width of 2×50μm and source-drain space of 2.4μm.The T-gate was defined by electron beam lithography in a trilayer of PMMA/A1/UⅧ.The exposure dose and the development time were optimized,and followed by an appropriate residual resist removal process.These devices also demonstrated excellent DC and RF characteristics:the extrinsic maximum transconductance,the full channel current, the threshold voltage,the current gain cutoff frequency and the maximum oscillation frequency of the HEMTs were 765 mS/mm,591 mA/mm,-0.5 V,150 GHz and 201 GHz,respectively.The HEMTs are promising for use in millimeter-wave integrated circuits.     

Selective photochemical dry etching of GaAs/AlGaAs and InGaAs/InAlAs heterostructures

Selective photochemical dry etching of GaAs layers on AlGaAs using HCl gas and InGaAs layers on InAlAs using CH/sub 3/Br gas is studied. A low pressure mercury lamp was used as the deep UV light source. A selectivity of more than 150 for GaAs over AlGaAs and more than 60 for InGaAs over InAlAs was obtained.<>     

The importance of electrochemistry-related etching in thegate-groove fabrication for InAlAs/InGaAs HFETs

For the first time, the surface metal on nonalloyed ohmic electrodes is found to significantly change the profiles of gate grooves, when resist openings are employed to monitor drain current during wet-chemical gate recess for sub-micron InAlAs/lnGaAs heterojunction field-effect transistors (HFETs). The surface metal of Ni enhances the etching rate in comparison with that in the absence of electrodes by a factor of 4 and 10, laterally and vertically, which is favorable to fabricate deep gate grooves with small side etching. The Pt surface metal, however, leads to preferential etching of InGaAs over InAlAs, which can be useful to realize large side etching. The existence of an electrochemistry-related etching component, which arises when the ohmic electrodes are present during recess etching, is considered to be responsible for these behaviors     

Optimization of charge and multiplication layers of 20-Gbps InGaAs/InAlAs avalanche photodiode

We calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch-through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3-dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps.