Submicrometer CMOS device fabrication using an X-ray stepper

CMOS devices with submicrometer minimum features have been fabricated using X-ray/photo hybrid lithography. The device fabrication process utilized thirteen lithography steps, including four X-ray lithography levels, such as local oxidation of silicon (LOCOS) [1], gate, contact, and wiring, that required the most critical dimension control and alignment accuracy. A step and repeat exposure system and a SiNxmembrane mask were used for the X-ray lithography process. The SiNxmembrane mask was improved in its flatness and effective contrast by employing a stress compensating structure and a secondary electron trapping film. As a result, CMOS devices with 0.4-µm effective channel length were fabricated using a single-layer resist process.     

纳米压印制作半导体激光器的分布反馈光栅

分布反馈(DFB)光栅的制作是半导体激光器芯片的关键工艺,通过纳米压印技术在InP基片表面涂覆的光刻胶上压印出DFB光栅图形,并分别通过湿法腐蚀和干法刻蚀技术将光栅图形转移到InP基片上。所制作的DFB光栅周期为240nm(对应于1 550nm波长的DFB激光器),光栅中间具有λ/4相移结构。采用纳米压印技术制作的DFB光栅相对于通常双光束干涉法制作的光栅具有更好的均匀性以及更低的线条粗糙度,而且解决了双光束干涉法无法制作非均匀光栅的技术难题。相对于电子束直写光刻法,采用纳米压印技术制作DFB光栅具有快速与低成本的优势。采用纳米压印技术在InP基片上成功制作具有相移结构的DFB光栅,为进一步进行低成本高性能的半导体激光器芯片的制作奠定了良好基础。     

Investigations on a microfabricated FWTWT oscillator

A vacuum tube oscillator fabricated by the deep etch X-ray lithography: lithographie, galvanoformung, abformung (LIGA) process was successfully developed for the first time. For the proof-of-concept experiment involving a delayed feedback oscillator, a folding-waveguide traveling-wave tube (FWTWT) was fabricated by computer numerical control milling in advance. With a 12.4-kV and 150-mA electron beam, a Ka-band FWTWT amplifier shows a linear gain of 25 dB and a bandwidth of 10%. Applying a delayed feedback scheme, the threshold feedback strengths for the onset of oscillation and for self-modulation were measured to be -30 dB and -16 dB, respectively. The optimum value of the feedback strength for the single-frequency oscillation at 32.5 GHz was about -18 dB with a net electronic efficiency of 6%. The LIGA-fabricated FWTWT circuit was constructed by a lithographic process using the synchrotron X-ray source at the Pohang Light Source. The resulting accuracy and average surface roughness were less than 10 and 1 /spl mu/m, respectively. The LIGA-fabricated Ka-band amplifier shows a linear gain of 15 dB and bandwidth of 1.7% with a 12.4-kV, 47-mA electron beam. The threshold for the onset of oscillation was about -11 dB and the optimum value of feedback strength for a single frequency oscillation at 35 GHz with a net electronic efficiency of 3.5% was about -8 dB.     

Vertical InP/InGaAsP tapers for low-loss optical fibre-waveguide coupling

The authors have realised vertically tapered and antireflection-coated waveguides in InP/InGaAsP with 1.7 dB coupling loss and relaxed alignment tolerances to lensed single-mode fibres with spot diameters of 3.8 mu m. The waveguide tapers are fabricated by a dip-etch process that is well suited for integration with optical waveguide circuits.<>     

Embedded channel polyimide waveguide fabrication by direct electronbeam writing method

A new embedded channel polyimide waveguide fabrication process by a direct electron beam writing method (DEBWM) is described. The new technique uses an electron-beam induced effect to directly alter the refractive indices of the two-layer polyimide. Both the core and the lower cladding have been fabricated at the same time in two-layer polyimides using electron beam with 25 keV energy. The obtained embedded channel waveguide was made of two kinds of polyimides, one for lower cladding and one for core and other claddings. Guide losses are 0.3 dB/cm for both TE and TM polarized incident lights and guiding mode is single-mode for TE. The optical properties of the waveguide and a relationship between the doses of electron beam and optical losses or loss dependence on wavelength are also mentioned     

基于相位掩模板的常规光纤制备弱反射光栅

为了探索采用常规单模光纤制备弱反射光纤光栅的可行性,以降低材料成本和传输损耗,基于相位掩模板法,在常规单模光纤上刻制弱反射光纤布喇格光栅(WFBG),并进行了实验验证.建立相位掩模板刻栅系统光场统一方程,分析光场分布对光纤布喇格光栅(FBG)中心波长和反射率的影响;采用传输矩阵法分析相位掩模板长度、平均折射率变化对FB...     

Fabrication of nickel stamp with improved sidewall roughness for optical devices

We proposed the simple and attractive fabrication method of nickel stamp with improved sidewall roughness for polymeric optical devices. For this, the imprinted optical devices patterns under optimum imprinting conditions were annealed to improve the sidewall roughness generated by the DRIE process in the silicon stamp fabrication. The annealed sidewall roughness is reduced to 24.6 nm, nearly decreasing by 76% compared with the result before the annealing. Then, low cost and durable nickel stamp with improved sidewall roughness was fabricated by the annealed polymeric patterns being used as original master for electroforming process. And, we verified the superiority of the improved nickel stamp by comparing the optical propagation losses for optical waveguides to be fabricated, respectively, using the nickel stamp and original silicon stamp. The optical waveguides fabricated by the imprint lithography using the improved nickel stamp was demonstrated that their optical losses were reduced as 0.21 dB/cm, which was less than the propagation loss for polymeric waveguides using the conventional original silicon stamp. This result could show the effectiveness of the fabricated nickel stamp with improved sidewall roughness. Furthermore, we were able to successfully fabricate a polymeric 1 × 8 beam splitter device using the improved nickel stamp. And, the insertion loss for eight channels obtained to be from 10.02 dB to 10.91 dB.     

用于单片集成的InP阵列波导光栅设计和制备

InP 阵列波导光栅(AWG)是InP 基单片多波长转换器中的重要单元。采用深脊型波导结构,设计了一种10通道、通道间隔200GHZ(1.6nm)的偏振无关型InP基阵列波导光栅。采用外延技术、光刻、感应耦合等离子体刻蚀技术等在实验室制造出了这种AWG。经过测试,插入损耗约为-8dB,串扰小于-17dB,中心通道和旁边通道的通道均匀性基本上在3dB左右。     

Realization of an Ultracompact Low-Loss Photonic Crystal Corner Mirror

We report on the realization and characterization of an ultracompact, low-loss, and broadband corner mirror based on photonic crystals (PCs). By modifying the boundary layers of the PC region, extra losses of dB per corner mirror are achieved for transverse-electronic polarization for silicon-on-insulator ridge waveguides fabricated by electron beam lithography and inductively coupled plasma etching. Dimensions of the PC corner mirror are less than, which are only about one tenth of conventional waveguide corner mirrors.     

Design of single-mode step-tapered waveguide sections

Single-mode step-tapered waveguide sections are analyzed in an effort to determine how the various device parameters, specifically, taper function, mask spot size, and taper length, affect power loss. The results indicate that 1) for short to medium length tapers, linear tapers exhibit the lowest loss, whereas for long tapers, all of the taper functions exhibit essentially the same loss; 2) for single-mode transitions with waveguide widths in the range2-15 mum, the loss in a step-tapered waveguide section can be nearly minimized as long as the mask spot size is chosen such that there are at least 20-25 steps in the taper; and 3) the length of a given taper for minimum power loss is strongly influenced by the asymmetry of the waveguide structure.     

高高宽比硬X射线聚焦波带片的制作

相对于软X射线显微成像,硬X射线显微成像对菲涅尔波带片的吸收体厚度提出了更高的要求.采用电子束光刻和X射线光刻复制的方法,在聚酰亚胺薄膜上成功制作了高高宽比的菲涅尔波带片.首先利用电子束光刻和微电镀技术制作了X射线光刻的掩模,然后利用X射线光刻和微电镀制作了高高宽比、线条侧壁陡直的菲涅尔波带片.复制后的波带片最外环宽度500 nm,直径1 mm,吸收体金厚度为3.6μm,高宽比达到7.2,可用于10 keV～25 keV的硬X射线成像.     

A New Approach of Lateral RF MEMS Switch

This paper presents a novel lateral series microwave switch fabricated on a silicon-on-insulator (SOI) substrate with a finite ground coplanar waveguide (FGCPW) configuration which is laterally actuated by the electrostatic force. The switch is built with a cantilever beam in the direction of the signal line and a fixed electrode is located opposite the cantilever beam. The mechanical structures are fabricated using SOI deep reactive ion etching (DRIE) and shadow mask technology. The fabricated lateral RF MEMS switch has an isolation of 16 dB at 20 GHz. The insertion loss of the switch is 1 dB and return loss is 15 dB at 20 GHz. The threshold voltage is 19.2 V and switching time is 30 s.     

Photonic integrated circuits by DUV-induced modification of polymers

The results achieved with polymer Y-splitters, codirectional couplers, and multimode interference couplers, realized by deep ultraviolet lithography are presented. The devices are designed and fabricated for the 1.55-/spl mu/m wavelength region and have a waveguide loss of 1 dB/cm. The waveguide width is 7.5 /spl mu/m. The fiber-chip coupling loss is 0.5 dB per facet. The polarization-dependent loss is <0.15 dB.     

Optical fiber up-tapers with high beam expansion ratios forcomponent fabrication

Optical fibre up-tapers with beam expansion ratios of 10, about twice the previously achieved value for the same taper outer diameter, have been fabricated and characterized. The increased beam expansion is achieved with a near step-index profile for the core of the taper. The excess coupling loss between two tapers is less than 0.1 dB. A lateral offset of more than 20 μm or an axial displacement of 4 mm between tapers caused an excess loss of 1 dB. The angular tolerance for this loss is a manageable 0.3°. These tapers permit, for a given beam expansion ratio, the manufacture of smaller outer diameter, more compact structures of self-aligned beam expansion. They also permit the insertion of optical elements into the expanded beam for the fabrication of inline single-mode passive fiber components     

Efficient Planar-Integrated Free-Space Optical Interconnects Fabricated by a Combination of Binary and Analog Lithography

Design, fabrication, and experimental testing of an integrated microoptical module for interconnection are reported. The systems integration is based on the concept of planar-integrated free-space optics. The module combines diffractive-reflective and refractive microoptics. The diffractive elements were fabricated by binary lithography and reactive ion etching. The refractive elements were made by analog lithography using a high-energy beam sensitive mask and replication in Ormocer. The fabricated module implemented a simple one-dimensional optical interconnect. Two versions were implemented for which insertion losses of approximately 8 and 4.5 dB were measured, respectively.      

Monolithic waveguide zinc-oxide-on-silicon convolver

A monolithic waveguide zinc-oxide-on-silicon convolver has been constructed and operated at a centre frequency of 125 MHz. The zinc oxide is originally deposited over the whole substrate and then etched to form the waveguide. The waveguide width is 1/10 of the beam width at the input transducers, which should yield a 20 dB improvement in efficiency over a normal convolver with a beam width equal to the transducer width, after accounting for the loss in the input tapers. Such an improvement was observed in experimental devices.     

8通道-1.6nm Si纳米线阵列波导光栅的设计与制作

设计了基于绝缘层上硅(SOI)材料的8通道Si纳米线阵列波导光栅(AWG),器件的通道间隔为1.6nm,面积为420μm×130μm。利用传输函数法模拟了器件传输谱,结果表明,器件的通道间隔为1.6nm,通道间串扰为17dB。给出了结合电子束光刻(EBL)和感应耦合等离子(ICP)刻蚀技术制备器件的详细流程。光谱测试结果分析表明,器件通道间隔为1.3～1.6nm,通道串扰为3dB,中心通道损耗为11.6dB。     

一种采用双面对准的硅LIGA掩模制作研究

深Ｘ射线光刻是制作高深宽比ＭＥＭＳ结构的一个重要的方法。提出一种基于硅工艺和双面对准技术的ＬＩＧＡ掩模技术,工艺十分简单。采用该掩模,可进一步解决深Ｘ射线光刻中的重复对准多次曝光问题,给出了该掩模设计制作工艺过程及深Ｘ射线光刻结果,整个过程包括常常氮化夺、采用Ｋａｒｌ Ｓｕｓｓ双面对准曝光机进行ＵＶ光刻、电化学沉积金吸收体、体硅腐蚀形成支撑等。利用该掩模在北京ＢＥＰＣ的Ｘ射线光刻光束线上进行曝光。     

Semiconductor lasers with 2-D-photonic crystal mirrors based on awet-oxidized Al2O3-mask

We have fabricated and investigated AlGaAs-InGaAs-based ridge waveguide (RWG) lasers with two-dimensional (2-D) triangular photonic crystal (PC) mirrors using a wet-oxidized Al₂O₃ mask for the dry etching of the PC at one end of the ridge. The laser structure includes a 60-nm-thick AlAs layer positioned in the upper cladding, which is converted into Al₂O₃ after the definition of the PC by electron beam lithography and shallow etching. Etching of the holes is then continued using the Al₂O₃ mask, to a final depth of 600 nm. The continuous-wave characteristics of the lasers show a clear dependence on the period of the PC including a significant decrease of the threshold current and an increase of the efficiency for properly adjusted crystal parameters     

Low-loss near-infrared passive optical waveguide components formedby electron beam irradiation of silica-on-silicon

Results are presented for a range of near infrared single-mode passive channel waveguide optical components fabricated in PECVD silica-on-silicon by electron beam irradiation. The devices include S-bends, Mach-Zehnder interferometers, Y-junction tree-structured splitters, and directional couplers. It is shown that low loss may be obtained through appropriate choice of waveguide bend radius and fabrication parameters; fiber-device insertion losses of ≈2 dB and ≈1 dB are achieved for 1×8 splitters and 3-dB directional couplers, respectively, at λ=1.525 μm