Analysis of the propagation losses of InP/InGaAsP trench waveguides fabricated by focused ion beam

Focused ion beam was used to fabricate 2 mm-long, 4 μm-wide and 4 μm-deep multimode trench waveguides in InP/InGaAsP. An automated stitching method was developed to fabricate mm-long structures using alignment marks. The waveguides were sputtered or etched using I₂ at room temperature and 150 °C stage temperature. The propagation losses induced by the different fabrication techniques were measured and ranged between 50 and 82 dB/cm. A damaged layer with implanted Ga and the sidewall roughness are identified to be the most important causes for the losses. FIB is shown to be a single-step fabrication technique for rapid-prototyping of photonic structures in InP/InGaAsP.     

Improved cutoff frequency in vertical bipolar transistors fabricated with focused ion beam lateral base profiles

Improved high-frequency performance in vertical bipolar transistors in which the active base region is fabricated with focused ion beam (FIB) lateral doping profiles is demonstrated. Profiles which reduce base resistance, current crowding, and high-level injection effects have the most significant effect on high-frequency characteristics.     

Optical waveguides fabricated on polymer substrate by electron beam

In the field of optical telecommunication, polymers are an interesting class of materials for the fabrication of passive optical devices. Electron beam (EB) irradiation appears as a promising method to achieve structures presenting a layer with a modified index of refraction, and therefore to generate optical waveguiding. The poly(diethylene glycol bis(allyl carbonate)) studied here fulfils the requirements of high transparency and is consequently widely used by the optical industry. A scanning electron microscope delivers the EB with a highest energy of 30 keV. The electrons induce an increase of the substrate refractive index (≥8×10⁻³ for an electronic fluence ≥5×10¹⁴ e/cm²) on a thickness corresponding to the penetration depth of the electrons in the material (≤10 μm for a 25 keV EB). Some optical characteristics are presented such as, the surface refractive index, the effective indices and, therefore, the index profile of the waveguides.     

Lateral-mode discrimination in ridge waveguides by misaligned totalinternal reflection mirrors

Lateral-mode discrimination by misaligned total internal reflection (TIR) mirrors in multimode ridge waveguide structures is proposed. The effects of angular misalignment in TIR mirrors and index steps in ridge waveguides on the modal reflectivity is analyzed by a plane wave expansion method. The modal reflectivity of a high order mode decreases more rapidly than that of a fundamental mode as the angular misalignment of TIR mirrors increases. It is found that a fundamental mode can have high modal reflectivity (~0.9) with significant lateral-mode discrimination over high-order modes if the ridge waveguides have large index steps     

Electron beam and ion beam fabricated microwave switch

A combination of electron beam and ion beam techniques were used in conjunction with conventional planar technology to fabricate a junction field-effect microwave switch. A digital tape-controlled scanning electron beam was used to expose mask patterns in polymethyl methacrylate resist whose line widths (≤1 um) are inaccessible to conventional photolithography; ion beam sputtering was used to remove a thin gold undercoat from within the exposed patterns, thereby maintaining the good edge resolution; and ion implantation was used to dope the closely spaced interdigitated source and drain regions thus exposed by the preceding process steps in the gold contact mask.     

离子束刻蚀法制作菲涅耳透镜

由于衍射光学元件独特色的色散特性及体积小、重量轻可进行复制等优点,它在国防、生产及科研等领域的作用越来越重要,应用于光学成像系统,不仅能改善系统成像质量,而且能实现系统的轻量化、小型化,增加系统设计的自由度。使用离子束刻蚀法制作的16阶菲涅耳透镜应用于折衍混合CCD相机;测量菲涅耳透镜的衍射效率并分析了影响衍射效率的因素。     

Semiconductor microlenses fabricated by one-step focused ion beamdirect writing

We fabricated a refractive semiconductor micro-lenses using a focused ion beam (FIB) direct writing technique. The simple one-step FIB process produced high-quality micro-lenses of silicon, the most popular and low cost semiconductor material used in optoelectronics. A spherical Si microlens with a nominal lens diameter of 48 μm exhibited a radius curvature and focal length of 100 and 40 μm, respectively. The maximum derivation between the measured and designed profiles is less than λ/100. The surface roughness, RMS, measured by use of atomic force microscope in 1× 1 μm² square area, is 1.1 nm. This microlens fabrication method could be readily applicable due to the simplicity in processing and the high-quality results     

Distortion of a simple Gaussian beam on reflection from off-axis ellipsoidal mirrors

We examine the distortion of a simple linearly polarised Gaussian beam on reflection from an off-axis ellipsoidal mirror. Expressions are derived for the distorted reflected fields and for the loss of power into higher order and cross-polarised modes.     

Low loss channel waveguides fabricated in fused silica by germaniumion implantation

The authors report the first low loss channel waveguides (0.10 0.15 dB/cm) formed in fused silica by the implantation of MeV Ge ions. The loss coefficient α was measured as a function of ion dose (8×10¹³-8×10¹⁶ ion/cm²) and annealing temperature (250 to 600°C) at 1300 nm. The as-implanted waveguides exhibited a minimum value of α=0.9 dB/cm at an intermediate range of dose with a reduction to 0.10-0.15 dB/cm after annealing at 500°C     

Optical waveguides fabricated by electric-field controlled ion exchange in glass

Electric-field assisted silver-sodium ion exchange fabrication of low-loss waveguides in glass has been demonstrated. The process can be very fast and the index distribution controllable.     

Laterally coupled DBR laser emitting at 1.55 /spl mu/m fabricated by focused ion beam lithography

By using focused ion beam lithography high performance 1.55-/spl mu/m emitting distributed Bragg reflector lasers were realized suitable for high-speed optical telecommunication. Threshold currents of 8 mA and continuous-wave efficiencies of 0.37 W/A for 600-/spl mu/m-long devices were achieved. Stable single-mode emission with sidemode suppression ratios of > 40 dB were observed for the entire operation range. By relative intensity noise measurements an intrinsic 3-dB modulation frequency of > 10 GHz was estimated for a single-mode output power of 23 mW.     

Bismuth nano-Hall probes fabricated by focused ion beam milling fordirect magnetic imaging by room temperature scanning Hall probemicroscopy

Bismuth nano-Hall probes with dimensions ~120 × 120 nm were fabricated by focused ion beam milling and used for the direct room temperature magnetic imaging of crystalline garnet thin films and strontium ferrite permanent magnets by scanning Hall probe microscopy. At driving currents of 40 μA, the Hall coefficient and magnetic field sensitivity of the Bi nano-Hall probes were 3.3 × 10^-4 Ω/G and 7.2 G/√Hz, respectively     

Prediction of nanopattern topography using two-dimensional focused ion beam milling with beam irradiation intervals

Beam irradiation intervals are a critical parameter in the fabrication of nanopatterns via focused ion beam (FIB) milling. The beam irradiation intervals are defined in terms of the overlap. In this paper, the nanopattern height on a silicon surface is predicted using a mathematical FIB milling model that varies the overlap. The proposed model takes into account the angle dependence of the sputtering yield and redeposition effect, together with the superposition of a bi-Gaussian beam. The model was verified by comparing the results of a nanopattern machining experiment to those of a simulation based on the model. The simulation calculated the final two-dimensional geometry from ion milling parameters. The results of the simulation indicate that the proposed model is more precise than one that only considers the superposition of a Gaussian beam.     

Creation of convex microlenses in PDMS with focused MeV ion beam

In this work the creation of convex microlenses is presented in polydimethylsiloxane using shrinkage of the polymer due to energetic ions. The creation process is based on the observation that the PDMS shrinks due to irradiation and the surface of the unirradiated areas will have a regular curvature between the irradiated places. The created microlenses were arranged in arrays, the diameters were varied between 15 and 200 μm. The properties of the lenses were investigated using an AFM and a profilometer. The profile of the lenses turned out to be parabolic, the focal lengths were found to be between 18 and 180 μm, that can be adjusted with the delivered ion fluence and the lens diameter.     

A comparison of focused ion beam and electron beam induced deposition processes

Focused ion and electron beams are used for local deposition of conducting or insulating films. Major applications are integrated circuit design edit, prototype modification, repair of masks, and machining of microsystems. In this paper, the dependence of the deposition rates versus the beam parameters for both, ion beam and electron beam induced deposition were investigated and compared with each other. At the same time, a more precise consideration of the influence of secondary electrons on the deposition process was accomplished.     

Electron beam testing of VLSI circuits assisted by focused ion beam etching

Electron beam testing assisted by focused ion beam etching was examined. Before electron beam testing (EB testing), a small window was made in the passivation film by focused ion beam etching (FIB etching). EB testing was performed through this window. This method was useful because charge buildup on the passivation film is avoided during EB testing. The threshold voltage shift caused by FIB etching was permitted until the residual film thickness on the gate electrode became 0.5μm. This technique was applied to measure the internal voltage waveform of the 256K bit dynamic RAM and confirmed that it was effective for functional testing and failure analysis of VLSI circuits.     

Electron backscattering diffraction investigation of focused ion beam surfaces

A focused ion beam (FIB) instrument has been used to mill surfaces in single-crystal Si and single-crystal Cu for subsequent electron backscattering diffraction (EBSD) analysis. The FIB cuts were performed using a 30 keV and a 5 keV Ga⁺ ion beam at a stage tilt of 20° to provide a readily obtainable 70° surface for direct EBSD investigation in a scanning electron microscope (SEM). The quality of the patterns is related to the amount of FIB damage induced in the Cu and Si. These or similar methods should be directly transferable to a FIB/SEM dual beam instrument equipped with an EBSD detector.     

Electrical characterization of platinum deposited by focused ion beam

Focused ion beam (FIB) systems are commonly used to image, repair and modify integrated circuits by cutting holes in passivation to create vias or to selectively break metal tracks. The ion beam can also be used to deposit a metal, such as platinum, to create new connections. These techniques are very useful tools for debugging designs and testing possible changes to the circuit without the expense of new mask sets or silicon. This paper presents test structures which can be used to characterize a FIB induced platinum deposition process. Sheet resistance test structures have been fabricated using a FIB tool and the results of testing these structures are presented. The sheet resistance data has been used to fabricate platinum straps with a known resistance. This extends the capability of the focused ion beam system beyond the deposition of simple conducting straps. The design of the test structures has been improved through the use of current flow simulation to investigate the effects of geometry and misalignment on the measurement accuracy. The results of these simulations are also presented.     

Reliability of a focused ion beam repair on digital cmos circuits

The usefulness of FIB technology for device modification is commonly recognized in the industry. Yet, very little is known concerning the reliability of these circuit changes. This paper presents the reliability assessment of a “standard” FIB repair on digital CMOS circuits. The overall conclusion is positive : the lifetime of a “standard” FIB repair is found to be more than a few months, which is largely sufficient for prototyping.