Chemically assisted ion beam etching of gallium nitride

Chemically assisted ion beam etching of gallium nitride (GaN) grown by metalorganic chemical vapor deposition has been characterized using an Ar ion beam and Cl₂gas. The etch rate of GaN was found to increase linearly with Ar ion beam current density, increase linearly then saturate with Ar ion beam energy, vary slightly with Cl₂ flow rate, and lastly, increase moderately with substrate temperature. Etch rates as high as 330 nm/min were obtained at high beam energies and 210 nm/min at a more nominal level of 500 eV. The anisotropy of etched profiles improved in the presence of Cl₂ in comparison to those etched by Ar ion milling only. Elevated substrate temperatures further enhanced the anisotropy to obtain near-vertical profiles for fairly deep-etched structures. Auger electron spectroscopy was used to investigate etch-induced surface changes. Oxygen contamination was observed on the as-etched surface but a dilute HC1 treatment restored the stoichiometry of the material to its unetched state.     

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.     

Reactive ion etching for VLSI

Reactive Ion Etching (RIE) is a dry etching technique that is used to etch 1-µm and submicrometer patterns into films of silicon and silicon compounds. RIE is suitable for VLSI applications because etching is anisotropic and proceeds via chemical reactions with the substrate. Anisotropic etching allows faithful reproduction of resist patterns into the films that make up a device, and chemical etching allows development of selective etching by manipulating the composition of the plasma. The RIE reactor is described and examples of its use to fabricate 1-µm MOSFET's are given. Concerns arising from the presence of a voltage between the substrates and the plasma, radiation damage of SiO2and contamination of silicon, are discussed.     

Electron beam testing of ultra large scale integrated circuits

Electron beam testing is finding increasing acceptance within the semiconductor industry as a design analysis tool. In this paper the needs of semiconductor engineers are reviewed. These are then compared with the performance of currently available electron beam test systems as well as with the predicted limitations of the technology. In addition, some recent work is described which has demonstrated superior performance in several ways when compared to current available equipment.     

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.     

Broadband quantum dot superluminescent LED with angled facet formed by focused ion beam etching

Broadband quantum dot superluminescent light emitting diodes (LEDs) are realised by focused ion beam etching an angled facet in an edge emitting dot-in-well laser diode structure. The device exhibits a large and flat emission spectral width up to 142 nm at 0.3 mW, maximum CW output power as high as 3 mW, and effective facet reflectivity <1times10^-6     

Monolithic integration of wavelength-scale diffractive structures on red vertical-cavity lasers by focused ion beam etching

We report the fabrication and characterization of wavelength-scale diffractive optical elements etched directly on the surface of red (660 nm) vertical-cavity surface-emitting lasers. The structures were fabricated by focused ion beam etching. Linear and two-dimensional (2-D) grating configurations were investigated. Each showed excellent suppression of the zeroth-order diffracted beam. Compared to the power from an unetched laser, /spl sim/22% of the emission was coupled into the first order for linear gratings and 12% for the 2-D structures. Polarization was independent of grating orientation for grating pitches as small as 1/spl lambda/. Threshold current increases of 35%-40% were measured.     

Electron beam induced current investigations of active electrical defects in silicon due to reactive ion etching and reactive ion beam etching processes

Reactive ion etching and reactive ion beam etching are common tools for anisotropic etch processes in silicon microdevice fabrication; but, unfortunately, they also create radiation damage in the etched surface. We have studied the electrically active defects by measuring the recombination of carriers with the help of the electron beam induced current (EBIC) mode of a secondary electron microscope. We have measured the temperature behavior of the samples by annealing studies and the temperature dependent EBIC signal for several p-doped silicon wafers and obtained different shaped curves. Theoretical EBIC models developed with the assumption of a reduced net carrier concentration in the etched areas agree with our experimental results.     

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。     

Low threshold ridge waveguide single quantum well laser processed by chemically assisted ion beam etching

Fundamental lateral mode ridge waveguide lasers have been developed utilizing chemically assisted ion beam etching. The lasers exhibited mean threshold currents of 12.6 mA with close to 100 percent yield and differential quantum efficiencies as high as 69 percent.     

Mechanistic framework for dry etching, beam assisted etching and tribochemical etching

A mechanistic framework is presented for impact assisted etch reactions. The consecutive reaction steps are assumed to be activated thermally and in parallel mechanically by fast particle impacts. The model explains the complicated temperature dependencies observed in dry etching and beam assisted etching, and it correlates the side wall profiles to the rate determining steps in the etch mechanisms. The framework is used to describe Reactive Ion Beam Etching (RIBE) experiments on InP with Ar⁺ ions and chlorine, in comparison with our recent Reactive Ion Etching (RIE) experiments of magnetic alloys in HCl plasmas. The framework is also applicable to other non-thermally activated etch reactions, as encountered in tribo-chemical etching and laser chemical etching.     

High speed electron-beam testing of VLSI circuits by backscattered electron detection

A scheme which is predicted to increase the time resolution of electron beam testers by more than an order of magnitude to a value of around 400 fs is described. The new proposal is based on using multi-channel angular backscattered detection which can be used in conjunction with the normal operating mode of electron beam testers.<>     

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.     

Partitioning algorithm to enhance pseudoexhaustive testing ofdigital VLSI circuits

This brief introduces a partitioning algorithm, which facilitates pseudoexhaustive testing, to detect and locate faults in digital VLSI circuits. The algorithm is based on an analysis of circuit's primary input cones and fanout (PIFAN) values. An invasive approach is employed, which creates logical and physical partitions by automatically inserting reconfigurable test cells and multiplexers. The test cells are used to control and observe multiple partitioning points, while the multiplexers expand the controllability and observability provided by the test cells. The feasibility and efficiency of our algorithm are evaluated by partitioning numerous ISCAS 1985 and 1989 benchmark circuits containing up to 5597 gates. Our results show that the PIFAN algorithm offers significant reductions in overhead and test time when compared to previous partitioning algorithms     

Evaluation of scanning capacitance microscopy sample preparation by focused ion beam

Due to the continuous reduction of the critical dimensions of semiconductor devices, it becomes very important to know the two dimensional (2D) doping profile for electrical performance of devices. Scanning Capacitance Microscopy (SCM) is a powerful technique for qualitative analysis of 2D doping species distribution, measuring small capacitance variations with high spatial resolution. For 2D carrier profiling, the region of interest must be accessible to the profiling instrument. SCM samples require cross-sectioning to expose the inner sample at a visible surface. In some analysis, the failure is localized at a very accurate address up to hundreds of nanometers. With the traditional polishing method of sample preparation it is very difficult to reach the exact location. For this reason we are investigating a new way to prepare SCM sample with Focused Ion Beam (FIB) and plasma etch in order to accurately choose the scanning zone. This paper presents a method to obtain SCM scans after a sample preparation by FIB and the influence of the FIB and the Plasma etcher on cross-sectioned SCM samples.     

Integrated AlGaAs two-beam LD-PD array fabricated by reactive ion beam etching

Monolitically integrated AlGaAs two-beam laser diode (LD)- photodiode (PD) arrays are described. LDs and PDs have etched facets fabricated by reactive ion beam etching (RIBE). LDs in the array exhibit threshold currents as low as 18 mA and external quantum efficiencies of more than 30% per facet. A PD can detect more than 20% of a light beam emitted from an LD facing it. Crosstalk between the two LD-PD columns (separated by 50 ?m), on the other hand, is suppressed to less than ?20 dB by an AlGaAs optical barrier (5 ?m thick) fabricated between them.     

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.