Scanning Electron Acoustic Microscopy Studies of III-V Compounds: Epitaxial Layers and Devices

Scanning electron acoustic microscopy (SEAM) can be used as a tool to visualize integrated circuit failures caused by lithographic processes, metallic overlayer adherence problems, major subsurface defects, and presence of alloyed compounds formed between ohmic contacts and epitaxial layers. Major defects and doping striations are also visualized by SEAM. For highly doped epitaxial layers a dependence has been found between the doping level and the electron acoustic signal

Scanning Electron Acoustic Microscopy and Scanning Electron Microscopic Imaging of III-V Compounds Devices

Scanning electron acoustic microscopy (SEAM) and SEM infrared imaging (SEMIR) use both a modulated electron beam to generate thermal waves which produce acoustic waves detected by a transducer in the case of SEAM and affect the surface temperature which is directly monitored by the infrared emission. Both techniques are used to visualize non-adherence zones in III-V compounds devices. SEAM is applied to metallic layers like Au, Au-Ti, W-Mo-Ge deposited on a GaAs substrate. SEAM images are correlated with global adherence measurements. SEMIR is applied to dielectric layers, like Si3N4/InP. An estimation of the surface temperature is given. Sensitivity and spatial resolution of both techniques are given and compared

Can Cathodoluminescence and Scanning Electron Acoustic Microscopy be Considered Complementary Techniques?

Cathodoluminescence (CL) and Scanning Electron Acoustic Microscopy (SEAM) give complementary information on direct bandgap semiconductors when dopant impurities are introduced. CL deals with the electrical properties of the semiconductor and SEAM deals with the thermal and elastic properties and eventually with the piezoelectric properties in low doped III-V compounds. As function of the introduction of impurities for the doping of the semiconductor, the Near-Band-Edge (NBE) CL emission increases up to a maximum. and decreases when the impurities are no longer introduced in electrically active sites, but create complexes giving rise to the appearance of a Deep Level (DL) emission. The increase of the SEAM signal is related to the reduction of the thermal conductivity as function of the introduction of the impurities when the lattice contribution of the thermal conductivity is preponderant versus the electronic contribution. For highly doped III-V compounds, variation in elastic properties and presence of strain in the layers may also be evoked to explain the increase of the SEAM signal. Examples of evolution of both CL and SEAM signals are given for introduced impurities, such as, Be, C, Si in GaAs. CL and SEAM are also compared from the point of view of probed depth and spatial resolution

Electron Acoustic Signal of Metallic Layers Over a Semiconductor Substrate

Calculations have been made for the electron acoustic signal in the case of one and two metallic layers deposited over a semiconductor substrate. The temperature distribution as function of the depth has been determined by taking into account the power absorbed in the metallic layers and the substrate. We have considered strain-free and constrained layers. Experimental results have been obtained for a single metallic layer (Au, W, Pd, Mo, Mn, Ti) deposited over GaAs and for Au-Ti contacts. Comparison between experiments and calculations allows us to determine whether the layers are constrained or not

Chemical Composition of GaAs Oxide Layers by Auger In-Depth Profiles and X-Ray Photoelectron Spectroscopy Experiments

GaAs oxide layers resulting from an oxygen plasma etching have been studied by Auger in-depth profiles and angle-resolved XPS experiments. From the Auger profiles, using the sequential layer sputtering (SLS) treatment, a quantitative determination of thickness and composition of the oxide layers has been performed. A model with several layers has been deduced. From the angle-resolved X-ray photoelectron spectroscopy (XPS) experiments, another model with several layers of different chemical compounds has also been deduced. The oxide layer is non-uniform in thickness and composition. Two or three different oxide layers are formed depending on the probed area. The interface layer is made of a mixture of Ga2O3 and elemental arsenic. The intermediate layer consists of an equal mixture of Ga2O3 and As2O3 with a small amount of As2O5. From the Auger experiments, an upper layer of Ga2O3 is found in the central part of the wafer, corresponding to a more important loss of arsenic due to a thermal effect

Cathodoluminescence Spectroscopy: An Accurate Technique for the Characterization of the Fabrication Technology of GaAlAs/GaAs Heterojunction Bipolar Transistors

Cathodoluminescence (CL) spectroscopy and imaging performed at low temperature have been used to qualify the heterojunction bipolar transistor fabrication technology, particularly the etching and ion implantation steps. CL has been used to optimize low defect technological processes. The protection of the active region during the insulation process has been optimized. The best result is obtained when using a bilayer of silicon nitride and photoresist. In order to minimize it, the damage induced by the etching process has also been studied. The best result is obtained when combining Ar ion beam etching and chemical etching. The possibilities to perform localized spectroscopy, to visualize the different emitting regions and to achieve semiquantitative signal analysis, makes CL a powerful microcharacterization method

Electron-beam-induced shift in the apparent position of a pinned vortex in a thin superconducting film

When an electron beam strikes a superconducting thin film near a pinned vortex, it locally increases the temperature-dependent London penetration depth and perturbs the circulating supercurrent, thereby distorting the vortex's magnetic field toward the heated spot. This phenomenon has been used to visualize vortices pinned in SQUIDs using low-temperature scanning electron microscopy. In this paper I develop a quantitative theory to calculate the displacement of the vortex-generated magnetic-flux distribution as a function of the distance of the beam spot from the vortex core. The results are calculated using four different models for the spatial distribution of the thermal power deposited by the electron beam.Comment: 9 pages, 6 figures, resubmitted to PRB with referee-suggested revisions, includes new paragraph on numerical evaluatio

Development of the Bélanger Equation and Backwater Equation by Jean-Baptiste Bélanger (1828)

A hydraulic jump is the sudden transition from a high-velocity to a low-velocity open channel flow. The application of the momentum principle to the hydraulic jump is commonly called the Bélanger equation, but few know that Bélanger's (1828) treatise was focused on the study of gradually varied open channel flows. Further, although Bélanger understood the rapidly-varied nature of the jump flow, he applied incorrectly the Bernoulli principle in 1828, and corrected his approach 10 years later. In 1828, his true originality lay in the successful development of the backwater equation for steady, one-dimensional gradually-varied flows in an open channel, together with the introduction of the step method, distance calculated from depth, and the concept of critical flow conditions

Application of scanning electron acoustic microscopy to the characterization of n-type and semiinsulating GaAs

A series of GaAs wafers with different doping levels and electrical resistivity has been used to investigate the scanning electron acoustic microscopy (SEAM) application to the characterization of this material. It has been found that SEAM is particularly useful to characterize semi-insulating GaAs as compared with n-type material. The SEAM signal generation mechanisms in GaAs are discussed

USE OF SCANNING ELECTRON ACOUSTIC MICROSCOPY FOR III-V COMPOUNDS DEVICES ANALYSIS

The use of scanning electron acoustic microscopy (SEAM) in III-V compounds devices is demonstrated. The order of magnitude of the attainable resolution is given, depending of the depth of the observed defect. A spatial resolution nearly equal to the spot size is attainable. Examples of the use of SEAM in III-V compounds devices are given. The adherence of metallic layers, Au and Au-Ti on GaAs have been studied by SEAM and compared with global adherence measurements. The case of strong adherence problems for a strained WMoGe layer on GaAs is also studied