Shuichi Takeuchi

High contrast BSE Imaging under Ultra Low Voltage condition by FE-SEM with Energy Filtering

BSE imaging is a useful method to obtain compositional information, and also to reduce charging effect. Demands for compositional characterization at specimen surface are increasing in the field of material science and engineering. In order to characterize compositional structure at specimen surface, Low Loss BSE (LLE) imaging is suitable because of the reduction of the information generated by multiple inelastic scattered electrons [1]. BSE imaging using Ultra Low Voltage (ULV) condition may also suitable because of the reduction of the penetration depth of incident electron beam. However, it is difficult to obtain high contrast BSE image by conventional methods. To address this challenge, we developed a method of filtering signal to the top detector of the Hitachi SU8000 FE-SEM. It is necessary to study imaging parameters to obtain high quality, high contrast BSE image under ULV condition because the signal behavior at ULV condition does not follow the conventional theory used over 1 kV [2]. Here we report the result of fundamental experiments using a test specimen and some applications of this technology for advanced material.

Interpretation of Energy-Filtered BSE Images at Ultra Low Voltage Conditions

1. Application Development Department, Science & Medical Systems Design Division, Hitachi High-Technologies, 1040, Ichige, Hitachinaka, Ibaraki, 312-0033, Japan 2. 1st Department, Research and Development Division, Hitachi High-Technologies, 882, Ichige, Hitachinaka, Ibaraki, 312-8504, Japan 3. Advanced Microscope Systems Design Department, Science & Medical Systems Design Division, Hitachi High-Technologies, 882, Ichige, Hitachinaka, Ibaraki, 312-8504, Japan

A Study of the Behavior of SE and BSE in UltraLow Landing Voltage Condition

In the study, we set our motivation to consider the mechanism to explain such an interesting phenomena particularly happened at the ultra low voltage situation. At first we gathered a set of SE and BSE images simultaneously at ultra low voltage condition from various kinds of specimen. Second, we compared the SE and BSE image to investigate the difference. A simulation results by CASINO [3] was also applied for the theoretical consideration. In the study the recent cold FE-SEM (Hitachi SU8000) is used. The SEM is offering the SE/BSE filtering capability even at ultra low voltage condition as shown in Fig.1.

A Study of Beam Sensitive Materials Using High Resolution, ULV Scanning Electron Microscopy

Low voltage scanning electron microscopy has become common both for topmost surface imaging and reducing beam damage [1]. Lately, high resolution, ultra-low-voltage (ULV) imaging (less than 500 V) has been realized by beam retarding [2] and/or boosting [3] techniques. In this study, some beam sensitive materials are observed by the Hitachi S-4800, which employs a cold field emission source, snorkel type objective lens and a retarding function [4].

High Spatial Resolution and Wide Range EDS Analysis with FE-SEM

EDS analysis with SEM is widely used for structural and elemental characterization of bulk materials. Demand for high spatial resolution EDS analysis is increasing in the fields of semiconductor devices and material engineering. Spatial resolution of EDS analysis depends strongly on the interaction volume of primary electrons and a specimen, which depends on the incident energy of the primary electrons and the composition (Z number) or the density of the specimen, because characteristic X-ray originates from approximately same volume as the interaction volume. Low accelerating voltage and STEM with thin film specimens are generally used to reduce the interaction volume and realize the high spatial resolution analysis. However, probe current and the efficiency of X-ray generation tend to be reduced in the case of low accelerating voltage, and X-ray intensity tends to be low due to the thin film specimen in the case of the STEM method. In order to resolve these problems, SDD detectors with a large sized sensor which has high detection efficiency, and “windowless” type detectors which additionally improve the detection efficiency especially for low energy X-ray have been introduced [1][2]. In this work, we demonstrate the high spatial resolution EDS analysis for some kinds of materials with the combination of FE-SEM and the windowless type EDS detector.

Sample preparation technique for the revelation of a semiconductor dopant using an FE-SEM

It is challenging to obtain the dopant profile within semiconductor devices with sufficient contrast from FIB milled cross sections due to a damage layer being formed during the milling process. In order to obtain accurate and sufficient dopant profile information, we examined FIB processing conditions and Ar ion milling conditions using a standard sample. As a result, an accelerating voltage of 40 kV for FIB processing and an accelerating voltage of 0.5 kV in Ar ion milling is the most suitable combination for observing a dopant profile clearly. We also applied an optimized preparation protocol to a commercial NMOS sample to demonstrate dopant profile visualization.

Correlative Characterization of Graphene with the Linkage of SEM and KFM

Graphene has been one of the most attractive and promising materials because of its unique material properties and potential applications. Its properties depend strongly on the number of layers, so the reliable examination method to determine its thickness has been required [1]. ULV (Ultra low voltage) SEM (scanning electron microscopy) is one of the possible methods for determining its thickness by clarifying layer-sensitive images of graphene. To explore further into the mechanism of the SEM contrast on graphene images, it has been explained that the difference of thickness causes the difference of surface potential that can affect the SE (secondary electron) signal intensity [2]. It has also reported that the effect of the thickness of graphene layers on its surface potential was detected by AFM-based technique KFM (Kelvin force microscopy) [3]. In this study, we developed the linkage system of SEM and AFM with compatible sample holder with correlation technology between SEM, AFM, and KFM image at the same area of interest to reveal the relationship between SEM contrast, its height, and surface potential.

Application of a Semi-in-Lens FE-SEM to the Crystallographic Analysis with the EBSD Technique

1. Application Development Department, Science Systems Design Division, Hitachi High-Technologies, 1040, Ichige, Hitachinaka, Ibaraki, 312-0033, Japan 2. Electron Microscope Systems Design 1st Department, Science Systems Design Division, Hitachi High-Technologies, 882, Ichige, Hitachinaka, Ibaraki, 312-8504, Japan 3. NanoAnalysis Department, Oxford Instruments, IS Building, 3-32-42, Higashi-Shinagawa, Shinagawa-ku, Tokyo, 140-0002, Japan

Low voltage, high resolution SEM imaging for mesoporous materials

Mesoporous silicas (MPSs), which possess highly ordered structures with a pore size of 2–15 nm, must be widely applied to catalysts, adsorbents, membranes, and sensors. Direct SEM observation of MPSs provides detail information on the external and internal structures, though it consistently faces charge-up problems of insulating silica frameworks. Several skills such as choosing low resistance substrate or replica method succeed to avoid charge-up phenomena [1]. In this contribution, high resolution, direct SEM imaging of MPSs is tried under the condition of low voltages. A cold FEG SEM, which employs the snorkel type objective lens, retarding device [2] and E cross B (ExB) filter [3] for detecting secondary electron (SE) are used for this study.