Fabrication and Characterization of a High-Performance Multi-Annular Backscattered Electron Detector for Desktop SEM.

Wei-Ruei Lin,Yun-Ju Chuang,Chih-Hao Lee,Fan-Gang Tseng,Fu-Rong Chen

doi:10.3390/s18093093

Abstract

Scanning electron microscopy has been developed for topographic analysis at the nanometer scale. Herein, we present a silicon p-n diode with multi-annular configuration to detect backscattering electrons (BSE) in a homemade desktop scanning electron microscope (SEM). The multi-annular configuration enables the enhancement of the topography contrast of 82.11 nA/μm as compared with the commercial multi-fan-shaped BSE detector of 40.08 nA/μm. Additionally, we integrated it with lateral p-n junction processing and aluminum grid structure to increase the sensitivity and efficiency of the multi-annular BSE detector that gives higher sensitivity of atomic number contrast and better surface topography contrast of BSE images for low-energy detection. The responsivity data also shows that MA-AL and MA p-n detectors have higher gain value than the MA detector does. The standard deviation of measurements is no higher than 1%. These results verify that MA p-n and MA-AL detectors are stable and can function well in SEM for low-energy applications. It is demonstrated that the multi-annular (MA) detectors are well suited for imaging in SEM systems.

Highlights

The scanning electron microscope (SEM) has been widely applied to study surface topology and the shape of nano-objects in many research fields, ranging from semiconductors [1] to nano-materials [2], life sciences [3,4] and medicine [5]
The results show that multiple detectors placed at higher angles is preferable for topography reconstruction in SEM
To show the MA structure does give a better surface topography contrast as compared with a bonded on printed circuit board (PCB)

Summary

Introduction

The scanning electron microscope (SEM) has been widely applied to study surface topology and the shape of nano-objects in many research fields, ranging from semiconductors [1] to nano-materials [2], life sciences [3,4] and medicine [5]. In an SEM, there are two imaging modes, namely, secondary electron (SE) mode and backscattered electron (BSE) mode. Surface topographic (TOPO) variation is imaged, usually, by collecting SEs, since it results from electron–electron scattering from the surface of the specimen. The contrast of composition (COMPO) in atomic number of the specimen is readily obtained by the BSEs due to its results from an electron–nuclei scattering, and no energy transfer occurs. The SE detector has been usually the standard detector for studying topographic features because the backscattered electron image (BEI) inherently gives poorer spatial resolution than the secondary electron image (SEI). It is well known that BSE signals can show COMPO detail contrast and TOPO variation [6,7]. Studies suggest the COMPO and TOPO information can be recorded separately and even optimized using two semi-annular BSE detectors set at, respectively, the high and low take-off angle positions [8,9,10,11,12,13,14,15]

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Methods

Conclusion