Abstract
The purpose of this research is to fabricate a high sensitivity and high collecting efficiency backscattered electron detector. The detector is set in the Scanning Electron Microscope. The detector can collect the backscattered electrons and produce the signals during operation. Increasing the sensitivity and collecting efficiency of the backscattered electron detector improves the effect of the detector. This research uses the lateral P-N junctions to enhance the sensitivity of the detector. It also uses the Al grids to improve the collecting efficiency. The structure of the lateral P-N junctions can make the outer depletion region extend to the surface of the active areas. It can get rid of the dead layers on the surface of the active areas. The detector can collect the low energy electrons and improve its sensitivity. Nowadays, many researches use low energy electron beam to scan the samples to reduce the radiation damage to the samples. The backscattered electrons from the samples may have low energy due to the low energy electron beam. As a result, increasing the sensitivity of the detector can make the detector collect more low energy backscattered electrons effectively. The Al grids can increase more areas of the Al electrodes to contact the active areas. This structure may reduce the series resistance. Therefore, the electron-hole pairs produced from the active areas can be collected by the Al electrodes more easily. It can improve the collecting efficiency of the detector. After finishing the detector, the I-V curve and the dark current of the detector are measured to ensure its basic electric properties. The dynamic range and the collecting efficiency are also measured. Furthermore, the atomic number sensitivity is measured, too. The new backscattered electron detector has better collecting efficiency and atomic number sensitivity than the multi-annular shape backscattered electron detector which our research group made before.