Development of wave form measurement method for high acuracy of detection time in semiconductor X-ray detector

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The characteristics of materials and devices are considerably affected by trace elements such as impurity atoms localozed in semiconductor materials and the segregation of impurity atoms to the grain boundary on the nanometer scale. For this purpose, We developed a new analytical transmission electron microscope(TEM), called the coincidence TEM in 1995, which enabled elemental mapping by the coincidence measurement between the characteristic X-ray rand relevant energy-loss electrons. In the previous coincidence TEM system, a Si(Li) detector and a multi-anode position-sensitive phtomultiplier were attached to a TEM. Using these detectors, we succeeded in shorterning measurement time by selecting only specified energy-loss electrons after generating characteristic X-rays. The advanced coincidence TEM enabled to obtain an elemental mapping image in a shrter measurement rime, but no less than several hours was still needed for the coincidence measurement due to poor X-ray detection rime ac … More curacy of a Si(Li) detector. Minimizing the coincidence gate time delta t, which is a finite time window to determine whether X-rays and enemy-loss electrons are coincidentally detected, is one of the effective solutions to further reduce measurement time. in our previous works, the X ray detection time accuracy of a Si(Li) detector was still poor due to the use of an analog coincidence detection system and limits delta.-t to 100 nano second, although the performance of the high speed analog electronic circuit was satisfactoryIn the first year, we developed a off line type wave form measurement system which record the wave form of X-ray signal in every 10 nano second, and it result the accuracy of the detection time to 85 nano second. In the second year, we developed a DC rejection type pre-amplifier which reduce the noise level of the signal to 0.3mV Then we developed a 100MHz sampling system and coincidence selecting circuit with FPGA. Using these system, the accuracy of the detection time is reduced to 75 nano second. The limit of this inaccuracy is not due to the fluctuation of the rise time of the detection signal, but due to the noize of the detector. We suppose that the use of the low noise and the high speed detector like SDD (Silicon Drift Detector) reading more higher time accuracy Less