Measurement of the three-dimensional high frequency micro-magnetic stray fields beyond a magnetic head by electron tomography

利用反射电子束层析成像技术，研制了一种测量间隙长度为1 μm及以下磁头杂散磁场的测量系统。利用反射电子束层析成像技术对间隙长度为10 μm及以上的磁头进行磁杂散场测量，解决了高密度磁记录磁头磁场测量困难的问题。为了提高电子束受目标磁场偏转时偏转数据的测量精度，本文介绍了一种高精度的商用位置传感探测器PSD (Position Sensing Detector)，并对其性能进行了实验研究。首先，为了提高PSD的信噪比，对流压变换电路中反馈电阻的参数值进行了调整。其次，为了获得电子束位置检测的良好线性，通过改变物镜孔径大小和增大扫描电镜聚光镜激发电流来增大电子束入射到PSD上的电流。遗憾的是，尽管进行了这些改进，但PSD的空间分辨率在25 μm左右，并且由于改变物镜孔径大小导致电子探针束半径的增加而无法改善。最后，对磁头装样台进行了改进，提高了装样台判定的再现精度。通过这些改进，有望测量间隙长度在1 μm及以下的磁头的杂散磁场，用于高密度磁记录。

A new measuring system by reflection electron beam tomography has been developed to measure the stray magnetic fields of a magnetic head with gap length of 1 μm and under. We developed the measuring system to measure the magnetic stray fields of the magnetic head with gap length of 10 μm and over by reflection electron beam tomography, but it is difficult to measure the magnetic fields of a magnetic head for the high density magnetic record.In this study, in order to improve the measurement accuracy of deflection data of electron beams deflected by the objected magnetic fields, a high accurate commercial type PSD (Position Sensing Detector) is introduced and its performance was studied experimentally. First, to improve the S/N ratio of the PSD, the parameter value of the feedback resistance in the current - voltage transform circuit was adjusted. Second, to obtain the good linearity of position detection of the electron beam, the incident current of electron beams onto the PSD is increased by changing the aperture size of the object lens and also increasing the excitation current of the condenser lens of the SEM. Unfortunately, though these modifications were done, the spatial resolute of the PSD was around 25 μm and can not be improved due to the resulting increment of the radius of the electron probe beams by changing the aperture size of the object lens. Finally, the sample stage for holding the magnetic head was modified to improve the reproduced accuracy of the decision of the stage. From these modifications, it is expected to measure the stray magnetic fields of a magnetic head with gap length of 1 μm and under for the high density magnetic record.