Evaluation of 2D Dopant Profile around source and drain of MOSFETs

我们研究了硅MOSFET源极和漏极周围掺杂剂的2D分布评估。对于一维，换句话说，深度，轮廓西姆斯（二次离子质谱）是最广泛使用的。提出了利用西姆斯提取二维掺杂分布的新方法。注入的离子被散射并横向扩散。当掩模开口宽度由于散射而变得比横向扩展窄时，有效剂量减小，基于这一现象，我们可以通过西姆斯测量获得掩模开口与有效剂量之间的关系。通过假设横向扩展的适当分布函数，可以获得2D轮廓。为了证实这个想法，我们已经制作了样品与多晶硅或光刻胶作为注入B注入掩模。通过西姆斯的评估，我们发现，必须扩大掩模开口的纵横比，以提取轮廓。我们还尝试了SEM（扫描电子显微镜）分析。这种方法是基于二次电子发射率的变化，由于掺杂密度。为了提高空间分辨率，样品进行了抛光与低角度，然而，损坏可能是由于抛光阻止获得清晰的SEM图像。虽然进行了化学蚀刻以去除这种损伤，但没有获得具有良好质量的SEM图像，如解理面。

We have investigated evaluation of 2D profiling of dopants around the source and drain of silicon MOSFETs. For one-dimensional, in other words depth, pro filing SIMS (Secondary Ion Mass Spectroscopy) is most widely used. We have proposed the new method to extract 2D dopant distribution that utilizes SIMS. Implanted ions are scattered and laterally spread. When the mask opening width becomes narrower than the lateral spread due to the scattering, effective dose reduces.Based on this phenomena, we can obtain the relationship between the mask opening and the effective dose by SIMS measurement. By assuming adequate distribution function for the lateral spread, 2D profiles can be obtained. To confirm this idea, we have fabricated specimens with poly-Silicon or photoresist as the implantation mask for B implantation. By the SIMS evaluation, we have found that the aspect ratio of the mask opening must be enlarged to extract the profile. We also tried profiling with SEM (Scanning Electron Microscopy). This method is based on the variation in secondary electron emissivity due to the doping density. To improve spatial resolution, the specimens were polished with low angle, however, damage probably due to the polishing prevented obtaining clear SEM image. Though chemical etching to remove this damage was performed, the SEM image with good quality like a cleaved face has not been obtained.