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二维轮廓的评价。对于一维，即深度，二次离子质谱（SIMS）是最广泛使用的。我们提出了利用SIMS提取二维掺杂分布的新方法。注入的离子分散并横向扩散。当掩膜开口宽度小于散射引起的横向扩散时，有效剂量减小。基于这一现象，我们可以通过SIMS测量得到掩膜开度与有效剂量之间的关系。通过对横向扩散假设适当的分布函数，可以得到二维剖面。为了证实这一想法，我们用多晶硅或光刻胶制作了样品作为B植入的植入掩膜。通过SIMS评估，我们发现必须扩大掩模开口的宽高比才能提取轮廓。我们还尝试用扫描电子显微镜（SEM）进行分析。该方法基于掺杂密度引起的二次电子发射率的变化。为了提高空间分辨率，对样品进行了低角度抛光，但由于抛光可能造成的损伤，使其无法获得清晰的SEM图像。虽然进行了化学蚀刻以去除这种损伤，但没有获得像劈裂面一样质量良好的SEM图像。

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.