Observation of diameter dependent carrier distribution in nanowire-based transistors
Observation of diameter dependent carrier distribution in nanowire-based transistors
复制标题
纳米线晶体管中直径相关载流子分布的观察
作者：
A. Schulze;T. Hantschel;P. Eyben;A. Verhulst;R. Rooyackers;A. Vandooren;J. Mody;A. Nazir;D. Leonelli;W. Vandervorst
纳米线（NW）场效应晶体管（FET）的成功实现关键取决于该器件内部载流子分布的定量信息。因此，我们开发了一种基于高真空扫描扩展电阻显微镜（HV-SSRM）的方法，该方法允许以2纳米空间分辨率对全集成硅nw基隧道fet （tfet）进行二维（2D）定量载流子分析。我们表征过程的关键要素是优化的NW切割和抛光步骤，使用内部制造的超锋利金刚石尖端，在高真空下测量，以及专用的量化程序，用于考虑受表面状态影响的肖特基样尖端-样品接触。在植入的TFET源区域的情况下，我们发现共形性，结突发性和栅极重叠对NW直径有很强的依赖性，定量地与过程模拟一致。相比之下，砷掺杂的漏极区显示出意想不到的NW直径依赖于掺杂的失活。通过实验测量和器件模拟证实，在较小直径下观察到的低漏极掺杂通过较低的ttfet关断电流反映在器件特性中。
The successful implementation of nanowire (NW) based field-effect transistors (FET) critically depends on quantitative information about the carrier distribution inside such devices. Therefore, we have developed a method based on high-vacuum scanning spreading resistance microscopy (HV-SSRM) which allows two-dimensional (2D) quantitative carrier profiling of fully integrated silicon NW-based tunnel-FETs (TFETs) with 2 nm spatial resolution. The key elements of our characterization procedure are optimized NW cleaving and polishing steps, the use of in-house fabricated ultra-sharp diamond tips, measurements in high vacuum and a dedicated quantification procedure accounting for the Schottky-like tip–sample contact affected by surface states. In the case of the implanted TFET source regions we find a strong NW diameter dependence of conformality, junction abruptness and gate overlap, quantitatively in agreement with process simulations. In contrast, the arsenic doped drain regions reveal an unexpected NW diameter dependent dopant deactivation. The observed lower drain doping for smaller diameters is reflected in the device characteristics by lower TFET off-currents, as measured experimentally and confirmed by device simulations.