Gramse Georg, Brinciotti Enrico, Lucibello Andrea, Patil Samadhan B, Kasper Manuel, Rankl Christian, Giridharagopal Rajiv, Hinterdorfer Peter, Marcelli Romolo, Kienberger Ferry
Johannes Kepler University of Linz, Institute for Biophysics, Gruberstrasse 40, A-4020 Linz, Austria.
Nanotechnology. 2015 Mar 27;26(13):135701. doi: 10.1088/0957-4484/26/13/135701. Epub 2015 Mar 9.
The capability of scanning microwave microscopy for calibrated sub-surface and non-contact capacitance imaging of silicon (Si) samples is quantitatively studied at broadband frequencies ranging from 1 to 20 GHz. Calibrated capacitance images of flat Si test samples with varying dopant density (10(15)-10(19) atoms cm(-3)) and covered with dielectric thin films of SiO2 (100-400 nm thickness) are measured to demonstrate the sensitivity of scanning microwave microscopy (SMM) for sub-surface imaging. Using standard SMM imaging conditions the dopant areas could still be sensed under a 400 nm thick oxide layer. Non-contact SMM imaging in lift-mode and constant height mode is quantitatively demonstrated on a 50 nm thick SiO2 test pad. The differences between non-contact and contact mode capacitances are studied with respect to the main parameters influencing the imaging contrast, namely the probe tip diameter and the tip-sample distance. Finite element modelling was used to further analyse the influence of the tip radius and the tip-sample distance on the SMM sensitivity. The understanding of how the two key parameters determine the SMM sensitivity and quantitative capacitances represents an important step towards its routine application for non-contact and sub-surface imaging.
在1至20 GHz的宽带频率范围内，对扫描微波显微镜用于硅（Si）样品的校准亚表面和非接触电容成像的能力进行了定量研究。测量了具有不同掺杂剂密度（10(15)-10(19)原子厘米(-3)）并覆盖有SiO2介电薄膜（厚度为100-400纳米）的平坦Si测试样品的校准电容图像，以证明扫描微波显微镜（SMM）用于亚表面成像的灵敏度。在标准SMM成像条件下，在400纳米厚的氧化层下仍可检测到掺杂区域。在50纳米厚的SiO2测试焊盘上定量展示了抬起模式和恒定高度模式下的非接触SMM成像。针对影响成像对比度的主要参数，即探针尖端直径和尖端-样品距离，研究了非接触和接触模式电容之间的差异。使用有限元建模进一步分析了尖端半径和尖端-样品距离对SMM灵敏度的影响。理解这两个关键参数如何决定SMM灵敏度和定量电容是其用于非接触和亚表面成像常规应用的重要一步。
