以掃描探針測量矽半導體載子濃度

Abstract

掃描探針顯微術是近年來發展迅速的一種表面分析技術，具有非破壞性、二維量測、高空間解析度等諸多優點。KFM (Kelvin Probe Force Microscopy)是其中一種，能夠量測試片表面電位。藉由量測矽半導體的表面電位，KFM可望應用於載子濃度的二維量測。 本論文首先改良既有的KFM系統的回饋控制電路，以得到較佳的掃瞄結果。接著探討試片的表面處理，發現經過氧化處理與氫氟酸浸泡會使試片表面產生Si-F及Si-O鍵結而導致表面電位影像對比劣化，而使用丙酮超音波震盪、氫氟酸浸泡、去離子水沖洗，可有效消除上述鍵結，提升影像對比。此外，以KFM量測試片的表面電位差，以展阻、電容-電壓法、二次離子質譜儀分別量測試片的表面濃度，建立兩者之間的校正關係，並與理論值相比較，探討彼此產生差異的原因。本論文亦針對剖面量測作了先期研究，以對貼研磨的方式嘗試剖面試片的製作，並根據KFM量測的要求逐步加以改進，以期將來能夠利用KFM量測元件剖面的二維載子分佈。

Scanning probe microscopy (SPM) is one of the surface analysis techniques which are developed rapidly in recent years. It has advantages of non-destructive, 2-D measurement, and high spatial resolution. Kelvin probe force microscopy (KFM) is one application of the SPM technique. The KFM measures surface potential of sample. By means of measuring the surface potential of silicon semiconductor, KFM is capable of 2-D measurement of carrier distribution. Before the measurement of surface potential, the feedback control circuit was modified to improve the signal response. Then, this thesis studied sample preparation method. It was observed that the oxidized or HF-dipped sample surface was covered by Si-O or Si-F, respectively, and resulted in degraded contrast of surface potential image. These bonds were removed effectively and image contrasts were promoted after the samples were ultrasonic oscillated in acetone, dipped in HF, and rinsed by D.I. water. After the surface potential differences were measured by KFM, several methods including spreading resistance profiling (SRP) method, capacitance-voltage (C-V) method, and secondary ion mass spectroscopy (SIMS) were employed to determine the surface carrier/dopant concentration in order to setup the correlation between surface potential difference and surface carrier/dopant concentration. This thesis also beforehand studied on the preparation of cross-sectional sample. Although the results are not perfect, it is looked forward that KFM can be applied on 2-D carrier profiling of nano-devices.