P-N Junction Analysis using Electron Beam Induced Current (EBIC) Technique

The integrity of a P-type or N-type epitaxial layer, implanted wells, or dopants (i.e. P-epi, N-well, P-imp, N-imp, etc.) oftentimes can affect the performance of an integrated circuit (IC), especially in analog/mixed signal devices. At onsemi, we had encountered a poor P-N junction of a Zener diode that caused a Cross-Coupled-Switched-Cap voltage doubler to have a lower output voltage which eventually affected the performance of the IC. The integrity of any P-N junction can be electrically verified through curve tracing with in-SEM nano-probing and fault isolation (PEM, OBIRCH, etc.) techniques. However, physical defect revelation using junction stain, either top-down or in cross section, can be challenging due to the three-dimensional (3D) form of any P-N junction. With Electron Beam Induced Current (EBIC), we can easily identify an abnormal P-N junction through both topdown and cross section. This paper is to characterize EBIC analysis on IC cross sectional view in mapping the P-N junctions and provide the information of its doping profiles. In this paper, limitation of both chemical etching and EBIC will be discussed as well as introducing the use of ion mill after FIB cross section during cross sectional EBIC sample prep as a potential method for resolution enhancement. These findings add to the understanding in using this technique and further improvement to its application in failure analysis.