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.

With the ever shrinking semiconductor device features coupled with the increasing circuit density, optical level fault localization techniques such as Photon Emission Microscopy (PEM), Laser Signal Injection Microscopy (LSIM) and Thermal Hotspot Localization (THS) can only get you so far due to these limitations: magnification, spot size and drop in detection sensitive at higher magnification. Using a 100x objective can put you in the ball park. Test data such as ATE & ATPG can point you to a specific block of circuitry but still far from defect localization. With in-SEM fault isolation and localization techniques such as Voltage Contrast (VC), Electron Beam Induced/Absorb Current (EBIC/EBAC) and Resistive Contrast Imaging (RCI), the nano-scale defect can be further localized due to the advantage of the magnification and spot size. This paper offers the combined techniques of optical level fault localization (PEM, LSIM & THS) and in- SEM or E-beam techniques (VC, EBAC, RCI) to successfully perform fault localization when challenged with the above scenarios.

This paper presents two new methods using potassium hydroxide (KOH) as a wet etch technique to successfully stop on gate oxide and find the submicron gate oxide failures that correspond to failure response sites. Applications of this new technique to submicron gate oxide failures on both planar and deep trench MOSFET devices are reported in this paper.