A failure analysis work flow is presented demonstrating dislocation visualization, site isolation, TEM lamella preparation and defect characterization. A novel beam control technique allows visualizing dislocations with significantly improved spatial resolution in SEM using Electron Channeling Contrast Imaging. Site-specific TEM preparation on dislocations is therefore possible. The prepared thin lamella can be inspected in the SEM using STEM to study dislocations. This is a cost effective work flow without using TEM.

In this work, we discussed the fault isolation method for the Thin-Film Transistor (TFT). Many defects in the TFT can be directly observed by optical microscope; however, some defects are not visible in either optical microscope or SEM making the fault isolation effort very challenging. We demonstrated that OBIRCH can be used to find defect locations in TFT failures for leakage and shorts. The TFT is so fragile that the laser power and biasing voltage have to be very carefully controlled to avoid damaging the TFT. After identifying the defect location by OBIRCH hot spot detection, the defect was successfully captured with TEM analysis.

The Rotation Averaged Spectrum of TEM diffraction patterns can be sharpened by a Maximum-Likelihood deconvolution algorithm. The sharpened spectrum will help to improve the precision of TEM diffraction-based techniques, e.g.: phase identification and strain analysis.

The distribution of Si nanoparticles, both dimensional and spatial, is a key factor affecting the performance of non-volatile flash memory devices. A new FIB method has been developed to prepare ultra-thin plan view specimens, containing only the Si nanoparticle matrix thin film layer, from fully processed nanocrystalline flash memory devices. The morphology and distribution of Si nanoparticles were then studied by EFTEM 3D tomographic reconstruction.

In this paper, two failure analysis case studies are presented to demonstrate the importance of sample preparation procedures to successful failure analyses. Case study 1 establishes that Palladium (Pd) cannot be used as pre-FIB coating for SiO2 thickness measurement due to the spontaneously Pd silicide formation at the SiO2/Si interface. Platinum (Pt) is thus recommended, in spite of the Pt/SiO2 interface roughness, as the pre-FIB coating in this application. In the second case study, the dual-directional TEM inspection method is applied to characterize the profile of the “invisible” tungsten residue defect. The tungsten residue appears invisible in the planeview specimen due to the low mass-thickness contrast. It is then revealed in the cross-sectional TEM inspection.