Ask the Expert: X-ray Diffraction (XRD)
X-ray diffraction (XRD) is a powerful and versatile technique that can give detailed structural information about almost anything that is solid.
Microscopy Techniques in the Failure Analysis of Optoelectronics
Optoelectronic devices are playing an increasingly important role in the success of a wide variety of current consumer electronics and industrial applications. These semiconductor devices have been made reliable by careful design and technological advancement. Having carrier recombination rates thousands of times higher than other types of devices inevitably leads to degradation and ultimately failure that is often highly localized. To understand the root cause of failure, it is often very important to catch the problem as early as possible which is both a reliability testing as well as a characterization challenge as initiation sites can be as small as a few nanometers. EAG’s Microscopy group can help.
Microscopy in our failure analysis strategy:
EAG takes an integrated multi-technique approach to best determine cause(s) of failure. Samples are first screened with non-destructive techniques for bulk characterization and defect isolation. Once a defect is isolated, highly localized destructive techniques are applied to take a deeper look to establish the root cause.
EAG divides FA characterization tasks into three levels. In each level, we employ optimal techniques for device characterization, defect localization, and ultimately root cause failure analysis. While we can supply all three levels of service, typically our clients perform level one characterizations themselves which identify candidates for level two and level three inspections that EAG carries out.
Level one: Non-destructive, routine characterization techniques are utilized first. This step should be done to every device. These techniques have the lowest spatial resolutions if any at all.
In this step, we typically employ electrical measurements (LIV), along with optical microscopy techniques such as bright/dark field imaging, etc. to identify defective devices.
Level two: Once a defective device is identified in level one, the sample will be brought into a second non-destructive failure localization step.
In this step, we can use optical techniques like Electroluminescence (EL), Optical Beam Induced Resistance Change (OBIRCH), and Emission microscopy (EMMI), or Scanning Electron Microscopy (SEM) based techniques like Electron Beam-Induced Current (EBIC) and Cathodoluminescence (SEM-CL) to further view and isolate the failure site with spatially resolved images.
Level three: If further, deeper understanding is required, we then perform destructive analysis on the sample to take a detailed look at the microscopic structure of the offending defect(s).
In this step, we typically utilize focused ion beam (FIB) and dual beam instruments (FIB-SEM) for sample preparation and cross-sectional analysis of a defect site. For yet deeper analysis, we employ Transmission Electron Microscopy (TEM) or Scanning Transmission Electron Microscopy (STEM) with EDS or Electron Energy Loss Spectroscopy (EELS) to investigate crystal defects and local composition/chemistry changes.
This deep FA process results in direct evidence for the how and why a device has failed.
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