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OM Optical Microscope

An optical microscope (OM) illuminates the surface of a sample with visible light, using visible light to expose the macro morphology of components, materials, and structures through reflection, scattering, and optical contrast differences, providing an important reference point for subsequent analysis. In the processes of failure analysis, process development, and materials research, the OM is the first-line observation tool, assisting engineers in quickly grasping the overall condition of the sample and determining whether it is necessary to proceed to higher resolution techniques such as SEM, FIB, or TEM.
MA-tek equipment capabilities
Figure (a) 50-1000X (b) 100-500X / 40-200X / 5-75X (c) 50-1000X
MA-tek offers a variety of OM optical microscopes, covering a complete imaging capability from low magnification wide field observation to high magnification fine structure identification, capable of deeply presenting material structures, surface morphology, and process characteristics, meeting the observation needs of different fields such as semiconductors, packaging, and materials engineering.

 

magnification Magnification range Application
50–1000X High magnification, used for IC delayering, metal layer structure, interface observation, and detection of small defects (such as over-etch, IMD anomalies, etc.). High-resolution structural comparison, localization of small defects and process anomalies, Delayer fine layer analysis
100–500X Medium to high magnification, used for PCB/PCBA solder joints, packaging interfaces, film thickness, and metal distribution analysis. Solder joint IMC, packaging interface, metal layer and wire morphology
40–200X Medium magnification, used for grain analysis, delayering position confirmation, and preliminary structural inspection. Structural layer confirmation, grain analysis, etching profile scanning
5–75X Low magnification with a wide field of view, used for appearance inspection, cross-section scanning, wafer breakage, package delamination, and other macro defect localization. Appearance inspection, cross-section large field of view, package destruction, wafer defect scanning
Technical Principles

Optical microscope utilizationVisible light (wavelength 400–700 nm)When irradiating, different image contrasts are formed when the light interacts with the sample surface, resulting in reflection or scattering. However, since the wavelength of visible light is longer, the theoretical resolution of OM (i.e., the minimum distance at which two points can be resolved) is only about0.2 μmthis also makes OM'sThe maximum effective magnification is about 1000X.The function of OM is not to "analyze nanoscale details," but to "quickly obtain a complete macro structural condition," which is the starting point for all in-depth analysis.

 

  • Although the resolution is not as good as that of electron microscopes (SEM/TEM), OM has significant advantages:
  • Large field of view: can quickly scan large areas, making it the best tool for assessing process consistency and identifying large-scale defects.
  • High speed: suitable for mass production monitoring, process comparison, and failure localization.
  • High tolerance: suitable for various samples such as metal layers, silicon wafers, packages, PCBs, cross-sections, Delayer, etc.
  • Non-destructive: No vacuum or metal coating is required, allowing for rapid observation in the original state of the sample.
Analysis Application

Optical microscopes (OM) cannot resolve details at the nanoscale, but theirhigh field of view, high speed, low destructiveness and high toleranceThe characteristics make it the most commonly used and most valuable observation method in real-time in the fields of electronics, semiconductors, and materials. The following are the most representative analytical uses and engineering scenarios of OM in the industry:

 

Cross-section Analysis

After cross-section preparation, the overall structural arrangement and interface behavior of the sample can be clearly observed through OM, making it the most commonly used preliminary structural inspection method in packaging, PCB, module, and materials engineering.

 

Observable content Application scenarios
  • Metal layer thickness:Compare design specifications, confirm coating uniformity and process stability.
  • VIA / TSV structure integrity:Check the completeness of the filled holes, sidewall morphology, and whether there are voids, offsets, or shrinkage in the copper pillars or vias.
  • Solder morphology and wetting behavior:Evaluate whether the solder joints are uniform, whether there are any Voids, and whether the IMC layer (intermetallic compound) is abnormal.
  • Packaging interface observation:Including: die attach surface, molding filling, underfill distribution, etc.
  • Delamination, cracks, and failure behavior between materials:Used to locate failure positions and determine damage caused by mechanical/thermal stress.
  • Package development and structural verification

  • PCB/PCBA solder joint quality inspection

  • WLCSP, BGA, QFN packaging inspection

  • RA reliability structural failure analysis (after Drop, TC, HTS)

2. IC delayer structure confirmation

Delayer analysis (planar delayering) is the process of removing metal and dielectric layers layer by layer to observe the internal circuit structure without damaging the chip's operational logic. OM is the most important preliminary observation and process monitoring tool in IC delayering analysis.

 

Observable content Application Scenarios
  • Metal Routing:Confirm whether each layer of metal is arranged as designed, whether there are disconnections, short circuits, burnouts, and offsets.
  • Circuit Integrity (Integrity Check):Ensure that the delayering process has not caused any damage and confirm whether the location to be analyzed is correct.
  • Process Residue or Dry Etching Abnormality:such as polymer residues, incomplete cleaning of residual films, local corrosion, etc.
  • Large area defect localization:Burnout caused by overvoltage, hotspots caused by electromigration, metal open circuits, blackening, charring.
  • IC design verification, competitive product comparison
  • Failure Analysis (FA) locating open circuit / short circuit anomalies
  • Process comparison or batch difference analysis
  • Preliminary positioning after ESD, EOS, and latch-up failures

3. Precipitate Free Zone (PFZ) analysis

PFZ is a precipitate-depleted zone that appears near the grain boundaries in metallic materials (such as aluminum alloys) after heat treatment or deformation. It is an important parameter in materials engineering, used to assess the effects of heat treatment and material degradation.

 

Observable content Application Scenarios
  • The width and distribution of PFZ
  • Changes in the microstructure of Al alloys
  • The impact of precipitates on material strength, ductility, and reliability.
  • Aluminum wire (Al Wire) bonding (Wire Bond) evaluation
  • Packaging Material Reliability Analysis

  • Aluminum metal deposition process quality monitoring

  • Evaluation of Structural Changes After Heat Treatment

  • Long-term reliability testing (HTS, HTOL, Burn-in) after material degradation

4. Dislocation lines, etching anomalies, and crystal defect observation

OM can quickly identify surface defects caused by crystal growth, heat treatment, or etching processes, making it an important inspection item in the front-end-of-line (FEOL) processes and materials research.

 

Observable content Application Scenarios
  • Dislocation line: Misalignment caused by crystal growth defects or stress.
  • Dents and morphological changes caused by over-etching: Reflect whether the dry etching and wet etching processes are normal.
  • Process residues, surface profile: used to confirm etching rate, undercut, etching uniformity, etc.
  • Macroscopic defects such as crystal rupture, slip, and coating delamination.
  • Wafer FEOL process monitoring

  • Analysis of Failure Mechanisms in Material Heat Treatment

  • RA reliability post-crystal destruction verification

  • Observation of crystal slip caused by high temperature stress

5. Oxide stacking fault(Oxidation Induce Stacking Fault, OISF)Research

Oxide stacking faults are stacking faults generated during the high-temperature oxidation process due to the diffusion of twin defects or crystal defects. OM can clearly present the distribution and diffusion profile of oxide stacking faults, which is an important quality indicator of silicon wafer materials, used for growth and oxidation process analysis.

 

Observable content Application Scenarios
  • OISF environment position and radius
  • Defect diffusion behavior
  • Dislocation changes caused by the wafer oxidation process
  • Defect distribution of SOI and special substrates
  • Silicon wafer incoming material quality inspection

  • Evaluation of Oxidation Process Improvement

  • Comparison of silicon material suppliers

  • SOI (Silicon On Insulator) material analysis

Sign Up
01.16
2026
This seminar is themed "Silicon Exploration of the Future: The Intelligence Quest of AI × Silicon Photonics," emphasizing how the integration of AI, high-speed computing, silicon photonics, and advanced packaging technology redefines computing efficiency. The concept of "Intelligence Quest" symbolizes the identification and analysis of the best opportunities for future technological development through these key technologies.
For more information: https://www.matek.com/zh-TW/Seminar/detail/all/20250327
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