OM Optical Microscope
| 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 |
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.
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.
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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.
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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.
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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.
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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.
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