SIM combines non-contact optical sectioning and high-resolution 3D imaging across visible and infrared spectral ranges. Visible-light SIM is especially relevant for surface-sensitive dimensional checks in silicon photonics and optical interconnect structures, including line edge roughness, overlay, and bump or micro-bump characterization.
IR-SIM extends this capability to bonded interfaces, buried structures, and interface-relevant inspection tasks where visible-light access is limited.
SIM combines non-contact optical sectioning and high-resolution 3D imaging across visible and infrared spectral ranges. Visible-light SIM is especially relevant for surface-sensitive dimensional checks in silicon photonics and optical interconnect structures, including line edge roughness, overlay, and bump or micro-bump characterization.
IR-SIM extends this capability to bonded interfaces, buried structures, and interface-relevant inspection tasks where visible-light access is limited.
Structured Illumination Microscopy (SIM) is a non-contact optical 3D imaging method that can be implemented across different spectral ranges. In visible light, SIM is typically used for high-resolution 3D topography and non-destructive cross-sectioning views. In the infrared range, SIM can provide additional access to bonded structures and support interface-relevant inspection and 3D analysis.
Visible light
Nanometer-precise 3D topography across diverse material combinations
Surface topography, patterned wafers, for example on optical interconnects
Patterned wafer inspection, optical interconnects, MEMS, bump inspection
Visible light does not penetrate opaque or optically thick layers, limiting access to buried interfaces and subsurface structures.
Surface Defects
Transparent Layers
Photonic Structures
Infrared
Additional access for buried interfaces and bonded structures
Bonded wafer interfaces, layered structures, buried overlay marks
Wafer bonding, advanced packaging, 3D integration
IR light is progressively absorbed as it travels through silicon, limiting effective penetration depth in thicker stacks.
Through Silicon
Transparent Layers
Photonic Structures
Visible-light SIM delivers precise optical sectioning of transparent layers, such as oxides and nitrides, together with high-resolution 3D metrology for surface-sensitive dimensional checks. It is particularly effective where strong lateral detail, high throughput, and accurate topography are required. In semiconductor manufacturing, this makes visible-light SIM especially relevant for silicon photonics and optical interconnect structures, line edge roughness evaluation, overlay-related verification, bump and micro-bump characterization, and other applications in which dimensional accuracy and repeatable optical measurement are critical.
- Non-contact 3D measurement of topography and geometry in nanometer precision.
- 2D measurements such as Line Edge Roughness (LER) for optical components.
- Additional coverage for line/space process-window analysis, MEMS structure characterization, and wafer-level process monitoring
- Fast optical image acquisition, supporting review of defects, particles, scratches, and process excursions
- Excellent suitability for silicon photonics, waveguides, couplers, co-packaged optics (CPO), and near-packaged optics (NPO)
- Cross-section views on oxide or nitride layers
Line/Space pattern detected
Individual line resolved
- Differentiation between surface contamination and embedded defects
- Inspection of buried waveguides
- Cross-sections through transparent layers
- Non-destructive, fully optical inspection with no sample preparation required
Infrared SIM expands structured illumination microscopy into applications where visible-light SIM reaches its limits. Depending on the material system and wavelength used, IR-SIM can provide additional access to selected buried features and support analysis of bonded or layered structures. This makes IR-SIM especially relevant for semiconductor processes involving buried interfaces, hybrid bonding, and complex material stacks.
Structured illumination in the infrared range for enhanced optical contrast and sectioning
Bonding- and interface-relevant inspection where IR access is beneficial
Wafer bonding, advanced packaging, 3D integration, MEMS
Enhanced bond-interface contrast
Metal content in the stack limits the optical transparency
Infrared optical imaging through silicon or other IR-relevant material systems
Imaging through silicon and visualizing buried alignment or structural features
Wafer bonding alignment, failure analysis support
Established method for optical inspection through silicon
Limited topography capability and strongly dependent on optical contrast and material transparency
Acoustic inspection based on ultrasound reflections from internal interfaces
Detecting buried voids, delamination, cracks, and non-bonded regions
Wafer bonding inspection, advanced packaging, package integrity analysis
Strong for buried defect detection at internal interfaces
Does not provide optical surface detail or optical 3D information
IR microscopy, SAM, and IR-SIM are complementary rather than interchangeable.
IR microscopy is valuable for imaging through silicon, SAM is strong for buried void and delamination detection, and IR-SIM adds a structured optical approach for bonding- and interface-relevant semiconductor inspection to quantify defects additionally by z-dimension and by optical cross-sectioning view.
- Enhanced access to features not visible in the visible spectrum
- Improved suitability for selected material stacks and bonded structures
- Additional contrast mechanisms for process monitoring and defect review
- Strong potential for advanced packaging, wafer bonding, and 3D integration
What is the difference between visible SIM and IR-SIM?
Visible SIM is primarily used for high-resolution 3D surface topography. IR-SIM is used when a different optical window is needed for selected buried structures, bonded interfaces, or semitransparent material systems.
Why use Infrared SIM for wafer bonding applications?
IR-SIM is relevant for wafer bonding applications because it can provide additional optical access and gives contrast to the bonded interfaces and layered structures that are not assessable with visible-light inspection alone.
Can SIM inspect below the wafer surface?
Depending on the wavelength and material system, IR-SIM can provide access to selected features below the immediate surface. The achievable result depends on transparency, layer stack, and inspection target.
Which materials benefit from IR-based optical inspection?
IR-based optical inspection is particularly relevant for material systems such as silicon which becomes transparent in infrared wavelengths. It provides an optical sectioning view which appears similar to a cross-sectioning with the advantage of being non-destructive. In semiconductor applications, this can include bonded wafers and layered structures where visible-light SIM is limited by transparency, depth, or interface visibility due to low contrast.
Is SIM suitable for MEMS and advanced packaging?
Yes. SIM is well suited for MEMS and advanced packaging applications because it combines non-contact inspection with high-resolution optical 3D information. Visible-light SIM is especially effective for surface-sensitive 3D topography, while IR-SIM can add value for bonded structures, buried interfaces, and complex material stacks.
When should visible SIM be preferred over IR-SIM?
Visible SIM should be the preferred choice when maximum surface detail, high lateral contrast and precise topography are the main priorities. IR-SIM becomes more relevant as soon as the inspection task requires buried features, bonded interfaces, semi-transparent materials or a different optical window.
Why does SIM not require calibration prior to routine optical measurements?
Confovis patented SIM is based on the illumination of a static grid and does not rely on moving optical elements such as pinholes or mirrors. It also does not use a scanning or rastering laser source. Instead, static LED illumination is used to project the grid, which supports a stable optical setup and does not require user-side calibration before each measurement routine.
Confovis brings structured illumination technology into semiconductor inspection with a strong focus on practical metrology and inspection tasks. Our solutions are designed to translate advanced optical methods into robust, application-oriented systems for wafers, microstructures, and advanced packaging environments. With SIM extending from visible light to infrared, Confovis supports customers in addressing evolving requirements such as:
- Higher complexity in silicon photonics, optical interconnects, heterogeneous integration, and increasingly integration-dense photonic structures
- New demands in wafer bonding and hybrid bonding
- Inspection challenges in 3D integration and advanced packaging
- The need for flexible, non-contact optical inspection methods supporting both process development and production ramp
From high-resolution visible-light 3D metrology to infrared-enabled access for buried structures, SIM offers a versatile foundation for next-generation semiconductor metrology and inspection, including emerging silicon photonics and optical interconnect applications.
Confovis helps customers evaluate the right SIM approach for their application and process environment.
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