In semiconductor manufacturing, detecting defects early is critical to ensuring long-term device reliability and production yield. As semiconductor component dimensions shrink, traditional surface-level inspection is no longer sufficient. Subsurface and bonding defects—such as voids, bubbles, and microcracks—often escape visual detection, and can compromise electrical/optical performance and thermal integrity.
To detect defects and damage, manufacturers rely on advanced inspection techniques like infrared (IR) microscopy, X-ray, or ultrasonic imaging. While both methods offer non-destructive ways to peer beneath the surface, each comes with distinct strengths and limitations. This blog compares IR microscopy, X-ray, and ultrasonic technology in the context of semiconductor quality control, exploring their capabilities, resolution limits, and suitability for identifying hidden defects.
The Complexities of Semiconductor Inspection
Although inspection techniques aim to catch as many issues as possible, some of the most critical defects and thermomechanical stresses remain difficult to detect. From manufacturing flaws to stress-induced damage over time, these invisible threats can compromise both yield and long-term reliability. Below, we break down the most critical defects and thermomechanical stresses that semiconductor manufacturers must contend with.
The Hard-to-See Defects Undermining Semiconductor Quality
Critical defects in semiconductors include bonding issues, such as non-stick or misaligned wire or die bonds, and cracks in the silicon die that can result from handling or stress. Voids within solder joints or adhesives reduce mechanical and thermal performance, while delamination at material interfaces compromises reliability and moisture resistance. Bubbles trapped during adhesive can evolve into voids or cracks. Lastly, particle contamination like dust can cause electrical shorts or interfere with photolithography.
The Thermomechanical Stresses and Damage That Escape Detection
Key thermomechanical challenges include a coefficient of thermal expansion (CTE) mismatch between different materials, which causes mechanical strain and reliability issues. In addition, thermal cycling leads to fatigue in solder joints due to repeated expansion and contraction. Furthermore, die cracking or warpage can result from uneven thermal loads or stress during packaging. Another common issue is the popcorn effect, caused by moisture expansion during reflow, which can lead to internal delamination or fractures.
The Hard Work Behind Detecting Hidden Semiconductor Defects
Identifying subsurface and bonding defects is no easy task. While several inspection techniques are available, each comes with trade-offs in cost, resolution, and practicality. Manufacturers often face a difficult balance between accuracy and efficiency—especially when using destructive methods or advanced imaging tools like X-ray, Ultrasonic imaging, and IR microscopy.
Challenges with Destructive Testing Methods
Manufacturers often rely on destructive techniques like cross-sectioning, dye and pry, or decapsulation to detect internal defects. While these methods can provide detailed insights, they are expensive, time-consuming, and not viable for in-line or high-throughput inspection. Each analysis requires sample preparation and results in the loss of the semiconductor device, making it impractical for routine quality control. Additionally, because these tests are typically applied to a limited sample size, there's a risk of missing defects that could impact the broader production batch.
The Value of Non-Destructive Methods like X-ray and IR Microscopy
Non-destructive methods like X-ray and IR microscopy are, therefore, essential tools for semiconductor inspection, offering the ability to detect internal defects—such as voids, cracks, and misaligned bonds—without damaging the device. These techniques provide a clear view beneath opaque materials like silicon, allowing engineers to verify structural integrity and diagnose failure risks early in the process. By preserving the part under inspection, they support faster iterations, reduce waste, and ensure higher reliability throughout R&D and production.
How X-Ray Inspection Detects Subsurface and Bond Defects
X-ray inspection identifies subsurface and bond defects in semiconductors by using high-energy photons to penetrate silicon and reveal internal structures based on differences in material density. This technique can detect voids in solder joints, delamination, cracks, wire bond failures, and internal deformation caused by moisture or stress. While 2D X-ray provides quick overviews, 3D computed tomography (CT) offers more detailed insights. However, its resolution can be limited—especially for fine cracks or defects in low-density materials.
What IR Microscopy Sees That Other Techniques Might Miss
IR microscopy is particularly effective at detecting defects in semiconductor materials that are transparent to IR wavelengths, such as silicon. In addition to identifying cracks, delamination, and voids within the silicon die, it can detect more subtle issues. These include residual stress fractures, dislocations, and laser-induced damage that may go unnoticed through X-ray. Because it’s non-destructive and operates with high resolution, IR microscopy is well-suited for inspecting fine features, early-stage damage, and low-density materials that are otherwise difficult to image.
Why Is Ultrasonic Imaging Tricky for Inspecting Silicon Wafers?
Another method for inspecting semiconductors is ultrasonic technology, which uses high-frequency sound waves to characterize materials. While ultrasonic imaging is particularly useful for thick or opaque materials, it has several drawbacks when applied to surface metrology. Its resolution is generally lower than that of optical methods.
Moreover, it typically requires the sample to be immersed in water or coupled with a gel to enable efficient sound transmission. For delicate surfaces like silicon wafers, immersion can pose contamination risks, introduce surface defects, and create handling challenges—making this technique less suitable for high-precision, non-contact applications.
Why Consider IR Microscopy Over X-Ray and UltrasonicTechnologies?
IR microscopy offers several advantages over X-ray techniques, particularly for inspecting defects in silicon-based semiconductors. Since silicon is transparent to infrared light, IR microscopy can penetrate the die, revealing surface and subsurface defects such as cracks, delamination, and stress-induced fractures with high spatial resolution.
It is also non-destructive, non-ionizing, and typically easier to set up and operate than X-ray systems. Unlike X-ray, which can struggle with low-density materials and fine features, IR microscopy excels at detecting defects that don't involve significant density changes, making it ideal for early-stage damage and delicate structures.
Why Consider Jay Photonics’ IR Microscope for Semiconductor Inspection?
Jay Photonics offers a compelling alternative to traditional IR microscopes, delivering up to 2x better resolution to reveal even the smallest defects with high-definition clarity. Designed for seamless integration, the IR imaging technology can be added to any optical system operating in the visible spectrum—transforming existing microscopes into powerful IR inspection tools at a fraction of the cost.
The ready-to-use, portable solution installs in just two minutes and offers deep silicon imaging with superior resolution and image quality. As a cost-effective complement to existing equipment, the Jay Photonics IR microscope fits easily into semiconductor inspection workflows and can be used alongside traditional IR systems to address different needs across the development process.
Curious to see the difference for yourself?
Visit jayphotonics.com to learn more about how the Jay Photonics technology can enhance your inspection capabilities or to request a demo tailored to your setup.