A faster way to find yield-killing defects that are deeply buried within complex structures.
The semiconductor industry is defined by its relentless pursuit of smaller, faster, and more powerful chips. As we push into advanced 3D architectures like gate-all-around (GAA) transistors, a critical challenge emerges: finding the defects that kill yield. Many of these flaws are deeply buried within complex structures and impossible to see with traditional optical inspection.
This creates a significant inspection gap. PDF Solutions is addressing this gap with DirectScan, an approach powered by the eProbe e-beam inspection tool. This technology redefines e-beam inspection, transforming it from a slow, exhaustive process into a fast, intelligent, and design-aware solution that meets the demands of modern semiconductor manufacturing.
For decades, optical inspection has been the primary method for process control in fabs. However, the move to multi-level interconnects and 3D transistor designs means that many killer defects are no longer on the surface. They are hidden within the chip’s intricate layers, making them invisible to optical tools.
E-beam inspection, which uses electrons to detect electrically relevant defects, offers the necessary sensitivity. Yet, it has traditionally been too slow for high-volume manufacturing. Conventional e-beam tools operate by scanning large areas of a wafer, capturing full images, and comparing them to find anomalies. This raster-scanning method is inefficient because it spends most of its time scanning dielectric, or non-conductive, areas that provide no useful information.
The challenge is clear: the industry needs the precision of e-beam inspection at a throughput that can keep pace with production.
DirectScan introduces a fundamental shift in e-beam inspection with a technique called PointScan. Instead of scanning entire regions, eProbe functions like a contactless electrical tester. It intelligently jumps from one specific point of interest to another, measuring voltage contrast only where it matters.
This design-aware inspection is made possible by integrating the eProbe tool with PDF’s FIRE GDS analysis platform. The system knows the exact “GPS location” and layout characteristics of every point it inspects. It strategically targets critical locations, like transistor contacts or vias, while completely ignoring the empty spaces in between.
The efficiency gains are substantial. For example, in a back-end-of-line (BEOL) application, analysis showed that only 2.5% of the total area required inspection to find critical defects. By focusing only on these areas, PointScan avoids wasting time on the other 97.5%.
This targeted approach delivers throughput that is 20 to 100 times faster than conventional single-beam tools. It allows for the inspection of billions of devices per hour, making high-volume e-beam inspection a practical reality.
DirectScan is a fundamental shift in e-beam inspection using a technique called PointScan. eProbe intelligently jumps from one specific point of interest to another, measuring voltage contrast only where it matters instead of scanning entire regions.
The value of DirectScan extends beyond just finding defects faster. By integrating layout data, the system provides deep insights into why defects are occurring. For every inspection point, the system knows key attributes: Is it a gate or drain contact? What is its transistor type? How close is it to other features?
When a defect is found, its attributes are automatically recorded. This allows engineers to quickly analyze the data and calculate failure rates for specific layout configurations. They can immediately identify which design features are most vulnerable to process variations.
This capability transforms inspection from a simple pass/fail test into a powerful learning cycle. Engineers can use this actionable data to refine their processes and even improve future inspection recipes, focusing their efforts on the highest-risk areas. It accelerates the identification of product-specific weaknesses, shortening the time from root cause analysis to corrective action.
The precise and targeted nature of PointScan offers another crucial benefit: significantly reduced wafer charging. This is particularly important for emerging technologies like backside power delivery networks (BSPDNs) and 3D DRAM, which involve bonded wafers.
These structures create insulating layers that trap electrical charge during conventional e-beam inspection, distorting the beam and making accurate measurement impossible.
PointScan deposits dramatically less charge on the wafer, overcoming these issues and enabling reliable inspection of these advanced designs. PDF Solutions has already demonstrated successful applications on both BSPDN and 3D DRAM wafers.
Furthermore, PointScan enables entirely new inspection methods. With its “charge and sense” capability, the tool can intentionally charge one location and then measure the electrical effect at another. This has proven invaluable for detecting complex defects, such as shorts in dense DRAM arrays, that are impossible to find with traditional raster scanning.
Since its introduction, the eProbe system with DirectScan has been adopted by leading-edge logic fabs for high-volume manufacturing. Its applications span the entire process flow, from middle-of-line (MOL) gate structures to BEOL metal layers.
Key applications include:
The solution provides high-throughput product inspection, accelerates the learning cycle to identify process weaknesses, and enables inspection of advanced wafer structures that were previously challenging.
As semiconductor complexity continues to increase, the tools used to ensure quality and yield must evolve. Traditional inspection methods are no longer sufficient to find the buried, systematic, and electrically critical defects that dominate yield loss in advanced nodes.
DirectScan represents this evolution. By combining the targeted efficiency of PointScan with design-aware intelligence, it offers a solution that balances the sensitivity of e-beam technology with the throughput demands of modern manufacturing. This approach provides a clear path forward, empowering semiconductor companies to solve the inspection challenges of today and unlock the potential of the next generation of devices.
A detailed overview of PDF Solutions DirectScan solution can be found here.
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