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Title

High-Resolution Bi-Telecentric Imaging Solutions for Semiconductor Wafer Inspection

Abstract

This technical article explores the critical role of high-resolution bi-telecentric lenses in modern semiconductor wafer inspection.

As wafer geometries shrink and production speeds increase, standard optical systems often fail to meet the rigorous demands of precision and throughput.

This guide details the specific challenges of imaging silicon substrates—specifically the need for high light flux and motion blur reduction—and presents a robust machine vision solution.

By integrating high-sensitivity line scan cameras with specialized bi-telecentric optics, manufacturers can achieve superior defect detection and measurement accuracy.

Tags

  • Semiconductor Wafer Inspection
  • Bi-Telecentric Lenses
  • High Resolution Machine Vision
  • Line Scan Imaging
  • Optical Metrology

Table of Contents

  1. Challenges and Requirements of Wafer Inspection
  2. Core Advantages of Bi-Telecentric Lenses
  3. Detailed Solution Breakdown
  4. Matching High-Resolution Cameras and Lenses
  5. The Importance of High-Brightness Illumination
  6. Inspection Targets and Applications
  7. Conclusion

Main Text

1. Challenges and Requirements of Wafer Inspection

As semiconductor technology nodes shrink, wafer circuit structures become increasingly intricate, presenting unprecedented inspection challenges:

  • High Resolution: Detecting minute defects like scratches, particles, or pattern errors requires resolving features at the micron or sub-micron level.
  • High-Speed Inspection: Maximizing production efficiency demands rapid wafer movement, requiring cameras to capture clear images in extremely short exposure times to avoid motion blur.
  • High Depth of Field & Large Field of View: Slight wafer warping requires lenses with sufficient depth of field for full-area sharpness, while a large field of view improves scanning efficiency.
  • High Light Flux Demand: Short exposure times limit sensor light intake, necessitating ample illumination for good signal-to-noise ratio images.
Semiconductor wafer inspection

2. Core Advantages of Bi-Telecentric Lenses

Bi-telecentric lenses, with object-space and image-space telecentricity, are ideal for addressing these challenges, offering revolutionary advantages for precision measurement and inspection:

  • Zero Perspective Error: Image size remains unchanged with object movement within the depth of field, eliminating measurement errors from wafer unevenness or positioning inaccuracies.
  • High Resolution & High Contrast: Designed for high-resolution sensors, these lenses fully utilize line scan camera performance for sharp, clear image details.
  • Low Distortion: An extremely low distortion rate ensures geometric fidelity, making inspection results more reliable.
  • Unique Optical Design: Large entrance pupil diameters allow for greater light collection, meeting high light flux requirements for high-speed inspection.

3. Detailed Solution Breakdown

To address rigorous wafer inspection demands, we provide a verified, high-performance machine vision solution.

4. Matching High-Resolution Cameras and Lenses

  • Camera: The Dalsa 16k 5µm line scan camera, with 16,000 pixels and a 5µm pixel size, offers an ultra-wide field of view and exceptional resolution for large-area, high-precision wafer scanning.
  • Lens: Our DTCA24K-75-M95-AL bi-telecentric lens is perfectly matched to the camera. Designed for 24K and smaller line scan cameras, its high-resolution capabilities resolve 5µm details, maximizing system performance through precise pixel size and field of view matching.

5. The Importance of High-Brightness Illumination

During high-speed movement, extremely short camera exposure times require a high-brightness light source.

  • Light Source Selection: We use a Red Line Light. Red light’s longer wavelength offers better silicon material penetration for subsurface defect detection. The line light design aligns with line scan camera scanning, concentrating light energy on the imaged line for high illumination intensity.

6. Inspection Targets and Applications

This solution meets core inspection targets:

  • High Resolution & Light Flux: Clearly images 5µm wafer structures, ensuring image quality during high-speed movement.
  • Camera Matching: Perfectly matches high-resolution line scan cameras like the 16K 5µm or 24K 3.5µm, allowing for future upgrades.
  • High-Precision Analysis: Achieves 5µm level analysis accuracy for advanced process node inspection needs.
  • Handling High Speed & Short Exposure: The lens’s high light-gathering capability and high-brightness light source solve insufficient lighting issues from short exposure times during high-speed motion.

This solution is widely used in front-end and back-end semiconductor manufacturing, including:

  • Wafer surface particle and scratch detection
  • Photoresist pattern defect inspection
  • Wafer scribe line inspection
  • Pad and bump dimension measurement and defect inspection

7. Conclusion

In semiconductor wafer inspection, the pursuit of speed, precision, and reliability is endless. Adopting our high-resolution bi-telecentric lens paired with high-performance line scan cameras and specialized illumination provides a complete, powerful solution. This setup meets current 5µm inspection requirements and lays a solid foundation for future stringent inspection challenges with its superior optical performance.