In the precision-driven world of semiconductor manufacturing, a single nanometer-level defect on a wafer surface can directly lead to reduced chip yield rates or even cause an entire production line to halt. Traditional microscopic inspection technologies, constrained by focusing speed, accuracy, and the contamination risks associated with contact-based detection, struggle to meet the stringent defect detection requirements of advanced processes. Laser autofocus microscopy systems, however, are emerging as a critical tool for enhancing yield and controlling costs in the semiconductor industry. This is due to their three core advantages: non-contact operation, micron/nanometer-level precision, and real-time dynamic focusing.

I. Non-Contact Inspection: Safeguarding the “Zero Damage” Bottom Line for Wafers

Semiconductor manufacturing demands near-obsessive cleanliness on wafer surfaces. Traditional contact-based inspection tools (such as probes) may introduce scratches, electrostatic charges, or particle contamination through mechanical friction, leading to wafer scrap. The laser autofocus microscopy system employs coaxial laser scanning technology. It forms a point light source on the wafer surface via a laser beam and utilizes a detection pinhole to receive the reflected light spot, eliminating any physical contact throughout the process. For instance, during wafer coating, the system can precisely detect coating thickness uniformity, preventing oxidation failures caused by coating defects while ensuring zero damage to the wafer surface.

II. Micron/Nanometer-Level Precision: Detecting “Invisible Killer” Defects

As chip manufacturing processes advance below 3nm, defect sizes on wafers are approaching the limits of optical detection. Laser autofocus microscopy systems achieve ±0.1μm focusing precision through laser autofocus algorithms and high-precision motion control modules, enabling clear identification of nanoscale defects such as photoresist residue and etching non-uniformity. During development and etching monitoring, the system measures etch depth and width deviations in real time, ensuring transistor channel dimensions meet design specifications. Data from a leading wafer fab indicates that implementing this system has reduced pattern misalignment rates in the lithography process and shortened inspection time per wafer.

III. Real-Time Dynamic Focusing: Resolving the “High Speed + High Precision” Paradox

Semiconductor production lines strive for “zero downtime” operation, but traditional microscopes often lose focus during high-speed scanning due to vibration or wafer warping. The laser autofocus microscope system employs a closed-loop feedback control mechanism. It uses laser sensors to monitor real-time changes in the spot pattern and combines this with an AI-based defocus prediction algorithm to complete focus compensation within milliseconds. For instance, during chip packaging bump inspection, the system can simultaneously track the height and coplanarity of hundreds of bumps, ensuring stable signal transmission. Tests by a packaging company indicate this technology enhances bump coplanarity inspection efficiency while reducing misjudgment rates.

IV. Expansion of Industry Application Scenarios: Full-chain Coverage from Wafer to Endpoint

• Wafer Manufacturing：Coating uniformity inspection, photoresist thickness measurement, etch endpoint monitoring.

• Advanced Packaging：Interlayer alignment for 3D stacked chips, TSV through-hole defect identification.

• Failure Analysis：Failure localization of internal metal interconnect layers in chips and tracking of electromigration phenomena.

The evolution of laser autofocusing microscopy systems fundamentally reflects the semiconductor industry's perpetual pursuit of “smaller, faster, and more reliable” solutions. With the widespread adoption of new technologies like EUV lithography and GAA transistors, these systems are advancing toward sub-nanometer precision and multi-spectral fusion detection capabilities.