Particle Inspection by Single Camera-Based 3D Stereoscopy
Authors: Lee Hyun Jae , Sung Gugyeong , Chun Heebum , Lee ChaBum 
Published: August 2024

Abstract
Surface inspection of semiconductor wafers plays a pivotal role in ensuring the quality and reliability of semiconductor products. Conventional wafer inspection technologies have harnessed various methodologies to enhance the precision of inspection systems. However, as the semiconductor industry relentlessly pushes the boundaries of technology, these conventional methods primarily designed for single-wafer surfaces confront novel challenges. The unyielding pursuit of shrinking critical dimensions (CD) has intensified the need for more measurements, underscoring the significance of precise and reliable inspection systems. In a landscape where the technology is requiring higher resolutions and precision, various inspection methods are developed. However, as the instrumentation become precise, the cost of the system increased. High-cost instruments increase the gap between the industry and research. For this reason, the low cost with high precision inspection method should be developed.
This paper introduces an innovative approach to particle inspection within semiconductor silicon wafers, employing single camera-based 3D stereoscopy reconstruction (SCSR). Conventional stereoscopy methods encounter limitations, primarily stemming from the dimensions of the cameras used. To surmount these limitations, we propose the utilization of a single-camera system for generating highly detailed depth maps of submicron-sized particles. For the precise measurement of small defects, a smaller baseline becomes a requirement. The single-camera stereoscopic method offers the flexibility to control the baseline, enabling the measurement of smaller defects in comparison to conventional methods. Furthermore, we leverage the inherent transparency of semiconductor wafers to infrared (IR) light. Through the use of a halogen lamp as the IR light source, the emitted light efficiently penetrates the wafer. Subsequently, Short-Wave Infrared (SWIR) cameras are employed to capture images, thereby revealing particle defects that would remain concealed from standard visible cameras.
In experimental validation, we conducted a comparative analysis between visible cameras and SWIR cameras to ascertain the dimensions of particles on the wafer surface. We harnessed the capabilities of SCSR methods to create 3D depth maps. The results unequivocally demonstrate the exceptional potential of the single-camera stereoscopic method for particle inspection. In conclusion, our innovative approach harnesses single camera-based 3D stereoscopy, surmounting the limitations posed by traditional stereoscopy methods. By capitalizing on the transparency of semiconductor wafers to SWIR light, we have enabled the detection of particle defects that were previously elusive. The experimental validation underscores the promise of our method for inspecting particles on silicon wafers. Our approach promises to be a valuable asset to the semiconductor industry, where the pursuit of smaller CD and 3D technologies necessitates advanced inspection systems.