In the precision manufacturing chain of the semiconductor industry, wafer inspection is a key link to ensure chip yield. With the continuous breakthrough of chip manufacturing processes towards 7nm and below, strict requirements have been put forward for the accuracy and efficiency of detection technology. At present, the mainstream wafer inspection technologies in the industry - optical inspection, electron beam inspection, and atomic force microscopy inspection - play important roles in different inspection scenarios based on their respective technical principles, jointly building a "protective net" for wafer quality.

Optical inspection technology, based on the core principle of "propagation and interaction of light", is a widely used fundamental technology in wafer inspection. Its essence is to emit a specific wavelength of light beam onto the wafer surface through a high-resolution optical system, and capture wafer information using the reflection, refraction, scattering, and interference characteristics of light. When a beam of light shines on scratches, defects, or abnormal areas on the surface of a wafer, the propagation path of light changes. High precision image sensors convert these changes into electrical signals, which are processed by algorithms to generate data on the location, size, and type of defects. This technology has the advantages of non-contact and high speed, with a detection speed of tens of frames per second, suitable for batch defect screening throughout the entire wafer manufacturing process, especially in the appearance defect detection of processes above 28nm, with outstanding efficiency.

Electron beam detection technology relies on the interaction between electrons and matter to achieve ultra-high precision detection, and is the core detection method of advanced processes. The principle is to focus a high-energy electron beam on the surface of the wafer through an electron gun. After the electrons collide with the atoms of the wafer material, signals such as secondary electrons and backscattered electrons are excited. The electronic signals excited by different materials and structures in different regions vary. By collecting these signals through detectors and converting them into images, nanoscale defects and circuit features can be accurately identified. The resolution of this technology can reach the level of 0.1nm, which can effectively detect small defects that cannot be recognized by optical detection. However, the detection speed is relatively slow, making it more suitable for key step detection in advanced processes below 7nm, such as photoresist pattern accuracy verification and metal wiring defect investigation.

Atomic force microscopy detection technology focuses on "interatomic forces" to achieve atomic level morphology characterization of wafer surfaces. The core component is a cantilever beam with nanoscale probes. When the probe approaches the wafer surface, the probe atoms and the wafer surface atoms will generate van der Waals forces and other interaction forces, causing slight deformation of the cantilever beam. By using laser beam reflection method to detect this deformation and combining it with feedback control system to adjust the distance between the probe and the wafer in real time, the atomic level surface morphology can be converted into three-dimensional image data. This technology can not only detect surface defects, but also obtain physical properties such as surface roughness and elastic modulus. It is suitable for high-precision scenarios such as wafer surface coating quality inspection and nanostructure size measurement, providing micro level data support for process optimization.

The three detection technologies each have their own focus and complement each other, jointly meeting the diversified needs of wafer detection. Optical detection relies on efficiency for batch screening, electron beam detection overcomes advanced process challenges with precision, and atomic force microscopy detection assists technology research and development with microscopic characterization. In the process of advancing towards higher precision in the semiconductor industry, a deep understanding of the core principles of various technologies is necessary to select testing solutions based on actual needs and provide reliable guarantees for every aspect of chip manufacturing.