Infrared camera for defect detection in the production of semiconductor materials

Electronic equipment has become very common in today's society, and silicon wafers have passed through the carrier of electronic equipment. It can be said that they are inseparable from each of us. The key material for semiconductors is silicon. A wafer is a very thin semiconductor substrate used to make electronic integrated circuits. There are various types of semiconductor materials. One of the more commonly used semiconductor materials in electronic devices is silicon (Si).

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Silicon wafers are a key part of integrated circuits. It is made by slicing a high-purity, almost defect-free single-crystal silicon rod and used as a substrate for manufacturing microelectronic devices in and on the wafer surface. Wafers are made through multiple micromachining process steps, such as masking, etching, doping, and metallization.

Integrated circuits, often called ICs, have become a major component of almost all electronic equipment. IC is the transplantation and printing of microstructures of a large number of electronic circuits and components onto the surface of semiconductor crystal (such as Si) materials. Components, circuits, and substrates are manufactured on a single wafer. Hundreds of ICs can be fabricated on a single thin silicon wafer at the same time and then divided into multiple individual IC chips.

Silicon wafer cracks endanger the quality of the final product: Silicon wafers can accumulate residual stress during growth, cutting, grinding, etching, and polishing. Therefore, silicon wafers may crack during the entire manufacturing process. If cracks are not detected, those wafers containing cracks will form useless products in subsequent production. Cracks may also occur when an integrated circuit is divided into separate ICs. Therefore, to reduce manufacturing costs, it is important to check for impurities, cracks in the raw material substrate, and detect defects during processing before further processing.

Silicon has the property of transmitting infrared rays. Therefore, indium gallium arsenide (InGaAs) cameras are suitable for the short-wave infrared (SWIR) wavelength range of 0.9 ~ 1.7µm, allowing users to see through semiconductor silicon substrates. The characteristics of short-wave infrared penetration of semiconductor materials have brought great benefits to the semiconductor material manufacturing process. Infrared images can highlight defects (such as cracks) inside the silicon wafer.

The following figure is an infrared imaging detection system for cracks inside a silicon substrate. It shows that in an infrared microscope, a short-wave infrared (SWIR) camera is used to detect defects in the semiconductor manufacturing process.

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Figure 1: Silicon wafer defect inspection system with SWIR camera

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Figure 2: Comparison of defects detected in silicon wafers between ordinary cameras and SWIR cameras

It can be seen from the two pictures in Fig. 2 that the imported short-wave infrared camera using the Vision Image Agent can clearly capture the defects and cracks that may occur inside the IC chip. The camera uses a high-performance InGaAs sensor designed to meet higher industry standards and is equipped with an active thermoelectric cooling device (TEC1), enabling low-noise imaging at different ambient temperatures. The camera is compact, rugged, and offers multiple mounting options for easy integration.

This SWIR camera is affordable and has enough resolution to detect defects, making it ideal for cost-sensitive applications. The camera is equipped with a GigE Vision interface, with a maximum frame rate of 344fps at full resolution. The infrared imaging inspection it implements can improve the quality control process of silicon wafers and reduce inspection costs.