Infrared Semiconductor Inspection is used to maximize production processes and optimize product yields. Product quality, failure detection and failure evaluation are rapidly becoming primary factors in the semiconductor sector, both at the wafer level and on the package and die level. Longwave Infrared Technology (LIT) is a new methodology to address these new demands. It is capable of detecting even very small flaws in semiconductors at high temperature using a principle similar to that employed by industrial viscosity testers. We review recent developments in LIT.
In the past, inspections of semiconductors used physical techniques such as surface charges, bulk spectroscopy, or chemical methods. These techniques were effective for defects which were small and could easily be missed using conventional methods. However, these traditional techniques had difficulty detecting larger defects which require advanced tools such as scanning electron microscopy (SEM). Also, the rate of growth of materials such as semiconductors was too fast for traditional inspection methods to keep up.
Infrared light is a unique form of electromagnetic radiation that is virtually unaffected by air, water, or solids. This enables Infrared Semiconductor Inspection to detect minute defects that become magnified when heat is applied. The use of infrared light for semiconductor inspection has revolutionized chip production. For example, a single chip composed of millions of individual atoms is scanned with an Infrared Scanning Camera. Each atom’s location is precisely recorded for easy retrieval at a later time.
As the sample’s temperature increases, mechanical strain is applied which heats the semiconductor material. When the temperature reaches absolute zero, however, the sample becomes brittle and cannot be examined any further. The most commonly used instrument for this type of inspection is the Infrared Thermogravimeter. Its name is somewhat confusing, since it is also called a Microwave Amplifier and an Ultrasonic Massager.
A variation of the traditional method employed in semiconductor inspections is the Electron Beam Detector. This instrument uses a scanning tunneling microscope to look for defects in the wafers. The electrons are emitted from metallic impurities such as iron traces, lead, copper, and aluminum, which often cause interference with the high frequency radio waves emitted by the scanner. This method has made incredible improvements in chip fabrication while simultaneously reducing cost and labor.
There are numerous benefits to using infrared technology in the inspection of semiconductors. First, it can detect and measure temperatures as low as -below 50 Kelvin. Second, it can be used on a wide variety of substrates including metals, plastics, and composite materials. Third, it has the ability to measure with a high degree of accuracy and provide detailed images that are difficult or impossible to achieve using other methods. Fourth, it can be configured to vary the wavelengths and scan frequencies for better accuracy.
While it has many advantages, many questions remain about its viability in the inspection of semiconductors. For example, certain metals that use high levels of metal ions in their manufacturing process may not be sensitive to heat, which makes them poor candidates for this technique. Another question is how infrared light can melt or conduct heat, especially in an environment where temperatures are well below the flash point of semiconductors.
With these potential limitations, however, the practicality of infrared technology in semiconductor inspection is growing. Some manufacturers have already started using this method in their products. In addition, the cost of using infrared technology in semiconductors has continued to decline. For example, integrated circuits that incorporate infrared light into their design have been able to utilize the method in place of traditional scanning. The popularity of this method has also led to the development of advanced tools and infrared illumination systems for inspection purposes. This combination of benefits has led to a significant increase in the accuracy of semiconductor inspection.
