SEMICONDUCTOR INSPECTION


SWIR-crazy: a look at the latest wafer testing tech


Hunting defects in the soon-to-be trillion- dollar semiconductor industry is big business. Anita Chandran explores the latest wafer inspection technology


I


ntegrated circuits based on semiconductor platforms underpin much of our current technology:


everything from electronic devices and sensors to solar panels. Te demand for such platforms is ever


increasing, with consultancy firm McKinsey anticipating that the semiconductor industry will be worth more than $1tn by 20301


, up from about $600bn in 2021. It


is estimated that about 70% of this growth will be driven by applications in electric vehicles, data storage, and wireless communications. Te need for high-yield, reliable


manufacturing processes has pushed the need for excellent semiconductor wafer inspection technologies. Wafer inspection involves imaging semiconductor chips throughout the fabrication process to spot defects. But the inspection process is costly and time-consuming, with hundreds of steps involved in manufacturing a single chip – a process that can take up to two months. Te growing need to address such issues has led to the semiconductor inspection industry itself becoming significant – currently valued at $5bn, and expected to grow to $8.9bn by 2031, according to Allied Market Research2 Manufacturers continually seek faster,


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higher-resolution imaging solutions for chip inspection to help boost the rate of fabrication. State-of-the-art cameras are therefore being developed and blue skies research undertaken in a bid to increase yield and efficiency in one of the world’s most important industries.


Short-wave infrared machine vision Most semiconductor devices are made from silicon wafers. Silicon is


largely opaque to visible light, but its transmissivity to light in the short-wave infrared (SWIR) spectrum is much higher, rendering it transparent at wavelengths greater than 1,050nm. As a result, many camera technologies used for chip inspection are based on SWIR sensors. Most of these systems utilise indium gallium arsenide (InGaAs) sensors with a sensitivity range from 900 to 1,700nm. By illuminating silicon semiconductor chips with SWIR light, these cameras can detect tiny features such as micro-cracks or contaminant particles. “To see small features and failures you


need a good signal-to-noise ratio. In order for that, you need a camera that is highly sensitive,” says Marc Larive, Strategic Marketing Manager of Xenics, a sensor and


14 IMAGING AND MACHINE VISION EUROPE APRIL/MAY 2023


camera developer for semiconductor wafer inspection in chip fabrication. Xenics’ cameras aim to achieve the vital trade-off between the high sensitivity required for SWIR detectors in semiconductor inspection, and pixel resolution. While the sensitivity of a camera is directly proportional to pixel size, going to smaller pixel sizes is not always the best solution. “In visible cameras, the aim is to get the


smallest pixel size possible, because you can obtain high resolutions,” says Larive. “But in SWIR this isn’t so because you don’t have a lot of natural light. You’re looking for tiny defects, so light budget is an issue. At Xenics, we found a very good trade-off with a pixel size of 20 microns – you can detect very small items, small failures with it.”


@imveurope | www.imveurope.com


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