Analyzing Chips at the Atomic Level

GF labs use the latest technologies to see what is nearly invisible

by Gary Dagastine

“Semiconductor manufacturing isn’t rocket science, you know – it’s much harder” is a running joke in many semiconductor fabs. While rocket scientists may disagree, there’s no question that designing and manufacturing today’s essential chips include many incredibly difficult engineering challenges.

After all, we’re talking about small pieces of silicon which may contain millions or billions of transistors. They are made from 40, 60 or more layers of materials with unique electrical characteristics, and with feature sizes approaching the dimensions of DNA molecules – only a few nanometers. The transistors are interconnected in increasingly complicated ways, such that if all the wiring within a fingernail-sized chip were laid end-to-end, it would be measured in meters.

But how can we know what’s actually going on in such a complex system? How can we learn if there are design issues, electrical faults, thermal effects or other surprises that will impact performance? Further, how can we ensure that the manufacturing process is as efficient as possible?

The answers can be found through wide range of characterization techniques in our global analytical laboratories.  GlobalFoundries (GF) boasts some of the leading technical experts in this field, along with one of the industry’s most well-equipped laboratories, outfitted with the latest electron microscopes and other tools needed to inspect and evaluate these tiny and impossibly complex devices.

GF’s very own C.S.I. unit

“We’re the C.S.I. unit at GlobalFoundries,” said Julie Lee, director of the global analytical laboratories at GF’s headquarters and manufacturing facility in Malta, New York. “We collect physical evidence from a chip during the manufacturing process, look at it in exquisite detail to see how its performance can be improved, and recommend to the fab how to accommodate those improvements.”

The lab Lee leads is the company’s newest facility for physical, material, electrical, optical and packaging analysis. It is part of a global analytical laboratories’ organization with branches in the U.S., Singapore and Germany, staffed by more than 250 engineers and technicians with a wide range of expertise who support the fab on a 24/7 basis.

Among other advanced instrumentation, it features state-of-the-art transmission electron microscopes (TEMs), which can magnify objects up to 2 million times. This capability enables visualization at the atomic level so that, for example, the “doping” of silicon (i.e., the impurities added to it to modify its electrical properties) can be seen and evaluated. TEMs also enable the analysis of errors that can’t be seen directly, such as electrical faults.

As semiconductor dimensions have scaled to smaller sizes, the microscopes needed to look at their features have also evolved, and GF’s laboratory contains a mix of optical and electron-based technologies, said Dr. Frieder Baumann, Principal Member of the Technical Staff at GF.

“Optical microscopes used to be the workhorse, but now they are mostly used with photonic devices such as GF’s Fotonix™ platform,” he said “We also have a number of scanning electron microscopes (SEMs), which offer high throughput and a resolution of a few nanometers. We use them to look at specific material layers, such as a chip’s resist layer, and to check for cracks in a chip’s interconnect, or wiring. While SEMs were the workhorse microscopy technology in past years, today their main use here at GF is for inline inspection to keep the manufacturing process flowing smoothly.”

Getting a closer look with TEMs

The latest evolution of microscopy is the TEM, which provides a larger field of view and much greater resolution than SEMs, and also permits users to instantly see on a screen exactly what is going on in the chip sample under study.

“TEMs have evolved from a pure imaging tool into a versatile instrument for comprehensive physical and compositional characterization, in conjunction with new techniques that we use to prepare samples for study,’ Baumann said. “It has become almost unthinkable to conduct modern semiconductor manufacturing without using a focused ion beam (FIB) tool to prepare a sample, and a TEM to understand what is going on inside it.”

The analytical laboratories team in Malta, New York, and other GF sites uses a suite of TEM tools, including both older and newer models, to study several thousand samples per month company-wide around the world.

“It’s amazing to think how far TEM technology has come in such a short time, and how versatile today’s machines are,” Baumann said. For example, automotive is a key market for GF, and a embedded memory is increasingly important for automotive applications because it is nonvolatile and stands up to the harsh real-world environments in which vehicles operate. “Thanks to our advanced TEM capabilities, we are one of only a few within the industry who can fully characterize every single element in the memory cell to determine that it is, in fact, built and operating properly.”    

Life in the Labs

In addition to advanced microscopy, the labs offer a wide range of techniques and are involved in many aspects of manufacturing operations, from incoming chemical analysis through manufacturing processing and customer feedback.  

“Just as GF’s fabs around the globe transfer technology and capabilities to one another to establish multiple sources of production worldwide, our worldwide labs also participate and support technology transfers,” Lee said. “We as a global lab organization are staffed with materials engineers, physicists, mathematicians, and technicians. On a regular basis, we share knowledge and lessons learnt between the global teams across all verticals of physical, chemical and electrical analysis, discussing specific issues, and capitalizing on what we’ve learned to improve GF’s overall manufacturing performance.”  

At the end of the day, Lee said the lab also brings her and her colleagues a great deal of personal satisfaction. “I find it very rewarding to be in an environment focusing on problem-solving and innovation.  It is especially satisfying when solutions are found as well as witnessing the growth of our team members.”