Researchers at the National Institute of Standards and Technology (NIST) have begun an ambitious project to attack a vexing problem in the semiconductor industry: rigorous flow control of the many gases used in making semiconductor microchips.
Fluid scientist Jodie Pope sitting in front of the computer that controls the benchtop semiconductor flow standard.
Credit: C. Suplee/NIST
“Flowmeter manufacturers need specified uncertainties – precisely measured levels of confidence – and dependably reproducible performance to manage all the gases they use,” said Jodie Pope of NIST’s Fluid Metrology Group. “And right now, in many cases, that requirement can’t be met – especially for some of the new and often hazardous gases recently introduced into the fabrication process.”
Making a typical microprocessor for a modern personal computer takes several weeks and hundreds of process steps inside sealed chambers. During that time, different gases are applied to or deposited on the chip over a wide range of temperature and pressure conditions to create the chemical compositions and etch the physical features that result in more than a billion transistors on a surface the size of a fingernail.
The FMG’s benchtop prototype semiconductor gas flow standard. Gas enters from the right and has two stages of pressure regulation before entering a mass flow controller (MFC), the meter under test, and then a back pressure regulator that holds the downstream pressure at the meter under test constant. A valve isolates the collection tanks, which are a pair of finned tubes with 0.025m outside diameter.
Credit: NIST
As chip components have grown smaller, so has the need for ultra-low gas flows – as little as one-tenth of a cubic centimeter per minute for some operations – that can be exactly controlled and do not vary more than a frac ..
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