When Cambridge NanoTech Inc. first started manufacturing atomic layer deposition (ALD) systems in 2003, the company was experiencing frustrating clogs in the system’s valves, which were also underperforming when exposed to heat. The result was lots of downtime.

“The first valves we were using needed to be replaced once a month,” explains Dr. Jill Becker, founder of Cambridge NanoTech. “That meant operators had to cool the system down, go in there with wrenches, take everything apart, and replace the valves with ones that were sure to cause downtime again in the future. When you think about manufacturing efficiency, you just can’t have this sort of maintenance headache.”

CONSERVING PRECURSORS
Cambridge NanoTech’s ALD systems are used in research and development and manufacturing operations for semiconductor wafers, nanoelectronics, optics, and microelectromechanical systems (MEMS), in addition to novelty applications such as coatings for drill bits, router bits, and even butterfly wings.

These systems are highly valued not only for their dependability but also for efficient use of expensive precursor gas.

The ALD process deposits thin films of precursor materials onto substrates one atomic layer at a time to impart such properties as conductivity, chemical resistance, and strength. With help from Swagelok® ALD valves, Cambridge NanoTech has designed gas delivery assemblies that achieve precise, controlled delivery of precursor gas.

One reason for the precise timing is the ability of one ALD valve to perform two functions—precursor delivery and purging. The alternative would be to construct a subassembly of several valves, which can introduce timing variability. Inconsistent precursor and purge gas delivery times result in an increase in the quantity of precursors consumed, which, in turn leads to higher cost of ownership.

In its most basic form, the ALD valve design consists of three ports. Carrier gas enters through one port and exits through another. Precursor gas enters through a third port, which is a small, precise orifice that delivers minimum chemical volume. This threeport configuration works by delivering a steady flow of carrier gas into the ALD chamber. At precisely timed intervals the carrier gas flow is interrupted by a brief pulse (<15 milliseconds) of precursor gas. The carrier gas moves the precursor into the deposition chamber where precursor atoms attach to the substrate being coated.

“Through precise delivery of precursor gas, nearly all of the gas is used in the deposition process,” Becker said. “The delivery is so precise that a system running at full capacity 24/7 may take three months or longer to use a 25cc cylinder of precursor.”

CUSTOM CONFIGURATIONS
An objective of Cambridge NanoTech is to provide ALD tools that are versatile, expandable, and tailored to the specific needs of the customer.

“It doesn’t matter if we offer 25 different configurations. There will be customers who want a different version,” Becker explains.