Mobile Cleanrooms - Key to Semiconductor Manufacturing Construction

Reviewed by Davis Verheyen
  • November 30, 2021

The pandemic and its resulting impact on the global supply chain has had a number of knock-on effects that will continue to be felt in the years to come. Perhaps the most noticeable is the shortage of microchips which are found in every bit of technology from toys to mobile devices to automobiles and beyond. In order to address this production shortage as much as to ease logistics, many of the biggest makers of semiconductors are “onshoring” their fabrication plants (“fabs”) in the U.S.. Samsung, Intel and TSMC have collectively broken ground, nearing construction or begun the permitting process for four fabs in the state of Arizona alone.1,2,3

Because of the extremely small sizes involved, the manufacturing process needs to be as clean as possible. Chip features are measured in nanometers – or one millionth of a millimeter. With the smallest structure on a chip measuring a mere 10 nanometer, a stray human hair with a diameter of 2.5 nanometers and lengths in the tens of thousands of nanometers, can ruin quite a few chips.4 This requirement for cleanliness applies not only to the solid components that go into these silicon wafers, but extends also to the dozens of gases used to create the tiny circuits. As a result, the stainless steel tubing used to deliver those gases must be ultra-clean themselves and that cleanliness starts with its own assembly process.

Ultra Clean Assembly for Ultra Clean Production

Semiconductor manufacturing is performed in cleanrooms with among the highest standards of any industry – ISO 4. Focusing on particles measuring between 0.5µ and 5.0µ (µ=micron, measurements in thousandths of a millimeter), they require 300-540 complete changes of air per hour to achieve less than 352 particles per cubic meter of that smallest size.5

Contamination in an ultra-clean gas pipeline is never good. But in a line carrying pure oxygen, a particle can ignite and burn a hole through the tubing wall. Such a small hole could be undetectable, but it could potentially compromise the purity of the gas as well the cleanliness of the entire room. To avoid this situation, the tubing commonly needs to be assembled in an ISO 4 cleanroom. Traditionally, the tubing was formed and orbital welded (the joints welded around their circumference), given a final clean and sealed for transport at an offsite cleanroom. This presents challenges both in the time needed to get the parts on site as well as the potential risk of contamination in transport. Any delays in transportation can throw off a schedule. And, if tubing was compromised during the shipping and handling process, then the project is further delayed while a replacement is formed and shipped.

Mobile Cleanrooms for On-Site Assembly

However, the advent of mobile cleanrooms which have been purpose-designed for ultra-pure welding reduce the time, risks and expense of forming cleanroom tubing offsite without compromising cleanliness standards. Part of Astro Pak’s fleet was recently contracted for a similar project. Three trailers were deployed where needed on the construction site and together, over 100 miles of stainless steel tubing was assembled and installed.

The 53-foot tandem axle semi-trailers are rated up to ISO 4 cleanliness standards and were built from the chassis-up for use in ultra-pure welding applications. The clients were able to configure and weld the tubing and perform the final cleaning with no downtime due to transit. And, because they were on-site, they were able to make configuration adjustments in real-time without having to send out an order for modifications back to an offsite location.

Timeliness is Crucial

One added complication of the current logistical situation has made mobile cleanrooms even more attractive. A shortage of drivers coupled with a surge demand for freight transportation has put pressure on hauling firms. Contractors working on fabs are finding that shipping expenses have risen as much as 30% higher than they were last year. Any unplanned additional shipments directly affect the profit on the job.

Mobile cleanrooms bypass that bottleneck. Because of their demonstrable success, there has been a very noticeable increase in interest in their use. “We’ve been getting a lot of calls inquiring about their availability,” said Davis Verheyen who heads Astro Pak’s mobile cleanroom unit, noting that calls have increased 90-120% over the past year. “We can have a trailer on-site within five days of the contract being signed, and we’re building new ones as fast as we can because we expect demand to heighten even more in the coming months.”

Even after the pandemic and the logistical squeeze pass into history, mobile cleanrooms are expected to grow as the go-to tool in the construction of cleanliness critical facilities.