Why vibration control is key to semiconductor manufacturing

Posted on 23 May 2023 by The Manufacturer

Semiconductor manufacturing has received a lot of media attention in recent years. However, one crucial element to chip manufacturing that goes under the radar is the need for vibration control.

In this article, we reveal the inside story of Mason UK’s effort to provide effective vibration control at Europe’s largest semiconductor manufacturing facility.

It’s April 24, 2020, and only one flight is leaving Heathrow. Adam Fox, Director of Mason UK, is one of only four people on that flight. The entire terminal is empty and only Boots is open for lunch. A formal letter is required to explain the need for his travel. The project he is working on is classified as essential works.

His destination, which we cannot formally disclose, is one of the largest manufacturing sites in Europe. Its purpose is the production of semiconductor chips. Periodically, fabrication plants, or fabs as they are more commonly known, require equipment upgrades. On this occasion, however, there is an entirely new plant to be constructed. So important is this project that work continues as scheduled during a global lockdown.

The development of advanced semiconductors will be essential in producing meaningful advances in artificial intelligence and recent supply chain issues are forcing Western governments to invest in sovereign capability. In early 2022, the European Commission put forward the European Chips Act with the intention of addressing the supply shortage and strengthening Europe’s position within the global chip production market. Companies like Intel are looking to expand into Europe, with a new manufacturing plant due to open in Magdeburg in Germany in 2027.

Although these manufacturing sites can be vast, most of the equipment is not directly used in the manufacture of silicon chips. Manufacturing at the nanoscale requires highly controlled conditions, so the fabs require an extensive range of heating, cooling and filtration systems. This plant equipment makes up approximately 90% of the equipment located at a typical fab.

This equipment ensures the correct temperature, humidity level and particulate level for the optimal production of chips. However, while solving one problem, it also introduces another. Mechanical systems and HVAC systems all generate vibration which, if left unmitigated, could disrupt sensitive precision manufacturing processes and interfere with chip production. ‘‘Vibration control is key to making these things work,’’ Adam explained.

From specification to design

Providing effective mitigation for this vibration is a highly specialised area where few companies have the required capabilities. For those that are involved, it all begins with the specification. Chip manufacturers require repeatability. They want all of their plants to be built the same way, whether they are in Israel or Taiwan. Of course, local conditions mean some adjustments will be necessary, but the basic principles must be strictly adhered to. These principles are contained in the specification.

‘‘These are effectively our blueprints for how we are going to manage the construction of these buildings,’’ said Adam. ‘‘Ordinarily, contractors might try to save money by deviating from the specification or favouring cheaper suppliers. For projects like this, compromises on quality and departures from the specification, however small, are not an option. The cost of factory downtime is so high that minimising the risk of failure is essential, which rules out using cheaper, lower quality components.’’

The specification is key for providing the right intent and the products to be used, but it does not cover design. ‘‘If you have a duct run, for example, it will tell you what you need to isolate and will specify spring mounts of a certain deflection. It will not tell you which ones to use, where to put them or, critically, what the load is. Details like this are left to the contractor to figure out.’’

Despite the scale of this project, Mason took on significant responsibility for the design. This allowed the contractor to stick to those elements they knew best, while leaving the area of vibration control to Mason’s expertise. Although this arrangement is unusual, the extra engagement was an important factor in the contractor’s decision to work with Mason.

The challenge of scale

Isolating against vibration involves a system of specialised products that interrupt and absorb the path for vibration transmission. For this project, the key product was spring mounts. These are usually used for applications where low frequency (sub 8Hz) vibrations are present.

One of the unique features of this project was the vast scale. In total, there were approximately 130 kilometres of piping and 3.2 kilometres of ductwork. The project therefore required a staggering 3,800 mounts. ‘‘I’ve worked on all sorts of projects at this stage of my career, but nothing can touch this one in terms of scale. Nothing is even close,’’ Adam reflected.

As well as the quantity of products supplied and the logistical challenge it presented, the size of some of these products is also worthy of mention. In general, larger pipes require a higher level of isolation. As some of the ducts were up to four meters in diameter, there were some unusually large spring mounts that were required. George Taylor, a project engineer who was heavily involved in the work, recalled his surprised when he first encountered the size of the mounts. ‘‘I knew the mounts needed to be large because of the load, but actually seeing them they appeared unusually large.’’

In addition to the mounts, Mason supplied 1,600 acoustic hangers, from which pipework and ducts were suspended, as well as 400 pipe connectors. Many of the products were supplied bespoke, with housings designed specifically to deal with factors such as wind loading and thermal expansion.

Engineering challenges

There was an additional agreement with the contractors whereby Mason would assist with the installation as well as the design, given the critical importance of getting this right. The spring mounts and hangers are designed to be easy to install, and include features for this purpose, but attention to detail is key as even millimetres matter.

Adam and his colleagues were therefore on site regularly, assisting with installation, training staff and carrying out installation inspections. Adjusting a mount or a hanger incorrectly can lead to load in the wrong place and prevent the isolator from working, so the team’s experience was useful in ensuring everything would work as intended.

Transporting and installing all of this equipment was a huge endeavour for logistics, planning and collaboration. Mason was assisted in this regard by Asgard Engineering. Having a local agent like this is key to ensuring success in these projects. Asgard was able to act as the conduit for Mason products into Ireland and in addition to regular site visits from Mason’s team, they were able to provide the local support that was essential for the customer.

In addition to controlling for vibration, Mason’s solutions also need to accommodate factors like wind loading and thermal expansion. Designing systems that can handle both the demands of vibration isolation and these additional factors is especially challenging. This problem was especially significant for a lot of the duct work, as this was mounted externally and therefore subject to wind loading and sun loading. ‘‘If a duct wants to expand, you cannot stop it doing that. So if you constrain it, something is going to break.’’

Many of the mounts supplied were therefore bespoke, designed specifically to accommodate the additional loads and movement the ducts would be subject to, and to allow for this movement but within limits. These mounts are therefore restrained mounts, with customised housing that is more robust than you would expect with an off the shelf product.

Once the mounts were customised to allow for factors like wind loading, it was then necessary to ensure that each mount went to the correct location. ‘‘A lot of work was done to deliver this level of detail and provide the assurance it was going to work.’’ Once more, the assistance of Asgard was key in delivering this outcome. Every mount was provided with a unique label to identify it and the exact location it would be sent to.

The fact that this project was complete without significantly overrunning the schedule might be surprising to many. All projects contain engineering challenges and setbacks, but those involved had the additional obstacle of completing this work in the middle of a global pandemic. “It’s a testimony to all involved that we were able to complete it within the schedule,” reflected Marc Power, engineering manager at Asgard Engineering.

However, the story doesn’t end there. Although the fab may be up and running, regular site inspections and adjustments will continue. Both Mason and Asgard will continue to provide ongoing support. In fact, at the time of writing, George is currently attending the site to carry out inspections and Adam is due to return the following month. Working under the radar, they are part of a specialised group of engineers whose work is essential in ensuring the world continues to receive its supply of silicon chips.

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