How Proper Hose Installation Can Reduce Semiconductor Fab Costs

Small Changes to Hose Installation Practices Can Mean Big Semiconductor Manufacturing Savings

Maintaining precise temperature control in semiconductor manufacturing processes is crucial. The chemical reactions that take place during atomic layer deposition (ALD), atomic layer etch (ALE), and other processes used to create viable wafers often generate extreme temperatures, and without precise temperature control, film thickness and process efficiency can suffer. Exposure to high temperatures also means that wafers and the equipment used to produce them must be adequately cooled to avoid suffering damage.

Electrostatic chucks within semiconductor manufacturing tools’ process chambers are supplied with temperature-regulating fluid to cool the wafer and prevent issues. How cost-effectively they can do their jobs depends on what’s happening outside the tool, however—in the subfabs that house temperature control units (or “chillers”) and in the hoses that feed frigid fluids up to the constantly running tools on the production floor.

The efficacy of these “thermal loops” that involve circulating fluid from tools to chillers via a system of hoses and back again can have significant repercussions for the profitability of a semiconductor fab. Downtime related to chiller failure or cleanup of puddles caused by hose condensation in the subfab can lead to significant productivity losses for fab operators. Even when downtime is avoided, improper hose insulation or installation and routing techniques can lead to significantly elevated energy costs, driving up operating expenses.

In this article, we will discuss how to avoid this last issue—improper hose installation and routing in semiconductor fabs. You can find more information specifically on solving semiconductor fabrication challenges by ensuring you have properly insulated hoses in this related article. To better understand how to optimize wafer manufacturing yield with proper thermal controls at a high-level, check out this article on the subject.

Best Practices for Insulated Hose Installation and Routing in Semiconductor Fabs

It is a common misperception that the best way to address significant changes in fluid temperatures between chillers and tools is to add more hose insulation or to change hoses. In some cases, a lack of insulation or your choice of hose is the problem. Using low thermal conductivity aerogel insulation or a vacuum-insulated metal hose can help you prevent energy loss as fluid and operating environment temperatures become increasingly extreme. But in other cases, subpar hose performance can be attributed to how the hoses are installed and routed, regardless of how they are insulated. Although space can be limited in various semiconductor manufacturing applications, it is necessary to follow best practices for hose installation and routing as much as possible to ensure the best product performance.

Hose Installation and Construction Considerations

A hose’s construction and installation may affect the thermal stability of the fluid it transfers. Consider end connections, for example. In some cases, you may need to consider insulating bare end connections with insulation to avoid condensation even if the rest of the hose is already insulated. Furthermore, you need to be sure those end connections are installed correctly to avoid unwanted leakage or heat transfer.

The end connections that come with insulated hoses can vary, but for Swagelok^® FV vacuum-jacketed hoses and some Swagelok^® Y-insulated hoses, for example, the end connections are annealed tube stubs. These tube stubs can be connected to other components or equipment via butt welds, Swagelok^® quick connects, Swagelok VCR^® metal gasket face seal fittings, or Swagelok^® tube fittings. If you are using a Swagelok tube fitting connection, it’s important to ensure you are following the proper installation instructions to avoid unwanted leakage or heat transfer. See the installation instructions in Figure 1 for details.

 
Fully insert the tube into the fitting and against the shoulder; rotate the nut finger-tight.

 
Mark the nut at the 6 o’clock position.

While holding the fitting body steady, tighten the nut one and one-quarter turns to the 9 o’clock position.

 

Figure 1: Swagelok Tube Fitting Installation

Because this is an initial “swage,” a Swagelok gap inspection gauge can be utilized to ensure the fitting has been sufficiently tightened. See Figure 2 below.

Typically, hoses that are over 1” come with pre-swaged nuts and ferrules. Pre-swaged nuts over 1" require 1/2 turn.

Hose Routing Considerations

Regardless of how well a hose is constructed, how a hose is routed throughout a facility can have significant impact on how that hose performs. This is especially true in cases where the media temperatures within the hoses reach extremely cold or hot temperatures, as condensation and hot spots become more likely to occur based on routing alone. Below are several best practices to follow to avoid routing-related issues.

Maintain a Minimum Straight Length: Always follow minimum straight length requirements published in hose product catalogs. Bending hoses too close to the end connections may tear into the hose causing leakage, hose rupture, or reduced hose life.

Incorrect 

Correct  

Incorrect 

Correct 

Figure 3: Minimum Straight Length – Incorrect and Correct Examples

Maintain the Minimum Bend Radius: Likewise, follow published minimum bend radius requirements. Installing hoses with tighter bends may kink the hose and reduce hose life. Additionally, bending the hose may stretch or compress the hose insulation, negatively affecting its performance capabilities.

Insulation stretches and thins on outside of bend 

 

Insulation compresses on inside of bend

Figure 4: Minimum Bend Radius – Impact on Insulation

Design to Avoid Hose Strain: Hose strain can happen naturally as gravity pulls a hose body down, straining the hose near the connection point. Elbow fittings and adapters should be used to minimize or relieve hose strain, especially at the end connections. A different hose length may be necessary once the elbow or adapter is installed, but designing your systems in a way that counteracts hose strain should increase your hose longevity.

 

 
Incorrect

 
Correct

Figure 5: Hose Strain – Incorrect and Correct Examples

Be Mindful About Bending in Planes: Avoid twisting the hose. Bend hoses in one plane only to prevent undo strain on the hose. For a compound bend, use multiple hose pieces or other isolation methods.

 

 
Incorrect

 
Correct

Figure 6: Bending in Planes – Incorrect and Correct Examples

Maintain Proper Spacing: When hoses transporting cold or hot fluids are routed too close to each other, the surface temperature of the hoses can be impacted due to a lack of appropriate flow of ambient temperature air between the hoses. When cold hoses are routed too close together, the surface of the hose may fall below the dew point, causing condensation to form. When hot hoses are routed too close to each other, hot spots can develop that are above allowable temperature parameters.

The smaller the distance (d) between the hoses, the closer the air temperature (T_ambient) between the hoses will be to the media temperature (Tm) in the hose. A general recommendation is to keep wrapped insulated hoses (such as those using Swagelok Y insulation) at least three times the hose’s outer diameter apart to avoid condensation. When this is challenging in tight spaces, consider using hose spacers to force hoses apart. Even an inch or two of space can make a big difference for thermal management!

Learn More About How to Properly Route Hose

Why Does Getting Semiconductor Hose Installation Right Matter?

While hoses may seem like uncomplicated components compared to other high-tech equipment located throughout a semiconductor fab, the impact of how well you choose, install, route, and maintain hoses can be significant. Consider this example to understand how much of a difference hoses can make:

• Say a tool’s process chamber needs to receive cooling fluid at -20°C, but because the hoses running to and from the chiller are improperly insulated, installed, or routed, the chiller may have to overcompensate and have a setpoint of -25°C for -20°C fluid to reach the process chamber. Once that fluid is circulated back to the chiller, it may have warmed to -17°C, causing a Δ5°C that the chiller must account for.
• If it costs $0.13/hr for every 1°C of cooling required and assuming the chiller runs constantly 52 weeks a year, that $5,600 in energy costs for one chiller per year
• If there are 10 chillers supporting this tool, the annual energy cost is $56,000 to cool one tool. If there are 100 of these tools in the fab, that is $5.7 million in energy costs per year to cool tools.
• If hoses are properly insulated, installed, and routed, however, that difference between the temperature of fluid leaving and entering a chiller might realistically be reduced to Δ1°C
  

In this scenario, our cost to cool 100 tools using the above parameters falls to ~$1.1 million per year—a savings of $4.6 million per year based simply on cooling cost reductions alone!

Besides energy savings, there are benefits tied to reduced maintenance and increased component lifespans as well as potential for increased tool uptime and yield when best practices are followed for semiconductor hose selection, installation, and routing. If you could use assistance in optimizing your hose-related practices, Swagelok engineers can provide product testing and selection support, energy audits of your thermal loops, and various hose advisory services. Speak with an expert to see how you can reduce costs and boost productivity by taking a different approach to hose management.

Contact a Hose Specialist