The Role of Passive Air and Active Air Vibration Isolation in Semiconductor Research and Fabrication

To compete in the semiconductor industry, manufacturers are required to consistently achieve ultra-prTo compete in the semiconductor industry, manufacturers are required to consistently achieve ultra-precision outcomes at scales, yields, and performance requirements that stretch the capabilities of modern manufacturing. Semiconductor manufacturers are faced with extremely challenging and continuously escalating technical hurdles, including:

• Increasing Scale and Complexity

With feature sizes now reaching the nanometer scale, even the tiniest inaccuracies in processes can lead to significant defects, impacting performance and yield. The trend toward integrating more functionality into smaller chips, known as System on Chip (SoC) designs, further intensifies the need for precision.

• Higher Performance Standards

Modern applications require semiconductors to operate at increasingly higher speeds and efficiencies, often requiring investment in capital equipment. Return on Investment (ROI) for capital expenditures is critical to financial performance.

• Increasingly Sensitive Manufacturing Processes

Processes such as photolithography, etching, and deposition require precise alignment and stability. Manufacturers must ensure that each step of the fabrication process is meticulously controlled, often involving hundreds of stages. Variability at any point can compromise the finished product.

As semiconductor devices become more intricate and performance demands escalate, so does the need for extreme environmental stability. Proper vibration isolation is critical in achieving precision outcomes in semiconductor research and fabrication. Unstable environments can lead to:

• Yield Loss

Stability is crucial in semiconductor manufacturing; any disturbances can lead to defects, resulting in lower yield rates. Yield loss translates directly into increased production costs and reduced profitability for manufacturers.

• Product Failures

Defective chips may lead to failures in various applications, from consumer electronics to critical systems in aerospace or medical devices. These failures can pose safety risks, lead to costly recalls, and damage brand reputation, or result in regulatory sanctions, financial penalties, and loss of business licenses. 

• Increased Operational Costs

Instability often leads to higher operational costs. Increased downtime due to equipment failure, extensive rework, and retesting operations can inflate budgets and elongate project timelines.

Pneumatic Air Mount Vibration Isolation: A Quick Overview 

Pneumatic air mount vibration isolation systems are advanced passive isolation systems that use compressed air and flexible diaphragms to attenuate low-frequency vibrations. The compressed air within the air springs acts as a highly effective medium for absorbing and dissipating vibrational energy. By adjusting the air pressure, the stiffness and damping characteristics of the isolator can be tuned to optimize performance for different loads and vibration frequencies. These systems are widely used in industries requiring sub-micron stability, including semiconductor manufacturing throughout fabrication and metrology applications.

How Pneumatic Vibration Isolation Works

Pneumatic air mounts consist of:

• Air chambers (bladders or bellows): Filled with compressed air, these provide vertical and horizontal compliance.
• Damping mechanisms: These can include orifice damping, squeeze film damping, or active valves to limit oscillation.
• Leveling valves: Maintain a consistent height despite changes in load or air pressure.

Air mounts act like mechanical low-pass filters, effectively reducing the transmission of vibrations above their natural frequency. When a disturbance (e.g., floor vibration) occurs, the air chamber compresses slightly, absorbing the motion and reducing the energy transferred to the supported equipment. The combination of mass, spring (air), and damping creates a low natural frequency, typically between 1–3 Hz, which is critical in isolating low-frequency vibrations common in buildings and industrial settings.

Key Benefits of Pneumatic Isolation Systems:

• Exceptional Isolation at Critical Frequencies: Effective isolation in the critical low-frequency range, which is where most building and environmental vibrations occur.
• Self-contained and highly reliable: Systems often have no electrical or external utility requirements.
• Bi-directional: Isolating both the main object from vibrations but also isolating supporting systems from the vibrations of the main object itself.
• Low Maintenance, High Uptime: Minimal parts to service. That means fewer interruptions to research and manufacturing.
• Cost-Effective Performance: Delivers high isolation performance without the cost or complexity of active systems.
• Cleanroom Compatibility: Many systems are cleanroom-ready, supporting strict contamination control standards.

Active-Air Vibration Isolation Systems

Active-Air systems provide automated leveling compensation and a wide load range. Utilizing a compressed air source, air is fed into or bled from the air springs to maintain a preset “zero deflection” level and compensate for load changes. The worksurface will automatically maintain level regardless of load addition or removal. 

Passive-Air Vibration Isolation Systems

Passive-Air systems provide a cost-effective solution for applications with static loads that require infrequent leveling, or where a compressed air source is not available. Manual leveling is performed as needed using an external air source or an optional hand pump. 

Passive-Air vs. Active-Air Systems

Feature	Passive Air Isolation	Active Air Isolation
Adjustment	Periodic manual leveling required	Automated self-leveling adjustments
Compressed Air Requirement	No air supply needed	Requires compressed air source
Cost and Maintenance	Lower initial cost, periodic leveling needed	Higher upfront costs, low maintenance
Performance	Effective isolation in the critical low-frequency range	Effective isolation in the critical low-frequency range

When to Use Pneumatic Isolation 

Pneumatic systems are a cost-effective and robust baseline for most semiconductor fabs, offering vastly superior performance over basic passive systems with minimal complexity or maintenance burden. Simple systems like marble slabs on rubber feet rely on mass (marble) and low-stiffness supports (rubber) to passively dampen vibrations. While these setups are effective in mid to high-frequency ranges (>10 Hz), they fail to attenuate low-frequency vibrations (5 -10 Hz), which are often impactful in semiconductor environments.

Feature		Rubber Feet + Mass	Pneumatic Air Mounts
Natural Frequency		~10–20 Hz	~1–3 Hz
Isolation @ 10 Hz		Limited	>90%
Horizontal Isolation		Minimal	Integrated
Damping Control		None	Tunable/engineered
Settling Time		Slower	Faster
Active Leveling Capability		None	Automatic leveling available

Air-mount vibration isolation technology offers a highly effective solution for isolating sensitive equipment from a wide range of vibrations, particularly in demanding environments like manufacturing facilities. Their tunability, low natural frequency, available active leveling, and superior damping capabilities provide a significant performance advantage over simple passive isolation methods.

Applications in the Semiconductor Industry

The semiconductor industry demands extremely precise manufacturing processes at the nanometer scale. Even minute vibrations can lead to misalignment and defects in the delicate lithography and metrology equipment. Consequently, pneumatic air mount vibration isolation is suitable for several key applications: 

• Supporting Lithography Equipment: Wafer steppers and scanners, critical for patterning integrated circuits, are highly susceptible to vibration. Pneumatic isolators provide the stability required for these machines to achieve nanometer-level accuracy.
• Isolating Metrology and Inspection Tools: Equipment used for measuring and inspecting semiconductor wafers, such as scanning electron microscopes (SEMs) and atomic force microscopes (AFMs), require vibration-free environments to ensure accurate and reliable results.
• Protecting Wafer Handling Systems: Automated systems that move delicate wafers between processing stations also benefit from vibration isolation to prevent damage and ensure precise positioning.
• Creating Ultra-Stable Platforms: Pneumatic mounts are used to create stable platforms for various sensitive manufacturing and testing equipment, effectively decoupling them from building vibrations and other external disturbances.

Cost vs. Performance Trade-Offs

When selecting vibration isolation systems, balancing between cost and performance is crucial. It’s easy to over-engineer lab infrastructure, especially when uptime and data quality are critical. However, value isn’t about price alone. It’s about performance, long-term stability, minimal disruption, and ease of operation.

• Initial Cost: Passive-Air systems require a lower initial investment compared to Active-Air systems. This can free up capital for other critical lab investments. 
• Maintenance: All pneumatic air mounts generally provide a low total cost of ownership due to their simpler design. Active-Air systems remove the need for periodic manual leveling that is required in Passive-Air systems.
• Adaptability and ROI: While Active-Air isolation systems offer adaptability, the reliability, simplicity, and cost-effectiveness of Passive-Air systems can provide substantial long-term ROI, especially in validated setups with minimal changes.

Conclusion: Choosing the Right Vibration Isolation Solution

Selecting the optimal vibration isolation system is critically important to isolate tools from building vibrations that can disrupt alignment, imaging, or etching processes. There’s no one-size-fits-all solution. 

The following questions should be considered when choosing a vibration isolation workstation or system for your particular application:

• What is the operating environment in which the equipment to be isolated will be used?
  • Cleanroom, Factory, Office? 
  • What is the building’s structure?
  • Is the building near a highway? or a railroad?
• Is there a compressed air source available?
• Is there any site survey data available?
• What is the manufacturer’s specification of “allowable vibration” for the equipment to be isolated?
• What is the “footprint” of the equipment to be isolated?
• What is the weight of the equipment to be isolated?
• If the load distribution is not uniform, what is the load at the heaviest end or corner?
• What is the height of the cg (center of gravity) for the equipment to be isolated? 
• Is there a moving load that you are trying to isolate? 
• What is the load distribution at the mounting points when the moving load is at its minimum and maximum displacement? 

At Kinetic Systems Inc., our team of experts is available to help you navigate these considerations, ensuring your lab is equipped with the most suitable vibration isolation solutions tailored to your specific needs. For a deeper dive into vibration isolation solutions for semiconductor labs, schedule a consultation with our engineers.