Mechanical design plays an important role in the safety and compliance of semiconductor manufacturing equipment. While electrical systems often receive significant attention during equipment development, mechanical components can introduce hazards of their own.
SEMI S2 addresses a broad range of environmental, health, and safety considerations for semiconductor manufacturing equipment, including mechanical design. Critical mechanical parts must be properly rated for their intended use, and mechanical systems may be reviewed for factors of safety associated with lifting, structural integrity, pressure, and other hazards.
Considering these requirements during the design process can help manufacturers identify potential issues before equipment reaches the evaluation stage.
What You Can Expect From the Video and Blog
In this blog, we will look at several mechanical design considerations that can affect SEMI S2 compliance, including:
- Lifting equipment and structural design
- Factors of safety
- Seismic considerations
- Piping and tubing
- Pressure ratings
- Mechanical design documentation
- The value of addressing compliance during the design phase
Understanding these areas early can make it easier to prepare equipment for evaluation and reduce the likelihood that mechanical issues require design changes later.
Mechanical Design and SEMI S2
SEMI S2 is the Environmental, Health, and Safety Guideline for Semiconductor Manufacturing Equipment. The guideline has grown considerably since its introduction and now works alongside numerous related standards and guidelines. Mechanical design is one of several major areas addressed by SEMI S2, along with electrical design, process considerations, ergonomics, exhaust ventilation, and fire risk.
For manufacturers, this means mechanical safety should be considered as part of the overall equipment design rather than treated as a separate concern at the end of development.
An important part of demonstrating compliance is documentation. Critical mechanical components need to be appropriately rated for their intended use, while design documentation provides evidence that applicable requirements have been considered.
Lifting Equipment and Structural Design
Lifting equipment is an important mechanical consideration for semiconductor manufacturing equipment. SEMI S2 design work requires mechanical lifting and structural details to be addressed.
Lifting equipment should be validated using a 3x factor of safety. Detailed calculations and load testing should also be used to validate the lifting design before implementation.
These considerations are particularly important because semiconductor manufacturing equipment can include large and complex assemblies that must be transported, installed, serviced, or repositioned.
Designers should therefore consider lifting requirements before the equipment reaches its final configuration. Lifting points, supporting structures, and associated components should be incorporated into the engineering process with the appropriate calculations and supporting documentation.
The July 2024 revision of SEMI S2 also includes further requirements concerning lifting equipment and hinged loads, reinforcing the importance of addressing these hazards during equipment development.
Understanding Factors of Safety
Factors of safety are an important part of mechanical design under SEMI S2.
Mechanical components can be evaluated for factors of safety related to both lifting and pressure. The purpose is not simply to determine whether a component can function under normal conditions, but to establish that the mechanical design appropriately accounts for the forces and stresses associated with its intended application.
For lifting equipment specifically, it is important to support the design with calculations and load testing.
Addressing these requirements while components are still being selected and equipment structures are being developed can help prevent problems from being discovered later in the conformity process.
Seismic Design Considerations
Seismic safety is another mechanical consideration addressed by SEMI S2.
Section 19 addresses mechanical seismic requirements. Equipment should be designed so that, when anchored according to the documentation supplied to the equipment user, anticipated seismic forces will not cause the equipment to overturn. Components should also not fail or yield in a way that creates a risk of injury or an adverse environmental impact classified as Medium or higher under SEMI S10.
This makes seismic considerations both a design and documentation issue.
The equipment itself must be designed appropriately, but the documentation supplied to the end user also needs to establish how the equipment is intended to be anchored.
Waiting until an evaluation is underway to consider seismic requirements can create unnecessary complications if the existing structure or anchoring approach is not adequate.
Piping, Tubing, and Pressure
Mechanical compliance extends beyond the primary equipment structure. Piping and tubing can also be important, particularly when equipment handles liquids or gases.
The strength and pressure ratings of mechanical piping and tubing is a specific consideration. Both rigid and flexible piping carrying liquids or gases should be capable of withstanding foreseeable internal and external stresses. Piping should also be firmly attached or otherwise protected against external stresses and strains.
An appropriate factor of safety should be included based on the application.
This means designers need to consider more than whether a pipe or tube is capable of carrying the process material. Its pressure rating, installation, support, and exposure to mechanical stress can all become relevant to the equipment’s overall safety.
Documentation Is Part of Mechanical Compliance
A compliant mechanical design also needs supporting documentation.
SEMI S2 design work requires documentation as evidence of compliance. We recommend collecting relevant data sheets and material property sheets during the design process and maintaining those documents so they can ultimately become part of the top-level technical file.
For mechanical systems, supporting information can be especially important when demonstrating component ratings, material properties, lifting calculations, load testing, pressure ratings, or other design decisions.
Creating this documentation as the equipment is developed is generally more efficient than attempting to reconstruct the engineering basis for those decisions later.
Start With a Risk Assessment
Mechanical compliance should also be considered within the broader risk assessment process.
We recommend performing an initial risk assessment and identifying the sections of SEMI S2 that apply to the equipment.
This approach helps engineering teams determine which mechanical requirements are relevant to a particular system.
Not every piece of semiconductor manufacturing equipment presents exactly the same hazards. One system may have substantial lifting and seismic considerations, while another may introduce significant pressure or process-related concerns. Identifying those hazards early helps focus design efforts on the requirements that actually apply.
Designing for Compliance Instead of Correcting for Compliance
One of the most effective approaches to SEMI S2 compliance is incorporating applicable requirements into the design process from the beginning.
The conformity process can include product requirements, hazard risk analysis, standards identification, design guides, design review, prototype safety, and alpha and beta system reviews before moving into formal conformity assessment activities.
For mechanical engineering teams, this creates an opportunity to identify potential compliance concerns while changes are still relatively easy to make.
We also recommend consulting applicable standards during design, maintaining relevant technical documentation, using design templates, and selecting approved or proven components where appropriate.
The objective is to make compliance part of equipment development rather than something addressed only after the design is complete.
How HTDS Can Help
High Tech Design Safety works with semiconductor and industrial equipment manufacturers on equipment design, third-party evaluation, testing, and conformity to applicable standards. Our work includes areas such as electrical power, ventilation, radiation, lasers, chemicals, and other equipment hazards.
For manufacturers working toward SEMI S2 compliance, HTDS can provide design guidance, templates, pre-audit support, critical component resources, and design services.
Engaging compliance expertise during equipment development can help engineering teams understand applicable requirements before major design decisions are finalized.
Summary
Mechanical design is an important part of preparing semiconductor manufacturing equipment for SEMI S2 evaluation. Lifting systems, structural design, seismic stability, piping, tubing, pressure ratings, factors of safety, and supporting documentation can all influence conformity.
Key points to remember include:
- Critical mechanical parts should be appropriately rated for their intended use.
- Lifting equipment should be supported by appropriate calculations, load testing, and the required factor of safety.
- Seismic requirements should be considered alongside the equipment’s documented anchoring requirements.
- Rigid and flexible piping should account for pressure, internal and external stresses, support, and appropriate factors of safety.
- Mechanical design decisions should be documented throughout equipment development.
- An initial risk assessment can help identify which SEMI S2 requirements apply to the equipment.
- Addressing these considerations during design can help reduce compliance issues later in the project.
SEMI S2 compliance is most effective when safety and conformity requirements are incorporated into the engineering process rather than added after the equipment is already complete.
High Tech Design Safety can work with manufacturers during the design and evaluation process to identify applicable requirements, review equipment designs, and support the path toward SEMI S2 conformity.
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