The semiconductor industry operates at the cutting edge of material science, where precision and performance are non-negotiable. Converting silica sand into semiconducting silicon wafers and then into the chips that are essential to our modern computing processors requires painstaking execution at every step. The AI race and even aspects of national sovereignty hang in the balance. Making these leading-edge semiconductor chips is arguably the most complex manufacturing process ever undertaken. With semiconductor revenues set to grow to over US$1 trillion in the next few years, the stakes are stratospheric.

While the spotlight often focuses on silicon, the unsung heroes of this industry are the performance plastics used to create the tools and fixtures that handle the delicate silicon wafers. They guide and contain the expensive wafers and chips during complex electrical tests. These plastics must withstand extreme thermal conditions, corrosive chemicals and mechanical stresses, all while maintaining ultra-high purity to prevent contamination during the processing.

While most plastics make excellent insulators, some wafer handling and test fixture applications seek the advantages of electrically static dissipative (ESD) plastics that bleed off stray or accumulated voltages that would otherwise collect, potentially damaging sensitive conductors on the wafer or chip. The selection and use of these performance plastics are further complicated by a web of international regulatory requirements governing material safety, environmental impact and trade. This article explores critical aspects of this challenging landscape.

The journey of a semiconductor wafer from raw silicon to a finished microchip is fraught with processes that expose it to a variety of harsh conditions. High-temperature processes, such as thermal cycling during electrical testing, require fixture materials that can maintain their structural and dimensional integrity without warping, softening or outgassing. Simultaneously, the complex geometries and tight tolerances of these fixtures demand materials that can be precisely and reliably machined. Finished processor and bare-die test fixtures are the sophisticated carriers that hold and position wafers during a variety of tests, including electrical probing. Electrical test and burn-in processes may subject the wafer and its fixture to fluctuating temperatures. The plastic must be able to endure a wide temperature range, from sub-zero to well over 100°C, without significant dimensional change. For example, polyetheretherketone (PEEK) is a high-performance plastic frequently used in these applications due to its exceptional thermal stability and mechanical properties at elevated temperatures. Other options include polyimides (PI) and polyphenylene sulfide (PPS), which offer similar resistance to high temperatures. Developments in polyamide-imide (PAI) and polyetherimide (PEI) also open up opportunities in these demanding test fixtures as well as wafer handling, transport tools and other applications in semiconductor processing.

The fixture and test socket materials must be dimensionally stable to maintain the precise alignment of the spring-loaded probes that use the plastic as a combination guide, holder and fixture to contact a chip, chiplet or circuit board. Any thermal deformation could lead to misaligned probes, causing inaccurate test results or even damaging the delicate circuitry.

The challenge of thermal stability is not just about temperature resistance but also about thermal expansion. A low coefficient of thermal expansion (CTE) is vital to ensure that the fixture’s dimensions remain consistent throughout the thermal cycling of the test. When key dimensions are measured in microns, uncontained thermal expansion will compromise test accuracy.

Machinability in this context refers to a material’s ability to be cut, drilled and shaped with high precision, minimal tool wear and a clean finish. The intricate geometries of semiconductor test fixtures, which can feature complex cavities, channels and fine-pitch holes, demand a material that can be machined with exceptional accuracy.

High-performance plastics like PEEK, polyetherimide, PEI, PAI and Polyimide are excellent candidates for Computer Numerical Control (CNC) machining in the semiconductor industry. These materials offer specific properties that are advantageous for precise manufacturing:

• Low stress levels: Materials with low internal stress minimize the risk of warping during and after machining, which is crucial for maintaining tight tolerances.
• Minimal burr formation: The formation of burrs (small, raised edges of material) during machining can compromise dimensional accuracy and potentially contaminate the cleanroom environment. Using the right material, along with optimized machining parameters, helps to minimize burr formation.
• Dimensional stability: The ability of the plastic to maintain its shape and size under mechanical stress is essential for creating reliable fixtures.

The choice of machining technique also plays a role. CNC machining has become the standard for producing complex plastic components for semiconductors due to unmatched precision and repeatability. But the human element still matters — hats off to the many talented toolmakers who understand these materials, as managing the speeds, feeds and dimensional characteristics is art as well as science.

The semiconductor industry is a heavily regulated sector, and the plastics used in its manufacturing processes are no exception. These regulations are driven by concerns over environmental impact, worker safety and the potential for contaminants to affect the purity of semiconductor processes and ultimately affect the yields of finished chips.

Environmental regulations, particularly in the European Union and the United States, have a profound impact on material selection in the semiconductor industry.

• Restriction of Hazardous Substances (RoHS): This EU directive restricts the use of specific hazardous materials in electrical and electronic equipment. For semiconductor plastics, this means avoiding materials containing heavy metals like lead, mercury and cadmium. Compliance requires manufacturers to reformulate materials and implement rigorous testing to ensure parts are safe.
• Registration, Evaluation, Authorization and Restriction of Chemicals (REACH): Another EU regulation, REACH, mandates the registration of chemicals and restricts the use of certain hazardous substances. This has significantly increased documentation requirements and production costs for semiconductor components, including plastics, by requiring transparency in chemical compositions.
• Per- and Polyfluoroalkyl Substances (PFAS): Emerging regulations, particularly in the EU and some U.S. states, are targeting PFAS — often called “forever chemicals” — due to their persistence in the environment. This could pose a major challenge for the semiconductor industry, which relies on high-performance fluoropolymers (such as PTFE and FEP) that contain PFAS.

Beyond governmental regulations, a number of industry standards ensure product quality and consistency.

International Organization for Standardization (ISO) standards, such as ISO 9001 for quality management and ISO 14001 for environmental management, are critical for demonstrating compliance and ensuring consistent manufacturing processes. For plastic components specifically, ISO standards define requirements for characteristics like measurement tolerances, crucial to high-precision components.

Formed in 1898, ASTM International (formerly the American Society for Testing and Materials) is a not-for-profit global leader in the development and delivery of voluntary consensus standards. ASTM standards provide standardized methods for testing and evaluating the physical, mechanical and chemical properties of plastic materials, covering a wide range of tests from tensile and impact strength to chemical resistance and environmental exposure. ASTM standards for semiconductor plastics focus on critical properties like low outgassing (ASTM E595), chemical resistance (ASTM D543) and electrical insulation (ASTM standards for electrical insulating materials).

SEMI has been used to create more than 1,000 industry approved Standards and Safety Guidelines in key topics including safety, materials, packaging, traceability and cybersecurity in order to improve semiconductor manufacturing operations and several SEMI standards apply to testing plastics for their suitability in key process areas.

The use of advanced plastics in semiconductor equipment is also subject to international trade regulations. Export controls, such as the U.S. International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR), govern the global movement of sensitive technologies, including some materials and manufacturing equipment. Companies must navigate these complex rules to ensure their materials and products are not used for unauthorized purposes. Furthermore, intellectual property protection is a constant concern, with patents and trade secrets safeguarding innovations in both the plastics and semiconductor fields.

The intersection of material science and regulatory compliance will continue to drive innovation in the plastics used for semiconductor manufacturing. The push for more sustainable and environmentally friendly materials is accelerating research into PFAS-free alternatives that can still meet the industry’s rigorous performance demands. At the same time, ongoing advancements in manufacturing techniques like CNC machining will enable the creation of even more complex and precise fixtures.

The role of plastic components in semiconductor manufacturing is understated but crucial. Their thermal and mechanical stability and machinability are core facilitators of wafer and electrical testing, while regulatory compliance ensures their safe, ethical and environmentally sound use. As the industry continues its relentless drive toward miniaturization and higher performance, the demand for innovative plastics that can meet increasingly stringent requirements will only grow. Success in this evolving landscape will hinge on a deep understanding of material properties, manufacturing processes and the complex web of regulations that govern the semiconductor ecosystem.