Semiconductor use has grown significantly due to consumer demand for tech-based lifestyles that revolve around consumer electronics, connected appliances, electric vehicles, IoT, and more. This shift is also seen in non-consumer and capital goods as robotics and Industry 4.0 have taken hold. The semiconductor industry’s progression toward increasingly smaller and more complex devices requires materials that can endure the demanding conditions of fabrication processes. Engineering and high-performance polymers are critical in this regard, offering properties essential for both the manufacturing steps and the final product’s performance.
Properties of Engineering and High-Performance Polymers
The demanding applications of the semiconductor industry require engineering and high-performance polymers that can perform well in harsh environments, including exposure to high temperatures, corrosive chemicals, and vacuums, as well as having resistance to extreme wear. While each thermoplastic has a set of characteristics that make it suitable for one application over another, as a class of materials, they provide the following benefits:
- Thermal stability
- Chemical resistance to aggressive process chemicals
- Mechanical strength for structural integrity
- Surface resistivity properties (e.g., insulative, electrostatic dissipative and conductive)
- Dimensional stability and precision
- Low outgassing in vacuum applications
- Static dissipative grades
- Low particle generation
- Ionic purity
Semiconductor Fabrication
In semiconductor fabrication, there are frontend and backend processes. Frontend processes focus on wafer fabrication, while backend processes focus on assembling the integrated circuit. Frontend processes include lapping and polishing, thermal oxidation, photoresist coating, photolithography, development, etching, ashing, deposition, ion implantation, and planarization.
These processes are often repeated in complex sequences to build the many layers and structures needed in modern semiconductor devices. Each step must be precisely controlled to achieve the desired electrical properties and physical dimensions.
Backend processes include backend wafer inspection/probe testing, dicing, die/wire bonding, packaging, and function and burn-in testing.
Many of these processes use polymers directly and indirectly (chemical and water delivery systems). Semiconductor fabrication uses both wet and dry processes that require polymers with distinctive characteristics. Retainer rings used in fabrication and testing fixtures also benefit from engineering and high-performance plastics.
Engineering and High-Performance Polymers in Dry Semiconductor Processes
Dry semiconductor processes are critical techniques used in manufacturing semiconductor devices. They are referred to as dry processes because they do not use wet chemicals. Dry processes are generally preferred in modern semiconductor fabrication for their precision, control, and ability to work at a small scale (nanometers), which is essential for today’s advanced electronic devices. They also tend to produce less chemical waste compared to wet processes, making them more environmentally friendly.
Processes that require high-performance polymers include ashing, plasma etching (RIE/DRIE), deposition (PVD, PE-CVD, ICP-PECVD), atomic layer deposition (ALD), and ion implantation.
Plastics traditionally used in dry processes include polyimide (PI), polyether ether ketone/polybenzimidazole (PEEK/PBI), polyamide-imide (PAI), polyetherketoneetherketoneketone (PEKEKK), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyetherimide (PEI), polysulfone (PSU), polyoxymethylene (POM), polyethylene terephthalate (PET), and polycarbonate (PC).
Engineering and High-Performance Polymers in Wet Semiconductor Processes
Unlike dry processes, wet processes in semiconductor frontend manufacturing involve using liquid chemicals to perform various steps in fabricating integrated circuits and other semiconductor devices. These processes are essential for cleaning, etching, and doping, among other tasks.
Processes that use engineering and high-performance plastics include wet bench, single wafer etch, batch spray, coater/developer, electroplating, and chemical mechanical planarization (CMP).
The harsh process environments and nature of semiconductor fabrication require materials that offer chemical resistance, wear resistance, heat resistance (~100°C), ionic purity, and electrostatic discharge (ESD) protection, including conductivity and static dissipation (SD).
Engineering and high-performance plastics traditionally used include conductive and anti-static grades of polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyetherimide (PEI), polysulfone (PSU), polyoxymethylene (POM), polyethylene terephthalate (PET), polycarbonate (PC), polyvinylidene fluoride (PVDF) and Polytetrafluoroethylene (PFTE).
Retaining Rings and Engineering and High-Performance Polymers
In semiconductor manufacturing, modern chips have many layers, and each layer must be perfectly flat to ensure that the tiny circuits and components line up correctly. Chemical mechanical planarization (CMP) is used to achieve high levels of flatness and uniformity on the wafer surface. This critical step ensures the high performance and reliability of electronics. Retaining rings hold the wafer in place with uniform pressure to prevent damage and control the polishing area.
Engineering and high-performance plastics are increasingly being used for CMP retaining rings due to their superior properties, such as:
- High strength and modulus
- Chemical resistance
- Wear resistance
- Low coefficient of friction
- Dimensional stability
- Thermal stability
The selection of the right polymer material for CMP retaining rings is critical. The material must have the necessary properties to withstand the harsh CMP environment and provide the required level of performance.
High-performance polymers traditionally used for CMP retainer rings include polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyethylene terephthalate (PET), and polycarbonate (PC).
Polymers in Testing Fixture Design
Testing fixtures, such as test sockets and inspection fixtures, play a vital role in the quality assurance and quality control of semiconductors. Test fixtures must be fabricated from materials that offer dimensional stability with low water absorption, stiffness for machinability, wear resistance from repeated cycles, rigidity, low dielectric constant, low outgassing, and ESD properties. Additionally, testing may expose the fixtures to extreme temperature fluctuations (-60°C to nearly 200°C).
Materials used for test fixtures traditionally include anti-static grades of polyimide (PI), polyamide-imide (PAI), polyether ether ketone (PEEK), and polyetherimide (PEI).
Trust Ensinger for Semiconductor Plastics
We work directly with engineers to understand their challenges at any stage of the semiconductor manufacturing process. Our solutions may consist of stock shapes or custom machined or molded components, providing flexibility with design and costs. Our plastics and solutions are designed to meet the industry’s demanding and harsh environmental requirements. With comprehensive plastic manufacturing capabilities, we can deliver a solution to meet your needs.
Talk to one of our engineers today about your semiconductor fabrication challenges.