Semiconductor and Electronics Manufacturing Equipment

The plastics used in wet benches and cabinets must be resistant to the aggressive chemicals used for etching and cleaning semiconductor wafers. They must also maintain extremely high levels of purity and not leech contaminates into process fluids. For some processes, the plastics must be able to operate safely and reliably at elevated temperatures.

Wet benches are assembled via thermoplastic welding. Consistent welding and fabrication characteristics as well as outstanding aesthetics are critical-to-quality for the plastic sheet materials used for these applications.

Plastic sheet, rod, and tube are used for the following applications in semiconductor cleanrooms:

• Cabinets
• Carts
• Fume hoods
• Furniture
• Gowning rooms
• Sinks
• Tanks
• Wet benches
• Windows and guards
• Workstations

Curbell supplies the PP, PVC, CPVC, and fluoropolymer materials shown below for semiconductor cleanroom wet benches and workstations. The best material for a wet bench application depends on the mechanical property requirements, the process chemicals, the operating temperature, the necessary flammability characteristics, and the level of purity required.

FM 4910 Listed Materials

The materials specified for cabinets and workstations in semiconductor cleanrooms are often required to meet Factory Mutual 4910 standards for fire propagation and smoke generation. Curbell’s FM 4910 listed products are as follows:

• Flame Retardant Polypropylene
• PVC and CPVC
• PVDF
• PFA
• ECTFE (Halar®)

Simona’s FM 4910 Material Selection Chart and Vycom’s Flametec® Fire Safe Materials Chart compare the different types of FM 4910 listed plastic sheet materials.

FREQUENTLY ASKED QUESTIONS

Semiconductor test sockets need to have good mechanical properties and excellent wear characteristics so that they will maintain their dimensions for many cycles of use.

Test socket applications may require plastics that can operate at temperatures ranging from as low as -55 °C to as high as 155 °C (-67 °F to 311 °F). The plastics specified for these applications need to have low particulate generation and low outgassing to minimize contamination of the IC chips during testing.

The plastics used for test sockets also need to have good machinability, low moisture absorption, low rates of thermal expansion, and excellent dimensional stability so that tight pitch, small diameter holes can be cleanly and precisely drilled into the material.

Some semiconductor test socket applications require materials with specific electrical properties such as low dielectric constants, low dissipation factors, or the ability to dissipate static electricity.

Curbell supplies a number of materials for semiconductor test sockets including:

• PPS
• Ultem®
• PEEK
• PAI
• DuPont™ Vespel® Polyimide

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FREQUENTLY ASKED QUESTIONS

The plastics used for chemical mechanical planarization equipment need to have outstanding chemical resistance and long wear life in abrasive slurries. They also must not generate contamination that can damage semiconductor wafers.

A number of different plastics are used for CMP processes depending on the mechanical property requirements, the chemical environment, the slurry being used, and the desired price point for the component. Curbell supplies a wide range of plastic materials for CMP including polycarbonate and semicrystalline PET, however various grades of PPS and PEEK are most often used for these applications.

The PPS (polyphenylene sulfide) and PEEK (polyetheretherketone) materials used for CMP clamping rings are available in several different formulations. Detailed information on each grade of PPS and PEEK for CMP can be found using the links to each material.

• TECATRON® SE – Hardest and stiffest PPS formulation
• TECATRON® SX – Longer wearing and tougher than TECATRON® SE

Figure 1: Wear Resistance Comparison of TECATRON® SE and TECATRON® SX

PEEK materials can be used for CMP when greater strength, stiffness, and wear resistance are required.  Two grades of PEEK that are used for CMP applications are shown below.

• TECAPEEK® SE – Stronger, stiffer, and longer wearing than PPS materials
• TECAPEEK® CMP – PEEK formulation with enhanced ductility and wear resistance

FREQUENTLY ASKED QUESTIONS

The plastics used for handling semiconductor wafers need to be strong, stiff, and dimensionally stable. They also have to have outstanding wear resistance to withstand repeated handling cycles. Additionally, they need to be non-sloughing and have low outgassing and low particulate generation to minimize the chance of contaminating the semiconductor chips being manufactured. For some applications, the plastic materials contacting the wafers need to be able to operate at elevated temperatures.

Wafer handling applications for plastics include the following:

• Bearings
• Bushings
• Die-pickup collets
• End effectors
• Guides
• Insulators
• Spin chucks
• Vacuum pads
• Vacuum wand tips
• Wafer carriers
• Wafer chucks
• Wafer clamping rings
• Wafer guides
• Wear strips

Curbell supplies the following plastic materials for wafer handling applications:

• DuPont™ Vespel® Polyimide
• FEP
• PVDF (Kynar®)
• PEEK
• PFA
• PAI (Torlon® PAI)
• Ultem®

Vacuum chamber applications are particularly challenging since they may involve elevated temperatures and aggressive process chemicals. PEEK, Torlon® PAI, and DuPont™ Vespel® polyimide are often used for these applications. Semitron® MPR 1000 is a proprietary material manufactured by Mitsubishi Chemical Advanced Materials that is also used for vacuum chamber applications. Semitron® MPR 1000 has superior resistance to oxygen plasma than many other high-performance polymers.

Vacuum chamber windows are frequently manufactured from thick, optically transparent polycarbonate sheet.

FREQUENTLY ASKED QUESTIONS

For certain semiconductor manufacturing processes, the plastics that come into contact with integrated circuits must be formulated to prevent the buildup and discharge of static electricity. Static electricity discharge can damage electronic components resulting in yield loss.

Surface resistivity describes the ability of a plastic material to dissipate static electricity. Plastics with surface resistivities in certain defined ranges are described as antistatic, static dissipative, or conductive per the diagram shown below.

Opaque ESD Engineering Plastic Materials

Opaque engineering plastics typically achieve ESD properties through the use of conductive additives. Some ESD additives are permanent and others may migrate out of a material over time. The surface resistivity effects from some ESD additives are dependent on the moisture levels in the environment. Other additives exhibit consistent resistivity in both dry and humid conditions.

Applications for ESD engineering plastics include:

• Assembly fixtures
• Testing fixtures
• Integrated circuit chip trays and carriers
• PCB board handling fixture

The correct ESD engineering plastic to use for an application will depend on the desired surface resistivity range, the operating temperature, compatibility with process chemicals, dimensional stability requirements, and the desired mechanical properties.

Curbell offers a number of opaque materials for ESD applications including:

• UHMW
• Acetal
• PET
• Ultem®
• PTFE
• PEEK
• PAI
• DuPont™ Vespel® Polyimide

Transparent ESD Plastic Materials

Transparent ESD acrylic, polycarbonate, PVC, and CPVC sheet materials achieve their electrical properties through the use of surface coatings. The correct transparent ESD plastic to use for an application will depend on the surface resistivity required, the required optical transparency and haze, the operating temperature, chemical resistance requirements, flammability requirements, and the desired mechanical properties.

Curbell offers a number of transparent materials for ESD applications including:

• Arcylic
• Polycarbonate
• PVC
• CPVC

FREQUENTLY ASKED QUESTIONS

Printed circuit board assembly fixtures and solder pallets need to have excellent mechanical properties and dimensional stability as well as low thermal conductivity. The also need to have good machinability and be able to withstand the elevated temperatures and the chemicals associated with soldering applications.

Some PCB fixture and solder pallet applications require anti-static properties to prevent static discharge from damaging sensitive electronic circuits.

Röchling’s Durostone® family of PCB Solder Pallet Materials are state-of-the art composites for wave solder pallet and assembly fixture applications. Detailed information about these materials can be found in Röchling’s PCB Solder Pallet Materials guide.

DuPont™ Vespel® SP-1 is a dimensionally stable, high temperature plastic material that is used for many electronics assembly fixture applications.

FREQUENTLY ASKED QUESTIONS

Fluoropolymers including FEP, PFA, PTFE, ETFE, ECTFE, PCTFE, and PVDF are frequently used for fluid handling components in wet benches. Applications include:

• Valves
• Manifolds
• Seals
• Pumps
• Filters
• Sensors
• Pipes
• Fittings
• Flexible tubing