Wet Bench Wafer Holder

Semiconductor manufacturing tools utilise a broad range of components made of high performance plastics. In particular, wet process tools rely on chambers, tanks, piping systems, and parts made of thermoplastics due to their high level of chemical and corrosion resistance. By choosing the optimum polymer family, plastic components can withstand even the harshest combination of chemicals used to process and clean the wafers. 

Strength, chemical resistance, and copy exact for wafer mobility parts

While the wet process tanks and chemical supply systems are often made of fluoropolymers offering the highest level of chemical resistance, such materials do not offer sufficient strength and rigidity for mechanically stressed parts. For example, wafer mobility components in the wet process tools are often made of high performance thermoplastics like PEEK due to its excellent mechanical properties in combination with good chemical resistance. Wafer mobility components include wafer holders or wafer carriers which are commonly used to insert the wafers into the process tanks and move the wafers between different process steps. Besides the requirement of mechanical properties, wafer mobility parts need to provide elevated levels of ionic purity and maintain copy exact compliance. 

PEEK enables highest level of wafer position accuracy

In this case study, the shape TECAPEEK SX natural, semiconductor grade unfilled PEEK, has been selected for a wet bench wafer holder. The function of the wafer holders is to dip multiple wafers into several chemical processing baths. The PEEK parts are holding the wafers from the sides to allow the liquid chemicals unobstructed access to the wafers when inserting to the bath. The number of wafers being held is maximised to enhance better wafer throughput, while maintaining sufficient and consistent spacing between the wafers to allow the liquids to pass through. The material must be highly dimensional stable to maintain the tight tolerances of the slot pitch spacing, thus maintain the wafer position accuracy. Moreover, the material needs to provide elevated levels of strength and rigidity, as well as wear resistance to maintain dimensional accuracy and maximise part lifetime under high wafer load and hundreds of thousands of cleaning cycles. PEEK fulfills the requirements for dimensional stability over an extended period due to high stiffness and creep resistance, as well as low water absorption. PEEK offers an excellent combination of elevated mechanical properties with a high level of chemical resistance.

 

You can take a closer look at Ensinger's wet bench wafer holder made of TECAPEEK SX by zooming and rotating here:

TECAPEEK SX natural – the perfect match

TECAPEEK SX natural is a semiconductor grade unfilled PEEK, processed to sheets, rods, and tubes in compliance with semiconductor copy exact requirements with the most stringent contamination and quality controls. In this way, TECAPEEK SX natural ensures the highest level of cleanliness and quality performance consistency, exceeding industry standard levels and securing reliable operations. Moreover, TECAPEEK SX natural succeeded in reducing internal stresses to a minimum through optimization of the manufacturing process, enabling improved dimensional stability during machining. As a result, the most demanding tolerances of high-end wafer holders can be met.

TECAPEEK SX natural

TECAPEEK SX is a Victrex® PEEK polymer modified for Semiconductor industry applications.
As a general guideline, the following table provides an overview of resistance to common chemicals used in wet process tools, under room temperature and without mechanical load. This information is not an assurance or guarantee of the chemical resistance of our products, as the chemical resistance of plastic highly depends on the temperature, formulation, and operating conditions. Please contact us for further information about chemical resistance and material selection advice.

Chemical resistance at room temperature

Chemical
Formula
Concentration [%]
PI
PEEK
PPS
PEI 
PVDF 
PTFE 
PET 
POM-C
Deionized water H2O - +
Hydrofluoric HF  50   (+) 
Sulfuric acid H2SO4  95-97 (+) 
Hydrogen peroxide H2O2  30 (+)  (+) 
2-propanol (isopropanol, IPA) CH3CHOHCH3  100
Acetone CH3COCH3 100 (+)  (+)C 
Ethanol (CH3)OCH3  95
Hydrochloric acid  HCI  37
Ammonia solution  NH3  25 (+)     
Orthophosphoric acid  H3PO4  85  
Nitric acid HNO3  69   (+)     
Acetic acid  CH3COOH 100 (+)  (+) 
Comment: + = good, (+) = limited; - = unstable