Semiconductor thin film processing equipment typically utilizes a variety of sealing materials, depending on the application. FKM (e.g. Viton®), Buna, and Silicone are examples of commonly used materials that are widely available and relatively inexpensive. In limited cases a sealing application can be addressed with FVMQ (Fluorosilicone) or ‘High Performance FKM’ materials. The most demanding applications, such as aggressive gas plasmas or wet chemistries, or high temperatures, usually require an FFKM material, such as Kalrez®. FFKM seals are compatible with a wide range of chemicals, can hold up under temperatures as high as 327°C, and can resist aggressive plasma attack.

Thin film processes using ammonia, such as HDPCVD, SACVD, ALD, and FCVD are appropriate for the use of FFKM seals. However, even within the FFKM seals class, there are specific formulations that perform more favorably, so it is best to seek a recommendation from a trusted supplier.

If you are a semiconductor FAB technician or engineer trouble shooting equipment sealing issues on a process using ammonia, be on the lookout for one or more of the following symptoms:

  • Seals have gotten darker in color.
  • Seals have become stickier.
  • Seals exhibit a high amount of compression set
    or flatness. 
  • If you are using FKM seals, they tend to get
    harder.

Temperature and concentration: Typically ammonia is used in semiconductor applications between 80°C and 180°C. The higher the temperature, the faster the sealing surfaces will be degraded. Also, the concentration of the NH3 in the gas is important. A high concentration (>20%) will significantly impact seal life.

Color Change: Typically, seals will become darker after NH3 exposure. A change in color doesn’t necessarily mean the seal will fail immediately; but it is a warning sign.

For more help determining FFKM seal compatibility by application and fluid chemistry, we recommend "KAG" Kalrez Application Guide and "CRG" Chemical Resistance Guide. Click here for more information.

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IES Technical Sales provides outsourced technical sales and distribution services in the northeast U.S., and is located in Danvers, MA. Contact Us to learn more about DuPont Kalrez® or for general inquiries about vacuum, thin-film, temperature, fluid handling, and related metrology.