Plasma-Resistant Seals for Semiconductor Fabs

In a semiconductor fab, plasma-resistant seals protect both the tool and the wafer. Particles, outgassing, and plasma erosion from a single O-ring can lead to wafer defects and costly downtime. Therefore, fab seals must be exceptionally pure as well as resistant to heat and aggressive chemistry. This article covers the best compounds for CVD and etch, the materials that are safe for cleanroom use, and ways to reduce sticking during wafer transfer. For material guidance across other industries, see our Complete Guide to Elastomer Seal Materials.

Harsh Environments of Semiconductor Tools

Semiconductor tools create some of the harshest seal environments anywhere. Seals face high heat, aggressive plasma, hot wet chemicals, amines, and remote NF3 cleans. Additionally, every seal is a potential source of particles and outgassing. As a result, semiconductor elastomer seal materials must be pure as well as tough. Marco’s semiconductor O-rings page lists the full compound range.

Best Elastomer Compounds for CVD Equipment Seals

Chemical vapor deposition combines high temperature with reactive precursors and fluorine-based chamber cleans. Therefore, FFKM perfluoroelastomer is the standard choice for CVD chamber lids, gate valves, and gas-line seals.

Markez® Z1400: the highest-temperature Markez grade. It holds long-term compression set up to 335°C, with short exposures to 350°C. It is also low-outgassing and high-purity.
Markez® Z1403: a white compound with improved plasma resistance, higher purity, and low extractables. It is rated to 600°F (316°C).
Markez® Z1419: a dark brown, non-carbon-black grade. It offers excellent plasma resistance and low outgassing to 572°F (300°C).

Low-Outgassing, Deposition-Compatible Materials That Prevent Wafer Defects

Wafer defects often trace back to the seal. Carbon-black fillers, metal oxides, and low-molecular-weight fractions can outgas or shed particles. As a result, the best plasma-resistant seals use high-purity, non-carbon-black formulations.

In practice, three Markez grades lead this category. First, Z1218 is a violet high-purity, plasma-resistant specialty compound with long service life. Second, Z1407 is a clear amber, semiconductor and laser-grade with excellent plasma resistance. Third, Z1403 combines high purity with low outgassing and cleanroom manufacture. Together, these grades reduce particle generation during both deposition and etch.

For oxygen and ozone ash steps, blue fluorosilicone is another option. For example, Marco F1001 is built for O3 and O2 ash, and some etch applications.

O-Ring Materials Safe for Semiconductor Cleanrooms

Cleanroom-safe O-ring materials share three traits. They have low extractables, low particle generation, and low outgassing. In addition, they arrive clean and double-bagged.
High-purity FFKM is the safest choice inside process chambers. Outside the chamber, white or brown FKM and platinum-cured silicone often work well at lower cost. Marco also provides cleanroom packaging services and O-ring inspection to protect purity from the mold to the tool.

Reducing Stickiness and Adhesion for Wafer Transfer

Sticking seals slow slit valves and load locks. Worse, a sudden release can jolt a wafer or shed particles. Stickiness usually rises with temperature, compression time, and surface smoothness.

Several fixes help. First, choose a low-sticking FFKM grade. For example, Markez Z1400 is rated for low sticking force on aluminum and quartz. Also consider Marco’s slit valve door seal solution, which targets installation errors, particle generation, and service life on the Applied Materials P-5000. Second, for wafer pads, Marco P1000 polyurethane is very pure and highly abrasion resistant. Third, PTFE or Parylene O-ring coatings lower surface friction in non-plasma areas. However, validate any coating before using it in a plasma zone.

Elastomer Materials by Industry and Application

Visit our Complete Guide to Elastomer Seal Materials to consult our quick reference tables for typical temperature ranges and elastomer seal materials by application. Read on to find application-specific recommendations for other industries.

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Plasma-Resistant Seals and Elastomer Seal Materials for Semiconductor Fabs