SO3 Cleaning

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The sulfur trioxide gas cleaning process for substrates such as semiconductor wafers and flat panel displays is based on the use of sulfur trioxide gas (SO3) to render tough, process-hardened organic films such as photoresist, water-soluble and readily removable at temperatures below 100º C.

The process offers a simple technology for cleaning semiconductor wafers, flat-panel displays, and other microelectronic substrates without the use of oxidizing plasmas or hazardous, liquid chemicals.  As a consequence, this new, gas-phase cleaning technology has powerful advantages in capability, cost, and environmental impact over conventional cleaning and resist stripping methods.

The Sulfur Trioxide Cleaning Process
This unusual new process requires only exposure to dry, sulfur trioxide gas, followed by a simple water rinse, for most applications.  No plasma ashing, no halogen gases, and no liquid chemicals are required for thorough removal of a wide variety of tough, organic films and residues.

Since only sulfur chemistries are employed, many low-k dielectric materials which are sensitive to oxygen-plasma chemistry can be cleaned without damage.

This simple, low-temperature, dry-in / dry-out process is effective across a wide range of typical semiconductor stripping and cleaning applications, including heavy-dose ion implanted photoresist. 

The wide range of capability of the SO3 process makes it possible for a single SO3 cleaning tool to replace the two pieces of cleaning equipment now required by conventional cleaning technology.

Conventional cleaning typically requires a plasma ashing operation in one tool, followed by an ashing-residue cleaning operation, using wet chemicals, in a second tool.   By reducing two operations to one, substantial cost savings and cycle time reductions can be achieved.