A batch of wafers in a suitable process cassette are spun at high speeds while being sprayed with solvent, rinsed with DI water, then spun dry. Some spin tools accommodate a single cassette of wafers while others accommodate several cassettes per run. These tools do a good job and are in just about every FAB.
However, spin tools do have some drawbacks compared to submersion wet benches:
· Spin tools require a balanced load. If some wafers are missing from the lot, the entire lot can be destroyed, and sometimes the tool itself is damaged.
· Missing wafers are common enough. It's a nuisance for operators to manage a situation of adding dummy wafers, usually manually by vacuum wand. Then, removing those dummy wafers afterwards.
· Spinning is said to be hard on wafers and is thought to contribute to chips, micro cracks, and occasional wafer breakage.
· Drying by mechanical spin is not as efficient as with IPA Vapor or Marangoni style drying.
1. Resist and residue removal (post ash clean)
2. Post Etch polymer Cleans
3. Post CMP Cleaning
4. Lift Off (usually in less sophisticated FABs)
Just a few submersion style solvent wet benches are found in most FABs compared to the many acid wet benches used in FEOL. For years, the worlds leading wet bench suppliers refused to manufacture solvent benches. Perhaps this is why spin spray tools grabbed lots of BEOL market share. Or, maybe spin cleaners are the better tool for the Job? Either way, its worth mentioning Spin Tools in this wet bench focused website because almost every FAB has them.
Common BEOL Wet Bench Chemistries: