Post-etch Residue Removal

Dry-etching in conjunction with photolithographic techniques is widely used in semiconductor fabrication processes. The etching process includes the removal of residues with special chemicals, such as EKC265™. Residue cleaning is an important factor that can influence the final IC quality.

Until now, there is was no possibility for online monitoring of the cleaning process. At irregular intervals, lab samples of the cleaning solution are taken and analyzed by FTIR instruments. This procedure has to be done manually, is very costly and does not achieve the needed continous monitoring of the cleaning solution. It has been found, that an increase of the cleaning agents concentration, e.g. EKC265™ (due to evaporation of the water) affects the cleaning performance negatively. Thus, some cleaned charges of wafers cannot be used for further manufacturing and need to be re-cleaned. This is a significant loss of efficiency and means additional costs.

As a superior alternative, the online process refractometer PIOX R continously monitors the cleaning agents quality to avoid failing washing cycles and to inform about the actual water content in the cleaning solution. PIOX R is installed in the bypass (directly in the Spinse Rinse Dryer) and monitors the concentration of the cleaning agent, such as EKC265™ (output as water content in w%) and guarantees the quality of the cleaning liquid, optimises the wafer cleaning results and increases the possible liquid bath lifetime.

Advantages:

  • Increasing efficiency in residue cleaning: 200 Euro per failed cleaning cycle if cleaning solution quality is out of limits
  • Reliable process control through online monitoring
  • Directly integrated in the Spin Rinse Dryer by compact PIOX R design
  • Highly accuracte, reliable and drift free with customised outputs
  • Integrated diagnostics with predictive maintenance (Signal amplitude shows validity of the measurement)

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