As temperature and concentration of the etching solution have major impact on the wet etch rates, various etching processes can be optimized and etch end points determined when the etchant concentration is known. For instance, the Potassium hydroxide, KOH etch process can be optimized when the composition of heated KOH/H2O solution is continuously monitored with Vaisala K-PATENTS® semicon refractometer. As etching progresses, some KOH (namely OH- ions) is consumed in the process and fresh etchant needs to be replaced.
With Vaisala K-PATENTS® semicon refractometer the fabs can:
Vaisala’s application note explains how a semicon refractometer can improve process with recommended installation points for best performance.
Dissolved silicate increases the concentration reading. The application note also explains how to compensate this offset with simple balance calculation and without introducing any extra measurements.
Download the full application note here: