Changes to the SPM Process Improves Efficiency and Results

The sulfuric acid peroxide measure (SPM) is the process that effectively strips and cleans silicon wafers, however due to the decomposition of the hydrogen peroxide it suffers from instability. Heated baths can speed up the process, but they can affect the concentration of the hydrogen peroxide. Periodically adding the mixture with extra hydrogen peroxide, on the other hand, will maintain its concentration but it can affect the strip rate. As a result, the SPM mixture needs to be changed as frequently, and leads to high costs of chemicals and frequent downtime on wet bench stations.

Modutek has addressed the SPM issues with its new “bleed and feed” spiking system, which uses a double clean-and-dirty tank process. This newSPM strip and clean process starts by draining a programmable amount of mixture prior to each process step. Next, a programmable amount of sulfuric acid is added to a clean tank. Now both tanks have the programmable amount of hydrogen peroxide.

With the “bleed and feed” method, a complete chemical change is now only required about once a week as compared to two or three times a day. It also helps in reducing downtime and enables the process to get up again quickly. Result is less frequent changes and use of costly chemicals.

The “bleed and feed” system is also PLC-controlled, and the periodic adding/spiking of chemicals enables the mixture to be used continuously for longer periods of time. In addition this updated process is more efficient in delivering better cleaning and stripping performance.

For additional details about the SPM process upgrade on Modutek’s wet bench stations, read the complete article entitled “Changes to the SPM Process Improves Efficiency and Results.” If you need more information or have questions, please send an email to modutek@modutek.com or call Modutek at 866-803-1533.