Tetramethylammonium hydroxide-solutions (TMAH) are used in the semiconductor production as developer in lithographic processes or as cleaning agent before chemical mechanical polishing processes (CMP).
Mostly, the developer solution is applied to wafer’s surface very quickly and has to allow a complete and even surface wetting. This is required to ensure a constant and surface-geometry independent etching process.
An optimal wetting can be achieved by using surface active agents. Due to a time-dependent and dynamic wetting procedure it is required to choose adequate surfactants in the right concentration. The selection and monitoring of the surfactant concentration can be optimally supported by the parameter dynamic surface tension.
SITA offers several solutions for monitoring the surface tension in bath solutions. SITA Tensiometers are based on the bubble pressure method and allow measuring the surface tension from a highly dynamic up to a quasistatic surface tension range.
The diagram shows the dynamic surface tension of different surfactants in TMAH developer solutions.
- SITA clean line ST
Inline-Measurement of Surfactant Concentration
A continuous and automatic measurement of the surface tension for controlling the surfactant concentration in TMAH solutions can be carried out by a process monitoring Tensiometer, SITA clean line ST.
This measuring system is directly implemented in the process, measures the surface tension in regular intervals and compares data with predefined surface tension limit values. In case of measuring deviations, a signal is sent via interfaces in order to ensure an immediate reaction. The measuring device’s data storage has a capacity of at least one year. In case that long-term data storage is required, it is possible to transfer the measuring data to the computer via serial port.
Further information about inline-measurement in the process […]
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