Endpoint Control for Thick Photoresist Removal

Complete removal of thick photoresist needs proper endpoint detection

Applying microwave (MW) plasma to remove thick resist such as used for micro-machinery and microelectromechanical systems (MEMS) requires adequate endpoint detection to limit the unnecessary exposure of sensitive structures and surfaces to reactive gases. The unique properties of microwave assisted plasma allow easy and accurate endpoint detection using temperature sensors.

Microwave Plasma – Isotropic resist removal with least thermal load

RF-plasma exposes the substrate to a relative high amount of charged species (ions) related to the energy distribution in the plasma. These ions transfer kinetic energy when hitting the surface of the substrate causing it to heat up. Depending on the process conditions, this heating-up is critical for the integrity of the substrate, hence cooling is required to stay within the specified temperature range. In the case of Muegge’s microwave assisted remote plasma source, the energy transfer is extremely low, no charged particles are released into the process chamber. As a result the substrate remains cold, the only heat-source it is the chemical reaction of the exothermic resist removal. The related temperature change can be used to track the progress of the cleaning process.

MUEGGE’s solution – accurate, reliable and repeatable

Although optical endpoint detection is mature and reliable, it requires substantial invest into additional equipment like interferometry and sophisticated control algorithms. For less demanding applications (e.g. photoresist removal) customers are looking into less complex solutions. Temperature as indicator for the reaction progress is an obvious choice but usually not easy to track because of physical side-effects of the plasma generated species (e.g. temperature raise due to sputtering).

Radical based photoresist removal allows precise tracking of

the heat released by the chemical reaction only. Data collection is easy to realize, reliable and repeatable.

Endpoint detection for different substrate samples

Figure 1: Example of end point detection at two different samples by sensing the individual substrate temperature

Advantages of temperature-based endpoint detection

Different applications require different technologies for endpoint control in high volume production. Using the measurement of substrate`s temperature during photoresist-removal offers a reliable method to detect endpoint, however, RF-plasma technology produces too much noise to separate the reaction-heat from other heating-up mechanisms. Microwave-assisted photoresist removal allows to collect temperature data with sufficient resolution for endpoint detection. Temperature sensors work reliably for the typical pressure range of microwave-assisted plasma, no additional hardware is required. The signal is stable and free of interference as it only depends on the chemical reaction taking place on the substrate. Over-etch can be easily derived from the endpoint, changes in the process chamber (e.g. leaks, gas-flow) will reflect in the endpoint curve and help to adjust preventive maintenance cycles. The detection is inherently very stable and does not need re-calibration in case of process adjustments. It is a feature of the Muegge microwave systems (STP series) and proven in high volume production.


Ähnliche Beiträge

Whitepaper Power-to-X Applications based on Microwave Heating and Microwave Plasma Technology
Der Fortschritt steckt im Detail. Informieren Sie sich über aktuelle Erkenntnisse und fortschrittliche Anwendungsentwicklungen in der Mikrowellen- und Plasmatechnologie - direkt von unseren Experten, zugeschnitten …
Mehr erfahren
Power-to-X Applications Explainer Video – Power-to-X
MUEGGE provides solutions for breaking down the greenhouse gases CO2 and methane by atmospheric plasma. Watch our explainer video and learn how our microwave assisted plasma …
Mehr erfahren
Power-to-X Applications Video of MUEGGE’s Atmospheric Plasma Source
The unique properties of the Atmospheric Plasma Source (APS) can be used for applications formerly not available for plasma technology, like Power-to-X and related renewable …
Mehr erfahren
Power-to-X Applications Decontamination of Process Water containing Organic Residues using an Atmospheric Pressure Microwave Plasma Process
The thermo-catalytic reforming process (TCR® process) developed through a collaboration between MUEGGE and the Fraunhofer Institute for Environmental, Safety and Energy Technology (Fraunhofer UMSICHT) produces …
Mehr erfahren

Tel.: +49 (0) 6164 – 9307 – 0

Fax: +49 (0) 6164 – 9307 – 93



Hochstrasse 4 – 6

64385 Reichelsheim


Tel.: +1-209-527-8960

Fax: +1-209-527-5385


Gerling Applied Engineering, Inc.

P.O. Box 580816

Modesto, CA 95358-0816



Sie benötigen eine besondere Lösung für Ihren individuellen Prozess?