ProTEK PSB coating as an alternative polymeric protection mask for KOH bulk etching of silicon
The utilization of a newly developed photosensitive polymeric coating, ProTEK PSB plays a significant role in realizing simple process steps in the fabrication of MEMS devices using bulk micromachining technology. The photosensitive coating which serves as an alternative to the conventional silicon...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Springer
2013
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/30323/ http://irep.iium.edu.my/30323/ http://irep.iium.edu.my/30323/ http://irep.iium.edu.my/30323/1/Microsystem_Technologies_published_version_APRIL_2013.pdf |
| Summary: | The utilization of a newly developed photosensitive polymeric coating, ProTEK PSB plays a significant role in realizing simple process steps in the fabrication of MEMS devices using bulk micromachining technology. The photosensitive coating which serves as an alternative
to the conventional silicon nitride mask of bulk potassium
hydroxide (KOH) etching in devising MEMS devices,
particularly in suspended microcantilever structure, is
reported in this study. Although the polymeric coating
ProTEK PSB acts as an excellent outer protective layer
from any pinhole issues, the coating’s lateral etching in the KOH solution is dominant, which results in an undercut
problem. Therefore, few investigations have been carried
out to identify the most suitable condition for the ProTEK
PSB deposition on Si substrate. Initial investigation was
done on the effect of Si surface modification on the stability of the ProTEK PSB in KOH etching. It was observed
that the surface treatment may reduce the undercut ratio for
a short period of KOH etching. However, for the extended
hours, the surface treatment is not effective enough to
improve the stability of the polymeric coating. Therefore,
combinations of ProTEK PSB on three substrates were
studied in order to obtain a minimum undercut to etch
depth ratio of the polymeric coating in KOH bulk etching.
The study showed that the combination of ProTEK PSB
patterned on thermal oxide results in the most effective
etching condition attributed by minimum undercut ratio.
Further investigation was carried out on the effect of the
KOH etching concentration on the stability of the ProTEK
PSB coating over the long hours of bulk etching process.
Three concentrations of KOH etchants, KOH 20 wt%,KOH 45 wt% and KOH with isopropyl alcohol (KOH+IPA) were investigated. The results showed that the stability of the polymeric coating was excellent in KOH 20 wt% concentration with a very minimal undercut ratio of 0.05–0.07. In conclusion, the utilization of the polymeric coating ProTEK PSB serves as an alternative etch mask in KOH wet etching which offers simpler and cheaper device fabrication in bulk micromachining technology. |
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