Skip to main content
SpringerLink
Log in

ProTEK PSB coating as an alternative polymeric protection mask for KOH bulk etching of silicon

  • Technical Paper
  • Published:
Microsystem Technologies Aims and scope Submit manuscript

Abstract

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.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12

Similar content being viewed by others

References

  • Bodas DS, Khan-Malek C (2007) Hydrophilization and hydrophobic recovery of PDMS by oxygen plasma and chemical treatment––an SEM investigation. Sens Actuators B 123:368–373

    Article  Google Scholar 

  • Bodas DS, Mahapatra SK, Gangal SA (2005) Comparative study of spin coated and sputtered PMMA as an etch mask material for silicon micromachining. Sens Actuators A: Physical 120(2):582–588

    Article  Google Scholar 

  • Liu C (2012) Foundation of MEMS, 2nd edn. Pearson Education Limited, England

    Google Scholar 

  • Ljungberg K, Soderbag A, Backland Y (1993) Spontaneous bonding of hydrophobic silicon surface. Appl Phys Lett 62(12):1362–1364

    Article  Google Scholar 

  • Maji D, Lahiri SK, Das S (2012) Study of hydrophilicity and stability of chemically modified PDMS surface using piranha and KOH solution. Surf Interface Anal 44:62–69

    Article  Google Scholar 

  • Malhotra JD, Brand GJ, Zhong XF (2007) Use of silane-based primer on silicon wafers to enhance adhesion of edge-protective coatings during wet etching: application of the TALON wrap process. SPIE, Proc 6462

    Google Scholar 

  • Malhotra JD, Zhong XF, Planje C, Brand G, Yess K (2008) A spin-on photosensitive polymeric etch protection mask for anisotropic wet etching of silicon. J Micromech Microeng 18:1–8

    Google Scholar 

  • Powell O, Harrison HB (2001) Anisotropic etching of 100 and 110 planes in (100) silicon. J Micromech Microeng 11:217–220

    Article  Google Scholar 

  • Rahim RA, Bais B, Majlis BY (2008) Design and analysis of MEMS piezoresistive SiO2 cantilever-based sensor with stress concentration region for biosensing applications, In: Proceedings of 2008 IEEE international conference on semiconductor electronics (ICSE 2008), Kuala Lumpur, Malaysia, pp 211–215

  • Rahim RA, Bais B, Majlis BY (2009) Hybrid simulation approach on MEMS piezoresistive microcantilever sensor for biosensing applications. Adv Mater Res 74:243–246

    Article  Google Scholar 

  • Seidel H, Csepregi L, Heuberger A, Baumgartel H (1990) Anisotropic etching of crystalline silicon in alkaline solutions. J Electrochem Soc 137(11):3612–3625

    Article  Google Scholar 

  • Takahashi T, Makihata M, Esashi M, Tanaka S (2010) Evaluation and application of resist for alkaline wet etching. IEEJ Trans Sensors Micromach 130:421–425

    Article  Google Scholar 

  • Williams KR, Gupta K, Wasilik M (2003) Etch rates for micromachining processing-part II. J Microelectromech Syst 12(6):761–778

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, 50728, Kuala Lumpur, Malaysia

    Rosminazuin Ab Rahim

  2. Department of Electrical Electronics and Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia

    Badariah Bais

  3. Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia

    Burhanuddin Yeop Majlis & Gandi Sugandi

Authors
  1. Rosminazuin Ab Rahim
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Badariah Bais
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Burhanuddin Yeop Majlis
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Gandi Sugandi
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Rosminazuin Ab Rahim.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Rahim, R.A., Bais, B., Majlis, B.Y. et al. ProTEK PSB coating as an alternative polymeric protection mask for KOH bulk etching of silicon. Microsyst Technol 19, 905–914 (2013). https://doi.org/10.1007/s00542-013-1794-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00542-013-1794-z

Keywords

Search

Navigation