Elsevier

Microelectronics Journal

Volume 37, Issue 2, February 2006, Pages 133-136
Microelectronics Journal

Mass patterning of polysiloxane layers using spin coating and photolithography techniques

https://doi.org/10.1016/j.mejo.2005.04.054Get rights and content

Abstract

Polysiloxane (PSX) containing 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator has been used as a photosensitive polymer. Thus, thin PSX films have been deposited by spin coating and patterned thanks to standard ultraviolet (UV) photolithography. The influences of the different technological parameters (PSX dilution, spin speed, UV exposure time) have been studied in so as to understand the polysiloxane deposition and cross-linking phenomena. Finally, the whole process has been optimised. Results evidence the realisation of high quality PSX patterns for the development of mass-fabricated ion sensitive layers in the field of chemical microsensors.

Introduction

Within the framework of microtechnologies, polymers seem very promising materials. Indeed, their multitude gives access to a wide range of multidisciplinary properties in order to bring solutions to many technological problems. The field of chemical sensors has not been an exception to the rule. Thus, photosensitive polymers based on poly-vinyl alcohol (PVA), poly-vinyl chloride (PVC), polymethacrylate (PolyHEMA) or polysiloxane (PSX), have been used for the preparation of chemical or biochemical sensitive membranes by manual dip coating and exposure to ultraviolet (UV) radiation [1], [2], [3], [4], [5]. However, irrespective of the polymer chosen, such processes have not been fully reproducible or/and reliable. In order to assess the chemical sensors industrial development, mass-fabrication processes deviated from silicon microelectronics have to be carried out. Solutions involve the development of spin coating and photolithography techniques even if the spinning process is known to be responsible for the loss of large amounts of chemical products. Nevertheless, they have been successfully developed for the deposition and mass patterning of thin poly-vinyl alcohol PVA layers [6] and their use should be extended to other photosensitive polymers.

This paper deals with the development op spin coating and ultraviolet (UV) photolithography techniques applied to standard photosensitive polysiloxane (PSX) copolymer. The different technological parameters (PSX dilution, spin speed, UV exposure time) have been studied in so as to understand the photosensitive PSX copolymer deposition and UV cross-linking phenomena. Thus, the whole process has been optimised for the mass patterning of polysiloxane-based ion sensitive layers in the field of chemical microsensors.

Section snippets

Experiments

The polysiloxane (PSX) copolymer RMS-033 containing methacrylate groups was purchased from ABCR. The 3-(methacryloxy)propyl trimethoxysilane (MPTS), the 2,2-dimethoxy-2-phenylacetophenone (DMPA) photoinitiator, the tetrahydrofuran (THF) solvent as well as the others standard chemical products used were obtained from Sigma-Aldrich.

According to the Warsaw University of Technology [5], the photosensitive polymer was formed from 99% of PSX and 1% of DMPA, and then dissolved into THF to reach

Results and discussion

In order to understand the polysiloxane cross-linking phenomena during the photolithography process, the influence of the UV exposure has been studied for different spin coating steps and for the different PSX solutions. Fig. 1, Fig. 2 represent, respectively the variations of the polysiloxane thickness h (after the development step into xylene) as a function of the UV exposure time tUV for different spin speeds ω and for the different PSX solutions, i.e. for the different dilutions into THF x0

Conclusion

The mass patterning of photosensitive polysiloxane (PSX) layers has been investigated. A technological process based on spin coating and ultraviolet photolithography techniques has been proposed. PSX deposition, cross-linking and diffraction phenomena have been studied and understood even if some discrepancies with the spin-coating deposition hydrodynamic theory have been evidenced. Finally, optimisation of the whole technological process has lead to the fabrication of high quality,

Acknowledgements

This work was supported by the European FP5 project ‘SEWING’ (System for European water monitoring—contract no IST-2000-20084).

References (7)

There are more references available in the full text version of this article.

Cited by (0)

View full text