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Journal of Micro/Nanolithography, MEMS, and MOEMS

Study of stress and adhesion strength in SU-8 resist layers on silicon substrate with different seed layers
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Paper Abstract

We present the details of our study on the internal stresses and adhesion strengths of SU-8 structures to different substrate seed layers. The effect of adhesion promoter—methacryloxy [propl] trimethoxysilane (MPTS), and OmniCoat—and different seed layer combinations (Ti/Cu/Ti, Ti/Cu, Cr/Au, and Cr/Au/Cr) was examined for internal stress and adhesion strength in 650-μm-thick SU-8 films. Increased stress and poor adhesion have led to the delamination of SU-8 in some cases. Adhesion and stress have proven to be the function of process parameters such as soft bake (time and temperature), exposure dose, post-exposure bake (time and temperature), and development time. We have found that a <100> silicon wafer containing a titanium-copper-titanium (Ti/Cu/Ti) seed layer with MPTS as the adhesion promoter yielded a thick SU-8 film with a lower value of stress and consequently better adhesion for processing in deep x-ray lithography (DXRL). A detailed correlation of the effects of adhesion and internal stress on the SU-8 film is discussed. An analysis of the possible chemical bonding interactions occurring between SU-8, and its adhesion promoter and/or substrate is also presented.

Paper Details

Date Published: 1 July 2007
PDF: 9 pages
J. Micro/Nanolith. 6(3) 033006 doi: 10.1117/1.2778644
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 6, Issue 3
Show Author Affiliations
Richard L. Barber, Swinburne Univ. of Technology (Australia)
Muralidhar K Ghantasala, Western Michigan Univ. (United States)
Ralu Divan, Argonne National Lab. (United States)
Derrick C. Mancini, Argonne National Lab. (United States)
Erol C. Harvey, Swinburne Univ. of Technology (Australia)

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