Investigation of the bond strength between the photo-sensitive polymer SU-8 and gold

Abstract

We present the results from a thorough investigation of the bond strength between the photo-polymer SU-8 and Au. The data were obtained by pull-test experiments, below the glass transition temperature of the polymer. The different aspects that we investigated were: (i) the effect of using different adhesion promoters between the SU-8 and Au; (ii) the influence of the processing sequence, keeping either Au or SU-8 as the bottom layer; (iii) the importance of the UV exposure dosage of the SU-8. For comparison, also the bond strength between SU-8 and other materials was measured. For SU-8 and Au without any adhesion promoter we find a bond strength of 4.8 ± 1.2 MPa for a 7.5-μm-layer of SU-8. The value of the bond strength can be increased additionally by up to 75% using an adhesion promoter and fully optimising the processing conditions of the SU-8.