A quantitative study on the adhesion property of cured SU-8 on various metallic surfaces

SU-8 has received wide attention in recent years because of its application in the fabrication of high aspect ratio microstructures and devices. This negative resist is known for its excellent lithography properties using ultraviolet light source. As the microfabrication technology based on UV-lithography of SU-8 finds wide applications, a good understanding and characterization of cured SU-8 polymer on various substrate materials are therefore very important. A good adhesion on various substrate materials is essential to both the fabrication process and to the functionality of any final products that have cured SU-8 as part of the structural material. There are very limited studies reported in this important area in the literature. This paper presents a theoretical and experimental work to quantitatively study the adhesion properties of cured SU-8 on some of the most commonly used metallic surface materials. The adhesion strengths of cured SU-8 samples on Au, Ti, Cu, Cr, and Ni coated glass substrates were measured following ASTM-C633 standard. A detailed analysis of the experimental results was also provided based on the atomic structures and electron configurations of the respective metals.