Formation of metal interconnects and their resistance-change behavior during tensile stretching for stretchable packaging applications

We examined the resistance-change behavior of thin Pt and Au films on the PDMS elastomeric substrate. A maximum Young's modulus of 1.74 MPa was obtained for the PDMS substrate by adjusting the mixing ratio between base polymer and its curing agent to 10:1. Parylene coating on the PDMS surface was effective as an adhesion layer between metal interconnects and PDMS substrate. Without a Parylene coating, the resistance of a 150 nm-thick Pt film increased from 18.7 Ω to 3000 Ω with stretching to 20% strain and became open at strains larger than 20%. On the other hand, the resistance of a Pt film, sputtered on a Parylene-treated PDMS, was initially 10.3 Ω before loading, increased to 99.3 Ω at 30% elongation, and then decreased to 23.8 Ω after complete unloading. Thin Au metallization has better resistance properties for stretchable interconnect applications than Pt thin film. The resistance of a 150 nm-thick Au film on a Parylene-coated PDMS substrate was 1.3 Ω before loading, increased to 19 Ω at 30% elongation, and then returned to 1.3 Ω after complete unloading.