The influence of substrate on the adhesion behaviors of atomic layer deposited aluminum oxide films

Aluminum oxide (Al2O3) films were produced on n-type (001) Si, SiO2 and polyimide (PI) substrates by atomic layer deposition method (ALD). The surface morphologies of the coatings were characterized by XRD and AFM, respectively. The adhesive properties of the deposits were investigated as a function of the nature of the substrate using the micro-scratch test. The Al2O3 ALD films on SiO2, Si and PI substrates exhibited quite different scratch morphologies and failure modes. For about 100 nm thick Al2O3 ALD films, the critical loads are 304.6 ± 8, 144.6 ± 8 and 41.6 ± 3 mN on SiO2, Si and PI substrates, respectively, while the corresponding calculated adhesion energies are 18.7, 3.8 and 0.12 J/m2. So the large difference in adhesion energy was discussed from the growth mechanisms of Al2O3 on SiO2, Si and PI substrates.