The influence of surface micro-roughness on bondability

Paper in proceeding, 1995

The requirements on a surface in terms of micro-roughness necessary to achieve spontaneous bonding on wafer contact have been investigated. Wafers from four different manufacturers, all having their special surface characteristics, were evaluated using atomic force microscopy. Their room temperature bondability was investigated using the contact wave velocity and the surface energy of the formed bond as parameters. Different wet cleaning procedures were used to modify the micro-roughness of the silicon surface. It is found that the surface rms roughness value is not a good measure for judging the bondability of a surface. Instead we propose the use of the Fourier spectrum of the surface roughness. The occurrence of low, ~0.001 Å-1, spatial frequency components of large amplitude in the Fourier spectrum of the surface roughness may affect the bondability of the surface negatively while higher frequency components are not as important