FUSION BONDING OF ROUGH SURFACES WITH POLISHING TECHNIQUE FOR SILICONMICROMACHINING

Surface roughness is one of the crucial factors in silicon fusion bond ing. Due to the enhanced surface roughness, it is almost impossible to bond wafers after KOH etching. This also applies when wafers are heav ily doped, have a thick LPCVD silicon nitride layer on top or have a L PCVD polysilicon layer of poor quality. It has been demonstrated that these wafers bond spontaneously after a very brief chemical mechanical polishing step. An adhesion parameter, that comprises of both the mec hanical and chemical properties of the surface, is introduced when dis cussing the influence of surface roughness on the bendability. Fusion bonding, combined with a polishing technique, will broaden the applica tions of bonding techniques in silicon micromachining.