Radius of Curvature Considerations for Direct Wafer Bonding.

A study of the bondability of silicon samples that deviate from the ideal flatness (radius of curvature, R, greater 100 m) of industrial standard wafers is the major objective of this work. A theoretical model is developed to predict the force required to conform two silicon samples and the resultant radius of curvature of the pair; this model is based on the elastic deformation of thin plates. Experimental verification of this model is also examined. Silicon samples with a radius of curvatures as small as 15 m are used. These large deflections of the silicon samples are created by deposition of plasma enhanced chemical vapor deposition (PECVD) nitride film. Utilizing a NH3 plasma surface treatment prelude to bonding and a 300 °C pressure anneal for 1 h , conformal silicon samples were formed.