JAST 2007 Abstract

Deformation of Bowed Silicon Chips Due to Adhesion and Applied Pressure


Andy Pamp and George G. Adams


Summary

One potential method to accomplish high-rate nanomanufacturing is to develop processes which allow for rapid transfer of nano-scaled devices from a template to a device wafer. In order to accomplish this transfer, the device wafer must make intimate contact with the template. A similar situation exists in wafer bonding, except that in that case the two wafers remain in bonded contact due to the work of adhesion even after the applied pressure is removed. In high-rate nanomanufacturing intimate contact must be maintained during transfer, while allowing for easy separation afterwards.

Wafers typically have waviness and bow which cause a deviation of many micrometers from flatness over the 15-mm length scale of a typical chip. This non-flatness can be a serious problem in the transfer of nanometer-scale elements. In this investigation, a model is developed to examine the effects of applied pressure, bow radius, and the work of adhesion on the flattening of a spherically/cylindrically bowed chip. This model uses elastic plate theory and the work of adhesion. An operating window is found which provides intimate contact while allowing for separation once the pressure is removed.

It is also shown that the effect of adhesion is to produce a discontinuity in the internal bending moment, at the separation boundary, which is proportional to the square-root of the product of the work of adhesion and the flexural rigidity. This “moment-discontinuity” method can be applied to other problems involving adhesion of elastic plates.

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