Study of damage and stress induced by backgrinding in Si wafers

In this paper, a profound study of the subsurface damage induced by backgrinding Si wafers is presented. It is shown that a thin amorphous layer (30-80 nm) is generated during backgrinding. Below the amorphous layer, there is a polycrystalline zone. Its thickness (about 0.5 mum) is obtained from Raman spectroscopy measurements. Below that layer, there is a strained crystalline zone. Its stress can be roughly calculated from warpage measurements of the wafer. The stress is also measured directly by Raman spectroscopy. A new analytical model is established to study the stress propagation with depth. The model fits the Raman spectroscopy measurements very well. The measurements show that the stress is reduced to zero after dry etching of the wafers.