Reliability of thinned silicon ICs

Ultra thin ICs will play an important role in future packaging applications for smart and flexible systems. Thinned silicon gets more and more mechanically flexible with thickness below 50 µm and can be bended with a low radius of curvature. But it still remains a brittle material and therefore the applied thinning and dicing technology has to be analyzed. The influence of the thinning techniques, grinding, wet-chemical etching and polishing on the material properties of thinned silicon was investigated by Atomic Force Microscopy (AFM), carrier lifetime measurements and X-ray inspection. Experimental results are correlated to mechanical fracture tests. The investigations prove the suitability of the stress-relief processes etching and polishing for the restoration of crystalline quality. However, for silicon wafers in the thickness range of 100 µm to 50 µm backgrinding process causes an increasing depth of damage. This will lead to important consequences for the choice of appropriate wafer thinning techniques if ultra thin ICs are fabricated