Residual stresses in polymeric passivation and encapsulation materials

Abstract

The residual stresses caused by polyiinide (Pi 5878 and PI 2566), and silieone (3‐6550 and 1‐2577) films used as passivation/encapsulation layers in microelectronic circuit manufacturing are investigated by X‐ray curvature measurements. For both PI types, the maximum stress is between 20–40 MPa. This stress is independent of film thickness for films thinner than 10 μm. For films thicker than this value, however, some dependency of the film stress on film thickness is observed. The variation of stress during the cure cycle is significantly different for PI 5878 and PI 2566. This is due to void nucleation and growth in the 5878 films during solvent volatilization. The silieone films have no residual stress at room temperature for all thicknesses. The compensating stresses in the Si wafer are insignificant for all cases studied. Copyright © 1988 Society of Plastics Engineers