Internal stresses and lifetime evaluation of PECVD isolating layers

In this study, we measured and optimized the stress induced by plasma enhanced chemical vapor deposited isolating layers on silicon wafers by high-resolution X-ray diffraction. Plasma enhanced chemical vapor deposition (PECVD) is a well-known process to fabricate thin isolating layers for electronic structures. Device lifetime of micro-electromechanical systems (MEMS) is correlated to aging, where aging of a crystal is related to local changes of the stress and of the stress profile within the device with time. The more stress, the easier the device will be subject to failure. Thus a reduction of stresses will often be a necessary and so will be their measurement. Applying Hooke's law, stresses can be determined from strain measurements. Even minute strains and strain variations can be determined using X-ray diffraction techniques. In this study we used X-ray rocking curve measurements and X-ray curvature measurements to investigate the strain and the strain relaxation of uncoated and PECVD coated silicon wafers