Contactless Fault Isolation of Ultra Low k Dielectrics in Soft Breakdown Condition

Abstract

We are able to localize dielectric soft break downs (SBD) in porous low k materials with photon emission measurements. Up to now it was only possible to isolate hard breakdowns with several orders of magnitude higher leakage current than SBD level. This work presents soft breakdown localisations down to a leakage current level of 100pA (260GΩ) and less. The contactless and non-destructive fault isolation of soft breakdowns is an important step to plan physical analysis of the soft breakdowns. The test samples used were provided by the interuniversity microelectronics centre (IMEC). Differences between an InGaAs detector and a Si-CCD detector for photon emission measurements are presented in this work. A short evaluation for optical beam induced resistance change (OBIRCH) as an alternative contactless fault isolation method is given. For photon emission measurements with a Si-CCD detector, long integration times up to 2000s have been applied to detect emission from a leakage current of less than 1nA (33GΩ}). A way to nearly freeze the degradation for a long time is presented. Due to the noise of an InGaAs detector the integration time is limited to 100s. Use of a silicon solid immersion lens increases the numerical aperture and the detection sensitivity. Resulting in a detectable emission by a leakage current of 100pA (260GΩ}). Optical beam induced resistance change (OBRICH) was also evaluated as a contactless fault isolation method for localising defects in these dielectric structures. For the OBRICH leakage paths of resistances up to 1MΩ} had been found, which is orders of magnitude less sensitive than photon emission.