Nondestructive, at-line measurement of dielectric constant for VLSI intermetal dielectrics

Shrinking VLSI metallization schemes require new intermetal dielectrics (IMD) with low dielectric constant, K. Materials being considered are doped glasses, polymers, porous material and composites. Both the magnitude and the variability of the dielectric constant must be measured for these new dielectrics, hence, a new need to make reliable, accurate and cost-effective at-line measurements of the dielectric constant has emerged. We have developed a technique using commercially available, non contact capacitive probe and spectral ellipsometry tools to measure K to an accuracy of better than 5% at K<4.0. The accuracy and measurement system error improves as K decreases, so that measurements at K=2.0 should be accurate to 2%.