Electrical assessment of planarisation for CMP [inter-layer dielectrics]

Experimental measurements of an electrical test structure for use in assessment of the degree of planarisation of inter-layer dielectrics are presented and compared with theoretical predictions. The test structure consists of two sets of metal combs separated by a dielectric. For each structure the combs on the two layers overlap each other by some degree, with adjacent structures having the overlap in one direction progressionally offset by 0.2 /spl mu/m. It is demonstrated theoretically that the structure is robust to expected levels of oxide thickness variation.