Noncontact electrical metrology of Cu/low-k interconnect for semiconductor production wafers

摘要

We have demonstrated a technique capable of in-line measurement of dielectric constant of low-it interconnect films on patterned wafers utilizing a test key of ～50 X 50 μm~2 in size. The test key consists of a low-k film backed by a Cu grid with >50% metal pattern density and < 0.25 μm pitch, which is fully compatible with the existing dual-damascene interconnect manufacturing processes. The technique is based on a near-field scanned microwave probe and is noncontact, noninvasive, and requires no electrical contact to or grounding of the wafer under test. It yields <0.3% precision and ±2% accuracy for the film dielectric constant.