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

TL;DR

This paper presents a noncontact, in-line microwave measurement technique for dielectric constant of low-k interconnect films on patterned wafers, compatible with semiconductor manufacturing, achieving high precision and accuracy.

Contribution

It introduces a novel near-field microwave probe method for in-line dielectric constant measurement on patterned wafers without contact or grounding.

Findings

Achieves <0.3% precision in dielectric constant measurement.

Demonstrates compatibility with existing manufacturing processes.

Provides 2% accuracy for dielectric constant measurements.

Abstract

We have demonstrated a technique capable of in-line measurement of dielectric constant of low-k interconnect films on patterned wafers utilizing a test key of ~50x50 \mu m in size. The test key consists of a low-k film backed by a Cu grid with >50% metal pattern density and <250 nm 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.