Non-Destructive Monitoring of Silicon Consumption During Shallow Trench Isolation Formation on 45nm Node Devices Using Spectroscopic Ellipsometry

In previous publications, two-dimensional profile metrology using spectroscopic ellipsometry (SE) has been demonstrated as a viable technique for non-destructive measurement of the full 2-dimensional STI profile down through the 65 nm half-pitch node. In this paper, extendibility of this technique, also known as SpectraCD, down to the 45 nm half-pitch node will be demonstrated, along with successful measurement of the amount of silicon consumed during various steps in the STI process flow. Process splits were run to evaluate the capability of SE to detect profile variations that include: 1) overhang/recess of the etch hard mask from silicon, 2) thickness of trench sidewall passivation layer, and 3) silicon consumption after sidewall passivation step. Effective tracking of these parameters will be demonstrated with comparison to cross-section TEM measurements where possible. In addition, measurement repeatability (precision) and multi-tool measurement matching data will be presented to support the readiness of SE for 45 nm STI process control.