In the 90nm node and beyond, Critical Dimension Uniformity (CDU) control is essential for today's high performance IC devices. The desired control of CDU is just under 2nm (3 sigma) across a 300mm wafer with 577 die. In this study we used an Opti-Probe 7341 RT/CD system that combines broadband (190-840 nm) spectroscopic ellipsometry (SE), spectroscopic reflectometry (BB), single wavelength (673 nm) beam profile reflectometry (BPR) and single wavelength (633nm) absolute ellipsometry (AE). All of the above technologies were used to characterize the optical dispersions of the individual films in the stack of interest, resist/barc/sion/poly/oxide/silicon. We then used these dispersion results and the SE and BB technologies to characterize the CDU of the patterned wafer. With the SE technology we measured CDU's in the range of 1.9-2.0 nm compared with BB measured CDU's in the range of 4-5 nm, both SE and BB wavelength were in the range of 240 nm-780 nm. However, if the wavelength range of SE and BB were extended to 190nm-840 nm, the CDU with SE stayed at the same level while that of BB reduced a factor of 2 to about 2.0-2.5 nm.
This paper presents measurement results of the 3-D contact hole profiles using RT/CD technology for various diameter-to-space (D/S) ratios and film stacks. The key controlling parameters (hole depth, diameter, sidewall angle, and hole openness, etc.) for lithography processing of contacts and vias were studied in terms of measurement sensitivity on samples with different pitches and D/S ratios and film stacks. Good correlation (R<sup>2</sup> ~ 0.99) between CD-SEM and RT/CD was obtained for the sample structures. The static and dynamic measurement stability of contact diameter and contact depth was better than 1 nm using simple profile modeling.