Scatterometry feasibility studies for 0.13-micron flash memory lithography applications: enabling integrated metrology

Abstract

A series of experiments were performed to determine if the ThermaWave INTEGRA TM CCDi reflectometer combined with Timbre Technologies' Optical Digital Profiler TM (ODP) software could meet the requirements for lithography cell integration and process control of critical 0.13-micron Flash memory applications. Shallow Trench Isolation (STI), First Poly Gate, Stacked Gate and Aluminum Interconnect layers were examined as a part of this study. ODP models were developed for each of these applications and their output was compared to Critical Dimension Scanning Electron Microscopy (CDSEM) and cross-section SEM to demonstrate adequate correlation to incumbent metrology techniques. ODP is shown herein to correlate to CDSEM while providing the throughput required to measure every wafer without creating a bottleneck for the lithography cell. Experimental results also suggest that, in many cases, ODP can deliver profile determination beyond the fundamental capability of standard in-line metrology techniques.

Application of integrated scatterometry measurements for a wafer-level litho feedback loop in a high-volume 300 mm DRAM production environment

“…The system uses an unpolarized normal-incidence reflectometer for spectral acquisition, in combination with a Profiler Application Server (PAS) for matching the obtained spectra to the spectra modeled by the Timbre TeraGen system. Stack modeling is done using Rigorous Coupled Wave Analysis (RCWA) [4,5]. The software allows measurement of 2-dimensional line/space arrays as well as measurement of 3-dimensional contact-hole (CH) arrays.…”