Process optimization for shallow trench isolation etch using computational models

Abstract

The critical dimensions of advanced semiconductor manufacturing processes have decreased to a few tens of nanometers while the aspect ratios have increased beyond 100. The performance of plasma etch patterning processes as well as the cost and time of the development cycle are critical to the success of ramping a new technology node toward profitable high-volume manufacturing. In this paper, a computational patterning software, ProETCH®, has been developed with rigorous physics and advanced algorithms for modeling the etch patterning process, with the featured capabilities in calibrating the reaction mechanisms and optimizing the etch process. A shallow trench isolation etch process using self-aligned double patterning was investigated. A reaction mechanism of silicon etch by Ar/Cl2 plasma was developed to address the surface reactions, and a plasma hypermodel was introduced to correlate process operating conditions to plasma parameters at the wafer surface. The parameters of the reaction mechanism and the plasma hypermodel were calibrated with experimental data obtained from cross-sectional scanning electron microscope (XSEM) images. The calibrated model is used to identify the different fundamental pathways that contribute to the observed profile metrics in XSEMs. The model was then used for process development and optimization by solving the forward and inverse problems. In the forward problem, the model is used to predict the etching profile at different process conditions. Predictions for both interpolation conditions (process parameters within the range used for developing the model) and extrapolation conditions (process parameters outside of the range used for developing the model) agree well with the experimental data with the root mean square error less than 4 nm (1 nm resolution used for the mesh). In the inverse problem, the developed model is used to search for process conditions (e.g., values of bias power and pressure), which could result in desirable profiles. The solutions to the inverse problem demonstrate a degeneracy in process space of the etching process for a given target profile.

Multi-step process optimization on high aspect ratio etching for memory devices

“…Process optimization using computational tools is attracting attention nowadays [5][6][7][8][9] . The basic approach in using computational techniques for HAR etching is to deal with a forward problem 5 .…”

“…This makes it incompatible with multi-step optimization, in which intermediate states will be variable, and with handling the physical and chemical phenomenon in an extrapolated regime. Therefore, we are now evaluating ProETCH® [7][8][9] which has a rigorous physical model to handle inverse problems by incorporating etching profile evolution and physical and chemical reaction mechanisms. Others have used this tool to optimize STI etching 9 as an inverse problem with patterns that have different incoming geometries (pairs/adjacent).…”

“…Therefore, we are now evaluating ProETCH® [7][8][9] which has a rigorous physical model to handle inverse problems by incorporating etching profile evolution and physical and chemical reaction mechanisms. Others have used this tool to optimize STI etching 9 as an inverse problem with patterns that have different incoming geometries (pairs/adjacent). In this paper, we evaluated multi-step process optimization for MH RIE process, and analyzed the proposed solution by ProETCH® using experimental data and post-analysis of simulation data.…”