Boaz Brill

Product-driven material characterization for improved scatterometry time-to-solution

This paper discusses a novel methodology of material characterization that directly utilizes the scatterometry targets on the product wafer to determine the optical properties (n&k) of various constituent materials. Characterization of optical constants, or dispersions, is one of the first steps of scatterometry metrology implementation. A significant benefit of this new technique is faster time-to-solution, since neither multiple single-film depositions nor multi-film depositions on blanket/product wafers are needed, making obsolete a previously required-but very time-consuming-step in the scatterometry setup. We present the basic elements of this revolutionary method, describe its functionality as currently implemented, and contrast/compare results obtained by traditional methods of materials characterization with the new method. The paper covers scatterometry results from key enabling metrology applications, like high-k metal gate (postetch and post-litho) and Metal 2 level post-etch, to explore the performance of this new material characterization approach. CDSEM was used to verify the accuracy of scatterometry solutions. Furthermore, Total Measurement Uncertainty (TMU) analysis assisted in the interpretation of correlation data, and shows that the new technique provides measurement accuracy results equivalent to, and sometimes better than, traditional extraction techniques.

A holistic metrology approach: multi-channel scatterometry for complex applications

Improvement in metrology performance when using a combination of multiple optical channels vs. standard single optical channel is studied. Two standard applications (gate etch 4x and STI etch 2x) are investigated theoretically and experimentally. The results show that while individual channels might have increased performance for few individual parameters each - it is the combination of channels that provides the best overall performance for all parameters.

LER detection using dark field spectroscopic reflectometry

Line edge roughness (LER) is an increasingly important issue as lithography scales down. Currently LER is usually measured using scanning electron microscopy (SEM) tools; however, using optical techniques to measure LER may have potential benefit due to less resist damage and higher throughput. In this paper, we explore the detection and potential measurement of LER using dark field spectroscopic reflectometry. We provide a proof of feasibility by showing LER spectra collected on several different applications, which behave consistently with scattering from small particles (Rayleigh) and decrease sharply with wavelength. Additionally, the dependence of the spectra on film thickness bears resemblance to thin film measurements. Finally, we also provide preliminary simulation results showing similar spectral characteristics to the measured spectra.

Alternative approach for direct APC using scatterometry data

Scatterometry is a promising method, capable of providing accurate profile information for a large range of applications. However, applying scatterometry to the production environment and applying it to APC is still difficult. In this paper we propose an alternative approach in which we apply a Neural Network to directly correlate scatterometry raw data and the lithography process control parameters. The proposed method is much easier to use than normal scatterometry, and can therefore be applied to APC much faster.