An Optical Critical Dimension (OCD) Study with Standard Structures

Optical Critical Dimension (OCD) technique, also known as optical scatterometry, is designed to obtain three-dimensional periodic optical information from device architectures and has achieved great success in IC industry over the past decades. Because it is not image based, OCD technique is not constrained by the diffraction effects that limit image resolution. The major benefit of optical scatterometry is that it can provide rich geometrical information, i.e., CD, SWA, trench depth, film thickness, in one quick single measurement. Furthermore, it provides measurement data with the benefit of none-destruction and high throughput, and thus can be used to acquire in-line measurement data with high-sampling. In our previous work, we have reported OCD model building method and model verification procedures. Then, what is the limit of this metrology method? In this paper, we will study the response of OCD model to a few standard structures in order to understand the mechanism of OCD signal response within the theoretical framework of optical ellipsometry, which can be used as a basis for the understanding of its extendability to the detection of smaller, thinner, more refractive structures in future technology nodes.