| Popis: |
Scatterometry is a novel optical metrology based on the analysis of light diffracted from a periodic sample. In the past the technology has been applied successfully to a variety of different grating types found in the manufacture of microelectronic devices. The scope of these applications, however, has been limited to structures that are singly periodic (periodicity = 1) in nature, i.e., gratings that are simple line and space structures with one periodic dimension. Rigorous coupled wave theory (RCWT), the underlying theory behind scatterometry measurements, can be applied to structures with a higher dimension of periodicity (periodicity > 1), although the computation is much more complex. In this paper we will discuss the application of scatterometry to structures with higher dimensions of periodicity, such as arrays of contact holes and DRAM cells. Details of the model, such as computation time and considerations for choosing a proper shape for the diffracting structures, will be presented. Sensitivity of the various parameters, such as the multiple critical dimensions and sidewall angles, will be discussed. Finally, results of measurements on contact hole and typical DRAM storage node patterns will be summarized. When compared to SEM, we will show correlation results that are greater than 0.9 for most applications, indicating that the technology can be applied successfully to such complicated structures. System matching between tools for these applications will also be discussed. |
