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Hybrid Metrology

The accelerated pace of the semiconductor industry in recent years creates growing demand from dimensional metrology equipment (toolsets such as Optical CD, SEM, AFM etc). To keep up with these ever-increasing metrology challenges Nova has revolutionized dimensional metrology capabilities by introducing Hybrid Metrology. With this technology, data gained from different toolsets are combined to achieve superior information about the measured sample and better insight into the process. Nova’s revolutionary approach properly applies the hybridization of such toolset in a way that dramatically decouples parameters that are otherwise badly coupled in each toolset separately. With hybridization one can, thus, gain not only enhanced performance of the measurement, but also the confidence imparted by the contribution of additional toolsets.

Highlights & Benefits

  • 1+1>2: Hybrid metrology offers cross-fertilization among several metrology tools that operate on different technologies. In particular:
    • One metrology unit can provide information about the sample that the other cannot provide and vice versa
    • Common information that can be gained from all the tools can be used to cross-reference each other for improved accuracy.
    • Interfering correlations between parameters is reduced, thus providing better accuracy.
  • Optimal exploitation: As most metrology tools are already available at customer site, the benefit obtained by using both tools is very large.
  • Metrology tools balance: As hybrid metrology combines information from different technologies, there is usually a more efficient way to allocate each tool to a sample, and to improve overall performance (in terms of speed and measurement accuracy).

Throughout the years, the semiconductor industry has adopted a variety of dimensional metrology capabilities.  Today’s metrology requirements are much more comprehensive than the historical CD measurement. Advanced processes require precise detection of multiple intricate details on the complex structures, such as the sidewall angle (SWA), profile, spacer widths, spacer pull-down, epitaxial proximity, footing/undercut, overfill/underfill, etc. All these features need to be controlled to single angstrom levels.  Nova’s ability to hybridize measurements from multiple equipment types or toolsets to enable or improve the measurement of one or more critical parameters is termed Hybrid Metrology (HM).

Usually, one tool cannot measure all key parameters as required by process specifications in-line. To circumvent this, process development often uses destructive metrology—cross-sectional secondary electron microscopy (X-SEM), transmission electron microscopy (TEM), etc.— for process characterization. These offline tools are slow, expensive, and provide minimal sampling.

Under Nova’s Hybrid Metrology ecosystem (Fig. 1), data from one toolset can be exchanged with another toolset and used in a complementary or synergistic way to improve the overall measurement performance. Hybrid Metrology methodology enables Nova’s customers to successfully measure complex structures that are currently difficult to reliably measure with individual toolsets.

The figure shows how introduction of hybridization decouples two geometrical parameters (named SWA and TCD) that are unphysically coupled without hybridization.