Development of a trench depth measurement system for VLSI dynamic random access memory vertical capacitor cells using...

Area of Science:

• Semiconductor Manufacturing
• Metrology
• Optical Engineering

Background:

• Accurate trench depth measurement is critical for VLSI dynamic random access memory (DRAM) vertical capacitor cell fabrication.
• Existing methods may lack the precision required for sub-micron feature characterization.

Purpose of the Study:

• To develop a practical and accurate system for measuring trench depths in VLSI DRAM capacitor cells.
• To demonstrate the system's capability in characterizing trench depth and reflection coefficients.

Main Methods:

• Development of a measurement system incorporating an optical head, Michelson interferometer, and host computer.
• Utilization of a He-Ne laser for monitoring prism displacement and coherent averaging of interferograms.
• Application of the system to test wafer trenches for depth and reflection coefficient analysis.

Main Results:

• The developed system achieves a measurement accuracy of +/-0.1 micrometers within a 2-5 micrometer depth range.
• The system successfully demonstrated trench depth and reflection coefficient distributions on test wafers.
• Coherent averaging of interferograms enhanced measurement precision.

Conclusions:

• The Michelson interferometer-based system provides a practical and accurate solution for VLSI DRAM trench depth metrology.
• The system's ability to map trench depth and reflection coefficients offers valuable insights for process control and optimization.
• This technology contributes to advancing the precision required in semiconductor fabrication.