Quantitative evaluation of process induced strain in MOS transistors by Convergent Beam Electron Diffraction

Area of Science:

• Materials Science
• Solid State Physics
• Microscopy

Background:

• Accurate measurement of strain and stress is crucial for understanding the performance and reliability of complex microelectronic devices.
• Existing methods may lack the spatial resolution or sensitivity required for nanoscale analysis.

Purpose of the Study:

• To develop and validate a method for quantitatively measuring strain and stress in complex devices like periodic MOS transistors.
• To achieve high spatial resolution (approx. 2 nm) and sensitivity (up to 50 MPa) in stress measurements.

Main Methods:

• Utilized Convergent Beam Electron Diffraction (CBED) experiments and simulations.
• Performed Finite Element calculations to model stress and strain.
• Extracted a lamella using Focus Ion Beam (FIB) for Transmission Electron Microscope (TEM) cross-section observation.
• Analyzed High-Order Laue Zone (HOLZ) line broadening in CBED patterns to quantify stress relaxation.

Main Results:

• Demonstrated the quantitative determination of strain and stress in a lamella and subsequently in the bulk device.
• Successfully applied the developed procedure to a complex device structure.
• Fitted intrinsic material strains/stresses in nickel silicide (NiSi) and nitride (Si(3)N(4)) layers through trial and error.

Conclusions:

• The combined CBED, simulation, and Finite Element approach is effective for nanoscale stress and strain analysis in complex microelectronic devices.
• HOLZ line broadening is a viable indicator for quantitative stress determination.
• The method provides valuable insights into material behavior within integrated circuits.