Enhancing doping contrast and optimising quantification in the scanning electron microscope by surface treatment and...

Area of Science:

• Materials Science
• Semiconductor Physics
• Surface Chemistry

Background:

• Two-dimensional dopant profiling using scanning electron microscopy (SEM) is crucial for integrated device manufacturing, enabling high-throughput, non-contact process diagnostics and failure analysis.
• Standard surface preparation techniques, such as electrochemical etching, are vital for obtaining clean, hydrogen-terminated silicon surfaces in ULSI microfabrication.
• However, these preparation methods can significantly alter doping contrast, which is fundamental for accurate quantitative dopant profiling.

Purpose of the Study:

• To investigate the impact of ammonium-fluoride treatment on dopant profiling in SEM.
• To assess the effectiveness of this treatment in enhancing quantitative calibration for dopant concentration.
• To evaluate the necessity of energy-filtering techniques for accurate surface potential determination across semiconductor p-n junctions.

Main Methods:

• Utilized ammonium-fluoride treatment for silicon surface preparation prior to SEM analysis.
• Performed quantitative calibration using univariate analysis for secondary electron (SE) energies as low as 1 eV.
• Conducted energy-filtering measurements to analyze surface potential variations across semiconductor p-n junctions.

Main Results:

• Ammonium-fluoride treatment enabled dopant contrast differentiation primarily through surface band-bending.
• The treatment significantly enhanced the quality of linear quantitative calibration, even at low SE energies.
• Energy-filtering measurements indicated potential limitations of existing linear analytical models for surface potential determination without deconvolution.
• Quantification trends suggest energy-filtering might be unnecessary if surface fields and contamination are effectively managed.

Conclusions:

• Ammonium-fluoride treatment is a promising method for improving two-dimensional dopant profiling in SEM.
• This approach enhances quantitative calibration accuracy for semiconductor process diagnostics and failure analysis.
• While advanced models may be needed for precise surface potential mapping, practical applications can succeed with proper surface management techniques.