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High Resolution Measurements of Two-dimensional Dopant Diffusion in Silicon
1Istituto Nazionale di Metodologie e Tecnologie per la Microelettronica, CNR-IMETEM, Stradale Primosole 50, I-95121 Catania, Italy
Summary
This study details electrochemical selective etching of doped silicon (Si). Optimized methods achieve high sensitivity for delineating boron and arsenic dopants, enabling precise 2D doping profile measurements.
Area of Science:
- Materials Science
- Electrochemistry
- Semiconductor Physics
Background:
- Delineating dopant profiles in silicon is crucial for semiconductor device fabrication.
- Understanding the influence of electrochemical parameters on etching selectivity is key to improving resolution.
Purpose of the Study:
- To investigate the electrochemical selective etching of doped silicon.
- To determine the dependence of etching selectivity on bias voltage and chemical solutions.
- To measure 2D doping diffusion profiles with high resolution.
Main Methods:
- Transmission electron microscopy (TEM) analyses.
- Spreading resistance measurements.
- Electrochemical selective etching using varying bias voltages and chemical solutions (buffered HF, HF:HNO3:CH3COOH, HF:HCl).
Main Results:
- Etching selectivity improved with bias voltage for B-doped Si in buffered HF, delineating concentrations as low as 1 x 10^17 cm^-3 at 1 V.
- HF:HNO3:CH3COOH or HF:HCl mixtures enhanced sensitivity to 1 x 10^16 cm^-3.
- As-doped Si in buffered HF was delineated to 2 x 10^17 cm^-3 independently of bias voltage (2-4 V).
- Accurate 2D doping diffusion profiles were measured, revealing effects of implant angles.
Conclusions:
- Electrochemical selective etching is a powerful technique for high-resolution dopant profile analysis in silicon.
- Optimized electrochemical parameters and solutions significantly enhance delineation sensitivity.
- The method allows precise evaluation of doping distribution influenced by implantation angles.