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Light Enhanced Hydrofluoric Acid Passivation: A Sensitive Technique for Detecting Bulk Silicon Defects
Published on: January 4, 2016
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Atomic level termination for passivation and functionalisation of silicon surfaces.
Nicholas E Grant1, Alex I Pointon1, Richard Jefferies1
1School of Engineering, University of Warwick, Coventry, CV4 7AL, UK. nicholas.e.grant@warwick.ac.uk john.d.murphy@warwick.ac.uk.
Nanoscale
|August 14, 2020
Summary
Chemical treatments are crucial for high-quality silicon surfaces. A mixed hydrofluoric acid and hydrochloric acid solution offers superior surface passivation compared to hydrofluoric acid alone.
Area of Science:
- Materials Science
- Surface Chemistry
- Semiconductor Device Fabrication
Background:
- Chemical treatments are vital for creating high-quality interfaces in materials and functionalizing surfaces.
- Controlling surface termination, such as hydrogen and fluorine termination on silicon, is critical for device performance.
Purpose of the Study:
- To investigate the effects of hydrogen and fluorine termination on (100)-orientation silicon surfaces at various length scales.
- To compare the effectiveness of different chemical treatments, specifically hydrofluoric acid (HF) and a mixture of HF and hydrochloric acid (HCl), for surface passivation.
- To understand the mechanisms of surface passivation through chemical and field-effect interactions.
Main Methods:
- Lifetime measurements at the centimeter scale to assess surface passivation quality.
- X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) at the nanometer scale to analyze surface morphology and termination.
- Modeling of lifetime data to elucidate passivation mechanisms.
- Atomic layer deposition (ALD) of Al2O3 for surface passivation studies.
Main Results:
- Temporary surface passivation of silicon was achieved using both HF(2%):HCl(2%) and HF(50%) solutions.
- Surface passivation improved with immersion time in HF(2%):HCl(2%) but degraded with immersion time in HF(50%).
- HF(50%) treatment resulted in a roughened, fluorine-terminated surface at the nanoscale.
- Superacid-derived passivation was significantly more effective on surfaces pre-treated with HF(2%):HCl(2%) compared to HF alone.
- Al2O3 passivated surfaces showed similar performance regardless of HF(2%):HCl(2%) or HF(50%) pre-treatment, likely due to a silicon dioxide interlayer.
Conclusions:
- The choice of chemical pre-treatment significantly impacts the quality of functionalized silicon surfaces.
- A mixed HF:HCl solution provides superior surface passivation compared to concentrated HF.
- Understanding surface termination chemistry is essential for optimizing semiconductor interfaces and device performance.
