Micropipes in SiC Single Crystal Observed by Molten KOH Etching

Area of Science:

• Materials Science
• Solid State Physics
• Crystal Defect Analysis

Background:

• Micropipes are critical defects in silicon carbide (SiC) crystals, significantly degrading the performance of SiC-based devices.
• Understanding micropipe characteristics is crucial for advancing SiC semiconductor technology.

Purpose of the Study:

• To investigate the etching behavior of micropipes in 4H-SiC and 6H-SiC wafers.
• To identify new methods for distinguishing micropipes from other crystal defects.
• To optimize etching conditions for differentiating micropipes from threading screw dislocations (TSDs).

Main Methods:

• Molten potassium hydroxide (KOH) etching of 4H-SiC and 6H-SiC wafers.
• Raman scattering spectroscopy to analyze crystal spectra.
• Laser confocal microscopy, scanning electron microscopy (SEM), and optical microscopy for defect characterization.

Main Results:

• A novel Raman peak near -784 cm^-1 was observed in SiC crystals containing micropipes.
• This new peak is potentially linked to polymorphic transformation within micropipe etch pits during etching.
• Optimal etching conditions were determined to differentiate micropipes from threading screw dislocations (TSDs).
• Micropipe etch pits were classified into two distinct types based on morphology and formation.

Conclusions:

• The newly identified Raman peak offers a potential new method for distinguishing micropipes from other defects in SiC.
• The study provides optimized etching parameters for differentiating micropipes and TSDs.
• Classification of micropipe etch pits enhances understanding of their formation mechanisms.