Quantitative electron holographic tomography for the 3D characterisation of semiconductor device structures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Semiconductor Device Physics

Background:

• Understanding the 3D electrostatic potential in semiconductor devices is crucial for performance and reliability.
• Surface effects and sample preparation artifacts, such as focused ion beam (FIB) damage, can significantly alter local electronic properties.

Purpose of the Study:

• To investigate the 3D electrostatic potential distribution in silicon p-n junction semiconductor devices.
• To quantify the impact of specimen thickness, surface proximity, and FIB damage on electrostatic potential.
• To determine the critical thickness required for semiconductor devices to exhibit bulk-like properties.

Main Methods:

• Combined electron tomography and electron holography for 3D electrostatic potential mapping.
• Acquisition and reconstruction of holographic tilt series from silicon p-n junction specimens.
• Quantitative analysis of electrostatic potential variations in specimens of varying thicknesses.

Main Results:

• 3D electrostatic potential variations were observed due to surfaces and FIB-induced damage.
• Bulk-like electrostatic properties were measured in the center of thicker specimens.
• Higher electrically active dopant concentrations were found in the specimen center compared to surfaces.

Conclusions:

• A critical specimen thickness of approximately 350nm is necessary for silicon p-n junctions to retain bulk-like electrostatic properties.
• Specimen preparation methods, including FIB, introduce artifacts that influence electrostatic potential measurements near surfaces.
• Accurate 3D electrostatic potential mapping requires careful consideration of specimen thickness and preparation-induced effects.