Electron Beam Induced Current (EBIC) is a powerful SEM-based technique for characterizing semiconductor devices. When the electron beam generates electron-hole pairs in a semiconductor, built-in electric fields at p-n junctions or Schottky barriers separate these carriers, producing a measurable current. This current signal reveals the location and quality of junctions, the presence of electrically active defects, and the transport properties of carriers.

How EBIC Works

The focused electron beam penetrates the semiconductor and creates electron-hole pairs through ionization. In regions with an electric field (junctions, barriers), these carriers are separated before they can recombine. The resulting current flows through an external circuit and is measured by a sensitive current amplifier.

As the beam scans across the sample, the EBIC signal is used to form an image. Bright regions indicate efficient carrier collection (active junction areas), while dark regions show poor collection (defects, inactive areas, or regions far from the junction).

Key Parameters

What EBIC Reveals

Junction Location and Delineation

EBIC directly images p-n junctions with nanometer resolution. Cross-sectional EBIC shows junction depth and uniformity. Plan-view imaging reveals junction area and edge effects. This is essential for verifying device fabrication and analyzing failures.

Defect Detection

Electrically active defects reduce carrier lifetime and appear as dark spots or lines in EBIC images. Types of defects visible include:

• Dislocations: Threading dislocations, misfit dislocations at interfaces
• Grain Boundaries: Recombination at grain boundaries in polycrystalline materials
• Precipitates: Metal precipitates and other recombination centers
• Stacking Faults: Crystallographic defects in epitaxial layers

Diffusion Length Measurement

By measuring how EBIC signal decreases with distance from a junction, the minority carrier diffusion length can be extracted. This fundamental parameter indicates material quality and predicts device performance. Longer diffusion lengths mean better carrier collection and efficiency.

Device Failure Analysis

EBIC localizes failures in semiconductor devices by identifying regions where carrier collection is abnormal. Failed devices often show characteristic EBIC patterns that reveal the failure mechanism.

Applications

Solar Cells

• Junction Quality: Verify uniform junction formation across large-area cells
• Defect Mapping: Identify grain boundaries and dislocations that limit efficiency
• Passivation Assessment: Evaluate surface passivation effectiveness
• Diffusion Length: Measure carrier collection efficiency in different regions

Integrated Circuits

• Junction Profiling: Verify transistor junction locations and depths
• Latch-up Analysis: Identify parasitic thyristor structures
• ESD Damage: Locate electrostatic discharge damage sites
• Process Monitoring: Detect process-induced defects

LEDs and Laser Diodes

• Active Region Mapping: Visualize light-emitting regions
• Defect Correlation: Correlate dark spots with performance degradation
• Current Spreading: Analyze current distribution uniformity

Power Devices

• Junction Termination: Verify edge termination structures
• Defect Detection: Identify killer defects in power MOSFETs and IGBTs
• SiC and GaN: Characterize wide-bandgap semiconductor devices

Sample Requirements

• Electrical Contacts: Two contacts are needed—typically to p and n regions, or signal and ground
• Surface Condition: Clean surfaces preferred; native oxides are usually acceptable
• Cross-sections: Mechanical polishing or FIB preparation for depth profiling
• Passivation: Some samples may need surface passivation to reduce surface recombination

EBIC vs Other Techniques

• vs Optical Beam Induced Current (OBIC): EBIC offers higher spatial resolution (nm vs μm) and works in vacuum
• vs Cathodoluminescence: EBIC measures electrical response; CL measures optical emission. Complementary for optoelectronics
• vs EDS/EBSD: EBIC reveals electrical activity; EDS shows composition; EBSD shows crystal structure

Advanced Techniques

Depth-Resolved EBIC

By varying beam energy, the generation volume depth changes. This allows profiling of defects and junctions as a function of depth without physical cross-sectioning.

Temperature-Dependent EBIC

Heating or cooling the sample while imaging reveals defect activation energies and identifies different defect types based on their temperature behavior.

Quantitative EBIC

With careful modeling, EBIC signal intensity can be related to defect density and recombination strength, enabling quantitative defect characterization.