研究目的
Investigating the use of helium ion microscopy (HIM) for defect localization and nanofabrication in conductive structures using voltage contrast, with a focus on improving failure analysis in semiconductor devices at nanoscale dimensions.
研究成果
Helium ion microscopy with passive voltage contrast is an effective method for high-resolution, low-damage defect localization and nanofabrication in conductive structures at nanoscale. XeF2 gas assistance enhances etching rates and prevents re-deposition, enabling clean isolation. The technique can diagnose hidden defects and localize series defects using ion beam irradiation, making it valuable for semiconductor failure analysis and process evaluation.
研究不足
The study is limited to Ti3N4 metal layers; applicability to other conductive materials is suggested but not verified. Re-deposition of conductive materials during ion beam etching without XeF2 can prevent voltage contrast, and issues like black halos from XeF2 etching may occur. Neon ion beam etching, while faster, may cause more damage and is less controllable for dense nanostructures. The method may not work well for thin insulating layers (<200 nm) due to re-deposition short circuits.
1：Experimental Design and Method Selection:
The study uses helium ion microscopy (HIM) for high-resolution imaging and nanofabrication, comparing it with gallium focused ion beam (Ga-FIB) and scanning electron microscopy (SEM). Passive voltage contrast (PVC) is employed to detect defects in conductive nanostructures. Ion beam etching with and without XeF2 gas assistance is used for nanofabrication.
2：Sample Selection and Data Sources:
The tested sample consists of 25-nm patterned Ti3N4 nanostructures on a 20 nm SiO2 layer on a Si substrate, designed to test process uniformity and control in semiconductors.
3：List of Experimental Equipment and Materials:
A Zeiss ORION NanoFab multi-ion beam system for imaging and etching, an Oxford Instruments OmniGIS II gas injection system for XeF2 delivery, and a Fibics NanoPatterning and Visualization Engine (NPVE) for pattern generation. Materials include Ti3N4 metal layer, SiO2, Si substrate, and XeF2 gas.
4：Experimental Procedures and Operational Workflow:
Helium and neon ion beams at energies of 25-30 keV and beam currents of 0.4 to 2.0 pA are used for etching defined patterns (e.g., 10 nm × 80 nm boxes). XeF2 gas is delivered at ~8×10^-6 Torr pressure. Imaging is performed to observe voltage contrast before and after etching. Defect localization involves moving the HIM image view along defective stripes.
5：4 to 0 pA are used for etching defined patterns (e.g., 10 nm × 80 nm boxes). XeF2 gas is delivered at ~8×10^-6 Torr pressure. Imaging is performed to observe voltage contrast before and after etching. Defect localization involves moving the HIM image view along defective stripes.
Data Analysis Methods:
5. Data Analysis Methods: Voltage contrast images are analyzed to identify defective regions. Etching rates and line widths are measured and compared with and without XeF2 assistance. Statistical analysis of dosage effects and contrast observations is conducted.
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