Using High-Resolution SEM and TEM for Advanced Semiconductor Packaging
Semiconductor packaging is undergoing significant changes. For years, the focus was on shrinking the pitch of micro-bumps and Through-Silicon Vias (TSVs). Now, driven by the insatiable demand for more bandwidth, lower power consumption, and reduced latency, the industry has adapted the latest technology of direct copper-to-copper (Cu-Cu) hybrid bonding.
This shift from micro-scale interconnects to direct, atomic-scale bonds marks a fundamental change in what we need to measure and control. The challenge is no longer just seeing the bump; it’s about characterizing the interface itself. Reliability and yield are now decided by nanometer-scale details: oxide layers, voids, contaminants, and crystal grain alignment.
To succeed in this new paradigm of heterogeneous integration, packaging engineers need a complementary analytical toolkit. JEOL's Field Emission SEM (FE-SEM) and atomic-resolution Transmission Electron Microscopy (TEM/STEM) provide the complete workflow required to characterize these critical interfaces, from the die level down to the atomic scale.
What Must Be Measured Now
In an era of hybrid bonding and high-density interconnects, the list of critical-to-quality parameters has grown longer and moved to a much smaller scale. Success depends on precise control over:
- Interface Cleanliness & Planarity: Pre-bond oxide thickness and surface uniformity are paramount for a successful bond.
- Post-Bond Integrity: Detecting nanometer-scale voids, gaps, and contaminants at the bond interface.
- Dimensional Control: Measuring copper recess and dielectric thickness with nanometer precision.
- Alignment: Verifying die-to-wafer alignment at the nanometer level.
- Crystallography & Chemistry: Understanding the copper grain structure, orientation, and the presence of unwanted oxides or contamination at the bond line.
- Legacy Joint Reliability: In traditional micro-bumps, identifying and quantifying Intermetallic Compound (IMC) phases that dictate long-term reliability.
JEOL SEM for High-Throughput Packaging Inspection
For rapid, high-throughput inspection of large areas, JEOL’s FE-SEM is the first line of defense.
The JSM-IT800/IT810 FE-SEM with integrated Energy Dispersive X-ray Spectroscopy (EDS) is ideal for characterizing micro-bump arrays, hybrid bond pads, and Redistribution Layers (RDLs).
- Imaging Modes: Use Secondary Electron (SE) imaging for high-resolution topographical detail and Backscattered Electron (BSE) imaging for powerful materials contrast, which is perfect for distinguishing between solder, IMCs, copper, and underfill materials.
- Automated Workflows: Our SEM Center software enables automated recipes for inspecting hundreds of bond pads, providing statistically significant data on pad integrity and defects.
The quality of any analysis depends on the quality of the specimen. The JEOL Cross Section Polisher™ (CP) uses a broad, low-energy argon ion beam to create large, clean, and artifact-free cross-sections of challenging multi-material stacks containing solder, copper, and polymers. Standard and cooling stage options prevent heat damage to sensitive materials, while air-isolation transfer options protect the sample from atmospheric contamination.
JEOL HR-TEM/STEM for Interfaces That Decide Reliability
When an interface fails, or when you need to certify a new process, you must go beyond the resolution limits of SEM. JEOL's aberration-corrected TEM/STEM provides undeniable, atomic-scale proof.
The JEM-ARM300F (GRAND ARM) is designed for this exact challenge.
- Sub-Ångstrom Imaging: High-Angle Annular Dark-Field (HAADF) STEM imaging can easily resolve nanometer-scale oxide layers, voids, and defects directly at the Cu-Cu bond interface.
- Chemical Analysis: Integrated EDS and Electron Energy Loss Spectroscopy (EELS) can perform line scans across the bond to map the precise location and concentration of oxygen, carbon, and other contaminants. EELS can even determine the oxidation state of copper, distinguishing between problematic oxides and pure metal.
- Crystallographic Information: Using diffraction modes, you can analyze crystal grain orientation and measure nanoscale strain, both of which are critical for predicting bond reliability.
Workflow Examples: From Process Control to Failure Analysis
1. Verifying a Hybrid Bond Interface:- Create a cross-section of the bond area using the JEOL Cross Section Polisher™.
- Use a JSM-IT800 FE-SEM for a rapid survey and EDS mapping to confirm the location and general composition.
- Prep site-specific TEM lamella targeting the bond interface using JEOL dual beam PS500i.
- In the JEM-ARM300F, acquire a STEM-EELS oxygen map across the interface. The resulting data can be used to set clear pass/fail criteria (e.g., oxide thickness must be <1 nm, void area fraction must be <0.5%).
2. Assessing Micro-bump Reliability:
- Use the CP to create a clean cross-section through a series of solder bumps.
- In the SEM, use Backscattered Electron (BSE) imaging to clearly highlight the different Intermetallic Compound (IMC) layers.
- Use integrated EDS to perform phase identification and quantify the elemental composition of each IMC layer.
- For advanced failure analysis, a TEM sample can be prepared to measure IMC layer thickness with nanometer precision and investigate the morphology of any micro-voids.
Reporting for Actionable Engineering Insights
A comprehensive engineering report moves beyond pretty pictures. It translates raw data into actionable metrics. Using JEOL's integrated suite, your reports can include:
- Histograms of bond pad alignment error.
- Distributions of oxide thickness measurements from EELS data.Three
- Void size and area fraction distributions.
- Quantification of IMC phase fractions and layer thicknesses.
This data allows you to set firm, statistically validated acceptance windows for your
semiconductor packaging processes, directly linking nanoscale metrology to device reliability and yield.
Ready to see your interface? Set up a JEOL packaging interface study—SEM + ARM-class TEM recipe designed for your pad stack and pass/fail metrics.