Physical Failure Analyses for Solving Problems (Registration Required)
Instructor: Wentao Qin, Microchip
Pricing
Member- $325
Member (Student) – $199
NonMember – $425
NonMember (Student) – $199
Physical failure analysis needs to provide structure-property correlation for the root-cause finding, and calls for expertise of multiple disciplines, including:
- physics (probe formation, probe-sample interaction, optics, solid state and semiconductor physics),
- chemistry (inorganic and organic chemistry, thermodynamics and kinetics of reactions, electrochemistry/corrosion), and
- materials science (phase equilibrium, phase transformation, and mechanics).
Part #1 – Mechanism of a latent leakage between metal lines
Abstract – A latent leakage escapes initial electrical testing but emerges at reliability test or even in a customer application. Such an issue was discovered at reliability test. An amorphous carbonaceous particle with a significant fraction of sp2 bonding was found between adjacent metal lines. The particle received thermal energy from wafer processing and the reliability test, which caused densification, carbon enrichment, and likely graphitization of the particle catalyzed by the metals. The conductivity increase led to the latent leakage. Preventive measures are stated.
Keywords: Reduction reaction, Hybridization of atomic orbitals, sp1/sp2/sp3 hybridization, Bonding and antibonding orbitals, Pyrolysis, Thermodynamics, Free energy, Graphitization.
Part #2 – Mechanism of a latent via resistance
Abstract – The via resistance increase after data retention bake caused device failure. The post W Chemical Mechanical Planarization (WCMP) cleaning left residual WO3 on the W plug. The WO3 had been reduced by the Ti of the overlaying metal line, through which TiO2 formed. Al diffused through grain boundaries of TiN to reduce the WO3 and TiO2. The higher thermodynamic stability of TiO2 and Al2O3, and likely void formation from mechanical stress, contributed to the via resistance increase. Solution to the problem is stated.
Keywords: Chemical-mechanical planarization, Pourbaix diagram, electron shielding, electronegativity, covalent bond, ionic bond, metallic bond, bond energy, formation enthalpy.
Part #3 – Study of corrosion mechanisms of copper and gold ball bonds based on structure-property correlation and electrochemical investigation
Abstract – Wire bonding is a predominant connection technique in microelectronic packaging, playing a crucial role in a wide array of modern applications, from medical devices and aerospace technology to automotive innovations, the Internet of Things (IoT) and artificial intelligence (AI). The dependability of the packaging is intrinsically linked to the reliability of the foundational wire bonds. Part 3 of the course delves into the interpretation of corrosion mechanisms that lead to reliability issues in both copper (Cu) and gold (Au) ball bonds, integrating perspectives from both microstructural analysis and electrochemical studies. It is observed that corrosion in Cu ball bonds begins with the pitting of the most Cu-rich layer (MCRL) underneath a layer of chlorinated water, progresses to crevice corrosion, and may be further aggravated by stress corrosion cracking. Within the MCRL, aluminum (Al) tends to be oxidized preferentially, while copper (Cu) atoms are largely unaffected and aggregate to form nanoparticles. Strategies for mitigating this corrosion are outlined. Preliminary evidence also points to similar corrosion mechanisms in Au ball bonds.
Keywords: Copper wire bonding, gold wire bonding, corrosion, microstructures, electrochemical analyses, interface, intermetallic, corrosion potential, Pourbaix diagram, chlorine, chloride ions, crevice corrosion, hydrogen embrittlement, stress corrosion cracking (SCC), dealloying, automotive.