Under Pressure: Solving High Viscosity Material Challenges in Advanced Packaging
One of the most persistent challenges to support heterogenous integration in advanced packaging is managing the range of high-viscosity (HV) materials—including photoresists, polyimides, epoxies, and glues. The material purity and compositional integrity are essential to the performance and reliability of interconnect patterning, redistribution layers (RDL), dielectric insulation, bonding structures, and protective encapsulation among the wide variety of uses of these materials.
Focusing specifically on the photoresists and polyimides, the viscosity range is wider than front end photoresists to pattern transistors. This creates unique dispense and filtration needs to sustain process uptime and prevent inline and latent defects in advanced packaging applications.
| Category | Viscosity Range (cP) | Typical Use Cases / Circuit Patterning Role |
| FEOL (Front End of Line) | 2-300 | High-resolution photochemicals including EUV and traditional i-line, KrF, ArF, and E-Beam |
| Advanced Packaging | 5 – 10,000+ | High viscosity photoresists, polyimides, epoxies, and glues for RDL, TSV, mold, dielectric layers, stress buffer coatings, passivation, underfill, die attach, wafer bonding, lid sealing, encapsulation, mechanical support, etc. |
AP Key Defect Mechanisms
The financial stakes are at their peak as all components are integrated into one package. Several defects can be prevented to limit the risk of device failure with the removal of particles, metals, organics, and microbubbles:
- Voids, Delamination, and Poor Adhesion: Entrapped air during chemical mixing or dispense can lead to voids and delamination, especially in epoxies and adhesives. These defects often escape inline visual inspection but manifest as electrical test failures or long-term reliability issues.
- Microbridge Defects: Residual particles, metals, and organics bridging across features can cause shorts and leakage paths, particularly problematic in fine-pitch interconnects and hybrid bonding.
- Line Width Roughness, Adhesion Loss, and Dielectric Breakdown: HV materials like photoresists, polyimides and epoxies are prone to trapping particles. Even a few nanometers of pattern edge deviation can impact electrical performance, especially in high-speed applications.
AP Solutions for Yield Improvement
- Advanced Filtration and Degassing: Ultra-high retention UPE filters tailored for viscous chemistries remove gels, agglomerates, and microbubbles before dispense, reducing the risk of voids and delamination in all high-viscosity materials.
- Precision Dispense and Filtration Systems: Two-stage dispense systems separate filtration and dispense functions, optimizing fluid integrity and filtration efficiency. Real-time diagnostics simplify recipe programming and filter priming, minimizing the formation of microbridge defects and ensuring uniform coating—critical for die-to-wafer bonding and encapsulation.
- Clean Packaging and Handling: Cleanroom-compatible containers and sealed delivery systems prevent particulate, metals, and organic contamination from the chemical manufacturing site to the fab dispense nozzle, preserving the integrity of sensitive materials like photoresists, polyimides, and adhesives.
The Path Forward
As advanced packaging continues to push boundaries, yield engineers must evolve their defect mitigation strategies. By leveraging Entegris’ integrated filtration-to-dispense-to-packaging solutions, they can reduce variability, improve reliability, and protect yield across a broader spectrum of materials with varying resistance to flow.
Join us as collaboration partners or bring your individual process needs to solve these challenges. Contact our Experts to get started.
