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Indium-Based Micro-Bump Array Fabrication Technology with Added Pre-Reflow Wet Etching and Annealing
Paweł Kozłowski1, Krzysztof Czuba1, Krzysztof Chmielewski1
1Łukasiewicz Research Network-Institute of Microelectronics and Photonics, al. Lotników 32/46, 02-668 Warsaw, Poland.
Materials (Basel, Switzerland)
|November 13, 2021
Summary
Optimized indium micro-bump fabrication yields smooth, uniform ~8 μm layers for infrared photodetector bonding. A novel pre-etching and annealing process ensures reliable, repeatable results for microelectronics applications.
Area of Science:
- Materials Science
- Microelectronics Engineering
Background:
- Indium micro-bumps are critical for bonding infrared photodetectors and focal plane arrays.
- Achieving uniform, smooth micro-bumps is essential for reliable device performance.
Purpose of the Study:
- To investigate and optimize the fabrication technology of micrometer-sized indium bumps.
- To achieve smooth surface morphology and high uniformity in indium bump arrays.
Main Methods:
- Optimized thermal evaporation of indium to deposit ~8 μm-thick layers.
- Investigated surface roughness (Ra = 11 nm) and its relation to atomic packing density.
- Developed a fabrication process involving pre-etching in 10% HCl and annealing at 120 °C in N2.
Main Results:
- Achieved indium layers with ~8 μm thickness and low surface roughness (Ra = 11 nm).
- Demonstrated bump uniformity across samples and prevention of internal oxidation.
- Validated a reliable, repeatable, simple, and quick fabrication approach.
Conclusions:
- The optimized thermal evaporation and post-processing steps significantly improve indium micro-bump quality.
- The developed fabrication method ensures high-density packing, uniformity, and reliability for microelectronic interconnections.
- This technology is suitable for advanced infrared detector and focal plane array applications.
