Abstract
Indium-based micro-bump arrays, among other things, are used for the bonding of infrared photodetectors and focal plane arrays. In this paper, several aspects of the fabrication technology of micrometer-sized indium bumps with a smooth surface morphology were investigated. The thermal evaporation of indium has been optimized to achieve ~8 μm-thick layers with a small surface roughness of Ra = 11 nm, indicating a high packing density of atoms. This ensures bump uniformity across the sample, as well as prevents oxidation inside the In columns prior to the reflow. A series of experiments to optimize indium bump fabrication technology, including a shear test of single columns, is described. A reliable, repeatable, simple, and quick approach was developed with the pre-etching of indium columns in a 10% HCl solution preceded by annealing at 120 °C in N2.
Highlights
Indium-based micro-bump arrays, among other things, are used for the bonding of infrared photodetectors and focal plane arrays
Indium is widely used for electrical interconnections in various semiconductor devices due to its physicochemical properties. This is especially true for the production of infrared photodetectors and focal plane arrays
The oxide present present on the the surface surface has much higher higher In Figure the results obtained during the oxide formation of indium columnshas areaa summelting point than that of a pure metal
Summary
Indium-based micro-bump arrays, among other things, are used for the bonding of infrared photodetectors and focal plane arrays. A flip-chip method is used for the bonding process [2] The development of this technology for infrared detectors and focal plane arrays faces many challenges, as the need for higher-resolution devices with ever smaller pixel pitches arises [3]. There are still various aspects of the technology that can be improved or simplified depending on the specific application This holds especially true for the fabrication of indium bump arrays, where the reliability, repeatability, homogeneity, simplicity, and cost-effectiveness are the most important issues. Indium is widely used for electrical interconnections in various semiconductor devices due to its physicochemical properties This is especially true for the production of infrared photodetectors and focal plane arrays. The low melting point of indium (156 ◦ C) and high plasticity guarantees no structural damage to both the detector and mount/readout electronics [12,13]
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