Implementation of Flip-Chip Microbump Bonding between InP and SiC Substrates for Millimeter-Wave Applications.

Area of Science:

• Materials Science
• Electrical Engineering
• Semiconductor Device Physics

Background:

• Millimeter-wave (mmW) wireless communication demands advanced interconnect technologies for high-frequency applications.
• Integrating dissimilar materials like indium phosphide (InP) and silicon carbide (SiC) presents significant fabrication challenges.
• Flip-chip bonding with microbumps (μ-bumps) is a key technique for high-density electronic packaging.

Purpose of the Study:

• To demonstrate a robust flip-chip microbump bonding process for InP-to-SiC substrates.
• To achieve high-yield and reliable interconnects for mmW wireless communication.
• To characterize the performance of fabricated coplanar waveguide (CPW) lines and novel devices.

Main Methods:

• Utilized a multi-step process including SiO2 dielectric passivation, sputtering metallization, and electroplating for flat-top μ-bumps.
• Developed a dicing technique to prevent dielectric layer peeling.
• Employed SnAg-to-Au solder bonding for robust interconnections.

Main Results:

• Fabricated 10 mm InP-to-SiC CPW lines with 100 μ-bumps, demonstrating uniform performance across twelve lines.
• Achieved an average insertion loss of 0.25 dB/mm with deviation within ±10% at 30 GHz.
• Attained return losses exceeding 15 dB, comparable to conventional CPW lines.
• Successfully fabricated and investigated the DC and RF characteristics of the first InP-to-SiC resonant tunneling diode.

Conclusions:

• The developed flip-chip μ-bump bonding process is effective for InP-to-SiC integration in mmW applications.
• The fabricated CPW lines exhibit excellent RF performance, meeting the demands of high-frequency communication.
• This work represents a significant advancement in heterogeneous integration for next-generation wireless systems and novel semiconductor devices.