Masataka Mizukoshi

Carbon nanotube bumps for LSI interconnect

We demonstrate, for the first time, carbon nanotube (CNT) flip chip bumps for LSI modules. The CNT bump is composed of a bundle of multi-walled CNTs. Resilient and flexible CNT bumps make flip chip LSI modules resistant to thermal stress. Furthermore, CNT bumps have a low electrical resistance and robustness over electromigration. In the experiment, the CNT bumps were used to connect a test evaluation group (TEG) chip and a host substrate, and their electrical resistance was evaluated. We found that the electrical contacts of CNT bumps with the chip and the substrate are important. For a good electrical contact, the CNT bumps were coated with gold and fixed to the chip and substrate. The resultant CNT bump with a diameter of 170 mum and a height of 100 mum exhibited a low resistance of 2.3 Omega. We then evaluated the flexibility of CNT bumps by pressing the TEG chip and measuring the displacement. The displacement between the TEG chip and host substrate was 10-20% of the bump height, demonstrating an excellent flexibility.

Transient liquid-phase sintering using silver and tin powder mixture for die bonding

In this research, we develop transient liquid-phase bonding by uniaxial pressing using a Ag?Sn system. The Ag?Sn system was fabricated using Ag and Sn fine powder paste at optimized the proportions. The die bonding was performed for Cu substrates and metalized Si chips, and the sintering process was analyzed by cross-sectional observation. Die shear strength of bonded specimens was also measured. As a result, Ag?Sn completely formed a solid solution, also, Sn and Cu from substrates formed an intermetallic compound. The die shear strength was approximately 40 MPa obtained at 50 wt % Ag proportion of paste at 260, 280, and 300 ?C sintering.

Surface Activated Bonding between Au layer and vertically aligned Multi-Wall Carbon Nanotubes

In this research, vertically aligned Muti-Walled Carbon Nanotubes (CNTs) and Au-layer were bonded by Surface Activated Bonding method. Vertically aligned CNTs were grown by acetylene-CVD with Fe catalyst and were formed bump shape with 200 µm diameter and around 200 µm height. These CNT bumps and Au layer were cleaned and activated by Argon Fast Atom Beam (Ar-FAB) process and bonded with some load. As a result, MWNTs-Au bonding was succeeded on condition that CNT bumps and Au layer were Ar-FAB processed longer than 300 sec, and bonding pressure was larger than 0.17 MPa, and the average resistance of CNT was 130 kΩ. Furthermore, when the bonding pressure was 0.7 MPa, the average resistance of one was 16 Ω.