Low temperature fine pitch vertical wafer level interconnection using copper nanoparticles

Low temperature fine pitch vertical wafer level interconnection using copper nanoparticles

Carisey, Y.C.P.

Zhang, G.Q. (mentor)

Mechanical, Maritime and Materials Engineering

Materials Science & Engineering

2014-11-25

Nowadays, the demand for enhanced performance and reliability in micro and nano systems is growing, especially for fine pitch wafer level integration. Due to reliability and processing issues, lead containing solders are still allowed and being used in high demanding microelectronics bonding application. Potential for reliable environmental friendly low temperature interconnects relies in the exceptional properties of Metallic Nanoparticle Pastes (MNPs). Combined with lithographically based stencil-printing of copper paste, the study proposes an insight in optimization of the paste use for wafer level fine pitch vertical interconnection. Copper nanoparticle is investigated as interconnect material. Despite its high oxidation tendency, Copper is compatible with the current interconnect materials used in microelectronics, has good electrical properties and is cheap as compared to silver or gold. In commercial available copper MNPs, organic coating is added to protect oxidation and to enable sintering by a combined effect of coating evaporation and temperature increase. The study investigates the fine pitch bonding process and the coated nanoparticle paste sintering behavior. Advanced electrical measurement structures for contact and sheet resistance are studied and integrated on newly designed test wafers optimized for bonding measurement. A high potential nanocopper paste fusing and oxidation behavior is then extensively studied during heating via in situ X-ray diffraction (XRD) analysis and Transmission Electron Microscope (TEM) observations. Finally, sintering of the paste is evaluated and wafer bonding is successfully performed. Hardness of dried paste is measured to be 8.37 ± 0.6 Vickers Hardness (HV). Stencil printing method and wafer bonding is presented and discussed in detail. Good electrical resistivity of 78.4 ± 14.5 m?.µm (4.6 times that of theoretical bulk copper) is measured on sintered paste for 10 minutes at 260? C in 700 mBar forming gas (H2/N2) environment.

interconnect
nanoparticle
sintering
stencil printing

http://resolver.tudelft.nl/uuid:1b9a667d-40c6-4743-8466-6d4614505ada

2015-11-25

Student theses

master thesis

(c) 2014 Carisey, Y.C.P.