Metal nanoink and process for producing the metal nanoink, and die bonding method and die bonding apparatus using the metal nanoink

Abstract

Metal nanoink for bonding an electrode of a semiconductor die and an electrode of a substrate and/or bonding an electrode of a semiconductor die and an electrode of another semiconductor die by sintering under pressure is produced by injecting oxygen into an organic solvent in the form of oxygen nanobubbles or oxygen bubbles either before or after metal nanoparticles whose surfaces are coated with a dispersant are mixed into the organic solvent. Bumps are formed on the electrode of the semiconductor die and the electrode of the substrate by ejecting microdroplets of the metal nanoink onto the electrodes, the semiconductor die is turned upside down and overlapped in alignment over the substrate, and then, the metal nanoparticles of the bumps are sintered under pressure by pressing and heating the bumps between the electrodes. As a result, generation of voids during sintering under pressure is minimized.

1 . A die bonding method for bonding an electrode of a semiconductor die and an electrode of a substrate or bonding an electrode of a semiconductor die and an electrode of another semiconductor die, comprising:
 an overlapping step of placing a semiconductor die on which a bump is formed on an electrode by ejecting microdroplets of metal nanoink in which metal nanoparticles whose surfaces are coated with a dispersant and oxygen in the form of nanobubbles are mixed into an organic solvent face down over a substrate on which a bump is formed on an electrode by ejecting microdroplets of the metal nanoink or another semiconductor die on which a bump is formed on an electrode by ejecting microdroplets of the metal nanoink, and overlapping the electrode of the semiconductor die and the electrode of the substrate or the electrode of the semiconductor die and the electrode of the other semiconductor die with the bumps interposed therebetween; and   a pressure sintering step of sintering the metal nanoparticles of the bumps under pressure by pressing and heating the bumps between the electrodes to electrically bond the electrodes,   wherein the concentration of oxygen in the organic solvent is supersaturated.   
     
     
         2 . A die bonding apparatus for bonding an electrode of a semiconductor die and an electrode of a substrate or bonding an electrode of a semiconductor die and an electrode of another semiconductor die, comprising:
 an ejection head for ejecting microdroplets of metal nanoink in which metal nanoparticles whose surfaces are coated with a dispersant and oxygen in the form of nanobubbles are mixed into an organic solvent to form a bump on an electrode so that the concentration of oxygen in the organic solvent is supersaturated;   an overlapping mechanism for placing a semiconductor die on which the bump is formed face down over a substrate on which a bump is formed on an electrode by ejecting microdroplets of the metal nanoink or another semiconductor die on which a bump is formed on an electrode by ejecting microdroplets of the metal nanoink, and overlapping the electrode of the semiconductor die and the electrode of the substrate or the electrode of the semiconductor die and the electrode of the other semiconductor die with the bumps interposed therebetween; and   a pressing and heating mechanism for pressing and heating the bumps between the electrodes for sintering the metal nanoparticles of the bumps under pressure to electrically bond the electrodes.