Mitsubishi Kinzoku Kabushiki Kaisha

Mitsubishi Denki Kabushiki Kaisha

Toshiaki Ono

Naoyuki Hosoda

Naoki Uchiyama

Masaki Morikawa

Hideaki Yoshida

Ryusuke Kawanaka

An inexpensive, very fine wire of high-purity copper is disclosed as an alternative to the fine gold wire which is currently used in the bonding of semiconductor devices. The very fine wire of high-purity copper is prepared from a copper ingot that contains 0-2 ppm of S, 0-2 ppm of Ag, 0-1 ppm of Se and 0-1 ppm of Te as incidental impurities with the total content of these and any other incidental impurities present being held at a level not exceeding 10 ppm. By subjecting it to an appropriate heat treatment, the wire acquires an elongation of 5-22%, a breaking strength of 14-33 kg/mm.sup.2, and a Vickers hardness of 38-50, the latter value being measured with respect to said high-purity copper in an ingot form. By reducing the amounts of these impurities to even lower levels, very fine wires are obtained that can be used in the bonding of a semiconductor device without abnormally shaped loops being formed or wire breakage being experienced and the characteristics of the wires can be adapted to specific conditions of use by performing an appropriate heat treatment.

Wire for bonding a semiconductor device

The present invention eliminates the problems associated with the use of oxygen-free copper and other high-purity copper materials as bonding wires. In accordance with one aspect of the present invention, at least one rare earth element, or at least one element selected from the group consisting of Mg, Ca, Ti, Zr, Hf, Li, Na, K, Rb and Cs, or the combination of at least one rare earth element and at least one elemented selected from the above-specified group is incorporated in high-purity copper as a refining component in an amount of 0.1-100 ppm on a weight basis, and the high-purity copper is subsequently refined by zone melting. The very fine wire drawn from the so refined high-purity copper has the advantage that it can be employed in high-speed ball bonding of a semiconductor chip with a minimum chance of damaging the bonding pad on the chip by the ball forming at the tip of the wire. In accordance with another aspect of the present invention, 0.5-3 ppm of a rare earth element and/or Y is further incorporated as an alloying component in the zone-refined high-purity copper.

The present invention eliminates the problems associated with the use of oxygen-free copper and other high-purity copper materials as bonding wires. At least one rare earth element, or at least one element selected from the group consisting of Mg, Ca, Ti, Zr, Hf, Li, Na, K, Rb and Cs, or the combination of at least one rare earth element and at least one elemented selected from the above-specified group is incorporated in high-purity copper as a refining component in an amount of 0.1-100 ppm on a weight basis, and the high-purity copper is subsequently refined by zone melting. The very fine wire drawn from the so refined high-purity copper has the advantage that it can be employed in high-speed ball bonding of a semiconductor chip with a minimum chance of damaging the bonding pad on the chip by the ball forming at the tip of the wire.

Growing community of inventors

Osaka, Japan

Toshiaki Ono