At&t Bell Laboratories

Other

Chien-Hsun Lee

King Lien Tai

Avishay Katz

Yiu-Man Wong

Donlad D Bacon

One or more metallized chip terminals of an electronic device, such as an integrated circuit chip or a laser chip, in one embodiment are temporarily bonded to one or more metallized substrate pads of a wiring substrate, as for the purpose of electrically testing the electronic device. The composition of the metallized chip terminals is suitably different from that of the metallized substrate pads. The pads and terminals are aligned and electrically connected together with a solder located between them under pressure and a temperature above the melting point of the solder. The solder is cooled, and electrical tests of the electronic device are performed by means of electrical access from testing circuitry to the chip terminals through the substrate pads. Then the solder is heated again above its melting point while being immersed in a liquid flux, whereby the liquid solder wets the metallized chip terminals but not the metallized substrate pads, and the device is gently mechanically pulled away from the wiring substrate and is cooled thereafter. This substrate can thereafter be reused for testing other electronic devices that have similarly suitably metallized terminals. In another embodiment, testing can be performed or not as may be desired; and, as for the purpose of chip operation as an integrated circuit or laser, the chip can be allowed to remain permanently bonded to the substrate in the form of a heat-sinking or heat-spreading submount, or it can be allowed to remain only temporarily bonded to the submount and subsequently pulled away from the submount for the purpose of reuse of the submount for another chip.

Debondable metallic bonding method

A laser device is bonded to a diamond submount by means of a procedure including (1) codepositing an auxiliary layer, on a layer of barrier metal that has been deposited overlying the submount, followed by (2) depositing a wetting layer on the auxiliary layer, and (3) by depositing a solder layer comprising alternating metallic layers, preferably of gold and tin sufficient to form an overall tin-rich gold-tin eutectic composition. The barrier metal is typically W, Mo, Cr, or Ru. Prior to bonding, a conventional metallization such as Ti-Pt-Au (three layers) is deposited on the laser device's bottom ohmic contact, typically comprising Ge. Then, during bonding, the solder layer is brought into physical contact with the laser device's metallization under enough heat and pressure, followed by cooling, to form a permanent joint between them. The thickness of the solder layer is advantageously less than approximately 5 .mu.m. The wetting layer is preferably the intermetallic compound Ni.sub.3 Sn.sub.4, and the auxiliary layer is formed by codepositing the metallic components of this intermetallic together with the barrier metal.

Permanent metallic bonding method

A device such as a laser is bonded to a submount such as diamond by a process in which the submount is successively coated with an adhesion layer such as titanium, a barrier layer such as nickel, and a gold-tin solder-metallization composite layer formed by sequential deposition on the barrier layer a number (preferably greater than seven) of multiple alternating layers of gold and tin, the last layer being gold having a thickness that is equal to approximately one-half or less than the thickness of the (next-to-last) tin layer that it contacts immediately beneath it. The bonding is performed under applied heat that is sufficient to melt the solder-metallization composite layer. Prior to the bonding, (in addition to the submount) the device advantageously is coated with gold and optionally with a similar gold-tin solder-metallization composite layer, at least at locations where it comes in contact with the gold-tin solder-metallization composite layer.

Growing community of inventors

North Plainfield, NJ, United States of America

Chien-Hsun Lee