International Business Machines Corporation

Robert T Howard, Jr

Stuart E Greer

Herman S Hoffman

A process is described for selective removal of unwanted metallization from the surface of a semiconductor device. The process comprises the usual deposition of a configurable image defining layer on the surface of the device upon which a suitable pad limiting metallurgy (PLM) has already been deposited. The layer is then opened over the pad limiting metallurgy using standard techniques and coated with a layer of the terminal metal. The coated device is then heated to just above the melting point of the terminal metal causing the melted metal, through surface tension to form a ball of metal on the PLM and to form small globules of metal on the surface of the layer and then permitted to cool. When cooled the layer is removed using the usual techniques. Because the coating of terminal metal is no longer a continuous layer on the surface of the mask, removal of the polymer mask can be accomplished in about one-tenth of the time required when compared to a deposited terminal metal layer that is not melted. Also because of the effects of surface tension the metal coating need only be one-half the thickness required under the prior art techniques.

Lift-off process for terminal metals

Solder reflow or solder chip joining can be accomplished in a fluxless system by conducting the solder reflow or chip joining procedure in a carrier gas which comprises from about 0.1 to about 10% by volume SiH.sub.4, based on the volume of carrier gas and SiH.sub.4. A preferred carrier gas for the reflow is hydrogen and a preferred carrier gas for the chip joining is nitrogen.

Fluxless soldering process using a silane atmosphere

A method of treating ceramic materials used in semiconductor packaging applications to reduce their emission of alpha particles. Ceramic materials made of aluminum oxide particles bonded together with a siliceous binding material, are etched to remove the siliceous material from a surface portion of the ceramic. Since the typically used siliceous materials have alpha particle emitting elements in them by removing this siliceous material from a surface layer of the ceramic material the sources of alpha particles which are most likely to cause failures in electronic devices are removed. Alpha particle sources deeper in the ceramic pose a far lesser threat to the device because these relatively low energy, high volume particles suffer a substantial attenuation as they pass through aluminum oxide particles.

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Essex Junction, VT, United States of America

Robert T Howard, Jr