Santa Barbara Research Center

Set North America, LLC

Ontos Equipment Systems, Inc.

US Government As Represented by the Secretary of the Army

Raytheon Company

Eric Frank Schulte

Charles A Cockrum

Justin K Markunas

Francis I Gesswein

David R Rhiger

Jeffrey Brian Barton

Jeffrey M Peterson

William L Ahlgren

Ichiro Kasai

Eric D Olson

Robert Emmett Hughlett

Michael Dow Stead

Matthew Sheldon Phillips

Methods and systems for low-force, low-temperature thermocompression bonding. The present application teaches new methods and structures for three-dimensional integrated circuits, in which cold thermocompression bonding is used to provide reliable bonding. To achieve this, reduction and passivation steps are preferably both used to reduce native oxide on the contact metals and to prevent reformation of native oxide, preferably using atmospheric plasma treatments. Preferably the physical compression height of the elements is set to be only enough to reliably achieve at least some compression of each bonding element pair, compensating for any lack of flatness. Preferably the thermocompression bonding is performed well below the melting point. This not only avoids the deformation of lower levels which is induced by reflow techniques, but also provides a steep relation of force versus z-axis travel, so that a drastically-increasing resistance to compression helps to regulate the degree of thermocompression.

Thermocompression bonding with passivated gold contacting metal

Thermocompression bonding with passivated silver-based contacting metal

Thermocompression bonding with passivated tin-based contacting metal

Thermocompression bonding using metastable gas atoms

Thermocompression bonding with passivated copper-based contacting metal

Thermocompression bonding with passivated nickel-based contacting metal

3D packaging with low-force thermocompression bonding of oxidizable materials

Methods and systems for using the downstream active residuals of a reducing-chemistry atmospheric plasma to provide multiple advantages to pre-plating surface preparation with a simple apparatus. As the downstream active species of the atmospheric plasma impinge the substrate surface, three important surface preparation processes can be performed simultaneously:

Simultaneous hydrophilization of photoresist and metal surface preparation: methods, systems, and products

An atmospheric pressure plasma system includes an atmospheric pressure plasma source that generates a glow discharge-type plasma. The atmospheric pressure plasma source comprises a plasma head, a heating element and an active cooling element and the heating element and active cooling element control the plasma head temperature to a set-point temperature independent of variations in plasma generating power or plasma power ON/OFF status.

System and method for plasma head thermal control

After CMP and before an epitaxial growth step, the substrate is prepared by an atmospheric plasma which includes not only a reducing chemistry, but also metastable states of a chemically inert carrier gas. This removes residues, oxides, and/or contaminants. Optionally, nitrogen passivation is also performed under atmospheric conditions, to passivate the substrate surface for later epitaxial growth.

Epitaxial growth using atmospheric plasma preparation steps

A template wafer fabrication process is disclosed for high density indium bumping of microchips by using an innovative template wafer upon which the bumps are initially fabricated. Once fabricated, these bumps are transferred to the microchip, after which can be hybridized to another microchip. Such a template wafer is reusable, and thus provides an economical way to fabricate indium bumps. Reusability also eliminates nonuniformities in bump shape and size in serial processing of separate microchips, which is not the case for other indium bump fabrication processes. Such a fabrication process provides a way to form relatively tall indium bumps and accomplishes this without the standard thick photoresist liftoff process. The described process can be suitable for bump pitches under 10 microns, and is only limited by the resolution of the photolithography equipment used.

Template wafer fabrication process for small pitch flip-chip interconnect hybridization

A method of removing oxidation from certain metallic contact surfaces utilizing a combination of relatively simple and inexpensive off-the-shelf equipment and specific chemistry. The method being a very rapid dry process which does not require a vacuum or containment chamber, or toxic gasses/chemicals, and does not damage sensitive electronic circuits or components. Additionally, the process creates a passivation layer on the surface of the metallic contact which inhibits further oxidation while allowing rapid and complete bonding, even many hours after surface treatment, without having to remove the passivation layer. The process utilizes a room-ambient plasma applicator with hydrogen, nitrogen, and inert gasses.

Method of plasma preparation of metallic contacts to enhance mechanical and electrical integrity of subsequent interconnect bonds

A process is disclosed for high density indium bumping of microchips by using an innovative template wafer upon which the bumps are initially fabricated. Once fabricated, these bumps are transferred to the microchip, after which can be hybridized to another microchip. Such a template wafer is reusable, and thus provides an economical way to fabricate indium bumps. Reusability also eliminates nonuniformities in bump shape and size in serial processing of separate microchips, which is not the case for other indium bump fabrication processes. Such a fabrication process provides a way to form relatively tall indium bumps and accomplishes this without the standard thick photoresist liftoff process. The described process can be suitable for bump pitches under 10 microns, and is only limited by the resolution of the photolithography equipment used.

Template wafer and process for small pitch flip-chip interconnect hybridization

Template process for small pitch flip-chip interconnect hybridization

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Santa Barbara, CA, United States of America

Eric Frank Schulte