Patent Application
20190237400
This presentation relates to integrated components, and in particular to an integrated component that comprises both an integrated circuit and a metallic interlocking structure that allows removably connecting the integrated circuit. This presentation also relates to a method of manufacturing such integrated component having a metallic interlocking structure. This presentation also relates to an integrated component assembly comprising two such integrated components removably connected together by their interlocking structures.
High-performance electrical and mechanical contacts and interconnects are highly desirable for system-level integration of multiple semiconductor components and technologies in 3D integration technologies (such as wafer-to-wafer bonding or die-to-wafer assembly). However, the state-of-the-art bonding technologies typically require processes based on heat and/or pressure and are not re-workable (meaning that a bond is permanent, and cannot be reworked if damaged).
It is known to use interlocking structures to temporarily assemble a discrete electronic component on a printed circuit board, for example by providing the printed circuit board with a socket that interlocks with the pins of the electronic components and connects electrically the pins to the printed circuit boards. Such known structures can use spring or bump contacts, or can use the resiliency of the pins they interlock with to create temporary electrical contact structures. However, all known interlocking structures suitable for temporary connections are relatively large structures that require to be manufactured separately, then assembled to some electronic components to allow connecting temporarily said electronic components to other electronic components having complementary interlocking structures. For example, known interlocking structures comprise a pin grid array IC package that can be assembled to an IC, where the pin grid array package allows connecting temporarily the IC to other ICs mounted on a board equipped with a pin grid array socket.
Some known silicon-etched microstructures form MEMS “hook and loop” structures. However, such structures only allow a single assembly and they do not allow removably connecting integrated circuits. Other known means that create room temperature bonding require smashing contacts together to create a good electrical contact but the resulting bond cannot be undone without destroying one or both components.
There remains a need for an easy way to manufacture interlocking structures that allows reworkable electrically conductive die bonding at fine pitch, low force, and low temperature.
This presentation discloses a metallic interlocking structure that provides a scalable, re-workable electrically conductive die bonding at fine pitch, requiring low force, and low interlocking process temperature.
This presentation discloses a nano/micro-scale electrically-conductive interlocking structure that can be made using a new combination of standard IC manufacturing process steps which 1) is low resistance, 2) is mechanically-compliant, 3) allows for “bonding” both mechanically and electrically some circuit pads (or bumps) without heat and with minimal application force (⅕ of a standard thermo-compression bonding), and 4) can be re-worked or re-used multiple times.
Embodiments of the interlocking structure according to this presentation comprise microstructures arranged in an array to form an electrically conductive interlocking structure capable of being interlocked with a corresponding (e.g. identical or complementary) electrically conductive interlocking structure according to this presentation. This presentation thus effectively allows electrically and mechanically bonding together two surfaces provided each with one of said electrically conductive interlocking structures. According to this presentation, the “bonding” of two interlocking structures together can be done at room temperature and allows creating an electrical contact between two integrated circuits connected each to one of the electrically conductive interlocking structures. Further, the bond can be physically removed in a non-destructive manner by pulling the two interlocking structures apart and both integrated circuits can for example be connected to other integrated circuits having compatible electrically conductive interlocking structures. Such possibility of reworking (un-bonding, re-bonding) an integrated component having an integrated circuit with electrically conductive interlocking structures according to this presentation is useful for e.g. testing and filtering yielding parts. Depending on the friction force exerted by the interlocking structures on each other, the bond between two interlocking structures according to this presentation can either be re-workable or permanent.
Embodiments of this presentation provide for an integrated component having a metallic interlocking structure; the integrated component having: an integrated circuit integrated in a substrate, the substrate having a top surface; the integrated circuit comprising a first conducting line; and a first metallic interlocking structure comprising a first array of free-standing metallic columns formed on said top surface.
According to an embodiment of this presentation, said free-standing metallic columns are electrically connected to said first conducting line.
According to an embodiment of this presentation, said first array of free-standing metallic columns is arranged such that introducing said columns, along an axis of said columns, between the columns of a second array of free-standing metallic columns having dimensions of a same order as the first array brings the columns of the two arrays in frictional contact and temporarily attaches the first and second arrays.
According to an embodiment of this presentation, said free-standing metallic columns have each a diameter smaller than two micrometers and are distant from each other (center to center) by at most 10 micrometers. According to an embodiment of this presentation, said free-standing metallic columns have each a diameter smaller than one micrometer and are distant from each other (center to center) by at most 5 micrometers.
According to an embodiment of this presentation, at least one free-standing metallic column has a top portion with a dimension, normal to an axis of said column, larger than a base of said column.
According to an embodiment of this presentation, a horizontal metallic beam connects the top of at least two neighboring free-standing metallic columns.
According to an embodiment of this presentation, the integrated component comprises a second conducting line that is distinct from said first conducting line; and a second metallic interlocking structure comprising a second array of free-standing metallic columns, formed on said top surface and electrically connected to said second conducting line.
Other embodiments of this presentation provide for an integrated component assembly comprising: a first integrated component as recited above; and a second integrated component as recited above, arranged upside down such that the first metallic interlocking structure of the second integrated component interlocks with the first metallic interlocking structure of the first integrated component.
According to an embodiment of this presentation, the friction between the lengths of the columns of the second integrated component with the lengths of the columns of the first integrated component maintains the first and second integrated components removably attached to each other.
According to an embodiment of this presentation, at least some columns of one of the first and second integrated components have a top portion larger than their base; and the friction of said larger top portions with the lengths of the columns of the other of the first and second integrated components maintains the first and second integrated components removably attached to each other.
Other embodiments of this presentation provide for a method of manufacturing an integrated component having a metallic interlocking structure; the method comprising: providing an integrated component having a substrate with a top surface and having an integrated circuit integrated in said substrate, the integrated circuit comprising a first conducting line; and forming on said top surface a first metallic interlocking structure comprising a first array of free-standing metallic columns.
According to an embodiment of this presentation, said forming on said top surface a first metallic interlocking structure comprising a first array of free-standing metallic columns comprises electrically connecting said metallic columns to said first conducting line.
According to an embodiment of this presentation, the method comprises dimensioning said first array of free-standing metallic columns such that introducing said columns, along an axis of said columns, between the columns of a second array of free-standing metallic columns having dimensions of a same order as the first array brings the columns of the two arrays in frictional contact and temporarily attaches the first and second arrays.
According to an embodiment of this presentation, the method comprises forming said free-standing metallic columns each with a diameter smaller than two micrometers; and comprises forming said free-standing metallic columns distant from each other by at most 10 micrometers. According to an embodiment of this presentation, the method comprises forming said free-standing metallic columns each with a diameter smaller than one micrometer; and comprises forming said free-standing metallic columns distant from each other by at most 5 micrometers.
According to an embodiment of this presentation, the method comprises forming at least one free-standing metallic column with a top portion having a dimension, normal to an axis of said column, larger than a base of said column.
According to an embodiment of this presentation, the method comprises forming a horizontal metallic beam that connects the top of at least two neighboring free-standing metallic columns.
According to an embodiment of this presentation, said integrated circuit comprises a second conducting line; the method further comprising forming a second metallic interlocking structure comprising a second array of free-standing metallic columns on said top surface and electrically connected to said second conducting line.
According to an embodiment of this presentation, said forming on said top surface a first metallic interlocking structure comprising a first array of free-standing metallic columns electrically connected to said first conducting line provides for: depositing on said top surface a precursor metal layer electrically connected to said first conducting line; electroplating said precursor metal layer; forming on said electroplated precursor metal layer a column mask layer having recesses where the columns are to be formed; filling the recesses of the mask by electroplating; and removing the column mask.
According to an embodiment of this presentation, the method further comprises, after filling the recesses of the mask by electroplating and before removing the column mask: forming a column-top mask having recesses with a diameter larger than the column; depositing at the bottom of the recesses of the column-top mask a column-top precursor metal layer; electroplating said column-top precursor metal layer; filling the recesses of the column-top mask by electroplating; and removing the column-top mask.
According to an embodiment of this presentation, the method comprises manufacturing said metallic interlocking structure using steps compatible with the back-end-of-the-line process used for manufacturing the integrated circuit.
Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description.
For a more complete understanding of this presentation and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:
It should be understood at the onset that, although example embodiments are illustrated below, the present technology may be implemented using any number of techniques, whether currently known or not. The present technology should in no way be limited to the example implementations, drawings, and techniques illustrated below. Additionally, the drawings are not necessarily drawn to scale.
A purpose of a metallic interlocking structure according to this presentation is to enable high performance interconnections between two chips, or between a chip and a board or wafer, while still allowing for chip replacement (2 functions that are typically mutually exclusive). According to embodiments of this presentation, the metallic interlocking structure is manufactured with processes compatible with integrated circuits fabrication and can therefore be readily implemented on semiconductor wafers, in particular without degrading the original circuit performance.
According to an embodiment of this presentation, each free-standing metallic column 30 is a cylinder having a circular base. The base of the cylinder of each column 30 can also be elliptic or have any desired polygonal shape. According to an embodiment of this presentation, the diameter of the cylinder (or more generally, the largest lateral dimension of the column) is at least five times smaller than the height of each column 30.
According to an embodiment of this presentation, each column 30 has a diameter smaller than two micrometers and the columns are distant from each other by at most 10 micrometers. According to an embodiment of this presentation the columns 30 of array 28 are distant from each other such that another column of another array of columns of similar dimensions can only be introduced in between them by making frictional contact with the columns 30. For example, the array 28 of free-standing metallic columns 30 can be dimensioned such that introducing said columns 30, along said columns axis, between the columns of a second identical array (not shown) of free-standing metallic columns will bring the columns of the two arrays in frictional contact, thus temporarily attaching the first and second arrays.
According to an embodiment of this presentation, integrated circuit 12 comprises a second conducting line 22 distinct from first conducting line 18; and a second metallic interlocking structure 32 comprising a second array of free-standing metallic columns 34 formed on top surface 16 of substrate 14 and electrically connected to second conducting line 22. According to an embodiment of this presentation, any number of I/O pads of integrated circuit 12 can be connected to an array of columns such as illustrated with arrays 28 or 32.
As detailed hereafter, each array of columns such as 28, 32 can be used for implementing a removable connection to a corresponding array formed on a substrate to which integrated component 10 is to be attached, each array on said substrate being itself electrically connected to a circuit on the substrate to which integrated circuit 12 is to be connected. As detailed hereafter, an array of columns according to this presentation, such as 28, 32, can repeatedly be interlocked with, and unlocked from, a corresponding array of columns, wherein the frictional interaction of the arrays 28, 32 interlocked with the substrate arrays maintain component 10 attached to the substrate, thus advantageously replacing the use of non-permanent electrically conductive glues.
According to an embodiment of this presentation, component 10 can additionally or alternatively comprise one or more further arrays 36, 38, for example identical structurally to any of array 28, 32 but not connected to integrated circuit 12. Unconnected arrays 36, 38 can be arranged to interlock with corresponding unconnected arrays (not shown) on the substrate to which component 10 is to be attached, thus helping secure component 10 to the substrate by providing additional frictional interlocking between the component and the substrate. The unconnected arrays 36, 38 may further allow a better control of the growth of the other arrays 28, 32 by electroplating (detailed hereafter). The Inventors have noted that when only a small number of metallic interlocking structures is grown, if the current source used is not precise enough to send only the right amount of current, the growth of the metallic interlocking structures can be too fast and difficult to control. Growing additional metallic interconnecting structures helps reduce the current in each metallic interconnecting structure, thus making the growth of the metallic interconnecting structures by electroplating easier to control.
There are many exemplary applications for a component having an integrated interlocking structure according to this presentation:
For example, microfabricated 3D arrays featuring tiled architectures, in which multiple chips are bonded side-by side, tile-like, to form a large array. Should any of the individual chips in the array a) be misaligned, b) not perform well, and/or c) degrade over time, then, if they were attached to the array with the metallic interlocking structure according to this presentation, they could be removed and replaced. In contrast, tiled arrays currently assembled with state-of-the-art thermo-compression bonding are final. Any defects/degradation results in loss of the entire array. For such applications, a metallic interlocking structure according to this presentation provides significant cost savings with negligible interconnect performance trade-offs.
In traditional multi-chips modules (for example a 10 GHz Transmit and Receive module for phased array applications), multiple chips from diverse technologies are typically “die-attached” to a metal heat spreader/base board. Because each module is very expensive, integrators use reworkable glue to attach the chips. These glues (e.g., silver epoxy) have low thermal conductivity but allow for chip removal if the chip fails. Enabling replacement of a module chip if it fails saves an entire module. A metallic interlocking structure according to this presentation advantageously replaces and outperforms these conductive glues, providing as detailed hereafter conductive bonding performances comparable to the ones from permanent materials (e.g., eutectic solder), while being removable.
A metallic interlocking structure according to this presentation can enable high-performance testing of a chip having said structure on an advanced test board/wafer, by temporarily bonding the chip to said test board/wafer.
In addition, the Inventors have shown that a metallic interlocking structure according to this presentation can also be used to permanently bond chips using a room temperature process at low force. This is a significant advance over known thermo-compression bonding (au-au) or high-force room temperature indium bumping.
A metallic interlocking structure according to this presentation does not need an increased temperature to operate (no mismatch between materials with different coefficient of thermal expansion) and does not need high force (so one can do very large area bonding and assembly).
A metallic interlocking structure according to embodiments of this presentation allows for example to establish temporary electrical contacts for rapid prototyping, testing, and integration of technologies which would previously require labor-intensive processes and would either not be re-workable/non-permanent or would have poor electrical conductivity.
A metallic interlocking structure according to this presentation can also be scaled to produce bonding sites on the order of 5 micrometer by 5 micrometer, where the bonding-site pitch—center to center distance—can be as low as 10 micrometer. Generally speaking, the center to center distance between two bonding sites along a given direction can be twice the bonding site dimensions in the same direction; or can be larger; or can be lower, down to being the same as the bonding site dimensions in the same direction.
A metallic interlocking structure according to this presentation allows lowering costs for repairs since a component in a system-level package can be replaced if it is or becomes defective. Also, if a tested part is deemed good, additional force can be applied to make the bond permanent. Such additional force can for example push the interpenetrating column deeper, thus increasing the surfaces in contact of the various columns until the friction forces are so high that the component cannot be retrieved without being damaged.
Application in Infra-Red Focal Plane Arrays (FPAs): metallic interlocking structures according to this presentation can replace indium bonding and enable tighter pitches and lower cost for large-scale FPAs, enabling higher resolution images at higher yield (>5× improvement).
Advantageously, metallic interlocking structures according to this presentation also allow absorbing any Coefficient of Thermal Expansion (CTE) mismatch during system operation between a chip and a substrate to which the chip is attached, thus reducing the chances of damage due to such mismatch, thanks to bond compliance.
Application in millimeter wavelength phased arrays: metallic interlocking structures according to this presentation are a superior approach to flip-chip bonding (integration of SiGe chip with GaN PAs or LNAs) that allow reducing the cost associated with reworking/assembly (lowering cost by a factor of >5× due to re-work capability).
Application to integration of photonic or MEMS devices with silicon CMOS electronics: metallic interlocking structures according to this presentation can dramatically reduce assembly and rework costs, for example for chip-scale LIDAR such as those needed for autonomous driving and UAVs.
Embodiments of this presentation also include an integrated component assembly as illustrated in
Advantageously, forming the columns by electroplating allows forming metallic columns having a very high aspect ratio (for example at least 5 times higher than they are wide). It is to be understood that the columns can be uniform, as illustrated for example in
Advantageously, the fabrication steps illustrated in
It is noted that the cross-section of the columns can be circular, square, rectangular, ellipsoid, triangular, or have any shape appropriate such that a first array of columns according to an embodiment of this presentation develops a predetermined friction with an interlocking second array of columns according to an embodiment of this presentation.
Embodiments of this presentation provide for room temperature bondable metal contacts that are de-bondable and re-useable on a micro-scale.
Embodiments of this presentation provide for the fabrication of high density pillar arrays for mechanical and electrical structures such as interconnects, contact pads, solder bumps (as dense as e.g. 0.8 micrometer pillars with 2 micrometer pitch).
Embodiments of this presentation provide for making temporary/re-workable bonds permanent with the addition of additional force at temperatures from 22° C.+ and up to 150° C.
Embodiments of this presentation provide for distance between columns about the diameter of the columns.
The foregoing Detailed Description of exemplary and preferred embodiments is presented for purposes of illustration and disclosure in accordance with the requirements of the law. It is not intended to be exhaustive nor to limit the invention to the precise form(s) described, but only to enable others skilled in the art to understand how the invention may be suited for a particular use or implementation. The possibility of modifications and variations will be apparent to practitioners skilled in the art. No limitation is intended by the description of exemplary embodiments which may have included tolerances, feature dimensions, specific operating conditions, engineering specifications, or the like, and which may vary between implementations or with changes to the state of the art, and no limitation should be implied therefrom. Applicant has made this presentation with respect to the current state of the art, but also contemplates advancements and that adaptations in the future may take into consideration of those advancements, namely in accordance with the then current state of the art. Reference to a feature element in the singular is not intended to mean “one and only one” unless explicitly so stated. Moreover, no element, component, nor method or process step in this presentation is intended to be dedicated to the public regardless of whether the element, component, or step is explicitly recited in this presentation. No element disclosed herein is to be construed under the provisions of 35 U.S.C. Sec. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for . . . ” and no method or process step herein is to be construed under those provisions unless the step, or steps, are expressly recited using the phrase “comprising the step(s) of . . . .”
The present application claims priority of U.S. provisional application No. 62/625,313, filed on Feb. 1, 2018 and entitled “INTEGRATED CIRCUIT WITH METALLIC INTERLOCKING STRUCTURE”, which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62625313 | Feb 2018 | US |
