Warpage management for fan-out mold packaged integrated circuit

An integrated circuit includes a stacked conductive layer interposer and a first die at least partially encapsulated in a mold material. The first die is mechanically and electrically attached to a top surface of the stacked conductive layer interposer using solder bumps. The integrated circuit further includes a first warpage correction layer.

FIELD OF THE INVENTION

This disclosure relates to integrated circuits (ICs) and, more particularly, to warpage management for fan-out mold packaged ICs.

BACKGROUND

Fan-out mold packaging is an IC packaging technology that seeks to provide an increased number of external contacts for the IC compared to other packaging technologies. Fan-out mold packaging attaches a die to an interposer structure. The interposer structure has a larger area than the die attached thereto. The die is encapsulated by mold material that fills space above the interposer structure that otherwise would be unoccupied by the die. The increased area of the interposer structure allows more external contacts to be included than would be the case were the IC implemented using only the die without the interposer structure. The increased number of external contacts is obtained without having to increase the size of the die. Increasing die size tends to be more expensive than using the interposer structure and the added mold material.

As briefly noted, more than one die may be encapsulated in the mold material and attached to the interposer structure. In the case of a multi-die IC, The dies are spaced apart within the mold encapsulation. The spacing between the dies allows for an interposer structure of greater area to be attached to the dies, thereby providing additional space for the inclusion additional external contacts for the IC.

During manufacture and testing, ICs implemented using fan-out mold packaging technology are subjected to high levels of stress. The stress may induce warpage in the IC that may result in defects. For example, warpage may cause breakage in the metal interconnects of the interposer structure.

SUMMARY

An integrated circuit (IC) includes a stacked conductive layer interposer and a first die at least partially encapsulated in a mold material. The first die is mechanically and electrically attached to a top surface of the stacked conductive layer interposer using solder bumps. The IC includes a first warpage correction layer.

In one aspect, the first warpage correction layer is formed on a bottom surface of the stacked conductive layer interposer. In that case, the first warpage correction layer can be formed of a non-conductive material. In another aspect, the first warpage correction layer is formed on a top surface of the IC. In that case, the top surface of the IC is formed of a top surface of the first die and the mold material. Further, the first warpage correction layer can be formed of a conductive material or a non-conductive material.

The IC can include a second die at least partially encapsulated in the mold material. The second die is mechanically and electrically attached to the top surface of the stacked conductive layer interposer using solder bumps. In a further aspect, the first warpage correction layer is formed on a top surface of the IC wherein the top surface of the first die, a top surface of the second die, and the mold material form the top surface of the IC.

The IC also can include a second warpage correction layer. In one aspect, the first warpage correction layer is formed on a bottom surface of the stacked conductive layer interposer. The second warpage correction layer is formed on a top surface of the IC. In that case, the top surface of the IC is formed of a top surface of the first die and the mold material.

A method of manufacturing an IC includes providing a stacked conductive layer interposer and a first die at least partially encapsulated in a mold material. The first die is mechanically and electrically attached to a top surface of the stacked conductive layer interposer using solder bumps. The method further includes applying a first warpage correction layer.

In one aspect, applying the first warpage correction layer includes forming the first warpage correction layer on a bottom surface of the stacked conductive layer interposer. In that case, the first warpage correction layer can be formed of a non-conductive material. In another aspect, applying the first warpage correction layer includes forming the first warpage correction layer on a top surface of the IC. In that case, the top surface of the IC is formed by a top surface of the first die and the mold material. Accordingly, the first warpage correction layer can be formed of a conductive material or a non-conductive material.

The method also can include providing a second die at least partially encapsulated in the mold material and mechanically and electrically attached to the top surface of the stacked conductive layer interposer using solder bumps. In a further aspect, applying the first warpage correction layer includes forming the first warpage correction layer on a top surface of the IC, wherein the top surface of the IC is formed of the first die, the second die, and the mold material.

The method further can include applying a second warpage correction layer. Applying the first warpage correction layer can include forming the first warpage correction layer on a bottom of the stacked conductive layer interposer. Applying the second warpage correction layer can include forming the second warpage correction layer on a top surface of the IC. In that case, the top surface of the IC is formed of a top surface of the first die and the mold material.

DETAILED DESCRIPTION OF THE DRAWINGS

This disclosure relates to integrated circuits (ICs) and, more particularly, to warpage management for fan-out mold packaged ICs. In accordance with the inventive arrangements disclosed herein, warpage of an IC implemented using fan-out mold packaging may be controlled and/or managed by applying one or more additional IC process layers referred to as warpage correction layers. A warpage correction layer may be added to a top surface of the IC, to a bottom surface of a stacked conductive layer interposer of the IC, or to both the top surface of the IC and the bottom surface of the stacked conductive layer interposer.

Typically, a fan-out packaged IC suffers from warpage in which the edges of the stacked conductive layer interposer warp or flare upward as a smile or a U-shape. Advantageously, this warpage may be countered or corrected by application or formation of one or more waprage correction layers. The warpage correction layers apply a downward force to the edges of the IC that counters the warpage. The amount of corrective force applied by the IC by the warpage correction layer(s) varies in accordance with the type of material used for the warpage correction layer(s), the location of the warpage correction layer(s), and the thickness of the warpage correction layer(s).

FIG. 1is a block diagram illustrating a cross-sectional side view of an exemplary IC100. IC100is implemented using fan-out mold packaging. In the example ofFIG. 1, IC100is implemented using multiple dies. It should be appreciated, however, that the various arrangements described within this disclosure may be implemented using a single die, two dies, or more than two dies using fan-out mold packaging. The number of dies shown is not intended as a limitation.

IC100includes dies105and110embedded, or encapsulated, within mold material115. Each of dies105and110is at least partially encompassed or encapsulated by mold material115. As pictured, each of dies105and110is surrounded by mold material on each side with the exception of a top surface of each die of dies105and110. The top surface of die105, die110, and mold material115form a top surface of IC100prior to application of warpage correction layer190.

Dies105and110are mechanically and electrically attached to an interposer120using a plurality of solder bumps125. In one aspect, solder bumps125are implemented as micro-bumps. Application of mold material115also helps to mechanically attach dies105and110to interposer120. Interposer120is implemented as a stacked conductive layer interposer. As defined within this disclosure, the term “interposer” means a stacked conductive layer interposer. A stacked conductive layer interposer is a wire and/or interconnects structure having a plurality of stacked, patterned conductive layers. A stacked conductive layer interposer includes no silicon substrate portion between the bottom or lowest patterned conductive layer and the solder bumps that attach the stacked conductive layer interposer to a package substrate. In this regard, no through vias or through silicon vias are required to connect signals from die105and/or die110to a package substrate.

Interposer120is mechanically and electrically attached to a package substrate130through a plurality of solder bumps135. In one aspect, solder bumps135are implemented as controlled collapse chip connection (C4) balls. In one aspect, package substrate130is implemented using any of a variety of known organic materials. Pads140are formed on a top surface of package substrate130. Pads140are formed of a conductive material such as metal. Accordingly, solder bumps135contact pads140, thereby electrically and mechanically attaching interposer120to substrate package130.

Interposer120includes a plurality of alternating conductive and insulating layers. A patterned conductive layer145is formed to include a conductive material150shown with shading that implements a plurality of wires and/or vias. Conductive material150may be aluminum, gold, copper, nickel, various silicides, and/or the like. Portions of patterned conductive layer145that are unoccupied by conductive material150, e.g., those portions of conductive material150that were removed, are occupied or filled by insulating material155.

Interposer120includes a next patterned conductive layer160. Patterned conductive layer160includes conductive material150forming one or more wires and/or vias. Portions of patterned conductive layer160that have been removed are occupied or filled by insulating material155. As illustrated, above each of the portions of insulating material155within patterned conductive layer160is a further layer165. Layer165can be an oxide layer forming an interlayer dielectric (ILD) layer or an inter-metal dielectric (IMD) layer.

Interposer120includes a next patterned conductive layer170. Patterned conductive layer170includes conductive material150forming one or more wires and/or vias. Portions of patterned conductive layer170that have been removed are occupied or filled by insulating material155. As illustrated, above each of the portions of insulating material155within patterned conductive layer170is a layer165. Layer165can be an oxide layer forming an ILD layer or an IMD layer. As pictured, no silicon substrate exists as part of interposer120between patterned conductive layer170and solder bumps135.

Layer175is a passivation layer formed as part of interposer120. Layer175is patterned to accommodate solder bumps135. For example, layer175is patterned using a contact dielectric etch process to remove material. In one aspect, layer175is implemented as an oxide such as undoped silicon glass (USG) or thermal oxide (Tox). Layer180is a passivation layer formed as part of interposer120. Layer180is patterned to accommodate solder bumps135. In one aspect, layer180is implemented as an organic polyimide passivation layer. Under bump metallization (UBM)185is then added to interposer120to which solder bumps135are attached.

Warpage within interposer120can occur for a variety of reasons. In one aspect, warpage may occur during a reflow process used to attach interposer120to package substrate130. In another aspect, the mold encapsulation process may cause warpage of interposer120. The curing of mold material115, for example, tends to shrink more than other materials of interposer120and/or dies105and110. In a further aspect, UBM185may induce a high amount of stress that can contribute to warpage and, as such, cracking in patterned conductive layers145,160, and/or170of interposer120. Warpage occurs, in large part, due to the varying thermal coefficients of the different materials used to form IC100and the heating that occurs as part of IC manufacture and/or testing. In general, warpage with respect to interposer120occurs in the direction of warpage line197. As discussed and illustrated by warpage line197, warpage refers to an upward flaring of the edges of interposer120causing interposer120to take on a smile shape or a U-shape.

Advantageously, a warpage correction layer190is applied to the top surface of IC100. Warpage correction layer190applies a compressive force to IC100that counters warpage. Warpage correction layer190can be applied at any of a variety of stages once dies105and110are attached to interposer120and encapsulated, at least partially, with mold material115as pictured.

In one aspect, warpage correction layer190is implemented as a conductive layer such as a metal film layer, an organic film, an inorganic film, or a silicon dummy chip. Exemplary materials used to form warpage correction layer190when implemented as a conductive layer, e.g., a metal film, include, but are not limited to, titanium, gold, tungsten, silicon, and the like. Exemplary materials used to form warpage correction layer190when implemented as an organic coating or film include, but are not limited to, polybenzoxazole, polyimide, polyamide, benzocyclobutene, and the like.

For purposes of clarity and illustration, a general description of the manufacture of an interposer and the attachment of dies thereto, as described with reference toFIG. 1, follows. Formation of interposer120can begin with a P-wafer having a silicon substrate upon which passivation layer175is formed. The silicon substrate beneath passivation layer175is not illustrated as the silicon substrate material is later removed. Above passivation layer175, patterned conductive layers170,160, and145are formed substantially as described with reference toFIG. 1. Back end of line (BEOL) processes may be used to form interposer120, which also may be referred to as a metal stack-up.

Dies105and110are attached to the top surface of patterned conductive layer145using solder bumps125. A mold encapsulation process is performed which adds mold material115to at least partially encapsulate dies105and110. A mechanical grinding and/or polishing process is performed that thins the silicon substrate beneath passivation layer175. The remainder of the silicon substrate is removed from beneath passivation layer175using a selective silicon etch process. The exposed passivation layer175is treated for further processing. With passivation layer175exposed, a further etch process is performed on passivation layer175to create spaces for solder bumps135.

Passivation layer180is applied to passivation layer175. Next, UBM185is applied to the bottom of interposer120where solder bumps135will be formed. Having applied UBM185, solder bumps135are formed. The wafer further may be diced. Interposer120may also be attached to package substrate130.

As discussed, warpage correction layer190may be applied at any of a variety of different points during the previously described process. For example, warpage correction layer190may be applied any time after mold encapsulation of dies105and110. The particular material used to form warpage correction layer190and the thickness of warpage correction layer190may be selected to counter warpage effects from stress applied to interposer120. A thicker warpage correction layer190will counter or correct for a larger amount of warpage than will thinner warpage correction layer190.

FIG. 2is a block diagram illustrating a cross-sectional side view of IC100according to another aspect. IC100is implemented substantially as described with reference toFIG. 1. Instead of including warpage correction layer190on a top surface of IC100, a warpage correction layer195is formed on a bottom surface of interposer120. As shown, warpage correction layer195is formed on a bottom surface of interposer120. For example, warpage correction layer195is formed over passivation layer185. Further, solder bumps135are exposed through warpage correction layer195in order to attach interposer120to package substrate130.

Warpage correction layer195is formed as a non-conductive layer. For example, warpage correction layer195can be implemented as an organic coating using any of the various exemplary materials previously described. In any case, warpage correction layer195may be applied to the bottom surface of interposer120once UBM185is applied and prior to the formation of solder bumps135. Warpage correction layer195may be patterned, e.g., etched, to create gaps for the formation of solder bumps135.

Like warpage correction layer190, warpage correction layer195applies a force to interposer120that is counter to warpage line197. As such, warpage correction layer195applies a force that pulls edges of interposer120downward thereby countering warpage and resulting in a substantially flat or un-warped interposer120.

FIG. 3is a block diagram illustrating a cross-sectional side view of IC100according to another aspect. IC100is implemented substantially as described with reference toFIGS. 1 and 2. In the example pictured inFIG. 3, however, both warpage correction layer190is applied to a top surface of IC100and warpage correction layer195is applied to a bottom surface of interposer120. In the case of both warpage correction layer190and warpage correction layer195, each may be implemented as previously described with reference toFIG. 1andFIG. 2. The warpage counter effect resulting from use of two warpage correction layers as pictured inFIG. 3is cumulative, thereby providing increased force compared to using only a single warpage correction layer to counter warpage.

FIG. 4is a block diagram illustrating a cross-sectional side view of IC100according to another aspect. IC100is implemented substantially as described with reference toFIG. 1. In the example ofFIG. 4, warpage correction layer190is implemented as a portion or block of silicon wafer also known as a dummy silicon block that is attached to the top surface of IC100using a die attach adhesive199. A “die attach adhesive” means a material that is used to stack and mechanically attach one IC structure such as a die or a dummy silicon block to another IC structure such as a different die and/or mold material. Examples of die attach adhesives include, but are not limited to, materials considered die attach films, dicing die attach films, die attach pastes, self-filleting die attach pastes, and the like. In one aspect, die attach adhesive199is non-conductive.

FIG. 5is a graph illustrating warpage correction for an IC using a warpage correction layer.FIG. 5illustrates the reduction in warpage that can be achieved in an IC through the use of a warpage correction layer. The x-axis indicates thickness of the top warpage correction layer measured in μm. The y-axis indicates warpage of the IC as measured in μm.FIG. 5illustrates warpage reduction in an IC configured as described with reference toFIG. 4. Thus, the warpage correction layer, e.g., warpage correction layer190, is implemented as a silicon block attached to the top surface of IC100using a die attach adhesive, e.g., die attach adhesive199.

FIG. 5illustrates that with no top warpage correction layer, corresponding to a thickness of zero on the x-axis, warpage in the IC is approximately 130 μm. With a top warpage correction layer having a thickness of approximately 300 μm, warpage in the IC is reduced to approximately 58 μm. With a top warpage correction layer having a thickness of approximately 580 μm, warpage in the IC is reduced to approximately 28 μm. Finally, with a top warpage correction layer having a thickness of approximately 775 μm, waprage in the IC is further reduced to approximately 20 μm.

FIG. 6is a flow chart illustrating an exemplary method600of implementing an IC having one or more warpage correction layers. Method600can be implemented using any of a variety of IC manufacturing techniques and equipment known to the skilled artisan.

In block605, an interposer is provided. The interposer is a stacked conductive layer interposer. Such a structure is also referred to as a “silicon-less” interposer. The interposer includes one or more dies partially encapsulated by mold material. The one or more dies are mechanically and electrically attached to a top surface of the interposer using solder bumps.

In block610, a first warpage correction layer is applied to the IC. In one aspect, the first warpage correction layer is formed on a bottom surface of the interposer. In another aspect, the first warpage correction layer is formed on a top surface of the IC. The top surface of the IC is formed by a top surface of the first die and the mold material. In the case where the IC includes more than one die, the top surface is formed by the top surface of each die and the mold material. The first warpage correction layer may be implemented as a metal film layer or as an organic coating.

In block615, a second warpage correction layer optionally is applied to the IC. In one aspect, the second warpage correction layer is applied to either the top surface of the IC or to the bottom surface of the interposer depending upon the location of the first warpage correction layer. For example, when the first warpage correction layer is applied to the top surface of the IC, the second warpage correction layer is applied to the bottom of the interposer. In another example, when the first warpage correction layer is applied to the bottom surface of the interposer, the second warpage correction layer is applied to the top surface of the IC. The second warpage correction layer may be implemented as a metal film or as an organic coating.

In one aspect, when both first and second warpage correction layers are used, both may be implemented as a metal film or both may be implemented as an organic coating. In another aspect, each warpage correction layer may be different. For example, the warpage correction layer applied to the top of the IC may be a metal film while the warpage correction layer applied to the bottom of the interposer may be an organic coating. In another example, the warpage correction layer applied to the top of the IC may be an organic coating, while the warpage correction layer applied to the bottom of the interposer is a metal film.

In applying the first and/or second warpage correction layers, the material used for each respective warpage correction layer and the thickness of such layer(s) can depend upon the amount of correction required. Thicker layers will provide more warpage correction than thinner warpage correction layers.

In accordance with the inventive arrangements described within this disclosure, warpage effects that typically occur for fan-out mold packaged ICs may be counteracted through the use of one or more warpage correction layers. The warpage correction layers may be applied to a top surface of the IC, to a bottom surface of an interposer of the IC, or to both. By using one or more warpage correction layers as described herein, defects within the IC such as cracked metal wires and/or interconnects within the interposer may be avoided. As discussed, the techniques described herein may be applied to fan-out mold packaged ICs having one die or a plurality of dies without limitation.

For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the various inventive concepts disclosed herein. The terminology used herein, however, is for the purpose of illustrating the features described and is not intended to be limiting.

For example, the terms “a” and “an,” as used herein, are defined as one or more than one. The term “plurality,” as used herein, is defined as two or more than two. The term “another,” as used herein, is defined as at least a second or more. The term “coupled,” as used herein, is defined as connected, whether directly without any intervening elements or indirectly with one or more intervening elements, unless otherwise indicated. Two elements also can be coupled mechanically, electrically, or communicatively linked through a communication channel, pathway, network, or system.

The term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes” and/or “including,” when used in this disclosure, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will also be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms, as these terms are only used to distinguish one element from another.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of process(es), machine(s), manufacture(s), and/or systems utilizing one or more of the features described herein. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

The features described within this disclosure can be embodied in other forms without departing from the spirit or essential attributes thereof. Accordingly, reference should be made to the following claims, rather than to the foregoing disclosure, as indicating the scope of such features and implementations.