IC PACKAGE WITH INTERFACE REGION

An integrated circuit (IC) package includes a die having a interface region situated on a surface of the die. The interface region is configured to be exposed to an environment of the IC package. The IC package also includes a metal wall mounted on the surface of the die that circumscribes the interface region and extends from the surface of the die to a wall height. The metal wall has a first region and a second region that is stacked on the first region, the first region having a first thickness and the second region having a second thickness. The second thickness is greater than the first thickness. The IC package further includes a molding encasing a remaining portion of the die. The molding has a height that extends from the surface of the die to a level that is less than the wall height of the metal wall.

TECHNICAL FIELD

This description relates to an integrated circuit (IC) package that includes an interface region exposed to an environment of the IC package.

BACKGROUND

A semiconductor package is a metal, plastic, glass, or ceramic casing containing one or more discrete semiconductor devices or integrated circuits. Individual components are fabricated on semiconductor wafers (commonly silicon) before being diced into die, tested, and packaged. The package provides conductive members (e.g., leads) that enable connecting to an external environment, such as a printed circuit board (PCB). Moreover, the package provides protection against threats such as mechanical impact, chemical contamination, and unintended light exposure. Also, the package facilitates the dissipation of heat produced by the device, with or without the aid of a heat spreader. There are thousands of package types in use.

Some semiconductor packages, such as integrated circuit (IC) chips are molded out of an epoxy plastic that provides adequate protection of the semiconductor devices, and mechanical strength to support the connections (e.g., leads) and handling of the semiconductor package.

SUMMARY

A first example relates to an integrated circuit (IC) package that includes a die having a interface region situated on a surface of the die. The interface region is configured to be exposed to an environment of the IC package. The IC package also includes a metal wall mounted on the surface of the die that circumscribes the interface region and extends from the surface of the die to a wall height. The metal wall has a first region and a second region that is stacked on the first region. The first region has a first thickness and the second region has a second thickness, the second thickness being greater than the first thickness. The IC package further includes a molding encasing a remaining portion of the die. The molding has a height that extends from the surface of the die to a level that is less than the wall height of the metal wall.

A second example relates to a method for forming an IC package. The method includes etching a pattern in a layer of resist overlaying a surface of a die. The pattern includes an etched cavity circumscribing an interface region on the surface of the die. The etched cavity extends from the surface of the die to a first height. The method also includes depositing metal in the etched cavity to form a metal wall circumscribing the interface region of the die. The metal wall has a first region having a first width. The first region extends from the surface of the die to the first height. The metal wall has a second region stacked on the first region, the second region having a second width greater than the first width and the second region extending from the first height to a second height. The method includes stripping the resist from the surface of the die and applying a mold to encase the die, such that the interface region is exposed to an environment. The mold extends from the surface of the die to a height less than the second height of the metal wall.

DETAILED DESCRIPTION

This description relates to an integrated circuit (IC) package with an interface exposed to an environment of the IC package, and a method for making the IC package. The IC package includes a die with the interface region situated on a surface of the die. In some examples, the IC package is a sensor (e.g., a temperature sensor or a pressure sensor), and the interface region is exposed to the environment of the IC package to detect conditions of the environment (e.g., detect the temperature or pressure in the environment). In other examples, the IC package is an output device (e.g., a light emitting device), where light (or other output) is injected into the environment from the interface region.

The IC package has a metal wall mounted on the surface of the die that circumscribes the interface region and extends from the surface of the die to a wall height. The metal wall is formed of copper or other metal. The metal wall includes a first region and a second region that is stacked on the first region. The first region has a first thickness and the second region has a second thickness, the second thickness being greater than the first thickness. As an example, a cross section of the wall has a mushroom shape or nail shape. A molding encases a remaining portion of the die. The molding has a height that extends from the surface of the die to a level that is less than the wall height of the metal wall. The metal wall ensures that during fabrication of the IC package, the molding does not flow over the metal wall and obstruct the interface region from viewing the environment of the IC package.

FIG.1illustrates a cross-section of an IC package100. The IC package100is employable as a sensor (e.g., a temperature sensor, a pressure sensor, etc.) or as an optical device (e.g., a light emitting device). The IC package100includes a die104that has a first surface106mounted on an interconnect108(e.g., a lead frame). More particularly, the first surface106of the die104is mounted on (e.g., adhered to) a die pad112of the interconnect108.

The die104includes a second surface116that opposes the first surface106. The second surface116of the die104includes an interface region120that is exposed to an environment of the IC package100. Stated differently, the interface region120is situated on the second surface116of the die104. The IC package100is encased in a molding124formed of plastic (or other non-conductive material). The interface region120is circumscribed by a metal wall128that provides a barrier between the interface region120of the die104and the molding124. The metal wall128is formed of a metallic material, such as copper.

The interface region120enables the IC package100to sense or interact with the environment in which the IC package100is designed to operate. A portion of the interface region120has an unobstructed view of the environmental external to the IC package100. In some examples, the interface region120includes circuitry for sensing a temperature or pressure of the environment. In other examples, the interface region120includes circuitry for injecting an optical output (e.g., a light source) into the environment.

FIG.2illustrates an overhead view200and an expanded cross sectional view210of a region130ofFIG.1. Thus, for purposes of simplification of explanation,FIGS.1-3employ the same reference numbers to denote the same structures. Guidelines between the overhead view200and the expanded cross sectional view210are included to improve readability.

As illustrated in the overhead view200, the interface region120is circumscribed by the metal wall128. Moreover, as illustrated in the overhead view200, the metal wall128acts as a barrier to prevent molding124from obstructing the view of the interface region120.

As illustrated in the expanded cross sectional view210, the metal wall128has a first end214mounted on the second surface116of the die104. The metal wall128has a wall height corresponding to a distance between the first end214proximal to the second surface116of the die104and a second end218that is distal to the second surface116of the die104, as indicated by the arrow222. In some examples, the wall height is about 150 micrometers (μm). Unless otherwise stated, in this description, ‘about’ preceding a value means+/−10 percent of the stated value. Moreover, the metal wall128has a first region226that extends from the second surface116of the die104to a first height, as indicated by arrows230. The metal wall128has a second region234that extends from the first height to the second end218by a second height, as indicated by arrows238. The first height is about 90 μm and the second height is about 60 μm, such that the second height of the metal wall128combined provide the overall height of the metal wall128.

The first region226has a first width (e.g., about 80 μm), as indicated by the arrows242, and the second region234has a second width (e.g., about 120 130 μm), as indicated by the arrows246. That is, the second width is greater than the first width. A portion of the first region226that is most proximal (closest) to the second surface116is formed of remnants of a seed layer228. Thus, the second region234includes a portion that extends beyond the first region226by about 40 μm on each side, as indicated by the arrows250. Accordingly, a portion of the second region234of the metal wall128overhangs the interface region120of the die104. The second region234of the metal wall128has a semicircle cross-section shape, such that a cross section of the metal wall128has a mushroom shape. The molding124has a height that extends from the second surface116of the die104to a height less than the height of the second region234. In some examples, the molding has a height equal to or greater than the height of the first region226.

As illustrated by the overhead view200, the metal wall128has a ring shape (e.g., a circular cross-section) in the provided example. However, in other examples, the metal wall128has a different shape, such as an oval or rectangular cross section. In examples where the metal wall128has a ring shape, the metal wall128has a diameter of 55 μm or more, as indicated by the arrows254of the expanded cross sectional view210.

Referring back toFIG.1, wire bonds132extend from the second surface116of the die104to pads136of the interconnect108. The pads136enable the IC package100to communicate with other circuit components. Accordingly, the wire bonds132electrically couple the second surface116of the die104to the pads136of the interconnect108. By including the metal wall128with the second region234ofFIG.2, during fabrication, the molding124is impeded from flowing over the metal wall128. Impeding the molding124from breaching the metal wall128in turn prevents the molding124from obstructing a view of the interface region120of the die104. Accordingly, an overall performance of the IC package100is improved relative to one with a shorter wall that allows the molding124to flow over a corresponding interface region.

FIG.3illustrates a cross-section of an alternative IC package300. The IC package300is employable as a sensor (e.g., a temperature sensor, a pressure sensor, etc.) or as an optical device (e.g., a light emitting device). The IC package300is similar to the IC package100ofFIG.1. Thus, for purposes of simplification of explanation,FIGS.1and3employ the same reference numbers to denote the same structures. Moreover, some reference numbers are not re-introduced. The IC package300includes the die104that is mounted on (e.g., adhered to) the die pad112of the interconnect108. The die104includes the second surface116that opposes the first surface106. The second surface116of the die104includes the interface region120that is exposed to an environment of the IC package100. The IC package300is encased in a molding124formed of plastic (or other non-conductive material).

The interface region120is circumscribed by a metal wall304that provides a barrier between the interface region120of the die104and the molding124. The metal wall304is formed of a metallic material, such as copper.

FIG.4illustrates an overhead view400and an expanded cross sectional view410of a region312ofFIG.3. Thus, for purposes of simplification of explanation,FIGS.4and5employ the same reference numbers to denote the same structures. Guidelines between the overhead view400and the expanded cross sectional view410are included to improve readability.

As illustrated in the overhead view400, the interface region120is circumscribed by the metal wall128. Moreover, as illustrated in the overhead view400, the metal wall128acts as a barrier to prevent the molding124from obstructing the view of the interface region120.

As illustrated in the expanded cross sectional view410, the metal wall304has a first end414mounted on the second surface116of the die104. The metal wall304has a wall height corresponding to a distance between the first end414proximal to the second surface116of the die104and a second end418that is distal to the second surface116of the die104, as indicated by the arrow422. In some examples, the wall height is about 130 micrometers (μm). Moreover, the metal wall304has a first region426that extends from the second surface116of the die104to a first height, as indicated by arrows430. The metal wall304has a second region434that extends from the first height to the second end418by a second height, as indicated by arrows438. The first height is about 90 μm and the second height is about 40 μm, such that the second height of the metal wall304combined provide the overall height of the metal wall304.

The first region426has a first width (e.g., about 80 μm), as indicated by the arrows442and the second region434has a second width (e.g., about 120-130 μm), as indicated by the arrows446. That is, the second width is greater than the first width. A portion of the first region426that is most proximal (closest) to the second surface116is formed of remnants of a seed layer428. That is, the second width is greater than the first width. Thus, the second region434includes a portion that extends beyond the first region426by about 40 μm on each side, as indicated by the arrows450. Thus, a portion of the second region434of the metal wall304overhangs the interface region120of the die104. The second end418of the second region434has a planer surface, such that a cross section of the metal wall128has a shape similar to a nail.

As illustrated by the overhead view400, the metal wall304has a ring shape (e.g., a circular cross-section) in the provided example. However, in other examples, the metal wall304has a different shape, such as an oval or rectangular cross section. In examples where the metal wall304has a ring shape, the metal wall304has a diameter of 55 μm or more, as indicated by the arrows454of the expanded cross sectional view210.

Referring back toFIG.3, by including the metal wall304with the second region434ofFIG.2, during fabrication, the molding124is impeded from flowing over (breaching) the metal wall304. Impeding the molding124from breaching the metal wall304in turn prevents the molding124from obstructing a view of the interface region120of the die104. Accordingly, an overall performance of the IC package300is improved relative to one with a shorter wall that allows the molding124to flow over a corresponding interface region.

FIGS.5-12illustrate methods for forming an IC package, such as the IC package100ofFIG.1. For purposes of simplification of explanation,FIGS.5-12employ the same reference numbers to denote the same structure.

In a first stage, as illustrated inFIG.5, at500, a die600is provided. In some examples, the die600is implemented with the die104ofFIGS.1-4. More particularly, a first side616of the die600is mountable on a die pad of an interconnect (e.g., a lead frame). A second side620of the die600includes an interface region624configured to interact with an environment of the IC package. In some examples, the die600is a sensor, and the interface region624enables the die600to sense the environment. In other examples, the interface region624provides light to the environment.

In a second stage, as illustrated inFIG.6, at505, a seed layer628for growing metal (e.g., copper) is deposited on the second side620of the die600(e.g., with a spudder deposition operation). Also, at505, a layer of resist628(e.g., photoresist) is applied to the second side620of the die600, overlaying the seed layer628. In a third stage, as illustrated inFIG.7at510, the resist628is etched to provide a cavity636for a metal wall. The cavity636circumscribes the interface region624. Thus, in some examples, the cavity636has a circular shape.

In a fourth stage, as illustrated inFIG.8, at515, a metal is deposited in the cavity636to form a metal wall640that circumscribes the interface region624. The metal (e.g., copper) is deposited, for example, with plating (e.g., over plating copper), solder ball attachment or a deposition of solder paste. The metal is deposited to a height that exceeds a height of the resist628. For instance, if the resist628has a height of about 90 μm, the resultant metal wall640has a height of about 150 μm. Moreover, the resultant metal wall640has a first region that extends from the second side620of the die600to a top of the cavity636, and a second region that flows over the resist628to form a head with a semicircle shaped cross section. Accordingly, as illustrated, the metal wall640has a mushroom shaped cross section.

In a fifth stage, as illustrated inFIG.9, at520, a remaining portion of the resist628and the seed layer626are stripped from the second side620of the die600. In some examples, the resist628and the seed layer626are stripped with chemical wet etching. Also, at520, the remaining seed layer626is etched from the second side620of the die600. Remnants of the seed layer626form a portion of the metal wall640closest to the second side620of the die600. Accordingly, the metal wall640circumscribes the interface region624of the die600. Also, in some examples, a portion644of the second region of the metal wall640overhangs the interface region624.

In a sixth stage, as illustrated inFIG.10, at525, the die600is mounted on an interconnect646(e.g., a lead frame). More specifically, the first side616of the die600is mounted on a die pad647of the interconnect646. In a seventh stage, as illustrated inFIG.11, at530, wire bonds648are attached to the second side620to couple the die600to pads652(e.g., leads) of the interconnect646. In an eighth stage, as illustrated inFIG.12, at535, a molding656is applied to encase the die600to form the IC package660. To apply the molding656, the molding (e.g., plastic) is heated and flows over the interconnect646and the die600. However, the molding656is prevented from flowing over the second region of the metal wall640. In particular, a thickness of the molding between the second side620of the die600and a top of the molding656is less than a height of the metal wall640. Accordingly, the molding656is prevented from flowing over the interface region624of the die600. Accordingly, the molding656does not obstruct a view of the environment for the interface region624of the die600.

FIGS.13-21illustrate an alternative method for forming an IC package, such as the IC package300ofFIG.3. For purposes of simplification of explanation,FIGS.13-21employ the same reference numbers to denote the same structure.

In a first stage, as illustrated inFIG.13, at700, a die800is provided. In some examples, the die800is implemented with the die104ofFIGS.1-4. More particularly, a first side816of the die800is mountable on a die pad of an interconnect (e.g., a lead frame). A second side820of the die800includes an interface region824configured to interact with an environment of the IC package. In some examples, the die800is a sensor, and the interface region824enables the die800to sense the environment. In other examples, the interface region824provides light to the environment.

In a second stage, as illustrated inFIG.14, at705, a seed layer826for growing metal (e.g., copper) is deposited to the second side820of the die800(e.g., with a spudder deposition operation). Additionally at705a layer of resist828(e.g., photoresist) is applied to the second side820of the die800to overlay the seed layer826. In a third stage, as illustrated inFIG.15at710, the resist828is etched to form a cavity836for a metal wall. The cavity836circumscribes the interface region824. Thus, in some examples, the cavity836has a circular shape.

In a fourth stage, as illustrated inFIG.16, at715, a metal is deposited in the cavity836to form a metal wall840that circumscribes the interface region824. The metal (e.g., copper) is deposited, for example, with a solder ball attachment or a deposition of solder paste. The metal is deposited to a height that exceeds a height of the resist828. For instance, if the resist828has a height of about 90 μm, the resultant metal wall840has a height of about 150 μm. Moreover, the resultant metal wall840has a first region that extends from the second side820of the die800to a top of the cavity836, and a second region that flows over the resist828to form a head with a semicircle shaped cross section. Accordingly, as illustrated, the metal wall840initially has a mushroom shaped cross section.

In a fifth stage, as illustrated inFIG.17, at720, a remaining portion of the resist828is stripped from the second side820of the die800. In some examples, the resist828is stripped with a chemical wet etch. Also, at720, the remaining seed826is etched from the second side820of the die800. Remnants of the seed layer826form a portion of the metal wall840closest to the second side820of the die800. Accordingly, the metal wall840circumscribes the interface region824of the die800. Also, in some examples, a portion844of the second region of the metal wall840overhangs the interface region824.

In a sixth stage, as illustrated inFIG.18, at725, the second region of the metal wall840is cut in a fly-cutting operation (e.g., with a laser or a saw). In some examples, about 20 μm of the second region of the metal wall840is cut at725, such that the resultant metal wall840has a height of about 130 μm (e.g., about 90 μm in the first region and about 40 μm in the second region). As a result, as illustrated, the metal wall840has a nail shaped cross section.

In a seventh stage, as illustrated inFIG.19, at730the die800is mounted on an interconnect846(e.g., a lead frame). More specifically, at730, the first side816of the die800is mounted on a die pad847of the interconnect846. In an eighth stage, as illustrated inFIG.20, at735, wire bonds848are attached to the second side820to couple the die800to pads852(e.g., leads) of the interconnect846. In a ninth stage, as illustrated inFIG.21, at740, a molding856is applied to encase the die800to form the IC package860. To apply the molding856, the molding (e.g., plastic) is heated and flows over the interconnect846and the die800. However, the molding856is prevented from flowing over the second region of the metal wall840. In particular, a thickness of the molding between the second side820of the die800and a top of the molding656is less than a height of the metal wall840. Accordingly, the molding856is prevented from flowing over the interface region824of the die800. Accordingly, the molding856does not obstruct a view of the environment for the interface region824of the die800.

FIG.22illustrates a flowchart of an example method900for forming an IC package, such as the IC package100ofFIG.1or the IC package300ofFIG.3. At903, in a sputter deposition operation, a seed layer is deposited on a surface of a die (e.g., the die600ofFIG.6). Additionally, at903, a layer of resist (e.g., the resist628ofFIG.6) is also deposited on the surface of the die. At905, a pattern is etched in the layer of resist overlaying the surface of a die. The pattern includes an etched cavity (e.g., the cavity636ofFIG.7) circumscribing an interface region (e.g., the interface region624ofFIG.7) on the surface of the die. The etched cavity extends from the surface of the die to a first height.

At910, metal is deposited in the etched cavity to form a metal wall (e.g., the metal wall640ofFIG.1) circumscribing the interface region of the die. The metal wall includes a first region having a first width, the first region extending from the surface of the die to the first height, and a second region stacked on the first region, the second region having a second width greater than the first width and the second region extending from the first height to a second height. Accordingly, at910, the metal wall has a mushroom shaped cross section. At915, the resist is stripped from the surface of the die (e.g., with a chemical etching process). At918, the seed layer is etched from the surface of the die.

At920, the second region of the metal wall is fly cut, such that the metal wall has a nail shaped cross section. In some examples, the operation at920is omitted. At925, the die is mounted on an interconnect (e.g., the interconnect108ofFIGS.1-4). More particularly, the die is mounted on a die pad of the interconnect. In some examples at925, wire bonds (e.g., the wire bonds132ofFIG.1) are attached to the surface of the die an pads of the interconnect to electrically couple the die with the pads of the interconnect. At930a mold is applied to the interconnect and the die to encase the die. However, the mold does not flow over the metal wall, such that the interface region is exposed to an environment, and the mold extends from the surface of the die to a height less than the height of the metal wall.