Integrated circuit wave device and method

In described examples of forming an integrated circuit wave device, a method includes: (a) affixing an integrated circuit die relative to a substrate; (b) creating a form relative to the integrated circuit die and the substrate; and (c) forming a wave shaping member having a shape conforming at least in part to a shape of the form.

BACKGROUND

This relates to an integrated circuit wave device and a method of manufacturing it, where the device may be a transmitter, receiver, transceiver, emitter or detector operable in connection with emitting or detecting waves (e.g., electromagnetic waves, pressure waves, etc.), and where the waves may be within a bandwidth selected from various ranges, such as from radio frequency to ultraviolet (i.e., through the visible spectrum and beyond).

Integrated circuit wave devices have myriad functions and applications, and may be generally categorized by virtue of the bandwidth of waves communicated either to, or from, the device. Typically, such a device is formed as an integrated circuit package, with a part of the package including one or more elements for either detecting or emitting a wave. More specifically, an integrated circuit package typically includes one or more semiconductor chips (or “dies”) that are affixed relative to one another and to a substrate in some type of casing, which is often a metal, plastic, glass or ceramic, and where the casing inclusive of what it encloses is referred to as a whole as the package. Thus, a die or dies includes the wave transmitting or receiving element(s), hereafter referred to as a communication element. For example, radio frequency (RF) or infrared (IR) communication elements may be used to wirelessly transmit signals, in numerous applications. As another example, IR communication elements may be used in imaging or motion detection. In yet another example, communication elements may be used for power measurements. In any event, the operation and efficacy of the device is based in part on the proper communication of the wave to/from the communication element, so sufficiently directing the wave with respect to the element is important.

A conventional wave directing apparatus, including either lenses or reflectors, may be positioned external from the package, but relative to its communication element. Such lenses or reflectors improve signal strength, such as by focusing waves and also in connection with either sensing directionality or beam forming in a known output direction. Such approaches can improve signal performance, but they also have potential drawbacks. For example, the positioning and affixation of wave directing apparatus requires additional manufacturing steps beyond the construction of the package itself. As another example, components external from the package, including these wave directing apparatus, are more readily susceptible to being damaged or displaced as they are not necessarily protected in the same manner as components encapsulated within the package.

SUMMARY

In described examples of forming an integrated circuit wave device, a method includes: (a) affixing an integrated circuit die relative to a substrate; (b) creating a form relative to the integrated circuit die and the substrate; and (c) forming a wave shaping member having a shape conforming at least in part to a shape of the form.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments relate to an integrated circuit wave device and the method of manufacturing it.FIG. 1illustrates various steps of such a method10, andFIGS. 2A through 7illustrate the integrated circuit wave device100in various views and stages of the product formation. Additional details are described in co-owned U.S. Patent Application Publication No. 2017/0330841, which is hereby incorporated herein by reference.

InFIG. 1, the method10is shown with a first step12, which is necessarily preceded by various additional method steps as known, where the preceding steps form or provide various components that are shown inFIG. 2A. For example,FIG. 2Aillustrates a perspective view of various components of wave device100. In step12, a circuit die102is attached relative to a first surface104S1of a substrate104. Circuit die102may be of various types and, for purposes of example embodiments, it includes apparatus and functionality for either transmitting/emitting or receiving/detecting (or both) a wave (i.e., either a signal or noise), the wave being of a particular device bandwidth referred to herein as BWD. Accordingly, for example, die102is shown to include a wave surface102WSfor either transmitting/emitting or receiving/detecting the wave. One die with one communication surface is shown and described, but alternative embodiments may include either multiple die (e.g., in an array) or multiple communication surfaces per the one or more die.

Substrate104is constructed of various materials, and one consideration is that the material of substrate104be selected in anticipation of the type and/or bandwidth BWDof the wave that is communicated relative to device100. Specifically, the substrate104material is selected to readily permit the wave to transmit through substrate104with little or no change in the signal direction or strength, so the substrate material does not have strong absorbance (i.e., at most a negligible effect) in the bandwidth BWDof interest so that a substantial portion of the wave passes through the material. For example, where the bandwidth BWDis in the visible spectrum because the anticipated wave is visible light, then preferably the material for substrate104is transparent to the passage of the signal (i.e., the light). Such transmission of the wave signal through the material of substrate104is desired, so as to ultimately be communicated to/from wave surface102WS.

The attachment of step12may be of various techniques and may involve additional structure, withFIG. 2Aillustrating one example. For example, a first lead frame106is affixed to an upper surface of substrate104. Step12affixes circuit die102so that it is adjacent lead frame106, as further shown inFIG. 2B. Specifically,FIG. 2Billustrates a cross-sectional view ofFIG. 2A(along line2B therein), from which it is apparent that lead frame106is between a first surface104S1of substrate104and die102. As further shown inFIG. 2A, additional lead frames108and110may be affixed to substrate104, where these lead frames provide electrical connectivity points relative to die102. Also, for example, step12includes the connection of conductors108Cand110C(e.g., bond wires) as between each lead frame108and110to a respective conductive pad on die102.

Referring again toFIG. 1and method10, a step14follows step12. In step14, a shaped material form is formed relative to a region of circuit die102. In various example embodiments, the shaped form is created using a sublimatable material, which is a material that may be subsequently sublimated, whereas alternative may be used in other embodiments as described hereinbelow. For the use of a sublimatable material, and as detailed in the above-incorporated U.S. Patent Application Publication No. 2017/0330841, materials such as various types of polyols can sublimate or shrink/delaminate at temperatures outside the wire bonding process windows and molding process windows (described hereinbelow). In that earlier patent application, such sublimation leaves a cavity within the package, so as to alleviate certain structural stresses. In contrast, and as described hereinbelow in various example embodiments, the sublimatable material provides a sublimatable form, where the term “form” is used in the sense of comparable structures (such as a mold, cast, shape or matrix), because the form provides a precursor shape for forming an adjacent structure next to (or otherwise in conformance with at least a portion of the shape of) the form, as further described hereinbelow. With respect to step14,FIG. 3Arepeats the perspective view illustration ofFIG. 2A, andFIG. 3Brepeats the cross-sectional view illustration ofFIG. 2B, but after the step14form described inFIG. 1is formed. In the example ofFIG. 3A, the step14form is shown as a hemispherical form112. Preferably, hemispherical form112fully surrounds circuit die102(items covered by form112are shown with dashed lines inFIG. 3A), and otherwise is formed in part above lead frames106,108and110, thereby also covering conductors108Cand110C. Depending on the physical/chemical properties of the polyols and applicable process temperature windows, the selected sublimatable materials for form112may be applied as solids that can be extruded as a melting bead at certain temperatures for depositing over select portions of the die/substrate/bond wires. In another variation, the sublimatable materials may be dissolved in suitable solvents and applied as a solution of appropriate viscosity using a syringe dispensing mechanism that dispenses a bead over the die portions and surrounding substrate and bond wire portions (hereinafter referred to as “encapsulated components”). The solvent may be evaporated from the bead, thereby leaving a “glob” of the material over the circuit die102. In yet another variation, a select sublimatable material may be applied as a liquid at room temperature, whereupon it may be cured by radiation (e.g., UV, IR, etc.) that creates cross-linking of chemical bonds to solidify as a bump. Also, the step14application or completion of hemispherical form112, insofar as its sublimatable material is concerned, may involve a heat (e.g., cure/bake) stage or stages.

Referring again toFIG. 1and method10, a step16follows step14. In step16, a conforming wave shaping member (or plural members) is formed adjacent part or all of the sublimatable form created in step14. For ease of illustration, a perspective view is not shown, butFIG. 4again illustrates the cross-sectional side view ofFIG. 3B, with the addition of a wave shaping member114(as created in step14) formed adjacent sublimatable form112. In the illustrated example, wave shaping member114is hemispherical, so at least the inner edge of wave shaping member114conforms to a part or all of the shape of form112, and therefore it provides an inner concave surface1141CS(and preferably parabolic) relative to integrated circuit die102. Thus, in the illustrated example, wave shaping member114may be created by a conforming layer having a thickness, preferably uniform, positioned atop the entirety of sublimatable form112. Further, member114is referred to as “wave shaping” because the material used for member114is preferably one suited for altering the directionality of waves at the bandwidth BWD. Accordingly, for example, if the bandwidth BWDis within the visible spectrum, then the material used for wave shaping member114is reflective to that spectrum, so that light impinging on the inner concave surface of member114will reflect inwardly in the direction of die102. In this manner, the change in wave directionality is “wave shaping,” as further described hereinbelow.

In another aspect of step16and wave shaping member114, and in an example embodiment, an aperture116(or multiple apertures) is/are created through member114, so as to allow an air channel between the exterior of member114and the sublimatable material of sublimatable form112. For example,FIG. 4shows a single aperture116located near or at the upper apex of the curvature of member114. The diameter of aperture116also may be selected, such as in a range of 0.1 to 100's of wavelengths. Aperture116is shown as part of the step16formation of the wave shaping member(s) but, in an alternative embodiment, the aperture(s) can be formed as a separate step, after forming the wave shaping member, such as cutting, drilling and the like, and with various tools for doing so (e.g., laser).

Referring again toFIG. 1and method10, a step18follows step16. In step18, an integrated circuit packaging material is applied over the device, preferably so as to encapsulate wave shaping member114and the remainder of the components affixed to substrate104. For this step,FIG. 5illustrates the cross-sectional side view ofFIG. 4, with the addition of an encapsulating mold118, formed according to step18by applying a select molding material over the desired circuit components. Additional steps may be required in connection with integrated circuit packaging. The molding materials may be selected from plastics, epoxy resins, etc. that may be formulated to contain various types of inorganic fillers, such as fused silica, catalysts, flame retardants, stress modifiers, adhesion promoters and other additives, preferably based on the specific product/part requirements, although other types of molding/packaging materials also may be used. In one example implementation, the select molding material may be applied by a packaging tool having a needle that is brought into contact with the wave shaping member114, whereupon the select molding material is deposited around the needle, thereby also creating at least one aperture120in fluid (e.g., air) communication with aperture116, where aperture120preferably has a dimension comparable to aperture116. Usually, intense heat may be applied to the molding material, which may be liquefied and shaped into the desired structure. Also, the select molding material having aperture120may be cured in one or more stages in a mold cure process. In another example, film assist molding may be used, so a film (or two films) is/are subjected to a vacuum, so as to conform to a separable mold form and to thereby define a region into which thereafter a molding material is filled, so the film therefore isolates the mold from the molding material. Thus, after the molding material cures, the mold form is separable, so as to release the encapsulated device that cured in the region, with the film having kept clean the mold form surfaces. In any event, with this process, aperture120may be realized as part of the film-protected mold form. Yet another example may use injection molding of many devices at once as an array or large contiguous mass, followed by sawing or other technique to separate individual devices from the mold.

Referring again toFIG. 1and method10, a step20follows step18. In step20, the sublimatable material from step14is sublimated, so the material is exposed to proper processes so as to transition the substance directly from the solid to the gas phase without passing through the intermediate liquid phase. For this step,FIG. 6illustrates the cross-sectional side view ofFIG. 5, where the patterned fill of the former material112in above-described Figures (i.e., from inside the concave shape of member114) is shown as gone, so as to represent: the phase change of the substance to gas; and, as a result of the sublimation processes, the resultant sublimated gas is exhausted through apertures116and120, as shown by dotted arrows in the Figure. In view of the steps and structure described hereinabove, an interior cavity remains on the concave side of wave shaping member114, which may be occupied generally by the ambient material (e.g., air) remaining after the sublimated gas is exhausted from that area. The sublimation may be achieved in various ways consistent with the type of sublimatable material used in in the above-described step14. For example, heat, radiation or other phase-change energy or process(es) may be applied to gasify the sublimatable material of hemispherical form112at suitable temperatures (i.e., sublimation/evaporation), such as relative to usual backend packaging flow conditions.

Before proceeding, step20may be modified or omitted if a non-sublimatable material or materials is/are used for the step14formation of a shaped form. For example, the material used for the form in alternative embodiments may be of a type that responds to a treatment (e.g., heat), so part of the material sublimates directly from solid phase to gas, while other parts transition from solid to liquid in step20so as to be removable (e.g., by flowing) through apertures116and120, again as shown by dotted arrows in theFIG. 6. As yet another alternative, step20(and others pertaining to aperture creation and closure) may be eliminated entirely in an alternative embodiment, wherein the step14form is created by a material that remains solid and is not removed via an aperture, which would be achieved by substituting in step14a material that remains as part of the final package and is of a type that does not substantially attenuate the bandwidth BWDof interest (e.g., clear polymer, where the bandwidth BWDis visible light).

Referring again toFIG. 1and method10, a step22follows step20. In step22, a cover, seal or other closure is formed over the step18aperture of the packaging material. For this step,FIG. 7illustrates the cross-sectional side view ofFIG. 6, where a cover122is formed over aperture120, thereby enclosing any open area within the concavity of wave shaping member114. Cover122may be formed in various ways. For example, aperture120may be covered or otherwise sealed with a film layer, such as one comprising a B-stage film or screen-printed encapsulant layer, and selection of a particular film layer to seal the package may depend on the size or shape of aperture120. Generally, step22completes the packaging of wave device100, although additional processes could be added.

Referring toFIG. 1, the final step24is shown to process waves.FIG. 7also illustrates this step, which can occur in connection with testing and or later use of wave device100. In the example ofFIG. 7, waves are directed at a second surface104S2of substrate104, which is opposite surface104S1to which circuit die102is affixed (directly, or via intermediate structure, such as lead frame106). Substrate104is preferably constructed of material(s) that permits the wave having a bandwidth BWDto pass through the substrate with reduced absorbance. Accordingly, as shown inFIG. 7, as the waves are directed to surface104S2, the signals pass through substrate104and impinge upon the concave surface of wave shaping member114. In this example, the waves are light and wave shaping member114is a parabolic reflector, so as a result the directionality of the incoming waves (or rays) is reflected to a different direction. Accordingly, for example, the earlier sublimatable form112is shaped and dimensioned, so that the confirming and resulting wave shaping member114will provide a desired change in directionality of the incoming wave, which in this embodiment is a reflective angle of incidence toward wave surface102WS, as shown inFIG. 7. Moreover, after waves are reflected as described, they pass from the reflector to wave surface102WS, via the communication channel of air that remains inside the concave region of member114, with that channel having been earlier evacuated of the sublimatable material/gas. As a result, the reflected signal experiences zero loss, as the air through which it passes is a zero loss material. Lastly, while the directionality of the waves is shown inFIG. 7for wave device10receiving a signal, if instead wave surface102WSprovides a transmitting functionality, then the signal directionality is reversed, while the other benefits described hereinabove are still achieved. Accordingly, in such an instance, wave surface102WSmay operate to transmit waves toward the inner concave surface114ICSof member114, in which case such waves would then be reflected toward surface104S1of substrate104and then through substrate104, thereby providing a directional transmission of such waves, such as toward or in the direction of an intended target or receiving device.

In view of the description hereinabove, an example methodology and structure result in a semiconductor wave device with an integrated wave signal directionality feature, so as to improve manufacturability, device longevity, and so as to efficiently communicate energy from the wave signal to/from the receiver/transmitter of the wave device. Other wave shaping members may be situated, relative to one more integrated circuit die, as formed adjacent or in conformity with a sublimatable form that is subsequently sublimated, leaving the wave shaping member affixed and encapsulated in the wave device package. Another example embodiment is described hereinbelow.

FIG. 8illustrates a cross-sectional view of an alternative embodiment wave device200, which also may be constructed according to method10ofFIG. 1, but which results in various different structural aspects. Accordingly, steps relating to method10are generally referenced hereinbelow, but their additional details are described hereinabove. Also, various illustrations and descriptions herein use cross-sectional views, which are helpful in understanding the overall device's three dimensions.

Referring toFIG. 8, the first step12of method10attaches a circuit die202relative to a first surface204S1of a substrate204, where circuit die202may include apparatus and functionality for either transmitting or receiving (or both transmitting and receiving) a wave with bandwidth BWD. Substrate204is constructed of various materials. But with respect to wave device200, in contrast to the above-described device100, the material of substrate204is not required to be transmissive to bandwidth BWD, because the waves are not ultimately transmitted through that structure in this example embodiment. In any event, the attachment of die202relative to substrate204may include various techniques and structures, whereFIG. 8also shows such affixation with a first lead frame206first attached to substrate204, and circuit die202attached adjacent lead frame206. Although not shown from the cross-sectional perspective, additional lead frames also may be, and are likely to be, affixed to substrate204, with conductors (e.g., bond wires) also connected between each such lead frame and respective conductive pads on die202. CompletingFIG. 8, step14of method10forms a shaped sublimatable material relative to a region of circuit die202, and a sublimatable form212is created in this example, which is illustrated as having a stair-step profile. Form212may be created using various processes, including 3-D printing for example, where form212provides a precursor shape for forming an adjacent and shape-conforming structure next to the form, as further described hereinbelow.

With respect to wave device200, and as now introduced in the cross-sectional view ofFIG. 9A, theFIG. 1steps16and18are combined with respect to a single structure. More particularly, a conforming wave shaping member218(or plural members) is/are formed adjacent the sublimatable form212. In this example embodiment, conforming wave shaping member218(step16of method10) is an integrated circuit packaging material (step18of method10) applied over the device, preferably so as to encapsulate the sublimatable form212and the remainder of the items affixed to substrate204. For this step,FIG. 9Aillustrates the cross-sectional view ofFIG. 8, with the addition of an encapsulating molding material that therefore provides a wave shaping member218, formed according to step18by applying a select molding material over the desired circuit components and performing any additional steps as may be required in connection with integrated circuit packaging. For the example device200ofFIG. 9A(and Figures described hereinbelow), ultimately waves are to pass through the molding materials of member218, akin to such waves passing through substrate104in the above-described device100. Thus, for device200, the molding materials(s) forming member218are selected with a consideration of the type and/or bandwidth BWDof the wave that is communicated relative to device100, so that such materials readily permit the wave to transmit through member218with little or no change in the signal strength, so the molding material does not have strong absorbance in the bandwidth BWDof interest. Also in connection withFIG. 9A, a lateral aperture220is also created in fluid (e.g., air) communication with the sublimatable form212.

FIG. 10illustrates the cross-sectional view fromFIG. 9A, further demonstrating step20of method10as applied to device200. Thus,FIG. 10depicts that sublimatable form212fromFIG. 9Ais sublimated, again by process(es) to transition the substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Accordingly, the sublimatable material encapsulated by encapsulating mold218turns to gas and is exhausted via aperture220, as shown by dotted arrows in the Figure. Therefore, in a resulting device200, an interior cavity remains relative to the surface of circuit die212, and waves may propagate with little or no interference from the air in that cavity.

FIG. 11illustrates the cross-sectional view fromFIG. 10, further demonstrating steps22and24of method10, as applied to device200. As a first observation inFIG. 11, a cover222may be formed over the aperture220that was formerly in the packaging material, as shown inFIG. 10. Thus, cover222encloses any open cavity between encapsulating mold218and circuit die202. As a second observation,FIG. 11shows the final step24fromFIG. 1to process waves. Mold218comprises materials that readily permit the wave to transmit through it, with little or no change in the signal direction or strength. As a result,FIG. 11shows such waves directed toward, and passing through, mold218. However, the stair-step shape of mold218presents a surface facing circuit die202and thereby creates a refractive directionality of the waves, so as to focus or direct the waves more toward the communication surface202CSof die202. For example, mold218, either alone or in combination with the air interface from the cavity left behind after sublimation of form212, again provides wave shaping directionality of the waves toward circuit die202(or, in an alternative embodiment, die202includes a transmitter, and such directionality may be achieved away from circuit die202). In any event, therefore, mold218provides a lens, so as to change the direction of waves impinging on a first surface of the lens relative to the waves as they depart from a second surface of the lens.

Having described the formation of device200and its operation, various alternatives are possible. For example, additional devices2001and2002are shown, respectively, inFIGS. 9B and 9C, where the process flow in those Figures is comparable to the stage of formation as described hereinabove in connection withFIG. 9A. With respect to both devices2001and2002, in connection with device200ofFIG. 9A, a laterally created aperture220may be difficult, infeasible or otherwise undesirable during certain process flows. Alternatively, therefore, devices2001and2002both include vertical apertures2201and2002, respectively, as may be implemented in connection with both conventional molding processes and the above-described film assist molding approach. In device2001, vertical aperture2201is positioned toward a far (e.g., right, as shown) vertical edge of sublimatable form212, so as to serve the exhausting function described hereinabove, while still permitting a vertical implementation of the aperture through the integrated circuit packaging material wave shaping member218. This positioning is desirable, because it reduces the effect (if any) that the remaining bore of the aperture could have on disturbing the path of waves to/from device2001. However, as an additional example embodiment,FIG. 9Cillustrates for device2002that form212includes a lateral extension212LEX, so as to provide a path for aperture2202to be positioned even a greater distance laterally relative to communication surface202CS. Thus, after aperture2202is closed (similar to cover222inFIG. 11) and device2002is subsequently operated, waves are less likely to be disturbed as emitted or detected by circuit202, due to the additional lateral displacement accomplished via lateral extension212LEX.

In view of the description hereinabove, various example embodiments provide improvements to: a method of creating; and a resulting integrated circuit wave device that communicates waves with a bandwidth that is minimally affected as the waves pass through an external portion of the device and are shaped internally of the device, either to or from an encapsulated integrated circuit die. Example embodiments may be created for waves of various bandwidths, with radio frequency (RF), visible light and infrared (IR) communication elements. Directionality and/or focus also may be used to a central point or to multiple points, such as with an array of sensors or transmitters. Further, such internal wave shaping is achieved by creating a form and an adjacent shape, where the form: is thereafter sublimated, leaving behind an air cavity and a wave shaping member; or is of a material that has at most a negligible effect on the bandwidth BWDof the waves passing through it. The wave shaping member may have many forms, such as lenses (e.g., Fresnel) or reflector shapes, where the shaping device may include singular or multiple such devices. Moreover, different example embodiments may be created for different respective bandwidths BWD, and the device may thereby provide (or be incorporated into) numerous apparatus or applications, such as photodetctors/photosensors, cameras, range finders, focusing devices, targeting systems, automotive detectors and numerous others.