BACKGROUND OF THE INVENTION
The present invention relates to packaging of microelectronic devices, especially the packaging of semiconductor devices. The present invention also relates to stacked microelectronic packages including stacked microelectronic packages fabricated at the wafer level and to methods of making such packages.
Microelectronic elements generally comprise a thin slab of a semiconductor material, such as silicon or gallium arsenide, commonly called a die or a semiconductor chip. Semiconductor chips are commonly provided as individual, prepackaged units. The active circuitry is fabricated in a first face of the semiconductor chip (e.g.,
a front surface) . To facilitate electrical connection to the active circuitry, the chip is provided with bond pads on the same face. The bond pads are typically placed in a regular array either around the edges of the die or, for many memory devices, in the die center. The bond pads are generally made of a conductive metal, such as copper, or aluminum, around 0.5pm thick. The bond pads could include a single layer or multiple layers of metal. The size of the bond pads will vary with the device type but will typically measure tens to hundreds of microns on a side.
In some unit designs, the semiconductor chip is mounted to a substrate or chip carrier, which is in turn mounted on a circuit panel, such as a printed circuit board. Semiconductor chips are typically packaged with substrates to form microelectronic packages having terminals that are electrically connected to the chip contacts. The package may then be connected to test equipment to determine whether the packaged device conforms to a desired performance standard. Once tested, the package may be connected to a large circuit, e.g., a circuit in an electronic product such as a computer or a cell phone.
In order to save space, certain conventional designs have stacked multiple microelectronic chips within a package. This allows the package to occupy a surface area on a substrate that is less than the total surface area of the chips in the stack. However, conventional stacked packages have disadvantages of complexity, cost, thickness and testability.
Size is a significant consideration in any physical arrangement of chips. The demand for more compact physical arrangements of chips has become even more intense with the rapid progress of portable electronic devices. Merely by way of example, devices commonly referred to as "smart phones" integrate the functions of a cellular telephone with powerful data processors, memory and ancillary devices such as global positioning system receivers, electronic cameras, and local area network connections along with high-resolution displays and associated image processing chips. Such devices can provide capabilities such as full internet connectivity, entertainment including full-resolution video, navigation, electronic banking and more, all in a pocket-size device. Complex portable devices require packing numerous chips into a small space. Moreover, some of the chips have many input and output connections, commonly referred to as "I/O's." These I/O's must be interconnected with the I/O's of other chips. The interconnections should be short and should have low impedance to minimize signal propagation delays. The components which form the interconnections should not greatly increase the size of the assembly. Similar needs arise in other applications as, for example, in data servers such as those used in internet search engines. For example, structures which provide numerous short, low-impedance interconnects between complex chips can increase the bandwidth of the search engine and reduce its power consumption.
In spite of the above advances, there remains a need for improved semiconductor device and carrier packages and stacked packages that are reliable, thin, testable, and that are economical to manufacture. These attributes of the present invention are achieved by the construction of the microelectronic package as described hereinafter. US2008/142946
describes a package structure comprising a substrate with a pre-formed die receiving cavity and/or terminal contact metal pads formed within an upper surface of the substrate. A die is disposed within the receiving cavity by adhesion and a dielectric layer is formed on the die and the substrate. At least one redistribution built up layer, RDL, is formed on the dielectric layer and coupled to the die via contact pad. A connecting structure, for example, UBM is formed over the redistribution built up layer. Terminal conductive bumps are coupled to the UBM.
discloses a method for arranging one or more electronic components on a carrier. The electronic components have a number of contact points arranged on a first surface. The carrier has a second main surface and a third main surface. In the carrier there are also arranged one or more first apertures with a depth extending from the second main surface towards the third main surface. WO2000/70679
discloses a carrier for one or more electronic components and comprising spaces provided for the components on at least one surface. The carrier comprises at least partly conductive Low Temperature Cofire Ceramic, LTCC, material, so that the carrier in addition to provide mechanical support for the components can also conduct heat generated by the components. CN1815734
discloses a method for forming a canal structure on a base plate. An array of LEDs and an array of driving ICs are placed in a corresponding canal structure. Then, an insulating layer is formed on a surface of the base plate, array of LEDs and array of driving ICs. An electrical connection between two pins is formed using a micro imaging procedure. A cutting procedure completes each encapsulation unit, and the encapsulated unit is adhered on PCB.
discloses a method for fabricating a chip-embedded interposer, comprising forming at least one cavity on a silicon substrate, forming a plurality of through vias penetrating the silicon substrate, providing an integrated circuit chip having a plurality of I/O pads, and forming rerouting conductors connected to the I/O pads and to the through vias. A stack structure having different kinds of chips can be incorporated at a wafer level using the interposer.
discloses a substrate including an inorganic material base board having a recess and at least one penetration hole provided around the recess, and a semiconductor device accommodated in the recess and including at least one electrode pad provided on a surface of the semiconductor device. A resin filling is provided in the penetration hole and has at least one through-hole for electrically connecting a top surface and a back surface of the resin filling. An insulating layer covers the surfaces of the semiconductor device, the resin filling and the inorganic material base board and has a first opening corresponding to the through-hole and a second opening corresponding to the electrode pad. A conductive wiring is formed on a surface of the insulating layer for electrically connecting the through-hole and the electrode pad.
W2003/105222 discloses a component module comprsing one or more electronic components, positioned between a substrate and a dielectric layer in a recess of the substrate in such a way that the terminals of the component face upwards towards the dielectric layer. The contact is achieved by means of a strip conductor structure located on the upper side of the dielectric layer, the conductors making contact both with the terminals of the component and with the external terminals located on polymer bumps by means of vias. The external terminals on polymer bumps can be formed on the underside of the substrate or on the upper side of the dielectric layer.
discloses a semiconductor chip that includes a semiconductor substrate having an opening portion and a frame portion defining a periphery of the opening portion. At least one electric element is provided on the frame portion, and has at least one electrode terminal. A first insulation film is formed on the frame portion so that the electrode terminal is partially exposed at the first insulation film to form a plurality of electrode pads.
relates to an embedded chip printed circuit board in which a space required for embedding a chip is formed to a desired depth depending on various thicknesses of chips to be embedded. Thus, the circuit line for the electrical connection between the embedded chip and the circuit pattern layer can be formed to be relatively short, thereby maximizing space efficiency and decreasing inductance at high frequencies.
discloses a stacked electronic packaging structure with packaging units.
SUMMARY OF THE INVENTION
The invention is described according to the microelectronic unit of claim 1.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are a sectional view and a corresponding top-down plan view illustrating a packaged chip and chip carrier assembly in accordance with an example not covered by claim 1.
FIG. 2 is a sectional view illustrating a packaged chip in accordance with an embodiment of the invention.
FIG. 3 is a schematic depiction of a system according to an embodiment of the invention.
In the embodiments shown and described herein, microelectronic units can be planarized. Planarized microelectronic units can advantageously be incorporated in stacked assemblies. Reducing the number of different sizes of
microelectronic units can also facilitate stacking of the microelectronic units.
FIGS. 1A and 1B are a sectional view and a corresponding top-down plan view illustrating exemplary packaged chip and chip carrier assembly . As illustrated in FIGS. 1A and 1B, a microelectronic unit 10 includes a microelectronic element 20 mounted to a carrier structure 30.
The microelectronic element 20 can include a semiconductor substrate, made for example from silicon, in which one or a plurality of semiconductor devices (e.g., transistors, diodes, etc.) is disposed in an active semiconductor region thereof located at and/or below the top surface 21. The thickness of the microelectronic element 20 between the top surface 21 and a bottom surface 22 that is remote from the front surface typically is less than 200 µm, and can be significantly smaller, for example, 130 µm, 70 µm or even smaller. The microelectronic element 20 includes a plurality of conductive contacts 23 located at the top surface 21 thereof for electrical connection to other conductive elements.
While not specifically shown in FIGS. 1A and 1B, the semiconductor devices in the active semiconductor region typically are conductively connected to the conductive contacts 23. The semiconductor devices, thus, are accessible conductively through wiring incorporated within one or more dielectric layers of the microelectronic element 20. In some embodiments, the contact pads at the front surface of the microelectronic element may not be directly exposed at the front surface of the microelectronic element. Instead, the contact pads may be electrically connected to traces extending to terminals that are exposed.
As used in this disclosure, a statement that an electrically conductive element is "exposed at" a surface of a dielectric element indicates that the electrically conductive element is available for contact with a theoretical point moving in a direction perpendicular to the surface of the dielectric element toward the surface of the dielectric element from outside the dielectric element. Thus, a terminal or other conductive element which is exposed at a surface of a dielectric element may project from such surface; may be flush with such surface; or may be recessed relative to such surface and exposed through a hole or depression in the dielectric.
While essentially any technique usable for forming conductive elements can be used to form the conductive elements described herein, non-lithographic techniques as discussed in greater detail in the co-pending application entitled Non- Lithographic Formation of Three-Dimensional Conductive Elements, filed on even date herewith (Attorney Docket No. Tessera 3.0- 614), can be employed. Such non-lithographic techniques can include, for example, selectively treating a surface with a laser or with mechanical processes such as milling or sandblasting so as to treat those portions of the surface along the path where the conductive element is to be formed differently than other portions of the surface. For example, a laser or mechanical process may be used to ablate or remove a material such as a sacrificial layer from the surface only along a particular path and thus form a groove extending along the path. A material such as a catalyst can then be deposited in the groove, and one or more metallic layers can be deposited in the groove.
The carrier structure 30 defines a recess 40 extending from a front surface 31 thereof partially through the carrier structure towards a rear surface 32. The carrier structure 30 can be made from a semiconductor, for example, silicon.
The recess 40 includes an inner surface 41 located at the bottom of the recess that is farthest away from the front surface 31 of the carrier structure 30. The recess 40 includes a lateral edge surface 42 (i.e., a sidewall of the recess 40) that extends between the inner surface 41 of the recess and the front
surface 31 of the carrier structure 30. The recess 40 includes a lateral edge surface 42 (i.e., a sidewall of the recess 40) that extends between the inner surface 41 of the recess and the front surface 31 of the carrier structure 30. The recess 40 may extend more than half-way from the front surface 31 towards the rear surface 32, such that a height of the recess 40 in a direction perpendicular to the front surface 31 is greater than a height of the remaining portion of the carrier structure 30 extending between the inner surface 41 and the rear surface 32.
The recess 40 can have any top-view shape, including for example, a rectangular channel, as shown in FIG. 1B. As shown in FIGS. 1A and 1B, the recess 40 includes a single microelectronic element 20. In other embodiments, the recess can include any number of microelectronic elements 20. In one example, the recess can include a plurality of microelectronic elements. In some examples, the recess 40 can have any three-dimensional shape, including for example, a cylinder, a cube, or a prism, among others.
As shown in FIG. 1A, the lateral edge surface 42 extends from the front surface 31 of the carrier structure 30 through the carrier structure at an angle that is normal to a horizontal plane defined by the front surface 31. In other embodiments, the lateral edge surface 42 can extend from the front surface 31 at any angle to the front surface 31, including, for example, an angle between about 60 and about 100 degrees. The lateral edge surface 42 can have a constant slope or a varying slope. For example, the angle or slope of the lateral edge surface 42 relative to the horizontal plane defined by the front surface 31 can decrease as the lateral edge surface penetrates further towards the inner surface 41.
The carrier structure 30 also defines a plurality of holes 50 extending from the front surface 31 thereof through the carrier structure to the rear surface 32, and a plurality of conductive vias 60, each conductive via extending through a respective hole 50. In the embodiment described with respect to FIGS. 1A and 1B, there are six holes 50 and respective conductive
vias 60. In other examples, there can be any number of holes and conductive vias extending through the carrier structure. For example, in the embodiment shown in FIG. 11A, there are eighteen holes extending through the carrier structure.
The holes 50 can be arranged in any geometric configuration within the carrier structure 30. For example, the holes 50 can arranged along a single common axis, or the holes 50 can be arranged in two parallel rows, as shown in FIGS. 1B and 11. In other examples (not shown), the holes 50 can be arranged in a cluster, grid, ring, or any other shape.
Each hole 50 includes an inner surface 51 that extends through the carrier structure 30. As shown in FIG. 1A, the hole 50 has a width W1 at the front surface 31 and a width W2 at the rear surface 32 which is greater than W1 such that the hole is tapered in a direction from the rear surface towards the front surface. In other examples, as shown for example in FIG. 8A, one or more holes can have a constant width, and one or more holes can be tapered in a direction from the front surface towards the rear surface.
The inner surface 51 of each hole 50 can have a constant slope or a varying slope. For example, the angle or slope of the inner surface 51 relative to the horizontal plane defined by the front surface 31 of the carrier structure 30 can decrease in magnitude (become less positive or less negative) as the inner surface 51 penetrates further from the front surface 31 to the rear surface 32 of the carrier structure.
Each hole 50 can have any top-view shape, including for example, a round shape, as shown in FIG. 1B (in FIG. 1B, each hole 50 has a frusto-conical three-dimensional shape). In some embodiments, each hole 50 can have a square, rectangular, oval, or any other top-view shape. In some examples, each hole 50 can have any three-dimensional shape, including for example, a cylinder, a cube, or a prism, among others.
Each conductive via 60 extends within a respective hole 50 and defines an outer surface 61 that extends along the height of the conductive via between the front surface 31 and the rear surface 32 of the carrier structure 30. Each conductive via 60 can be made from a metal or an electrically conductive compound of a metal, including for example, copper or gold.
Each conductive via 60 is electrically connected to a front conductive contact 62 at the front surface 31 and a rear conductive contact 63 at the rear surface 32. Each front conductive contact 62 and rear conductive contact 63 (or any of the other conductive contacts disclosed herein), if exposed at an external surface of the microelectronic unit 10 (e.g., the front surface 31, the rear surface 32, a major surface 71 of a dielectric region 70, or a dielectric layer 72 or 73 overlying the respective surfaces 31 or 32), is suitable to be used as a terminal for electrical connection to an external element.
As shown, the conductive via 60 is also in registration with the conductive contacts 62 and 63 (i.e., the conductive via 60 and the conductive contacts 62 and 63 share a common central axis). In other examples, the conductive via may have a different central axis than either or both of the front and rear conductive contacts. Each conductive contact 62 and 63 can be made from any electrically conductive metal, including for example, copper or gold. As shown, the conductive contacts 62 and 63 have a round top-view shape. In other examples, the conductive contacts 62 and 63 and any of the conductive contacts disclosed herein can have any top-view shape, including an oval, triangle, square, rectangle, or any other shape.
Each conductive via 60 is also electrically connected to one or more conductive contacts 23 of the microelectronic element 20. As shown in FIGS. 1A and 1B, each conductive via 60 is electrically connected to a respective conductive contact 23 through a terminal 24, a conductive trace 64 extending along the front surface 31 of the carrier structure 30, and the front conductive contact 62. In other examples, each conductive via 60 can be electrically connected to one or more conductive contacts 23 in any other configuration.
The combination of one or more of the terminal 24, the conductive contact 62, and the conductive trace 64 can also be considered to be an "extended bond pad" that is suitable for connection to an external element (not shown).
As shown, each conductive via 60 is electrically connected to a respective conductive bond material 65 exposed at a bottom surface of the rear conductive contact 63, for electrical interconnection to an external element (not shown) . In other examples, the conductive bond material 65 can be replaced with any other electrical interconnection element (e.g., conductive nanoparticles), or the conductive bond material 65 can be omitted (e.g., when diffusion bonding is used).
The conductive via 60, the conductive contacts 62 and 63, the traces 64, and the terminals 24 are all electrically insulated from the microelectronic element 20 by a dielectric region or layer. For example, the traces 64 are insulted from the carrier structure 30 by a dielectric region 70 having a major surface 71, the front conductive contacts 62 are insulated from the front surface 31 by a dielectric layer 72, and the rear conductive contacts 63 are insulated from the rear surface 32 by a dielectric layer 73. Each conductive via 60 is also insulated from the hole 50 by a dielectric layer extending along the inner surface 51 thereof (not shown).
As shown in FIG. 1A, the conductive via 60 can fill all of the volume within the hole 50 inside of a dielectric layer that electrically insulates the carrier structure 30 from the conductive via 60. In other words, the outer surface 61 of the conductive via 60 conforms to a contour of the inner surface 51 of the respective hole 50.
In other examples, the conductive via 60 may not fill all of the volume inside of a dielectric layer that insulates the hole 50. In one example, the outer surface 61 of the conductive via 60 may not conform to a contour of the inner surface 51 of the respective hole 50. In such an example, a dielectric region can fill the hole 50, an aperture can be drilled through the dielectric region, and the aperture can be plated to form the conductive via.
The conductive via 60 can be formed either solid or hollow depending upon the process conditions. For example,
the conductive via 60 can be formed by a conformal plating of the dielectric layer that insulates the hole 50, such that there is an internal aperture extending through the center of the conductive via. This internal aperture can be filled with a dielectric material, or it can be left open.
As shown, each conductive via 60 has a frusto-conical shape.
The dielectric region 70 fills the portion of the recess 40 that is not occupied by the microelectronic element 20, and the dielectric region 70 can provide good dielectric isolation with respect to the microelectronic element 20. The dielectric region 70 can be compliant, having a sufficiently low modulus of elasticity and sufficient thickness such that the product of the modulus and the thickness provide compliancy. Specifically, such a compliant dielectric region 70 can allow the conductive elements attached thereto to flex or move somewhat relative to the microelectronic element 20 and/or the carrier structure 30 when an external load is applied to the conductive elements. In that way, the bond between the conductive elements of the microelectronic unit 10 and terminals of an external element such as a circuit panel (not shown) can better withstand thermal strain due to mismatch of the coefficient of thermal expansion ("CTE") between the microelectronic unit 10 and the circuit panel.
In the embodiments shown, the major surface 71 of the dielectric region 70 extends above a plane defined by the front surface 31 of the carrier structure 30. In other examples, the major surface 71 can extend to be approximately in the same plane that is defined by the front surface 31 of the carrier structure 30.
The dielectric layers 72 and 73 can include an inorganic or organic dielectric material or both. The dielectric
layers 72 and 73 may include an electrodeposited conformal coating or other dielectric material, for example, a photoimageable polymeric material, for example, a solder mask material.
Each terminal 24 is exposed at the major surface 71 of the dielectric region 70 for interconnection to an external element. Each terminal 24 can be aligned with the recess 40 and can be disposed wholly or partly within an area of the carrier structure 30 defined by the recess 40. As seen in FIG. 1A, the terminal 24 is wholly disposed within an area defined by the recess 40. As shown, a plane defined by a top surface 25 of the terminal 24 is substantially parallel to the plane defined by the front surface 31 of the carrier structure 30. In addition to or instead of electrically interconnecting the terminal 24 to an external element, the front conductive contact 62 can serve as a terminal and can be electrically interconnected to an external element.
As shown, the top surface 25 of the terminal 24 is located above the plane defined by the front surface 31 of the carrier structure 30.
As shown in FIG. 1B, the terminals 24 and the front conductive contacts 62 have the shape of a conductive bond pad. In other embodiments, the terminals 24 and the conductive contacts 62 can be any other type of conductive contact, including for example, a conductive post.
FIG. 2 illustrates a microelectronic unit 310 in accordance with an embodiment of the invention. The
microelectronic unit 310 is similar to the microelectronic unit 10 described above and shown in FIG. 1A, but the microelectronic unit 310 differs in the location of the holes that extend through the carrier structure and the conductive vias that extend through the holes.
Rather than having holes and conductive vias extending from the rear surface through the carrier structure towards the front surface as shown in FIG. 1A, the microelectronic unit 310 includes holes 250 and conductive vias 260 that extend from a major surface 271 of a dielectric region 270 through the carrier structure 230 to the rear surface 232 thereof. Similar to the microelectronic unit 10, in the microelectronic unit 310, the conductive vias 260 are insulated from the carrier structure 230 by a dielectric layer and/or a dielectric region that surrounds an outer surface 261 of the conductive vias 260.
The structures discussed above can be utilized in construction of diverse electronic systems. For example, a system 1800 in accordance with a further embodiment of the invention includes a microelectronic unit 1806 as described above and illustrated in Figure 2, in conjunction with other electronic components 1808 and 1810. In the example depicted, component 1808 is a semiconductor chip whereas component 1810 is a display screen, but any other components can be used. Of course, although only two additional components are depicted in FIG. 3 for clarity of illustration, the system may include any number of such components.
Structure 1806 and components 1808 and 1810 are mounted in a common housing 1801, schematically depicted in broken lines, and are electrically interconnected with one another as necessary to form the desired circuit. In the exemplary system shown, the system includes a circuit panel 1802 such as a flexible printed circuit board, and the circuit panel includes numerous conductors 1804, of which only one is depicted in FIG. 3, interconnecting the components with one another. However, this is merely exemplary; any suitable structure for making electrical connections can be used.
The housing 1801 is depicted as a portable housing of the type usable, for example, in a cellular telephone or personal digital assistant, and screen 1810 is exposed at the surface of the housing. Where structure 1806 includes a light-sensitive element such as an imaging chip, a lens 1811 or other optical device also may be provided for routing light to the structure. Again, the simplified system shown in FIG. 3 is merely exemplary; other systems, including systems commonly regarded as fixed structures, such as desktop computers, routers and the like can be made using the structures discussed above.