Microelectronic devices and methods for manufacturing microelectronic devices

Microelectronic devices and methods for manufacturing microelectronic devices are disclosed herein. In one embodiment, a method includes constructing a radiation sensitive component in and/or on a microelectronic device, placing a curable component in and/or on the microelectronic device, and forming a barrier in and/or on the microelectronic device to at least partially inhibit irradiation of the radiation sensitive component. The radiation sensitive component can be doped silicon, chalcogenide, polymeric random access memory, or any other component that is altered when irradiated with one or more specific frequencies of radiation. The curable component can be an adhesive, an underfill layer, an encapsulant, a stand-off, or any other feature constructed of a material that requires curing by irradiation.

TECHNICAL FIELD

The present invention is related to microelectronic devices and methods for manufacturing microelectronic devices.

BACKGROUND

Microelectronic devices generally have a die (i.e., a chip) that includes integrated circuitry having a high density of very small components. In a typical process, a large number of dies are manufactured on a single wafer using many different processes that may be repeated at various stages (e.g., implanting, doping, photolithography, chemical vapor deposition, physical vapor deposition, plasma enhanced chemical vapor deposition, plating, planarizing, etching, etc.). The dies typically include an array of very small bond-pads electrically coupled to the integrated circuitry. The bond-pads are the external electrical contacts on the die through which the supply voltage, signals, etc., are transmitted to and from the integrated circuitry. The wafer is then thinned by backgrinding and the dies are separated from one another (i.e., singulated) by dicing the wafer. After the dies have been singulated, they are typically “packaged” to couple the bond-pads to a larger array of electrical terminals that can be more easily coupled to the various power supply lines, signal lines, and ground lines.

Conventional processes for packaging dies include electrically coupling the bond-pads on the dies to an array of pins, ball-pads, or other types of electrical terminals, and then encapsulating the dies to protect them from environmental factors (e.g., moisture, particulates, static electricity, and physical impact). In one application, the bond-pads are electrically connected to contacts on an interposer substrate that has an array of ball-pads. For example,FIG. 1schematically illustrates a conventional packaged microelectronic device2including a microelectronic die10, an interposer substrate20attached to the die10with an adhesive30, a plurality of wire-bonds32electrically coupling the die10to the substrate20, a casing50protecting the die10from environmental factors, and a plurality of solder balls60attached to the substrate20. After assembly, the adhesive30and the casing50are typically cured to form a robust packaged device2.

Another type of microelectronic device is a “flip-chip” semiconductor device. These devices are referred to as “flip-chips” because they are typically manufactured on a wafer and have an active side with bond-pads that initially face upward. After manufacture is completed and a die is singulated, the die is inverted or “flipped” such that the active side bearing the bond-pads faces downward for attachment to an interposer substrate. The bond-pads are usually coupled to terminals, such as conductive “bumps,” that electrically and mechanically connect the die to the interposer substrate. The bumps on the flip-chip can be formed from solders, conductive polymers, or other materials. In applications using solder bumps, the solder bumps are reflowed to form a solder joint between the flip-chip component and the substrate, which leaves a small gap between the flip-chip and the interposer substrate. To enhance the integrity of the joint between the microelectronic component and the substrate, an underfill material may be introduced into the gap. The underfill material bears some of the stress placed on the components and protects the components from moisture, chemicals, and other contaminants. After flowing the underfill material into the gap between the flip-chip component and the substrate, the underfill material is cured.

Conventional methods for curing underfill materials, encapsulants, adhesives, and other compounds include either heating the curable material with various techniques or irradiating the curable material with microwave energy at a fixed frequency. One advantage of irradiating the material is that the time required to cure the material is reduced. Curing materials with microwave energy at a fixed frequency, however, has several drawbacks. For example, when microwave energy is applied to a microelectronic substrate, arcing and/or excessive heat accumulation may occur and cause localized damage to the substrate and the component to which the substrate is mounted. Arcing results from the build-up of a charge differential between different components or between one or more of the electronic elements within the components. When the difference in potential exceeds the resistance of a dielectric medium, such as air, the result is a release of the built-up charge through the dielectric medium manifested by an arc between the two oppositely charged components. Moreover, microwave energy may heat certain portions of the conductive circuitry more rapidly than other portions, which may damage the circuitry.

One existing approach to address such drawbacks of curing materials with fixed-frequency microwave energy is to vary the frequency of the applied microwave energy. Sweeping the frequency prevents the build-up of a charge differential and the excessive accumulation of heat. As a result, variable frequency microwave curing typically avoids arcing and the associated localized damage to microelectronic components. One problem with this approach, however, is that applying microwave energy over a range of frequencies may adversely affect other components within the microelectronic device. For example, doped silicon, polymeric random access memory, and chalcogenide are irreversibly changed when exposed to microwave energy at certain frequencies. Specifically, with regard to doped silicon, microwave energy can cause dopant atoms to diffuse throughout a substrate and render the doped structure and other features in the substrate defective. As a result, there exists a need to improve the process of curing materials in microelectronic devices.

DETAILED DESCRIPTION

The following disclosure describes several embodiments of microelectronic devices and methods for manufacturing microelectronic devices. An embodiment of one such method includes constructing a radiation sensitive component in and/or on a microelectronic device, placing a curable component in and/or on the microelectronic device, and forming a barrier in and/or on the microelectronic device to at least partially inhibit irradiation of the radiation sensitive component. The radiation sensitive component can be doped silicon, chalcogenide, polymeric random access memory, or any other component that is altered when irradiated with one or more specific frequencies of radiation. The curable component can be an adhesive, an underfill layer, an encapsulant, a stand-off, or any other feature constructed of a material that requires curing by irradiation.

In another embodiment, a method includes providing a substrate having a radiation sensitive component and constructing a conductive barrier at the substrate for at least partially reflecting radiation directed toward the radiation sensitive component during curing. The conductive barrier can be formed on an exterior surface of the substrate or internally within the substrate. Alternatively, the barrier can be formed on and/or in another substrate or member adjacent to the first substrate.

In another embodiment, a method includes (a) constructing a microelectronic device having a substrate, a radiation sensitive component in and/or on the substrate, a curable component in and/or on the substrate, and a shield in and/or on the substrate, (b) irradiating the microelectronic device at a plurality of frequencies to at least partially cure the curable component, and (c) while irradiating the device, at least partially reflecting the radiation directed toward the radiation sensitive component with the shield.

Another aspect of the invention is directed to microelectronic devices. In one embodiment, a microelectronic device includes a substrate, a radiation sensitive component at the substrate, a curable component at the substrate, and a barrier at the substrate. The barrier is configured to at least partially inhibit irradiation of the radiation sensitive component during curing. For example, the barrier may have a thickness selected to at least partially reflect the radiation directed toward the radiation sensitive component and may be of sufficient thickness to reflect the incident radiation.

Specific details of several embodiments of the invention are described below with reference to microelectronic devices including microelectronic dies and interposer substrates, but in other embodiments the microelectronic devices can include other components. For example, the microelectronic devices can include a microfeature workpiece upon which and/or in which micromechanical components, data storage elements, optics, read/write components, or other features are fabricated. Microfeature workpieces can be semiconductor wafers such as silicon or gallium arsenide wafers, glass substrates, insulative substrates, and many other types of materials. Moreover, the microelectronic devices can include a single microelectronic component or an assembly of multiple components. Several details describing well-known structures or processes often associated with fabricating microelectronic dies and microelectronic devices are not set forth in the following description for purposes of brevity and clarity. Also, several other embodiments of the invention can have different configurations, components, or procedures than those described in this section. A person of ordinary skill in the art, therefore, will accordingly understand that the invention may have other embodiments with additional elements, or the invention may have other embodiments without several of the elements shown and described below with reference toFIGS. 2-8.

Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from other items in reference to a list of at least two items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same features and/or types of other features and components are not precluded.

B. Embodiments of Microelectronic Devices and Systems for Manufacturing the Devices

FIG. 2is a schematic view of a microelectronic device140and a system100for curing one or more components of the device140in accordance with one embodiment of the invention. The illustrated system100includes a radiation chamber110, a radiation generator120for generating electromagnetic radiation in the chamber110, and a support member130for carrying the microelectronic device140in the chamber110. The illustrated radiation generator120generates variable-frequency microwave radiation122for irradiating the microelectronic device140to cure one or more components in the device140. In several applications, the range of frequencies is between approximately 0.9 GHz and 90 GHz, although in other embodiments the range of frequencies can include frequencies less than 0.9 GHz or more than 90 GHz. In either case, the range of frequencies is selected based on the material(s) to be cured because different materials may have different optimal curing frequencies. By varying the frequency, the radiation generator120reduces and/or eliminates (a) arcing between various components of the microelectronic device140, and (b) excessive heat accumulation at localized portions of the device140. In additional embodiments, however, the radiation generator120may generate microwave radiation at a fixed frequency or other types of electromagnetic radiation at a fixed or variable frequency for curing one or more components of the microelectronic device140.

The support member130is configured to support and position the microelectronic device140relative to the radiation generator120so that the device140is exposed to the microwave radiation122. The illustrated support member130has a surface132on which the microelectronic device140rests such that the device140is exposed within the chamber110. In other embodiments, the support member130may enclose the microelectronic device140to inhibit heat from radiating from the edges of the device140and maintain a generally uniform temperature throughout the device140during curing. As a result of the uniform temperature, the curable components are expected to cure generally uniformly throughout the microelectronic device140. In either case, the support member130can be composed of quartz, alumina, boron nitride, or other suitable materials for carrying the microelectronic device140without contaminating the device140. Suitable support members130and systems100are manufactured by Lambda Technologies of Morrisville, N.C.

The illustrated microelectronic device140includes a radiation sensitive component150(shown schematically), a curable component160(shown schematically), and a barrier170positioned to inhibit irradiation of the radiation sensitive component150. The radiation sensitive component150is a constituent or element of the device140that can be damaged or otherwise irreversibly affected by exposure to the microwave radiation122. The radiation sensitive component150, for example, can be doped silicon, chalcogenide, polymeric random access memory, or any other component that is irreversibly altered when irradiated with the radiation122generated by the radiation generator120. For example, when a heavily doped structure in a silicon substrate is sufficiently irradiated, the dopant atoms can diffuse throughout the substrate and potentially render the doped structure and other features in the substrate defective. The curable component160is a constituent or element of the device140that requires exposure to the microwave radiation122generated by the radiation generator120for curing. The curable component160can be an adhesive, an underfill layer, an encapsulant, a stand-off, or any other feature constructed of a material that requires curing by irradiation.

The radiation sensitive component150and the curable component160can be formed in and/or on the same substrate, or they can be different members of an assembly. Although the illustrated microelectronic device140includes a single radiation sensitive component150and a single curable component160, in other embodiments, the microelectronic device140may have multiple radiation sensitive components and/or multiple curable components. Moreover, in embodiments in which the radiation generator120irradiates the device140with electromagnetic radiation outside of the microwave range, the radiation sensitive component150is irreversibly affected by the particular frequency of radiation generated by the radiation generator120and the curable component160is at least partially cured by the particular frequency of radiation.

The barrier170is a structure formed in and/or on the microelectronic device140to inhibit irradiation of the radiation sensitive component150during curing of the curable component160. As such, the barrier170reflects and/or absorbs radiation directed toward the radiation sensitive component150to prevent the microwave radiation122from damaging or otherwise irreversibly changing the component150. The barrier170can be an external and/or internal structure on the device140and be composed of a conductive material that is generally reflective of the microwave radiation122. For example, suitable barrier materials include silver, copper, gold, and other conductive materials. In either case, the barrier170has a thickness T selected to reflect sufficient microwave radiation122such that the radiation122does not render the radiation sensitive component150defective. The thickness T is based on the composition of the barrier material. Specifically, barriers composed of highly conductive materials can be thinner than barriers composed of less conductive materials. The barrier170can be formed by depositing a layer of material onto the device using plating, electroplating, electroless deposition, chemical vapor deposition, plasma deposition, stenciling, or other suitable processes.

The barrier170can be a temporary or permanent structure on the microelectronic device140. For example, the barrier170can be formed on and/or in the microelectronic device140before curing the curable component160and subsequently removed via etching, sputtering, or other suitable processes after curing the component160. Alternatively, the barrier170may not be removed after curing, but rather can remain on the microelectronic device140throughout at least the remainder of the manufacturing process. As described below with reference toFIG. 5, in several embodiments in which the barrier170is a permanent structure on the microelectronic device140, the barrier170can also be a ground plane, or a plurality of electrical traces, or the barrier170may perform another function in the device140in addition to reflecting the microwave radiation122.

One feature of the microelectronic device140illustrated inFIG. 2is that the device140includes a barrier170for inhibiting irradiation of the radiation sensitive component150. An advantage of this feature is that the curable component160can be irradiated with variable-frequency microwave radiation to at least partially cure the component160without exposing the radiation sensitive component150to particular frequencies of microwave radiation that irreversibly alter the component150. Although the curable component160could be irradiated at a fixed microwave frequency that may not damage the radiation sensitive component150, variable-frequency microwave radiation is preferable because it reduces and/or eliminates (a) the build-up of a charge differential between different components in a microelectronic device, and (b) excess heat accumulation at localized portions of the device.

C. Additional Embodiments of Microelectronic Devices

FIG. 3is a schematic side cross-sectional view of a microelectronic device240in accordance with another embodiment of the invention. The illustrated microelectronic device240includes a microelectronic die242and an interposer substrate280carrying the die242. The microelectronic die242includes an integrated circuit244(shown schematically in broken lines), a doped region250within the integrated circuit244, an active side246, a backside248opposite the active side246, a plurality of terminals252(e.g., bond-pads) arranged in an array on the active side246, and a plurality of traces254electrically coupling the terminals252to the integrated circuit244. The doped region250of the integrated circuit244is a radiation sensitive component in the illustrated die242. As such, if the doped region250were exposed to the microwave radiation122(FIG. 2), the doped region250could be irreversibly altered. For example, the microwave radiation122may heat the doped region250such that the dopant atoms diffuse throughout the integrated circuit244and render the die242and the integrated circuit244defective. In other embodiments, the die242can include other radiation sensitive components in lieu of or in addition to the doped region250.

The interposer substrate280can be a printed circuit board or other support member for carrying the die242. In the illustrated embodiment, the interposer substrate280includes a first side282with a plurality of first contacts286and a second side284with a plurality of pads288. The first contacts286can be arranged in an array for electrical connection to corresponding terminals252on the die242. The pads288can be arranged in arrays to receive a plurality of electrical couplers (e.g., solder balls) to connect the interposer substrate280to an external device. The interposer substrate280further includes a plurality of conductive traces289electrically coupling the contacts286to corresponding pads288.

The illustrated microelectronic device240further includes (a) an adhesive260coupling the backside248of the die242to the first side282of the interposer substrate280, and (b) a barrier270disposed on the active side246of the die242. The adhesive260can be an adhesive film, epoxy, tape, paste, or other suitable material for bonding the die242to the interposer substrate280. In the illustrated embodiment, the adhesive260is a curable component that is cured via exposure to the microwave radiation122(FIG. 2) generated by the radiation generator120(FIG. 2). The barrier270is configured to shield the doped region250from irradiation during the curing process. Specifically, the barrier270is sized and positioned to reflect the microwave radiation122directed toward the doped region250and inhibit the radiation122from impinging upon the doped region250. The barrier270is also configured to minimize the reflection of microwave radiation directed toward the adhesive260so that the radiation generator120can irradiate and cure the adhesive260. For example, in the illustrated embodiment, the microwave radiation122can diffract around the barrier270such that the radiation122irradiates the section of the adhesive260below the doped region250but does not irradiate the doped region250. In other similar embodiments, the entire strip of adhesive260may not be irradiated depending on the thickness of the die242, the size and position of the barrier270, the position of the radiation generator120, and other factors.

D. Additional Embodiments of Barriers for Microelectronic Devices

FIGS. 4-6illustrate different configurations of barriers for use with microelectronic devices in accordance with several embodiments of the invention. For example,FIG. 4is a schematic isometric view of a microelectronic device340including a microelectronic die242and a barrier370encasing a portion of the die242. The illustrated die242is generally similar to the die242described above with reference toFIG. 3. For example, the die242includes an active side246, a backside248opposite the active side246, and a plurality of ends249(illustrated individually as249a-c) extending between the active side246and backside248. The illustrated barrier370covers a portion of the active side246, a portion of a first end249a, a portion of a second end249b, and a fourth end (not shown) of the die242.

FIG. 5is a schematic isometric view of a microelectronic device440including a barrier470covering only a portion of the active side246of the die242. The size and position of the barrier470are selected to inhibit irradiation of a radiation sensitive component(s) in the die242without unnecessarily reflecting radiation directed toward a curable component(s) in or proximate to the die242.

FIG. 6is a schematic isometric view of a microelectronic device540including a plurality of barrier members570(identified individually as570a-d) on the die242. The individual barrier members570are sized and configured to inhibit irradiation of the radiation sensitive component(s) within the die242. The illustrated barrier members570are spaced apart to minimize the reflection of radiation directed toward the curable component(s). Although the illustrated embodiment includes four barrier members570, in other embodiments, a different number of barrier members can be formed on the die242.

E. Additional Embodiments of Microelectronic Devices

FIG. 7is a schematic side cross-sectional view of a microelectronic device640in accordance with another embodiment of the invention. The microelectronic device640is generally similar to the microelectronic device240described above with reference toFIG. 3. For example, the microelectronic device640includes a microelectronic die642attached to an interposer substrate280. The illustrated microelectronic die642, however, includes an integrated circuit644(shown schematically in broken lines), a doped region250(shown schematically) in the integrated circuit644, and a barrier670in the integrated circuit644. In the illustrated embodiment, the barrier670performs several functions. For example, the barrier670can be a ground plane, one or more traces, or another conductive structure in the integrated circuit644such that the barrier670both (a) reflects radiation directed toward the doped region250, and (b) carries signals or provides a ground line within the integrated circuit644. As a result, the thickness of the barrier670must be sufficient to perform both requirements. In other embodiments, the barrier670may be positioned in the integrated circuit644but serve no purpose other than shielding the doped region250from radiation. In additional embodiments, the barrier670may be formed in the die642but not be part of the integrated circuit644.

FIG. 8is a schematic side cross-sectional view of a microelectronic device740in accordance with another embodiment of the invention. The microelectronic device740includes a substrate742, a contact pad744on the substrate742, a doped region750(identified as750a-b) over the contact pad744, and a barrier770shielding the doped region750. The illustrated doped region750includes a first doped material750aon the contact pad744and a second doped material750bstacked on the first doped material750a. The first and second doped materials750a-bare different materials separated by a diffusion zone751. The barrier770is positioned over the first and second doped materials750a-bto reflect and/or block radiation directed toward the doped materials750a-b. Accordingly, the barrier770inhibits radiation from irreversibly altering the doped region750, such as causing the dopant atoms in the first doped material750ato diffuse across the diffusion zone751and into the second doped material750b. In other embodiments, additional layers of doped material may be included in the doped region750.

From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. For example, many of the elements of one embodiment can be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the invention is not limited except as by the appended claims.