Antenna in package device having substrate stack

An antenna-in-package (AiP) device includes a substrate stack having a ceramic substrate attached to an organic substrate, where a dielectric constant of the ceramic substrate is higher than a dielectric constant of the organic substrate. An antenna is on a top side of the ceramic substrate. An integrated circuit (IC) die is flip chip attached to a bottom side of the ceramic substrate or to a top surface of the organic substrate. The IC die includes a radio circuit including at least a transmitter, and there is at least one interconnect for coupling the radio circuit to the antenna.

FIELD

This Disclosure relates to packaged semiconductor devices having integrated antennas.

BACKGROUND

The millimeter-wave (mmWave) frequency spectrum is generally defined to be 30 gigahertz (GHz) to 300 GHz, which corresponds to wavelengths from 10 mm to 1 mm. A number of communications applications such as uncompressed high definition video streaming, mobile distributed computing, wireless gaming, Internet access, and high data rate large file transfer can all be supported by communications using the mmWave frequency spectrum, such as using 60 GHz to 80 GHz radios. Typical antenna types for mmWave radio systems comprise reflector, lens, patch, dipole, slot, Vivaldi, dielectric resonator, and horn antennas.

An antenna-in-package (AiP) mmWave device combines an antenna (or antennas) with an integrated circuit (IC) radio die into a standard surface mounted chipscale package device, which miniaturizes the wireless system. The interconnection between the IC radio die and the antenna in the AiP device needs to provide a low return loss and low insertion loss over the signal frequency range. AiP is recognized as having a useful antenna arrangement for highly integrated mmWave radios for high-speed short-range wireless communications because of the relatively high gain and broad bandwidth generally provided.

Known AiP devices include several different configurations. At the package interface with the antenna, a high dielectric constant substrate such as a ceramic substrate typically being aluminum oxide (Al2O3) that has a relative dielectric constant (εr) of about 9.8, is helpful for enhancing antenna performance. Conventional packaging substrates comprise organic material layers (e.g., FR4 which is a composite material comprising woven fiberglass cloth with an epoxy resin binder that is flame resistant (self-extinguishing)) are popular because of their cost benefits, although they have more limited dielectric properties. Also, although ceramic substrates have higher εr values as compared to organic substrates which may have a typical εr value of about 3, they are more expensive. Ceramic substrates also generally provide better reliability as compared to organic substrates.

SUMMARY

Disclosed aspects solve performances problem for AiP devices. For example, there are performance requirements in high frequency (60 GHz to 80 GHz) communication applications, where it is generally difficult to achieve good device performance and cost efficiency with known AiP devices. In particular, efficient integrated antennas operating at mm-wave frequencies generally need a metallic reflector positioned away from the antenna at a distance λ/4, where λ is the wavelength. MmWave (also called millimeter band) is the band of spectrum between 30 GHz and 300 GHz.

At frequencies 60 GHz to 80 GHz the λ is around 5 mm in air and 3 mm in a dielectric material that has a typical εr=3. As a result, if one wants to provide an integrated antenna using the top metal layer of a typical multi-layer organic substrate that has an εr=3, the metallic layer reflector generally needs to be on the bottom metal layer of the organic substrate that is about 3 mm thick, which is too thick to implement in most applications. In addition, the lateral (x,y) dimensions of the antenna generally scale with the square root of εr, so that a lower dielectric constant organic substrate results in an increase in the lateral dimensions of the antenna, thus increasing of the overall area of the antenna.

Disclosed aspects include an AiP device comprising a substrate stack that enables high performance for AiP. The substrate stack comprise a ceramic substrate attached to an organic substrate, where the dielectric constant of the ceramic substrate is higher as compared to a dielectric constant of the organic substrate. An antenna is on a top side of the ceramic substrate. An IC die is positioned between the ceramic substrate and the organic substrate. A mold compound fills the gap between the ceramic substrate and the organic substrate. The IC die includes a radio circuit including at least a transmitter, and the ceramic substrate includes at least one interconnect (e.g., a copper filled through-via) for coupling the radio circuit to the antenna.

DETAILED DESCRIPTION

The high dielectric constant of a ceramic substrate of a disclosed substrate stack enables higher antenna performance (e.g., 13 GHz of bandwidth and 7 dBi of gain for a dielectric resonator antenna operating at 60 GHz) as compared to antenna performance using conventional organic substrates. As known in the art of antennas, when one calculates the gain of an antenna and compares it to an isotropic antenna the unit of the gain is dBi, where the ‘i’ stands for an isotropic antenna that by definition has a 0 dB power rating.

Substrate materials with high dielectric constant such as aluminum oxide can miniaturize the antenna size without degrading its performance, which is useful for applications needing small device form factors. Disclosed AiP devices can be offered at a lower cost as compared to AiP devices formed on typical ceramic substrates due to the lower cost organic substrate portion. Thus, disclosed AiP devices having ceramic/organic substrate stacks enable a cost competitive, high performance AiP device. The ceramic substrate with its relatively high dielectric constant improves the antenna performance, while the organic substrate provides cost advantages relative to ceramic substrates.

As used herein a ceramic material takes on its ordinary material science definition being an inorganic, non-metallic, often crystalline oxide, nitride or carbide material. The ceramic material generally withstands chemical erosion that occurs in other materials subjected to acidic or caustic environments, and the ceramic materials generally can withstand very high temperatures typically up to 1,000° C. to 1,600° C. As noted above one example ceramic material used for package substrates is aluminum oxide also known as alumina. An alumina substrate may include an organic binder and a plasticizer that are added to assist in its fabrication.

FIG. 1Ashows a cross-sectional depiction of an example AiP device100comprising an antenna140on a ceramic substrate130that is attached to an organic substrate120bonded below. A dielectric constant material of the ceramic substrate130is higher as compared to the dielectric constant of the organic substrate120. The IC die180is flip chip attached to a bottom side of the ceramic substrate130. The dielectric constant of the ceramic substrate130can be at least 3 times a dielectric constant of the organic substrate120.

The IC die180includes at least a transmitter182coupled to the antenna140. The ceramic substrate130includes a patterned metal layer131on one side of the ceramic substrate130and a patterned metal layer132on the opposite side of the ceramic substrate130. The metal layer131comprises metal traces including a trace136that is coupled to an antenna140. The metal layer132includes a metal pad133that is coupled to the trace136by a metal (e.g., copper) filled through-hole via (through-via)137, and a metallic reflector134is below the antenna140.

The interconnect path beside the via137may also include a coplanar waveguide (CPW) portion, and the trace136may comprise a microstrip between the IC die180and the antenna140that generally provides an impedance that matches an interconnect impedance to an impedance of the antenna for a maximum power transfer. As known in antenna theory, if the antenna is impedance matched to its feeding transmission line, then the input impedance of the transmission line does not depend on the length of the transmission line. A commonly used design rule is that the impedance matching is considered good when the return loss is lower than −10 dB in the band of operation.

The metal reflector134is not always needed, such as when the antenna140comprises a dielectric resonator antenna. The ceramic substrate130is generally 300 μm to 800 μm thick to provide a λ/4 spacing between the antenna140and the metal reflector134. The organic substrate120is generally 600 μm to 1,000 μm (1 mm) thick, so that in a typical embodiment the organic substrate120is thicker as compared to a thickness of the ceramic substrate130.

The IC die180includes a radio circuit185that comprises at least frequency synthesizing and driving circuitry181that is coupled to transmit circuitry182. The radio circuit185generally also includes receive circuitry so that a transceiver is provided. An output of the transmit circuitry182(and receive circuitry if provided) is coupled to a bond pad186on the IC die180that generally has a bonding feature thereon such as solder capped copper pillar that is connected to the metal pad133on the bottom surface of the ceramic substrate130. An input to the frequency synthesizing and driving circuitry181is coupled to a bond pad187on the IC die180that generally has a bonding feature thereon such as solder capped copper pillar that is connected to the metal pad135on the bottom surface of the ceramic substrate130that is coupled to a bottom side of the organic substrate120by a metal ball127coupled to a metal pad129and then a through-via123.

The organic substrate120includes a patterned bottom metal layer including metal pads121that have solder balls161thereon which collectively provide a BGA which enables mounting the AiP device100to another substrate, such as to land pads on a printed circuit board (PCB). Pads other than metal pad129on the top metal layer of the organic substrate120are shown coupled to a metal layer132shown on the bottom of the ceramic substrate130by the metal balls127. There is shown a mold compound190for filling the gap between the organic substrate120and the ceramic substrate130.

FIG. 1Bshows a cross-sectional depiction of an example AiP device150comprising an integrated antenna140on a ceramic substrate130attached to an organic substrate120. The IC die180is shown flip chip attached to a top surface (e.g., metal pads on a top metal layer) of the organic substrate120. The organic substrate120has metal pads124and126on its top surface.

FIG. 1Cshows a cross-sectional depiction of an example AiP device170comprising an integrated antenna140on a ceramic substrate130attached to a multi-level organic substrate shown as120a. The IC die180as inFIG. 1Ais flip chip attached to a bottom side of the ceramic substrate130. The AiP device170is shown including the multi-level organic substrate120ahaving at least one embedded IC172and at least one embedded passive device174.

One of the embedded ICs172is shown coupled to a metal pad129on the top side of the multi-level organic substrate120athat couples to the bond pad187on the IC die180, and one of the embedded passives174is also shown coupled to metal pad122on the top side of the multi-level organic substrate120a. The embedded IC172can comprise a low frequency circuit such as a power management circuit including a DC-DC converter or a voltage regulator, low frequency clocking circuit, or a logic circuit. The embedded passive device174can comprise a capacitor, an inductor, or a resistor. There is also shown a mmWave filter176located on the top surface of the ceramic substrate130coupled to the antenna140, that more generally can be positioned before or after the antenna140.

FIGS. 2A-2Hshow example steps for an assembly flow for forming a disclosed AiP device, such as the AiP device100shown inFIG. 1A, having an integrated antenna140on the ceramic substrate130attached to an organic substrate120, where the IC die180is flip chip attached to a bottom side of the ceramic substrate130. The IC die180is shown attached to the ceramic substrate130before the bonding together of the respective substrates130/120. InFIG. 2Athe ceramic substrate130is provided with a patterned metal layer131including antenna140and a patterned metal layer132including metal reflector134and metal pads139.

A non-conductive paste196that generally comprises an underfill material functioning as a die attachment is dispensed on the metal layer132lateral to the metal reflector134with the results shown inFIG. 2B. There are other forms of underfill dispense that also can be used, such as capillary underfill. As with the AiP device100shown inFIG. 1A, the metal layer131includes an antenna140. As shown inFIG. 2C, the IC die180including solder189as caps on the metal pillars188on the bond pads186and187is thermo-compression flip chip attached to the metal pads139on the ceramic substrate130through the non-conductive paste196. As known in the art of semiconductor device assembly, thermo-compression bonding is the most common method of flip chip attach with copper pillar interconnects. However other suitable bonding techniques may also be used.

Thermo-compression bonding is known to be a bonding technique generally useful for wafer to wafer bonding, not for bonding involving at least one package substrate bonding as disclosed herein, where thermo-compression bonding is also referred to as diffusion bonding, pressure joining, thermo-compression welding or solid-state welding. In thermo-compression bonding, two metals, are brought into atomic contact applying force and heat simultaneously. The diffusion generally needs atomic contact between the surfaces due to the atomic motion. The atoms migrate from one crystal lattice to the other one based on crystal lattice vibration. This atomic interaction sticks the interface together. The thermo-compression bonding with Al or Cu surfaces generally involves temperatures ≥400° C. to ensure sufficient hermetical sealing.

InFIG. 2Dan organic substrate120is shown provided with metal pads129its top surface.FIG. 2Eshows in-process result after metal balls127are formed on the metal pads129. The metal balls127in one specific arrangement can be nickel plated copper balls.FIG. 2Fshows in-the process AiP device after thermo-compression bonding of the ceramic substrate130to the organic substrate120, andFIG. 2Gshows the in-process AiP device following molding to form a mold compound190that fills a gap between the substrates, followed by forming metal balls161on the metal pads121on the bottom side of the organic substrate120with the result shown inFIG. 2H. Although suggested by the views shown inFIG. 2H, the metal balls127are not electrically connected to the metal reflector134.

FIGS. 3A-3Gshow example steps for an assembly flow for forming a disclosed AiP device, similar to the AiP device150shown inFIG. 1B, having an integrated antenna140on the ceramic substrate130attached to an organic substrate120, where the IC die180is flip chip attached to a top surface of the organic substrate120.FIG. 3Ashows a result after dispensing a non-conductive paste196on metal pads124,126on an organic substrate120.FIG. 3Bshows the step of thermo-compression flip chip attaching an IC die180so that the solder capped pillars189/188on the bond pads187of the IC die180attached to the metal pads124,126. The IC die180is thus attached to the organic substrate120before the bonding of the two substrates (the ceramic substrate130and the organic substrate120).

FIG. 3Cshows a ceramic substrate130provided with an antenna140on one side and a metal reflector134on the other.FIG. 3Dshows the ceramic substrate130after forming balls127on the metal pads133,138.FIG. 3Eshows the in-process AiP device after thermo-compression bonding of the two substrates120and130.FIG. 3Fshows the in-process AiP device after molding to form a mold compound190that fills a gap between the substrates120and130.FIG. 3Gshows the AiP device after forming a BGA161on a bottom side of the AiP device.

Advantages of disclosed AiP devices include the antenna140being on a ceramic substrate130having an εr of about 10, enables miniaturization of the antenna140as compared to when using a conventional organic substrate, without degrading performance. This also allows the placement of reflectors such as the metal reflector134on the backside of a relatively thin ceramic substrate130needed by most antenna types as compared to the thickness needed for λ/4 if one were to use a conventional organic substrate.

Moreover, attaching the IC die180to a ceramic substrate130having a relatively high dielectric constant provides better coefficient of thermal expansion (CTE) matching between the semiconductor substrate of the IC die180(which generally comprises silicon) and the ceramic substrate130. The organic substrate120lowers the package cost and has good coefficient of thermal expansion (CTE) match with a PCB. Also, low frequency circuits and passive devices such as resistors capacitors and inductors can be implemented in lower metal layer(s) of a multi-level organic substrate120a, such as shown inFIG. 1Cdescribed above.

Disclosed aspects can be integrated into a variety of assembly flows to form a variety of different AiP devices and related products. The semiconductor die may include various elements therein and/or layers thereon, including barrier layers, dielectric layers, device structures, active elements and passive elements including source regions, drain regions, bit lines, bases, emitters, collectors, conductive lines, conductive vias, etc. Moreover, the semiconductor die can be formed from a variety of processes including bipolar, insulated-gate bipolar transistor (IGBT), CMOS, BiCMOS and MEMS.

Those skilled in the art to which this Disclosure relates will appreciate that many variations of disclosed aspects are possible within the scope of the claimed invention, and further additions, deletions, substitutions and modifications may be made to the above-described aspects without departing from the scope of this Disclosure.