FIELD OF THE INVENTION

Embodiments of the invention relate generally to optoelectronic packaging assemblies, semiconductor device stacking assemblies, optical transceiver modules, and optical data transfer and communication.

BACKGROUND INFORMAT ION

The transition from electrical data transmission to optical data transmission between and among computers, chips, server boards, servers, and devices provides significant impro ements in bandwidth and distance over which a signal can be sent, but it presents challenges in areas such as thermal management, materials compatibility, optical alignment, and cost effectiveness. Assemblies incorporating hybrid lasers are being created that provide bandwidths of 00 Gbps for input/output between server racks combining compute, storage, and networking resources. These assemblies require that the optical transceiver modules be packaged in a manner that meets challenging performance demands, in general, the package for the semiconductor chip protects the chip from damage and supplies electronic connections that connect the

semiconductor chip to power supplies and other electronic components (performing, fo

example, input/output functions). As semi conductor chips trend toward igher bandwidth performance and end users need smaller form factors, the packaging of optoelectronic devices must meet size, thermal management, power delivery, interconnect density, cost, alignment, and integration challenges.

BRIEF DESCRIPTION OF THE FIGURES

The material described and illustrated herein is provided for purposes of exemplifying aspec ts of the invention and i s not meant to be limiting of the scope of the invention. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. Further, where appropriate, referenc labels ha e been repeated among figures to indicate corresponding or analogous elements. In the figures:

FIGURES 1 A~B are schematic diagrams illustrating views of an optoelectronic stacking packaging assembly employing an underfill dam.

FIGURES 2A-B are schematic diagrams illustrating views of an additional optoelectronic stacking packaging assembly employing an underfill dam.

FIGURES 3A-B are schematic diagrams illustrating views of an optoelec tronic packaging assembly employing an underfill dam. FIGURES 4A-B are sc hematic diagrams illustrating views of an additional optoelectronic packaging assembly employing an underfill dam.

FIGURE 5 is a schematic diagram of an optoelectronic laser chip.

FIGURES 6A-B are schematic diagrams of an optoelectronic packaging assembly including iens(es),

FIGURE 7 is a schematic diagram of an optoelectronic packaging assembly.

DETAILED DESCRIPTION OF THE IN VENTION

I the following description, specific details are presented to provide an understanding of embodiments of the invention. Embodiments may be practiced without one or more of these specific detaiis and frequently specific details of one embodiment may be practiced with other disclosed embodiments, as will be apparent to one of skill in the art. In other instances, well- know features are not described in detail i order to not obscure the description.

Optoelectronic packaging assemblies described herein are useful, for example, for optical dat transfer i high performance computing applications, board to board in data centers, memory to CPU, switeh/FPG A (field programmable gate array } for chip to chip interconnects, and memory extension. Embodiments of the inventio provide small form factors, lowered costs, and improved reliability fo optical data transfer.

Figure LA provides an optoelectronic packaging assembly in which an IC (integrated circuit) chip 100 is directly flip-chip bonded to a laser chip 105. In embodiments of the invention, the IC (integrated circuit) chip 100 (or die) is not directly bonded to the packaging substrate 1 10. The IC chip 100 is driver for laser chip 105, In embodiments IC chip 100 is a distributed drive and is capable of dri ving a plurality of optical modulators (not shown) in the laser chip 105 that can modulate a laser beam. In further embodiments of the invention, the driver IC chip 100 is a thinned die and has, for example, a thickness of 5O±! 0 pro (about 50 μηι) in its smallest dimension. Additionally, the driver IC chip 100 can be thinned to 50 pro or less in height or between 100 pm and 20 pro in height. Optionally, a thermal management

component 1 15, such as a heat spreader or heat, sink, is in thermal contact with a surface of the lase chip 105. Optionally, a layer of a material, such as a thermal interface material (not shown), is between the thermal management component 1 15 and the laser chip .105, Optionally, the laser chip 105 comprises optical components 120 that steer light 121 out of the laser chip 105, Optical components 120 direct laser light from laser chip 105 and can be optics that turn the light 90 degrees, such as 45 degree mirrors. Electrically conducting pillars, bumps, pins, or posts 125 on laser chip 105 join up with corresponding electrically conducting pillars, bumps, pins, or posts 130 on driver chip ΪΟ0 and electrically operably couple laser chip 1 5 with driver chip 100. Conducting pillars, bumps, pins, or posts 135 on laser chip 105 join up with conducting pillars, blimps, pins, or posts 140 on the packaging substrate 1 10 and operably electrically couple laser chip 105 with substrate 1 10. Conducting pillars, bumps., pins, or posts 125 and 135 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 130 and 140, respectively, through optional solde material 145 and 147. In alternate embodiments, no solder material 145 and 147 is present and the conducting pillars, bumps, pins, or posts 125 and 135 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 330 and 140, respecti vely, through a

thermocompression bonding, thermosonic bonding, and/or epox bonding process, for example.

The surface of laser chip 105 also comprises a chip-on-substrate dam 150. An

underfill 155 is placed between substrate 1 10 and laser chip 105, Chip-on-substrate dam 150 aids in preventing the flow of underfill 155 into the optical overhang area 160 of laser chip 105 during an underfill fill process, such as, for example, a capillary underfill process.

Chip-on-substrate dam 150 is optionally bonded to a corresponding metal region 165 of packaging substrate 1 10 through, for example, solder material 148. Other bonding materials are possible. Optional metal region 165 is not operably electrically connected to packaging substrate 1 10.

I additional embodiments, the surface of the laser chi 1 5 comprises a chip-on-chip dam 170. An underfill layer 175 is placed between laser chip 1 5 and I chip 1 0. The chip-on-chip dam 170 aids in preventing the flow of underfill 1 75 into unwanted areas during a underfill fill process, such as, for example, a capillary underfill process

Optionally, packaging substrate 110 comprises a passivation layer 80 on a surface.

Passivation layer 1 SO can comprise features 1 SI that provide boundaries for solder material and underfill layers. Features 181 can be, for example, raised regions, bumps, or pillars.

A connector 185 connects the package substrate 1 10 to board 190. The connector 185 is, for example, an electrical connector that allows the optoelectronic assembly package to be removably attached to the board 1 0, such as a low insertion force (LIF) connector or a socket connector. Board .190 provides electrical connections to other IC devices, such as. for example, processors and/or memory and is, for example a printed circuit board or other ty pe of motherboard or server board.

Figure I B is a view of a side of the laser chip 1.05 and the view does not include the IC chip 100 and the packaging substrate 1 10. In the view of Figure IB a larger number of conducting pillars 135 that join up with conducting posts 140 on the packaging substrate 1 10 have been provided. Additionally, in the view of Figure 1 B a larger number of conducting pillars 125 thai join up with conducting posts 130 on the IC chip 100 have been provided. Oilier numbers conducting pillars 125 and 135 are also possible. The chip-on -substrate dam 150 and the chip-on-chip dam 170 are also visible m Figure IB. Optical transmission holes 195 allow laser Sight to exit laser chip 105. In embodiments of the invention, optical transmission holes 1.95 are vertically inverted taper holes.

Figure 2A illustrates a additional optoelectronic packaging assembly in which an IC chip 200 is directly flip-chip bonded to a laser chip 205. In embodiments of the invention, the IC chip 200 is not directly bonded to the packaging substrate 210. The IC chip 200 is a driver for laser chip 205. In embodiments IC chip 200 is a distributed driver and is capable of driving a plurality of optical modulators (not shown) that ca modulate a laser beam in the laser chip 205. in further embodiments of the invention, the driver IC chip 200 is a thinned die and has, for example, a thickness of 50±I0 μιη (about 50 μηι) in its smallest dimension. Additionally, the dri ver IC chip 200 can be thinned to 50 urn or less in height or between 100 μιη and 20 pm in height. Optionally, a thermal management component 215, such as a heat spreader or heat sink, is in thermal contact wi th a surface of the laser chip 205. Optionally, a layer of a ma terial, such as a thermal interface material (not shown), is between the thermal management component 2 i 5 and the laser chip 205. Optionally, the laser chip 205 comprises optical components 220 that steer light 221 out of the laser chip 205. Optical components 220 direct laser light from laser chip 205 and can be optics that turn the light 90 degrees, such as 45 degree mirrors. Electrically conducting pillars, bumps, pins, or posts 225 on laser chip 205 join up with corresponding electrically conducting pillars, bumps, pins, or posts 230 on driver chip 200 and electrically operably couple laser chip 205 with driver chip 200. Conducting pillars, bumps, pins, or posts 235 on laser chip 205 join up with conducting pillars, bumps, pins, or posts 240 on the packaging substrate 210 and operably electrically couple laser chip 205 with substrate 210. Conducting pillars, bumps, pins, or posts 225 and 235 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 230 and 240, respectively, through an optional solder material 245 and 247. In alternate embodiments, no solder material 245 and 247 is present and the conducting pillars, bumps, pins, or posts 225 and 235 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 230 and 240, respectively, through a tberinocompression bonding, fhermosonic bonding, and/or epoxy bonding process, for example.

The surface of laser chip 205 also comprise a cMp-oa-substrate dam 250. An

underfill 255 is placed between substrate 210 and laser chip 205. Chip-on-subsnrate dam 250 aids in preventing the flow of underfill 255 into the optica! overhang area 260 of laser chip 205 during an underfill fill process, such as, for example, a capillary underfill process.

In additional embodiments, the surface of the laser chip 205 comprises a chip-on-chip dam 270. An underfill layer 275 is placed between laser chip 205 and IC chip 100. The chip-on-chip dam 270 aids in preventing the flow of underfill 275 into unwanted areas during an underfill fill process, such as. for example, a capillary underfill process

Optionally, packaging substrate 210 comprises a passivation layer 280 on a surface.

Passivation layer 2S0 can comprise features 2S1 that provide boundaries for solder material and underfill layers. Features 281 can be, for example, raised regions, bumps, or pillars.

A connector 285 connects the package substrate 210 to board 290. The connector 285 is, for example, an electrical connector that allows the optoelectronic assembly package to be removably attached to the board 290, such as a L1F connector or a socket connector. Board 290 pro vides electrical connections to other IC dev ices, such as, for example, processors and/or memory and is, for example a printed circuit board or other type of motherboard or server board.

Figure 2B is a view of a side of the laser chip 205 and the view does not include the IC chip 200 and the packaging substrate 210. In the view of Figure 2B a larger number of conducting pil lars 235 that join up wi th conducting posts 240 on the packaging substrate 210 have been provided. Additionally; in the view of Figure 2B a larger number of conducting pillars 225 that join up with conducting posts 230 on the IC chip 200 have been provided. Other numbers conducting pillars 225 and 235 are also possible. The chip-on-substrate dam 250 and the chip-on-chip dam 270 are also visible in Figure 2B. Optical transmission holes 295 allow laser light to exit laser chip 205. In embodiments of the invention, optical transmission

holes 295 are vertically inverted taper holes.

Figure 3A illustrates an additional optoelectronic packaging assembly in which a detector chip 305 (or die) is bonded to a package substrate 310. Optionally, a thermal management component 315, such as a heat spreader or a heat sink, is in thermal contact with a surface of the detector chip 305. Further optionally, a layer of a material, such as a therma! interface material (not shown) is between the thermal management component 315 and the detector chip 305. The detector chip 305 can comprise optional optical components 320 that steer light 321 into the one or more photodetectors (or photosensors) present in detector chip 305. Optical components 320 can be optics that turn light 90 degrees, such as 45 degree mirrors. Othe numbers of optical components 320 are also possible. In further alternate embodiments, the laser light can enter the chip without being turned 90 degrees and it is possible that no mirrors are present. Electrically conducting pillars, bumps, pins, or posts 335 on defector chip 305 joi up with conducting pillars, bumps, pins, or posts 340 on the packaging substrate 310 and operably electrically couple detector chip 305 with substrate 310. Conducting pillars, bumps, pins, or posts 335 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 340 through an optional solder material 347. In alternate embodiments, no solder material 3 7 is present and the conducting pillars, bumps, pins, or posts 335 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or posts 340,

respectively, through a thermocompression bonding, thermosonic bonding, and/or epoxy

bonding process, for example,

The surface of detector chip 305 also comprises a chip-on-subslrate dam 350. An underfill 355 is placed between substrate 310 and detector chip 305. Chip-cm-substrate dam 350 aids i preventing the flow of underfill 355 into the optical overhang area 360 of detector chip 305 during an underfill fill process, such as, for example, a capillary underfill process. Chip-on-substrate dam 350 is optionally bonded to a corresponding metal region 365 of

packaging substrate 310 through, for example, solder material 348. Other bonding materials are possible. Optional metal region 365 is not operabSy electrically connected to packaging substrate 310.

Optionally, packaging substrate 310 comprises a passivatio layer 380 on a surface.

Passivation layer 380 can comprise features 381 that provide boundaries for solder material and underfill layers. Features 381 can be. for example, raised regions, bumps, or pillars.

A connector 385 connects the package substrate 310 to board 390. The connector 385 is, for example, an electrical connector that allows the optoelectronic assembly package to be removably attached to the board 390, such as a LIF connector or a socket connector . Board 390 provides electrical connections to other 1C devices, such as, for example, processors and/or memory and is, for example a printed circuit board or other type of motherboard or server board.

Figure 3B is view of a side of the detector chip 305 and the view does not include the packaging substrate 310. In the view of Figure 3B a larger number of conducting pillars 335 that join up with conducting posts 340 on the packaging substrate 310 have been provided. Other numbers conducting pillars 335 are also possible. The chip-on-substrate dam 350 is aiso visible in Figure 3B. Optical transmission holes 395 allow laser light to enter detector chip 305. In embodiments of the invention, optical transmission holes 395 are vertically inverted taper holes.

Figure 4A illustrates a further optoelectronic packaging assembly in which a detector chip 405 (or die) is bonded to a package substrate 410. Optionally, a thermal management component 415, such as a heat spreader or heat sink, is in thermal contact with a surface of the detector chip 405. Further optionally, a layer of a material, such as a thermal interface material (not shown) is between the thermal management component 415 and the detector chip 405. The detector chip 405 can comprise optical components 420 that steer light 421 into the one or more photodetectors (or photosensors) in detector chip 405. Optical components 420 can be optics that turn light 90 degrees, such as 45 degree mirrors. Other numbers of optical components 420 are also possible, in further alternate embodiments, the laser light can enter the chip without being turned 90 degrees and it is possible that no mirrors are present. Electrically conducting pillars, blimps, pins, or posts 435 on detector chip 405 join up with conducting pillars, bumps, pins, or posts 440 on the packaging substrate 410 and operabSy electrically couple detector chip 405 with substrate 410. Conducting pillars, bumps, pins, or posts 435 are electrically connected and joined with corresponding conducting pillars, humps, pins, or posts 440 through an optional solder material 447. In alternate embodiments, no solder material 447 is present and the conducting pillars, bumps, pins, or posts 435 are electrically connected and joined with corresponding conducting pillars, bumps, pins, or post 440, respectively, through a

thermocompression bonding, thermosomc bonding, and/or epox bonding process, for example.

The surface of detector chip 405 also comprises a chip-on-substrate dam 450. An underfill 455 is placed between substrate 410 and detector chip 405. Chip-on-substrate dam 450 aids in preventing the flow of underfill 455 into the optical overhang area 360 of detector chip 405 during an underfill fill process, such as, for example, a capillary underfill; process.

Optionally, packaging substrate 410 comprises a passivation layer 480 on a surface.

Passivation layer 480 can comprise features 381 that provide boundaries for solder material and underfill layers. Features 481 can be, for example, raised regions, bumps, or pillars.

A connector 485 connects the package substrate 410 to board 490, The connector 485 is, for example, an electrical connector that allows the optoelectronic assembly package to be removably attached to the board 490, such as a LTF connector or a socket connector. Board 490 provides electrical connections to other IC devices, such as, for example, processors and/or memory and is, for example a printed circuit board or other type of motherboard or server board.

Figure 4B is a view of a side of the detector chip 405 that is operably coupled to the packaging substrate 410. in the view of Figure 4B a large number of conducting pillars 435 that join up with conducting posts 440 on the packaging substrate 410 have been provided. Other numbers conducting pillars 435 are also possible. The chip-on-substrate dam 450 is also visible in Figure 4B. Optical transmission holes 495 allow laser light to enter detector chip 405.

Figure 5 diagrams interior ieatures of a laser chip 505. Laser chip 505 is comprised of lasers 510 and waveguides 515 that conduct light .from lasers 510 to optional optica!

components 520. Optical components 520 direct laser light from laser chip 505 and can be optics that turn the light 90 degrees, such as 45 degree mirrors. Other numbers of optical components 520 are also possible. Laser light is output in a direction perpendicular to the direction the light travels though waveguides 51 . In further alternate embodiments, the laser light can exit from the chip in a direction parallel to the direction light travels through

waveguides 515. In embodiments of the invention, lasers 510 are, tor example, vertical cavity surface emitting lasers (VCSELs), diode lasers, or hybrid semiconductor lasers. Hybrid semiconductor lasers are laser devices that comprise both silicon optical elements and light-emitting elements. The light-emitting elements can be, for example, comprised of indium phosphide. Although 12 lasers 510 are shown, other numbers of lasers 51.0 are possible. In embodiments of the invention, laser chip 505 comprises from 2 to 32 lasers. A plurality of optical modulators 525 are provided for each waveguide 515. In embodiments of the invention, 2 to 20, 5 to 15, or 7 to 15 optical modulators are provided for each waveguide 515.

Figure 6 A illustrates the optical overhang region of an optoelectronic package assembly. The optical overhang region is the region of the optoelectronic chip that extends beyond the packaging substrate. Laser chip 605 and detector chip 607 are packaged on packaging substrate 610. The optical overhang areas of laser chip 605 and detector chip 607 allow attachment of lens pieces 615 and 616 for Sight input/output into one or more optical input/output coupling assemblies (not shown). The optical input¼itput coupling assembly (not shown) interconnects an optoelectronic assembly with, for example, fiber optic cables having connector assemblies on both ends that when connected to another device allow the device that an optoelectronic package is incorporated into to optically communicate (transfer data to and receive data from) the other device. In embodiments of the invention, lens pieces 615 and 16 comprise silicon. Figure 6B is a view of a different side of an optoelectronic chip 605 and an attached lens 615 (the assembly is similar for optoelectronic chip 60? and lens piece 616). Lens pieces 615 and 616 comprise a plurality of lenses 6Ϊ 8. Although twelve lenses 618 are shown, other larger or smaller numbers of lenses 18 are also possible. Optionally, the lenses 618 are pari of a multi-lens array on lens pieces 615 and 616. The lenses 618 are aligned with laser chip 605 (or detector chip 607) vertically inverted taper holes, for light output (or input) and attached to laser chip 605 (or detecior chip 60?) through bonding material 620. In embodiments of the invention, the bonding material 620 is a low- temperature curable adhesive, such as a TCP (non-conductive paste) or NCF (non-conductive film) adhesive material. The bond between a lens piece 615 or 616 can be formed, for example, using a low-temperature curable adhesive through a thermo-compression bonding process using z-height control. In embodiments of the invention, the lens pieces 615 and 616 are provided with alignment fiducial s that correspond to alignment fiducials o laser chip 605 or detector chip 607.

Figure 7 illustrates an optoelectronic package assembly in which a packaging substrate 710 comprises laser chip 705 and detector chip 707. A laser driver 700 is located between the packaging substrate 710 and the laser chip 705. The laser driver 700 is operabiy coupled to the laser chip 705. A receiver chip 715 is operabiy coupled to the detector chip 707 through the packaging substrate 710. The receiver chip 715 can comprise, for example, transtmpedance amplifiers for each channel of data input. In general, a transimpedance amplifier (T A) converts a current signal from a photodeteetor into a voltage signal and amplifies it The receiver chip 715 can also comprise, a plurality of amplifiers in series (per transimpedance amplifier) that amplify the signals from the transimpedance amplifiers. Lens pieces 720 and 721 are attached to laser chip 705 and detector ch p 707, respectively. A microcontroller chip 725 and bias iC dies 730 (for voltage regulation) are also provided on the packaging substrate. In alternate embodiments, some or all of the functions of the receiver chip 715 microcontroller chip 725 and bias IC dies 730 are combined into erne die. In further alternate embodiments, the receiver chip 715 is directly connected to detector chip 707 m a stacking assembly m which the receiver chip 715 is not directly attached to the packaging substrate 710

Electrically conducting pillars, bumps, pins, or posts are comprised of a conducting material such as, for example, a metai such as copper, gold, aluminum, tungsten, platinum, or an alloy thereof. Electrical interconnections and metal-metal bonding between conducting pillars, pads, bumps, columns, pins, or other conducting structures, that are formed without solder, can be accomplished, for example, through thennoeompression bonding, thermosontc bonding, and/or epoxy bonding of the chips, in embodiments of the invention, the pillars, pads, bumps, columns, pins, or other conducting structures can be comprised of gold or copper and

thennocompression bonding is used to join them. Passivation layers can he comprised of, for example, S1O2, SiN, and SiON. Underfill material can be, for example, fiowable dielectric material, such as, for example, an epoxy with or without filler particles, or a polymer or inorganic material with or without filler panicles.

A detector chip is a substrate comprising one or more photosensors or photodetectors. in embodiments of the invention the detector chip comprises a plurality of photodetectors, such as, for example, 2 to 32 photodetectors. Photosensors and photodetectors include, for example, avalanche photodiodes or PIN diodes.

Persons skilled in the relevant art appreciate that modifications and variations are possible throughout the disclosure as are substitutions for various components shown and described. Reference throughout this specification to "erne embodiment" or "an embodiment" means that a particula feature, structure, material, or characteristic described in connection with th embodiment is included in at least one embodiment of the invention, but does not necessarily denote that they are present in every embodiment. Various additional layers and/or structures may be included and/or described features may be omitted in other embodiments.