High-speed signaling interface with broadside dynamic wave coupling

A contact-less high-speed signaling interface and method provide for the communication of high-speed signals across an interface, such as a die-substrate interface or die-die interface. The interface includes a transmission-line structure disposed on a dielectric medium to carry a high-speed forward incident signal, and another transmission-line structure disposed on another dielectric medium and substantially aligned with the other transmission-line structure to generate a coupled high-speed signal in a direction opposite to the incident signal.

TECHNICAL FIELD

The present invention pertains to semiconductor packaging, and in particular to high-speed signaling across an interface, such as a die-substrate interface or a die-die interface.

BACKGROUND

Semiconductor devices, such as a die or chip, are typically coupled with a substrate made from organic-type or ceramic-type material. The substrate may provide power and ground to the semiconductor devices as well as communication paths for I/O data signals. As semiconductor devices operate at continually higher data rates and higher frequencies, high-speed communications are necessary between a die and substrate, or between two dies. Conventional interfaces between a semiconductor device and a substrate and conventional interfaces between two semiconductor devices, typically utilize bonding wires, vias, solder bumps, and/or controlled-collapsed-chip-connections (e.g., C4). One problem with these conventional interfaces is that they are typically capacitive or inductive resulting in the inability to effectively communicate high-speed and/or high-frequency signals. For example, bond wires and vias can be inductive. Another problem with these conventional interfaces is that they typically have a narrow bandwidth inhibiting communication of broadband or wideband signals. Because high-speed digital signals may have a broad frequency spectrum, the use of conventional interfaces may be unsuitable for present and future die substrate and die-die data signal communications.

Another problem with conventional die-substrate interfaces is the coefficient of thermal expansion (CTE) mismatch between a die and a substrate. This mismatch may result in excessive mechanical stresses on the semiconductor device and may result in reliability problems. Yet another problem with conventional die-substrate and die-die interfaces is that conventional signaling typically uses the low-frequency portion of the electromagnetic spectrum resulting in high power consumption.

Thus there is a general need for an improved interface for high-speed signaling.

DETAILED DESCRIPTION

The following description and the drawings illustrate specific embodiments of the invention sufficiently to enable those skilled in the art to practice it. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The scope of the invention encompasses the full ambit of the claims and all available equivalents.

FIG. 1is a block diagram of a system utilizing a contact-less high-speed signaling interface in accordance with an embodiment of the present invention. System100may be part of any processing or computing system, or other electronic device, which utilizes high-speed signaling between components. For example, die102may communicate high-speed digital signals with substrate104over interface106. Die102may be a semiconductor chip or die, and may be comprised of, for example, Silicon, Germanium, Silicon Germanium, Silicon Carbide, Gallium Arsenide, Gallium Nitride, Indium Arsenide, Indium Phosphide, Sapphire, Diamond, and combinations thereof. Die102may alternatively be an organic or ceramic substrate. Substrate104may also be a semiconductor chip or die, or an organic or ceramic substrate. Accordingly, interface106may be used for die to die as well as die to substrate communications.

Signaling interface106may be a contact-less high-speed signaling interface and may comprise transmission-line structure (TLS)110disposed on die102and transmission-line structure (TLS)112on substrate104. For signals sent from die102to substrate104, transmission-line structure110may propagate a high-speed forward incident signal in a forward direction, while transmission-line structure112may generate a coupled high-speed signal in a reverse direction to the high-speed forward incident signal. For signals sent from substrate104to die102, transmission-line structure112may propagate a high-speed forward incident signal in a forward direction, while transmission-line structure110may generate a coupled high-speed signal in a reverse direction to the high-speed forward incident signal. Transmission-line structures110and112may be substantially aligned with each other to efficiently generate the coupled signal. Embodiments of signaling interface106are described in more detail below.

Accordingly, high-speed digital communication may be achieved over a contactless interface, which may be between two dies, or a die and a substrate. This may be particularly beneficial when the die and substrate have significantly different coefficients of thermal expansion (CTE) as in the case of a semiconductor die or chip and an organic substrate. It should be noted that the illustration of system100, including interface106, is a functional illustration and may not be representative of an actual physical implementation.

In one embodiment, die102may include signal processing element114which may process the coupled signal received from interface106to generate substantially the original digital signal provided to interface106from substrate104. For example, element114may perform an integration on the signal to compensate at least for some of the differentiating effects on the signal resulting from the coupling. The processed signal may be provided to system elements116. Substrate104may also include a signal-processing element (not illustrated), which may process the coupled signal received from interface106. System elements116may include any system element not illustrated including processors, memory I/O, etc.

In one embodiment, die102may also include radio module (RM)118which may modulate a data signal on a high frequency carrier for transmission across interface106. The carrier frequency may be within the coupling bandwidth of the interface. In this embodiment, radio module118may also be used to demodulate a modulated data signal received across interface106from substrate104.

Although system100is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software configured elements, such as processors including digital signal processors (DSPs), and/or other hardware elements. Although a single interface106is illustrated, in other embodiments of the present invention, additional interfaces may provide additional communication paths between die102and substrate104.

Embodiments of the present invention include an improved interface and method for high-speed signaling. In some embodiments, the interface and method may not necessarily require electrical contact between a die and substrate, or a die and another die. In some embodiments, the interface and method may be suitable for high-speed communications between a die and a substrate, or a die and another die. In some embodiments, the interface and method does not necessarily require matched CTEs between a die and substrate. In some embodiments, the interface and method may provide broadband communications between a die and a substrate, or a die and another die. In some embodiments, the method and interface may reduce power consumption by avoiding low-frequency portions of the electromagnetic spectrum. In some embodiments, the interface and method provide a good impedance match for high-speed signals.

FIG. 2illustrates a broadside-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Signaling interface200may be suitable for use as signaling interface106(FIG.1). Signaling interface200is comprised of transmission-line structure202which may be located on a die or a substrate (e.g., die102(FIG.1)), and transmission-line structure204which may be located on another die or another substrate (e.g., substrate104(FIG.1)). In this broadside-coupled embodiment, transmission-line structure202may be a planar transmission-line structure comprised of conductive elements residing in a first plane, and transmission-line structure104may be a planar transmission-line structure comprised of conductive elements residing in a second plane. The second plane may be substantially parallel to the first plane so that coupling region206of the transmission-line structures are in an above and below orientation, (e.g., on top of each other) to provide broadside coupling. In the illustration, transmission-line structure202may reside in the plane of the paper, while transmission-line structure204may reside in a plane either above or below the paper. In one embodiment, gap201may be provided between the transmission-line structures in the coupling regions. The gap may be comprised of air, vacuum or a dielectric, for example. Examples of broadside-coupled interfaces are described in more detail below.

As illustrated, transmission-line structure202may propagate/carry a high-speed forward incident signal in direction212and transmission-line structure204may generate a coupled signal in reverse direction214. Transmission-line structure202may have termination210at an end of transmission-line structure202to terminate the high-speed forward incident signal. Termination210may be a broadband resistive termination (e.g., an integrated resistive film) to substantially reduce reflections of the high-speed forward incident signal. Transmission-line structure204may have termination208at an end of transmission-line structure204. Termination208may also be a broadband resistive termination.

In one embodiment, the terminations may be selected for matched operation of the interface to provide a coupling factor of approximately less than −3 dB. This may have advantages in feedback control between cascaded components of a communication channel, and may permit load-independent matching of the interface. In addition, a matched termination may provide an increased immunity of the system to noise and electrostatic discharge (ESD) effects.

In one embodiment, coupling region206may have a length being approximately a quarter-wavelength of an arithmetic mean of odd and even mode guided wavelengths at about the center frequency of operation. Therefore, depending on the specific dielectric environment, an operational frequency range of 20 to 60 GHz, for example, may be achieved. This permits broadband operation with a large relative bandwidth. In some embodiments, a signaling technique that uses pulse amplitude modulation (PAM) may be used with an appropriate carrier.

FIG. 3illustrates an edge-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Signaling interface300may be suitable for use as signaling interface106(FIG.1). Signaling interface300is comprised of transmission-line structure302which may be located on a die or a substrate (e.g., die102(FIG.1)), and transmission-line structure304which may be located on another die or another substrate (e.g., substrate104(FIG.1)). In this edge-coupled embodiment, transmission-line structure302may be a planar transmission-line structure comprised of planar elements residing in parallel planes, and transmission-line structure304may be a planar waveguide comprised of corresponding planar elements also residing in corresponding planes. Corresponding planar elements of transmission-line structures302and304may be substantially aligned to provide edge coupling in coupling region306. In this embodiment, each transmission-line structure302and304may have planar elements residing in parallel planes.

For example, transmission-line structure302may have planar elements residing in both the plane of the paper and one or more planes either above and/or below the paper. Transmission-line structure304may have corresponding planar elements residing in both the plane of the paper and one or more planes either above and/or below the paper. In one embodiment, gap301may be provided between the transmission-line structures in the coupling regions. The gap may be comprised of air, vacuum or a dielectric, for example. Examples of broadside-coupled interfaces are described in more detail below. As illustrated, transmission-line structure302may propagate/carry a high-speed forward incident signal in direction312and transmission-line structure304may generate a coupled signal in reverse direction314. Transmission-line structure302may have termination310at an end of transmission-line structure302to terminate the high-speed forward incident signal. Termination310may be a broadband resistive termination to substantially reduce reflections of the high-speed forward incident signal. Transmission-line structure304may have termination308at an end of transmission-line structure304. Termination308may also be a broadband resistive termination.

In embodiments, the transmission-line structures may have a narrower width in the coupling regions (e.g., regions206,306) and may have a wider width outside the coupling regions. The coupling regions of the transmission-line structures may be in almost any shape, and in some embodiments, may be in a spiral shape, an “S” shape, a straight line (as illustrated) or a curved line. In embodiments, interfaces200and300may operate similar to a microwave directional coupler.

FIG. 4illustrates a cross-section of a coupling region of a broadside-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Cross-section400illustrates one example of a cross-section that may correspond with a cross section of coupling region206of interface200(FIG.2). In this embodiment, transmission-line structures410and412are coplanar waveguides residing in separate parallel planes. In this embodiment, die402may correspond with die102(FIG.1), and transmission-line structure410may correspond with transmission-line structure110(FIG. 1) and transmission-line structure202(FIG.2), while substrate404may correspond with substrate104(FIG.1), and transmission-line structure412may correspond with transmission-line structure112(FIG. 1) and transmission-line structure204(FIG.2). In one embodiment, transmission-line structures410and412may comprise finite ground coplanar waveguides (FGCPW). Center conductors414,416may be substantially aligned in the coupling region to provide broadside coupling. Nothing requires that the conductors of transmission-line structure410be the same size as conductors of transmission-line structure412. Furthermore, the impedance of transmission-line structures410and412may be different. Gap401may be provided between die402and substrate404in the coupling region.

FIG. 5illustrates a cross-section of a coupling region of a broadside-coupled contact-less high-speed signaling interface in accordance with another embodiment of the present invention. Cross-section500illustrates another example of a cross-section that may correspond with a cross section of coupling region206of interface200(FIG.2). In this embodiment, transmission-line structures510and512are comprised of coplanar strips residing in separate parallel planes. In this embodiment, die502may correspond with die102(FIG.1), and transmission-line structure510may correspond with transmission-line structure110(FIG. 1) and transmission-line structure202(FIG.2), while substrate504may correspond with substrate104(FIG.1), and transmission-line structure512may correspond with transmission-line structure112(FIG. 1) and transmission-line structure204(FIG.2). In this embodiment, transmission-line structures510and512may comprise a pair of differential signaling lines residing in parallel planes. In yet another embodiment, transmission-line structures510and512may also comprise a single-ended transmission line residing in parallel planes with one of the strips serving as a reference conductor. It should be noted that nothing requires that the conductors of transmission-line structure510be the same size as conductors of transmission-line structure512. Furthermore, the impedance of transmission-line structures510and512may be different. Gap501may be provided between die502and substrate504in the coupling region.

FIG. 6illustrates a cross-section of a coupling region of a broadside-coupled contact-less high-speed signaling interface in accordance with another embodiment of the present invention. Cross-section600illustrates yet another example of a cross-section that may correspond with a cross section of coupling region206of interface200(FIG.2). In this embodiment, transmission-line structures610and612are microstrip transmission lines having signal tracks614and616residing in different parallel planes. In this embodiment, the microstrip structures may have reference conductors618and620, which may reside in opposite parallel planes. Reference conductors618and620may, for example, be ground planes. Signal conductors614,616may be substantially aligned in the coupling region to provide broadside coupling. In this embodiment, die602may correspond with die102(FIG.1), and transmission-line structure610may correspond with transmission-line structure110(FIG. 1) and transmission-line structure202(FIG.2), while substrate604may correspond with substrate104(FIG.1), and transmission-line structure612may correspond with transmission-line structure112(FIG. 1) and transmission-line structure204(FIG.2). Nothing requires that the conductors of transmission-line structure610be the same size as conductors of transmission-line structure612. Furthermore, the impedance of transmission-line structures610and612may be different. Gap601may be provided between die602and substrate604in the coupling region.

FIG. 7illustrates a cross-section of a coupling region of an edge-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Cross-section700illustrates one example of a cross-section that may correspond with a cross section of coupling region306of interface300(FIG.3). In this embodiment, transmission-line structures710and712are stripline structures with reference conductors706and708residing substantially in one plane, reference conductors718and720residing substantially in another plane, and signal conductors714and716residing substantially in yet a third plane. In this embodiment, die702may correspond with die102(FIG.1), and transmission-line structure710may correspond with transmission-line structure110(FIG. 1) and transmission-line structure302(FIG.3), while die704may correspond with substrate104(FIG.1), and transmission-line structure712may correspond with transmission-line structure112(FIG. 1) and transmission-line structure304(FIG.3). Center conductors714,716may be substantially aligned in the coupling region to provide edge coupling. Nothing requires that the conductors of transmission-line structure710be the same size as conductors of transmission-line structure712. Furthermore, the impedance of transmission-line structures710and712may be different. Gap701may be provided between die702and die704in the coupling region.

In this embodiment, die702and die704may be coupled to substrate722by a conventional attachment technique, such as by solder or bond wires. In one embodiment, substrate722may be a substrate for a multichip module.

FIG. 8illustrates a cross-section of a coupling region of an edge-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Cross-section800illustrates one example of a cross-section that may correspond with a cross section of coupling region306of interface300(FIG.3). In this embodiment, transmission-line structures810and812are microstrip structures with reference conductors818and820residing substantially in one plane, and signal conductors814and816residing substantially in another plane. In this embodiment, die802may correspond with die102(FIG.1), and transmission-line structure810may correspond with transmission-line structure110(FIG. 1) and transmission-line structure302(FIG.3), while die804may correspond with substrate104(FIG.1), and transmission-line structure812may correspond with transmission-line structure112(FIG. 1) and transmission-line structure304(FIG.3). Signal conductors814,816may be substantially aligned in the coupling region to provide edge-side coupling. Nothing requires that the conductors of transmission-line structure810be the same size as conductors of transmission-line structure812. Furthermore, the impedance of transmission-line structures810and812may be different. Gap801may be provided between die802and die804in the coupling region.

In this embodiment, die802and die804may be coupled to substrate822by a conventional attachment technique, such as by solder or bond wires. In one embodiment, substrate822may be a substrate for a multichip module.

FIG. 9illustrates a cross-section of a coupling region of an edge-coupled contact-less high-speed signaling interface in accordance with an embodiment of the present invention. Cross-section900illustrates one example of a cross-section that may correspond with a cross section of coupling region306of interface300(FIG.3). In this embodiment, transmission-line structures910and912are stacked microstrip structures with reference conductors918and920residing substantially in one plane, signal conductors914and916residing substantially another plane, and signal conductors906and908residing substantially in yet a third plane. In this embodiment, die902may correspond with die102(FIG.1), and transmission-line structure910may correspond with transmission-line structure110(FIG. 1) and transmission-line structure302(FIG.3), while die904may correspond with substrate104(FIG.1), and transmission-line structure912may correspond with transmission-line structure112(FIG. 1) and transmission-line structure304(FIG.3). Corresponding signal conductors914,916may be substantially aligned in the coupling region to provide edge coupling. Corresponding signal conductors906and908may also be substantially aligned in the coupling region to provide edge coupling. Nothing requires that the conductors of transmission-line structure910be the same size as conductors of transmission-line structure912. Furthermore, the impedance of transmission-line structures910and912may be different. Gap901may be provided between die902and die904in the coupling region.

In this embodiment, die902and die904may be coupled to substrate922by a conventional attachment technique, such as by solder or bond wires. In one embodiment, substrate922may be a substrate for a multichip module.

FIG. 10is a flow chart of a high-speed signal communication procedure in accordance with an embodiment of the present invention. Procedure1000may be performed by some elements of system100(FIG. 1) although other elements may also be used to perform procedure1000. Procedure1000may be used to communicate high-speed signals across a contact-less interface between a die and a substrate. In operation1002, a high-speed forward incident signal may be received in a first transmission-line structure. The incident signal may be in a forward direction. In operation1004, the incident signal may be coupled to a second transmission-line structure. The first and second transmission-line structures may be disposed on separate dielectric mediums. In operation1006, the high-speed forward incident signal may be terminated in a first termination coupled to the first transmission-line structure. In operation1008, a coupled signal is generated in a reverse direction to the incident signal in the second transmission-line structure. In operation1010, coupled signals in the forward direction are terminated in a second termination coupled to the second transmission-line structure.

In one embodiment, operation1012may be performed. In this embodiment, the high-speed forward incident signal may be a digital signal, and operation1012may include integrating the coupled high-speed signal to generate a digital signal substantially corresponding with the high-speed forward incident signal.

Although the individual operations of procedure1000are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently and nothing requires that the operations be performed in the order illustrated.

FIG. 11illustrates a cascaded interface in accordance with an embodiment of the present invention. Cascaded interface1100may be used in system100(FIG. 1) in place of interface106to provide signaling between substrate1102and a plurality of elements on die1104, or vice-versa. Cascaded interface1100provides for the coupling of forward incident signal1106propagating on transmission-line structure1108to each of a plurality of transmission-line structures1110. Interfaces112between the transmission-line structures may be either broadside coupled interfaces such as those described inFIGS. 2,4,5and6, or edge coupled interfaces such as those described inFIGS. 3,7,8and9.

Thus, an improved interface for high-speed signaling that does not require electrical contact between a die and substrate, or between a die and another die, has been described. The foregoing description of specific embodiments reveals the general nature of the invention sufficiently that others can, by applying current knowledge, readily modify and/or adapt it for various applications without departing from the generic concept. Therefore such adaptations and modifications are within the meaning and range of equivalents of the disclosed embodiments. The phraseology or terminology employed herein is for the purpose of description and not of limitation. Accordingly, the invention embraces all such alternatives, modifications, equivalents and variations as fall within the spirit and scope of the appended claims.