Patent Application
20100127937
The following description relates generally to an antenna for wireless communication, and more particularly to an antenna integrated in a semiconductor chip through use of semiconductor fabrication structures such as through-silicon vias or crack stops.
Wireless communication devices are becoming increasingly prevalent. In general, wireless communication enables communication of information over some distance without the use of a physical carrier of the information (e.g., wires). Depending on the type of wireless communication technology employed, a device may support short-range communication (such as infrared (IR) communication used for remote controls, Bluetooth, etc.) and/or long-range communication (such as cellular telephony communication). Various types of wireless communication devices are known in the art. Examples of wireless communication devices include various types of fixed, mobile, and portable two-way radios (e.g., Professional LMR (Land Mobile Radio), SMR (Specialized Mobile Radio), Consumer Two Way Radio including FRS (Family Radio Service), GMRS (General Mobile Radio Service) and Citizens band (“CB”) radios, the Amateur Radio Service (Ham radio), consumer and professional Marine VHF radios, etc.), mobile telephones (e.g., cellular telephones, cordless telephones, etc.), pagers, personal digital assistants (PDAs), pagers, wireless handheld devices (e.g., Blackberry™ wireless handheld), global positioning system (GPS) units, wireless computer peripherals (e.g., wireless mice, keyboards, printers, etc.), wireless sensors, RFID devices, video gaming devices, and any device having a communication interface for a wireless communication protocol, such as radio frequency (RF), Bluetooth, IEEE 802.11, WiFi, etc. Wireless communication devices may support point-to-point communication, point-to-multipoint communication, broadcasting, cellular networks, and/or other wireless network communication.
In wireless communication devices, an antenna is generally included for transmitting and receiving signals. The antenna is conventionally fabricated outside of a semiconductor chip (e.g., “off-silicon”). Thus, a wireless communication device may include one or more semiconductor chips, which may include various logic for performing operations desired for the wireless communication, such as a processor and/or other logic for generating information to communicate and/or for processing received communication, as examples. In addition, the wireless communication device may further include an antenna, and the antenna is conventionally fabricated outside of the above-mentioned semiconductor chips of the device. Thus, the antenna may be referred to as being an external antenna since it is fabricated outside of a semiconductor chip rather than being an integral part of a semiconductor chip. Such an external antenna may be communicatively interfaced or coupled to one or more of the semiconductor chips in some way within the wireless communication device. Thus, conventionally the semiconductor chip and antenna are often each pre-fabricated separately, and may coupled together in a post-semiconductor-fabrication manner (i.e., after the semiconductor fabrication, such as lithography, deposition, etching, and/or other processes commonly performed for semiconductor fabrication of the chip). The external antenna conventionally occupies an undesirably large amount of space within the wireless communication device, in addition to the space consumed by the one or more semiconductor chips.
In some instances, an antenna is fabricated on a semiconductor chip. That is, in some instances an antenna may be formed on a chip during semiconductor fabrication of the chip. Conventionally, such antennas are fabricated on the silicon die by coating a large part of the die's surface. For instance, an antenna may be implemented on-chip by depositing metal on a layer of the semiconductor chip, wherein such a horizontally-oriented antenna may consume an undesirable amount of space on the surface of a layer of the chip. In addition, such an implementation requires use of metal strips that are dedicated solely for implementing an antenna.
Embodiments of the present disclosure are directed generally to an antenna structure integrated in a semiconductor chip. According to one embodiment, an integrated antenna structure implemented in an integrated circuit is provided. The integrated antenna structure comprises a semiconductor fabrication structure. In certain embodiments, the semiconductor fabrication structure comprises a through-silicon via (TSV). Additionally or alternatively, in certain embodiments, the semiconductor fabrication structure comprises a crack stop structure. In certain embodiments, the antenna structure comprises an antenna element. The antenna element may be formed by a TSV and/or crack stop structure. In certain embodiments, the antenna structure comprises a directional element. The directional element may be formed by a TSV and/or crack stop structure.
According to another exemplary embodiment, a method of fabricating an antenna structure integrated in a semiconductor chip is provided. The method includes forming a semiconductor fabrication structure to implement the antenna structure. The semiconductor fabrication structure comprises at least one of: a) one or more TSVs, and b) one or more crack stop structures.
According to still another embodiment, an integrated circuit is provided that includes a TSV and a crack stop structure. At least one of the TSV and the crack stop structure forms an antenna structure.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the technology of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
For a more complete understanding of the present invention, reference is now made to the following description taken in conjunction with the accompanying drawings.
Embodiments of the present disclosure are directed generally to an antenna structure integrated in a semiconductor chip. As used herein, an antenna structure refers generally to an antenna element and/or any associated directional elements (e.g., reflectors, directors, etc.), which may aid in the efficiency of the antenna element. Thus, an “antenna structure” may refer either to an antenna element, an associated directional element, or both. For instance, in some embodiments, a chip having an integrated antenna structure may have an antenna element with no associated directional element implemented therewith, whereas in other embodiments a chip having an integrated antenna structure may include both an antenna element and an associated directional element.
Systems and methods for forming an antenna structure for wireless communication in which the antenna structure is integrated in a semiconductor chip are provided. In certain embodiments, the antenna structure is implemented in the chip through use of semiconductor fabrication structures. As used herein, “semiconductor fabrication structures” that are used for implementing an antenna structure are defined as a through-silicon via (TSV), crack stop, or both. Rather than forming an antenna structure separate from a semiconductor die (and thereafter coupling the antenna structure with a pre-fabricated semiconductor die), certain embodiments form an antenna structure when fabricating a semiconductor die such that the antenna structure is integrally formed in the semiconductor die.
Exemplary embodiments of a resulting semiconductor chip having an integrated antenna structure so formed are also described. Of course, as should be recognized by those of ordinary skill in the art, the concepts and techniques described herein are not limited to any specific implementation or configuration of an integrated antenna structure, but rather antenna structures of various different configurations (e.g., shapes, lengths, etc.) that may be desired for a given application may be formed in accordance with the concepts and techniques disclosed herein.
Certain embodiments utilize semiconductor fabrication structures present in a semiconductor chip for implementing an antenna structure. A “semiconductor fabrication structure,” as that term is used herein, refers generally to any TSV structure, crack stop structure, or both a TSV structure and crack stop structure formed during fabrication of the semiconductor chip. Thus, such semiconductor fabrication structures refer generally to structures formed on the chip during the chip's fabrication, as distinguished from structures that are formed external to or separate from the chip.
In certain embodiments, semiconductor fabrication structures serve a dual purpose of mechanically or otherwise structurally aiding in the fabrication of the semiconductor chip, as well as being leveraged for implementing an antenna structure. For instance, a crack stop may be utilized during fabrication of a semiconductor (e.g., a crack stop may be implemented about the periphery of a functional portion of a die to prevent the spread of any cracks occurring when the die is diced from the wafer into the functional portion of the die), and the crack stop may also be utilized for implementing an antenna structure on the die.
In certain embodiments, all or a portion of the semiconductor fabrication structures used for implementing an antenna structure may be used for the sole purpose of implementing an antenna, rather than also having the dual purpose of aiding in fabrication of the chip.
In one embodiment, an antenna array is constructed using a TSV in a semiconductor die or die stack. For instance, arrays of TSVs may be fabricated on a die with connecting pads on the top and bottom surfaces of the die. The die may be held singly or stacked successively on another die until a desired via length is achieved. The die may have suitable metal layer connections alternately connecting the vias in a serpentine structure (or other desired antenna configuration). In certain embodiments, no more than two metal layers are needed for implementing an antenna array in this manner. An exemplary embodiment enables a high-frequency, short-range antenna array to be constructed in this manner such that it is integrated in the semiconductor chip (e.g., using such semiconductor fabrication structures as TSVs). In one embodiment, a single die is used as the antenna, the single die being stacked on an RF die.
In certain embodiments, the die stack in which the antenna structure is implemented (e.g., by TSVs) may include or be attached to a functional die, also using TSVs. Thus, the resulting semiconductor chip may include both an active functional area (e.g., for implementing desired circuitry/logic of a wireless communication device, such as a processor and/or other logic), as well as an antenna structure.
In one exemplary embodiment, an antenna element (e.g., antenna array) is implemented by TSVs within a chip. In addition, one or more directional elements may be implemented by a crack stop structure. Such crack stop structure may be arranged about the periphery of the chip's active area, and may serve to prevent stress cracks from spreading into the chip's active area (e.g., during dicing of the chip from the wafer). In addition, the crack stop structure may be configured to serve the dual purpose of acting as a directional element for the antenna element, thereby increasing the antenna element's efficiency.
In another exemplary embodiment, an antenna element (e.g., antenna array) is implemented by a crack stop structure within a chip. In addition, one or more directional elements may be implemented by TSVs, thereby increasing the antenna element's efficiency.
Before further describing exemplary embodiments of semiconductor chips having an integrated antenna structure formed therein, common semiconductor fabrication processes are briefly discussed for illustrative purposes. It should be recognized that embodiments of the present disclosure are not limited to the illustrative semiconductor fabrication processes described herein. Instead any semiconductor fabrication process in addition to or instead of those described herein that are suitable for forming a desired semiconductor die having an integrated antenna structure formed therewith may be employed.
Semiconductor fabrication processes refer generally to processes for creating a semiconductor chip. Exemplary semiconductor fabrication processes that are commonly employed in conventional semiconductor fabrication include deposition processes, removal processes, patterning processes, and processes for modifying electrical properties. Deposition processes are conventionally employed for growing, coating, or otherwise transferring material onto a substrate (e.g., wafer) (through use of such techniques as physical vapor deposition (PVD), chemical vapor deposition (CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE), and/or atomic layer deposition (ALD) among others). Removal processes are conventionally employed for removing material from the substrate (e.g., wafer) either in bulk or selectively (through use of etch processes, chemical-mechanical planarization (CMP), etc., as examples). Patterning may include a series of processes that shape or alter the existing shape of the deposited materials, and is often referred to generally as lithography. Modification of electrical properties may be performed through doping transistor sources and drains, followed by furnace anneal or rapid thermal anneal (RTA) for activating the implanted dopants, or through reduction of dielectric constant in low-k insulating materials via exposure to ultraviolet light in UV processing (UVP), as examples. Any one or more of these, and in some instances other semiconductor fabrication processes, may be used for creating a semiconductor chip.
The term “semiconductor fabrication structure” encompasses any TSV structure, crack stop structure, or both a TSV structure and crack stop structure formed through the above-mentioned and/or other semiconductor fabrication processes that may be employed for fabricating a semiconductor chip. As discussed further herein, using such a fabrication structure for implementing an antenna structure results in a chip that has an antenna structure integrally formed therein.
One process that is sometimes used in semiconductor fabrication is formation of a through-silicon via (TSV). In general, TSV refers to a vertical hole (via) passing completely through a silicon wafer or die (or through multiple stacked dies). In many cases, the vertical hole is used for forming an electrical connection through the die. For instance, a metal strip is commonly formed in the TSV to provide an electrical connection through the die. TSV technology is commonly employed in, for example, creating three-dimensional (“3D”) packages and 3D integrated circuits. In general, a 3D package contains two or more chips (integrated circuits) stacked vertically so that they occupy less space. In many 3D packages, the stacked chips are wired together along their edges; and this edge wiring slightly increases the length and width of the package and usually requires an extra “interposer” layer between the chips. In some 3D packages, TSVs are employed in place of such edge wiring, wherein the TSVs create vertical connections through the body of the chips such that the resulting package has no added length or width.
A 3D integrated circuit (“3D IC” or “3D chip”) generally refers to a single chip constructed by stacking silicon wafers and/or dies and interconnecting them vertically so that they behave as a single device. By using TSV technology, 3D ICs can pack a great deal of functionality into a small “footprint.” In addition, critical electrical paths through the device can be drastically shortened, leading to faster operation.
Of course, TSV is not limited in application to the above-mentioned 3D packages and 3D chips, but may likewise be employed in other semiconductor chip structures. Any techniques now known or later developed for forming TSVs may be employed in accordance with embodiments of the present invention that make use of such TSVs for forming an antenna structure.
Another process commonly used in semiconductor fabrication is known as chip crack stop. As mentioned above, semiconductor chips are typically formed on a silicon wafer. The chips are typically placed adjacent to one another on the wafer, and after fabrication processes are completed, the wafer is diced by cutting the wafer along kerfs. This separates the chips from each other. The dicing processes may induce stress into the chips. This stress may cause stress cracks to form through the semiconductor chip structure. That is, cracks may spread into the active/functional areas of the individual semiconductor dies. Cracks may also form due to latent stresses in the semiconductor chip structure. Thus, crack stop structures are commonly arranged about the periphery of the active area of a die to prevent the spreading of cracks into the active area. A crack stop is typically fabricated using a ring-type structure of conductive material. Any techniques now known or later developed for forming chip crack stops may be employed in accordance with embodiments of the present invention.
An exemplary technique for forming such an integrated antenna element 101 according to one embodiment is shown in the corresponding cross-sectional view of
In this exemplary embodiment of
In the above example, the dies 103-105 in which the TSVs are included for implementing the integrated antenna structure may be attached to a functional die, such as the functional die 102. Such attachment may be achieved also using TSVs, which may or may not be part of the antenna structure. Also, the fabrication steps for fabricating the dies 103-105 for forming the antenna structure can be combined with the fabrication of the functional die 102, or such dies 103-105 may be separately fabricated and attached to the functional die 102 (e.g., dies 103-105 may be obtained from a different foundry source). In addition, as shown in
As one exemplary application of an embodiment of a chip having an integrated antenna element 101, such as that of chip 100 of
where c is the speed of light.
Compared to an unfolded antenna element, a folded antenna element has a lower efficiency, but the inefficiency resulting from folding is improved by an increase in length of the antenna element. Assuming a 2× length increase of the antenna element to compensate for folding losses, the target length for the antenna element in the above example becomes 30 millimeters (mm). Assuming TSV pitch of 20 micrometers (um) and height of 35 um, the length of one L-shaped portion of the antenna element 101 is 55 um. Thus, in this example, the number of single-line L-shaped antenna elements to be implemented equals 545 (i.e., 30 mm/55 um). Arranging in a square array, with a 20 um pitch, the 545 elements can be accommodated in 23 rows of 23 L-shaped elements each, which consumes an area of 460 um×460 um (approximately 0.5 mm×0.5 mm).
Although the example above was with respect to a target center frequency of 5 GHz, the present disclosure is not limited to such frequency. By adding additional die to the stack, the frequency can be reduced. In one embodiment, the center frequency is only 1 GHz, although again, such a frequency is a non-limiting example.
As discussed further herein, antenna gain can be improved by adding directional elements, and antenna efficiency can be improved by adding inductive/capacitive compensating elements to lower antenna reactance compared to its resistance. Assuming that compensating passive elements consume 3× antenna area, the total area consumed is approximately 0.5 mm×1.5 mm. Conventional on-chip antenna areas are typically about 7 mm×7 mm. The smallest conventional on-chip antenna is about 4 mm×4 mm, and these require special materials such as glass or special manufacturing/placement to achieve. Thus, certain embodiments of the exemplary integrated antenna structure described herein (such as that of
The exemplary embodiment of
Illustrative formation techniques and applications of chip crack stops can be found in U.S. Pat. Nos. 6,022,791; and 6,495,918; and in U.S. Patent Application Publication No. 2006/0220250. Of course, techniques for forming and/or using chip crack stops are not limited to those disclosed in the above-mentioned illustrative patents and published patent application, and any techniques now known or later developed for forming chip crack stops may be employed in accordance with embodiments of the present disclosure.
In certain embodiments, the chip crack stop 201 is configured to not only serve as a chip crack stop (for impeding the progression of silicon cracks into the active area 202) but also to serve as a portion of an antenna structure. In certain embodiments, the chip crack stop 201 is configured as an antenna element. For instance, the chip crack stop 201 may include a metal structure arranged in a serpentine or other suitable shape to act as an antenna element. In other embodiments, the chip crack stop 201 may be configured as a directional element for an antenna element. For instance, the chip 200 may include an antenna element 101, which may be implemented by TSVs in the manner discussed above with
Thus, chip crack stops, such as the chip crack stop 201 of
Alternatively, in certain embodiments, the chip crack stop 201 may be implemented as the main antenna element, and TSVs may be used to implement a directional/efficiency element. Thus, chip crack stops and TSVs can be used in various different tandems to create a miniaturized and integrated on-chip antenna structure.
Certain embodiments of the present disclosure enable an antenna structure to be integrated into a semiconductor chip. Through integration on silicon, space savings may be achieved compared to a planar antenna implemented on a system board, package substrate or silicon. The exemplary concepts and techniques disclosed herein may be employed to create large antenna arrays and/or antennas having a wide variety of shapes to achieve desirable transmission characteristics for a given application. Further, in certain embodiments, minimal contact/travel losses are encountered due to integration of the antenna structure on silicon. Also, certain embodiments afford flexibility to combine different antenna configurations with different sources of supply. And, certain embodiments enable an integrated antenna structure to be achieved in a semiconductor chip through use of existing manufacturing/semiconductor fabrication methods. Those of ordinary skill in the art should recognize that such an integrated antenna structure is suitable for use in a wide variety of applications, particularly for many high frequency/short range wireless communication applications.
In
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the technology of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
