Patent Application
20140264731
1. Field of the Invention
Generally, the present disclosure relates to the manufacture of FET semiconductor devices, and, more specifically, to various embodiments of a programmable e-fuse for use on integrated circuit products.
2. Description of the Related Art
In modern integrated circuits, a very high number of individual circuit elements, such as field effect transistors in the form of CMOS, NMOS, PMOS elements, resistors, capacitors and the like, are formed on a single chip area. Typically, feature sizes of these circuit elements are decreased with the introduction of every new circuit generation, to provide currently available integrated circuits with an improved degree of performance in terms of speed and/or power consumption. In addition to the large number of transistor elements, a plurality of passive circuit elements, such as capacitors, resistors and the like, are typically formed in integrated circuits that are used for a plurality of purposes, such as for decoupling.
Due to the reduced dimensions of circuit elements, not only the performance of the individual transistor elements may be increased, but also their packing density may be improved, thereby providing the potential for incorporating increased functionality into a given chip area. For this reason, highly complex circuits have been developed which may include different types of circuits, such as analog circuits, digital circuits and the like, thereby providing entire systems on a single chip (SoC). Furthermore, in sophisticated micro-controller devices, an increasing amount of storage capacity may be provided on a chip with the CPU core, thereby also significantly enhancing the overall performance of modern computer devices.
For a variety of reasons, the various circuit portions may have significantly different performance capabilities, for instance with respect to useful lifetime, reliability and the like. For example, the operating speed of a digital circuit portion, such as a CPU core and the like, may depend on the configuration of the individual transistor elements and also on the characteristics and performance of the metallization system coupled to the CPU core. Consequently, the combination of the various circuit portions in a single semiconductor device may result in a significantly different behavior with respect to performance and reliability. Variations in the overall manufacturing process flow may also contribute to further variations in the performance capabilities between various circuit portions. For these reasons, in complex integrated circuits, frequently, additional mechanisms are used so as to allow the circuit itself to adapt or change the performance of certain circuit portions to comply with the performance characteristics of other circuit portions. Such mechanisms are typically used after completing the manufacturing process and/or during use of the semiconductor device. For example, when certain critical circuit portions no longer comply with corresponding device performance criteria, adjustments may be made, such as re-adjusting an internal voltage supply, re-adjusting the overall circuit speed and the like, to correct such underperformance.
In computing, e-fuses are used as a means to allow for the dynamic real-time reprogramming of computer chips. Speaking abstractly, computer logic is generally “etched” or “hard-coded” onto a silicon chip and cannot be changed after the chip has been manufactured. By utilizing an e-fuse, or a number of individual e-fuses, a chip manufacturer can change some aspects of the circuits on a chip. If a certain sub-system fails, or is taking too long to respond, or is consuming too much power, the chip can instantly change its behavior by blowing an e-fuse. Programming of an e-fuse is typically accomplished by forcing a large electrical current through the e-fuse. This high current is intended to break the e-fuse structure, which results in an “open” electrical path. In some applications, lasers are used to blow effuses. Fuses are frequently used in integrated circuits to program redundant elements or to replace identical defective elements. Further, fuses can be used to store die identification or other such information, or to adjust the speed of a circuit by adjusting the resistance of the current path. Device manufacturers are under constant pressure to produce integrated circuit products with increased performance and lower power consumption relative to previous device generations. This drive applies to the manufacture and use of e-fuses as well.
Prior art e-fuses come in various configurations.
All of the e-fuses depicted in
The present disclosure is directed to various embodiments of a programmable e-fuse for use on integrated circuit products that may solve or reduce one or more of the problems identified above.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
Generally, the present disclosure is directed to various embodiments of a programmable e-fuse for use on integrated circuit products. One illustrative e-fuse device disclosed herein includes first and second conductive structures, a first electrically conductive heat cage element that is conductively coupled to the first conductive structure, wherein the first heat cage element is adapted to carry an electrical current, a second electrically conductive heat cage element that is conductively coupled to the second conductive structure, wherein the second heat cage element is adapted to carry the electrical current, and a programmable, electrically conductive e-fuse element that is conductively coupled to each of the first and second electrically conductive heat cage elements and adapted to carry the electrical current, wherein the e-fuse element is positioned adjacent to each of the first and second electrically conductive heat cage elements.
Another illustrative e-fuse device disclosed herein includes first and second conductive structures and a conductive serpentine-shaped structure that comprises a programmable, electrically conductive e-fuse element. A first conductive leg of the serpentine structure is conductively coupled to the first conductive structure and a second conductive leg of the serpentine structure is conductively coupled to the second conductive structure, wherein at least a portion of the e-fuse element is positioned between at least a portion of the first and second conductive legs.
The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Various illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
The present disclosure is directed to various embodiments of a programmable e-fuse for use on integrated circuit products. As will be readily apparent to those skilled in the art upon a complete reading of the present application, the various embodiments of the novel e-fuses disclosed herein may be employed on any type of integrated circuit product, including, but not limited to, logic devices, memory devices, etc. With reference to the attached figures, various illustrative embodiments of the novel e-fuse structures disclosed herein will now be described in more detail.
In one embodiment, the e-fuse 100 disclosed herein has a generally serpentine-shaped configuration or “Z” shaped configuration as depicted in the drawings. In such a configuration, one end of the serpentine-shaped structure is conductively coupled to the first conductive structure 102A and the other end of the serpentine structure is conductively coupled to the second conductive structure 102B. Stated another way, a first conductive leg 108A of the serpentine structure is conductively coupled to the first conductive structure 102A and a second conductive leg 108B of the serpentine structure is conductively coupled to the second conductive structure 102B, wherein at least a portion of the e-fuse element 106 is positioned between at least a portion of the first and second conductive legs 108A, 108B.
The physical size, i.e., the cross-sectional area, of the heat cage elements 108A, 108B and the e-fuse element 106 may be the same or they may be different. In some embodiments, the cross-sectional area of the e-fuse element 106 may be less than the cross-sectional area of the heat cage elements 108A, 108B. In some embodiments, the heat cage elements 108A, 108B and the e-fuse element 106 are all positioned, at least partially, in the same plane, e.g., a substantially horizontal or vertical plane. Stated another way, in one embodiment, the conductive serpentine-shaped structure may all be positioned in the same plane. In some embodiments, the first heat cage element 108A, the second heat cage element 108B and the programmable, electrically conductive e-fuse element 106 are all a part of a single continuous conductive line structure. In another embodiment, the first heat cage element 108A, the second heat cage element 108B and the programmable, electrically conductive e-fuse element 106 are separate line-type structures that are conductively coupled together by other line-type structures.
In terms of design, the physical size of the e-fuse element 106 and heat cage elements 108A, 108B may vary depending upon the particular application. The axial length 107 of the e-fuse 100 may also vary depending upon the particular application. In general, the components of the e-fuse 100 may be made of any conductive material, e.g., a metal, polysilicon, and it may or may not have a metal silicide layer as part of the materials of construction. The e-fuse 100 may be manufactured using traditional manufacturing techniques, depending upon the materials of construction, e.g., damascene techniques, deposition/etch techniques, etc.
In operation, a programming current is passed through the e-fuse 100 until such time as a portion of the e-fuse element 106 ruptures due to resistance heating. However, unlike prior art e-fuse structures, due to the presence of the heat cage elements or legs 108A, 108B, the programming current for the novel e-fuse 100 disclosed herein is significantly lower than that of the prior art e-fuse devices wherein the actual fuse element is not positioned adjacent to any structures similar to the heat cage elements 108A, 108B. During operation, the heat cage elements 108A, 108B also conduct current and heat up due to resistance heating.
However, due to the presence of other surrounding, non-conducting materials, such as surrounding insulation materials (not shown), the heat generated in the heat cage elements 108A, 108B dissipates, to at least some degree, outwardly away from the heat cage elements 108A, 108B, as indicated by the arrows 109, thereby decreasing the temperature, to some degree, of the heat cage elements 108A, 108B. However, since the e-fuse element 106 is positioned adjacent to the heated heat cage elements 108A, 108B, the temperature of the e-fuse element 106 cannot dissipate heat as rapidly as does the heat cage elements 108A, 108B. Simply put, the heated heat cage elements 108A, 108B reduce the amount of heat lost from the e-fuse element 106 as it is heated during programming operations. Thus, the temperature of the e-fuse element 106 will be greater than that of the heat cage elements 108A, 108B. Accordingly, as current flows through the e-fuse 100, the e-fuse element 106 will eventually reach a temperature at which time it will rupture, as intended, and this rupturing will occur prior to the heat cage elements 108A, 108B rupturing. To take advantage of the heating effect of the heat cage elements 108A, 108B, they should be placed in relative close proximity to the e-fuse element 106. In one illustrative example where the e-fuse element 106 has a width 106W, the spacing 110 between the e-fuse element 106 and the heat cage elements 108A, 108B may be on the order of about 2-3 times the width 106W, although such spacing may vary depending upon the particular application.
As will be recognized by those skilled in the art after a complete reading of the present application, the novel e-fuse 100 disclosed herein may be implemented in a vast variety of configurations. Moreover, the novel e-fuse 100 may be employed at any metallization level and at any location within an integrated circuit product. To that end,
The novel e-fuse 100 disclosed herein provides significant advantages relative to prior art e-fuse designs. A computer simulation was conducted to compare the performance of the prior art e-fuse 21 depicted in
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
