Patent Application
20090039331
1. Technical Field
The disclosure relates generally to integrated circuit (IC) chip fabrication, and more particularly, to phase change material structures.
2. Background Art
Electronic fuses are used in IC chips to, for example, correct inoperative parts by turning on or off sections. Current electronic fuse (efuse) technology is based on techniques such as electromigration, rupture or agglomeration. These fuse technologies suffer from a number of drawbacks. For example, they are single use, take up large areas, involve quite large amounts of power/current, and are very slow, e.g., microseconds. As fuse technology develops, higher performance is desirable to, for example, reduce the area taken up by the fuse, address sun-setting of the non-standard high voltages/currents required (e.g., for electromigration fuses), provide multiple use reprogrammable fuses, and enhance speed.
Phase change material is a type of material capable of resistance changes depending on the mechanical phase of the material. Phase change material is used for phase change memory (PCM), which may also be known as ovonic unified memory (OUM), chalcogenide random access memory (CRAM) or phase-change random access memory (PRAM). Phase change material has not been used for fuse technology.
Almost all PCMs are built using a chalcogenide alloy, typically a mixture of germanium (Ge), antimony (Sb) and tellurium (Te), which is referred to as GST. One GST alloy has the formula: Ge2Sb2Te5. Under high temperature (over 600° C.), a chalcogenide becomes liquid and by subsequent rapid cooling it is frozen into an amorphous glass-like state and its electrical resistance is high. By heating the chalcogenide to a temperature above its crystallization point, but below the melting point, it will transform into a crystalline state with a much lower resistance. In addition, when the material is set to a particular state representing a resistance value, the value is retained until reset by another phase change of the material. The phase switching can be completed very quickly, e.g., under 10 ns. During use as a PCM, the phase of the phase change material is typically changed by heat created by a small pulse of electrical power. Typically, this heat is provided by an internal heater, which presents reproducibility and manufacturing challenges.
Structures including a phase change material are disclosed. The structure may include a first electrode; a second electrode; a phase change material electrically connecting the first electrode and the second electrodes for passing a current therethrough; and a tantalum nitride heater layer about the phase change material for converting the phase change material between an amorphous, insulative state and a crystalline, conductive state by application of a second current to the phase change material. The structure may be used as a fuse or a phase change material random access memory (PRAM).
A first aspect of the disclosure provides a structure comprising: a first electrode; a second electrode; a phase change material electrically connecting the first electrode and the second electrode for passing a current therethrough; and a tantalum nitride heater layer about the phase change material for converting the phase change material between an amorphous, insulative state and a crystalline, conductive state by application of a second current to the phase change material.
A second aspect of the disclosure provides a structure comprising: a first copper electrode; a second copper electrode; a phase change material electrically connecting the first copper electrode and the second copper electrode for passing a first current therethrough; and a tantalum nitride heater layer about the phase change material for converting the phase change material between an amorphous, insulative state and a crystalline, conductive state by application of a second current to the phase change material; and a contact to each copper electrode, wherein the first copper electrode is positioned in one metal layer of an integrated circuit (IC) chip, and the second copper electrode is positioned in another metal layer of the IC chip.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
Turning to the drawings,
In
Structures 100, 200 are surrounded by one or more dielectric layers 170, 270 which may include but is/are not limited to: silicon nitride (Si3N4), silicon oxide (SiO2), fluorinated SiO2 (FSG), hydrogenated silicon oxycarbide (SiCOH), porous SiCOH, boro-phosho-silicate glass (BPSG), silsesquioxanes, carbon (C) doped oxides (i.e., organosilicates) that include atoms of silicon (Si), carbon (C), oxygen (0), and/or hydrogen (H), thermosetting polyarylene ethers, SiLK (a polyarylene ether available from Dow Chemical Corporation), JSR (a spin-on silicon-carbon contained polymer material available form JSR Corporation), other low dielectric constant (<3.9) material, or layers thereof.
In one embodiment, each electrode includes copper (Cu), however, other conductive materials may also be employed. Further, in one embodiment, phase change material 110, 210 may include a germanium (Ge), antimony (Sb) and tellurium (Te) alloy (commonly referred to as GST) or a germanium (Ge), antimony (Sb) and silicon (Si) alloy (GeSbSi). Other phase change materials may also be employed within the scope of the disclosure.
Structures 100, 200 may function as a fuse or a phase change random access memory (PRAM) cell. TaN heater layer 120 may obviate the need for a separate heater as is conventionally used, and allows for easier manufacturing and/or reproducibility using existing complementary metal-oxide semiconductor (CMOS) back-end-of-line (BEOL) processing technology. Sufficient additional current may be applied by applying an increased current to the two electrodes 102, 202, 104, 204, or by applying an additional current to an electrode via a second contact thereto (not shown, within page). In any event, the increased heat created by application of additional current is sufficient to convert the crystalline phase change material 110, 210 to be sufficiently amorphous 110, 210 so as to be conductive. The conversion from amorphous to crystalline does not have to be complete. In this situation, structures 100, 200 may act as multiple use, reprogrammable fuses, analogous to how PCM are used for memory applications. Structures 100, 200 may also function as a phase change random access memory (PRAM) cell. Where structures 100, 200 are used as PRAM, they will typically require a smaller cell size/higher packing density, but the operation of a single PRAM cell is the same as that of the fuse in terms of programming and sensing currents.
Structures 100, 200 may be formed using any now known or later developed CMOS BEOL processing technology.
The methods and structures as described above are used in the fabrication of integrated circuit chips. The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor.
The foregoing description of various aspects of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of the disclosure as defined by the accompanying claims.
