BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic diagram of a voltage regulator according to an embodiment of the invention.
FIGS. 2, 4 and 5 are schematic diagrams of laminated magnetic material structures according to embodiments of the invention.
FIG. 3 is a flow diagram depicting a technique to form a laminated magnetic material structure according to an embodiment of the invention.
FIG. 6 is a schematic diagram of a computer system according to an embodiment of the invention.
DETAILED DESCRIPTION
Referring to FIG. 1, in accordance with embodiments of the invention described herein, an integrated voltage regulator 10 is fabricated on a semiconductor die. The voltage regulator 10 includes an inductive element 15 (an inductor or transformer, as examples), which has a magnetic core that is formed from a laminated magnetic material structure 20. The structure 20, as further described below, includes overlaying magnetic metal layers that are separated by high-resistivity layers, such as layers of metal nitride, for example. Thus, instead of being formed from a single magnetic metal layer having a thickness T, the structure 20 has n magnetic metal layers, each of which has a thickness T/n. Due to the intervening high-resistivity layers, eddy currents in the magnetic core are significantly diminished, as compared to a magnetic device that has a single magnetic metal layer.
The structure 20 may serve a variety of different applications, other than its use in a voltage regulator, as the voltage regulator 10 is depicted in FIG. 1 for purposes of illustrating one out of many possible applications of the structure 20. As shown in FIG. 1, in accordance with some embodiments of the invention, the voltage regulator 10 may be a switching-type regulator that uses switching circuitry 24 for purposes of energizing and de-energizing the inductive element 15 to convert an input voltage (called “VIN”) into a regulated output voltage (called “VOUT”). Among its other features, the voltage regulator 10 may include a controller 26 that possibly monitors one or more parameters of the regulator 10, such as the VIN and VOUT voltages, and controls the switching circuitry 24 accordingly to regulate the VOUT voltage.
Referring to FIG. 2, in accordance with some embodiments of the invention, the structure 20 is fabricated on a semiconductor substrate 50 and is generally formed from n overlaying plated magnetic layers, or films 60 (magnetic films 601, 602 . . . 60n, being depicted as examples). The structure 20 also includes n intervening high resistivity metal nitride layers 58 (metal nitride layers 581 and 58n, being depicted as examples) that are interdisposed between adjacent magnetic films 60 for purposes of reducing eddy current losses. As depicted in FIG. 2, in accordance with some embodiments of the invention, each high resistivity metal nitride layer 58 may be located over an associated plated magnetic film 60 in the laminated structure 20.
For purposes of facilitating the plating of the magnetic films 60, initiation layers 56 (initiation layers 561, 562 and 56n, being depicted as examples) are deposited on the substrate 50 (for the initiation layer 561) and the metal nitride layers 58 (for the initiation layers 562 . . . 56n). The composition of the initiation layer 56 depends on whether electroplating or electroless plating is used for purposes of forming the magnetic films 60.
More specifically, in accordance with some embodiments of the invention, electroplating is used to form the magnetic films 60. For these embodiments of the invention, a metal such as Ni, Co, or Cu may be deposited by vapor deposition on the substrate 50 for purposes of forming the first initiation layer 561. The initiation layer 561 increases the adhesion of the magnetic film 60 to the substrate 50 and provides a source of nucleation for the ensuing magnetic film 601. After the initiation layer 561 is deposited, the magnetic film 601 is then plated on top of the layer 562. Next, a high-resistivity metal nitride layer 581 is deposited on the plated magnetic film 601. This is proceeded by the deposition of another initiation layer 562, which is followed by the plating of another magnetic film 602, etc.
For embodiments of the invention in which the magnetic films are formed by electroless plating, each initiation layer 56 may be a palladium monolayer, which is formed with a palladium immobilization process, such as the one described in U.S. patent application Publication No. 2004/0248403A1, entitled, “METHOD FOR FORMING ELECTROLESS METAL LOW RESISTIVITY INTERCONNECTS,” which published on Dec. 9, 2004.
As can be appreciated from FIG. 2, the above-described lamination process forms a repeating lamination structure 70, a structure that includes at its base a high-resistivity metal nitride layer 58, a middle overlaying initiation layer 56 and an upper magnetic film 60 that overlays the initiation layer 56. The lamination structure 70 is repeated (as depicted by exemplary lamination structures 701, 70n-1 and 70n in FIG. 2), depending on the number of magnetic films 60 in the overall structure 20.
Although FIG. 2 depicts four magnetic metal layers (i.e., magnetic films 60), the structure 20 may include more or fewer magnetic metal layers, depending on the particular embodiment of the invention. Thus, in accordance with some embodiments of the invention, the structure 20 may include two (n=2) magnetic metal layers; and as another example, in other embodiments of the invention, the structure 20 may include seven (n=7) magnetic metal layers. Thus, many variations are possible and are within the scope of the appended claims.
To summarize, in accordance with some embodiments of the invention, a technique 100 that is depicted in FIG. 3 may be used to form lamination structure 20. Referring to FIG. 3 in conjunction with FIG. 2, in accordance with some embodiments of the invention, a base layer is first deposited (block 102), such as the initiation layer 561, for purposes of forming the bottom of the structure 20. The base layer may be a seed layer (i.e., a layer greater than 200 Å) that serves as an electrical contact for electroplating; or alternatively, the base layer may be a thin nucleation layer (a layer between 10 to 20 Å) that initiates electroless plating.
Next, pursuant to the technique 100, a magnetic film is plated (block 106) within an environment of an external magnetic field. Following the example depicted in FIG. 2, this corresponds to the formation of the magnetic film 601. As examples, the magnetic film 60 may include Co, Ni and/or Fe as the primary metal, with alloying elements of B, P, W, C and O. The external magnetic field, in accordance with some embodiments of the invention, has a strength of approximately 500 to 1000 Oe at the wafer surface and is aligned parallel with the film, plane. The thickness of the magnetic film 60 is 1/n of the final desired thickness is the number of laminations to be formed.
Next, pursuant to the technique 100, a high-resistivity metal nitride film (corresponding to the metal nitride layer 581) is deposited (block 110) by such vapor deposition methods as physical vapor deposition (PVD), chemical vapor deposition (CVD) or atomic layer deposition (ALD), as examples. In accordance with some embodiments of the invention, the thickness of each metal nitride film 58 is on the order of 100 Å, depending on the targeted film resistance. Typical metal nitrides may include such materials as TaN, TiN, WN, and MoN. In accordance with some embodiments of the invention, carbon (C) or silicon (Si) may be part of the metal nitride alloy. For example, in accordance with some embodiments of the invention, the metal nitride layer may be TaSiN. The metal nitride layer 58 may be deposited with a high nitrogen content in order to maximize its resistivity. As more specific examples in accordance with some embodiments of the invention, a TaN film with a resistivity of 3,000 μΩ·cm may be deposited via PVD at a nitrogen gas content of greater than 25 percent.
Next, according to the technique 100, an initiation layer 56 (such as the initiation layer 561 depicted in FIG. 2) is deposited (block 114). For purposes of electroplating the magnetic film 60, the initiation layer 56 may include such metals as Ni, Co and Cu, which may be deposited by vapor deposition. These metals serve to both increase adhesion of the magnetic material to the metal nitride layer 58 and provide a source of nucleation for the ensuing magnetic film. Alternatively, block 114 may include depositing a palladium (Pd) monolayer, which may be accomplished, for example, by using the above-mentioned palladium immobilization process in application Publication No. 2004/0248403A1.
If more laminations are to be formed (diamond 116), then the next magnetic film layer 60 is plated, pursuant to block 106, and the above-described lamination process repeats.
Many variations are possible and are within the scope of the appended claims. For example, referring to FIG. 4, in accordance with some embodiments of the invention, a laminated magnetic structure 130 may replace the structure 20. The structure 130 is similar to the structure 20, with like reference numerals being used to denote similar elements. The structures 20 and 130 differ as follows. In particular, unlike the structure 20, the structure 130 includes a high-resistivity metal nitride layer 134, which is disposed between the substrate 50 and the bottom initiation layer 561. The metal nitride layer 134 aids in integrating the structure 130 into additional circuitry, which may include, for example, an oxide layer (not shown) that is in contact with the metal nitride layer 134.
Referring to FIG. 5, as an example of another variation, a laminated magnetic material structure 150 may replace either structure 20 or 130, in accordance with other embodiments of the invention. The structure 150 is similar to the structure 20, with like reference numerals being used to denote similar elements. The structures 20 and 150 differ as follows. In particular, unlike the structure 20, the structure 150 includes a high-resistivity metal nitride layer 154 that is formed on the magnetic film 60n for purposes of integrating the structure with other circuitry that is fabricated on the substrate. Thus, many variations are possible and are within the scope of the appended claims.
The laminated magnetic material structure 20 (see FIG. 1) may be used in a variety of different applications, such as an exemplary computer system 200 that is depicted in FIG. 6. For example, the voltage regulator 10 of FIG. 1 may supply power to various components of the computer system 200, such as a processor 206 (one or more microprocessors or microcontrollers, as examples) and a memory, such as a dynamic random access memory (DRAM) 210.
While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of the invention.
Patent Application
20080075974
