Patent Publication Number: US-7906170-B2

Title: Apparatus, method, and system capable of producing a moveable magnetic field

Description:
FIELD OF THE INVENTION 
     The disclosed embodiments of the invention relate generally to semiconductor wafer manufacturing, and relate more particularly to magnetic fields used during semiconductor wafer manufacturing. 
     BACKGROUND OF THE INVENTION 
     A key requirement for the production of magnetic films for microelectronic inductors is the deposition of aligned, soft magnetic fields onto full wafers. Any capital equipment to support this film deposition will need to incorporate a solution that maintains the magnetic field alignment or risk a high degree of magnetic isotropy where, undesirably, the magnetic domains are oriented randomly. Some existing electroplating systems do have a magnetic field aligned to a deposition chamber, yet these systems only apply the magnetic field to a stationary substrate, and thus suffer from limitations in terms of temperature control and thickness uniformity. Accordingly, there exists a need for a plating tool with an applied magnetic field that is rigidly linked to a moving wafer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosed embodiments will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying figures in the drawings in which: 
         FIG. 1  is a perspective view of an apparatus capable of producing a moveable magnetic field according to an embodiment of the invention; and 
         FIG. 2  is a flowchart illustrating a method of producing an aligned magnetic field in a magnetic film according to an embodiment of the invention. 
     
    
    
     For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements. 
     The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. 
     The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In one embodiment of the invention, an apparatus capable of producing a moveable magnetic field comprises a moveable support structure and a magnetic field source supported by the moveable support structure, where the magnetic field source is in a fixed position relative to the moveable support structure. The magnetic field source generates a magnetic field at a wafer surface of at least approximately 50 Oersted (Oe) (for some embodiments the magnetic field strength is at least approximately 250 Oe), and the magnetic field is aligned so as to produce magnetic anisotropy in a plane of the moveable support structure. Embodiments of the invention will enable wafer movement while the magnetic field is fixed relative to the wafer, which may produce better temperature control and thickness uniformity than is possible with stationary systems. More specifically, temperature fluctuations may lead to unwanted fluctuations in the deposited thin magnetic film, and thickness variations can lead to processing problems later on in the semiconductor manufacturing process. 
     The synchronized movement of a magnetic field with a moving wafer or wafers such that the wafer(s) are always in a constant magnetic environment, as made possible by embodiments of the present invention, allows for the production of an integrated silicon voltage regulator (ISVR), another inductor application, or the like having well-defined magnetic properties, e.g, having magnetic anisotropy in the plane of the wafer. Embodiments of the invention may accomplish this by taking the natural domains of a thin magnetic film and aligning them in a single direction. The application of an aligned magnetic field during deposition can significantly reduce the coercivity of the resulting magnetic film. The target coercivity of soft magnetic materials for ISVR applications is less than 1 Oe, to minimize transformer power losses. 
     Referring now to the figures,  FIG. 1  is a perspective view of an apparatus  100  capable of producing a moveable magnetic field according to an embodiment of the invention. As illustrated in  FIG. 1 , apparatus  100  comprises a moveable support structure  110  and a magnetic field source  120  supported by moveable support structure  110 . Magnetic field source  120  is in a fixed position relative to moveable support structure  110 . In one embodiment, moveable support structure  110  rotates in the direction of an arrow  190 . In a different embodiment, the rotation could be in another direction. 
     In one embodiment, magnetic field source  120  generates a magnetic field at a wafer surface of at least approximately 50 Oe (with even higher field strengths—perhaps as high as 250 Oe or even higher—generally preferred for at least some embodiments), and the resulting magnetic field is aligned so as to produce magnetic anisotropy in a plane of moveable support structure  110 . In other words, and as further discussed below, magnetic field source  120  may be arranged such that it produces a continuous straight magnetic field across a substrate or wafer in the plane of a film during deposition. In other words, magnetic field source  120  may be arranged such that it produces parallel or substantially parallel field lines at all or substantially all locations on the wafer or wafers being processed. 
     In one embodiment, moveable support structure  110  and magnetic field source  120  may be integrated within a plating tool (not shown). In one embodiment, magnetic field source  120  is a permanent magnet, while in a different embodiment, magnetic field source  120  is an electromagnet. Permanent magnets are likely much heavier than electromagnets (weighing perhaps one hundred pounds or more for a 250 Oe field strength) but are simpler and produce straighter north-south magnetic field lines. 
     Moveable support structure  110  is capable of receiving a semiconducting wafer  130  on which a magnetic film  140  may be deposited, and moveable support structure  110  is further capable of holding semiconducting wafer  130  in the plane of moveable support structure  110 . As an example, the plane of moveable support structure  110  can be substantially parallel to a surface  141  of magnetic film  140  and to a surface of semiconducting wafer  130 . In one embodiment, magnetic film  140  has a coercivity of less than approximately 1.0 Oe. In the same or another embodiment, magnetic film  140  comprises cobalt and at least one of tungsten, boron, iron, and phosphorus. 
     In the illustrated embodiment, semiconducting wafer  130  has a side  131  and an opposing side  132 , and magnetic field source  120  comprises a permanent magnetic bar  121  located at side  131  and a permanent magnetic bar  122  located at side  132 . As illustrated, permanent magnetic bar  121  has a first axis with a north pole at a first end thereof and a south pole at an opposing second end thereof, and permanent magnetic bar  122  has a second axis with a north pole at a first end thereof and a south pole at an opposing second end thereof. Note that permanent magnetic bars  121  and  122  are thus aligned in attraction with each other. In one embodiment, magnetic field source  120  comprises a first plurality of permanent magnetic bars, including permanent magnetic bar  121 , located at side  131  of semiconducting wafer  130  and further comprises a second plurality of permanent magnetic bars, including permanent magnetic bar  122 , located at side  132  of semiconducting wafer  130 . 
     As illustrated in  FIG. 1 , permanent magnetic bar  121  has a height  125  and permanent magnetic bar  122  has a height  126 . Semiconducting wafer  130  has a height  135 . In one embodiment, height  125  and height  126  are each at least as great as height  135 , thus allowing, for example, for multiple wafers to be processed at once. In the same or another embodiment, semiconducting wafer  130  and magnetic film  140  together have a height  139 , and height  125  and height  126  are each at least as great as height  139 . Similarly, permanent magnetic bar  121  has a depth  127  and permanent magnetic bar  122  has a depth  128 , while semiconducting wafer  130  has a depth (or diameter)  137 . In one embodiment, depth  127  and depth  128  are each at least as great as depth  137 . 
       FIG. 2  is a flowchart illustrating a method  200  of producing an aligned magnetic field in a magnetic film according to an embodiment of the invention. A step  210  of method  200  is to provide a moveable support structure including a magnetic field source capable of generating a magnetic field at a wafer surface of at least approximately 50 Oersted. As an example, the moveable support structure can be similar to moveable support structure  110  that is shown in  FIG. 1 . As another example, the magnetic field source can be similar to magnetic field source  120  that is also shown in  FIG. 1 . 
     A step  220  of method  200  is to cause the magnetic field source to be in a fixed position relative to the moveable support structure. 
     A step  230  of method  200  is to align the magnetic field so as to produce magnetic anisotropy in a plane of the moveable support structure. 
     A step  240  of method  200  is to place a semiconducting wafer in the plane of the moveable support structure. As an example, the semiconducting wafer can be similar to semiconducting wafer  130  that is shown in  FIG. 1 . 
     A step  250  of method  200  is to deposit the magnetic film while rotating the support structure. As an example, the magnetic film can be similar to magnetic film  140  that is shown in  FIG. 1 . In one embodiment, step  250  comprises depositing a film comprising cobalt. In the same or another embodiment, step  250  comprises depositing a cobalt-tungsten-boron film. In the same or another embodiment, step  250  comprises electrolessly depositing the magnetic film. 
     Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the spirit or scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be limiting. It is intended that the scope of the invention shall be limited only to the extent required by the appended claims. For example, to one of ordinary skill in the art, it will be readily apparent that the apparatus and related methods and systems discussed herein may be implemented in a variety of embodiments, and that the foregoing discussion of certain of these embodiments does not necessarily represent a complete description of all possible embodiments. 
     Additionally, benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims. 
     Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents.