Patent Publication Number: US-2009230445-A1

Title: Magnetic Memory Devices Including Conductive Capping Layers

Description:
CLAIM OF PRIORITY 
     This application is a divisional of U.S. patent application Ser. No. 11/350,545 which claims priority under 35 U.S.C. § 119 from Korean Patent Application No. 2005-32001, filed on Apr. 18, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference as if set forth in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods of forming semiconductor devices and, more particularly, to methods of forming semiconductor memory devices and resulting semiconductor memory devices. 
     BACKGROUND 
     A magnetic memory device is a kind of a non-volatile memory device in which data is programmed or erased using a magnetic field. With the potential benefits of high speed, low density, and/or non-volatility, magnetic memory devices are increasingly becoming attractive as novel memory devices. 
     A typical magnetic memory device employs a magnetic tunnel junction (MTJ) pattern as a data storage element. The resistance of the MTJ pattern varies with an external magnetic field, which leads to a change in the amount of current flowing through the MTJ pattern. The change in the amount of the current is sensed to indicate a logic “1” or a logic “0”. 
     Generally, an MTJ pattern includes two magnetic layers and a tunnel barrier layer interposed therebetween. One of the magnetic layers has a changeable magnetization orientation when a magnetic field is applied, while the other has a fixed magnetization orientation even when a magnetic field is applied. Therefore, the two magnetic layers may have the same magnetization orientation or opposite magnetization orientations. The resistance of the MTJ pattern in which the two magnetic layers have the same magnetization orientation is lower than when the two magnetic layers are in different magnetization orientations. 
     A method of forming a conventional magnetic memory device will now be described with reference to  FIG. 1  and  FIG. 2 . 
     Referring to  FIG. 1 , a bottom magnetic layer  2 , a tunnel barrier layer  3 , a top magnetic layer  4 , and a conductive capping layer  5  are formed in order on a substrate  1 . The bottom magnetic layer  2  has a fixed magnetization orientation. That is, the magnetization orientation of the bottom magnetic layer  2  may be continuously fixed even when an external magnetic field is applied. Furthermore, the magnetization orientation of the top magnetic layer  4  is changeable with an external magnetic field. 
     Referring to  FIG. 2 , the conductive capping layer  5 , the top magnetic layer  4 , the tunnel barrier layer  3 , and the bottom magnetic layer  2  are successively patterned to form a bottom magnetic pattern  2   a , a tunnel barrier pattern  3   a , a top magnetic pattern  4   a , and a capping pattern  5   a  that are stacked in order on the substrate  1 . The bottom magnetic pattern  2   a , the tunnel barrier pattern  3   a , and the top magnetic pattern  4   a  form a MTJ pattern. 
     During an etch process to form the MTJ pattern, an etch byproduct  6  may be produced on a sidewall of the MTJ pattern. Since the etch byproduct  6  may include conductive materials from the bottom and/or top magnetic patterns  2   a  and  5   a , it may become conductive, which may cause a short-circuit between the bottom and top magnetic patterns  2   a  and  5   a . Thus, the desired property of the MTJ pattern (namely, that the resistance varies with the magnetization orientations of the magnetic patterns  2   a  and  5   a ) may be lost, which may result in a malfunction of the magnetic memory device. 
     SUMMARY 
     Some embodiments of the present invention provide methods of forming magnetic memory devices. In some embodiments, a first magnetic layer, a tunnel barrier layer, and a second magnetic layer are sequentially formed on a semiconductor substrate. The first magnetic layer may have a fixed magnetization orientation, and the second magnetic layer may have a changeable magnetization orientation. A conductive capping pattern is formed on the second magnetic layer, and portions of the second magnetic layer are oxidized using the conductive capping pattern as a mask, to form an unoxidized second magnetic pattern that is disposed below the conductive capping pattern. The oxidized portion of the second magnetic layer is removed to expose the tunnel barrier layer and opposite sidewalls of the second magnetic pattern. The second magnetic layer may include a ferromagnetic material such as iron (Fe), nickel (Ni), and/or cobalt (Co). 
     In some embodiments, a first magnetic layer, a tunnel barrier layer, and a second magnetic layer may be sequentially formed on a substrate. The first magnetic layer may have a fixed magnetization orientation and the second magnetic layer may include cobalt-iron-boron (CoFeB). A conductive capping pattern may be formed on the second magnetic layer, and the second magnetic layer may be oxidized using the conductive capping pattern as a mask to form a second magnetic pattern that is an unoxidized portion of the second magnetic layer disposed below the conductive capping pattern. The oxidized portion of the second magnetic layer may be removed to expose the tunnel barrier layer and opposite sidewalls of the second magnetic pattern. The exposed tunnel barrier layer and the first magnetic layer may be successively patterned to form a first magnetic pattern and a tunnel barrier pattern. A second surface of the tunnel barrier layer may be larger than a first surface of the second magnetic pattern. Removing the oxidized portion of the second magnetic layer may be done by means of an etch process using an etch gas including argon gas, chlorine gas, and/or oxygen gas. 
     A magnetic memory device according to some embodiments of the invention includes a first magnetic layer having opposing sidewalls, a tunnel barrier layer on the first magnetic layer, the tunnel barrier layer having a top surface and having opposing sidewalls aligned with the opposing sidewalls of the first magnetic layer, and a second magnetic layer on the tunnel barrier layer, the second magnetic layer having a bottom surface that may be narrower than the top surface of the tunnel barrier layer and opposing side surfaces that are spaced apart from the opposing side surfaces of the tunnel barrier layer. A conductive capping layer having opposing sidewalls aligned with the opposing sidewalls of the second magnetic layer is on the second magnetic layer. 
     The first magnetic layer may include a pinning layer, a first pinned layer, an inversion layer, and a second pinned layer. The first and second pinned layers include a ferromagnetic material, the pinning layer may include an antiferromagnetic material configured to fix a magnetization orientation of the first pinned layer, and the inversion layer may be configured to fix a magnetization orientation of the second pinned layer to be opposite to the magnetization orientation of the first pinned layer. The tunnel barrier layer may include aluminum oxide and/or magnesium oxide. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate certain embodiment(s) of the invention. In the drawings: 
         FIG. 1  and  FIG. 2  are cross-sectional views illustrating operations associated with forming a conventional magnetic memory device. 
         FIG. 3  through  FIG. 10  are cross-sectional views illustrating operations associated with forming magnetic memory devices according to some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
     Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” or “top” or “bottom” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. For example, a layer designated as a “top” layer of a structure may become a bottom layer if the structure is inverted. 
     Embodiments of the invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. The thickness of layers and regions in the drawings may be exaggerated for clarity. Additionally, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a discrete change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the invention. 
     Referring to  FIG. 3 , device isolation layers (not shown) are formed in a semiconductor substrate  100  to define active regions. A gate electrode  104  is formed to cross over the active regions with a gate insulator  102  interposed therebetween. The gate insulator  102  may be made of silicon oxide and/or a high-k dielectric, such as metal oxide (e.g., hafnium oxide and/or aluminum oxide) having a higher dielectric constant than silicon oxide. The gate electrode  104  may include a conductive material, such as doped polysilicon, metal (e.g., tungsten or molybdenum), conductive metal nitride (e.g., titanium nitride or tantalum nitride), and/or metal silicide (e.g., tungsten silicide or cobalt silicide). 
     Using the gate electrode  104  as a mask, impurity ions are implanted to form impurity diffusion layers  106  at active regions on opposite sides of the gate electrode  104 . The impurity diffusion layer  106  may correspond to source/drain regions, and the gate electrode  104  and the impurity diffusion layer  106  may together form a metal oxide semiconductor (MOS) transistor. An insulative capping pattern (not shown) may be formed on the gate electrode  104 . Further, a gate spacer (not shown) may be formed on opposite sidewalls of the gate electrode  104 . 
     A lower interlayer dielectric  108  is formed on the surface of the semiconductor substrate  100  including the gate electrode  104  and the impurity diffusion layer  106 . A top surface of the lower interlayer dielectric  108  may be planarized. The lower interlayer dielectric  108  may include, for example, silicon oxide. 
     A digit line  110  is formed on the lower interlayer dielectric  108 . The digit line  110  may be disposed in parallel with the gate electrode  104 . In order to possibly provide enhanced integration density, the digit line  110  may overlap the gate electrode  104 . The digit line  110  and the gate electrode  104  are insulated from one another by the lower interlayer dielectric  108 . A middle interlayer dielectric  112  is formed on an entire surface of the semiconductor substrate  100  including the digit line  110 . A top surface of the middle interlayer dielectric  112  may be planarized. The middle interlayer dielectric  112  may include, for example, silicon oxide. 
     Referring to  FIG. 4 , a contact hole  114  is formed by successively penetrating the middle and lower interlayer dielectrics  112  and  108  disposed at one side of the digit line  110  to expose the impurity diffusion layer  106 . A contact plug  116  is formed to at least partially fill the contact hole  114 . The contact plug  116  and the digit line  110  are spaced to be electrically insulated from each other. 
     In order to reduce the aspect ratio of the contact hole  114 , the contact hole  114  may be formed to expose a buffer pattern (not shown) that is formed between the lower and the middle interlayer dielectrics  108  and  112  and that is spaced apart from the digit line  110 . In that case, the contact plug  116  is electrically connected to the buffer pattern. The buffer pattern may be made of the same material as the digit line  110 . The buffer pattern is connected to a top surface of a lower contact plug (not shown), which is coupled to the impurity diffusion layer  106 , through the lower interlayer dielectric  108 . 
     A bottom electrode layer  118 , a bottom magnetic layer  128 , a tunnel barrier layer  130 , a top magnetic layer  132 , and a conductive capping layer  135  are sequentially formed on the middle interlayer dielectric  112 . The bottom electrode layer  118  is electrically connected to a top surface of the contact plug  116 . In order to provide a relatively low reactivity, the bottom electrode layer  118  may include a conductive material that may act as a barrier layer. For example, the bottom electrode layer  118  may include a conductive metal nitride such as, for example, titanium nitride, tantalum nitride and/or tungsten nitride. 
     The bottom magnetic layer  128  may have a fixed magnetization orientation. The bottom magnetic layer  128  may include a pinning layer  120 , a first pinned layer  122 , an inversion layer  124 , and a second pinned layer  126  that may be stacked in order on the bottom electrode layer  118 . 
     Each of the first and second pinned layers  122  and  126  is made of a ferromagnetic material including, for example, iron (Fe), nickel (Ni), and/or cobalt (Co). In some embodiments, each of the first and second pinned layers  122  and  126  may include CoFe, NiFe and/or CoFeB. Of the first and second pinned layers  122  and  126 , the second pinned layer  126  disposed near the top magnetic layer  132  may be thinner than the first pinned layer  122 . 
     The pinning layer  120  includes a material capable of fixing the magnetization orientation of the first pinned layer  122  in one direction. Accordingly, the pinning layer  120  may include an antiferromagnetic material such as, for example, FeMn, IrMn, PtMn, MnO, MnS, MnTe, MnF 2 , FeF 2 , FeCl 2 , NiO, and/or Cr. The inversion layer  124  may include a material capable of fixing the magnetization orientation of the second pinned layer  126  to be opposite to the magnetization of the first pinned layer  122 . Accordingly, the inversion layer  124  may include, for example, ruthenium (Ru), iridium (Ir), and/or rhodium (Rh). 
     The tunnel barrier layer  130  may include, for example, aluminum oxide and/or magnesium oxide. The top magnetic layer  132  may include a material whose magnetic orientation is changeable with an external magnetic field. Accordingly, the top magnetic layer  132  may include a ferromagnetic material such as, for example, iron (Fe), nickel (Ni), and/or cobalt (Co). Namely, the top magnetic layer  132  may include, for example, CoFe, NiFe and/or CoFeB. 
     The conductive capping layer  135  may include a conductive metal nitride, such as titanium nitride, tantalum nitride and/or tungsten nitride. Referring to  FIG. 5 , the conductive capping layer  135  may be patterned to form a conductive capping pattern  135   a  on the top magnetic layer  132 . The conductive capping pattern  135   a  may be disposed to overlap the digit line  110 . In regions other than the region in which the conductive capping pattern  135   a  is formed, the top magnetic layer  132  is exposed. The conductive capping pattern  135   a  may form an island-shaped pattern. In particular, the conductive capping pattern  135   a  may appear rectangular when viewed from above. 
     Referring to  FIG. 6  and  FIG. 7 , an oxidation process is performed on the semiconductor substrate  100  including the conductive capping pattern  135   a  to oxidize the top magnetic layer  132 . That is, using the conductive capping pattern  135   a  as a mask, the top magnetic layer  132  may be oxidized. As a result, the top magnetic layer  132  may be segmented into an unoxidized portion  132   a  and an oxidized portion  132   b . The unoxidized portion  132   a  is disposed below the conductive capping pattern  135   a , and the oxidized portion  132   b  may surround the unoxidized portion  132   a.    
     The unoxidized portion  132   a  defines as a top magnetic pattern  132   a . Since the top magnetic layer  132  is made of a ferromagnetic material, the top magnetic pattern  132   a  may form a ferromagnetic pattern. The oxidized portion  132   b  of the top magnetic layer  132  is an oxidized ferromagnetic material  132   b . Hereinafter, the oxidized portion  132   b  of the top magnetic layer may be referred to as the oxidized ferromagnetic material  132   b.    
     The oxidized portion  132   b  is removed by means of an etch process to expose sidewalls of the top magnetic pattern  132   a  and the tunnel barrier layer  130 . In some embodiments, the oxidized portion  132   b  may be removed completely. Using the conductive capping pattern  135   a  as a mask, the top magnetic pattern  132   a  is formed to overlap the digit line  110 . An etch gas used to etch the oxidized ferromagnetic material  132   b  may include, for example, at least argon gas (Ar) and chlorine gas. In addition, the etch gas may further include oxygen gas. In the etch process, an inflow rate of the chlorine gas may be much lower than that of the argon gas. Specifically, the inflow rate of the chlorine gas may equal about to 0.1 to 2.0 percent of the inflow rate of the argon gas. Further, the etch process may utilize a bias power of from about 30 to about 70 watts. 
     There may be a very high etch selectivity between the oxidized ferromagnetic material  132   b  and the tunnel barrier layer  130 . In particular, the etch selectivity between the oxidized ferromagnetic material  132   b  and the tunnel barrier layer  130  may be higher than the etch selectivity between the top magnetic pattern (i.e., unoxidized ferromagnetic)  132   a  and the tunnel barrier layer  130 . This may be because oxygen elements in the oxidized ferromagnetic  132   b  may reduce the coupling of other elements therein. Therefore, although the tunnel barrier layer  130  may have a very small thickness of about 10 angstroms, the oxidized ferromagnetic material  132   b  may be removed using the tunnel barrier layer  130  as an etch-stop layer. Accordingly, the bottom magnetic layer  128  below the tunnel barrier layer  130  may not be exposed in the etch process. As a result, a short-circuit may not occur between the top magnetic pattern  132   a  and the bottom magnetic layer  128  even if etch byproducts are produced in the etch process. 
     A test was conducted to confirm an etch selectivity between an oxidized ferromagnetic material and a tunnel barrier layer, and an etch selectivity between a ferromagnetic material and the tunnel barrier layer. Samples 1, 2, and 3 were prepared for the test. A layer of Al 2 O 3  layer acting as a tunnel barrier layer, a layer of CoFeB being ferromagnetic, and a layer of CoFeBO x  being oxidized ferromagnetic were formed in the samples 1, 2, and 3, respectively. Under the same etch recipe, an etch process was performed for the samples 1, 2, and 3. 
     The etch process applied to the test used an etch gas including argon gas, chlorine gas, and oxygen gas. In the etch recipe for the etch process, an inner pressure of a process chamber was 10 mTorr; an inflow rate of the argon gas was 200 sccm, an inflow rate of the chlorine gas was 1 sccm, and an inflow rate of the oxygen gas was 20 sccm. Source power for plasmatically activating these etch gases was 1,500 watts, and bias power applied to a chuck on which these samples are loaded was 50 watts. Etch rates of the above material layers are shown in the table [TABLE 1]. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Kind of Layers 
                 Etch Rate (Å/sec) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Al 2 O 3   
                 0.0014 
               
               
                   
                 CoFeB 
                 0.0260 
               
               
                   
                 CoFeBO x   
                 0.0339 
               
               
                   
                   
               
            
           
         
       
     
     As shown in the table [TABLE 1], CoFeBO x  of the sample 3 has a higher etch rate than CoFeB of the sample 2, i.e., CoFeBO x  is etched faster than CoFeB. Etch selectivities between these material layers were computed using the etch rates of the table [TABLE 1] and are shown in the table [TABLE 2]. 
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Etch Selectivity 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 CoFeB/Al 2 O 3   
                 18.5 
               
               
                   
                 CoFeBO x /Al 2 O 3   
                 24.2 
               
               
                   
                   
               
            
           
         
       
     
     As shown in the table [TABLE 2], an etch selectivity between CoFeBO x  and Al 2 O 3  is 24.2, which is higher than an etch selectivity (18.5) between CoFeB and Al 2 O 3 . 
     As evidenced by the above-described test, an oxidized ferromagnetic material may have a higher etch rate than an unoxidized ferromagnetic material. Therefore, an etch selectivity between the oxidized portion  132   b  of the top magnetic layer  132  and the tunnel barrier layer  130  may relatively high. As a result, the oxidized portion  132   b  may be efficiently removed using the tunnel barrier layer  130  as an etch-stop layer. Although etch byproducts may be produced in the etch process, a short-circuit may not occur between the top magnetic pattern  132   a  and the bottom magnetic layer  128  because the bottom magnetic layer  128  may remain covered with the tunnel barrier layer  130 . 
     As previously stated, the inflow rate of the chlorine gas may be equal to about 0.1 to 2.0 percent of the inflow rate of the argon gas. The amount of the chlorine gas used may be much smaller than that of the argon gas used. Since chlorine gas has a high reactivity, use of a smaller amount of the chlorine gas enables the etch process to have a higher etchability than an etchability based on chemical reaction. The bias power of the etch process may be relatively low (from about 30 to about 70 watts), which may reduce etch damage to the tunnel barrier layer  130  and/or may enhance an etch selectivity between the oxidized portion  132   b  of the top magnetic layer  132  the tunnel barrier layer  130  (as atomic coupling of the oxidized portion  132   b  may be weakened by oxygen elements). 
     The above-described effects may be obtained even if the tunnel barrier layer  130  is made of magnesium oxide. 
     The oxidized portion  132   b  of the top magnetic layer  132  is removed by means of the etch process to expose opposite sidewalls of the top magnetic pattern  132   a.    
     The oxidized portion  132   b , i.e., the oxidized ferromagnetic material  132   b  of the top magnetic layer  132 , may have an antiferromagnetic property. Accordingly, if the oxidized ferromagnetic material  132   b  partially remains on the sidewall(s) of the top magnetic pattern  132   a , the magnetization orientation of the top magnetic pattern  132   a  may be fixed due to the remaining oxidized ferromagnetic material  132   b . Thus, the property of a magnetic tunnel junction pattern may be lost, which may cause a malfunction of a magnetic memory device. 
     However, according to some embodiments of the invention, the oxidized portion  132   b  of the top magnetic layer  132  may be completely removed by means of the etch process to reduce or possibly prevent the magnetization direction of the top magnetic pattern  132   a  from becoming fixed on one direction. 
     Referring to  FIG. 7 , a mask pattern  137  may be formed on portions of the semiconductor substrate  100  where the oxidized portion  132   b  of the top magnetic layer  132  has been removed. The mask pattern  137  is provided on the conductive capping pattern  135   a  and the top magnetic pattern  132   a . In particular, in some embodiments, the mask pattern  137  may fully cover the opposite sidewalls of the top magnetic pattern  132   a . Namely, a planar area of the mask pattern  137  may be larger than a top surface of the conductive capping pattern  135   a . Thus, the mask pattern  137  may be provided on a portion of the tunnel barrier layer  130  in the vicinity of the conductive capping pattern  135   a . Also the mask pattern  137  may extend laterally over the contact plug  116 . The mask pattern  137  may be a photoresist pattern. 
     Referring to  FIG. 8 , using the mask pattern  137  as a mask, the tunnel barrier layer  130 , the bottom magnetic layer  128 , and the bottom electrode layer  118  are successively etched to form a bottom electrode  118   a , a bottom magnetic pattern  128   a , and a tunnel barrier pattern  130   a  which are sequentially stacked on the substrate  100 . The bottom magnetic pattern  128   a  includes a pinning pattern  120   a , a first pinned pattern  122   a , an inversion pattern  124   a , and a second pinned pattern  126   a , which are sequentially stacked on the substrate  100 . The bottom magnetic pattern  128   a , the tunnel barrier pattern  130   a , and the top magnetic pattern  132   a  may together form a magnetic tunnel junction pattern. 
     A top surface of the tunnel barrier pattern  130   a  is larger than a bottom surface of the top magnetic pattern  132   a , and the bottom magnetic pattern  128   a  has a sidewall aligned with a sidewall of the tunnel barrier pattern  130   a . In addition, the sidewall of the top magnetic pattern  132   a  and the sidewall of the bottom magnetic pattern  128   a  may be spaced apart from each other. 
     In an etch process to form the tunnel barrier pattern  130   a  and the bottom magnetic pattern  128   a , the conductive capping pattern  135   a  may be provided on the top surface of the top magnetic pattern  132   a  and the mask pattern  137  may be provided on an exposed sidewall of the top magnetic pattern  132   a . Therefore, although byproducts may be produced in the etch process to form the patterns  130   a  and  128   a , a short-circuit may not occur between the patterns  132   a  and  128   a.    
     The first and second pinned patterns  122   a  and  126   a  are ferromagnetic patterns each having a fixed magnetization orientation. Accordingly, magnetic fields generated by the first and second pinned patterns  122   a  and  126   a  may affect the top magnetic pattern  132   a . The magnetization orientations of the first and second patterns  122   a  and  126   a  may be opposite to each other due to the presence of the inversion pattern  124   a . Hence, the magnetic fields affecting the top magnetic pattern  132   a  may be offset by the first and second pinned patterns  122   a  and  126   a . As a result, the top magnetic pattern  132   a  may not be affected by the magnetic fields established from the first and second patterns  122   a  and  126   a . Moreover, the second pinned pattern  126   a  may be thicker than the first pinned pattern  122   a . Therefore, it may be possible to counterbalance a magnetic field intensity difference resulting from a difference in distance between the first and second pinned patterns  122   a  and  126   a  and the top magnetic pattern  132   a.    
     Referring to  FIG. 9 , the mask pattern  137  is removed. An upper interlayer dielectric  142  may be formed on a surface of the semiconductor substrate  100  above the conductive capping pattern  135   a  and the MTJ pattern  140 . The upper interlayer dielectric  142  may include, for example, silicon oxide. 
     A top surface of the conductive capping pattern  135   a  may be exposed. A way to expose the top surface of the conductive capping pattern  135   a  is now described. The upper interlayer dielectric  142  is planarized down to the top surface of the conductive capping pattern  135   a . Thus, the top surface of the conductive capping pattern  135   a  is at least partially exposed. Alternatively, a contact hole (not shown) may be formed to penetrate the upper interlayer dielectric  142 . That is, at least a portion of the top surface of the conductive capping pattern  135   a  may be exposed by the contact hole. 
     When the top magnetic layer  132  is oxidized, an oxide layer may be formed on the top surface of the conductive capping pattern  135   a . The oxide layer is removed when the top surface of the conductive capping pattern  135   a  is exposed. That is, the oxide layer formed on the top surface of the conductive capping pattern  135   a  is removed when the upper interlayer dielectric  142  is planarized and/or the contact hole is formed. 
     Referring to  FIG. 10 , a bitline  144  is formed on the upper interlayer dielectric  142  to cross over the digit line  110 . The bitline  144  is electrically connected to the exposed conductive capping pattern  135   a . The bitline  144  covers the top magnetic pattern  132   a . The top magnetic pattern  132   a  is disposed between the bitline  144  and the digit line  110 . In other words, the top magnetic pattern  132   a  is disposed at an intersection of the bitline  144  and the digit line  110 . As a result, the magnetization orientation of the top magnetic pattern  135   a  may vary with magnetic fields established between the bitline  144  and the digit line  110 . 
     According to some embodiments of the invention, a top magnetic layer is oxidized using a conductive capping pattern as a mask to enhance an etch selectivity between a tunnel barrier layer and a portion where the top magnetic layer is removed. Thus, an oxidized portion of the top magnetic layer may be efficiently removed using the tunnel barrier layer as an etch-stop layer. Since a bottom magnetic layer is covered with the tunnel barrier layer during an etch process to remove the oxidized portion of the top magnetic layer, a short-circuit may not occur between the top magnetic pattern and the bottom magnetic layer even if etch byproducts are produced in the etch process. The oxidized portion of the top magnetic layer may be fully removed to expose opposite sidewalls of a top magnetic pattern. The oxidized portion of the top magnetic layer, which has an antiferromagnetic property, may be removed to reduce or prevent degradation in characteristics of the top magnetic pattern. 
     In the drawings and specification, there have been disclosed typical embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.