Patent Publication Number: US-2015072440-A1

Title: Method of manufacturing magnetoresistive element

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/875,478, filed Sep. 9, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a method of manufacturing a magnetoresistive element. 
     BACKGROUND 
     An MRAM (magnetic random access memory) chip employed as a nonvolatile semiconductor storage uses a magnetoresistive element as a storage element. The magnetoresistive element has a structure in which a tunnel barrier layer (non-magnetic layer) is sandwiched between a storage layer (magnetic layer) and a reference layer (magnetic layer). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing an example of a magnetoresistive element of a first embodiment; 
         FIG. 2  is a cross-sectional view showing an example of a magnetoresistive element of a second embodiment; 
         FIG. 3  to  FIG. 8  are cross-sectional views showing a manufacturing method of the magnetoresistive element shown in  FIG. 2 ; 
         FIG. 9  to  FIG. 11  are block diagrams showing an example of a multi-chamber; 
         FIG. 12  is an illustration showing an example of a manufacturing device executing RIE; 
         FIG. 13  is a block diagram showing an example of a magnetic random access memory; and 
         FIG. 14  is a cross-sectional view showing an example of a memory cell. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a method of manufacturing a magnetoresistive element, the method comprises: forming a non-magnetic layer on a first magnetic layer; forming a second magnetic layer on the non-magnetic layer; and patterning the second magnetic layer by a RIE using an etching gas including a noble gas and a hydrocarbon gas; and patterning the non-magnetic layer and the first magnetic layer after patterning the second magnetic layer. 
     The embodiments will be hereinafter described with reference to the attached drawings. 
     First Embodiment 
       FIG. 1  shows a magnetoresistive element of First Embodiment. 
     First magnetic layer  11  is disposed on underlayer UL. Non-magnetic layer  12  is disposed on first magnetic layer  11 . Second magnetic layer  13  is disposed on non-magnetic layer  12 . Hard mask layer HM is disposed on second magnetic layer  13 . 
     Second magnetic layer  13  is patterned by, for example, RIE using an etching gas including a noble gas and a hydrocarbon gas, and using hard mask layer HM as a mask. In other words, second magnetic layer (for example, CoFeB, etc.)  13  is etched by the noble gas, and generates a carbon compound by reacting with carbon in the hydrocarbon gas. 
     For this reason, patterning of second magnetic layer  13  of the present embodiment can enhance etching anisotropy as compared with, for example, RIE using halogen gas. 
     In addition, the patterning is executed while generating the carbon compound, and non-magnetic layer (for example, MgO, etc.)  12  does not react with carbon in the hydrocarbon gas. Since the carbon compound is deposited on a surface of non-magnetic layer  12  at the time when the surface of non-magnetic layer  12  is exposed, non-magnetic layer  12  is protected by this deposit. 
     Accordingly, in the patterning of second magnetic layer  13 , non-magnetic layer  12  serving as a base of second magnetic layer  13  can be prevented from being etched. 
     For example, when one of first magnetic layer  11  and second magnetic layer  13  is a storage layer having variable magnetization and the other is a reference layer having invariable magnetization, stopping the etching of second magnetic layer  13  on the surface of non-magnetic layer (tunnel barrier layer)  12 , what is called “stop on tunnel barrier” can be executed. 
     Side wall insulating layers SWM are formed on side walls of second magnetic layer  13  after patterning second magnetic layer  13 . First magnetic layer  11  is patterned by, for example, RIE using a noble gas, and using hard mask layer HM and side wall insulating layers SWM as masks, after forming side wall insulating layers SWM. 
     First magnetic layer  11  and second magnetic layer  13  may be in a perpendicular magnetization type having perpendicular magnetization or an in-plane magnetization type having in-plane magnetization. 
     The etching gas used for the patterning of first magnetic layer  11  and second magnetic layer  13  may contain nitrogen gas, hydrogen gas, etc. It is desirable, however, that these gases should not contain oxygen gas or an oxygen compound gas to prevent oxidization of first magnetic layer  11  and second magnetic layer  13 . 
     Furthermore, an interface layer (magnetic layer) may be disposed between first magnetic layer  11  and non-magnetic layer  12 , and between non-magnetic layer  12  and second magnetic layer  13 . In this case, the interface layer between non-magnetic layer  12  and second magnetic layer  13  is etched by RIE using an etching gas including a noble gas and hydrocarbon gas, similarly to second magnetic layer  13 . 
     Accordingly, the etching of second magnetic layer  13  can be certainly stopped when the surface of non-magnetic layer  12  is exposed, as compared with, for example, executing the patterning of second magnetic layer  13  by physical etching (for example, IBE), RIE using halogen gas, etc. 
     Second Embodiment 
       FIG. 2  shows a magnetoresistive element of Second Embodiment. 
     Underlayer UL is disposed on lower electrode LE, first magnetic layer  11  is disposed on underlayer UL, non-magnetic layer (tunnel barrier layer)  12  is disposed on first magnetic layer  11 , and second magnetic layer  13  is disposed on non-magnetic layer  12 . Second magnetic layer  13  may comprise layers such as first layer  13   a  and second layer  13   b  or may be a single layer. 
     Shift cancel layer SCL is disposed on second magnetic layer  13 . Shift cancel layer SCL can cancel a stray magnetic field applied from second magnetic layer  13  onto first magnetic layer  11  when, for example, first magnetic layer  11  is a storage layer and second magnetic layer  13  is a reference layer. 
     Shift cancel layer SCL thus comprises a magnetic layer having a perpendicular and invariable magnetization direction, similarly to the reference layer. The invariable magnetization direction indicates that the magnetization direction is invariable to a predetermined write current. 
     Cap layer CAP is disposed on shift cancel layer SCL. Hard mask layer HM is disposed on cap layer CAP. 
     Hard mask layer HM is of, for example, W, Ta, TaN, Ti, TiN, etc. Cap layer CAP is of, for example, Pt, W, Ta, Ru, etc. Shift cancel layer SCL is of, for example, CoPt, CoMn, CoPd, etc. 
     First layer  13   a  in second magnetic layer  13  is of, for example, CoFeB, etc. Second layer  13   b  in second magnetic layer  13  is of, for example, CoPt, CoMn, CoPd, etc. Non-magnetic layer  12  is of, for example, MgO, AlO, etc. First magnetic layer  11  is of, for example, CoFeB, etc. 
     Underlayer UL is of, for example, Hf, AlN, TaAlN, etc. Lower electrode LE is of, for example, W, Ta, TaN, Ti, TiN, etc. 
     The structure shown in  FIG. 2  is formed by, for example, a first etching process using hard mask layer HM as a mask and a second etching process using hard mask layer HM and side wall insulating layers (side wall mask layers) SWM as masks. 
     In the first etching process, cap layer CAP, shift cancel layer SCL, and second magnetic layer  13  are etched. In the second etching process, non-magnetic layer  12 , first magnetic layer  11 , and underlayer UL are etched. Protective layer PL is formed after the first and second etching processes. 
     Each of Side wall mask layers SWM and protective layer PL comprises, for example, an insulator layer of silicon nitride, silicon oxide, etc. 
       FIG. 3  to  FIG. 8  show an example of a manufacturing method for obtaining the structure shown in  FIG. 2 . 
     First, underlayer UL is formed on lower electrode LE, first magnetic layer  11  is formed on underlayer UL, non-magnetic layer (tunnel barrier layer)  12  is formed on first magnetic layer  11 , and second magnetic layer  13  is formed on non-magnetic layer  12 , as shown in  FIG. 3 . Second magnetic layer  13  comprises first layer  13   a  and second layer  13   b.    
     Subsequently, shift cancel layer SCL is formed on second magnetic layer  13 , cap layer CAP is formed on shift cancel layer SCL, and hard mask layer HM is formed on cap layer CAP. 
     Next, a first patterning process is executed as shown in  FIG. 4 . In the first patterning process, cap layer CAP, shift cancel layer SCL and second magnetic layer  13  are etched by using hard mask layer HM as a mask. The first patterning process will be described later. 
     Next, insulating layer (for example, silicon nitride) I to cover hard mask layer HM, cap layer CAP, shift cancel layer SCL, and second magnetic layer  13  is formed by, for example, CVD, as shown in  FIG. 5 . 
     Subsequently, side wall insulating layers (side wall mask layers) SWM to cover the side walls of hard mask layer HM, cap layer CAP, shift cancel layer SCL, and second magnetic layer  13  are formed by etching insulating layer I, by the etching method such as IBE and RIE, as shown in  FIG. 6 . 
     Next, a second patterning process is executed as shown in  FIG. 7 . In the second patterning process, non-magnetic layer  12 , first magnetic layer  11  and underlayer UL are etched by using hard mask layer HM and side wall mask layers SWM as masks. The details of the second etching process will be described later. 
     Finally, protective layer (for example, silicon nitride) PL to cover the magnetoresistive element is formed on lower electrode LE as shown in  FIG. 8 . 
     The structure shown in  FIG. 2  is completed in the above-described steps. 
     The first patterning process will be described here. 
     The first patterning process is a process for sequentially etching cap layer CAP, shift cancel layer SCL, and second magnetic layer  13  as shown in  FIG. 4 . 
     In the Second Embodiment, at least the etching of first layer  13   a  in second magnetic layer  13  in contact with non-magnetic layer  12  is executed by RIE using an etching gas containing a noble gas and hydrocarbon gas. In the first patterning process, what is called “stop on tunnel barrier” is thereby executed certainly. 
     Table 1 shows a first example of combination of the etching methods which can be employed in the first patterning process. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 First Patterning process 
                 A 
                 B 
                 C 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Upper layer ↑ 
                 Cap layer CAP 
                 RIE 
                 IBE 
                 IBE 
               
               
                 Layer 
                 Shift cancel layer SCL 
                 with noble 
                 RIE 
                 RIE 
               
            
           
           
               
               
               
               
               
               
            
               
                 Lower layer ↓ 
                 Second magnetic  
                 Second layer 13b  
                 gas and 
                 with noble 
                 with noble 
               
               
                   
                 layer 13 
                 First layer 13a 
                 hydrocarbon  
                 gas and 
                 gas and  
               
               
                   
                   
                   
                 gas 
                 hydrocarbon  
                 hydrocarbon  
               
               
                   
                   
                   
                   
                 gas 
                 gas 
               
               
                   
               
            
           
         
       
     
     In Case A, in Table 1, all of cap layer CAP, shift cancel layer SCL, and second magnetic layer  13  are etched by the RIE using an etching gas including a noble gas and hydrocarbon gas. If all of the layers are thus etched by the RIE using the etching gas including a noble gas and hydrocarbon gas, the first patterning process can be completed in a single chamber. Advantages such as simplification of the process and reduction of the manufacturing costs can be therefore achieved. 
     In Case B, in Table 1, cap layer CAP and shift cancel layer SCL are etched by physical etching, for example, IBE and, subsequently to this, second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, cap layer CAP and shift cancel layer SCL are etched by the physical etching. The physical etching is superior to the RIE in view of an etching anisotropy and an etching speed. 
     Therefore, advantages such as improvement of accuracy in processing the magnetoresistive element and reduction of the etching time can be achieved by etching these layers that are not in contact with the non-magnetic layer (tunnel barrier layer) by the physical etching. 
     In this combination, however, two different etching methods, i.e., physical etching and RIE, are employed. For this reason, to execute the first patterning process, the magnetoresistive element (wafer) needs to be conveyed from a first chamber in which the physical etching is executed to a second chamber in which the RIE is executed. 
     Thus, in Case B, a multi-chamber comprising first chamber C1 in which the physical etching is executed and second chamber C2 in which the RIE is executed is prepared as shown in, for example,  FIG. 9 , when the first patterning process is executed. 
     In the multi-chamber, the magnetoresistive element (wafer) is conveyed from first chamber C1 to second chamber C2 in a state in which the magnetoresistive element is not exposed to air, i.e., the magnetoresistive element is not oxidized. 
     In Case C, in Table 1, each of cap layer CAP, shift cancel layer SCL, and second layer  13   b  in second magnetic layer  13  is etched by the physical etching, for example, IBE and, subsequently to this, first layer  13   a  in second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, not only cap layer CAP and shift cancel layer SCL, but second layer  13   b  in second magnetic layer  13  are etched by the physical etching. Therefore, in Case C, the same advantages as those in Case B can be achieved, and the accuracy in processing the magnetoresistive element can be more improved and the etching time can be more reduced than those in Case B. 
     Table 2 shows a second example of combination of the etching methods which can be employed in the first patterning process. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 First Patterning process 
                 D 
                 E 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Upper layer ↑ 
                 Cap layer CAP 
                 RIE 
                 RIE 
               
               
                 Layer 
                 Shift cancel layer SCL  
                 with noble gas 
                 with noble gas 
               
            
           
           
               
               
               
               
               
            
               
                 Lower layer ↓ 
                 Second magnetic 
                 Second layer 13b 
                 (no hydrocarbon gas) 
                 (no hydrocarbon gas) 
               
               
                   
                 layer 13 
                 First layer 13a 
                 RIE 
                 RIE 
               
               
                   
                   
                   
                 with noble 
                 with noble 
               
               
                   
                   
                   
                 gas and 
                 gas and 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 hydrocarbon gas 
                 hydrocarbon gas 
               
               
                   
               
            
           
         
       
     
     The second example is an example in which the physical etching (IBE) is replaced with the RIE using a noble gas (and not including hydrocarbon gas) in Case B and Case C shown in Table 1. 
     In Case D, in Table 2, cap layer CAP and shift cancel layer SCL are etched by the RIE using a noble gas and, subsequently to this, second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, at least second magnetic layer  13  in contact with the non-magnetic layer (tunnel barrier layer) is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. In the first patterning process, what is called “stop on tunnel barrier” can be therefore executed certainly. 
     In addition, all of cap layer CAP, shift cancel layer SCL and second magnetic layer  13  are etched by the RIE in this combination. Thus, if the first patterning process is completed in a single chamber by changing the etching gas in the chamber, advantages such as the simplification of the process and the reduction of manufacturing costs can be achieved. 
     In Case D, too, however, the first patterning process may be executed in first chamber C1 in which the RIE using a noble gas is executed and second chamber C2 in which the RIE using the etching gas including a noble gas and hydrocarbon gas, as shown in  FIG. 9 . 
     In this case, the magnetoresistive element (wafer) is conveyed from first chamber C1 to second chamber C2 in a state in which the magnetoresistive element is not exposed to air, i.e., the magnetoresistive element is not oxidized. 
     In Case E, in Table 2, each of cap layer CAP, shift cancel layer SCL, and second layer  13   b  in second magnetic layer  13  is etched by the RIE using a noble gas and, subsequently to this, first layer  13   a  in second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, not only cap layer CAP and shift cancel layer SCL, but second layer  13   b  in second magnetic layer  13  are etched by the RIE using a noble gas. Therefore, in Case E, the same advantages as those in Case D can be achieved. 
     Table 3 shows a third example of combination of the etching methods which can be employed in the first patterning process. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 First Patterning process 
                 F 
                 G 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Upper layer ↑ 
                 Cap layer CAP 
                 IBE 
                 IBE 
               
               
                 Layer 
                 Shift cancel layer SCL 
                 RIE 
                 RIE 
               
            
           
           
               
               
               
               
               
            
               
                 Lower layer ↓ 
                 Second magnetic 
                 Second layer 13b 
                 with noble gas 
                 with noble gas 
               
               
                   
                 layer 13 
                 First layer 13a 
                 (no hydrocarbon gas) 
                 (no hydrocarbon gas) 
               
               
                   
                   
                   
                 RIE 
                 RIE 
               
               
                   
                   
                   
                 with noble 
                 with noble 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 hydrocarbon gas 
                 hydrocarbon gas 
               
               
                   
               
            
           
         
       
     
     The third example is an example in which the first patterning process is executed by three etching methods, i.e., physical etching (IBE), RIE using a noble gas (and not including hydrocarbon gas), and RIE using an etching gas including a noble gas and hydrocarbon gas. 
     In Case F, in Table 3, cap layer CAP is etched by the physical etching, for example, the IBE and shift cancel layer SCL is etched by the RIE using a noble gas and, subsequently to this, second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, at least second magnetic layer  13  in contact with the non-magnetic layer (tunnel barrier layer) is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. In the first patterning process, what is called “stop on tunnel barrier” can be therefore executed certainly. 
     In this combination, three different etching methods, i.e., the physical etching, RIE using a noble gas, and RIE using the etching gas including a noble gas and hydrocarbon gas are employed. For this reason, to execute the first patterning process, a multi-chamber comprising first chamber C1 in which the physical etching is executed, second chamber C2 in which the RIE using a noble gas is executed, and third chamber C3 in which the RIE using a noble gas and hydrocarbon gas is executed, is prepared as shown in, for example,  FIG. 10 . 
     In the multi-chamber, the magnetoresistive element (wafer) is conveyed among first chamber C1, second chamber C2 and third chamber C3 in a state in which the magnetoresistive element is not exposed to air, i.e., the magnetoresistive element is not oxidized. 
     This process can be modified to executing the physical etching in first chamber C1, executing the RIE in second chamber C2, and executing CVD in third chamber C3 as shown in  FIG. 11 . In this case, third chamber C3 is used for, for example, the processes for forming insulating layer I as shown in  FIG. 5 . 
     In addition, the first patterning process of the present embodiment can also be executed by using, for example, first chamber C1 in which the physical etching is executed and second chamber C2 in which the RIE is executed as shown in  FIG. 9 . 
     In Case G, in Table 3, cap layer CAP and shift cancel layer SCL are etched by the physical etching, for example, the IBE and second layer  13   b  in second magnetic layer  13  is etched by the RIE using a noble gas and, subsequently to this, first layer  13   a  in second magnetic layer  13  is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. 
     According to this combination, at least first layer  13   a  in second magnetic layer  13  in contact with the non-magnetic layer (tunnel barrier layer) is etched by the RIE using the etching gas including a noble gas and hydrocarbon gas. The same advantages as those in Case F can be therefore achieved in Case G. 
     An example of the etching gas used in the first patterning process will be described here. 
     The etching gas includes a noble gas and hydrocarbon gas. 
     The noble gas is, for example, Ar gas or Xe gas. The hydrocarbon gas includes one of methane, ethane, propane, butane, pentane, ethylene, and acetylene. 
     Desirably, the etching gas is nonoxidative, which indicates that oxygen gas or oxygen compound gas is not included in the etching gas. In addition, the etching gas may include hydrogen gas or nitrogen gas as a reducing gas. 
     An example of the etching gas is described below: 
     Noble gas: Ar gas (50 sccm-1,000 sccm)
 
Hydrocarbon gas: CH 4  gas (10 sccm-200 sccm)
 
Reducing gas: H 2  gas (5 sccm-500 sccm)
         N 2  gas (5 sccm-20 sccm)       

     A proportion (volume ratio) Ar/CH 4  between Ar gas and CH 4  gas is desirably within a range from 1% to 83% and, further desirably, within a range from 5% to 50%. 
     In addition, a bias power required to ionize the etching gas is desirably within a range from 50 W to 800 W. In particular, when a 300 mm wafer is used, the bias power is desirably within a range from 100 W to 500 W. 
     Moreover, a pressure in the chamber in which the RIE is executed is desirably within a range from 5 mT to 300 mT and, further desirably, within a range from 7 mT to 20 mT. 
     Next, the second patterning process will be described. 
     The second patterning process is a process for sequentially etching non-magnetic layer  12 , first magnetic layer  11  and underlayer UL as shown in  FIG. 7 . 
     The second patterning process is executed by a combination of the physical etching, for example, IBE with the RIE using a noble gas (and not including hydrocarbon gas). 
     Table 4 shows an example of combination of the etching methods which can be employed in the second patterning process. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Second patterning process 
                 A 
                 B 
                 C 
                 D 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Upper layer ↑ 
                 Non-magnetic layer 12 
                 IBE 
                 RIE 
                 IBE 
                 IBE 
               
               
                 Layer 
                 First magnetic layer 11 
                   
                   
                 RIE 
                 RIE 
               
               
                 Lower layer ↓ 
                 Foundation layer UL 
               
               
                   
               
            
           
         
       
     
     Since the second patterning process can be executed by well-known technology, descriptions of the process are omitted here. 
     Third Embodiment 
     In Third Embodiment, a method of stopping etching of a second magnetic layer on a non-magnetic layer, or example, certainly controlling “stop on tunnel barrier” when the non-magnetic layer is exposed will be described. 
     In the First and Second Embodiments ( FIG. 1  to  FIG. 8 ), the etching of second magnetic layer  13  on non-magnetic layer  12  is etched by RIE using an etching gas including a noble gas and hydrocarbon gas. 
     The noble gas (for example, Ar gas) physically etches second magnetic layer  13  by colliding with second magnetic layer  13 . In other words, the noble gas is used mainly for the purpose of anisotropically etching second magnetic layer  13 . 
     In addition, the hydrocarbon gas (for example, CH 4  gas) forms a carbon compound (complex) by reacting with transition elements (for example, Co, Fe, etc.) in second magnetic layer  13 . In other words, the hydrocarbon gas has an action of etching second magnetic layer  13 . 
     The hydrocarbon gas further has the following action. 
     When a surface of non-magnetic layer  12  is exposed, in the first patterning process, the hydrocarbon gas is brought into contact with a surface of second magnetic layer  13 . However, since the hydrocarbon gas does not react with non-magnetic layer (for example, MgO)  12 , non-magnetic layer  12  is not etched by the hydrocarbon gas. 
     In addition, when the surface of non-magnetic layer  12  is exposed, the carbon compound formed of carbon in the hydrocarbon gas and the transition elements in second magnetic layer  13  is deposited on the surface of non-magnetic layer  12 . The carbon compound has an action of preventing non-magnetic layer  12  from being etched by the noble gas. 
     Thus, an amount of generation (i.e., amount of deposition) of the carbon compound needs to be controlled in order to achieve both the etching anisotropy and the etching selection ratio (“stop on tunnel barrier”). 
     Thus, the amount of generation of the carbon compound can be controlled based on a flow rate of the hydrocarbon gas, a rate (volume ratio or mass ratio) of carbon atoms in the hydrocarbon gas. For example, the amount of generation of the carbon compound is greater as the flow rate of the hydrocarbon gas is higher and as the rate of carbon atoms in the hydrocarbon gas is higher. 
     For example, a rate of carbon in propane (C 3 H 8 ) gas is higher than a rate of carbon in methane (CH 4 ) gas. Accordingly, when propane (C 3 H 8 ) gas is used as the hydrocarbon gas, the amount of generation of the carbon compound is greater than that when methane (CH 4 ) gas is used as the hydrocarbon gas. 
     The amount of generation of the carbon compound can be varied in the first patterning process. In Cases A to G in Tables 1-3, for example, the flow rate, type, etc. of the hydrocarbon gas may be controlled such that the amount of generation of the carbon compound after exposure of the surface of the non-magnetic layer (tunnel barrier layer) is greater than the previous amount of generation of the carbon compound. 
     For example, in Case A in Table 1, the flow rate, type, etc. of the hydrocarbon gas may be controlled such that the amount of generation of the carbon compound at the etching of first layer  13   a  in second magnetic layer  13  is greater than the amount of generation of the carbon compound at the etching of the other layers. 
     Under such control, stopping the etching of the second magnetic layer on the non-magnetic layer, for example, “stop on tunnel barrier” is certainly executed when the non-magnetic layer is exposed. 
       FIG. 12  shows an example of a chamber in which the RIE is executed. 
     Wafer  33  is arranged on wafer table (electrode)  32  in chamber  31 . The noble gas, hydrocarbon gas and additive gas (reducing gas) are supplied from gas suppliers  34 ,  35 , and  36 , respectively, into chamber  31  through gas pipe  37 . These gases evenly spread on wafer  33  by shower plate (electrode)  38 . 
     A pressure in chamber  31  is measured by pressure gauge  39 . High-frequency power supplies  40  and  41  are connected to wafer table  32  and shower plate  38 , respectively. 
     Then, the RIE is executed by generating plasma of the etching gas in chamber  31  and by accelerating ions of the etching gas toward wafer  33  while controlling electric power of high-frequency power supplies  40  and  41  and the pressure in chamber  31 . 
     In such a chamber, the amount of generation of the carbon compound can be controlled in the first patterning process by controlling the flow rate, type, etc. of the hydrocarbon gas supplied into chamber  31 . 
     (Example of Application) 
     Application of the magnetoresistive element of the above-described embodiments to a magnetic random access memory will be described here. 
     A 1T-1MTJ type memory cell array wherein a memory cell comprises a magnetoresistive element and a select transistor will be hereinafter described as one of examples of application. 
       FIG. 13  shows an example of an equivalent circuit of the 1T-1MTJ type memory cell array. 
     Memory cell array  10  comprises arrayed memory cells MC. Each of memory cells MC comprises magnetoresistive element MTJ and select transistor (FET) SW. 
     Magnetoresistive element MTJ and select transistor (FET) SW are serially connected, each having an end connected to first bit line BL 1  and the other end connected to second bit line BL 2 . A control terminal (gate terminal) of select transistor SW is connected to word line EL. 
     First bit line BL 1  extends in a first direction, having an end connected to bit line driver/sinker  15 . Second bit line BL 2  extends in the first direction, having an end connected to bit line driver/sinker and read circuit  16 . 
     However, the circuit may be modified to connect first bit line BL 1  to bit line driver/sinker and read circuit  16  and to connect second bit line BL 2  to bit line driver/sinker  15 . 
     In addition, bit line driver/sinker  15  and bit line driver/sinker and read circuit  16  may be disposed at positions opposite to each other or the same position. 
     Word line WL extends in a second direction, having an end connected to word line driver  17 . 
       FIG. 14  shows an example of the memory cell. 
     Select transistor SW is disposed in active area AA in semiconductor substrate  18 . Active area AA is surrounded by element isolating/insulating layer  19  in semiconductor substrate  18 . In this example, element isolating/insulating layer  19  has an STI (Shallow Trench Isolation) structure. 
     Select transistor SW comprises source/drain diffusion layers  20   a  and  20   b  in semiconductor substrate  18 , gate insulation layer  21  on a channel between the layers, and gate electrode  22  on gate insulation layer  21 . Gate electrode  22  functions as word line WL. 
     Interlayer insulation layer  23  covers select transistor SW. A top surface of interlayer insulation layer  23  is flat, and lower electrode LE is disposed on interlayer insulation layer  23 . Lower electrode LE is connected to source/drain diffusion layer  20   b  of select transistor SW via contact plug  24 . 
     Magnetoresistive element MTJ is disposed on lower electrode LE. Upper electrode  25  is disposed on magnetoresistive element MTJ. Upper electrode  25  functions as, for example, hard mask HM to be used for processing of magnetoresistive element MTJ. 
     Protective layer PL covers the side walls of magnetoresistive element MTJ. 
     Interlayer insulation layer  26  is disposed on protective layer PL to cover magnetoresistive element MTJ. A top surface of interlayer insulation layer  26  is flat, and first bit line BL 1  and second bit line BL 2  are disposed on interlayer insulation layer  26 . First bit line BL 1  is connected to upper electrode  25 . Second bit line BL 2  is connected to source/drain diffusion layer  20   a  of select transistor SW via contact plug  27 . 
     CONCLUSION 
     According to the above-described embodiments, etching the magnetic layer alone disposed on the tunnel barrier layer, i.e., stopping the etching on the tunnel barrier layer surface (what is called “stop on tunnel barrier”) can be certainly executed, at the two-step patterning of the magnetoresistive element. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.