Process for producing magnetoresistive element and apparatus for producing magnetoresistive element
By modifying the metal layer of the MTJ device by ion bombardment before the oxidation treatment, the problems of tunnel barrier thickness and stoichiometric uniformity are solved, and an MTJ device with high TMR ratio and low R×A product is realized, which is suitable for high-density automatic Rotational torque MRAM applications.
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no. 1 approach
[0056] figure 1 A typical stack structure of a tunneling magnetoresistive (TMR) sensor or memory element is shown. Most MTJs each include a ferromagnetic pinned layer 110 , a synthetic antiferromagnetic pinned layer 120 , a tunnel barrier 130 , and a ferromagnetic free layer 140 . exist figure 1 In the stack structure shown, the composite antiferromagnetic pinned layer 120 is formed by including a ferromagnetic pinned layer 121 , a nonmagnetic separator 122 , and a ferromagnetic reference layer 123 .
[0057] First, the surface of the substrate 101 is etched by plasma treatment to remove any impurities. An underlying layer 102 (eg, Ta / CuN / Ta / CuN / Ru) is deposited on the surface of the plasma-treated substrate 101 , and an antiferromagnetic pinning layer 110 (eg, IrMn) is deposited on the underlying layer 102 . Thereafter, a ferromagnetic pinned layer 121 (such as Co 70 Fe 30 ). A metal spacer 122 (such as Ru) is deposited on the ferromagnetic pinned layer 121 , and a fe...
Embodiment approach
[0075] For the first embodiment, it is expected to obtain a 2 The R×A product and the MTJ with a TMR ratio above 160%. The MTJ prepared by the method demonstrated in the first embodiment is suitable for high-density / high-performance spin-transfer torque MRAM applications.
no. 2 approach
[0077] Figure 5B The deposition sequence of MgO according to the second embodiment is shown.
[0078] In a second embodiment, a metallic Mg layer 131 is deposited on the CoFeB ferromagnetic reference layer 123 to have a thickness of 1.6 nm. The metallic Mg layer was etched away by 0.4 nm and its microstructure was immediately modified by plasma treatment to form the MgO tunnel barrier 132 . Thereafter, a 0.3 nm Mg capping layer 139 is deposited on the MgO tunnel barrier 132 .
[0079] As mentioned above, metal Mg deposition is preferably performed by DC-sputtering, which suppresses particle generation. Also, in the plasma treatment, plasma of Ar gas is generated at an Ar gas flow rate of 30 sccm by supplying, for example, 30 W of RF power as the plasma generation power. Under such plasma treatment conditions, plasma treatment was performed at a Mg etching rate of 0.02 nm / sec for 20 seconds to etch the 1.6 nm metal Mg layer 131 by 0.4 nm to become a 1.2 nm metal Mg layer 13...
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