Magnetic tunnel junction (MTJ) to reduce spin transfer magnetization switching current

• US 7,598,579 B2
• Filed: 01/30/2007
• Issued: 10/06/2009
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: MagIC Technologies Inc (TDK Corporation)
• Inventors: Tong, Ru-Ying, Horng, Cheng T.
• Primary Examiner(s): Phung; Anh
• Assistant Examiner(s): BERNSTEIN, ALLISON
• Application Number:
  US11/699,875
• Publication Number:
  US 20080179699A1
• Time in Patent Office: 980 Days
• Field of Search: 257/421, 257/427, 257/E21.665, 365/158, 365/171
• US Class Current: 257/421
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

A MTJ that minimizes spin-transfer magnetization switching current (Jc) in a Spin-RAM to <1×10⁶ A/cm² is disclosed. The MTJ has a Co₆₀Fe₂₀B₂₀/MgO/Co₆₀Fe₂₀B₂₀ configuration where the CoFeB AP1 pinned and free layers are amorphous and the crystalline MgO tunnel barrier is formed by a ROX or NOX process. The capping layer preferably is a Hf/Ru composite where the lower Hf layer serves as an excellent oxygen getter material to reduce the magnetic “dead layer” at the free layer/capping layer interface and thereby increase dR/R, and lower He and Jc. The annealing temperature is lowered to about 280° C. to give a smoother CoFeB/MgO interface and a smaller offset field than with a 350° C. annealing. In a second embodiment, the AP1 layer has a CoFeB/CoFe configuration wherein the lower CoFeB layer is amorphous and the upper CoFe layer is crystalline to further improve dR/R and lower RA to ≦10 ohm/μm².

Claims

1. An MTJ element for reducing spin-transfer magnetization switching current in a magnetic device, comprising:

a pinned layer having an AP2/coupling layer/AP1 configuration wherein the AP2 layer is formed on an AFM layer and the AP1 layer is a composite made of a lower amorphous CoFeB layer and an upper crystalline CoFe layer;

a crystalline MgO tunnel barrier formed on the upper crystalline CoFe AP1 pinned layer;

an amorphous CoFeB free layer formed on the MgO tunnel barrier, both of said amorphous lower AP1 CoFeB layer and amorphous CoFeB free layer have an identical composition represented by Co_xFe_yB_z where x is from about 40 to 60 atomic %, y is from about 20 to 40 atomic %, and z is from about 15 to 25 atomic %;

and a composite capping layer formed on the CoFeB free layer wherein the composite capping layer is comprised of a lower layer that contacts the free layer and an upper layer, and said lower layer is made of a metal having an oxidation potential greater than that of Co, Fe, and Ta to provide a high oxygen gettering capability.

2. The MTJ element of claim 1 wherein the magnetic device is a Spin-RAM.

3. The MTJ element of claim 1 wherein the lower amorphous CoFeB AP1 pinned layer and amorphous CoFeB free layer have a Co₆₀Fe₂₀B₂₀ composition.

4. The MTJ element of claim 1 wherein the lower layer in the composite capping layer is comprised of Hf or Zr.

5. The MTJ element of claim 4 wherein the composite capping layer has a Hf/Ru configuration in which the lower Hf layer has a thickness from about 5 to 50 Angstroms and the upper Ru layer has a thickness from about 20 to 100 Angstroms.

6. The MTJ element of claim 1 wherein the AP2 portion of the pinned layer is comprised of CoFe and the coupling layer is Ru.

7. The MTJ element of claim 1 wherein the upper crystalline CoFe AP1 pinned layer has a Co₇₅Fe₂₅ composition.