The Nanoelectronics Research Institute (NeRI) of the National Institute of Advanced Industrial Science and Technology (AIST) has developed technology for fabricating a new type of high-performance TMR device with single-crystal electrodes on a silicon LSI chip.

With this new technology, increased signal intensity and improved magnetic characteristics due to quantum-size effects were realized when the thickness of the ferromagnetic electrode of the TMR device was reduced to the nanometer scale. Such technology may help to solve problems in increasing the capacity of nonvolatile memory (MRAM), which is anticipated to replace DRAM.

A maximum TMR ratio was exhibited when the thickness of the single-crystal ferromagnetic electrode ((001)-oriented Fe) was in the vicinity of 1 nm. AIST has already developed the thin-film production technology for attaining this thickness. Specifically, AIST has developed techniques for eliminating crystal grains by making the electrodes of the TMR device single crystalline, using a MgO seed layer to make the electrode surface flat at the atomic scale, thereby producing a highly oriented, atomically flat electrode layer on an arbitrary substrate.

• Improved TMR device signal intensity (TMR ratio) due to quantum-size effects
  
  AIST has used single-crystal thin-film manufacturing technology to produce a TMR device with single-crystal ferromagnetic electrodes that are thin (thickness of 2nm or less) and extremely flat. This is the first demonstration of increased TMR ratio due to quantum-size effect.
• Use of single-crystal electrodes to achieve ultraflatness
  
  By making the electrodes of the TMR device single crystalline, AIST has succeeded in eliminating crystal grains and made the electrode surface flat at the atomic level.
• Development of new techniques for fabricating high-performance TMR devices on a silicon LSI chip
  
  AIST has previously developed techniques for producing a highly oriented, ultraflat electrode layer on an arbitrary substrate using a MgO seed layer. These same techniques have now been used to fabricate a high-performance TMR device on a silicon LSI chip.

Future goals are to improve the characteristics of TMR devices equipped with single-crystal electrodes and to realize ultra-Gbit-level MRAM.

This research (Improvement of TMR Device Signal Intensity (TMR Ratio) Using Quantum Size Effects) was based on a collaborative research agreement between AIST and the Japan Science and Technology Corporation and was carried out as a project for the promotion of strategic creative research in the area Functional Control of Electrons, Photons, Etc. as part of the research theme Creating Novel Functions by Spin Injection in Solids.