Information

Sputtering Targets for MRAM


MRAM is one of nonvolatile memories utilizing magneto-resistive effect. Because no consumption of electric power is needed to keep continual memory state, it is ideal. Additionally read-write speed of MRAM is very fast and never fatigue in decades. Recently, to achieve farther speed and more integrated memories, collecting researcher's attentions are STT-MRAM elements, of which techniques utilize perpendicular magnetic TMR for the portion of the magneto-resistive elements, and spin transfer torque to rewrite data.

An example of perpendicular magnetic TMR cell structure

Development example of high performance MTJ element in Center for Innovative Integrated Electronic Systems, Tohoku Univ.

 
垂直磁化TMR素子の構造例 cf.
http://www.cies.tohoku.ac.jp/english/
program/research/program_01.html

Schematic diagram of cross section structure of perpendicular magnetization TMR elements developed by AIST
垂直磁化TMR素子の構造例 cf.
http://www.aist.go.jp/aist_j/press_release/
pr2010/pr20100513/pr20100513.html

 

Material for MRAM

The structure of MRAM is separated roughly to the magneto-resistive element part and to the transistor part. Kojundo widely deals in PVD/CVD/ALD materials for thin film depositions to manufacture them. In particular for the magneto-resistive element part, we have provided sputtering targets and EB-tablets which are made of pure-metal, alloy and oxides from the first stage of such developments with various purities and shapes. We are ready to customize your materials depending on ways of use or purpose, and even to develop newly or in to special shapes.

Material examples for the magneto-resistive element

Magnetic layer

Co-Fe-B
Co-Fe, Tb-Fe-Co, Ni-Fe, Ni-Fe-Co
Co/Pt, Fe/Pt
Mn Alloy, e.g., Mn-Ga
Co-based Heusler alloys, such as Co2(FeMn)Si

Barrier layer

MgO, Mg

Spacer layer

Ru, Cu, Ta

Antimagnetic layer

Ir-Mn, Pt-Mn

Electrode

Cr, Au, Ru, Ta


Material examples for the transistor part

For gate insulator

HfO2、HfO2-Al2O3、La2O3、La2O3-Mo、Y2O3

For electrode/wiring

W、Ti、TiN、Al、Cu、Ta

Interlayer dielectric film

BPSG(SiO2-B2O3-P2O5)

Protective film

Si3N4


Material examples for CVD and ALD

For TaN

TAIMATA*、TBTEMT

For TiN

TDMAT

For SiO2/Si3N4

3DMAS、4DMAS、TEMASi

For HfO2

TDMAHf、HfCl4

* Our original products          

1. Low particle MgO target

Magnesium oxide is a functional material which is essential to the template layer for media and the TMR head in the next generation HDD, and also the MTJ element for MRAM. We Kojundo promptly started supplying appropriate sputtering targets for MTJ in 2002. It is necessary to improve material performance to improve recording performance. We have realized to supply magnesium oxide target which is marked by “High Purity”, “High Density” and “Low Particle” under our motto that high-purity materials always bring technical innovation.





MgO target, mirror-polished


2. Co-Fe-B target (Sintered or Molten)

We have been providing Co-Fe-B targets by sintering and/or melting methods. We can utilize both sintering and melting process facilities, so that it is possible to develop products by using either process in accordance with customer’s requests. Co-Fe-B is generally made by sintering process because of its brittleness. But we worked on the process development since the earliest industrial stage. Thus, we successfully established our melting process. Kojundo provides melting type targets with low oxygen specification. Please feel free to contact us for the available composition ratio and shape.





Melting type Co-Fe-B target
Purity 3N
Oxygen (Analysis example) < 30 ppm



MR ratio of the TMR element used our MgO target and CoFeB target

 

3. Melting type Ru target

It is pointed out that the quality of Ru targets such as the amount of oxygen largely affects the film properties and performance of the device, so that such quality improvement is essential. Thus, Kojundo has succeeded in low oxygen and low carbon Ru targets by melting technology.

Analysis example for Ru target
Element Analysis (ppm)
Molten Sintered (conventional)
C 10 ← 90% down ←

100

O 10 ← 90% down ← 100
N < 10 ←← 10

 

4. New materials: Mn-Ga target and Co-based Heusler alloy target

By making full use of both sintering and melting process, Kojundo produces a various kind of Mn alloy targets as well as Co-based Heusler alloy targets which are expected to be new materials for magnetic layers. They are generally brittle materials and mainly made by sintering process. On the other hand, our customers frequently request us to make low oxygen specification products for magnetic layer use and large size targets. We continue to make efforts for providing melting type targets. Mn alloy, MnxGa100-x (55≦x≦75) has recently attracted attention as precious-metal-free and rare-earth-free magnetic materials. We are now ready to provide our customers the large size melting type targets.


2015.4