82
W. C. Law and S. De W. Wong
Fig. 14 Schematic diagram of the main chamber within the sputtering system
trajectory path along the magnetic field lines for further ionization events. This eliminates the need for high working gas pressure that may be unfavorable for film quality
and efficient target utilization. The type of inert gas (Ar, Kr, Xe) used to generate
plasma ions can also help to improve uniformity by ensuring efficient transfer of
momentum. The sputtering pressure and applied power can control the deposition
rate to ensure film adhesion and minimal stress. Finally, the spindle rotary speed
in which the sample is mounted onto and the target to substrate distance allows for
uniform distribution of sputtered material.
6.4 Vibrating Sample Magnetometer
Vibrating sample magnetometer (VSM) is a standard tool in magnetization characterization and crucial for MRAM development. With a detection range of down to 10
–6
emu with a noise level of <10
–7 emu, VSM is suitable for measuring pre-patterned
pMTJ thin film samples. The operating principle of VSM relies on the Faraday’s
law of induction, where an induced electromagnetic force (EMF) is generated from
a magnetic sample when it is mechanically vibrating between a set of pick up coils.
The voltage is detected by a lock in amplifier which takes reference to the frequency
of vibration. A piece of Nickel standard is used as a calibration sample to establish a
conversion ratio between V emf picked up by a lock in amplifier and its known mass
magnetization. The Nickel standard, like any samples to be tested, is to be placed on
a clean quartz rod and secured with teflon tape, vacuum grease, double side tape or
W. C. Law and S. De W. Wong
Fig. 14 Schematic diagram of the main chamber within the sputtering system
trajectory path along the magnetic field lines for further ionization events. This eliminates the need for high working gas pressure that may be unfavorable for film quality
and efficient target utilization. The type of inert gas (Ar, Kr, Xe) used to generate
plasma ions can also help to improve uniformity by ensuring efficient transfer of
momentum. The sputtering pressure and applied power can control the deposition
rate to ensure film adhesion and minimal stress. Finally, the spindle rotary speed
in which the sample is mounted onto and the target to substrate distance allows for
uniform distribution of sputtered material.
6.4 Vibrating Sample Magnetometer
Vibrating sample magnetometer (VSM) is a standard tool in magnetization characterization and crucial for MRAM development. With a detection range of down to 10
–6
emu with a noise level of <10
–7 emu, VSM is suitable for measuring pre-patterned
pMTJ thin film samples. The operating principle of VSM relies on the Faraday’s
law of induction, where an induced electromagnetic force (EMF) is generated from
a magnetic sample when it is mechanically vibrating between a set of pick up coils.
The voltage is detected by a lock in amplifier which takes reference to the frequency
of vibration. A piece of Nickel standard is used as a calibration sample to establish a
conversion ratio between V emf picked up by a lock in amplifier and its known mass
magnetization. The Nickel standard, like any samples to be tested, is to be placed on
a clean quartz rod and secured with teflon tape, vacuum grease, double side tape or