78
W. C. Law and S. De W. Wong
Fig. 12 Frequency-swept FMR spectra of a typical pMTJ stack presented in a contrast plot. The
y-axis is the microwave frequencies swept at a step size of 10 MHz, while the x-axis is the external
magnetic field at coarser step size. The color contrast indicates the intensity of the transmitted
microwave power, where the black corresponds to the absorption of microwave due to FMR. Dashed
lines in blue, red and white are guides to the eye which corresponds to the FMR conditions for FL,
HL2 and HL1 respectively
commonly deployed as a non-destructive inline metrology tool, allowing for thickness calibration and uniformity check. Since the fabrication of patterned MTJ devices
is extremely time and resource intensive (ranging from weeks to months depending
on the level of complexity and tool availability), the CIPT technique can be utilized
in thin film MTJ stacks to characterize local distribution of the electrical transport
properties, or to perform full wafer mapping to check for film uniformity. Another
advantage of this thin film characterization is the process variations inherent to device
patterning can be excluded, allowing for systematic and efficient troubleshooting.
CAPRES, in junction with IBM and Infineon Technologies, have developed a sophisticated CIPT metrology system to simultaneously measure the TMR, RA and sheet
resistances of the top electrode R T and bottom electrodes R B . In the case MTJ stack
analysis by CIPT, the probe spacings would be narrower to ensure tunneling through
the MTJ.
Within the probe head, a multiplexer is used to select a combination of 4 out of the
12 collinear probes with ultra-narrow spacing (on the order of a few μms). A small
current I is typically sent through the outer probes while the voltage V is measured
by the inner probes connected to a high impedance electrometer. To further eliminate
error contribution from the contact resistance, a small AC current in conjunction with
a lock-in amplifier can be used. In the CAPRES model, a permanent magnet was
used to perform the magnetic field sweep which is calibrated prior to measurements.
W. C. Law and S. De W. Wong
Fig. 12 Frequency-swept FMR spectra of a typical pMTJ stack presented in a contrast plot. The
y-axis is the microwave frequencies swept at a step size of 10 MHz, while the x-axis is the external
magnetic field at coarser step size. The color contrast indicates the intensity of the transmitted
microwave power, where the black corresponds to the absorption of microwave due to FMR. Dashed
lines in blue, red and white are guides to the eye which corresponds to the FMR conditions for FL,
HL2 and HL1 respectively
commonly deployed as a non-destructive inline metrology tool, allowing for thickness calibration and uniformity check. Since the fabrication of patterned MTJ devices
is extremely time and resource intensive (ranging from weeks to months depending
on the level of complexity and tool availability), the CIPT technique can be utilized
in thin film MTJ stacks to characterize local distribution of the electrical transport
properties, or to perform full wafer mapping to check for film uniformity. Another
advantage of this thin film characterization is the process variations inherent to device
patterning can be excluded, allowing for systematic and efficient troubleshooting.
CAPRES, in junction with IBM and Infineon Technologies, have developed a sophisticated CIPT metrology system to simultaneously measure the TMR, RA and sheet
resistances of the top electrode R T and bottom electrodes R B . In the case MTJ stack
analysis by CIPT, the probe spacings would be narrower to ensure tunneling through
the MTJ.
Within the probe head, a multiplexer is used to select a combination of 4 out of the
12 collinear probes with ultra-narrow spacing (on the order of a few μms). A small
current I is typically sent through the outer probes while the voltage V is measured
by the inner probes connected to a high impedance electrometer. To further eliminate
error contribution from the contact resistance, a small AC current in conjunction with
a lock-in amplifier can be used. In the CAPRES model, a permanent magnet was
used to perform the magnetic field sweep which is calibrated prior to measurements.