Technology of anisotropic magneto resistive sensor on silicon substrate
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Sensitivity and measurement
The output voltage of the Wheatstone bridge can be explained by:
11 The sensitivity of the sensor measurement results
12 Thus the sensitivity can be improved by using a material that AMR effect with the
characteristics of high and low field H0. Linear behavior of the sensor with an error of less than 5 in the range of a-H0 2 for H0 2. It is possible, to improve the measurement range
by applying a magnetic field compensation ie, with compensation-null bridge. Since the sensor is always operating in the region of zero field, the non-linearity will have no effect.
The maximum resolution in this case depends on the stability of the magnetic film.
In addition, the layout of the magnetoresistive element forming the Wheatstone bridge must be optimized. Demagnetising achieve homogeneous and small field, an elliptical
shape AMR array is proposed [6]. By using the compensation coil integrator output, the sensor can be operated in zero magnetic field. Linear output response V0 voltage versus
applied field Ha is comparable resistor R for the applicable compensation coils. Both compensation flips and coil conductor in the form of a thin layer mean deric, shown in Figure
4.
Figure 4. Electronic circuits with flip Lf and compensation Lc rolls Hauset et al., 2000.
There are two definitions of the sensitivity of AMR sensors in bridge arrangement: 1. S0 = two DHY UB, and 2 × SU = Umax two DHY UB. The advantage of the second
definition is that it also takes into account the maximum energy dissipation Pmax = UB, MAX2 R on the sensor. The supply voltage can not be done suddenly becomes high. For a
comparison of the sensitivity of the sensor, use the first definition in this paper, as is done by most of the literature.
3. Metodology
The design of this sensor includes a sensor system design, NiCr alloy deposition with DC-Sputtering method with and without the influence of a magnetic magnetization and
characterization. In the first stage is to design AMR sensors. Here is the explanation.
S. Widodo, T. Kristiantoro
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Materials AMR
Magnetoresistive film materials consist of: •
high coefficient on high.
• Low temperature dependence of .
• low anisotropy field Hk.
• Low Coersivitas
• zero magnetostriction
• Have a high stability.
The materials most suitable is a compound or alloy Alloy of elements such as Ni, Fe, Co Especially the material of Permalloy Ni
81
Fe
19
or alloy Ni
80
Cr
20
. By using magnetoresistive anisotropy effects to design a magnetoresistive microsensor with a thin layer of permalloy to
detect the small magnetic field: 0.1 to 5 mT.
Barber pole
To reduce losses, barber pole structure consists of a series of strips of high electrical conductivity by forcing the flow of current into a 45 ° angle to the x-axis. The layout of the
optimum width and barber pole-pole distance is important [7]. Mathematically, a barber- pole represented by introducing additional angle ψ = 45 °, which is the angle between the
axis and currents.
Linearized
Magnetoresistive effect can be linearized by depositing aluminum lines Barber-Pole, at the top of the strip line permalloy at 45 angle with the axis of the strip see Figure 5.
Aluminum has a higher conductivity than permalloy, Barber-Pole effect is to rotate the direction of flow at an angle of 45 and effectively change the angle of rotation of the
magnetization relative to the flow of for 45 .
Figure 5. linearization magnetoresistive effect.
Sensitivity and measurement range
Thus the sensitivity can be improved by using a material that AMR effect with the characteristics of high and low field H0. This sensor shows a linear state with an error of less
than 5 in the range of a-H0 2 for H0 2. It is possible to increase the range of measurements to apply a magnetic field compensation ie, with compensation-null bridge.
Since the sensor always operates zero field region, the non-linearity will have no effect. The maximum resolution in this case depends on the stability of the magnetic film. In addition,
the layout of the magnetoresistive element forming the Wheatstone bridge must be optimized.
Technology of anisotropic magneto resistive sensor on silicon substrate
SWUP
SC.170
4. Results and discussion
