JP2015227866A - Magnetic field sensor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission-line thin-film magnetic field sensor which no longer requires approximately 12 hours of sputtering film deposition work that was conventionally required for laminating approximately 6 μm of an SrTiO thin film constituting a sensor element, and which offers a sensor element size that is reduced to the order of several millimeters square.SOLUTION: A sensor element of the present invention has an SrTiO thin film with a modified thickness, or 50% of the conventional thickness, but offers magnetic field sensitivity that is approximately 95% of conventional sensors. Compact size and high sensitivity for the sensor element was achieved by re-examining overall size and thickness of a magnetic thin film and thickness of the SrTiO thin film constituting the sensor element and reviewing a pattern shape of transmission lines.

Description

  The present invention relates to a film structure and a manufacturing method of a thin film magnetic field sensor.

  With the rapid advancement of advanced information technology, miniaturization, weight reduction, and intelligentization of devices are being promoted in portable electronic devices, computers, information communication devices, medical devices and mechatronics devices. Covers a variety of fields such as motor control, non-destructive inspection, direction sensor, biomagnetic measurement, and the like.

Phenomenon that has a transmission line structure, the magnetic permeability and skin effect change as a function of the magnetic field when a high-frequency carrier current is passed through the magnetic material and an external magnetic field is applied, resulting in changes in resistance, inductance, and impedance A thin-film magnetic field sensor utilizing the above has been developed.

The inventor has developed a transmission line type thin film magnetic field sensor using a bulk ceramic substrate (Non-Patent Document 1). Since this sensor can be integrated, it can be applied to various applications. A high-sensitivity magnetic field sensor and a thin-film magnetic field sensor utilizing the effect of shortening the wavelength of a carrier of several GHz have been developed by using a SrTiO thin film (strontium titanate) as a dielectric thin film. (Non-patent document 2) Using these, biomagnetic measurement such as a cardiac magnetic field, which was conventionally possible only with a superconducting quantum interference magnetic flux meter (SQUID), was realized for the first time as a thin-film magnetic field sensor operating at room temperature.

Ken Kojima, Koji Sato, Shin Sasagami, Tetsuya Ozawa, Shinki Kobayashi, Kenichi Arai, “High Sensitivity of Transmission Line Type Thin Film Magnetic Field Sensor Using High Dielectric Constant Substrate”, Journal of the Magnetics Society of Japan Vol. 35 , No. 3, pp. 277-280 (2011). Hiroaki Uetake, Shin Nobugami, Yoshinori Saito, Tomoaki Chiba, Tetsuya Ozawa, Nobuaki Kobayashi, Kenichi Arai, “High-sensitivity transmission line type thin film magnetic field sensor using dielectric thin film”, IEEJ Magnetics Study Group, MAG -13-055 (2013). S. Yabukami, K. Kato, T. Ozawa, N. Kobayashi, KI Arai Coplanar Line Thin Film Sensor and Measurement of MCG without Magnetic Shielding Journal of the Magnetics Society of Japan Vol.38, No. 2-1, pp. 25 -28 (2014).

In Non-Patent Document 2, high-sensitivity magnetic field sensitivity (100 degrees / Oe or more) was obtained by laminating about 6 microns of SrTiO thin film due to the effect of shortening the wavelength of the carrier signal, but a 6 micron SrTiO thin film was formed. Sputtering for about 12 hours is necessary to form a film, which is a problem from the viewpoint of time or cost. Another problem is that the characteristics of the sensor element produced by thermal degradation of the thin film itself deteriorate due to long-time sputtering.

In the sensor element shown in Non-Patent Document 2, the dimension of the magnetic thin film used as the magnetic body was 18.2 mm × 1.15 mm. Miniaturization is insufficient for applications where higher spatial resolution is required or for insertion into a living body for measurement.

  In order to solve the above-mentioned problem, the thickness of the SrTiO thin film was changed in various ways to produce a sensor, the sensitivity of the sensor was evaluated, and the quantitative relationship between the thickness of the SrTiO and the sensitivity was clarified. If the film thickness is 50% of the 6 μm thickness (3 mm), the magnetic field detection sensitivity is about 95% compared to the 6 μm thickness, and if the film thickness is 33% (2 μm), the magnetic field detection sensitivity is About 85% could be maintained.

  Furthermore, in order to reduce the size of the sensor element, in addition to the film thickness of the SrTiO thin film, the external dimensions and film thickness of the magnetic thin film, and the pattern of the coplanar line were examined in addition to the prototype level. As a result, a high sensitivity magnetic field sensitivity of 100 degrees / Oe or more can be realized with a sensor element having an area of about 1/2 to about 1/20 of the magnetic thin film area of the sensor element shown in Non-Patent Document 2. Was made.

  Since a relatively thin magnetic field detection sensitivity can be obtained with a relatively thin SrTiO thin film, problems such as thermal deterioration due to long-time sputtering for about 12 hours, long-time sputtering, and high cost have been solved. In addition, useful knowledge about the relationship between the shape, film thickness, and pattern of each thin film constituting the sensor element has been obtained, and the design guidelines for the small magnetic field sensor have been clarified. It is possible to contribute to mass production of a small and highly sensitive transmission line type magnetic field sensor.

Structure (plan view) of the sensor according to the first embodiment Structure of sensor according to embodiment 1 (cross-sectional view) 5 is a flowchart illustrating a method for manufacturing the sensor element according to the first embodiment. Configuration diagram of measurement method according to Example 1 Phase change with respect to magnetic field according to Example 1 Phase change with respect to frequency according to the first embodiment Gain change with respect to magnetic field according to Embodiment 1 Gain change with respect to frequency according to the first embodiment Comparison of gain and magnetic field sensitivity of SrTiO thin film and SiO ₂ thin film according to Example 1 Comparison of electrical length of SrTiO thin film and SiO ₂ thin film according to Example 1 Gain and magnetic field sensitivity with respect to film thickness of SrTiO thin film according to Example 1 Magnetic field sensitivity to the film thickness of the SrTiO thin film according to Example 1 Structure (plan view) of sensor element according to embodiment 2 Structure of sensor element according to Example 2 (cross-sectional view) Phase change with respect to magnetic field of sensor element according to embodiment 2 Change of gain with respect to magnetic field of sensor element according to embodiment 2 Phase change with respect to film thickness change of amorphous CoNbZr thin film according to Example 2 Gain change with respect to film thickness change of amorphous CoNbZr thin film according to Example 2 Change in DC magnetic field that gives maximum phase sensitivity to change in film thickness of amorphous CoNbZr thin film according to Example 2 Change in carrier frequency giving maximum phase sensitivity to change in film thickness of amorphous CoNbZr thin film according to Example 2 The figure explaining pattern B of the meander type coplanar line concerning the modification of Example 2 The figure explaining the pattern C of the meander type coplanar line which concerns on the modification of Example 2. FIG.

Examples of the present invention will be described below in order. First, Example 1 is demonstrated based on FIGS.
FIG. 1 shows the structure of a prototype sensor element 11. This sensor is intended to obtain a large phase change with respect to the magnetic field by utilizing the wavelength shortening effect of the dielectric thin film. FIG. 2 shows an AB cross section of FIG. The sensor element 11 is configured on the surface of the glass substrate 5, and includes a linear coplanar line 13, a SrTiO thin film 1, and an amorphous CoNbZr (cobalt niobium zirconium) thin film 2 made of a Cu (copper) thin film 3 (underlying a Cr (chromium) thin film 4). Become.

The amorphous CoNbZr thin film 2 had a size of 10.2 mm × 1.15 mm.
The area ratio of the magnetic thin film is reduced to 56% compared with the area of Non-Patent Document 2. The linear coplanar line 13 has a conductor width of 300 μm and an adjacent conductor interval of 50 μm so that the characteristic impedance is about 50Ω. Furthermore, the film thickness of the SrTiO thin film 1 was set to 0.5 μm to 6 μm. This is because the effective dielectric constant of the coplanar line 13 is intended to be increased by increasing the thickness of the dielectric.

FIG. 3 is a flowchart showing a method for manufacturing the sensor element 11. The sensor element 11 was laminated on the surface of the glass substrate 5 by a lift-off process. Below, a manufacturing method is demonstrated based on this flowchart.
First, the glass substrate 5 is cleaned (S1, where S is an abbreviation for a step, and so on). In this example, a potash glass having a thickness of 1 mm and a square of about 25 mm was prepared and washed with a phosphorus-free soap solution and an organic solvent.

Subsequently, a resist pattern for the magnetic film is formed on the surface of the glass substrate 5 (S2). In this example, ten resist patterns for the magnetic film are arranged in the substrate. A negative resist was used as the resist.
Next, a magnetic film is formed (S3). Here, an amorphous CoNbZr thin film 2 was formed by RF sputtering (high frequency sputtering) with a power of 200 W and an Ar gas pressure of 20 mTorr and a film thickness of 5 μm.
After film formation, resist stripping is performed (S4). After immersion in an acetone solution, an unnecessary film was peeled off to obtain a magnetic film pattern.

Next, heat treatment in a magnetic field is performed (S5). The heat treatment conditions were as follows: heat treatment in a rotating magnetic field at 400 ° C. for 2 hours, and heat treatment in a static magnetic field at 200 ° C. for 1 hour. The magnetic field strength was set to 0.3T. As a result, a weak uniaxial magnetic anisotropy of about 3 Oe was imparted in the width direction of the coplanar line. If necessary, the characteristics of the magnetic film can be monitored at this stage. The static magnetic field heat treatment in this step can be omitted.

Subsequently, an SrTiO film, which is a ferroelectric film, is formed as an insulating layer (S6). In this example, the film was formed by RF sputtering. The sputtering conditions were an Ar gas pressure of 20 mTorr, a power of 180 W, and a substrate heating mechanism set temperature of 130 ° C. In this example, the SrTiO thin film 1 was formed on the entire substrate.

Next, a resist pattern for creating a coplanar line is formed (S7). The resist used was the same negative resist as S2.
Subsequently, a conductive thin film is formed (S8). Here, Cr was used as a base for improving the adhesion of the film. After the Cr thin film 4 was formed to a thickness of 0.2 μm by RF sputtering, the Cu thin film 3 was continuously formed by RF sputtering to a thickness of about 4 μm.
Next, resist stripping is performed (S9). Here, after dipping in an acetone solution, an unnecessary film was peeled off to obtain a pattern of the coplanar line 13.

  Subsequently, the substrate is heat-treated in a magnetic field (S10). The heat treatment conditions were as follows: heat treatment in a rotating magnetic field at 320 ° C. for 2 hours, heat treatment in a static magnetic field at 200 ° C. for 1 hour, and the magnetic field strength set to 0.3T. The purpose of the heat treatment in the magnetic field is to remove the influence that the formation of the SrTiO thin film 1 (S6) and the formation of the conductive thin film (S8) performed after the magnetic film formation is performed in the magnetic field, and again 0 Finally, uniaxial anisotropy is imparted with a magnetic field strength of 3T. Furthermore, by performing heat treatment at a temperature of 320 ° C., the underlying Cr thin film 4 and the upper Cu thin film 3 forming the coplanar line 13 are diffused, and an alloy layer is formed at the Cr / Cu interface. It has the effect of improving the adhesion between the two.

Next, the glass substrate on which the plurality of magnetic field sensors 11 are formed is cut into a predetermined dimension (S11). Here, it cut | disconnected to the external dimension of 15 mm x 2 mm using the dicer. As a result, ten magnetic field sensors 11 were obtained from a glass substrate of about 25 mm square.

  The above is the basic manufacturing method of the sensor element 11, but the material and dimensions of the glass substrate 5 and the material and forming method of the coplanar line 13 can be selected as appropriate. For example, the glass may be soda lime glass. It has sufficient strength even at the heat treatment temperature of 400 ° C. shown in this production method, and the thermal expansion coefficient is close to that of potash glass.

  The coplanar line 13 can be subjected to nickel base gold plating on the Cu surface by a plating method. Moreover, after forming the Cu thin film 3 by RF sputtering, a Cr and Au (gold) thin film can be continuously formed without breaking the vacuum. By these methods, oxidation of the coplanar line 13 can be prevented, and contact resistance with a wafer probe to be described later can be reduced.

  Further, the coplanar line 13 can be formed by a printing method. In the printing method, silver or the like having excellent conductivity can be selected as the wiring material. Moreover, in the printing method, it is easy to increase the film thickness, and the gain of the sensor element 11 can be improved.

The relative dielectric constant of the SrTiO thin film 1 was about 31 by a separate experiment. This is a value obtained by measuring the impedance of the open-ended coplanar line and matching the electric field analysis result by the finite element method.
Further, in order to compare the wavelength shortening effect of the dielectric, the same size sensor using the SiO ₂ thin film (thickness 2 μm) instead of the SrTiO thin film 1 was prepared by the above flowchart.

FIG. 4 is a diagram showing a method of measuring the phase difference of the sensor element 11 by the network analyzer 6. The sensor element 11 is arranged at the center of the Helmholtz coil 10, a wafer probe (Picoprobe 40-GSG-150) is brought into electrical contact with the electrode of the sensor element 11, and the network analyzer 6 (HP8752A) is connected via the coaxial cable 9. ). A DC magnetic field was applied in the direction of the hard axis of the amorphous CoNbZr thin film 2 which is a magnetic thin film of the sensor element 11 using a DC power supply 12 (R6243 manufactured by Advantest) to change it statically. The amplitude and phase difference of the transmission coefficient (S ₂₁ ) of the network analyzer 6 were measured according to changes in the magnetic field.

The network analyzer 6 and the DC power source 12 were controlled by the GP-IB 7 via the personal computer 8. The frequency range of the network analyzer 6 was changed from 0.3 MHz to 3 GHz. The bandwidth was 3 kHz, the number of averaging was 16 times, and the frequency point was 200 points. A frequency scan from 0.3 MHz to 3 GHz was performed for each bias magnetic field and stored. The measurement results are shown below.

5 to 8 show examples of measurement results of the phase change and amplitude of the sensor carrier with respect to the applied magnetic field for the sensor element 11 having the dimensions shown in FIG. FIG. 5 shows the phase change with respect to the magnetic field. The abscissa represents the applied DC magnetic field, and the phase change became maximum near the carrier frequency of about 2.1 GHz in the vicinity of 3 Oe. The inclination exceeded 100 degrees / Oe, which is a standard for application to the measurement of cardiac magnetic fields, and a value of 120 degrees / Oe was obtained. FIG. 6 shows the phase change with respect to frequency. The phase change increases as the frequency increases.

FIG. 7 shows the gain change with respect to the magnetic field. In the vicinity of 3 Oe, the amplitude attenuation is about -26 dB. This value exceeded -40 dB, at which the deterioration of the S / N ratio due to an increase in noise became apparent in the Dual Mixer Time Difference (DTMD) method connected as a signal processing circuit. Assuming measurement of the healthy person's cardiac magnetic field, etc., the phase change sensitivity must be 100 degrees / Oe or more, and the carrier attenuation must be within -40 dB. did. FIG. 8 shows a change in gain with respect to frequency. Gain degrades with increasing frequency.

FIG. 9 is a comparison of the phase change sensitivity and attenuation when the SiO ₂ thin film is used. In the phase change sensitivity using the SrTiO thin film 1, the average phase change sensitivity was improved by about 1.6 times that of the sensor using the SiO ₂ thin film.

FIG. 10 compares the electrical lengths of the SrTiO thin film 1 and SiO ₂ . The frequency dependence of the phase when no magnetic field was applied was compared with a magnetic field sensor made using a SiO ₂ thin film. When the SrTiO thin film 1 was used, the phase shortened by about 20% compared to the phase of the SiO ₂ thin film.

11 and 12 show the gain and magnetic field detection sensitivity when the thickness of the SrTiO thin film 1 is changed from 0.5 μm to 6 μm. The symbol is an average value of the measurement results of 10 samples, and the error bar represents the standard deviation. Compared with the case where the film thickness of the SrTiO thin film 1 is 6 μm, the magnetic field detection sensitivity is about 95% when the film thickness is 50% (3 μm), and the magnetic field detection sensitivity is about 85% when the film thickness is 33% (2 μm). It was. The sputtering time of 6 μm thickness is about 12 hours, and it has been found that the film formation time can be reduced without significantly degrading the sensitivity.

Next, Example 2 will be described with reference to FIGS. The external dimensions of the amorphous CoNbZr thin film shown in Example 1 were 10.2 mm × 1.15 mm. Example 2 shows an example in which the outer dimensions are reduced for the purpose of downsizing.
FIG. 13 shows the sensor element 31. FIG. 14 shows an AB cross section of FIG. The sensor element 31 is formed on the surface of the glass substrate 25 and is composed of a meander type coplanar line 26, a SrTiO thin film 21, and an amorphous CoNbZr thin film 22 made of a Cu thin film 23 (underlying is a Cr thin film 24).

  The external dimensions of the amorphous CoNbZr thin film 22 are shown in Table 1. Here, the dimension in the easy axis direction was changed to 5 levels, and the dimension in the hard axis direction was fixed at 1 mm. The minimum dimension is 0.95 mm × 1.0 mm of level 1 and the maximum dimension is 2.45 mm × 1.0 mm of level 5. Further, the ratio of the area of the amorphous CoNbZr thin film 22 at each level and the area of the thin film of Non-Patent Document 2 is shown in the area ratio column of Table 1. At level 5, it is reduced to 11.7% (about 1/8), and at level 1, it is reduced to 4.5% (about 1/22).

  As shown in FIG. 14, the meander type coplanar line 26 has a signal line conductor width of 110 μm, a ground line conductor width of 50 μm, an adjacent conductor interval of 20 μm, and a signal line center interval of 300 μm. Adjacent ground wires are spaced 50 μm apart. The spacing between the adjacent ground wires is 0 μm, that is, the pattern in which the ground wires are in close contact with each other with no gap will be discussed in Modification 2 and Modification 3 of Example 2 described later. Hereinafter, the pattern of the meander type coplanar line 26 in which the distance between the ground wires is 50 μm is referred to as a pattern A. The sensor elements shown in Example 2 are all pattern A meander type coplanar lines.

As shown in Table 1, the number of meander type coplanar lines 26 (number of lines) corresponding to each level of the external dimensions of the amorphous CoNbZr thin film 22 is 3, 4, 5, 6, and 8, respectively. . The case of level 5 will be described with reference to FIG. 13. Eight meander lines are arranged at equal intervals of 300 μm. The outside of the ground wire is disposed at a position of 125 μm from the center of the first and eighth meander lines. Therefore, the width of the transmission line is designed to be 2350 μm (125 × 2 + 300 × 7 = 2350). The width direction dimension of the magnetic film of level 5 is 2450 μm, and both ends of the magnetic body are 50 μm outside the transmission line.
Table 2 shows a list of conditions in the case of the present embodiment and the subsequent modifications. Details of each item in Table 2 will be described in each embodiment. The line pattern is a pattern of the meander type coplanar line 26.

Below, the manufacturing method of the sensor element shown in FIG.13 and FIG.14 is described briefly according to a flowchart. The manufacturing method is based on the flowchart shown in the manufacturing method of Example 1 shown in FIG. 3 except for the outer dimensions, thickness, pattern, heat treatment conditions, etc. of the constituent films.
First, the glass substrate 25 is cleaned (S1). Also in the present example, the glass substrate 25 was the same size as in Example 1, and a potash glass having a thickness of 1 mm and approximately 25 mm square was used. Subsequently, a Cu thin film 23 (the base is a Cr thin film 24) was formed on the entire back surface of the glass substrate 25 by RF sputtering. The film thickness was 2 μm. Heat treatment was performed after film formation. This thin film is provided with the intention of making the temperature of the back surface of the glass substrate 25 uniform in the manufacturing process and suppressing the temperature distribution in the glass substrate surface as much as possible. However, the drawing display was omitted.

  Subsequently, a resist pattern for the magnetic thin film is formed on the surface of the glass substrate 25 (S2), and then a magnetic film is formed (S3). Here, the amorphous CoNbZr thin film 22 was formed by RF sputtering at a power of 200 W and an Ar gas pressure of 5 mTorr. The film thickness ranges from 0.3 μm to 2 μm in 7 levels, that is, 0.3 μm, 0.5 μm, 0.75 μm, 1.0 μm, 1.25 μm, 1.5 μm, and 2.0 μm. Here, a thin film thickness is selected as compared with the amorphous CoNbZr thin film (5 μm) in the case of Example 1, and this is because the shape anisotropy is taken into consideration. The thickness was reduced as the outer dimension of the amorphous CoNbZr thin film was reduced, and the demagnetizing field was prevented from increasing. Thereafter, resist stripping (S4) was performed.

  Subsequently, heat treatment in a magnetic field is performed (S5). The rotary magnetic field heat treatment was performed at 300 ° C. for 2 hours, and the static magnetic field heat treatment was performed at 200 ° C. for 1 hour. The magnetic field strength was set to 0.3T. This imparted weak uniaxial anisotropy.

  Subsequently, a SrTiO thin film 21 which is a ferroelectric thin film is formed as an insulating layer (S6). In this example, the film was formed by RF sputtering. The sputtering conditions were an Ar gas pressure of 20 mTorr, a power of 200 W, and a substrate heating temperature of 160 ° C. In this embodiment, the SrTiO thin film 21 has a thickness of 3 μm and is constant at any film thickness level of the amorphous CoNbZr22.

  Next, after forming a resist pattern for forming the coplanar line 26 (S7), a conductive thin film is formed (S8). An RF sputtering method was used to form a Cu thin film 23 of 2 μm and an underlying Cr thin film 24 of 0.1 μm. Subsequently, resist stripping (S8) is performed.

  Next, the substrate is heat-treated in a magnetic field (S10), and finally uniaxial anisotropy is imparted. The heat treatment conditions were as follows: heat treatment in a rotating magnetic field at 300 ° C. for 2 hours, and static magnetic field heat treatment at 200 ° C. for 1 hour. The description of the cutting of the glass substrate (S11) is omitted.

  The measurement method is the same as in Example 1, but the network analyzer 6 used HP8722ES, and the frequency range was changed from 10 MHz to 10 GHz. In Example 1, a Helmholtz coil for applying a magnetic field was used, but in Example 2, an electromagnet capable of applying a magnetic field from below was used from the viewpoint of not hindering the operability of the wafer probe.

  FIG. 15 is a diagram showing a change in phase with respect to the magnetic field when the thickness of the amorphous CoNbZr thin film 22 is 0.75 μm. FIG. 16 is a diagram showing a gain change with respect to the magnetic field in the case of the film thickness. In FIG. 15, the phase change becomes the maximum value near the carrier frequency of about 3.65 GHz in the vicinity of 7 Oe. Its value is 30.2 degrees / Oe. On the other hand, as shown in FIG. 16, the gain decreased as the applied magnetic field increased, and became about −15 dB in the vicinity of 7 Oe.

  FIG. 17 shows the phase change value with respect to the film thickness change of the amorphous CoNbZr thin film 22. Phase change of six sensor elements for seven levels of the thickness of the amorphous CoNbZr thin film 22, that is, 0.3 μm, 0.5 μm, 0.75 μm, 1.0 μm, 1.25 μm, 1.5 μm and 2.0 μm The average value and standard deviation (error bar display) were shown. A black circle indicates a case where the number of meander lines is eight, and a white circle indicates a case where the number of meander lines is six. The display method of the horizontal axis, the number of sensors, symbols and the like in FIGS.

In FIG. 17, the larger the meander line number, the more the phase change amount tends to be slightly larger, but it seems that the longer coplanar line length contributes. When the thickness of the amorphous CoNbZr thin film 22 is in the range of 0.5 μm to 1.0 μm, the maximum value of the phase change exceeds 25 degrees / Oe. When the film thickness is 0.3 μm, the maximum value of the phase change exceeds 20 degrees / Oe when the number of meander lines is 8, but in the range of 0.5 μm to 1.0 μm. Not worth the value. That is, if the amorphous CoNbZr thin film 22 is thin, it is considered that the amount of magnetization as a magnetic material is insufficient and the sensitivity is insufficient. Therefore, the amorphous CoNbZr thin film 22 needs to have a certain volume or more.

On the other hand, when the amorphous CoNbZr film thickness 22 is 2 μm, even when the meander line number is 8, the maximum value of the phase change is about 13 degrees / Oe. Although not described in detail, the maximum value of the phase change remained at a value of several degrees / Oe in the 5 μm sensor element having the same thickness of the amorphous CoNbZr thin film 22 as that of the first embodiment. This is because the demagnetizing field is increased by increasing the film thickness. From the above, it is necessary to appropriately select the film thickness range of the amorphous CoNbZr thin film 22 in order to reduce the size of the sensor element.

  In FIG. 18, the gain with respect to the film thickness change of the amorphous CoNbZr thin film 22 is shown. Here, the gain is an attenuation amount when giving the maximum phase sensitivity, as shown in FIG. The gain deteriorates as the film thickness of the amorphous CoNbZr thin film 22 increases. For example, in the figure, when the meander line number is 6, when the thickness of the amorphous CoNbZr thin film 22 is 0.5 μm, it is about −9.5 dB, but when the film thickness is 1.0 μm, it is about −15 dB. At 2.0 μm, it decreases to about −22 dB. This is because eddy current loss increases as the thickness of the magnetic film increases.

  The gain when the number of meander lines is 8 is −11.5 dB when the thickness of the amorphous CoNbZr thin film 22 is 0.5 μm, but is −20 dB when the film thickness is 1.0 μm, and about -20 dB when the film thickness is 2.0 μm. Reduced to -30 dB. Compared with the case where the number of meander lines is 6, the gain decreases, but this is because the line length becomes relatively long due to the increase in the number of meander lines and the resistance value of the transmission line increases.

  Subsequently, the value of the DC magnetic field that gives the maximum phase sensitivity is shown in FIG. The value of the DC magnetic field that gives the maximum phase sensitivity increases linearly as the film thickness of the amorphous CoNbZr thin film 22 increases. The standard deviation value was a small value. For example, when the meander line number is 8, when the film thickness of the amorphous CoNbZr thin film 22 is 0.3 μm, the direct current magnetic field is about 3 Oe, and when the film thickness is 0.5 μm, it is 4.2 Oe. When the film thickness was 2.0 μm, it increased to 15.6 Oe at 1.0 μm. The value of this magnetic field did not deviate greatly even when the number of meander lines was six.

Generally, this direct current magnetic field corresponds to the magnetic permeability along the easy axis direction of the amorphous CoNbZr thin film 22. As described above, the static magnetic field temperature in the heat treatment in the rotating magnetic field (S11) was constant at 200 ° C. in all samples. Therefore, the magnitude of the anisotropic magnetic field of the amorphous CoNbZr thin film 22 seems to be almost the same. Therefore, when the film thickness of the Amorphous CoNbZr thin film 22 is large, the influence of the demagnetizing field is increased, and therefore the value of the DC magnetic field that gives the maximum phase sensitivity is also expected to increase.

FIG. 20 is a diagram showing the carrier frequency that gives the maximum phase sensitivity to the change in film thickness of the amorphous CoNbZr thin film 22. This frequency increases as the thickness of the amorphous CoNbZr thin film 22 increases. Specifically, for example, when the number of meander lines is 8, it is about 2.3 GHz when the amorphous CoNbZr thin film 22 is 0.3 μm, about 3 GHz when the film thickness is 0.5 μm, and about 3 GHz when the film thickness is 1.0 μm. It increased to about 5.4 GHz at 4 GHz and a film thickness of 2.0 μm. This is presumably because the demagnetizing field increases as the film thickness increases, and the frequency that provides the maximum phase sensitivity increases.

In this sensor element, it is desirable that the value of the direct-current magnetic field that gives the maximum phase sensitivity described above is small, and the amorphous CoNbZr thin film 22 is selected with an appropriate thickness. That is, as the film thickness of the amorphous CoNbZr thin film 22 is reduced, the demagnetizing field is reduced. Therefore, the DC magnetic field that gives the maximum phase sensitivity is reduced. On the other hand, if the amorphous CoNbZr thin film 22 is too thin, It seems that the amount of magnetization is insufficient and the sensitivity is insufficient. Considering these, the sensor element must be designed.

  Next, Modification 1 of Example 2 will be described with reference to Table 3. In the first modification, the film thickness of the amorphous CoNbZr thin film 22 was set to 1 μm, which had a large phase change value in the second example. On the other hand, the SrTiO thin film 21 was 3 μm in Example 2, but was 1 μm in Modification 1. The meander type coplanar line is pattern A. The manufacturing method of the sensor element 31 according to the first modification is the same as that in the second embodiment except for the above-described changes. The prepared sample was measured by the same method as in Example 2. Table 3 shows the phase sensitivity and gain when the number of meander lines is 8. Table 3 shows a numerical value when the amorphous CoNbZr thin film has the same thickness of 1 μm and the SrTiO thin film 21 has a thickness of 3 μm as the reference value 1. In each table below, the film thickness of the amorphous CoNbZr thin film of the sample of the example and the reference value is the same.

  According to Table 3, the average value of the phase sensitivity of the five samples was 39.4 degrees / Oe, and the maximum phase sensitivity was 75.5 degrees / Oe. The gain at the maximum phase sensitivity was −39.9 dB and within −40 dB. Although not shown in Table 2, the maximum phase sensitivity was obtained under the condition that the DC magnetic field was about 9.0 Oe and the carrier frequency was about 4.35 GHz.

On the other hand, the average value of the phase sensitivities of the six samples with the reference value 1 created using the SrTiO thin film 21 having a thickness of 3 μm is 26.9 degrees / Oe, and the maximum phase sensitivity is 32.4 degrees / Oe. there were. Both of the numerical values of the present example are larger than the value of the reference value 1. This shows that the characteristics were further improved by reducing the film thickness of SrTiO. This is considered to be due to an increase in capacitance due to the proximity of the coplanar line 26 and the amorphous CoNbZr thin film 22 and an increase in the contribution of the magnetic thin film.

Subsequently, Modification 2 of Example 2 will be described with reference to FIG. 21 and Tables 4 to 6. In the sensor element 31 according to the modified example 2, the outer dimensions of the amorphous CoNbZr thin film 22 are the level 2, the level 3 and the level 5 shown in Table 1, and the film thickness is 1 μm where the value of the phase change is large in the example 2. Alternatively, the thickness was set to 0.5 μm. Further, the thickness of the SrTiO thin film 21 was further reduced to 0.5 μm.

Next, a meander type coplanar line (hereinafter referred to as a pattern B) used in Modification 2 will be described with reference to FIG. FIG. 21A shows a pattern B in a case where the level 3 shown in Table 4 described later and the number of meander lines is 5. The drawing also shows a rectangular magnetic thin film. Here, the pattern in the area indicated by the broken line is a probing area where the wafer probe mentioned above is brought into contact. FIG. 4B shows a corresponding pattern A. The difference between the two patterns is whether the interval between adjacent ground lines is 0 μm or 50 μm except in the vicinity of the probing region. In FIG. 4C, the four different portions of the difference are hatched. Pattern B has a larger ground area.

  The manufacturing method of the sensor element of the modification 2 is the same as the manufacturing method in the embodiment 2 except for the above changes. The completed sample was measured by the same method as in Example 2. Table 4 shows the results when the outer dimension of the amorphous CoNbZr thin film 22 is level 3, the film thickness is 1.0 μm, and the meander line number is 5. In Table 4, when the film thickness of the SrTiO thin film 21 is 3 μm as the reference value 2, the value of the coplanar line is pattern A (Example 2), and as the reference value 3, the film thickness of the SrTiO thin film 21 is 0.5 μm, The meander type coplanar line 26 represents the numerical value of the pattern A sample.

According to Table 4, the average value of the phase sensitivity of the six samples of this example was 66.5 degrees / Oe, and the maximum phase sensitivity was 118.5 degrees / Oe. The gain at the maximum phase sensitivity was −39.7 dB, and was within −40 dB. Although not shown in Table 3, the maximum phase sensitivity was obtained under the condition that the DC magnetic field was about 6.3 Oe and the carrier frequency was about 2.55 GHz.

For the reference value 2, the average value of the phase sensitivity was 14.7 degrees / Oe, and the maximum phase sensitivity was 19.2 degrees / Oe. Comparing these numerical values, the present embodiment greatly exceeds the numerical value of the reference value 2 for both the average value of the phase sensitivity and the maximum phase sensitivity. In addition to further reducing the film thickness of the SrTiO thin film 21, the effect of changing the ground wire pattern of the meander type coplanar line 26 appears.

On the other hand, with the reference value 3 in which the coplanar line 26 is still the pattern A and only the thickness of the SrTiO thin film 21 is reduced, the average value of the phase sensitivity and the maximum phase sensitivity value of the sample are 25.2 degrees / Oe and 39.8 degrees, respectively. / Oe. Both of these numerical values do not reach the present embodiment. From this, it can be considered that the pattern shape of the meander type coplanar line 26 greatly affects the characteristics of the sensor element.

Next, Table 5 shows the results when the outer dimension of the amorphous CoNbZr thin film 22 is level 2, the film thickness is 1.0 μm, and the meander line number is 4. Here, as a reference value, the SrTiO thin film 21 has the same value of 0.5 μm, and the meander type coplanar line 26 indicates the numerical value of the pattern A sample.

In this example shown in Table 5, the average value of the phase sensitivity was 72.2 degrees / Oe, and the maximum phase sensitivity was 135.1 degrees / Oe. The gain at the maximum phase sensitivity was −39.2 dB and within −40 dB. Although not shown in Table 5, the highest phase sensitivity was obtained under the condition that the DC magnetic field was about 8.4 Oe and the carrier frequency was about 2.75 GHz.
On the other hand, the average value of the phase sensitivity and the value of the highest phase sensitivity of the reference value 4 are 18.9 degrees / Oe and 23.5 degrees / Oe, respectively. The numerical values of the present embodiment are greatly improved with respect to the reference value 4 in both the average value of phase sensitivity and the maximum phase sensitivity.

In the examples shown in Tables 4 and 5, the film thickness of the amorphous CoNbZr thin film 22 was 1.0 μm, and Table 6 shows the case where the film thickness is 0.5 μm. Table 6 shows the case where the amorphous CoNbZr thin film 22 has a thickness of 0.5 μm and the number of meander lines is 8. The value of the reference value 5 is a numerical value when the amorphous CoNbZr thin film has the same thickness of 0.5 μm and the thickness of the SrTiO thin film is 3 μm (Example 2). According to Table 6, the average value of the phase sensitivity of the four samples was 75.1 degrees / Oe, and the maximum phase sensitivity was 129.1 degrees / Oe. The gain at the maximum phase sensitivity was −38.6 dB and within −40 dB. Although not shown in Table 5, the maximum phase sensitivity was obtained under the condition that the DC magnetic field was about 4.0 Oe and the carrier frequency was about 1.75 GHz.

On the other hand, the average value of the phase sensitivity and the value of the maximum phase sensitivity of the reference value 5 were 22.6 degree / Oe and 26.6 degree / Oe, respectively. Even when the amorphous CoNbZr thin film 22 is 0.5 μm, both the average value and the maximum phase sensitivity of the phase sensitivity greatly exceed the reference value 5. The effect of further reducing the film thickness of the SrTiO thin film 21 and changing the pattern of the ground wire of the meander type coplanar line 26 is also shown in this case.

Subsequently, a third modification of the second embodiment will be described with reference to FIG. In Modified Example 3, a case where the pattern (pattern B) of the meander type coplanar line 26 is further modified will be described. Here, this is referred to as a pattern C. In the sensor element manufactured in this example, the outer shape level of the amorphous CoNbZr thin film 22 was set to level 1. That is, the outer dimension of the amorphous CoNbZr thin film 22 is 0.95 mm × 1.0 mm. As described above, this dimension is reduced to about 4.5% in terms of area compared to the outer dimension of the thin film of the sensor element shown in Non-Patent Document 2. The film thickness of the amorphous CoNbZr thin film 22 was 1 μm, which had a large phase change value in Example 2, and the thickness of the SrTiO thin film 21 was 0.5 μm.

The pattern C of the meander type coplanar line 26 used in this embodiment is shown in FIG. Here, a pattern area surrounded by a broken line in the drawing is a probing area. FIG. 5B shows a pattern B which is the case of the above-described modification example 2. In pattern B, three 50 μm gaps are left in the ground wire near the probing area. On the other hand, the pattern C does not have these three gaps. The distance between the ground wires in the vicinity of the probing region is also 0 μm, that is, a pattern in which the ground wires are in contact with each other and has a wider ground area.

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The manufacturing method in this example is the same as the manufacturing method in Example 2 except for the above-described changes. The completed sample was measured by the same method as in Example 2. The results are shown in Table 7. Here, a sample in which the meander type coplanar line 26 is the pattern B is set as the reference value 6. The difference between them is only the pattern of the coplanar line 26.
According to Table 7, the average value of the phase sensitivity of the six samples of this example was 156.2 degrees / Oe, and the maximum phase sensitivity was 339.0 degrees / Oe. The gain at the maximum phase sensitivity was −37.3 dB and within −40 dB. Although not shown in Table 7, the maximum phase sensitivity was obtained under the condition that the DC magnetic field was about 7.7 Oe and the carrier frequency was about 2.75 GHz.

On the other hand, as for the numerical value of the reference value 6, the average value of the phase sensitivity is 63.5 degrees / Oe, and the maximum phase sensitivity is 86.3 degrees / Oe. Although the numerical value of the maximum phase sensitivity of the reference value 6 is also a numerical value exceeding 80, in this embodiment, the average value also exceeds 100 degrees / Oe, and the pattern deformation of the ground wire near the probing region of the meander type coplanar line 26 is changed. It can be said that it was effective.

According to the above embodiment, in the sensor element using the amorphous CoNbZr thin film of several mm square as the magnetic body, the outer dimensions and film thickness of the amorphous CoNbZr thin film that is a component of the sensor, and the film thickness of the SrTiO thin film that is the dielectric material. In addition, by appropriately setting the shape of the coplanar line pattern constituting the transmission line, it is possible to provide a practical sensor having a phase change sensitivity of 100 degrees / Oe or more and a carrier attenuation of -40 dB or less. It was shown that.

1, 21 SrTiO thin film 2, 22 Amorphous CoNbZr thin film 3, 23 Cu thin film 4, 24 Cr thin film 5, 25 Glass substrate 6 Network analyzer 7 GP-IB
8 PC 9 Coaxial cable 10 Helmholtz coil 11, 31 Sensor 12 Power supply 13, 26 Coplanar line

Claims (8)

In a magnetic field sensor having a structure in which a magnetic thin film and a coplanar conductor are laminated on an insulating substrate via a dielectric thin film, the dielectric thin film is made of strontium titanate (SrTiO) and has a thickness of less than 6 μm. Magnetic field sensor characterized by.   2. The magnetic field sensor according to claim 1, wherein the insulating substrate is made of glass, and the magnetic thin film is amorphous CoNbZr.   3. The magnetic field sensor according to claim 2, wherein the laminated coplanar conductor is a linear type or a meander type.   4. The magnetic field sensor according to claim 3, wherein the amorphous CoNbZr film has a thickness of 2 [mu] m or less, and the SrTiO thin film has a thickness of 3 [mu] m or less.   4. The magnetic field sensor according to claim 3, wherein the magnetic field sensor has a meander-type coplanar line, and has a structure in which ground wires of adjacent meander lines are not separated from each other.   4. The magnetic field sensor according to claim 3, wherein said magnetic field sensor has a meander type coplanar line, and a ground wire of an adjacent meander line is not separated except in the vicinity of a probing region of a pattern. . A method of manufacturing a magnetic field sensor having a structure in which a magnetic thin film and a coplanar conductor are laminated on an insulating substrate via a dielectric thin film,
Forming a magnetic thin film on an insulating substrate;
Forming SrTiO to be less than 6 μm on the magnetic film;
And a step of forming a coplanar line on the SrTiO film. A method of manufacturing a magnetic field sensor having a structure in which a magnetic thin film and a coplanar conductor are laminated on an insulating substrate via a dielectric thin film,
Forming an amorphous CoNbZr thin film on a glass substrate by sputtering;
Forming SrTiO to be less than 6 μm on the amorphous CoNbZr thin film by sputtering;
And a step of forming a coplanar line on the SrTiO film.

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