JP2545926B2 - Current detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a current detector for detecting a current to be measured flowing in a conductor in a state of being electrically insulated from the conductor.

[Conventional technology]

Conventionally, as such a current detector, a current detector has been proposed in which a current to be measured is passed through a coil to generate a magnetic field, which is detected by a hall element or a magnetoresistive element.

[Problems to be Solved by the Invention] However, according to the conventional current detector, since the reactance component due to the coil enters the circuit of the measured current, the response of the output is deteriorated. In addition, it is difficult to integrate the coil and the detection element, and there is a limit to miniaturization because it is a separate part, and further, there is a limit to the assembly accuracy such as the gap between the coil and the detection element. There was a problem that it was necessary to make adjustments.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a current detector which is sufficiently small and highly accurate as compared with the conventional one.

[Means for solving the problem]

In order to achieve the above-mentioned object, the current detector of the present invention has a thin film conductive film on which a current to be measured flows and a magnetic sensitive film formed of a thin film ferromagnetic resistance element on a substrate in an electrically insulated state. It is characterized by being formed in.

When the magnetic sensitive film is formed above the conductive film and the pattern width of the magnetic sensitive film is W _M and the pattern width of the conductive film is W _AL , W _M / W _AL ≧ 1.3 is set. You may.

 Further, the conductive film may be aluminum.

Further, the thin film conductive film through which the current to be measured flows and the magnetic sensitive film composed of the thin film current magnetoresistive element are formed on the insulating substrate in an electrically insulated state, and the conductive film and the magnetic sensitive film are provided. Are arranged in parallel on the insulating substrate at a distance from each other and at the same height.

The current magnetoresistive element may be a Hall element.

[Action]

According to the above means, the measured current flowing in the conductive film generates a magnetic field proportional to the magnitude of the current, and when the magnetic field is applied to the magnetosensitive film, the strength of the magnetic field is electrically generated by the current-magnetic effect. As a result, the magnitude of the measured current can be detected. Further, since the conductive film and the magnetic film formed on the substrate are all thin films, they can be formed in a small size and with high precision by the semiconductor thin film technology and photolithography technology.

Further, by stacking the layers using the ferromagnetic magnetoresistive element, the sensitivity can be increased and the size can be further reduced.

Also, by setting the pattern width to W _M / W _AL ≧ 1.3, the rate of resistance change becomes high and the resistance is almost saturated.

Further, in the invention according to claim 4, the conductive film and the magnetic sensitive film are formed on the same plane on the same substrate, so that the formation thereof is facilitated.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 is a view showing a first embodiment of the present invention, in which FIG. 1 (a) is a plan view thereof, and FIG. 1 (b) is a line A- in FIG. 1 (a).
A sectional view taken on line A is shown. In the figure, reference numeral 4 designates an insulating substrate, and a thin film of a ferromagnetic magnetoresistive element made of a Ni—Fe alloy as a current magnetic effect element according to the present invention is deposited on the insulating substrate 4 by vapor deposition, followed by photolithography technique. Thus, the magnetic sensitive film 1 is formed by etching into a predetermined pattern. Then, the magnetic sensitive film 1 is covered with the insulating film 2 made of, for example, a SiO ₂ film by sputtering. Further, an aluminum thin film is attached on the insulating film 2 by vapor deposition, and the conductive film 3 is formed by etching into a predetermined pattern by a photolithography technique.

Here, in addition to the above, as the ferromagnetic magnetoresistive element, Fe, C
Any material containing o, Ni or the like as a main component may be used. Further, when the ferromagnetic magnetoresistive element receives a magnetic field from a direction orthogonal to the direction of current flow, the resistance value of that portion decreases.

Therefore, according to this embodiment, the current I is applied to the conductive film 3 in the direction indicated by the upward arrow in the drawing, that is, in the direction from the end 5 to the end 6.
Flowing, a magnetic field H having an intensity proportional to the magnitude of the current I is generated in the direction indicated by the arrow pointing to the left in the figure. Here, when a constant current is applied between both ends 7 and 8 of the magnetic sensitive film 1 in the direction indicated by the dotted arrow in the figure, the magnetic field H is horizontal to the magnetic sensitive film 1 and It is applied in a direction orthogonal to the direction of current flow. When the magnetic field H is received, the resistance value of the magnetic sensitive film 1 changes in proportion to the magnetic field strength. Therefore, by detecting this resistance value, the current I
The size of can be detected. Further, since the magnetic sensitive film 1 and the conductive film 3 are electrically insulated by the insulating film 2 in this current detector, the current can be measured without affecting the current to be measured.

Further, according to the present embodiment, there are the following effects. That is, unlike the prior art, it is not necessary to pass the current to be measured through the coil, so that the reactance component does not enter, and the output response is improved accordingly.

The magnetic sensitive film 1, the insulating film 2, and the conductive film 3 formed on the insulating substrate 4 are all formed into a thin film, and they are formed by a semiconductor thin film technique or photolithography technique. In the depth direction, fine processing is possible with good controllability, and it is possible to form with extremely high precision and small size. Further, according to the present embodiment, since the magnetic sensitive film 1, the insulating film 2 and the conductive film 3 are laminated, the occupied area on the insulating substrate 4 is very small, and the size can be further reduced. .

Since a ferromagnetic magnetoresistive element is used as the current magnetic effect element, it is compared with other Hall elements or semiconductor magnetoresistive elements (for example, InSb), etc. Since the sensitivity is high as shown, it can be used satisfactorily even in a small current range, and the temperature coefficient of the semiconductor magnetoresistive element is -2 at a constant current.
% / ° C, and Hall element is -0.13% / ° C,
In the case of a ferromagnetic magnetoresistive element, the value is -0.05% / ° C, and since the value is small, a current detector having relatively good characteristics can be constructed.

In the first embodiment, the conductive film 3 is formed on the magnetic sensitive film 1.
However, needless to say, the same effect can be expected by forming the magnetic sensitive film 1 on the upper side of the conductive film 3.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 (a) is a perspective view of the second embodiment, and FIG. 3 (b).
Is a sectional view taken along line BB. In the figure, reference numeral 11 denotes an insulating substrate, and an aluminum thin film is deposited on the insulating substrate 11 by vapor deposition and is etched into a predetermined pattern by a photolithography technique to form a first conductive film 12. Then, the insulating film 13 is covered by sputtering,
After depositing a thin film of a ferromagnetic magnetoresistive element on the insulating film 13 by vapor deposition, the magnetic sensitive film 14 is etched by a predetermined pattern.
To form. After that, in the same manner as above, the insulating film 1
5, the second conductive film 16 made of aluminum is formed, and the contact holes 20 are formed in the insulating films 13 and 15 so that the contact holes 20 are filled with aluminum,
The first conductive film 12 and the second conductive film 16 are connected. Then, the protective film 17 is formed to form the current detector of this embodiment. In the figure, 18a and 18b are current terminals to be measured, and 19a and 19b are both terminals of the magnetic sensitive film 14.

Therefore, according to the second embodiment described above, the measured current i is
When flowing from 18a to the terminal 18b, the magnetic sensitive film 14 is horizontal from both the upper and lower first and second conductive films 12 and 16 and has a current flowing direction (direction from the terminal 19a to the terminal 19b, or vice versa). The magnetic field H is received in the direction orthogonal to the (direction), and the resistance value decreases. Therefore, by measuring the resistance value, the magnitude of the measured current i can be detected. The same effect as that of the first embodiment can be expected in the second embodiment. However, comparing both the embodiments, when the measured current of the same magnitude is applied to the conductive film, the magnetic sensitivity is reduced. Since the strength of the magnetic field received by the film is doubled, the output is larger and the sensitivity is improved in the second embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 (a) is a plan view of the third embodiment, and FIG. 4 (b).
Is a sectional view taken along the line CC. In the figure, 21 is an insulating substrate, and a conductive film 22 made of an aluminum thin film is formed in a predetermined region on the insulating substrate 21. Then, on the insulating substrate 21, a magnetic sensitive film 23 made of a thin film of a current magnetic effect element is formed in a predetermined pattern in parallel with the conductive film 22. In the third embodiment, a Hall element made of InSb, GaAs or the like or a semiconductor magnetoresistive element made of InSb or the like is suitable as the current magnetic effect element.

Therefore, according to the third embodiment, when the current I to be measured is passed through the conductive film 22 in the direction shown by the arrow in the figure, the magnetic sensitive film 23 receives the magnetic field H from the direction perpendicular to its plane. Therefore, when a Hall element is used as the current magnetic effect element, the direction in which the current i of the magnetic sensitive film 23 flows (from the terminal 24a to the terminal 2 in the figure)
4b) and a direction of the magnetic field H, that is, a potential difference of a magnitude proportional to the strength of the magnetic field H is generated in the direction perpendicular to the direction of the magnetic field H, that is, from the terminal 25a to the terminal 25b. By doing so, the magnitude of the measured current I can be detected. When a semiconductor magnetoresistive element is used as the current magnetic effect element, the magnetic sensitive film is proportional to the strength of the magnetic field H.
Since the resistance value of 23 increases, the magnitude of the measured current I can be detected by measuring the resistance value.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 (a) is a plan view of the fourth embodiment, and FIG. 5 (b).
Is a cross-sectional view taken along the line D-D. This embodiment is an example in which the magnetic sensitive film is formed on the upper side of the conductive film in the first embodiment, and each component can be formed by the same steps as in the first embodiment.

Conductive film 33 formed in a predetermined pattern on insulating substrate 34
, The current I to be measured flows from the end portion 35 toward the end portion 36. The magnetic sensitive film 31 is laminated on the conductive film 33 via the insulating film 32, and when the measured current I flows through the conductive film 36,
A magnetic field H having an intensity proportional to the magnitude of the current acts on the magnetic sensitive film 31. As a result, the resistance value between the both ends 37, 38 of the magnetic sensitive film 31 changes in proportion to the magnetic field strength by the same action as in the first embodiment, and the current I is detected by detecting this resistance value. The size of can be detected.

FIG. 6 is a characteristic diagram showing the relationship between the pattern ratio of the magnetic sensitive film 31 and the conductive film 33 in the current detector according to the fourth embodiment and the rate of change in resistance of the magnetic sensitive film 31 at that time. As shown in FIG. 5 (b), the pattern width W _M of the magnetic sensitive film 31 and the pattern width W _AL of the conductive film 33 are used and expressed as W _M / W _AL ,
The resistance change rate is the resistance value when the current I = 0mA is R
When the resistance value at (0) and the current I = 50 mA is R (50), it is represented by (R (0) -R (50)) / R (0). still,
The measurement was performed using a ferromagnetic magnetoresistive element made of a Ni—Fe alloy as the magnetic sensitive film 31.

From FIG. 6, by setting W _M / W _AL ≧ 1.3, the rate of resistance change can be set to the highest value and the sensitivity of the detector can be increased. Further, since the resistance change value is almost saturated, it is possible to provide a detector that can reduce the influence of manufacturing error and the like and can perform stable current detection. The following is considered as the reason why such characteristics are obtained. Since the magnetic field H generated by the current I acts in a ring shape centering on the conductive film 33,
Inevitably, the magnetic field H also acts on the portion of the conductive film 33 that is wider than the pattern in the width direction. Therefore, by making the pattern width W _M of the magnetic sensitive film 31 wider than the pattern width W _AL of the conductive film 33, such a width direction component of the magnetic field H can be effectively applied to the magnetic sensitive film 31. . Further, since the magnetic sensitive film 31 is formed so as to surround the conductive film 33 at the edge portion of the pattern of the conductive film 33, the magnetic field H generated by the current I flowing through the conductive film 33 is shown in FIG. It is considered that the resistance change rate is increased in order to effectively traverse the magnetic sensitive film 31, as indicated by the dotted line. Also, the resistance change rate is almost saturated by setting W _M / W _AL ≧ 1.3.
When W _M / W _AL = 1.3, the magnetic field H acts most effectively on the magnetic sensitive film 31, so that the rate of change in resistance becomes the highest, and W _M / W _AL >
At 1.3, the magnetic field strength is inversely proportional to the square of the distance (in this case, the distance between the conductive film 33 and the magnetic sensitive film 31), and therefore the conductive film 33 is
It is considered that the resistance value hardly changes in the magnetic sensitive film 31 in the portion away from, and the resistance change rate is saturated.

Further, when using the current detector as described above, in order to process a weak signal obtained as a resistance value between both ends 37, 38 of the magnetic sensitive film 31, in general, an operational amplifier ( Although the operational amplifier will be connected, the offset voltage of the operational amplifier is usually about 3 mV or less, so if the resistance change rate is 0.3% or more, current detection can be performed without problems even if there is an offset. Therefore, from Figure 6, W _M / W _AL
It should be set to ≧ 0.6.

Next, using the current detectors of the first to fourth embodiments, an electric circuit for actually detecting the current to be measured is referred to as a seventh circuit.
This will be described with reference to FIGS. Incidentally, the reference numeral in the drawing is the first
This corresponds to the configuration of the first embodiment shown in the figure.

In the example shown in FIG. 7, the magnetic sensitive film 1 and the other resistors R ₁ , R ₂ and R ₃ form a full bridge, and the electrode (end) 8 is connected to one input of the comparator 40. However, the electrode A is connected to the other input. According to this circuit, by adjusting the resistance values of the resistors R ₁ and R ₂ and setting the potential of the electrode A to a desired value, the comparator when the predetermined current I is reached.
A signal is output by 40, and an arbitrary current value I
Can be detected.

In the example shown in FIG. 8, the magnetic sensitive film 1 and the other resistors R ₄ , R ₅ , and R ₆ form a full bridge, and the electrode B is connected to the + input of the voltage follower composed of the operational amplifier 41, and the electrode ( The end portion 8 is connected to the + input of the non-inverting amplifier circuit composed of the operational amplifier 42 and the resistors R ₇ and R ₈ . According to this circuit, an output proportional to the measured current 1 is obtained from the output terminal of the non-inverting amplifier circuit.

In the example shown in FIG. 9, the magnetic sensitive film 1 is formed in two places, and a full bridge is formed by these and the resistors R ₉ and R ₁₀ .
This circuit has the advantage of doubling the sensitivity.

Although the present invention has been described above with reference to the above embodiments, the present invention is not limited thereto and can be variously modified without departing from the gist thereof. For example, as a method of forming a magnetic sensitive film and a conductive film, In addition to vapor deposition, sputtering, ion beam deposition, CVD, etc. can be adopted. As a method for forming an insulating film, CVD, etc. can also be adopted in addition to sputtering, and the insulating film is Si ₃ N ₄ etc. It may be a thin film. Further, the substrate referred to in the present invention may be, for example, a semiconductor substrate on which an insulating film is formed in addition to the insulating substrate. In that case, if a semiconductor element is formed in the semiconductor substrate, it can be easily integrated with the IC.

〔The invention's effect〕

As described above, according to the present invention, since the conductive film and the magnetic sensitive film are formed on the substrate in an electrically insulated state, it is possible to provide a sufficiently small and highly accurate current detector. There is an excellent effect.

Also, by stacking with a ferromagnetic magnetoresistive element,
The sensitivity can be increased and the size can be further reduced.

Also, by setting the pattern width to W _M / W _AL ≧ 1.3,
It is possible to further improve the sensitivity and provide a stable current detector.

Further, in the invention according to claim 4, since the conductive film and the magnetic sensitive film are formed on the same plane of the substrate, they can be easily formed.

[Brief description of drawings]

FIG. 1 (a) is a plan view of the first embodiment of the present invention, FIG. 1 (b) is a sectional view taken along the line AA in FIG. 1 (a), and FIG. 2 is a current in a current magnetic effect element. Relationship between value and output, 3rd
FIG. 3 (a) is a perspective view of the second embodiment of the present invention, and FIG. 3 (b).
Is a sectional view taken along line BB in FIG. 3 (a), FIG. 4 (a) is a plan view of a third embodiment of the present invention, and FIG. 4 (b) is C in FIG. 4 (a). FIG. 5A is a plan view of the fourth embodiment of the present invention, and FIG. 5B is a D view in FIG. 5A.
FIG. 6 is a characteristic view showing the relationship between the pattern width ratio and the resistance change rate in the fourth embodiment, and FIGS. 7 to 9 show the device using the current detector of the present invention. It is an electric circuit diagram. 1 ... Magnetic sensitive film, 2 ... Insulating film, 3 ... Conductive film, 4 ... Insulating substrate.

Front Page Continuation (72) Inventor Toshikazu Arashi 1-1, Showamachi, Kariya, Aichi Prefecture, Nippon Denso Co., Ltd. (72) Inventor, Ichiro Izawa, 1-1, Showamachi, Kariya City, Aichi Nippon Denso Co., Ltd. (72 ) Inventor Hiroshi Sakurai, 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nippon Denso Co., Ltd. (56) Reference JP-A-61-97574 (JP, A)

Claims (5)

(57) [Claims] 1. A thin film conductive film through which a current to be measured flows and a magnetic sensitive film composed of a thin film ferromagnetic magnetoresistive element are formed on a substrate in an electrically insulated state. A current detector characterized in that a magnetically sensitive film is laminated on the substrate with an insulating film interposed therebetween. 2. The magnetic-sensitive film is formed on the upper side of the conductive film, and when the pattern width of the magnetic-sensitive film is W _M and the pattern width of the conductive film is W _AM , W _M The current detector according to claim 1, wherein / W _AM ≧ 1.3 is set. 3. The conductive film is aluminum.
The current detector described. 4. A thin film conductive film through which a current to be measured flows and a magnetic sensitive film composed of a thin film current magnetoresistive element are formed on an insulating substrate in a state of being electrically insulated, A current detector characterized in that the magnetic sensitive films are arranged in parallel on the insulating substrate while being separated from each other and at the same height. 5. The current detector according to claim 4, wherein the current magnetoresistive element is a Hall element.