TMR full-bridge magnetic sensor and preparation method thereof
阅读说明：本技术 一种tmr全桥磁传感器及其制备方法 (TMR full-bridge magnetic sensor and preparation method thereof ) 是由 刘明 胡忠强 周子尧 毛若皓 关蒙萌 于 2019-10-23 设计创作，主要内容包括：TMR全桥磁传感器,包括：基片和设置于所述基片上的TMR单元,所述TMR单元包括自由层、钉扎层和隧道层,4组TMR单元桥式连接形成全桥结构,4组TMR单元分别位于全桥结构的4个桥臂上；所述TMR单元的长宽比不等于1,位于相邻桥臂上的TMR单元的长轴相互垂直,位于相对桥臂上的TMR单元的长轴相互平行。本发明根据TMR单元的长轴方向来布置全桥结构上的TMR单元,使相邻桥臂上的TMR单元的长轴方向互相垂直,相对桥臂上的TMR单元的长轴方向相互平行,从而通过在磁场退火时施加特定角度的外加磁场,得以一次性在单一芯片上形成全桥结构,大大降低了单一芯片全桥磁传感器制备工艺的难度和生产成本。(TMR full bridge magnetic sensor includes: the TMR unit comprises a free layer, a pinning layer and a tunnel layer, wherein 4 groups of TMR units are connected in a bridge manner to form a full-bridge structure, and 4 groups of TMR units are respectively positioned on 4 bridge arms of the full-bridge structure; the length-width ratio of the TMR units is not equal to 1, the long axes of the TMR units on the adjacent bridge arms are perpendicular to each other, and the long axes of the TMR units on the opposite bridge arms are parallel to each other. The TMR units on the full-bridge structure are arranged according to the long axis direction of the TMR units, so that the long axis directions of the TMR units on adjacent bridge arms are mutually vertical and are mutually parallel relative to the long axis direction of the TMR units on the bridge arms, and therefore, the full-bridge structure can be formed on a single chip at one time by applying an external magnetic field with a specific angle during magnetic field annealing, and the difficulty and the production cost of the preparation process of the single-chip full-bridge magnetic sensor are greatly reduced.)
A TMR full bridge magnetic sensor, comprising: the TMR unit comprises a free layer, a pinning layer and a tunnel layer, wherein 4 groups of TMR units are connected in a bridge manner to form a full-bridge structure, and 4 groups of TMR units are respectively positioned on 4 bridge arms of the full-bridge structure;
the method is characterized in that:
the length-width ratio of the TMR units is not equal to 1, the long axes of the TMR units on the adjacent bridge arms are perpendicular to each other, and the long axes of the TMR units on the opposite bridge arms are parallel to each other.
2. The TMR full bridge magnetic sensor of claim 1, wherein: the TMR unit has an aspect ratio of > 10.
3. A TMR full bridge magnetic sensor as claimed in claim 1 or 2, wherein: the TMR unit is rectangular or elliptical in shape.
4. The TMR full bridge magnetic sensor of claim 1, wherein: the long axis direction of the TMR unit is parallel to the direction of the bridge arm where the TMR unit is located.
5. The TMR full bridge magnetic sensor of claim 1, wherein: the substrate is also provided with 4 electrodes which comprise a pair of input electrodes and a pair of output electrodes, and each electrode is respectively connected with two adjacent bridge arms.
6. A TMR full bridge magnetic sensor as claimed in claim 1 or 2 or 4 or 5, wherein: the magnetic moment directions of the pinning layers of the TMR units on the adjacent bridge arms are different, and the magnetic moment directions of the pinning layers of the TMR units on the opposite bridge arms are the same.
The preparation method of the TMR full-bridge magnetic sensor is characterized by comprising the following steps:
providing a substrate;
depositing TMR units and electrodes on the substrate, wherein 4 groups of TMR units are connected in a bridge manner to form a full-bridge structure, each bridge arm of the full-bridge structure is provided with one group of TMR units, long axes of the TMR units on adjacent bridge arms are mutually vertical, and long axes of the TMR units on opposite bridge arms are mutually parallel;
and carrying out magnetic field annealing treatment on the TMR unit, wherein an included angle of 45 degrees is formed between the direction of the applied magnetic field and the long axis direction of the TMR unit during annealing, after annealing is finished, the magnetic moment directions of the pinning layers of the TMR units on adjacent bridge arms are different, and the magnetic moment directions of the pinning layers of the TMR units on opposite bridge arms are the same.
8. The method for manufacturing the TMR full bridge magnetic sensor according to claim 7, wherein: the TMR unit has an aspect ratio of > 10.
9. The method for manufacturing the TMR full bridge magnetic sensor according to claim 7 or 8, wherein: the TMR unit is rectangular or elliptical in shape.
10. The method for manufacturing the TMR full bridge magnetic sensor according to claim 7, wherein: the electrodes comprise a pair of input electrodes and a pair of output electrodes, and the electrodes are connected with two adjacent bridge arms.
Technical Field
The invention belongs to the technical field of magnetic field detection, and particularly relates to a full-bridge magnetic sensor with a single chip.
Background
A magnetic sensor is a sensor that can detect the direction, intensity, and position of a magnetic field, and has been widely used in many fields. A TMR (Tunnel magnetoresistive) type magnetoresistive sensor is one of magnetic sensors, has advantages of low offset, high sensitivity and good temperature performance, and has come to be applied in the industrial field in recent years. The Magnetoresistance of the TMR type sensor can change along with the change of the magnitude and the direction of an external magnetic field, the sensitivity of the TMR type sensor is superior to that of a Hall effect sensor, an AMR (anisotropic magneto resistance) type sensor and a GMR (giant magneto resistance) magnetic sensor, the TMR type sensor has better temperature stability and lower power consumption, and the TMR type magnetic sensor can be conveniently combined with the existing semiconductor process in the processing process, so that the TMR type sensor has more application prospects.
The magnetic resistance sensor of the full-bridge structure can effectively improve the sensitivity and the temperature stability of the device. The TMR sensor of the full bridge structure requires the magnetization directions of the pinned layers of the TMR cells on adjacent arms to be opposite because the change in the magnetic resistance of the TMR sensor itself is derived from the relative orientations of the free layer and the pinned layer. However, the TMR units prepared at one time on the same chip usually have the same whole process, so the magnetization directions of the pinned layers of each TMR unit on the same chip are the same, and it is difficult to form a full-bridge structure on a single chip at one time. Current approaches to achieving single-chip on-bridge are laser annealing and fractional deposition. Laser annealing is a method of pinning magnetization directions of pinned layers of different regions in opposite directions using a laser annealing apparatus, but since the laser annealing apparatus is expensive, the production cost is high. The fractional deposition is to deposit pinning layers with different magnetization directions twice and then grow, but when the fractional deposition is carried out twice, the first layer is easily affected when the second layer grows, and the performance of the device is finally affected.
Disclosure of Invention
The invention aims to provide a single-chip TMR full-bridge sensor capable of reducing the difficulty of a preparation process and the production cost and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical solutions:
TMR full bridge magnetic sensor includes: the TMR unit comprises a free layer, a pinning layer and a tunnel layer, wherein 4 groups of TMR units are connected in a bridge manner to form a full-bridge structure, and 4 groups of TMR units are respectively positioned on 4 bridge arms of the full-bridge structure; the length-width ratio of the TMR units is not equal to 1, the long axes of the TMR units on the adjacent bridge arms are perpendicular to each other, and the long axes of the TMR units on the opposite bridge arms are parallel to each other.
Further, the length-width ratio of the TMR unit is more than 10.
Further, the TMR unit is rectangular or elliptical in shape.
Furthermore, the long axis direction of the TMR unit is parallel to the direction of the bridge arm where the TMR unit is located.
Furthermore, the substrate is also provided with 4 electrodes, the 4 electrodes comprise a pair of input electrodes and a pair of output electrodes, and each electrode is respectively connected with two adjacent bridge arms.
Furthermore, the magnetic moment directions of the pinning layers of the TMR units on the adjacent bridge arms are different, and the magnetic moment directions of the pinning layers of the TMR units on the opposite bridge arms are the same.
According to the technical scheme, the TMR units on the full-bridge structure are arranged according to the long axis direction of the TMR units, so that the long axis directions of the TMR units on adjacent bridge arms are mutually vertical and are mutually parallel relative to the long axis direction of the TMR units on the bridge arms, an external magnetic field with a specific angle is applied during magnetic field annealing, the full-bridge structure is formed on a single chip at one time, and the difficulty and the production cost of the preparation process of the single-chip full-bridge magnetic sensor are greatly reduced. In the full-bridge magnetic sensor obtained after annealing, the magnetic moments of the TMR unit pinning layers on adjacent bridge arms are different in direction, and the magnetic moments of the TMR unit pinning layers on opposite bridge arms are basically the same in direction, so that the TMR units on the adjacent bridge arms have opposite response to the same sensitive direction, form opposite corresponding trends of magnetic resistance to an applied field, and realize differential output of magnetic field detection.
The invention also provides a preparation method of the TMR full-bridge magnetic sensor, which comprises the following steps:
providing a substrate;
depositing TMR units and electrodes on the substrate, wherein 4 groups of TMR units are connected in a bridge manner to form a full-bridge structure, each bridge arm of the full-bridge structure is provided with one group of TMR units, long axes of the TMR units on adjacent bridge arms are mutually vertical, and long axes of the TMR units on opposite bridge arms are mutually parallel;
and carrying out magnetic field annealing treatment on the TMR unit, wherein an included angle of 45 degrees is formed between the direction of the applied magnetic field and the long axis direction of the TMR unit during annealing, after annealing is finished, the magnetic moment directions of the pinning layers of the TMR units on adjacent bridge arms are different, and the magnetic moment directions of the pinning layers of the TMR units on opposite bridge arms are the same.
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.
FIG. 1 is a schematic diagram of a TMR cell in a TMR type magnetoresistive sensor;
FIG. 2 is a schematic illustration of the magnetic moment direction of the pinned layer of the free layer of a TMR cell;
FIG. 3 is a diagram showing the relationship between the variation of the magnetic moment directions of the resistance, free layer and pinned layer of the TMR unit and the applied magnetic field;
FIG. 4 is a schematic diagram showing the relative relationship of the magnetic moment directions of the free layer and the pinned layer;
FIG. 5a is a schematic diagram showing the variation of the magnetic moment directions of the free layer under the action of an applied magnetic field when the magnetic moment directions of the free layer and the pinned layer are parallel to each other;
FIG. 5b is a graph showing the relationship between the resistance and the applied magnetic field strength of a TMR unit in which the magnetic moment directions of the free layer and the pinned layer are parallel to each other under the application of an applied magnetic field;
FIG. 6a is a schematic diagram showing the change in the magnetic moment direction of the free layer under the action of an applied magnetic field when the magnetic moment directions of the free layer and the pinned layer are antiparallel;
FIG. 6b is a graph of resistance versus applied magnetic field strength for a TMR cell having antiparallel magnetic moment directions of the free and pinned layers under the application of an applied magnetic field;
FIG. 7 is a schematic structural diagram of an embodiment of the present invention;
FIG. 8 is a schematic diagram showing the magnetization direction of the pinned layer of a TMR cell of example 4 of the present invention after annealing;
FIG. 9 is a diagram of a Wheatstone full bridge circuit according to an embodiment of the invention;
FIG. 10 is a graph showing the trend of the magnetoresistance of two adjacent TMR units under the action of an external magnetic field applied in the y-axis direction;
FIG. 11 is a graph showing the variation trend of the output voltage under the action of the external magnetic field applied along the y-axis direction according to the embodiment of the present invention.
Detailed Description
In order to make the aforementioned and other objects, features and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic diagram showing a structure of a TMR element in a TMR type sensor, as shown in fig. 1, the TMR element includes a free layer, a
As shown in fig. 3 (R in fig. 3 denotes the resistance value of the TMR cell, and H denotes the field strength of the applied magnetic field), the resistance value of the TMR cell is related to the relative magnetization state of
Under the action of the applied
Fig. 7 is a schematic structural diagram of a TMR full bridge sensor according to an embodiment of the present invention, as shown in fig. 7, 4 sets of TMR cells (a1, a2, a3, a4) and 4 electrodes (P1, P2, P3, P4) are deposited on a substrate (not shown) of the sensor, each set of TMR cells has the same structure, and has a free layer, a pinned layer and a tunnel layer. The 4 groups of TMR units are connected in a bridge mode to form a full-bridge structure, the 4 groups of TMR units are respectively positioned on 4 bridge arms of the full-bridge structure, and each electrode is respectively connected with two adjacent bridge arms. Of the 4 electrodes, one pair of electrodes (P1, P3) is an input electrode, and the other pair of electrodes (P2, P4) is an output electrode. The length and width of the TMR unit of the invention are not equal, namely the length-width ratio of the TMR unit is not equal to 1, and the shape of the TMR unit can be rectangle or ellipse. For convenience of explanation, a center line of the TMR element in the length direction is defined as a long axis, and the long axis direction of the TMR element is parallel to the direction of the arm on which it is located. To ensure a large shape anisotropy field inside the TMR cell, the aspect ratio of the TMR cell should be large so that the shape anisotropy field in the free layer is larger than the influence of the external magnetic field. If the TMR cell has a small aspect ratio, resulting in a small internal shape anisotropy field that is not sufficiently balanced with the applied annealing field, the pinned layer will have a magnetic moment oriented along the applied field after annealing, and no bridging will occur. Preferably, the TMR cell may have an aspect ratio greater than 10. The specific value of the length-width ratio of the TMR unit is an empirical value and is also related to the formula of the free layer, so that the length-width ratio can be set according to different conditions.
The TMR units on the 4 bridge arms are opposite in pairs, wherein the long axes of the adjacent TMR units are vertical to each other, and the long axes of the opposite TMR units are parallel to each other. The direction of the anisotropic field inside the TMR cell is along the long axis direction of the TMR cell, and the direction of the shape anisotropic field inside the TMR cell is different because the long axis direction of the TMR cell is different. The TMR unit in the full bridge structure is arranged according to the long axis direction, when annealing, by applying an external magnetic field with a specific angle (the direction of the external magnetic field is along the diagonal direction of the TMR full bridge structure, namely, the included angle with the long axis direction of the TMR unit is 45 degrees), the internal magnetic moment of the TMR unit is subjected to the combined action of the external magnetic field and the internal shape anisotropy field, the magnetization direction of the pinning layer can be changed according to the arrangement direction (long axis direction) of the TMR unit, and therefore the pinning layer of each TMR unit can correspondingly form different magnetic moment directions.
The preparation method of the TMR full-bridge sensor comprises the following steps:
providing a substrate;
depositing 4 sets of TMR units and electrodes on the substrate, for example, forming TMR units on the substrate by magnetron sputtering, wherein the 4 sets of TMR units are connected in a bridge manner to form a full-bridge structure and are connected to the input and output electrodes, and the TMR units are located on the bridge arms of the full-bridge structure, wherein the long axes of the TMR units on adjacent bridge arms are perpendicular to each other and parallel to each other relative to the long axes of the TMR units on the bridge arms, as shown in fig. 7; defining two diagonal lines in the full-bridge structure as an x-axis and a y-axis respectively, namely, the direction from P3 to P1 is the y-axis, the direction from P4 to P2 is the x-axis, x1 is the direction forming an angle of 45 degrees with the x-axis, y1 is the direction forming an angle of 45 degrees with the y-axis, when the TMR unit is deposited, the long axis direction of the TMR units a1 and a3 and the x-axis1The axes are parallel, the long axis directions of the TMR units a2 and a4 are parallel to y1The axes are parallel;
the TMR cell is subjected to magnetic field annealing treatment, as shown in fig. 8, an applied
Taking this embodiment as an example, when an external magnetic field is applied to the sensor along the y-axis direction, the resistance changes of different TMR units are different, because the magnetization direction of the pinned layer of the adjacent TMR unit along the y-axis is opposite, and the magnetization direction of the pinned layer of the opposite TMR unit along the y-axis is the same, so the adjacent TMR unit has opposite magnetic resistance change trends in the y-axis direction, and the adjacent TMR unit has opposite responses to the same sensitive direction, forming a full-bridge output. The method can deposit the full-bridge structure on the same chip at one time, thereby greatly reducing the difficulty and the cost of the production process.
The full-bridge circuit of the present invention is shown in fig. 9, wherein R1, R2, R3 and R4 in fig. 9 respectively represent the magneto resistances of four groups of TMR cells a1, a2, a3 and a4, and when a constant bias is applied to both ends (P1 and P3) of the full-bridge structure, the voltage output of the full-bridge circuit is
Fig. 10 is a graph showing the trend of the magnetoresistance of the TMR cells a1, a2 in the sensor with respect to the applied magnetic field along the y-axis, a constant voltage is applied to the input electrodes (P1, P2) of the full-bridge sensor, and when the magnetic field along the y-axis changes, the trend of the output voltage of the sensor output electrodes (P2, P4) is as shown in fig. 11.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
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