TWI851345B - Three-axis magnetic field sensor - Google Patents

Abstract

A three-axis magnetic field sensor includes a semiconductor substrate, a first transistor sensing unit with a rectangular structure extending along a first direction, a second transistor sensing unit with a rectangular structure extending along a second direction orthogonal to the first direction, at least one third transistor sensing unit with a fan-shaped structure, a plurality of isolation units surrounding the first, second and third transistor sensing units, and a plurality of grooves located outside the isolation units. The first and second transistor sensing units are used to measure the magnetic field change of a planar magnetic field, the at least one third transistor sensing unit is used to measure the magnetic field change of a perpendicular magnetic field, and the fan-shaped structure is used to limit the moving direction of carriers in the magnetic field to improve the sensing sensitivity.

Description

Three-axis magnetic field sensor

The present invention relates to a sensing element, in particular to a three-axis magnetic field sensor.

Magnetic field sensors are widely used in various electronic devices to monitor magnetic field changes and convert the monitoring results into electrical signals for external output. For example, the Hall effect sensor is mainly used to measure the carrier displacement caused by the Lorentz force generated by the Hall effect, so as to measure the change of the magnetic field. In addition to measuring the change of the magnetic field intensity, it can also sense the change of the magnetic field direction.

However, existing Hall effect sensors are usually used to measure the magnetic field changes in a single axis (such as the X-axis or Y-axis) of a planar magnetic field to avoid the sensing results being affected by the interference of magnetic fields in different axes (such as inter-axial coupling). With the complexity and refinement of the structure of existing electronic devices, the requirements for the sensing sensitivity and miniaturization of magnetic field sensors are also higher. Therefore, how to develop a multi-axis magnetic field sensor with good sensitivity is one of the key points in related fields.

Therefore, the purpose of the present invention is to provide a three-axis magnetic field sensor.

Therefore, the three-axis magnetic field sensor of the present invention includes a semiconductor substrate, a first transistor sensing unit, a second transistor sensing unit, at least a third transistor sensing unit, a plurality of isolation units, and a plurality of grooves.

The semiconductor substrate has a first conductivity type doping.

The first transistor sensing unit is disposed on the semiconductor substrate and extends along a first direction to form a rectangular structure, and is used to measure the magnetic field change in a second direction orthogonal to the first direction.

The second transistor sensing unit is disposed on the semiconductor substrate and extends along the second direction to form a rectangular structure for measuring the magnetic field change in the first direction.

The at least one third transistor sensing unit is disposed on the semiconductor substrate and has a fan-shaped structure, and is used to measure a magnetic field change in a third direction orthogonal to the first direction and the second direction. The fan-shaped structure has a top angle and an arc-shaped area relative to the top angle. Each third transistor sensing unit includes an emitter at the top angle, two collectors located at opposite sides of the arc-shaped area and away from the emitter, two bases located at a side of the collectors opposite to the emitter, and a gate between the emitter and the collectors.

The isolation units are formed downward from the surface of the semiconductor substrate, and the isolation units have isolation grooves respectively surrounding the first transistor sensing unit, the second transistor sensing unit and the at least one third transistor sensing unit, and oxides filled in the isolation grooves.

The grooves are formed downward from the surface of the semiconductor substrate and are located outside the isolation units.

The effect of the present invention is that the fan-shaped structure design of the third transistor sensing units can effectively limit the migration path of the carrier under the action of the magnetic field, so as to improve the sensing sensitivity of the third transistor sensing units. In addition, the first transistor sensing unit, the second transistor sensing unit and the at least one third transistor sensing unit, which are used to measure the magnetic field changes of the plane magnetic field and the vertical magnetic field, are integrated into one, which is conducive to the lightweight and miniaturization of the three-axis magnetic field sensor.

200: Planar magnetic field sensing module

300: Vertical magnetic field sensing module

2: Semiconductor substrate

3: First transistor sensing unit

31, 41: Base

32, 42: Jiji

33, 43: Shooting

34, 44: Isolation area

341, 441: concave part

342, 442: oxides

4: Second transistor sensing unit

5: The third transistor sensing unit

51: Shooting

52: Jiji

521: Sensing end

53: Base

54: Gate

55: Episode 2 Extreme

6: Isolation unit

61: Isolation groove

62: Oxide

7: Groove

8: Electrode unit

81:Connection pad

82: Extension electrode

9: Covering unit

91: Oxide layer

92: Connecting hole

93: Passivation layer

T: Temperature sensor

X: First direction

Y: Second direction

Z: Third direction

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a top view schematic diagram illustrating an embodiment of the three-axis magnetic field sensor of the present invention; FIG. 2 is a cross-sectional schematic diagram illustrating the cross-sectional structure of the first transistor sensing unit of the three-axis magnetic field sensor along the II-II cut line of FIG. 1; FIG. 3 is a cross-sectional schematic diagram illustrating the cross-sectional structure of the second transistor sensing unit of the three-axis magnetic field sensor along the III-III cut line of FIG. 1; FIG. 4 is a cross-sectional schematic diagram illustrating the cross-sectional structure of the third transistor sensing unit of the three-axis magnetic field sensor along the IV-IV cut line of FIG. 1; and FIG. 5 is a cross-sectional schematic diagram illustrating the cross-sectional structure of the third transistor sensing unit of the three-axis magnetic field sensor along the V-V cut line of FIG. 1.

The relevant technical content, features and effects of the present invention will be clearly presented in the following detailed description of the embodiments with reference to the drawings. In addition, it should be noted that the drawings of the present invention only represent the relative relationship between the structure and/or position of the components and are not related to the actual size of each component.

Referring to FIG. 1 , FIG. 2 and FIG. 3 , an embodiment of the three-axis magnetic field sensor of the present invention comprises a semiconductor substrate 2, a planar magnetic field sensing module 200 disposed on the semiconductor substrate 2, a vertical magnetic field sensing module 300 disposed on the semiconductor substrate 2, a plurality of isolation units 6, a plurality of grooves 7, a temperature sensor T, an electrode unit 8, and a covering unit 9. Among them, FIG1 does not depict the electrode unit 8 and the covering unit 9 formed on the top surface of the semiconductor substrate 2, so as to show the relative positions of the planar magnetic field sensing module 200, the vertical magnetic field sensing module 300, the isolation units 6, the grooves 7, and the temperature sensor T in the top view structure. FIG2 and FIG3 are cross-sectional structures along the II-II and III-III cutting plane lines of FIG1, respectively, and show the electrode unit 8 and the covering unit 9.

The semiconductor substrate 2 is made of a semiconductor material selected from elemental semiconductors (e.g., silicon), III-V semiconductors (e.g., gallium arsenide), or IV-IV semiconductors (e.g., silicon carbide), and has a first conductivity type doping.

The planar magnetic field sensing module 200 includes a first transistor sensing unit 3 for measuring magnetic field changes in a second direction Y, and a second transistor sensing unit 4 for measuring magnetic field changes in a first direction X orthogonal to the second direction Y. In this embodiment, the first transistor sensing unit 3 and the second transistor sensing unit 4 are bipolar junction transistors (BJT), and the first direction X and the second direction Y are respectively the X-axis direction and the Y-axis direction along the plane direction of the surface of the semiconductor substrate 2 as an example for explanation.

The first transistor sensing unit 3 is disposed on the semiconductor substrate 2 as shown in FIG. 2 and extends along the first direction X to form a rectangular structure, including a base 31 arranged at intervals along the first direction X, two collectors 32 respectively located on opposite sides of the base 31, two isolation regions 34 respectively located on the side of each collector 32 opposite to the base 31, and two emitters 33 respectively located on the side of the isolation regions 34 opposite to the collector 32.

The base 31 is a first conductivity type doped region formed downward from the surface of the semiconductor substrate 2, and its doping concentration is higher than the doping concentration of the semiconductor substrate 2. The collectors 32 and the emitters 33 are second conductivity type doped regions formed downward from the surface of the semiconductor substrate 2. The isolation regions 34 are disposed between the collectors 32 and the emitters 33, and each isolation region 34 is composed of a recess 341 formed downward from the surface of the semiconductor substrate 2 and an oxide 342 filled in the recess 341, so as to limit the migration path of multiple carriers in the semiconductor substrate 2, and prevent the carriers from directly moving along the surface of the semiconductor substrate 2, thereby generating leakage current. In this embodiment, the first conductivity type doping is P-type doping, the second conductivity type doping is N-type doping, and the oxide 342 is selected from silicon dioxide (SiO ₂ ) as an example, but the actual implementation is not limited thereto.

When the first transistor sensing unit 3 is placed in a planar magnetic field and a bias voltage is applied for detection, an induced current is generated inside the semiconductor substrate 2, causing multiple carriers to move from the emitters 33 toward the collectors 32. Under the action of the planar magnetic field, the carriers will be offset based on the Lorentz force generated by the Hall effect, causing the carrier concentrations received by the collectors 32 to differ, and different current signals are obtained respectively. The magnetic field change of the planar magnetic field along the second direction Y (i.e., the Y-axis direction) can be obtained based on the two current signals.

The second transistor sensing unit 4 is disposed on the semiconductor substrate 2 as shown in FIG. 3 and has a similar structure to the first transistor sensing unit 3. The difference between the second transistor sensing unit 4 and the first transistor sensing unit 3 is that the second transistor sensing unit 4 is extended into a rectangular structure along the second direction Y, and the base 41, collector 42, isolation region 44, and emitter 43 of the second transistor sensing unit 4 are arranged at intervals along the second direction Y. Therefore, the second transistor sensing unit 4 is placed in a planar magnetic field and a bias voltage is applied for detection, and the magnetic field change in the planar magnetic field in the first direction X (i.e., the X-axis direction) can be evaluated based on the current signals measured by the two collectors 42.

Referring to Figures 1, 4 and 5, the spacing distance between the vertical magnetic field sensing module 300 and the planar magnetic field sensing module 200 is not less than 200μm to avoid interference between them and affect the detection results. In this embodiment, the vertical magnetic field sensing module 300 includes a plurality of third transistor sensing units 5, and the third transistor sensing units 5 are illustrated as a bipolar junction transistor. The third transistor sensing units 5 are used to measure the magnetic field change in a third direction Z that is orthogonal to the first direction X and the second direction Y, and the third direction Z is a Z-axis direction perpendicular to the surface of the semiconductor substrate 2.

The third transistor sensing units 5 are disposed on the semiconductor substrate 2 and are in a fan-shaped structure. The fan-shaped structure has a top angle and an arc-shaped area relative to the top angle, and the top angle is between 30 degrees and 150 degrees.

Each third transistor sensing unit 5 includes an emitter 51 located at the top corner, two collectors 52 located at opposite sides of the arc-shaped region and away from the emitter 51, two bases 53 located at one side of the collectors 52 opposite to the emitter 51, a gate 54 between the emitter 51 and the collectors 52, and two second collectors 55 located at one side of the bases 53 opposite to the gates 54.

The gate 54 is disposed on the surface of the semiconductor substrate 2 , and a migration path range of a plurality of carriers moving from the emitter 51 to the collectors 52 is located within the projection range of the gate 54 . In this embodiment, the gate 54 is made of polysilicon material, the base 53 is a first conductive type doping region formed downward from the surface of the semiconductor substrate 2, and its doping concentration is higher than the doping concentration of the semiconductor substrate 2, the collectors 52 and the emitters 51 are second conductive type doping regions formed downward from the surface of the semiconductor substrate 2, and the first conductive type doping is P-type doping, and the second conductive type doping is N-type doping.

Preferably, the third transistor sensing units 5 are symmetrically distributed, so when the third transistor sensing units 5 are affected by other planar magnetic fields, the symmetrically arranged third transistor sensing units 5 can cooperate to offset the interference from the planar magnetic field, thereby reducing the cross sensitivity of the vertical magnetic field sensing module 300 and improving its accuracy in sensing the magnetic field changes of the vertical magnetic field.

In this embodiment, the vertical magnetic field sensing module 300 has four third transistor sensing units 5 arranged symmetrically in a cross shape, and the third transistor sensing units 5 are opposite to each other in the fan-shaped structure. The cross sensitivity of the vertical magnetic field sensing module 300 can be effectively reduced. In addition, the third transistor sensing units 5 are connected to each other in a parallel electrical connection to enhance the current signal measured from the collectors 52, thereby improving the sensing sensitivity of the vertical magnetic field sensing module 300.

When the third transistor sensing units 5 are placed in a vertical magnetic field for detection, an induced current is generated inside the semiconductor substrate 2 under the action of the vertical magnetic field, causing multiple carriers to move from the emitter 51 located at the top corner toward the collectors 52, and the carriers will be offset due to the Hall effect during the migration process, so the carrier concentrations received by the collectors 52 located on the two opposite sides of the arc-shaped area will be different, thereby obtaining different current signals. According to the current signals, the magnetic field change of the vertical magnetic field in the third direction Z (i.e., the Z-axis direction) can be evaluated. The fan-shaped structure is designed to limit the migration path of the carriers, which is beneficial for the carriers to move more concentratedly toward the collectors 52, thereby improving the sensing sensitivity of the third transistor sensing units 5.

It should be noted that, as shown in FIG. 1 , in this embodiment, the collector 52 of each third transistor sensing unit 5 is an L-shaped structure and has sensing ends 521 extending along the first direction X and the second direction Y, respectively, which can be beneficial for sensing carriers with different migration paths. However, in actual implementation, the shape and location of the collectors 52 can be varied, as long as they are disposed on opposite sides of the corresponding arc-shaped area, and can sense the difference in carrier concentration on both sides of the arc-shaped area, and the invention is not limited thereto.

In some embodiments, the third transistor sensing units 5 may not be provided with the second collectors 55 according to the device design requirements.

In other embodiments, the number and location of the third transistor sensing units 5, and the relative position relationship between the planar magnetic field sensing module 200 and the vertical magnetic field sensing module 300 may vary according to the component design requirements, as long as the spacing distance between the third transistor sensing units 5 and the first transistor sensing unit 3 and the second transistor sensing unit 4 is not less than 200μm, and the extending directions of the rectangular structures of the first transistor sensing unit 3 and the second transistor sensing unit 4 are perpendicular to each other. It is not limited to the examples in the figure. For example, the vertical magnetic field sensing module 300 may also have only a single third transistor sensing unit 5, or have two symmetrically distributed third transistor sensing units 5 that are opposite to each other at the top angle.

In other embodiments, the first transistor sensing unit 3, the second transistor sensing unit 4 and the third transistor sensing units 5 may also be field-effect transistors (FETs), then the emitters 33, 43, 51 serve as sources, the collectors 32, 42, 52 serve as drains, the bases 31, 41, 53 serve as bodies, and the first transistor sensing unit 3 and the second transistor sensing unit 4 each have two gates (not shown) disposed on the surface of the semiconductor substrate 2 and disposed between the sources and the drains.

Referring to Figures 1 to 5 again, the isolation units 6 are shallow trench isolation (STI) structures, which are used to reduce the leakage current of the first transistor sensing unit 3, the second transistor sensing unit 4, and the third transistor sensing units 5 during the detection process. The isolation units 6 have a plurality of isolation grooves 61 formed downward from the surface of the semiconductor substrate 2 and respectively surrounding the first transistor sensing unit 3, the second transistor sensing unit 4, and the third transistor sensing unit 5, and oxides 62 filled in the isolation grooves 61, and the oxides 62 are selected from silicon dioxide.

The grooves 7 are formed downward from the surface of the semiconductor substrate 2 and are located outside the isolation units 6. In addition to further reducing the possibility of leakage current generated by the first transistor sensing unit 3, the second transistor sensing unit 4 and the third transistor sensing unit 5, it is also beneficial to the overall weight reduction of the device.

The temperature sensor T is disposed on the semiconductor substrate 2. Since the migration rate of the carriers is affected by the temperature of the semiconductor substrate 2 itself, which in turn affects the current signals measured by the collectors 32, 42, and 52, the temperature sensor T is used to measure the temperature signal of the semiconductor substrate 2 during the test, so as to serve as a basis for the correction of the test results.

The electrode unit 8 is made of conductive material and has a plurality of connection pads 81 which are respectively arranged on the emitters 33, 43, 51, the collectors 32, 42, 52 and the bases 31, 41, 53 of the first transistor sensing unit 3, the second transistor sensing unit 4 and the third transistor sensing unit 5 and form ohmic contact for external electrical connection.

The covering unit 9 covers the electrode unit 8, the first transistor sensing unit 3, the second transistor sensing unit 4, and the third transistor sensing units 5, and has an oxide layer 91 coated on the surface of the semiconductor substrate 2, a plurality of through holes 92 formed inside the oxide layer 91 and extending to the connection pads 81, and a passivation layer 93 formed on the surface of the oxide layer 91. The electrode unit 8 also has a plurality of extended electrodes 82 filled in the through holes 92 and electrically connected to the connection pads 81. The extended electrodes 82 are externally connected through the through holes 92 or extend to the surface of the oxide layer 91 to be electrically connected to the outside.

In this embodiment, the oxide layer 91 is made of silicon dioxide, covering the first transistor sensing unit 3, the second transistor sensing unit 4, the third transistor sensing units 5, and the electrode unit 8. The passivation layer 93 is made of silicon nitride material, and the grooves 7 are formed from the surface of the passivation layer 93 downward to the inside of the semiconductor substrate 2.

In summary, the three-axis magnetic field sensor of the present invention utilizes the fan-shaped structure design of the third transistor sensing units 5 to limit the migration path of the carriers, so as to improve the sensing sensitivity of the third transistor sensing units 5, and the symmetrically distributed third transistor sensing units 5 can reduce the cross sensitivity and improve the accuracy of sensing the magnetic field change of the vertical magnetic field. In addition, by integrating the planar magnetic field sensing module 200 and the vertical magnetic field sensing module 300 into a single sensing element, it is beneficial to the lightweight and miniaturization of the three-axis magnetic field sensor, so the purpose of the present invention can be achieved.

However, the above is only an example of the implementation of the present invention, and it cannot be used to limit the scope of the implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

200: Planar magnetic field sensing module

300: Vertical magnetic field sensing module

2: Semiconductor substrate

3: First transistor sensing unit

31, 41: Base

32, 42: Jiji

33, 43: Shooting

34, 44: Isolation area

4: Second transistor sensing unit

5: The third transistor sensing unit

51: Shooting

52: Jiji

521: Sensing end

53: Base

54: Gate

55: Episode 2 Extreme

6: Isolation unit

7: Groove

T: Temperature sensor

X: First direction

Y: Second direction

Claims (9)

A three-axis magnetic field sensor comprises: a semiconductor substrate having a first conductive type doping; a first transistor sensing unit arranged on the semiconductor substrate and extending along a first direction to form a rectangular structure for measuring a magnetic field change in a second direction orthogonal to the first direction; a second transistor sensing unit arranged on the semiconductor substrate and extending along the second direction to form a rectangular structure for measuring a magnetic field change in the first direction; at least one third transistor sensing unit arranged on the semiconductor substrate and forming a fan-shaped structure for measuring a magnetic field change in a third direction orthogonal to the first direction and the second direction, the fan-shaped structure having a top angle and a bottom angle relative to the top angle. The arc-shaped region of the semiconductor substrate is provided, and the third transistor sensing unit includes an emitter located at the top corner, two collectors located at opposite sides of the arc-shaped region and away from the emitter, two bases located at a side of the collectors opposite to the emitter, and a gate between the emitter and the collectors; a plurality of isolation units are formed downward from the surface of the semiconductor substrate, and the isolation units have isolation grooves respectively surrounding the first transistor sensing unit, the second transistor sensing unit and the at least one third transistor sensing unit, and oxides filled in the isolation grooves; and a plurality of grooves are formed downward from the surface of the semiconductor substrate and located outside the isolation units. The three-axis magnetic field sensor as described in claim 1 comprises a plurality of the third transistor sensing units arranged symmetrically. The three-axis magnetic field sensor as described in claim 2 comprises four third transistor sensing units arranged symmetrically in a cross shape, and the third transistor sensing units are opposite to each other at the top corners of their fan-shaped structures. The three-axis magnetic field sensor as described in claim 1, wherein the first transistor sensing unit includes a base arranged at intervals along the first direction, two collectors located at opposite sides of the base, and two emitters located at each collector on a side opposite to the base, and the second transistor sensing unit includes a base arranged at intervals along the second direction, two collectors located at opposite sides of the base, and two emitters located at each collector on a side opposite to the base. A three-axis magnetic field sensor as described in claim 1, wherein the at least one third transistor sensing unit also has two second collectors respectively located on the side of the bases opposite to the collectors. The three-axis magnetic field sensor as described in claim 4 further comprises an electrode unit made of a conductive material, having a plurality of connection pads respectively disposed on the emitters, collectors and bases of the first transistor sensing unit, the second transistor sensing unit, and the at least one third transistor sensing unit. The three-axis magnetic field sensor as described in claim 6 further comprises a covering unit having an oxide layer coated on the surface of the semiconductor substrate and covering the first transistor sensing unit, the second transistor sensing unit, the at least one third transistor sensing unit and the electrode unit, a plurality of through holes formed in the oxide layer and extending to the connection pads, and a passivation layer formed on the surface of the oxide layer. The electrode unit also has a plurality of extension electrodes electrically connected to the connection pads and extending outward through the through holes. The grooves are formed from the surface of the passivation layer downward to the inside of the semiconductor substrate. The three-axis magnetic field sensor as described in claim 1 also includes a temperature sensor disposed on the semiconductor substrate. A three-axis magnetic field sensor as described in claim 1, wherein the top angle of the fan-shaped structure of the at least one third transistor sensing unit is between 30 degrees and 150 degrees, and the spacing distance between the third transistor sensing unit and the first transistor sensing unit and the second transistor sensing unit is not less than 200 μm.