JP2024068095A - Hall element, Hall sensor, and method for manufacturing Hall element - Google Patents

Abstract

[Problem] To improve the signal-to-noise ratio. [Solution] A Hall element 1 includes a substrate 2, an active layer 32 forming a two-dimensional electron gas film on the substrate, a laminate 3 including first and second buffer layers 31, 33 laminated respectively on the upper and lower sides of the active layer, an insulating film 4 formed on the laminate, and electrodes 6a to 6d connected to the active layer via contact holes 4a to 4d provided in the insulating film, the electrodes including electrodes 6a, 6b facing each other in the X-axis direction and electrodes 6c, 6d facing each other in the Y-axis direction, and the ratio of a shape factor determined by the distance between contact regions 3a, 3b where the two electrodes 6a, 6b connect to the active layer, the width where they face each other, and the extent of the region between them in the Y-axis direction to a shape factor determined by the distance between contact regions 3c, 3d where the two electrodes 6c, 6d connect to the active layer, the width where they face each other, and the extent of the region between them in the X-axis direction is determined according to the difference in mobility in the active layer in the X-axis and Y-axis directions. [Selected Figure] Fig. 6

Description

The present invention relates to a Hall element, a Hall sensor, and a method for manufacturing a Hall element.

As a Hall element, which is a type of magnetic sensor, a two-dimensional electron gas film-UP type Hall element is conceivable, which improves the ratio of the output voltage generated to the driving voltage, i.e., the sensitivity, by adopting an active layer that forms a two-dimensional electron gas film, and reduces noise by providing an electrode (UP) via an insulating film on a laminate including the active layer, thereby improving the S/N ratio. Such an UP type Hall element is disclosed, for example, in Patent Document 1.
Patent Document 1: JP 2018-160631 A

In a first aspect of the present invention, a laminate including a substrate, an active layer forming a two-dimensional electron gas film on the substrate, and a first buffer layer and a second buffer layer laminated on the lower and upper sides of the active layer, respectively, an insulating film formed on the laminate, and four electrodes respectively connected to the active layer via openings provided in the insulating film, the four electrodes including two first electrodes facing each other in a first direction in a two-dimensional plane and two second electrodes facing each other in a second direction intersecting the first direction, and among the openings provided in the insulating film, two first openings connecting the two first electrodes to the active layer are provided. A Hall element is provided in which the ratio (Gin/Gout) of a first shape factor (Gin) determined from the separation distance (Lin), the opposing width (Win) of the two first openings, and the extent of the region between the two first openings in the second direction, to a second shape factor (Gout) determined from the separation distance (Lout) of two second openings connecting the two second electrodes to the active layer, the opposing width (Wout) of the two second openings, and the extent of the region between the two second openings in the first direction, is determined according to the difference in mobility in the first direction and the second direction in the active layer.

In a second aspect of the present invention, a Hall sensor is provided that includes the Hall element of the first aspect and detects the intensity of a magnetic field entering the active layer of the Hall element.

In a third aspect of the present invention, the present invention includes a step of forming a laminate on a substrate, the laminate including an active layer forming a two-dimensional electron gas film, and a first buffer layer and a second buffer layer laminated on the lower side and the upper side of the active layer, respectively; a step of forming an insulating film on the laminate; a step of forming an opening in the insulating film; and a step of forming four electrodes, the four electrodes being respectively connected to the active layer through the openings provided in the insulating film, the four electrodes including two first electrodes facing each other in a first direction in a two-dimensional plane and two second electrodes facing each other in a second direction intersecting the first direction, and the two first electrodes are connected to the active layer through the openings provided in the insulating film. A method for manufacturing a Hall element is provided in which the ratio (Gin/Gout) of a first shape factor (Gin) determined from the distance (Lin) between two connecting first openings, the width (Win) between the two first openings, and the extent of the region between the two first openings in the second direction, to a second shape factor (Gout) determined from the distance (Lout) between two second openings connecting the two second electrodes to the active layer, the width (Wout) between the two second openings, and the extent of the region between the two second openings in the first direction, is determined according to the difference in mobility in the first direction and the second direction in the active layer.

Note that the above summary of the invention does not list all of the features of the present invention. Also, subcombinations of these features may also be inventions.

1 is a perspective view showing an overall configuration of a Hall element according to the present embodiment. 1 shows an exploded perspective view of a Hall element. 2 shows the top configuration of a Hall element as viewed from above. 1D shows the internal configuration of a Hall element on an XZ cross section relative to a reference line DD in FIG. 1C. 1 shows an overall configuration of a Hall sensor including a Hall element according to an embodiment of the present invention, as viewed from above. 2B shows the internal structure of the Hall sensor on a cross section taken along the reference line BB in FIG. 2A. 4 shows a manufacturing flow of the Hall element according to the present embodiment. 4 shows a state of the Hall element in a substrate preparation step in the manufacturing flow of the element. 4 shows a state of the Hall element in a laminate formation step in the manufacturing flow of the element. 4 shows a state of the Hall element during an opening formation step in the manufacturing flow of the element. 4 shows a state of the Hall element in a dielectric film formation step in the manufacturing flow of the element. 4 shows a state of the Hall element during a dielectric film etching step in the manufacturing flow of the element. 4 shows a state of the Hall element during a laminate etching step in the manufacturing flow of the element. 4 shows a state of the Hall element during a protective film formation step in the manufacturing flow of the element. 4 shows a state of the element in a contact hole formation step in the manufacturing flow of the Hall element. 4 shows a state of the Hall element during an electrode formation step in the manufacturing flow of the element. This shows the anisotropy of indium arsenide (InAs) crystals. The state of the upper surface of the active layer, the shape of the pseudo-GC, and its size parameters are shown. 1 shows an example of a change in the form factor ratio. 13 shows another example of a change in the form factor ratio. The simulation and measurement results of the anisotropy of the constant voltage sensitivity with respect to the form factor ratio are shown. 1 shows the pattern of contact holes (contact regions) used in a simulation of the anisotropy of constant voltage sensitivity. The numerical ranges of the parameters used in the simulation are shown below. 4 shows measurement results of sensitivity anisotropy in Hall elements according to an example and a comparative example. 1 shows the results of a simulation of the sensitivity anisotropy of a Hall element.

The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

1A to 1D show the structure of the Hall element 1 according to this embodiment. Here, FIG. 1A shows the overall structure of the Hall element 1 in a perspective view, FIG. 1B shows the exploded structure of the Hall element 1 in a perspective view, FIG. 1C shows the top structure of the Hall element 1 in a top view, and FIG. 1D shows the internal structure of the Hall element 1 on an XZ cross section with respect to a reference line DD (i.e., a reference line connecting the centers of the opposing electrodes 6a and 6b) in FIG. 1C. The Hall element 1 is an element that detects the magnetic field strength in a direction perpendicular to the opposing direction of the electrodes 6a and 6b and the opposing direction of the electrodes 6c and 6d by detecting the Hall electromotive force generated between another opposing electrode, i.e., the electrodes 6c and 6d, when a drive voltage is applied between the opposing electrodes, for example, the electrodes 6a and 6b, to pass a current through the element body.

Here, in the Hall element, by using indium arsenide (InAs) as the material for the active layer, a two-dimensional electron gas film (also called an ultra-high mobility film) with ultra-high mobility can be formed. However, due to its crystal structure, the ultra-high mobility film grows in one axial direction in a two-dimensional plane, and grain boundaries are generated in the axial direction intersecting this, resulting in different mobilities in the two axial directions, which is expected to cause anisotropy in sensitivity and result in noise. The Hall element 1 comprises a substrate 2, a laminate 3, an insulating film 4, and multiple electrodes 6a to 6d.

The substrate 2 is a base material for forming the laminate 3, which is the element body, and may be a semiconductor substrate containing a compound semiconductor such as gallium arsenide (GaAs). The substrate 2 has a square or nearly square shape when viewed from above. The diagonal direction on the substrate 2 where the electrodes 6a and 6b described later are arranged facing each other is defined as the X-axis direction, another diagonal direction on the substrate 2 that intersects with this (orthogonal in this embodiment) and where the electrodes 6c and 6d described later are arranged facing each other is defined as the Y-axis direction, and the thickness direction of the substrate 2 that is orthogonal to these X-axis and Y-axis directions is defined as the Z-axis direction.

The laminate 3 is the element body supported on the substrate 2. The laminate 3 has a square or nearly square shape when viewed from above, and is somewhat smaller than the substrate 2. As described below, by arranging the electrodes 6a to 6d on the laminate 3, the laminate 3 (active layer 32) can be spread over almost the entire upper surface of the substrate 2, thereby mitigating current concentration and achieving low noise. The laminate 3 includes the active layer 32, a first buffer layer 31, and a second buffer layer 33.

The active layer (also called the magnetosensitive surface) 32 is a layer that generates a Hall electromotive force, and is formed to a thickness of 15 nm, including a compound semiconductor such as indium arsenide (InAs). The active layer 32 has a relatively low energy conduction band. On the upper surface of the active layer 32, the regions located inside the contact holes 4a to 4d of the insulating film 4 described later and having the same shape (or similar shape) as these are called the contact regions 3a to 3d. In the contact regions 3a to 3d, the electrodes 6a to 6d are connected to the active layer 32. In addition, by rounding at least one corner of the top view shape of the contact regions 3a to 3d (triangular in this example), it is possible to reduce the concentration of the current flowing between the electrodes 6a to 6d and the active layer 32 in the contact regions 3a to 3d at the end of the region.

The first buffer layer 31 and the second buffer layer 33 are layers for reducing the lattice mismatch between the substrate 2 and the active layer 32, and are formed to thicknesses of 600 nm and 35 nm, respectively, containing a compound semiconductor such as AlGaAsSb having a lattice constant close to InAs. The first buffer layer 31 and the second buffer layer 33 have a relatively high energy conduction band, for example, about 1.3 eV higher than the active layer 32.

On the substrate 2, a first buffer layer 31 and a second buffer layer 33 are stacked respectively above and below the active layer 32 (such a stacked structure 3 is called an ultra-high mobility film), so that the active layer 32 forms a two-dimensional electron gas film in which electrons are not diffused by impurities and have a high mobility of, for example, 20,000 cm ² /Vs or more. Note that openings for forming contact holes 4a to 4d are provided in the second buffer layer 33.

The first buffer layer 31 and the second buffer layer 33 are not limited to being made of the same material, and may be made of different materials. Furthermore, a 150 nm-thick buffer layer containing GaAs may be provided under the first buffer layer 31, and a 10 nm-thick buffer layer containing gallium arsenide antimonide (GaAsSb) may be provided on the second buffer layer 33. In addition, a cap layer containing, for example, GaAs may be provided on the second buffer layer 33 to protect the active layer 32 from damage caused by the manufacturing process.

The insulating film 4 is formed on the stack 3 and is a film for insulating and protecting the active layer 32 from corrosion, and includes one or more types of dielectric material. The insulating film 4 may include at least one of silicon oxide (SiO) and silicon nitride (SiN). It may also include at least one of low dielectric constant films (low-k films), such as fluorosilicate glass (FSG), parylene, carbon-doped SiO (SiOC), fluorohydrocarbon, Teflon (registered trademark), methylsilsesquioxane (MSQ), hydrogensilsesquioxane (HSQ), polyimide, aromatic hydrocarbon polymer (SiLK), polyarylene ether (PAE), fluorinated amorphous carbon, and porous silica.

The insulating film 4 has, as an example, the same shape and size as the stack 3, and contact holes 4a to 4d are formed that penetrate the insulating film 4 in the Z-axis direction near the four corners and reach the upper surface of the active layer 32 through the openings in the second buffer layer 33. As an example, the contact holes 4a to 4d have a right-angled triangular shape when viewed from above, with the apex formed by the two hypotenuses facing the corners of the insulating film 4, the two hypotenuses aligned parallel to the two sides of the insulating film 4, and the base facing the opposing corner of the insulating film 4.

Here, the shape of the contact holes 4a to 4d is not limited to a right-angled triangle when viewed from above, but may be a triangle, quadrant, sector, quarter ellipse, or other shape that is symmetrical with respect to the center line (diagonal of the active layer 32) connecting the opposing contact holes 4a, 4b or 4c, 4d. Here, one side of the pattern, such as the base of the triangle, is arranged toward the opposing opening. As a result, one side of each of the opposing contact holes 4a, 4b forms a rectangular region between them where current is concentrated. The opposing side may be curved or bent outward (toward the corner of the adjacent active layer 32).

In this embodiment, the insulating film 4 includes a dielectric film 41 and a protective film 42. The dielectric film (also called a hard mask) 41 is disposed on the entire upper surface of the stack 3 and partially within the openings of the second buffer layer 32, and the above-mentioned contact holes 4a to 4d are formed. The protective film 42 is formed on the upper surface of the dielectric film 41. The insulating film 4 has a thickness of 135 nm or more, preferably 270 nm or more, and more preferably 540 nm or more. The dielectric film 41 may be formed, for example, using SiO, and the protective film 42 may be formed, for example, using SiN.

The electrodes 6a to 6d include two electrodes facing each other in a uniaxial direction for applying a drive voltage (or drive current) to the active layer 32, and two electrodes facing each other in a direction intersecting the uniaxial direction for detecting a Hall electromotive force (called a Hall output) generated in the active layer 32. In this embodiment, the electrodes 6a and 6b facing each other in the X-axis direction and the electrodes 6c and 6d facing each other in the Y-axis direction are included. In addition, in explaining the function of the Hall element 1, the two electrodes 6a and 6b are considered to be input (in) electrodes, and the two electrodes 6c and 6d are considered to be output (out) electrodes, but the two electrodes 6a and 6b function as output electrodes and the two electrodes 6c and 6d function as input electrodes, and the Hall element 1 can be periodically switched between the input electrodes and the output electrodes to perform a chopping operation such as the spinning current method. The electrodes 6a to 6d are formed using a metal such as gold or titanium, or a conductive material such as polysilicon.

As an example, the multiple electrodes 6a to 6d have a square or approximately square shape when viewed from above, are arranged near the four corners of the insulating film 4, and are electrically connected to the four corners of the active layer 32 via the contact holes 4a to 4d, respectively. When viewed from above, each electrode, for example, electrode 6a, has its -X side corner (-X corner) located between the -X side corner of the insulating film 4 and the apex of the contact hole 4a (or contact region 3a) or on the apex of the contact hole 4a, and the two sides forming the -X corner are arranged in parallel between the two sides of the insulating film 4 and the two oblique sides of the contact hole 4a (or contact region 3a) or overlap with the two oblique sides of the contact hole 4a, and the +X corner facing the -X corner is arranged toward the opposing electrode 6b. As a result, the -X corner of the electrode 6a is positioned directly above the contact hole 4a, the extended portion 6a1 on the +X corner side is extended onto the insulating film 4 from above the contact hole 4a toward the electrode 6b opposite the electrode 6a, and the electrode 6a is further connected to the -X side of the active layer 32 via the contact hole 4a provided in the insulating film 4.

The electrodes 6a to 6d do not have to have the same shape, and may have different shapes for input and output electrodes. Furthermore, the electrodes 6a to 6d do not have to be arranged on the insulating film 4, and may extend outward from the insulating film 4 (i.e., from the contact holes 4a to 4d) onto the substrate 2.

2A and 2B show the configuration of a Hall sensor 10 including a Hall element 1 according to this embodiment. Here, FIG. 2A shows the overall configuration of the Hall sensor 10 from a top view, but with the mold member 19 visible. FIG. 2B shows the internal configuration of the Hall sensor 10 on a cross section taken along reference line BB in FIG. 2A. The Hall sensor 10 includes a Hall element 1, a protective layer 9, lead terminals 12a to 12d, bonding wires 13a to 13d, and a mold member 19. As an example, the Hall sensor 10 of this embodiment has a cubic shape extending in the left-right direction of the drawing.

Hall element 1 is configured as described above. Hall element 1 is placed in the center of the sensor body.

The protective layer 9 is a film provided on the lower surface of the Hall element 1 to protect the element body. The protective layer 9 can be formed using a conductor such as a conductive resin like silver paste, an insulating paste containing epoxy-based thermosetting resin and silicon dioxide (SiO ₂ ), an insulator such as SiN or SiO ₂ , or a semiconductor such as a silicon (Si) substrate, a germanium (Ge) substrate, or a combination of these.

The lead terminals 12a to 12d are interfaces for inputting a drive voltage from an external circuit to the Hall element 1 and outputting the Hall electromotive force from the Hall element 1 to the external circuit. The lead terminals 12a to 12d are formed into a rectangular plate shape using a metal such as copper, and are arranged at the four corners of the sensor body when viewed from above. The lead terminals 12a to 12d each have an exterior plating layer 14a, 14c containing, for example, tin (Sn) on the bottom surface.

The bonding wires 13a to 13d are components that connect the electrodes 6a to 6d of the Hall element 1 to the upper surfaces of the lead terminals 12a to 12d, respectively. The bonding wires 13a to 13d are formed using a conductive material such as gold wire. The Hall element 1 can be electrically connected to an external circuit via the bonding wires 13a to 13d and the lead terminals 12a to 12d.

The molding member 19 is a member that seals and packages the Hall element 1, the lead terminals 12a to 12d, and the bonding wires 13a to 13d. The molding member 19 is made of a resin material that can withstand the high heat during reflow, such as an epoxy-based thermosetting resin, and is molded into a cube shape to cover the upper surface of the Hall element 1, etc.

The Hall sensor 10 detects the Hall electromotive force generated between the electrodes 6a and 6d of the Hall element 1 through the lead terminals 12a and 12b by inputting a driving voltage to the electrodes 6a and 6b of the Hall element 1 through the lead terminals 12c and 12d, and detects the Hall electromotive force generated between the electrodes 6a and 6b of the Hall element 1 through the lead terminals 12a and 12b, thereby detecting the strength of the magnetic field entering the active layer 32 of the Hall element 1. Here, the direction in which the driving voltage is applied (called the driving direction) is periodically switched from electrode 6a to electrode 6b, from electrode 6c to electrode 6d, from electrode 6b to electrode 6a, and from electrode 6d to electrode 6c (so-called chopping operation), thereby modulating the Hall output at a high frequency and filtering out noise or offset components to improve the signal-to-noise ratio.

Figure 3 shows the manufacturing flow for the Hall element 1 according to this embodiment.

In step S1, as shown in FIG. 4A, an individualized substrate 2 is prepared.

In step S2, as shown in FIG. 4B, a stack 3 is formed on the substrate 2. A first buffer layer 31, an active layer 32, and a second buffer layer 33 are stacked in this order on the substrate 2 by epitaxially growing compound semiconductors using metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). The manufacturing conditions, such as the semiconductor materials and film thicknesses, are as described above.

In step S3, as shown in FIG. 4C, openings are formed in the laminate 3. Here, ion milling is used to form openings near the four corners of the laminate 3 in top view, penetrating the second buffer layer 33 and reaching a portion of the active layer 32.

In step S4, as shown in FIG. 4D, a dielectric film (hard mask) 41 is formed on the laminate 3. A film containing one or more dielectrics is formed by plasma chemical vapor deposition (plasma CVD). In the plasma CVD method, a high frequency of, for example, 400 kHz is applied to convert the raw material gas and carrier gas into plasma. The manufacturing conditions of the dielectric film 41, such as the material and film thickness, are as described above. As a result, the dielectric film 41 is formed on the laminate 3, and the film material is filled into the openings of the second buffer layer 33.

In step S5, as shown in FIG. 4E, the dielectric film 41 is etched. Here, a resist mask is formed on the dielectric film 41, and the outer edge of the dielectric film 41 is removed by dry etching when viewed from above.

In step S6, as shown in FIG. 4F, the stack 3 is etched. Here, the dielectric film 41 is used as a hard mask to remove the outer edge of the stack 3 in top view by ion milling, forming a step (mesa) of the stack 3 and the dielectric film 41 on the substrate 2.

In step S7, as shown in FIG. 4G, a protective film 42 is formed on the substrate 2 and the dielectric film 41. A film containing one or more dielectrics is formed by plasma chemical vapor deposition (plasma CVD). In the plasma CVD method, a high frequency of, for example, 400 kHz is applied to convert the raw material gas and carrier gas into plasma. The manufacturing conditions of the protective film 42, such as the material and film thickness, are as described above. As a result, an insulating film 4 including the dielectric film 41 and the protective film 42 is formed on the laminate 3.

In step S8, as shown in FIG. 4H, contact holes 4a to 4d are formed near the four corners of the dielectric film 41 and the protective film 42 (i.e., the insulating film 4), respectively. Here, in top view, a planar pattern having openings of the same size and shape as the contact holes 4a to 4d is provided at each of the four corners of the upper surface of the protective film 42, and the dielectric film 41 and the protective film 42 are dry-etched using this as a mask. As a result, four contact holes 4a to 4d that are triangular in top view and reach the active layer 32 through the openings in the second buffer layer 33 are formed near the four corners of the dielectric film 41 and the protective film 42. At the same time, the outer edge of the protective film 42 is removed.

In step S9, as shown in FIG. 4I, electrodes 6a to 6d are formed near the four corners of the upper surface of the protective film 42. Here, by filling the contact holes 4a to 4d with a conductive material by plating, vapor deposition, sputtering, or the like and forming a pattern on the upper surface of the protective film 42, the electrodes 6a to 6d can be formed, which connect to the active layer 32 via the contact holes 4a to 4d. The electrodes 6a and 6b face each other in the X-axis direction, and the electrodes 6c and 6d face each other in the X-axis direction. The manufacturing conditions of the electrodes 6a to 6d, such as the material, shape, size, etc., are as described above. This completes the manufacture of the Hall element 1.

Figure 5 shows the crystal structure of the active layer 32 formed using InAs. InAs grows epitaxially in a specific direction due to the anisotropy of the crystal structure. Therefore, InAs crystals are unlikely to have grain boundaries in that specific direction (the direction of the white arrow in the figure), and many grain boundaries appear in the perpendicular direction (the direction of the solid black arrow in the figure). Carriers moving through the crystal are scattered at the grain boundaries, so the mobility of the active layer 32 becomes relatively large in the specific direction and relatively small in the perpendicular direction (the perpendicular direction), which causes anisotropy in mobility.

As an example, a Hall element 1 was manufactured by stacking an AlGaAsSb buffer layer (first buffer layer 31) having a thickness of 530 nm, an InAs active layer (active layer 32) having a thickness of 52 nm, an AlGaAsSb buffer layer (second buffer layer 33) having a thickness of 53 nm, and a GaAs cap layer having a thickness of 7 nm on a GaAs substrate (substrate 2) by MBE, and the mobility in the specific direction and the orthogonal direction was measured for each of about 2000 samples of the Hall element 1. The average mobility in the specific direction was 21413.5 cm ² /Vs, while the average mobility in the orthogonal direction was 20860.3 cm ² /Vs, and the anisotropy of the mobility was 2.6%. Thus, in the case of InAs, the anisotropy of the mobility is typically about 2%.

In the Hall element 1 according to this embodiment, for example, the crystal orientation of the active layer 32 is determined so that the specific direction corresponds to the X-axis direction and the perpendicular direction corresponds to the Y-axis direction. If the arrangement and shape of the electrodes 6a to 6d (contact holes 4a to 4d or contact regions 3a to 3d) are designed symmetrically in the X-axis direction and the Y-axis direction, anisotropy occurs between the sensitivity (also called the sensitivity in the in direction) when a drive voltage is input to the input electrodes 6a and 6b and the Hall electromotive force is detected from the output electrodes 6c and 6d, and the sensitivity (called the sensitivity in the out direction) when a drive voltage is input to the output electrodes 6c and 6d and the Hall electromotive force is detected from the input electrodes 6a and 6b. The sensitivity is the ratio of the Hall electromotive force to the drive voltage and is proportional to the mobility of carriers in the active layer 32. This anisotropy of sensitivity can cause noise when processing the Hall output (Hall electromotive force) in a chopping operation.

When the width of the path of the current flowing through the active layer 32 is almost constant in the electrode separation direction, such as when the element body (i.e., the active layer 32) has a Greek cross (GC) shape when viewed from above, the anisotropy of the sensitivity between the in direction and the out direction can be offset or suppressed by adjusting the length and width of the current path, i.e., the separation distance and facing width of the contact regions 3a to 3d (regions inside the contact holes 4a to 4d) where the electrodes 6a to 6d and the active layer 32 come into contact. The separation distance of the contact regions 3a to 3d may be substituted by their center-to-center distance. The facing width is the width of one side of the contact regions 3a, 3b or 3c, 3d (or contact holes 4a, 4b or 4c, 4d) where the opposing electrodes 6a, 6b or 6c, 6d come into contact with the active layer 32, and may be the width in the direction perpendicular to the direction in which the two electrodes 6a, 6b or 6c, 6d face each other.

For example, if the sensitivity in the in direction is greater than the sensitivity in the out direction, the anisotropy in sensitivity can be offset or suppressed by setting the distance between the contact regions 3a, 3b where the two electrodes 6a, 6b in the in direction contact the active layer 32 relatively large (and/or the opposing width small) and the distance between the contact regions 3c, 3d where the two electrodes 6c, 6d in the out direction contact the active layer 32 relatively small (and/or the opposing width large).

In the Hall element 1 according to this embodiment, the active layer 32 has a square or nearly square shape in top view, and the contact areas 3a to 3d that contact the electrodes 6a to 6d are located near the four corners. Therefore, the width of the current path between the electrodes 6a and 6b is not constant along the direction of separation between them, and the current flows out of one of the contact areas 3a and 3b, for example, and spreads in the opposite diagonal direction (the direction in which the contact areas 3c and 3d face each other), and flows into the other electrode while narrowing beyond the center of the active layer 32. Therefore, in order to suppress the anisotropy of sensitivity in the Hall element 1, it is necessary to consider not only the length and width of the current path, i.e., the separation distance and facing width of the contact areas 3a to 3d (the areas inside the contact holes 4a to 4d), but also the spread of the current path.

Figure 6 shows the state of the upper surface of the active layer 32 of the Hall element 1, the pseudo-GC shape, and its size parameters. Note that contact holes 4a-4d are located near the four corners of the active layer 32, and contact regions 3a-3d are located inside them. The sizes of the contact holes 4a-4d and the contact regions 3a-3d do not necessarily need to be equal, and a protective film 42 may be formed in a triangular frame-shaped region located inside the contact holes 4a-4d and outside the contact regions 3a-3d. Here, we consider the shape and arrangement of the contact regions 3a-3d where current flows from the electrodes 6a-6d to the active layer 32 or into the electrodes 6a-6d, but since the thickness of the protective film 42 is usually sufficiently small, it may be considered to be the shape and arrangement of the contact holes 4a-4d.

The shape and arrangement of the contact regions 3a to 3d determine the pseudo-GC shape represented by the dotted line in the figure. Here, the shape factor Gin for the input direction is determined from the separation distance Lin in the X-axis direction of the two contact regions 3a and 3b where the input electrodes 6a and 6b connect to the active layer 32, the width Win of their opposing faces, and the extent of the area between them in the Y-axis direction. Here, the extent of the area between the two contact regions 3a and 3b in the Y-axis direction can be given, for example, by the separation distance Lout between the two contact regions 3c and 3d. Therefore, the current path between the electrodes 6a and 6b is represented by a rectangular pseudo path with a length Lin and a width (Win+Lout)/2. As a result, the shape factor for the input direction is given as Gin=2Lin/(Win+Lout).

On the other hand, the shape factor Gout in the output direction is determined from the separation distance Lout in the Y-axis direction of the two contact areas 3c, 3d where the output electrodes 6c, 6d connect to the active layer 32, the width Wout where they face each other, and the extent of the area between them in the X-axis direction. Here, the extent of the area between the two contact areas 3c, 3d in the X-axis direction can be given by, for example, the separation distance Lin between the two contact areas 3a, 3b. Therefore, the current path between the electrodes 6c, 6d is represented by a rectangular pseudo-path with a length Lout and a width (Wout+Lin)/2. As a result, the shape factor Gout in the output direction is given as Gout=2Lout/(Wout+Lin).

The width of the area between the two contact areas 3a and 3b in the Y-axis direction represents the width of the path of the current flowing in the active layer 32 between the two contact areas 3a and 3b, and therefore may be given by the distance between the contact areas 3a and 3c or 3a and 3d, or the length of one side of the active layer 32, rather than the distance Lout between the two contact areas 3c and 3d. The width of the area between the two contact areas 3c and 3d in the X-axis direction represents the width of the path of the current flowing in the active layer 32 between the two contact areas 3c and 3d, and therefore may be given by the distance between the contact areas 3a and 3c or 3b and 3c, or the length of one side of the active layer 32, rather than the distance Lin between the two contact areas 3a and 3b.

In the Hall element 1 according to this embodiment, the ratio (form factor ratio) Gin/Gout of the form factors Gin and Gout in the input and output directions is determined based on the pseudo GC shape according to the difference in mobility (also called the anisotropy of mobility) in the X-axis direction (in direction) and the Y-axis direction (out direction) in the active layer 32. The form factor ratio Gin/Gout can be adjusted by increasing or decreasing at least one of Lin, Win, Lout, and Wout. This offsets or suppresses the anisotropy of sensitivity between the in direction and the out direction associated with the anisotropy of the mobility of the active layer 32. In particular, when the arrangement of the grain boundaries in the active layer 32 is oriented in the Y-axis direction (out direction) as in the Hall element 1 according to this embodiment, the anisotropy of sensitivity can be suppressed or offset by making the form factor ratio Gin/Gout greater than 1.

Figure 7A shows an example of the change in the fill factor ratio Gin/Gout. As an example, Lin = 150 μm, Win = Wout = 30 μm. By increasing Lout from 120 μm to 180 μm, the fill factor ratio Gin/Gout decreases at a gentler rate from about 1.5 to about 0.7. Note that if Lin is increased instead of Lout, the fill factor ratio Gin/Gout will exhibit reciprocal behavior to that shown in the figure.

Figure 7B shows another example of the change in the form factor ratio Gin/Gout. As an example, Lin = Lout = 150 μm, and Win = 30 μm. By increasing Wout from 24 μm to 36 μm, the form factor ratio Gin/Gout increases approximately linearly from about 0.968 to about 1.032. Note that if Win is increased instead of Wout, the form factor ratio Gin/Gout will exhibit reciprocal behavior to that shown in the figure.

8A and 8B show the simulation and measurement results of the anisotropy of the constant voltage sensitivity with respect to the form factor ratio Gin/Gout, respectively, and the shapes of the contact regions 3a to 3d that were adopted. The anisotropy of the constant voltage sensitivity is defined as the ratio of the Hall output detected from the output electrodes 6c and 6d when a constant driving voltage is applied to the input electrodes 6a and 6b to the Hall output detected from the input electrodes 6a and 6b when a driving voltage of the same strength is applied to the output electrodes 6c and 6d. The shapes of the contact regions 3a to 3d were approximately quadrant (patterns 1 and 2), right triangle (pattern 3), kite shape (pattern 4), and wedge shape (pattern 5). For each of patterns 1 to 5, the values of Lin and Win were fixed as shown in FIG. 8C, and the values of Lout and Wout were changed to give the form factor ratio Gin/Gout, and the anisotropy of the sensitivity was calculated by a simulation based on the finite element method (FreeFEM++ was used in this example). In addition, the sensitivity anisotropy was measured for patterns 1 to 3.

The sensitivity anisotropy was 0.5 to -0.5% in the range of Gin/Gout = 1.010 to 1.020 for pattern 1, Gin/Gout = 1.002 to 1.022 for pattern 2, Gin/Gout = 1.020 to 1.042 for pattern 3, Gin/Gout = 1.016 to 1.036 for pattern 4, and Gin/Gout = 1.020 to 1.040 for pattern 5. The measured values were 0.32 to -0.12% in the range of Gin/Gout = 1.04 to 1.06. There was no discrepancy between the simulation results and the measured values, which shows that the simulation accurately reproduces the sensitivity anisotropy of the Hall element 1.

The allowable range of sensitivity anisotropy can be determined based on the noise level of a typical Hall sensor, for example. The Hall element 1 has a typical sensitivity of 0.8 mV/V/mT, and the sensitivity anisotropy for the Hall output when used at room temperature with a typical magnetic field strength of 30 mT and a drive voltage of 0.5 V is set to a range that is the same level as the noise level of a typical Hall sensor (up to 60 μVrms), i.e., ±0.5%. From the simulation results shown in FIG. 8A, when the arrangement of the crystal grain boundaries in the active layer 32 is oriented in the Y-axis direction (out direction), the sensitivity anisotropy can be kept within the allowable range within the form factor ratio Gin/Gout = 1.002 to 1.042.

Figure 9 shows the measurement results of the sensitivity anisotropy in the Hall element 1 of the embodiment and the Hall element of the comparative example. In the Hall element 1 of the embodiment, pattern 1 was used as the shape of the contact areas 3a to 3d, and the shape factor ratio Gin/Gout was set to 1.015 with Lin = 182.24 μm, Win = 17.5 μm, Lout = 181.04 μm, and Wout = 17.9 μm. The measurement result of the sensitivity anisotropy was 0.1%, which was sufficiently small and within the allowable range. In the Hall element 1 of the comparative example, pattern 2 was used as the shape of the contact areas 3a to 3d, and the shape factor ratio Gin/Gout was set to 1.0 with Lin = 172.67 μm, Win = 7.07 μm, Lout = 172.67 μm, and Wout = 7.07 μm. The measurement result of the sensitivity anisotropy was 1.6%, which was far beyond the allowable range.

Figure 10 shows the results of a simulation of the sensitivity anisotropy of the Hall element 1. For the Hall element 1 used in the simulation, patterns 2, 1, and 3 were used as the shapes of the contact regions 3a to 3d for the three samples, respectively. For sample 1, the fill factor ratio Gin/Gout was set to 1.003 with Lin = 194.2 μm, Win = 7.5 μm, Lout = 194.1 μm, and Wout = 7.9 μm. For sample 2, the fill factor ratio Gin/Gout was set to 1.019 with Lin = 182.2 μm, Win = 17.5 μm, Lout = 180.8 μm, and Wout = 18.3 μm. For sample 3, the fill factor ratio Gin/Gout was set to 1.040 with Lin = 172.7 μm, Win = 29.5 μm, Lout = 169.6 μm, and Wout = 30.7 μm. The simulation results for sensitivity anisotropy were 0.5%, 0.0%, and -0.5% for samples 1 to 3, respectively, all of which were within the allowable range.

These measurement and simulation results show that the sensitivity anisotropy can be kept within an acceptable range when the fill factor ratio Gin/Gout is in the range of 1.002 to 1.042.

The Hall element 1 according to this embodiment comprises a substrate 2, an active layer 32 forming a two-dimensional electron gas film on the substrate 2, a laminate 3 including a first buffer layer 31 and a second buffer layer 33 laminated on the lower and upper sides of the active layer 32, an insulating film 4 formed on the laminate 3, and four electrodes 6a to 6d connected to the active layer 32 via contact holes 4a to 4d provided in the insulating film 4, the four electrodes 6a to 6d including two electrodes 6a, 6b facing each other in the X-axis direction and two electrodes 6c, 6d facing each other in the Y-axis direction, and among the contact holes 4a to 4d provided in the insulating film 4, The ratio (Gin/Gout) of the shape factor (Gin) determined by the distance (Lin) between the contact regions 3a and 3b where the two electrodes 6a and 6b connect to the active layer 32, the width (Win) where they face each other, and the extent of the region between them in the Y-axis direction, to the second shape factor (Gout) determined by the distance (Lout) between the two contact regions 3c and 3d where the two electrodes 6c and 6d connect to the active layer 32, the width (Wout) where they face each other, and the extent of the region between them in the X-axis direction, is determined according to the difference in mobility in the X-axis direction and the Y-axis direction in the active layer 32. By determining the ratio of the first shape factor (Gin) to the second shape factor (Gout) according to the difference in mobility in the X-axis direction and the Y-axis direction in the active layer 32, the anisotropy of the sensitivity between the in direction and the out direction due to the difference in mobility in the active layer 32 can be suppressed or offset, and the generation of noise can be avoided.

The Hall sensor 10 according to this embodiment includes a Hall element 1 and detects the strength of the magnetic field entering its active layer 32 with a high signal-to-noise ratio.

The manufacturing method of the Hall element 1 according to this embodiment includes the steps of forming a laminate 3 on a substrate 1, the laminate 3 including an active layer 32 forming a two-dimensional electron gas film, a first buffer layer 31 and a second buffer layer 33 laminated on the lower and upper sides of the active layer 32, forming an insulating film 4 on the laminate 3, forming contact holes 4a to 4d in the insulating film 4, and forming four electrodes 6a to 6d, each of which is connected to the active layer 32 via the contact holes 4a to 4d provided in the insulating film 4, the four electrodes 6a to 6d including two electrodes 6a, 6b facing each other in the X-axis direction and two electrodes 6c, 6d facing each other in the Y-axis direction. Of the contact holes 4a to 4d provided in the insulating film 4, two electrodes 6a, The ratio (Gin/Gout) of a first shape factor (Gin) determined from the distance (Lin) between the two contact holes 4a, 4b connecting the electrodes 6c, 6d to the active layer 32, the width (Win) at which the two contact holes 4a, 4b face each other, and the extent of the region between the two contact holes 4a, 4b in the Y-axis direction, to a second shape factor (Gout) determined from the distance (Lout) between the two contact holes 4c, 4d connecting the two electrodes 6c, 6d to the active layer 32, the width (Wout) at which the two contact holes 4c, 4d face each other, and the extent of the region between the two contact holes 4c, 4d in the X-axis direction, is determined according to the difference in mobility in the X-axis direction and the Y-axis direction in the active layer 32. By determining the ratio of the first shape factor (Gin) to the second shape factor (Gout) according to the difference in mobility in the X-axis direction and the Y-axis direction in the active layer 32, the anisotropy of the sensitivity between the in direction and the out direction caused by the difference in mobility in the active layer 32 can be suppressed or offset, and the generation of noise can be avoided.

The present invention has been described above using an embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiment. It is clear from the claims that forms with such modifications or improvements can also be included in the technical scope of the present invention.

The order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before" or "prior to," and it should be noted that the processes may be performed in any order, unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is necessary to perform the processes in that order.

1...Hall element, 2...substrate, 3...laminated body, 3a-3d...contact area, 4...insulating film, 4a-4d...contact holes, 6a-6d...electrodes, 6a1...extension, 9...protective layer, 10...Hall sensor, 12a-12d...lead terminals, 13a-13d...bonding wires, 14a, 14c...exterior plating layer, 19...molding member, 31...first buffer layer, 32...active layer, 33...second buffer layer, 41...dielectric film (hard mask), 42...protective film.

Claims (10)

A substrate;
a laminate including an active layer that forms a two-dimensional electron gas film on the substrate, and a first buffer layer and a second buffer layer that are laminated on the lower side and the upper side, respectively, of the active layer;
an insulating film formed on the laminate;
four electrodes each connected to the active layer via an opening provided in the insulating film, the four electrodes including two first electrodes opposed to each other in a first direction in a two-dimensional plane and two second electrodes opposed to each other in a second direction intersecting the first direction;
a ratio (Gin/Gout) of a first shape factor (Gin) determined by a distance (Lin) between two first openings connecting the two first electrodes to the active layer, a width (Win) at which the two first openings face each other, and an extent of a region between the two first openings in the second direction, to a second shape factor (Gout) determined by a distance (Lout) between two second openings connecting the two second electrodes to the active layer, a width (Wout) at which the two second openings face each other, and an extent of a region between the two second openings in the first direction, is determined according to a difference in mobility in the active layer in each of the first direction and the second direction. The Hall element according to claim 1, wherein the extent of the region between the two first openings in the second direction is given by the distance (Lout) between the two second openings, and the extent of the region between the two second openings in the first direction is given by the distance (Lin) between the two first openings. The first shape factor is given by Gin=2Lin/(Win+Lout), and the second shape factor is given by Gout=2Lout/(Wout+Lin),
3. The Hall element according to claim 2, wherein when the alignment of the crystal grain boundaries in the active layer is oriented in the second direction, Gin/Gout=1.002 to 1.042. The Hall element of claim 1, wherein the ratio (Gin/Gout) is greater than 1 when the alignment of the grain boundaries in the active layer is oriented in the second direction. The Hall element according to claim 1, wherein the opening corresponding to at least one of the four electrodes has a shape with one side facing the opposing opening. The Hall element according to claim 5, wherein the corresponding opening has a shape that is symmetrical with respect to a center line connecting the corresponding opening and the opposing opening. The Hall element according to claim 1, wherein at least one of the four electrodes extends on the insulating film from an opening corresponding to the electrode toward another electrode that faces the electrode. The Hall element according to claim 1, wherein the active layer contains InAs, and at least one of the first buffer layer and the second buffer layer contains AlGaAsSb. A Hall sensor comprising the Hall element according to claim 1, which detects the strength of a magnetic field entering the active layer of the Hall element. forming a laminate on a substrate, the laminate including an active layer forming a two-dimensional electron gas film, and a first buffer layer and a second buffer layer laminated on a lower side and an upper side of the active layer, respectively;
forming an insulating film on the stack;
forming an opening in the insulating film;
forming four electrodes each connected to the active layer via an opening provided in the insulating film, the four electrodes including two first electrodes opposed to each other in a first direction in a two-dimensional plane and two second electrodes opposed to each other in a second direction intersecting the first direction;
a ratio (Gin/Gout) of a first shape factor (Gin) determined by a distance (Lin) between two first openings connecting the two first electrodes to the active layer, a width (Win) between the two first openings facing each other, and an extent of a region between the two first openings in the second direction, to a second shape factor (Gout) determined by a distance (Lout) between two second openings connecting the two second electrodes to the active layer, a width (Wout) between the two second openings facing each other, and an extent of a region between the two second openings in the first direction, is determined according to a difference in mobility in the active layer in each of the first and second directions.

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