Patent ID: 12218266

DETAILED DESCRIPTION

Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. In the drawings used in the following description, featured parts may be enlarged parts for convenience so that the features of the present disclosure are easier to understand, and dimensional ratios and the like of the respective components may be different from actual ones. Materials, dimensions, and the like exemplified in the following description are examples, the present disclosure is not limited thereto, and modifications can be appropriately made in a range in which advantageous effects of the present disclosure are exhibited.

Directions will be defined. A lamination direction of a magnetic element10is defined as a z direction, one direction within a plane orthogonal to the z direction is defined as an x direction, and a direction orthogonal to the x direction and the z direction is defined as a y direction. The z direction is an example of the lamination direction. Hereinafter, a +z direction may be expressed as an “upward” direction and a −z direction may be expressed as a “downward” direction. The +z direction is a direction from a second ferromagnetic layer2to a first ferromagnetic layer1. The upward and downward directions do not always coincide with a direction in which gravity is applied.

FIG.1is a cross-sectional view of a photodetection element100according to the first embodiment. The photodetection element100replaces a change in a state of applied light with an electrical signal. A resistance value of the photodetection element100in the z direction changes with the state of the applied light. An output voltage from the photodetection element100changes with the state of the applied light. The light in the present specification is not limited to visible light and also includes infrared light having a wavelength longer than that of the visible light and ultraviolet light having a wavelength shorter than that of the visible light. The wavelength of the visible light is, for example, 380 nm or more and less than 800 nm. The wavelength of the infrared light is, for example, 800 nm or more and 1 mm or less. The wavelength of the ultraviolet light is, for example, 200 nm or more and less than 380 nm.

The photodetection element100includes, for example, the magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer20, an insulating layer30, and a substrate40.

The magnetic element10has, for example, the first ferromagnetic layer1, the second ferromagnetic layer2, a spacer layer3, and a cap layer4. The spacer layer3is located between the first ferromagnetic layer1and the second ferromagnetic layer2. The cap layer4covers an upper surface of the magnetic element10in the lamination direction. The cap layer4is, for example, on the first ferromagnetic layer1. The magnetic element10may have other layers in addition to these.

The magnetic element10is, for example, a magnetic tunnel junction (MTJ) element in which the spacer layer3is made of an insulating material. In this case, in the magnetic element10, a resistance value in the z direction (a resistance value when a current flows in the z direction) changes in accordance with a relative change between a state of magnetization of the first ferromagnetic layer1and a state of magnetization of the second ferromagnetic layer2. Such an element is also called a magnetoresistance effect element.

The first ferromagnetic layer1is a photodetection layer whose magnetization state changes when light is applied thereto from the outside. The first ferromagnetic layer1is also called a magnetization free layer. The magnetization free layer is a layer including a magnet whose magnetization state changes when a prescribed external force has been applied. The prescribed external force is, for example, light which is applied from the outside, a current flowing in the z direction of the magnetic element10, or an external magnetic field. The state of the magnetization of the first ferromagnetic layer1changes with an intensity of light that is applied to the first ferromagnetic layer1.

The first ferromagnetic layer1includes a ferromagnet. The first ferromagnetic layer1includes at least one of magnetic elements such as Co, Fe, and Ni. The first ferromagnetic layer1may include nonmagnetic elements such as B, Mg, Hf, and Gd in addition to the above-described magnetic elements. The first ferromagnetic layer1may be, for example, an alloy including a magnetic element and a nonmagnetic element. The first ferromagnetic layer1may include a plurality of layers. The first ferromagnetic layer1is, for example, a CoFeB alloy, a laminate in which a CoFeB alloy layer is sandwiched between Fe layers, and a laminate in which a CoFeB alloy layer is sandwiched between CoFe layers.

The first ferromagnetic layer1may be an in-plane magnetization film having an axis of easy magnetization in a direction within a film surface (any direction within the xy plane) or may be a perpendicular magnetization film having an axis of easy magnetization in a direction (the z direction) perpendicular to the film surface.

A thickness of the first ferromagnetic layer1is, for example, 1 nm or more and 5 nm or less. The thickness of the first ferromagnetic layer1may be, for example, 1 nm or more and 2 nm or less. If the thickness of the first ferromagnetic layer1is thin when the first ferromagnetic layer1is a perpendicular magnetization film, the effect of applying perpendicular magnetic anisotropy from the layers above and below the first ferromagnetic layer1is strengthened and perpendicular magnetic anisotropy of the first ferromagnetic layer1increases. That is, when the perpendicular magnetic anisotropy of the first ferromagnetic layer1is high, a force for the magnetization M1to return in the z direction is strengthened. On the other hand, when the thickness of the first ferromagnetic layer1is thick, the effect of applying the perpendicular magnetic anisotropy from the layers above and below the first ferromagnetic layer1is relatively weakened and the perpendicular magnetic anisotropy of the first ferromagnetic layer1is weakened.

The volume of a ferromagnet becomes small when the thickness of the first ferromagnetic layer1becomes thin. The volume of a ferromagnet becomes large when the thickness of the first ferromagnetic layer1becomes thick. The susceptibility of the magnetization of the first ferromagnetic layer1when external energy has been applied is inversely proportional to a product (KuV) of the magnetic anisotropy (Ku) and the volume (V) of the first ferromagnetic layer1. That is, when the product of the magnetic anisotropy and the volume of the first ferromagnetic layer1becomes small, the reactivity to light increases. From this point of view, the magnetic anisotropy of the first ferromagnetic layer1may be appropriately designed and then the volume of the first ferromagnetic layer1may be reduced so that the reaction to light increases.

When the thickness of the first ferromagnetic layer1is thicker than 2 nm, an insertion layer made of, for example, Mo and W may be provided within the first ferromagnetic layer1. That is, the first ferromagnetic layer1may be a laminate in which the ferromagnetic layer, the insertion layer, and the ferromagnetic layer are laminated in that order in the z direction. Interfacial magnetic anisotropy at an interface between the insertion layer and the ferromagnetic layer enhances the perpendicular magnetic anisotropy of the entire first ferromagnetic layer1. A thickness of the insertion layer is, for example, 0.1 nm to 0.6 nm.

The second ferromagnetic layer2is a magnetization fixed layer. The magnetization fixed layer is a layer made of a magnet whose magnetization state is less likely to change than that of the magnetization free layer when prescribed external energy has been applied. For example, in the magnetization fixed layer, a direction of magnetization is less likely to change than that in the magnetization free layer when prescribed external energy has been applied. Also, for example, in the magnetization fixed layer, a magnitude of magnetization is less likely to change than that in the magnetization free layer when prescribed external energy is applied. For example, coercivity of the second ferromagnetic layer2is greater than that of the first ferromagnetic layer1. The second ferromagnetic layer2has an axis of easy magnetization in the same direction as the first ferromagnetic layer1. The second ferromagnetic layer2may be either an in-plane magnetization film or a perpendicular magnetization film.

For example, the material constituting the second ferromagnetic layer2is similar to that of the first ferromagnetic layer1. The second ferromagnetic layer2may be, for example, a laminate in which Co having a thickness of 0.4 nm to 1.0 nm, Mo having a thickness of 0.1 nm to 0.5 nm, a CoFeB alloy having a thickness of 0.3 nm to 1.0 nm, and Fe having a thickness of 0.3 nm to 1.0 nm are laminated in that order.

The magnetization of the second ferromagnetic layer2may be fixed by, for example, magnetic coupling to the third ferromagnetic layer via a magnetic coupling layer. In this case, a combination of the second ferromagnetic layer2, the magnetic coupling layer, and the third ferromagnetic layer may be called a magnetization fixed layer.

The third ferromagnetic layer is magnetically coupled to, for example, the second ferromagnetic layer2. The magnetic coupling is, for example, antiferromagnetic coupling and is caused by Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. The material constituting the third ferromagnetic layer is, for example, similar to that of the first ferromagnetic layer1. The magnetic coupling layer is, for example, Ru, Ir, or the like.

The spacer layer3is a nonmagnetic layer arranged between the first ferromagnetic layer1and the second ferromagnetic layer2. The spacer layer3includes a layer made of a conductor, an insulator, or a semiconductor or a layer including a current carrying point formed of a conductor within an insulator. A thickness of the spacer layer3can be adjusted in accordance with orientation directions of the magnetization of the first ferromagnetic layer1and the magnetization of the second ferromagnetic layer2in an initial state to be described below.

For example, when the spacer layer3is made of an insulator, the magnetic element10has a magnetic tunnel junction (MTJ) including the first ferromagnetic layer1, the spacer layer3, and the second ferromagnetic layer2. Such an element is called an MTJ element. In this case, the magnetic element10can exhibit a tunnel magnetoresistance (TMR) effect. For example, when the spacer layer3is made of a metal, the magnetic element10can exhibit a giant magnetoresistance (GMR) effect. Such an element is called a GMR element. The magnetic element10may be called the MTJ element, the GMR element, or the like, which differs according to the constituent material of the spacer layer3, but they may also be collectively called magnetoresistance effect elements.

When the spacer layer3is made of an insulating material, materials including aluminum oxide, magnesium oxide, titanium oxide, silicon oxide, and the like can be used. Also, these insulating materials may include elements such as Al, B, Si, and Mg and magnetic elements such as Co, Fe, and Ni. A high magnetoresistance change rate can be obtained by adjusting the thickness of the spacer layer3so that a strong TMR effect is exhibited between the first ferromagnetic layer1and the second ferromagnetic layer2. In order to use the TMR effect efficiently, the thickness of the spacer layer3may be about 0.5 to 5.0 nm or about 1.0 to 2.5 nm.

When the spacer layer3is made of a nonmagnetic conductive material, a conductive material such as Cu, Ag, Au, or Ru can be used. In order to use the GMR effect efficiently, the thickness of the spacer layer3may be about 0.5 to 5.0 nm or about 2.0 to 3.0 nm.

When the spacer layer3is made of a nonmagnetic semiconductor material, a material such as zinc oxide, indium oxide, tin oxide, germanium oxide, gallium oxide, or indium tin oxide (ITO) can be used. In this case, the thickness of the spacer layer3may be about 1.0 to 4.0 nm.

When a layer including a current carrying point made of a conductor within a nonmagnetic insulator is applied as the spacer layer3, a structure may be formed to include a current carrying point made of a nonmagnetic conductor of Cu, Au, Al, or the like within the nonmagnetic insulator made of aluminum oxide or magnesium oxide. Also, the conductor may be made of a magnetic element such as Co, Fe, or Ni. In this case, the thickness of the spacer layer3may be about 1.0 to 2.5 nm. The current carrying point is, for example, a columnar body having a diameter of 1 nm or more and 5 nm or less when viewed from a direction perpendicular to a film surface.

The cap layer4is between the first ferromagnetic layer1and the first electrode11. The cap layer4prevents damage to the lower layer during the process and enhances the crystallinity of the lower layer during annealing. The thickness of the cap layer4is, for example, 3 nm or less so that sufficient light is applied to the first ferromagnetic layer1. The cap layer4is, for example, MgO, W, Mo, Ru, Ta, Cu, Cr, or a laminated film thereof.

The magnetic element10may also have a base layer, a perpendicular magnetization inducing layer, and the like. The base layer is between the second ferromagnetic layer2and the second electrode12. The base layer is a seed layer or a buffer layer. The seed layer enhances the crystallinity of the layer laminated on the seed layer. The seed layer is, for example, Pt, Ru, Hf, Zr, or NiFeCr. A thickness of the seed layer is, for example, 1 nm or more and 5 nm or less. The buffer layer is a layer that alleviates lattice mismatch between different crystals. The buffer layer is, for example, Ta, Ti, W, Zr, Hf, or a nitride of these elements. A thickness of the buffer layer is, for example, 1 nm or more and 5 nm or less.

A perpendicular magnetization inducing layer is formed when the first ferromagnetic layer1is a perpendicular magnetization film. The perpendicular magnetization inducing layer is laminated on the first ferromagnetic layer1. The perpendicular magnetization inducing layer induces perpendicular magnetic anisotropy of the first ferromagnetic layer1. The perpendicular magnetization inducing layer is, for example, magnesium oxide, W, Ta, Mo, or the like. When the perpendicular magnetization inducing layer is magnesium oxide, magnesium oxide may be oxygen-deficient to increase conductivity. A thickness of the perpendicular magnetization inducing layer is, for example, 0.5 nm or more and 2.0 nm or less.

The first electrode11is in contact with a first surface of the magnetic element10. The first surface is a surface of the magnetic element10on a side of the first ferromagnetic layer1(a first ferromagnetic layer side) in the z direction. The first electrode11has, for example, transparency with respect to a wavelength range of the light applied to the magnetic element10.

The first electrode11includes, for example, an oxide having transparency with respect the wavelength range of the light applied to the magnetic element10. The first electrode11is a transparent electrode including a transparent electrode material of an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO). The first electrode11may be configured to have a plurality of columnar metals in these transparent electrode materials. In this case, a film thickness of the first electrode11is, for example, 10 nm to 300 nm. It is not essential to use the above-described transparent electrode material as the first electrode11and light from the outside may be allowed to reach the first ferromagnetic layer1using a metallic material such as Au, Cu, or Al with a thin film thickness. When a metal is used as the material of the first electrode11, the film thickness of the first electrode11is, for example, 3 to 10 nm. In particular, Au has higher transmittance for light having a wavelength near a blue wavelength of light than other metallic materials. Also, the first electrode11may have an antireflection film on an irradiation surface to which light is applied.

The second electrode12is made of a conductive material. The second electrode12is made of, for example, metals such as Cu, Al, Au, and Ru. Ta and/or Ti may be laminated on the top and bottom of the above metals. Also, a laminated film of Cu and Ta, a laminated film of Ta, Cu, and Ti, and a laminated film of Ta, Cu, and TaN may be used. Also, TiN and/or TaN may be used as the second electrode12. A film thickness of the second electrode12is for example, 200 nm to 800 nm.

The second electrode12may be made transparent to light applied to the magnetic element10. As the material of the second electrode12, as in the first electrode11, for example, a transparent electrode material of an oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium gallium zinc oxide (IGZO) may be used. Even if light is applied from the first electrode11, the light may reach the second electrode12according to the intensity of the light. In this case, the second electrode12is configured to include a transparent electrode material of an oxide, so that the reflection of light at an interface between the second electrode12and a layer in contact with the second electrode12can be limited as compared with the case where the second electrode12is made of a metal.

The first high thermal conductivity layer20is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer20is located, for example, outside of the magnetic element10in the in-plane direction and covers at least a part of a sidewall of the magnetic element10. The first high thermal conductivity layer20is connected to the magnetic element10via, for example, the insulating layer30. The first high thermal conductivity layer20surrounds, for example, the circumference of at least a part of the magnetic element10. For example, the first high thermal conductivity layer20surrounds the circumference of the first ferromagnetic layer1of the magnetic element10. The first high thermal conductivity layer20is in contact with, for example, the first electrode11. When the first high thermal conductivity layer20and the first electrode11come into contact with each other, a heat path from the first high thermal conductivity layer20to the wiring via the first electrode11is formed and heat can be efficiently dissipated from the magnetic element10.

The first high thermal conductivity layer20has higher thermal conductivity than the first electrode11. The first high thermal conductivity layer20has higher thermal conductivity than, for example, the insulating layer30. The thermal conductivity of the first high thermal conductivity layer20is, for example, greater than 40 W/m·K. A part of the heat generated by the magnetic element10is dissipated via the first high thermal conductivity layer20.

The first high thermal conductivity layer20is, for example, a metal. The first high thermal conductivity layer20is, for example, nonmagnetic. If the first high thermal conductivity layer20is nonmagnetic, no leakage magnetic field is generated from the first high thermal conductivity layer20and it is possible to limit deterioration of the magnetic characteristics of the magnetic element10. When the first high thermal conductivity layer20is a nonmagnetic metal, for example, even if the first electrode11is a metal and the first electrode11has a higher thermal conductivity than the first high thermal conductivity layer20, the first high thermal conductivity layer20has high thermal conductivity. Thus, even if the first electrode11has higher thermal conductivity than the first high thermal conductivity layer20, heat can be efficiently dissipated from the magnetic element10. The first high thermal conductivity layer20includes, for example, copper, gold, or silver.

The first high thermal conductivity layer20may be an insulator. When the first high thermal conductivity layer20is made of an insulator, the first high thermal conductivity layer20includes, for example, silicon carbide, aluminum nitride, or boron nitride.

The insulating layer30is located between the magnetic element10and the first high thermal conductivity layer20. The insulating layer30covers, for example, the circumference of the magnetic element10. The insulating layer30is, for example, an oxide of Si, Al, or Mg, a nitride, or an oxynitride. The insulating layer30is, for example, silicon oxide (SiOx), silicon nitride (SiNx), silicon carbide (SiC), chromium nitride, silicon nitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), and zirconium oxide (ZrOx), or the like.

The photodetection element100is manufactured by a laminating process, an annealing process, and a processing process on each layer. First, the second electrode12, the second ferromagnetic layer2, the spacer layer3, the first ferromagnetic layer1, and the cap layer4are laminated on the substrate in that order. Each layer is formed by, for example, sputtering.

Subsequently, the laminated film is annealed. An annealing temperature is, for example, 250° C. to 450° C. When the substrate is a circuit board, the laminated film may be annealed at 400° C. or higher. Subsequently, the laminated film is processed into a prescribed columnar body by photolithography and etching. The columnar body may be a cylindrical body or a prismatic body. For example, the shortest width when the columnar body is viewed from the z direction may be 10 nm or more and 2000 nm or less or 30 nm or more and 500 nm or less.

Subsequently, the insulating layer30is formed to cover the side surface of the columnar body. The insulating layer30may be laminated a plurality of times. Subsequently, the first high thermal conductivity layer20is formed on the insulating layer30. Subsequently, the upper surface of the cap layer4is exposed from the insulating layer30and the first high thermal conductivity layer20by chemical mechanical polishing (CMP) and the first electrode11is manufactured on the cap layer4. In the above-described process, the photodetection element100is obtained.

Next, some examples of the operation of the photodetection element100will be described. Light whose intensity changes is applied to the first ferromagnetic layer1. An output voltage from the photodetection element100changes when light is applied to the first ferromagnetic layer1. In the first operation example, the case where the intensities of the light applied to the first ferromagnetic layer1are two levels of a first intensity and a second intensity will be described. The intensity of light of the second intensity is set to be greater than the intensity of light of the first intensity. The first intensity may correspond to the case where the intensity of light applied to the first ferromagnetic layer1is zero.

FIGS.2and3are diagrams for describing a first operation example of the photodetection element100according to the first embodiment.FIG.2is a diagram for describing a first mechanism of the first operation example andFIG.3is a diagram for describing a second mechanism of the first operation example. In the upper graphs ofFIGS.2and3, the vertical axis represents an intensity of light applied to the first ferromagnetic layer1and the horizontal axis represents time. In the lower graphs ofFIGS.2and3, the vertical axis represents a resistance value of the magnetic element10in the z direction and the horizontal axis represents time.

First, in a state in which light of the first intensity is applied to the first ferromagnetic layer1(hereinafter called an initial state), magnetization M1of the first ferromagnetic layer1is parallel to magnetization M2of the second ferromagnetic layer2and a resistance value of the magnetic element10in the z direction is a first resistance value R1, and a magnitude of an output voltage from the magnetic element10indicates a first value. The resistance value of the magnetic element10in the z direction is obtained by causing a sense current Is to flow through the magnetic element10in the z direction to generate a voltage across both ends of the magnetic element10in the z direction and using Ohm's law from a voltage value. An output voltage from the magnetic element10is generated between the first electrode11and the second electrode12. In the case of the example shown inFIG.2, the sense current Is flows in a direction from the first ferromagnetic layer1to the second ferromagnetic layer2. By causing the sense current Is to flow in the above direction, spin transfer torque in a direction, which is the same as that of the magnetization M2of the second ferromagnetic layer2, acts on the magnetization M1of the first ferromagnetic layer1, and the magnetization M1becomes parallel to the magnetization M2in the initial state. Also, by causing the sense current Is to flow in the above direction, it is possible to prevent the magnetization M1of the first ferromagnetic layer1from being inverted during operation.

Next, the intensity of the light applied to the first ferromagnetic layer1changes from the first intensity to the second intensity. The second intensity is greater than the first intensity and the magnetization M1of the first ferromagnetic layer1changes from the initial state. The state of the magnetization M1of the first ferromagnetic layer1in the state in which no light is applied to the first ferromagnetic layer1is different from the state of the magnetization M1of the first ferromagnetic layer1in the second intensity. The state of the magnetization M1is, for example, a tilt angle with respect to the z direction, a magnitude, or the like.

For example, as shown inFIG.2, when the intensity of the light applied to the first ferromagnetic layer1changes from the first intensity to the second intensity, the magnetization M1is tilted in the z direction. Also, for example, as shown inFIG.3, when the intensity of the light applied to the first ferromagnetic layer1changes from the first intensity to the second intensity, the magnitude of the magnetization M1becomes small. For example, when the magnetization M1of the first ferromagnetic layer1is tilted in the z direction due to an irradiation intensity of light, a tilt angle thereof is larger than 0° and smaller than 90°.

When the magnetization M1of the first ferromagnetic layer1changes from the initial state, the resistance value of the magnetoresistance effect element10in the z direction is a second resistance value R2and a magnitude of the output voltage from the magnetic element10is a second value. The second resistance value R2is larger than the first resistance value R1and the second value of the output voltage is larger than the first value. The second resistance value R2is between the resistance value (the first resistance value R1) when the magnetization M1and the magnetization M2are parallel and the resistance value when the magnetization M1and the magnetization M2are antiparallel.

In the case shown inFIG.2, spin transfer torque in a direction, which is the same as that of the magnetization M2of the second ferromagnetic layer2, acts on the magnetization M1of the first ferromagnetic layer1. Therefore, the magnetization M1tries to return to a state in which the magnetization M1is parallel to the magnetization M2and the magnetic element10returns to the initial state when the intensity of the light applied to the first ferromagnetic layer1changes from the second intensity to the first intensity. In the case shown inFIG.3, when the intensity of the light applied to the first ferromagnetic layer1returns to the first intensity, the magnitude of the magnetization M1of the first ferromagnetic layer1returns to the original magnitude and the magnetic element10returns to the initial state. In either case, the resistance value of the magnetic element10in the z direction returns to the first resistance value R1. That is, when the intensity of the light applied to the first ferromagnetic layer1changes from the second intensity to the first intensity, the resistance value of the photodetection element100in the z direction changes from the second resistance value R2to the first resistance value R1.

The output voltage from the photodetection element100changes in correspondence with a change in the intensity of the light applied to the first ferromagnetic layer1and the change in the intensity of the applied light can be transformed into a change in the output voltage from the photodetection element100. That is, the photodetection element100can replace the light with an electrical signal. For example, the case where the output voltage from the photodetection element100is greater than or equal to a threshold value is treated as a first signal (for example, “1”) and the case where the output voltage is less than the threshold value is treated as a second signal (for example, “0”).

Although the case where the magnetization M1is parallel to the magnetization M2in the initial state has been described as an example here, the magnetization M1may be antiparallel to the magnetization M2in the initial state. In this case, the resistance value of the magnetic element10in the z direction decreases as the state of the magnetization M1changes (for example, as the change in the angle of the magnetization M1increases from the initial state). When the initial state is the case where the magnetization M1is antiparallel to the magnetization M2, the sense current may flow in a direction from the second ferromagnetic layer2to the first ferromagnetic layer1. By causing the sense current to flow in the above direction, spin transfer torque in a direction opposite to that of the magnetization M2of the second ferromagnetic layer2acts on the magnetization M1of the first ferromagnetic layer1and the magnetization M1becomes antiparallel to the magnetization M2in the initial state.

In the first operation example, the case where the light applied to the first ferromagnetic layer1has two levels of the first intensity and the second intensity has been described as an example, but in the second operation example, the case where the intensity of the light applied to the first ferromagnetic layer1changes at multiple levels or in an analog manner will be described.

FIGS.4and5are diagrams for describing a second operation example of the photodetection element100according to the first embodiment.FIG.4is a diagram for describing a first mechanism of the first operation example andFIG.5is a diagram for describing a second mechanism of the first operation example. In the upper graphs ofFIGS.4and5, the vertical axis represents an intensity of light applied to the first ferromagnetic layer1and the horizontal axis represents time. In the lower graphs ofFIGS.4and5, the vertical axis represents a resistance value of the magnetic element10in the z direction and the horizontal axis represents time.

In the case ofFIG.4, when the intensity of the light applied to the first ferromagnetic layer1changes, the magnetization M1of the first ferromagnetic layer1is tilted from the initial state due to external energy generated by the application of the light. An angle between the direction of the magnetization M1of the first ferromagnetic layer1when no light is applied to the first ferromagnetic layer1and the direction of the magnetization M1when light is applied to the first ferromagnetic layer1is greater than 0° and less than 90°.

When the magnetization M1of the first ferromagnetic layer1is tilted from the initial state, the resistance value of the magnetoresistance effect element10in the z direction changes. The output voltage from the magnetic element10changes. For example, the resistance value of the magnetic element10in the z direction changes to a second resistance value R2, a third resistance value R3, and a fourth resistance value R4in accordance with the tilt of the magnetization M1of the first ferromagnetic layer1and the output voltage from the magnetic element10changes to a second value, a third value, and a fourth value. The resistance value increases in the order of the first resistance value R1, the second resistance value R2, the third resistance value R3, and the fourth resistance value R4. The output voltage from the magnetic element10increases in the order of the first value, the second value, the third value, and the fourth value.

In the magnetic element10, when the intensity of the light applied to the first ferromagnetic layer1has changed, the output voltage from the magnetic element10(the resistance value of the magnetic element10in the z direction) changes. For example, when the first value (the first resistance value R1) is defined as “0,” the second value (second resistance value R2) is defined as “1,” the third value (third resistance value R3) is defined as “2,” and the fourth value (fourth resistance value R4) is defined as “3,” the photodetection element100can output information of four values. Although the case where four values are read is shown as an example here, the number of values to be read can be freely designed by setting the threshold value of the output voltage from the magnetic element10(the resistance value of the magnetic element10). Also, the photodetection element100may output an analog value as it is.

Also, as in the case ofFIG.5, when the intensity of the light applied to the first ferromagnetic layer1changes, the magnitude of the magnetization M1of the first ferromagnetic layer1decreases from the initial state due to the external energy generated by the application of the light. When the magnetization M1of the first ferromagnetic layer1decreases from the initial state, the resistance value of the magnetoresistance effect element10in the z direction changes. The output voltage from the magnetic element10changes. For example, the resistance value of the magnetic element10in the z direction changes to the second resistance value R2, the third resistance value R3, and the fourth resistance value R4in accordance with the magnitude of the magnetization M1of the first ferromagnetic layer1. The output voltage from the magnetic element10changes to the second value, the third value, and the fourth value. Therefore, as in the case ofFIG.4, the photodetection element100can output the difference in these output voltages (resistance values) as multi-valued or analog data.

Also, in the case of the second operation example, as in the case of the first operation example, when the intensity of the light applied to the first ferromagnetic layer1returns to the first intensity, the magnetization M1of the first ferromagnetic layer1returns to the original state and the magnetic element10returns to the initial state.

Although the case where the magnetization M1is parallel to the magnetization M2in the initial state has been described as an example here, the magnetization M1may also be antiparallel to the magnetization M2in the initial state in the second operation example.

As described above, the photodetection element100according to the first embodiment can replace the light with an electrical signal by replacing the light applied to the magnetic element10with the output voltage from the magnetic element10. Also, the presence of the first high thermal conductivity layer20having high thermal conductivity on the outside of the magnetic element10that generates heat with the application of light can promote heat dissipation from the magnetic element10. That is, when the application of light to the first ferromagnetic layer1is stopped, the magnetic element10is quickly cooled and the magnetization M1is quickly restored to the initial state. When the magnetization M1of the first ferromagnetic layer1returns to the initial state quickly, the response characteristics of the photodetection element100to light are improved. In other words, the speed of the response characteristic of the photodetection element100to light is increased.

Although the first embodiment has been described above in detail with reference to the drawings, the first embodiment is not limited to this example.

First Modified Example

FIG.6is a cross-sectional view of a photodetection element101according to a first modified example. The photodetection element101includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer21, insulating layers30and31, and a substrate40. In the first modified example, components similar to those in the first embodiment are denoted by similar reference signs and the description thereof will be omitted.

The first high thermal conductivity layer21is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer21is connected to the magnetic element10via, for example, the insulating layer30. The first high thermal conductivity layer21surrounds, for example, the circumference of at least a part of the magnetic element10. For example, the first high thermal conductivity layer21surrounds the circumference of the first ferromagnetic layer1of the magnetic element10. The first high thermal conductivity layer21is in contact with, for example, the first electrode11. The first high thermal conductivity layer21is sandwiched between the insulating layer30and the insulating layer31.

The first high thermal conductivity layer21has higher thermal conductivity than the first electrode11. The first high thermal conductivity layer21is made of a material similar to that of the first high thermal conductivity layer20.

The insulating layer31covers an upper surface of the first high thermal conductivity layer21. The insulating layer31sandwiches the first high thermal conductivity layer21with the insulating layer30. The insulating layer31is made of a material similar to that of the insulating layer30.

Because the photodetection element101according to the first modified example has the first high thermal conductivity layer21, the photodetection element101has effects similar to those of the photodetection element100.

Second Modified Example

FIG.7is a cross-sectional view of a photodetection element102according to a second modified example. The photodetection element102includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer22, insulating layers30and31, and a substrate40. In the second modified example, components similar to those in the first modified example are denoted by similar reference signs and the description thereof will be omitted.

The first high thermal conductivity layer22is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer22is different from the first high thermal conductivity layer21according to the first modified example in that the first high thermal conductivity layer22is not in contact with the first electrode11.

Because the photodetection element102according to the second modified example has the first high thermal conductivity layer22, the photodetection element102has effects similar to those of the photodetection element100.

Third Modified Example

FIG.8is a cross-sectional view of a photodetection element103according to a third modified example. The photodetection element103includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer20, an insulating layer30, a substrate40, and a second high thermal conductivity layer50. In the third modified example, components similar to those in the first embodiment are denoted by similar reference signs and the description thereof will be omitted.

The second high thermal conductivity layer50is in contact with a sidewall of the first electrode11. The second high thermal conductivity layer50surrounds, for example, the circumference of the first electrode11. The second high thermal conductivity layer50has higher thermal conductivity than the first electrode11. The second high thermal conductivity layer50is in contact with, for example, the first high thermal conductivity layer20. When the second high thermal conductivity layer50and the first high thermal conductivity layer20come into contact with each other, heat can be expelled from the first high thermal conductivity layer20toward the second high thermal conductivity layer50and heat is efficiently dissipated from the magnetic element10. A material similar to that of the first high thermal conductivity layer20can be applied to the second high thermal conductivity layer50. The first high thermal conductivity layer20and the second high thermal conductivity layer50may be made of the same material or different materials.

Because the photodetection element103according to the third modified example has the first high thermal conductivity layer20, the photodetection element103has effects similar to those of the photodetection element100. Also, the photodetection element103has the second high thermal conductivity layer50, so that the photodetection element103is more excellent in heat dissipation.

Fourth Modified Example

FIG.9is a cross-sectional view of a photodetection element104according to a fourth modified example. The photodetection element104includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer23, an insulating layer32, and a substrate40. In the fourth modified example, components similar to those in the first embodiment are denoted by similar reference signs and the description thereof will be omitted.

The first high thermal conductivity layer23is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer23is in direct contact with the magnetic element10. The first high thermal conductivity layer23is in direct contact with, for example, at least a part of the side surface of the first ferromagnetic layer1. The first high thermal conductivity layer23surrounds the circumference of at least a part of the magnetic element10. For example, the first high thermal conductivity layer23surrounds the circumference of the first ferromagnetic layer1of the magnetic element10.

The first high thermal conductivity layer23has higher thermal conductivity than the first electrode11. The first high thermal conductivity layer23is made of a material similar to that of the first high thermal conductivity layer20.

A part of the insulating layer32is located between the magnetic element10and the first high thermal conductivity layer23. The insulating layer32is made of a material similar to that of the insulating layer30. The insulating layer32covers at least a portion below a lower end3U of the spacer layer3within a sidewall of the magnetic element10. By covering the portion below the lower end3U of the spacer layer3, the insulating layer32can prevent the first high thermal conductivity layer23and the second ferromagnetic layer2from being short-circuited even if the first high thermal conductivity layer23is a conductor.

Because the photodetection element104according to the fourth modified example has the first high thermal conductivity layer23, the photodetection element104has effects similar to those of the photodetection element100. Also, when the first high thermal conductivity layer23is in direct contact with the first ferromagnetic layer1, the heat generated in the first ferromagnetic layer1can be dissipated more efficiently. Also, when the first high thermal conductivity layer23is a conductor, the insulating layer32prevents the first high thermal conductivity layer23and the second ferromagnetic layer2from being short-circuited, so that the deterioration of the magnetic characteristics of the magnetic element10can be limited.

Fifth Modified Example

FIG.10is a cross-sectional view of a photodetection element105according to a fifth modified example. The photodetection element105includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer25, and a substrate40. In the fifth modified example, components similar to those in the first embodiment are denoted by similar reference signs and the description thereof will be omitted.

The first high thermal conductivity layer25is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer25is in direct contact with the magnetic element10. The first high thermal conductivity layer25surrounds the circumference of the magnetic element10.

The first high thermal conductivity layer25has higher thermal conductivity than the first electrode11. The first high thermal conductivity layer25is an insulator. The thermal conductivity of the first high thermal conductivity layer25is, for example, greater than 40 W/m·K. The first high thermal conductivity layer25includes, for example, silicon carbide, aluminum nitride, or boron nitride.

Because the photodetection element105according to the fifth modified example has the first high thermal conductivity layer25, the photodetection element105has effects similar to those of the photodetection element100. Also, because the first high thermal conductivity layer25has an insulating property, it can be in direct contact with the entire side surface of the magnetic element10. As a result, the photodetection element105can efficiently dissipate heat from the magnetic element10.

Sixth Modified Example

FIG.11is a cross-sectional view of a photodetection element106according to a sixth modified example. The photodetection element106includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer26, a substrate40, and a high resistivity layer60. In the sixth modified example, components similar to those in the first embodiment are denoted by similar reference signs and the description thereof will be omitted.

The first high thermal conductivity layer26is located outside of the first ferromagnetic layer1when viewed from the z direction. The first high thermal conductivity layer26is in direct contact with, for example, the first ferromagnetic layer1. The high resistivity layer60may be provided between the first high thermal conductivity layer26and the first ferromagnetic layer1. The first high thermal conductivity layer26surrounds, for example, the circumference of the first ferromagnetic layer1.

The first high thermal conductivity layer26has higher thermal conductivity than the first electrode11. The first high thermal conductivity layer26is an insulator. The thermal conductivity of the first high thermal conductivity layer26is, for example, greater than 40 W/m·K. The first high thermal conductivity layer26includes, for example, silicon carbide, aluminum nitride, or boron nitride.

The high resistivity layer60is located between the first high thermal conductivity layer26and the second electrode12. A part of the high resistivity layer60may be located between the magnetic element10and the first high thermal conductivity layer26. The high resistivity layer60has higher resistivity than the first high thermal conductivity layer26.

The high resistivity layer60is, for example, an insulator. The high resistivity layer60depends on a material constituting the first high thermal conductivity layer26, but is, for example, aluminum oxide (Al2O3), zirconium oxide (ZrO2), silicon oxide (SiO2), silicon nitride (Si3N4), forsterite (2MgO·SiO2), yttrium oxide (Y2O3), aluminum nitride (AlN), or boron nitride (BN).

For example, when the first high thermal conductivity layer26is silicon carbide (SiC), the high resistivity layer60may be aluminum oxide (Al2O3), zirconium oxide (ZrO2), silicon oxide (SiO2), silicon nitride (Si3N4), forsterite (2MgO·SiO2), yttrium oxide (Y2O3), aluminum nitride (AlN), or boron nitride (BN). For example, when the first high thermal conductivity layer26is aluminum nitride (AlN) or boron nitride (BN), the high resistivity layer60may be silicon oxide (SiO2).

Because the photodetection element106according to the sixth modified example has the first high thermal conductivity layer26, the photodetection element106has effects similar to those of the photodetection element100. Also, the high resistivity layer60is provided between the first electrode11and the second electrode12, so that the insulating property between the first electrode11and the second electrode12can be enhanced.

Seventh Modified Example

FIG.12is a cross-sectional view of a photodetection element107according to a seventh modified example. The photodetection element107includes, for example, a magnetic element10, a first electrode11, a second electrode12, a first high thermal conductivity layer26, a substrate40, and a low dielectric constant layer70. In the seventh modified example, components similar to those in the sixth modified example are denoted by similar reference signs and the description thereof will be omitted.

The low dielectric constant layer70is located between the first high thermal conductivity layer26and the second electrode12. A part of the low dielectric constant layer70may be located between the magnetic element10and the first high thermal conductivity layer26. The low dielectric constant layer70has a lower dielectric constant than the first high thermal conductivity layer26.

The low dielectric constant layer70is, for example, an insulator. The low dielectric constant layer70depends on the material constituting the first high thermal conductivity layer26, but, is for example, silicon oxide (SiO2), silicon nitride (Si3N4), forsterite (2MgO·SiO2), aluminum nitride (AlN), or boron nitride (BN).

For example, when the first high thermal conductivity layer26is silicon carbide (SiC), the low dielectric constant layer70may be silicon oxide (SiO2), silicon nitride (Si3N4), forsterite (2MgO·SiO2), aluminum nitride (AlN), or boron nitride (BN). For example, when the first high thermal conductivity layer26is aluminum nitride (AlN), the low dielectric constant layer70may be silicon oxide (SiO2), forsterite (2MgO·SiO2), or boron nitride (BN). For example, when the first high thermal conductivity layer26is boron nitride (BN), the low dielectric constant layer70may be silicon oxide (SiO2).

Because the photodetection element107according to the seventh modified example has the first high thermal conductivity layer26, the photodetection element107has effects similar to those of the photodetection element100. Also, the low dielectric constant layer70is provided between the first electrode11and the second electrode12, so that the capacitance between the first electrode11and the second electrode12can be reduced.

The present disclosure is not limited to the above-described embodiments and modified examples and various modifications and changes can be made within the scope of the subject matter of the present disclosure described within the scope of the claims. For example, the feature configurations of the above-described embodiment and modified examples may be combined.

The photodetection element according to the above-described embodiment and modified example can be applied to an optical sensor device such as an image sensor, a transceiver device of a communication system, or the like.

FIG.13is a block diagram of the transceiver device1000according to the first application example. The transceiver device1000includes a receiving device300and a transmission device400. The receiving device300receives an optical signal L1and the transmission device400transmits an optical signal L2.

The receiving device300includes, for example, a photodetection element301and a signal processing unit302. The photodetection element301is any one of the photodetection elements100to107according to any one of the above-described embodiments and modified examples. The photodetection element301converts the optical signal L1into an electrical signal. The operation of the photodetection element301may be either the first operation example or the second operation example. Light including the optical signal L1having a change in an intensity of light is applied to the first ferromagnetic layer1of the photodetection element301. A lens may be disposed on the side of the first ferromagnetic layer1in the lamination direction of the photodetection element301, so that light condensed through the lens may be applied to the first ferromagnetic layer1. The lens may be formed in the wafer process of forming the photodetection element301. Also, the light passing through the waveguide may be applied to the first ferromagnetic layer1of the photodetection element301. The light applied to the first ferromagnetic layer1of the photodetection element301is, for example, laser light. The signal processing unit302processes the electrical signal obtained in the conversion process of the photodetection element301. The signal processing unit302receives a signal included in the optical signal L1by processing the electrical signal generated from the photodetection element301.

The transmission device400includes, for example, a light source401, an electrical signal generation element402, and a light modulation element403. The light source401is, for example, a laser element. The light source401may be located outside of the transmission device400. The electrical signal generation element402generates an electrical signal on the basis of the transmission information. The electrical signal generation element402may be integrated with the signal conversion element of the signal processing unit302. The light modulation element403modulates light output from the light source401on the basis of the electrical signal generated by the electrical signal generation element402and outputs the optical signal L2.

FIG.14is a conceptual diagram of an example of a communication system. The communication system shown inFIG.14has two terminal devices500. The terminal device500is, for example, a smartphone, a tablet, a personal computer, or the like.

Each of the terminal devices500includes a receiving device300and a transmission device400. An optical signal transmitted from the transmission device400of one terminal device500is received by the receiving device300of the other terminal device500. The light used for transmission/receiver between the terminal devices500is, for example, visible light. The receiving device300has one of the above-described photodetection elements100to107as the photodetection element301. Because the above-described photodetection elements100to107are excellent in heat dissipation, the communication system shown inFIG.14can implement high-speed communication.

FIG.15is a conceptual diagram of a cross-section of an optical sensor device2000according to the second application example. The optical sensor device2000includes, for example, a circuit board110, a wiring layer120, and a plurality of optical sensors S. Each of the wiring layer120and the plurality of optical sensors S is formed on the circuit board110.

Each of the plurality of optical sensors S includes, for example, a photodetection element100, a wavelength filter F, and a lens R. Although an example in which the photodetection element100is used is shown inFIG.15, the photodetection elements101to106may be used instead of the photodetection element100. Light passing through the wavelength filter F is applied to the photodetection element100. As described above, the photodetection element100replaces the light applied to the magnetic element10with an electrical signal. The photodetection element100may operate in the second operation example.

The wavelength filter F selects light of a specific wavelength and transmits light of a specific wavelength range. The wavelength range of light transmitted by each wavelength filter F may be the same or different. For example, the optical sensor device2000may include an optical sensor S (hereinafter referred to as a blue sensor) having a wavelength filter F that transmits light in blue (a wavelength range of 380 nm or more and less than 490 nm), an optical sensor S (hereinafter referred to as a green sensor) having a wavelength filter F that transmits light in green (a wavelength range of 490 nm or more and less than 590 nm), and an optical sensor S (hereinafter referred to as a red sensor) having a wavelength filter F that transmits light in red (a wavelength range of 590 nm or more and less than 800 nm). The blue sensor, the green sensor, and the red sensor are set as one pixel, and the optical sensor device2000can be used as an image sensor by arraying these pixels.

The lens R condenses light toward the magnetic element10. Although one photodetection element100is disposed below one wavelength filter F in the optical sensor S shown inFIG.15, a plurality of photodetection elements100may be disposed below one wavelength filter F.

The circuit board110has, for example, an analog-to-digital converter111and an output terminal112. An electrical signal sent from the optical sensor S is replaced with digital data by the analog-to-digital converter111and is output from the output terminal112.

The wiring layer120has two or more wirings121. There is an interlayer insulating film122between the two or more wirings121. The wiring121is electrically connected between each of the optical sensors S and the circuit board110and is electrically connected to each calculation circuit formed on the circuit board110. Each of the optical sensors S and the circuit board110are connected, for example, via through-wiring passing through the interlayer insulating film122in the z direction. Noise can be reduced by shortening an inter-wiring distance between each of the optical sensors S and the circuit board110.

The wiring121has conductivity. The wiring121is, for example, Al, Cu, or the like. The interlayer insulating film122is an insulator that provides insulation between the wirings of the multilayer wiring and between the elements. The interlayer insulating film122is, for example, an oxide, a nitride, or an oxynitride of Si, Al, or Mg. The interlayer insulating film122is, for example, silicon oxide (SiOx), silicon nitride (SiNx), silicon carbide (SiC), chromium nitride, silicon nitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al2O3), zirconium oxide (ZrOx), or the like.

The above-described optical sensor device2000can be used, for example, in a terminal device.FIG.16is a schematic view of an example of a terminal device600. The left side ofFIG.16is a front surface of the terminal device600and the right side ofFIG.16is a back surface of the terminal device600. The terminal device600has a camera CA. The above-described optical sensor device2000can be used as an image sensor of this camera CA. Although a smartphone is shown as an example of the terminal device600inFIG.16, the present disclosure is not limited to this case. The terminal device600is, for example, a tablet, a personal computer, a digital camera, or the like other than the smartphone.