Sensor having protruding surface
A magnetic sensor includes an insulating layer including a protruding surface, a first MR element, and a second MR element. The protruding surface includes a first curved surface portion. The first curved surface portion includes a first portion including an upper end portion of the protruding surface, and a second portion continuous with the first portion at a position away from the upper end portion of the protruding surface. When the shape of the protruding surface is regarded as a function Z, the mean value of the absolute value of a second derivative Z″ of the function Z corresponding to the first portion is smaller than the mean value of the absolute value of the second derivative Z″ of the function Z corresponding to the second portion.
1. A sensor configured to detect a predetermined physical quantity, comprising:
a substrate including a top surface;
a support member disposed on the substrate; and
a sensor element configured to change in a physical property depending on the predetermined physical quantity, wherein
the support member includes a protruding surface protruding in a direction away from the top surface of the substrate and inclined at least partially with respect to the top surface of the substrate,
the sensor element includes a functional layer constituting at least a part of the sensor element,
the functional layer is disposed on the protruding surface,
the protruding surface includes an upper end portion farthest from the top surface of the substrate, and also includes a first curved surface portion including the upper end portion of the protruding surface and protruding in the direction away from the top surface of the substrate, and a second curved surface portion continuous with the first curved surface portion and located between the first curved surface portion and the top surface of the substrate in a direction perpendicular to the top surface of the substrate, and
the protruding surface is shaped such that when a shape of the protruding surface in a cross section perpendicular to the top surface of the substrate is regarded as a function Z having as a variable a position on a virtual straight line that is parallel to each of the cross section and the top surface of the substrate, a mean value of an absolute value of a second derivative Z″ of the function Z corresponding to the first curved surface portion is smaller than a mean value of an absolute value of the second derivative Z″ of the function Z corresponding to the second curved surface portion.
2. The sensor according to claim 1 , wherein a value of the second derivative Z″ of the function Z corresponding to the first curved surface portion is a negative value, and a value of the second derivative Z″ of the function Z corresponding to the second curved surface portion is a positive value.
3. The sensor according to claim 1 , wherein the functional layer is disposed on the first curved surface portion.
4. The sensor according to claim 1 , wherein the first curved surface portion is shaped such that a value of the second derivative Z″ of the function Z corresponding to the first curved surface portion is less than or equal to 0.
5. The sensor according to claim 1 , wherein the first curved surface portion is shaped such that a value of a first derivative Z′ of the function Z corresponding to the first curved surface portion decreases or increases in a direction closer to one end of the first curved surface portion in a predetermined direction parallel to the top surface of the substrate from another end of the first curved surface portion in the predetermined direction.
6. The sensor according to claim 1 , wherein
the second curved surface portion is a curved surface protruding in a direction closer to the top surface of the substrate.
7. The sensor according to claim 6 , wherein the protruding surface is shaped such that a value of the second derivative Z″ of the function Z corresponding to a boundary between the first curved surface portion and the second curved surface portion is 0.
8. The sensor according to claim 1 , wherein a dimension of the protruding surface in a direction perpendicular to the top surface of the substrate is greater than or equal to 1.4 μm (micrometer) and less than or equal to 3.0 μm.
9. The sensor according to claim 1 , wherein
the predetermined physical quantity is at least one of a direction or a strength of a target magnetic field, and
the sensor element is a magnetic detection element configured to detect a change in at least one of the direction or the strength of the target magnetic field.
10. The sensor according to claim 9 , wherein
the magnetic detection element is a magnetoresistive element, and
the functional layer includes a plurality of magnetic films.
11. The sensor according to claim 10 , wherein the magnetoresistive element further includes a nonmagnetic metal layer disposed between the protruding surface and the plurality of magnetic films.