Pressure sensor element

Abstract

Provided is a pressure sensor element capable of suppressing a decrease in detection sensitivity over a wide range of pressures. The pressure sensor element comprises: an electrically conductive base; an intermediate layer stacked on the base and having an opening portion; and an electrode stacked on the intermediate layer and having a diaphragm portion facing the opening portion. The opening portion includes a through-hole penetrating through the intermediate layer in a stacking direction, and a pair of recessed portions provided at an upper surface of the intermediate layer so as to sandwich the through-hole. The intermediate layer is provided with a base-side electrically conductive layer that constitutes a bottom surface of the pair of recessed portions. The diaphragm portion faces the base-side electrically conductive layer with the pair of recessed portions interposed therebetween, faces the base with the through-hole interposed therebetween, and is electrically insulated from the base-side electrically conductive layer and the base. The pressure sensor element further comprises a pair of opposing portions that protrude from at least one of the base-side electrically conductive layer and the diaphragm portion to the pair of recessed portions. The pair of opposing portions are located in positions that overlap end portions of the pair of recessed portions on the through-hole side thereof when viewed from the stacking direction.

Description

pressure sensor element

[0001] The present disclosure relates to a pressure sensor element for detecting pressure.

[0002] 2. Description of the Related Art Pressure sensor elements capable of detecting capacitance changes over a wide range from low pressure to high pressure are known (see, for example, Patent Documents 1 and 2).

[0003] The pressure sensor element disclosed in Patent Document 1 includes a first electrode and a second electrode insulated from each other by a space. The second electrode is deflected by the application of pressure. A change in capacitance between the first electrode and the second electrode is detected based on the resulting change in the distance between the first electrode and the second electrode. The pressure acting on the second electrode is measured based on the detected change in capacitance.

[0004] In the pressure sensor element disclosed in Patent Document 1, a pedestal protrudes from a second electrode into space. The pedestal is annular in plan view. When the pressure acting on the second electrode is low, the pedestal is separated from the first electrode. At this time, the outer and inner pedestal portions of the second electrode bend as a single membrane. When the pressure acting on the second electrode increases, the second electrode bends, causing the pedestal to contact the first electrode. When the second electrode bends while the pedestal is in contact with the first electrode, the outer and inner pedestal portions of the second electrode bend as separate membranes. These separate membranes have higher rigidity than the single membrane. Therefore, these separate membranes can be used to detect capacitance changes corresponding to high pressure.

[0005] The pressure sensor element disclosed in Patent Document 2 includes a fixed electrode and a diaphragm that face each other with a gap between them. The diaphragm bends when pressure is applied. A change in capacitance between the fixed electrode and the diaphragm is detected based on the change in the gap between the fixed electrode and the diaphragm. The pressure acting on the diaphragm is measured based on the detected change in capacitance.

[0006] The pressure sensor element disclosed in Patent Document 2 has a convex portion at the center of a fixed electrode covered with an insulating film. The gap between the center of the fixed electrode and the diaphragm is narrower than the gap between the periphery of the fixed electrode and the diaphragm. Therefore, when high pressure acts on the diaphragm, the center of the fixed electrode and the diaphragm come into contact via the insulating film. At this time, a change in the gap at the periphery of the fixed electrode is detected, thereby detecting a change in capacitance between the fixed electrode and the diaphragm.

[0007] JP 2018-521317 A JP 2005-321257 A

[0008] In the pressure sensor element disclosed in Patent Document 1, if the distance between the first electrode and the second electrode is widened, the detection sensitivity of the capacitance change when the pressure acting on the second electrode is low decreases. On the other hand, if the distance between the first electrode and the second electrode is narrowed, the second electrode is more likely to come into contact with the first electrode when the pressure acting on the second electrode is high. If the second electrode comes into contact with the first electrode, the capacitance change cannot be detected.

[0009] In the pressure sensor element disclosed in Patent Document 2, when high pressure is applied to the diaphragm, the center of the fixed electrode is in contact with the diaphragm via an insulating film, so the cap at the center of the fixed electrode does not change. Therefore, the change in capacitance between the fixed electrode and the diaphragm is detected only by the change in the gap at the peripheral portion of the fixed electrode. This results in a lower detection sensitivity for capacitance changes compared to a configuration in which the change in capacitance between the fixed electrode and the diaphragm is detected by the change in the gap both at the center and the peripheral portion of the fixed electrode.

[0010] An object of the present disclosure is to provide a pressure sensor element that can suppress a decrease in detection sensitivity for capacitance changes against the action of a wide range of pressures from low pressure to high pressure.

[0011] a conductive electrode laminated on the opposite side of the intermediate layer from the base and having an opening; and a conductive electrode electrically insulated from the base, the conductive electrode having a diaphragm portion overlapping the opening when viewed from the stacking direction, the opening having a through hole penetrating the intermediate layer in the stacking direction, and a pair of recesses recessed in the stacking direction, the pair of recesses being provided on the electrode side surface of the intermediate layer so as to sandwich the through hole and be continuous with the through hole; the intermediate layer comprises a base-side conductive layer constituting the bottom surfaces of the pair of recesses and electrically connected to the base; the diaphragm portion faces the base-side conductive layer across the pair of recesses in the stacking direction and faces the base across the through hole in the stacking direction; and the conductive electrode further comprises protrusions provided on a surface of at least one of the base-side conductive layer and the diaphragm portion on the pair of recesses side, the protrusions protruding into the pair of recesses, The convex portion has a pair of opposing portions that face each other with a gap in the width direction, which is the direction in which the pair of recesses sandwich the through hole, and the pair of opposing portions are positioned so as to overlap the ends of the pair of recesses on the through hole side when viewed from the stacking direction.

[0012] According to the present disclosure, it is possible to provide a pressure sensor element that can suppress a decrease in detection sensitivity over a wide range of pressures from low pressure to high pressure.

[0013] 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure. Schematic plan view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the second embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure. Schematic end view of a portion corresponding to FIG. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure.

[0014] An example of the present disclosure will now be described with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses. The drawings are schematic, and the ratios of dimensions and the like do not necessarily correspond to reality. In the following description, terms indicating specific directions or positions (e.g., terms including "upper," "lower," "right," "left," "front," and "rear") may be used as necessary. However, the use of terms indicating specific directions or positions is intended to facilitate understanding of the present disclosure with reference to the drawings, and the meanings of these terms do not limit the technical scope of the present disclosure.

[0015] <First embodiment> Fig. 1 is a schematic end view of a pressure sensor element according to a first embodiment of the present disclosure. Fig. 2 is a schematic plan view of a portion of the pressure sensor element according to the first embodiment of the present disclosure, excluding electrodes. Fig. 1 and Figs. 3 to 7 and 9 to 12, which will be described later, are schematic end views of a portion corresponding to the cross section A-A in Fig. 2.

[0016] The pressure sensor element 1 shown in Figures 1 and 2 is for detecting pressure. The pressure sensor element 1 is a capacitance type element. In the first embodiment, the pressure sensor element 1 is a MEMS (Micro Electro Mechanical Systems) element. The pressure sensor element 1 is mounted on, for example, a mobile object such as an automobile, or a consumer device such as a smartphone or a smartwatch.

[0017] The pressure sensor element 1 has a rectangular parallelepiped shape. However, the shape of the pressure sensor element 1 is not limited to a rectangular parallelepiped shape (a quadrilateral shape when viewed from the stacking direction 101). For example, the pressure sensor element 1 may have a polygonal shape other than a quadrilateral when viewed from the stacking direction 101, or may have a cylindrical shape.

[0018] 1 and 2 , the pressure sensor element 1 includes a base 10, an intermediate layer 20, an electrode 30, and a protrusion 40. The intermediate layer 20 is laminated on the base 10. The electrode 30 is laminated on the intermediate layer 20 on the side opposite to the base 10. The protrusion 40 is provided on the intermediate layer 20.

[0019] In the first embodiment, the base 10 is rectangular in plan view when viewed from a stacking direction 101, which is the direction in which the base 10, the intermediate layer 20, and the electrode 30 are stacked. The base 10 is conductive. In the first embodiment, the base 10 is made of silicon (Si). The material for forming the base 10 is not limited to silicon. As described above, the shape of the pressure sensor element 1 is not limited to a rectangular parallelepiped shape. Therefore, for example, if the pressure sensor element 1 is cylindrical, the base 10 is circular in plan view. In other words, the base 10 is not limited to a rectangular shape in plan view.

[0020] In the first embodiment, the intermediate layer 20 has a rectangular shape in a plan view. Like the base 10, the intermediate layer 20 is not limited to a rectangular shape in a plan view. The intermediate layer 20 includes a first base-side insulating layer 21 having insulating properties, a base-side conductive layer 22 having conductivity, and a second base-side insulating layer 23 having insulating properties. The first base-side insulating layer 21 is laminated on the base 10. The base-side conductive layer 22 is laminated on the first base-side insulating layer 21 on the side opposite the base 10. The second base-side insulating layer 23 is laminated on the base-side conductive layer 22 on the side opposite the first base-side insulating layer 21.

[0021] In the first embodiment, the first base-side insulating layer 21 and the second base-side insulating layer 23 are made of silicon dioxide (SiO ２ ), and the base-side conductive layer 22 is made of polysilicon (Poly-Si). The material forming the first base-side insulating layer 21 and the second base-side insulating layer 23 is not limited to silicon dioxide. The material forming the first base-side insulating layer 21 and the material forming the second base-side insulating layer 23 may be different materials. The material forming the base-side conductive layer 22 is not limited to polysilicon.

[0022] The base side conductive layer 22 has a fixed electrode 221 and a surrounding conductive layer 222 that surrounds the fixed electrode 221 in a plan view.

[0023] A gap 22A is formed between the fixed electrode 221 and the surrounding conductive layer 222. As a result, the fixed electrode 221 and the surrounding conductive layer 222 are electrically insulated from each other.

[0024] As shown in FIG. 1, the fixed electrode 221 is electrically connected to the base 10 via a through-hole 21A that penetrates the first base-side insulating layer 21 in the stacking direction 101 .

[0025] 1 and 2 , the intermediate layer 20 has an opening 20A. In the first embodiment, the opening 20A has a through hole 20B and a pair of recesses 20C and 20D. The through hole 20B penetrates the intermediate layer 20 in the stacking direction 101. The pair of recesses 20C and 20D are formed in an upper surface 20E of the intermediate layer 20 and are recessed from the upper surface 20E of the intermediate layer 20 in the stacking direction 101. The upper surface 20E of the intermediate layer 20 is the surface of the intermediate layer 20 that faces the electrode 30.

[0026] The through hole 20B extends in the longitudinal direction 103. The longitudinal direction 103 is a direction parallel to the long sides of the rectangle of the pressure sensor element 1 in a plan view. The longitudinal direction 103 is a direction perpendicular to the stacking direction 101. The through hole 20B communicates with the gap 22A at both ends in the longitudinal direction 103. The bottom surface of the through hole 20B is formed by the upper surface of the base 10. The side surfaces of the through hole 20B are formed by the side surfaces of the first base-side insulating layer 21 and the base-side conductive layer 22. The depth D1 of the through hole 20B is the same as the thickness of the intermediate layer 20 (the total thickness of the first base-side insulating layer 21, the base-side conductive layer 22, and the second base-side insulating layer 23).

[0027] The pair of recesses 20C, 20D penetrate the second base-side insulating layer 23. On the other hand, the pair of recesses 20C, 20D are not provided in the base-side conductive layer 22 or the first base-side insulating layer 21. The pair of recesses 20C, 20D communicate with the gap 22A. The upper surface of the base-side conductive layer 22 (the surface of the base-side conductive layer 22 facing the pair of recesses 20C, 20D) forms the bottom surface 20Ca of the recess 20C and the bottom surface 20Da of the recess 20D. More specifically, the fixed electrode 221 and a portion of the surrounding conductive layer 222 form the bottom surfaces 20Ca, 20Da. The side surfaces of the second base-side insulating layer 23 form the side surfaces of the pair of recesses 20C, 20D. The depth D2 of the pair of recesses 20C, 20D is the same as the thickness of the second base-side insulating layer 23. The depth D2 of the pair of recesses 20C and 20D is shallower than the depth D1 of the through hole 20B.

[0028] The pair of recesses 20C, 20D face each other with a gap in between in the short direction 102. The short direction 102 is a direction parallel to the short sides of the rectangle of the pressure sensor element 1 in a plan view. The short direction 102 is a direction perpendicular to the stacking direction 101 and the longitudinal direction 103. The short direction 102 is an example of a width direction. Note that the short direction 102 and the longitudinal direction 103 do not necessarily have to be perpendicular to each other, as long as they intersect each other.

[0029] A through hole 20B is provided between the pair of recesses 20C, 20D. That is, the pair of recesses 20C, 20D sandwich the through hole 20B in the short direction 102. Each of the pair of recesses 20C, 20D communicates with the through hole 20B. That is, the pair of recesses 20C, 20D are provided contiguous with the through hole 20B.

[0030] As shown in FIG. 1 , the electrode 30 is laminated on the second base-side insulating layer 23 of the intermediate layer 20. In the first embodiment, the electrode 30 has a rectangular shape in a plan view. As with the base 10 described above, the electrode 30 is not limited to a rectangular shape in a plan view. The electrode 30 is conductive. The electrode 30 is electrically insulated from the base 10.

[0031] In the first embodiment, the electrode 30 is made of silicon (Si). However, the material for forming the electrode 30 is not limited to silicon.

[0032] The electrode 30 has a diaphragm portion 31. The diaphragm portion 31 is a portion of the electrode 30 that faces the opening 20A of the intermediate layer 20. In other words, the diaphragm portion 31 is a portion of the electrode 30 that overlaps the opening 20A when viewed from the stacking direction 101. The diaphragm portion 31 is capable of bending. For example, when pressure acts on one main surface 30A of the electrode 30, the diaphragm portion 31 bends downward, i.e., toward the opening 20A.

[0033] The diaphragm portion 31 faces the base-side conductive layer 22 in the stacking direction 101 via the pair of recesses 20C and 20D, and faces the base 10 in the stacking direction 101 via the through-hole 20B.

[0034] 1 and 2, the protrusions 40 are provided on the upper surface of the fixed electrode 221 of the base-side conductive layer 22, i.e., on each of the bottom surfaces 20Ca and 20Da of the pair of recesses 20C and 20D. The protrusions 40 protrude upward from the bottom surfaces 20Ca and 20Da. In other words, the protrusions 40 protrude from the bottom surfaces 20Ca and 20Da into the pair of recesses 20C and 20D.

[0035] In the first embodiment, the protrusions 40 have insulating properties. In the first embodiment, the protrusions 40 are made of silicon dioxide (SiO ２ The material forming the protrusion 40 is silicon dioxide (SiO ２ ) and silicon nitride (SiN).

[0036] The protrusion 40 includes a pair of opposing portions 41 and 42. In the first embodiment, the protrusion 40 is configured with a pair of opposing portions 41 and 42. The opposing portion 41 is provided on the bottom surface 20Ca. The opposing portion 42 is provided on the bottom surface 20Da.

[0037] The pair of opposing portions 41, 42 are provided at the ends of the bottom surfaces 20Ca, 20Da on the through hole 20B side in the short direction 102. In other words, the pair of opposing portions 41, 42 are located at positions that overlap the ends of the pair of recesses 20C, 20D on the through hole 20B side in a plan view.

[0038] Each of the pair of opposing portions 41, 42 extends linearly along the longitudinal direction 103. The pair of opposing portions 41, 42 are parallel to each other. The longitudinal direction 103 is an example of an extension direction.

[0039] The pair of opposing portions 41, 42 face each other with a gap therebetween in the direction in which the pair of recesses 20C, 20D sandwich the through hole 20B. In the first embodiment, the direction in which the pair of recesses 20C, 20D sandwich the through hole 20B is the short direction 102.

[0040] 2, in plan view, the region of the diaphragm portion 31 whose position in the short side direction 102 is between the pair of opposing portions 41, 42 is rectangular. In other words, in plan view, the region surrounded by four imaginary straight lines LN1, LN2, LN3, and LN4 shown by dashed dotted lines in FIG. 2 is rectangular.

[0041] The imaginary straight line LN1 is a line that passes over the opposing portion 41 and extends along the longitudinal direction 103. The imaginary straight line LN3 is a line that passes over the opposing portion 42 and extends along the longitudinal direction 103. The imaginary straight lines LN1 and LN3 extend to the outside of the pair of opposing portions 41 and 42 in the longitudinal direction 103. The imaginary straight line LN2 is a line that extends along the short direction 102 on the side surface 23A facing one side in the longitudinal direction 103 among the side surfaces (surfaces extending in the stacking direction 101) of the second base-side insulating layer 23. The imaginary straight line LN4 is a line that extends along the short direction 102 on the side surface 23B facing the other side in the longitudinal direction 103 among the side surfaces of the second base-side insulating layer 23. The imaginary straight lines LN2 and LN4 intersect with the imaginary straight lines LN1 and LN3, respectively.

[0042] In the first embodiment, the length L of each of the pair of opposing portions 41 and 42 along the longitudinal direction 103 is longer than the distance G between the pair of opposing portions 41 and 42 in the lateral direction 102 .

[0043] In the first embodiment, the gap G between the pair of opposing portions 41, 42 in the short-side direction 102 is longer than the shortest distance D3 in the short-side direction 102 between each of the pair of opposing portions 41, 42 and the outer edge of the opening 20A.

[0044] 3 and 4 are schematic end views of the pressure sensor element according to the first embodiment of the present disclosure when a low pressure is applied to the electrode and a high pressure is applied to the electrode, respectively.

[0045] Hereinafter, with reference to FIGS. 3 and 4, the operation of the diaphragm portion 31 of the electrode 30 when pressure acts on one main surface 30A of the electrode 30 and the detection of the electrostatic capacitance in response to this operation will be described.

[0046] As described above, the diaphragm portion 31 faces the base-side conductive layer 22 in the stacking direction 101 via the pair of recesses 20C, 20D, and faces the base 10 in the stacking direction 101 via the through hole 20B. As a result, as shown by the dashed lines in FIG. 3 , the diaphragm portion 31 and the fixed electrode 221 that face each other via the recess 20C form a capacitor C1. The diaphragm portion 31 and the fixed electrode 221 that face each other via the recess 20D form a capacitor C2. The diaphragm portion 31 and the base 10 that face each other via the through hole 20B form a capacitor C3. A circuit in which these three capacitors C1, C2, and C3 are equivalently connected in parallel can be realized.

[0047] The base 10 and the electrode 30 including the diaphragm portion 31 can each be electrically connected to an external device or element via a terminal (not shown). This allows the pressure acting on one main surface 30A of the electrode 30 to be measured by an external device or element based on the total capacitance of the three capacitors C1, C2, and C3.

[0048] When pressure acts on one main surface 30A of the electrode 30, the diaphragm portion 31 of the electrode 30 bends downward toward the base 10, as shown in Figure 3. When the pressure acting on the one main surface 30A is small, the amount of bending of the diaphragm portion 31 is small. At this time, the diaphragm portion 31 is separated from the pair of opposing portions 41, 42 of the convex portion 40. Therefore, the diaphragm portion 31 bends as a single membrane.

[0049] As the diaphragm portion 31 flexes, the distance in the stacking direction 101 between the diaphragm portion 31 and the base-side conductive layer 22 and the distance in the stacking direction 101 between the diaphragm portion 31 and the base 10 each become smaller. These changes in distance increase the capacitance of each of the capacitors C1, C2, and C3. Based on the changes in the capacitance of each of the capacitors C1, C2, and C3, the current flowing in an external device or element and the voltage applied to the external device or element change. The pressure acting on one main surface 30A of the electrode 30 is measured based on these changes in current and voltage.

[0050] When a pressure higher than the above acts on the one main surface 30A, the amount of deflection of the diaphragm portion 31 increases. At this time, the diaphragm portion 31 comes into contact with the pair of opposing portions 41, 42. If the diaphragm portion 31, while in contact with the pair of opposing portions 41, 42, further deflects downward toward the base 10, as shown in FIG. 4, the portions of the diaphragm portion 31 corresponding to the capacitors C1, C2, and C3 deflect as three separate membranes. The rigidity of each portion of the diaphragm portion 31 corresponding to each of these three membranes is greater than the rigidity of the diaphragm portion 31 corresponding to a single membrane (see FIG. 3). Therefore, in the state shown in FIG. 4, the diaphragm portion 31 is less likely to deflect than in the state shown in FIG. 3. As a result, the upper limit of pressure measurable by the pressure sensor element 1 can be increased.

[0051] According to the first embodiment, when the deflection amount of the diaphragm portion 31 is small, i.e., when low pressure is acting on the diaphragm portion 31, the diaphragm portion 31 does not contact the pair of opposing portions 41, 42. At this time, low pressure acting on the diaphragm portion 31 can be measured with high sensitivity based on the change in capacitance between the diaphragm portion 31 and the base-side conductive layer 22 and the change in capacitance between the diaphragm portion 31 and the base 10. When the deflection amount of the diaphragm portion 31 is large, i.e., when high pressure is acting on the diaphragm portion 31, the diaphragm portion 31 comes into contact with the pair of opposing portions 41, 42. At this time, the diaphragm portion 31 functions as a separate membrane between the pair of opposing portions 41, 42 and on both outer sides of the pair of opposing portions 41, 42. In this case, the rigidity of each of these separate membranes is high. Therefore, high pressure acting on the diaphragm portion 31 can be measured with high sensitivity.

[0052] According to the first embodiment, when viewed from the stacking direction 101, the through hole 20B is located between the pair of opposing portions 41, 42, and the pair of recesses 20C, 20D are located on both outer sides of the pair of opposing portions 41, 42. Here, the depth D1 of the through hole 20B is deeper than the depth D2 of the pair of recesses 20C, 20D. Therefore, when a high pressure is applied to the diaphragm portion 31, it is possible to reduce the possibility that the diaphragm portion 31, which is deflected between the pair of opposing portions 41, 42, will come into contact with the base 10.

[0053] When the diaphragm portion is square as viewed from the stacking direction 101, when pressure acts on the diaphragm portion, the amount of displacement of the diaphragm portion is greatest at a single point at the center of the diaphragm portion, and the amount of displacement decreases with increasing distance from the center. In contrast, in the first embodiment, when viewed from the stacking direction 101, the portion of the diaphragm portion 31 surrounded by the four imaginary lines LN1, LN2, LN3, and LN4 is rectangular. In the diaphragm portion 31 that is rectangular as viewed from the stacking direction 101 as in the first embodiment, when pressure acts on the diaphragm portion 31, the amount of displacement of the diaphragm portion 31 is greatest at the center along the short sides of the rectangle, and the amount of displacement decreases with increasing distance from the center. This portion with the greatest amount of displacement extends along the long sides of the rectangle. In other words, in the diaphragm portion 31 that is rectangular as viewed from the stacking direction 101, the portion with the greatest amount of displacement of the diaphragm portion 31 is a line, not a point. That is, in the diaphragm portion 31 that is rectangular when viewed from the stacking direction 101, the region where the displacement of the diaphragm portion is constant can be made larger than in the diaphragm portion that is square when viewed from the stacking direction 101. This makes it possible to detect with high accuracy the change in capacitance caused by the deflection of the portion of the diaphragm portion 31 that is surrounded by the four imaginary straight lines LN1, LN2, LN3, and LN4.

[0054] For example, if the diaphragm portion is circular, the only way to adjust the size of the diaphragm portion is to change the diameter of the circle. According to the first embodiment, the portion of the diaphragm portion 31 surrounded by the four imaginary lines LN1, LN2, LN3, and LN4 is rectangular. In this case, the size of the diaphragm portion 31 can be adjusted in two ways: by changing the length of the long side of the rectangle, or by changing the length of the short side of the rectangle. Therefore, in the first embodiment, the size and shape of the diaphragm portion can be more freely changed to match the shape of the pressure sensor element than in a configuration in which the diaphragm portion is circular.

[0055] According to the first embodiment, the rectangle enclosed by the four imaginary straight lines LN1, LN2, LN3, and LN4 can be a rectangle whose long sides are in the extension direction (longitudinal direction 103) of each of the pair of opposing portions 41, 42. This allows the pair of opposing portions 41, 42 to be elongated in the extension direction, thereby increasing the contact area when the diaphragm portion 31 is in contact with the pair of opposing portions 41, 42. This increases the stability of the diaphragm portion 31 when in contact with the pair of opposing portions 41, 42.

[0056] According to the first embodiment, the distance G between the pair of opposing portions 41, 42 in the short-side direction 102 is longer than the shortest distance D3 between each of the pair of opposing portions 41, 42 and the outer edge of the opening 20A in the short-side direction 102. In this case, regardless of whether the shape of the opening 20A is square or rectangular, the region between the pair of opposing portions 41, 42 can be rectangular.

[0057] Fig. 5 is a schematic end view of a portion of a modified example of the pressure sensor element according to the first embodiment of the present disclosure, which corresponds to Fig. 1. As shown in Fig. 5, the convex portion 40 may be provided on the diaphragm portion 31.

[0058] The protrusions 40 are provided on the surface of the diaphragm portion 31 on the side of the pair of recesses 20C and 20D (in other words, on the lower surface of the diaphragm portion 31). The protrusions 40 protrude downward from the diaphragm portion 31. In other words, the protrusions 40 protrude from the diaphragm portion 31 toward the pair of recesses 20C and 20D.

[0059] 1 and 2, the protrusion 40 shown in FIG. 5 also includes a pair of opposing portions 41, 42. Each of the pair of opposing portions 41, 42 extends along the longitudinal direction 103. The pair of opposing portions 41, 42 face each other at a distance in the short-side direction 102. The pair of opposing portions 41, 42 are positioned so as to overlap the ends of the pair of recesses 20C, 20D on the through-hole 20B side in a plan view. In other words, the positions of the pair of opposing portions 41, 42 shown in FIG. 5 in the short-side direction 102 are the same as the positions of the pair of opposing portions 41, 42 shown in FIGS. 1 and 2 in the short-side direction 102.

[0060] The convex portion 40 may be provided on both the base-side conductive layer 22 and the diaphragm portion 31. In other words, the convex portion 40 may be provided on at least one of the base-side conductive layer 22 and the diaphragm portion 31.

[0061] The pair of opposing portions 41, 42 do not have to extend linearly. For example, the pair of opposing portions 41, 42 may be curved or may extend in a wavy manner.

[0062] The pair of opposing portions 41 and 42 do not have to be parallel to each other.

[0063] The pair of opposing portions 41 and 42 may have a shape extending in a direction other than the longitudinal direction 103 , for example, a shape extending in the lateral direction 102 .

[0064] The pair of opposing portions 41 and 42 do not have to have a shape that extends linearly in one direction (the longitudinal direction 103 in the first embodiment).

[0065] The protrusion 40 does not have to be composed of only a pair of opposing portions 41, 42. For example, the protrusion 40 may have, in addition to the pair of opposing portions 41, 42, a portion connecting one end 41A, 42A of the pair of opposing portions 41, 42. In this case, the protrusion 40 has a substantially U-shape in plan view. Also, for example, the protrusion 40 may have, in addition to the pair of opposing portions 41, 42, a portion connecting one end 41A, 42A of the pair of opposing portions 41, 42 and a portion connecting the other end 41B, 42B of the pair of opposing portions 41, 42. In this case, the protrusion 40 has a rectangular ring shape in plan view.

[0066] Fig. 6 is a schematic end view of a portion of a modified example of the pressure sensor element according to the first embodiment of the present disclosure, which corresponds to Fig. 1. Fig. 7 is a schematic end view of a portion of a modified example of the pressure sensor element according to the first embodiment of the present disclosure, which corresponds to Fig. 1.

[0067] 6 and 7 , the protrusions 40 may be made of a conductive material. For example, the protrusions 40 may be made of polysilicon, which is the same material as the base-side conductive layer 22. In this case, the protrusions 40 may be formed integrally with the base-side conductive layer 22.

[0068] If the convex portions 40 are conductive, there is a risk that the diaphragm portion 31 that is deflected by the application of pressure and the base-side conductive layer 22 will be electrically connected via the convex portions 40. Therefore, in order to prevent electrical connection between the diaphragm portion 31 and the base-side conductive layer 22, the pressure sensor element 1 having the conductive convex portions 40 further includes an insulating film 50 that is insulating.

[0069] 6, the convex portion 40 is provided on the base-side conductive layer 22 (on the surface of the base-side conductive layer 22 facing the pair of concave portions 20C and 20D), similarly to the configuration shown in Fig. 1. In this case, the insulating film 50 is provided on the surface of the diaphragm portion 31 facing the opening 20A.

[0070] 7, the convex portion 40 is provided on the diaphragm portion 31 (on the surface of the diaphragm portion 31 facing the pair of concave portions 20C and 20D), similarly to the configuration shown in Fig. 5. In this case, the insulating film 50 is provided on the base-side conductive layer 22 and the surface of the base 10 facing the opening 20A.

[0071] It is sufficient that the insulating film 50 is provided at a position that prevents electrical connection at least between the diaphragm portion 31 and the base-side conductive layer 22. For example, in the configuration shown in FIG. 6 , the insulating film 50 is provided on the entire surface of the diaphragm portion 31 that faces the opening 20A. However, the insulating film 50 may be provided only on a portion of that surface that faces the protrusion 40 in the stacking direction 101. For example, in the configuration shown in FIG. 7 , the insulating film 50 is provided on the base-side conductive layer 22 and the surface of the base 10 that faces the opening 20A. However, the insulating film 50 may be provided only on the base-side conductive layer 22 and not on the base 10.

[0072] The insulating film 50 may be provided so as to cover the protrusions 40 .

[0073] As described above, the insulating film 50 covers at least one of the convex portion 40 and the portion of the diaphragm portion 31 that comes into contact with the convex portion 40 when the diaphragm portion 31 is bent. In a configuration having the insulating film 50, the insulating film 50 is present between the diaphragm portion 31 and the convex portion 40, or between the base-side conductive layer 22 and the convex portion 40. This prevents the diaphragm portion 31 that is bent due to the application of pressure and the base-side conductive layer 22 from being electrically connected via the convex portion 40.

[0074] 6 and 7, since the protrusions 40 are made of a conductive material, the protrusions 40 can be formed integrally with another conductive material, for example, the base-side conductive layer 22. This allows the number of manufacturing steps for the pressure sensor element 1 to be reduced.

[0075] On the other hand, if the protrusion 40 is made of a conductive material, bending of the diaphragm portion 31 may result in electrical connection between the diaphragm portion 31 and the base 10 or the base-side conductive layer 22 via the protrusion 40. Therefore, according to the configurations shown in Figures 6 and 7, the insulating film 50 can prevent the above-mentioned electrical connection.

[0076] 8 is a schematic plan view of a pressure sensor element according to a second embodiment of the present disclosure, excluding the electrodes. The pressure sensor element 1A according to the second embodiment differs from the pressure sensor element 1 according to the first embodiment in that the pair of opposing portions 41, 42 of the convex portion 40 are provided with a plurality of protrusions 43. Differences from the first embodiment will be described below. Points in common with the pressure sensor element 1 according to the first embodiment are denoted by the same reference numerals, and explanations thereof will be omitted in principle, and will be described only when necessary.

[0077] 8 , the pair of opposing portions 41, 42 include a plurality of protrusions 43. Each of the plurality of protrusions 43 protrudes in the stacking direction 101 from the fixed electrode 221 of the base-side conductive layer 22 toward the pair of recesses 20C, 20D. The plurality of protrusions 43 are arranged at intervals along the longitudinal direction 103. As a result, the plurality of protrusions 43 as a whole are linearly shaped along the longitudinal direction 103.

[0078] In Fig. 8, both of the pair of opposing portions 41, 42 are provided with a plurality of protrusions 43, but only one of the pair of opposing portions 41, 42 may be provided with a plurality of protrusions 43. In Fig. 8, each of the pair of opposing portions 41, 42 is configured with a plurality of protrusions 43 over the entirety, but it may also be configured with a plurality of protrusions 43 over a portion, with the remaining portion being configured in a linear shape.

[0079] According to the second embodiment, the pair of opposing portions 41, 42 includes a plurality of protrusions 43 arranged at intervals from each other. The plurality of protrusions 43 come into contact with the deflected diaphragm portion 31. Therefore, the contacting diaphragm portion 31 is more likely to deflect than in a configuration in which each of the pair of opposing portions 41, 42 extends linearly. As a result, the detection accuracy of the capacitance change due to the deflection of the diaphragm portion 31 can be improved.

[0080] <Third embodiment> Figure 9 is a schematic end view of a portion of a pressure sensor element according to a third embodiment of the present disclosure, corresponding to Figure 1. The pressure sensor element 1B according to the third embodiment differs from the pressure sensor element 1 according to the first embodiment in that it further includes an inner layer 60. Differences from the first embodiment will be described below. Points in common with the pressure sensor element 1 according to the first embodiment are denoted by the same reference numerals, and explanations thereof will be omitted in principle, and will be described only when necessary.

[0081] 9, the pressure sensor element 1B further includes an inner layer 60. The inner layer 60 is laminated on the surface of the diaphragm portion 31 on the opening 20A side (the lower surface of the diaphragm portion 31). The inner layer 60 is laminated between the pair of opposing portions 41, 42 of the diaphragm portion 31 in the short direction 102. The inner layer 60 is laminated on the portion of the surface of the diaphragm portion 31 on the opening 20A side that faces the through hole 20B.

[0082] The inner layer 60 includes an electrode-side conductive layer 61 having conductivity and an electrode-side insulating layer 62 having insulation. The electrode-side insulating layer 62 is laminated on the diaphragm portion 31. The electrode-side conductive layer 61 is laminated on the electrode-side insulating layer 62 on the side opposite to the diaphragm portion 31. In other words, the electrode-side insulating layer 62 is located between the electrode-side conductive layer 61 and the diaphragm portion 31. The electrode-side conductive layer 61 is electrically connected to the electrode 30 via a through-hole 61A that penetrates the electrode-side insulating layer 62 in the lamination direction 101.

[0083] In the third embodiment, the electrode-side conductive layer 61 is formed of polysilicon, and the electrode-side insulating layer 62 is formed of silicon dioxide. The electrode-side conductive layer 61 is not limited to polysilicon, and the material forming the electrode-side insulating layer 62 is not limited to silicon dioxide.

[0084] The electrode-side insulating layer 62 is located at the same position as the second base-side insulating layer 23 of the intermediate layer 20 in the stacking direction 101. This allows the electrode-side insulating layer 62 and the second base-side insulating layer 23 to be stacked in the same step during the manufacturing process of the pressure sensor element 1B. In the third embodiment, the electrode-side insulating layer 62 has the same thickness as the second base-side insulating layer 23, but may have a thickness different from that of the second base-side insulating layer 23.

[0085] The electrode-side conductive layer 61 is located at the same position as the base-side conductive layer 22 of the intermediate layer 20 in the stacking direction 101. This allows the electrode-side conductive layer 61 and the base-side conductive layer 22 to be stacked in the same step during the manufacturing process of the pressure sensor element 1B. In the third embodiment, the electrode-side conductive layer 61 has a different thickness from the base-side conductive layer 22, but may have the same thickness as the base-side conductive layer 22.

[0086] Fig. 10 is a schematic end view of a portion of a modified pressure sensor element according to the third embodiment of the present disclosure, which corresponds to Fig. 1. As shown in Fig. 10, in the third embodiment, a convex portion 40 may be provided on the diaphragm portion 31, similar to the modified pressure sensor element according to the first embodiment shown in Fig. 5.

[0087] Fig. 11 is a schematic end view of a portion of a modified pressure sensor element according to the third embodiment of the present disclosure, which corresponds to Fig. 1. Fig. 12 is a schematic end view of a portion of a modified pressure sensor element according to the third embodiment of the present disclosure, which corresponds to Fig. 1. As shown in Figs. 11 and 12, an insulating film 50 may be provided in the third embodiment as in the modified pressure sensor element according to the first embodiment shown in Figs. 6 and 7.

[0088] 11, the insulating film 50 is provided on the surfaces of the diaphragm portion 31 and the inner layer 60 that face the opening 20A. For example, in the configuration shown in Fig. 12, the insulating film 50 is provided on the surfaces of the base-side conductive layer 22 and the base 10 that face the opening 20A.

[0089] According to the third embodiment, in addition to adjusting the gap between the electrode 30 and the base 10 or the base-side conductive layer 22 by changing the thickness (length in the stacking direction 101) of the intermediate layer 20, the gap can also be adjusted by changing the thickness of the inner layer 60. This increases the degree of freedom in adjusting the gap.

[0090] Forming a layer that is too thick is more difficult than forming a layer with an appropriate thickness. According to the third embodiment, the inner layer 60 includes an electrode-side conductive layer 61 and an electrode-side insulating layer 62. That is, the inner layer 60 has two layers. Therefore, the inner layer 60 can be made thick as a whole without excessively increasing the thickness of each of the electrode-side conductive layer 61 and the electrode-side insulating layer 62. Therefore, according to the third embodiment, it is easier to make the inner layer 60 thick than in a configuration in which the inner layer 60 is a single layer.

[0091] In the above-described embodiments, examples have been described in which the opening 20A has the through hole 20B and the pair of recesses 20C and 20D, but the opening 20A may have only the through hole 20B. In this case, the side surface of the through hole 20B is defined by the intermediate layer 20 (the first base-side insulating layer 21, the base-side conductive layer 22, and the second base-side insulating layer 23). The protrusion 40 is provided on the base 10 (more specifically, on the surface of the base 10 facing the opening 20A) instead of being provided on the base-side conductive layer 22, and protrudes into the opening 20A.

[0092] In a pressure sensor element in which the opening 20A has only the through-hole 20B, a capacitor is formed by the diaphragm portion 31 and the base 10. The diaphragm portion 31 bends as a single membrane when not in contact with the protrusion 40. The diaphragm portion 31 bends as multiple membranes when in contact with the protrusion 40.

[0093] The opening 20A may have only one recess without the through hole 20B. In this case, the bottom surface of the recess corresponds to the bottom surface of the opening 20A. The protrusion 40 is provided on the bottom surface of the recess and protrudes into the opening 20A (the recess).

[0094] The bottom surface of the one recess may be any layer of the intermediate layer 20. For example, if the bottom surface of the one recess is the conductive base-side conductive layer 22, the diaphragm portion 31 and the base-side conductive layer 22 form a capacitor.

[0095] In the above-described embodiments, examples have been described in which the intermediate layer 20 includes the first base-side insulating layer 21, the base-side conductive layer 22, and the second base-side insulating layer 23. However, the configuration of the intermediate layer 20 is not limited to the configuration described above. For example, the intermediate layer 20 may be configured as a single insulating layer. In this case, for example, a capacitor is formed by the diaphragm portion 31 and the base 10.

[0096] The pressure sensor element described above can also be expressed as follows.

[0097] (1) A pressure sensor element according to one aspect of the present disclosure comprises: a conductive base; an intermediate layer laminated on the base and having an opening; and a conductive electrode laminated on the intermediate layer on the side opposite the base, the intermediate layer having a diaphragm portion overlapping the opening when viewed from the stacking direction, the conductive electrode being electrically insulated from the base, wherein the opening comprises: a through hole penetrating the intermediate layer in the stacking direction; and a pair of recesses recessed in the stacking direction, the through hole being provided on either side of the through hole and continuous with the through hole on the surface of the intermediate layer on the electrode side, the pair of recesses being recessed in the stacking direction; the intermediate layer comprises a base-side conductive layer that forms bottom surfaces of the pair of recesses and is electrically connected to the base; the diaphragm portion faces the base-side conductive layer across the pair of recesses in the stacking direction and faces the base across the through hole in the stacking direction; and further comprises protrusions provided on a surface of at least one of the base-side conductive layer and the diaphragm portion on the pair of recesses side, protruding into the pair of recesses, The convex portion has a pair of opposing portions that face each other with a gap in the width direction, which is the direction in which the pair of recesses sandwich the through hole, and the pair of opposing portions are positioned so as to overlap the ends of the pair of recesses on the through hole side when viewed from the stacking direction.

[0098] (2) A pressure sensor element according to one aspect of the present disclosure comprises: a conductive base; an intermediate layer stacked on the base and having an opening; a conductive electrode stacked on the intermediate layer on the side opposite the base, the conductive electrode having a diaphragm portion that overlaps the opening when viewed from the stacking direction, and the conductive electrode being electrically insulated from the base; and a convex portion provided on a surface of at least one of the base and the diaphragm portion on the opening side and protruding into the opening, the convex portions each extending along an extension direction on the surface on the opening side and comprising a pair of opposing portions that face each other with a gap in between in a width direction that intersects with the extension direction, and the region of the diaphragm portion whose width direction position is between the pair of opposing portions is rectangular when viewed from the stacking direction.

[0099] (3) In the pressure sensor element of (1), the pair of opposing portions may extend in an extension direction intersecting the width direction, and when viewed from the stacking direction, the region of the diaphragm portion whose position in the width direction is between the pair of opposing portions may be rectangular.

[0100] (4) In the pressure sensor element of (2) or (3), the length of each of the pair of opposing portions along the extension direction may be longer than the distance between the pair of opposing portions in the width direction.

[0101] (5) In the pressure sensor element according to any one of (2) to (4), at least one of the pair of opposing portions may include a plurality of protrusions arranged at intervals along the extending direction.

[0102] (6) Any one of the pressure sensor elements (1) to (5) may further include an inner layer laminated on a surface of the diaphragm portion between the pair of opposing portions in the width direction and on the opening side, and the inner layer may include an electrode-side conductive layer having conductivity electrically connected to the electrode.

[0103] (7) In the pressure sensor element of (6), the inner layer may further include an electrode-side insulating layer having insulating properties and positioned between the electrode-side conductive layer and the diaphragm portion.

[0104] (8) In the pressure sensor element of any one of (1) to (7), the spacing between the pair of opposing portions in the width direction may be longer than the shortest distance in the width direction between each of the pair of opposing portions and an outer edge of the opening.

[0105] (9) In the pressure sensor element of any one of (1) to (8), the convex portion may be made of a conductive material, and the pressure sensor element may further include an insulating film having insulating properties that covers at least one of the convex portion and a portion that comes into contact with the convex portion when the diaphragm portion is deflected.

[0106] Any of the various embodiments described above may be combined appropriately to achieve the effects of each of them.

[0107] In addition, the various embodiments may have only some of the features of the pressure sensor element of the present disclosure.

[0108] An example is described below.

[0109] The pressure sensor element 1 according to the first embodiment has a first feature and a second feature. The first feature is that the opening 20A has a through hole 20B with a depth D1 and a pair of recesses 20C and 20D with a depth D2 shallower than the depth D1. The second feature is that the area surrounded by the four imaginary straight lines LN1, LN2, LN3, and LN4 in a plan view is rectangular.

[0110] The pressure sensor element may have the first characteristic point but not the second characteristic point. The pressure sensor element of (1) above may include a pressure sensor element that has the first characteristic point but not the second characteristic point.

[0111] Conversely, the pressure sensor element may have the second characteristic point but not the first characteristic point. The pressure sensor element of (2) above may include a pressure sensor element that has the second characteristic point but not the first characteristic point.

[0112] The pressure sensor element (3) is a pressure sensor element having both the first and second characteristic points.

[0113] While the present invention has been fully described in connection with preferred embodiments, with appropriate reference to the drawings, various changes and modifications will become apparent to those skilled in the art, and it is to be understood that such changes and modifications are included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

[0114] REFERENCE SIGNS LIST 1 Pressure sensor element 10 Base 20 Intermediate layer 20A Opening 20B Through hole 20C Recess 20Ca Bottom surface 20D Recess 20Da Bottom surface 20E Upper surface (surface of intermediate layer on electrode side) 22 Base-side conductive layer 30 Electrode 31 Diaphragm portion 40 Convex portion 41 Opposing portion 41A One end portion 41B Other end portion 42 Opposing portion 42A One end portion 42B Other end portion 43 Protrusion 50 Insulating film 60 Inner layer 61 Electrode-side conductive layer 62 Electrode-side insulating layer 101 Stacking direction 102 Short side direction (width direction) 103 Longitudinal direction (extension direction) LN1 Imaginary straight line LN2 Imaginary straight line LN3 Imaginary straight line LN4 Imaginary straight line

Claims

1. A conductive electrode comprising: a conductive base; an intermediate layer laminated on the base and having an opening; and a conductive electrode laminated on the side of the intermediate layer opposite the base, the intermediate layer having a diaphragm portion overlapping the opening when viewed from the stacking direction, the conductive electrode being electrically insulated from the base, the opening having a through hole penetrating the intermediate layer in the stacking direction, and a pair of recesses recessed in the stacking direction, the through hole being provided on a surface of the intermediate layer on the electrode side, the through hole being continuous with the through hole and sandwiching the through hole therebetween, the intermediate layer comprising a base-side conductive layer constituting bottom surfaces of the pair of recesses and electrically connected to the base, the diaphragm portion facing the base-side conductive layer across the pair of recesses and facing the base in the stacking direction via the through hole, and further comprising protrusions provided on a surface of at least one of the base-side conductive layer and the diaphragm portion on the pair of recesses side and protruding into the pair of recesses, The convex portion has a pair of opposing portions that face each other with a gap in the width direction, which is the direction in which the pair of recesses sandwich the through hole, and the pair of opposing portions are positioned to overlap with the ends of the pair of recesses on the through hole side when viewed from the stacking direction.

2. A pressure sensor element comprising: a conductive base; an intermediate layer laminated on the base and having an opening; a conductive electrode laminated on the side of the intermediate layer opposite the base, having a diaphragm portion overlapping the opening when viewed from the stacking direction, and being electrically insulated from the base; and a convex portion provided on a surface on the opening side of at least one of the base and the diaphragm portion and protruding into the opening, wherein the convex portions each extend along an extension direction on the surface on the opening side and have a pair of opposing portions opposed to each other with a gap in between in a width direction intersecting the extension direction, and wherein a region of the diaphragm portion whose position in the width direction is between the pair of opposing portions is rectangular when viewed from the stacking direction.

3. A pressure sensor element as described in claim 1, wherein the pair of opposing portions extend in an extension direction intersecting the width direction, and when viewed from the stacking direction, the region of the diaphragm portion whose position in the width direction is between the pair of opposing portions is rectangular.

4. The pressure sensor element according to claim 2 or 3, wherein the length of each of the pair of opposing portions along the extension direction is longer than the distance between the pair of opposing portions in the width direction.

5. A pressure sensor element according to any one of claims 2 to 4, wherein at least one of the pair of opposing portions has a plurality of protrusions arranged at intervals along the extension direction.

6. A pressure sensor element as described in any one of claims 1 to 5, further comprising an inner layer laminated on a surface of the diaphragm portion between the pair of opposing portions in the width direction and on the opening side, the inner layer comprising an electrode-side conductive layer having conductivity electrically connected to the electrode.

7. The pressure sensor element according to claim 6, wherein said inner layer further comprises an electrode-side insulating layer having insulating properties and located between said electrode-side conductive layer and said diaphragm portion.

8. A pressure sensor element according to any one of claims 1 to 7, wherein the distance between the pair of opposing portions in the width direction is longer than the shortest distance in the width direction between each of the pair of opposing portions and the outer edge of the opening.

9. A pressure sensor element as described in any one of claims 1 to 8, wherein the convex portion is made of a conductive material, and further comprising an insulating film having insulating properties covering at least one of the convex portion and the portion that comes into contact with the convex portion when the diaphragm portion is deflected.

Images