Pressure sensor element

Abstract

To provide a pressure sensor element that can suppress the decrease in detection sensitivity over a wide range of pressures. [Solution] The pressure sensor element comprises a conductive base, an intermediate layer laminated on the base and having an opening, and an electrode laminated on the intermediate layer and having a diaphragm portion facing the opening. The opening has a through hole penetrating the intermediate layer in the lamination direction, and a pair of recesses provided on the upper surface of the intermediate layer so as to sandwich the through hole. The intermediate layer comprises a base-side conductive layer that forms the bottom surface of the pair of recesses. The diaphragm portion faces the base-side conductive layer via the pair of recesses and faces the base via the through hole, and is electrically insulated from the base-side conductive layer and the base. The pressure sensor element further comprises a pair of opposing portions protruding from at least one of the base-side conductive layer and the diaphragm portion into the pair of recesses. The pair of opposing portions are positioned to overlap the ends of the pair of recesses on the through hole side when viewed from the lamination direction.

Description

Technical Field

[0001] The present disclosure relates to a pressure sensor element that detects pressure.

Background Art

[0002] Pressure sensor elements capable of detecting capacitance changes over a wide range from low pressure to high pressure are known (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 that are insulated from each other by a space. The second electrode deflects when pressure acts thereon. A change in capacitance between the first electrode and the second electrode is detected based on a change in the distance between the first electrode and the second electrode at this time. The pressure applied to the second electrode is measured based on the detected change in capacitance.

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

[0005] The pressure sensor element disclosed in Patent Document 2 includes a fixed electrode and a diaphragm that face each other with a gap interposed therebetween. The diaphragm deflects when pressure acts thereon. A change in capacitance between the fixed electrode and the diaphragm is detected based on a change in the gap between the fixed electrode and the diaphragm at this time. The pressure applied to the diaphragm is measured based on the detected change in capacitance.

[0006] In the pressure sensor element disclosed in Patent Document 2, a protrusion is provided 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 is applied to 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 allows for the detection of a change in capacitance between the fixed electrode and the diaphragm. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 2018-521317 [Patent Document 2] Japanese Patent Publication No. 2005-321257 [Overview of the project] [Problems that the invention aims to solve]

[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 sensitivity to detecting capacitance changes 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 possibility of the second electrode coming into contact with the first electrode increases when the pressure acting on the second electrode is high. When the second electrode comes into contact with the first electrode, capacitance changes 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 periphery of the fixed electrode. Consequently, the sensitivity for detecting the change in capacitance between the fixed electrode and the diaphragm is reduced 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 at both the center and the periphery of the fixed electrode.

[0010] The present disclosure aims to provide a pressure sensor element that can suppress a decrease in the detection sensitivity of capacity changes under a wide range of pressures, from low to high. [Means for solving the problem]

[0011] A pressure sensor element according to one aspect of this disclosure is A conductive base, An intermediate layer having an opening is laminated on the base, The intermediate layer is laminated on the side opposite to the base, and has a diaphragm portion that overlaps the opening when viewed from the lamination direction, and comprises a conductive electrode that is electrically insulated from the base, The aforementioned opening is The intermediate layer has through holes that penetrate in the stacking direction, The intermediate layer has a pair of recesses on the electrode side surface that sandwich the through hole and are continuous with respect to the through hole, and are recessed in the stacking direction, The intermediate layer comprises a base-side conductive layer that forms the bottom surface of the pair of recesses and is electrically connected to the base. The diaphragm portion faces the base-side conductive layer in the stacking direction via the pair of recesses, and faces the base in the stacking direction via the through-hole, The base-side conductive layer and the diaphragm portion are further provided with a convex portion that protrudes into the pair of recesses on at least one of the surfaces facing the pair of recesses, The aforementioned protrusion comprises a pair of opposing portions that are spaced apart from each other in the width direction, which is the direction in which the pair of recesses straddle the through hole. The pair of opposing portions are positioned to overlap the ends of the pair of recesses on the through-hole side when viewed from the stacking direction. [Effects of the Invention]

[0012] According to this 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. [Brief explanation of the drawing]

[0013] [Figure 1] Schematic end view of the pressure sensor element according to the first embodiment of the present disclosure [Figure 2] Schematic plan view of the portion excluding the electrodes in the pressure sensor element according to the first embodiment of the present disclosure [Figure 3] Schematic end view of the pressure sensor element according to the first embodiment of the present disclosure when a low pressure acts on the electrodes [Figure 4] Schematic end view of the pressure sensor element according to the first embodiment of the present disclosure when a high pressure acts on the electrodes [Figure 5] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure [Figure 6] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure [Figure 7] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the first embodiment of the present disclosure [Figure 8] Schematic plan view of the portion excluding the electrodes in the pressure sensor element according to the second embodiment of the present disclosure [Figure 9] Schematic end view of the portion corresponding to Fig. 1 in the pressure sensor element according to the third embodiment of the present disclosure [Figure 10] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure [Figure 11] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure [Figure 12] Schematic end view of the portion corresponding to Fig. 1 in the modified example of the pressure sensor element according to the third embodiment of the present disclosure [Modes for Carrying Out the Invention]

[0014] An example of this disclosure is described below with reference to the accompanying drawings. The following description is essentially illustrative and is not intended to limit this disclosure, its applications, or its uses. The drawings are schematic, and the proportions of the dimensions, etc., do not necessarily correspond to reality. In addition, the following description may use terms that indicate a specific direction or position (for example, terms including "up," "down," "right," "left," "front," and "back") as needed. However, the use of terms that indicate a specific direction or position is for the purpose of facilitating the understanding of this disclosure with reference to the drawings, and the meaning of those terms does not limit the technical scope of this disclosure.

[0015] <First Embodiment> Figure 1 is a schematic end view of a pressure sensor element according to the first embodiment of this disclosure. Figure 2 is a schematic plan view of the portion of the pressure sensor element according to the first embodiment of this disclosure excluding the electrodes. Figure 1, as well as Figures 3-7 and 9-12 described later, are schematic end views of the portion corresponding to cross-section AA in Figure 2.

[0016] The pressure sensor element 1 shown in Figures 1 and 2 is for detecting pressure. The pressure sensor element 1 is a capacitive 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, mobile devices such as automobiles, or consumer electronics such as smartphones and smartwatches.

[0017] The pressure sensor element 1 is rectangular in shape. However, the shape of the pressure sensor element 1 is not limited to a rectangular shape (a shape that is a rectangle when viewed from the stacking direction 101). For example, the pressure sensor element 1 may be a polygon other than a rectangle when viewed from the stacking direction 101, or it may be cylindrical.

[0018] As shown in Figures 1 and 2, the pressure sensor element 1 comprises 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 side of the intermediate layer 20 opposite to the base 10. The protrusion 40 is provided on the intermediate layer 20.

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

[0020] In the first embodiment, the intermediate layer 20 is rectangular in plan view. Similar to the base 10, the intermediate layer 20 is not limited to being rectangular in plan view. The intermediate layer 20 comprises a first base-side insulating layer 21 having insulating properties, a base-side conductive layer 22 having conductive properties, 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 side of the first base-side insulating layer 21 opposite to the base 10. The second base-side insulating layer 23 is laminated on the side of the base-side conductive layer 22 opposite to 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 formed of silicon dioxide (SiO2), and the base-side conductive layer 22 is formed of polysilicon (Poly-Si). The materials forming the first base-side insulating layer 21 and the second base-side insulating layer 23 are 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. This provides electrical insulation between the fixed electrode 221 and the surrounding conductive layer 222.

[0024] As shown in Figure 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 lamination direction 101.

[0025] As shown in Figures 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 on the 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 is on the electrode 30 side.

[0026] The through-hole 20B extends in the longitudinal direction 103. The longitudinal direction 103 is parallel to the longer side of the rectangle of the pressure sensor element 1 in a plan view. The longitudinal direction 103 is perpendicular to the stacking direction 101. The through-hole 20B communicates with the gap 22A at both ends of the longitudinal direction 103. The bottom surface of the through-hole 20B is formed by the top surface of the base 10. The side surface of the through-hole 20B is formed by the side surface 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 and 20D penetrate the second base-side insulating layer 23. On the other hand, the pair of recesses 20C and 20D are not provided in the base-side conductive layer 22 and the first base-side insulating layer 21. The pair of recesses 20C and 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 on the side of the pair of recesses 20C and 20D) constitutes the bottom surface 20Ca of recess 20C and the bottom surface 20Da of recess 20D. In detail, the fixed electrode 221 and a part of the surrounding conductive layer 222 constitute the bottom surfaces 20Ca and 20Da. The side surface of the second base-side insulating layer 23 constitutes the side surface of the pair of recesses 20C and 20D. The depth D2 of the pair of recesses 20C and 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 and 20D are spaced apart from each other and face each other in the short-side direction 102. The short-side direction 102 is the direction parallel to the short side of the rectangle of the pressure sensor element 1 in a plan view. The short-side direction 102 is perpendicular to the stacking direction 101 and the long-side direction 103. The short-side direction 102 is an example of the width direction. Note that the short-side direction 102 and the long-side direction 103 do not necessarily have to be perpendicular to each other; they only need to intersect each other.

[0029] A through hole 20B is provided between a pair of recesses 20C and 20D. In other words, the pair of recesses 20C and 20D sandwich the through hole 20B in the shorter direction 102. Each of the pair of recesses 20C and 20D is in communication with the through hole 20B. In other words, the pair of recesses 20C and 20D are provided continuously with respect to the through hole 20B.

[0030] As shown in Figure 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 is rectangular in plan view. Similar to the base 10 described above, the electrode 30 is not limited to being rectangular in 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). The material used to form the electrode 30 is not limited to silicon.

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

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

[0034] As shown in Figures 1 and 2, the protrusions 40 are provided on the upper surface of the fixed electrode 221 of the base-side conductive layer 22, that is, on the bottom surfaces 20Ca and 20D of the pair of recesses 20C and 20D, respectively. The protrusions 40 project upward from the bottom surfaces 20Ca and 20D. In other words, the protrusions 40 project from the bottom surfaces 20Ca and 20D into the pair of recesses 20C and 20D.

[0035] In the first embodiment, the protrusion 40 is insulating. In the first embodiment, the protrusion 40 is formed of silicon dioxide (SiO2) or silicon nitride (SiN). The material constituting the protrusion 40 is not limited to silicon dioxide (SiO2) or silicon nitride (SiN).

[0036] The protrusion 40 comprises a pair of opposing portions 41 and 42. In the first embodiment, the protrusion 40 is composed of 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 and 42 are provided at the ends of the bottom surfaces 20Ca and 20D on the through-hole 20B side in the shorter direction 102. In other words, the pair of opposing portions 41 and 42 are located in a position that overlaps with the ends of the pair of recesses 20C and 20D on the through-hole 20B side in a plan view.

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

[0039] The pair of opposing portions 41 and 42 are spaced apart from each other in the direction in which the pair of recesses 20C and 20D sandwich the through hole 20B. In the first embodiment, the direction in which the pair of recesses 20C and 20D sandwich the through hole 20B is the short-side direction 102.

[0040] As shown in Figure 2, in a plan view, the region where the diaphragm portion 31 is located at a position 102 in the shorter direction between the pair of opposing portions 41 and 42 is rectangular. In other words, in a plan view, the region enclosed by the four virtual lines LN1, LN2, LN3, and LN4 shown by dashed lines in Figure 2 is rectangular.

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

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

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

[0044] Figure 3 is a schematic end view of the pressure sensor element according to the first embodiment of this disclosure when low pressure is acting on the electrode. Figure 4 is a schematic end view of the pressure sensor element according to the first embodiment of this disclosure when high pressure is acting on the electrode.

[0045] The operation of the diaphragm portion 31 of the electrode 30 when pressure is applied to one main surface 30A of the electrode 30, and the detection of capacitance corresponding to this operation, will be explained below with reference to Figures 3 and 4.

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

[0047] Each of the base 10 and the electrode 30, including the diaphragm portion 31, can be electrically connected to external devices or elements via terminals (not shown). This allows external devices or elements to measure the pressure applied to one main surface 30A of the electrode 30 based on the sum of the capacitances of the three capacitors C1, C2, and C3.

[0048] When pressure is applied to 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 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 and 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 between the diaphragm portion 31 and the base-side conductive layer 22 in the stacking direction 101, and the distance between the diaphragm portion 31 and the base 10 in the stacking direction 101, both decrease. Due to these changes in distance, the capacitances of capacitors C1, C2, and C3 increase. Based on the changes in the capacitances of capacitors C1, C2, and C3, the current flowing through external devices and elements, and the voltage applied to external devices and elements, 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 an even higher pressure than described above acts on 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 and 42. When the diaphragm portion 31, in contact with the pair of opposing portions 41 and 42, further deflects downward toward the base 10, as shown in Figure 4, the portion of the diaphragm portion 31 corresponding to capacitor C1, the portion corresponding to capacitor C2, and the portion corresponding to capacitor C3 each 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 one membrane (see Figure 3). Therefore, in the state shown in Figure 4, the diaphragm portion 31 is less likely to deflect than in the state shown in Figure 3. As a result, the upper limit of the pressure that can be measured by the pressure sensor element 1 can be increased.

[0051] According to the first embodiment, when the amount of deflection of the diaphragm portion 31 is small, that is, when low pressure is acting on the diaphragm portion 31, the diaphragm portion 31 does not contact the pair of opposing portions 41 and 42. At this time, the low pressure acting on the diaphragm portion 31 can be measured with high sensitivity based on the capacitance change between the diaphragm portion 31 and the base-side conductive layer 22, and the capacitance change between the diaphragm portion 31 and the base 10. When the amount of deflection of the diaphragm portion 31 is large, that is, when high pressure is acting on the diaphragm portion 31, the diaphragm portion 31 contacts the pair of opposing portions 41 and 42. At this time, the diaphragm portion 31 functions as a separate membrane between the pair of opposing portions 41 and 42 and on both outer sides of the pair of opposing portions 41 and 42. In this case, the rigidity of each of these separate membranes increases. Therefore, the 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, a through hole 20B is located between a pair of opposing parts 41 and 42, and a pair of recesses 20C and 20D are located on both outer sides of the pair of opposing parts 41 and 42. Here, the depth D1 of the through hole 20B is deeper than the depth D2 of the pair of recesses 20C and 20D. Therefore, when high pressure is acting on the diaphragm part 31, the possibility of the diaphragm part 31 bending between the pair of opposing parts 41 and 42 and coming into contact with the base 10 can be reduced.

[0053] When the diaphragm is square when viewed from the stacking direction 101, the displacement of the diaphragm is greatest at a single point in the center of the diaphragm, and decreases as you move away from the center. In contrast, in the first embodiment, when viewed from the stacking direction 101, the portion of the diaphragm 31 enclosed by the four virtual lines LN1, LN2, LN3, and LN4 is rectangular. In the rectangular diaphragm 31 as viewed from the stacking direction 101, when pressure is applied to the diaphragm 31, the displacement of the diaphragm 31 is greatest at the center along the shorter side of the rectangle, and decreases as you move away from the center. The portion with the greatest displacement extends along the longer side of the rectangle. In other words, in the rectangular diaphragm 31 as viewed from the stacking direction 101, the portion with the greatest displacement of the diaphragm 31 is a line, not a point. In other words, in a rectangular diaphragm portion 31 viewed from the stacking direction 101, the area over which the displacement of the diaphragm portion is constant can be larger than in a square diaphragm portion viewed from the stacking direction 101. This makes it possible to detect with high accuracy the change in capacitance due to deflection in the portion of the diaphragm portion 31 enclosed by the four virtual lines LN1, LN2, LN3, and LN4.

[0054] For example, if the diaphragm is circular, the only way to adjust the size of the diaphragm is to change the diameter of the circle. According to the first embodiment, the portion of the diaphragm 31 enclosed by the four virtual lines LN1, LN2, LN3, and LN4 is rectangular. In this case, there are two ways to adjust the size of the diaphragm 31: changing the length of the longer side of the rectangle and changing the length of the shorter side of the rectangle. Therefore, in the first embodiment, the size and shape of the diaphragm can be freely changed to match the shape of the pressure sensor element, compared to a configuration where the diaphragm is circular.

[0055] According to the first embodiment, the rectangle enclosed by the four virtual lines LN1, LN2, LN3, and LN4 can be made into a rectangle whose longer side is the extension direction (longitudinal direction 103) of each of the pair of opposing parts 41 and 42. This allows the pair of opposing parts 41 and 42 to be made longer in the extension direction, thereby increasing the contact area when the diaphragm part 31 is in contact with the pair of opposing parts 41 and 42. This increases the stability of the diaphragm part 31 when it is in contact with the pair of opposing parts 41 and 42.

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

[0057] Figure 5 is a schematic end view of a modified pressure sensor element according to the first embodiment of the present disclosure, showing a portion corresponding to Figure 1. As shown in Figure 5, the protrusion 40 may be provided on the diaphragm portion 31.

[0058] The protrusion 40 is provided on the surface of the diaphragm portion 31 facing the pair of recesses 20C and 20D (in other words, the lower surface of the diaphragm portion 31). The protrusion 40 protrudes downward from the diaphragm portion 31. In other words, the protrusion 40 protrudes from the diaphragm portion 31 into the pair of recesses 20C and 20D.

[0059] The protrusion 40 shown in Figure 5, like the protrusions 40 shown in Figures 1 and 2, also comprises a pair of opposing portions 41 and 42. Each of the pair of opposing portions 41 and 42 extends along the longitudinal direction 103. The pair of opposing portions 41 and 42 are spaced apart from each other in the short direction 102. In a plan view, the pair of opposing portions 41 and 42 are positioned to overlap the ends of the through-holes 20B in the pair of recesses 20C and 20D. In other words, the position of the pair of opposing portions 41 and 42 in the short direction 102 shown in Figure 5 is the same as the position of the pair of opposing portions 41 and 42 in the short direction 102 shown in Figures 1 and 2.

[0060] The protrusion 40 may be provided on both the base-side conductive layer 22 and the diaphragm portion 31. In other words, the protrusion 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 parts 41 and 42 do not have to extend in a straight line. For example, the pair of opposing parts 41 and 42 may be curved or extend in a wavy manner.

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

[0063] The pair of opposing portions 41 and 42 may have shapes that extend in directions other than the longitudinal direction 103, for example, shapes that extend in the short direction 102.

[0064] The pair of opposing portions 41 and 42 do not necessarily have to be linearly extending in one direction (the longitudinal direction 103 in the first embodiment).

[0065] The protrusion 40 does not have to consist only of the pair of opposing parts 41 and 42. For example, the protrusion 40 may have a portion connecting one end 41A and 42A of the pair of opposing parts 41 and 42. In this case, the protrusion 40 will be roughly U-shaped in plan view. Alternatively, for example, the protrusion 40 may have a portion connecting one end 41A and 42A of the pair of opposing parts 41 and 42, and a portion connecting the other end 41B and 42B of the pair of opposing parts 41 and 42. In this case, the protrusion 40 will be a rectangular ring in plan view.

[0066] Figure 6 is a schematic end view of the portion corresponding to Figure 1 in a modified example of the pressure sensor element according to the first embodiment of this disclosure. Figure 7 is a schematic end view of the portion corresponding to Figure 1 in a modified example of the pressure sensor element according to the first embodiment of this disclosure.

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

[0068] If the protrusion 40 is conductive, there is a risk that the diaphragm portion 31, which is bent by the applied pressure, and the base-side conductive layer 22 may be electrically connected via the protrusion 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 in which the protrusion 40 is conductive is further provided with an insulating film 50.

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

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

[0071] The insulating film 50 only needs to be provided in a position that prevents electrical connection between the diaphragm portion 31 and the base-side conductive layer 22. For example, in the configuration shown in Figure 6, the insulating film 50 is provided on the entire surface of the diaphragm portion 31 facing the opening 20A. However, the insulating film 50 may be provided only on the portion of the surface facing the convex portion 40 and the lamination direction 101. For example, in the configuration shown in Figure 7, the insulating film 50 is provided on the base-side conductive layer 22 and on the surface of the base 10 facing 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 protrusion 40.

[0073] As described above, the insulating film 50 covers at least one of the portion of the diaphragm 31 that contacts the protrusion 40 when the diaphragm 31 bends, and the protrusion 40 itself. In the configuration with the insulating film 50, the insulating film 50 is located between the diaphragm 31 and the protrusion 40, or between the base-side conductive layer 22 and the protrusion 40. Therefore, it is prevented that the diaphragm 31, which is bent by the pressure applied, and the base-side conductive layer 22 are electrically connected via the protrusion 40.

[0074] According to the configuration shown in Figures 6 and 7, since the protrusion 40 is made of a conductive material, the protrusion 40 can be formed integrally with another conductive material, such as the base-side conductive layer 22. This reduces the manufacturing steps for the pressure sensor element 1.

[0075] On the other hand, if the protrusion 40 is made of a conductive material, the diaphragm portion 31 may bend, causing the diaphragm portion 31 to be electrically connected to the base 10 or the base-side conductive layer 22 via the protrusion 40. Therefore, with the configuration shown in Figures 6 and 7, the insulating film 50 can prevent the aforementioned electrical connection.

[0076] <Second Embodiment> Figure 8 is a schematic plan view of the portion of the pressure sensor element according to the second embodiment of this disclosure, excluding the electrodes. The difference between the pressure sensor element 1A according to the second embodiment and the pressure sensor element 1 according to the first embodiment is that the pair of opposing portions 41 and 42 of the convex portion 40 are provided with a plurality of protrusions 43. The differences from the first embodiment will be described below. Parts common to the pressure sensor element 1 according to the first embodiment are given the same reference numerals, and their descriptions will be omitted in principle, and will be described as necessary.

[0077] As shown in Figure 8, the pair of opposing portions 41 and 42 are provided with a plurality of protrusions 43. Each of the plurality of protrusions 43 projects in the stacking direction 101 from the fixed electrode 221 of the base-side conductive layer 22 toward the pair of recesses 20C and 20D. Each of the plurality of protrusions 43 is spaced apart along the longitudinal direction 103. As a result, the plurality of protrusions 43 as a whole are linear along the longitudinal direction 103.

[0078] In Figure 8, both of the pair of opposing parts 41 and 42 are provided with multiple protrusions 43, but only one of the pair of opposing parts 41 and 42 may be provided with multiple protrusions 43. In Figure 8, each of the pair of opposing parts 41 and 42 is composed of multiple protrusions 43 throughout, but it may be composed of multiple protrusions 43 only in part, and the remaining part may be linear.

[0079] According to the second embodiment, the pair of opposing parts 41 and 42 are provided with a plurality of protrusions 43 that are spaced apart from each other. The plurality of protrusions 43 come into contact with the bent diaphragm part 31. Therefore, compared to a configuration in which each of the pair of opposing parts 41 and 42 extends linearly, the diaphragm part 31 that is in contact with them is more easily bent. As a result, the accuracy of detecting changes in capacitance due to the bending of the diaphragm part 31 can be improved.

[0080] <Third Embodiment> Figure 9 is a schematic end view of the portion of the pressure sensor element corresponding to Figure 1 in the third embodiment of this disclosure. The difference between the pressure sensor element 1B of the third embodiment and the pressure sensor element 1 of the first embodiment is that it further comprises an inner layer 60. The differences from the first embodiment will be described below. Common parts with the pressure sensor element 1 of the first embodiment are denoted by the same reference numerals, and their descriptions will be omitted in principle, and will be described as necessary.

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

[0082] The inner layer 60 comprises an electrode-side conductive layer 61 having conductivity and an electrode-side insulating layer 62 having insulation properties. The electrode-side insulating layer 62 is laminated on the diaphragm portion 31. The electrode-side conductive layer 61 is laminated on the side of the electrode-side insulating layer 62 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 made of polysilicon, and the electrode-side insulating layer 62 is made 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 in the same position as the second base-side insulating layer 23 of the intermediate layer 20 in the lamination direction 101. This allows the lamination process of the electrode-side insulating layer 62 and the second base-side insulating layer 23 to be the same 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 it may have a different thickness from the second base-side insulating layer 23.

[0085] The electrode-side conductive layer 61 is located in the same position as the base-side conductive layer 22 of the intermediate layer 20 in the stacking direction 101. This allows the stacking process for the electrode-side conductive layer 61 and the base-side conductive layer 22 to be the same 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 it may also have the same thickness as the base-side conductive layer 22.

[0086] Figure 10 is a schematic end view of a modified pressure sensor element according to the third embodiment of this disclosure, showing the portion corresponding to Figure 1. As shown in Figure 10, in the third embodiment, as with the modified example shown in Figure 5 of the first embodiment, the protrusion 40 may be provided on the diaphragm portion 31.

[0087] Figure 11 is a schematic end view of the portion corresponding to Figure 1 in a modified example of the pressure sensor element according to the third embodiment of this disclosure. Figure 12 is a schematic end view of the portion corresponding to Figure 1 in a modified example of the pressure sensor element according to the third embodiment of this disclosure. As shown in Figures 11 and 12, in the third embodiment as well, an insulating film 50 may be provided, similar to the modified examples shown in Figures 6 and 7 of the first embodiment.

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

[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 of the intermediate layer 20 (length in the stacking direction 101), 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 of appropriate thickness. According to the third embodiment, the inner layer 60 comprises an electrode-side conductive layer 61 and an electrode-side insulating layer 62. In other words, the inner layer 60 has two layers. Therefore, the inner layer 60 can be made thicker overall without making the thickness of each of the electrode-side conductive layer 61 and the electrode-side insulating layer 62 extremely thick. Thus, according to the third embodiment, it is easier to make the inner layer 60 thicker than in a configuration where the inner layer 60 is a single layer.

[0091] In the embodiments described above, an example was described in which the opening 20A has a through hole 20B and a pair of recesses 20C and 20D, but the opening 20A may have only a through hole 20B. In this case, the side surface of the through hole 20B is partitioned by the intermediate layer 20 (first base-side insulating layer 21, base-side conductive layer 22, and 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 on the base-side conductive layer 22, and protrudes into the opening 20A.

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

[0093] The opening 20A may have only one recess and not a through hole 20B. In this case, the bottom surface of the single recess corresponds to the bottom surface of the opening 20A. The protrusion 40 is provided on the bottom surface of the single recess and protrudes into the opening 20A (the single recess).

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

[0095] In the embodiments described above, an example was described in which the intermediate layer 20 comprises a first base-side insulating layer 21, a base-side conductive layer 22, and a 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 consist of 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 is A conductive base, An intermediate layer having an opening is laminated on the base, The intermediate layer is laminated on the side opposite to the base, and has a diaphragm portion that overlaps with the opening when viewed from the lamination direction, and comprises a conductive electrode that is electrically insulated from the base, The aforementioned opening is The intermediate layer has through holes that penetrate in the stacking direction, The intermediate layer has a pair of recesses on the electrode side surface that are provided so as to sandwich the through hole and are continuous with respect to the through hole, and are recessed in the stacking direction, The intermediate layer comprises a base-side conductive layer that forms the bottom surface of the pair of recesses and is electrically connected to the base, The diaphragm portion faces the base-side conductive layer in the stacking direction via the pair of recesses, and faces the base in the stacking direction via the through-hole, The base-side conductive layer and the diaphragm portion are further provided with a convex portion that protrudes into the pair of recesses on at least one of the surfaces facing the pair of recesses, The aforementioned protrusion comprises a pair of opposing portions that are spaced apart from each other in the width direction, which is the direction in which the pair of recesses straddle the through hole. The pair of opposing portions are positioned 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 is A conductive base, An intermediate layer having an opening is laminated on the base, A conductive electrode is laminated on the side of the intermediate layer opposite to the base, has a diaphragm portion that overlaps with the opening when viewed from the lamination direction, and is electrically insulated from the base. The base and the diaphragm portion are provided on the surface facing the opening and have a protrusion that extends toward the opening, Each of the protrusions extends along the extension direction on the surface facing the opening, and comprises a pair of opposing portions that are spaced apart from each other in the width direction intersecting the extension direction. When viewed from the stacking direction, the region of the diaphragm where its position in the width direction is between the pair of opposing portions is rectangular.

[0099] (3) In the pressure sensor element of (1), The pair of opposing portions may extend in an extension direction intersecting the width direction. 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 any one of the pressure sensor elements from (2) to (4), At least one of the pair of opposing portions may have a plurality of protrusions arranged at intervals along the extending direction.

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

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

[0104] (8) In any one of the pressure sensor elements from (1) to (7), The distance 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 the outer edge of the opening.

[0105] (9) In any one of the pressure sensor elements from (1) to (8), The aforementioned protrusion may be made of a conductive material. The pressure sensor element may further include an insulating film that covers at least one of the portion of the diaphragm that contacts the protrusion due to its bending and the protrusion itself.

[0106] Furthermore, by appropriately combining any of the various embodiments described above, the effects of each embodiment can be achieved.

[0107] Furthermore, in the various embodiments described above, only some of the feature points of the pressure sensor element of this disclosure may be present.

[0108] An example is given below.

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

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

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

[0112] Furthermore, the pressure sensor element described in (3) above is a pressure sensor element having both the first characteristic point and the second characteristic point.

[0113] Although the present invention has been fully described in relation to preferred embodiments with reference to the drawings as appropriate, various modifications and alterations will be obvious to those skilled in the art. Such modifications and alterations should be understood to be included within the scope of the invention as defined in the appended claims, as long as they do not fall outside that scope. [Explanation of symbols]

[0114] 1. Pressure sensor element 10 bases 20 Middle Class 20A opening 20B through hole 20C recess 20Ca bottom 20D recess 20Da bottom 20E Top surface (the side facing the electrode of the intermediate layer) 22. Conductive layer on the base side 30 electrodes 31 Diaphragm section 40 Convex part 41 Opposite section 41A One end 41B Other end 42 Opposing part 42A One end 42B Other end 43 Protrusion 50 insulating film 60 Inner layer 61 Electrode side conductive layer 62 Electrode-side insulating layer 101 Lamination direction 102 Short side direction (width direction) 103 Longitudinal direction (extension direction) LN1 Virtual Line LN2 Virtual Line LN3 Virtual Line LN4 Virtual Line

Claims

1. A conductive base, An intermediate layer having an opening is laminated on the base, The intermediate layer is laminated on the side opposite to the base, and has a diaphragm portion that overlaps with the opening when viewed from the lamination direction, and comprises a conductive electrode that is electrically insulated from the base, The aforementioned opening is The intermediate layer has through holes that penetrate in the stacking direction, The intermediate layer has a pair of recesses on the electrode side surface that are provided so as to sandwich the through hole and are continuous with respect to the through hole, and are recessed in the stacking direction, The intermediate layer comprises a base-side conductive layer that forms the bottom surface of the pair of recesses and is electrically connected to the base, The diaphragm portion faces the base-side conductive layer in the stacking direction via the pair of recesses, and faces the base in the stacking direction via the through-hole, The base-side conductive layer and the diaphragm portion are further provided with a convex portion that protrudes into the pair of recesses on at least one of the surfaces facing the pair of recesses, The aforementioned protrusion comprises a pair of opposing portions that are spaced apart from each other in the width direction, which is the direction in which the pair of recesses straddle the through hole. The pair of opposing portions are pressure sensor elements located in positions that overlap with the ends of the pair of recesses on the through-hole side when viewed from the stacking direction.

2. A conductive base, An intermediate layer having an opening is laminated on the base, A conductive electrode is laminated on the side of the intermediate layer opposite to the base, has a diaphragm portion that overlaps with the opening when viewed from the lamination direction, and is electrically insulated from the base. The base and the diaphragm portion are provided on the surface facing the opening and have a protrusion that extends toward the opening, Each of the protrusions extends along the extension direction on the surface facing the opening, and comprises a pair of opposing portions that are spaced apart from each other in the width direction intersecting the extension direction. A pressure sensor element in which, 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.

3. The pair of opposing portions extend in an extension direction intersecting the width direction, The pressure sensor element according to claim 1, wherein, 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. The pressure sensor element according to claim 2 or 3, wherein at least one of the pair of opposing portions is provided with a plurality of protrusions spaced apart along the extending direction.

6. The diaphragm portion further comprises an inner layer laminated on the surface between the pair of opposing portions in the width direction, which is on the opening side, The pressure sensor element according to any one of claims 1 to 3, wherein the inner layer comprises an electrode-side conductive layer having conductivity that is electrically connected to the electrode.

7. The pressure sensor element according to claim 6, further comprising an insulating electrode-side insulating layer located between the electrode-side conductive layer and the diaphragm portion.

8. The pressure sensor element according to any one of claims 1 to 3, wherein the distance between the pair of opposing portions in the width direction is longer than the shortest distance between each of the pair of opposing portions and the outer edge of the opening in the width direction.

9. The aforementioned protrusion is made of a conductive material. The pressure sensor element according to any one of claims 1 to 3, further comprising an insulating film that covers at least one of the portion that contacts the protrusion due to the bending of the diaphragm portion and the protrusion portion.

Images