KR20140048996A - Capacitance type pressure sensor, method for manufacturing same, and input device - Google Patents

Abstract

The dielectric layer 33 is formed on the upper surface of the fixed electrode 32, and the recess 34 is provided on the surface of the dielectric layer 33. A conductive diaphragm 38 (part of the plate 37) having the recess 34 covered thereon and the upper plate 37 laminated on the surface of the dielectric layer 33 and having a thin film shape above the recess 34. Excrete). The first contact surface 35 and the second contact surface 36 for contacting the diaphragm 38 are formed on the surface of the dielectric layer 33 in the recess 34. The first contact surface 35 and the second contact surface 36 are horizontal planes, for example, and the first contact surface 35 and the second contact surface 36 are separated by a step which is a vertical plane. The second contact surface 36 is at a position higher than the first contact surface 35.

Description

CAPACITANCE TYPE PRESSURE SENSOR, METHOD FOR MANUFACTURING SAME, AND INPUT DEVICE}

The present invention relates to a capacitive pressure sensor, a method for manufacturing the same, and an input device, and more particularly, to a capacitive pressure sensor in a touch mode in which a diaphragm bent by pressure contacts a dielectric layer and detects pressure. . The present invention also relates to an input device using the capacitive pressure sensor.

In a typical capacitive pressure sensor, a conductive diaphragm (movable electrode) and a fixed electrode are opposed to each other with a gap therebetween, and pressure is detected from a change in capacitance between the diaphragm and the fixed electrode that is bent by pressure. However, in the case where the pressure sensor is a micro device manufactured by MEMS technology using a silicon substrate or the like, if the diaphragm is subjected to a large pressure and largely bent, the diaphragm may be broken.

For this reason, a pressure sensor has been proposed in which a dielectric layer is provided on the surface of a fixed electrode, and a diaphragm bent by pressure contacts the dielectric layer, and the capacitance between the diaphragm and the fixed electrode changes by a change in the contact area thereof. Such a pressure sensor may be called a touch mode (capacitive) capacitive pressure sensor.

As a touch mode capacitive pressure sensor, there exist some which are described in the nonpatent literature 1, for example. 1: (A) is sectional drawing which shows the pressure sensor 11 of nonpatent literature 1. As shown in FIG. In this pressure sensor 11, the fixed electrode 13 which consists of a metal thin film is formed in the upper surface of the glass substrate 12, and the dielectric film 14 is formed in the upper surface of the glass substrate 12 on the fixed electrode 13. Forming. The through hole 15 is opened in the dielectric film 14, and the electrode pad 16 provided on the upper surface of the dielectric film 14 passes through the through hole 15 and is connected to the fixed electrode 13. The silicon substrate 17 is laminated on the upper surface of the dielectric film 14, the recess 18 is provided on the upper surface of the silicon substrate 17, and the recess 19 is provided on the lower surface, and the recess 18 is provided. ) And the recesses 19 are formed with a thin diaphragm 20. The diaphragm 20 is provided in the position which overlaps with the fixed electrode 13. In addition, the lower surface of the silicon substrate 17 is a P + layer 21 doped with B (boron) at a high concentration, thereby providing conductivity to the diaphragm 20 and having the function of a movable electrode. Between the lower surface of the diaphragm 20 and the dielectric film 14, a gap 22 of several μm is formed by the recess 19.

FIG. 1B is a diagram illustrating a relationship (pressure-capacitance characteristic) between the pressure of the pressure sensor 11 and the capacitance, and is described in Non-Patent Document 1. As shown in FIG. When pressure is applied to the diaphragm 20 of the pressure sensor 11, the diaphragm 20 bends in response to the applied pressure and contacts the dielectric film 14 at a certain pressure. In the section (non-contact area) in which the pressure in FIG. 1B is from 0 to Pa, the diaphragm 20 is not in contact with the dielectric film 14. The section in which the pressure is from Pa to Pb (contact start region) represents a state from which the diaphragm 20 contacts the dielectric film 14 and then reliably contacts with a certain area. In the section where the pressure is from Pb to Pc (operation region), the area of the portion where the diaphragm 20 is in contact with the dielectric film 14 gradually increases with increasing pressure. In the section where the pressure is from Pc to Pd (saturation region), almost the entire surface of the diaphragm 20 is in contact with the dielectric film 14, so that the contact area is hardly increased even if the pressure is increased.

According to the pressure-capacitance characteristic of FIG. 1B, although the change of capacitance is small in the uncontacted region where the diaphragm 20 does not contact, the rate of change of capacitance (increase rate) gradually increases when the contact start region is reached. In addition, although linearity is improved in the operating region, the rate of change in capacitance gradually decreases, and when the saturated region is reached, the capacitance hardly increases.

In the pressure sensor 11 of the touch mode, if the contact area between the diaphragm 20 and the dielectric film 14 is S, the thickness of the dielectric film 14 is d, and the dielectric constant of the dielectric film 14 is? The capacitance C between the diaphragm 20 and the dielectric film 14 can be expressed by the following formula (1).

 C = Co + ε · (S / d)... (Equation 1)

Here, Co is the capacitance in the non-contact region.

Since the thickness d and the dielectric constant ε of the dielectric film 14 do not change, according to Equation 1, as the pressure P increases, the contact area S of the diaphragm 20 increases, and as a result, the pressure sensor It can be seen that the capacitance C of (11) increases. However, according to FIG. 1 (B), the pressure-capacitance characteristic draws a parabolic curve from the start of contact to the saturation region. Therefore, it is thought that the contact area S (or capacitance difference C-Co) is qualitatively proportional to P ⁿ ( ^where 0 <n <1).

By the way, in a pressure sensor, although high sensitivity is calculated | required in the low pressure area | region, although a low sensitivity may be sufficient in a high pressure area | region, there are many cases where it presses with low sensitivity in a high pressure area | region, for example, may want to widen a measuring range instead.

However, in the structure of the pressure sensor as described in Non-Patent Document 1, if the sensitivity is reduced in the low pressure region, the measurement sensitivity is increased in the high pressure region, and it is difficult to manufacture a pressure sensor with high sensitivity in the low pressure region and low sensitivity in the high pressure region. . Further, even if the diaphragm diameter and thickness, the dielectric constant and thickness of the dielectric layer are optimized to obtain the optimum measurement sensitivity in the low pressure region and the high pressure region, the design is difficult.

In addition, in the pressure sensor described in Non-Patent Document 1, it is difficult to detect that the pressure being measured has reached the maximum value (maximum pressure) of the measurement range, and a rear end circuit is required if this is to be detected.

In addition, Patent Document 1 discloses a semiconductor pressure sensor in which a stepped backup portion is provided on an upper surface of a silicon substrate facing a diaphragm. However, the pressure sensor disclosed in Patent Document 1 detects the pressure by detecting the deflection of the diaphragm by a torsion detecting element (piezo resistor), and is different from the capacitive pressure sensor. In addition, the pressure sensor merely causes the diaphragm to deform along the edges of the backup portion (upper end of the step wall surface), and does not allow the height of the sensitivity to be different in the low pressure region and the high pressure region.

Patent Document 1: Japanese Patent No. 3144314

[Non-Patent Document 1] Yamamoto Min, and 4 others, "Touch Mode Capacitive Pressure Sensor," Fujikuragibo, Fujikura Co., October 2001, No. 101, p. 71-74

The present invention has been made in view of the above technical problem, and an object thereof is that the measurement sensitivity can be easily changed in response to the measurement range of pressure, and the pressure easily reaches the maximum value of the measurement range. The present invention provides a capacitive pressure sensor in a touch mode that can be detected and a manufacturing method thereof. Moreover, it is related with the input device which applied the said sensor.

A first capacitive pressure sensor according to the present invention is a capacitive pressure comprising a fixed electrode, a dielectric layer formed above the fixed electrode, and a conductive diaphragm formed with a gap between the dielectric layer and a gap therebetween. In the sensor, a portion of the dielectric layer facing the diaphragm has a plurality of contact regions for contacting the diaphragm, and when the thickness of the dielectric layer is d and the dielectric constant of the dielectric layer is? The value of the ratio (ε / d) is discontinuously changed at the boundary of. In addition, the value of ratio (epsilon / d) is discontinuously changing in the boundary of each contact area | region, It is epsilon at the position which is perpendicular to the said boundary of one contact area | region at the boundary of contact area | region. The value of / d and the value of (epsilon) / d in the position near to the said boundary of one contact area | region are different.

In the first capacitive pressure sensor of the present invention, when the contact surface of the diaphragm contacts the dielectric layer beyond the boundary of the contact region, the relationship between the contact area and the capacitance (capacitance characteristic) changes, so the range of the measured pressure It is possible to change the pressure-capacity characteristics by For example, the measurement sensitivity can be made high in the low pressure region, and the measurement sensitivity can be made low in the high pressure region. In addition, detection of the highest pressure in the measurement range also becomes easy.

In one embodiment of the first capacitive pressure sensor of the present invention, the thickness of the dielectric layer may be changed discontinuously at the boundary between the respective contact regions. As this aspect, thickness may be changed in the surface side of a dielectric layer, and thickness may be changed in the back surface side.

When the thickness of the dielectric layer is changed on the surface side, a stepped step may be provided on the surface of the dielectric layer at the boundary between the respective contact regions. In particular, the surfaces of the contact areas may be different from the diaphragm in a state where no pressure is applied. In this case, since the elasticity of the diaphragm changes discontinuously when the diaphragm exceeds the boundary of each contact area, the pressure-capacitance characteristic can be changed more remarkably by the range of the measured pressure.

According to another embodiment of the first capacitive pressure sensor of the present invention, when the pressure applied to the diaphragm increases, the diaphragm sequentially contacts a contact region having a small value of the ratio (ε / d). I am doing it. According to this embodiment, it is possible to increase the measurement sensitivity in the low pressure region and to decrease the measurement sensitivity in the high pressure region.

Particularly, when the surface of each contact region is measured such that the height measured from the bottom of the dielectric layer is sequentially increased according to the order in which the diaphragms contact when a large pressure is gradually applied to the diaphragm, The measurement sensitivity can be made high and the measurement sensitivity can be made low in the high pressure region.

In the case where the thickness of the dielectric layer is changed on the rear surface side, a stepped step may be formed on the upper surface of the fixed electrode in a region facing the diaphragm. In this case, the surface of each said contact area | region can also be formed flat as a whole, and a diaphragm can be deformed smoothly.

In particular, when the thickness of the dielectric layer under the contact surface is configured to thicken sequentially in the order in which the diaphragm comes in contact when the diaphragm is gradually applied with high pressure, the measurement sensitivity is increased in the low pressure region, and the high pressure is applied. It is possible to lower the measurement sensitivity in the area.

When the surface of the contact area is a plane parallel to the diaphragm in a state where no pressure is applied, the surface of the dielectric layer is easily processed.

As still another embodiment of the first capacitive pressure sensor of the present invention, the dielectric constant of the dielectric layer may be discontinuously changed at the boundary between the respective contact regions. Even in this case, when the contact surface of the diaphragm contacts the dielectric layer beyond the boundary of the contact region, the relationship between the contact area and the capacitance (capacitance characteristic) changes, so that the pressure-capacitance characteristic may be changed by the range of the measured pressure. Can be. For example, the measurement sensitivity can be made high in the low pressure region, and the measurement sensitivity can be made low in the high pressure region.

A second capacitive pressure sensor according to the present invention is a capacitive pressure comprising a fixed electrode, a dielectric layer formed above the fixed electrode, and a conductive diaphragm formed with a gap therebetween. In the sensor, a portion of the dielectric layer facing the diaphragm has a plurality of contact regions for contacting the diaphragm, and at the boundary between the contact regions, the surface of the dielectric layer has a stepped step. It features.

In the second capacitive pressure sensor of the present invention, since the elasticity of the diaphragm is discontinuously changed when the diaphragm exceeds the boundary of each contact area, the pressure-capacitance characteristic can be changed more remarkably by the range of the measured pressure. Can be. For example, the measurement sensitivity can be made high in the low pressure region, and the measurement sensitivity can be made low in the high pressure region.

A method for manufacturing a capacitive pressure sensor according to the present invention is a method for manufacturing a capacitive pressure sensor in which a step is provided on the surface side of a dielectric layer to vary the thickness of a contact region, the first being above the fixed electrode. A step of forming a dielectric film of the above, a step of partially removing the first dielectric film by etching to form a first opening having a stepped edge, and from above the first dielectric film Forming a second dielectric film above the fixed electrode; partially removing the second dielectric film by etching to form a second opening having a stepped edge; and the first and second A step of forming a third dielectric film above the fixed electrode from above the second dielectric film is provided. In addition, the first opening need not penetrate the first dielectric film. The second opening need not also penetrate the second dielectric film. In addition, the area of the second opening may be made smaller or larger than that of the first opening.

According to this manufacturing method, it is possible to manufacture a capacitive pressure sensor in which the thickness of the contact region is varied by providing a step on the surface side of the dielectric layer by a simple MEMS process.

1 (A) is a schematic sectional view showing a pressure sensor according to a conventional example. Fig. 1B is a diagram showing a relationship between pressure and capacitance in a pressure sensor of the conventional example shown in Fig. 1A.
2A is a schematic plan view of a pressure sensor according to Embodiment 1 of the present invention. (B) is a schematic sectional drawing along the XX line of FIG. 2 (A).
3 (A) and 3 (B) are a schematic plan view and a schematic sectional view of a state in which the diaphragm of the pressure sensor according to Embodiment 1 of the present invention is excluded.
4A to 4D are explanatory diagrams showing a deformed state of the diaphragm when a large pressure is gradually applied to the diaphragm.
Fig. 5 is a diagram showing the relationship between the pressure and the rate of change of capacitance in the pressure sensor according to the embodiment of the present invention and the pressure sensor of the conventional example.
6A to 6E are cross-sectional views illustrating a manufacturing process of the pressure sensor according to the first embodiment of the present invention.
7A to 7D are cross-sectional views illustrating a manufacturing process of the in-phase pressure sensor, illustrating a process following FIG. 6E.
8A to 8C are cross-sectional views illustrating the manufacturing steps of the in-phase pressure sensor, showing a process following FIG. 7D.
9 (A) and 9 (B) are cross-sectional views illustrating a manufacturing process of an in-phase pressure sensor, showing a process following FIG. 8 (C).
10A is a schematic plan view of a pressure sensor according to Embodiment 2 of the present invention. 10B is a schematic plan view of the dielectric layer used in the pressure sensor.
11 is a schematic sectional view of a pressure sensor according to Embodiment 3 of the present invention.
12 is a schematic sectional view of a pressure sensor according to Embodiment 4 of the present invention.
13 is a schematic cross-sectional view of a pressure sensor according to Embodiment 5 of the present invention.
14 is a schematic sectional view of a pressure sensor according to Embodiment 6 of the present invention.
15 is a schematic cross-sectional view of an input device according to Embodiment 7 of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various design modifications can be made without departing from the gist of the present invention.

(Embodiment 1)

Hereinafter, the structure of the pressure sensor 11 by embodiment of this invention is demonstrated with reference to FIG. 2 and FIG. FIG. 2 (A) is a schematic plan view of the pressure sensor 11, and FIG. 2 (B) is a sectional view taken along the line X-X of FIG. 2 (A). 3 (A) is a schematic plan view showing the dielectric layer 33 used for the pressure sensor 11, and FIG. 3 (B) shows the fixed electrode 32 and the dielectric layer (used in the pressure sensor 11). It is a schematic sectional drawing which shows 33).

In this pressure sensor 11, the dielectric layer 33 is formed on the fixed electrode 32 which consists of electroconductive materials, such as a low resistance silicon substrate and a metal film. The dielectric layer 33 is made of a dielectric material such as SiO ₂ , SiN, TEOS, or the like. A recess 34 (concave portion) is provided on the upper surface of the dielectric layer 33. In the recess 34, a plurality of contact surfaces (surfaces of the contact regions) having different heights measured from the lower surface of the dielectric layer 33 are formed. In the example of illustration, the 1st contact surface 35 of the low position provided circularly in the center part of the recess 34, and the 2nd contact surface 36 of the high position provided in the annular shape around the 1st contact surface 35 are provided. have. The boundary between the first contact surface 35 and the second contact surface 36 is a vertical plane perpendicular to the lower surface of the dielectric layer 33 (hereinafter referred to as step wall surface), and the first contact surface 35 ) And the second contact surface 36, the height of the contact surface is changing in a step shape.

On the upper surface of the dielectric layer 33, a thin film-like upper plate 37 made of a conductive material such as a low resistance silicon substrate is formed. The said board 37 has covered the upper surface of the recess 34. As shown in FIG. An upper electrode pad 40 or a wiring 41 is provided on the upper surface of the upper plate 37 by a metal material, and the upper electrode pad 40 or the wiring 41 is electrically connected to the upper plate 37. Doing. The upper surface of the plate 37 is covered with a protective film 39 made of an insulating film such as SiO ₂ or SiN or a resin such as polyimide. The upper electrode pad 40 is exposed from the protective film 39. Thus, the diaphragm for pressure reduction is formed by the area | region which horizontally aired from the upper side of the recess 34 among the said board 37 and the protective film 39.

In this pressure sensor 11, pressure is applied to the diaphragm 38. 4A to 4D show aspects when the diaphragm 38 is pressed by the flexible tip of the pressing body 43. The pressure gradually increases from FIG. 4A toward FIG. 4D. The change in capacitance at this time is qualitatively as follows.

The diaphragm 38 is fixed with the diaphragm 38 while the diaphragm 38 is pressed at a small pressure and does not contact the dielectric layer 33 before the diaphragm 38 lightly contacts the dielectric layer 33 as shown in Fig. 4A. The change in capacitance between the electrodes 32 may be considered small and almost constant. The capacitance at this time (constant) is represented by Co.

When the pressure applied to the diaphragm 38 gradually increases to contact the first contact surface 35, and as shown in FIG. 4B, the area S1 at which the diaphragm 38 contacts the first contact surface 35 gradually increases, As a result, the capacitance C between the diaphragm 38 and the fixed electrode 32 changes as shown in Equation 2 below.

 C = Co + (? / D1) S1... (Equation 2)

Alternatively, if ΔC = (C-Co) / Co is defined as the specific capacitance,

 ΔC = (C-Co) / Co = (ε · S1) / (d1 · Co)... (Equation 3)

. Is the dielectric constant of the dielectric layer 33, and d1 is the thickness of the dielectric layer 33 (contact region) below the first contact surface 35. In the example of FIG.

When the pressure exerted on the diaphragm 38 increases and the diaphragm 38 reaches the upper end of the stepped wall surface, the diaphragm 38 gradually starts to contact the second contact surface 36 therefrom. As shown in FIG. 4C, the capacitance C when the diaphragm 38 contacts the edge (the upper end of the step wall surface) of the second contact surface 36 is determined by the diaphragm 38. When the maximum contact area with respect to the 1st contact surface 35 is set to S1max, it is represented by following formula (4).

 C = Co + (ε / d 1) S 1 max. (Equation 4)

Or ΔC = (C-Co) / Co = (ε · S1mac) / (d1 · Co)... (Equation 5)

Further, as the pressure applied to the diaphragm 38 increases, the area where the diaphragm 38 contacts the second contact surface 36 gradually increases. The capacitance C when the diaphragm 38 contacts the second contact surface 36 with the contact area S2 is represented by the following expression (6).

 C = Co + (ε / d 1) S 1 max + (ε / d 2) S 2. (Equation 6)

Or ΔC = (εS1mac) / (d1Co) + (εS2) / (d2Co)... (Formula 7)

Here, d2 is the thickness of the dielectric layer 33 (contact area) below the second contact surface 36.

The coefficient of the contact area S1 in Equation 3 is different from the coefficient of the contact area S2 in Equation 7. Therefore, the pressure-capacity characteristics change when the diaphragm 38 is in contact with the first contact surface 35 and the pressure-capacity characteristics when the diaphragm 38 is in contact with the second contact surface 36. We can see that the way of change is different. In particular, when the thickness d1 of the dielectric layer 33 below the first contact surface 35 is smaller than the thickness d2 of the dielectric layer 33 below the second contact surface 36, the measurement in the low pressure region is performed. It turns out that a sensitivity becomes high and the measurement sensitivity in a high pressure area becomes low.

In addition, when the contact area of the diaphragm 38 increases, the area of the freely deformable area of the diaphragm 38 becomes small, so that the elasticity of the diaphragm 38 gradually increases. And when the diaphragm 38 abuts on the edge (the upper end of the step wall surface) of the second contact surface 36, the area of the freely deformable area of the diaphragm 38 becomes discontinuously small. The elasticity of the diaphragm 38 suddenly increases before and after the diaphragm 38 abuts the edge of the second contact surface 36. As a result, the measurement sensitivity is high when the diaphragm 38 is in contact with the first contact surface 35, and the measurement sensitivity is low when the diaphragm 38 is in contact with the second contact surface 36. Therefore, in the pressure sensor 31 of Embodiment 1, even in such a phenomenon, the measurement sensitivity in a low pressure area | region becomes high and the measurement sensitivity in a high pressure area | region becomes low.

FIG. 5 shows the pressure-capacity characteristics of the pressure sensor (Embodiment 1) according to Embodiment 1 of the present invention and the pressure-capacity characteristics of the pressure sensor (conventional example) described in Non-Patent Document 1. FIG. to be. This property is obtained by simulation. 5, the horizontal axis represents pressure P, and the vertical axis represents specific capacitance ΔC = (C-Co) / Co between the diaphragm (movable electrode) and the fixed electrode. Here, C is the capacitance when the pressure is P, Co is the capacitance in the non-contact region.

Since the contact area of the diaphragm 38 is almost proportional to (P ⁿ ) ( ^where 0 <n <1), the pressure-capacity characteristic represented by Equation 2-4 draws a parabolic curve. Therefore, Equations 2-4 and 5 are matched.

However, while the pressure-capacity characteristics of the pressure sensor of the conventional example are smoothly changed in a parabolic shape over the whole, the pressure-capacity characteristics of the pressure sensor of the first embodiment are the first and second diaphragms 38. The manner of change is different before and after the pressure Pe when abutting the upper end of the stepped wall surface between the contact surfaces 35 and 36.

That is, in the pressure sensor of the prior art, the method of the change of the measurement sensitivity in the whole measurement range is following the constant rule. Therefore, if it is designed so that a desired measurement sensitivity can be obtained in the low pressure region, the measurement sensitivity in the high pressure region is also determined thereby, so that it cannot be designed so as to be arbitrarily high in the low pressure region and low in the high pressure region. Similarly, the saturation state of the capacitance near the maximum pressure Pf in the pressure measurement range cannot be arbitrarily designed.

In contrast, in the pressure sensor 11 according to the first embodiment of the present invention, in the state where the pressure is smaller than Pe and the diaphragm 38 contacts only the first contact surface 35 (low pressure region), the measurement sensitivity is high. It is designed to be. However, in a state where the pressure is larger than Pe and the diaphragm 38 is also in contact with the second contact surface 36 (high pressure region), the thickness d2 of the dielectric layer 33 below the second contact surface 36 is the first. Since it is larger than the thickness d1 of the dielectric layer 33 below the contact surface 35, the measurement sensitivity is lower than that of the low pressure region. Therefore, according to Embodiment 1, the pressure sensor 11 which has high measurement sensitivity in the low pressure area | region and low measurement sensitivity in the high pressure area | region can be manufactured. In addition, since the measurement sensitivity may be low in the high pressure region, by selecting the thickness d2 of the dielectric layer 33 below the second contact surface 36 or the area of the second contact surface 36 appropriately, the maximum of the measurement range is achieved. The capacitance can be designed so that the change in capacitance becomes small as the capacitance approaches the saturation value at the pressure Pf. Therefore, it can be detected that the pressure P measured from the change of capacitance becomes almost the maximum pressure Pf.

Next, the manufacturing process of the said pressure sensor 11 is demonstrated. 6 to 9 are views showing in detail the manufacturing process of the pressure sensor 11. In addition, although the manufacturing process of FIGS. 6-9 demonstrates the process of manufacturing one pressure sensor, normally, several pressure sensors are produced on a wafer at once.

The pressure sensor 11 is manufactured by dividing into the said board side and the fixed electrode side. First, the manufacturing method of the said board side is demonstrated by FIG. 6 (A)-(E). FIG. 6 (A) shows a state where a metal film 40a such as Al or Au is formed by sputtering or vapor deposition on the entire upper surface of the plate 37 made of a silicon substrate or the like. The metal film 40a on the plate 37 is patterned by a photolithography process, and as shown in Fig. 6B, an upper electrode made of a metal film 40a on the top surface of the plate 37. The pad 40 and the wiring 41 are formed. Subsequently, as shown in FIG. 6 (C), the entire upper surface of the plate 37 from the upper electrode pad 40 or the wiring 41 is formed by SiO ₂ by a method such as sputtering, CVD, or coating. It is covered with the protective film 39 which consists of resin materials, such as insulating films, such as polyimide, and the like. The passivation layer 39 is partially provided with an opening window 50 on the upper surface of the upper electrode pad 40, and as shown in FIG. 6D, the upper electrode pad 40 is at least partially from the passivation layer 39. Is exposed. The method of opening the protective film 39 may be dry etching with a reactive gas or wet etching with a chemical liquid (etching liquid). Thereafter, by grinding, polishing or etching the lower surface of the plate 37, the thickness of the plate 37 is made thin as shown in Fig. 6E, and the plate 37 and the protective film 39 are formed. A thin film diaphragm 38 is formed.

Next, the manufacturing method on the fixed electrode side will be described with reference to Figs. 7A to 8D and Figs. 8A to 8C. 7A shows a dielectric film made of a dielectric material such as SiO ₂ , SiN, TEOS, etc. on the entire upper surface of a fixed electrode 32 made of a low resistance silicon substrate or the like by thermal oxidation, sputtering, CVD, or the like ( 33a) is shown. The thickness of the dielectric film 33a is determined so as to be equal to the step between the first contact surface 35 and the second contact surface 36. The dielectric film 33a is etched by wet etching using a chemical liquid or dry etching using a reactive gas, and an opening 51 (first opening) is formed in the center portion as shown in Fig. 7B. do. The opening 51 of the dielectric film 33a is formed in a region that is roughly equivalent to zero which becomes the recess 34. As shown in Fig. 7C, the dielectric film 33b is formed on the entire upper surface of the fixed electrode 32 on the dielectric film 33a by using a dielectric material such as the dielectric film 33a. . The dielectric film 33b is etched by wet etching using a chemical liquid or dry etching using a reactive gas, and an opening 52 (second opening) is formed in the center portion as shown in Fig. 7D. do. The opening 52 of the dielectric film 33b has a smaller area than the opening 51 and is formed in a region roughly the same as the first contact surface 35. Next, as shown in Fig. 8A, the dielectric films 33a and 33b are formed from the dielectric film 33b to the entire upper surface of the fixed electrode 32 by thermal oxidation, sputtering, CVD, or the like. The dielectric film 33c is formed using the same dielectric material. As a result, the dielectric layer 33 is formed by the dielectric films 33a, 33b, 33c. In addition, the dielectric layer 33 may be formed by another method. That is, after depositing a relatively large dielectric layer 33 on the upper surface of the fixed electrode 32, the dielectric layer 33 is etched to form a recess 34 having a first contact surface 35 and a second contact surface 36. May be formed.

Thereafter, if necessary, the bottom surface of the fixed electrode 32 is ground, polished, or etched to reduce the thickness of the fixed electrode 32 as shown in Fig. 8B. On the lower surface of the fixed electrode 32, as shown in FIG. 8C, a metal film such as Al or Au is formed, wet etched with a chemical solution, or dry etched using a reactive gas to pattern the metal film. The electrode pad 42 is formed.

Subsequently, the plate 37 is bonded on the dielectric layer 33 by using a bonding method such as normal temperature bonding, fusion bonding, resin bonding, eutectic bonding, and the like, and a pressure sensor as shown in Fig. 9A. Get 31. After that, as shown in FIG. 9B, the protective film 53 is formed on the entire lower surface of the fixed electrode 32 and the lower electrode pad 42, and the opening window 54 is formed on the protective film 53. The lower electrode pad 42 may be exposed by opening the opening window 54. In addition, when the pressure sensor 11 is produced by the wafer in multiple numbers at one time, the wafer is diced after that and cut by the individual pressure sensor 11 after that.

In addition, although the opening 52 opened in the dielectric film 33b in the process of FIG. 7D has a smaller area than the opening 51 of the dielectric film 33a, on the contrary, the opening of the dielectric film 33b is reversed. The 52 may be made larger than the opening 51.

(Embodiment 2)

10A is a schematic plan view of the pressure sensor 61 according to the second embodiment of the present invention. 10B is a schematic plan view of the dielectric layer 33 used for the pressure sensor 61. In this pressure sensor 61, all of the recess 34, the 1st contact surface 35, the 2nd contact surface 36, and the diaphragm 38 are formed in rectangular shape.

According to this embodiment, after the diaphragm 38 fully contacts the first contact surface 35 or the second contact surface 36 in the short-side direction, the contact surface to the first contact surface 35 or the second contact surface 36 is Since it extends to a long side direction, the pressure capacity characteristic different from Embodiment 1 can be acquired.

Moreover, the planar shape of the recess 34, the 1st contact surface 35, and the 2nd contact surface 36 can be various shapes, such as square, an ellipse, a hexagon, and an octagon, besides circular or rectangular shape.

(Embodiment 3)

11 is a schematic cross-sectional view of the pressure sensor 62 according to Embodiment 3 of the present invention. In this pressure sensor 62, since the 2nd contact surface 36 inclines obliquely downward toward the 1st contact surface 35, the diaphragm 38 becomes easy to contact the 2nd contact surface 36. As shown in FIG.

(Fourth Embodiment)

12 is a schematic cross-sectional view of the capacitive pressure sensor 63 in the touch mode according to the fourth embodiment of the present invention. In this pressure sensor 63, the convex part 71 is formed by projecting the upper surface of the fixed electrode 32 in the area | region which opposes the center part of the diaphragm 38. As shown in FIG. Further, in the dielectric layer 33 formed on the upper surface of the fixed electrode 32, a recess 34 is formed in a region facing the diaphragm 38, and the upper surface of the dielectric layer 33 in the recess 34 is formed. Is formed flat. Therefore, the thickness of the dielectric layer 33 is thin in the first contact surface 35 located in the center portion of the recess 34 and located just above the convex portion 71. The thickness of the dielectric layer 33 is thicker on the second contact surface 36 located at the outer circumferential portion of the recess 34 and facing the upper surface 72 of the fixed electrode 32 that is lower than the convex portion 71. It is.

In the pressure sensor 63 of the fourth embodiment, the contact surface of the diaphragm 38 is widened from the first contact surface 35 to the second contact surface 36, and as the contact area of the diaphragm 38 becomes larger, the above-described equation 2 The capacitance changes as described by -7. Therefore, the method of increasing the capacitance differs when only the first contact surface 35 is in contact with the second contact surface 36. That is, it is possible to make the measurement sensitivity high in the low pressure region and decrease the measurement sensitivity in the high pressure region.

(Embodiment 5)

13 is a schematic cross-sectional view of the capacitive pressure sensor 64 in the touch mode according to the fifth embodiment of the present invention. In this pressure sensor 64, the recess 34 is provided in the upper surface of the fixed electrode 32. As shown in FIG. In the recess 34, a plurality of planes having different heights measured from the lower surface of the fixed electrode 32 are formed. In the example of illustration, the 1st plane 73 of the low position located in the center part of the recess 34, and the 2nd plane 74 of the high position located around the 1st plane 73 are provided. The boundary between the first plane 73 and the second plane 74 is a vertical plane (step wall surface) perpendicular to the bottom surface of the fixed electrode 32, and the first plane 73 and the second plane 74. The height of the plane changes in the shape of steps between.

In addition, a dielectric layer 33 having a uniform thickness is formed on the upper surface of the fixed electrode 32. Thus, a recess 34 is formed on the top surface of the dielectric layer 33, and in the recess 34, the first contact surface 35 and the second plane 74 of the lower position located above the first plane 73 are formed. A high contact second contact surface 36 is formed.

In the pressure sensor 64 of Embodiment 5, although the thickness of the dielectric layer 33 is uniform, the surface of the dielectric layer 33 is formed in the recess 34 in step shape. Therefore, as described in the first embodiment, when the diaphragm 38 abuts the edge (the upper end of the step wall surface) of the second contact surface 36, the area of the diaphragm 38 that can be freely deformed is not known. Since it is continuously smaller, the elasticity of the diaphragm 38 suddenly increases before and after the diaphragm 38 abuts the edge of the second contact surface 36. As a result, the measurement sensitivity is high when the diaphragm 38 is in contact with the first contact surface 35, and the measurement sensitivity is low when the diaphragm 38 is in contact with the second contact surface 36. Therefore, in the pressure sensor 31 of Embodiment 1, even in such a phenomenon, the measurement sensitivity in a low pressure area | region becomes high and the measurement sensitivity in a high pressure area | region becomes low.

(Embodiment 6)

14 is a schematic cross-sectional view of the capacitive pressure sensor 65 in the touch mode according to the sixth embodiment of the present invention. In this pressure sensor 65, dielectric layers 75 and 76 are formed on the upper surface of the fixed electrode 32, and recesses 34 are provided on the upper surfaces of the dielectric layers 75 and 76. As shown in FIG. At the bottom of the recess 34, the center portion of the recess 34 is formed of a dielectric layer 76 having a relatively high dielectric constant, and the outer peripheral portion of the recess 34 is formed of a dielectric layer 75 having a relatively low dielectric constant. . In the recess 34, the upper surface of the dielectric layer 76 is the first contact surface 35, and the upper surface of the dielectric layer 75 is the second contact surface 36. Further, at the bottom of the recess 34, the thickness of the dielectric layer 75 and the thickness of the dielectric layer 76 are almost equal, and the first contact surface 35 and the second contact surface 36 are flat surfaces of the same height. have.

In this pressure sensor 65, even if the diaphragm 38 is pressed, the change of the capacitance C between the diaphragm 38 and the fixed electrode 32 is small and almost constant until it comes in contact with the dielectric layers 75 and 75. You may think that. When the capacitance (constant value) at this time is represented by Co, the specific capacitance ΔC = (C-Co) / Co between the diaphragm 38 and the fixed electrode 32 changes as follows.

When the pressure is applied to the diaphragm 38 to contact the first contact surface 35, and the area S1 in which the diaphragm 38 contacts the first contact surface 35 gradually increases, the diaphragm 38 and the fixed electrode ( The specific capacitance ΔC between 32) changes as shown in Equation 8 below.

 ΔC = (ε1 · S1) / (d · Co)... (Equation 8)

Where ε1 is the dielectric constant of the dielectric layer 76 and d is the thickness of the dielectric layers 75 and 76 at the bottom of the recess 34.

When the pressure exerted on the diaphragm 38 becomes large and the contact surface of the diaphragm 38 widens to the entirety of the first contact surface 35, the specific capacitance ΔC at that time sets the area of the first contact surface 35 to S1max. Then, it is represented by the following expression (9).

 ΔC = (ε1 · S1mac) / (d · Co). (Formula 9)

When the pressure applied to the diaphragm 38 becomes greater and the contact surface of the diaphragm 38 widens to the second contact surface 36, the contact area between the diaphragm 38 and the second contact surface 36 is S2, and the dielectric layer ( When the dielectric constant of 75) is ε2, the specific capacitance ΔC is represented by the following expression (10).

 ΔC = (ε1 · S1mac) / (d · Co) + (ε2 · S2) / (d · Co)... (Formula 10)

The coefficient of the contact area S1 in Equation 8 and the coefficient of the contact area S2 in Equation 10 are different. Therefore, the pressure-capacity characteristics change when the diaphragm 38 is in contact with the first contact surface 35 and the pressure-capacity characteristics when the diaphragm 38 is in contact with the second contact surface 36. We can see that the way of change is different. In particular, when the dielectric constant epsilon 1 of the dielectric layer 76 below the first contact surface 35 is larger than the dielectric constant epsilon 2 of the dielectric layer 75 below the second contact surface 36, the measurement sensitivity is measured in the low pressure region. Becomes high, and the measurement sensitivity in a high pressure area becomes low.

(Seventh Embodiment)

15 is a cross-sectional view showing the structure of a plate-shaped input device 81 according to the seventh embodiment of the present invention, for example, a touch panel. This input device 81 arrange | positions many sensor parts 82 which have the structure similar to the pressure sensor which concerns on this invention in array form (for example, square shape or honeycomb shape). In addition, each sensor part 82 is electrically independent, and can independently detect the pressure applied to each sensor part 82 individually. According to such an input device 81, the point pressed with a finger etc. like a touch panel can be detected, and the pressurization intensity of each point can also be detected.

31, 61 to 65: pressure sensor
32: fixed electrode
33: dielectric layer
34: recess
35: first contact surface (contact surface)
36: second contact surface (contact surface)
37: upper plate
38: diaphragm
40: phase electrode pad
42: lower electrode pad

Claims (16)

A fixed electrode,
A dielectric layer formed above the fixed electrode;
In the capacitive pressure sensor having a conductive diaphragm formed with a gap between the dielectric layer,
A portion of the dielectric layer facing the diaphragm has a plurality of contact regions for contacting the diaphragm,
When the thickness of the dielectric layer is d and the dielectric constant of the dielectric layer is ε, the value of the ratio (ε / d) is discontinuously changed at the boundary between the respective contact regions. . The method of claim 1,
Capacitive pressure sensor, characterized in that the thickness of the dielectric layer is discontinuously changed at the boundary between the contact areas. 3. The method of claim 2,
Capacitive pressure sensor, characterized in that the surface of the dielectric layer has a stepped step at the boundary between each contact area. The method of claim 3,
The surface of each contact region has a different distance from the diaphragm in a state where no pressure is applied. The method of claim 1,
And when the pressure applied to the diaphragm increases, the diaphragm sequentially contacts the contact area having a small value of the ratio (ε / d). The method of claim 3,
The surface of each contact region has a height measured from the bottom of the dielectric layer, in order to increase in order according to the order in which the diaphragm contacts when a large pressure is gradually applied to the diaphragm. . 3. The method of claim 2,
The surface of each said contact area | region is formed as the whole flat, The capacitive pressure sensor characterized by the above-mentioned. 8. The method of claim 7,
A capacitive pressure sensor, characterized in that a stepped stepped step is formed on an upper surface of the fixed electrode in a region facing the diaphragm. 3. The method of claim 2,
The thickness of the dielectric layer under the contact surface is thickened sequentially in accordance with the order in which the diaphragm contacts when a large pressure is gradually applied to the diaphragm. The method of claim 1,
The surface of the contact region is a capacitive pressure sensor, characterized in that all of the surfaces in parallel with the diaphragm in the absence of pressure. The method of claim 1,
At the boundary between the contact areas, the dielectric constant of the dielectric layer is changed discontinuously. A fixed electrode,
A dielectric layer formed above the fixed electrode;
In the capacitive pressure sensor having a conductive diaphragm formed with a gap between the dielectric layer,
A portion of the dielectric layer facing the diaphragm has a plurality of contact regions for contacting the diaphragm,
Capacitive pressure sensor, characterized in that the surface of the dielectric layer has a stepped step at the boundary between each contact area. A method for manufacturing the capacitive pressure sensor according to claim 3,
Forming a first dielectric film above the fixed electrode;
Partially removing the first dielectric film by etching to form a first opening having a stepped edge;
Forming a second dielectric film on the first dielectric film above the fixed electrode;
Partially removing the second dielectric film by etching to form a second opening having a stepped edge;
And forming a third dielectric film above the fixed electrode from above the first and second dielectric films. 14. The method of claim 13,
The area of the said 2nd opening is smaller than the said 1st opening, The manufacturing method of the capacitive pressure sensor characterized by the above-mentioned. 14. The method of claim 13,
The area of the said 2nd opening is larger than the said 1st opening, The manufacturing method of the capacitive pressure sensor characterized by the above-mentioned. An input device comprising the pressure sensor according to claim 1.

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