JP2016099302A - Physical quantity sensor, pressure sensor, altimeter, electronic apparatus and moving body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physical quantity sensor capable of improving the detection sensitivity, and to provide a pressure sensor, an altimeter, an electronic apparatus and a moving body including such physical quantity sensor.SOLUTION: A physical quantity sensor 1 has a concave part 26 which opens in a thickness direction. The physical quantity sensor 1 includes: a diaphragm part 20 which warps and deforms when receiving a pressure; and a piezoresistive element 5 which is disposed on the diaphragm part 20 being overlapped with the concave part 26 in a plainer view, and which outputs an electric signal due to a strain.SELECTED DRAWING: Figure 4

Description

The present invention relates to a physical quantity sensor, a pressure sensor, an altimeter, an electronic device, and a moving object.

A pressure sensor including a diaphragm that is bent and deformed by pressure reception is widely used (see, for example, Patent Document 1). In general, such a pressure sensor detects the pressure applied to the diaphragm by detecting the deflection of the diaphragm with a sensor element arranged on the diaphragm.

For example, a semiconductor pressure sensor according to Patent Document 1 includes a thin diaphragm portion formed on a part of a semiconductor substrate, a strain detection element (piezoresistor) formed on the surface of the diaphragm portion,
Have Further, a V-groove digging portion for improving pressure detection sensitivity is formed in the peripheral region of the piezoresistor on the surface of the diaphragm portion of the semiconductor pressure sensor according to Patent Document 1.

However, in the semiconductor pressure sensor according to Patent Document 1, the strain detection element is arranged at a position away from the digging portion even though the stress generated in the diaphragm portion due to pressure is locally increased in the digging portion. There is a problem that the detection sensitivity cannot be sufficiently improved.

JP-A-8-247874

An object of the present invention is to provide a physical quantity sensor capable of improving detection sensitivity,
It is another object of the present invention to provide a pressure sensor, an altimeter, an electronic device, and a moving body including such a physical quantity sensor.

Such an object is achieved by the present invention described below.
[Application Example 1]
The physical quantity sensor of the present invention has a concave portion that opens in the thickness direction, and a diaphragm portion that is bent and deformed by pressure reception;
A sensor element that overlaps the concave portion in plan view and is arranged in the diaphragm portion and outputs an electrical signal due to distortion;
It is characterized by providing.

According to such a physical quantity sensor, the stress (strain) generated in the diaphragm portion due to the bending deformation due to pressure reception can be locally increased in the concave portion. Therefore, the bending deformation of the diaphragm portion can be detected with high sensitivity by the sensor element arranged at a position overlapping the concave portion in plan view. Therefore, detection sensitivity can be improved.

[Application Example 2]
In the physical quantity sensor according to the aspect of the invention, it is preferable that the sensor element has a portion along the wall surface of the recess in a cross-sectional view.

Thereby, the stress generated in the concave portion of the diaphragm portion can be detected more efficiently by the sensor element.

[Application Example 3]
In the physical quantity sensor of the present invention, it is preferable that the width of the concave portion is reduced toward the bottom side in a cross-sectional view.

Thereby, when the diaphragm part is comprised using the silicon single crystal, a recessed part can be formed easily and with high precision by anisotropic etching.

[Application Example 4]
In the physical quantity sensor of the present invention, it is preferable that the sensor element has a V-shaped portion in a cross-sectional view.

Thereby, when the cross section of a recessed part makes V shape, at least one part of a sensor element can be arrange | positioned along the wall surface of a recessed part by sectional view.

[Application Example 5]
In the physical quantity sensor of the present invention, the sensor element is preferably a piezoresistive element.

Thereby, the stress (strain) generated in the diaphragm portion can be efficiently detected by the sensor element.

[Application Example 6]
In the physical quantity sensor according to the aspect of the invention, it is preferable that the concave portion extends along an outer peripheral portion of the diaphragm portion.

As a result, the stress (strain) generated in the concave portion of the diaphragm portion due to the bending deformation due to pressure reception
Can be increased efficiently.

[Application Example 7]
In the physical quantity sensor according to the aspect of the invention, it is preferable that a plurality of the concave portions are arranged side by side along the outer periphery of the diaphragm portion.

As a result, the stress (strain) generated in the concave portion of the diaphragm portion due to the bending deformation due to pressure reception
Can be increased efficiently.

[Application Example 8]
The pressure sensor of the present invention includes the physical quantity sensor of the present invention.
Thereby, the pressure sensor which has the outstanding detection sensitivity can be provided.

[Application Example 9]
The altimeter according to the present invention includes the physical quantity sensor according to the present invention.
Thereby, the altimeter which has the outstanding detection sensitivity can be provided.

[Application Example 10]
An electronic apparatus according to the present invention includes the physical quantity sensor according to the present invention.

Thereby, an electronic device including a physical quantity sensor having excellent detection sensitivity can be provided.

[Application Example 11]
The moving body of the present invention includes the physical quantity sensor of the present invention.

Thereby, a moving object provided with the physical quantity sensor which has the outstanding detection sensitivity can be provided.

It is sectional drawing which shows the physical quantity sensor which concerns on 1st Embodiment of this invention. It is a top view which shows arrangement | positioning of the piezoresistive element (sensor element) of the physical quantity sensor shown in FIG. 1, and the recessed part of a diaphragm part. It is a figure for demonstrating the effect | action of the physical quantity sensor shown in FIG. 1, Comprising: (a) is sectional drawing which shows a pressurization state, (b) is a top view which shows a pressurization state. It is a partial expanded sectional view of the physical quantity sensor shown in FIG. It is a graph which shows the relationship between the position of a diaphragm part, and an atmospheric pressure sensitivity ratio. It is a figure which shows the manufacturing process of the physical quantity sensor shown in FIG. It is a figure which shows the manufacturing process of the physical quantity sensor shown in FIG. It is a figure which shows the manufacturing process of the physical quantity sensor shown in FIG. It is sectional drawing which shows the physical quantity sensor which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows an example of the pressure sensor of this invention. It is a perspective view which shows an example of the altimeter of this invention. It is a front view which shows an example of the electronic device of this invention. It is a perspective view which shows an example of the moving body of this invention.

Hereinafter, a physical quantity sensor, a pressure sensor, an altimeter, an electronic device, and a moving body of the present invention will be described in detail based on each embodiment shown in the accompanying drawings.

1. Physical quantity sensor <First embodiment>
FIG. 1 is a cross-sectional view showing a physical quantity sensor according to the first embodiment of the present invention, and FIG. 2 is a plan view showing an arrangement of piezoresistive elements (sensor elements) of the physical quantity sensor shown in FIG. is there. 3A and 3B are diagrams for explaining the operation of the physical quantity sensor shown in FIG. 1, wherein FIG. 3A is a sectional view showing a pressurized state, and FIG. 3B is a plan view showing the pressurized state. In the following, for convenience of explanation, the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”.

A physical quantity sensor 1 shown in FIG. 1 includes a substrate 2 having a diaphragm portion 20, a plurality of piezoresistive elements 5 (sensor elements) that are functional elements arranged in the diaphragm portion 20, and a cavity S (pressure) together with the substrate 2. A laminated structure 6 forming a reference chamber) and an intermediate layer 3 disposed between the substrate 2 and the laminated structure 6.

Hereinafter, each part which comprises the physical quantity sensor 1 is demonstrated sequentially.
-Board-
The substrate 2 includes a semiconductor substrate 21, an insulating film 22 provided on one surface of the semiconductor substrate 21, and an insulating film 23 provided on the surface of the insulating film 22 opposite to the semiconductor substrate 21. Have.

The semiconductor substrate 21 includes a silicon layer 211 (handle layer) made of single crystal silicon.
And an SOI in which a silicon oxide layer 212 (box layer) made of a silicon oxide film and a silicon layer 213 (device layer) made of single crystal silicon are stacked in this order.
It is a substrate. The semiconductor substrate 21 is not limited to the SOI substrate, and may be another semiconductor substrate such as a single crystal silicon substrate.

The insulating film 22 is, for example, a silicon oxide film and has an insulating property. Further, the insulating film 23 is, for example, a silicon nitride film, and has an insulation property and resistance to an etching solution containing hydrofluoric acid. Here, the semiconductor substrate 21 (silicon layer 213) and the insulating film 23 (
Since the insulating film 22 (silicon oxide film) is interposed between the insulating film 22 and the silicon nitride film, the insulating film 22 can relieve stress generated during the formation of the insulating film 23 to the semiconductor substrate 21. it can. The insulating film 22 can also be used as an inter-element isolation film when a semiconductor circuit is formed on and above the semiconductor substrate 21. Note that the insulating films 22 and 23 are not limited to the above-described constituent materials, and any one of the insulating films 22 and 23 may be omitted as necessary.

A patterned intermediate layer 3 is disposed on the insulating film 23 of the substrate 2. The intermediate layer 3 is formed so as to surround the periphery of the diaphragm portion 20 in a plan view (hereinafter simply referred to as “plan view”) viewed from the thickness direction of the substrate 2. A step portion corresponding to the thickness of the intermediate layer 3 is formed on the center side (inner side) of the diaphragm portion 20. Thereby, when the diaphragm part 20 bends and deform | transforms by receiving pressure, stress can be concentrated on the boundary part between the level | step-difference parts of the diaphragm part 20. FIG. Therefore, the detection sensitivity can be improved by disposing the piezoresistive element 5 at the boundary portion (or the vicinity thereof).

The intermediate layer 3 is made of, for example, single crystal silicon, polycrystalline silicon (polysilicon), or amorphous silicon. The intermediate layer 3 may be configured by doping (diffusing or implanting) impurities such as phosphorus and boron into single crystal silicon, polycrystalline silicon (polysilicon), or amorphous silicon, for example. In this case, since the intermediate layer 3 has conductivity, for example, when a MOS transistor is formed on the substrate 2 outside the cavity S, a part of the intermediate layer 3 can be used as the gate electrode of the MOS transistor. . A part of the intermediate layer 3 can also be used as a wiring.

Such a substrate 2 is provided with a diaphragm portion 20 which is thinner than the surrounding portion and is bent and deformed by receiving pressure. The diaphragm portion 20 is formed by providing a bottomed recess 24 on the lower surface of the semiconductor substrate 21. That is, the diaphragm portion 20 is configured to include the bottom portion of the concave portion 24 opened on one surface of the substrate 2. This diaphragm part 2
0 has a pressure receiving surface 25 on its lower surface. In the present embodiment, as shown in FIG. 2, the diaphragm portion 20 has a square (rectangular) plan view shape.

In the substrate 2 of the present embodiment, the recess 24 penetrates the silicon layer 211, and the diaphragm portion 20 is composed of four layers of a silicon oxide layer 212, a silicon layer 213, an insulating film 22, and an insulating film 23. Here, as will be described later, the silicon oxide layer 212 can be used as an etching stop layer when the recess 24 is formed by etching in the manufacturing process of the physical quantity sensor 1, and the thickness of the diaphragm portion 20 for each product. Variations can be reduced.

Note that the recess 24 does not penetrate the silicon layer 211, and the diaphragm 20 is the silicon layer 21.
1 thin-walled portion, silicon oxide layer 212, silicon layer 213, insulating film 22 and insulating film 23 may be included.

Further, in the substrate 2, a plurality of concave portions are formed on the upper surface of the portion corresponding to the diaphragm portion 20 of the silicon layer 213, thereby forming a plurality of concave portions 26 on the surface of the diaphragm portion 20 on the cavity portion S side. ing. In addition, about this recessed part 26 and the matter relevant to this,
This will be described in detail later.

-Piezoresistive element (functional element)-
As shown in FIG. 1, the plurality of piezoresistive elements 5 are respectively formed on the cavity portion S side of the diaphragm portion 20. Here, the piezoresistive element 5 includes the silicon layer 2 of the semiconductor substrate 21.
13 is formed. In particular, the piezoresistive element 5 is disposed at a position overlapping the concave portion 26 of the diaphragm portion 20 in plan view.

As shown in FIG. 2, the plurality of piezoresistive elements 5 are composed of a plurality of piezoresistive elements 5 a, 5 b, 5 c, and 5 d disposed on the outer periphery of the diaphragm portion 20.

A piezoresistive element 5a, a piezoresistive element 5b, a piezoresistive element 5c, and a piezoresistive element 5d are arranged in correspondence with the four sides of the diaphragm portion 20 having a quadrangular shape in plan view.

The piezoresistive element 5 a extends along a direction parallel to the corresponding side of the diaphragm portion 20. A pair of wirings 21 drawn to the outside is provided at both ends of the piezoresistive element 5a.
4a is electrically connected. Similarly, the piezoresistive element 5 b extends along a direction parallel to the corresponding side of the diaphragm portion 20. A pair of wirings 214b drawn to the outside is electrically connected to both ends of the piezoresistive element 5b.

On the other hand, the piezoresistive elements 5c are configured as a pair, and each extend along a direction perpendicular to the corresponding side of the diaphragm portion 20. The pair of piezoresistive elements 5c is electrically connected in series by the wiring 51c, and is connected to the pair of wirings 214 to the outside.
c is electrically connected. Similarly, the piezoresistive elements 5d are configured as a pair, and each extend along a direction perpendicular to the corresponding side of the diaphragm portion 20. And
The pair of piezoresistive elements 5d is electrically connected to a pair of wirings 214d that are led out to the outside in a state of being connected in series by the wiring 51d.

Hereinafter, the wirings 214a, 214b, 214c, and 214d are collectively referred to as “wiring 21.
4 ".

The piezoresistive element 5 and the wiring 214 are each made of silicon (single crystal silicon) doped (diffused or implanted) with impurities such as phosphorus and boron. Here, the impurity doping concentration in the wiring 214 is higher than the impurity doping concentration in the piezoresistive element 5. Note that the wiring 214 may be made of metal.

Further, the plurality of piezoresistive elements 5 are configured such that, for example, resistance values in a natural state are equal to each other.

The piezoresistive element 5 as described above constitutes a bridge circuit (Wheatstone bridge circuit) via the wiring 214 and the like. A driving circuit (not shown) that supplies a driving voltage is connected to the bridge circuit. In this bridge circuit, a signal (voltage) corresponding to the resistance value of the piezoresistive element 5 is output. Thereby, the diaphragm part 20
Can be efficiently detected by the piezoresistive element 5.

-Laminated structure-
The laminated structure 6 is formed so as to define a cavity S between itself and the substrate 2 described above.
Here, the laminated structure 6 is disposed on the piezoresistive element 5 side of the diaphragm portion 20, and defines (configures) the cavity portion S (internal space) together with the diaphragm portion 20 (or the substrate 2).

The laminated structure 6 includes an interlayer insulating film 61 formed on the substrate 2 so as to surround the piezoresistive element 5 in plan view, a wiring layer 62 formed on the interlayer insulating film 61, a wiring layer 62, and an interlayer An interlayer insulating film 63 formed on the insulating film 61; a wiring layer 64 formed on the interlayer insulating film 63 and having a covering layer 641 having a plurality of pores 642 (openings); the wiring layer 64 and the interlayer A surface protective film 65 formed on the insulating film 63 and a sealing layer 66 provided on the covering layer 641 are provided.

The interlayer insulating films 61 and 63 are each composed of, for example, a silicon oxide film. The wiring layers 62 and 64 and the sealing layer 66 are each made of a metal such as aluminum. Further, the sealing layer 66 seals the pores 642 included in the coating layer 641. The surface protective film 65 is a silicon nitride film, for example.

In such a laminated structure 6, the structure including the wiring layer 62 and the wiring layer 64 excluding the covering layer 641 is disposed on one surface side of the substrate 2 so as to surround the piezoresistive element 5 in plan view. "Wall". The covering layer 641 constitutes a “ceiling part” that is disposed on the opposite side of the substrate 2 from the wall part and constitutes the cavity part S (internal space) together with the wall part.

Moreover, such a laminated structure 6 can be formed using a semiconductor manufacturing process such as a CMOS process. Note that a semiconductor circuit may be formed on and above the silicon layer 213. This semiconductor circuit has active elements such as MOS transistors, and other circuit elements such as capacitors, inductors, resistors, diodes, and wires (including wires connected to the piezoresistive element 5) formed as necessary. ing.

The cavity S defined by the substrate 2 and the laminated structure 6 is a sealed space. The cavity S functions as a pressure reference chamber that serves as a reference value for the pressure detected by the physical quantity sensor 1. In this embodiment, the cavity S is in a vacuum state (300 Pa or less). By making the cavity S into a vacuum state, the physical quantity sensor 1 can be used as an “absolute pressure sensor” that detects pressure based on the vacuum state, and the convenience is improved.

However, the cavity S may not be in a vacuum state, may be atmospheric pressure, may be in a reduced pressure state where the atmospheric pressure is lower than atmospheric pressure, or is a pressurized state where the atmospheric pressure is higher than atmospheric pressure. It may be. The cavity S may be filled with an inert gas such as nitrogen gas or a rare gas.

The configuration of the physical quantity sensor 1 has been briefly described above.
As shown in FIG. 3A, the physical quantity sensor 1 having such a configuration includes a diaphragm unit 20.
The diaphragm portion 20 is deformed in accordance with the pressure P received by the pressure receiving surface 25, and FIG.
As shown in (b), the piezoresistive elements 5a, 5b, 5c and 5d are distorted, and the piezoresistive element 5
The resistance values of a, 5b, 5c, and 5d change. Accordingly, piezoresistive elements 5a, 5b,
The output of the bridge circuit formed by 5c and 5d changes, and the magnitude of the pressure received by the pressure receiving surface 25 can be obtained based on the output.

More specifically, in the natural state before the deformation of the diaphragm portion 20 as described above, for example, when the resistance values of the piezoresistive elements 5a, 5b, 5c, 5d are equal to each other, the piezoresistive elements 5a, 5b Is equal to the product of the resistance values of the piezoresistive elements 5c and 5d, and the output (potential difference) of the bridge circuit is zero.

On the other hand, when the diaphragm portion 20 is deformed as described above, as shown in FIG. 3B, the piezoresistive elements 5a and 5b are subjected to tensile strain along the longitudinal direction and compressive strain along the width direction. At the same time, compressive strain along the longitudinal direction and tensile strain along the width direction are generated in the piezoresistive elements 5c and 5d. Therefore, the diaphragm portion 2 as described above
When the deformation of 0 occurs, the resistance value of the piezoresistive elements 5a and 5b and the piezoresistive elements 5c and 5d
One of the resistance values increases, and the other resistance value decreases.

Due to the distortion of the piezoresistive elements 5a, 5b, 5c and 5d, the piezoresistive element 5a
A difference between the product of the resistance value of 5b and the product of the resistance values of the piezoresistive elements 5c and 5d occurs, and an output (electric signal) corresponding to the difference (potential difference) is output from the bridge circuit. Based on the output from the bridge circuit, the magnitude (absolute pressure) of the pressure received by the pressure receiving surface 25 can be obtained.

Here, when the deformation of the diaphragm portion 20 as described above occurs, the piezoresistive element 5a.
One of the resistance values of the resistance value of 5b and the resistance values of the piezoresistive elements 5c and 5d increases.
Since the other resistance value decreases, the change in the difference between the product of the resistance values of the piezoresistive elements 5a and 5b and the product of the resistance values of the piezoresistive elements 5c and 5d can be increased. The output from can be increased. As a result, the pressure detection sensitivity can be increased.

(Diaphragm recess)
Hereinafter, the recessed part 26 formed in the diaphragm part 20 and the matter relevant to it are explained in full detail.

4 is a partially enlarged cross-sectional view of the physical quantity sensor shown in FIG. FIG. 5 is a graph showing the relationship between the position of the diaphragm portion and the atmospheric pressure sensitivity ratio. Note that the “barometric pressure sensitivity ratio” in FIG. 5 is a ratio of barometric pressure sensitivity (stress value / barometric pressure) based on a piezoresistive position (0.88 here) without a recess (broken line in the figure). In addition, “Distance from center of diaphragm” in FIG.
The center of the diaphragm portion is “0” (reference), and the outer peripheral edge of the diaphragm portion is “1”.

As described above, the diaphragm portion 20 has a plurality of concave portions 26 opened in the thickness direction. In the present embodiment, as shown in FIG. 4, a recess 2131 is formed on the upper surface of the silicon layer 213 of the diaphragm portion 20. The wall surface of the recess 2131 is covered with the insulating films 22 and 23, but the insulating films 22 and 23 are deformed following the wall surface of the recess 2131. As a result, a recess 26 is formed which is covered with the insulating films 22 and 23 and has a shape corresponding to the recess 2131. According to the diaphragm portion 20 having such a concave portion 26, as shown in FIG.
6 can be increased locally.

Such a plurality of recesses 26 are disposed corresponding to the plurality of piezoresistive elements 5 (see FIG. 2), and each piezoresistive element 5 is disposed so as to overlap the corresponding recesses 26 in plan view. Has been. Thereby, the bending deformation of the diaphragm portion 20 can be detected with high sensitivity by each piezoresistive element 5. Therefore, the detection sensitivity of the physical quantity sensor 1 can be improved. Here, the plurality of recesses 26 includes four recesses 26a, 26b, 26c, and 26d corresponding to the four piezoresistive elements 5a, 5b, 5c, and 5d, respectively.

Further, as shown in FIG. 2, the plurality of recesses 26 are diaphragm portions 20 that form a rectangle in plan view.
It is arranged corresponding to each side. Thereby, the plurality of recesses 26 are formed in the diaphragm portion 20.
A plurality of them are arranged side by side along the outer periphery of the. Thereby, the stress (distortion) which arises in each recessed part 26 of the diaphragm part 20 with the bending deformation by pressure receiving can be raised efficiently. This is because, when the diaphragm portion 20 that is rectangular in plan view is bent and deformed, the stress generated in each side is larger than the corner portion of the diaphragm portion 20.

Moreover, each recessed part 26 is a groove | channel extended along the outer peripheral part (each side) of a diaphragm part.
Thereby, the stress (distortion) which arises in each recessed part 26 of the diaphragm part 20 with the bending deformation by pressure receiving can be raised efficiently. This is a diaphragm portion 2 that forms a rectangle in plan view.
This is because, when 0 is bent and deformed, each concave portion 26 is easily deformed as compared with a case where it extends in a direction perpendicular to each side of the diaphragm portion 20.

Further, as shown in FIG. 4, each piezoresistive element 5 has a portion along the wall surface of each concave portion 26 corresponding to the sectional view. Thereby, the stress produced in each recess 26 of the diaphragm portion 20 can be detected more efficiently by the sensor element.

Each recess 26 has a V-shaped cross section, as shown in FIG. As described above, the width of each concave portion 26 is reduced toward the bottom side in a cross-sectional view, so that the concave portion 2 can be easily and accurately formed by anisotropic etching with respect to the silicon layer 213 made of silicon single crystal.
131 can be formed. In addition, the cross-sectional shape of each recessed part 26 is not limited to V shape,
For example, it may be U-shaped or rectangular.

In addition, each piezoresistive element 5 is formed along the wall surface of each corresponding recess 26 and has a V-shaped portion in sectional view. Thus, in the case of the present embodiment in which the cross section of each recess 26 is V-shaped, at least a part of each piezoresistive element 5 can be arranged along the wall surface of the recess 26 in a cross-sectional view.

Further, the depth d of each concave portion 26 is not particularly limited, but is preferably 0.1 or more and 0.5 or less, and 0.2 or more and 0.4 or less with respect to the thickness t of the diaphragm portion 20. More preferably, it is preferably 0.5 μm or more and 2 μm or less.
m or more and 1.5 μm or less is preferable. Thereby, generation | occurrence | production of the local stress in each recessed part 26 of the diaphragm parts 20 which was mentioned above can be produced effectively, maintaining the required intensity | strength of the diaphragm part 20. FIG.

In addition, the width of each recess 26 is preferably about 0.5 or more and 1.5 or less with respect to the depth d of each recess 26. While maintaining the required strength of the diaphragm part 20, it is possible to effectively generate local stresses in the respective recesses 26 of the diaphragm part 20 as described above.

(Manufacturing method of physical quantity sensor)
Next, a method for manufacturing the physical quantity sensor 1 will be briefly described.

6-8 is a figure which shows the manufacturing process of the physical quantity sensor shown in FIG. Hereinafter, a method for manufacturing the physical quantity sensor 1 will be described with reference to these drawings.

[Element formation process]
First, as shown in FIG. 6A, a semiconductor substrate 21 which is an SOI substrate is prepared.

Then, as shown in FIG. 6B, the recess 2131 is formed in the silicon layer 213 of the semiconductor substrate 21.
Form.

A method for forming the recess 2131 is not particularly limited, but it is preferable to use anisotropic etching by wet etching. Accordingly, the concave portion 2131 having a V-shaped cross section as described above can be formed easily and with high accuracy.

Thereafter, by doping (ion implantation) an impurity such as phosphorus (n-type) or boron (p-type) into the silicon layer 213 of the semiconductor substrate 21 so as to overlap the recess 2131 in plan view.
As shown in FIG. 6C, a plurality of piezoresistive elements 5 are formed. Although not shown, the wiring 214 is also formed in the same manner as the piezoresistive element 5.

For example, when ion implantation of boron is performed at +80 keV, the ion implantation concentration into the piezoresistive element 5 is set to about 1 × 10 ¹⁴ atoms / cm ² . Further, the concentration of ion implantation into the wiring 214 is made larger than that of the piezoresistive element 5. For example, when boron is ion-implanted at 10 keV, the ion implantation concentration into the wiring 214 is set to about 5 × 10 ¹⁵ atoms / cm ² .
Further, after the ion implantation as described above, for example, annealing is performed at about 1000 ° C. for about 20 minutes.

[Insulating film forming process]
Next, as illustrated in FIG. 7A, the insulating film 22, the insulating film 23, and the intermediate layer 3 are formed in this order on the silicon layer 213.

The insulating films 22 and 23 can be formed by, for example, a sputtering method, a CVD method, or the like. The intermediate layer 3 is formed, for example, by depositing polycrystalline silicon by a sputtering method, a CVD method or the like, and then doping (ion-implanting) impurities such as phosphorus or boron into the film as necessary, followed by patterning by etching. Can be formed.

[Interlayer insulation film / wiring layer formation process]
Next, as shown in FIG. 7B, the sacrificial layer 41, the wiring layer 62, and the sacrificial layer 4 are formed on the insulating film 23.
2 and the wiring layer 64 are formed in this order.

Each of the sacrificial layers 41 and 42 is partially removed by a cavity forming process described later.
The remaining portions are the interlayer insulating films 61 and 63. The formation of the sacrificial layers 41 and 42 is respectively
A silicon oxide film is formed by sputtering, CVD, or the like, and the silicon oxide film is patterned by etching.

Further, the thicknesses of the sacrificial layers 41 and 42 are not particularly limited.
It is set to about not less than nm and not more than 5000 nm.

The wiring layers 62 and 64 are formed by patterning after forming a layer made of aluminum, for example, by sputtering or CVD.

Here, the thicknesses of the wiring layers 62 and 64 are not particularly limited.
It is set to about not less than nm and not more than 900 nm.

Such a laminated structure composed of the sacrificial layers 41 and 42 and the wiring layers 62 and 64 is a normal CM.
It is formed using an OS process, and the number of stacked layers is appropriately set as necessary. That is, more sacrificial layers and wiring layers may be stacked as necessary.

[Cavity formation process]
Next, by removing a part of the sacrificial layers 41 and 42, a cavity S (cavity) is formed between the insulating film 23 and the covering layer 641, as shown in FIG. Thereby, interlayer insulating films 61 and 63 are formed.

The cavity S is formed by removing a part of the sacrificial layers 41 and 42 by etching through the plurality of pores 642 formed in the coating layer 641. Here, when wet etching is used as such etching, an etching solution such as hydrofluoric acid or buffered hydrofluoric acid is supplied from the plurality of pores 642, and when dry etching is used, hydrofluoric acid gas or the like is supplied from the plurality of pores 642. Etching gas is supplied. In such etching, the insulating film 23 functions as an etching stop layer. In addition, since the insulating film 23 has resistance to the etching solution, the lower constituent parts (for example, the insulating film 22 and the piezoresistive element 5) with respect to the insulating film 23.
, Wiring 214 and the like) from the etching solution.

Here, before such etching, the surface protective film 6 is formed by sputtering, CVD, or the like.
5 is formed. Thereby, during the etching, the interlayer insulating film 61 of the sacrificial layers 41 and 42 is obtained.
, 62 can be protected. As a constituent material of the surface protective film 65, for example, a silicon oxide film, a silicon nitride film, a polyimide film, an epoxy resin film, or the like is used.
Those having resistance to protect from dust, scratches and the like are mentioned, and a silicon nitride film is particularly preferable. Although the thickness of the surface protective film 65 is not particularly limited, for example, 500 nm or more 2
000 nm or less.

[Sealing process]
Next, as shown in FIG. 8A, a sealing layer 66 made of a silicon oxide film, a silicon nitride film, a metal film such as Al, Cu, W, Ti, TiN, or the like is formed on the coating layer 641 by a sputtering method. ,
Each pore 642 is sealed by a CVD method or the like. Thus, the cavity S is sealed with the sealing layer 66, and the laminated structure 6 is obtained.

Here, the thickness of the sealing layer 66 is not particularly limited.
It is about 0 nm or less.

[Diaphragm formation process]
Next, after grinding the lower surface of the silicon layer 211 as necessary, a part of the lower surface of the silicon layer 211 is removed (processed) by etching, thereby forming the recess 2 as shown in FIG.
4 is formed. Thereby, the diaphragm part 2 which opposes the coating layer 641 through the cavity S is provided.
0 is formed.

Here, when part of the lower surface of the silicon layer 211 is removed, the silicon oxide layer 212 functions as an etching stop layer. Thereby, the thickness of the diaphragm part 20 can be prescribed | regulated with high precision.

Note that a method for removing a part of the lower surface of the silicon layer 211 may be dry etching, wet etching, or the like.
The physical quantity sensor 1 can be manufactured through the processes as described above.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 9 is a cross-sectional view showing a physical quantity sensor according to the second embodiment of the present invention.

Hereinafter, although 2nd Embodiment of this invention is described, it demonstrates centering around difference with embodiment mentioned above, The description of the same matter is abbreviate | omitted.

This embodiment is the same as the first embodiment described above except that the cavity (pressure reference chamber) is provided on the opposite side of the diaphragm from the sensor element.

A physical quantity sensor 1 </ b> A shown in FIG. 9 includes a substrate 2 and a substrate 7 that seals the opening of the recess 24 of the substrate 2. Thus, by sealing the opening of the recess 24 with the substrate 7, the recess 2
The space in 4 can be used as a cavity. Here, the substrate 7 is hermetically bonded to the silicon layer 211 of the substrate 2. Thereby, the space in the recessed part 24 becomes airtight space. Therefore, in the present embodiment, the surface of the diaphragm portion 20 on the concave portion 26 side is the pressure receiving surface 25A.
The recess 26 is arranged on the pressure receiving surface 25A side.
The detection sensitivity can also be improved by the second embodiment as described above.

2. Next, a pressure sensor (a pressure sensor of the present invention) including the physical quantity sensor of the present invention will be described. FIG. 10 is a cross-sectional view showing an example of the pressure sensor of the present invention.

As shown in FIG. 10, the pressure sensor 100 of the present invention includes a physical quantity sensor 1, a casing 101 that houses the physical quantity sensor 1, and a calculation unit 102 that calculates a signal obtained from the physical quantity sensor 1 to pressure data. ing. The physical quantity sensor 1 includes a calculation unit 102 via a wiring 103.
And are electrically connected.

The physical quantity sensor 1 is fixed to the inside of the housing 101 by fixing means (not shown). Further, the housing 101 has a through-hole 104 through which the diaphragm unit 20 of the physical quantity sensor 1 communicates with, for example, the atmosphere (outside the housing 101).

According to such a pressure sensor 100, the diaphragm portion 20 receives pressure through the through hole 104. The pressure-received signal is transmitted to the calculation unit via the wiring 103 to calculate pressure data. The calculated pressure data can be displayed via a display unit (not shown) (for example, a monitor of a personal computer).

3. Next, an example of an altimeter (the altimeter of the present invention) including the physical quantity sensor of the present invention will be described. FIG. 11 is a perspective view showing an example of an altimeter according to the present invention.

The altimeter 200 can be worn on the wrist like a wristwatch. In addition, altimeter 200
Is mounted with a physical quantity sensor 1 (pressure sensor 100) and a display unit 201.
The altitude of the current location from the sea level or the atmospheric pressure of the current location can be displayed.

The display unit 201 can display various information such as the current time, the user's heart rate, and weather.

4). Next, a navigation system to which an electronic device including the physical quantity sensor of the present invention is applied will be described. FIG. 12 is a front view showing an example of an electronic apparatus of the present invention.

The navigation system 300 includes map information (not shown), position information acquisition means from GPS (Global Positioning System), self-contained navigation means using a gyro sensor, acceleration sensor, and vehicle speed data, physical quantity sensor 1, The display unit 301 displays predetermined position information or course information.

According to this navigation system, altitude information can be acquired in addition to the acquired position information. By obtaining altitude information, for example, when traveling on an elevated road that shows approximately the same position as a general road, if you do not have altitude information, you are traveling on an ordinary road or on an elevated road The navigation system was unable to determine whether or not the vehicle was being used, and the general road information was provided to the user as priority information. Therefore, in the navigation system 300 according to the present embodiment, altitude information can be acquired by the physical quantity sensor 1, and a change in altitude due to entering from an ordinary road to an elevated road is detected, and navigation information in the traveling state of the elevated road is obtained. Can be provided to the user.

The display unit 301 is, for example, a liquid crystal panel display or an organic EL (Organic Electr).
o-Luminescence) display and other devices that can be made smaller and thinner.

The electronic device provided with the physical quantity sensor of the present invention is not limited to the above-described ones. For example, a personal computer, a mobile phone, a medical device (for example, an electronic thermometer, a blood pressure meter, a blood glucose meter, an electrocardiogram measuring device, an ultrasonic diagnostic device) , Electronic endoscope), various measuring instruments, instruments (for example, vehicles, aircraft, ship instruments), flight simulators, and the like.

5. Next, the moving body (the moving body of the present invention) to which the physical quantity sensor of the present invention is applied will be described. FIG. 13 is a perspective view showing an example of the moving body of the present invention.

As shown in FIG. 13, the moving body 400 includes a vehicle body 401 and four wheels 402, and is configured to rotate the wheels 402 by a power source (engine) (not shown) provided in the vehicle body 401. ing. Such a moving body 400 includes a navigation system 30.
0 (physical quantity sensor 1) is built in.

As described above, the physical quantity sensor, pressure sensor, altimeter, electronic device, and moving body of the present invention have been described based on the illustrated embodiments, but the present invention is not limited thereto, and the configuration of each part is the same. Any structure having a function can be substituted. Moreover, other arbitrary components may be added.

Further, the number, arrangement, shape, and the like of the piezoresistive elements (functional elements) provided in one diaphragm part are not limited to the above-described embodiment. For example, in the above-described embodiment, the piezoresistive element is also provided at the center part of the diaphragm part. A resistance element may be arranged.

In addition, the shape and position of the concave portion formed in the diaphragm portion are not limited to the above-described embodiment. For example, the concave portion may be arranged on the central portion side of the diaphragm portion or in the circumferential direction of the diaphragm portion. A ring may be formed along.

In the above-described embodiment, the case where the wall surface of the recess formed in the diaphragm portion is covered with the insulating film has been described as an example. However, the insulating film may be omitted. In the above-described embodiment, the recess is formed in the silicon layer of the diaphragm portion, but other layers such as an insulating film disposed on the silicon layer are processed without forming the recess in the silicon layer. A recess may be formed.

DESCRIPTION OF SYMBOLS 1 ... Physical quantity sensor 1A ... Physical quantity sensor 2 ... Substrate 3 ... Intermediate layer 5 ... Piezoresistive element 5a ... Piezoresistive element 5b ... Piezoresistive element 5c ... Piezoresistive element 5d ... Piezoresistive element 6 Laminated structure 7 Substrate 20 Diaphragm portion 21 Semiconductor substrate 22 Insulating film 23 Insulating film 24 Recess 25 25 Pressure receiving surface 25A Pressure receiving surface 26 Recess 26a Concave part 26b ... concave part 26c ... concave part 26d ... concave part 41 ... sacrificial layer 42 ... sacrificial layer 51c ... wiring 51d ... wiring 61 ... interlayer insulating film 62 ... wiring layer 63 ... interlayer insulating film 64 ... ··· Wiring layer 65 · · · Surface protective film 66 · · · Sealing layer 100 · · · Pressure sensor 101 · · · Case 102 · · · Arithmetic unit 103 · · · Wiring 104 · · · Through hole 200 · · · Altimeter 201 · · · Display portion 211 · · · ... Silicon layer 21 Silicon oxide layer 213 Silicon layer 214 Wiring 214a Wiring 214b Wiring 214c Wiring 214d Wiring 300 Navigation system 301 Display unit 400 Moving body 401 Car body 402 ... Wheel 641 ... Cover layer 642 ... Pore 2131 ... Recess P ... Pressure S ... Cavity

Claims (11)

A diaphragm portion having a recess opening in the thickness direction, and being bent and deformed by pressure,
A sensor element that overlaps the concave portion in plan view and is arranged in the diaphragm portion and outputs an electrical signal due to distortion;
A physical quantity sensor comprising: The physical quantity sensor according to claim 1, wherein the sensor element has a portion along the wall surface of the recess in a cross-sectional view. The physical quantity sensor according to claim 1, wherein the concave portion has a width that decreases toward a bottom side in a cross-sectional view. The physical quantity sensor according to claim 3, wherein the sensor element has a V-shaped portion in a cross-sectional view. The physical quantity sensor according to claim 1, wherein the sensor element is a piezoresistive element. The physical quantity sensor according to claim 1, wherein the concave portion extends along an outer peripheral portion of the diaphragm portion. 7. The physical quantity sensor according to claim 1, wherein a plurality of the concave portions are arranged side by side along the outer periphery of the diaphragm portion at intervals. A pressure sensor comprising the physical quantity sensor according to claim 1. An altimeter comprising the physical quantity sensor according to any one of claims 1 to 7. An electronic apparatus comprising the physical quantity sensor according to claim 1. A moving body comprising the physical quantity sensor according to claim 1.

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