JP2016080491A - Physical quantity sensor, electronic apparatus and movable body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physical quantity sensor capable of improving pressure detection accuracy, and further to provide an electronic apparatus provided with the physical quantity sensor and a movable body.SOLUTION: A pressure sensor unit 2 comprises: a recess portion 41 having a diaphragm 10 on a bottom portion; and a gelatinous or liquid pressure propagation member 5 being filled in the recess portion 41 and covering the diaphragm 10. An opening portion of the recess portion 41 has a first connection surface 41b connecting the other surface 40b and a wall surface 41a of the recess portion 41 in at least a part thereof. The first connection surface 41b has an angle against a pressure receiving surface 10a of the diaphragm 10 is less than that of the wall surface 41a.SELECTED DRAWING: Figure 1

Description

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

Conventionally, as a physical quantity sensor, a concave portion is formed on the back surface, and a thin portion on the surface side corresponding to the concave portion is configured as a diaphragm, and a sensor chip having a piezoresistor on the surface and the back surface of the sensor chip are bonded to the concave portion. And a pedestal having a through hole that leads to the diaphragm, and a pressure sensor having a configuration in which the diameter of the opening on the sensor chip side in the through hole of the pedestal is smaller than the diameter of the recess in the sensor chip is known (for example, Patent Document 1).
The pressure sensor is configured such that pressure is introduced into the diaphragm from the through hole of the pedestal via the gel member, and a signal corresponding to the pressure applied by the piezoresistance effect is output from the sensor chip.

JP 2007-3449 A

Since the pressure sensor has a configuration in which the diameter of the opening on the sensor chip side in the through hole of the pedestal is smaller than the diameter of the concave part in the sensor chip, the peripheral part of the through hole of the pedestal with respect to the concave part of the sensor chip, It will stick out in the form of an eaves.
Thereby, in the pressure sensor, there is a possibility that bubbles generated between the gel member and the wall surface of the concave portion of the sensor chip stay in the protruding portion of the pedestal and do not come out to the pedestal side.
As a result, when the pressure sensor introduces pressure from the pedestal through hole to the diaphragm through the gel member, a part of the pressure is absorbed by the accumulated bubbles, so that the original pressure is not applied to the diaphragm. There is a fear.
For this reason, there is a possibility that the pressure detection accuracy of the pressure sensor is lowered.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A physical quantity sensor according to this application example includes a recess having a diaphragm at the bottom, and a gel-like or liquid pressure propagation member filled in the recess and covering the diaphragm, and the opening of the recess The portion has a first connection surface that connects at least part of the opening surface and the wall surface of the recess, and the first connection surface has an angle with respect to the pressure receiving surface of the diaphragm that is smaller than the wall surface. And

According to this, in the physical quantity sensor, the first connection surface serves as a guide surface, and bubbles generated between the pressure propagation member and the wall surface of the recess can easily escape from the opening along the first connection surface.
As a result, in the physical quantity sensor, a part of the external pressure is absorbed by the bubbles, and a pressure close to the original pressure is applied to the pressure receiving surface of the diaphragm via the pressure propagation member. .
Therefore, the physical quantity sensor can improve the pressure detection accuracy as compared with the conventional one (for example, the configuration of Patent Document 1, the same applies hereinafter).

  Application Example 2 In the physical quantity sensor according to the application example described above, it is preferable that the first connection surface has a linear portion in a cross-sectional shape cut along a surface perpendicular to the wall surface along the normal line direction of the pressure receiving surface. .

  According to this, in the physical quantity sensor, since the first connection surface has the straight portion in the cross-sectional shape, bubbles generated between the pressure propagation member and the wall surface of the recess are formed along the straight portion of the first connection surface. It becomes easy to come out from the opening.

  Application Example 3 In the physical quantity sensor according to the application example described above, it is preferable that the first connection surface has a curved portion in a cross-sectional shape cut along a plane perpendicular to the wall surface along a normal direction of the pressure receiving surface. .

  According to this, in the physical quantity sensor, since the first connection surface has a curved portion in the cross-sectional shape, bubbles generated between the pressure propagation member and the wall surface of the recess are formed along the curved portion of the first connection surface. It becomes easy to come out from the opening.

  Application Example 4 In the physical quantity sensor according to the application example, it is preferable that the concave portion is provided in a silicon substrate, and the first connection surface is a (111) surface of the silicon substrate.

  According to this, in the physical quantity sensor, since the first connection surface is the (111) surface of the silicon substrate, for example, the first connection surface can be easily formed by wet etching using the crystal anisotropy of the silicon substrate. it can.

  Application Example 5 In the physical quantity sensor according to the application example, it is preferable that the first connection surface is provided in an annular shape in a plan view.

  According to this, since the physical quantity sensor is provided with the first connection surface in an annular shape, bubbles generated between the pressure propagation member and the wall surface of the recess are formed along the first connection surface from the opening to the outside. Furthermore, it becomes easy to come off.

  Application Example 6 In the physical quantity sensor according to the application example, it is preferable that the wall surface is along a normal direction of the pressure receiving surface.

According to this, since the wall surface is along the normal line direction of the pressure receiving surface, the physical quantity sensor can make the planar size of the recess smaller than when the wall surface is inclined to the outside of the recess.
As a result, the physical quantity sensor can be reduced in planar size.

  Application Example 7 In the physical quantity sensor according to the application example, the physical quantity sensor further includes a second connection surface that connects the pressure receiving surface and the wall surface, and the second connection surface has an angle of the diaphragm with respect to the pressure receiving surface. It is preferable that the cross-sectional shape cut by a plane smaller than the wall surface and perpendicular to the wall surface along the normal line direction of the pressure receiving surface is a straight line.

According to this, in the physical quantity sensor, since the cross-sectional shape of the outer peripheral portion of the diaphragm is stably formed by the second connection surface having a straight cross-sectional shape, the stress generated in the outer peripheral portion when the diaphragm is bent Can be reduced.
As a result, the physical quantity sensor can improve the pressure detection accuracy as compared with the case where there is no second connection surface.

  Application Example 8 In the physical quantity sensor according to the application example described above, it is preferable that the recess is provided in a silicon substrate, and the second connection surface is a (111) surface of the silicon substrate.

  According to this, in the physical quantity sensor, since the second connection surface is the (111) surface of the silicon substrate, for example, the second connection surface is easily formed by wet etching using the crystal anisotropy of the silicon substrate. it can.

  Application Example 9 An electronic apparatus according to this application example includes the physical quantity sensor described in any one of the application examples described above.

  According to this, since the electronic device of this configuration includes the physical quantity sensor described in any one of the above application examples, the effect described in any one of the above application examples is achieved, and excellent performance is achieved. It can be demonstrated.

  Application Example 10 A moving body according to this application example includes the physical quantity sensor described in any one of the application examples.

  According to this, since the moving body of this configuration includes the physical quantity sensor described in any one of the above application examples, the effect described in any one of the above application examples is achieved, and excellent performance is achieved. It can be demonstrated.

It is a schematic diagram which shows schematic structure of a pressure sensor, (a) is a schematic plan view, (b) is a schematic cross section in the AA of (a). The circuit diagram for a model detection of a pressure sensor. The flowchart which shows the main manufacturing processes of the manufacturing method of a pressure sensor. (A)-(d) is a schematic cross section explaining a main manufacturing process in order. (E)-(g) is a schematic cross section explaining a main manufacturing process in order. The model perspective view which shows the altimeter as an example of the electronic device provided with the physical quantity sensor. The schematic front view which shows the navigation system as another example of the electronic device provided with the physical quantity sensor. The model perspective view which shows the motor vehicle as an example of the mobile body provided with the physical quantity sensor.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.

(Embodiment)
A pressure sensor having a pressure detection function will be described as an example of the physical quantity sensor.
FIG. 1 is a schematic diagram showing a schematic configuration of a pressure sensor, FIG. 1 (a) is a schematic plan view, and FIG. 1 (b) is a schematic cross-sectional view taken along line AA in FIG. 1 (a). is there. FIG. 2 is a schematic detection circuit diagram of the pressure sensor. In the plan view, some components are omitted. Further, for convenience of explanation, the dimensional ratio of each component is different from the actual one.

  First, the configuration of the pressure sensor 1 will be described. As shown in FIG. 1, the pressure sensor 1 includes a pressure sensor unit 2, a pedestal 3 to which the pressure sensor unit 2 is electrically connected, and a cylindrical container that is fixed to the pedestal 3 and accommodates the pressure sensor unit 2. 4 and a pressure propagation member 5 that is filled in the container 4 to protect the pressure sensor unit 2 and that propagates pressure from the outside to the pressure sensor unit 2. Here, the pressure sensor unit 2 corresponds to a physical quantity sensor.

The pressure sensor unit 2 includes a substrate 40 and a hollow portion layer 50 that covers the one surface 40a side of the substrate 40, has a substantially rectangular planar shape, and is configured in a substantially rectangular parallelepiped shape.
The pressure sensor unit 2 is arranged on the one surface 40a side of the substrate 40, receives the distortion, and outputs a signal, and the other surface 40b in which the one surface 40a of the substrate 40 has a front-back relationship. On the side, the concave portion 41 provided to cover the piezoresistive element 20 in a plan view, the diaphragm 10 provided at the bottom of the concave portion 41, and the gel-like filling the concave portion 41 and covering the diaphragm 10 Alternatively, a liquid pressure propagation member 5 is provided.
In addition, the pressure sensor unit 2 is for detection in which a pressure reference chamber S that is a cavity that overlaps the diaphragm 10 in a plan view and the piezoresistive element 20 as shown in FIG. Circuit 30.

Diaphragm 10 is formed on the other side of substrate 40 using a semiconductor substrate such as an SOI substrate (a substrate in which a SiO ₂ (also referred to as silicon dioxide or silicon oxide film) layer is inserted between a silicon substrate layer and a silicon layer). By providing the recess 41 on the side of the surface 40 b, it is formed at the bottom of the recess 41. In addition, the recessed part 41 is formed in the substantially rectangular shape by planar view.
Here, an SOI substrate is used as the substrate 40, and the recess 41 is provided by etching the silicon substrate layer 43 until it reaches the SiO ₂ layer 44 (details of the manufacturing method will be described later).

The opening part of the recessed part 41 has the 1st connection surface 41b which connects the other surface 40b as an opening surface and the wall surface 41a of the recessed part 41 at least in part.
The 1st connection surface 41b is provided so that the angle with respect to the pressure receiving surface 10a of the diaphragm 10 may become smaller than the wall surface 41a.
The first connection surface 41b is provided so that a cross-sectional shape (the shape of FIG. 1B) cut along a surface perpendicular to the wall surface 41a along the normal direction of the pressure receiving surface 10a has a straight line portion. It is preferable.

Here, since the concave portion 41 is provided in the silicon substrate layer 43 as a silicon substrate, the first connection surface 41b has a (111) plane of the silicon substrate layer 43 (the angle with respect to the pressure receiving surface 10a is about 54.7 degrees). It is preferable that
Moreover, it is preferable that the 1st connection surface 41b is provided cyclically | annularly by planar view. Here, even if the first connection surface 41b is partially interrupted, it is defined as being provided in an annular shape.
The wall surface 41a is preferably along the normal direction of the pressure receiving surface 10a (specifically, substantially perpendicular to the pressure receiving surface 10a).

It is preferable that the recessed part 41 further has the 2nd connection surface 41c which connects the pressure receiving surface 10a and the wall surface 41a.
The second connection surface 41c has a cross-sectional shape obtained by cutting the diaphragm 10 at an angle with respect to the pressure receiving surface 10a that is smaller than the wall surface 41a and perpendicular to the wall surface 41a along the normal direction of the pressure receiving surface 10a (FIG. 1B). Is preferably a straight line.
Here, since the recess 41 is provided in the silicon substrate layer 43, the second connection surface 41 c is preferably the (111) surface of the silicon substrate layer 43.

The piezoresistive element 20 is formed in a substantially rectangular shape by doping (diffusing or implanting) impurities such as phosphorus and boron into the silicon layer 45 of the substrate 40. The piezoresistive element 20 has a property that the resistance value linearly changes in accordance with applied stress (distortion due to the deflection of the diaphragm 10).
The piezoresistive element 20 is provided so as to correspond to each of the four sides of the substantially rectangular outline of the diaphragm 10. (For convenience, the reference numeral 20 is used for the description of the entire piezoresistive element, and the reference numerals 21 to 24 are used for the individual description.)

The piezoresistive elements 21 to 24 are disposed inside the diaphragm 10 and in the immediate vicinity of the sides 11 to 14 of the contour.
More specifically, for the side 11 of the diaphragm 10, a piezoresistive element 21 is arranged in the vicinity of the center of the side 11 with the longitudinal direction extending along the side 11, and for the side 12 facing the side 11, the piezoresistive element 21. The resistance element 22 is arranged in the vicinity of the center of the side 12 along the side 12 in the longitudinal direction.
For the side 13 adjacent to the side 11 of the diaphragm 10, a piezoresistive element 23 is arranged near the center of the side 13 along the direction perpendicular to the side 13, and the side facing the side 13. 14, a piezoresistive element 24 is arranged in the vicinity of the center of the side 14 with its longitudinal direction being along the direction orthogonal to the side 14.
That is, the piezoresistive elements 21 to 24 are arranged so that their longitudinal directions are all the same. Note that wirings for connecting the piezoresistive elements 21 to 24 are omitted. Note that a plurality of piezoresistive elements 21 to 24 may be grouped in series.

As shown in FIG. 2, the piezoresistive elements 21 to 24 are connected to the detection circuit 30 and constitute a bridge circuit (Wheatstone bridge circuit).
The piezoresistive elements 21 to 24 are configured to have the same resistance value.

The pressure reference chamber S is inside the cavity layer 50 and has a substantially rectangular parallelepiped shape. The diaphragm 10 has a substantially rectangular outline that is slightly smaller at the bottom of the substantially rectangular shape in plan view. Will be provided.
The pressure reference chamber S is sealed in a vacuum state (for example, a degree of vacuum of 10 Pa or less). Thereby, the pressure reference chamber S becomes a reference of the pressure detected by the pressure sensor unit 2, and the pressure sensor 1 functions as an absolute pressure sensor.
Note that the pressure reference chamber S may not be in a vacuum state, and may be, for example, an atmospheric pressure state or a pressurized state filled with an inert gas such as nitrogen, argon, or helium, or may be depressurized from the atmospheric pressure. It may be in a reduced pressure state.

  In the pressure reference chamber S, for example, an insulating film (passivation film) 46 is formed on the one surface 40a side of the substrate 40 by using a semiconductor manufacturing process, and then a sacrificial layer 51 ′ composed of an oxide film layer 51 and the like is sequentially deposited. Then, the metal layer 52 is sequentially deposited so as to surround the sacrificial layer 51 ′ and cover the sacrificial layer 51 ′, and then a plurality of through holes 53 are provided in the metal layer 52 covering the sacrificial layer 51 ′. After the selective release etching of the sacrificial layer 51 ′, the through hole 53 is provided in the cavity layer 50 by sealing with the sealing layer 54. (Here, for convenience, the inside of the pressure reference chamber S is shown as a sacrificial layer 51 '.)

Terminals 31, 32, 33, and 34 are provided at the four corners of the outer surface of the cavity layer 50 on the sealing layer 54 side.
The terminal 31 is connected between the piezoresistive element 21 and the piezoresistive element 23 and the terminal 32 is connected between the piezoresistive element 22 and the piezoresistive element 24 by a wiring (not shown) in which the metal layer 52 and the like are patterned. The terminal 33 is connected between the piezoresistive element 22 and the piezoresistive element 23, and the terminal 34 is connected between the piezoresistive element 21 and the piezoresistive element 24.

The pedestal 3 is formed in a substantially rectangular flat plate shape using a glass epoxy substrate (epoxy substrate with glass fiber) or the like, and internal terminals 61, 62, 63, 64 are provided in the range inside the container 4 on the main surface 3 a on the container 4 side. Is provided.
The internal terminals 61 to 64 are respectively connected to external terminals 71, 72, 73, and 74 provided on one end side of the main surface 3a of the pedestal 3 by wiring not shown. More specifically, the internal terminal 61 is connected to the external terminal 71, the internal terminal 62 is connected to the external terminal 72, the internal terminal 63 is connected to the external terminal 73, and the internal terminal 64 is connected to the external terminal 74.

  In the pressure sensor unit 2, terminals 31 to 34 are connected to internal terminals 61 to 64 of the pedestal 3 via bonding wires 80, respectively. More specifically, the terminal 31 is connected to the internal terminal 61, the terminal 32 is connected to the internal terminal 62, the terminal 33 is connected to the internal terminal 63, and the terminal 34 is connected to the internal terminal 64. As a result, the pressure sensor unit 2 is electrically connected to the base 3.

  The container 4 is formed in a cylindrical shape (round pipe shape) using a metal (for example, stainless steel such as SUS304 or SUS316, white or titanium, or the like) or a resin (for example, ABS resin, PC resin, PBT resin, or the like). The pressure sensor unit 2 is fixed to the main surface 3a of the base 3 with an adhesive member (not shown) so as to accommodate the pressure sensor unit 2. In addition, the shape of the container 4 is not limited to a round pipe shape, and may be a square pipe shape.

The container 4 is filled with a gel-like pressure propagation member 5. The pressure propagation member 5 is also filled in the recess 41 of the pressure sensor unit 2 and covers the diaphragm 10.
For the pressure propagation member 5, it is preferable to use a gel material such as a fluorine-based gel, a silicone-based gel, or a fluorosilicone-based gel.
The pressure propagation member 5 is filled from the main surface 3a of the pedestal 3 to a height at which the pressure sensor unit 2 sinks, protects the pressure sensor unit 2, and propagates external pressure to the pressure sensor unit 2 (diaphragm 10). Fulfills the function of
The pressure propagation member 5 may be liquid as long as it can perform the above function.

  The pressure sensor 1 is supplied with a drive voltage (AVDC) from an external drive circuit (not shown) of the control IC, for example, via the external terminal 73 and the internal terminal 63 and to the external terminal 74. The terminal 34 is grounded (grounded) via the internal terminal 64. As a result, the pressure sensor 1 outputs the midpoint potential in the detection circuit 30 to the external terminals 71 and 72 via the terminals 31 and 32 and the internal terminals 61 and 62.

Next, the operation of the pressure sensor 1 (pressure sensor unit 2) will be described.
As shown in FIG. 2, the pressure sensor 1 includes a potential difference between the terminals 31 and 32 caused by a change in the resistance value of the piezoresistive elements 21 to 24 due to the bending (deformation) of the diaphragm 10 when pressure is applied from the outside. The pressure value is derived from
The piezoresistive elements 21 and 22 are set so that the longitudinal direction is compressed and the resistance value is reduced by the diaphragm 10 being bent, and the piezoresistive elements 23 and 24 are set by the diaphragm 10 being bent. The longitudinal direction is extended so that the resistance value is increased.

In the pressure sensor 1, the diaphragm 10 does not bend in a state where no pressure is applied, so that the resistance values of the piezoresistive elements 21 to 24 are not changed and remain equal to each other.
As a result, in the pressure sensor 1, the potential difference between the terminals 31 and 32 becomes 0, and the derived pressure value becomes 0.

When pressure is applied from the outside to the pressure sensor 1, the diaphragm 10 bends, for example, toward the pressure reference chamber S, so that the resistance values of the piezoresistive elements 21 and 22 become small, and the piezoresistive elements 23 and 24. The resistance value increases.
Thereby, in the pressure sensor 1, since the midpoint potential of the terminals 31 and 32 changes and a potential difference is generated between the terminals 31 and 32, a pressure value corresponding to the potential difference is derived based on a lookup table or the like. .
In addition, it is known that the stress produced when the diaphragm 10 bends is so large that it is close to the outline. From this, it is preferable that the piezoresistive element 20 is disposed immediately inside the contour of the diaphragm 10 in order to improve the pressure detection sensitivity (in other words, increase the change in the resistance value).

As described above, in the pressure sensor unit 2 as a physical quantity sensor, the first connection surface 41b serves as a guide surface, and bubbles are generated between the pressure propagation member 5 and the wall surface 41a of the recess 41 when the pressure propagation member 5 is filled. However, it becomes easy to come out from the opening along the first connection surface 41b.
As a result, the pressure sensor unit 2 reduces the absorption of a part of the pressure from the outside by the bubbles, and a pressure close to the original pressure is applied to the pressure receiving surface 10a of the diaphragm 10 via the pressure propagation member 5. Will be.
Therefore, the pressure sensor unit 2 can improve pressure detection accuracy as compared with the conventional case.

  Moreover, the pressure sensor unit 2 has a linear part in the cross-sectional shape (shape of FIG.1 (b)) which the 1st connection surface 41b cut | disconnected by the surface orthogonal to the wall surface 41a along the normal line direction of the pressure receiving surface 10a. Therefore, bubbles generated between the pressure propagation member 5 and the wall surface 41a of the concave portion 41 can easily escape from the opening portion to the outside along the straight portion of the first connection surface 41b.

The first connection surface 41b is provided so that the cross-sectional shape (the shape of FIG. 1B) cut along a surface perpendicular to the wall surface 41a along the normal direction of the pressure receiving surface 10a has a curved portion. (For example, the cross-sectional shape may be provided so as to curve toward the opening side).
According to this, in the pressure sensor unit 2, since the first connection surface 41 b has a curved portion in the cross-sectional shape, bubbles generated between the pressure propagation member 5 and the wall surface 41 a of the recess 41 are converted into the first connection surface. It becomes easy to come out from the opening along the curved portion 41b.

  Further, since the first connection surface 41 b is the (111) surface of the silicon substrate layer 43, the pressure sensor unit 2 has, for example, the first connection surface by wet etching using crystal anisotropy of the silicon substrate layer 43. 41b can be formed easily.

  Further, in the pressure sensor unit 2, since the first connection surface 41 b is provided in an annular shape, bubbles generated between the pressure propagation member 5 and the wall surface 41 a of the recess 41 are related to the circumferential position of the recess 41. Therefore, it is easy to come out from the opening along the first connection surface 41b.

Further, in the pressure sensor unit 2, since the wall surface 41a is along the normal direction of the pressure receiving surface 10a, the planar size of the recess 41 is larger than the case where the wall surface 41a is inclined to the outside of the recess 41 (on the container 4 side). Can be reduced.
As a result, the pressure sensor unit 2 can be reduced in planar size. In other words, more pressure sensor units 2 can be manufactured from wafer-like substrates 40 of the same size.
Thereby, the pressure sensor unit 2 can contribute to miniaturization of the planar size of the pressure sensor 1.

Further, the pressure sensor unit 2 has a cross-sectional shape cut along a plane perpendicular to the wall surface 41a along the normal direction of the pressure receiving surface 10a and having an angle with respect to the pressure receiving surface 10a of the diaphragm 10 smaller than that of the wall surface 41a (FIG. 1B). ) Has a second connection surface 41c that is a straight line.
Thereby, since the cross-sectional shape of the outer peripheral part of the diaphragm 10 is formed stably, the pressure sensor unit 2 can reduce the dispersion | variation in the stress produced in the outer peripheral part when the diaphragm 10 bends.
As a result, the pressure sensor unit 2 can improve the pressure detection accuracy as compared with the case where the second connection surface 41c is not provided.

  Moreover, since the 2nd connection surface 41c is the (111) surface of the silicon substrate layer 43, the pressure sensor unit 2 is the 2nd connection surface by wet etching using the crystal anisotropy of the silicon substrate layer 43, for example. 41c can be formed easily.

Next, an example of the manufacturing method of the pressure sensor 1 will be described.
FIG. 3 is a flowchart showing main manufacturing steps of the pressure sensor manufacturing method, and FIGS. 4A to 4D and FIGS. 5E to 5G are schematic diagrams for sequentially explaining the main manufacturing steps. It is sectional drawing. In addition, the cross-sectional position of each figure is the same as that of FIG.1 (b).

  As shown in FIG. 3, the manufacturing method of the pressure sensor 1 includes a piezoresistive element forming step, a pressure reference chamber forming step, a concave portion forming first step, a concave portion forming second step, a pedestal connecting step, and a pressure propagation. And a member filling step.

[Piezoresistive element formation process]
First, as shown in FIG. 4A, the piezoresistive element 20 is formed on the one surface 40 a side of the wafer-like substrate 40.
Specifically, the silicon layer 45 on the one surface 40a side of the substrate 40 is doped with an impurity such as phosphorus or boron at a position closest to the inside of the outline of the diaphragm 10 to be formed later, so that the piezoresistor described above is obtained. Element 20 (21-24) is formed.

[Pressure reference chamber formation process]
Next, as shown in FIG. 4B, an insulating film 46 made of Si ₃ N ₄ (also called silicon nitride or silicon nitride) is formed on one surface 40a of the substrate 40, and then a CVD method or the like is performed. A sacrificial layer 51 ′ composed of an oxide film (for example, SiO ₂ film) layer 51 or the like is sequentially deposited, surrounds the sacrificial layer 51 ′, and further covers a metal layer (wiring layer) by sputtering or the like so as to cover from above. The sacrificial layer 51 ′ and the metal layer 52 are deposited alternately in a plurality of layers.

  Next, a plurality of through holes 53 are provided in the metal layer 52 covering the sacrificial layer 51 ′, and the sacrificial layer 51 ′ is selectively release etched from the through holes 53 by dry etching or wet etching, and then in vacuum (for example, The pressure reference chamber S is formed inside the cavity layer 50 by sealing the through-hole 53 with the sealing layer 54 using a sputtering method or the like at a degree of vacuum of 10 Pa or less.

At this time, terminals 31 to 34 are formed at the four corners on the outer surface of the cavity layer 50 on the sealing layer 54 side by using a sputtering method or the like, and connected to the piezoresistive element 20 by wiring in which the metal layer 52 and the like are patterned.
Note that the inside of the pressure reference chamber S may not be in a vacuum state, and may be, for example, an atmospheric pressure state or a pressurized state filled with an inert gas such as nitrogen, argon, or helium, or a pressure lower than the atmospheric pressure. It may be in a reduced pressure state.

[Recess formation first step]
Next, as shown in FIG. 4C, the other surface 40b side of the substrate 40 is shaved using a back grinding method or the like, and the thickness of the substrate 40 (for example, about 700 μm) is changed to a desired thickness (for example, 150 μm). The resist 101 is applied to the other surface 40b of the substrate 40 using a spin coating method or the like, and the resist 101 is slightly smaller than the original planar shape of the recess 41 using a photolithography method or the like. Pattern so as to be.

Then, as shown in FIG. 4 (d), forming a protective film by Bosch process (c-C ₄ F ₈ (eight fluoride cyclobutane) gas, isotropic SF ₆ (sulfur hexafluoride) gas The silicon substrate layer 43 of the substrate 40 is etched until it reaches the SiO ₂ layer 44 from the other surface 40b by dry etching (deep silicon etching) using a process that alternately repeats the etching step, and the planar shape is originally A concave portion 41 ′ slightly smaller than the shape is formed. Thereby, diaphragm 10 'is formed in the bottom part of recessed part 41'.

At this time, as shown in FIG. 5 (e), which is an enlarged view of the B portion in FIG. 4 (d), the cross-sectional shape of the wall surface 41a ′ of the recess 41 ′ is an uneven shape in which arcs are continuous by the Bosch process. It has become. The shape of the arc (degree of curvature) depends on the dry etching state, varies greatly, and has no reproducibility.
Accordingly, the cross-sectional shape (the shape of the connecting portion between the wall surface 41a ′ of the silicon substrate layer 43 and the SiO ₂ layer 44 in FIG. 5E) of the outer peripheral portion (the portion including the contour) of the diaphragm 10 ′ varies greatly. If this is the case, the pressure detection sensitivity may vary, and the pressure detection accuracy may be adversely affected.

In addition, a polymer film ((CF ₂ ) _n ) having water repellency is firmly formed as a protective film 47 on the wall surface 41 a ′, and as it is, the pressure propagation member 5 and the recess 41 are filled when the pressure propagation member 5 described later is filled. Adhesion with '(diaphragm 10') is hindered, and there is a possibility that pressure from the outside may not be accurately propagated to the diaphragm 10 'due to a gap (bubble).
In order to solve at least a part of these problems, the inventor provided the following second step of forming a recess.

[Recess formation second step]
Next, as shown in FIG. 5F, after removing the resist 101 by ashing or the like, for example, a KOH (potassium hydroxide) aqueous solution, a TMAH (tetramethylammonium hydroxide) aqueous solution, an EDP (ethylenediamine pyrocatechol) aqueous solution, or the like. Using an alkaline etching solution, the recess 41 ′ is wet-etched (anisotropic etching) using the crystal anisotropy of the silicon substrate layer 43.
As a result, the protective film 47 is decomposed and removed, and the wall surface 41a is formed smoothly with unevenness, the first connection surface 41b and the second connection surface 41c which are (111) surfaces of the silicon substrate layer 43, A recess 41 having a diaphragm 10 is formed.

The shape of the recess 41 is adjusted by the etching time of wet etching.
As an example, since the etching rate of the silicon substrate layer 43 is about 0.4 μm / minute, when the etching amount for the recess 41 ′ is set to about 2 μm to 3 μm, the etching time is about 5 minutes to 8 minutes.

Through the steps so far, the pressure sensor unit 2 before filling the pressure propagation member 5 (for the sake of convenience, the reference numeral remains 2) is completed.
The pressure sensor unit 2 stably forms the cross-sectional shape of the outer peripheral portion of the diaphragm 10 by the second step of forming the concave portion, thereby reducing variations in stress generated in the outer peripheral portion when the diaphragm 10 is bent. can do.

Moreover, the protective film 47 is removed from the pressure sensor unit 2 by the second recess formation step, and the affinity between the pressure propagation member 5 and the recess 41 is improved.
Therefore, the pressure sensor unit 2 improves the adhesion between the pressure propagation member 5 and the recess 41 (diaphragm 10) when the pressure propagation member 5 is filled, and the pressure from the outside is accurately propagated to the diaphragm 10. become.

[Pedestal connection process]
Next, the pressure sensor unit 2 is connected to the base 3 as shown in FIG. Specifically, the terminals 31 to 34 of the pressure sensor unit 2 are connected to the internal terminals 61 to 64 of the base 3 by, for example, soldering using the bonding wires 80. As a result, the pressure sensor unit 2 is electrically connected to the base 3.
Next, the container 4 is fixed to the main surface 3 a of the base 3 with an adhesive member (not shown) so as to accommodate the pressure sensor unit 2.

[Pressure propagation member filling process]
Next, as shown in FIG. 1 (b), the container 4 is filled with a pressure propagation member 5. Specifically, using a filling device such as a dispenser, the pressure propagation member 5 is filled from the main surface 3a of the base 3 to a height at which the pressure sensor unit 2 sinks.
As a result, the pressure propagation member 5 is also filled in the recess 41 of the pressure sensor unit 2, and the diaphragm 10 is covered with the pressure propagation member 5.

Next, the pressure is reduced using a vacuum chamber or the like to remove bubbles in the pressure propagation member 5 and the container 4. At this time, the first connection surface 41b and the second connection surface 41c serve as guide surfaces, and air bubbles can easily escape from the recess 41.
Next, for example, the pressure propagation member 5 is cured by being left for about 24 hours in an environment of 30 ° C. to 40 ° C.
The pressure sensor 1 as shown in FIG. 1 is obtained through the above steps.

As described above, in the manufacturing method of the pressure sensor 1, since the sectional shape of the outer peripheral portion of the diaphragm 10 of the pressure sensor unit 2 is stably formed by the second step of forming the recess, the diaphragm 10 is bent. The variation in stress generated in the outer peripheral portion can be reduced.
As a result, the manufacturing method of the pressure sensor 1 can improve the pressure detection accuracy of the pressure sensor 1 as compared with the case where the concave portion 41 is formed only in the first step of forming the concave portion.

In addition, in the manufacturing method of the pressure sensor 1, the protective film 47 is removed by the second step of forming the recess, and the affinity between the pressure propagation member 5 and the recess 41 is improved.
From this, the manufacturing method of the pressure sensor 1 improves the adhesion between the pressure propagation member 5 and the recess 41 (diaphragm 10) when the pressure propagation member 5 is filled, and accurately propagates the pressure from the outside to the diaphragm 10. be able to.
As a result, the manufacturing method of the pressure sensor 1 can improve the pressure detection accuracy of the pressure sensor 1 as compared with the case where the concave portion 41 is formed only in the first step of forming the concave portion.

(Electronics)
Next, an electronic device including the physical quantity sensor described above will be described.
FIG. 6 is a schematic perspective view showing an altimeter as an example of an electronic apparatus including a physical quantity sensor.

The altimeter 200 can be worn on the wrist like a wristwatch. In addition, a pressure sensor 1 having a pressure sensor unit 2 as a physical quantity sensor is mounted inside the altimeter 200, and the altitude from the sea level at the current location or the atmospheric pressure at the current location is displayed on the display unit 201. .
In addition to the altitude and atmospheric pressure, the display unit 201 displays various information such as the current time, the user's heart rate, and weather.

As described above, since the altimeter 200 of this configuration includes the pressure sensor 1, the effects described in the above embodiment are achieved, and excellent performance (for example, highly accurate altitude detection performance) is exhibited. be able to.
For example, if the pressure sensor 1 is mounted on a wristwatch or the like having a waterproof mechanism, the wristwatch or the like can be provided with a function as a high-precision water depth gauge by detecting water pressure with high accuracy.

Next, another example of an electronic device including the above-described physical quantity sensor will be described.
FIG. 7 is a schematic front view showing a navigation system as another example of an electronic apparatus including a physical quantity sensor.

  The navigation system 300 includes map information (not shown), position information acquisition means from a GPS (Global Positioning System), self-contained navigation means using a gyro sensor, acceleration sensor, and vehicle speed data, and pressure as a physical quantity sensor. A pressure sensor 1 including the sensor unit 2 and a display unit 301 that displays predetermined position information or course information are provided.

The navigation system 300 can acquire altitude information by the pressure sensor 1 in addition to the acquired position information.
In conventional navigation systems that do not have altitude information, when general roads and elevated roads are overlapped, it is impossible to distinguish between general roads and elevated roads, so priority information is available even when traveling on elevated roads. There was a problem that navigation information in general road driving was provided to the user.
On the other hand, in the navigation system 300, by acquiring altitude information, it becomes possible to discriminate between ordinary roads and elevated roads, so that navigation information on elevated road traveling can be reliably given to the user during elevated road traveling. Can be provided.

  Note that the display unit 301 of the navigation system 300 is configured to be small and thin by using, for example, a liquid crystal panel display, an organic EL (Organic Electro-Luminescence) display, or the like.

  As described above, since the navigation system 300 of this configuration includes the pressure sensor 1, the effects described in the above-described embodiment are achieved, and excellent performance (for example, accuracy by acquiring high-accuracy altitude information is obtained). Providing high navigation information).

  Note that the electronic device provided with the physical quantity sensor described above is not limited to the above-described one, and 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 wave) Diagnostic devices, electronic endoscopes), various measuring instruments, instruments (for example, instruments for vehicles, aircraft, ships), flight simulators, and the like.

(Moving body)
Next, a moving body provided with the above-described physical quantity sensor will be described.
FIG. 8 is a schematic perspective view illustrating an automobile as an example of a moving object including a physical quantity sensor.

As shown in FIG. 8, the automobile 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.
The automobile 400 includes a pressure sensor 1 including a pressure sensor unit 2 as a physical quantity sensor, for example, an altitude detection sensor such as a navigation device and an attitude control device, an air pressure detection sensor for wheels 402, and a combustion chamber of an engine. It is used as a pressure detection sensor.

  According to this, since the automobile 400 includes the pressure sensor 1, the effect described in the above embodiment is achieved, and excellent performance (for example, high-accuracy navigation performance according to altitude, high altitude according to altitude). Highly responsive attitude control performance, highly accurate air pressure management performance, highly accurate combustion chamber pressure management performance, etc.).

  The physical quantity sensor described above is not limited to the automobile 400 described above, and is preferably used as, for example, an altitude detection sensor of a mobile body including a self-propelled robot, a self-propelled transport device, a train, a ship, an airplane, an artificial satellite, and the like. In any case, the effect described in the above embodiment can be achieved, and a mobile body that exhibits excellent performance can be provided.

DESCRIPTION OF SYMBOLS 1 ... Pressure sensor, 2 ... Pressure sensor unit as physical quantity sensor, 3 ... Base, 3a ... Main surface, 4 ... Container, 5 ... Pressure propagation member, 10 ... Diaphragm, 10 '... Diaphragm before completion, 10a ... Pressure receiving surface 11, 11, 13, 14,... Edge of the diaphragm, 20, 21, 22, 23, 24, piezoresistive element, 30, detection circuit, 31, 32, 33, 34, terminal, 40, substrate, 40 a ... one surface, 40b ... the other surface, 41 ... a recess, 41 '... a recess before completion, 41a ... a wall surface, 41a' ... a wall surface before completion, 41b ... a first connection surface, 41c ... a second connection surface, 43 A silicon substrate layer as a silicon substrate, 44 ... SiO ₂ layer, 45 ... silicon layer, 46 ... insulating film, 47 ... protective film, 50 ... cavity layer, 51 ... oxide film layer, 51 '... sacrificial layer, 52 ... Metal layer 53 ... through hole 54 ... Stop layer, 61, 62, 63, 64 ... internal terminal, 71, 72, 73, 74 ... external terminal, 80 ... bonding wire, 101 ... resist, 200 ... altimeter as electronic equipment, 201 ... display unit, 300 ... electronic A navigation system as a device, 301 ... a display unit, 400 ... an automobile as a moving body, 401 ... a vehicle body, 402 ... a wheel, S ... a pressure reference chamber.

Claims (10)

A recess having a diaphragm at the bottom;
A gel-like or liquid pressure propagation member filled in the recess and covering the diaphragm,
The opening of the recess has a first connection surface connecting at least part of the opening surface and the wall surface of the recess,
The physical quantity sensor, wherein the first connection surface has an angle with respect to the pressure receiving surface of the diaphragm smaller than that of the wall surface.   2. The physical quantity sensor according to claim 1, wherein the first connection surface has a linear portion in a cross-sectional shape cut along a surface perpendicular to the wall surface along a normal direction of the pressure receiving surface.   3. The physical quantity sensor according to claim 1, wherein the first connection surface has a curved portion in a cross-sectional shape cut along a surface perpendicular to the wall surface along a normal direction of the pressure receiving surface. .   4. The physical quantity sensor according to claim 1, wherein the recess is provided in a silicon substrate, and the first connection surface is a (111) surface of the silicon substrate. 5.   The physical quantity sensor according to any one of claims 1 to 4, wherein the first connection surface is provided in an annular shape in a plan view.   The physical quantity sensor according to claim 1, wherein the wall surface is along a normal line direction of the pressure receiving surface. A second connection surface connecting the pressure receiving surface and the wall surface;
The second connection surface has an angle with respect to the pressure receiving surface of the diaphragm smaller than that of the wall surface, and a cross-sectional shape cut by a surface orthogonal to the wall surface along a normal direction of the pressure receiving surface is a straight line. The physical quantity sensor according to claim 1, wherein:   The physical quantity sensor according to claim 7, wherein the recess is provided in a silicon substrate, and the second connection surface is a (111) surface of the silicon substrate.   An electronic apparatus comprising the physical quantity sensor according to any one of claims 1 to 8.   A moving body comprising the physical quantity sensor according to any one of claims 1 to 8.

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