Patent Application
20150090029
1. Technical Field
The present invention relates to a physical quantity sensor, a pressure sensor, an altimeter, an electronic apparatus, and a moving object.
2. Related Art
In the related art, as a sensor detecting a pressure, a pressure detecting device is known as disclosed in JP-A-5-36993.
The pressure detecting device described in JP-A-5-36993 has a substrate that is a film shape and has a diaphragm deformable in a thickness direction, and a strain gauge that is disposed on the substrate. When a pressure is applied to the diaphragm, the diaphragm is deflected and a resistance value of the strain gauge changes in response to a deflection amount thereof. It is possible to detect the pressure applied to the diaphragm by detecting a potential difference generated due to a variation amount of the resistance value of a piezo-resistance element as a signal of a pressure change.
However, in the pressure detecting device having such a configuration, there is a problem that sensitivity is generally low.
An advantage of some aspects of the invention is to provide a physical quantity sensor having good sensitivity, a pressure sensor, an altimeter, an electronic apparatus, and a moving object.
The invention can be implemented as the following application examples.
This application example is directed to a physical quantity sensor including: a diaphragm section that is deformed to be deflected by receiving a pressure; a fixed electrode that is provided in the diaphragm section; and a movable electrode that has a movable section that is away from the fixed electrode and is disposed opposite to the fixed electrode, in which a shape of the diaphragm section in a plan view is a longitudinal shape, and in which a shape of the fixed electrode in a plan view is a longitudinal shape extending along a longitudinal direction of the diaphragm section.
With this configuration, it is possible to detect the pressure received by the diaphragm section with high accuracy and it is possible to provide the physical quantity sensor having good sensitivity.
In the physical quantity sensor according to the application example described above, it is preferable that the movable electrode has a support section that is provided in the diaphragm and a connection section that connects the support section and the movable section.
In the physical quantity sensor according to the application example described above, it is preferable that the fixed electrode and the support section are arranged along a lateral direction of the diaphragm section.
With this configuration, it is possible to specifically increase a variation amount of a gap between the fixed electrode and the movable electrode by deflection of the diaphragm section due to receiving of the pressure.
In the physical quantity sensor according to the application example described above, it is preferable that the lateral direction of the fixed electrode and the lateral direction of the diaphragm section are the same as each other.
With this configuration, it is possible to significantly increase the variation amount of the gap between the fixed electrode and the movable electrode by deflection of the diaphragm section due to receiving of the pressure.
In the physical quantity sensor according to the application example described above, it is preferable that the shape of the diaphragm section in a plan view is configured such that L2/L1 is within a range of 1.5 or more and 3.0 or less when a length in the longitudinal direction is L1 and a length in the lateral direction is L2.
With this configuration, when the diaphragm section is deformed to be deflected by receiving the pressure, it is possible to greatly change the gap (separation distance) between the fixed electrode and the movable electrode and thereby it is possible to further achieve improvement of accuracy of the physical quantity sensor.
This application example is directed to a pressure sensor including: the physical quantity sensor according to the application example described above.
With this configuration, it is possible to obtain the pressure sensor having high reliability.
This application example is directed to an altimeter including: the physical quantity sensor according to the application example described above.
With this configuration, it is possible to obtain the altimeter having high reliability.
This application example is directed to an electronic apparatus including: the physical quantity sensor according to the application example described above.
With this configuration, it is possible to obtain the electronic apparatus having high reliability.
This application example is directed to a moving object including: the physical quantity sensor according to the application example described above.
With this configuration, it is possible to obtain the moving object having high reliability.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, a physical quantity sensor, a pressure sensor, an altimeter, an electronic apparatus, and a moving object according to the invention will be described with reference to each embodiment illustrated in the drawings.
A physical quantity sensor 1 of
A substrate 6 is formed as a planar shape and, for example, can be configured by laminating an insulation film 62 and a silicon nitride film 63 in this order on a semiconductor substrate 61 configured of a semiconductor such as silicon. A shape of such a substrate 6 in a plan view is not specifically limited and, for example, can be rectangular such as substantially square and substantially rectangular or circular.
Furthermore, the substrate 6 is provided with a diaphragm section 64 that is thinner than peripheral portions and is deformed to be deflected by receiving pressure. The diaphragm section 64 is formed by providing a concave section 65 having a bottom on a lower surface of the substrate 6. Such a diaphragm section 64 is substantially rectangular in a plan view and a lower surface thereof is a pressure receiving surface 641. A thickness of the diaphragm section 64 is not specifically limited and, for example, is preferably 10 μm or more and 50 μm or less, and is further preferably 15 μm or more and 25 μm or less. Therefore, the diaphragm section 64 can be sufficiently deflected to be deformed.
Moreover, in the substrate 6 of the embodiment, the concave section 65 does not pass through the semiconductor substrate 61 and the diaphragm section 64 is configured of three layers of the semiconductor substrate 61, the insulation film 62, and the silicon nitride film 63, but, for example, the concave section 65 may pass through the semiconductor substrate 61 and the diaphragm section 64 may be configured of two layers of the insulation film 62 and the silicon nitride film 63.
A functional element 7 has a fixed electrode 71 and a movable electrode 72 provided on the diaphragm section 64 of the substrate 6. Furthermore, the movable electrode 72 has a support section 721, a movable section 722 that is disposed opposite to the fixed electrode 71 with a space therebetween, and an elastically deformable connection section 723 that connects the support section 721 and the movable section 722 on the substrate 6.
Furthermore, a film thickness of the fixed electrode 71 is not specifically limited, but can be 0.1 μm or more and 1.0 μm or less. Furthermore, a film thickness of the movable electrode 72 is not specifically limited, but can be 0.1 μm or more and 1.0 μm or less.
An element ambient structure 8 is formed to define the cavity section 5 in which the functional element 7 is disposed. The element ambient structure 8 having such a configuration includes an interlayer insulation film 81 that is formed so as to surround the functional element 7 on the substrate 6, a wiring layer 82 that is formed on the interlayer insulation film 81, an interlayer insulation film 83 that is formed on the wiring layer 82 and the interlayer insulation film 81, a wiring layer 84 that is formed on the interlayer insulation film 83 and has a coating layer 841 including a plurality of fine holes (openings), a surface protection film 85 that is formed on the wiring layer 84 and the interlayer insulation film 83, and a sealing layer 86 that is formed on the coating layer 841.
A semiconductor circuit (not illustrated) is built into the semiconductor substrate 61 and above thereof. The semiconductor circuit has a circuit element such as an active element such as a MOS transistor and a circuit element such as a capacitor, an inductor, a resistor, a diode, wiring (including wiring connected to the fixed electrode 71, wiring connected to the movable electrode 72, the wiring layers 82 and 84), and the like which are formed if necessary.
The cavity section 5 defined by the substrate 6 and the element ambient structure 8 functions as a storage section for storing the functional element 7. Furthermore, the cavity section 5 is a space that is sealed. The cavity section 5 functions as a pressure reference chamber that is a reference value of a pressure that is detected by the physical quantity sensor 1. In the embodiment, the cavity section 5 is in a vacuum state (300 Pa or less). It is possible to use the physical quantity sensor 1 as an “absolute pressure sensor” detecting the pressure with reference to the vacuum state and to improve convenience by making the cavity section 5 have the vacuum state.
However, the cavity section 5 may not be in the vacuum state and may be at atmospheric pressure and may be in a reduced pressure state that is lower than atmospheric pressure, and may be a pressurized state that is higher than atmospheric pressure.
As described above, the configuration of the physical quantity sensor 1 is briefly described. As illustrated in
As described above, the physical quantity sensor 1 is configured such that since the cavity section 5 is in the vacuum state, if a pressure P is applied to the pressure receiving surface 641, the diaphragm section 64 is deformed to be deflected on the side of the cavity section 5. Moreover, in
In the physical quantity sensor 1, the arrangement of the functional element 7 or the shape of the diaphragm section 64 is featured so as to detect the received pressure with high accuracy. Hereinafter, detailed description will be given regarding this.
As illustrated in
Furthermore, a shape of the diaphragm section 64 in a plan view is rectangular. Furthermore, respective shapes of the fixed electrode 71 and the movable section 722 in a plan view are rectangular extending along the longitudinal direction of the diaphragm section 64. A leading end portion (free end portion) of the movable section 722 is included in the fixed electrode 71 in a plan view. The lateral direction of the fixed electrode 71 and the lateral direction of the movable section 722 are parallel to the lateral direction of the diaphragm section 64. Thus, naturally, the longitudinal direction of the fixed electrode 71 and the longitudinal direction of the movable section 722 are parallel to the longitudinal direction of the diaphragm section 64.
As described above, since the end 725 of the support section 721 is provided on the center O and the fixed electrode 71 is provided on the side of the thick section 66 more than the support section 721, when the diaphragm section 64 is deflected, the gap G increases.
Furthermore, as described above, since the fixed electrode 71 and the support section 721 are arranged along the lateral direction of the diaphragm section 64, a difference in a displacement amount between the support section 721 and the fixed electrode 71 when the diaphragm section 64 is deflected can be further increased. This is because the side of the lateral direction of the diaphragm section 64 is displaced at a steep angle with respect to the substrate 6 more than the side of the longitudinal direction of the diaphragm section 64 when the diaphragm section 64 is deformed to be deflected.
Specifically, the lateral direction of the fixed electrode 71 and the lateral direction of the support section 721 are parallel to the lateral direction of the diaphragm section 64. That is, since the lateral direction of the fixed electrode 71 and the lateral direction of the diaphragm section 64 are the same direction as each other, the effects described above are remarkably exerted.
Moreover, for example, “parallel” includes that the lateral direction of the fixed electrode 71 and the lateral direction of the support section 721 are inclined by substantially 2 degrees to 3 degrees with respect to the lateral direction of the diaphragm section 64 in addition to being completely parallel to each other.
Furthermore, in the embodiment, the shape of the diaphragm section 64 is rectangular, but if the diaphragm section 64 is a longitudinal shape other than rectangular, when the arrangement direction of the fixed electrode 71 and the support section 721 is parallel to a direction straight to the direction in which the diaphragm section 64 is extended, it is possible to obtain the same effects as described above.
Furthermore, a center portion O6, specifically, the center O in which the functional element 7 is provided is a greatly deflected portion when the pressure is applied. Thus, since the support section 721 can be greatly displaced, it is possible to further increase the variation amount of the gap (variation amount of the separation distance G).
Furthermore, the center portion O6, specifically, the center O of the diaphragm section 64 tends to be greatly deflected as a length L1 of the diaphragm section 64 in the longitudinal direction is long with respect to a length L2 in the lateral direction. Therefore, it is possible to further increase the variation amount of the gap by further lengthening the length L1 with respect to the length L2 and thereby it is possible to obtain the physical quantity sensor 1 having good sensitivity.
A relationship between the length L2 of the diaphragm section 64 in the lateral direction and the length L1 in the longitudinal direction is not specifically limited, but L1/L2 is preferably 1.5 or more and 3.0 or less, and further preferably 1.7 or more and 2.8 or less, and still further preferably 1.8 or more and 2.5 or less. Therefore, it is possible to specifically increase the variation amount of the gap and it is possible to achieve both reduction in size and high sensitivity of the physical quantity sensor 1. Moreover, in the embodiment, L1/L2 is substantially 2.0.
Furthermore, the length L1 of the diaphragm section 64 in the longitudinal direction is preferably 50 μm or more and 110 μm or less and the length L2 of the diaphragm section 64 in the lateral direction is not specifically limited, but is preferably 10 μm or more and 70 μm or less.
An area S1 of the fixed electrode 71 in a plan view is not specifically limited, but is preferably 100 μm2 or more and 800 μm2 or less. Furthermore, an area S5 of the diaphragm section 64 in a plan view is not specifically limited, but is preferably 1000 μm2 or more and 7000 μm2 or less. Therefore, it is possible to achieve the reduction in size of the physical quantity sensor 1.
Furthermore, the gap G between the movable section 722 and the fixed electrode 71 is preferably 0.3 μm or more and 1.0 μm or less in a state where the diaphragm section 64 is not deformed to be deflected. Therefore, it is possible to further effectively actuate the functional element 7 and it is possible to deflect the diaphragm section 64, and it is possible to avoid the contact between the fixed electrode 71 and the movable section 722. Thus, it is possible to prevent damage to the fixed electrode 71 and the movable section 722.
Hereinafter, examination results for the variation amount of the gap with respect to the length L1 of the diaphragm section 64 in the longitudinal direction are described with reference to
A horizontal axis of the graph illustrated in
Dimensions of each section of the physical quantity sensor 1 used for the examination are as follows.
The length L1 of the diaphragm section 64 in the longitudinal direction is 80 μm, the length L2 in the lateral direction is 40 μm, and the film thickness of the diaphragm section 64 is 2.07 μm. Furthermore, the length of the fixed electrode 71 in the longitudinal direction is 39.75 μm and the length in the lateral direction is 11.25 μm. Furthermore, the length of the movable electrode 72 in the longitudinal direction is 30.0 μm and the length in the lateral direction is 9.0 μm. Furthermore, the length of the movable section 722 in the lateral direction is 3.78 μm. Furthermore, in the natural state, the gap G between the movable section 722 and the fixed electrode 71 is 0.6 μm. Furthermore, each film thickness of the fixed electrode 71 and the movable electrode 72 is 0.3 μm.
Furthermore, the functional element 7 was provided so that the end 725 of the support section 721 was positioned on the center O of the diaphragm section 64. Furthermore, the pressure applied to the diaphragm section 64 was 100 kPa.
Furthermore, as an examination method, an detection method was used in which the position of the functional element 7 was not changed and the length L1 of the diaphragm section 64 in the longitudinal direction was changed, and the variation amount of the gap was detected for each length L1.
It was found that the variation amount of the gap was increased as the length L1 was long from the graph illustrated in
Furthermore, if the length L1 is longer than 60 μm, it was found that the variation amount of the gap was specifically increased. The length L1 (60 μm) was 1.5×L2 or more in terms of the relationship with the length L2 of the diaphragm section 64 in the lateral direction.
Furthermore, if the length L1 is substantially 120 μm, great change cannot be seen in the variation amount of the gap. The length L1 (120 μm) was 3.0×L2 in terms of the relationship with the length L2 of the diaphragm section 64 in the lateral direction.
As described above, the length L1 satisfied a numerical value range (1.5×L2 or more and 3.0 L×2 or less) as described above, in the relationship with the length L2 and thereby it was found that it is possible to sufficiently achieve both the reduction in size and the high sensitivity.
Furthermore, the sensitivity when the length L1 was 40 μm and the sensitivity when the length L1 was 80 μm were calculated respectively based on the measured variation amount of the gap.
The sensitivity when the length L1 was 40 μm was 3.29 ppm/kPa. Furthermore, the sensitivity when the length L1 was 80 μm was 8.49 ppm/kPa. It was found that it is possible to improve the sensitivity of the physical quantity sensor 1 by forming the diaphragm section 64 in the longitudinal shape extending in the longitudinal direction.
Next, a manufacturing method of the physical quantity sensor 1 will be briefly described.
First, as illustrated in
The silicon oxide film 62 functions as an inter-element isolation film when forming the semiconductor substrate 61 and a semiconductor circuit above thereof. Furthermore, the silicon nitride film 63 has durability with respect to etching that is performed in a release process that is performed thereafter and functions as a so-called etching-stop layer. Moreover, the silicon nitride film 63 is formed on a limited range including a plane range in which the functional element 7 is formed by the patterning process and a range of a part of element (capacitor) and the like inside the semiconductor circuit. Therefore, failure is eliminated when forming the semiconductor substrate 61 and the semiconductor circuit above thereof.
Next, as illustrated in
Next, as illustrated in
Next, as illustrated in
Next, as illustrated in
Next, as illustrated in
First, as illustrated in
Next, as illustrated in
Next, as illustrated in
A laminated structure of the interlayer insulation film and the wiring layer is formed by a usual CMOS process and the number of the lamination is appropriately set if necessary. That is, more wiring layers may be laminated through the interlayer insulation film if necessary.
First, as illustrated in
Next, as illustrated in
First, as illustrated in
Removing of the interlayer insulation films 81 and 83, and the sacrifice layer 22 can be performed by wet etching in which hydrofluoric acid, buffered hydrofluoric acid, and the like as etching solution are supplied from the plurality of fine holes 842, or by dry etching in which hydrofluoric acid gas and the like as etching gas are supplied from the plurality of fine holes 842.
Next, as illustrated in
Finally, as illustrated in
Moreover, a method for removing a part of the semiconductor substrate 61 is not limited to the dry etching and may be wet etching and the like.
It is possible to manufacture the physical quantity sensor 1 by the processes described above. Moreover, a circuit element such as an active element, a capacitor, an inductor, a resistor, a diode, and wiring of the MOS transistor included in the semiconductor circuit of the physical quantity sensor 1 may be made in the middle of an appropriate process described above (for example, the functional element forming process, the insulation film forming process, the coating layer forming process, and the sealing layer forming process). For example, an inter-circuit element isolation film may be formed together with the silicon oxide film 62, a gate electrode, a capacitor electrode, wiring, and the like may be formed together with the fixed electrode 71 or the movable electrode 72, a gate insulation film, a capacitor dielectric layer, and an interlayer insulation film, may be formed together with the sacrifice layer 22 and the interlayer insulation films 81 and 83, or circuit wiring may be formed together with the wiring layers 82 and 84.
Next, a second embodiment of a physical quantity sensor according to the invention will be described.
Hereinafter, the second embodiment of the physical quantity sensor according to the invention will be described with reference to the drawings and will be described focusing on differences from the embodiment described above and the description of the same matters will be omitted.
The second embodiment is similar to the first embodiment other than that the position of the functional element 7 is different.
As illustrated in
Similar to the first embodiment, the fixed electrode 71 is displaced on the side of the cavity section 5 following the deflection of the diaphragm section 64 by providing the fixed electrode 71 on the diaphragm section 64. On the other hand, since a part of the movable electrode 72 is provided in the thick section 66, the movable electrode 72 is suppressed from displacing to the cavity section 5 more than the fixed electrode 71. Therefore, as illustrated in
Furthermore, a distance L5 between the center O of the diaphragm section 64 and the end 725 of the support section 721 on the side of the fixed electrode 71 with respect to the length L2 of the diaphragm section 64 in the lateral direction is preferably 0.43×L2 or more and 0.4875×L2 or less and further preferably 0.44×L2 or more and 0.47×L2 or less, and still further preferably 0.45×L2 or more and 0.465×L2 or less. It is possible to specifically increase the variation amount of the gap G by providing the support section 721 in a position satisfying the range described above. Thus, it is possible to obtain the physical quantity sensor 1 having specifically good sensitivity.
Hereinafter, examination results of the variation amount of the gap with respect to the distance L5 are described with reference to
A horizontal axis of the graph illustrated in
Furthermore, the graph indicates an average value of the variation amount of the gap in a region X (see
Moreover, the dimensions of each section of the physical quantity sensor 1 used for examination are the same as those of the first embodiment.
Furthermore, as an examination method, a method was used in which the separation distance between the fixed electrode 71 and the support section 721 was not changed and the distance L5 was changed by moving the functional element 7 in the lateral direction of the diaphragm section 64, and the variation amount of the gap was detected for each distance L5. Moreover, a pressure applied to the diaphragm section 64 was 100 kPa.
It was found that the absolute value of the variation amount of the gap was specifically increased when the distance L5 was 17.5 μm or more and 19.5 μm or less from the graph of
Furthermore, the sensitivity when the distance L5 was 0 μm and the sensitivity when the distance L5 was 18.5 μm were calculated respectively based on the measured variation amount of the gap.
The sensitivity when the distance L5 was 0 μm was 8.49 ppm/kPa. Furthermore, the sensitivity when the distance L5 was 18.5 μm was 12.11 ppm/kPa. It was found that it is possible to improve the sensitivity of the physical quantity sensor 1 by biasing the functional element 7 to the side of the thick section 66 from the center O.
Next, a pressure sensor (the pressure sensor according to the invention) including the physical quantity sensor according to the invention will be described.
As illustrated in
The physical quantity sensor 1 is fixed on the inside of the housing 101 by a fixing unit (not illustrated). Furthermore, in the housing 101, the diaphragm section 64 of the physical quantity sensor 1 is provided with, for example, a through hole 104 communicating with the atmosphere (outside of the housing 101).
According to such a pressure sensor 100, the diaphragm section 64 receives the pressure through the through hole 104. The received signal is transmitted to the calculating section through the wiring 103 and is calculated for the pressure data. The calculated pressure data can be displayed through a display section (not illustrated) (for example, a monitor of a personal computer and the like).
Next, an example of an altimeter (the altimeter according to the invention) including the physical quantity sensor according to the invention will be described.
An altimeter 200 can be worn on the wrist as a wristwatch. Furthermore, the physical quantity sensor 1 (pressure sensor 100) is built into the altimeter 200 and an altitude above sea level of a present location or an air pressure of the present location and the like can be displayed on a display section 201.
Moreover, various types of information such as a present time, a heart rate of a user, and the weather can be displayed in the display section 201.
Next, a navigation system to which the electronic apparatus including the physical quantity sensor according to the invention is applied will be described.
A navigation system 300 includes a position information obtaining unit that obtains position information from map information (not illustrated) and a Global Positioning System (GPS), an autonomous navigation unit composed of a gyro sensor, an acceleration sensor, and vehicle speed data, the physical quantity sensor 1, and a display section 301 that displays predetermined position information or route information.
According to the navigation system, it is possible to obtain height information in addition to the obtained position information. By obtaining the height information, for example, when traveling on an elevated road of which substantially the same position is indicated as that of a general road in the position information, the navigation system cannot determine whether a vehicle travels on the general road or on the elevated road if the height information is not included so that the information of the general road is provided to a user as preferred information. Thus, in the navigation system 300 according to the embodiment, it is possible to obtain the height information by the physical quantity sensor 1 and a height change is detected due to entering the elevated road from the general road, and it is possible to provide the navigation information in the traveling state of the elevated road to the user.
Moreover, the display section 301 is configured to be compact and slim such as a liquid crystal panel display, or an Organic Electro-Luminescence (Organic EL) display.
Moreover, the electronic apparatus to which the physical quantity sensor according to the invention is incorporated is not limited to embodiments described above, and, for example, can be applied to a personal computer, a cellular phone, medical equipment (for example, an electronic thermometer, a blood pressure meter, a blood glucose meter, an electrocardiogram measuring device, an ultrasonic diagnostic apparatus, an electronic endoscope), various measuring equipment, instruments (for example, gauges for a vehicle, an aircraft and a ship), a flight simulator, and the like.
Next, a moving object (moving object according to the invention) to which the physical quantity sensor according to the invention is applied will be described.
As illustrated in
As described above, the pressure sensor, the altimeter, the electronic apparatus, and the moving object according to the invention are described with reference to the illustrated embodiments, but the invention is not limited to the embodiments and the configuration of each part can be replaced by another arbitrary configuration matter having the same function. Furthermore, another arbitrary configuration matter or process may be added.
Furthermore, in the above embodiments, a case where the shape of the diaphragm section is rectangular in a plan view is described, but the shape is not specifically limited as long as the shape of the diaphragm section in a plan view is the longitudinal shape. For example, a polygonal shape such as hexagonal, a circular shape such as oval, and the like may be used. Furthermore, the polygonal shape includes one in which corners are rounded and outer edges are curved rather than straight. These configurations apply to the shape of the fixed electrode in a plan view.
Furthermore, in the above embodiments, a case where the shape of the movable electrode in a plan view is rectangular is described, but the shape of the movable electrode in a plan view is not specifically limited. For example, a polygonal shape such as square and hexagonal, a circular shape such as circular and oval, and the like may be used. Furthermore, the polygonal shape includes one in which the corners are rounded and the outer edges are curved rather than straight.
Moreover, in the first embodiment, a case where the end of the support section is disposed on the center of the diaphragm section is described, but the end of the support section may be provided in a position out of the center of the diaphragm section.
Furthermore, in the above embodiments, a case where the support section is provided in the diaphragm section or a case where the support section is provided over the diaphragm section and the thick section is described, but an entire region of the support section may be provided in the thick section.
Furthermore, in the above embodiments, a case where the area of the fixed electrode in a plan view is greater than that of the movable section of the movable electrode is described, but the area of the fixed electrode in a plan view may be equal to that of the movable section of the movable electrode and may be smaller than that of the movable section of the movable electrode.
The entire disclosure of Japanese Patent Application No. 2013-205752, filed Sep. 30, 2013 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-205752 | Sep 2013 | JP | national |
