JP2020088017A - Detection device - Google Patents

Abstract

To improve the noise resistance of a detection device.SOLUTION: A detection device includes a semiconductor substrate, a humidity detection unit 21 and a temperature detection unit 22 that are provided above the semiconductor substrate and output a signal according to a physical quantity, and a noise suppressing unit composed of a plurality of semiconductor layers stacked such that the polarities are alternately inverted in the semiconductor substrate 70 below the humidity detection unit. Further, a voltage that reversely biases each pn junction formed between the plurality of semiconductor layers is applied to the noise suppression unit. The noise suppression unit also includes a diffusion layer 106 formed on the surface layer of the semiconductor substrate. The diffusion layer functions as a resistor that generates heat when a current flows.SELECTED DRAWING: Figure 9

Description

The present invention relates to a detection device such as a humidity detection device.

As a detection device, for example, a humidity detection device includes an electrostatic capacitance type device using a moisture sensitive film formed of a polymer material whose dielectric constant changes according to the amount of absorbed water as a dielectric. In this capacitance type humidity detection device, a humidity sensitive film is arranged between the electrodes, and the humidity (relative humidity) is obtained by measuring the capacitance between the electrodes (for example, refer to Patent Document 1).

In the humidity detection device described in Patent Document 1, a sensor unit whose electrostatic capacity changes depending on humidity and a circuit unit which performs a process of converting charges output from the sensor unit into a voltage are arranged side by side on a substrate. ing.

As a circuit unit used in such a capacitance type humidity detecting device, a configuration is known in which charges output from a sensor unit are converted into a voltage by a charge amplifier (for example, refer to Patent Document 2). In addition to the charge amplifier, the circuit section is provided with a drive circuit for driving the sensor section with a rectangular-wave AC drive signal.

Patent No. 5547296 Patent No. 6228865

In the humidity detecting device described in Patent Document 1, the sensor unit and the circuit unit are arranged in parallel, but the sensor unit and the circuit unit are formed in a chip shape on the circuit unit because of the demand for downsizing and cost reduction. It is assumed to have a stack structure in which the sensor unit is mounted.

When the sensor unit and the circuit unit are arranged side by side, they are separated from each other, so that the influence of noise transmitted between them is small, but when the stack structure is adopted, the sensor unit and the circuit unit are Are close to each other, so there is concern about the influence of noise.

In particular, as described above, when the sensor unit is driven by the AC drive signal from the circuit unit, a large amount of noise can occur in both the sensor unit and the circuit unit, so it is desirable to improve noise resistance. .

An object of the present invention is to improve noise resistance.

The disclosed technology is such that polarities are alternately inverted in a semiconductor substrate, a detection unit provided above the semiconductor substrate and outputting a signal according to a physical quantity, and the semiconductor substrate below the humidity detection unit. And a noise suppression unit including a plurality of semiconductor layers stacked on top of each other.

According to the present invention, noise resistance can be improved.

It is a figure which illustrates the schematic structure of the humidity detection apparatus which concerns on 1st Embodiment. It is sectional drawing which shows the cross section which follows the AA line in FIG. 1 schematically. It is a top view of the humidity detecting device in a state where the mold resin is removed. It is a schematic plan view which shows the structure of a sensor chip. It is a circuit diagram which illustrates the structure of an ESD protection circuit. It is a figure which illustrates the layer structure of the NMOS transistor which comprises an ESD protection circuit. It is a circuit diagram which illustrates the composition of a humidity primary detecting element. It is a circuit diagram which illustrates the structure of a temperature detection part. It is a schematic sectional drawing for demonstrating the element structure of a sensor chip. It is a top view which illustrates the shape of a lower electrode and an upper electrode. It is a top view which illustrates the shape and the guard ring of the n-type diffusion layer which comprises a heating part. It is a figure which illustrates the equivalent circuit of a noise suppression part. It is a figure which illustrates the structure of an ASIC chip. It is a figure which illustrates the structure of a humidity measurement processing part. It is a timing chart explaining a measurement sequence.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components may be denoted by the same reference numerals, and duplicate description may be omitted. In the present disclosure, the humidity in the case where it is simply described as humidity means relative humidity.

<First Embodiment>
[Schematic configuration]
The configuration of the humidity detecting device 10 according to the first embodiment of the present invention will be described.

FIG. 1 is a diagram illustrating a schematic configuration of a humidity detection device 10 according to the first embodiment. FIG. 1A is a plan view of the humidity detecting device 10 as viewed from above. FIG. 1B is a bottom view of the humidity detecting device 10 as viewed from below. FIG. 1C is a side view of the humidity detecting device 10 as viewed from the lateral direction. 2 is a cross-sectional view schematically showing a cross section taken along the line AA in FIG.

The humidity detecting device 10 has a substantially rectangular planar shape, and one of two opposing two sides is parallel to the X direction and the other is parallel to the Y direction. The X direction and the Y direction are orthogonal to each other. Further, the humidity detecting device 10 has a thickness in the Z direction orthogonal to the X direction and the Y direction. The planar shape of the humidity detecting device 10 is not limited to the rectangular shape, and may be a circle, an ellipse, a polygon, or the like.

The humidity detecting device 10 includes a sensor chip 20 as a first semiconductor chip, an ASIC (Application Specific Integrated Circuit) chip 30 as a second semiconductor chip, a mold resin 40 as a sealing member, and a plurality of lead terminals 41. Have.

The sensor chip 20 is stacked on the ASIC chip 30 via a first DAF (Die Attach Film) 42. That is, the sensor chip 20 and the ASIC chip 30 have a stack structure.

The sensor chip 20 and the ASIC chip 30 are electrically connected by a plurality of first bonding wires 43. The ASIC chip 30 and the lead terminals 41 are electrically connected by the second bonding wires 44.

The thus laminated sensor chip 20 and ASIC chip 30, the plurality of first bonding wires 43, the plurality of second bonding wires 44, and the plurality of lead terminals 41 are sealed by the mold resin 40 and packaged. ing. This package method is called a PLP (Plating Lead Package) method.

As will be described later in detail, the second DAF 45 used for packaging by the PLP method remains on the lower surface of the ASIC chip 30. The second DAF 45 has a role of insulating the lower surface of the ASIC chip 30. The second DAF 45 and a plurality of lead terminals 41 are exposed on the lower surface of the humidity detecting device 10.

Each lead terminal 41 is made of nickel or copper. The first DAF 42 and the second DAF 45 are each made of an insulating material made of a mixture of resin and silica. The mold resin 40 is a light-shielding black resin such as an epoxy resin containing a mixture of carbon black and silica.

An opening 50 for exposing a part of the sensor chip 20 from the molding resin 40 is formed on the upper surface side of the humidity detecting device 10. The opening 50 has, for example, a tapered wall portion, and the opening area becomes smaller as it goes downward. Of the openings 50, the lowermost portion where the sensor chip 20 is actually exposed is called an effective opening 51.

When forming the opening 50, the mold is pressed against the sensor chip 20 and sealed with the mold resin 40. At this time, the pressing force applied to the sensor chip 20 and the ASIC chip 30 by the mold may cause damage such as chip cracking. In order to prevent this damage, the thickness T1 of the sensor chip 20 and the thickness T2 of the ASIC chip 30 are preferably 200 μm or more, respectively.

FIG. 3 is a plan view of the humidity detecting device 10 with the mold resin 40 removed. As shown in FIG. 3, each of the sensor chip 20 and the ASIC chip 30 has a substantially rectangular planar shape, and has two sides parallel to the X direction and two sides parallel to the Y direction. The sensor chip 20 is smaller than the ASIC chip 30 and is stacked on the surface of the ASIC chip 30 via the first DAF 42.

The sensor chip 20 is provided with a humidity detecting section 21, a temperature detecting section 22, and a heating section 23 in a region exposed by the effective opening 51. The heating unit 23 is formed on the lower surface side of the humidity detecting unit 21 so as to cover the formation region of the humidity detecting unit 21. That is, the area of the heating unit 23 is larger than that of the humidity detecting unit 21. As described above, the mold resin 40 as the sealing member seals the sensor chip 20 and the like with the humidity detecting unit 21 and the temperature detecting unit 22 exposed.

In addition, a plurality of bonding pads (hereinafter, simply referred to as pads) 24 are formed at the ends of the sensor chip 20. In this embodiment, six pads 24 are formed. The pad 24 is formed of, for example, aluminum or aluminum silicon alloy (AlSi).

The ASIC chip 30 is a semiconductor chip for signal processing and control, and includes a humidity measurement processing unit 31, a temperature measurement processing unit 32, a heating control unit 33, and a failure determination unit 34 (all of which are shown in FIG. 13) described later. Has been done.

Further, a plurality of first pads 35 and a plurality of second pads 36 are provided in a region of the surface of the ASIC chip 30 which is not covered with the sensor chip 20. The first pad 35 and the second pad 36 are made of, for example, aluminum or aluminum silicon alloy (AlSi).

The first pad 35 is connected to the corresponding pad 24 of the sensor chip 20 via the first bonding wire 43. The second pad 36 is connected to the corresponding lead terminal 41 via the second bonding wire 44. The lead terminal 41 is arranged around the ASIC chip 30.

At the time of manufacturing, the mounting position of the ASIC chip 30 is determined with the lead terminal 41 as a reference. The mounting position of the sensor chip 20 on the ASIC chip 30 is determined based on either the position of the ASIC chip 30 or the lead terminal 41. The opening 50 is formed by a transfer molding method or the like using a mold, and the position of this mold is determined with the lead terminal 41 as a reference.

Reference numeral 25 shown in FIG. 3 represents a formation permissible region of the humidity detecting portion 21 and the temperature detecting portion 22 on the sensor chip 20. The formation allowance region 25 is formed so as to be surely exposed from the opening 50 even when the largest displacement occurs between the ASIC chip 30, the sensor chip 20, and the mold during mounting. It is set within 50 forming regions. If the humidity detecting portion 21 and the temperature detecting portion 22 are formed in the formation permitting region 25, the humidity detecting portion 21 and the temperature detecting portion 22 are surely exposed from the opening 50 regardless of the positional deviation.

[Configuration of sensor chip]
Next, the configuration of the sensor chip 20 will be described.

FIG. 4 is a schematic plan view showing the configuration of the sensor chip 20. The pad 24 described above is a terminal used for voltage application from the outside and potential detection. In FIG. 4, the plurality of pads 24 shown in FIG. 3 are shown separately from the pads 24a to 24f. When it is not necessary to distinguish the pads 24a to 24f, they are simply referred to as the pads 24.

The pad 24a functions as a ground electrode terminal (GND) that is grounded to the ground potential. The pad 24a is electrically connected to each part such as the temperature detecting part 22 and the heating part 23 via a wiring or a substrate. The pad 24a is electrically connected to the p-type semiconductor substrate 70 (see FIG. 9) that constitutes the sensor chip 20.

The pad 24b is a signal terminal (TS) electrically connected to the lower electrode 83 of the humidity detector 21. The pad 24c is a first drive terminal (T1) electrically connected to the upper electrode 84 of the humidity detector 21. The pad 24d is a second drive terminal (T2) electrically connected to the reference electrode 82 (see FIG. 9) of the humidity detector 21.

The pad 24e is a temperature detection terminal (TMP) electrically connected to the temperature detection unit 22. The pad 24e is used to acquire a temperature detection signal. The pad 24f is a heating terminal (HT) electrically connected to the heating unit 23. The pad 24f is used to supply a drive voltage for driving the heating unit 23.

An electrostatic discharge (ESD) protection circuit 60 is connected to each of the pads 24b to 24f other than the pad 24a. Each ESD protection circuit 60 is connected between each of the pads 24b to 24f as input terminals or output terminals and the pad 24a as a ground electrode terminal. In the present embodiment, the ESD protection circuit 60 is composed of one diode 61. The diode 61 has an anode side connected to the pad 24a and a cathode side connected to any of the pads 24b to 24f.

The ESD protection circuit 60 is preferably arranged near the pads 24b to 24f so as to be separated from the effective opening 51 as much as possible. Since the ESD protection circuit 60 is covered with the mold resin 40, unnecessary charge generation due to the photoelectric effect does not occur.

[Configuration of ESD protection circuit]
Next, the configuration of the ESD protection circuit 60 will be described.

FIG. 5 is a circuit diagram illustrating the configuration of the ESD protection circuit 60. As shown in FIG. 5, the diode 61 forming the ESD protection circuit 60 is formed of, for example, an N-channel MOS (Metal-Oxide-Semiconductor) transistor (hereinafter referred to as an NMOS transistor). Specifically, the diode 61 is a NMOS transistor whose source, gate, and back gate are short-circuited (so-called diode connection). This short circuit portion functions as an anode. The drain of this NMOS transistor functions as a cathode.

FIG. 6 is a diagram illustrating a layered structure of an NMOS transistor included in the ESD protection circuit 60. This NMOS transistor has two n-type diffusion layers 71 and 72 formed on the surface layer of a p-type semiconductor substrate 70 for forming the sensor chip 20, a contact layer 73, and a gate electrode 74. The gate electrode 74 is formed on the surface of the p-type semiconductor substrate 70 via a gate insulating film 75. The gate electrode 74 is arranged between the two n-type diffusion layers 71 and 72.

For example, the n-type diffusion layer 71 functions as a source and the n-type diffusion layer 72 functions as a drain. The contact layer 73 is a low resistance layer (p-type diffusion layer) for electrical connection with the p-type semiconductor substrate 70 as a back gate. The n-type diffusion layer 71, the gate electrode 74, and the contact layer 73 are commonly connected and short-circuited. This short circuit portion functions as an anode, and the n-type diffusion layer 72 functions as a cathode.

The p-type semiconductor substrate 70 is, for example, a p-type silicon substrate. The gate electrode 74 is formed of metal or polycrystalline silicon (polysilicon). The gate insulating film 75 is formed of, for example, an oxide film such as silicon dioxide.

[Configuration of humidity detector]
Next, the configuration of the humidity detector 21 will be described.

FIG. 7 is a circuit diagram illustrating the configuration of the humidity detector 21. As shown in FIG. 7, the humidity detecting section 21 has a humidity detecting capacitor 80 and a reference capacitor 81.

One electrode (lower electrode 83) of the humidity detecting section 21 is connected to the pad 24b as the signal terminal TS. The other electrode (upper electrode 84) of the humidity detector 21 is connected to the pad 24c as the first drive terminal T1. One electrode of the reference capacitor 81 is common with one electrode (lower electrode 83) of the humidity detecting section 21. The other electrode (reference electrode 82) of the reference capacitor 81 is connected to the pad 24d as the second drive terminal T2.

The humidity detecting capacitor 80 is provided with a moisture sensitive film 86 described below between the electrodes. The moisture sensitive film 86 is formed of a polymer material such as polyimide that absorbs moisture in the air and has a dielectric constant that changes according to the amount of absorbed moisture. Therefore, the capacitance of the humidity detecting capacitor 80 changes according to the amount of water absorbed by the moisture sensitive film 86.

The reference capacitor 81 is provided with a second insulating film 111 (see FIG. 9) described later between the electrodes. The second insulating film 111 is formed of an insulating material such as silicon dioxide (SiO ₂ ) that does not absorb moisture. Therefore, the capacitance of the reference capacitor 81 does not change, or even if it changes, it is very small.

The amount of water contained in the moisture sensitive film 86 corresponds to the humidity around the humidity detecting device 10. Therefore, by detecting the difference between the capacitance of the humidity detecting capacitor 80 and the capacitance of the reference capacitor 81. , Relative humidity can be measured. The relative humidity is measured by the humidity measurement processing unit 31 (see FIG. 13) in the ASIC chip 30.

[Configuration of temperature detector]
Next, the configuration of the temperature detection unit 22 will be described.

FIG. 8 is a circuit diagram illustrating the configuration of the temperature detection unit 22. The temperature detection unit 22 is a bandgap type temperature sensor that detects a temperature by utilizing a characteristic in which the electrical characteristics of the semiconductor bandgap change proportionally with a temperature change. For example, the temperature detection unit 22 includes one or a plurality of bipolar transistors having two terminals by connecting any two of a base, an emitter, and a collector. The temperature can be measured by detecting the resistance value between the two terminals.

As shown in FIG. 8, in the present embodiment, the temperature detection unit 22 is configured by connecting a plurality of (e.g., 8) npn-type bipolar transistors 90 whose base and collector are connected in parallel. By connecting the plurality of bipolar transistors 90 in parallel in this manner, the junction area of the pn junction is increased and the ESD resistance is improved.

The emitter of the bipolar transistor 90 is connected to the pad 24a as the ground electrode terminal. The base and collector of the bipolar transistor 90 are connected to the pad 24e as a temperature detecting terminal.

The temperature measurement is performed by the temperature measurement processing unit 32 (see FIG. 13) in the ASIC chip 30 based on the potential of the pad 24e.

[Element structure of sensor chip]
Next, the element structure of the sensor chip 20 will be described.

FIG. 9 is a schematic cross-sectional view for explaining the element structure of the sensor chip 20. In FIG. 9, the pads 24a, 24b, 24c, 24e are shown in the same cross section as the humidity detecting section 21, the temperature detecting section 22, and the heating section 23, but this facilitates understanding of the structure. However, it does not mean that they actually exist in the same cross section. The cross sections of the humidity detecting unit 21, the temperature detecting unit 22, and the heating unit 23 are also simplified for easy understanding of the structure, and the positional relationship of each unit is different from the actual one.

As shown in FIG. 9, the sensor chip 20 is formed using the p-type semiconductor substrate 70 described above. A first deep n-well 100a and a second deep n-well 100b are formed on the p-type semiconductor substrate 70. The temperature detector 22 is formed in the first deep n-well 100a. The heating unit 23 is formed in the second deep n-well 100b.

P-type diffusion layers 103a and 103b are formed in the surface layer of the p-type semiconductor substrate 70 in which neither the first deep n-well 100a nor the second deep n-well 100b is formed. P-type contact layers 104a and 104b are formed on the surface layers of the p-type diffusion layers 103a and 103b, respectively. The contact layers 104a and 104b are low resistance layers (p-type diffusion layers) for electrically connecting a predetermined wiring layer formed on the p-type semiconductor substrate 70 and the p-type semiconductor substrate 70.

A p well 101 and an n well 102 are formed in the surface layer of the first deep n well 100a. An n-type diffusion layer 91 and a p-type diffusion layer 92 are formed on the surface layer of the p-well 101. An n-type diffusion layer 93 is formed on the surface layer of the n-well 102. The n-type diffusion layer 91, the p-type diffusion layer 92, and the n-type diffusion layer 93 configure the npn-type bipolar transistor 90 described above, and function as an emitter, a base, and a collector, respectively.

A p-well 105 is formed on the surface of the second deep n-well 100b. One or more n-type diffusion layers 106 are formed on the surface layer of the p-well 105. In this embodiment, a plurality of n-type diffusion layers 106 are formed. For example, each n-type diffusion layer 106 extends in a direction orthogonal to the paper surface and has a one-dimensional lattice shape as a whole (see FIG. 11). The n-type diffusion layer 106 has a predetermined resistance value (for example, a sheet resistance value of about 3Ω), and functions as a resistor that generates heat when a current flows. That is, the n-type diffusion layer 106 constitutes the heating unit 23 described above.

On the surface layer of the second deep n-well 100b, an n-type diffusion layer 109a is formed around the p-well 105 in which the n-type diffusion layer 106 forming the heating unit 23 is formed. An n-type contact layer 109b is formed on the surface layer of the n-type diffusion layer 109a.

The n-type diffusion layer 109a is formed so as to surround the periphery of the p-well 105. The p-type diffusion layer 103b described above is formed so as to surround the periphery of the n-type diffusion layer 109a. The n-type diffusion layer 109a and the p-type diffusion layer 103b form a guard ring 200 (see FIG. 11) described later.

Each layer in the p-type semiconductor substrate 70 is formed using a normal semiconductor manufacturing process (CMOS process). Therefore, the n-type diffusion layer 106 as a resistor is formed in the same manufacturing process as the n-type diffusion layers 91 and 93 included in a part of the temperature detection unit 22. The n-type diffusion layers 106, 91, 93 and the contact layer 109b are simultaneously formed by an ion implantation step of implanting impurities into the substrate by ion-implanting n-type impurities (for example, phosphorus). That is, the n-type diffusion layer 106 as a resistor has the same depth from the surface of the p-type semiconductor substrate 70 as the n-type diffusion layers 91 and 93 included in a part of the temperature detection unit 22. The n-type diffusion layer 106 may have the same depth from the surface of the p-type semiconductor substrate 70 as the p-type diffusion layer 92 included in a part of the temperature detection unit 22.

Note that the n-type diffusion layers 106, 91, 93 and the contact layer 109b can be formed by a thermal diffusion process in which impurities are added by heat treatment instead of the ion implantation process.

Further, the n-type diffusion layers 71, 72 of the ESD protection circuit 60 described above are also formed in the same manufacturing process (ion implantation process or thermal diffusion process) as the n-type diffusion layers 106, 91, 93 and the contact layer 109b. . The contact layer 73 is formed in the same manufacturing process (ion implantation process or thermal diffusion process) as the p-type diffusion layer 92 and the contact layers 104a and 104b.

A first insulating film 110, a second insulating film 111, and a third insulating film 112 are sequentially stacked on the surface of the p-type semiconductor substrate 70. These are formed of an insulating material such as silicon dioxide (SiO ₂ ) or silicon nitride (SiN).

A first wiring layer 120 is formed on the first insulating film 110. A second wiring layer 121 is formed on the second insulating film 111. The second insulating film 111 covers the first wiring layer 120. The third insulating film 112 covers the second wiring layer 121. The first wiring layer 120 and the second wiring layer 121 are made of a conductive material such as aluminum.

A first plug layer 122 having a plurality of first plugs for connecting the first wiring layer 120 to the p-type semiconductor substrate 70 is formed in the first insulating film 110. A second plug layer 123 having a plurality of second plugs for connecting the first wiring layer 120 and the second wiring layer 121 is formed in the second insulating film 111. The first plug layer 122 and the second plug layer 123 are formed of a conductive material such as tungsten.

For example, the wiring 94 for connecting the base and collector of the bipolar transistor 90 described above is formed by the first wiring layer 120, and is formed in the p-type diffusion layer 92 and the n-type diffusion layer 93 via the first plug layer 122. Connected. Further, the wiring 94 is connected to the pad 24e as the temperature detecting terminal via the second plug layer 123 and the second wiring layer 121. The n-type diffusion layer 91 as the emitter of the bipolar transistor 90 is connected to the pad 24a as the ground electrode terminal via the first plug layer 122, the first wiring layer 120, and the second wiring layer 121.

The wiring 107 for grounding one end of the heating unit 23 to the ground potential is formed by the first wiring layer 120 and is connected to the n-type diffusion layer 106 and the contact layer 104b via the first plug layer 122. The wiring 108 for connecting the other end of the heating unit 23 to the pad 24f as a heating terminal is connected to the n-type diffusion layer 106 and the contact layer 109b via the first plug layer 122, and the second It is connected to the pad 24f via the plug layer 123 and the second wiring layer 121.

The reference electrode 82 of the reference capacitor 81 is formed of the first wiring layer 120, and via the second plug layer 123 and the second wiring layer 121, the pad 24d as the second drive terminal T2 (not shown in FIG. 9). ) Is connected to.

The lower electrode 83 of the humidity detecting capacitor 80 is formed by the second wiring layer 121 and is connected to the pad 24b as the signal terminal TS. Further, the wiring 85 for connecting the upper electrode 84 of the humidity detecting capacitor 80 to the pad 24c as the first drive terminal T1 is formed by the second wiring layer 121. The lower electrode 83 is arranged at a position facing the reference electrode 82 via the second insulating film 111.

The pads 24a to 24f are formed of a conductive material such as aluminum on the third insulating film 112, penetrate the third insulating film 112, and are connected to the second wiring layer 121.

A moisture sensitive film 86 is formed on the third insulating film 112. The moisture sensitive film 86 has a thickness of 0.5 μm to 1.5 μm and is made of a polymer material that easily adsorbs and desorbs water molecules depending on humidity. The moisture sensitive film 86 is, for example, a polyimide film having a thickness of 1 μm. The polymer material forming the moisture sensitive film 86 is not limited to polyimide, and may be cellulose, polymethylmethacrylate (PMMA), polyvinyl alcohol (PVA), or the like.

The upper surface of the moisture sensitive film 86 is flat, and the flat upper electrode 84 is formed on this upper surface. The upper electrode 84 is formed at a position facing the lower electrode 83 via the moisture sensitive film 86. Part of the upper electrode 84 is connected to the wiring 85. The upper electrode 84 is a conductive film made of, for example, aluminum having a thickness of 200 nm. Further, in the upper electrode 84, a plurality of openings 84a are formed in order to efficiently take in water molecules in the air into the moisture sensitive film 86.

An overcoat film 87 is provided on the moisture sensitive film 86 so as to cover the upper electrode 84. The overcoat film 87 is formed of a polymer material, for example, the same material as the moisture sensitive film 86. The overcoat film 87 has a thickness of, for example, 0.5 μm to 10 μm.

The moisture sensitive film 86 and the overcoat film 87 have openings for exposing the pads 24a to 24f.

Thus, the lower electrode 83 and the upper electrode 84 form a parallel plate humidity detecting capacitor 80. The lower electrode 83 and the reference electrode 82 form a parallel plate reference capacitor 81. The humidity detecting capacitor 80 and the reference capacitor 81 are arranged above the heating unit 23.

Therefore, when the heating unit 23 generates heat, the moisture sensitive film 86 between the lower electrode 83 and the upper electrode 84 is heated. As a result, the moisture-sensitive film 86 adsorbs water molecules in an amount corresponding to humidity as the temperature rises due to heating, so that the dielectric constant changes and the capacitance of the humidity detecting capacitor 80 decreases. Further, the temperature detection unit 22 detects a temperature rise caused by the heating unit 23.

FIG. 10 is a plan view illustrating the shapes of the lower electrode 83 and the upper electrode 84. As shown in FIG. 10, both the lower electrode 83 and the upper electrode 84 have a rectangular shape. The upper electrode 84 is formed so as to cover the lower electrode 83.

The opening 84a is preferably as small as possible, and the smaller the size, the more the leakage of the electric field into the air is prevented. In reality, many openings 84a are formed. The opening 84a is not limited to a square shape, and may be an elongated strip shape or a circular shape. The openings 84a may be arranged in a staggered pattern. The openings 84a are preferably circular and staggered.

Although not shown in FIG. 10, a rectangular reference electrode 82 is formed below the lower electrode 83.

FIG. 11 is a plan view illustrating the shape of the n-type diffusion layer 106 that constitutes the heating unit 23. As shown in FIG. 11, the n-type diffusion layer 106 has a one-dimensional lattice shape in which a plurality of elongated strip-shaped regions are arranged in parallel. One end of the one-dimensional lattice-shaped n-type diffusion layer 106 is connected to the wiring 107 described above, and the other end is connected to the wiring 108 described above. The heating unit 23 is located below the temperature detection unit 22 so as to cover the entire temperature detection unit 22.

Further, FIG. 11 shows a guard ring 200 including an n-type diffusion layer 109a and a p-type diffusion layer 103b. The n-type diffusion layer 109a is connected to the second deep n-well 100b and is given the potential of the pad 24f as the heating terminal HT. The n-type diffusion layer 109a is electrically connected to the p-well 105 via the wiring 107 and applies a ground potential to the p-well 105.

The guard ring 200 stabilizes the potential of the noise suppressor 210 (see FIG. 12) formed in the p-type semiconductor substrate 70 below the humidity detector 21.

The reference electrode 82 is arranged between the noise suppression unit 210 and the lower electrode 83.

[Noise suppressor]
Next, the function and action of the noise suppression unit will be described.

FIG. 12 is a diagram illustrating an equivalent circuit of the noise suppression unit 210 formed on the p-type semiconductor substrate 70. In FIG. 12, CJ1 represents the junction capacitance of the pn junction formed between the n-type diffusion layer 106 and the p well 105. CJ2 represents the junction capacitance of the pn junction formed between the p well 105 and the second deep n well 100b. CJ3 represents the junction capacitance of the pn junction formed between the second deep n-well 100b and the p-type semiconductor substrate 70.

R1 represents the diffusion resistance of the n-type diffusion layer 106. R2 represents the diffusion resistance of the p-well 105. R3 represents the diffusion resistance of the second deep n-well 100b. The substrate resistance of the p-type semiconductor substrate 70 is shown.

The noise suppression unit 210 is composed of the n-type diffusion layer 106, the p-well 105, the second deep n-well 100b, and the p-type semiconductor substrate 70. That is, the noise suppression unit 210 is configured by stacking four semiconductor layers whose polarities are alternately inverted. In the present embodiment, the noise suppression unit 210 has an npnp type structure.

The power supply voltage VDD, for example, is supplied to the pad 24f as the heating terminal HT via the pull-down resistor RP and the switch circuit SW. When the heating unit 23 is driven, the switch circuit SW is turned on, and the power supply voltage VDD is applied to the pad 24a as a drive voltage. At this time, the n-type diffusion layer 106 as a resistor generates heat, and each pn junction included in the noise suppression unit 210 is in a reverse bias state.

When the heating unit 23 is not driven, the switch circuit SW is turned off and brought into a pull-down state, and the pad 24a is connected to the ground via the pull-down resistor RP.

The arrow Np in FIG. 12 represents the magnitude of the peak voltage of noise generated in the ASIC chip 30 and heading to the humidity detection unit 21. In this way, the noise suppression unit 210 attenuates the peak voltage of noise by dividing the noise peak voltage with the capacitors formed by the respective pn junctions. The noise N whose peak voltage is attenuated by the noise suppressor 210 is transmitted to the humidity detector 21. In the humidity detection unit 21, the influence of noise on the humidity detection operation is suppressed.

The noise suppressing unit 210 has the same suppressing effect on the noise generated in the sensor chip 20 and traveling toward the ASIC chip 30.

[Configuration of ASIC chip]
Next, the configuration of the ASIC chip 30 will be described.

FIG. 13 is a block diagram illustrating the configuration of the ASIC chip 30. As shown in FIG. 13, the ASIC chip 30 includes a humidity measurement processing unit 31, a temperature measurement processing unit 32, a heating control unit 33, and a failure determination unit 34.

First, the configuration of the humidity measurement processing unit 31 will be described.

FIG. 14 is a diagram illustrating a configuration of the humidity measurement processing unit 31. As shown in FIG. 14, the humidity measurement processing unit 31 includes a drive unit 300, a charge amplifier 301, a control unit 302, and an AD converter (ADC) 303.

The drive unit 300 includes a first drive circuit DRV1 and a second drive circuit DRV2. The charge amplifier 301 is a charge-voltage conversion (CV conversion) unit including a capacitor C1, an operational amplifier OP1, and a switch circuit SW1.

The first drive circuit DRV1 applies a first drive signal, which is a rectangular-wave AC drive signal, to the first drive terminal T1 of the sensor chip 20 under the control of the control unit 302. The second drive circuit DRV2 is, under the control of the control unit 302, a second drive terminal T2 of the sensor chip 20 which is a rectangular wave AC drive signal and which is a reverse drive of the first drive signal. Apply a signal. The high level of the first drive signal and the second drive signal is, for example, equal to the power supply voltage VDD, and the low level thereof is, for example, equal to the ground potential GND.

The first drive signal and the second drive signal have opposite phases. That is, when the first drive signal is high level, the second drive signal is low level, and when the first drive signal is low level, the second drive signal is high level.

The capacitor C1 has one end connected to the signal terminal TS of the sensor chip 20 and the other end connected to the output of the operational amplifier OP1.

The inverting input terminal of the operational amplifier OP1 is connected to the signal terminal TS, and the reference voltage Vref is input to the non-inverting input terminal. The reference voltage Vref is, for example, an intermediate value between the high level and the low level in the first drive signal and the second drive signal.

Since the operational amplifier OP1 has a very large voltage gain, the voltage of the signal terminal TS becomes substantially equal to the reference voltage Vref. Further, since the operational amplifier OP1 has a very high input impedance at the inverting input terminal, almost no current flows into the inverting input terminal. The operational amplifier OP1 outputs a voltage Vo obtained by amplifying the difference between the voltage of the signal terminal TS and the reference voltage Vref.

The switch circuit SW1 is a circuit for discharging the electric charge accumulated in the capacitor C1, and is connected in parallel with the capacitor C1. The switch circuit SW1 is turned on or off under the control of the control unit 302.

The ADC 303 converts the output voltage Vo of the operational amplifier OP1 into a digital signal Ds under the control of the control unit 302.

The control unit 302 controls each unit in the ASIC chip 30. The control unit 302 causes the drive unit 300 to generate a drive signal, the switch circuit SW1 to discharge the capacitor C1, and the ADC 303 to perform an analog-digital conversion operation based on a predetermined measurement sequence.

FIG. 15 is a timing chart explaining the measurement sequence. In the measurement sequence, the control unit 302 controls each unit so that the reset period Trst and the charge transfer period Tchg are alternately repeated. In the reset period Trst, the control unit 302 turns on the switch circuit SW1 to discharge the electric charge of the capacitor C1, and sets the first drive signal to the high level and the second drive signal to the low level. In the charge transfer period Tchg, the control unit 302 turns off the switch circuit SW1 to put the capacitor C1 in a chargeable state, sets the first drive signal to the low level, and sets the second drive signal to the high level.

By this control, during the charge transfer period Tchg, the voltage Vo represented by the following equation (1) is output from the charge amplifier 301.

Vo=VDD×(Cs−Cr)/C1+Vref (1)
Here, Cs is the capacitance of the humidity detecting capacitor 80, and Cr is the capacitance of the reference capacitor 81.

The control unit 302 performs the humidity calculation process using the digital signal Ds output from the ADC 303 to calculate the relative humidity (%RH).

The temperature measurement processing unit 32 detects the potential of the pad 24e as the temperature detecting terminal and calculates the temperature corresponding to the detected potential.

The heating control unit 33 applies a predetermined drive voltage (for example, the power supply voltage VDD described above) to the pad 24f serving as a heating terminal to cause a current (for example, about 10 mA) to flow through the heating unit 23 to generate heat. The heating control unit 33 controls the amount of heat generated by controlling the voltage applied to the pad 24f.

The failure determination unit 34 makes a failure determination based on the relative humidity measured by the humidity measurement processing unit 31 and the temperature measured by the temperature measurement processing unit 32. The failure determination unit 34 gives instructions to the heating control unit 33 regarding the start and end of heating of the heating unit 23 at the time of failure determination.

For example, the failure determination unit 34 acquires the humidity H1 from the humidity measurement processing unit 31 and the temperature T1 from the temperature measurement processing unit 32 in the initial state where the heating unit 23 does not generate heat. Then, the failure determination unit 34 causes the heating unit 23 to start heating, and after a lapse of a certain time, acquires the humidity H2 from the humidity measurement processing unit 31 and acquires the temperature T2 from the temperature measurement processing unit 32 again.

When the temperature rises due to heating (T2>T1) and the humidity falls due to heating (H2<H1), the failure determination unit 34 determines that the humidity detection device 10 is normal, and in other cases. First, it is determined that the humidity detecting device 10 is in a failure state.

[effect]
As in the above measurement sequence, the ASIC chip 30 generates an AC drive signal and applies the AC drive signal to the humidity detection unit 21 of the sensor chip 20, so that large noise may occur in the ASIC chip 30. According to the present embodiment, the noise suppression unit 210 arranged below the humidity detection unit 21 (on the side of the ASIC chip 30) attenuates the peak voltage of the noise from the ASIC chip 30 to the humidity detection unit 21. The influence of noise on the portion 21 is suppressed, and noise resistance is improved.

In order to suppress such noise, it is conceivable to interpose an insulating layer between the sensor chip 20 and the ASIC chip 30. However, disposing the insulating layer between the chips reduces the size and the thickness. This is not preferable because it is necessary to thin each chip from the request.

[Modification]
In the above embodiment, the noise suppression unit 210 is composed of four semiconductor layers stacked so that the polarities are alternately inverted, but the number of semiconductor layers forming the noise suppression unit is not limited, It may be two or more.

Further, although the sensor chip 20 is configured by the p-type semiconductor substrate 70 in the above-described embodiment, it may be configured by using an n-type semiconductor substrate instead.

Further, in the above embodiment, the humidity detecting unit 21 is a capacitance change type humidity sensor, but as a resistance change type humidity sensor such as a piezoresistive type that detects a change in resistance of the moisture sensitive film due to absorption and dehumidification. Good.

The present invention can also be applied to a detection device that detects a physical quantity other than humidity. That is, instead of the humidity detection unit 21, it is possible to provide a detection unit that outputs a signal according to a physical quantity other than humidity.

Further, in the present disclosure, the positional relationship between the two elements represented by the words “cover” and “upper” means that the first element is indirectly provided on the surface of the second element via the other element. Both when provided and when provided directly.

Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and various modifications are made to the above-described embodiments without departing from the scope of the present invention. And substitutions can be added.

10 Humidity Detection Device (Detection Device), 20 Sensor Chip (First Semiconductor Chip), 21 Humidity Detection Part (Detection Part), 22 Temperature Detection Part, 23 Heating Part, 24 Bonding Pad, 25 Forming Allowable Area, 30 ASIC Chip ( Second semiconductor chip), 40 mold resin, 50 opening, 60 ESD protection circuit, 80 humidity detecting capacitor, 81 reference capacitor, 82 reference electrode, 83 lower electrode, 84 upper electrode, 84a opening, 86 moisture sensitive film, 106 n-type diffusion layer, 200 guard ring, 210 noise suppressor, 300 driver, 301 charge amplifier (charge-voltage converter)

Claims (9)

A semiconductor substrate,
A detection unit which is provided above the semiconductor substrate and outputs a signal according to a physical quantity,
In the semiconductor substrate below the detection unit, a noise suppression unit composed of a plurality of semiconductor layers stacked so that the polarity is alternately inverted,
And a detection device. The detection device according to claim 1, wherein a voltage that applies a reverse bias to each pn junction formed between the plurality of semiconductor layers is applied to the noise suppression unit. The noise suppression unit includes a diffusion layer formed on the surface layer of the semiconductor substrate,
The detection device according to claim 1, wherein the diffusion layer functions as a resistor that generates heat when a current flows. The detection device according to claim 1, wherein the detection unit has a humidity detection capacitor in which a moisture sensitive film is arranged between a pair of electrodes, and outputs a signal according to humidity. The humidity detecting capacitor,
A lower electrode formed above the semiconductor substrate,
An upper electrode formed on the moisture-sensitive film,
The moisture-sensitive film disposed between the lower electrode and the upper electrode,
The detection device according to claim 4, further comprising: The detection unit,
The lower electrode,
A reference electrode disposed between the noise suppression unit and the lower electrode,
An insulating film disposed between the reference electrode and the lower electrode,
The detection device according to claim 5, comprising a reference capacitor configured by. 7. The detection device according to claim 4, wherein the moisture sensitive film is made of polyimide. A first semiconductor chip including the semiconductor substrate and the detection unit;
A second semiconductor chip including a drive unit that drives the detection unit, and a charge-voltage conversion unit that converts the charge output from the detection unit into a voltage;
Have
The detection device according to claim 1, wherein the first semiconductor chip is stacked on the second semiconductor chip. The detection device according to claim 8, wherein the drive unit applies an AC drive signal to the detection unit.

Images