JP5849836B2 - Humidity sensor - Google Patents

Description

  The present invention relates to a pair of electrodes formed on the same surface of a substrate so as to face each other, a protective film for protecting the electrode from corrosion due to moisture, and a moisture sensitive film disposed on the protective film so as to cover the electrode It is related with the humidity sensor which has.

  A humidity sensor having a pair of electrodes formed on the same surface of the substrate so as to face each other, a protective film that protects the electrodes from corrosion due to moisture, and a moisture-sensitive film disposed on the protective film so as to cover the electrodes For example, the thing of patent document 1 is known.

JP 2006-133191 A

  As described in Patent Document 1, in a conventional humidity sensor, a conductive material such as aluminum is deposited on one surface of a substrate by a technique such as vapor deposition or sputtering to form a film, and the formed film is A pair of electrodes is formed by patterning into a predetermined shape.

  As a result of examination by the present applicant, it has been clarified that in the conventional humidity sensor, the linearity of the sensor sensitivity deteriorates on the high humidity side.

  In view of the above problems, an object of the present invention is to provide a humidity sensor capable of suppressing deterioration in linearity of sensor sensitivity on the high humidity side.

To achieve the above object, the present invention covers a substrate (20), a pair of electrodes (31, 32) disposed on a common surface (20a) of the substrate so as to face each other, and the electrodes. As described above, the humidity having a protective film (33) that protects the electrode from corrosion due to moisture and a moisture-sensitive film (34) that is disposed on the protective film so as to cover between the electrodes. All electrodes have a multilayer structure in which films are arranged in multiple layers on one surface, and the uppermost layer is formed using a conductive material and is in contact with the protective film At least one of the layers is formed using a conductive material having corrosiveness to moisture, and a base portion (38) in which one layer of the film is disposed on one surface of the substrate, and a film on the base portion. And an upper portion (39) in which at least one layer is disposed. Have, respectively, the electrodes (31, 32), any layer that forms the upper base portion (39) is, while being arranged to enclose the layer located below the said given layer, the lower A connection connecting the central portion (39a) located above the positioned layer, the peripheral portion (39b) disposed on one surface (20a) of the substrate (20), and the central portion (39a) and the peripheral portion (39b). And having a portion (39c), the cross-sectional shapes orthogonal to one surface are each independently a convex shape.

  As a result of intensive studies by the present applicant, the sensor sensitivity linearity deterioration on the high humidity side is formed by one surface (20a) of the substrate (20) and the electrodes (31, 32) in the protective film (33). It has been clarified that the portion corresponding to the step difference (hereinafter referred to as the step portion) is tightly bent.

  On the other hand, in the present invention, the cross-sectional shape of the electrode is a convex shape formed by arranging a plurality of films. For this reason, compared with the conventional structure in which the electrode of the same thickness was formed by the film | membrane of one layer, the height per step | paragraph becomes low. For example, in the case of an electrode having a two-layer structure in which the upper part (39) made of a single layer film is arranged so as to cover only a part of the upper surface of the base part (38), the upper surface of the upper part and the base part Steps are formed between the upper surface of the substrate, the upper surface of the base portion, and one surface of the substrate. Accordingly, each level difference is lower than a configuration in which only one level difference exists. Thereby, the curvature of the level | step-difference part in a protective film (33) can be made loose. Therefore, it is possible to suppress linearity deterioration of sensor sensitivity on the high humidity side.

  In addition, the protective film can effectively suppress corrosion of the electrode (a layer formed using a conductive material having corrosiveness to moisture).

In addition, since a plurality of steps are formed by the one surface (20a) of the substrate (20) and the electrodes (31, 32), the bending of the stepped portion in the protective film (33) can be moderated. Moreover, since the film | membrane which comprises an electrode (31, 32) becomes gentle as the upper layer, a curve of a level | step-difference part can be made looser. Furthermore, since the upper layer is arranged in a wider range, the facing area of the pair of electrodes (31, 32) can be increased. As described above, the sensor sensitivity can be further increased.

  Further, a further feature of the present invention is that in the electrodes (31, 32), all layers are formed using the same conductive material having corrosiveness against moisture.

  According to this, the structure and manufacturing process of a humidity sensor can be simplified. Moreover, all the layers can be made to function as an electrode substantially.

  A further feature of the present invention is that the electrodes (31, 32) include a layer formed using an electrically insulating material.

  Thus, a layer made of an electrically insulating material may be used. In the present invention, since the arbitrary layer forming the upper portion (39) is disposed so as to wrap the layer positioned below the arbitrary layer, it has a layer made of an electrically insulating material, The facing area can be increased.

To achieve the above object, the present invention covers a substrate (20), a pair of electrodes (31, 32) disposed on a common surface (20a) of the substrate so as to face each other, and the electrodes. As described above, the humidity having a protective film (33) that protects the electrode from corrosion due to moisture and a moisture-sensitive film (34) that is disposed on the protective film so as to cover between the electrodes. All electrodes have a multilayer structure in which films are arranged in multiple layers on one surface, and the uppermost layer is formed using a conductive material and is in contact with the protective film At least one of the layers is formed using a conductive material having corrosiveness to moisture, and a base portion (38) in which one layer of the film is disposed on one surface of the substrate, and a film on the base portion. And an upper portion (39) in which at least one layer is disposed. In each of the electrodes (31, 32), an arbitrary layer forming the upper portion (39) covers only a part of the upper surface of the surface of the layer adjacent to the arbitrary lower layer on the lower side. By being arranged in this manner, all the electrodes are characterized in that the cross-sectional shapes orthogonal to one surface are independently convex.

Even with such an electrode configuration, since there are a plurality of steps, the step portion of the protective film (33) can be gently bent. That is, the same effects as those of the other inventions described above can be achieved.

  Further, the present invention is further characterized in that in the electrodes (31, 32), each layer is formed using different conductive materials.

  According to this, all the layers can be made to function as an electrode substantially. Therefore, since the opposing area can be increased in the pair of electrodes (31, 32), the sensor sensitivity can be further increased.

  A further feature of the present invention is that the electrodes (31, 32) include a layer formed using an electrically insulating material. Thus, a layer made of an electrically insulating material may be used.

  A further feature of the present invention resides in that the pair of electrodes (31, 32) has a comb-tooth shape, and the comb teeth are arranged so as to face each other.

  According to this, since the facing area can be increased in the pair of electrodes (31, 32), the sensor sensitivity can be further increased.

  Further, according to a further feature of the present invention, the humidity sensitive film (34) has a change in relative dielectric constant due to the adsorption of moisture, and the humidity detector (30) is adapted to change the humidity of the atmosphere with a pair of electrodes (31, 31). 32) is detected as a change in capacitance. Further, the humidity-sensitive film (34) has an impedance that changes due to moisture adsorption, and the humidity detector (30) detects a change in the humidity of the atmosphere as a change in the impedance of the moisture-sensitive film (34). is there.

  According to a further feature of the present invention, the substrate (20) has a semiconductor substrate (21) and an insulating film (23) formed on the main surface of the semiconductor substrate (21), and the electrodes (31, 32). Is to be disposed on the insulating film (23) of the substrate (20).

  According to this, the processing circuit for processing the signal output from the humidity detection section (30) can be configured on the same substrate (20). Further, since the insulating film (23) is provided, leakage of current from the electrodes (31, 32) and the like can be prevented.

It is a perspective view which shows schematic structure of a humidity detection apparatus provided with the humidity sensor of 1st Embodiment. For convenience, the protective gel is omitted. It is a top view which shows schematic structure of the humidity sensor which concerns on 1st Embodiment. For convenience, lines connected to the detection electrode, the reference electrode, and the pad are shown by solid lines. Moreover, the protective gel is shown with the broken line. It is the figure which simplified the cross-sectional structure which follows the III-III line of FIG. In contrast to FIG. 2, the wiring connecting the detection electrode and the pad is omitted, and the number of detection electrodes and dummy wirings is reduced. It is sectional drawing which shows schematic structure of an electrode periphery. In conventional humidity sensor, it is sectional drawing which shows schematic structure of an electrode periphery. It is a figure which shows the relationship between relative humidity and a capacity | capacitance change amount, the triangle (triangle | delta) shows the actual measurement result of a thing of a conventional structure, and the circle (circle) shows the actual measurement result of a reference example. It is an expanded sectional view of the area | region enclosed with the broken line VII of FIG. It is sectional drawing for demonstrating the difference in the level | step-difference part of the protective film by an electrode structure, (a) is a conventional structure, (b) has shown what concerns on this embodiment. It is sectional drawing which shows a modification, and respond | corresponds to FIG.8 (b). In the humidity sensor which concerns on 2nd Embodiment, it is sectional drawing which shows schematic structure of an electrode periphery, and respond | corresponds to FIG.8 (b). It is sectional drawing which shows a modification, and respond | corresponds to FIG.8 (b). It is sectional drawing which shows another modification, and respond | corresponds to FIG.8 (b). It is sectional drawing which shows another modification, and respond | corresponds to FIG.8 (b).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, common or related elements are given the same reference numerals. Further, in order to clarify the formation range, in the plan view of FIG. 2, the moisture sensitive film 34 and the dam moisture sensitive film 62 are hatched. The thickness direction of the substrate 20 is simply referred to as the thickness direction, and the opposing direction of the paired electrodes 31 and 32 is simply referred to as the opposing direction.

(First embodiment)
FIG. 1 shows a humidity detecting device 100 including a humidity sensor chip 10 of the present embodiment. The humidity detection device 100 includes a case 110 formed in a bottomed rectangular tube shape using a synthetic resin or the like, lead islands 111 and 112 fixed to the inner surface of the bottom of the case 110, and a die mount on the island 111. The humidity sensor chip 10, the circuit chip 113 die-mounted on the island 112, and a lead 114 having one end exposed inside the case 110 and the other end extending outside the case 110.

  The humidity sensor chip 10 and the circuit chip 113 are electrically connected via the bonding wire 115, and the circuit chip 113 and the lead 114 are electrically connected via the bonding wire 116. Although not shown, the bonding wires 115 and 116 and their connection parts (pads) are covered with a protective gel described later.

  Thus, in this embodiment, the humidity sensor chip 10 and the circuit chip 113 are separate chips. The humidity sensor chip 10 corresponds to the humidity sensor described in the claims.

  Next, a schematic configuration of the humidity sensor chip 10 will be described.

  As shown in FIGS. 2 and 3, the humidity sensor chip 10 includes a pad 40 as an external connection terminal that is protected by the protective gel 50 in a state where the humidity detection unit 30 and the bonding wire 115 are connected to the same substrate 20. The dam part 60 which suppresses the flow of the protective gel 50 is provided.

  In the present embodiment, the substrate 20 includes a semiconductor substrate 21 and an insulating film 23 formed on the main surface of the semiconductor substrate 21. Specifically, a silicon substrate is employed as the semiconductor substrate 21, and an impurity diffusion layer 22 is formed on the main surface side surface layer of the semiconductor substrate 21 over the entire surface. In the present embodiment, the diffusion layer 22 is p conductivity type. An insulating film 23 is disposed on the diffusion layer 22, and a contact hole 23 a is formed in one part of the insulating film 23. In the present embodiment, the insulating film 23 is formed by laminating a silicon oxide film and a BPSG film in this order from the semiconductor substrate 21 side. Note that the humidity detection unit 30, the pad 40, and the dam unit 60 are formed on the insulating film 23. For this reason, the surface opposite to the semiconductor substrate 21 in the insulating film 23 is the one surface 20 a of the substrate 20.

  The humidity detection unit 30 has a pair of electrodes 31 and 32 disposed to face each other on the one surface 20 a of the substrate 20. The humidity detection unit 30 includes at least a detection capacitor unit 30d, and further includes a reference capacitor unit 30r in the present embodiment. The detection capacitor unit 30d has a pair of detection electrodes 31d and 32d arranged to face each other on the one surface 20a of the substrate 20. The reference capacitance unit 30r has a pair of reference electrodes 31r and 32r arranged to face each other at a position different from the detection electrodes 31d and 32d on the one surface 20a.

  In these detection electrodes 31d and 32d and reference electrodes 31r and 32r, the planar shape orthogonal to the thickness direction is not particularly limited. In the present embodiment, as shown in FIG. 2, the detection electrodes 31 d and the detection electrodes 32 d are both comb-shaped, and are alternately arranged so that the comb teeth mesh with each other and face each other. With the comb-like shape as described above, it is possible to increase the areas facing each other while reducing the arrangement area of the detection electrodes 31d and 32d. As a result, the amount of change in capacitance between the detection electrodes 31d and 32d, which changes with changes in ambient humidity, increases, and the sensor sensitivity is improved. Similarly, both the reference electrode 31r and the reference electrode 32r have a comb-teeth shape, and are alternately arranged so that the comb teeth mesh with each other and face each other. Further, as shown in FIG. 2, the detection electrodes 31d and 32d and the reference electrodes 31r and 32r having a comb shape have different facing areas between the electrodes and the number of comb teeth. Specifically, the number of detection electrodes 31d and 32d is larger than that of reference electrodes 31r and 32r, and the facing area is also larger.

  On the other hand, in the detection electrodes 31d and 32d and the reference electrodes 31r and 32r, the cross-sectional structure orthogonal to the one surface 20a is a characteristic part of the present embodiment. Details of this will be described later.

  The detection electrodes 31d and 32d and the reference electrodes 31r and 32r, that is, the electrodes 31 and 32 have a multilayer structure (see FIGS. 7 and 8B) in which films are arranged in multiple layers as described later. The configuration is the same for the electrodes 31 and 32. In addition, at least one of the layers in contact with the protective film 23 includes a layer formed using a conductive material (for example, an aluminum-based material) that is corrosive to moisture. In this embodiment, all the layers of the electrodes 31 and 32 are formed using the same aluminum material. That is, all the layers are formed using the same conductive material that is corrosive to moisture. Therefore, like the detection electrodes 31 d and 32 d illustrated in FIG. 3, the protective film 33 is formed on all the electrodes 31 and 32, and the moisture sensitive film 34 is formed via the protective film 33. Yes.

  The protective film 33 is for preventing the electrodes 31 and 32 formed using a conductive material corrosive to moisture from being corroded by moisture. In the present embodiment, a silicon nitride film formed by a plasma CVD method is employed as the protective film 33. The protective film 33 is formed not only on the electrodes 31 and 32 but also on the surface 20 a of the substrate 20 in a portion excluding the pad 40.

  On the protective film 33, a moisture sensitive film 34 is formed so as to cover the detection electrodes 31 d and 32 d and the detection electrodes 31 d and 32 d and cover the reference electrodes 31 r and 32 r and the reference electrodes 31 r and 32 r. In the present embodiment, the moisture sensitive film 34 that covers the detection electrodes 31 d and 32 d and the moisture sensitive film 34 that covers the reference electrodes 31 r and 32 r are integrated as one moisture sensitive film 34. As the constituent material of the moisture sensitive film 34, a known material such as a polyimide-based material can be employed. In this embodiment, a polyimide-based material is employed, and is formed by applying a polyamide, which is a precursor, by spin coating or printing, followed by heat curing (imidization treatment).

  In the humidity detector 30 configured as described above, the detection electrode 31d constituting the detection capacitor 30d is electrically connected to the corresponding pad 41 by the wiring 35 as shown in FIG. The detection electrode 32d constituting the detection capacitor unit 30d and the reference electrode 32r constituting the reference capacitor unit 30r are electrically connected to the corresponding pads 42 by a common wiring 36. In addition, the reference electrode 31 r constituting the reference capacitance unit 30 r is electrically connected to the corresponding pad 43 by the wiring 37. That is, a capacitor consisting of a pair of detection electrodes 31d and 32d and a capacitor consisting of a pair of reference electrodes 31r and 32r are connected in series between the pads 41 and 43, and the pad 42 is connected to the connection point (midpoint) of these capacitors. It has been configured.

  These wirings 35 to 37 are formed on one surface 20 a of the substrate 20, that is, on the same plane as the electrodes 31 and 32. Moreover, like the electrodes 31 and 32, it is formed including a film formed using a conductive material having corrosiveness against moisture. In this embodiment, one layer of a film formed using an aluminum-based material is arranged. However, the same configuration as the electrodes 31 and 32, that is, a two-layer structure may be adopted. The wirings 35 to 37 are also covered with the protective film 33 described above.

  The pad 40 includes pads 41 to 43 that are electrically connected to the electrodes 31d, 32d, 31r, and 32r that constitute the humidity detecting unit 30. These pads 41 to 43 are portions of the corresponding wirings 35 to 37 that are exposed from the opening of the protective film 33 near the end opposite to the humidity detection unit 30. Therefore, the pads 41 to 43 also have the same film configuration as the wirings 35 to 37.

  In the present embodiment, a pad 44 electrically connected to the diffusion layer 22 is further provided. A wiring 45 formed along the edge of the planar rectangular substrate 20 is connected to the pad 44, and the wiring 45 is exposed from the opening of the protective film 33 as shown in FIG. The part is a pad 44. The wiring 45 is also formed on one surface 20 a of the substrate 20, that is, on the same plane as the electrodes 31 and 32. Further, it has the same film configuration as the wirings 35 to 37 and is covered with the protective film 33 described above. As shown in FIG. 3, the wiring 45 is formed so as to fill the contact hole 23 a formed in the insulating film 23, and is electrically connected to the diffusion layer 22. Therefore, by applying a constant potential (for example, ground potential) to the pad 44, the diffusion layer 22 can function as a shield layer against electromagnetic waves through the wiring 45.

  These pads 40 (41 to 44) are covered with the protective gel 50 in a state where the bonding wires 115 are connected. Therefore, the humidity sensor chip 10 does not have the protective gel 50 before the bonding wire 115 is connected to the pad 40. The protective gel 50 is for preventing the pad 40 from being corroded by moisture, and is made of a water-resistant material such as a fluorine-based gel. The protective gel 50 is formed by applying around the pad 40 using a dispenser and then curing. For this reason, the protective gel 50 has fluidity at the time of application.

  When the protective gel 50 applied to the periphery of the pad 40 flows toward the humidity detection unit 30 and adheres to the moisture sensitive film 34, the properties of the moisture sensitive film 34 change, and the detection accuracy concerning the atmospheric humidity decreases. It might be. For this reason, in order to suppress that the protective gel 50 applied to the periphery of the pad 40 flows into the humidity detection unit 30 side and adheres to the moisture sensitive film 34, the humidity detection unit 30 and the pad 40 on the one surface 20 a of the substrate 20 are suppressed. A dam portion 60 is formed between them.

  As the dam portion 60, a structure that protrudes from the one surface 20 a of the substrate 20 can be adopted. When the protective film 33 is formed in a portion excluding the pad 40, the protective film 33 is included as the dam portion 60, and the dam portion 60 is provided with a protruding height higher than the thickness of the protective film 33. In the present embodiment, the dam portion 60 includes a film formed using a conductive material that is corrosive to moisture like the electrodes 31 and 32, and is on the same plane as the electrodes 31 and 32 (one surface 20 a of the substrate 20). It has a dummy wiring 61 as a dam wiring formed. In this embodiment, the electrodes 31 and 32 have the same configuration, that is, a two-layer structure. The dam portion 60 is also formed using the same material as the moisture sensitive film 34, and also has a dam moisture sensitive film 62 that covers at least a part of the dummy wiring 61. As described above, the dam portion 60 has a laminated structure of the dummy wiring 61, the dam moisture sensitive film 62, and the protective film 33. In the present embodiment, the dummy wiring 61 is a wiring that is electrically separated from the electrodes 31 and 32 and the pad 40 constituting the humidity detection unit 30 and does not provide an electrical connection function. However, in the configuration in which the processing circuit of the humidity detection unit 30 is integrated on the semiconductor substrate 21, the dam unit 60 may be formed by using a part of the wiring configuring the processing circuit. In FIG. 3, for convenience, the electrodes 31, 32 d and the dummy wiring 61 are shown in the same layer structure as the wiring 45 including the pad 44.

  Next, a cross-sectional structure of the electrodes 31 and 32 that are characteristic portions of the humidity sensor chip 10 will be described with reference to FIG.

  As illustrated by the detection electrodes 31d and 32d in FIG. 4, all the electrodes 31 and 32 have a multilayer structure in which films are arranged in multiple layers with respect to the one surface 20a of the substrate 20. A base portion 38 in which one layer of film is disposed on the base portion 38, and an upper portion 39 in which at least one layer of film is disposed on the base portion 38. In this multilayer structure, the uppermost layer is formed using a conductive material, and at least one of the layers in contact with the protective film 23 is formed using a conductive material that is corrosive to moisture. And the cross-sectional shape orthogonal to the one surface 20a of the board | substrate 20 has comprised the convex shape each independently. In the present embodiment, as shown in FIG. 4, the upper portion 39 is made of a single layer film, and each of the electrodes 31 and 32 has a two-layer structure. In addition, as described above, the electrodes 31 and 32 are formed by arranging two layers made of the same aluminum-based material, and the lowermost layer constituting the base portion 38 and the uppermost layer constituting the upper portion 39 are: Both are formed using a conductive material that is corrosive to moisture.

  Moreover, the arbitrary layer which forms the upper part 39 is arrange | positioned so that the layer located below this arbitrary layer may be wrapped. In other words, in any two adjacent layers, the upper layer is disposed so as to wrap around the lower layer. This arbitrary layer includes a central portion 39a located above a layer located below the arbitrary layer, a peripheral portion 39b disposed on one surface 20a of the substrate 20, a central portion 39a, and a peripheral portion 39b. And a connecting portion 39c for connecting the two. In the present embodiment, since the upper portion 39 is only one layer, the layer constituting the upper portion 39 corresponds to the above arbitrary layer, and the layer constituting the base portion 38 is below the arbitrary layer. Corresponds to the layer located.

  By the way, the capacitance between the pair of electrodes 31 and 32 is determined by the opposing capacitance formed in the direction along the one surface 20a of the substrate 20 and the fringe capacitance formed around the thickness direction. Although the relative dielectric constant of the moisture-sensitive film 34 does not change according to the relative humidity, the entire relative dielectric constant including moisture changes depending on the amount of moisture adsorbed. For this reason, the greater the influence of the moisture sensitive film 34 on the capacitance formed between the electrodes 31 and 32, the greater the slope of the capacitance value with respect to humidity change. In the configuration having the protective film 33, the electrodes 31 and 32 are provided with a predetermined interval so that the influence of the moisture sensitive film 34, that is, the influence of the fringe capacitance is increased. FIG. 4 illustrates a fringe capacitance Cf formed by surrounding the detection electrodes 31d and 32d in the thickness direction.

  In the humidity sensor chip 10 configured as described above, the capacitance value of the capacitor configured in the detection capacitor unit 30d and the capacitance value of the capacitor configured in the reference capacitor unit 30r vary according to the relative humidity of the atmosphere. In addition, the detection capacitance unit 30d and the reference capacitance unit 30r have different inclinations of the capacitance value with respect to the humidity change, whereby each capacitance value becomes a straight line having a different inclination and intercept with respect to the relative humidity. In other words, a difference in sensitivity is given to the detection capacitor 30d and the reference capacitor 30r. Therefore, the relative humidity in the atmosphere can be measured from the capacitance change accompanying the humidity change of the detection capacitor unit 30d and the reference capacitor unit 30r.

  Further, since the moisture sensitive film 34 made of the same material is formed on the detection electrodes 31d and 32d and the reference electrodes 31r and 32r, the temperature characteristics of the moisture sensitive film 34 (difference in moisture absorption / release characteristics depending on the temperature). ), The influence of the sensor output temperature characteristics (sensitivity temperature characteristics) and the aging degradation of the moisture sensitive film 34 can be canceled.

  Next, an example of a method for manufacturing the humidity sensor chip 10 will be described.

  First, a semiconductor substrate 21 made of silicon in a wafer state is prepared, and a silicon oxide film is formed on the main surface by thermal oxidation. Next, impurities are ion-implanted into the main surface side surface layer of the semiconductor substrate 21 through the silicon oxide film to form the diffusion layer 22. Next, a BPSG film is formed on the silicon oxide film and used as the insulating film 23 together with the silicon oxide film. Then, after forming a contact hole 23a at a predetermined position of the insulating film 23, an aluminum-based material is deposited on the entire surface 20a of the substrate 20, and patterned by reactive ion etching to form the electrodes 31, 32, pads 40 (41-41). 44) and the dummy wiring 61 are formed. At this time, the electrodes 31 and 32 and the dummy wiring 61 have a two-layer structure by repeatedly performing deposition and patterning of an aluminum-based material.

  Next, a silicon nitride film as a protective film 33 is formed over the entire surface 20a of the substrate 20, and is patterned to expose the pads 40 (41 to 44). Then, for example, a precursor is applied on one surface 20a of the substrate 20 by spin coating, and after curing, the moisture sensitive film 34 and the moisture sensitive film 62 for dams are formed by patterning.

  Next, the humidity sensor chip 10 can be obtained by dicing the substrate 20 into chips.

  Next, the effect of the main characteristic part of the humidity sensor chip 10 according to the present embodiment will be described. Hereinafter, effects will be described in comparison with the conventional humidity sensor chip 10 and the reference example.

  FIG. 5 is a cross-sectional view for explaining the structure of the electrodes 31 and 32 in the conventional humidity sensor chip 10. 5 shows only the detection electrodes 31d and 32d out of the electrodes 31 and 32, the reference electrodes 31r and 32r have the same structure as the detection electrodes 31d and 32d.

  In the conventional humidity sensor chip 10, a conductive material such as aluminum is deposited on one surface 20 a of the substrate 20 by a technique such as vapor deposition or sputtering to form one film, and the formed film is formed, for example, by reactive ions. A pair of electrodes 31 and 32 are formed by patterning into a predetermined shape by etching. Further, in the patterning, the reactive ion etching conditions are such that the side surfaces of the electrodes 31 and 32 are substantially perpendicular to the one surface 20a of the substrate 20, and the residue of the aluminum-based material (etching residue) on the one surface 20a of the substrate 20 Concerned about the occurrence of this, over-etching is performed. For this reason, the conventional electrodes 31 and 32 (detection electrodes 31d and 32d) have reverse tapered shapes as shown in FIG. In other words, the distance between the side surfaces facing each other in the pair of electrodes 31 and 32 becomes wider as the surface 20a of the substrate 20 is closer.

  A triangle Δ shown in FIG. 6 indicates the result of the applicant creating the humidity sensor chip 10 having the structure shown in FIG. 5 and measuring the relationship between the relative humidity and the amount of change in capacity. The details are described in Japanese Patent Application No. 2011-268156 (hereinafter referred to as the previous application) by the present applicant. In this measurement, in the humidity sensor chip 10, the height of aluminum as the electrodes 31 and 32 is 0.7 μm, the length of the lower surface of the electrodes 31 and 32 in the facing direction is 2.7 μm, and the facing direction of the detection electrodes 31d and 32d. (Distance between the lower surfaces) is 7.8 μm, the distance between the reference electrodes 31r and 32r (distance between the lower surfaces) is 4.8 μm, the thickness of the silicon nitride film as the protective film 33 is 1.6 μm, The thickness of polyimide as the moisture sensitive film 34 is 2 μm. Further, the angle θ formed between the upper surface and the side surface is set to less than 90 degrees. The broken line shown in FIG. 6 is a straight line with a constant inclination (hereinafter, referred to as a comparison line) for comparison of linearity.

  As indicated by a triangle Δ in FIG. 6, on the high humidity side (for example, 70% RH or more), the inclination is larger than the comparison line indicated by the broken line in FIG. Thus, on the high humidity side, it became clear that the amount of change in capacity with respect to relative humidity, that is, the linearity of sensor sensitivity deteriorates, specifically, the sensor sensitivity is bent.

  Further, when the electrodes 31 and 32 have a reverse taper shape, as shown in FIGS. 5 and 7, in the protective film 33 formed so as to cover the electrodes 31 and 32, the one surface 20 a of the substrate 20 and the electrodes 31 and 32 are formed. The portion 33a (hereinafter, referred to as a stepped portion 33a) corresponding to the step formed by the bending of the step is tight (a sharp angle). In the previous application, the applicant of the present application presumed that the reason why the linearity of the sensor sensitivity deteriorates on the high humidity side when the stepped portion 33a is tightly bent is as follows. When the step portion 33a is tightly bent, the step portion 33a becomes a depression as shown in FIG. 7, and when the moisture sensitive film 34 is formed, the depression is not filled with the moisture sensitive film 34. A gap 70 is formed between the moisture sensitive film 34. The moisture adsorbed on the moisture sensitive film 34 is condensed (collected) in the gap 70 formed by the depressed step portion 33a, and the above-described fringe capacitance Cf (see FIG. 5) is affected by the moisture. Thereby, it was estimated that the sensor sensitivity bends on the high humidity side.

  On the other hand, the present applicant has proposed the humidity sensor chip 10 (reference example) including the electrodes 31 and 32 having an angle θ of 90 degrees or more in the previous application. Then, this humidity sensor chip 10 is prepared, and the relationship between the relative humidity and the capacity change amount is measured as described above. The results are shown by crosses in FIG. In this measurement, the heights of the electrodes 31 and 32, the facing distance, and the thicknesses of the protective film 33 and the moisture sensitive film 34 are the same as those in the conventional configuration described above. Further, the angle θ formed between the upper surface and the side surface is set to an angle larger than 90 degrees.

  As indicated by a cross in FIG. 6, the low humidity side and the high humidity side had almost the same inclination as the comparison line indicated by the broken line in FIG. 6 and substantially coincided with the comparison line.

  Further, when the angle θ is 90 degrees or more, and particularly larger than 90 degrees, the protective film 33 is compared with the configuration having the conventional electrodes 31 and 32 (reversely tapered electrodes 31 and 32) shown in FIG. It became clear that the stepped portion 33a becomes gentle. That is, by making the stepped portion 33a gentle, it is possible to suppress the generation of the gap 70 between the protective film 33 and the moisture sensitive film 34 and to suppress the deterioration of the linearity of the sensor sensitivity at high humidity. In the application.

  In response to this, in this embodiment, in order to make the stepped portion 33a of the protective film 33 gentle, the cross-sectional shapes of the electrodes 31 and 32 are convex due to the multilayer arrangement of the films. As illustrated by the detection electrode 31d in FIG. 8A, in the conventional humidity sensor chip 10, the electrodes 31 and 32 are formed by disposing one layer of the film. For this reason, only one step is formed by the one surface 20a of the substrate 20 and the electrodes 31, 32, and the height of one step is equal to the thickness t1 of the electrodes 31, 32, so that the step 33a in the protective film 33 is bent. It becomes tight.

  On the other hand, in the present embodiment, as exemplified by the detection electrode 31d in FIG. 8B, the electrodes 31 and 32 are formed by arranging multiple layers (two layers) of films. For this reason, two steps are formed by the one surface 20a of the substrate 20 and the electrodes 31 and 32, and the heights t2 and t3 for one step are lower than the thickness t1 of the electrodes 31 and 32, respectively. Therefore, as shown in FIG. 8B, the bending of the stepped portion 33a in the protective film 33 can be moderated. As a result, the relationship between the relative humidity and the amount of change in capacity has the same inclination as the comparison line indicated by the broken line in FIG. 6 as in the above-described reference example, and is considered to substantially coincide with the comparison line. That is, it is possible to suppress linearity degradation of sensor sensitivity on the high humidity side. In FIG. 8B, the side surface of the base portion 38 and the side surface of the upper portion 39 are substantially perpendicular to the one surface 20a. However, as shown in FIG. As compared with the above, the bending of the stepped portion 33a in the protective film 33 can be moderated.

  Further, according to the present embodiment, the protective film 33 can effectively suppress corrosion of the electrodes 31 and 32.

  Further, according to the present embodiment, since the uppermost layer is made of a conductive material, the facing distance contributing to the fringe capacitance Cf in the pair of electrodes 31 and 32 can be shortened as compared with the configuration in which the uppermost layer is made of an electrically insulating material. Can do. Thereby, sensor sensitivity can be raised.

  In addition to the above-described configuration, in the present embodiment, in the electrodes 31 and 32, a layer excluding the lowermost layer constituting the base portion 38 has a central portion 39a positioned above a layer positioned below the layer. A peripheral portion 39b disposed on one surface 20a of the substrate 20 and a connecting portion 39c that connects the central portion 39a and the peripheral portion 39b. And the arbitrary layers except the lowest layer are arrange | positioned so that the layer located below this arbitrary layer may be wrapped. For this reason, a level | step difference becomes gentle, so that the curve of the level | step-difference part 33a in the protective film 33 can be made looser. Furthermore, since the upper layer is arranged in a wider range, the facing area contributing to the fringe capacitance Cf in the pair of electrodes 31 and 32 can be increased. Therefore, the sensor sensitivity can be further increased.

  In addition to the above configuration, in the present embodiment, in the electrodes 31 and 32, all layers are formed using the same conductive material having corrosiveness against moisture. The configuration / manufacturing process of the humidity sensor chip 10 can be simplified. In this way, all layers can be formed using the same conductive material because an arbitrary layer except the lowermost layer is disposed so as to wrap around a layer located below the arbitrary layer. . Moreover, all the layers can be made to function as an electrode substantially.

  Next, the effect of the subordinate part in the humidity sensor chip 10 according to the present embodiment will be described.

  In the present embodiment, each of the pair of electrodes 31 and 32 has a comb-teeth shape and is disposed so that the comb teeth are engaged with each other and face each other. With such a configuration, since the facing area of the pair of electrodes 31 and 32 can be increased, the sensor sensitivity can be further increased.

  In this embodiment, the substrate 20 includes the semiconductor substrate 21 and the insulating film 23 formed on the main surface of the semiconductor substrate 21, and the electrodes 31 and 32 are disposed on the insulating film 23 of the substrate 20. ing. With this configuration, the processing circuit that processes the signal output from the humidity detection unit 30 can be configured on the same substrate 20. In other words, the circuit chip 113 shown in FIG. 1 can be dispensed with. In addition, since the insulating film 23 is provided, leakage of current from the electrodes 31 and 32 can be prevented.

(Modification)
In the present embodiment, an example is shown in which the films constituting the electrodes 31 and 32 are made of the same conductive material (aluminum-based material) in all layers. However, a plurality of layers may be formed using different conductive materials. For example, in the configuration shown in FIG. 4, the base portion 38 may be formed using polysilicon doped with impurities, and the upper portion 39 may be formed using an aluminum-based material.

  Further, the uppermost layer is formed using a conductive material, and at least one of the layers in contact with the protective film 23 satisfies the condition that it is formed using a conductive material having corrosiveness against moisture. For example, the electrodes 31 and 32 may include a layer formed using an electrically insulating material. For example, in the example shown in FIG. 9, the base portion 38 is a layer formed using an electrically insulating material, and the upper portion 39 is a layer formed using an aluminum-based material. In the present embodiment, since any layer except the lowermost layer is disposed so as to wrap a layer positioned below the arbitrary layer, the electrode 31 has a layer made of an electrically insulating material. , 32 can be enlarged.

(Second Embodiment)
In the present embodiment, description of portions common to the humidity sensor chip 10 shown in the above embodiment is omitted.

  The feature of this embodiment is that in the electrodes 31 and 32, the arbitrary layer forming the upper portion 39 covers only a part of the upper surface of the surface of the layer adjacent to the arbitrary lower layer on the lower side. It is to be arranged. In other words, in any two adjacent layers, the upper layer is arranged so as to cover only a part of the upper surface of the lower layer.

  As exemplified by the detection electrode 31 d in FIG. 10, in the electrodes 31 and 32 having a two-layer structure, the layer that forms the upper portion 39 is only a part of the upper surface of the surface of the layer that forms the lower portion 38. It is arranged to cover. And the cross-sectional shape of the electrodes 31 and 32 is convex shape. The layer forming the base portion 38 is formed using, for example, polysilicon doped with impurities, and the layer forming the upper portion 39 is formed using a conductive material different from the base portion 38, for example, an aluminum-based material. Is formed. That is, in the electrodes 31 and 32, each layer is formed using different conductive materials.

  Thus, in the present embodiment, the upper portion 39 is disposed so as to cover only a part of the upper surface of the base portion 38. Therefore, steps are formed between the upper surface of the upper portion 39 and the upper surface of the base portion 38, and between the upper surface of the base portion 38 and the one surface 20 a of the substrate 20. Accordingly, the height t2 and t3 of each step is lower than the thickness t1 of the electrodes 31 and 32. Thereby, like the first embodiment, the bending of the stepped portion 33a in the protective film 33 can be moderated. Therefore, it is possible to suppress linearity deterioration of sensor sensitivity on the high humidity side.

  In addition to the above configuration, in the present embodiment, in the electrodes 31 and 32, all layers are formed using different conductive materials. According to this, all the layers can be made to function as an electrode substantially. Therefore, the facing area contributing to the fringe capacitance Cf in the pair of electrodes 31 and 32 can be increased. That is, the sensor sensitivity can be further increased.

(Modification)
In the present embodiment, in the electrodes 31 and 32, the base portion 38 is formed using polysilicon doped with impurities, and the top portion 39 is formed using an aluminum-based material. However, the base portion 38 may be formed using an aluminum-based material, and the upper portion 39 may be formed using polysilicon doped with impurities.

  Further, the uppermost layer is formed using a conductive material, and at least one of the layers in contact with the protective film 23 satisfies the condition that it is formed using a conductive material having corrosiveness against moisture. For example, the electrodes 31 and 32 may include a layer formed using an electrically insulating material. For example, in the example shown in FIG. 11, the base portion 38 is formed using an electrical insulating material, and the top portion 39 is formed using an aluminum-based material.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The electrodes 31 and 32 are not limited to a two-layer structure. It is good also as three or more layers. In other words, the upper portion 39 only needs to have at least one layer of film disposed on the lower portion 38, and the upper portion 39 may have two or more layers. As in the first embodiment, the detection electrode 31d illustrated in FIG. 12 is arranged such that an arbitrary layer except the lowermost layer wraps a layer positioned below the arbitrary layer. All layers have a three-layer structure formed using the same aluminum-based material. In other words, the upper portion 39 has a two-layer structure having the intermediate layer 80 and the uppermost layer 81. In this configuration, the step of the uppermost layer 81 becomes gentler as the number of layers forming the electrodes 31 and 32 increases. Therefore, the bending of the stepped portion 33a in the protective film 33 can be made more gradual. In addition, each structure shown in each said embodiment is employable also about three or more layers. For example, in the configuration shown in FIG. 12, at least one of the layers (lowermost layer) forming the intermediate layer 80 and the base portion 38 may be a layer formed using an electrically insulating material. In the structure shown in the second embodiment, the electrodes 31 and 32 may have three or more layers. According to this, as the number of layers forming the electrodes 31 and 32 is increased, the height of one step is lowered, so that the bending of the stepped portion 33a in the protective film 33 can be made more gradual.

  In this embodiment, the humidity detection part 30 showed the example provided with the detection capacity | capacitance part 30d and the reference capacity | capacitance part 30r. However, the humidity detection unit 30 may include at least the detection capacity unit 30d.

  Further, as the humidity sensor chip 10, an example of a capacitive humidity sensor that detects a change in the humidity of the atmosphere as a change in the capacitance of the pair of electrodes 31 and 32 has been shown. However, the detection principle is not limited to this. For example, in a resistance-type humidity sensor that includes a pair of electrodes 31 and 32, and the humidity-sensitive film 34 has an impedance that changes due to moisture adsorption, and detects a humidity change in the atmosphere as a change in the impedance of the moisture-sensitive film 34. Also, the electrode structure described above can be adopted.

  As the substrate 20, a substrate made of an inorganic material such as glass can be adopted. In this case, the insulating film 23 can be dispensed with.

  The shape of the electrodes 31 and 32 is not limited to the comb shape. The electrodes 31 and 32 may be formed on the one surface 20a of the substrate 20 so as to face each other.

  In the said embodiment, the example which makes a cross-sectional convex shape the electrodes 31 and 32 by arrange | positioning a film | membrane in multiple layers was shown. However, like the detection electrode 31d illustrated in FIG. 13, the electrodes 31 and 32 having a convex cross section may be adopted by half-etching a single layer film. According to the detection electrode 31d shown in FIG. 13, since two steps are formed by the one surface 20a of the substrate 20 and the detection electrode 31d (electrodes 31 and 32), the same as in FIGS. 10 and 11 shown in the second embodiment. There is an effect.

  In the above embodiment, the humidity sensor chip 10 has an example in which the dam portion 60 is configured to include the dummy wiring 61 and the dam moisture sensitive film 62. However, a configuration without the dam portion 60 can also be adopted.

10 ... Humidity sensor chip (humidity sensor)
20 ... substrate 20a ... one side 30 ... humidity detectors 31, 32 ... electrodes (a pair of electrodes)
33 ... Protective film 33a ... Step part 34 ... Moisture sensitive film 38 ... Base part 39 ... Upper part 70 ... Gap

Claims (10)

A substrate (20);
A pair of electrodes (31, 32) disposed on a common surface (20a) of the substrate so as to face each other, and disposed on the one surface so as to cover the electrodes, and protect the electrodes from corrosion due to moisture A humidity detector (30) having a protective film (33) to be formed, and a moisture sensitive film (34) disposed on the protective film so as to cover the electrodes and the electrodes,
All the electrodes are
The film has a multilayer structure in which films are arranged in multiple layers with respect to the one surface, the uppermost layer is formed using a conductive material, and at least one of the layers in contact with the protective film is corrosive to moisture. Formed using a conductive material having,
A base portion (38) in which one layer of the film is disposed on one surface of the substrate; and an upper portion (39) in which at least one layer of the film is disposed on the base portion. ,
In the electrodes (31, 32), an arbitrary layer forming the upper portion (39) is disposed so as to wrap a layer positioned below the arbitrary layer, and is positioned on the lower side. The central part (39a) located above the layer, the peripheral part (39b) disposed on one surface (20a) of the substrate (20), and the central part (39a) and the peripheral part (39b) are connected. And a connecting portion (39c), wherein each of the cross-sectional shapes orthogonal to the one surface independently forms a convex shape. The humidity sensor according to claim 1 , wherein all layers of the electrodes (31, 32) are formed using the same conductive material having corrosiveness against moisture. The humidity sensor according to claim 1 , wherein the electrodes (31, 32) include a layer formed using an electrically insulating material. A substrate (20);
A pair of electrodes (31, 32) disposed on a common surface (20a) of the substrate so as to face each other, and disposed on the one surface so as to cover the electrodes, and protect the electrodes from corrosion due to moisture A humidity detector (30) having a protective film (33) to be formed, and a moisture sensitive film (34) disposed on the protective film so as to cover the electrodes and the electrodes,
All the electrodes are
The film has a multilayer structure in which films are arranged in multiple layers with respect to the one surface, the uppermost layer is formed using a conductive material, and at least one of the layers in contact with the protective film is corrosive to moisture. Formed using a conductive material having,
A base portion (38) in which one layer of the film is disposed on one surface of the substrate; and an upper portion (39) in which at least one layer of the film is disposed on the base portion. ,
In the electrodes (31, 32), the arbitrary layer forming the upper portion (39) is arranged so as to cover only a part of the upper surface of the surface of the layer adjacent to the arbitrary lower layer on the lower side. Thus , the humidity sensor is characterized in that the cross-sectional shapes orthogonal to the one surface are each independently a convex shape. The humidity sensor according to claim 4 , wherein each layer of the electrodes (31, 32) is formed using different conductive materials. The humidity sensor according to claim 4 , wherein the electrodes (31, 32) include a layer formed using an electrically insulating material. The pair of electrodes (31, 32) each have a comb-teeth shape, and are arranged so that the respective comb teeth are engaged with each other and face each other. Humidity sensor. The moisture sensitive film (34) has a relative dielectric constant that changes due to moisture adsorption.
The said humidity detection part (30) detects the humidity change of atmosphere as a change of the electrostatic capacitance between a pair of said electrodes (31, 32), The one of Claims 1-7 characterized by the above-mentioned. Humidity sensor. The moisture sensitive film (34) is one whose impedance changes due to moisture adsorption,
The humidity sensor according to any one of claims 1 to 7, wherein the humidity detector (30) detects a change in humidity of the atmosphere as a change in impedance of the moisture sensitive film (34). The substrate (20) has a semiconductor substrate (21) and an insulating film (23) formed on the main surface of the semiconductor substrate (21).
The humidity sensor according to any one of claims 1 to 9, wherein the electrodes (31, 32) are arranged on an insulating film (23) of the substrate (20).

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