Ion sensor and method for manufacturing an ion sensor

Abstract

An ion sensor includes a substrate and a plurality of detection portions. Each detection portion includes an ID portion, an ICG electrode, a TG electrode, an SG electrode, an electrode pad, and an ion-sensitive membrane. The SG electrode is disposed between the ICG electrode and the TG electrode on a main surface of the substrate. The electrode pad is electrically connected to the SG electrode and is disposed on an opposite side of the substrate from the SG electrode. The ion-sensitive membrane is disposed on a surface of the electrode pad and changes in potential in response to changes in ion concentration of an aqueous solution in contact with the ion-sensitive membrane. The width of the ion-sensitive membrane in a direction opposite the ICG electrode and the TG electrode is greater than the separation width of the ICG electrode and the TG electrode.

Description

Technical Field

[0001] This invention relates to an ion sensor and a method for manufacturing the ion sensor. Background Technology

[0002] Non-Patent Document 1 discloses an ion sensor sensitive to odors. This ion sensor employs an open-type pixel structure (hereinafter referred to as an "open-type structure"). Specifically, in each pixel, an opening is provided between a first electrode (ICG electrode) and a second electrode (TG electrode) on a semiconductor substrate, and an ion-sensing film (Si3N4) is disposed at the bottom of the opening. A polyaniline sensing film, serving as a medium containing the substance to be detected (e.g., an odorant), is formed on this ion-sensing film.

[0003] Existing technical documents

[0004] Non-patent literature

[0005] Non-Patent Literature 1: Naoya Niina, Tatsuya Iwata, Kenichi Hashizume, Shunichiro Kuroki, and Kazuaki Sawada (2017), Gas Distribution Imaging Using a Charge-Transfer Sensor Array with Polyaniline Sensing Film, 64th Spring Academic Lecture of the Chinese Society of Applied Physics, 16p-416-6. Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the ion sensor described above, sufficient contact area between the ion sensing membrane and the medium is required to obtain adequate sensitivity. On the other hand, in the open-type structure described in Non-Patent Document 1, since the medium enters the opening as part of it, the contact area between the medium and the ion sensing membrane depends on the opening size. Furthermore, there are limits to the size of the opening, considering factors such as pixel size and pixel pitch. Therefore, in the aforementioned open-type structure, it is difficult to ensure a sufficient contact area.

[0008] One aspect of the present invention is to provide an ion sensor that can effectively improve sensitivity and a method for manufacturing the ion sensor.

[0009] Technical means to solve the problem

[0010] An ion sensor according to one aspect of the present invention includes: a substrate; and a plurality of pixels disposed on a first surface of the substrate; each pixel having a charge storage portion, a first electrode, a second electrode, a third electrode, a fourth electrode, and an ion sensing film; the charge storage portion is formed in a region along the first surface of the substrate, and stores charge for injection into a potential well formed in the portion overlapping with the third electrode when viewed from the thickness direction of the substrate; the first electrode is disposed on the first surface and configured to control the amount of charge injected from the charge storage portion into the potential well; the second electrode is disposed on... On the first surface, it is configured to control the transfer of charge from the potential trap to the outside; the third electrode is on the first surface and is disposed between the first electrode and the second electrode; the fourth electrode is electrically connected to the third electrode and is disposed on the opposite side of the substrate, separated by the third electrode; an ion sensing film is disposed on the surface of the fourth electrode opposite to the substrate side, and its potential changes in response to changes in the ion concentration of the medium in contact with the ion sensing film; the width of the ion sensing film in the opposite direction between the first electrode and the second electrode is greater than the spacing width between the first electrode and the second electrode.

[0011] In the aforementioned ion sensor, a third electrode is disposed on the first surface of the substrate between the first electrode and the second electrode. Furthermore, the third electrode is electrically connected to a fourth electrode on which an ion-sensing membrane is disposed. This achieves the function of an ion sensor. Specifically, changes in the potential of the ion-sensing membrane can be transmitted to the substrate via the fourth and third electrodes. Consequently, the depth of the potential trap can be varied according to the change in the potential of the ion-sensing membrane. As a result, the ion concentration of the object being examined, which is in contact with the medium in contact with the ion-sensing membrane, can be detected based on the amount of charge extracted to the outside through the control of the first and second electrodes (i.e., an amount corresponding to the depth of the potential trap).

[0012] Here, assuming a structure with an opening between the first and second electrodes and an ion-sensing membrane at the bottom of this opening (a so-called open-type structure), the width of the ion-sensing membrane is limited by the opening size, preventing it from being wider than the distance between the first and second electrodes. On the other hand, in the aforementioned ion sensor, by employing a structure where the potential change of the ion-sensing membrane is transmitted to the substrate via the third and fourth electrodes, a structure is achieved where the width of the ion-sensing membrane is greater than the distance between the first and second electrodes. This ensures sufficient contact area between the ion-sensing membrane and the medium, and effectively improves the sensitivity of the ion sensor.

[0013] The surface of the fourth electrode opposite to the substrate side can be a flat surface, and the ion sensing film can also be formed flatly along the opposite surface. According to the above structure, compared to the case using the above-described open-type structure, the medium disposed on the ion sensing film can be in full contact with the ion sensing film. Therefore, the sensitivity of the ion sensor can be further and effectively improved.

[0014] The first electrode and the third electrode can be spaced apart from each other, and the first gap width between the first electrode and the third electrode can also be set to a range that does not create a potential barrier that hinders the injection of charge from the charge accumulation section to the potential well. According to the above structure, sufficient charge transfer efficiency from the charge accumulation section to the potential well is ensured.

[0015] The second and third electrodes can be spaced apart from each other, and the second gap width between the second and third electrodes can also be set to a range that does not create a potential barrier that hinders the transfer of charge from the potential well to the outside. Based on the above structure, sufficient charge transfer efficiency from the potential well to the outside is ensured.

[0016] The width of the third electrode in the opposite direction can also be more than 80% of the spacing between the first and second electrodes. Based on the above structure, the generation of the aforementioned potential barrier can be better suppressed.

[0017] When viewed from the thickness direction, a portion of the first electrode can also overlap with the third electrode. Based on this structure, the unevenness of the charge accumulated in the potential well can be reduced.

[0018] A portion of the first electrode may also be disposed on the opposite side of the substrate, separated from the third electrode. According to the above structure, compared to the case where a portion of the first electrode is disposed between the substrate and the third electrode, the voltage required to form a potential well in the region of the substrate overlapping with the third electrode can be reduced.

[0019] The width of the first portion of the first electrode that overlaps with the third electrode in the opposite direction can also be smaller than the width of the second portion of the first electrode that does not overlap with the third electrode in the opposite direction. According to the above structure, accidental leakage of charge from the potential well to the charge accumulation section can be suppressed.

[0020] The width of the first part can also be less than 25% of the width of the second part. Based on the above structure, accidental leakage of charge from the potential well to the charge accumulation section can be better suppressed.

[0021] When viewed from the thickness direction, a portion of the second electrode may also overlap with the third electrode. Based on this structure, an improvement in the charge transfer efficiency from the potential well to the outside can be achieved.

[0022] A portion of the second electrode may also be disposed on the opposite side of the substrate, separated from the third electrode. According to the above structure, compared to the case where a portion of the second electrode is disposed between the substrate and the third electrode, the voltage required to form a potential well in the region of the substrate overlapping with the third electrode can be reduced.

[0023] The width of the third portion of the second electrode that overlaps with the third electrode in the opposite direction can also be smaller than the width of the fourth portion of the second electrode that does not overlap with the third electrode in the opposite direction. Based on the above structure, accidental leakage of charge from the potential well to the outside can be suppressed.

[0024] The width of the third part can also be less than 25% of the width of the fourth part. Based on the above structure, accidental leakage of charge from the potential well to the outside can be better suppressed.

[0025] A single pixel can contain multiple ion-sensing films that react with different ions. Multiple fourth electrodes can be disposed corresponding to each of the multiple ion-sensing films, or multiple third electrodes can be disposed corresponding to each of the multiple fourth electrodes. Based on this structure, the amount of information obtained from a single pixel can be further increased. That is, the concentrations of multiple ions can be detected using a single pixel.

[0026] Another aspect of the present invention relates to a method for manufacturing an ion sensor having a substrate and a first electrode, a second electrode, and a third electrode formed on the substrate, comprising: a step of forming a first insulating film on the substrate; a step of forming a first electrode, a second electrode disposed separately from the first electrode, and a third electrode disposed between the first electrode and the second electrode and separately from both the first electrode and the second electrode on the first insulating film; a step of forming a second insulating film on the substrate covering the first electrode, the second electrode, and the third electrode; and a step of forming a portion of the third electrode... The process involves: forming an opening in the second insulating film and forming a metal wiring electrically connected to the third electrode within the opening; forming a fourth electrode electrically connected to the metal wiring along the surface of the second insulating film opposite to the substrate side; and forming an ion-sensing film on the surface of the fourth electrode opposite to the substrate side, which changes potential according to changes in the ion concentration of the contact medium. In the process of forming the ion-sensing film, the width of the ion-sensing film in the opposing direction between the first and second electrodes is greater than the distance between the first and second electrodes. According to the above-described method for manufacturing an ion sensor, an ion sensor exhibiting the aforementioned effects can be obtained.

[0027] Another aspect of the present invention relates to a method for manufacturing an ion sensor having a substrate and a first electrode, a second electrode, and a third electrode formed on the substrate, comprising: a step of forming a first insulating film on the substrate; a step of forming a third electrode on the first insulating film; a step of forming a second insulating film covering the surface of the third electrode; a step of forming a first electrode such that, when viewed from the thickness direction of the substrate, a portion of the first electrode overlaps with the third electrode via the second insulating film to form a first electrode, and a portion of the second electrode such that, when viewed from the thickness direction of the substrate, a portion of the second electrode overlaps with the third electrode via the second insulating film to form a second electrode; and a step of forming a layer covering the first electrode on the substrate. The process includes: forming a third insulating film containing a first electrode, a second electrode, and a third electrode; forming an opening in the third insulating film with a portion of the third electrode exposed, and forming a metal wiring electrically connected to the third electrode within the opening; forming a fourth electrode electrically connected to the metal wiring along the surface of the third insulating film opposite to the substrate side; and forming an ion-sensing film on the surface of the fourth electrode opposite to the substrate side, which changes potential according to changes in the ion concentration of the contact medium; in the process of forming the ion-sensing film, the width of the ion-sensing film in the opposing direction between the first and second electrodes is greater than the distance between the first and second electrodes. According to the above-described method for manufacturing an ion sensor, an ion sensor exhibiting the aforementioned effects can be obtained.

[0028] The effects of the invention

[0029] According to one aspect of the present invention, an ion sensor that can effectively improve sensitivity and a method for manufacturing the ion sensor can be provided. Attached Figure Description

[0030] Figure 1 This is a schematic top view of the ion sensor according to the first embodiment.

[0031] Figure 2 It is a diagram of the cross-sectional structure of the pattern display detection unit (pixel).

[0032] Figure 3 This is a diagram showing an example of the operation of the detection unit in the ID-driven mode.

[0033] Figure 4 This is a diagram showing an example of the operation of the detection unit in the ICG driving mode.

[0034] Figure 5 This is a diagram showing an example of the potential barriers between the ICG electrode and the SG electrode, and between the TG electrode and the SG electrode.

[0035] Figure 6 It is a diagram showing the configuration dimensions of the ICG electrode, TG electrode, and SG electrode.

[0036] Figure 7 This is a diagram showing the manufacturing process of the ion sensor according to the first embodiment.

[0037] Figure 8 This is a schematic diagram showing the cross-sectional structure of the detection section of the ion sensor according to the second embodiment.

[0038] Figure 9 This is a diagram showing an example of the operation of the detection unit of the ion sensor according to the second embodiment.

[0039] Figure 10 This is a diagram showing the manufacturing process of the ion sensor according to the second embodiment.

[0040] Figure 11 This is a schematic diagram showing the cross-sectional structure of the detection section of the ion sensor according to the third embodiment.

[0041] Figure 12 This is a diagram showing the first modified example of the ion sensor.

[0042] Figure 13 This is a diagram showing the second modified example of the ion sensor. Detailed Implementation

[0043] The following is a reference to the appendix. Figure 1 The embodiments of the present invention will be described in detail below. In the description of the accompanying drawings, the same or equivalent elements are referred to by the same reference numerals, and repeated descriptions are omitted.

[0044] [First Implementation]

[0045] Figure 1 This is a schematic top view of the ion sensor 1 according to the first embodiment. Figure 1 The right side of the pattern is displayed in the common layout example of each of the 5 detection sections. Figure 2 It is a patterned display along Figure 1 A diagram showing the cross-sectional structure of the detection section 5 of line II-II. (See diagram for reference.) Figure 2 As shown, the ion sensor 1 is a sensor device configured to detect the ion concentration of an object to be inspected (not shown) in contact with the aqueous solution 3 by immersing the surface of the ion sensor 1 in an aqueous solution 3 (medium). The object to be inspected can be solid, liquid, or gaseous.

[0046] The ion sensor 1 is a sensor in which a plurality of detection units 5 arranged in a two-dimensional pattern are formed on a substrate 100. The ion sensor 1 is a so-called charge-transfer type CMOS image sensor. The plurality of detection units 5 are arranged in a two-dimensional pattern of M rows and N columns (e.g., 256 rows and 256 columns) in a pixel forming region R (in this embodiment, a rectangular region provided in the center of the chip) provided on the chip of the ion sensor 1, thereby forming a pixel array. M and N are integers of 2 or more. One detection unit 5 corresponds to one detection unit (pixel). The size (pixel size) of one detection unit 5 is, for example, 15 μm × 15 μm.

[0047] During measurement, the aqueous solution 3 is dripped onto the surface of the plurality of detection units 5 contained within the pixel forming region R. Thus, as... Figure 2 As shown, the surface of each detection unit 5 is covered by an aqueous solution 3 during measurement. The aqueous solution 3 can be, for example, an SSC solution, a pH standard solution, or a cell culture medium. Furthermore, during measurement, a reference voltage Vref is applied to the aqueous solution 3 via an electrode (not shown). The electrode used to apply the reference voltage Vref can be, for example, an external electrode such as a glass electrode, or an electrode embedded in the ion sensor 1 (for example, an electrode embedded in the passivation layer 120 and electrically connected to the aqueous solution 3 through an opening in the passivation layer 120). The electrode can be formed of any material that can contact the aqueous solution 3 to apply voltage.

[0048] like Figure 1 and Figure 2 As shown, each detection unit 5 is formed on a main surface 100a (first surface) of the substrate 100. The substrate 100 is a semiconductor substrate of a first conductivity type (for example, p-type) formed of silicon, for example. In each detection unit 5, a second conductivity type region, namely an input diode section 21 (hereinafter referred to as "ID section 21") (charge accumulation section), a floating diffusion section 31 (hereinafter referred to as "FD section 31"), and a reset drain section 41 (hereinafter referred to as "RD section 41"), are formed along the region of the main surface 100a of the substrate 100. A diffusion layer 11 of the first conductivity type (for example, p-type) is formed between the ID section 21 and the FD section 31 of the substrate 100. A first conductivity type region 12 doped with the first conductivity type is formed on the surface of the diffusion layer 11.

[0049] On the main surface 100a of the substrate 100, an input control gate electrode 22 (hereinafter "ICG electrode 22") (first electrode), a transfer gate electrode 32 (hereinafter "TG electrode 32") (second electrode), a reset gate electrode 42 (hereinafter "RG electrode 42"), and a sensing gate electrode 51 (hereinafter "SG electrode 51") (third electrode) are formed (arranged) via an insulating protective film 110. The protective film 110 is a so-called gate insulating film (gate oxide film). As the protective film 110, SiO2 or the like can be used. The protective film 110 is, for example, a thin film with a thickness of about 10 nm. In addition, on the main surface 100a of the substrate 100, an amplifier (signal amplifier 33) that amplifies the output signal corresponding to the amount of charge stored in the FD section 31, and a source follower circuit, i.e., an output circuit 34, that outputs the output signal amplified by the amplifier 33 are provided.

[0050] SG electrode 51 is on the main surface 100a, at a distance D1 from the thickness direction of the substrate 100 (refer to...). Figure 2 During observation, it is positioned between the ICG electrode 22 and the TG electrode 32, overlapping with the first conductivity type region 12. Furthermore, an insulating passivation layer 120 is formed on the main surface 100a to cover each electrode (ICG electrode 22, TG electrode 32, RG electrode 42, and SG electrode 51, etc.) disposed on the main surface 100a. For example, SiO2 can be used as the passivation layer 120. Alternatively, Si3N4 can also be used as the passivation layer 120.

[0051] A flat electrode pad 52 (the fourth electrode) is provided on the surface 120a of the passivation layer 120 opposite to the substrate 100 side. That is, the electrode pad 52 is disposed on the opposite side of the substrate 100, separated from the SG electrode 51. The electrode pad 52 is electrically connected to the SG electrode 51. In this embodiment, the electrode pad 52 is electrically connected to the SG electrode 51 via a metal wiring 53 embedded in an opening (contact hole) formed in the passivation layer 120. Figure 2 In one example, the electrode pad 52 is embedded in the passivation layer 120, and the surface 52a of the electrode pad 52 opposite to the substrate 100 side is flush with the surface 120a of the passivation layer 120. However, the electrode pad 52 may also be disposed on the passivation layer 120. In this case, the height of the surface 52a of the electrode pad 52 is a position that is only a thickness away from the substrate 100 than the height of the surface 120a of the passivation layer 120.

[0052] A thin-film ion-sensing membrane 13 is provided on the surface 52a of the electrode pad 52. The ion-sensing membrane 13 has the property of changing its potential (membrane potential) according to the change in ion concentration of the medium in contact with the ion-sensing membrane 13 (in this embodiment, an aqueous solution 3 immersed in the surface of the ion sensor 1). As the ion-sensing membrane 13, for example, Si3N4 can be used. The thickness of the ion-sensing membrane 13 is, for example, about 100 nm. The width of the ion-sensing membrane 13 on the opposite direction D2 between the ICG electrode 22 and the TG electrode 32 is greater than the spacing between the ICG electrode 22 and the TG electrode 32. In addition, the surface 52a of the electrode pad 52 is a flat surface, and the ion-sensing membrane 13 is formed flatly along the surface 52a of the electrode pad 52. In addition, "flat surface" here means a surface formed in a manner that is generally flat when viewed macroscopically, without the opening structure described below. Therefore, for example, a surface 52a with a fine uneven structure (e.g., an uneven structure with a height sufficiently small than the thickness of the measured object, i.e., the medium (aqueous solution 3)) provided to increase the contact area and improve the adhesion between the electrode pad 52 surface 52a and the ion sensing film 13, is also equivalent to the "flat surface" described above. Furthermore, as... Figure 2 As shown, the ion-sensing membrane 13 is positioned further outward than the electrode pad 52. That is, when viewed from the thickness direction D1, the ion-sensing membrane 13 has a portion extending beyond the electrode pad 52. While this portion of the ion-sensing membrane 13 does not contribute to the sensitivity of the ion sensor 1, it serves to prevent the surface 52a of the electrode pad 52 from being exposed to the outside. Thus, for example, the seepage of the aqueous solution 3 into the surface 52a of the electrode pad 52 can be better suppressed.

[0053] Next, the functional structure and operating principle of the detection unit 5 will be explained. The detection unit 5 includes a sensing unit 10, a supply unit 20, a moving / accumulating unit 30, and a removal unit 40. In this embodiment, the charge is electrons.

[0054] The sensing section 10 is the region in the substrate 100 opposite to the SG electrode 51. More specifically, the sensing section 10 is the region between the ICG electrode 22 and the TG electrode 32, where the SG electrode 51 is opposite to the first conductivity type region 12 via the protective film 110. That is, the sensing section 10 is a sensing region constructed by stacking the diffusion layer 11, the first conductivity type region 12, the protective film 110, and the SG electrode 51. If stimulation is applied to the aqueous solution 3 or the object to be examined (ion concentration measurement) for the purpose of examination, the ion concentration of the aqueous solution 3 changes accordingly to the state of the object to be examined. Such stimulation includes, for example, simply contacting the aqueous solution 3 with the object to be examined, or applying physical, chemical, or pharmaceutical stimulation to the aqueous solution 3 or the object to be examined while the aqueous solution 3 is in contact with the object to be examined. As a result, a potential change corresponding to the change in the ion concentration of the aqueous solution 3 is generated in the ion sensing membrane 13. This potential change of the ion sensing membrane 13 is transmitted to the first conductivity type region 12 via the electrode pad 52, the metal wiring 53, and the SG electrode 51. As a result, the depth of the potential well 14 formed in the portion (sensing part 10) that overlaps with the SG electrode 51 when viewed from the thickness direction D1 in the substrate 100 varies.

[0055] The supply unit 20 is composed of the ID unit 21 and the ICG electrode 22. The ID unit 21 is the part that stores the charge to be injected into the potential well 14. The ICG electrode 22 is the part that controls the amount of charge injected from the ID unit 21 into the potential well 14.

[0056] The moving / accumulating section 30 is composed of a TG electrode 32 and an FD section 31. The TG electrode 32 is the part that controls the transfer of charge from the potential well 14 to the FD section 31 (external). The FD section 31 is the part that accumulates the charge transferred from the potential well 14. Specifically, by changing the voltage of the TG electrode 32, the potential of the region in the substrate 100 opposite to the TG electrode 32 (hereinafter referred to as the "TG region") can be changed, and the charge filling the potential well 14 is transferred and accumulated in the FD section 31.

[0057] The removal section 40 is composed of an RG electrode 42 and an RD section 41. The removal section 40 is used to reset (remove) the charge accumulated in the FD section 31. Specifically, by changing the voltage of the RG electrode 42, the potential of the region in the substrate 100 opposite to the RG electrode 42 (hereinafter referred to as the "RG region") can be changed, and the charge accumulated in the FD section 31 can be discharged to the RD section 41 (VDD).

[0058] Next, the operation of the detection unit 5 will be explained. Figure 3This shows an example of operation where the potential of the ID section 21 is changed by setting the potential of the ICG electrode 22 to a certain state, and charge is injected into the potential trap 14 from the ID section 21 (hereinafter referred to as "ID driving mode"). Figure 4 This shows an example of operation where the potential of the ICG electrode 22 is changed by setting the potential of the ID section 21 to a certain state, and charge is injected into the potential trap from the ID section 21 (hereinafter referred to as "ICG driving mode").

[0059] (ID-driven approach)

[0060] Reference Figure 3 The ID driving method will be explained below. First, if the above-mentioned stimulus is applied to the aqueous solution 3 or the object under inspection, resulting in a change in the ion concentration of the aqueous solution 3, a potential change is generated in the ion sensing membrane 13 in contact with the aqueous solution 3. This potential change in the ion sensing membrane 13 is transmitted to the diffusion layer 11 (first conductivity type region 12) via the electrode pad 52, the metal wiring 53, and the SG electrode 51. Thus, as Figure 3 As shown in (A), the depth of the potential trap 14 varies in response to the potential change of the ion sensing membrane 13.

[0061] Next, as Figure 3 As shown in (B), the potential of the ID section 21 decreases, and charge accumulates in the ID section 21. The charge accumulated in the ID section 21 exceeds the region in the substrate 100 opposite to the ICG electrode 22 (hereinafter referred to as the "ICG region") and is injected into the potential well 14. At this time, the potential of the TG region is controlled to be lower than that of the ID section 21. Therefore, the charge injected into the potential well 14 will not exceed the TG region and reach the FD section 31.

[0062] Next, as Figure 3 As shown in (C), the potential of the ID section 21 is returned (raised) to its original value, and charge is extracted from the ID section 21. As a result, the charge consumed at the height of the pre-set ICG region potential remains in the potential well 14. The amount of charge remaining in the potential well 14 corresponds to the depth of the potential well 14.

[0063] Next, as Figure 3 As shown in (D), by increasing the voltage of the TG electrode 32, the charge remaining in the potential well 14 is transferred to the FD section 31. Afterwards, the voltage of the TG electrode 32 returns to its original value, thus becoming... Figure 3 The state shown in (E) is as follows. In this state, an output signal corresponding to the amount of charge accumulated in the FD section 31 is output to a measuring unit (not shown) via amplifier 33 and output circuit 34. Thus, in the measuring unit, the ion concentration of the object under test is detected based on the change in the output signal from the reference potential. Next, as... Figure 3As shown in (F), by increasing the voltage of the RG electrode 42, the charge accumulated in the FD section 31 is discharged to the RD section 41. The RD section 41 is connected to the VDD power supply. Thus, negatively charged charges are drawn into the RD section 41.

[0064] Alternatively, the above can be repeated multiple times. Figure 3 The operation of (B) to (E) increases the amount of charge stored in the FD section 31, and amplifies the output signal by repeating the operation. Alternatively, the output signal can be amplified through this repetitive operation, thus eliminating the need for amplifier 33. This can be achieved by performing repetitive... Figure 3 The (B) to (E) actions (cumulative actions) are used to improve resolution.

[0065] (ICG driving method)

[0066] Next, refer to Figure 4 This section explains the ICG driver method. The ICG driver method will... Figure 3 The actions of (A) to (C) are replaced by Figure 4 The actions of (A) to (C). First, as... Figure 4 As shown in (A), the potential of the ID section 21 is set to a certain value that is lower than the potential of the potential well 14 and higher than the potential of the TG region. On the other hand, the potential of the ICG region is lower than the potential of the ID section 21. Next, as Figure 4 As shown in (B), charge is supplied from the ID section 21 to the potential well 14 by making the potential of the ICG region higher than the potential of the potential well 14. Next, as... Figure 4 As shown in (C), by lowering the potential of the ICG region below the potential of the ID section 21 again, charge remains in the potential well 14 up to the preset potential height of the ID section 21. Through the above description, a charge at the same potential as the ID section 21 is accumulated in the potential well 14. The subsequent operation of the ICG driving mode and... Figure 3 The actions of (D) to (F) are the same.

[0067] Next, refer to Figure 5 and Figure 6 The arrangement (positional relationship) of the ICG electrode 22, TG electrode 32, and SG electrode 51 is explained. The ICG electrode 22, TG electrode 32, and SG electrode 51 need to be insulated from each other. Therefore, as... Figure 5 As shown, the ICG electrode 22 and the SG electrode 51 are arranged apart from each other. Similarly, the TG electrode 32 and the SG electrode 51 are arranged apart from each other.

[0068] Figure 5 (A) to (C) correspond to Figure 4(ICG driving method) (A) to (C). Here, when the spacing between the ICG electrode 22 and the SG electrode 51 is greater than a certain value, there is a concern that a potential barrier 61 may be generated, hindering the injection of charge from the ID section 21 into the potential well 14. That is, even if the voltage of the ICG electrode 22 is controlled such that the potential of the ICG region is higher than the potential of the potential well 14, as... Figure 5 As shown in (B), a potential barrier 61 can be generated in the region between the ICG electrode 22 and the SG electrode 51, which remains at a potential lower than that of the potential well 14. When the potential barrier 61 is generated, the charge injection from the ID section 21 to the potential well 14 is blocked by the potential barrier 61, and the charge transfer efficiency from the ID section 21 to the potential well 14 deteriorates.

[0069] Similarly, if the spacing between the TG electrode 32 and the SG electrode 51 is greater than a certain value, there is a concern that a potential barrier 62 may be generated, hindering the transfer of charge from the potential well 14 to the FD section 31. That is, as... Figure 3 As shown in (D), even if the voltage of the TG electrode 32 is controlled such that the potential of the TG region is higher than that of the potential well 14, a potential barrier 62 can still be generated in the region between the TG electrode 32 and the SG electrode 51, maintaining a potential lower than that of the potential well 14. When the potential barrier 62 is generated, charge injection from the potential well 14 to the FD section 31 is blocked by the potential barrier 62, and the charge transfer efficiency from the potential well 14 to the FD section 31 deteriorates.

[0070] Therefore, in the ion sensor 1, the spacing width d2 (first spacing width) between the ICG electrode 22 and the SG electrode 51 is set in a manner that does not generate a potential barrier 61 (see reference). Figure 6Here, the condition (upper limit value) for the spacing width d2 of the potential barrier 61, which is used to prevent the injection of charge from the ID section 21 into the potential well 14, depends on the magnitude of the voltage applied to the ICG electrode 22, the thickness of the protective film 110, and the impurity concentration of the first conductivity type region 12. More specifically, the greater the voltage applied to the ICG electrode 22, the greater the upper limit value of the spacing width d2. In addition, the greater the thickness of the protective film 110, the greater the upper limit value of the spacing width d2. However, in this case, the voltage applied to the ICG electrode 22 needs to be increased by the same amount as the thickness of the protective film 110. In addition, the greater the impurity concentration (the higher the concentration) of the first conductivity type region 12, the smaller the upper limit value of the spacing width d2. The upper limit value of the spacing width d2 is calculated by conducting experiments and simulations using parameters such as the applied voltage to the ICG electrode 22, the thickness of the protective film 110, and the impurity concentration of the first conductivity type region 12. In the ion sensor 1, based on the applied voltage to the ICG electrode 22, the thickness of the protective film 110, and the impurity concentration in the first conductivity type region 12, an upper limit value for the spacing width d2 to avoid generating a potential barrier 61 is calculated, and the spacing width d2 is set within a range not exceeding the calculated upper limit value. This ensures sufficient charge transfer efficiency from the ID section 21 to the potential well 14.

[0071] Similarly, the spacing width d3 (second spacing width) between the TG electrode 32 and the SG electrode 51 is set in a manner that does not generate a potential barrier 62 (see reference). Figure 6 Here, the condition (upper limit value) for the spacing width d3 of the potential barrier 62, which is used to prevent the transfer of charge from the potential well 14 to the FD section 31 from being obstructed, depends on the magnitude of the voltage applied to the TG electrode 32, the thickness of the protective film 110, and the impurity concentration of the first conductivity type region 12. More specifically, the greater the voltage applied to the TG electrode 32, the greater the upper limit value of the spacing width d3. In addition, the greater the thickness of the protective film 110, the greater the upper limit value of the spacing width d3. However, in this case, the voltage applied to the TG electrode 32 needs to be increased by the same amount as the thickness of the protective film 110. In addition, the greater the impurity concentration (the higher the concentration) of the first conductivity type region 12, the smaller the upper limit value of the spacing width d3. The upper limit value of the spacing width d3 is calculated by conducting experiments and simulations using parameters such as the applied voltage to the TG electrode 32, the thickness of the protective film 110, and the impurity concentration of the first conductivity type region 12. In the ion sensor 1, based on the applied voltage to the TG electrode 32, the thickness of the protective film 110, and the impurity concentration in the first conductivity type region 12, an upper limit value for the spacing width d3 to prevent the formation of a potential barrier 62 is calculated, and the spacing width d3 is set within a range not exceeding the calculated upper limit value. This ensures sufficient charge transfer efficiency from the potential well 14 to the FD section 31.

[0072] As an example, the width w of the SG electrode 51 in the opposite direction D2 (refer to...) Figure 6 ) is the spacing d1 between ICG electrode 22 and TG electrode 32 (refer to Figure 6 The spacing width d2 between the ICG electrode 22 and the SG electrode 51, and the spacing width d3 between the TG electrode 32 and the SG electrode 51, are each set to be about 10% or less of the spacing width d1 between the ICG electrode 22 and the TG electrode 32. In this way, by setting the arrangement and size of the ICG electrode 22, the TG electrode 32, and the SG electrode 51, the generation of the aforementioned barriers 61 and 62 can be better suppressed under general conditions related to the applied voltage to the ICG electrode 22 and the TG electrode 32, the thickness of the protective film 110, and the impurity concentration of the first conductivity type region 12.

[0073] Next, refer to Figure 7 An example of the manufacturing method of the ion sensor 1 will be described. Here, the manufacturing process of the parts associated with the ICG electrode 22, TG electrode 32 and SG electrode 51 of each pixel (each detection unit 5) will be described.

[0074] First, such as Figure 7 As shown in (A), a substrate 100 is prepared, and a protective film 110 (first insulating film) serving as a gate oxide film is formed on the main surface 100a of the substrate 100. The protective film 110 is formed between the ID portion 21 and the FD portion 31 in a predetermined area where at least the ICG electrode 22, the TG electrode 32, and the SG electrode 51 are disposed.

[0075] Next, as Figure 7 As shown in (B), an ICG electrode 22, a TG electrode 32, and an SG electrode 51 are formed on the protective film 110. The ICG electrode 22, TG electrode 32, and SG electrode 51 are formed using, for example, polysilicon. The TG electrode 32 is disposed separately from the ICG electrode 22. Furthermore, the SG electrode 51 is disposed between the ICG electrode 22 and the TG electrode 32, separated from both the ICG electrode 22 and the TG electrode 32.

[0076] Next, as Figure 7 As shown in (C), a passivation layer 120 (second insulating film) covering the ICG electrode 22, TG electrode 32, and SG electrode 51 is formed on the main surface 100a of the substrate 100. Next, as... Figure 7 As shown in (D), an opening (contact hole) is formed in the passivation layer 120 with a portion of the SG electrode 51 exposed, and a metal wiring 53 (embedded) electrically connected to the SG electrode 51 is formed in the opening.

[0077] Next, as Figure 7As shown in (E), electrode pads 52, electrically connected to the metal wiring 53, are formed in a flat plate shape on the surface 120a of the passivation layer 120. Next, as... Figure 7 As shown in (F), an ion-sensing film 13 is formed on the surface 52a of the electrode pad 52. Here, the ion-sensing film 13 is formed such that the width of the ion-sensing film 13 in the opposite direction D2 is greater than the spacing width between the ICG electrode 22 and the TG electrode 32. Through the above, the pixel structure (detection unit 5) described above is obtained. Furthermore, in Figure 7 In (F), only a portion of the detection unit 5 is shown. Therefore, the width of the ion sensing film 13 is the same as the width of the electrode pad 52, but the ion sensing film 13 can also be formed further outward than the electrode pad 52. More specifically, in the above manufacturing method, when the electrode pad 52 is formed on the passivation layer 120, the surface 52a and side surfaces of the electrode pad 52 are exposed to the outside. Therefore, the ion sensing film 13 can also be formed in a way that covers the surface 52a and side surfaces of the electrode pad 52, as well as the portion of the passivation layer 120 further outward than the electrode pad 52. With the ion sensing film 13 formed in this way, the surface 52a and side surfaces of the electrode pad 52 can be prevented from being exposed to the outside, and the penetration of the aqueous solution 3 into the surface 52a of the electrode pad 52 can be better suppressed.

[0078] In the ion sensor 1 described above, an SG electrode 51 is disposed on the main surface 100a of the substrate 100 between the ICG electrode 22 and the TG electrode 32. Furthermore, the SG electrode 51 is electrically connected to the electrode pad 52 on which the ion sensing membrane 13 is disposed. This enables the sensor to function as an ion sensor 1. Specifically, changes in the potential of the ion sensing membrane 13 can be transmitted to the substrate 100 (specifically, the area overlapping the SG electrode 51 when viewed from the thickness direction D1 along the main surface 100a of the substrate 100) via the electrode pad 52 and the SG electrode 51. This allows the depth of the potential well 14 to change in response to changes in the potential of the ion sensing membrane 13. As a result, the ion concentration of the object being examined in contact with the medium (in this embodiment, an aqueous solution 3) in contact with the ion sensing membrane 13 can be detected based on the amount of charge extracted to the outside (FD section 31) by controlling the ICG electrode 22 and the TG electrode 32 (voltage control).

[0079] Here, assuming a structure is adopted where an opening (a recess without a passivation layer) is formed between the ICG electrode 22 and the TG electrode 32, and an ion-sensing membrane is formed at the bottom of this opening (open-type structure), the width of the ion-sensing membrane is limited by the opening size, preventing the width of the ion-sensing membrane from exceeding the spacing between the ICG electrode 22 and the TG electrode 32. On the other hand, in the ion sensor 1, by employing a structure that transmits the potential change of the ion-sensing membrane 13 to the substrate 100 via the aforementioned SG electrode 51 and electrode pads 52, a structure is achieved where the width of the ion-sensing membrane 13 is greater than the spacing between the ICG electrode 22 and the TG electrode 32. This ensures sufficient contact area between the ion-sensing membrane 13 and the aqueous solution 3, and effectively improves the sensitivity of the ion sensor 1.

[0080] Furthermore, in the ion sensor 1, a structure is achieved whereby the SG electrode 51 is disposed directly above the substrate 100 via only an extremely thin (10 nm in this embodiment) protective film 110, allowing an electric field to be easily transmitted from the bottom surface of the SG electrode 51 (the surface on the side of the protective film 110) to the substrate 100 (a structure that facilitates channel formation). Therefore, the depletion implantation (i.e., the formation of the first conductivity type region 12) required for easily forming a channel on the substrate 100, as needed in the aforementioned open-type structure, can be omitted. That is, the first conductivity type region 12 can also be omitted in the ion sensor 1. Along with this, the negative voltage required for depletion implantation (i.e., the negative voltage used to turn off the channel in the region directly below the ICG electrode 22, TG electrode 32, and RG electrode 42 of the substrate 100) can also be omitted.

[0081] Furthermore, the surface 52a of the electrode pad 52 is a flat surface, and the ion sensing membrane 13 is formed flatly along the surface 52a. According to the above structure, compared to the case using the above-described open-type structure, the medium (aqueous solution 3) disposed on the ion sensing membrane 13 can be in full contact with the ion sensing membrane 13. Therefore, the sensitivity of the ion sensor 1 can be further and effectively improved.

[0082] [Second Implementation]

[0083] Figure 8 This is a schematic diagram showing the cross-sectional structure of the detection unit 5A of the ion sensor 1A according to the second embodiment. The ion sensor 1 replaces the detection unit 5A (see reference 5A). Figure 2 The detection unit 5A differs from the ion sensor 1 in that it has a pixel structure, but the other structures of the ion sensor 1A are the same as those of the ion sensor 1A. The detection unit 5A differs from the detection unit 5 in that it mainly replaces the ICG electrode 22 and the TG electrode 32, and has ICG electrode 22A and TG electrode 32A.

[0084] like Figure 8As shown, when viewed in the thickness direction D1, a part of the ICG electrode 22A overlaps with the SG electrode 51. In the present embodiment, in order to insulate the ICG electrode 22A from the SG electrode 51, a protective film 130 is formed to cover the upper surface (the surface opposite to the protective film 110 side) and the side surface of the SG electrode 51. That is, a part of the ICG electrode 22A contacts the SG electrode 51 via the protective film 130. The protective film 130 can be formed of, for example, the same material as the protective film 110 (e.g., SiO2). The thickness of the protective film 130 is, for example, about 50 nm.

[0085] The width w11 in the relative direction D2 of the part (the first part) of the ICG electrode 22A that overlaps with the SG electrode 51 is smaller than the width w12 in the relative direction D2 of the part (the second part) of the ICG electrode 22A that does not overlap with the SG electrode 51. This is based on the following reason. That is, if the width w12 of the second part is not sufficient, the ICG region cannot function as a gate region that controls the charge flow between the ID part 21 and the potential well 14, and charge leakage from the potential well 14 to the ID part 21 may occur. Therefore, the ICG electrode 22A overlaps with the SG electrode 51 in such a way that "w11 < w12". More preferably, the ICG electrode 22A overlaps with the SG electrode 51 in such a way that the width w11 of the first part is 25% or less of the width w12 of the second part (that is, in such a way that "w11 ≦ 0.25 × w12" holds). According to the above structure, accidental charge leakage from the potential well 14 to the ID part 21 can be preferably suppressed.

[0086] In addition, when viewed in the thickness direction D1, a part of the TG electrode 32A overlaps with the SG electrode 51. In the present embodiment, a part of the TG electrode 32A contacts the SG electrode 51 via the above-mentioned protective film 130. The width w21 in the relative direction D2 of the part (the third part) of the TG electrode 32A that overlaps with the SG electrode 51 is smaller than the width w22 in the relative direction D2 of the part (the fourth part) of the TG electrode 32A that does not overlap with the SG electrode 51. This is based on the following reason. That is, if the width w22 of the fourth part is not sufficient, the TG region cannot function as a gate region that controls the charge flow between the potential well 14 and the FD part 31, and charge leakage from the potential well 14 to the FD part 31 may occur. Therefore, the TG electrode 32A overlaps with the SG electrode 51 in such a way that "w21 < w22". More preferably, the TG electrode 32A overlaps with the SG electrode 51 in such a way that the width w21 of the third part is 25% or less of the width w22 of the fourth part (that is, in such a way that "w21 ≦ 0.25 × w22" holds). According to the above structure, accidental charge leakage from the potential well 14 to the FD part 31 can be preferably suppressed.

[0087] Refer to Figure 9The effect of the pixel structure (detection unit 5A) of the ion sensor 1A will be further explained. Figure 9 (A) to (F) show the various steps of the operation of the detection unit 5A in the ICG driving mode. As described above, in the detection unit 5A, a portion where the ICG electrode 22A and the SG electrode 51 overlap is formed. Therefore, in the portion where the ICG electrode 22A and the SG electrode 51 overlap in the substrate 100, a potential region 63 is formed with a potential between the potential of the ICG region and the potential of the potential well 14. By forming such a region 63, the following effect is achieved. Assuming that in the case where region 63 is not formed (i.e., when the potential of the ICG region is flat), when the potential of the ICG region is lower than the potential of the ID portion 21 (i.e., from... Figure 9 The state of (B) towards Figure 9 During the state transition (C), it is uncertain whether the charge in the ICG region will move to the ID section 21 or to the potential well 14. Therefore, a deviation (noise) may occur regarding the amount of charge in the ICG region that moves to the potential well 14 (i.e., the amount of charge accumulated in the potential well 14). On the other hand, when region 63 is formed, if the potential of the ICG region is lower than the potential of the ID section 21, a potential difference can be generated from the ID section 21 to the potential well 14 in a stepped (approximately inclined) manner, thereby allowing the charge in the ICG region to move smoothly to the potential well 14. As a result, the deviation in the amount of charge accumulated in the potential well 14 can be reduced.

[0088] Furthermore, a portion (first portion) of the ICG electrode 22A is disposed on the opposite side of the substrate 100, separated from the SG electrode 51. That is, the edge of the SG electrode 51 is disposed between the ICG electrode 22A and the substrate 100. According to the above structure, compared with the case where a portion of the ICG electrode 22A is disposed between the substrate 100 and the SG electrode 51 (the ion sensor 1B of the third embodiment described below), the voltage value required to form a potential well 14 in the region of the substrate 100 overlapping with the SG electrode 51 can be reduced. Specifically, in the ion sensor 1B described below (refer to...) Figure 11 In the ion sensor 1A, a protective film 110 and a protective film 130 are formed between the SG electrode 151 and the substrate 100. In contrast, in the ion sensor 1A, only the protective film 110 is formed between the SG electrode 51 and the substrate 100. That is, in the ion sensor 1A, the distance between the SG electrode 51 and the substrate 100 is smaller than the thickness of the protective film 130 compared to the ion sensor 1B. This achieves the aforementioned effect (reducing the necessary voltage value).

[0089] Furthermore, in the detection unit 5A, a portion is formed where the TG electrode 32A and the SG electrode 51 overlap. Thus, in the portion of the substrate 100 where the TG electrode 32A and the SG electrode 51 overlap, a potential region 64 is formed with a potential difference between the potential of the TG region and the potential of the potential well 14. By forming such a region 64, charge transfer from the potential well 14 to the FD unit 31 can be facilitated (see reference). Figure 9 (D) improves charge transfer efficiency. That is, because a potential difference can be generated in a stepwise (generally inclined) manner from the potential well 14 to the FD section 31 through region 64, charge can be smoothly transferred from the potential well 14 to the FD section 31.

[0090] Furthermore, a portion (the third portion) of the TG electrode 32A is disposed on the opposite side of the substrate 100, separated from the SG electrode 51. That is, the edge of the SG electrode 51 is disposed between the TG electrode 32A and the substrate 100. According to the above structure, for the same reasons as above, compared with the case where a portion of the TG electrode 32A is disposed between the substrate 100 and the SG electrode 51 (the ion sensor 1B of the third embodiment described below), the voltage required to form a potential well 14 in the region of the substrate 100 overlapping with the SG electrode 51 can be reduced.

[0091] Next, refer to Figure 10 An example of the manufacturing method of the ion sensor 1A will be described. Here, the manufacturing process of the parts associated with the ICG electrode 22A, TG electrode 32A and SG electrode 51 of each pixel (each detection unit 5A) will be described.

[0092] First, such as Figure 10 As shown in (A), a substrate 100 is prepared, and a protective film 110 (first insulating film) serving as a gate oxide film is formed on the main surface 100a of the substrate 100. The protective film 110 is formed between the ID portion 21 and the FD portion 31 in a predetermined area where at least the ICG electrode 22A, the TG electrode 32A, and the SG electrode 51 are disposed. Next, the SG electrode 51 is formed on the protective film 110.

[0093] Next, as Figure 10 As shown in (B), a protective film 130 (second insulating film) is formed covering the surface of the SG electrode 51 (at least the surface in contact with the ICG electrode 22A and the TG electrode 32A). Next, as... Figure 10 As shown in (C), when viewed from the thickness direction D1, the ICG electrode 22A is formed by overlapping a portion of the ICG electrode 22A with the SG electrode 51 via the protective film 130. Similarly, when viewed from the thickness direction D1, the TG electrode 32A is formed by overlapping a portion of the TG electrode 32A with the SG electrode 51 via the protective film 130.

[0094] Next, the same steps as those used in the manufacturing method of the ion sensor 1 described above are performed (and... Figure 7 (The processes corresponding to (C) to (F)). That is, a passivation layer 120 (third insulating film) covering the ICG electrode 22A, TG electrode 32A, and SG electrode 51 is formed on the main surface 100a of the substrate 100. Next, an opening (contact hole) is formed in the passivation layer 120 with a portion of the SG electrode 51 exposed, and a metal wiring 53 electrically connected to the SG electrode 51 is formed in the opening. In addition, in this embodiment, the protective film 130 is formed to cover the entire upper surface of the SG electrode 51, so in the process of forming the opening in the passivation layer 120, an opening is also formed in the protective film 130 (see reference). Figure 8 Next, electrode pads 52, electrically connected to the metal wiring 53, are formed in a flat plate shape on the surface 120a of the passivation layer 120. Then, an ion-sensing film 13 is formed on the surface 52a of the electrode pads 52. Here, the ion-sensing film 13 is formed such that the width of the ion-sensing film 13 in the opposite direction D2 is greater than the spacing between the ICG electrode 22A and the TG electrode 32A. Through the above, the pixel structure (detection unit 5A) described above is obtained.

[0095] According to the ion sensor 1A described above, the generation of potential barriers 61 and 62 that may occur when the ICG electrode and the TG electrode and SG electrode are separated can be reliably prevented, and as described above, the efficiency of charge transfer from the ID section 21 to the potential well 14 and from the potential well 14 to the FD section 31 can be improved.

[0096] [Third Implementation]

[0097] Figure 11 This is a schematic diagram showing the cross-sectional structure of the detection unit 5B of the ion sensor 1B according to the third embodiment. The ion sensor 1B replaces the detection unit 5B (see reference 5B). Figure 2 The detection unit 5B differs from the ion sensor 1 in that it has a pixel structure, but the other structures of the ion sensor 1B are the same as those of the ion sensor 1. The detection unit 5B differs from the detection unit 5 in that it mainly replaces the SG electrode 51 and has an SG electrode 151.

[0098] When viewed from the thickness direction D1, the detection unit 5B has the same characteristics as the detection unit 5A in that a portion of the ICG electrode 22 overlaps with the SG electrode 151 and a portion of the TG electrode 32 overlaps with the SG electrode 151. However, in the detection unit 5A, a portion of the ICG electrode 22A and a portion of the TG electrode 32A are located higher than the SG electrode 51 (opposite to the substrate 100 side relative to the SG electrode 51), while in the detection unit 5B, a portion of the ICG electrode 22 and a portion of the TG electrode 32 are located lower than the SG electrode 151 (on the substrate 100 side relative to the SG electrode 51).

[0099] The detection unit 5B can be manufactured, for example, as follows: First, the ICG electrode 22 and the TG electrode 32 are formed on the protective film 110. Next, a protective film 130 is formed that at least covers the surface of the ICG electrode 22 (the upper surface and the inner side (the side of the TG electrode 32)) and the surface of the TG electrode 32 (the upper surface and the inner side (the side of the ICG electrode 22)). Then, when viewed from the thickness direction D1, the SG electrode 151 is formed on the protective film 130 such that a portion of the SG electrode 151 overlaps with a portion of the ICG electrode 22 via the protective film 130, and another portion of the SG electrode 151 overlaps with a portion of the TG electrode 32 via the protective film 130.

[0100] The ion sensor 1B described above, like the ion sensor 1A described above, can reliably prevent the generation of potential barriers 61 and 62.

[0101] [Variation Example]

[0102] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. For example, in ion sensors 1, 1A, and 1B, the plurality of detection units 5, 5A, and 5B may be arranged in a one-dimensional manner. In addition, the substrate 100 is not necessarily a semiconductor substrate, and may be a substrate other than a semiconductor, for example, on which a semiconductor region (e.g., a semiconductor film) is formed on the surface. Furthermore, the protective film 110 formed between each electrode member and the substrate 100 may be formed continuously. That is, the protective film 110 may be formed integrally on the main surface 100a of the substrate 100.

[0103] Furthermore, the medium disposed on the ion-sensing membrane 13 can also be a substance other than the aqueous solution 3 (e.g., a substance adsorption membrane that has the property of changing electrical properties when adsorbing odor substances). Here, the odor substance is a chemical substance that causes the odor (e.g., a substance composed of specific monomers or groups of molecules aggregated at a specific concentration). Examples of substance adsorption membranes include, for example, polyaniline sensing membranes that are sensitive to ammonia. In this case, the ion sensor 1 functions as an odor sensor for detecting odors. Furthermore, even when a solid substance adsorption membrane, not limited to adsorbing odor substances, is used as the medium, it can still function as... Figure 2 As shown, it is preferable to form the ion-sensing membrane 13 further outward than the electrode pad 52. In this case, during the process of forming the material adsorption membrane on the ion-sensing membrane 13, the penetration of solvents and other substances used in the film formation into the surface 52a of the electrode pad 52 can be better suppressed.

[0104] In addition, in the second and third embodiments described above, the SG electrode may also be configured to overlap only with one of the ICG electrode and the TG electrode, and be separated from the other of the ICG electrode and the TG electrode.

[0105] In addition, such as Figure 12 As shown, each detection unit 5, 5A, 5B (pixel) can include multiple (four in this example) ion sensing films 13A, 13B, 13C, 13D that react with different ions. Furthermore, multiple electrode pads 52 can be provided corresponding to each of the multiple ion sensing films 13A, 13B, 13C, 13D. That is, the electrode pads 52 with ion sensing film 13A, 13B, 13C, and 13D can be provided independently (separately). Therefore, multiple SG electrodes 51A, 51B, 51C, 51D can be provided independently (separately) in a manner corresponding to each of the multiple electrode pads 52 as described above. According to the above structure, more information can be obtained from a single pixel. That is, the concentrations of multiple ions can be detected through a single pixel. Specifically, the total concentration of multiple ions can be detected using a single pixel. For example, consider the case where ion-sensing membranes 13A to 13D are formed using materials that have the property of changing potential according to the ion concentrations of the first to fourth ions. Based on the above structure, for example in water quality testing, where a test is deemed pass (OK) if the first to fourth ions are not present (i.e., a test is deemed fail (NG) if at least one of the first to fourth ions is present), the determination can be made using only the information obtained from a single pixel.

[0106] Furthermore, in the above embodiments, such as Figure 1As shown, when viewed from the thickness direction D1, the ICG electrode 22 and the TG electrode 32 are formed in a rectangular shape of approximately the same size, and the SG electrode 51 disposed between them is also formed in a rectangular shape, but the shape and size of each electrode are not limited thereto. For example, in order to improve the charge transfer efficiency from the ID section 21 to the FD section 31, as... Figure 13 As shown, when viewed from the thickness direction D1, the ICG electrode 22 can also be formed in a rectangular shape smaller than the TG electrode 32, and the SG electrode 51 can be formed in a trapezoidal shape that becomes wider as it moves from the ICG electrode 22 side toward the TG electrode 32 side.

[0107] Explanation of symbols

[0108] 1, 1A, 1B… Ion sensor, 3… Aqueous solution (medium), 5, 5A, 5B… Detection unit (pixel), 13… Ion sensing film, 14… Potential trap, 21… ID unit (charge storage unit), 22, 22A… ICG electrode (first electrode), 31… FD unit (external), 32, 32A… TG electrode (second electrode), 51, 51A, 51B, 51C, 51D, 151… SG electrode (third electrode), 52… Electrode pad (fourth electrode), 53… Metal wiring, 61, 62… Barrier, 100… Substrate, 100a… Main surface (first surface), 110… Protective film (first insulating film), 120… Passivation layer (second insulating film, third insulating film), 130… Protective film (second insulating film).

Claims

1. An ion sensor, wherein, have: Substrate; and Multiple pixels are disposed on the first surface of the substrate. Each pixel includes a charge storage section, a first electrode, a second electrode, a third electrode, a fourth electrode, and an ion-sensing film. The charge accumulation portion is formed in a region along the first surface of the substrate, and accumulates charge for injection into the potential well formed in the portion overlapping with the third electrode when viewed from the thickness direction of the substrate. The first electrode is disposed on the first surface in a manner that controls the amount of charge injected from the charge accumulation section into the potential well. The second electrode is disposed on the first surface in a manner configured to control the transfer of charge from the potential well to the outside. The third electrode is located on the first surface and is disposed between the first electrode and the second electrode. The fourth electrode is electrically connected to the third electrode and is disposed on the opposite side of the substrate, separated by the third electrode. The ion-sensing membrane is disposed on the surface of the fourth electrode opposite to the substrate side, and its potential changes in response to changes in the ion concentration of the medium in contact with the ion-sensing membrane. The width of the ion-sensing membrane in the opposite direction between the first electrode and the second electrode is greater than the spacing between the first electrode and the second electrode. When viewed from the thickness direction, a portion of the first electrode overlaps with the third electrode.

2. The ion sensor as described in claim 1, wherein, The portion of the first electrode is disposed on the opposite side of the substrate, separated from the third electrode.

3. The ion sensor as described in claim 1, wherein, The width of the first portion of the first electrode that overlaps with the third electrode in the opposite direction is smaller than the width of the second portion of the first electrode that does not overlap with the third electrode in the opposite direction.

4. The ion sensor as described in claim 2, wherein, The width of the first portion of the first electrode that overlaps with the third electrode in the opposite direction is smaller than the width of the second portion of the first electrode that does not overlap with the third electrode in the opposite direction.

5. The ion sensor as described in claim 3, wherein, The width of the first part is less than 25% of the width of the second part.

6. The ion sensor as claimed in claim 4, wherein, The width of the first part is less than 25% of the width of the second part.

7. The ion sensor according to any one of claims 1 to 6, wherein, The second electrode and the third electrode are spaced apart from each other. The second gap width between the second electrode and the third electrode is set to a range that does not create a potential barrier that hinders the transfer of charge from the potential well to the outside.

8. The ion sensor according to any one of claims 1 to 6, wherein, The surface of the fourth electrode opposite to the substrate side is a flat surface. The ion-sensing membrane is formed flat along the opposite side of the surface.

9. The ion sensor as claimed in claim 7, wherein, The surface of the fourth electrode opposite to the substrate side is a flat surface. The ion-sensing membrane is formed flat along the opposite side of the surface.

10. The ion sensor according to any one of claims 1 to 6, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

11. The ion sensor as claimed in claim 7, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

12. The ion sensor as claimed in claim 8, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

13. The ion sensor as claimed in claim 9, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

14. An ion sensor, wherein, have: Substrate; and Multiple pixels are disposed on the first surface of the substrate. Each pixel includes a charge storage section, a first electrode, a second electrode, a third electrode, a fourth electrode, and an ion-sensing film. The charge accumulation portion is formed in a region along the first surface of the substrate, and accumulates charge for injection into the potential well formed in the portion overlapping with the third electrode when viewed from the thickness direction of the substrate. The first electrode is disposed on the first surface in a manner that controls the amount of charge injected from the charge accumulation section into the potential well. The second electrode is disposed on the first surface in a manner configured to control the transfer of charge from the potential well to the outside. The third electrode is located on the first surface and is disposed between the first electrode and the second electrode. The fourth electrode is electrically connected to the third electrode and is disposed on the opposite side of the substrate, separated by the third electrode. The ion-sensing membrane is disposed on the surface of the fourth electrode opposite to the substrate side, and its potential changes in response to changes in the ion concentration of the medium in contact with the ion-sensing membrane. The width of the ion-sensing membrane in the opposite direction between the first electrode and the second electrode is greater than the spacing between the first electrode and the second electrode. When viewed from the thickness direction, a portion of the second electrode overlaps with the third electrode.

15. The ion sensor of claim 14, wherein, The portion of the second electrode is disposed on the opposite side of the substrate, separated from the third electrode.

16. The ion sensor of claim 14, wherein, The width of the third portion of the second electrode that overlaps with the third electrode in the opposite direction is smaller than the width of the fourth portion of the second electrode that does not overlap with the third electrode in the opposite direction.

17. The ion sensor of claim 15, wherein, The width of the third portion of the second electrode that overlaps with the third electrode in the opposite direction is smaller than the width of the fourth portion of the second electrode that does not overlap with the third electrode in the opposite direction.

18. The ion sensor of claim 16, wherein, The width of the third part is less than 25% of the width of the fourth part.

19. The ion sensor of claim 17, wherein, The width of the third part is less than 25% of the width of the fourth part.

20. The ion sensor according to any one of claims 14 to 19, wherein, The first electrode and the third electrode are spaced apart from each other. The first gap width between the first electrode and the third electrode is set to a range that does not create a potential barrier that prevents charge from being injected from the charge accumulation section into the potential well.

21. The ion sensor according to any one of claims 14 to 19, wherein, The surface of the fourth electrode opposite to the substrate side is a flat surface. The ion-sensing membrane is formed flat along the opposite side of the surface.

22. The ion sensor of claim 20, wherein, The surface of the fourth electrode opposite to the substrate side is a flat surface. The ion-sensing membrane is formed flat along the opposite side of the surface.

23. The ion sensor according to any one of claims 14 to 19, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

24. The ion sensor of claim 20, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

25. The ion sensor of claim 21, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

26. The ion sensor of claim 22, wherein, Each pixel comprises a plurality of ion-sensing films that react with different ions. A plurality of fourth electrodes are provided corresponding to each of the plurality of ion-sensing membranes. A plurality of third electrodes are provided corresponding to each of the plurality of fourth electrodes.

27. A method for manufacturing an ion sensor, wherein, It is a method for manufacturing an ion sensor having a substrate and a first electrode, a second electrode, and a third electrode formed on the substrate. Include: The process of forming a first insulating film on the substrate; The process of forming the first electrode, the second electrode arranged apart from the first electrode, and the third electrode disposed between the first electrode and the second electrode on the first insulating film, such that a portion of the first electrode and the second electrode overlaps with the third electrode via the second insulating film; The process of forming a third insulating film covering the first electrode, the second electrode, and the third electrode on the substrate; The process of forming an opening in the third insulating film with a portion of the third electrode exposed, and forming a metal wiring electrically connected to the third electrode within the opening; The process of forming a fourth electrode, electrically connected to the metal wiring, along the surface of the third insulating film opposite to the substrate side; and The process of forming an ion-sensing film on the surface of the fourth electrode opposite to the substrate side, which causes a potential change corresponding to a change in the ion concentration of the contacting medium. In the process of forming the ion sensing membrane, the ion sensing membrane is formed such that the width of the ion sensing membrane in the opposite direction of the first electrode and the second electrode is greater than the spacing width between the first electrode and the second electrode.

28. A method for manufacturing an ion sensor, wherein, It is a method for manufacturing an ion sensor having a substrate and a first electrode, a second electrode, and a third electrode formed on the substrate. Include: The process of forming a first insulating film on the substrate; The process of forming the third electrode on the first insulating film; The process of forming a second insulating film covering the surface of the third electrode; The process of forming a first electrode by overlapping a portion of the first electrode with the third electrode via the second insulating film when viewed from the thickness direction of the substrate, and forming a second electrode by overlapping a portion of the second electrode with the third electrode via the second insulating film when viewed from the thickness direction of the substrate; A process of forming a third insulating film on the substrate, covering the first electrode, the second electrode, and the third electrode; The process of forming an opening in the third insulating film with a portion of the third electrode exposed, and forming a metal wiring electrically connected to the third electrode within the opening; The process of forming a fourth electrode, electrically connected to the metal wiring, along the surface of the third insulating film opposite to the substrate side; and The process of forming an ion-sensing film on the surface of the fourth electrode opposite to the substrate side, which causes a potential change corresponding to a change in the ion concentration of the contacting medium. In the process of forming the ion sensing membrane, the ion sensing membrane is formed such that the width of the ion sensing membrane in the opposite direction of the first electrode and the second electrode is greater than the spacing width between the first electrode and the second electrode.

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