JP2012207991A - Image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pseudo reference electrode integrated optical pH image sensor with higher sensor sensitivity.SOLUTION: An image sensor 4 includes: a semiconductor substrate 10 having a first conductivity type; a well region 12 disposed on the semiconductor substrate 10 and having a second conductivity type, which is opposite to the first conductivity type; a source region 14 and a drain region 16 disposed on the well region 12 and having the first conductivity type; a gate insulation film 18 disposed on the source region 14, the well region 12, and the drain region 16; a transfer gate electrode 20 disposed adjacent to the drain region 16 on the gate insulation film 18; an ion-sensitive film 19 disposed on the gate insulation film 18; a liquid sample 26 in contact with the ion-sensitive film 19; a passivation film 22 disposed on the source region 14, the drain region 16, and the transfer gate electrode 20; and a pseudo reference electrode 50 disposed on the passivation film 22 in contact with the liquid sample 26.

Description

  The present invention relates to an image sensor, and more particularly to a pseudo-reference electrode integrated optical pH image sensor.

  As an ion sensor composed of a conventional ion sensitive field effect transistor (ISFET), it is used to extract back gate photocurrent generated between the back gate and the source and between the back gate and the drain. A configuration is disclosed that includes a gate electrode and corrects the photocurrent generated at the source and drain of the ISFET using this backgate photocurrent (see, for example, Patent Document 1).

  Further, there is a hydrogen ion concentration distribution measuring device (see, for example, Patent Document 2) that measures a two-dimensional distribution of pH by arranging a plurality of ISFETs two-dimensionally.

  On the other hand, there is also disclosed an ISFET array in which the ISFET array according to Patent Document 2 is improved and an ISFET changeover switch MOSFET is provided for each ISFET array cell (see, for example, Patent Document 3).

  In biochemical measurement of DNA or the like, a configuration is also disclosed in which a light signal and a pH ion signal are acquired as a plurality of information at the same place by a CCD device capable of detecting (see, for example, Patent Documents 4 to 6). .

JP 2008-164359 A JP 05-33745 A Japanese Patent No. 4137239 Japanese Patent No. 4133028 Japanese Patent No. 4308374 Japanese Patent No. 4183789

  In the ISFET according to Patent Document 1, since optical readout is performed with a current flowing in a bulk, noise information is included in the optical readout current. Further, when arraying is performed, since optical reading is performed with a current flowing in the bulk, it is necessary to separate the p-well regions from each other between adjacent cells, the structure becomes complicated, and arraying is difficult.

  In the ISFET array according to Patent Document 2, it takes time to stabilize from one measurement to the next measurement.

  In the conventional optical multimodal image sensor, it is necessary to put the reference electrode in a solution separately from the semiconductor chip, and depending on the measurement object, the reference electrode may become a shielding object, which may make measurement difficult. That is, in the prior art, when acquiring fluorescence by irradiating an optical image or excitation light, the reference electrode creates a shadow, and the reference electrode becomes a shielding object by the measurement system, making it difficult to acquire light information. It was.

  In the prior art, the size of the measurement object is limited because of the reference electrode.

  An object of the present invention is to form a pseudo reference electrode on a circuit of a driving part or a processing part, thereby eliminating the need to newly install a light shielding electrode and a reference electrode, and improving the sensor sensitivity. The object is to provide a pH image sensor.

  According to one aspect of the present invention, a semiconductor substrate having a first conductivity type, a well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type, and the well region A source region and a drain region having a first conductivity type, the source region, the well region, a gate insulating film disposed on the drain region, and the drain region on the gate insulating film A transfer gate electrode disposed adjacent to the gate insulating film, an ion sensitive film disposed on the gate insulating film, a liquid sample in contact with the ion sensitive film, the source region, the drain region, and the transfer gate electrode An image sensor comprising: a passivation film disposed on the passivation film; and a pseudo reference electrode disposed on the passivation film in contact with the liquid sample. It is subjected.

  According to another aspect of the present invention, a plurality of word lines extending in a row direction, a plurality of bit lines orthogonal to the word line and extending in a column direction, and a drain for each of the plurality of word lines are provided. A plurality of connected vertical selection transistors; a vertical scanning circuit having gates connected to the plurality of vertical selection transistors; a horizontal selection transistor having sources connected to the plurality of bit lines; A horizontal scanning circuit to which the gates of the horizontal transistors are connected, and an ISFET cell disposed at an intersection of the word line and the bit line, the ISFET cell having a first conductivity type, and a semiconductor substrate; A well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type; and a well region disposed on the well region; A source region and a drain region, the source region, the well region, a gate insulating film disposed on the drain region, and a transfer disposed on the gate insulating film adjacent to the drain region. A gate electrode, an ion sensitive film disposed on the gate insulating film, a liquid sample in contact with the ion sensitive film, a passivation film disposed on the source region, the drain region, and the transfer gate electrode, There is provided an image sensor comprising a pseudo reference electrode disposed on the passivation film.

  According to another aspect of the present invention, a semiconductor substrate having a first conductivity type, a well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type, and the well region A source region, a drain region, and a reset region having a first conductivity type, a gate insulating film disposed on the well region, and on the gate insulating film, adjacent to the source region. An implantation control gate electrode; a transfer gate electrode disposed on the gate insulating film adjacent to the drain region; and a reset gate disposed on the gate insulating film between the drain region and the reset region. An electrode, an ion sensitive film disposed between the implantation control gate electrode and the transfer gate electrode on the gate insulating film, and a liquid sample in contact with the ion sensitive film. A passivation film disposed on the source region, the drain region, the implantation control gate electrode, the transfer gate electrode, the reset gate electrode and the reset region, and a pseudo reference electrode disposed on the passivation film, An image sensor is provided.

  According to another aspect of the present invention, a semiconductor substrate having a first conductivity type, a first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type, A source region and a drain region having a first conductivity type, disposed on the first well region, a gate insulating film disposed on the first well region, and an ion sensitive film disposed on the gate insulating film; A storage capacitor connected between the source region and the drain region, a liquid sample in contact with the ion sensitive film, a passivation film disposed on the source region and the drain region, and on the passivation film, An image sensor is provided that includes a pseudo reference electrode disposed in contact with the liquid sample.

  According to another aspect of the present invention, a semiconductor substrate having a first conductivity type, a first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type, A source region and a drain region having a first conductivity type disposed on the first well region, a gate insulating film disposed on the first well region, and the gate insulating film between the source region and the drain region A gate plug electrode disposed on the drain region; a drain plug electrode disposed on the drain region; a storage capacitor connected between the source region and the drain plug electrode; A light-shielding film disposed on the light-shielding film, an ion-sensitive film disposed on the light-shielding film, a liquid sample in contact with the ion-sensitive film, and a liquid sample on the ion-sensitive film. An image sensor and a pseudo reference electrode placed Te is provided.

  According to another aspect of the present invention, a plurality of word lines extending in a row direction, a plurality of bit lines orthogonal to the word line and extending in a column direction, and a drain for each of the plurality of word lines are provided. A plurality of connected vertical selection transistors; a vertical scanning circuit having gates connected to the plurality of vertical selection transistors; a horizontal selection transistor having sources connected to the plurality of bit lines; A horizontal scanning circuit to which the gates of the horizontal transistors are connected, and an ISFET cell disposed at an intersection of the word line and the bit line, the ISFET cell having a first conductivity type, and a semiconductor substrate; A first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type; and disposed on the first well region; A source region and a drain region having one conductivity type, a gate insulating film disposed on the first well region, an ion sensitive film disposed on the gate insulating film, and between the source region and the drain region A storage capacitor to be connected; a liquid sample in contact with the ion sensitive film; a passivation film disposed on the source region and the drain region; and disposed on the passivation film in contact with the liquid sample. An image sensor comprising a pseudo reference electrode is provided.

  According to the present invention, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the pseudo reference electrode integrated light with improved sensor sensitivity is obtained. A pH image sensor can be provided.

The typical bird's-eye view structure figure showing a mode that the sample cell was mounted on the image sensor concerning a 1st embodiment. The typical bird's-eye view structural drawing showing the mode of pH distribution detected using the image sensor corresponding to FIG. FIG. 3 is a schematic bird's-eye view structure diagram showing a state where a peripheral circuit unit is shielded from light in the image sensor according to the first embodiment. In the image sensor which concerns on 1st Embodiment, the typical plane pattern block diagram showing a mode that area | regions other than the peripheral circuit part and the ion detection part in a cell array were light-shielded using the pseudo reference electrode. 1 is a schematic circuit block configuration diagram of an image sensor according to a first embodiment. FIG. It is typical sectional structure of the image sensor cell which concerns on a comparative example, Comprising: The typical explanatory drawing of ion detection operation. (A) A schematic cross-sectional structure of an ISFET cell applicable to the image sensor according to the first embodiment, which is a schematic explanatory view of an ion detection operation, and (b) a schematic view of a sensor area in FIG. FIG. (A) A schematic cross-sectional structure diagram for explaining the principle of an ISFET cell applicable to the image sensor according to the first embodiment, (b) an enlarged schematic cross-sectional view of the ion detector of FIG. 1 (a). Structural drawing. It is typical sectional structure of the ISFET cell applicable to the image sensor which concerns on 1st Embodiment, Comprising: The typical explanatory drawing of ion detection operation | movement. The circuit block diagram explaining the ion detection operation | movement of the ISFET cell applicable to the image sensor which concerns on 1st Embodiment. The typical plane pattern block diagram for the principle explanation of the ISFET cell applicable to the image sensor which concerns on 1st Embodiment. An energy potential diagram at the time of light detection for explaining the principle of an ISFET cell applicable to the image sensor according to the first embodiment. An energy potential diagram at the time of ion detection for explaining the principle of an ISFET cell applicable to the image sensor according to the first embodiment. The typical cross-section figure of the ISFET cell which concerns on a comparative example. (A) The typical cross-section figure of the ISFET cell applicable to the image sensor which concerns on 2nd Embodiment, (b) The typical plane pattern block diagram of the sensor area of Fig.15 (a). (A) The schematic plane pattern block diagram of the image sensor which concerns on 2nd Embodiment, (b) The typical plane pattern block diagram of the ISFET cell of the image sensor which concerns on 2nd Embodiment. The typical circuit block block diagram of the ISFET cell applicable to the image sensor which concerns on 2nd Embodiment. The typical circuit block block diagram of the image sensor which concerns on 3rd Embodiment. The typical circuit block diagram of the ISFET cell applicable to the image sensor which concerns on 3rd Embodiment. FIG. 10 is a schematic cross-sectional view of an ISFET cell applicable to the image sensor according to the third embodiment, and is a schematic explanatory view of an ion detection operation. It is typical sectional structure of the ISFET cell which concerns on a comparative example, Comprising: The typical explanatory drawing of ion detection operation | movement. (A) A schematic cross-sectional structure of an ISFET cell applicable to the image sensor according to the third embodiment, which is a schematic explanatory view of an ion detection operation, and (b) a schematic view of a sensor area in FIG. FIG. The typical circuit block block diagram of the image sensor which concerns on 4th Embodiment. Explanatory drawing of the operation mode of FIG. (A) The typical circuit block diagram of the ISFET cell applicable to the image sensor which concerns on 4th Embodiment, (b) The simple circuit display figure of Fig.25 (a). (A) In the ISFET cell applicable to the image sensor according to the fourth embodiment, an operation explanatory diagram in the ON state of the selection circuit. (B) In the ISFET cell applicable to the image sensor according to the fourth embodiment. FIG. 6 is an operation explanatory diagram in a selection circuit OFF state. The typical cross-section figure of the ISFET cell applicable to the image sensor which concerns on 4th Embodiment. (A) Typical cross-section figure of ISFET cell applicable to the image sensor which concerns on 5th Embodiment, (b) Typical plane pattern block diagram of the sensor area of Fig.28 (a).

  Next, first to fifth embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Also, the following first to fifth embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention are components. The material, shape, structure, arrangement, etc. are not specified below. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

[First embodiment]
(Image sensor)
In the image sensor 4 according to the first embodiment in which ISFET cells C _ij constituted by ISFETs are arranged on the semiconductor substrate 10 in an array, the sample cell 100 is mounted on the image sensor 4. A schematic bird's-eye view structure is represented as shown in FIG. A schematic bird's-eye view structure showing the pH distribution 200 detected using the image sensor 4 corresponding to FIG. 1 is expressed as shown in FIG. As shown in FIGS. 1 and 2, each pH value pH _ij is detected corresponding to each ISFET cell C _ij , and a pH image is obtained.

  In the image sensor 4 according to the first embodiment, a schematic bird's-eye view structure showing a state where the peripheral circuit portion is shielded from light is expressed as shown in FIG. Here, the peripheral circuit section includes a vertical scanning circuit 30, a horizontal scanning circuit 32, a signal processing circuit 34, and the like. As the light-shielding film, an aluminum thin film layer, silver-silver chloride (Ag / AgCl), platinum (Pt), or the like similar to a pseudo reference electrode described later can be applied.

  In the image sensor 4 according to the first embodiment, a schematic planar pattern representing a state in which a specific region in the peripheral circuit portion (30, 32, 34) and the cell array region 1 is shielded by using the pseudo reference electrode 50 The configuration is represented as shown in FIG. In FIG. 4, in addition to peripheral circuit portions such as the vertical scanning circuit 30, the horizontal scanning circuit 32, and the signal processing circuit 34, an example in which the pseudo reference electrodes 50 are arranged in a stripe shape in a predetermined direction in the cell array region 1. It is shown. The pseudo reference electrode 50 has the role of both the reference electrode and the light shielding film, and the arrangement and structure of the pseudo reference electrode 50 will be described later.

The schematic circuit block configuration of the image sensor 4 according to the first embodiment includes a plurality of word lines WL1, WL2,..., WLm extending in the row direction and word lines WL1, WL2, as shown in FIG. ..., a plurality of bit lines BL1, BL2,..., BLn orthogonal to WLm and extending in the column direction, and a plurality of vertical selections each having a drain connected to the plurality of word line lines WL1, WL2,. transistor Q _V1, Q _V2, ..., and Q _Vm, a plurality of vertical selection transistors Q _V1, Q _V2, ..., a vertical scanning circuit 30, the gate of which is connected to the Q _Vm, a plurality of bit lines BL1, BL2, ... , BLn respect, the horizontal selection transistor Q _H1 having a source connected respectively, Q _H2, ..., and Q _Hn, a plurality of horizontal selection transistors Q _H1, Q _H2, ..., gates connected of Q _Hn It comprises a horizontal scanning circuit 32, the word lines WL1, WL2, ..., WLm and bit lines BL1, BL2, ..., and ISFET cell C _mn arranged in the intersection of BLn.

Here, as shown in FIG. 5, the ISFET cell C _mn is composed of a series circuit of an ion detection transistor Q _mn and a transfer gate transistor Q _G.

The image sensor 4 according to the first embodiment is connected between an output terminal obtained by commonly connecting the sources of the plurality of vertical selection transistors Q _V1 , Q _{V2 ,.} and MOSFET Q _LN, a plurality of horizontal selection transistors Q _H1, Q _H2, ..., and the power supply voltage V _DD to the drain connected to a power supply line which is obtained by common connection of Q _Hn, transfer in common the transfer gate electrode 20 and a transfer gate voltage V _TG connected to the gate line.

  Further, in the image sensor 4 according to the first embodiment, the sample cell is arranged on the semiconductor substrate on which the image sensor 4 is arranged, and when detecting reset information and optical information, the transfer gate electrode 20 of the ISFET cell 2 is detected. Is set to a low level in the off state, and when detecting pH ion information, it is set to a high level in the on state, and on / off control is performed by the potential of the transfer gate electrode 20, thereby reset information, optical information image information, Both pH ion distribution information can be detected.

In the image sensor 4 according to the first embodiment, the MOSFET Q _VN may be replaced with a resistor in order to realize a simpler configuration.

When the reset is read from the back gate (well region 12), the back gate (well region 12) must be separated from each other and made independent in each ISFET cell C _ij in the case of an array. In the image sensor 4 according to the embodiment, as shown in FIG. 5, the transfer gate electrode 20 can be made common and the transfer gate voltage V _TG can be applied.

(ISFET cell)
FIG. 6 is a schematic cross-sectional structure of an image sensor cell according to a comparative example, and a schematic explanatory diagram of an ion detection operation is expressed as shown in FIG. In the comparative example, as shown in FIG. 6, the reference electrode 24 has a capillary electrode structure sealed with glass, and a constant reference voltage V _REF is supplied to the capillary electrode. As shown in FIG. 6, a passivation film 22 disposed on the source region 14, the drain region 16, and the transfer gate electrode 20, and a light shielding film 50 a disposed on the passivation film 22 are provided. Here, an aluminum thin film layer or the like can be applied to the light shielding film 50a. Other configurations are the same as those in FIG.

  FIG. 7 is a schematic cross-sectional structure of the ISFET cell 2 applicable to the image sensor 4 according to the first embodiment, and a schematic description of the ion detection operation is expressed as shown in FIG. A schematic planar pattern configuration of the sensor area of (a) is expressed as shown in FIG.

  As shown in FIGS. 7A and 7B, the ISFET cell 2 applied to the image sensor 4 according to the first embodiment includes a semiconductor substrate 10 having a first conductivity type, and a semiconductor substrate 10. A first well region 12 having a second conductivity type opposite to the first conductivity type, and a source region 14 and a drain region 16 having a first conductivity type disposed on the first well region 12. A gate insulating film 18 disposed on the first well region; a transfer gate electrode 20 disposed on the gate insulating film 18 adjacent to the drain region 16; and an ion disposed on the gate insulating film 18 A sensitive film 19, a liquid sample 26 in contact with the ion sensitive film 19, a passivation film 22 disposed on the source region 14, the drain region 16 and the transfer gate electrode 20, and a passive film On the Shon film 22, and a pseudo reference electrode 50 disposed in contact with the liquid sample 26. A first well contact region 45 is formed in the first well region 12, and a substrate contact region 43 is formed in the semiconductor substrate 10.

  Here, as shown in FIG. 7, the ion detector 6 includes a well region 12 between the source region 14 and the drain region 16, a gate insulating film 18 disposed on the well region 12, and a gate insulating film 18. It consists of an ion sensitive film 19 arranged.

  Here, for example, tantalum oxide, alumina, or silicon nitride film can be applied to the gate insulating film 18. Alternatively, a structure in which a silicon nitride film is stacked on a silicon thermal oxide film, or a structure in which tantalum oxide is formed on a silicon thermal oxide film may be employed. Furthermore, a gate insulating film (ion-sensitive film) having a structure in which a silicon thermal oxide film, a silicon nitride film, and a tantalum oxide are stacked in this order is even better from the viewpoints of waterproofness by silicon nitride film, excellent sensitivity of tantalum oxide, and drift characteristics. .

  Since the light transmitted through the ion sensitive film is detected by the pn junction in the lower Si substrate, the ion sensitive film may be a material that transmits light in the target wavelength region. In the case of visible light, a silicon nitride film, tantalum oxide, and the like can be given.

The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the ion sensitive film 19. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

In FIG. 7, the pseudo reference electrode 50 can be formed of Ag / AgCl (silver silver chloride), Pt (platinum), or the like. A fixed reference voltage V _REF is supplied to the pseudo reference electrode 50. Ag / AgCl (silver silver chloride) can be directly formed by screen printing or the like. It can also be formed by a plating technique in which Ag is formed and electrolyzed in a solution such as KCl.

  In FIG. 7, the pseudo reference electrode 50 extends on the passivation film 22 other than the ion detector 6, controls the potential in the liquid sample 26, and is also used as a light shielding film.

As the passivation film 22, for example, a CVDSiO ₂ film, a CVD nitride film, a TEOS film, or a multilayer film thereof can be applied.

  Note that the structure shown in FIG. 7 can be formed by applying a CMOS forming technique. In FIG. 7, a channel stopper diffusion layer is formed below the LOCOS insulating film 17, but the illustration is omitted.

(ISFET cell operation)
A schematic cross-sectional structure of a basic ISFET cell 2 applied to the image sensor 4 according to the first embodiment is expressed as shown in FIG. 8A, and the ion detection unit of FIG. The enlarged schematic cross-sectional structure is expressed as shown in FIG.

  Moreover, the structure at the time of the ion detection operation | movement of the ISFET cell 2 applied to the image sensor 4 which concerns on 1st Embodiment is represented as shown in FIG. Furthermore, a circuit configuration for explaining the ion detection operation is expressed as shown in FIG. Here, FIG. 8A and FIG. 9 correspond to a schematic cross-sectional structure taken along line II in FIG.

The structure of FIG. 8A shows a simplified configuration of the structure of FIG. 7 in order to explain the operation of the ISFET cell. Therefore, the description overlapping with FIG. 7 is omitted. In FIG. 8A, the ion sensitive film 19 is omitted. For example, a tantalum oxide or a silicon nitride film can be applied to the gate insulating film 18. The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the gate insulating film 18. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

  The configuration during the ion detection operation to which the structure of FIG. 8A is applied is expressed as shown in FIG. The liquid sample 26 is in contact with the gate insulating film 18 of the ion detector 6, and the pseudo reference electrode 50 is disposed in contact with the liquid sample 26.

As shown in FIG. 10, the ISFET cell 2 is composed of a series circuit of an ion detection transistor Qi of the ion detector 6 and a transfer gate transistor Q _G by a transfer gate TG, and a power source is connected to the drain region 16 of the transfer gate transistor Q _G. The voltage V _D is connected, and the MOSFET Q _LN is connected to the source region 14 of the ion detection transistor Qi.

As shown in FIG. 10, in the ISFET cell 2, the reference voltage V _REF is applied to the pseudo reference electrode REFG on the gate of the ion detection transistor Qi. The gate part of the ion detection transistor Qi corresponds to the ion detection part 6 and receives an input ion signal based on the potential of the liquid interface. The output signal is obtained as the output voltage V _out of the source follower from the drain of the MOSFET Q _LN connected in series to the ion detection transistor Qi. As a result, the output voltage V _{out of the} source follower obtained from the drain terminal of the MOSFET Q _LN responds linearly to the input ion signal.

(Ion detection operation)
A schematic plane pattern configuration of the ISFET cell 2 is expressed as shown in FIG. Further, the energy potential diagram at the time of light detection of the ISFET cell 2 is expressed as shown in FIG. 12, and the energy potential diagram at the time of ion detection is expressed as shown in FIG.

  In the ISFET cell 2, the potential of the transfer gate electrode 20 is set to the low level in the off state when detecting reset information / light information, and to the high level in the on state when detecting pH ion information. Therefore, on / off control can be performed.

-Detection of reset information and optical information-
In the reset acquisition mode, as shown in FIG. 12, the potential of the transfer gate electrode 20 is set to a low level, and the transfer gate transistor Q _G is turned off. At this time, the flow of carriers (electrons) from the ion detector 6 to the drain region 16 is blocked by the potential barrier immediately below the transfer gate electrode (TG). In this state, electrons near the source region 14 flow out to the semiconductor substrate 10 side, while holes near the source region 14 flow into the source region 14.

-Detection of ion information-
Next, in the ISFET mode, as shown in FIG. 13, the potential of the transfer gate electrode 20 is set to the high level, and the transfer gate transistor Q _G is turned on. At this time, since the potential barrier height immediately below the transfer gate electrode (TG) is lowered, carrier (electron) inflow from the ion detector 6 to the drain region 16 is caused. In this state, electrons near the source region 14 flow out to the semiconductor substrate 10 side. On the other hand, holes near the source region 14 flow into the source region 14.

  Therefore, accurate ion information can be detected by subtracting the reset information / light information obtained in the reset acquisition mode from the obtained data in the ISFET mode.

  According to the image sensor according to the first embodiment, in the pH light multimodal image sensor, the pseudo reference electrode is formed on all of the circuits other than the sensing area on the chip or on a circuit such as a drive circuit or a processing circuit. Realize light shielding. Since the pseudo reference electrode is formed on the chip, when the optical image is acquired by irradiating light, the pseudo reference electrode affects the optical image and does not form a shadow.

  According to the image sensor according to the first embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is improved. An improved pseudo-reference electrode integrated optical pH image sensor can be provided.

  According to the image sensor according to the first embodiment, since the pseudo reference electrode serves as a light shielding film, it is not necessary to newly form a light shielding film.

  According to the image sensor of the first embodiment, since the pseudo reference electrode and the chip are integrated, measurement is possible even when the measurement solution is small.

[Second Embodiment]
A schematic cross-sectional structure of an ISFET cell according to a comparative example is expressed as shown in FIG. In the comparative example, as shown in FIG. 14, the reference electrode 24 has a capillary electrode structure sealed with glass, and a constant reference voltage V _REF is supplied to the capillary electrode. Further, as shown in FIG. 14, the passivation film 22 disposed on the source region 52, the drain region 54, the implantation control gate electrode 58 and the transfer gate electrode 20, the reset gate electrode 60 and the reset region 56, and the passivation film 22 The light shielding film 50a disposed on the light shielding film 50a and the passivation film 22a disposed on the light shielding film 50a. Other configurations are the same as those in FIG.

  A schematic cross-sectional structure of the ISFET cell 2 applicable to the image sensor according to the second embodiment is expressed as shown in FIG. 15A, and a schematic plane pattern configuration of the sensor area in FIG. Is expressed as shown in FIG. The image sensor according to the second embodiment corresponds to a CCD (Charge Coupled Device) type or a CID (Charge Injection Device) type image sensor.

  A schematic cross-sectional structure of the ISFET cell 2 applicable to the image sensor 4 according to the second embodiment includes a semiconductor substrate 10 having the first conductivity type, and a semiconductor substrate 10 as shown in FIG. A well region 12 having a second conductivity type opposite to the first conductivity type, and a source region 52, a drain region 54, and a reset region 56 disposed on the well region 12 and having the first conductivity type, The gate insulating film 18 disposed on the well region 12, the implantation control gate electrode 58 disposed on the gate insulating film 18 and adjacent to the source region 52, the drain region 54 on the gate insulating film 18, and the like. A transfer gate electrode 20 disposed adjacent to the gate insulating film 18, a reset gate electrode 60 disposed between the drain region 54 and the reset region 56, and a gate insulating film 8, the ion sensitive film 19 disposed between the implantation control gate electrode 58 and the transfer gate electrode 20, the liquid sample 26 in contact with the ion sensitive film 19, the source region 52, the drain region 54, and the implantation control gate electrode 58. , A passivation film 22 disposed on the transfer gate electrode 20, the reset gate electrode 60 and the reset region 56, and a pseudo reference electrode 50 disposed on the passivation film 22.

  Here, as shown in FIG. 15, the ion detector 6 includes the well region 12 between the source region 52 and the drain region 54, the gate insulating film 18 disposed on the well region 12, and the gate insulating film 18. It consists of an ion sensitive film 19 arranged.

  Here, for example, tantalum oxide, alumina, or silicon nitride film can be applied to the gate insulating film 18. Alternatively, a structure in which a silicon nitride film is stacked on a silicon thermal oxide film, or a structure in which tantalum oxide is formed on a silicon thermal oxide film may be employed. Furthermore, a gate insulating film (ion-sensitive film) having a structure in which a silicon thermal oxide film, a silicon nitride film, and a tantalum oxide are stacked in this order is even better from the viewpoints of waterproofness by silicon nitride film, excellent sensitivity of tantalum oxide, and drift characteristics. .

  Since the light transmitted through the ion sensitive film is detected by the pn junction in the lower Si substrate, the ion sensitive film may be a material that transmits light in the target wavelength region. In the case of visible light, a silicon nitride film, tantalum oxide, and the like can be given.

The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the ion sensitive film 19. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

In FIG. 15, the pseudo reference electrode 50 can be formed of Ag / AgCl (silver silver chloride), Pt (platinum), or the like. A fixed reference voltage V _REF is supplied to the pseudo reference electrode 50. Ag / AgCl (silver silver chloride) can be directly formed by screen printing or the like. It can also be formed by a plating technique in which Ag is formed and electrolyzed in a solution such as KCl.

  In FIG. 15, the pseudo reference electrode 50 extends on the passivation film 22 other than the ion detector 6 and controls the potential in the liquid sample 26 and is also used as a light shielding film.

  The structure shown in FIG. 15 can be formed by applying a CMOS forming technique. In FIG. 15, a channel stopper diffusion layer is formed below the LOCOS insulating film 17, but the illustration is omitted.

  The source region 52 is connected to the charge injection terminal ID, the injection control gate electrode 58 is connected to the injection control gate ICG, the transfer gate electrode 20 is connected to the transfer gate TG, and the drain region 54 is connected to the floating diffusion FD. The reset gate electrode 60 is connected to the reset gate RG, and the reset region 56 is connected to the reset power supply VRES.

Floating diffusion FD is connected to the gate of MOSFET Q _D. The drain of MOSFET Q _D power supply voltage V _D is applied, the output voltage V _out from the drain of MOSFET Q _LN connected between the source and the ground potential of the MOSFET Q _D is obtained.

  In the channel region between the source region 52 and the drain region 54, charges (electrons) injected from the source region 52 are transferred to the drain region 54 by controlling the potentials of the injection control gate electrode 58 and the transfer gate electrode 20.

  A reset MOSFET controlled by the gate potential of the reset gate electrode 60 is formed between the drain region 54 and the reset region 56. Therefore, the potential of the drain region 54 is controlled by the reset MOSFET.

  A schematic planar pattern configuration of the image sensor according to the second embodiment is expressed as shown in FIG. As shown in FIG. 16A, the pseudo reference electrode 50 is disposed on the vertical scanning circuit 30, the horizontal scanning circuit 32, and the signal processing circuit 34 that surround the cell array region 1. The pseudo reference electrode 50 is not particularly disposed on the bonding pad 36. An interlayer insulating film, a passivation film 22 and the like are interposed and insulated between the vertical scanning circuit 30, the horizontal scanning circuit 32, and the signal processing circuit 34 and the pseudo reference electrode 50 disposed above them. . In this case, the pseudo reference electrode 50 has a function as a light shielding film.

  A schematic planar pattern configuration of the ISFET cell of the image sensor according to the second embodiment is expressed as shown in FIG. In FIG. 16B, a schematic cross-sectional structure along the line II-II corresponds to FIG. Also in FIG. 16B, as apparent from FIG. 15A, the region other than the ion detector 6 is covered with the pseudo reference electrode 50.

A schematic circuit block configuration of the ISFET cell 2 of the image sensor 4 according to the second embodiment is expressed as shown in FIG. ISFET cell 2, as shown in FIG. 17, the ion detection transistor Qi of the ion detector 6 is constituted by a series circuit of the transfer gate transistor Q _G by the transfer gate TG, a reset drain region 54 of the transfer gate transistor Q _G MOSFET of use is connected to the source region of the ion detection transistor Qi (ion detection section 6), MOSFET Q _LN for charge injection is connected.

  According to the image sensor according to the second embodiment, in the CCD / CID type pH light multimodal image sensor, the pseudo reference electrodes are all on the circuit other than the sensing area on the chip, or on a circuit such as a drive circuit or a processing circuit. The light shielding is realized. Since the pseudo reference electrode is formed on the chip, when the optical image is acquired by irradiating light, the pseudo reference electrode affects the optical image and does not form a shadow.

  The schematic circuit block configuration of the image sensor 4 according to the second embodiment can be configured in the same manner as in FIG. 5 of the first embodiment.

  According to the image sensor according to the second embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is increased. An improved CCD / CID type pseudo-reference electrode integrated optical pH image sensor can be provided.

  According to the CCD / CID type image sensor according to the second embodiment, since the pseudo reference electrode serves as a light shielding film, it is not necessary to newly form a light shielding film.

  According to the CCD / CID type image sensor according to the second embodiment, since the pseudo reference electrode and the chip are integrated, measurement is possible even when the measurement solution is small.

[Third embodiment]
(Image sensor)
As shown in FIG. 18, a schematic circuit block configuration of the image sensor 4 according to the third embodiment includes a plurality of word lines WL1, WL2,..., WLm extending in the row direction and word lines WL1, WL2,. , WLm orthogonal to the plurality of bit lines BL1, BL2,..., BLn and a plurality of vertical selection transistors Q each having a drain connected to the plurality of word lines WL1, WL2,. _V1, Q _V2, ..., and Q _Vm, a plurality of vertical selection transistors Q _V1, Q _V2, ..., a vertical scanning circuit 30, the gate of which is connected to the Q _Vm, a plurality of bit lines BL1, BL2, ..., BLn respect, the horizontal selection transistor Q _H1, Q _H2 having a source connected respectively, ..., and Q _Hn, a plurality of horizontal transistors Q _H1, Q _H2, ..., the water gates of Q _Hn is connected Includes a scanning circuit 32, the word lines WL1, WL2, ..., WLm and bit lines BL1, BL2, ..., and ISFET cell C _mn arranged in the intersection of BLn.

Further, as shown in FIG. 19, a schematic circuit configuration of the ISFET cell 2 applied to the image sensor 4 according to the third embodiment is a transfer using an ion detection transistor Qi of the ion detection unit 6 and a transfer gate TG. a series circuit of gate transistors Q _G, is composed of a parallel circuit of a storage capacitor C _S which are connected between the sources of the drain and the ion detector transistor Qi of the transfer gate transistor Q _G, the drain region 16 of the transfer gate transistor Q _G A power supply voltage V _D is connected, and a MOSFET Q _LN is connected to the source region 14 of the ion detection transistor Qi.

As shown in FIG. 18, the image sensor 4 according to the third embodiment is connected to a power supply line obtained by commonly connecting the drains of a plurality of horizontal selection transistors Q _H1 , Q _{H2 ,.} It comprises a power supply voltage V _DD, a plurality of vertical selection transistors Q _V1, Q _V2, ..., the MOSFET Q _LN to the output terminal obtained connected between the ground potential by commonly connecting the source of Q _Vm.

The image sensor 4 according to the third embodiment, a plurality of horizontal selection transistors _{Q H1, Q H2, ...,} MOSFETQ LN to the drain of Q _Hn is connected between the output terminal obtained by commonly connected ground And a power supply voltage V _DD connected to a power supply line obtained by commonly connecting the sources of the plurality of vertical selection transistors Q _V1 , Q _V2 ,..., Q _Vm .

In the image sensor 4 according to the third embodiment, the sample cell 100 is arranged on the semiconductor substrate 10 on which the image sensor 4 is arranged, and when detecting reset information / light information, the transfer gate of the ISFET cell C _ij is used. By setting the transfer gate voltage V _TG of the electrode 20 to a low level in an off state, and detecting pH ion information, the transfer gate voltage V _TG is set to a high level in an on state, and on / off control is performed by the transfer gate voltage V _TG of the transfer gate electrode 20, Both image information of reset information / light information and pH ion distribution information can be detected.

In the image sensor 4 according to the third embodiment, the storage capacitor C _S is connected in parallel to the series circuit of the ion detection transistor Q _mn and the transfer gate transistor Q _G of each pixel, whereby the pixel charged storage capacitor C _S is the time of selection, by the storage capacitor C _S is discharged when non-pixel selection, can always be holding a driving state, the array operation of the image sensor 4 can be stabilized. That is, since the electric power is supplied from the storage capacitor C _S when it is not the pixel selection is capable of holding the operating state, stability is improved.

  In the ISFET cell 2 applied to the image sensor 4 according to the third embodiment, a mode for acquiring reset information and optical information and a mode for acquiring pH by adjusting the voltage applied to the transfer gate electrode 20. Therefore, accurate ion information can be detected.

In the ISFET cell 2 applied to the image sensor 4 according to the third embodiment, the storage capacitor C _S is connected in parallel to the series configuration of the ion detection transistor Q _mn and the transfer gate transistor Q _G. The storage capacitor C _S is charged in the on state in which the power supply voltage is applied between the drain D and the source S, and the storage capacitor C _S is always discharged in the off state in which the power supply voltage is not applied between the drain D and the source S. The driving state can be maintained, and stability is improved.

(ISFET cell)
20 is a schematic cross-sectional structure of an ISFET cell 2 applied to the image sensor 4 according to the third embodiment, and a schematic explanatory diagram of an ion detection operation is expressed as shown in FIG. Moreover, it is typical sectional structure of the image sensor cell which concerns on a comparative example, Comprising: The typical explanatory drawing of ion detection operation | movement is represented as shown in FIG.

  Moreover, it is typical sectional structure of the image sensor which concerns on 3rd Embodiment, Comprising: The typical explanatory drawing of ion detection operation | movement is represented as shown to Fig.22 (a), and the sensor of Fig.22 (a) is shown. A schematic planar pattern configuration of the area is expressed as shown in FIG. FIG. 22 corresponds to the detailed structure of FIG.

In the comparative example, as shown in FIG. 21, the reference electrode 24 has a capillary electrode structure sealed with glass, and a constant reference voltage V _REF is supplied to the capillary electrode. Further, as shown in FIG. 21, a passivation film 22 disposed on the source region 14, the drain region 16, and the transfer gate electrode 20 and a light shielding film 50 a disposed on the passivation film 22 are provided. Further, a passivation film 22a is provided on the light shielding film 50a. Other configurations are the same as those in FIG.

As shown in FIGS. 20, 22 (a) and 22 (b), the ISFET cell 2 applied to the image sensor 4 according to the third embodiment includes a semiconductor substrate 10 having a first conductivity type, A first well region 12 disposed on the semiconductor substrate 10 and having a second conductivity type opposite to the first conductivity type; a source region 14 disposed on the first well region 12 and having the first conductivity type; On the drain region 16, the gate insulating film 18 disposed on the first well region 12, on the gate insulating film 18, on the transfer gate electrode 20 disposed adjacent to the drain region 16, and on the gate insulating film 18 an ion-sensitive membrane 19 disposed, a storage capacitor C _S is connected between the source region 14 and drain region 16, the liquid sample 26 in contact with the ion-sensitive membrane 19, the source region 14, Trang It comprises a Fageto electrode 20 and the drain region 16 a passivation film 22 disposed on, on the passivation film 22, a pseudo reference electrode 50 disposed in contact with the liquid sample 26. As shown in FIG. 22A, a first well contact region 45 is formed in the first well region 12, and a substrate contact region 43 is formed in the semiconductor substrate 10.

The ISFET cell 2 is disposed on the semiconductor substrate 10 and has a second well region 23 having the first conductivity type, and a second well contact region 13 having the first conductivity type and disposed on the second well region 23. When disposed on the second well region 23 on the gate insulating film 18 may comprise a capacitor electrode 21 forming a storage capacitor C _S between the second well region 23.

In the ISFET cell 2, the drain region 16 is connected to the capacitor electrode 21, the source region 14 is connected to the well contact region 13, and a storage capacitor C _S is provided in parallel between the drain region 16 and the source region 14. May be.

  Further, in the ISFET cell 2, the passivation film 22 may be disposed so as to extend also on the second well region 23, and the pseudo reference electrode 50 may be disposed so as to extend also on the passivation film 22. good.

  Here, as shown in FIGS. 20 and 22A, the ion detector 6 includes a well region 12 between the source region 14 and the drain region 16, a gate insulating film 18 disposed on the well region 12, It consists of an ion sensitive film 19 disposed on the gate insulating film 18.

  Here, for example, tantalum oxide, alumina, or silicon nitride film can be applied to the gate insulating film 18. Alternatively, a structure in which a silicon nitride film is stacked on a silicon thermal oxide film, or a structure in which tantalum oxide is formed on a silicon thermal oxide film may be employed. Furthermore, a gate insulating film (ion-sensitive film) having a structure in which a silicon thermal oxide film, a silicon nitride film, and a tantalum oxide are stacked in this order is even better from the viewpoints of waterproofness by silicon nitride film, excellent sensitivity of tantalum oxide, and drift characteristics. .

  Since the light transmitted through the ion sensitive film is detected by the pn junction in the lower Si substrate, the ion sensitive film may be a material that transmits light in the target wavelength region. In the case of visible light, a silicon nitride film, tantalum oxide, and the like can be given.

The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the ion sensitive film 19. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

  As shown in FIGS. 22A and 22B, the pseudo reference electrode 50 extends on the passivation film 22 other than the ion detector 6, controls the potential in the liquid sample 26, and also shields the light. Also used as

The pseudo reference electrode 50 can be formed of Ag / AgCl (silver silver chloride), Pt (platinum), or the like. A fixed reference voltage V _REF is supplied to the pseudo reference electrode 50. Ag / AgCl (silver silver chloride) can be directly formed by screen printing or the like. It can also be formed by a plating technique in which Ag is formed and electrolyzed in a solution such as KCl.

  Note that the structure shown in FIGS. 20 and 22A can be formed by applying a CMOS forming technique. A channel stopper diffusion layer is formed below the LOCOS insulating film 17 but is not shown.

According to the image sensor of the third embodiment, the storage capacitor is connected in parallel to the ion detection transistor of each pixel, and the storage capacitor C _S is charged when the pixel is selected, and the storage capacitor is not selected. Since C _S is discharged, the driving state can be always maintained, and the array operation can be stabilized. That is, since the electric power is supplied from the storage capacitor C _S when it is not the pixel selection is capable of holding the operating state, stability is improved.

  According to the image sensor according to the third embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is improved. An improved pseudo-reference electrode integrated optical pH image sensor can be provided.

  According to the image sensor according to the third embodiment, since the pseudo reference electrode serves as a light shielding film, it is not necessary to newly form a light shielding film.

  According to the image sensor of the third embodiment, since the pseudo reference electrode and the chip are integrated, measurement is possible even when the measurement solution is small.

  According to the image sensor which concerns on 1st Embodiment, the pseudo | simulation reference electrode integrated optical pH image sensor which can be stabilized by a constant drive can be provided.

[Fourth embodiment]
(Image sensor)
A schematic circuit block configuration of the image sensor 4 according to the fourth embodiment is expressed as shown in FIG. In FIG. 23, the description of the operation mode in the ISFET cell C _mn is expressed as shown in FIG. As is apparent from FIGS. 23 and 24, the ion detection transistor Q _mn of the ISFET cell C _mn selected by the vertical selection transistor Q _Vm and the horizontal selection transistor Q _Hn includes the vertical selection transistor Q _Vm and the horizontal selection transistor Q _When both _Hn are in the ON state at the same time, they are in the ON state. When both the vertical selection transistor Q _Vm and the horizontal selection transistor Q _Hn are turned off at the same time, or when one of them is turned off, it is turned off.

As shown in FIG. 23, the image sensor 4 according to the fourth embodiment is orthogonal to the plurality of word lines WL1, WL2,..., WLm extending in the row direction and the word lines WL1, WL2,. , BLn extending in the column direction, and a plurality of vertical selection transistors Q _V1 , Q _V2 , drains connected to the word lines WL1, WL2,. .., Q _Vm and a plurality of vertical selection transistors Q _V1 , Q _V2 ,..., Q _Vm , respectively, and a plurality of bit lines BL1, BL2,. a source connected horizontal selection transistors Q _H1, Q _H2, ..., and Q _Hn, a plurality of horizontal transistors Q _H1, Q _H2, ..., the horizontal scanning circuit 32, each gate of Q _Hn is connected, word Line WL1, WL2, ..., includes WLm and bit lines BL1, BL2, ..., and ISFET cell C _mn arranged in the intersection of BLn.

Here, ISFET cell _{C 11, C 12, ...,} C 1n, C 21, C 22, ..., C 2n, ..., C m1, C m2, ..., C mn is ion detection transistor Q _11, respectively, Q ₁₂ , ..., Q _1n, Q ₂₁ , Q ₂₂ , ..., Q _2n , ..., Q _m1 , Q _m2 , ..., Q _mn and a parallel circuit of the storage capacitor C _S.

(ISFET cell)
A schematic circuit configuration of the ISFET cell 2 applied to the image sensor 4 according to the fourth embodiment is expressed as shown in FIG. 25A, and a simple circuit display of FIG. It is expressed as shown in (b).

As shown in FIG. 25, the ISFET cell 2 applied to the image sensor 4 according to the fourth embodiment includes a parallel circuit of an ion detection transistor Q _mn and a storage capacitor C _S.

Operation in the on-state drain D and source voltage between the source S is applied in ion detection transistor Q _mn is expressed as shown in FIG. 26 (a), the ion detection transistor Q _mn is in a conductive state, and storage The capacitor C _S is charged with the power supply voltage. The operation in the off state in which the power supply voltage is not applied between the drain D and the source S of the ion detection transistor Q _mn is expressed as shown in FIG. In this case, the ion detection transistor Q _mn, the discharge current of the charge accumulated in the storage capacitor C _S, is in the conducting state, and the storage capacitor C _S is in the discharged state.

In the ISFET cell 2, the storage capacitor C _S is connected in parallel to the ion detection transistor Q _mn , so that the storage capacitor C _S is charged in the ON state in which the power supply voltage is applied between the drain D and the source S, In the off state where the power supply voltage is not applied between the drain D and the source S, the storage capacitor C _S is discharged, so that the driving state can always be maintained and the stability is improved.

As shown in FIG. 23, the image sensor 4 in which the ISFETs according to the fourth embodiment are arranged in an array is obtained by commonly connecting the drains of a plurality of horizontal selection transistors Q _H1 , Q _{H2 ,.} Power supply voltage V connected to a power supply line obtained by commonly connecting the MOSFET Q _LN connected between the output terminal and the ground potential and the sources of the plurality of vertical selection transistors Q _V1 , Q _{V2 ,. With DD} .

The image sensor 4 in which the ISFETs according to the second embodiment are arranged in an array is connected to a power supply line obtained by commonly connecting the drains of a plurality of horizontal selection transistors Q _H1 , Q _{H2 ,.} and the power supply voltage V _DD and a plurality of vertical selection transistors Q _V1, Q _V2, ..., even if a MOSFET Q _LN to the output terminal obtained connected between the ground potential by commonly connecting the sources of the Q _Vm good.

In the image sensor 4 in which the ISFETs according to the fourth embodiment are arranged in an array, the ion detection transistors Q ₁₁ , Q ₁₂ ,..., Q _1n, Q ₂₁ , Q _{22 ,.} , Q _m1 , Q _m2 ,..., Q _mn are connected in parallel with a storage capacitor C _S , whereby the storage capacitor C _S is charged when a pixel is selected, and the storage capacitor C _S is discharged when no pixel is selected. By doing so, it is possible to always keep the driving state and to stabilize the array operation of the image sensor 4. That is, since the electric power is supplied from the storage capacitor C _S when it is not the pixel selection is capable of holding the operating state, stability is improved.

  A schematic cross-sectional structure of the ISFET cell 2 applied to the image sensor 4 according to the fourth embodiment is expressed as shown in FIG.

As shown in FIG. 27, the ISFET cell 2 applied to the image sensor 4 according to the fourth embodiment is disposed on the semiconductor substrate 10 and the first conductivity type. A first well region 12 having a second conductivity type opposite to the first conductivity region, and a source region 14 and a drain region 16 having a first conductivity type, disposed on the first well region 12, and disposed on the first well region. Gate insulating film 18, ion sensitive film 19 disposed on gate insulating film 18, storage capacitor C _S connected between source region 14 and drain region 16, and liquid sample in contact with ion sensitive film 19 26, a passivation film 22 disposed on the source region 14 and the drain region 16, and a pseudo reference electrode 5 disposed on the passivation film 22 in contact with the liquid sample 26. Provided with a door.

The ISFET cell 2 is disposed on the semiconductor substrate 10 and has a second well region 23 having the first conductivity type, and a second well contact region 13 having the first conductivity type and disposed on the second well region 23. When disposed on the second well region being arranged on the gate insulating film 18 may comprise a capacitor electrode 21 forming a storage capacitor C _S between the second well region 23.

In the ISFET cell 2, the drain region 16 is connected to the capacitor electrode 21, the source region 14 is connected to the well contact region 13, and a storage capacitor C _S is provided in parallel between the drain region 16 and the source region 14. May be.

  Further, the passivation film 22 may be arranged to extend also on the second well region 23, and the pseudo reference electrode 50 may be arranged to extend also on the passivation film 22.

  Here, as shown in FIG. 27, the ion detector 6 includes a well region 12 between the source region 14 and the drain region 16, a gate insulating film 18 disposed on the well region 12, and a gate insulating film 18. It consists of an ion sensitive film 19 arranged.

  Here, for example, tantalum oxide, alumina, or silicon nitride film can be applied to the gate insulating film 18. Alternatively, a structure in which a silicon nitride film is stacked on a silicon thermal oxide film, or a structure in which tantalum oxide is formed on a silicon thermal oxide film may be employed. Furthermore, a gate insulating film (ion-sensitive film) having a structure in which a silicon thermal oxide film, a silicon nitride film, and a tantalum oxide are stacked in this order is even better from the viewpoints of waterproofness by silicon nitride film, excellent sensitivity of tantalum oxide, and drift characteristics. .

  Since the light transmitted through the ion sensitive film is detected by the pn junction in the lower Si substrate, the ion sensitive film may be a material that transmits light in the target wavelength region. In the case of visible light, a silicon nitride film, tantalum oxide, and the like can be given.

The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the ion sensitive film 19. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

In FIG. 27, the pseudo reference electrode 50 can be formed of Ag / AgCl (silver silver chloride), Pt (platinum), or the like. A fixed reference voltage V _REF is supplied to the pseudo reference electrode 50. Ag / AgCl (silver silver chloride) can be directly formed by screen printing or the like. It can also be formed by a plating technique in which Ag is formed and electrolyzed in a solution such as KCl.

  In FIG. 27, the pseudo reference electrode 50 extends on the passivation film 22 other than the ion detector 6, controls the potential in the liquid sample 26, and is also used as a light shielding film.

  Note that the structure shown in FIG. 27 can be formed by applying a CMOS formation technique. In FIG. 27, a channel stopper diffusion layer is formed below the LOCOS insulating film 17 but is not shown.

According to the image sensor of the fourth embodiment, the storage capacitor is connected in parallel to the ion detection transistor of each pixel, and the storage capacitor C _S is charged when the pixel is selected, and the storage capacitor is not selected. Since C _S is discharged, the driving state can be always maintained, and the array operation can be stabilized. That is, since the electric power is supplied from the storage capacitor C _S when it is not the pixel selection is capable of holding the operating state, stability is improved.

  According to the image sensor according to the fourth embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is improved. An improved pseudo-reference electrode integrated optical pH image sensor can be provided.

  According to the image sensor of the fourth embodiment, since the pseudo reference electrode serves as a light shielding film, it is not necessary to newly form a light shielding film.

  According to the image sensor of the fourth embodiment, since the pseudo reference electrode and the chip are integrated, measurement is possible even when the measurement solution is small.

[Fifth embodiment]
A schematic cross-sectional structure of the ISFET cell 2 applicable to the image sensor 4 according to the fifth embodiment is expressed as shown in FIG. 28A, and a schematic plane pattern of the sensor area in FIG. The configuration is expressed as shown in FIG. The schematic circuit block configuration of the image sensor 4 according to the fifth embodiment is the same as that shown in FIG.

As shown in FIGS. 28A and 28B, the ISFET cell 2 applicable to the image sensor 4 according to the fifth embodiment includes a semiconductor substrate 10 having a first conductivity type, and a semiconductor substrate 10. A first well region 12 having a second conductivity type opposite to the first conductivity type, and a source region 14 and a drain region 16 having a first conductivity type disposed on the first well region 12. A gate insulating film 18 disposed on the first well region 12, a gate plug electrode 40 disposed on the gate insulating film 18 between the source region 14 and the drain region 16, and a drain region 16. a drain plug electrode 44 is connected between the source region 14 and the drain plug electrode 44, and a storage capacitor C _S having a laminated electrode 46, 48, Toru disposed on the gate plug electrode 40 The electrode film 42, the ion sensitive film 19 disposed on the transparent electrode film 42, the liquid sample 26 in contact with the ion sensitive film 19, and the pseudo disposed on the ion sensitive film 19 in contact with the liquid sample 26. And a reference electrode 50. A first well contact region 45 is formed in the first well region 12, and a substrate contact region 43 is formed in the semiconductor substrate 10.

  In addition, as shown in FIGS. 28A and 28B, a passivation film 22 disposed on the first well region 12 and the gate insulating film 18 on the semiconductor substrate 10 is provided. On the passivation film 22, the transparent electrode film 42 and the ion sensitive film 19 extend.

Here, as shown in FIGS. 28A and 28B, the ion detector 6 includes a well region 12 between the source region 14 and the drain region 16, and a gate insulating film disposed on the well region 12. 18, a gate plug electrode 40 disposed on the gate insulating film 18, a transparent electrode film 42 disposed on the gate plug electrode 40, and an ion sensitive film 19 disposed on the transparent electrode film 42. The gate plug electrode 40 and the transparent electrode film 42 can be formed of, for example, ITO, IZTO, SnO ₂ or the like.

  Here, for example, tantalum oxide, alumina, or silicon nitride film can be applied to the gate insulating film 18. Alternatively, a structure in which a silicon nitride film is stacked on a silicon thermal oxide film, or a structure in which tantalum oxide is formed on a silicon thermal oxide film may be employed. Furthermore, a gate insulating film (ion-sensitive film) having a structure in which a silicon thermal oxide film, a silicon nitride film, and a tantalum oxide are stacked in this order is even better from the viewpoints of waterproofness by silicon nitride film, excellent sensitivity of tantalum oxide, and drift characteristics. .

  Since the light transmitted through the ion sensitive film is detected by the pn junction in the lower Si substrate, the ion sensitive film may be a material that transmits light in the target wavelength region. In the case of visible light, a silicon nitride film, tantalum oxide, and the like can be given.

The potential of the channel region formed in the well region 12 below the gate insulating film 18 is changed by, for example, H ⁺ ions attached on the ion sensitive film 19. As a result, the current conduction state between the source region 14 and the drain region 16 is modulated. By detecting this current value, for example, the pH value can be detected.

  As shown in FIGS. 28A and 28B, the pseudo reference electrode 50 is arranged so as to surround the ISFET cell region.

The pseudo reference electrode 50 can be formed of Ag / AgCl (silver silver chloride), Pt (platinum), or the like. A fixed reference voltage V _REF is supplied to the pseudo reference electrode 50. Ag / AgCl (silver silver chloride) can be directly formed by screen printing or the like. It can also be formed by a plating technique in which Ag is formed and electrolyzed in a solution such as KCl.

  In FIG. 28, the pseudo reference electrode 50 extends on the passivation film 22 other than the ion detector 6, controls the potential in the liquid sample 26, and is also used as a light shielding film.

  The structure shown in FIG. 28 can be formed by applying a CMOS formation technique. In FIG. 28, a channel stopper diffusion layer is formed below the LOCOS insulating film 17, but the illustration is omitted.

According to the image sensor of the fourth embodiment, the storage capacitor is connected in parallel to the ion detection transistor of each pixel, and the storage capacitor C _S is charged when the pixel is selected, and the storage capacitor is not selected. Since C _S is discharged, the driving state can be always maintained, and the array operation can be stabilized. That is, since the electric power is supplied from the storage capacitor C _S when it is not the pixel selection is capable of holding the operating state, stability is improved.

  According to the image sensor according to the fifth embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is improved. An improved pseudo-reference electrode integrated optical pH image sensor can be provided.

  According to the image sensor of the fifth embodiment, since the pseudo reference electrode serves as a light shielding film, it is not necessary to newly form a light shielding film.

  According to the image sensor according to the fifth embodiment, since the pseudo reference electrode and the chip are integrated, measurement is possible even when the measurement solution is small.

In addition, according to the image sensor of the fifth embodiment, the storage capacitor C _S can be formed with a laminated structure, so that the degree of integration can be improved.

  Moreover, according to the image sensor which concerns on 5th Embodiment, since the ion detection part can be formed in the whole surface of an element area | region, the detection sensitivity of ion information can be improved.

  As described above, according to the present embodiment, by forming the pseudo reference electrode on the circuit of the driving part and the processing part, it is not necessary to newly install the light shielding electrode and the reference electrode, and the sensor sensitivity is improved. An improved pseudo-reference electrode integrated optical pH image sensor is provided.

(Other embodiments)
As described above, the present invention has been described according to the first to fifth embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The pseudo-reference electrode integrated optical pH image sensor of the present invention is applicable to cell pH sensors, pH ion distribution measurement, water quality investigation, water quality management, environmental measurement, beauty field, electrochemical field, medical measurement field, and the like. .

DESCRIPTION OF SYMBOLS 1 ... Cell array region 2 ... ISFET cell 4 ... Image sensor 6 ... Ion detection part 10 ... Semiconductor substrate 12 ... P well layer 13 ... N well contact region 14, 52 ... Source region 16, 54 ... Drain region 17 ... LOCOS insulating film 18 ... Gate insulating film 19 ... Ion sensitive film 20 ... Transfer gate electrode (TG)
21, 46, 48 ... capacitor electrode 22 ... passivation film 23 ... n well layer 24 ... reference electrode 26 ... liquid sample 30 ... vertical scanning circuit 32 ... horizontal scanning circuit 34 ... signal processing circuit 40 ... gate plug electrode 42 ... transparent electrode film 43 ... substrate contact region 44 ... drain plug electrode 45 ... p well contact region 50a ... light shielding film 50 ... pseudo reference electrode 56 ... reset region 58 ... injection control gate electrode 60 ... reset gate electrode 100 ... sample cell 200 ... pH distribution WL1, WL2,..., WLm... Word line (vertical scanning line)
BL1, BL2,..., BLn... Bit line (horizontal scanning line)
Q _V1 , Q _V2 ,..., Q _Vm ... Vertical selection transistors Q _H1 , Q _H2 , ..., Q _Hn ... Horizontal selection transistors Q _LN ... MOSFET
_{Qi, Q 11, Q 12,} ..., Q 1n, Q 21, Q 22, ..., Q 2n, ..., Q m1, Q m2, ..., Q mn ... ion detection transistor Q _G ... transfer gate transistor C _11, C _{12, ..., C 1n, C} 21, C 22, ..., C 2n, ..., C m1, C m2, ..., C mn ... ISFET cell C _S ... storage capacitor V _REF ... reference voltage V _D, V _DD ... power Voltage V _out ... Output voltage V _LN , V _TG ... Gate voltage V _TG ... Transfer gate voltage

Claims (20)

A semiconductor substrate having a first conductivity type;
A well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region and a drain region disposed on the well region and having a first conductivity type;
A gate insulating film disposed on the source region, the well region, and the drain region;
A transfer gate electrode disposed adjacent to the drain region on the gate insulating film;
An ion sensitive film disposed on the gate insulating film;
A liquid sample in contact with the ion sensitive membrane;
A passivation film disposed on the source region, the drain region and the transfer gate electrode;
An image sensor comprising: a pseudo-reference electrode disposed on the passivation film so as to be in contact with the liquid sample.   The image sensor according to claim 1, wherein the pseudo reference electrode is formed of silver silver chloride (Ag / AgCl) or platinum (Pt).   The potential of the transfer gate electrode is set to a low level in an off state when detecting reset information and optical information, and is set to a high level in an on state when detecting pH ion information. The on / off control is performed according to the potential of the transfer gate electrode. The image sensor according to claim 1, wherein the image sensor is an image sensor. A power supply voltage connected to the drain region;
And a MOSFET connected to the source region, and the whole becomes a source follower circuit for an input signal due to the potential of the liquid interface of the liquid sample, and an output obtained from the drain terminal of the MOSFET is linear with respect to the input signal. The image sensor according to claim 1, wherein the image sensor responds to the output. A plurality of word lines extending in the row direction;
A plurality of bit lines orthogonal to the word lines and extending in the column direction;
A plurality of vertical selection transistors each having a drain connected to the plurality of word lines;
A vertical scanning circuit having a gate connected to each of the plurality of vertical selection transistors;
A horizontal selection transistor having a source connected to each of the plurality of bit lines;
A horizontal scanning circuit to which a gate of each of the plurality of horizontal transistors is connected;
An ISFET cell disposed at an intersection of the word line and the bit line,
The ISFET cell is
A semiconductor substrate having a first conductivity type;
A well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region and a drain region disposed on the well region and having a first conductivity type;
A gate insulating film disposed on the source region, the well region, and the drain region;
A transfer gate electrode disposed adjacent to the drain region on the gate insulating film;
An ion sensitive film disposed on the gate insulating film;
A liquid sample in contact with the ion sensitive membrane;
A passivation film disposed on the source region, the drain region and the transfer gate electrode;
An image sensor comprising: a pseudo reference electrode disposed on the passivation film. A MOSFET connected between an output terminal obtained by commonly connecting sources of the plurality of vertical selection transistors and a ground potential;
A power supply voltage connected to a power supply line obtained by commonly connecting the drains of the plurality of horizontal selection transistors;
The image sensor according to claim 5, further comprising: a transfer gate voltage connected to a transfer gate line sharing the transfer gate electrode.   A sample cell is arranged on a semiconductor substrate on which the image sensor is arranged, and at the time of detecting reset information and optical information, the potential of the transfer gate electrode of the ISFET cell is set to a low level in an off state, and pH ion information is detected. In some cases, both the reset information, the image information of the optical information, and the pH ion distribution information are detected by setting the ON state to a high level and performing ON / OFF control according to the potential of the transfer gate electrode. Item 7. The image sensor according to Item 5 or 6. A semiconductor substrate having a first conductivity type;
A well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region, a drain region and a reset region disposed on the well region and having a first conductivity type;
A gate insulating film disposed on the well region;
An implantation control gate electrode disposed on the gate insulating film and adjacent to the source region;
A transfer gate electrode disposed adjacent to the drain region on the gate insulating film;
A reset gate electrode disposed between the drain region and the reset region on the gate insulating film;
An ion sensitive film disposed on the gate insulating film between the implantation control gate electrode and the transfer gate electrode;
A liquid sample in contact with the ion sensitive membrane;
A passivation film disposed on the source region, the drain region, the implantation control gate electrode, the transfer gate electrode, the reset gate electrode, and the reset region;
An image sensor comprising: a pseudo reference electrode disposed on the passivation film. A semiconductor substrate having a first conductivity type;
A first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region and a drain region disposed on the first well region and having a first conductivity type;
A gate insulating film disposed on the first well region;
An ion sensitive film disposed on the gate insulating film;
A storage capacitor connected between the source region and the drain region;
A liquid sample in contact with the ion sensitive membrane;
A passivation film disposed on the source region and the drain region;
An image sensor comprising: a pseudo-reference electrode disposed on the passivation film so as to be in contact with the liquid sample. A second well region disposed on the semiconductor substrate and having a first conductivity type;
A second well contact region disposed on the second well region and having a first conductivity type;
10. The image sensor according to claim 9, further comprising a capacitor electrode disposed on the gate insulating film on the second well region and forming the storage capacitor with the second well region.   11. The drain region is connected to the capacitor electrode, the source region is connected to the well contact region, and the storage capacitor is provided in parallel between the drain region and the source region. The image sensor described.   The image sensor according to claim 10, further comprising: a transfer gate electrode disposed adjacent to the drain region on the gate insulating film.   The said passivation film is extended and arrange | positioned also on the said 2nd well area | region, and the said pseudo reference electrode is extended and arrange | positioned also on the said passivation film, It is characterized by the above-mentioned. The image sensor according to any one of the above. A semiconductor substrate having a first conductivity type;
A first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region and a drain region disposed on the first well region and having a first conductivity type;
A gate insulating film disposed on the first well region;
A gate plug electrode disposed on the gate insulating film between the source region and the drain region;
A drain plug electrode disposed on the drain region;
A storage capacitor connected between the source region and the drain plug electrode and made of a laminated electrode;
A light-shielding film disposed on the gate plug electrode;
An ion sensitive film disposed on the light shielding film;
A liquid sample in contact with the ion sensitive membrane;
An image sensor, comprising: a pseudo reference electrode disposed in contact with the liquid sample on the ion sensitive film. A plurality of word lines extending in the row direction;
A plurality of bit lines orthogonal to the word lines and extending in the column direction;
A plurality of vertical selection transistors each having a drain connected to the plurality of word lines;
A vertical scanning circuit having a gate connected to each of the plurality of vertical selection transistors;
A horizontal selection transistor having a source connected to each of the plurality of bit lines;
A horizontal scanning circuit to which a gate of each of the plurality of horizontal transistors is connected;
An ISFET cell disposed at an intersection of the word line and the bit line,
The ISFET cell is
A semiconductor substrate having a first conductivity type;
A first well region disposed on the semiconductor substrate and having a second conductivity type opposite to the first conductivity type;
A source region and a drain region disposed on the first well region and having a first conductivity type;
A gate insulating film disposed on the first well region;
An ion sensitive film disposed on the gate insulating film;
A storage capacitor connected between the source region and the drain region;
A liquid sample in contact with the ion sensitive membrane;
A passivation film disposed on the source region and the drain region;
An image sensor comprising: a pseudo-reference electrode disposed on the passivation film so as to be in contact with the liquid sample. The ISFET cell is further disposed on the semiconductor substrate and has a second well region having a first conductivity type,
A second well contact region disposed on the second well region and having a first conductivity type;
The image sensor according to claim 15, further comprising: a capacitor electrode disposed on the gate insulating film on the second well region and forming the storage capacitor with the second well region.   The drain region is connected to the capacitor electrode, the source region is connected to the well contact region, and the storage capacitor is provided in parallel between the drain region and the source region. The image sensor described. 18. The image sensor according to claim 16, wherein the ISFET cell further includes a transfer gate electrode disposed adjacent to the drain region on the gate insulating film. A power supply voltage connected to a power supply line obtained by commonly connecting the drains of the plurality of horizontal selection transistors;
The image sensor according to any one of claims 15 to 18, further comprising a MOSFET connected between an output terminal obtained by commonly connecting sources of the plurality of vertical selection transistors and a ground potential. A MOSFET connected between an output terminal obtained by commonly connecting the drains of the plurality of horizontal selection transistors and a ground potential;
The image sensor according to claim 15, further comprising: a power supply voltage connected to a power supply line obtained by commonly connecting sources of the plurality of vertical selection transistors.

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