JP2011085557A - Semiconductor sensor and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor sensor which extends a sensing area of the semiconductor sensor and improves the detection accuracy. <P>SOLUTION: A sensitive film 4 is deposited on a silicon substrate 2 and formed with a sensing area 6 to which a to-be-detected object is attached. A P<SP>+</SP>diffusion layer (a P pocket) 7 is formed under the sensing area 6 in the sensitive film 4 within the silicon substrate 2. A N<SP>+</SP>diffusion layer 8 forms a P/N junction having a junction plane 50 facing the sensing area 6 between it and the P pocket 7. A P<SP>+</SP>diffusion layer 9 forms a source/drain along with the N<SP>+</SP>diffusion layer 8. A DC power supply 11 applies a reverse bias voltage between the P pocket 7 and the N<SP>+</SP>diffusion layer 8. A DC power supply 15 applies a voltage between the N<SP>+</SP>diffusion layer 8 and the P<SP>+</SP>diffusion layer 9 so as to flow a drain current corresponding to the quantity of the to-be-detected object attached to the sensing area 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor sensor and a manufacturing method for detecting a detection target attached to a sensing region.

  An FET (field effect transistor) such as a MOSFET widely used in an integrated circuit or the like can be applied to a charge sensor that detects an ion concentration in a solution. When an FET gate insulating film (hereinafter abbreviated as a gate) is exposed to a solution as a sensing region, ions in the solution adhere to the gate. The amount of ions attached changes the state of the channel between the source and drain, and changes the ease of current flow through the channel. Since the amount of ions attached to the gate is proportional to the ion concentration in the solution, the ion concentration in the solution can be measured by measuring the current flowing in the channel.

  An FET used as a charge sensor is also referred to as an ISFET (ion-sensitive field effect transistor) (see, for example, Patent Documents 1 to 4). ISFET has been applied to biosensing and the like in recent years in addition to the above-described ion sensing.

  On the other hand, a transistor whose operation principle is different from that of a normal FET has been proposed (for example, see Non-Patent Document 1). A main structural feature of this transistor is that a vertically stacked P / N junction is provided at the source. The vertically stacked P / N junction is a P / N junction in which a P-type semiconductor layer and an N-type semiconductor layer are stacked in the vertical direction. The vertically stacked P / N junction is formed immediately below the gate, and the junction surface faces the gate.

  In this transistor, when the potential on the gate side is changed, the distance between the valence band and the conduction band is shortened by largely bending the band of the vertically stacked P / N junction. For this reason, an interband tunneling current flows due to the tunnel effect. The operation principle of this transistor using the tunnel effect is completely different from that of a normal FET that controls the lateral current flowing in the channel formed under the gate.

JP-A-6-249824 JP 2000-187018 A JP 2002-156357 A Special table 2008-542733 gazette

Chenming Hu, Daniel Chou, Pratik Patel, Anupama Bowonder, "Green Transistor-A VDD Scaling Path for Future Low Power ICs", VLSI-TSA2008, P.14

  In an ISFET, a change in output occurs only after a substance to be detected is attached to a gate. From this point of view, the detection sensitivity of the ISFET should be improved if the area of the gate is increased and the amount of attached charge is increased.

  However, this idea is not necessarily correct. The current of the ISFET is proportional to the gate width (size in the direction perpendicular to the direction in which the drain current flows), but inversely proportional to the gate length (size in the direction parallel to the direction in which the current flows). For this reason, even if the sensing area is simply expanded (that is, both the gate width and gate length are increased), the increase in the amount of charge adhering to the increased area is offset by the decrease in current due to the increased gate length. Therefore, the detection sensitivity is not improved.

  This problem can be mitigated by increasing the gate width while reducing only the gate length using advanced manufacturing technology, but new manufacturing problems such as lower yields and higher costs during manufacturing. Will be held.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the semiconductor sensor and manufacturing method which can improve a detection sensitivity.

In order to achieve the above object, a semiconductor sensor according to the first aspect of the present invention includes:
A sensitive film formed on a semiconductor substrate and formed with a sensing region to which a detection target is attached;
A first impurity diffusion layer formed below the sensing region in the semiconductor substrate;
A second impurity diffusion layer that forms a P / N junction having a bonding surface facing the sensing region with the first impurity diffusion layer;
A third impurity diffusion layer forming a source / drain together with the second impurity diffusion layer;
First voltage applying means for applying a reverse bias voltage between the second impurity diffusion layer and the first impurity diffusion layer;
A second voltage application for applying a voltage between the second impurity diffusion layer and the third impurity diffusion layer in order to flow a drain current corresponding to the amount of the detection target attached to the sensing region. Means,
Is provided.

In this case, the sensitive membrane is
It is an ion sensitive membrane that attaches hydrogen ions in solution.
It is good as well.

In the sensitive membrane,
An antibody that attaches the antigen to be detected is fixed to the sensing region,
It is good as well.

The semiconductor substrate is P-type,
The first and third impurity diffusion layers are P-type;
The second impurity diffusion layer is N-type;
It is good as well.

The semiconductor substrate is N-type;
The first and third impurity diffusion layers are N-type;
The second impurity diffusion layer is P-type;
It is good as well.

The manufacturing method according to the second aspect of the present invention includes:
A method for manufacturing a semiconductor sensor of the present invention, comprising:
A first step of forming an impurity diffusion layer as a source in a predetermined region in the semiconductor substrate;
A second step of forming an impurity diffusion layer forming a P / N junction with the impurity diffusion layer at a depth shallower than the impurity diffusion layer in a region where the impurity diffusion layer is formed; When,
A third step of forming a sensitive film on which a sensing region for attaching a detection target is formed on the impurity diffusion layer formed by the second step;
including.

  According to the semiconductor sensor of the present invention, the first and second impurity diffusion layers below the sensing region of the sensitive film are vertically stacked P / N junctions having a joint surface facing the sensing region. Is formed. A reverse bias voltage is applied to the vertically stacked P / N junctions.

  When the detection target is attached to the sensing region, the band of the vertically stacked P / N junction changes according to the charge, and the interband distance between the valence band and the conduction band of the first and second impurity diffusion layers is changed. Shorter. For this reason, the band-to-band tunneling current flows through the vertically stacked P / N junction due to the tunnel effect. Due to the voltage applied between the second impurity diffusion layer and the third impurity diffusion layer, the interband tunneling current is output as the drain current.

  The magnitude of the drain current is proportional to the amount of detection target attached to the sensing region. Based on this linearity, the amount of adhesion of the detection target can be detected.

  The linearity is maintained even when the detection target is not uniformly attached to the sensing region. Therefore, in this semiconductor sensor, as the sensing area is expanded, the amount of adhesion of the detection target increases, and the band-to-band tunneling current, that is, the drain current also increases. Therefore, the detection sensitivity can be improved as the sensing area is expanded.

  Also, according to the semiconductor sensor of the present invention, since the detection sensitivity does not decrease even when the gate length is increased, it is possible to prevent a decrease in manufacturing yield and an increase in manufacturing cost.

It is sectional drawing which shows typically the structure of the transistor which comprises the semiconductor sensor which concerns on one Embodiment of this invention. It is sectional drawing which shows typically the whole structure of the semiconductor sensor of FIG. FIG. 2 is a band diagram of the transistor of FIG. 1 when a detection target is not attached. FIG. 2 is a band diagram of the transistor of FIG. 1 when a detection target is attached. It is sectional drawing for demonstrating the interband tunneling electric current which generate | occur | produces when one hydrogen ion adheres to a sensing area | region. It is sectional drawing for demonstrating the interband tunneling electric current which generate | occur | produces when two or more hydrogen ions adhere to a sensing area | region. It is sectional drawing of a semiconductor sensor with a small size of a sensing area. It is sectional drawing of a semiconductor sensor with a large size of a sensing area. It is sectional drawing of ISFET with a small size of a sensing area. It is sectional drawing of ISFET with a large sensing area size. It is a flowchart of the manufacturing process of the semiconductor sensor of FIG. It is sectional drawing (the 1) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing (the 2) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing (the 3) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing (the 4) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing for demonstrating the manufacturing process of a semiconductor sensor (the 5). It is sectional drawing (the 6) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing (the 7) for demonstrating the manufacturing process of a semiconductor sensor. It is sectional drawing for demonstrating the manufacturing process of a semiconductor sensor (the 8). It is sectional drawing (the 1) which shows an example of a structure of an antigen detection sensor. It is sectional drawing (the 2) which shows an example of a structure of an antigen detection sensor. FIG. 7 is a cross-sectional view illustrating a modification of the transistor in FIG.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings. The semiconductor sensor according to the present embodiment is a pH sensor that detects a hydrogen ion concentration in a solution, that is, pH.

  First, the structure of a transistor that is the basis of a semiconductor sensor will be described. As shown in FIG. 1, the transistor 1 according to the present embodiment is formed on a P-type silicon substrate 2 as a semiconductor substrate.

An insulating film 3 is formed on the silicon substrate 2. As the insulating film 3, for example, a SiO ₂ film or the like is used.

A sensitive film 4 is formed on the insulating film 3. The sensitive film 4 is an ion sensitive film that adheres hydrogen ions in a solution. As the sensitive film 4, for example, a film to which hydrogen ions are attached such as SiO ₂ , Si ₃ N ₃ , Al ₂ O ₃ , Ta ₂ O ₅ film can be used.

  On the sensitive film 4, an interlayer insulating film 5 is deposited. The region where the interlayer insulating film 5 is not deposited and the sensitive film 4 is exposed comes into direct contact with the solution whose pH is to be measured. Hereinafter, this region is also referred to as “sensing region 6”. When hydrogen ions adhere to the sensing region 6, the pH of the solution is detected.

A P ⁺ diffusion layer 7 as a first impurity diffusion layer is formed in the silicon substrate 2 below the sensing region 6. The P ⁺ diffusion layer 7 covers almost the entire sensing region 6. For example, an impurity such as boron (B) is added to the P ⁺ diffusion layer 7. Hereinafter, the P ⁺ diffusion layer 7 is also referred to as a P pocket 7.

Further, an N ⁺ diffusion layer 8 as a second impurity diffusion layer is formed in the silicon substrate 2. For example, an impurity such as phosphorus (P) is added to the N ⁺ diffusion layer 8. This N ⁺ diffusion layer 8 is the source of the transistor 1.

The P pocket 7 and the N ⁺ diffusion layer 8 form a vertically stacked P / N junction. This vertically stacked P / N junction is formed below the sensing region 6 and has a joint surface 50 facing the sensing region 6 (substantially parallel). The joint surface 50 of the vertically stacked P / N joint covers almost the entire sensing region 6.

Further, a P ⁺ diffusion layer 9 as a third impurity diffusion layer is formed in the silicon substrate 2. The P ⁺ diffusion layer 9 is formed at a predetermined interval from the N ⁺ diffusion layer 8. The P ⁺ diffusion layer 9 together with the N ⁺ diffusion layer 8 forms the source / drain of the transistor 1. That is, the P ⁺ diffusion layer 9 is the drain of the transistor 1.

  As shown in FIG. 2, the semiconductor sensor 100 according to the present embodiment is configured around the transistor 1 of FIG. The semiconductor sensor 100 further includes a reference electrode 10, a DC power supply 11, a solution tank 12, a DC power supply 15, and an ammeter 16.

The reference electrode 10 is installed above the sensing area 6. The reference electrode 10 is connected to the negative electrode side of the DC power supply 11. On the other hand, the positive electrode side of the DC power supply 11 is connected to the N ⁺ diffusion layer 8 as a source. Thereby, a reverse bias voltage is applied to the vertically stacked P / N junction formed by the N ⁺ diffusion layer 8 and the P ⁺ diffusion layer 7. The reference electrode 10 and the DC power source 11 form a first voltage applying unit. The silicon substrate 2 is also connected to the positive electrode side of the DC power supply 11.

  A solution basket 12 is formed on the sensitive film 4. The solution basket 12 is filled with the solution 13 to be detected. The solution 13 contains hydrogen ions 14. A part of the hydrogen ions 14 adheres to the sensing region 6.

An N ⁺ diffusion layer (source) 8 is connected to the positive electrode side of the DC power supply 15, and a P ⁺ diffusion layer (drain) 9 is connected to the negative electrode side. The DC power supply 15 applies a voltage between the N ⁺ diffusion layer (source) 8 and the P ⁺ diffusion layer (drain) 9. This voltage causes a drain current corresponding to the amount of hydrogen ions 14 attached to the sensing region 6 to flow. The ammeter 16 measures the drain current. Note that the silicon substrate 2 is also connected to the positive electrode side of the DC power supply 15.

  Next, the operation of the semiconductor sensor 100 according to one embodiment of the present invention will be described.

  First, the operation principle of the semiconductor sensor 100 will be described. 3 and 4 show band diagrams of energy levels in the transistor 1.

  When the sensing region 6 is not attached with hydrogen ions 14 and the potential on the gate side does not change as shown in FIG. 3, the sensing region 6 is turned off, no tunnel effect occurs, and a vertically stacked P / N junction. The band-to-band tunneling current does not flow through the joint surface 50.

On the other hand, the sensing region 6, the hydrogen ions 14 are attached, as shown in FIG. 4, the potential V _G changes the gate side, it turned on, string-effect P / N junction of the band is bent greatly. The bending of this band shortens the distance between the valence band of the P pocket 7 and the conduction band of the N ⁺ diffusion layer (source) 8, so that the tunnel effect causes the N ⁺ diffusion layer (source) from the P pocket 7. Electrons tunnel to 8 and an interband tunneling current flows through the junction surface 50 of the P / N junction.

  As described above, the operating principle of the semiconductor sensor 100 is completely different from that of a general MOSFET that controls a lateral current flowing in a channel formed under the gate.

Here, consider a case where one hydrogen ion 14 is attached to the sensing region 6 as shown in FIG. In this case, an interband tunneling current 17 is generated by a tunnel effect at a position corresponding to the location where the hydrogen ions 14 are attached in the sensing region 6. Since a voltage is applied between the N ⁺ diffusion layer (source) 8 and the P ⁺ diffusion layer (drain) 9, the generated tunneling current 17 is finally output as a drain current 18.

  Furthermore, as shown in FIG. 6, a case where a plurality of hydrogen ions 14 are attached to the sensing region 6 will be considered. Also in this case, a plurality of band-to-band tunneling currents 17 are generated by the tunnel effect at positions corresponding to the locations where the hydrogen ions 14 are attached in the sensing region 6. The band-to-band tunneling currents 17 are bundled and finally output as a drain current 18.

  As can be seen from a combination of FIGS. 5 and 6, the magnitude of the drain current 18 that is output depends on the amount of hydrogen ions 14 attached to the sensing region 6. That is, the higher the concentration of hydrogen ions 14 in the solution 13, the greater the number of hydrogen ions 14 adhering to the sensing region 6 and the larger the drain current 18.

  Thus, in the semiconductor sensor 100, the relationship between the concentration of the hydrogen ions 14 in the solution 13 and the drain current 18 is linear. Therefore, if the drain current 18 is measured, the pH of the solution 13 can be obtained from the measured value. The drain current 18 is measured by an ammeter 16. From the measured value, the pH of the solution 13 can be obtained.

  Since the drain current 18 is the sum of the generated band-to-band tunneling currents 17, the relationship between the concentration of the hydrogen ions 14 in the solution 13 and the drain current 18 is excellent in linearity. This point is also very different from a general MOSFET that controls a lateral current flowing in a channel formed under a gate.

  In the semiconductor sensor 100, the detection sensitivity can be increased as the sensing area 6 is increased. As shown in FIG. 7, when the sensing region 6 of the semiconductor sensor 100 is small and the gate length is short, the amount of the hydrogen ions 14 attached decreases, so that the generated drain current 18 decreases.

  On the other hand, as shown in FIG. 8, when the sensing region 6 of the semiconductor sensor 100 is large and the gate length is long, the amount of hydrogen ions 14 attached increases, so that the generated drain current 18 also increases.

  On the other hand, as shown in FIG. 9, in the ISFET 200, when the sensing region 6 is small and the gate length is short, the amount of hydrogen ions 14 attached decreases, but in the gate length direction of the sensing region 6, Therefore, the drain current 18 corresponding to the amount of hydrogen ions 14 flows.

  However, as shown in FIG. 10, when the sensing region 6 becomes large and the gate length becomes long, the attachment state of the hydrogen ions 14 to the sensing region 6 in the gate length direction becomes non-uniform. For this reason, the channel of the portion where the hydrogen ions 14 are not attached becomes narrow, and the drain current 18 becomes difficult to flow.

As described above, in the semiconductor sensor 100, the band-to-band tunneling current 17 that is the source of the drain current 18 flows in the vertical direction in the overlapping portion of the N ⁺ diffusion layer (source) 8 and the gate (sensing region 6). When 6 is expanded, the current driving force is rather lowered rather than improved.

  That is, in the semiconductor sensor 100, the increase in the sensing region 6, that is, the increase in the product of the gate width and the length of the overlapping portion of the source and gate results in an increase in the amount of charges attached to the hydrogen ions 14 and the output drain current 18. Directly connected to the increase. On the other hand, in the ISFET 200, the increase in the sensing region 6 causes a decrease in the current driving force.

  That is, the semiconductor sensor 100 according to the present embodiment is significantly different from the ISFET 200 in that the larger the sensing region 6 is, the larger current driving force can be obtained and the detection sensitivity can be improved.

  Next, the manufacturing process of the semiconductor sensor 100 will be described.

First, as shown in FIG. 11, element isolation is performed on the P-type silicon substrate 2 (step S1). More specifically, for example, as shown in FIG. 12, a field oxide film (SiO ₂ ) 20 is formed. Field oxide film 20 separates the active region therebetween. Elements are formed in the active region surrounded by the field oxide film 20.

  This element isolation process is a process for electrically isolating a plurality of elements formed on the same silicon substrate so as not to exert a parasitic effect.

  Returning to FIG. 11, subsequently, the source is formed on the silicon substrate 2 on which the field oxide film 20 is formed (step S2). More specifically, for example, as shown in FIG. 13, a photoresist 21 is applied on the silicon substrate 2, and exposure, development, and etching are performed, and the photoresist 21 corresponding to the source is removed. Subsequently, P ions 60 are implanted into the silicon substrate 2.

As a result, P ions 60 are implanted only in the region where the photoresist 21 is not applied. As a result, an N ⁺ diffusion layer (source) 8 is formed. After implantation of P ions 60, the photoresist 21 is removed.

Returning to FIG. 11, subsequently, drain formation is performed on the silicon substrate 2 on which the N ⁺ diffusion layer (source) 8 is formed (step S3). More specifically, for example, as shown in FIG. 14, a photoresist 21 is applied on the silicon substrate 2, and exposure, development, and etching are performed, and the photoresist 21 corresponding to the drain is removed. Then, B ions 61 are implanted into the silicon substrate 2.

Thereby, the B ions 61 are implanted only in the region where the photoresist 21 is not applied. As a result, a P ⁺ diffusion layer (drain) 9 is formed. The depth of the P ⁺ diffusion layer (drain) 9 is almost the same as that of the N ⁺ diffusion layer (source) 8. After the B ions 61 are implanted, the photoresist 21 is removed.

  Note that the order of steps S2 and S3 may be reversed.

Returning to FIG. 11, subsequently, P pocket formation is performed on the silicon substrate 2 on which the N ⁺ diffusion layer (source) 8 and the P ⁺ diffusion layer (drain) 9 are formed (step S4). More specifically, for example, as shown in FIG. 15, a photoresist 21 is applied on the silicon substrate 2, exposure, development, and etching are performed, and only the photoresist 21 in the region where the P pocket 7 is formed is removed. It is. Subsequently, P ions 60 are implanted into the silicon substrate 2.

As a result, P ions 60 are implanted only in the region where the photoresist 21 is not applied, and the P pocket 7 is formed. The depth of the P pocket 7 is shallower than that of the N ⁺ diffusion layer (source) 8. As a result, a vertically stacked P / N junction of the P pocket 7 and the N ⁺ diffusion layer (source) 8 is formed. After the ion implantation, the photoresist 21 is removed.

Returning to FIG. 11, subsequently, the insulating film 3 and the sensitive film 4 are formed on the silicon substrate 2 on which the N ⁺ diffusion layer (source) 8, the P ⁺ diffusion layer (drain) 9 and the P pocket 7 are formed. Is performed (step S5). More specifically, for example, as shown in FIG. 16, an insulating film 3 is formed on the silicon substrate 2 by using, for example, a thermal oxidation method, and the sensitive film is formed thereon by using, for example, a sputtering method. A film 4 is formed. The type of the sensitive film 4 is as described above, and a film forming method is appropriately selected according to the type.

  Returning to FIG. 11, subsequently, the interlayer insulating film 5 is deposited and the contact holes are formed on the silicon substrate 2 on which the insulating film 3 and the sensitive film 4 are formed (step S6). More specifically, as shown in FIG. 17, an interlayer insulating film 5 is deposited on the sensitive film 4 by using, for example, a chemical vapor deposition (CVD) method or the like. After this deposition, one contact hole is formed in each of the source and drain.

  Returning to FIG. 11, subsequently, an Al electrode is formed (step S7). More specifically, as shown in FIG. 18, an Al electrode 22 that is connected to the source and drain through the formed contact hole is formed by sputtering or the like. DC power supplies 11 and 15, an ammeter 16 and the like are connected to the Al electrode 22.

Returning to FIG. 11, finally, the sensing region 6 is formed (step S8). More specifically, as shown in FIG. 19, the sensing region 6 is formed by etching the interlayer insulating film 5 by SiO ₂ etching. The sensing region 6 is formed on the P pocket 7.

  The semiconductor sensor 100 according to the present embodiment is manufactured in this way. There is no restriction | limiting in particular in the size of the semiconductor sensor 100 to manufacture, The magnitude | size of the sensing area | region 6 can be suitably determined according to a detection target.

As described above in detail, according to the present embodiment, the P pocket 7 and the N ⁺ diffusion layer (source) 8 below the sensing region 6 of the sensitive film 4 are opposed to the sensing region 6. A vertically stacked P / N junction having 50 is formed. A reverse bias voltage is applied to the vertically stacked P / N junctions.

When the hydrogen ions 14 adhere to the sensing region 6, the band of the vertically stacked P / N junction changes according to the charge of the attached hydrogen ions 14, and the valence band of the P pocket 7 and the N ⁺ diffusion layer (source) 8 The distance to the conduction band is shortened. For this reason, the band-to-band tunneling current 17 flows through the junction surface 50 of the P / N junction due to the tunnel effect. Due to the voltage applied between the N ⁺ diffusion layer (source) 8 and the P ⁺ diffusion layer (drain) 9, the interband tunneling current 17 is output as the drain current 18.

  The magnitude of the drain current 18 is proportional to the amount of hydrogen ions 14 attached to the sensing region 6 (that is, the concentration of the hydrogen ions 14). Based on this linearity, the pH can be detected. In principle, this linearity is maintained in a wide range, so that it is excellent in linearity and enables high-precision sensing with a wide dynamic range.

  In addition, the linearity is maintained even when the hydrogen ions 14 are not uniformly attached to the sensing region. Therefore, in the semiconductor sensor 100, as the sensing region 6 is expanded, the adhesion amount of the hydrogen ions 14 increases, and the interband tunneling current 17, that is, the drain current 18, also increases. Due to this property, the detection sensitivity of the semiconductor sensor 100 can be increased as the sensing area 14 is expanded.

  That is, according to the semiconductor sensor 100 according to the present embodiment, the detection sensitivity can be easily improved by increasing the element size. Integrated circuits have been improved in performance based on a so-called scaling law in which performance and integration can be improved by miniaturization of a conventional MOSFET. On the other hand, the semiconductor sensor 100 according to the present embodiment can improve performance by increasing the area of the sensing region 6. That is, it can be said that the semiconductor sensor 100 has a feature called inverse scaling.

  The inverse scaling characteristic leads to being able to be manufactured with a simple manufacturing technique. As a result, it is possible to prevent a decrease in manufacturing yield and an increase in manufacturing cost.

  Moreover, if the area of the sensing region 6 is increased, a large current driving force can be obtained with a small gate voltage (voltage of the DC power supply 11). This feature also contributes to further improvement in detection sensitivity.

  The semiconductor sensor 100 according to the above embodiment is a sensor that detects the pH of the solution. However, the ions attached to the sensing region 6 may be other than the hydrogen ions 14. In this case, the semiconductor sensor 100 can be operated not as a pH sensor but as an ion sensor that detects the content of specific ions.

  The present invention is also applicable to an antigen detection sensor that detects an antigen.

  FIG. 20 shows a cross-sectional view of a semiconductor sensor 101 as an antigen detection sensor. As shown in FIG. 20, in the sensitive membrane 4, the antibody 30 is fixed to almost the entire surface of the sensing region 6.

  In the solution 35, different types of antigens 40, 41, and 42 are mixed. The antibody 30 attaches only the antigen 40 among the antigens 40-42.

  Similar to the semiconductor sensor 100 according to the embodiment, a drain current corresponding to the amount of the antigen 40 attached to the antibody 30 flows through the semiconductor sensor 101. Therefore, if the drain current is measured, the amount of the antigen 40 in the solution 35 can be measured.

  FIG. 21 shows a cross-sectional view of a semiconductor sensor 102 as an antigen detection sensor. As shown in FIG. 21, the semiconductor sensor 102 is different from the semiconductor sensor 101 of FIG. 20 in that the antibody 31 is fixed to the sensitive film 4 instead of the antibody 30. Antibody 31 attaches only antigen 41 among antigens 40-42. Therefore, the semiconductor sensor 102 can measure the amount of the antigen 41 in the solution.

  Thus, the antigen to be detected can be changed (antigen 40 → antigen 41) simply by changing the antibody of the sensitive membrane 3 (antibody 30 → antibody 31).

  As described above, the present invention can also be applied to biosensing. The present invention can be applied to any organic substance having electrical polarity.

  In the above embodiment, the silicon substrate 2 is P-type, the first and third impurity diffusion layers are P-type, and the second impurity diffusion layer is N-type. However, the present invention is not limited to this. As shown in FIG. 22, the silicon substrate 2 may be N-type, the first and third impurity diffusion layers may be N-type, and the second impurity diffusion layer may be P-type. Which type is selected can be appropriately determined in consideration of the detection target and the like.

  In the above-described embodiment, the joint surface 50 of the vertically stacked P / N junction is formed so as to cover almost the entire sensing region 6, but it is only necessary to cover most of the sensing region 6. However, it is most desirable that the joint surface 50 of the vertically stacked P / N joint covers the entire sensing region 6.

  In addition to the hydrogen ions 14 and the antigens 40 and 41, various objects such as a specific gas or an organic substance can be set as the detection target attached to the sensing region 6. Even if it is not charged per se, detection may be possible by binding to a charged substance.

  The present invention is suitable for detection of substances having electrical polarity such as ions. In particular, the present invention is suitable for measuring the pH of a solution, detecting an antibody, detecting a specific gas, and the like. Even if the substance to be detected does not have electrical polarity, it is possible to detect the substance by attaching a charged substance to the substance.

DESCRIPTION OF SYMBOLS 1 Transistor 2 Silicon substrate 3 Insulating film 4 Sensitive film 5 Interlayer insulating film 6 Sensing area 7 P ⁺ diffusion layer (P pocket)
8 N ⁺ diffusion layer (source)
9 P ⁺ diffusion layer (drain)
DESCRIPTION OF SYMBOLS 10 Reference electrode 11 DC power supply 12 Solution bottle 13 Solution 14 Hydrogen ion 15 DC power supply 16 Ammeter 17 Band-band tunneling current 18 Drain current 20 Field oxide film 21 Photoresist 22 Al electrode 30, 31 Antibody 35 Solution 40, 41, 42 Antigen 50 Joint surface 60 P ion 61 B ion 100, 101, 102 Semiconductor sensor 200 ISFET

Claims (6)

A sensitive film formed on a semiconductor substrate and formed with a sensing region to which a detection target is attached;
A first impurity diffusion layer formed below the sensing region in the semiconductor substrate;
A second impurity diffusion layer that forms a P / N junction having a bonding surface facing the sensing region with the first impurity diffusion layer;
A third impurity diffusion layer forming a source / drain together with the second impurity diffusion layer;
First voltage applying means for applying a reverse bias voltage between the second impurity diffusion layer and the first impurity diffusion layer;
A second voltage application for applying a voltage between the second impurity diffusion layer and the third impurity diffusion layer in order to flow a drain current corresponding to the amount of the detection target attached to the sensing region. Means,
A semiconductor sensor comprising: The sensitive membrane is
It is an ion sensitive membrane that attaches hydrogen ions in solution.
The semiconductor sensor according to claim 1. In the sensitive membrane,
An antibody that attaches the antigen to be detected is fixed to the sensing region,
The semiconductor sensor according to claim 1. The semiconductor substrate is P-type;
The first and third impurity diffusion layers are P-type;
The second impurity diffusion layer is N-type;
The semiconductor sensor according to claim 1, wherein the semiconductor sensor is a semiconductor sensor. The semiconductor substrate is N-type;
The first and third impurity diffusion layers are N-type;
The second impurity diffusion layer is P-type;
The semiconductor sensor according to claim 1, wherein the semiconductor sensor is a semiconductor sensor. A method of manufacturing a semiconductor sensor according to claim 1,
A first step of forming an impurity diffusion layer as a source in a predetermined region in the semiconductor substrate;
A second step of forming an impurity diffusion layer that forms a P / N junction with the impurity diffusion layer at a depth shallower than the impurity diffusion layer in a region where the impurity diffusion layer is formed; When,
A third step of forming a sensitive film in which a sensing region for attaching a detection target is formed on the impurity diffusion layer formed by the second step;
Manufacturing method.

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