Ion sensor manufacturing method, ion sensor adjustment method, and ion sensor system

Abstract

To provide a method of manufacturing ion sensors with reduced drift, and others.SOLUTION: An ion sensor manufacturing method disclosed herein comprises a first voltage application step of applying a first voltage to a gate to an ISFET (Ion Sensitive Field Effect Transistor), and a light irradiation step of irradiating the ISFET with light while being applied with the first voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a manufacturing method for an ion sensor that detects ions in an electrolyte, a method for adjusting an ion sensor, and an ion sensor system. [Background technology]

[0002] As an example of an ion sensor that detects ions in an electrolyte, one that uses an ISFET (Ion Selective Field Effect Transistor) is known. Examples of such an ion sensor are disclosed in Non-Patent Documents 1 and 2. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] P. Bergveld, Sensors and Actuators B 88 (2003) 1-20 [Non-Patent Document 2] S. Sinha et al., Microelectronics Journal 97 (2020) 104710 Summary of the Invention [Problem to be solved by the invention]

[0004] One aspect of the present disclosure provides a method for manufacturing an ion sensor with reduced drift. [Means for solving the problem]

[0005] A method for manufacturing an ion sensor according to one embodiment of the present disclosure includes a first voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor), and a light irradiation step of irradiating light to the ISFET while the first voltage is being applied.

[0006] Furthermore, an adjustment method for an ion sensor according to one embodiment of the present disclosure includes a voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor), and a light irradiation step of irradiating light to the ISFET in a state in which the first voltage is applied.

[0007] Moreover, an ion sensor system according to one embodiment of the present disclosure includes an ISFET (Ion Selective Field Effect Transistor), a power supply device for applying a voltage to a gate of the ISFET, a light source device for irradiating light to the ISFET, and a control device for controlling the application of the voltage by the power supply device and the irradiation of light by the light source device. Effect of the Invention

[0008] According to one aspect of the present disclosure, it is possible to realize a manufacturing method for an ion sensor with reduced drift. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a configuration of an ion sensor system according to a first embodiment. [Diagram 2] 5 is a flowchart showing an example of a manufacturing method or an adjustment method of the ion sensor in the ion sensor system according to the first embodiment. [Diagram 3] FIG. 1 shows the outline of a CV curve in an ISFET. [Figure 4] FIG. 13 is a diagram showing experimental results regarding reduction of drift. [Diagram 5] FIG. 13 is a diagram showing the results of Experimental Example 2. [Figure 6] FIG. 13 is a diagram showing the results of Experimental Example 3. [Figure 7] FIG. 13 is a diagram showing the results of Experimental Example 4. [Figure 8] FIG. 13 is a diagram showing the results of Experimental Example 5. [Figure 9] FIG. 11 is a diagram showing an example of the configuration of an ion sensor system according to a second embodiment. [Figure 10] FIG. 11 is a diagram showing an example of the configuration of an ion sensor system according to a third embodiment. [Figure 11] FIG. 13 is a diagram showing an example of a configuration of an ion sensor system according to a modified example of the third embodiment. [Figure 12] FIG. 13 is a diagram showing a configuration of an ISFET according to a fourth embodiment. [Figure 13] 13 is a graph showing the results of an experiment on drift of the ISFET according to the fourth embodiment. [Figure 14] This is a diagram summarizing the seven types of data shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment 1] Hereinafter, one embodiment of the present disclosure will be described in detail.

[0011] (Configuration of ion sensor system) Fig. 1 is a diagram showing an example of the configuration of an ion sensor system 1 according to embodiment 1. The ion sensor system 1 is a sensor system that measures the ion concentration in an electrolyte to be measured. As shown in Fig. 1, the ion sensor system 1 includes an ISFET (Ion Selective Field Effect Transistor) 10, a power supply device 20, a light source device 31, and a control device 40. The ion sensor system 1 further includes an electrolyte tank 60.

[0012] The ISFET 10 is an element that functions as an ion sensor. The ISFET 10 includes a source 11, a drain 12, a channel region 13, a gate 50, a thermal oxide film 14, an ion-sensitive film 15, and a semiconductor substrate 19. The ISFET 10 has a structure in which the thermal oxide film 14 and the ion-sensitive film 15 are stacked in this order on the semiconductor substrate 19. The source 11 and the drain 12 may be embedded in the semiconductor substrate 19 so as not to contact each other and so as to contact the thermal oxide film 14, respectively. In other words, the source 11 and the drain 12 may be embedded in the semiconductor substrate 19 so as to be aligned with the semiconductor substrate 19 and so as to contact the thermal oxide film 14, respectively.

[0013] The semiconductor substrate 19 is a substrate on which the ISFET 10 is formed. The semiconductor substrate 19 may be a p-type semiconductor or an n-type semiconductor. In this embodiment, the semiconductor substrate 19 may be formed of a p-type semiconductor. Specifically, the semiconductor substrate 19 may be formed of p-Si.

[0014] The source 11 and the drain 12 are electrodes for extracting a signal according to the amount of ions. The source 11 and the drain 12 may be a p-type semiconductor or an n-type semiconductor. When the semiconductor substrate 19 is a p-type semiconductor, the source 11 and the drain 12 may be an n-type semiconductor. When the semiconductor substrate 19 is an n-type semiconductor, the source 11 and the drain 12 may be a p-type semiconductor. In this embodiment, the source 11 and the drain 12 may be formed of an n-type semiconductor. Specifically, the source 11 and the drain 12 may be formed of n-Si.

[0015] The gate 50 is an electrode for controlling the current between the source 11 and the drain 12. When a voltage is applied to the gate 50, a current flows between the source 11 and the drain 12. In the following description, the magnitude of the voltage applied to the gate 50 at which a current flows between the source 11 and the drain 12 is referred to as a threshold voltage. The gate 50 may also function as a reference electrode.

[0016] The channel region 13 is a region in the semiconductor substrate 19 through which a current flows from the source 11 to the drain 12 when a voltage equal to or greater than a threshold voltage is applied to the gate 50. The material of the channel region 13 may be the same as the material of the semiconductor substrate 19.

[0017] However, the combination of semiconductors constituting the semiconductor substrate 19, the channel region 13, the source 11, and the drain 12 is not limited to the above example. For example, the source 11 and the drain 12 may be made of p-Si, and the semiconductor substrate 19 and the channel region 13 may be made of n-Si.

[0018] The thermal oxide film 14 is an insulating film that provides insulation between the channel region 13 and the gate 50. The thermal oxide film 14 may be made of, for example, SiO2. The thickness of the thermal oxide film 14 is not particularly limited as long as sufficient insulation is obtained, and may be, for example, 10 nm.

[0019] The ion-sensitive film 15 is a film whose potential changes according to the amount of ions on the surface. The ion-sensitive film 15 may be a film having a functional group on the surface that reacts with ions. The ion-sensitive film 15 may be a film formed of an inorganic material including, for example, Si3N4, Al2O3 (alumina), Ta2O5, HfO2, or ZrO2. The functional group that reacts with ions may be, for example, a hydroxyl group or a silanol group. The ion-sensitive film 15 may be an alumina film formed by, for example, an ALD (Atomic Layer Deposition) method. The ion-sensitive film 15 may be an alumina film formed by, for example, a sputtering method. The thickness of the ion-sensitive film 15 is not particularly limited as long as sufficient ion sensitivity is obtained, and may be, for example, 30 nm.

[0020] The power supply 20 applies a voltage to the gate 50 of the ISFET 10. The positive terminal of the power supply 20 is connected to the gate 50. The negative terminal of the power supply 20 is grounded.

[0021] The light source device 31 is a device that irradiates light onto the ISFET 10. Specifically, the light source device 31 may be arranged so as to irradiate light onto at least a region between the source 11 and the drain 12 of the ISFET 10. The light source device 31 may irradiate light onto the entire ISFET 10. By irradiating light onto the ISFET 10, drift in the ISFET 10 can be reduced, as described below. The light source device 31 may be arranged so as to irradiate light onto the ISFET 10. The light source device 31 may be arranged on the ion-sensitive membrane 15 side of the ISFET 10 or on the semiconductor substrate 19 side, but the arrangement position of the light source device 31 is not limited thereto. The light-emitting element included in the light source device 31 may be, for example, an LED (Light Emitting Diode), an incandescent light bulb, a discharge lamp, or a laser element.

[0022] The light source device 31 may irradiate light onto the ISFET 10 from the ion-sensitive membrane 15 side of the ISFET 10. The wavelength of the light irradiated onto the ISFET 10 by the light source device 31 may be 395 nm or more. The intensity of the light irradiated onto the ISFET 10 by the light source device 31 may be sufficient as long as electrons are excited from the valence band to the conduction band in the region between the source 11 and the drain 12 of the ISFET 10. For example, the intensity of the light irradiated onto the ISFET 10 by the light source device 31 may be 1 mW or more, but is not limited to this.

[0023] The control device 40 controls the application of voltage by the power supply device 20 and the irradiation of light by the light source device 31. In the ion sensor system 1, the control device 40 may apply a first voltage to the gate 50 of the ISFET 10. The control device 40 may also apply a second voltage to the gate 50 of the ISFET 10. The magnitude and application timing of the first voltage or the second voltage will be described later. The control device 40 may also control the start and end of light irradiation by the light source device 31.

[0024] The functions of the control device 40 can be realized, for example, by a program for causing a computer to function as the device. In this case, the control device 40 may include a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. In addition, some or all of the functions of the control device 40 may be realized by a logic circuit.

[0025] The electrolyte tank 60 is a tank that holds an electrolyte whose ion concentration is to be measured. The electrolyte is in contact with the ion-sensitive membrane 15 while held in the electrolyte tank 60. Therefore, the gate 50 is electrically connected to the ion-sensitive membrane 15 while immersed in the electrolyte.

[0026] The electrolyte to be measured may be, for example, an aqueous solution of potassium chloride, an aqueous solution of calcium chloride, or an aqueous solution of sodium chloride. When used in the biochemistry field, the electrolyte may be a phosphate buffer, an acetate buffer, a citrate buffer, a citrate phosphate buffer, a borate buffer, a tartrate buffer, a phthalate buffer, a phosphate buffered saline, a cacodylate buffer, a Britton-Robinson buffer, a Tris buffer, a Bis-Tris buffer, a HEPES buffer, an ADA buffer, a PIPES buffer, an ACES buffer, a coramine hydrochloride buffer, a MOPSO buffer, a MOPS buffer, a BES buffer, a TES buffer, a DIPSO buffer, a TAPSO buffer, an acetamidoglycine buffer, a glycylglycine buffer, a tricine buffer, a glycineamide buffer, a bicine buffer, a POPSO buffer, a HEPPSO buffer, a HEPPS buffer, a TAPS buffer, an AMPSO buffer, a CHES buffer, a CAPSO buffer, a CAPS buffer, or a MES buffer. The electrolyte may also be a liquid used in industrial applications, such as a plating solution or a cell culture solution.

[0027] The ion sensor system 1 may further include a switching mechanism (not shown) for switching between a state in which the gate 50 is immersed in the electrolyte and a state in which it is not immersed. In this case, the control device 40 can immerse the gate 50 in the electrolyte by the switching mechanism. The switching mechanism may be, for example, a movement mechanism that moves the gate 50 up and down just above the electrolyte tank 60.

[0028] The ion sensor system 1 may further include a temperature control mechanism (not shown) for controlling the temperature of the ISFET 10. In this case, the control device 40 may control the temperature of the ISFET 10 by the temperature control mechanism. The temperature control mechanism may be, for example, a heater. The control device 40 may increase the temperature of the ISFET 10 by the temperature control mechanism, for example, when the light source device 31 irradiates the ISFET 10 with light or before the ISFET 10 measures the ion concentration.

[0029] The ion sensor system 1 may further include a housing (not shown) that covers the ISFET 10. The housing may be made of a light-shielding material. During measurement by the ISFET 10, when light is incident on the ISFET 10, noise is generated in the output signal of the ISFET 10. By covering the ISFET 10 with the housing, the noise can be reduced.

[0030] The ion sensor system 1 may further include a power supply (not shown) for causing a current to flow between the source 11 and the drain 12, and a circuit (not shown) for measuring the magnitude of the current flowing between the source 11 and the drain 12. The circuit for measuring the magnitude of the current flowing between the source 11 and the drain 12 may include an ammeter. In this case, the control device 40 can measure the amount of ions in the electrolyte and evaluate the threshold voltage of the ISFET 10 based on the magnitude of the reference voltage and the magnitude of the current flowing between the source 11 and the drain 12.

[0031] (Operation of the ion sensor system) As described above, in the ion sensor system 1, the electrolyte held in the electrolyte tank 60 comes into contact with the ion-sensitive membrane 15. The potential of the ion-sensitive membrane 15 changes depending on the amount of ions in the electrolyte, i.e., the amount of ions on the surface of the ion-sensitive membrane 15, and the threshold voltage of the ISFET 10 changes accordingly.

[0032] In the ion sensor system 1, for example, a reference voltage at which the current between the source 11 and the drain 12 becomes a predetermined value may be used as a signal indicating the amount of ions. Also, the current between the source 11 and the drain 12 when the reference voltage is set to a predetermined value may be used as a signal indicating the amount of ions.

[0033] (Drift) In general, in ISFETs, a phenomenon occurs in which the threshold voltage changes over time when the properties of the electrolyte to be measured are not changed. This phenomenon is called drift. In an ideal ISFET, the drift is zero. However, when the conditions under which the ion sensor system is operated and the properties of the ion-sensitive membrane are unstable, the drift may not become zero.

[0034] In a MOS (Metal Oxide Si) device, the gate voltage V g is the flat band voltage V when the potential gradient becomes zero inside the semiconductor substrate. fb , band bending inside the semiconductor substrate φ s , and the voltage across the insulating film V ox Since this is equal to the sum of the above, the following equation (1) holds.

[0035]

number

[0036]

number

[0037]

number

[0038] φ´ MS An example of this is explained below. When the reference electrode is an Ag / AgCl electrode, the redox potential of the reference electrode is +0.208 V with respect to the redox potential of the standard hydrogen electrode. The redox potential of the standard hydrogen electrode is +4.44 V with respect to the vacuum level. Therefore, the value equivalent to the work function of the reference electrode is considered to be 4.44 + 0.208 = 4.648 V. On the other hand, when the semiconductor substrate is p-Si, the work function of the semiconductor substrate is 4.91 V. Therefore, φ' MS =4.648-4.91=-0.262V.

[0039] In equation (3), it is assumed that the difference between the work function of the reference electrode and the work function of the semiconductor substrate is constant, and as stated above, φ MS is a constant. Therefore, if the potential difference of the electrolyte between the reference electrode and the insulating film changes over time, the change is f This will appear as a change in (t).

[0040] Q f (t) is expressed by the following equation (4).

[0041]

number

[0042] C ox (t) is expressed by the following equation (5).

[0043]

number

[0044] The amount of charge q0 generated per unit area on the semiconductor substrate is expressed by the following equation (6).

[0045]

number

[0046]

number

[0047]

number

[0048]

number

[0049]

number

[0050]

number

[0051]

number

[0052]

number

[0053]

number

[0054] Therefore, ΔV th To reduce this, follow the guidelines (a) to (c) below.

[0055] (a) Capacitance of the insulating film C ox Increase (t) to reduce the effects of changes in charge, etc.

[0056] (b) Charge amount Q f Change in (t), difference in charge Q f (t)-q0, and C ox Decrease the rate of change β of (t) and decrease A and B.

[0057] (c) Let A and B be values ​​with similar absolute values ​​but opposite signs, and make A+B approach 0.

[0058] In the ion sensor system 1, the region between the source 11 and the drain 12 of the ISFET 10 is irradiated with light, whereby electrons in the region are excited from the valence band to the conduction band. Furthermore, a voltage is applied to the gate 50, so that electrons in the conduction band move to the thermal oxide film 14. That is, a charge amount Q f As a result, the charge Q f The change in (t) can be reduced. Therefore, the value of A in the formula (13) can be particularly reduced. That is, the ion sensor system 1 reduces drift by the above-mentioned guideline (b).

[0059] It can be said that such an ion sensor system 1 is one in which the ISFET 10 with reduced drift is manufactured as an ion sensor and measurement is performed using the ISFET 10. It can also be said that the ion sensor system 1 is one in which the ISFET 10 is adjusted as an ion sensor so as to reduce drift and measurement is performed using the ISFET 10.

[0060] (Ion sensor manufacturing and adjustment methods) 2 is a flowchart showing an example of a method for manufacturing or adjusting the ion sensor in the ion sensor system 1. A method for manufacturing or adjusting the ISFET 10 as the ion sensor in the ion sensor system 1 will be described below with reference to FIG.

[0061] In the example shown in Fig. 2, the electrolyte to be measured is held in advance in the electrolyte tank 60. First, the control device 40 immerses the gate 50 in the electrolyte (S1, immersion step). Next, the control device 40 evaluates the threshold voltage of the ISFET 10 (S2, threshold voltage evaluation step). Furthermore, the control device 40 determines a first voltage based on the threshold voltage evaluated in step S2 (S3, first voltage determination step).

[0062] The first voltage may be 1 V or more higher than the threshold voltage of the ISFET 10. By setting the first voltage at such a magnitude, the drift reduction effect can be effectively obtained. Moreover, the first voltage may be 6 V or more higher than the threshold voltage of the ISFET 10. By setting the first voltage at such a magnitude, the drift reduction effect can be even more effectively obtained.

[0063] The control device 40 applies a first voltage to the gate 50 of the ISFET 10 (S4, first voltage application step). At this time, the control device 40 applies the first voltage to the gate 50 in a state where the gate 50 is immersed in the electrolyte.

[0064] Furthermore, in parallel with step S4, the control device 40 irradiates light onto the ISFET 10 (S5, light irradiation step). The length of time for which the control device 40 irradiates light onto the ISFET 10 may be 5 seconds or more. The energy of the light may be, for example, energy greater than the band gap of Si. The wavelength of the light may be, for example, infrared light to visible light, specifically, in the range of 395 nm or more and 940 nm or less. Furthermore, when the first voltage is set to a voltage 2 V or more greater than the threshold voltage of the ISFET 10, the wavelength of the light may be ultraviolet light, that is, in the range of 395 nm or less. However, the energy of the light is not limited to these, and for example, the wavelength of the light may be 1100 nm or more, as described later.

[0065] After irradiating the ISFET 10 with light, the control device 40 stops irradiating the ISFET 10 with light (S6, light irradiation stopping step). The control device 40 also executes step S6 in parallel with step S4. That is, the light irradiation stopping step is performed in a state where the first voltage is applied to the gate 50.

[0066] Thereafter, the control device 40 re-evaluates the threshold voltage of the ISFET 10 (S7, threshold voltage evaluation step). The value of the threshold voltage here is different from the value in step S2 due to the processes in steps S4 to S6. Next, the control device 40 determines a second voltage based on the threshold voltage evaluated in step S7 (S8). The second voltage may be 1 V or more higher than the threshold voltage of the ISFET 10. The second voltage may be the same magnitude as the voltage applied to the gate 50 when measuring the ion concentration.

[0067] Furthermore, the control device 40 applies a second voltage to the gate 50 of the ISFET 10 (S9, second voltage application step). The time for which the control device 40 applies the second voltage to the gate 50 may be 1 minute or more and 3 minutes or less. By the control device 40 applying the second voltage to the gate 50 in this manner, drift can be further reduced.

[0068] This completes the manufacturing method or adjustment method for the ion sensor in the ion sensor system 1. This method may be performed, for example, one hour or one minute before the measurement of the ion concentration, and the timing of performing this method is not particularly limited.

[0069] However, the ion sensor system 1 does not necessarily have to include a switching mechanism for switching the state in which the gate 50 is immersed in the electrolyte and the state in which it is not immersed. If the ion sensor system 1 does not include a switching mechanism, the control device 40 does not execute step S1. In this case, for example, a user of the ion sensor system 1 may manually immerse the gate 50 in the electrolyte.

[0070] Moreover, the control device 40 does not necessarily have to execute steps S7 to S9. Even if the control device 40 does not execute steps S7 to S9, the drift in the ISFET 10 is reduced by the processes up to step S6. However, by the control device 40 executing steps S7 to S9, the drift in the ISFET 10 is reduced to a greater extent.

[0071] Furthermore, the control device 40 does not necessarily have to execute steps S2 to S4. When the control device 40 does not execute steps S2 to S4, a voltage called an open circuit voltage is applied to the gate 50 of the ISFET 10. The control device 40 can also manufacture an ISFET 10 with reduced drift by executing steps S5 and S6 on the ISFET 10 in a state in which the open circuit voltage is applied to the gate 50. However, the drift in the ISFET 10 is further reduced by the control device 40 executing steps S2 to S4 and executing steps S5 and S6 with the first voltage applied to the gate 50.

[0072] 2, the control device 40 executes step S6 while continuing step S4. Therefore, the control device 40 constantly applies the first voltage to the gate 50 during the period in which the ISFET 10 is irradiated with light. However, the control device 40 may execute step S6 immediately after first completing step S4. In other words, the control device 40 may irradiate the ISFET 10 with light for a short period of time without applying the first voltage to the gate 50.

[0073] Furthermore, the magnitude of the second voltage is not limited to the same as the voltage applied to the gate 50 when measuring the ion concentration as described above. The magnitude of the second voltage may be the same as the first voltage. The second voltage may be the magnitude determined in step S8, but step S8 may not be performed and the magnitude of the first voltage may be used as is.

[0074] As described above, the method of manufacturing an ion sensor and the method of adjusting an ion sensor according to the present disclosure include a first voltage application step and a light irradiation step, thereby reducing drift in the ISFET 10.

[0075] (Experimental Example 1) An experiment was conducted to examine the reduction in drift caused by implementing the manufacturing method for the ion sensor of the present disclosure. In the experiment, the above-mentioned A, B, and ΔV were measured for the ISFET 10 in which the manufacturing method for the ion sensor of the present disclosure was implemented and for the ISFET 10 in which the manufacturing method for the ion sensor of the present disclosure was not implemented. th was derived.

[0076] Fig. 3 is a diagram showing an outline of a CV curve for the ISFET 10. Fig. 3 is a graph in which the horizontal axis represents the voltage (V) applied to the gate 50 of the ISFET 10, and the vertical axis represents the capacitance (C) of the thermal oxide film 14.

[0077] Q in B mentioned above f A method for measuring (t)-q0 will be described below. First, a DC voltage and an AC voltage are applied to the gate 50, and a CV curve as shown in FIG. 3 can be obtained. From the CV curve, Cox (t) can be read off. Specifically, C in the accumulation region is C ox (t).

[0078] Furthermore, from the CV curve, V fb and V th Specifically, the value of V at which C is equal to the flat band capacitance is V fb The flat band capacitance is a function of the Debye length of the semiconductor substrate 19 and C ox From the above formula (3) and formula (2), V th can be calculated.

[0079] Using the value obtained from the CV curve, the charge Q is calculated using the following equation (15): f (t) can be found.

[0080]

number

[0081] 4 is a diagram showing experimental results regarding reduction in drift. In FIG. 4, reference numeral 401 is a graph showing the results for the ISFET 10 for which the ion sensor manufacturing method of the present disclosure was not performed. Reference numeral 402 is a graph showing the results for the ISFET 10 for which the ion sensor manufacturing method of the present disclosure was performed. In each graph, the dashed line indicates A, the dashed line indicates B, and the solid line indicates ΔV th In each graph, the horizontal axis indicates the elapsed time (minutes) and the vertical axis indicates the magnitude of the voltage (V).

[0082] The specific manufacturing conditions for the ISFET 10 used in the experiment are as follows. The central wavelength of the light irradiated to the ISFET 10 was 395 nm. However, since an LED was used as the light emitting element, the light irradiated to the ISFET 10 was not monochromatic light, but light that had a spread above and below the above central wavelength.

[0083] The intensity of the light irradiated to the ISFET 10 was 1 mW. This light intensity was measured by an illuminometer as the intensity of the light from the light source device 31 striking the surface of the ISFET 10 in a state where no electrolyte was held in the electrolyte tank 60. The light was irradiated for 5 minutes.

[0084] The first voltage was +6.1 V, which was the threshold voltage of the ISFET 10 before the application of the first voltage and the irradiation of light. The second voltage was +1.1 V, which was the threshold voltage of the ISFET 10 after the application of the first voltage and the irradiation of light. The threshold voltage of the ISFET 10 changes due to the application of the first voltage and the irradiation of light. For this reason, the threshold voltage of the ISFET 10 was evaluated before the application of the first voltage and before the application of the second voltage, respectively, to determine the first voltage and the second voltage.

[0085] As shown by reference numeral 401, in the ISFET 10 in which the manufacturing method of the ion sensor of the present disclosure was not performed, the value of A increased with time. On the other hand, the value of B decreased with time. However, the decrease in the value of B was smaller than the increase in the value of A. Therefore, ΔV th The value of increased over time.

[0086] As shown by reference numeral 402, in the ISFET 10 in which the manufacturing method for an ion sensor according to the present disclosure was performed, the value of A increased until 10 minutes, but remained almost constant thereafter. On the other hand, the value of B slightly decreased until 10 minutes, but remained almost zero thereafter. Therefore, in the ISFET 10 in which the manufacturing method for an ion sensor according to the present disclosure was performed, the change in ΔV over time was smaller than that in the ISFET 10 in which the manufacturing method for an ion sensor according to the present disclosure was not performed, in the range in which the elapsed time exceeded 10 minutes. thThe increase in the value of ΔV was small. th Therefore, it can be said that the drift was reduced in the ISFET 10 for which the manufacturing method for the ion sensor according to the present disclosure was carried out, compared to the ISFET 10 for which the manufacturing method for the ion sensor according to the present disclosure was not carried out.

[0087] (Experimental Example 2) An experiment was conducted to examine the effect of the time of irradiating the ISFET 10 with light on the reduction of drift. th After the pretreatment, the threshold voltage V th Measure again and V th The drift was measured by applying a voltage of +1.1 V to gate 50. The drift measurements were performed at 5 minute intervals over a period of 60 minutes.

[0088] 5 is a diagram showing the results of Experimental Example 2. In FIG. 5, reference numeral 501 indicates the drift ΔV th In the graph 501, the horizontal axis represents elapsed time (minutes) and the vertical axis represents drift ΔV th (V).

[0089] In the graph 501, the reference symbols 501a to 501g respectively indicate the results for the ISFET 10 which was subjected to the following pretreatment or which was not subjected to the pretreatment. 501a: No pre-processing was performed. 501b:V th A voltage of +6.1 V was applied to the gate 50 for 1 minute. The ISFET 10 was not irradiated with light. 501c:V th A voltage of +6.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was not irradiated with light. 501d:V th A voltage of +6.1 V was applied to the gate 50 for 5 seconds. The ISFET 10 was also irradiated with light. 501e:V thA voltage of +6.1 V was applied to the gate 50 for 1 minute. The ISFET 10 was also irradiated with light. 501f:V th A voltage of +6.1 V was applied to the gate 50 for 3 minutes. The ISFET 10 was also irradiated with light. 501g:V th A voltage of +6.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was also irradiated with light. The wavelength of the light irradiated in the reference symbols 501d to 501g was 395 nm, and the intensity was 1 mW. The type of light source and the method for measuring the intensity were the same as those described in the first experimental example.

[0090] It can be seen from the graph of reference numeral 501 that the drift was reduced by performing any of the above-mentioned pretreatments compared to the case where the pretreatments were not performed. In particular, it can be seen that the drift was significantly reduced after 5 minutes had passed when light was irradiated in the pretreatment.

[0091] In FIG. 5, reference numeral 502 denotes the V th and V after 5 minutes th The seven bars in the bar graph 502 correspond, from the left, to the bars 501a to 501g in the bar graph 501. From the graph in the bar graph 502, when light irradiation is performed in the pretreatment, even if the irradiation time is 5 seconds, the V th Therefore, in the manufacture or adjustment of the ISFET 10, it can be said that the light irradiation time should be 5 seconds or more.

[0092] (Experimental Example 3) An experiment was conducted to examine the effect of the magnitude of the voltage applied to the gate 50 when irradiating the ISFET 10 with light on the reduction of drift. th After the pretreatment, the threshold voltage V th Measure again and V thThe drift was measured by applying a voltage of +1.1 V to gate 50. The drift measurements were performed at 5 minute intervals over a period of 60 minutes.

[0093] 6 is a diagram showing the results of Experimental Example 3. In FIG. 6, reference numeral 601 indicates the drift ΔV th In the graph 601, the horizontal axis represents elapsed time (minutes) and the vertical axis represents drift ΔV th (V).

[0094] In the graph 601, the reference characters 601a to 601d indicate the results of the ISFET 10 which was subjected to the following pretreatments. 601a:V th A voltage of +6.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was not irradiated with light. 601b:V th A voltage of +6.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was also irradiated with light. 601c:V th A voltage of +4.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was also irradiated with light. 601d:V th A voltage of +2.1 V was applied to the gate 50 for 5 minutes. The ISFET 10 was also irradiated with light. The wavelength of the light irradiated at 601b to 601d was 395 nm, and the intensity was 1 mW. The type of light source and the method for measuring the intensity were the same as those described in the first experimental example.

[0095] From the graph of code 601, V th +2.1V to V th It can be seen that, regardless of the voltage applied to the gate 50 up to +6.1 V, the drift was reduced by irradiating light compared to the case where light was not irradiated.

[0096] In FIG. 6, reference numeral 602 denotes the V th and V after 5 minutes thThe four bar graphs in the reference numeral 602 correspond, from the left, to the reference numerals 601a to 601d in the reference numeral 601. From the graph in the reference numeral 602, when light irradiation is performed in the pretreatment, the voltage applied to the gate 50 is V th +2.1V to V th It can be seen that the time change of drift was about the same regardless of the voltage applied to the gate 50 during light irradiation, up to +6.1 V. th Anything above +2.1V is sufficient.

[0097] (Experimental Example 4) An experiment was carried out to examine the effect of applying a voltage to the gate 50 after irradiating the ISFET 10 with light on the reduction of drift. th The ISFET 10 is subjected to the first pretreatment. th A voltage of +6.1 V was applied to the gate 50 for 5 minutes, and the ISFET 10 was irradiated with light. After the pretreatment, the threshold voltage V th The V was measured again, and then, as a second pretreatment, the ISFET 10 was not irradiated with light. th A voltage of +1.1 V was applied to the gate 50. After the second pretreatment, V th The drift was measured by applying a voltage of +1.1 V to gate 50. The drift measurements were taken at 5 minute intervals over a period of 30 minutes.

[0098] 7 is a diagram showing the results of Experimental Example 4. In FIG. 7, reference numeral 701 indicates the drift ΔV th In the graph 701, the horizontal axis represents elapsed time (minutes) and the vertical axis represents drift ΔV th (V).

[0099] In the graph of reference numeral 701, reference numerals 701a to 701c respectively indicate the results for the ISFET 10 which was subjected to the second pretreatment described below, or which was not subjected to the second pretreatment. · 701a: The second pretreatment was not performed. 701b:V th A voltage of +1.1V was applied to gate 50 for 1 minute. 701b:V th A voltage of +1.1V was applied to gate 50 for 3 minutes.

[0100] In FIG. 7, reference numeral 702 denotes the V th and V after 5 minutes th The three bar graphs in reference numeral 702 correspond to reference numerals 701a to 701c in reference numeral 701, from the left.

[0101] From the graphs of reference numerals 701 and 702 in FIG. 7, V th It can be seen that the drift was reduced compared to the case where the second pretreatment was not performed in both the case where a voltage of +1.1 V was applied to the gate 50 for 1 minute and the case where it was applied for 3 minutes. Therefore, in the manufacture or adjustment of the ISFET 10, it can be said that the time for applying a voltage to the gate 50 as the second pretreatment can be 1 minute or more.

[0102] (Experimental Example 5) An experiment was conducted to examine the effect of the wavelength of light irradiated to the ISFET 10 on the reduction of drift. th After the pretreatment, the threshold voltage V th Measure V again without irradiating the ISFET 10 with light. th A voltage of +1.1V was applied to gate 50 for 3 minutes. Then, V th The drift was measured by applying a voltage of +1.1 V to gate 50. The drift measurements were taken at 5 minute intervals over a period of 30 minutes.

[0103] 8 is a diagram showing the results of Experimental Example 5. In FIG. 8, reference numeral 801 indicates the drift ΔV th In the graph 801, the horizontal axis represents elapsed time (minutes) and the vertical axis represents drift ΔV th (V).

[0104] In the graph 801, the reference characters 801a to 801d indicate the results of the ISFET 10 which was subjected to the following pretreatments, each of which lasted for 5 minutes. 801a: V at gate 50 th The gate was held without light irradiation with a voltage of +6.1 V applied. th A voltage of +1.1 V was not applied. 801b: V at gate 50 th With a voltage of +6.1 V applied, the ISFET 10 was irradiated with light having a wavelength of 395 nm. 801c: V on gate 50 th With a voltage of +6.1 V applied, the ISFET 10 was irradiated with light having a wavelength of 525 nm. 801d: V at gate 50 th With a voltage of +6.1 V applied, the ISFET 10 was irradiated with light having a wavelength of 940 nm.

[0105] In FIG. 8, reference numeral 802 denotes a th The four bar graphs in reference numeral 802 correspond, from the left, to reference numerals 801a to 801d in reference numeral 801.

[0106] 8, it can be seen that when ISFET 10 is irradiated with light while a voltage is applied to gate 50, drift is reduced regardless of whether the wavelength of the light is 395 nm, 525 nm, or 940 nm. Therefore, in manufacturing or adjusting ISFET 10, it is sufficient for the wavelength of light irradiated to ISFET 10 to be within the range of 395 nm to 940 nm, and in particular it may be visible light.

[0107] [Embodiment 2] Other embodiments of the present disclosure will be described below. For convenience of explanation, the same reference numerals will be given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0108] Fig. 9 is a diagram showing an example of the configuration of an ion sensor system 2 according to embodiment 2. The ion sensor system 2 differs from the ion sensor system 1 in that the ion sensor system 2 includes a light source device 32 instead of the light source device 31. For simplicity, the control device 40 is omitted in Fig. 9.

[0109] The light source device 32 may be disposed so as to irradiate light from the semiconductor substrate 19 side of the ISFET 10 onto at least a region between the source 11 and the drain 12 of the ISFET 10. The light source device 32 may irradiate light from the semiconductor substrate 19 side of the ISFET 10 onto the entire ISFET 10. By irradiating light onto the ISFET 10 from the semiconductor substrate 19 side, the ion sensor system 2 has greater freedom in design, such as the installation position of the gate 50, than the ion sensor system 1.

[0110] Furthermore, the wavelength of the light irradiated by the light source device 32 may be 1100 nm or more. Light with a wavelength of 1100 nm or more is not easily absorbed by the semiconductor substrate 19 made of Si. If the wavelength of the light irradiated by the light source device 32 is 1100 nm or more, the light can be efficiently irradiated to the ISFET 10 from the semiconductor substrate 19 side.

[0111] [Embodiment 3] Fig. 10 is a diagram showing an example of the configuration of an ion sensor system 3 according to embodiment 3. The ion sensor system 3 differs from the ion sensor system 1 in that it includes a plurality of ISFETs 10 and in that it includes a light source device. For simplicity, the power supply device 20, the control device 40, and the gate 50 are omitted in Fig. 10.

[0112] The ISFETs 10 may be arranged in an array. The ISFETs 10 may have at least a first ISFET and a second ISFET having different configurations. For example, the ISFETs 10 may have different concentrations of additives in one or more of the source 11, the drain 12, and the gate 50. The ISFETs 10 may have different thicknesses in one or more of the thermal oxide film 14, the ion-sensitive film 15, and the semiconductor substrate 19. The ISFETs may share a part of the configuration. For example, as shown in FIG. 10, the ISFETs may share one gate 50.

[0113] Moreover, the ion-sensitive membrane 15 in the above-mentioned example is sensitive to the proton concentration. In one or more of the multiple ISFETs 10, an ion-selective membrane sensitive to the concentration of a type of ion other than protons may be formed on the ion-sensitive membrane 15. An example of the ion-selective membrane is a plasticized polyvinyl chloride membrane mixed with an ionophore that binds to a specific ion. The ISFET 10 having such an ion-selective membrane is also sensitive to the concentration of ions such as K or Ca. By forming different types of ion-selective membranes for each ISFET 10 arranged in an array, a sensor capable of simultaneously measuring the concentrations of multiple types of ions can be realized.

[0114] 10. The light source device 33 irradiates light onto the plurality of ISFETs 10 from the ion-sensitive membrane 15 side of the ISFETs 10. The light source device 34 irradiates light onto the plurality of ISFETs 10 from the semiconductor substrate 19 side of the ISFETs 10. Each of the light source device 33 and the light source device 34 needs only to irradiate light onto an area including at least the areas between the sources 11 and the drains 12 of all of the ISFETs 10.

[0115] According to the ion sensor system 3, the ion concentration in the electrolyte can be measured by the ISFETs 10 having different configurations as described above. Therefore, according to the ion sensor system 3, the ion concentration can be measured with higher accuracy than the ion sensor system 1.

[0116] (Modification) Fig. 11 is a diagram showing an example of the configuration of an ion sensor system 3A according to a modified example of embodiment 3. The ion sensor system 3A differs from the ion sensor system 3 in that it includes a light source device 35 instead of the light source devices 33 and 34. For simplicity, the power supply device 20, the control device 40, and the gate 50 are omitted in Fig. 11.

[0117] The light source device 35 is a light source capable of irradiating light to only one of the multiple ISFETs 10 included in the ion sensor system 3A. The ion sensor system 3A may include a moving mechanism (not shown) for moving the light source device 35. Although only one light source device 35 is shown in FIG. 11, the ion sensor system 3A may include a plurality of light source devices 35. Furthermore, the light source device 35 may irradiate light to the ISFET 10 from the semiconductor substrate 19 side of the ISFET 10.

[0118] In such an ion sensor system 3A, in the above-mentioned light irradiation step, the control device 40 may irradiate each of the plurality of ISFETs 10 with light under different conditions. For example, the control device 40 may cause each of the plurality of ISFETs 10 to be irradiated with light having a different wavelength, intensity, and / or irradiation time.

[0119] In the ion sensor system 3A, the control device 40 may apply, in the above-mentioned first voltage application step, voltages under different conditions as the first voltage to each of the multiple ISFETs 10. For example, the control device 40 may make the magnitude and / or application time of the voltage applied as the first voltage different from each other to each of the multiple ISFETs 10.

[0120] In the ion sensor system 3A, the control device 40 can reduce drift in each of the ISFETs 10 more effectively by irradiating each of the multiple ISFETs 10 with light and / or applying the first voltage under appropriate conditions.

[0121] [Embodiment 4] Fig. 12 is a diagram showing a configuration of an ISFET 70 according to the fourth embodiment. The ISFET 70 can replace the ISFET 10 in the ion sensor system 1 shown in the first embodiment, for example. For simplicity, the gate 50 is omitted in Fig. 12. As shown in Fig. 12, the ISFET 70 includes a charge adjustment layer 16 in addition to the components included in the ISFET 10. The charge adjustment layer 16 may be laminated between the thermal oxide film 14 and the ion-sensitive film 15.

[0122] The charge adjustment layer 16 is a layer for adjusting the effective charge density in the electrolyte and the thermal oxide film 14. The charge adjustment layer 16 may be designed so that the value of B in the above formula (14) is 0. Alternatively, the charge adjustment layer 16 may be designed so that the value of B in the above formula (14) is a value whose absolute value is close to the value of A and whose sign is opposite. The charge adjustment layer 16 may be a semiconductor layer. The charge adjustment layer 16 may be a p-type semiconductor layer or an n-type semiconductor layer. The charge adjustment layer 16 may be, for example, a layer in which a material different from that of the ion-sensitive film 15 is laminated. Alternatively, the charge adjustment layer 16 may be, for example, a layer in which the same material as that of the ion-sensitive film 15 is laminated by a method different from that of the ion-sensitive film 15. The charge adjustment layer 16 may be, for example, formed of TEOS (Tetra Ethoxy Silane), or may be, for example, formed of alumina.

[0123] The ISFET 70 may further include a metal layer between the thermal oxide film 14 and the charge adjustment layer 16. In this case, the metal layer may be uniformly provided between the thermal oxide film 14 and the charge adjustment layer 16. Alternatively, the metal layer may be embedded in a part of the thermal oxide film 14 so as to be in contact with the charge adjustment layer 16.

[0124] (Experimental Example 6) 13 is a graph showing the results of an experiment on the drift of the ISFET 70. In FIG. 13, the graphs with the respective symbols indicate the following: Reference numeral 1301 denotes a graph showing the results of an experiment on an ISFET 70 not provided with a charge balancing layer 16, ie, an ISFET 10. Reference numeral 1302 denotes a graph showing the results of an experiment on an ISFET 70 in which a charge adjustment layer 16 is made of TEOS having a thickness of 20 nm. Reference numeral 1303 denotes a graph showing the results of an experiment on an ISFET 70 in which a charge adjustment layer 16 is made of TEOS having a thickness of 40 nm. Reference numeral 1304 denotes a graph showing the results of an experiment on an ISFET 70 in which a charge balancing layer 16 is made of TEOS having a thickness of 60 nm. Reference numeral 1305 denotes a graph showing the results of an experiment on an ISFET 70 in which the charge adjustment layer 16 is made of alumina having a thickness of 20 nm and formed by sputtering. Reference numeral 1306 denotes a graph showing the results of an experiment on an ISFET 70 in which the charge adjustment layer 16 is made of alumina having a thickness of 40 nm and formed by sputtering. Reference numeral 1307 denotes a graph showing the results of an experiment on an ISFET 70 in which the charge adjustment layer 16 is made of alumina having a thickness of 60 nm and formed by sputtering.

[0125] Experimental example 6 is an experimental example regarding the effect of the charge adjustment layer 16. For this reason, steps S2 to S6 shown in FIG. 2 were not performed during the manufacture of the ISFETs 70 indicated by the reference numerals 1301 to 1307. That is, during the manufacture of these ISFETs 70, only the application of the second voltage was performed. The method of determining the second voltage is the same as that described in the first embodiment. In each of the graphs indicated by the reference numerals 1301 to 1307, the dashed line indicates A in the above formula (14), the dashed line indicates B in the above formula (14), and the solid line indicates ΔV in the above formula (14). thIn each of the graphs 1301 to 1307, the horizontal axis represents elapsed time (minutes), and the vertical axis represents the above A, B, and ΔV th is the value (V).

[0126] FIG. 14 is a diagram summarizing the seven types of data shown in FIG. 13. In FIG. 14, reference numeral 1401 denotes A, B, ΔV th In the graph 1401, the black graph indicates ΔV th The gray graph indicates A, and the white graph indicates B. Reference numeral 1402 indicates the maximum value of β. Reference numeral 1403 indicates Q f (t)-q0. The reference numeral 1404 indicates the maximum value of 1 / (C ox 4 is a graph showing the maximum value of (t).

[0127] As shown in FIG. 14, the parameters indicating the drift characteristics of the ISFET 10 change depending on the presence or absence of the charge adjustment layer 16 and the manufacturing conditions thereof. For example, referring to reference numeral 1401, it can be seen that when there is no charge adjustment layer 16, the maximum value of the B term is negative, whereas when the charge adjustment layer 16 is made of alumina, the maximum value of the B term is positive. In particular, Q f With reference to reference numeral 1403 for (t)-q0, the presence of the charge adjustment layer 16 reduces Q f (t)-q0 is increasing in the positive direction. This is because the charge adjustment layer 16 has a positive Q f This can be interpreted as being due to the presence of alumina. When the charge adjustment layer 16 is made of alumina, Q f The more positive (t)-q0 becomes, the more Q f The value of (t) increases, resulting in a positive value for the B term.

[0128] Q fA method for reducing the value of (t)-q0 is to use TEOS for the charge adjustment layer 16 and to make the thickness of the charge adjustment layer 16 thinner than 20 nm. Another method is to reduce the fixed charges in the charge adjustment layer 16 by annealing, or to form the charge adjustment layer 16 from another material. An example of the other material is HfO2.

[0129] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0130] 〔summary〕 The present disclosure can also be expressed as follows.

[0131] The manufacturing method of an ion sensor according to aspect 1 of the present disclosure includes a first voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor), and a light irradiation step of irradiating light to the ISFET while the first voltage is being applied.

[0132] In accordance with aspect 2 of the present disclosure, in the manufacturing method of an ion sensor in aspect 1, the method further includes a threshold voltage evaluation step of evaluating a threshold voltage of the ISFET, and a first voltage determination step of determining the first voltage in the first voltage application step based on the threshold voltage.

[0133] The manufacturing method for an ion sensor according to aspect 3 of the present disclosure, in accordance with aspect 2, further includes a light irradiation stopping step of stopping the light irradiation, and a second voltage application step of applying a second voltage to the gate of the ISFET while the light irradiation is stopped.

[0134] A fourth aspect of the present disclosure relates to a method for manufacturing an ion sensor in accordance with the third aspect, wherein the irradiation stopping step is performed in a state in which the first voltage is being applied to the gate.

[0135] A fifth aspect of the present disclosure relates to a method for producing an ion sensor in any one of the second to fourth aspects, wherein the first voltage is greater than the threshold voltage by 1 V or more.

[0136] A sixth aspect of the present disclosure relates to a method for producing an ion sensor in any one of the second to fifth aspects, wherein the first voltage is greater than the threshold voltage by 6 V or more.

[0137] In the method for producing an ion sensor according to a seventh aspect of the present disclosure, in any one of the first to sixth aspects, the wavelength of the light is 395 nm or longer.

[0138] A manufacturing method for an ion sensor according to an eighth aspect of the present disclosure is directed to the seventh aspect, in which the wavelength of the light is 1100 nm or longer.

[0139] A ninth aspect of the present disclosure relates to a method for producing an ion sensor in accordance with the eighth aspect, wherein the light is irradiated onto a region between a source and a drain in the ISFET from a semiconductor substrate side of the ISFET.

[0140] A tenth aspect of the present disclosure relates to a method for producing an ion sensor in any one of the first to ninth aspects, wherein in the light irradiation step, the length of time for irradiating the light is 5 seconds or longer.

[0141] In the method for producing an ion sensor according to an eleventh aspect of the present disclosure, in any one of the first to tenth aspects, the light is irradiated onto a region between a source and a drain in the ISFET.

[0142] The method for manufacturing an ion sensor according to aspect 12 of the present disclosure, in any one of aspects 1 to 11, further includes an immersion step of immersing the gate in an electrolyte, and in the first voltage application step, the first voltage is applied while the gate is immersed in the electrolyte.

[0143] A method for manufacturing an ion sensor according to aspect 13 of the present disclosure is, in any one of aspects 1 to 12, wherein the ISFET is two or more ISFETs including a first ISFET and a second ISFET, and in the light irradiation step, light having different conditions is irradiated to the first ISFET and the second ISFET.

[0144] A method for manufacturing an ion sensor according to aspect 14 of the present disclosure is, in any one of aspects 1 to 12, wherein the ISFET is two or more ISFETs including a first ISFET and a second ISFET, and in the first voltage application step, voltages having different conditions are applied as the first voltage to the first ISFET and the second ISFET.

[0145] An adjustment method for an ion sensor according to aspect 15 of the present disclosure includes a voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor), and a light irradiation step of irradiating light to the ISFET while the first voltage is being applied.

[0146] The ion sensor system according to aspect 16 of the present disclosure includes an ISFET (Ion Selective Field Effect Transistor), a power supply device for applying a voltage to a gate of the ISFET, a light source device for irradiating light to the ISFET, and a control device for controlling the application of the voltage by the power supply device and the irradiation of light by the light source device. [Explanation of symbols]

[0147] 1, 2, 3, 3A Ion Sensor System 10, 70 ISFET 11 Source 12 Drain 13 Gate 19 Semiconductor Substrate 20 Power supply 31, 32, 33, 33・34, 34, 35 Light source device 40 Control device 50 Gates

Claims

1. a first voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor); a light irradiation step of irradiating the ISFET with light while the first voltage is being applied.

2. a threshold voltage evaluation step of evaluating a threshold voltage of the ISFET; The method for manufacturing an ion sensor according to claim 1 , further comprising: a first voltage determining step of determining the first voltage in the first voltage applying step based on the threshold voltage.

3. a light irradiation stopping step of stopping the irradiation of the light; The method for manufacturing an ion sensor according to claim 2 , further comprising: a second voltage application step of applying a second voltage to the gate of the ISFET while the irradiation of the light is stopped.

4. The method for manufacturing an ion sensor according to claim 3 , wherein the light irradiation stopping step is performed in a state where the first voltage is being applied to the gate.

5. The method for manufacturing an ion sensor according to claim 2 , wherein the first voltage is greater than the threshold voltage by 1 V or more.

6. The method for manufacturing an ion sensor according to claim 2 , wherein the first voltage is greater than the threshold voltage by 6 V or more.

7. The method for manufacturing an ion sensor according to claim 1 , wherein the wavelength of the light is 395 nm or more.

8. The method for producing an ion sensor according to claim 7, wherein the wavelength of the light is 1100 nm or more.

9. 9. The method for manufacturing an ion sensor according to claim 8, wherein the light is irradiated onto a region between a source and a drain in the ISFET from a semiconductor substrate side of the ISFET.

10. 2. The method for producing an ion sensor according to claim 1, wherein in said light irradiation step, the length of time for which said light is irradiated is 5 seconds or more.

11. The method for manufacturing an ion sensor according to claim 1 , wherein the light is irradiated onto a region between a source and a drain of the ISFET.

12. The method further includes the step of immersing the gate in an electrolyte solution; 2. The method for manufacturing an ion sensor according to claim 1, wherein in the first voltage application step, the first voltage is applied in a state where the gate is immersed in the electrolyte.

13. the ISFET is two or more ISFETs including a first ISFET and a second ISFET, The method for manufacturing an ion sensor according to claim 1 , wherein in the light irradiation step, the first ISFET and the second ISFET are irradiated with light having different conditions.

14. the ISFET is two or more ISFETs including a first ISFET and a second ISFET, 2. The method for manufacturing an ion sensor according to claim 1, wherein in the first voltage application step, voltages having different conditions are applied as the first voltage to the first ISFET and the second ISFET.

15. a voltage application step of applying a first voltage to a gate of an ISFET (Ion Selective Field Effect Transistor); a light irradiation step of irradiating light to the ISFET in a state in which the first voltage is applied.

16. An ISFET (Ion Selective Field Effect Transistor); a power supply for applying a voltage to a gate of the ISFET; A light source device that irradiates light onto the ISFET; a control device that controls the application of the voltage by the power supply device and the irradiation of light by the light source device.

Images