JP2023144935A - Method for manufacturing sensor with protective film - Google Patents

Abstract

To provide a method for manufacturing a sensor with a protective film which is not easily removed from an electrode, does not easily degrade when a biological substance is detected, and is strong and highly resistive, without lowering sensitivity of the sensor .SOLUTION: The method for manufacturing a sensor with a protective film includes the steps of: preparing a sensor, the sensor including an oxide layer having a rare-earth element and zirconium and a sensor unit formed on the oxide layer, the sensor unit including a first electrode, a second electrode, a third electrode, and a semiconductor film for connecting the first electrode and the second electrode to each other; forming a titanium film on the first electrode and the second electrode to have a thickness of 3nm to 20nm, both inclusive; and heating the titanium film at temperatures of 380°C to 400°C, both inclusive, under the presence of oxygen.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a sensor with a protective film.

A transistor sensor having a lanthanum zirconium oxide (LaZrO) layer is known as a sensor for detecting biological substances (Patent Document 1). Patent Document 1 has a source electrode, a drain electrode, a reference electrode, and a channel layer disposed between the source electrode and the drain electrode on the lanthanum zirconium oxide layer, and a biological material is placed on the surface of the channel layer. A transistor sensor has been disclosed in which a probe molecule for capturing is immobilized. A transistor sensor having such a configuration detects biological substances in the following manner. First, a sample liquid containing a biological substance is brought into contact with the channel layer, and the biological substance to be measured is bound to the probe molecule. Next, the sample solution is washed, a measurement solution such as a buffer solution is supplied to the channel layer, and the channel layer and the reference electrode are connected via the measurement solution. Then, the biological material is detected by measuring the voltage between the reference electrode and the source electrode and the current between the source electrode and the drain electrode.

JP2021-99330A

In the sensor disclosed in Patent Document 1, when detecting a biological substance, a sample liquid or a measurement liquid may adhere to the electrode, resulting in deterioration of the surface of the electrode. Therefore, it is necessary to cover the electrodes of the transistor sensor with an insulating film. However, lanthanum zirconium oxide may be altered by heating. If a transistor sensor containing lanthanum zirconium oxide is heated to a temperature exceeding 400°C, the lanthanum zirconium oxide layer may deteriorate, reducing the electrical characteristics of the sensor and reducing the detection sensitivity of biological substances. . Therefore, in a transistor sensor having lanthanum zirconium oxide, it is conceivable to use a photosensitive resin material such as a photosensitive resist that does not require heating as a coating material for the electrode. However, the protective film formed from photosensitive resin material is easily peeled off due to residual stress, and when detecting biological substances, ions generated by electrolysis of bases in the measurement solution chemically react with the photosensitive resin material, resulting in a protective coating. In some cases, the membrane deteriorated, making repeated use difficult.

This invention was made in view of the above-mentioned circumstances, and it forms a strong, high-resistance protective film that does not peel off from the electrode, does not easily deteriorate when detecting biological substances, and does not reduce the sensitivity of the sensor. An object of the present invention is to provide a method for manufacturing a sensor with a protective film that can be used.

In order to solve the above problems, a method for manufacturing a sensor with a protective film according to the present invention includes: an oxide layer containing a rare earth element and zirconium; and a sensor section formed on the oxide layer; preparing a sensor in which the sensor portion has a first electrode, a second electrode, a third electrode, and a semiconductor film connecting the first electrode and the second electrode; a step of forming a titanium film with a thickness of 3 nm or more and 20 nm or less; and a step of heating and oxidizing the titanium film at a temperature of 380° C. or more and 400° C. or less in the presence of oxygen. There is.

According to the method for manufacturing a sensor with a protective film of the present invention having such a configuration, the heating temperature of the titanium film is set to 400°C or less, so that the oxide layer containing rare earth elements and zirconium is not altered. Additionally, a protective film made of an oxidized titanium film can be formed on the surfaces of the first electrode and the second electrode. Furthermore, in the method for manufacturing a sensor with a protective film of the present invention, a titanium film having a thickness of 3 nm or more and 20 nm or less is heated at a temperature of 380°C or more in the presence of oxygen, so that the titanium film can be reliably oxidized. can. Furthermore, the protective film obtained by heating is made of titanium oxide, has high affinity with electrode materials, and has high corrosion resistance against various chemicals. Therefore, according to the method for manufacturing a sensor with a protective film having this configuration, a strong, high-resistance protective film that does not easily peel off from the electrode, does not easily deteriorate when detecting biological substances, and can be formed without reducing the sensitivity of the sensor. be able to.

Further, the method for manufacturing a sensor with a protective film of the present invention includes an oxide layer containing a rare earth element and zirconium, and a sensor section formed on the oxide layer, wherein the sensor section is connected to a first electrode. , preparing a sensor having a second electrode, a third electrode, and a semiconductor film connecting the first electrode and the second electrode; and forming a titanium film with a thickness of 3 nm or more on the first electrode and the second electrode. The structure includes a step of forming a film with a thickness of 10 nm or less, and a step of heating and oxidizing the titanium film at a temperature of 250° C. or higher and 400° C. or lower in the presence of oxygen.

In the method for manufacturing a sensor with a protective film of the present invention having such a configuration, a titanium film having a thickness of 3 nm or more and 10 nm or less is heated at a temperature of 250° C. or more and 400° C. or less in the presence of oxygen. The film can be reliably oxidized. Therefore, according to the method for manufacturing a sensor with a protective film having this configuration, a strong, high-resistance protective film that does not easily peel off from the electrode, does not easily deteriorate when detecting biological substances, and can be formed without reducing the sensitivity of the sensor. be able to.

According to the present invention, a method for manufacturing a sensor with a protective film can form a strong, high-resistance protective film that does not easily peel off from an electrode, does not easily deteriorate when detecting biological substances, and does not reduce the sensitivity of the sensor. It becomes possible to provide

FIG. 1 is a plan view of an example of a protective film-equipped sensor manufactured by a protective film-equipped sensor manufacturing method according to an embodiment of the present invention. 2 is a sectional view taken along line II-II in FIG. 1. FIG. FIG. 2 is a cross-sectional view showing a state in which the sensor with a protective film shown in FIG. 1 is brought into contact with a sample liquid containing a biological substance. 1 is a cross-sectional view of an example of a sensor used in a method for manufacturing a sensor with a protective film according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of an example of a state in which a titanium film is formed on a sensor in a method for manufacturing a sensor with a protective film according to an embodiment of the present invention. 2 shows the evaluation results of the protective film-equipped sensor obtained in Inventive Example 1, in which (a) is the measurement result of the On current, and (b) is the measurement result of the leakage current value. It is an evaluation result of the sensor with a protective film obtained in Example 2 of the present invention, in which (a) is the measurement result of the On current, and (b) is the measurement result of the leakage current value. These are the evaluation results of the sensor of Comparative Example 1 (without a protective film), in which (a) is the measurement result of the On current, and (b) is the measurement result of the leakage current value. These are the evaluation results of the protective film-equipped sensor obtained in Comparative Example 2, in which (a) is the measurement result of the On current, and (b) is the measurement result of the leakage current value.

A method for manufacturing a protective film-equipped sensor according to an embodiment of the present invention will be described below.

FIG. 1 is a plan view of an example of a protective film-equipped sensor manufactured by a method for manufacturing a protective film-equipped sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line II-II in FIG. 1. .
The sensor 1 with a protective film shown in FIGS. 1 and 2 includes a substrate 10, a conductive material layer 20 laminated on a part of the surface of the substrate 10, and a layer 20 formed on the surface of the substrate 10 so as to cover the conductive material layer 20. It has a stacked rare earth element-zirconium oxide layer 30 and a sensor section 40 formed on the rare earth element-zirconium oxide layer 30. The sensor section 40 includes a first electrode 41 , a second electrode 42 , a semiconductor film 50 connecting the first electrode 41 and the second electrode 42 , a reference electrode 43 , and a third electrode 44 connecting the reference electrode 43 . The first electrode 41 and the second electrode 42 are each covered with a protective film 60 except for the lead-out portions 41a and 42a. The third electrode 44 is covered with a protective film 60 except for the portion connected to the reference electrode 43 and the lead-out portion 44a.

As the substrate 10, for example, an insulating substrate and a semiconductor substrate can be used. Examples of insulating substrates include high heat-resistant glass, silicon substrates with silicon oxide coatings (SiO ₂ /Si substrates), alumina (Al ₂ O ₃ ) substrates, STO (SrTiO) substrates, and SiO ₂ layers on the surface of Si substrates. and one in which an STO (SrTiO) layer is formed via a Ti layer. Examples of semiconductor substrates include Si substrates, SiC substrates, and Ge substrates. The thickness of the substrate 10 is, for example, in a range of 10 μm or more and 1 mm or less.

The conductive member layer 20 is a conductive material layer containing a conductive material. The conductive member layer 20 may be formed only from a conductive material. Examples of the material of the conductive member layer 20 include metals such as platinum, gold, silver, copper, aluminum, molybdenum, palladium, ruthenium, iridium, tungsten, and titanium, metal materials such as alloys containing these metals, and indium. Metal oxides such as tin oxide (ITO) and ruthenium oxide (RuO ₂ ) can be used. The conductive member layer 20 may be a single-layer body consisting of one conductive material layer, or may be a laminate body consisting of two conductive material layers. The thickness of the conductive member layer 20 is, for example, within a range of 50 nm or more and 200 nm or less.

The rare earth element-zirconium oxide layer 30 is an oxide layer containing a rare earth element and zirconium. As the rare earth element, for example, lanthanum, yttrium, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium can be used. The atomic ratio of the rare earth element to zirconium in the rare earth element-zirconium oxide layer 30 is preferably 0.43 or more and 2.33 or less, and 1 or more and 2.33 or less, for example, when the rare earth element is 1. More preferably, it is .33 or less. The content of carbon (C) in the rare earth element-zirconium oxide layer 30 is preferably in the range of 0.5 atom % or more and 15 atom % or less. Further, the content of hydrogen (H) in the rare earth element-zirconium oxide layer 30 may be 2 atom % or more and 20 atom % or less. The thickness of the rare earth element-zirconium oxide layer 30 is, for example, within a range of 50 nm or more and 300 nm or less.

In plan view, the first electrode 41 (also referred to as a source electrode) has one end connected to the semiconductor film 50 and the other end passing around the semiconductor film 50 to the edge of the sensor section 40 on the opposite side. It is routed around to form a drawer portion 41a (see FIG. 1). The first electrode 41 is covered with a protective film 60 except for the lead-out portion 41a. The second electrode 42 (also referred to as a drain electrode) has one end connected to the semiconductor film 50 at a position facing the first electrode 41 in plan view, and the other end connected to the sensor portion in a straight line. It has a shape extending to the edge of 40, and serves as a pull-out portion 42a. Similar to the first electrode 41, the second electrode 42 is also covered with a protective film 60 except for the lead-out portion 42a. The drawer portions 41a and 42a are portions that are connected to external devices, respectively. As the material for the first electrode 41 and the second electrode 42, metal materials and metal oxides can be used. Examples of metal materials include high melting point metals such as platinum, and alloys thereof. Examples of metal oxides include indium tin oxide (ITO) and ruthenium oxide (RuO ₂ ). The first electrode 41 and the second electrode 42 may each be a single-layer body consisting of one electrode layer, or may be a multi-layer body consisting of two or more electrode material layers laminated. The thickness of the first electrode 41 and the second electrode 42 is, for example, within a range of 50 nm or more and 1000 nm or less.

The reference electrode 43 is an Ag/AgCl electrode. A third electrode 44 is connected to the lower surface of the reference electrode 43. The end of the third electrode 44 on the side opposite to the reference electrode 43 is routed around the edge of the sensor section 40 similarly to the first electrode 41 and the second electrode 42, and serves as a lead-out section 44a. (See Figure 1). As the material for the third electrode 44, metal materials and metal oxides can be used. Examples of the metal material and metal oxide are the same as those for the first electrode 41 and the second electrode 42.

The semiconductor film 50 (also referred to as a channel layer) is a film containing a semiconductor. The semiconductor film 50 may be formed only from a semiconductor. The semiconductor may be an inorganic semiconductor or an organic semiconductor. Preferably, the semiconductor film 50 is an indium oxide film. The indium oxide film may contain elements such as tin, zinc, zirconium, and gallium. These elements may be used alone or in combination of two or more. Probe molecules (not shown) for capturing biological substances to be detected are immobilized on the surface of the semiconductor film 50.

The protective film 60 is made of a titanium oxide film. The protective film 60 covers portions of the first electrode 41 and the second electrode excluding the lead-out portions 41a and 42a, the side surface of the third electrode, and a portion of the surface of the rare earth element-zirconium oxide layer 30. It is preferable that the protective film 60 has a sheet resistance of 1×10 ⁸ Ω/□ or more. The thickness of the protective film 60 is preferably in the range of 10 nm or more and 75 nm or less. An uncoated portion 30a is provided around the semiconductor film 50, which is not covered with the protective film 60 and comes into contact with a liquid for detecting a biological substance (sample liquid, measurement liquid). Probe molecules (not shown) for capturing biological substances to be detected may be immobilized on this uncovered portion 30a.

FIG. 3 is a sectional view showing a state in which the sensor with a protective film shown in FIG. 1 is brought into contact with a sample liquid containing a biological substance.
In FIG. 3, a sample liquid 70 containing a biological substance to be detected is supplied to the protective film-equipped sensor 1 so as to contact the semiconductor film 50, the reference electrode 43, and the uncovered portion 30a. As a result, the biological substance to be detected is captured by the probe molecules (not shown) fixed on the surface of the semiconductor film 50 and the probe molecules (not shown) fixed on the surface of the uncovered portion 30a. The captured biological material can be detected as follows. After cleaning the sample liquid 70, the measurement liquid is supplied so as to contact the semiconductor film 50, the reference electrode 43, and the uncoated portion 30a. The measurement liquid is a conductive liquid containing an acid or a base, such as a buffer solution. Then, the voltage between the third electrode 44 (reference electrode 43) and the first electrode 41 (source electrode) and the current between the first electrode 41 (source electrode) and the second electrode (drain electrode) are measured. Detecting the amount of captured biological material based on the measurements.

A method for manufacturing a sensor with a protective film according to an embodiment of the present invention includes a preparation step of preparing a sensor on which a protective film is to be formed, a film forming step of forming a titanium film on the surface of the sensor, and an oxidation step of the titanium film. oxidation step.

FIG. 4 is a cross-sectional view of an example of a sensor (a sensor on which a protective film is formed) used in the method for manufacturing a sensor with a protective film according to an embodiment of the present invention.
The sensor 2 shown in FIG. 4 is the same as the sensor with a protective film shown in FIGS. 1 and 2 except that it does not have the protective film 60 and the reference electrode 43, so the same components are denoted by the same reference numerals. Therefore, detailed explanation thereof will be omitted.

The sensor 2 can be manufactured, for example, as follows.
First, the conductive member layer 20 is formed on the substrate 10 with a mask placed thereon. The conductive member layer 20 can be formed using, for example, a sputtering method.
Next, the mask is removed, and a rare earth element-zirconium oxide layer 30 is formed on the substrate 10 and the conductive member layer 20. The rare earth element-zirconium oxide layer 30 can be formed using a coating method. For example, a rare earth element-zirconium solution is applied onto the substrate 10 and the conductive member layer 20, and the resulting coating film is pre-baked and dried in an oxygen-containing atmosphere, and then heated at 400°C or less. The rare earth element-zirconium oxide layer 30 can be formed by main firing at this temperature.

Next, a semiconductor film 50 is formed on the rare earth element-zirconium oxide layer 30. A semiconductor film can be formed by using a coating method and an etching method. For example, a raw material solution for a semiconductor film is coated on the rare earth element-zirconium oxide layer 30, the resulting coated film is pre-baked and dried in an oxygen-containing atmosphere, and then heated to a temperature of 400°C or less. By performing the main firing, a semiconductor film can be formed over the entire surface of the rare earth element-zirconium oxide layer 30. Next, the surface of the semiconductor film is coated with a photoresist using photolithography to cover the portion where the semiconductor film 50 will be formed, and then the portion not covered with the photoresist is removed using an etching solution to remove unnecessary parts. Remove the semiconductor film.

Next, a first electrode 41, a second electrode 42, and a third electrode 44 are formed. The first electrode 41, the second electrode 42, and the third electrode 44 can be formed using, for example, a sputtering method.
The sensor 2 can be prepared as described above.

In the film forming process, the lead-out part 41a of the first electrode 41 of the sensor section 40 of the sensor 2 prepared in the preparation process, the lead-out part 42a of the second electrode 42, and a part of the upper surface of the third electrode 44 and the lead-out part 44a are removed. Then, a titanium film is formed around the semiconductor film 50 except for the uncoated portion 30a. In the film forming process, it is preferable to form a titanium film in the above pattern, for example, by forming a titanium film on the entire surface of the sensor section 40 of the sensor 2 and then removing unnecessary titanium films.

FIG. 5 is a cross-sectional view of an example of a state in which a titanium film 60a is formed on the sensor 2. As shown in FIG.
As shown in FIG. 5, a titanium film 60a is formed on the entire surface of the sensor section 40 of the sensor 2. The titanium film 60a can be formed by a sputtering method. The thickness of the titanium film 60a is within the range of 3 nm or more and 20 nm or less (10 nm or more and 75 nm in terms of oxide). If the film thickness is less than 3 nm, the strength of the finally obtained titanium oxide film may be weakened. On the other hand, if the film thickness exceeds 20 nm, it may be difficult to uniformly oxidize titanium by firing at a temperature of 400° C. or lower.

Unnecessary titanium film can be removed using an etching method. Specifically, first, the surface of the titanium film 60a is coated with a photoresist at a portion where a titanium oxide layer will be formed using photolithography. Next, the unnecessary titanium film is removed by removing the portions not covered with the photoresist using an etching solution.

In the oxidation step, the titanium film is heated and oxidized in the presence of oxygen. The ambient oxygen concentration during heating is, for example, 20% by volume or more. The surrounding environment during heating may be an atmospheric environment.

The heating temperature is 400°C or less. If the heating temperature is higher than 400° C., the rare earth element-zirconium oxide layer 30 may be altered, the electrical characteristics of the protective film-equipped sensor 1 may be reduced, and the detection sensitivity of biological substances may be reduced. The heating temperature and heating time vary depending on the thickness of the titanium film. For example, if the heating temperature is in the range of 380°C or more and 400°C or less, and the film thickness is in the range of 3nm or more and 10nm or less, especially 3nm or more and 7nm or less, the heating time may be 10 minutes or less. good. When the film thickness exceeds 10 nm, especially when it is 15 nm or more, the heating time is preferably 20 minutes or more, and when the film thickness is in the range of 18 nm or more and 20 nm or less, the heating time is preferably 30 minutes or more. preferable. Further, when the thickness of the titanium film is within the range of 3 nm or more and 10 nm or less, particularly when it is within the range of 3 nm or more and 7 nm or less, the heating temperature may be within the range of 250° C. or more and 400° C. or less. When the film thickness is within the range of 3 nm or more and 10 nm or less, and the heating temperature is 250°C, the heating time is preferably 40 minutes or more, and when the heating temperature is 300°C, the heating time is preferably 30 minutes or more, and the heating temperature When the temperature is 350° C. or more and 400° C. or less, the heating temperature is preferably 10 minutes or more.

After the protective layer is formed as described above, a reference electrode 43 (Ag/AgCl) is formed on the upper surface of the third electrode 44.

According to the method for manufacturing a sensor with a protective film of the present embodiment configured as described above, since the heating temperature when oxidizing the titanium film is set to 400° C. or lower, the rare earth element-zirconium oxide layer 30 It is possible to form the protective film 60 on each of the parts of the first electrode 41 excluding the lead-out part 41a, the part of the second electrode 42 except the lead-out part 42a, and the side surfaces of the third electrode 44 without deteriorating the quality of the electrode. can. Further, since a titanium film having a thickness of 3 nm or more and 20 nm or less is heated at a temperature of 380° C. or more in the presence of oxygen, the titanium film can be reliably oxidized. Furthermore, the protective film obtained by heating is made of titanium oxide, has high affinity with electrode materials, and has high corrosion resistance against various chemicals. Therefore, according to the method for manufacturing a sensor with a protective film according to the present embodiment, a strong and high-resistance protective film that does not easily peel off from the electrode, does not easily deteriorate when detecting biological substances, and can be formed without reducing the sensitivity of the sensor. can do.

Further, according to the method for manufacturing a sensor with a protective film of the present embodiment, titanium film can also be produced by heating a titanium film having a thickness of 3 nm or more and 10 nm or less at a temperature of 250° C. or more and 400° C. or less in the presence of oxygen. The film can be reliably oxidized. Therefore, according to the method for manufacturing a sensor with a protective film according to this embodiment, a strong and high-resistance protective film that is difficult to peel off from electrodes, does not easily deteriorate when detecting biological substances, and can be produced without reducing the sensitivity of the sensor. It can be membraned.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical idea of the invention.

[Experiment example 1]
A sensor 2 without a protective film shown in FIG. 4 was prepared. The materials and manufacturing methods for each part are as follows.
Substrate 10: a silicon substrate (SiO ₂ /Si substrate) having a silicon oxide film with a thickness of 500 nm.
Conductive member layer 20: A Pt/Ti layer in which a platinum layer (thickness: 100 nm) is laminated on a titanium layer (thickness: 10 nm). The titanium layer and platinum layer were formed by sputtering.
Rare earth element-zirconium oxide layer 30: LaZrO layer with a thickness of 120 nm. The LaZrO layer is formed by applying a La _0.5 Zr _0.5 O solution by spin coating, preliminarily baking the resulting coating layer at 250°C in an oxygen-containing atmosphere, and then main baking it at 400°C. did. The La _0.5 Zr _0.5 O solution is prepared by mixing lanthanum acetate hemihydrate and zirconium butoxide at a ratio of 1:1 (molar ratio), and adding the resulting mixture to the La _{0.5 Zr 0.5} O solution _. It was prepared by dissolving it in propionic acid to a concentration of 0.2 mol/kg in terms of ₅ O concentration, and refluxing the resulting mixed solution at 110° C. for 30 minutes.
First electrode 41, second electrode 42, third electrode 44: Pt/ITO electrodes in which a platinum layer (thickness: 100 nm) is laminated on an ITO layer (thickness: 50 nm). The ITO layer and platinum layer were formed by sputtering.
Semiconductor film 50: In ₂ O _three layers with a thickness of 20 nm. The In ₂ O ₃ layer was formed by applying an In ₂ O ₃ solution by spin coating, preliminarily baking the obtained coating layer at 250° C. in an oxygen-containing atmosphere, and then main baking at 300° C. The In ₂ O ₃ solution was prepared by dissolving indium nitrate trihydrate in 2-methoxyethanol to give an In ₂ O ₃ concentration of 0.2 mol/kg, and the resulting solution was heated at 110°C for 30 min. Prepared by refluxing for minutes.

A titanium film was formed on the entire surface of the sensor section 40 of the prepared sensor 2 by using a sputtering method using a Ti target. The conditions for forming the titanium film were as follows.
Power: 300W
Pressure inside the chamber: 0.1Pa
T/S distance (distance between sensor 2 and target): 100mm,
Film thickness: 7 nm (oxide equivalent film thickness: 25 nm), 15 nm (oxide equivalent film thickness: 54 nm), 20 nm (oxide equivalent film thickness: 72 nm)

Next, a resist film adhesion improver (OAP, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied to the surface of the sensor 2 on which the titanium film was formed at 2000 rpm for 35 seconds, and then a resist solution (TSMR8900, Tokyo Ohka Kogyo Co., Ltd.) was applied to the surface of the sensor 2 on which the titanium film was formed. (manufactured by the same company) was applied by spin coating at 3000 rpm for 35 seconds. Thereafter, the resist solution was heated on a hot plate at 110° C. for 1 minute and 30 seconds to solidify the resist solution. Next, a positive photomask was attached to the resist film using a mask aligner (manufactured by SUSS), and patterning was performed by exposing the resist film to light at an integrated dose of 80 mJ/cm ² using a soft contact. The exposed sensor 2 was immersed in a developer (NMD-W, manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 2 minutes to remove unnecessary portions of the resist. Three trays containing ultrapure water were prepared for rinsing, and the trays were washed in turn while being rocked. After removing moisture by air blowing, it was heated on a hot plate at 150° C. for 5 minutes (post-baking). Next, the post-baked sensor 2 was immersed in an etching solution containing NaOH and H ₂ O ₂ at a ratio of 1:1 (mass ratio) for 28 seconds at room temperature to etch the patterned portion. The etched sensor 2 was immersed in a stripping solution (104, manufactured by Tokyo Ohka Kogyo Co., Ltd.), heated for 15 minutes at 80° C. using a hot plate, and then washed for 2 minutes using an ultrasonic cleaner. The cleaned sensor 2 was washed with a cleaning liquid (Strip Rinse-4, manufactured by Tokyo Ohka Kogyo Co., Ltd.) to remove the stripping liquid, and then rinsed with IPA and ultrapure water.
In this way, the lead-out part 41a of the first electrode 41 of the sensor section 40, the lead-out part 42a of the second electrode 42, a part of the upper surface and the lead-out part 44a of the third electrode 44, and the uncoated part 30a around the semiconductor film 50. A plurality of samples were prepared in which a titanium film was formed on the portions other than the .

The prepared sample was heated at a heating temperature of 250° C., 300° C., 350° C., and 400° C. for a heating time of 30 minutes to oxidize the titanium film. The sheet resistance of the titanium oxide film of the sample after heating was measured using a resistivity meter (Hiresta-UR (MCR-HT450), manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The results are shown in Table 1 below.

From the results in Table 1, it can be seen that the sample with a titanium film thickness of 7 nm has a high sheet resistance even at a heating temperature of 250° C., indicating that titanium is oxidized. On the other hand, for a sample with a titanium film thickness of 20 nm, the sheet resistance when the heating temperature was 350°C increased by 2.6 times compared to the sheet resistance when the heating temperature was 250°C, and the annealing temperature was 400°C. It can be seen that the sheet resistance increases rapidly.

[Experiment example 2]
A sample prepared in the same manner as in Experimental Example 1 was heated at a heating temperature of 400° C. and a heating time of 10 minutes, 20 minutes, and 30 minutes to oxidize the titanium film. The sheet resistance of the titanium oxide film of the sample after heating was measured in the same manner as in Experimental Example 1. The results are shown in Table 2 below.

From the results in Table 2, it can be seen that the sheet resistance of the samples with titanium film thicknesses of 15 nm and 20 nm also increases by increasing the annealing time.

From the above, it can be seen that when the thickness of the titanium film is within the range of 3 nm or more and 20 nm or less, titanium can be sufficiently oxidized if the heating temperature is 380° C. or higher. In particular, it can be seen that when the thickness of the titanium film is within the range of 3 nm or more and 10 nm or less, titanium can be sufficiently oxidized if the annealing temperature is 250° C. or higher.

[Example 1 of the present invention]
The lead-out part 41a of the first electrode 41 of the sensor section 40, the lead-out part 42a of the second electrode 42, a part of the upper surface and lead-out part 44a of the third electrode 44, and the semiconductor film 50 were prepared in the same manner as in Experimental Example 1. A sample in which a titanium film with a thickness of 7 nm was formed on the surrounding area except for the uncoated part 30a was heat-treated at 400° C. for 30 minutes to oxidize the titanium film. Next, a reference electrode 43 (Ag/AgCl) was formed on the upper surface of the third electrode 44 to obtain a sensor with a protective film.

[Example 2 of the present invention]
The lead-out part 41a of the first electrode 41 of the sensor section 40, the lead-out part 42a of the second electrode 42, a part of the upper surface and lead-out part 44a of the third electrode 44, and the semiconductor film 50 were prepared in the same manner as in Experimental Example 1. A sample in which a titanium film with a thickness of 20 nm was formed on the surrounding area except for the uncoated part 30a was heat-treated at 400° C. for 30 minutes to oxidize the titanium film. Next, a reference electrode 43 (Ag/AgCl) was formed on the upper surface of the third electrode 44 to obtain a sensor with a protective film.

[Comparative example 1]
A reference electrode (Ag/AgCl) was formed on the upper surface of the third electrode 44 of the sensor without a protective film prepared in Experimental Example 1 to obtain a sensor.

[Comparative example 2]
The lead-out part 41a of the first electrode 41 of the sensor part 40 of the sensor without a protective film prepared in Experimental Example 1, the lead-out part 42a of the second electrode 42, a part of the upper surface of the third electrode 44 and the lead-out part 44a, and the semiconductor A protective film was formed using a photosensitive resist around the film 50 except for the uncoated part 30a. Next, a reference electrode 43 (Ag/AgCl) was formed on the upper surface of the third electrode 44 to obtain a sensor with a protective film.

[evaluation]
The ON current and leakage current of the sensors of Inventive Examples 1 and 2 and Comparative Examples 1 and 2 were measured by the following methods. The results are shown in FIGS. 6 to 9. For the sensors with protective films obtained in Examples 1 and 2 of the present invention, ON current and leakage current were each measured repeatedly four times.

(Measurement method of ON current and leakage current)
ON current and leakage current were measured using semiconductor parameters. 200 μL of PbS (phosphate buffered saline, pH: 7.4) having a concentration of 1 mM was dropped so as to contact the semiconductor film 50, the reference electrode 43, and the uncoated portion 30a. When the voltage V _DS between the first electrode 41 and the second electrode is set to 0.2 V, and the voltage V _TG is applied to the reference electrode 43 under the conditions of 0 V to 1.2 V (5 mV/Step), a voltage flows to the semiconductor film 50. By measuring the current amount I _d , the On current value and leakage current value with respect to the applied voltage were obtained.

FIG. 6 shows the evaluation results of the protective film-equipped sensor obtained in Inventive Example 1, in which (a) is the measurement result of the ON current, and (b) is the measurement result of the leakage current value.
From the results shown in FIG. 6, it can be seen that the four measurement results are the same for both the On current and the leakage current, and that repeated use is possible. Furthermore, since the leakage current value with respect to the ON current value is as low as 10% or less, it can be seen that biological substances can be detected with high sensitivity by using this sensor with a protective film.

FIG. 7 shows the evaluation results of the protective film-equipped sensor obtained in Inventive Example 2, in which (a) is the measurement result of the ON current, and (b) is the measurement result of the leakage current value.
From the results in FIG. 7, it can be seen that the four measurement results for both the on current and the leakage current are equivalent, and that repeated use is possible. Furthermore, since the leakage current value with respect to the ON current value is as low as 10% or less, it can be seen that biological substances can be detected with high sensitivity by using this sensor with a protective film.

FIG. 8 shows the evaluation results of the sensor of Comparative Example 1 (without a protective film), where (a) is the measurement result of the On current, and (b) is the measurement result of the leakage current value.
From the results in FIG. 8, it can be seen that the leakage current value of the sensor of Comparative Example 1 is equal to or 10% or more of the On current value, which is higher than that of the sensor with a protective film of Invention Example 1 and Invention Example 2. , it can be seen that the sensitivity decreases. This is considered to be because the properties of the electrode surfaces changed due to direct contact between the first electrode and the second electrode with the measurement liquid.

FIG. 9 shows the evaluation results of the protective film-equipped sensor obtained in Comparative Example 2, in which (a) is the measurement result of the ON current, and (b) is the measurement result of the leakage current value.
From the results in FIG. 9, it can be seen that the leakage current value of the protective film-equipped sensor of Comparative Example 2 is equal to or 10% or more than the On-current value, and compared to the protective film-equipped sensor of Inventive Example 1 and Inventive Example 2. It can be seen that the sensitivity decreases because it is high. This is considered to be because the protective films of the first and second electrodes were peeled off when they came into contact with the measurement liquid, and the first and second electrodes came into direct contact with the measurement liquid.

1 Sensor with protective film 2 Sensor 10 Substrate 20 Conductive member layer 30 Rare earth element-zirconium oxide layer 30a Uncoated part 40 Sensor part 41 First electrode 41a Leading part 42 Second electrode 42a Leading part 43 Reference electrode 44 Third electrode 44a Drawer part 50 Semiconductor film 60 Protective film 60a Titanium film 70 Sample liquid

Claims (2)

It has an oxide layer containing a rare earth element and zirconium, and a sensor section formed on the oxide layer, and the sensor section includes a first electrode, a second electrode, a third electrode, and the first electrode. preparing a sensor having a semiconductor film connected to the second electrode;
forming a titanium film on the first electrode and the second electrode with a thickness of 3 nm or more and 20 nm or less;
A method for manufacturing a sensor with a protective film, comprising the step of heating the titanium film at a temperature of 380° C. or higher and 400° C. or lower in the presence of oxygen to oxidize the titanium film. It has an oxide layer containing a rare earth element and zirconium, and a sensor section formed on the oxide layer, and the sensor section includes a first electrode, a second electrode, a third electrode, and the first electrode. preparing a sensor having a semiconductor film connected to the second electrode;
forming a titanium film on the first electrode and the second electrode with a thickness of 3 nm or more and 10 nm or less;
A method for manufacturing a sensor with a protective film, comprising the step of heating the titanium film at a temperature of 250° C. or higher and 400° C. or lower in the presence of oxygen to oxidize the titanium film.

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