TWI452290B - Field-effect ion sensing device with dual-film differential structure - Google Patents

Description

Field effect type ion sensing device with double membrane differential structure

The invention relates to a pH sensor device, in particular to a pH sensor device formed by a field effect type ion sensing device with a double film differential structure.

pH sensor can be used in various industrial inspections in petrochemical, food, water, medical, environmental, electrical, semiconductor, optoelectronic, biotechnology, etc., including in traditional industries and high-tech industries. The measurement and application of pH are quite frequent and extensive.

Compared with traditional glass electrodes, Ion-Sensitive Field Effect Transistor (ISFET) mainly uses the principle of Metal Oxide Semiconductor Field Effect Transistor (MOSFET). After the gate electrode was removed, the element with the cerium oxide (SiO ₂ ) layer was placed in an aqueous solution, and it was found that the effect was the same as that of the glass electrode, that is, it had acid-base sensing characteristics.

The ion-sensing field-effect transistor component utilizes the pH response characteristics of different sensing films, the surface of which will form an electric double layer with a solution of different pH values, and the OH ^- ion group of the electric double layer is related to the surface density Ns. The Ns value of each type of insulating layer is its characteristic value. When the surface is exposed to an acid-base solution, site-bonding is involved in the chemical reaction as a separation. Since N _{s is} related to the acid-base equilibrium constants k _a and k _b , when the components are placed in solutions of different pH values, their k _a and k _b will be different, thus causing a change in N _s , which in turn affects the electrical double layer. The potential difference causes the difference in the threshold voltage of the ion-sensing field-effect transistor. When the fixed V _DS and V _G are provided, different pH will cause the difference of I _DS to be sensed and quantified.

Since ion-sensing field-effect transistors were published by P. Bergveld in 1970 (IEEE Transcactions on Bio-Medical Engineering, pp. 70-71, 1970), related research is ongoing. For example, improvements in materials, research and miniaturization of reference electrodes, and structural improvements have been discussed. The current patents for ion-sensing field-effect transistors include: U.S. Patent No. 5,414,284, which discloses that an ion-sensing field-effect transistor component and an ESD protection circuit are simultaneously fabricated on the same substrate; U.S. Patent No. 5,407,854, the disclosure of which is incorporated herein incorporated by reference in its entirety, the entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire disclosure Sensing, and using platinum metal as a reference electrode; U.S. Patent No. 5,350,701 discloses the use of a chemically synthesized phosphating-based sensing film on the gate region of a field-effect type ion sensing element for alkaline earth family The detection of the metal content, in particular for the sensing of the calcium ion content; U.S. Patent No. 5,319,226, the disclosure of which is incorporated herein by reference. On the sluice area, a field effect type ion sensing element having a yttria/niobium nitride/yttria structure is formed; U.S. Patent No. 5,314,833 is disclosed. Using gallium arsenide (GaAs) substrate, depositing a silicon thin film, and on this film in the implant arsenic (As ⁺⁾ and phosphorus (P ⁺⁾ ions, in the preparation of low ZU gate material to reduce the thermal effects of the elements, improve transistor U.S. Patent No. 4,812,220, the disclosure of which is incorporated herein by reference to U.S. Patent No. 4, 812,220, the disclosure of which is incorporated herein by reference. A MOS transistor and a field effect type ion sensing element are combined into a differential pair module system; U.S. Patent No. 4,609,932 discloses a laser drilling technique using MEMS technology to prepare a three-dimensional structure. Field effect type ion sensing element; and US Patent No. 4,358,274, discloses a differential system using a set of field effect type ion sensing elements, combined with a circuit readout module, thereby achieving temperature compensation. .

When forming field-effect ion sensing transistors, the most commonly used gate layers are yttrium oxide, tantalum pentoxide, aluminum oxide and hafnium oxide, and the most common is the use of germanium dioxide as a gate. The layer is contacted with the aqueous solution by the cerium oxide gate layer for sensing the interface potential generated by the aqueous solution on the surface of the cerium oxide layer for the purpose of sensing the concentration of the aqueous solution ions. In short, the ion-sensing field-effect transistor is an electrochemical and micro-electromechanical device that has the function of an ion-selective electrode (ISE) and also has the characteristics of a field-effect transistor. A novel ion sensing element that is distinct from conventional ion selective electrodes. However, the disadvantage of using erbium dioxide as a gate layer is that it has a leakage current, which is a problem to be solved by current ion sensing field effect transistor elements.

The invention relates to a field effect type ion sensing device with a double membrane differential structure, which can be used for a pH sensor device.

The invention adopts an inorganic film for sensing low hydrogen ions, and adopts a film with high deformation stress, and adjusts the sensitivity of the sensing film to hydrogen ion sensing by modulating the thickness of the film or changing the substrate type and doping concentration.

According to the above object, the present invention discloses a field effect type ion sensing device having a double film differential structure for sensing pH, comprising: a semiconductor substrate having an upper surface and a lower surface; and an insulating layer formed on the semiconductor a surface of the substrate; a first film layer formed on the insulating layer; a second film layer formed on a portion of the surface of the first film layer; and a metal contact layer formed on a portion of the lower surface of the semiconductor substrate.

The present invention discloses another field effect type ion sensing device having a double film differential structure for sensing pH, comprising: a semiconductor substrate having an upper surface and a lower surface; and an insulating layer formed on the semiconductor substrate a first film layer formed on the insulating layer; at least two adhesive layers formed on the first film layer for defining a sensing region on the first film; and a plurality of intermediate materials formed on the two layers Between the adhesive layers; a second film layer formed between the two adhesive layers and covering the plurality of intermediate materials; and a metal contact layer formed on a portion of the lower surface of the semiconductor substrate.

Therefore, the advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

The invention relates to a field effect type ion sensing device with double membrane differential structure for sensing pH. In order to fully understand the present invention, a detailed device structure will be presented in the following description.

Please refer to FIG. 1A, which is a schematic cross-sectional view showing a field effect type ion sensing device having a double film differential structure. As shown in FIG. 1A, a semiconductor substrate 10, particularly a P-type semiconductor substrate, is provided first. Next, in order to ensure a certain degree of flatness on the surface of the semiconductor substrate 10 and no native oxide. Therefore, during the subsequent process, the cleaning process is performed, in particular, the RCA process is used to clean the semiconductor substrate 10 to ensure that particulates, metal impurities, organic matter, and oxide layers can be completely removed and the semiconductor substrate 10 is not re-deposited. on. Next, a thickness of about 450 angstroms is formed on the semiconductor substrate 10 by thermal oxidation ( The ruthenium dioxide layer (SiO ₂ ) is used as an insulator 12 .

Then, since the cerium oxide has a high dielectric constant, it is used in the present embodiment to replace the gate oxide layer in the original gold oxide semiconductor field effect transistor (MOSFET) structure to avoid application of the gate oxide layer. After the voltage is applied to the field effect transistor, leakage current occurs due to the thinning of the gate oxide layer. In addition, the germanium dioxide has a large energy gap (Eg>5eV), good thermal stability and reliability, so it can be done. It is a sensing membrane in a light addressable potentiometric sensor (LAPS). Therefore, after the insulating layer 12 is formed on the semiconductor substrate 10, a layer of hafnium oxide (HfO ₂ ) having a thickness of about 350 angstroms (A) is formed as a first thin film layer 14 in an insulating layer by a sputtering method. 12 on.

Next, a rapid thermal annealing (RTA) step is performed on the semiconductor substrate 10 having the insulating layer 12 and the ceria layer as the first thin film layer 14, and the tempering time is about 1 minute, and The tempering temperature is about 700 °C.

Next, referring to FIG. 1A, a metal layer (not shown) is formed on the back surface of the semiconductor substrate 10 that has been subjected to the cleaning step; and then a pattern is formed on the metal layer by using a semiconductor process such as a lithography and etching process. The photoresist layer (not shown) is then removed by an etching step to form a metal contact layer 30 as an electrode. In the present embodiment, the metal contact layer 30 is made of aluminum.

Next, a hafnium oxide (HfTaO) layer is formed over the first thin film layer 14 by forming a photomask layer (not shown) over the first thin film layer 14 to cover Sensing a portion of the first film layer 14 of the film; then, by sputtering, in particular RF sputtering, without being covered by a mask layer (not shown) On the other portion of the first film layer 14, a ruthenium oxide layer having a thickness of about 200 angstroms (A) and serving as the second film layer 16 is formed. Therefore, the field effect type ion sensing device is formed by simultaneously utilizing the sensing film structure composed of the first film layer 14 and the second film layer 16 to sense the presence of hydrogen (H ⁺ ) ions.

Next, please refer to FIG. 1B, which is a schematic diagram showing a field effect type ion sensing device having a sensing film. In FIG. 1B, the reference electrode 40 placed above the structure of FIG. 1A provides a reference potential when measuring the pH, and a lighting device is disposed on the defined illumination area on the lower surface of the semiconductor substrate 10. 50, such as an infrared light emitting diode (IR LED), for providing a light source to illuminate the field effect type ion sensing device, and extracting the signal by the metal contact layer 30, and amplifying the signal through the op amplifier and A sensing electrode 14 is compared with the hydrogen ions sensed by the second sensing film 16 and compared with the reference potential provided by the reference electrode 40 to obtain the pH of the solution to be sensed.

Next, in FIG. 2A, a field effect type ion sensing device having a cerium oxide (HfO ₂ ) layer/yttria (HfTaO) layer sensing film structure after a thermal tempering step is shown at a pH of 2 (pH=2) to a buffer solution with a pH of 12 (pH=12), a graph of the current (I) and voltage (V) produced after sensing.

Also shown in Fig. 2B is a field effect type ion sensing device having a cerium oxide (HfO ₂ ) layer/yttria (HfTaO) layer sensing film structure after a thermal tempering step having a pH of 2 ( pH=2) to a buffer solution with a pH of 12 (pH=12), a graph of current (I) and voltage (V) produced after sensing.

Figure 2C shows a field effect type ion sensing device having a cerium oxide (HfO ₂ ) layer / yttria (HfTaO) layer sensing film structure after a thermal tempering step at a pH of 2 (pH = 2) A diagram showing the relationship between the current (I) and the voltage (V) generated after sensing by a buffer solution having a pH of 12 (pH = 12).

The small graph in Fig. 2C shows the relationship between voltage and pH, wherein the field effect type ion sensing device has a sensitivity of 10.26 and a linearity of 99.246. Therefore, it is apparent that a field effect type ion sensing device having a cerium oxide (HfO ₂ ) layer/yttria (HfTaO) layer sensing film structure has good sensitivity to pH.

3A is a schematic cross-sectional view showing another field effect type ion sensing device having a double film differential structure in the 3A, wherein the semiconductor substrate 10, the insulating layer 12, the first film layer 14 and the metal contact are in contact with each other. The formation, structure and function of the layer 30 are the same as those of the previous embodiments, and will not be further described herein. Here, it is to be noted that after performing the thermal tempering step on the first film layer 14, a plurality of glue layers 20 are formed on the first film layer 14, in this embodiment, by The plurality of glue layers 20 define a sensing region 15 on the first film layer 14. Next, the semiconductor substrate 20 having a plurality of adhesive layers 20 is subjected to a baking step at a temperature of 150 ° C for a baking time of about 40 minutes so that a plurality of adhesive layers 20 can be adhered to the surface of the first film layer 14.

Next, a cleaning step is performed to clean the semiconductor substrate 10 having a plurality of adhesive layers 20 which are baked and cured by using an alcohol, particularly ethanol and deionized water, to ensure the cleanliness of the semiconductor substrate 10 again. Then, the semiconductor substrate 10 was dried at room temperature for about 30 minutes.

Then, a silylating process is performed on the semiconductor substrate 10 such that a plurality of intermediates 22 are formed on the surface of the first thin film layer 14 on the sensing region 15, and the forming step includes: using toluene The mixed solution of hexamethyldiazide (HMDS, hexamethyldisilane) is diluted and contacted on the sensing region 15 of the semiconductor substrate 10 to make the ruthenium of the hexamethyldioxane and the first thin film layer (dioxide The ruthenium layer 14 reacts to form a plurality of ruthenium oxides (i.e., intermediates) 22 on the sensing region 14. In this embodiment, the volume ratio of hexamethyldioxane to methane is about 1:3 and the volume of the decane-based mixed solution formed is about 62 ul to 85 ul. Then, the semiconductor substrate 10 subjected to the decaneization step was dried at room temperature for about 30 minutes.

Next, referring also to FIG. 3A, polyvinyl chloride (PVC) is deposited on the sensing region 15 of the semiconductor substrate 10, and covers a plurality of intermediates 22 formed between the sensing regions 15 to form The second film layer 18 is a polyvinyl chloride film layer, and then dried at room temperature for at least 12 hours or more to complete a field effect type ion sensing device having a double layer sensing film. It should be noted that the polyvinyl chloride film layer 18 may be only polyvinyl chloride or a mixture of DNP and polyvinyl chloride. The ratio of the DNP configuration may be 50% of the mixture (DNP plus polyvinyl chloride). Between % and 80%, the weight of this mixture must be maintained at about 200 mg and must be dissolved in tetrahydrofuran (THF, Tetrahydrofuran) solution.

Next, referring to FIG. 3B, a schematic diagram of a field effect type ion sensing device having a double film differential structure is shown. In FIG. 3B, the reference electrode 40 placed above the structure of FIG. 3A provides a reference potential when measuring the pH, and a lighting device is disposed on the defined illumination area on the lower surface of the semiconductor substrate 10. 50, for example, an infrared light emitting diode (IR LED) for providing a light source to illuminate a sensing region of the field effect type ion sensing device, and extracting a signal through the metal contact layer 30 on the lower surface of the semiconductor substrate 10, via After the op amplifier amplifies the signal and compares the hydrogen ions sensed by the first sensing film 14 and the second sensing film 16 with the reference potential provided by the reference electrode 40, the pH of the solution to be sensed can be obtained. .

Further, in Fig. 3C, there is shown a schematic view of another preferred embodiment of the field effect type ion sensing device having a double film differential structure. The difference between the 3C and 3B is that the plurality of adhesive layers 20 formed on the first film layer 14 are formed in an array, and the surface of the first film layer 14 is divided into a plurality of sensing regions, and the same. After the decaneization step, a plurality of intermediates 22 are formed only on the surface of the first film layer 14 subjected to the decaneization step; then, in the same manner as the foregoing steps, the mixture containing the polyvinyl chloride is formed in the first step. The film layer 14 is covered with a plurality of intermediates 22 to complete the structure of a utility ion sensing device.

In Fig. 4A, the pH of the buffer solution is from 2 to 12, and when the irradiation device illuminates the sensing region of the field-effect ion sensing device, the signal is extracted by the metal contact layer 30. A plot of the current versus voltage produced by the conversion, in which the weight percent of its DNP is 60%.

Figure 4B shows that the weight percentage of DNP is 60%, and the pH of the buffer solution is also from 2 to 12, and when the irradiation device illuminates the sensing region of the field effect ion sensing device, the metal contact layer 30 A diagram showing the relationship between the current and voltage generated by the signal conversion.

The 4C figure is a graph that converts the 4B picture into a voltage and a pH, and the sensitivity is 24.32, and the linearity is 98.807.

4D is a weight percentage of DNP of 70%, and also the pH of the buffer solution is from 2 to 12, and when the irradiation device illuminates the sensing region of the field effect ion sensing device, by the metal contact layer 30 A diagram showing the relationship between current and voltage generated by signal conversion.

The 4E plot is a graph that converts the 4D graph into a voltage versus pH, which gives a sensitivity of 34.96 and a linearity of 99.004.

FIG. 4F is a graph showing that the weight percentage of DNP is 80%, and the pH of the buffer solution is also from 2 to 12, and when the irradiation device irradiates the sensing region of the field effect type ion sensing device, the metal contact layer 30 is used. A diagram showing the relationship between current and voltage generated by signal conversion.

The 4G graph is a graph that converts the 4F map into a voltage and a pH, and the sensitivity is 50.26 and the linearity is 98.294.

In addition, in FIG. 4H, the pH of the buffer solution is from 2 to 12, and when the irradiation device irradiates the sensing region of the field effect ion sensing device, the signal extracted by the metal contact layer 30 is passed through The relationship between current and voltage generated by signal conversion is different from that of Figure 4A in that there is only a polyvinyl chloride film and no DNP.

4I is a diagram for converting the 4H map into a voltage and a pH, and the degree of sensitivity of the polyvinyl chloride (second film layer 18) is 33 mV/pH, and the ruthenium dioxide layer (first film layer 14) can be obtained. The sensitivity is 59 mV/pH.

In the 4th figure, the weight percentage of DNP is 80%, and the invention has a polyvinyl chloride/ceria layer sensing film structure, the pH of the buffer solution is from 2 to 12, and when the irradiation device irradiates the field effect type ion sensation A diagram showing the relationship between current and voltage generated by signal conversion by the signal captured by the metal contact layer 30 when the sensing region of the device is measured.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the present invention should be included in the following. Within the scope of the patent application.

10. . . Semiconductor substrate

12. . . Insulation

14. . . First film layer

15. . . Sensing area

16. . . Second film layer

18. . . Second film layer

20. . . Glue layer

twenty two. . . Intermediate

30. . . Metal contact layer

40. . . Reference electrode

50. . . Irradiation device

1A is a schematic cross-sectional view of a field effect type ion sensing device having a dual film differential structure in accordance with the teachings of the present invention.

1B is a schematic diagram showing a field effect type ion sensing device having a dual film differential structure in accordance with the teachings of the present invention.

2A is a sensing solution having a cerium oxide layer sensing film structure. The present invention senses a current (I) and a voltage in a buffer solution having a pH of 2 (pH=2) to a pH of 12 (pH=12). (V) diagram. The small picture is the relationship between the voltage of the conversion and the pH.

2B is a schematic diagram of a structure having a yttria layer sensing film structure. The present invention senses a current (I) and a voltage in a buffer solution having a pH of 2 (pH=2) to a pH of 12 (pH=12). (V) diagram. The small picture is the relationship between the voltage of the conversion and the pH.

2C is a double-sensing film structure having a cerium oxide layer/yttria layer. The present invention senses in a buffer solution having a pH of 2 (pH=2) to a pH of 12 (pH=12). A plot of the resulting current (I) versus voltage (V). The small picture is the relationship between the voltage of the conversion and the pH.

3A is a schematic cross-sectional view showing another field effect type ion sensing device having a dual film differential structure in accordance with the teachings of the present invention.

3B is a schematic diagram showing a field effect type ion sensing device having a dual film differential structure in accordance with the teachings of the present invention.

3C is a schematic diagram showing another preferred embodiment of a field effect type ion sensing device having a dual film differential structure in accordance with the teachings of the present invention.

In Fig. 4A, the pH of the buffer solution is from 2 to 12, and the weight percentage of DNP is 60%, and when the irradiation device irradiates the sensing region of the field effect type ion sensing device, the metal contact layer is The relationship between the current and the voltage generated by the signal conversion.

4B is a 60% by weight of DNP, and the pH of the buffer solution is from 2 to 12, and is taken by the metal contact layer when the irradiation device illuminates the sensing region of the field effect ion sensing device. The relationship between the current and the voltage generated by the signal conversion.

Figure 4C is a graph showing the relationship between voltage and pH in Figure 4B.

4D shows that the weight percentage of DNP is 70%, and the pH of the buffer solution is from 2 to 12, and when the irradiation device irradiates the sensing region of the field effect ion sensing device, it is extracted by the metal contact layer. The relationship between the current and the voltage generated by the signal conversion.

Figure 4E is a graph showing the relationship between voltage and pH in the 4D graph.

Figure 4F shows that the weight percentage of DNP is 80%, and the pH of the buffer solution is from 2 to 12, and when the irradiation device irradiates the sensing region of the field effect ion sensing device, it is taken by the metal contact layer. The relationship between the current and the voltage generated by the signal conversion.

The 4G graph is a graph in which the 4F map is converted into a voltage and a pH.

In Fig. 4H, the pH of the buffer solution is from 2 to 12, and when the irradiation device illuminates the sensing region of the field-effect ion sensing device, the signal extracted by the metal contact layer is generated by signal conversion. A diagram of the relationship between current and voltage.

Figure 4I is a graph showing the relationship between voltage and pH in the 4H chart.

The present invention having a polyvinyl chloride/ceria layer double-sensing film structure in FIG. 4J is sensed in a buffer solution having a pH of 2 (pH=2) to a pH of 12 (pH=12). Diagram of current (I) versus voltage (V).

10. . . Semiconductor substrate

12. . . Insulation

14. . . First film layer

16. . . Second film layer

30. . . Metal contact layer

40. . . Reference electrode

50. . . Irradiation device

Claims (22)

A field effect type ion sensing device for a dual film differential structure, comprising: a substrate having an upper surface and a lower surface, wherein the substrate is a P-type germanium substrate; and an insulating layer is formed on the substrate The upper surface, wherein the insulating layer is a ceria layer; a first film layer is formed on the insulating layer, wherein the first film layer is a hafnium oxide (HfO ₂ ) layer; and a second film layer is formed And a metal contact layer formed on a portion of the lower surface of the substrate, wherein the metal contact layer is a metal aluminum, thereby forming the double film differential structure Field effect type ion sensing device. The sensing device of claim 1, wherein the second film layer is a hafnium oxide (HfTaO) layer. A field effect type ion sensing device for a dual film differential structure, comprising: a substrate having an upper surface and a lower surface, wherein the substrate is a P-type germanium substrate; and an insulating layer is formed on the substrate The upper surface, wherein the insulating layer is a ceria layer; a first film layer is formed on the insulating layer; and a second film layer is formed on a part of the surface of the first film layer, wherein the second layer The thin film layer is a hafnium oxide (HfO ₂ ) layer; and a metal contact layer is formed on a portion of the lower surface of the substrate, wherein the metal contact layer is a metal aluminum, thereby forming the double film differential structure. Field effect type ion sensing device. The sensing device of claim 3, wherein the first film layer is a layer of hafnium oxide (HfO ₂ ). A field effect type ion sensing device having a double film differential structure, comprising: a substrate having an upper surface and a lower surface, wherein the substrate is a P-type germanium substrate; and an insulating layer is formed on the substrate a surface, wherein the insulating layer is a germanium dioxide layer; a first thin film layer is formed on the insulating layer, wherein the first thin film layer is a hafnium oxide (HfO ₂ ) layer; and a second thin film layer is formed on a portion of the surface of the first film layer; a metal contact layer formed on a portion of the lower surface of the substrate such that a portion of the exposed surface of the substrate is a sensing region, wherein the metal contact The layer is a metal aluminum; a reference electrode is disposed above the second film layer for providing a reference potential during measurement; and a light source device is disposed on the lower surface of the substrate and interposed between the metal contacts Between the layers, wherein the light source device is an infrared light emitting diode (IR-LED), thereby forming the field effect type ion sensing device with a double film differential structure. The sensing device of claim 5, wherein the second film layer is a hafnium oxide (HfTaO) layer. A field effect type ion sensing device having a double film differential structure, comprising: a substrate having an upper surface and a lower surface, wherein the substrate is a P-type germanium substrate; and an insulating layer is formed on the substrate a surface, wherein the insulating layer is a germanium dioxide layer; a first thin film layer is formed on the insulating layer; and a second thin film layer, wherein the second thin film layer is a hafnium oxide (HfTaO) layer, formed on the surface a portion of the surface of the first film layer; a metal contact layer formed on a portion of the lower surface of the substrate such that a portion of the exposed surface of the substrate is a sensing region, wherein the metal contact The layer is a metal aluminum; a reference electrode is disposed above the second film layer for providing a reference potential during measurement; and a light source device is disposed on the lower surface of the substrate and interposed therebetween Between the metal contact layers, wherein the light source device is an infrared light emitting diode (IR-LED), thereby forming the field effect type ion sensing device having a double film differential structure. A field effect type ion sensing device having a double film differential structure, comprising: a substrate having an upper surface and a lower surface; an insulating layer formed on the upper surface of the substrate; a first thin film layer formed on a plurality of adhesive layers formed on the first film layer for defining a sensing region on the first film; a plurality of intermediates formed between the plurality of adhesive layers a second film layer formed between the plurality of glue layers and covering the intermediate materials; and a metal contact layer formed on a portion of the lower surface of the substrate, thereby forming the double film differential Structured field effect ion sensing device. The sensing device of claim 9, wherein the substrate is a P-type germanium substrate. The sensing device of claim 9, wherein the insulating layer is a ceria layer. The sensing device of claim 9, wherein the first film layer is a layer of hafnium oxide (HfO ₂ ). The sensing device of claim 9, wherein the intermediate device It is a decane compound. The sensing device of claim 9, wherein the second film layer is a poly(vinyl chloride) film layer. The sensing device of claim 9, wherein the metal contact layer is a metal aluminum. A field effect type ion sensing device having a double film differential structure, comprising: a substrate having an upper surface and a lower surface; an insulating layer formed on the upper surface of the substrate; a first thin film layer formed on a plurality of adhesive layers formed on the first film layer for defining a sensing region; a plurality of intermediates formed between the plurality of adhesive layers; and a second film layer formed Between the plurality of adhesive layers and covering the intermediates; a reference electrode disposed above the second thin film layer for providing a reference potential during measurement; a metal contact layer formed thereon a portion of the lower surface of the substrate such that a portion of the lower surface of the exposed substrate is a sensing region; and a light source device disposed on the lower surface of the substrate and interposed between the metal contact layers Forming the field effect type ion having a double film differential structure Sensing device. The sensing device of claim 16, wherein the substrate is a P-type germanium substrate. The sensing device of claim 16, wherein the insulating layer is a hafnium oxide layer. The sensing device of claim 16, wherein the first film layer is a layer of hafnium oxide (HfO ₂ ). The sensing device of claim 16, wherein the intermediate is a decane compound. The sensing device of claim 16, wherein the second film layer is a poly(vinyl chloride) film layer. The sensing device of claim 16, wherein the metal contact layer is a metal aluminum. The sensing device of claim 16, wherein the light source device is an infrared light emitting diode (IR-LED).