KR101497339B1 - Hydrogen sensor - Google Patents
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- KR101497339B1 KR101497339B1 KR20140064789A KR20140064789A KR101497339B1 KR 101497339 B1 KR101497339 B1 KR 101497339B1 KR 20140064789 A KR20140064789 A KR 20140064789A KR 20140064789 A KR20140064789 A KR 20140064789A KR 101497339 B1 KR101497339 B1 KR 101497339B1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/227—Sensors changing capacitance upon adsorption or absorption of fluid components, e.g. electrolyte-insulator-semiconductor sensors, MOS capacitors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
- G01N27/4141—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS specially adapted for gases
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/0004—Gaseous mixtures, e.g. polluted air
- G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
- G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
- G01N33/0036—Specially adapted to detect a particular component
- G01N33/005—Specially adapted to detect a particular component for H2
Abstract
According to the present invention, there is provided a thin film transistor comprising: a thin film transistor; and a hydrogen sensing unit connected in series to the gate of the thin film transistor, wherein the hydrogen sensing unit includes a Pd thin film, an insulating film formed below the Pd thin film, And the Pd thin film is connected to the gate of the thin film transistor. When the hydrogen sensing part is exposed to the hydrogen environment, the Pd thin film is swollen to form a part of the Pd- Thereby causing a capacitance change between the Pd thin film and the insulating film, and detecting hydrogen through the capacitance change.
Description
The present invention relates to a hydrogen sensor.
Hydrogen energy can be recycled and does not cause environmental pollution problems. However, if hydrogen gas leaks more than 4% in the atmosphere, there is a risk of explosion. Therefore, there is a problem that it is difficult to widely apply the hydrogen gas to real life unless safety is secured. Therefore, in addition to a study on utilization of hydrogen energy, development of a hydrogen gas detection sensor (hereinafter, simply referred to as a "hydrogen sensor") capable of early detection of leakage of hydrogen gas in actual use is proceeding in parallel.
On the other hand, as hydrogen energy is used, it is expected that automobile market will be formed first. In particular, considering the fact that research is being carried out in the direction of loading high-pressure hydrogen into a vehicle, development of a hydrogen safety sensor capable of detecting hydrogen leakage by applying it to a fuel part and an electric field system is required. In addition, hydrogen sensors are essential for the detection of hydrogen leakage to the details of the hydrogen storage and hydrogen supply system among the hydrogen fuel cell operating apparatuses, and the monitoring of the hydrogen concentration. In addition, helium gas has been used to detect gas leakage of equipment such as an air conditioner or a refrigerator using a refrigerant. However, in order to detect more accurately, a hydrogen sensor may be used to detect a leaked portion using hydrogen.
On the other hand, for hydrogen gas sensing applications, Pd has long been considered and intensively studied as a promising material for hydrogen sensors because of its simple manufacturing, low cost, size reduction and compatibility with conventional semiconductor integrated circuits. Particularly, Pd is changed by resistance change, volume expansion, work function change, H 2 Gas, and a lattice mechanism for Pd having a high response time and a high sensitivity is proposed among them. In this connection, there is known a hydrogen sensor in which palladium (Pd) or an alloy thin film thereof is disposed on an elastic substrate, the substrate is pulled to form a nanogap, and hydrogen is detected using such a nanogap 10-1067557). Although previously developed hydrogen sensors have relatively high detection limits of 4% H 2 , they are easy to manufacture and low cost and can be used as H 2 gas sensors for final warning systems. However, according to such a hydrogen sensor, troublesome problems such as the necessity of artificially forming a nanogap can be caused. Therefore, there is a need for a hydrogen sensor capable of detecting hydrogen by another principle.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a hydrogen sensor capable of detecting low concentration hydrogen in a manner different from conventional hydrogen sensors.
According to an aspect of the present invention, there is provided a thin film transistor comprising: a thin film transistor; and a hydrogen sensing unit connected in series to a gate of the thin film transistor, wherein the hydrogen sensing unit includes a Pd thin film, The Pd thin film is connected to the gate of the thin film transistor. When the hydrogen sensing part is exposed to the hydrogen environment, the Pd thin film is connected to the gate of the thin film transistor, Is partially separated from the insulating film to cause a capacitance change between the Pd thin film and the insulating film, and hydrogen is detected through the capacitance change.
In one embodiment, the thin film transistor may be an a-IGZO thin film transistor.
In one embodiment, when the hydrogen sensing part is exposed to a hydrogen environment, the Pd thin film is swollen to partially form an air gap between the Pd thin film and the insulating film, thereby reducing the contact area of the Pd thin film, Change.
In one embodiment, the thin film transistor further includes a resistance connected to a drain or a source of the thin film transistor, and the current changed by the capacitance change is converted into a voltage signal in the ON-OFF mode.
According to another embodiment of the present invention, there is provided a top-gate type thin-film transistor hydrogen sensor used for hydrogen detection, comprising: a substrate; An a-IGZO thin film formed on the substrate; Source / drain electrodes; An insulating film formed on the a-IGZO thin film and the source / drain electrode; And a Pd thin film gate electrode formed on the insulating film. When the hydrogen sensor is exposed to a hydrogen environment, the Pd thin film gate electrode swells up and is partly separated from the insulating film, so that capacitance between the Pd thin film gate electrode and the insulating film And the hydrogen is detected through the capacitance change.
In one embodiment, when the hydrogen sensor is exposed to a hydrogen environment, the Pd thin film gate electrode bulges to partially form an air gap between the Pd thin film gate electrode and the insulating film, and the contact area of the Pd thin film gate electrode Thereby changing the capacitance.
In one embodiment, the device further comprises a resistor connected to the drain or source electrode, wherein the current changed by the capacitance change is converted into a voltage signal in the ON-OFF mode.
According to the present invention, a new type of hydrogen sensor for detecting hydrogen is provided by changing a contact area of a Pd thin film upon exposure to a hydrogen environment to cause a capacitance change.
FIG. 1 is a schematic view of a hydrogen sensor element according to one embodiment of the present invention, schematically showing an embodiment before and after hydrogen exposure.
2 is a graph showing the capacitance-voltage characteristic of a Pd-MIM (metal-insulator-metal) under a 4% hydrogen exposure at room temperature and at a frequency of 10 kHz and in air. An equivalent circuit is also shown in the inset.
Figure 3 is a 4% hydrogen exposure (H 2 ON), and air conditions (H 2 OFF) under the initial a-IGZO TFT (black line) and Pd-MIM drain current obtained from the a-IGZO TFT is connected to the variable capacitor - gate voltage Transfer curve and the drain current versus time obtained under hydrogen exposure or non-exposure conditions in a-IGZO TFTs connected to Pd-MIMs.
4A is a schematic view of an a-IGZO TFT fabricated in one embodiment of the present invention, which is an inverted-stagger type TFT having a width-length of 100/10 mu m using a bottom gate. 4 (b) shows the transfer curve characteristic of the TFT.
5 (a) shows the voltage transfer curve of the operation of the hydrogen-sensing inverter of the present invention when the hydrogen is exposed to the Pd-MOS of the TFT at a drain voltage VDD of 1 V to 5 V (the intervening figure corresponds to the corresponding equivalent circuit) 5B shows a voltage gain (-dVout / dVin) curve of the operation of the hydrogen sensing inverter of the present invention when hydrogen is exposed to the Pd-MIM of the TFT at a drain voltage VDD of 1 V to 5 V, 5 (c) shows the output voltage over time in the inverter of the present invention at Vin = 3.5 V under the hydrogen ON / OFF condition.
Fig. 6 is a schematic view of a Pd / IGZO TFT, which schematically shows an embodiment before and after implanting hydrogen into the chamber.
7 is a schematic diagram of a hydrogen sensing system in accordance with one embodiment of the present invention, wherein a Pd / IGZO TFT is mounted on a PCB in a gas chamber.
8 (a) shows drain current-gate voltage transfer characteristics of Pd / IGZO TFT after hydrogen gas injection, FIG. 8 (b) shows transfer characteristics after cleaning by nitrogen in the chamber, (c) is a hysteresis curve of the drain current during absorption and desorption of hydrogen atoms on the Pd / IGZO TFT by 4% hydrogen gas injection and 100% nitrogen gas cleaning.
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, descriptions of technologies well known in the art are omitted. Even if these explanations are omitted, those skilled in the art will readily understand the characteristic features of the present invention through the following description.
In the present invention, the sensing mechanism is based on a hydrogen-induced lattice expansion (HILE) in a Pd film, which lattice expansion is caused by a Pd top-gate electrode on a-IGZO TFT and a Pd / SiO 2 / p + -Si (Pd-MIM), which results in a change in capacitance. In the present invention, based on this finding, a new sensor using a completely different hydrogen sensing principle is provided, one of which is a Pd-MIM-connected IGZO TFT and a load resistor for an inverter system, and the other is a Pd top- a-IGZO (amorphous InGaZnO) TFT. In particular, an inverter type sensor for H 2 sensing shows output voltage and dynamic behavior when exposed to high H 2 gas at room temperature. The Pd top-gate a-IGZO TFT was also fabricated as a hydrogen sensor and operated successfully. These IGZO TFT-based hydrogen sensors are very advantageous because they have excellent compatibility with ordinary semiconductor integrated circuits at room temperature under atmospheric pressure.
- H 2 sensing mechanism and CV characteristics of Pd / SiO 2 / p + -Si (Pd-MIM)
The present inventors produced a simple Pd / SiO 2 / p + -Si (Pd-MIM) as a hydrogen sensor in order to investigate physical / electrical changes before and after exposure to a high concentration of H 2 gas (4%). 1A and 1B show a schematic cross section of a Pd-MIM sensor and a microscope image of a pure Pd thin film surface of 50 nm thickness, respectively. After 4% H 2 exposure, as shown in FIG. 1D, a large swelling was observed over the entire surface of the Pd thin film. Fig. 1C shows the same phenomenon corresponding to the phase transformation from? -Phase to? -Phase. As shown schematically, it can be seen that the Pd thin film absorbing the hydrogen atoms is inflated and partially peeled off from SiO 2 .
Since Pd can absorb more than 1700 times H 2 gas in its H atomic form, the absorbed H atoms cause a phase transformation from PdHx α-phase to β-phase at high concentrations of H 2 in excess of 1.5%. At high concentrations of H 2 , the α-phase PdH becomes a β-phase PdHx compound and the excess H atoms cause dislocation defects and lattice expansion, whereby the lattice parameter can increase from 3.89 A ° to a maximum of 4.03 A ° have. This means that the volume of the Pd thin film can expand about 10% of its original volume. This volume expansion seems to result in separation between the Pd thin film and the substrate. In the present invention, this phenomenon is referred to as blistering or peeling off.
As a hydrogen sensor, Pd-MIM or Pd-MOS type sensors have been studied by many researchers and mainly use the change of work function of Pd material due to high concentration of H 2 gas. However, in the present invention, it is discovered and utilized that the unusual change in capacitance, which occurs upon exposure to hydrogen, is caused by volume expansion. A plot of Pd-MIM capacitance at 10 kHz is given in FIG. 2 and an equivalent circuit is shown in the inset of FIG. 2, where Pd-MIM is represented as a variable capacitor.
C Pd - MIM can be expressed as C Pd - MIM = ∈ A / d where A is the contact area (1.1 mm 2 ) between the Pd thin film and the SiO 2 layer and d is the thickness of the SiO 2 layer ), with a, ε is the dielectric constant of SiO 2. The C Pd - MIM is calculated to be about 190 pF, which is actually measured to be about 195 pF. However, after H 2 exposure, which was estimated to be only 15% of the contact area, the capacitance rapidly decreased to about 35 pF, and the capacitance was reduced to about 93% of the initial contact area after removing the H 2 exposure Which was recovered to about 180 pF, which means that the initial Pd film was recovered to some extent. The second H 2 exposure resulted in a capacitance of about 72 pF and a third exposure of about 35 pF, but was always recovered to about 180 pF after removing the gas exposure. The reduction in capacitance can be explained through the optical microscope image of FIG. 1D. A certain degree of swelling was manifested after hydrogen exposure in the image, so that the capacitance of the swelling portion of the capacitor was found to be about 10% of the total gate area and negligible. The H 2 -absorbed Pd thin film is phase-transformed into PdHx with volume expansion, thereby reducing the contact area on the insulator. The formation of swelling leads to a weakening of the adhesion between the substrate and the Pd thin film, thereby forming an unwanted air gap at the interface between the Pd thin film and the substrate and reducing the contact area of the Pd thin film. The total capacitance of the Pd thin film device is proportional to the contact area, so the total capacitance is varied. As a result, the fluctuating area brings about a change in the capacitance shown in Fig. Here, the present inventor employed an electrically stable a-IGZO TFT to improve reproducible and stable hydrogen sensing operation and at the same time to obtain a hydrogen response time (in FIG. 2, @ H2: in hydrogen), and the numbers indicate the order in which they are measured: 1, 2, 3, 4. Can be observed).
<H 2 sensing inverter composed of Pd-MIM and a-IGZO TFT>
Based on the variable capacitance of the Pd-MIM in response to the H 2 response, the present inventors have found that the Pd-MIM and the a-IGZO (via the connection of the capacitances of the IGZO TFT and the Pd-MIM, The TFTs were combined in series (eg, through a connection such as a wire) and the static drain current and copper current could be measured under H 2 exposure and atmospheric conditions. Prior to the connection of the Pd-MIM, the present inventor measured the drain current of the IGZO TFT first (see also Fig. 4, schematic sectional view). As shown in the TFT transfer curves of Figs. 3A and 4B, the TFT of the present invention was very stable (leakage current was less than about 10 pA and operation ON at about 1.3 V (the ON / OFF ratio was about 10 7 or more, Saturation field effect mobility of about 15 cm 2 / Vs). Figure 3a shows IV curves of a-IGZO TFTs connected to Pd-MIM under H 2 exposure and atmospheric conditions. When the Pd-MIM is connected in series, the total gate capacitance (C total ) of the equivalent circuit needs to be taken into consideration also in the Pd-MIM capacitance (C Pd-MIM ) as shown in the following equation (1) (C ox ).
As shown in FIG. 3B, the smaller C total leads to a slightly smaller drain current than by C ox only in the same on-stage V G. The drain current (V G = 20V) is about 10 -10 A and is reduced to about 2 x 10 -4 A due to the capacitance reduction due to the series connection to the Pd-MIM. In addition, the drain current is rapidly reduced to about 2 x 10 -6 A after H 2 exposure (H 2 ON) to Pd-MIM, which is attributed to a decrease in capacitance after the H 2 response. Interestingly, the drain current is restored to its previous value under the atmospheric condition (H 2 OFF). Here, the inventors selected V D = 1 V and V G = 7 V (represented by the vertical gray line in FIG. 3A) to obtain the H 2 ON / OFF response behavior of the time-domain. Figure 3b is to show a response time for a 4% H 2 in the Pd-MIM, the result appears to be consistent with the results of Figure 3a. In addition, the present inventors can confirm a faster response to H 2 ON than H 2 OFF because the phase transformation from the α-phase to the β-phase is shorter than the phase transformation from the β-phase to the α-phase .
(By the connection of the drain electrode of the IGZO TFT to the load resistor of Pd-MIM and R = 100M ?, see also the equivalent circuit of the inset of FIG. 5A). These elements and the load resistor are connected in series to form Pd-MIM We could fabricate an inverting system that measures the V out signal for the input voltage (V IN ) under H 2 exposure and atmospheric conditions. The voltage-transfer characteristic (VTC) curve of the inverter was well obtained under a low supply voltage (V DD ) of 1 V to 5 V, where a maximum voltage gain of about 8 at V DD of 5 V was obtained, V D = 5V and V G = 3.5V were selected to obtain ON / OFF response behavior of the time domain. Figure 5c shows the hydrogen-sensing behavior of the time-domain, which is consistent with the results of Figure 5b in terms of V OUT levels.
<Pd top as a hydrogen sensor - Gate type IGZO TFT>
For a second hydrogen sensor application, the present inventors fabricated a Pd top-gate type a-IGZO (Pd / IGZO) TFT by directly stacking a Pd gate electrode on an a-IGZO TFT. 6A and 6C show a schematic configuration of the Pd / IGZO TFT and an optical microscope image, respectively. Prior to the H 2 sensing operation, a Pd / IGZO TFT was mounted on the PCB in the gas chamber (FIG. 7, schematic configuration of the H 2 sensing system). According to the schematic configuration of FIG. 6C, it can be expected that the Pd electrode will swell on the a-IGZO TFT after 4% H 2 gas is injected into the chamber at room temperature and 1 atm. The Pd top gate electrode appeared to have swelling from the Al 2 O 3 gate insulation layer, although the Au / Ti source / drain electrode was shown to be unchanged corresponding to Figures 1c and 1d.
8A is a graph showing the relationship between the Pd / Pd value obtained after the lapse of N 2 gas atmosphere, 20 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds and 120 seconds after 4% H 2 gas was injected into the chamber at a drain bias of V D = The IV curve of the IGZO TFT is shown. As can be seen from the TFT initial transfer curve, the TFT of the present invention was operated at -0.2 V or higher and was very stable, the ON / OFF ratio was about 2.0 x 10 4 or more, and the saturation field effect mobility was about 1 cm 2 / V . The transfer curves showed reliable and electrically stable TFT characteristics up to 100 seconds and the OFF-current rapidly increased from about 10 -10 A to about 10 -6 A, while the ON-current increased after 120 seconds after the H 2 injection It was reduced from approximately 10 -5 a to about 10 -6 a. The drain current was maintained at about 1.3 × 10 -6 A from 140 seconds after the H 2 injection regardless of gate bias or gate field effect. This result demonstrates that the unfastened Pd electrode does not apply any gate field for the Al 2 O 3 insulator due to the phase transition from? To phase? Under a 4% H 2 atmosphere in the chamber . Conversely, FIG. 8B shows the IV curve of the TFT obtained after several seconds after cleaning with 100% N 2 gas under a H 2 gas atmosphere and at a drain bias of V D = 1V. The transfer curve shows unchanged characteristics for up to 150 s, and the OFF-current gradually decreases from about 10 -6 A to about 10 -10 A, while the ON-current is reduced to 170 after the 100% N 2 is injected into the chamber After about 10 < -6 > A to about 10 < -5 > A. During the desorption process of H atoms caused by changing the environment to pure N 2 atmosphere, the ON-current (and OFF-current) gradually changed. Therefore, the phase transition from the? -Phase to the? -Phase is made so that the Pd electrode comes into contact with the insulator, so that the gate bias can be applied to the TFT again after the cleaning of the N 2 gas. As shown in FIG. 8C, the curve shows the hysteretic behavior of the drain current of the Pd / IGZO TFT during phase transformation from? -Phase to? -Phase and again to? -Phase. The other curve shows two changes in drain current, a rapid change in current after 120 seconds after H 2 injection, and a gradual change in current after 290 seconds after N 2 implantation. This may be due to the greater interaction force of the Pd-H bond on the single beta phase than the force required to break the HH bond in the alpha phase formation. The response time is about 120 seconds and hysteresis exists in the Pd / IGZO TFT, but it is not too slow to respond, including the time when the chamber environment changes to 100% N 2 atmosphere. In addition, the Pd / IGZO TFT can exhibit a rapid change of OFF-current as a result of H 2 gas injection and can be a good hydrogen sensor showing good compatibility with the previous a-IGZO TFT.
The present inventors have developed a new Pd / SiO 2 / p + -Si (Pd-MIM) based on Pd top-gate type coupled to an electrically stable a-IGZO TFT utilizing hydrogen- A hydrogen sensor was fabricated. In a high hydrogen concentration environment, the excess hydrogen uptake process causes the formation of swell in the Pd electrode on the insulator, which results in a change in the contact area and hence in the capacitor, corresponding to the phase transition from alpha-phase to beta-phase. When the Pd-MIM is connected to the IGZO TFT, the sensor of this study exhibited hydrogen induced drain current and copper current. In addition, the present inventors constructed a Pd-MIM-connected IGZO TFT and a load resistor for an inverter system to verify dynamic operation. In addition, another Pd-gate type a-IGZO TFT was fabricated and confirmed to function well as a hydrogen sensor at room temperature under atmospheric conditions. The conclusion is that the implementation of IGZO TFTs can be a future process for the development of Pd-based sensors, as well as integrated arrays with improved performance of ZnO-based devices.
As described above, according to the present invention, when the Pd hydrogen sensing part is exposed to the hydrogen environment, the Pd thin film is partially swollen, which causes a capacitance change. Although it is possible to detect hydrogen by directly measuring such capacitance change, if such a hydrogen sensing portion is connected to the gate electrode of the TFT, the change of the capacitance changes the drain current. Further, by connecting a resistor to the drain of the TFT, the drain current can be transformed into the voltage signal in the ON-OFF mode (that is, by connecting the resistor, the inverter element can be constituted to convert the current signal into the voltage signal ). Thus, the thin film transistor can be connected to an external computing system to detect hydrogen more conveniently and easily.
<Experiment explanation>
: Manufacturing method of Pd-MIM type sensor
To fabricate a Pd-MIM type sensor, a 50 nm-Pd thin film was deposited on a cleaned 200 nm-thick SiO 2 / p + -Si substrate using DC magnetron sputtering. The size of the Pd electrode is about 1.1 mu m (L) x 1.0 mu m (W) in Fig. 1A. After Pd deposition. 4% H 2 gas was exposed to the Pd-MIM structure, and the optical microscope images of the Pd thin films before and after exposure to H 2 were compared in FIGS. 1C and 1D. CV characteristics of Pd-MIM were measured at 10 kHz using a semiconductor parameter analyzer (HP 4284A, Agilent Technologies).
: Manufacturing Method of Bottom Gate a-IGZO TFT
Next, the structure of the amorphous InGaZnO (a-IGZO) TFT was an inverted stagger type having a width / length (W / L) ratio of 100/10 탆 using a bottom gate. Plasma enhanced by using the chemical vapor deposition (PECVD) system, and depositing a patterned Cu / MoTi of 300 nm- thick SiO 2 on the gate electrode, the gate insulator layer. Thereafter, a 60 nm-thick active channel layer (a-IGZO) was deposited using a DC magnetron sputtering system. A SiO 2 etch stopper (75 nm) and a Mo source / drain electrode were sequentially formed to form a 300 nm-thick PECVD SiO 2 passivation layer. Both patterning processes were performed by lithography, including wet chemical etching and PECVD processes. Device annealing at 300 캜 in an air atmosphere was performed as a final step. Thereafter, a Pd-MIM sensor was connected to the electrically stable a-IGZO TFT device (at the gate electrode) in the probe station. The drain current-gate voltage transfer curve and the dynamic drain current were measured using a semiconductor parameter analyzer (
: Manufacturing method of Pd top-gate type a-IGZO TFT
Using an RF magnetron sputtering system, a 40 nm-thick a-IGZO thin film was deposited on the cleaned substrate. The IGZO active channel was then performed using port-lithography, which included a wet chemical etching process. To form the channel, a BOE 200: 1 etchant was used and the etch rate was ~ 4 nm / s at room temperature. Thereafter, a DC sputtering system was used to deposit Au / Ti (50 nm / 50 nm) source (S) and drain (D) electrodes and then patterned through a combination of photolithography and lift- . A 50 nm Al 2 O 3 gate insulating layer was deposited on the patterned Au / Ti (S / D) electrode and the IGZO active channel through an atomic layer deposition (ALD) system. Then, a 50 nm-thick Pd top gate electrode was formed as the S / D electrode in the same manner. For the H 2 reaction measurement of the Pd-gate type IGZO TFT, as shown in the schematic diagram of FIG. 7, a small gas chamber of about 250 ml volume, pure 100% N 2 (for cleaning) and 95% N 2 + 4% H 2 mass flow controller (MFC) for mixed gas (sensing). The pressure in the chamber was maintained at 1 atmospheric pressure. A Pd gate IGZO TFT was mounted on the PCB in the gas chamber. Supply and input voltages (V DD and V IN ) were applied using a semiconductor parameter analyzer (
Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto. That is, the embodiment can be variously modified and modified within the scope of the claims, which are also within the scope of the present invention. Accordingly, the invention is limited only by the claims and the equivalents thereof.
Claims (7)
A hydrogen sensing part connected in series to the gate of the thin film transistor,
Lt; / RTI >
The hydrogen sensing unit
Pd thin film,
An insulating film formed below the Pd thin film,
A metal film formed under the insulating film
And a Pd-MIM (metal-insulator-metal) structure,
The Pd thin film is connected to the gate of the thin film transistor,
When the hydrogen sensing part is exposed to a hydrogen environment, the Pd thin film is swollen and partly separated from the insulating film to cause a capacitance change between the Pd thin film and the insulating film, and hydrogen is detected through the capacitance change. Hydrogen sensor.
Claims [1]
An a-IGZO thin film formed on the substrate;
Source / drain electrodes;
An insulating film formed on the a-IGZO thin film and the source / drain electrode;
The Pd thin film gate electrode
/ RTI >
When the hydrogen sensor is exposed to a hydrogen environment, the Pd thin film gate electrode swells up and is partially separated from the insulating film, causing a capacitance change between the Pd thin film gate electrode and the insulating film, and detecting hydrogen through the capacitance change Wherein the hydrogen sensor is used for hydrogen detection.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20180091537A (en) * | 2017-02-07 | 2018-08-16 | (주) 월드테크 | Gas sensor |
| KR20190122489A (en) * | 2018-04-20 | 2019-10-30 | 광주과학기술원 | Hydrogen gas sensor and method for manufacturing the same |
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| KR20060025096A (en) * | 2004-09-15 | 2006-03-20 | 최시영 | Pd-black gate misfet type hydrogen sensor for high performance in air |
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| KR101990121B1 (en) | 2017-02-07 | 2019-06-19 | (주) 월드테크 | Gas sensor |
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