JP2996922B2 - Tin oxide thin film sensor for sensing hydrogen and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film sensor for sensing hydrogen and a method for manufacturing the same. More specifically, the present invention relates to a tin oxide thin film sensor for sensing hydrogen having excellent sensitivity and selectivity to hydrogen, using a tin oxide thin film manufactured by an ion beam evaporation method without using a catalyst, and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a sensor for detecting a reducing gas such as hydrogen, an oxide such as tin oxide (SnO ₂ ) formed into a block or a thick film is used. But,
These need to be formed by pressing a powdery raw material under pressure and then heat-treated at high temperature to form a sintered body, which is not only unsuitable for mass production, but also has a greater effect on the target gas than a thin-film sensor. Low sensitivity.

A thin film sensor having a thickness of about several hundreds to several thousand degrees is generally excellent in sensitivity, reproducibility and productivity, has low power consumption, and is advantageous in cost. However, a thin film sensor applicable for sensing hydrogen has not been published yet.

[0004] A method of increasing the sensitivity as a sensor by adding platinum or palladium to a tin oxide thin film has been studied. In such research, since a thin film is formed by physical sputtering or CVD, it is extremely difficult to adjust the thickness, directionality, crystallinity, density, and ultrafine pores of the thin film, and the manufacturing process thereof is difficult. Is also very complicated.

On the other hand, it has been disclosed by the present inventors that high-quality, high-density thin films can be formed on metals, semiconductors, and oxides using an ion beam (SK Koh).
Et al., JVST-A, Vol. 13, No. 4, 2123-2127 (1995)).

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thin-film type hydrogen sensing sensor having high sensitivity, selectivity and reproducibility to hydrogen, low power loss, and suitable for mass production. It is to provide a manufacturing method.

[0007]

Means for Solving the Problems The present inventors evaporate metal tin (Sn) using a metal gun, and at the same time, apply energy to oxygen by a gas ion gun to ionize and react on the surface of the base material. Tin oxide (SnO ₂ ) at room temperature
Finding to Obtain Evaporated Thin Films (SK Koh et al., Environmen
t Ungyong Mulli, Vol. 7, No. 2, 246-252 (1996)), and found that this can be applied for the purpose of the present invention.
The present invention has been completed.

That is, the tin oxide thin film sensor for sensing hydrogen of the present invention comprises a semiconductor substrate, an insulating film existing on the substrate,
A lower electrode present at a predetermined interval on the insulating film, and a tin oxide thin film present on the lower electrode and the insulating film; or a semiconductor substrate, an insulating film present on the substrate, It is characterized by including a tin oxide thin film present on an insulating film and an upper electrode present at a predetermined interval in the tin oxide thin film. Also, the manufacturing method is
Forming an insulating film on the semiconductor substrate; forming a lower electrode on the insulating film at a predetermined interval; and performing ion deposition on the lower electrode and the insulating film to form a tin oxide thin film. Performing the steps of forming sequentially; or
Forming an insulating film on the semiconductor substrate; forming a tin oxide thin film on the insulating film; and forming an upper electrode on the tin oxide thin film at predetermined intervals. Features.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a tin oxide thin film sensor for sensing hydrogen according to the present invention will be described in more detail with reference to FIGS. FIG. 1 is a plan view showing a typical example of the electrodes of the sensor, FIG. 2 is a cross-sectional view showing a first embodiment of the manufactured tin oxide thin film sensor, and FIG. It is sectional drawing which shows 2nd Embodiment.

In the first embodiment of the present invention, FIG.
As shown in FIG. 1, an insulating film (102), preferably a silicon dioxide (SiO ₂ ) film, having a thickness of preferably 0.1 to 2 μm, typically 1 μm, is formed on a semiconductor substrate (100), preferably a silicon substrate. Exists. On the insulating film (102), a lower electrode (104), preferably made of platinum or palladium, is present preferably in a thickness of 300-1 μm, typically 600 °, and on the electrode and in the insulating layer A tin oxide (SnO ₂ ) thin film (106) serving as a sensor is placed on a portion where no is present, preferably 100
It is present at a thickness of ~ 1,000 °, typically 400 °, and constitutes a tin oxide thin film sensor for hydrogen sensing.

In the second embodiment of the present invention, FIG.
As shown in FIG. 1, an insulating film (1) is formed on a semiconductor substrate (100).
02), tin oxide thin film (106) and upper electrode (10
4) exists in that order, and constitutes a tin oxide thin film sensor for hydrogen sensing. The material, preferred thickness and representative thickness of each part are the same as in the first embodiment, and are different from the first embodiment only in that the electrode is present on the tin oxide thin film.

In the method for manufacturing a tin oxide thin film sensor for sensing hydrogen according to the present invention, the insulating film and the upper or lower electrode are preferably formed by ion beam sputtering according to the sequence of the first or second embodiment. A tin oxide thin film is formed by an ion beam evaporation method.

The sputtering and vapor deposition using these ion beams are performed in a high vacuum of preferably 10 ^-4 to 10 ^-7 Torr, more preferably 10 ^-5 to 10 ^-6 Torr.
In order to obtain a tin oxide thin film having a small gradient of electric resistance with respect to a temperature change and having a stable sensor characteristic, the energy of oxygen ions during ion beam deposition is 0 to 100
The range of eV is preferred, and 0 eV is particularly preferred. Further, the structure of the sensor formed under such conditions is
It is preferable to use the upper electrode according to the embodiment, and it is particularly preferable that the upper electrode is a platinum electrode.

It is generally known that when a thin-film sensor is manufactured, high-quality, high-density thin films of various materials ranging from metals, semiconductors, and oxides can be manufactured in a low-temperature region by applying an ion beam. ing.

In the present invention, manufacturing equipment used for manufacturing a tin oxide thin film includes a metal gun using an existing ionized cluster beam (hereinafter, referred to as ICB) as an ion source and a gas ion gun in the form of a cold hollow cathode. And a hybrid ion beam source equipped with.

The gas ion gun has an advantage in that it can adjust the energy and current density of ionized gas ions to widely adjust various electric and optical properties different from the crystallinity of the thin film. In this case, there is an advantage that a high quality thin film can be manufactured with little loss of a deposition material.

More specifically, the gas ion gun is in the form of a cold hollow cathode equipped with, for example, a grid of 5 cm, and is typically at a distance of about 45 cm from the gas ion gun and ± 20 °. Is a broad ion source having an ion current density uniformity of 90% in the range of the angle, by adjusting the beam profile by changing the discharge current and the acceleration voltage, and accelerating the ions to 2 kV. .

On the other hand, as the ICB source, for example, the accelerating electrode has a cylindrical shape having a diameter of 3 cm, and is typically 45 cm from a nozzle of a crucible where clusters are generated.
To have a 50% ion current density at a distance,
It is preferable to mount a substrate.

The tin oxide thin film sensor formed as described above can be used effectively without doping. However, in order to further improve its electrical and chemical properties and sensitivity to hydrogen, doping is performed. May be applied. Doping can be performed by injecting, as a dopant, at least one metal selected from palladium, platinum, silver and aluminum, based on the tin oxide thin film.

In order to improve the thermal stability of the tin oxide thin film sensor formed according to the first or second embodiment, the thin film sensor is placed in air, preferably at 600 ° C. or lower.
More preferably 300 to 600 ° C., typically 500
C., preferably for 10 minutes to 2 hours, typically 1 minute.
Time heat treatment may be performed. If the heat treatment temperature exceeds 600 ° C., the thin film becomes completely SnO ₂ , which eliminates crystal defects and increases the crystal grain size, so that the reactivity to the target gas decreases and the sensitivity decreases.

[0021]

The tin oxide thin film sensor for sensing hydrogen provided by the present invention comprises an excellent tin oxide thin film and a platinum electrode or a palladium electrode, and is used only with a pure tin oxide thin film without doping or catalysis. However, it has excellent sensor characteristics such as high electrical sensitivity to hydrogen, and excellent selectivity and reproducibility. Further, the method for producing a tin oxide thin film sensor for sensing hydrogen of the present invention is suitable for mass production and can provide the above-described tin oxide thin film sensor with excellent productivity.

[0022]

The present invention will be described in more detail with reference to the following examples. The present invention is not limited by these examples.

The sensitivity of the prepared hydrogen sensing sensor to each gas to be measured was calculated by the formula (I) by measuring the electrical resistivity in air and in the gas of a predetermined concentration.

(Equation 1) Where R _{a is} the electrical resistivity of the sensor in air R _{g is} the electrical resistivity of the sensor in air containing the gas to be measured

The selectivity of the sensor was evaluated by comparing the sensitivity of the sensor to various gases.

Example 1 On a 10 mm × 5 mm Si substrate, at a high vacuum of 10 ⁻⁶ Torr,
SiO _{2 in} a mixed gas of argon and oxygen at a volume ratio of 3: ₂
Was performed by ion beam sputtering to provide a 1 μm thick SiO ₂ insulating layer. Next, a screen was formed on the insulating layer so as to form an electrode having a pattern of FIG.
r Platinum of thickness 60 by ion beam sputtering
The lower electrode was formed by vapor deposition at 0 °.

Next, oxygen is ionized by a gas ion gun to set the ion beam energy (Vi) to 0, 300, 500 or 1,000 eV, respectively, and ICB is used.
A tin oxide thin film having a thickness of 400 ° was deposited on the lower electrode and on a portion of the SiO ₂ insulating layer where the lower electrode was not formed by irradiating and evaporating Sn having a purity of 99.995% or more contained in the crucible. Was deposited. Take out this laminate,
A heat treatment was performed in air at 500 ° C. for 1 hour to produce a hydrogen sensor having a cross section shown in FIG.

The electrical resistance was measured for the four hydrogen sensing sensors thus obtained using platinum as the lower electrode and changing the ion beam energy when forming the tin oxide thin film. .

FIG. 4 shows a change in electric resistance with temperature. From FIG. 4, the oxygen ion energy is 0 eV
In this case, it is clear that the slope of the electric resistance with respect to the temperature change is particularly small, exhibits stable characteristics, and has extremely low activation energy.

Example 2 Except that the ion beam energy for forming a tin oxide thin film was 300 eV, the conditions for forming each component were the same as in Example 1, and the electrode formation position and electrode material were changed as follows. The changes in the electrical resistance of the three sensors obtained by changing the temperature were compared. (1) Platinum lower electrode (first embodiment) (2) Platinum upper electrode (second embodiment) (3) Palladium upper electrode (second embodiment)

FIG. 5 shows the result. As is clear from FIG. 5, when the energy of the oxygen ions is 300 eV, the structure of the sensor is preferably that of the upper electrode shown in FIG.

Example 3 The conditions for forming each component were the same as those in Example 1 except that the ion beam energy at the time of forming the tin oxide thin film was 0 eV and the platinum upper electrode according to the second embodiment was formed. In the same manner as in the above, a sensor having a tin oxide thin film was manufactured. A sensing test was performed using this sensor.

Using air containing 3,000 ppm of hydrogen, propane or methane, the sensitivity of each reducing gas was measured at a measurement temperature of 100 to 500 ° C.

FIG. 6 shows the result. As is apparent from FIG. 6, the sensitivity is low at temperatures up to 250 ° C. for propane and 450 ° C. for methane, and the sensitivity sharply increases above those temperatures. At 500 ° C., propane is 47.33.
% And methane showed a sensitivity of 21.23%. Hydrogen, on the other hand, uses pure tin oxide as a sensor thin film,
The sensitivity was 99.3% or more over the entire temperature range without doping or the like.

Next, at a measurement temperature of 150 ° C. or 250 ° C., the sensitivity was measured by changing the hydrogen concentration in the air between 100 and 5,000 ppm. FIG. 7 shows the result. At any temperature, the higher the concentration, the higher the sensitivity. At a measurement temperature of 250 ° C., particularly preferable characteristics were exhibited, and measurement at a fine concentration was also possible.

At a measurement temperature of 250 ° C., the hydrogen concentration is set to 1
Stepwise increase in the range of 00 to 5,000 ppm,
FIG. 8 shows the change of the output voltage when returning from 0 ppm to the air. FIG. 8 shows the response time (unit,
Second) and recovery time (unit, second) upon returning to air. The response characteristic reliably distinguished by the concentration was excellent within 11 seconds, and the recovery characteristic showed a fast recovery time of 4 seconds.

FIG. 9 shows the results of investigation of the response / recovery characteristics at a hydrogen concentration of 500 ppm while changing the measurement temperature.
And Table 1. Higher temperatures showed faster response / recovery times, and at 250 ° C. showed a response time of 12 seconds and a recovery time of 2 seconds, shorter than the industrially usable limit of 20 seconds.

[0037]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a typical plan view of an electrode of a tin oxide thin film sensor for sensing hydrogen of the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a tin oxide thin film sensor for sensing hydrogen according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of a tin oxide thin film sensor for sensing hydrogen according to a second embodiment of the present invention.

FIG. 4 shows a temperature of a sensor having a platinum lower electrode according to the present invention.
4 is a graph showing electric resistance characteristics.

FIG. 5 is a graph comparing temperature-electrical resistance characteristics of a sensor in which an electrode position and an electrode material are changed.

FIG. 6 is a graph showing the temperature-sensitivity characteristics of a sensor having a platinum upper electrode formed with a tin oxide thin film at an oxygen ion energy of 0 eV with respect to hydrogen, propane, and methane.

FIG. 7 is a graph showing a hydrogen concentration-sensitivity characteristic of a sensor having a platinum upper electrode formed by forming a tin oxide thin film at an oxygen ion energy of 0 eV.

FIG. 8 is a graph showing hydrogen concentration-output voltage characteristics of a sensor having a platinum upper electrode formed by forming a tin oxide thin film with oxygen ion energy of 0 eV.

FIG. 9 is a graph showing response / recovery characteristics at various temperatures of a sensor having a platinum upper electrode formed by forming a tin oxide thin film with oxygen ion energy of 0 eV.

[Explanation of symbols]

 Reference Signs List 100 semiconductor substrate 102 insulating film 104 electrode 106 tin oxide thin film

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Choi Yuan-gu, 903-5-gil, Dong-gu, Yangcheon-gu, Seoul, Republic of Korea 303-1202 New city apartment (72) Inventor Yoon Ye-soo Inventor 6, 6 Bepyang-dong, Gwacheon, Gyeonggi-do, Republic of Korea Residential Apartment 501-507 (72) Inventor Zhao Shun Planting 1004- 18-7, Juan 6-dong, Nam-gu, Incheon, Republic of Korea 7/5 (72) Inventor Choi Dong-soo Gwanggi 2-dong, Ansan-si, Gyeonggi-do, Republic of Korea No. 670 Sumigong Apartment 706-402 (72) Inventor Jin Jin-soo 440-19, Gukje-dong, Ansan-si, Gyeonggi-do, Republic of Korea (56) References JP-A-61-191954 (JP, A) JP-A-63-8548 (JP, A) JP-A-61-155848 (JP, A) JP-A-5-311407 (JP, A) JP-A-4-123254 (JP, U) (58) Fields investigated (Int. Cl. ⁷⁾ G01N 27/00-27/24 C23C 14/00-14/58

Claims (13)

(57) [Claims] 1. A semiconductor substrate having a thickness existing on the substrate.
An insulating film having a thickness of 0.1 to 2 μm, a lower electrode having a thickness of 300 to 1 μm which is present on the insulating film at a predetermined interval, and a thickness of 1 μm existing on the lower electrode and the insulating film;
A tin oxide thin film sensor for detecting hydrogen, comprising a tin oxide thin film having a thickness of 100 to 1,000 ° . 2. The tin oxide thin film sensor for sensing hydrogen according to claim 1, wherein the lower electrode is made of platinum or palladium. 3. A semiconductor substrate, wherein a thickness existing on the semiconductor substrate is
An insulating film having a thickness of 0.1 to 2 μm, and a thickness existing on the insulating film is
A tin oxide thin film of 100 to 1,000 mm , and a thickness of 300 mm existing on the tin oxide thin film at a predetermined interval.
A tin oxide thin film sensor for sensing hydrogen, comprising an upper electrode of about 1 μm. 4. The tin oxide thin film sensor for sensing hydrogen according to claim 3 , wherein the upper electrode is made of platinum or palladium. 5. The method according to claim 4 , wherein the upper electrode is platinum.
The tin oxide thin film sensor for sensing hydrogen according to the above. 6. forming an insulating film on the semiconductor substrate; forming a lower electrode on the insulating film at a predetermined interval; and forming a lower electrode on the lower electrode and the insulating film .
Under high vacuum, tin is ion crust beam source
While depositing, use a cold hollow cathode type ion gun
A method for producing a tin oxide thin film sensor for hydrogen sensing, comprising sequentially performing a step of forming a tin oxide thin film by irradiating the surface of a sample after ionizing oxygen . 7. The method according to claim 6 , wherein the lower electrode is formed by using an ion beam sputtering method. 8. A step of forming an insulating film on a semiconductor substrate; applying tin on the insulating film under a high vacuum by ion crusting.
While depositing with a beam source, a cold hollow cathode type
After ionizing oxygen with an ion gun,
Forming a tin oxide thin film by irradiating a surface with a tin oxide thin film; and forming an upper electrode on the tin oxide thin film at predetermined intervals with a predetermined interval. Method. 9. The method according to claim 8 , wherein the upper electrode is formed by using an ion beam sputtering method. 10. The method according to claim 1, wherein the tin oxide thin film is formed in a state where the energy of the oxygen ions is 0 to 100 eV.
9. The production method according to 6 or 8 . After 11. forming the tin oxide film, further, in the air, adding a step of performing heat treatment at 600 ° C. temperature below Claim 6 or 8 method according. 12. The method according to claim 6 , wherein after forming the tin oxide thin film, a step of injecting a dopant into the thin film is further performed. Wherein said dopant is platinum, palladium, selected from silver and aluminum, also claim 6
Is the production method of 8 .