JPH07333183A - Oxygen partial-pressure detecting element using metallic oxide semiconductor film and oxygen potentiometer equipped with the element and vacuum device - Google Patents

Abstract

PURPOSE:To provide an oxygen partial-pressure detecting element for actually measuring the partial pressure of oxygen by selectively adsorbing oxygen for measuring the concn. of oxygen, and an oxygen potentiometer equipped with the element. CONSTITUTION:An oxygen potentiometer is that in which a metallic oxide semiconductor as a detecting element for measuring the partial pressure of oxygen adsorbs oxygen on its surface so that the electric resistance of the film is changed, and when there is no reducing gas, it is utilized that the electric resistance denotes the concn. of oxygen. For instance, when a film of SnO2. is used, as it will be seen from the relationship between the partial pressure of nitrogen or oxygen and the resistance of the detecting part, the resistance varies depending on the partial pressure of oxygen in the vacuum of 1X10 [Pa] or more, but it does not depend on the partial pressure of nitrogen. As the metallic oxide semiconductor for forming metallic oxide semiconductor layers 6, 7, a tin oxide such as SnO2 is preferable. The semiconductors 6, 7 are usually of 0.1 to 10num. The shape of the overhang parts 2, 3 of the detecting elements is of a bridge structure or a cantilever structure, and the structure thereof can be arbitrarily determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen partial pressure detecting element, an oxygen partial pressure meter, and a vacuum device such as an oxide annealing device, a film forming device, and a vacuum case that needs to measure the oxygen partial pressure.

[0002]

[Prior art]

(1) Oxide thin films are widely used as insulating films and functional films for various devices.
It is a vacuum film forming method such as a vapor deposition method. In these film-forming methods, the oxygen partial pressure is greatly related to the film quality, and the stability of the oxygen partial pressure is directly related to the film stability. Therefore, in such a method for forming an oxide thin film or a film forming apparatus, it is important to accurately grasp the oxygen partial pressure. However, in many cases, the oxygen supply pressure is often used as a proxy for grasping the oxygen partial pressure. However, when there is a distribution of oxygen concentration in the device, the oxygen partial pressure at the place where the film growth progresses is There is a problem that it cannot be measured accurately. The same applies when the oxide thin film is annealed by oxidation. (2) As a partial pressure gauge capable of measuring the oxygen partial pressure, a magnetic field deflection type analyzer, a mass filter and the like are known. Generally speaking, magnetic field deflection analyzers are the most reliable for quantitative analysis, but they are large and heavy and can cause stray magnetic fields. Those that do not use a magnetic field are small in size, have a high analysis speed, and do not have a leakage magnetic field, but often have poor quantitativeness. In addition, the mass filter is small and can be attached anywhere in the vacuum device, and gas analysis during vapor deposition or sputtering can be performed, but the operating pressure is 1 × 10 ^-2 [Pa].
The following is ("Basics of thin film production", 2nd edition, written by Tatsuo Masaki, published by Nikkan Kogyo Shimbun). (3) When storing the sample, the sample which is deteriorated by moisture absorption by water or oxidation by oxygen when stored in the air is stored in a vacuum case. For samples that are altered by oxidation, the oxygen concentration is more important than the temperature, humidity, and vacuum level. However, it is well known that the sample storage vacuum case is equipped with a measuring device for measuring temperature, humidity and vacuum degree, but none is further equipped with a measuring device for measuring oxygen partial pressure. (4) It is known that a gas sensor uses a metal oxide semiconductor as a gas sensitive substance and utilizes a change in resistance value due to gas adsorption. These utilize the fact that when oxygen is sufficiently adsorbed, the resistance value changes because oxygen is desorbed in the coexistence of a reducing gas. Among such sensors, the applicant has already applied for a gas sensor using a tin oxide thin film (Japanese Patent Application Laid-Open No. 61-20114).
9, JP-A-57-60887).

[0003]

[Object] The present invention provides an oxygen partial pressure detecting element that measures oxygen partial pressure, not oxygen inflow amount by selectively adsorbing oxygen and measuring oxygen concentration, and an oxygen partial pressure meter including the element. The purpose is to provide a vacuum device.

[0004]

The present invention provides a detection element for measuring an oxygen partial pressure and an oxygen partial pressure meter equipped with the element, which uses a metal oxide semiconductor thin film layer as the detection element, thereby making it The oxygen partial pressure detecting element, the oxygen partial pressure meter, and the problems when measuring the oxygen partial pressure were solved.
The oxygen partial pressure detection element of the present invention is composed mainly of a metal oxide semiconductor thin film. However, in the present invention, the metal oxide semiconductor has an electric resistance of the film due to the adsorption of oxygen on the surface. The electric resistance is based on the fact that the electric resistance shows the oxygen concentration when the reducing gas is changed and the reducing gas is not present. For example, as can be seen from FIG. 7, which shows the relationship between the partial pressures of nitrogen and oxygen and the resistance value of the detector when using the SnO ₂ thin film,
The resistance value changes depending on the oxygen partial pressure at a low vacuum degree of 1 × 10 ^-2 [Pa] or more, but does not depend on the nitrogen partial pressure. As the metal oxide semiconductor forming the metal oxide semiconductor layer, tin oxide such as SnO ₂ is preferable, but oxides such as zinc and indium are also available. The metal oxide semiconductor layer may be a thin film or a thick film, but is usually 0.1 to 10 μm. As a method for producing the metal oxide semiconductor layer, a known thin film utilizing a physical method such as vapor deposition, sputtering, ion plating, or CVD, a vapor phase chemical reaction method such as CVD, or a liquid phase such as Sol-Gel method. A forming method can be mentioned. The detection element of the present invention has, for example, the following configuration. That is, an overhanging portion made of an electrically insulating material provided overhanging in the air, an oxide semiconductor layer for gas detection provided on the overhanging portion, an electrode lead in contact with the semiconductor layer, and substantially the same as the electrode lead. Although a gas detection device having a heater lead provided therein is known (Japanese Patent Laid-Open No. 61-191953), a device having such a structure is provided with a metal oxide semiconductor thin film for oxygen partial pressure detection. It is a thing. The projecting portion of the detection element may have a bridge structure as shown in FIG. 1 or a cantilever structure as shown in FIG. 3, and the shape thereof can be arbitrarily set.
2 shows a cross-sectional structure taken along line (A)-(A ') of the oxygen partial pressure detecting element having the cross-link structure shown in FIG. 1, and FIG. 4 shows the cantilever structure shown in FIG. (B)-(B ') shows the cross-section structure cut along the line.

[0005]

The present invention will be described in detail with reference to the following examples.

Example 1 FIGS. 5 and 6 show the structure of an element used in this example. S
On the overhanging portion formed on the i substrate and overhanging in the air and made of an electrically insulating material (the configuration diagram corresponds to FIG. 6)
In addition, the metal semiconductor layer is a SnO ₂ thin film [film thickness 0.3 (μ
m)] is provided. An oxygen partial pressure gauge corresponding to the invention of claim 3 was manufactured by forming an electrode lead in contact with the oxygen partial pressure detecting element and a heater lead arranged substantially in parallel with the electrode lead. In this example, a platinum thin film [Pt film thickness 0.1 (μm)] was used as an electrode, an oxide substrate was used here as Ta ₂ O ₅ , and Pt was used as an electrode lead.
However, various substrates and various oxides can be freely combined depending on the application. The electrode material is not limited to platinum (Pt), but other materials such as Pd, Au,
Examples thereof include Rh, Ir, Mo, W, Ni, Co and alloys thereof, which can be widely selected depending on the application. The electrically insulating member overhanging in the air is also Ta.
_{The material} is not limited to ₂ O ₅ , and other materials such as SiO ₂ , silicon nitride, oxysilicon nitride, alumina, and sialon can be used.

Example 2 FIG. 8 shows an example of a plasma vapor deposition apparatus equipped with the oxygen partial pressure detecting element described in Example 1. As a method of using the apparatus of FIG. 8, first, the bell jar 102 is opened, and the evaporation material for oxide formation is held in the evaporation source 104, and then the bell jar 102 is used.
Is closed and the pressure in the vacuum chamber 102 'is set to the order of 10 ^-4 [Pa] in advance by evacuation by a vacuum exhaust system (not shown), and then oxygen gas is introduced into the vacuum chamber 102' and the pressure is reduced. Is maintained at about 0.1 [Pa]. Here, if the oxygen partial pressure detection element 118 detects the oxygen partial pressure, the oxygen concentration near the film formation position is measured. Further, by providing the earth shield 119, noise can be reduced and more accurate measurement can be performed. In this atmosphere, the evaporation source 104 is heated by resistance heating, the counter electrode 110 is set to zero potential, a voltage of 100 [V] is applied to the grid 108, and a power of 400 [W] is applied to the filament 106. The input electric power for the resistance heating is controlled to control the film forming speed. In FIG. 8, the plasma vapor deposition apparatus is taken as an example, but similarly in other film forming apparatuses such as a sputtering apparatus and an annealing apparatus, by disposing the detection element near the substrate,
The oxygen concentration contributing to the oxidation of the film can be measured more accurately. Further, although not shown in the figure, it is possible to perform stable oxygen supply by providing a feedback circuit from the element output to the oxygen supply side. Furthermore, by providing a plurality of oxygen partial pressure detecting elements, it is possible to see the oxygen partial pressure distribution in the vacuum chamber 102 '.

Embodiment 3 FIG. 9 shows a diagram of a sample case equipped with the oxygen partial pressure detecting element described in Embodiment 1. After putting the sample in the sample case 30, connect the vacuum pump to the decompression port 31,
While checking with the vacuum gauge 32 and the oxygen partial pressure gauge 33, the pressure is reduced to a desired degree of vacuum and oxygen partial pressure.

[0009]

The oxygen partial pressure detecting element of the present invention has a simple oxygen partial pressure detecting mechanism, and therefore the detecting element and the oxygen partial pressure meter using the element can be miniaturized. Oxygen partial pressure can be measured near the position, making it easy to use. In particular, the oxygen partial pressure detection element according to claims 1 and 2 selectively adsorbs oxygen, and the electric resistance value changes depending on the oxygen concentration (when no reducing gas coexists). The pressure can be measured. Since the oxygen partial pressure detecting element according to the third aspect is provided with the earth shield in the surroundings, it is possible to perform measurement with little noise and with high sensitivity. Claim 4
Oxygen partial pressure gauge has a cantilever structure, so the heat transfer is fast and the detection speed is fast. In the film forming apparatus according to the fifth aspect, the oxygen partial pressure near the substrate can be measured up to a low vacuum degree, so that more stable film formation can be performed. In the annealing apparatus according to the sixth aspect, since the oxygen partial pressure can be measured near the substrate up to a low vacuum degree, annealing can be performed with stable oxygen supply. In the vacuum case of claim 7, since the oxygen partial pressure can be measured, the deterioration of the sample due to oxidation can be prevented. Moreover, since the oxygen partial pressure can be measured at a low degree of vacuum, it is not necessary to provide a dedicated port or perform differential exhaust.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a crosslinked oxygen partial pressure gauge of the present invention.

2 is a cross-sectional view taken along line (A)-(A ') of the oxygen partial pressure gauge of FIG.

FIG. 3 is a plan view showing an example of an oxygen partial pressure gauge having a cantilever structure of the present invention.

FIG. 4 is a sectional view taken along line (B)-(B ′) of the oxygen partial pressure gauge of FIG.

5 is a plan view showing a device configuration and a circuit of the oxygen partial pressure meter of FIG. 3. FIG.

FIG. 6 is a cross-sectional view of the tip of the cantilever of the oxygen partial pressure meter of FIG. 5 taken along the line (AA), showing the film structure.

FIG. 7 shows nitrogen and oxygen partial pressures and element resistance characteristics at a heater temperature of 450 ° C. obtained in the embodiment of the present invention.

FIG. 8 shows a plasma deposition apparatus used in an example of the present invention.

FIG. 9 shows a sample keeper used in an embodiment of the present invention.

[Explanation of symbols]

 0 Cavity 1 Substrate 2 Overhanging part 3 Overhanging part 4 Heater lead 5 Heater lead 5 Metal oxide semiconductor layer 7 Metal oxide semiconductor layer 8 Electrode lead (detection lead) 9 Electrode lead (detection lead) 10 Electrical insulating material 20 Sensor electrode 21 Sensor Electrode 22 Cavity 23 Substrate 24 Oxygen Partial Pressure Detection Section 25 Heater Electrode 30 Sample Case 31 Pressure Reduction Port 32 Vacuum Gauge 33 Oxygen Partial Pressure Meter 101 Base Plate 102 Belger 102 'Vacuum Tank 103 Supporting Electrode 104 Evaporation Source for Evaporation Material 105 Support-combined electrode 106 Filament 107 Support-combined electrode 108 Grid 109 Support-combined electrode 110 Substrate support-combined electrode 111 Substrate 112 Evaporation source power supply 113 Filament power supply 114 DC voltage power supply 115 Packing 116 Valve 11 7 Gas introduction port 118 Oxygen partial pressure detection element 119 Earth shield

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Ishida 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Zenichi Akiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (7)

[Claims] 1. An enzyme partial pressure detection element using a metal oxide semiconductor thin film whose electric conductivity changes with a change in oxygen partial pressure existing in an atmosphere. 2. The oxygen partial pressure detecting element according to claim 1, wherein the metal oxide semiconductor thin film is mainly composed of tin oxide having n-type semiconductivity. 3. The oxygen partial pressure detecting element according to claim 1 or 2, further comprising a ground shield around the oxygen partial pressure detecting element. 4. An overhanging portion made of an electrically insulating material, which is provided overhanging in the air, an oxygen partial pressure detecting element according to claim 1 or 2 provided on the overhanging portion, an electrode lead in contact with the element, and An oxygen partial pressure gauge having a heater lead provided in parallel with the electrode lead. 5. A film forming apparatus comprising the oxygen partial pressure gauge according to claim 4. 6. An oxide thin film annealing apparatus comprising the oxygen partial pressure gauge according to claim 4. 7. A vacuum case comprising the oxygen partial pressure gauge according to claim 4.