EP0660337A2 - Metalloxid-Dünnschichtwiderstand und Herstellungsverfahren - Google Patents

Metalloxid-Dünnschichtwiderstand und Herstellungsverfahren Download PDF

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Publication number
EP0660337A2
EP0660337A2 EP94120409A EP94120409A EP0660337A2 EP 0660337 A2 EP0660337 A2 EP 0660337A2 EP 94120409 A EP94120409 A EP 94120409A EP 94120409 A EP94120409 A EP 94120409A EP 0660337 A2 EP0660337 A2 EP 0660337A2
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EP
European Patent Office
Prior art keywords
oxide film
metal oxide
zinc
film resistor
producing
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94120409A
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English (en)
French (fr)
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EP0660337A3 (de
Inventor
Akiyoshi Hattori
Yoshihiro Hori
Akihiko Yoshida
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Publication of EP0660337A2 publication Critical patent/EP0660337A2/de
Publication of EP0660337A3 publication Critical patent/EP0660337A3/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/105—Varistor cores
    • H01C7/108—Metal oxide
    • H01C7/112—ZnO type

Definitions

  • the present invention relates to a metal oxide film resistor which has a wide application for configuring circuits in various electric appliances, and a method for producing such metal oxide film resistors.
  • Conventional metal oxide film resistors are generally configured with insulating substrates of rod-type made of mullite or alumina, metal oxide films comprising tin oxide or antimony-doped tin oxide (hereinafter referred to ATO) formed on the surfaces of the substrates, pairs of metal cap terminals press-fitted on both ends of the substrates, lead wires welded to the terminals, and electrically insulating protective films formed on the surfaces of the resistors.
  • ATO antimony-doped tin oxide
  • metal oxide film resistors those comprising a single phase of tin oxide have a very large temperature coefficient of resistance and their conditions for application are extremely limited, and are therefore not practical. For this reason, the ATO has now been put to practical use as the material for the metal oxide film in general.
  • the method for producing the metal oxide film is generally performed in a chemical process of forming a film such as spraying or chemical vapor deposition (CVD).
  • a film of ATO is formed on the surface of the substrate by spraying a vapor of an aqueous solution or an organic solvent solution containing stannic chloride and antimony trichloride to the substrate of rod-type which is placed in a furnace elevated to a temperature of 600 - 800°C.
  • a pair of metal cap terminals are press-fitted on both ends of the substrate, and a part of the film is cut or grooved in order to adjust the resistance of the film to have a desired value.
  • the metal oxide film resistor is completed by welding a pair of lead wires to the cap terminals, and forming a resin protective coating film on these components.
  • the metal oxide film resistor using the ATO film has a disadvantage that a specific resistance of the ATO film is relatively low, such as from about 1 ⁇ 10 ⁇ 3 to about 1 ⁇ 10 ⁇ 2 ⁇ cm. Therefore, the film thickness must be made considerably thin for making a resistance value of 100 k ⁇ or above, as far as using only one method of adjusting the resistance value, that is controlling of the film thickness.
  • a specific resistance of the ATO film is relatively low, such as from about 1 ⁇ 10 ⁇ 3 to about 1 ⁇ 10 ⁇ 2 ⁇ cm. Therefore, the film thickness must be made considerably thin for making a resistance value of 100 k ⁇ or above, as far as using only one method of adjusting the resistance value, that is controlling of the film thickness.
  • the present invention is proposed in order to overcome the above-mentioned disadvantages and deficiencies of the prior art, and is intended to provide a metal oxide film resistor having a desired resistance value in a wide range from 1 k ⁇ to 10 M ⁇ , and a stable and uniform quality.
  • the present invention provides a metal oxide film resistor comprising: an insulating substrate, a zinc oxide film formed on the surface of the insulating substrate, and a pair of terminals which are in contact with the zinc oxide film.
  • the metal oxide film further comprises an oxide of at least one metal selected from the group consisting of aluminum, magnesium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, indium, tin, antimony, lanthanum and cerium, in addition to the zinc oxide.
  • any compounds of these metals are referred to as an activator.
  • the present invention also provides a method for producing a metal oxide film resistor comprising the step of forming a zinc oxide film on a surface of an insulating substrate by thermally decomposing a zinc salt on the surface of the insulating substrate under an atmosphere containing oxygen or in a coexistence with a material capable of supplying oxygen.
  • the zinc salt is thermally decomposed on the surface of the insulating substrate to form a zinc oxide film on the surface of the substrate by supplying a vapor of a solution containing the zinc salt to the insulating substrate heated to a temperature at which the zinc salt thermally decomposes.
  • the above-mentioned thermal decomposition step can also be performed under an inert gas atmosphere such as nitrogen, not to mention an atmosphere containing oxygen. In the former case, the oxygen for forming the zinc oxide by the thermal decomposition of the zinc salt is supplied from the solution which dissolves the zinc salt.
  • the insulating substrate on which surface a coated film containing the zinc salt has been formed is heated under an atmosphere containing oxygen to a temperature or above at which the zinc salt thermally decomposes.
  • Another preferred embodiment of the method of the present invention comprises: the steps of, applying a solution containing at least a zinc salt, an organic compound capable of coordinating to zinc, and an organic solvent capable of dissolving the zinc salt and the organic compound to the insulating substrate to form a coated film containing the zinc salt, and firing the coated film to form a zinc oxide film under an atmosphere containing oxygen to form the zinc oxide film.
  • the above-mentioned solution containing the zinc salt further comprises: an inorganic salt or an organic salt of at least one metal selected from the group consisting of aluminum, magnesium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, indium, tin, antimony, lanthanum and cerium, in addition to the zinc salt.
  • FIG.1 is a cross-sectional side view showing a schematic configuration of the metal oxide film resistor built in accordance with an embodiment of the present invention.
  • FIG.2 is a cross-sectional side view showing a schematic configuration of an apparatus for producing the metal oxide film resistor built in accordance with an embodiment of the present invention.
  • FIG.3 is a cross-sectional side view showing a schematic configuration of an apparatus used for producing the metal oxide film resistor built in accordance with another embodiment of the present invention.
  • FIG.4 is a diagram showing electric characteristics of metal oxide film resistors built in accordance with the embodiments of the present invention.
  • the zinc oxide film of the present invention is produced by applying a solution comprising at least a zinc salt, an organic compound capable of coordinating to zinc and an organic solvent capable of dissolving the zinc salt and the organic compound to form a coated film on the surface of the insulating substrate, and by firing the coated film under an atmosphere containing oxygen.
  • any of the zinc salts can be employed as far as it contains a ligand that can be exchanged or substituted with the organic compound capable of coordinating to zinc.
  • zinc nitrate, zinc chloride, zinc sulfate, zinc oxalate and the like are employed as the zinc salt in addition to the exemplified zinc acetate.
  • the organic compound capable of coordinating to zinc is necessary for giving a solubility in the organic solvent to zinc by partly forming a coordination compound with zinc, and can be exemplified as ⁇ - or ⁇ -aminoalcohols such as 2-aminoethanol, ⁇ -diketones such as acetylacetone, ⁇ - or ⁇ -ketonic acids and any esters of the ketonic acids.
  • organic solvents can be employed as far as it can dissolve the organic compounds and inorganic compounds used in the present invention, and may be exemplified as aromatic hydrocarbons such as toluene and xylene, alcohols such as ethanol and isopropanol, acetic acid esters such as ethyl acetate and butyl acetate, ketones such as acetone and diethylketone, ethers such as tetrahydrofuran, etheralcohols such as methoxyethanol and ethoxyethanol, and the like.
  • aromatic hydrocarbons such as toluene and xylene
  • alcohols such as ethanol and isopropanol
  • acetic acid esters such as ethyl acetate and butyl acetate
  • ketones such as acetone and diethylketone
  • ethers such as tetrahydrofuran
  • etheralcohols such as methoxyethanol and ethoxyethanol, and the
  • the activator is a metal salt added to the film-forming composition in order to adjust the resistance value and the temperature coefficient of resistance (TCR) of the finished zinc oxide film
  • the metal element in the salt can be exemplified as aluminum, magnesium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, yttrium, zirconium, indium, tin, antimony, lanthanum and cerium.
  • metals are employed as their inorganic salts such as nitrate, chloride, sulfate and fluoride, or their organic salts, for example, a salt of carboxylic acid such as acetic acid salt and 2-ethylhexanoic acid salt, a salt of dicarboxylic acid such as oxalic acid salt, complex salts with acetylacetone, and the like.
  • inorganic salts such as nitrate, chloride, sulfate and fluoride
  • organic salts for example, a salt of carboxylic acid such as acetic acid salt and 2-ethylhexanoic acid salt, a salt of dicarboxylic acid such as oxalic acid salt, complex salts with acetylacetone, and the like.
  • a solution composed of at least a zinc salt, an organic compound capable of coordinating to zinc, and an organic solvent capable of dissolving the zinc salt and the organic compound is employed as a composition for forming the metal oxide film.
  • This refluxing treatment is performed in order to promote a reaction of the zinc salt or another salt of metal further added as an activator with the organic compound capable of coordinating to zinc, and is not necessarily indispensable for the preparation of the solution.
  • the refluxing treatment is an effective means for the preparation of the solution.
  • the organic compound capable of coordinating to zinc has a function of suppressing possible hydrolysis of the zinc salt by forming a coordination compound with zinc.
  • a part of the organic compound capable of coordinating to zinc which has failed to form a coordination compound with zinc and remains after an evaporation of the organic solvent, functions as an auxiliary solvent for the above-mentioned zinc salt until the thermal decomposition of the above-mentioned zinc salt is actually completed, and creates a situation wherein a deposition of the above-mentioned zinc salt takes place simultaneous with its thermal decomposition. Owing to the presence of the organic compound capable of coordinating to zinc in the solution, it is possible to obtain a very fine and dense film.
  • the organic compound capable of coordinating to zinc considerably participates in the thermal decomposition process of the zinc salt the characteristics of the obtained film are greatly influenced by the property (for instance, boiling point) of the compound. Therefore, an adequate selection of the species of organic compound is important.
  • a method for applying the metal oxide film-forming composition prepared in the above-mentioned manner to the surface of the substrate employed are a dip-coating process, a spraying method, a dispenser method and the like.
  • the substrate employed in the present invention should have an electrically insulating property at least on its surface, and is preferably exemplified as ceramic materials such as mullite, alumina, forsterite, steatite and cordierite.
  • the coated film of the composition for forming the metal oxide film is dried, and then fired to form the metal oxide film comprising zinc oxide or the one comprising zinc oxide as its principal component and the other oxide(s) of the metal M.
  • the temperature for performing the firing step is above a temperature at which the composition for forming the metal oxide film is thermally decomposed and is below a temperature at which the substrate deforms, and is preferably in a range from 400°C to 900°C.
  • the atmosphere under which the above-mentioned firing step is performed is air or an atmosphere including oxygen.
  • the thickness of the metal oxide film formed in this manner is usually in a range from several tens nm to several hundreds nm.
  • a more preferable method for producing the zinc oxide film of the present invention is a method to form the zinc oxide film on the surface of the insulating substrate by supplying a vapor of a solution containing the zinc salt to the insulating substrate heated to a temperature at or above which the zinc salt can be thermally decomposed and by decomposing the zinc salt on the surface of the insulating substrate to form a zinc oxide film on the surface of the substrate.
  • the above-mentioned zinc salt solution can further contain the metal salt(s) of the above-mentioned activator.
  • any of the solvents used for preparing the solution containing the above-mentioned zinc salt and the above-mentioned metal salt(s) can be employed as far as it can dissolve the above-mentioned zinc salt and other metal salt(s). They may be exemplified as alcohols such as ethanol and isopropanol, acetic acid esters such as ethyl acetate and butyl acetate, ketones such as acetone and diethylketone, etheralcohols such as methoxyethanol and ethoxyethanol, and the like.
  • the most preferable solvent is water.
  • acid such as hydrochloric acid, sulfuric acid and nitric acid or ammonia may be added to the solvent.
  • the temperature of heating the insulating substrate, whereto the vapor of the solution containing the zinc salt is supplied to be thermally decomposed in situ, must be lower than the melting point of the obtained metal oxide and also lower than the temperature at which the substrate deforms. The higher the temperature is, the more preferable the quality of the obtained metal oxide film becomes. A temperature ranging from 400°C to 900°C is generally preferable for this purpose.
  • the atmosphere under which the above-mentioned decomposition step is performed is an inert gas atmosphere such as nitrogen or argon in addition to air or an atmosphere including oxygen.
  • the thickness of the metal oxide film formed in this manner is usually in a range from several tens nm to several thousands nm.
  • the oxide film obtained by either of the above-mentioned methods it is preferable to further subject it to a heat-treatment under an inert gas atmosphere such as nitrogen or argon, a reducing gas atmosphere such as hydrogen or a mixed gas atmosphere of the inert gas and hydrogen.
  • an inert gas atmosphere such as nitrogen or argon
  • a reducing gas atmosphere such as hydrogen or a mixed gas atmosphere of the inert gas and hydrogen.
  • the atmospheric gas under which the heat-treatment is performed is preferably a nitrogen gas atmosphere or a mixed gas atmosphere of nitrogen and steam from the practical point of view.
  • the resistance value of the metal oxide film after the formation of the metal oxide film becomes constant within several hours; in the metal oxide film after the above-mentioned heat-treatment under an insert gas or reducing gas atmosphere, however, it takes several days until the resistance value becomes constant. It is believed that the behavior of the metal oxide film of varied resistance value is attributable to oxygen gas which has been adsorbed on the film during the formation of the metal oxide film. By this heat-treatment under an inert gas or reducing gas atmosphere, the oxygen gas which has been adsorbed during the formation of the metal oxide film desorbs therefrom and releases or emits conductive electrons. In this heat-treatment, since only a thermodynamically stable amount of oxygen is still left to be adsorbed, the variance or scatter in the resistance value attributable to the variance in the amount of the adsorbed oxygen decreases.
  • zinc oxide is a semi-conductor which has a large band gap of 3 eV or larger, and also a conductive material which has a high carrier (conductive electron) concentration. Therefore, by the above-mentioned heat-treatment under the inert gas or the reducing gas atmosphere, the carrier concentration of the zinc oxide increases and the resistance value decreases by the amount of the conductive electrons released or emitted as a result of the desorption of the oxygen gas which has been adsorbed during the formation of the metal oxide film. And, it is believed that since the amount of the conductive electrons in the conduction band becomes very large, the electrons in the lower band (valence band) are hardly excited to the conduction band even with the increase in the temperature.
  • the resistance value rather increases by a scattering of the conductive electrons induced by a lattice vibration, and thus the metal oxide film after the above-mentioned heat-treatment under the inert gas or reducing gas atmosphere demonstrates a positive temperature coefficient of resistance which is analogous to a metal.
  • the temperature during the heat-treatment under the inert gas or reducing gas atmosphere is too low, the adsorbed oxygen is hardly desorbed.
  • the temperature during the heat-treatment under the inert gas or reducing gas atmosphere is too high, the metal oxide film demonstrates a positive and large temperature coefficient of resistance, because the metal oxide film is reduced during the heat-treatment and thus a precipitation of a metal takes place.
  • the degree of reduction may differ from each other depending on the species of the inert gas or the reducing gas, and the upper limit of the heat-treatment temperature falls if a gas is of high reducing ability.
  • this heat-treatment is performed at a temperature ranging from 300°C to 700°C.
  • the specific resistance of single phase zinc oxide which constitutes the resistor element of the metal oxide film resistor of the present invention is in a range from about 1 ⁇ 10 ⁇ 2 ⁇ cm to about 1 ⁇ 102 ⁇ cm depending on the amount of oxygen defects present in the oxide film.
  • a film composed of zinc oxide including other metal element can have a specific resistance in a range from about 5 ⁇ 10 ⁇ 3 ⁇ cm to about 1 ⁇ 103 ⁇ cm.
  • each of these various metal elements added to the zinc oxide forms a solid solution or a complex oxide with the zinc oxide, or alternatively, becomes a metal oxide, thereby creating a state wherein it is mixed with zinc oxide.
  • the metal oxide film in accordance with the present invention can be considered to be in a state wherein the following three local states are mixed:
  • the metal oxide of various metals In a case wherein the amount of the metal oxide of various metals is smaller than the solubility limit, the metal oxide is completely dissolved in the zinc oxide in a solid state, but the respective metal oxides may differ from each other with respect to their solubility. And the zinc oxide doped with the metal oxide of various metals exists in a single phase. In a case wherein the amount of the metal oxide of various metals is larger than the solubility limit, all of the metal oxide is not completely dissolved in the zinc oxide in a solid state, and a part of the metal oxide is precipitated in the grain boundaries. And the precipitated metal oxide exists in a dispersed state in a matrix of zinc oxide doped with the metal oxide. Some metal oxide reacts with the zinc oxide to form a compound of the spinel form such as ZnM2O4 or ZnMO3 type.
  • FIG.1 shows a schematic configuration of the metal oxide film resistor produced in accordance with an embodiment of the present invention.
  • a metal oxide film 2 is formed on a surface of an insulating substrate 1 in the above-mentioned manner.
  • a pair of cap terminals 3 made of stainless steel plated with tin were press-fitted on both ends of the substrate 1 having been formed with the above-mentioned metal oxide film 2 and a pair of copper lead wires 4 plated with tin were welded to the cap terminals 3.
  • any terminals may be used as far as they can ohmically connected to the metal oxide film 2
  • the lead wires 4 any lead wires may be used as far as they can be ohmically connected to the cap terminals 3.
  • the surface of the above-mentioned metal oxide film 2 was coated with a protective film 5 made of a thermosetting resin.
  • the protective film 5 also covers the cap terminals 3. Any material may be used as the protective film 5 as far as it has an electrically insulating property and a humidity-resistant property, and may be the resin itself or the resin containing an inorganic filler. For curing the resin, a radiation of visible light or ultraviolet ray may also be used in place of the application of heat.
  • FIG.2 shows an apparatus for supplying a vapor of a solution containing the zinc salt on the surface of the heated insulating substrate and for forming a metal oxide film thereon.
  • a reaction tube 11 made of quartz accommodating the insulating substrate 1 on whose surface the metal oxide film is to be formed is fixed to a furnace core tube 12 made also of quartz with a pair of packing rings 13.
  • the furnace core tube 12 inserted in an electric furnace 14 is caused to rotate in the electric furnace 14 by chain 16 which is driven by an electric motor 15 at an appropriate revolving speed.
  • a material supplying container 18 containing the metal oxide film-forming composition 17 is connected with a gas supplying device 19 through a pipe 20, and with the reaction tube 11 through a pipe 21.
  • a multiplicity of the substrates 1 is first placed in the reaction tube 11 as shown by the drawing. While the reaction tube 11 is rotated, it is heated by the electric furnace 14 and kept at a temperature or above at which the metal oxide film-forming composition decomposes. In this state, a carrier gas supplied from the gas supplying device 19 is introduced into the material supplying container 18 through the pipe 20 and the vapor of the metal oxide film-forming composition is supplied to the reaction tube 11 through the pipe 21.
  • the above-mentioned vapor which has been supplied to the reaction tube 11 then decomposes by contacting the substrates and forms the metal oxide films on the surfaces of the substrates.
  • the carrier gas supplied from the gas supplying device 19 air, oxygen, or an inert gas such as nitrogen or argon is used.
  • the supplying amount of the vapor of the above-mentioned metal oxide film-forming composition is controlled.
  • the supplying amount of the vapor of the above-mentioned metal oxide film-forming composition may alternatively be controlled by heating the material supplying container 18 or by applying an ultrasonic radiation to the container 18.
  • the reaction tube 11 is rotated in order to ensure a uniform contact of the vapor containing the zinc salt with the entire surfaces of the substrates by rolling the substrates and to form the metal oxide films throughout the surfaces of the substrates uniformly.
  • a mechanical vibration may be applied to the reaction tube 11 for the same purpose.
  • the metal oxide film-forming composition is supplied to the reaction tube 11 by the pressurized carrier gas.
  • An apparatus shown by FIG.3 is configured by connecting a pressure reducing device 23 to an exhaust side of the reaction tube 11 through a pipe 22 and creates a pressure difference between the spaces inside the pipes 20 and 22. So that the pressure inside the reaction tube 11 is reduced to introduce the carrier gas into the material supplying container 18, and then the vapor of the metal oxide film-forming composition is supplied to the reaction tube 11.
  • the supplying amount of the vapor of the above-mentioned metal oxide film-forming composition may be controlled. Further, the supplying amount of the vapor of the above-mentioned metal oxide film-forming composition may alternatively be controlled by heating the material supplying container 18 or by applying an ultrasonic radiation to the container 18.
  • connection of the reaction tube 11 with the pipe 21 are configured with gas-tight sealing joints so that any gas or vapor should not be leaked even with the rotation of the reaction tube 11.
  • connection of the reaction tube 11 with the pipe 22 is configured in the same manner.
  • the substrate was a cylindrical rod made of a ceramic containing 92 wt% of alumina, having a diameter of 2 mm and a length of 10 mm.
  • the coated film of the above-mentioned metal oxide film-forming composition was dried at 60°C for 5 minutes, it was fired in the air at 800°C for 10 minutes to form a metal oxide film consisting mainly of zinc oxide.
  • the thickness of the film thus produced is about 50 nm.
  • a pair of cap terminals 3 were press-fitted on both ends of the substrate 1 having been formed with the above-mentioned metal oxide film 2, and a pair of lead wires 4 were welded to the cap terminals 3.
  • the surface of the above-mentioned metal oxide film 2 was coated with a paste of a thermosetting resin, dried and then cured by heating it at 150°C for 10 minutes to form an electrically insulating protective film 5 for completing the metal oxide film resistor of the present invention as shown by FIG.1.
  • Table 1 Metal M Resistance value(k ⁇ ) None 1,200 Al 5.0 Mg 31,000 Sc 44.0 Ti 14.0 V 520 Cr 3,500 Mn 57.0 Fe 1,600 Co 14,000 Ni 26,000 Cu 51,000 Y 12.0 Zr 72.0 In 3.0 Sn 9.0 Sb 37.0 La 23.0 Ce 300
  • Example 2 In a manner similar to that in Example 1 except for the use of zinc chloride ZnCl2 ⁇ 6H 2O as the zinc salt and the non-use of any activator, another metal oxide film resistor was prepared.
  • Example 2 In a manner similar to that in Example 1 except for the use of aluminum nitrate Al(NO3)3 ⁇ 9H 2O as the activator in an amount wherein a value represented by the formula Al/(Zn + Al) and converted in terms of mole number of the metals is 0.05, another metal oxide film resistor was prepared.
  • a metal oxide film-forming composition was prepared by mixing stannic chloride SnCl4 ⁇ 5H 2O, antimony trichloride SbCl3 and methanol in a proportion of 100 g, 6.4 g and 10 ml, respectively.
  • This composition was heated at 110°C to be converted into a state of smoke, and the generated smoke was blown onto a substrate rod kept at 650°C to form a metal oxide film consisting of the ATO.
  • a pair of cap terminals were press-fitted on both ends of the substrate rod having been formed with the above-mentioned ATO film, and then a pair of lead wires were welded to the cap terminals. Finally, the surface of the above-mentioned ATO film was coated with an electrically insulating protective film for completing the metal oxide film resistor.
  • FIG.2 An apparatus shown by FIG.2 was used for coating substrates of a cylindrical rod made of a ceramic containing 92 wt% of alumina (diameter: 3mm, length: 14 mm).
  • the substrate rods were placed in a reaction tube 11 and the above-mentioned metal oxide film-forming composition was placed in a material supplying container 18, respectively.
  • the temperature of the material supplying container 18 was kept at room temperature and a mist of the metal oxide film-forming composition was supplied through bubbling. Air was used as a carrier gas, and the flow rate of the gas was kept at 1 liter/minute and the substrate rods were heated up to 800°C.
  • the substrate rods in the reaction tube 11 were kept at 800°C for 60 minutes, and then 50 g of the above-mentioned metal oxide film-forming composition were supplied to the reaction tube 11 for the following 40 minutes to form the metal oxide film. Thereafter, the substrate rods were kept still at 800°C for the additional 60 minutes.
  • the thickness of the film thus formed was about 3000 nm.
  • Example 2 the coated substrate rods were heat-treated under a nitrogen atmosphere at 650°C for 5 hours. Thereafter, a pair of cap terminals as well as lead wires were attached to each of the substrate rods, and a protective film consisting of a thermosetting resin was formed on these components in a manner similar to that in Example 1.
  • the electric characteristics of the obtained metal oxide film resistors are shown by a diagram in FIG.4.
  • the diagram illustrates relationships between the resistance values as well as the temperature coefficients of resistance and the values M/(Zn + M) in a metal oxide film of a resistor configured with a zinc oxide film also containing oxide of aluminum or indium.
  • the resistance values of the resistors using Al as M and the temperature coefficients of resistance are represented by R Al and TCR Al
  • the resistance values of the resistors using In as M and the temperature coefficients of resistance are represented by R In and TCR In , respectively.
  • the temperature coefficients of resistance (TCR) are derived from the values measured at 25°C and at 125°C.
  • the apparatus shown by FIG.2 was used for coating each of the substrate rods with a metal oxide film with a thickness of about 1000 nm consisting mainly of zinc oxide under the same conditions as those in Example 5.
  • Example 6 Under the same conditions as in Example 6 except for the use of zinc acetate Zn(CH3COO)2 ⁇ 2H 2O as the zinc salt and the non-use of any activator, another metal oxide film resistor was prepared.
  • Example 6 Under the same conditions as in Example 6 except for the use of an apparatus shown by FIG.3 and the setting of the pressure-reducing device so as to make the flow rate of the carrier gas 1 liter/minute, another metal oxide film resistor was prepared.
  • a metal oxide film resistor was prepared in a manner similar to that in Comparative Example 1, except for the use of a substrate of cylindrical rod made of a ceramic containing 92 wt% of alumina (diameter: 3 mm, length: 14 mm).

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Apparatuses And Processes For Manufacturing Resistors (AREA)
  • Non-Adjustable Resistors (AREA)
EP94120409A 1993-12-24 1994-12-22 Metalloxid-Dünnschichtwiderstand und Herstellungsverfahren. Withdrawn EP0660337A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP326588/93 1993-12-24
JP32658893 1993-12-24
JP2020994 1994-02-17
JP20209/94 1994-02-17

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EP0660337A2 true EP0660337A2 (de) 1995-06-28
EP0660337A3 EP0660337A3 (de) 1995-11-08

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Publication number Priority date Publication date Assignee Title
DE3612620C1 (en) * 1986-04-15 1987-07-02 Swf Auto Electric Gmbh Circuit arrangement with a drive motor
JPH04201251A (ja) * 1990-11-29 1992-07-22 Matsushita Electric Ind Co Ltd セラミックス―金属積層体
FR2670200B1 (fr) * 1990-12-06 1993-05-28 Saint Gobain Vitrage Int Procede de formation d'une couche semi-conductrice d'oxyde de zinc dope a l'aluminium sur du verre, vitrage ainsi obtenu.
JPH05262524A (ja) * 1992-03-19 1993-10-12 Idemitsu Kosan Co Ltd 酸化亜鉛薄膜の製造方法

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