WO2013175794A1 - 電圧非直線性抵抗体およびこれを用いた積層バリスタ - Google Patents
電圧非直線性抵抗体およびこれを用いた積層バリスタ Download PDFInfo
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- WO2013175794A1 WO2013175794A1 PCT/JP2013/003273 JP2013003273W WO2013175794A1 WO 2013175794 A1 WO2013175794 A1 WO 2013175794A1 JP 2013003273 W JP2013003273 W JP 2013003273W WO 2013175794 A1 WO2013175794 A1 WO 2013175794A1
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- voltage
- grain boundary
- boundary layer
- nonlinear resistor
- varistor
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
- H01L29/8605—Resistors with PN junctions
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
-
- 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
-
- 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
- H01C7/18—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 comprising a plurality of layers stacked between terminals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/0203—Particular design considerations for integrated circuits
- H01L27/0248—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/22—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIBVI compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C1/00—Details
- H01C1/14—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors
- H01C1/148—Terminals or tapping points or electrodes specially adapted for resistors; Arrangements of terminals or tapping points or electrodes on resistors the terminals embracing or surrounding the resistive element
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/0203—Particular design considerations for integrated circuits
- H01L27/0248—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
- H01L27/0251—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices
- H01L27/0288—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices using passive elements as protective elements, e.g. resistors, capacitors, inductors, spark-gaps
Definitions
- the present invention relates to a multilayer varistor suitable for protecting electronic equipment from static electricity.
- the present invention relates to a voltage non-linear resistor used in the multilayer varistor.
- ESD static electricity
- semiconductor devices such as ICs used in electronic equipment may be damaged by static electricity (ESD) or their characteristics may be reduced.
- ESD static electricity
- recent semiconductor devices are required to operate at high speed, and accordingly, recent semiconductor devices are vulnerable to ESD.
- ESD static electricity
- a semiconductor device is destroyed by ESD, a serious failure such as malfunction or failure is caused in an electronic device.
- the importance of ESD countermeasures in various electronic devices has increased, and varistors using voltage nonlinear resistors that exhibit voltage nonlinearity are widely used as ESD countermeasure components.
- Varistors used for ESD countermeasures are required to have excellent ESD resistance so that the varistors can absorb ESD and are not destroyed by ESD. Further, in the state where there is no ESD intrusion, the varistor exists merely as a capacitance. For this reason, the varistor needs to have an appropriate capacitance value so as not to adversely affect the operation of the circuit.
- Such voltage non-linear resistors for ESD countermeasures are generally divided into two types, Pr type (for example, Patent Document 1) and Bi type (for example, Patent Document 2), depending on varistor characteristic expression additives.
- Pr type for example, Patent Document 1
- Bi type for example, Patent Document 2
- varistor characteristic expression additives for example, the Pr-based multilayer varistor is suitable for reducing the varistor voltage
- the Bi-based multilayer varistor is suitable for reducing the capacitance.
- the varistor voltage and the electrostatic capacity can be adjusted by appropriately using two kinds of material systems and further appropriately setting the thickness of the varistor layer between the electrodes and the overlapping area of the electrodes.
- the present invention is a voltage non-linear resistor with reduced voltage dependency of capacitance and a laminated varistor using the same.
- the voltage nonlinear resistor of the present invention includes a plurality of N-type ZnO crystal particles, a grain boundary layer, and oxide particles that are P-type semiconductors.
- the grain boundary layer is formed between a plurality of ZnO crystal grains and includes at least one kind of oxide of an alkaline earth metal.
- the oxide particles are arranged between the plurality of ZnO crystal particles via the grain boundary layer.
- the multilayer varistor of the present invention has a pair of internal electrodes, a varistor layer formed between the internal electrodes, and a pair of external electrodes electrically connected to the internal electrodes, and the varistor layer is It is composed of a voltage nonlinear resistor.
- FIG. 1A is a schematic cross-sectional view of a microstructure of a voltage nonlinear resistor according to an embodiment of the present invention.
- FIG. 1B is a cross-sectional transmission electron microscope (TEM) observation image of the voltage nonlinear resistor shown in FIG. 1A.
- FIG. 1C is a schematic diagram of FIG. 1B.
- FIG. 2A is a schematic diagram showing an energy barrier structure before application of a bias voltage at the grain boundary portion of the voltage nonlinear resistor according to the embodiment of the present invention.
- FIG. 2B is a schematic diagram showing an energy barrier structure after application of a bias voltage at the grain boundary portion of the voltage nonlinear resistor according to the embodiment of the present invention.
- FIG. 2C is a schematic diagram showing an energy barrier structure before applying a bias voltage at the grain boundary portion of the voltage nonlinear resistor different from the embodiment of the present invention.
- FIG. 2D is a schematic diagram showing an energy barrier structure after application of a bias voltage at a grain boundary portion of a voltage nonlinear resistor different from the embodiment of the present invention.
- FIG. 3 shows the relationship between the configuration of the Zener diode and the voltage dependency of the capacitance, and the voltage dependency of the capacitance of the multilayer varistor fabricated using the voltage nonlinear resistor in the embodiment of the present invention. It is a graph to show.
- FIG. 4 is a schematic cross-sectional view of a laminated varistor according to an embodiment of the present invention.
- FIG. 5 is a graph showing the voltage dependence of capacitance in each example of the multilayer varistor in the embodiment of the present invention and the conventional multilayer varistor.
- FIG. 6 is a graph showing the result of line analysis of the concentration distribution of Sr element and Co element in the grain boundary layer of voltage nonlinear resistance in the embodiment of the present invention.
- the electrostatic capacity of the conventional voltage nonlinear resistor is attributed to the grain boundary structure between ZnO crystal grains, which is a site where varistor characteristics are manifested. And since the width of the depletion layer in the double Schottky barrier formed in the interface part of ZnO crystal grain depends on voltage, it is thought that electrostatic capacitance has voltage dependence.
- FIG. 1A is a schematic cross-sectional view of the microstructure of voltage nonlinear resistor 4 in an embodiment of the present invention.
- FIG. 1B is a diagram showing a cross-sectional transmission electron microscope (TEM) observation image of the voltage nonlinear resistor 4. That is, FIG. 1B is an enlarged cross-sectional photograph of the sample prepared by slicing the voltage nonlinear resistor 4 by Ar milling and observed near the oxide particles 3 shown in FIG. 1A by high-resolution TEM.
- FIG. 1C is a schematic diagram of FIG. 1B.
- the voltage nonlinear resistor 4 includes a plurality of ZnO crystal particles 1, a grain boundary layer 2, and oxide particles 3.
- the grain boundary layer 2 includes at least one kind of alkaline earth metal and is disposed between the plurality of ZnO crystal particles 1.
- the oxide particles 3 are arranged between the plurality of ZnO crystal particles 1 via the grain boundary layer 2. That is, the grain boundary layer 2 is interposed in the grain boundary of the ZnO crystal grain 1, and the oxide particle 3 is present inside the grain boundary layer 2.
- the plurality of ZnO crystal particles 1 are bonded via the grain boundary layer 2 and the oxide particles 3.
- the oxide particles 3 are interposed between the plurality of ZnO crystal particles 1 with the grain boundary layer 2 interposed therebetween.
- the ZnO crystal particles 1, the grain boundary layer 2, and the oxide particles 3 can be observed by a high-resolution TEM.
- elemental analysis of the ZnO crystal particles 1, the grain boundary layer 2, and the oxide particles 3 can be performed using energy dispersive X-ray analysis (EDS).
- the grain boundary layer 2 and the oxide particles 3 are formed by sintering while allowing the ZnO crystal particles 1 and the alkaline earth metal oxide to coexist.
- the grain boundary layer 2 formed of an alkaline earth metal oxide reaches the grain boundaries of the plurality of ZnO crystal grains 1.
- the oxide particles 3 finally constitute a fine structure as an excess component.
- the voltage non-linear resistor 4 in which the voltage dependency of the electrostatic capacity is reduced can be stably manufactured by an industrial manufacturing process based on the solid phase reaction method. That is, it is preferable that the oxide particles 3 are formed of the same material as the grain boundary layer 2 because productivity is improved.
- the grain boundary layer 2 and the oxide particles 3 may be formed of different materials.
- a conventional voltage nonlinear resistor is composed of a plurality of ZnO crystal grains and a grain boundary layer.
- an acceptor level is formed at the connection interface between the surface of the ZnO crystal grains and the grain boundary layer, and varistor characteristics are exhibited due to excellent barrier characteristics in the polycrystalline structure.
- the oxide particle 3 exists inside the grain boundary layer 2.
- the structure is different from the conventional voltage nonlinear resistor.
- the grain boundary layer 2 in the voltage nonlinear resistor 4 is the origin of the development of barrier characteristics (varistor characteristics) in the polycrystalline structure. That is, also in the voltage non-linear resistor 4, the grain boundary layer 2 is considered to play the same role as the conventional voltage non-linear resistor.
- the grain boundary layer 2 is composed of SrCoO 3 .
- FIGS. 2A and 2B are schematic views showing the energy barrier structure of the voltage nonlinear resistor 4
- FIGS. 2C and 2D are schematic views showing the energy barrier structure of the conventional voltage nonlinear resistor.
- 2A and 2C show a case where no bias voltage is applied
- FIGS. 2B and 2D show a case where a bias voltage is applied.
- the energy barrier structure of the conventional voltage nonlinear resistor is ZnO crystal particles 21 / ZnO crystal particles 21. That is, it can be considered that the ZnO crystal particles 21 and the ZnO crystal particles 21 form an N-type / N-type electric conduction structure with the grain boundary layer 22 interposed therebetween.
- the width W5 of the grain boundary layer 22 (depletion layer) of the double Schottky barrier at the time of no bias formed at the interface portion of the ZnO crystal grain 21 is as shown in FIG. 2D when a bias voltage is applied.
- the width of the grain boundary layer 22 (depletion layer) becomes W6. Therefore, it is considered that the apparent capacitance change rate is increased.
- the energy barrier structure of the voltage nonlinear resistor 4 is ZnO crystal particles 1 / oxide particles 3 / ZnO crystal particles 1 as shown in FIG. 2A. Therefore, it can be considered that an N-type / P-type / N-type electric conduction structure is formed in which two barriers sandwich a grain boundary between the ZnO crystal particles 1 and the ZnO crystal particles 1.
- a grain boundary layer 2 (depletion layer) exists at both junction surfaces with oxide particles 3 (P type) sandwiched between ZnO crystal particles 1 (N type). It is a structure to do.
- the width W2 of the grain boundary layer 2 (depletion layer) on the NP side is equal to the grain boundary layer of the conventional voltage nonlinear resistor ( The depletion layer) becomes W4 in the same manner as the width W6.
- the width W1 of the grain boundary layer 2 (depletion layer) on the PN side decreases and changes to W3.
- the total width of the grain boundary layer 2 in the voltage application state of the voltage nonlinear resistor 4 is W3 + W4. At this time, it is considered that the decrease in W1 and the increase in W2 are offset, and the apparent capacitance change rate is reduced.
- the energy barrier structure model as described above can be verified by using a Zener diode (N / P type structure) configured at the NP interface.
- the grain boundary layer 2 (depletion layer) is formed at the interface of the N-type composition (ZnO crystal particles 1) sandwiching the P-type composition (oxide particles 3). Is formed.
- the basic unit structure of this model can be expressed by “NP + PN” in which two Zener diodes (N / P type structures) are connected.
- the varistor characteristic of “NP + PN” is determined by the barrier of only the NP junction that is reverse-biased since the PN junction is forward and hardly contributes.
- a model of the voltage nonlinear resistor 4 which is a polycrystal model can be expressed by repeatedly connecting Zener diodes with “NP + PN” as a basic unit. Specifically, NP ⁇ NP + PN ⁇ "NP + PN” + “NP + PN” ⁇ "NP + PN” + “NP + PN” + “NP + N” By repeatedly connecting, the varistor characteristics are expressed and the capacitance depends on the bias voltage. Reduction can be confirmed.
- FIG. 3 shows the result of measuring the rate of change in capacitance according to the applied voltage after connecting these Zener diodes (N / P type structure).
- N / P type structure the characteristic of the laminated varistor of the sample A in the Example mentioned later. From FIG. 3, it can be confirmed that the rate of change in capacitance decreases as the number of N / P-type repetitions increases, and asymptotically approaches the characteristics of sample A.
- the polycrystalline structure model in which a large number of “NP + PN” structures are connected has an effect of reducing the voltage dependency of the capacitance.
- the voltage nonlinear resistor 4 includes the oxide particles 3 serving as a P-type semiconductor, a plurality of ZnO crystal particles 1 that are N-type semiconductors, and a grain boundary layer 2 (depletion layer).
- the above-described “NP + PN” repetitive structure is included.
- the oxide particles 3 are not particularly limited as long as they are P-type semiconductors.
- the crystal structure of the oxide particles 3 can be confirmed by an X-ray diffraction pattern.
- the oxide particles 3 are scattered as a precipitated phase between the ZnO crystal particles 1 or in a gap formed by three or more ZnO crystal particles 1 and can be observed by a scanning electron microscope (SEM).
- SEM scanning electron microscope
- the precipitation amount of the oxide particles 3 can be estimated from the area ratio with the ZnO crystal particles 1 in cross-sectional observation.
- the precipitation amount of the oxide particles 3 is more preferably in the range of 0.5 atm% or more and 10 atm% or less with respect to the total amount of ZnO. If the precipitation amount of the oxide particles 3 is within this range, the voltage dependency of the capacitance can be further reduced.
- the alkaline earth metal contained in the oxide constituting the grain boundary layer 2 is preferably selected from the group consisting of Sr, Ca and Ba. As a result, a low varistor voltage and excellent non-linearity can be realized.
- the grain boundary layer 2 and the oxide particles 3 are not particularly limited, but are preferably a solid solution having a perovskite structure composed of an oxide of an alkaline earth metal. Thereby, a low varistor voltage and excellent non-linearity can be realized.
- the thickness of the grain boundary layer 2 (the distance between the plurality of ZnO crystal particles 1) is preferably 1 nm or more and 10 nm or less. Thereby, excellent voltage nonlinearity and strong ESD tolerance can be realized.
- the average crystal particle diameter of the ZnO crystal particles 1 is preferably 0.5 ⁇ m or more and 2 ⁇ m or less. Thereby, ESD tolerance can be improved and the voltage non-linear resistance body 4 suitable for an ESD protection varistor can be realized.
- the voltage nonlinear resistor 4 contains an Al component within the above range, the particle diameters of the ZnO crystal particles 1 and the oxide particles 3 are uniformized. Therefore, the crystal grains become dense during sintering, and the voltage nonlinear resistor 4 can express a lower varistor voltage.
- the reduction of the varistor voltage leads to improvement of the voltage nonlinearity ⁇ and the ESD tolerance ⁇ V 1 mA as the voltage nonlinear resistor 4, and the voltage nonlinear resistor 4 with higher reliability can be realized.
- V 1 mA The varistor voltage V 1 mA , the voltage nonlinearity ⁇ , and the ESD tolerance ⁇ V 1 mA will be described in detail in conjunction with the description of the examples. Further, generally, when the ceramic structure is made uniform, the mechanical strength of the voltage nonlinear resistor 4 is improved, so that the reliability against a thermal shock and a drop impact of the device is also increased.
- the laminated varistor 14 includes at least a pair of internal electrodes 12, a varistor layer 11 formed between the internal electrodes 12, and a pair of external electrodes 13 electrically connected to each of the internal electrodes 12.
- the varistor layer 11 is composed of a voltage nonlinear resistor 4.
- the external electrode 13 is formed at the end portion of the laminate composed of the internal electrode 12 and the varistor layer 11.
- the voltage nonlinear resistor 4 is formed between the pair of internal electrodes 12, and the material disposed on the upper and lower surfaces of the pair of internal electrodes 12 is not limited.
- the varistor characteristics may deteriorate due to atomic diffusion between different materials. Therefore, it is preferable that the same material as that of the voltage nonlinear resistor 4 formed between the pair of internal electrodes 12 is disposed on the upper and lower surfaces of the pair of internal electrodes 12 as shown in FIG.
- SrCO 3 powder and Co 2 O 3 powder are raw materials constituting the grain boundary layer 2 and the oxide particles 3. These are mixed in advance for 20 hours in a polyethylene ball mill containing stabilized zirconia cobblestone having a diameter of 1.0 mm and pure water, and the average particle size is set to 0.3 ⁇ m ⁇ 0.03 ⁇ m.
- the average particle size of the SrCO 3 powder and the Co 2 O 3 powder are easily spread uniformly on the surface of the ZnO powder.
- the fine structure of the voltage nonlinear resistor 4 is formed.
- these starting raw material powders are put into a polyethylene ball mill, stabilized zirconia cobblestone having a diameter of 2 mm and pure water are added and mixed for about 20 hours, so that the average particle diameter becomes 0.5 ⁇ m ⁇ 0.05 ⁇ m. Crush, then dehydrated and dried.
- the dried powder is granulated through a 20-mesh sieve, it is placed in a high-purity alumina crucible and calcined in the atmosphere at about 750 ° C. to 950 ° C. for 2 hours.
- the calcined powder is put into a polyethylene ball mill in the same manner as in the above mixing, and a stabilized zirconia cobblestone and pure water are added and pulverized for about 20 hours to obtain an average particle size of 0.5 ⁇ m ⁇ 0.1 ⁇ m. . Thereafter, it is dehydrated and dried until the water content becomes 0.1% or less.
- a slurry is prepared by mixing a powder obtained by dehydration and drying, an organic binder, and a dispersion medium. At this time, the dispersion is uniformly dispersed while suppressing aggregation so that the average particle size of the dispersion becomes 0.70 ⁇ m ⁇ 0.10 ⁇ m.
- the slurry thus prepared is formed into a sheet to produce a ceramic sheet.
- the average particle diameter means D50 evaluated from the volume particle size distribution by a laser diffraction scattering type particle size distribution apparatus. Specifically, the slurry in which the sample is dispersed is diluted with a dispersion medium for dilution, and then uniformly dispersed with a homogenizer. In this way, a measurement sample is prepared and put into an apparatus to measure the particle size distribution.
- the dispersion medium contained in the slurry is water, a sodium hexametaphosphate aqueous solution can be used as the dispersion medium for dilution. If the dispersion medium contained in the slurry is an organic solvent, ethanol can be used as a dispersion medium for dilution.
- a predetermined number of the above-described ceramic sheets are prepared, and the conductive paste for internal electrodes in which Ag—Pd alloy particles and an organic binder are mixed is printed on each ceramic sheet by a screen printing method to form a conductor layer.
- seat which has not printed the electrically conductive paste are laminated
- a laminate block is produced by pressurizing this laminate.
- the laminated body block is cut and separated into a desired size to produce individual laminated chips.
- This laminate chip is heated to about 500 ° C. in the atmosphere to remove the binder, and further fired at 1000 ° C. to 1100 ° C. in the atmosphere to produce a ceramic sintered body.
- the ceramic sintered body is barrel-polished to expose the internal electrodes 12 on both end faces of the ceramic sintered body. Thereafter, a glass insulating layer is formed on the side surface of the ceramic sintered body (a surface other than the surface where the internal electrode 12 is exposed).
- a conductive paste for an external electrode in which Ag—Pd alloy particles and an organic binder are mixed is applied to the surface where the internal electrode 12 is exposed, dried, and baked at 1000 ° C. or higher and 1100 ° C. in the atmosphere.
- the external electrode 13 is formed, and the laminated varistor 14 is completed.
- Sample A described in Table 1 is a laminated varistor 14 using the voltage nonlinear resistor 4.
- the starting material of sample A is 97.5 atm% of the main component ZnO powder, 1.25 atm% SrCO 3 powder, and 1.25 atm% Co 2 O 3 powder, and more chemically purified Al. It is a mixture to which 2 O 3 powder is added.
- the amount of Al 2 O 3 powder added is 0.002 mol per 1 mol of ZnO.
- the calcination temperature is 800 ° C.
- the binder removal temperature of the laminated chip is 400 ° C.
- the firing temperature in the air is 1030 ° C.
- the baking temperature of the external electrode 13 is 720 ° C.
- a Bi-based multilayer varistor is a sample B and a Pr-based multilayer varistor is a sample C as a + multilayer varistor manufactured using a conventional voltage nonlinear resistor.
- the starting materials of Sample B are 94.5 atm% of the main component ZnO powder, 0.1 atm% Bi 2 O 3 powder, 0.5 atm% CoO powder, 0.6 atm% MnO powder, 0
- This is a mixture in which a chemically high-purity Al 2 O 3 powder is further added to 3 atm% Sb 2 O 3 powder and 4.0 atm% SiO 2 powder.
- the amount of Al 2 O 3 powder added is 0.001 mol per 1 mol of ZnO.
- the starting material of sample C is 97.5 atm% of the main component ZnO powder, 0.6 atm% Pr 2 O 3 powder, 1.6 atm% CoO powder, and 0.1 atm% Cr 2 O 3 powder. And 0.2 atm% CaO powder to which a chemically pure Al 2 O 3 powder is added.
- the amount of Al 2 O 3 powder added is 0.01 mol per 1 mol of ZnO.
- the voltage non-linear resistors of Sample B and Sample C are prepared in the same manner as Sample A except for the starting materials.
- the varistor voltage V 1 mA of sample B is 12V class
- the varistor voltage V 1 mA of sample C is 8V class.
- Samples A to C all have the same external dimensions, the longitudinal direction is 1.0 mm, the width direction is 0.5 mm, and the thickness direction is 0.5 mm.
- the thickness of the varistor layer 11 disposed between the internal electrodes 12 is about 20 ⁇ m, the number of the internal electrodes 12 is 10, and the area per one layer (overlapping area of the internal electrodes 12) is about 0.06 mm 2 .
- varistor voltage V 1 mA , ⁇ indicating voltage non-linearity, ⁇ V 1 mA indicating ESD resistance, and voltage dependency ⁇ C of capacitance C are measured for 10 samples, and an average value is obtained.
- the varistor voltage V 1 mA is a voltage value between terminals when a current flows 1 mA
- the capacitance C is measured with a measurement frequency of 1 MHz, a measurement voltage of 1 Vrms, and no DC bias.
- the DC voltage applied at this time is normalized with the varistor voltage V 1 mA to obtain the electric charge rate. If there is voltage dependency of the capacitance, the rate of change ⁇ C of the capacitance C changes depending on the power application rate. Therefore, the change of the change rate ⁇ C with respect to the charging rate is evaluated.
- ESD resistance is evaluated according to IEC61000-4-2. That is, the varistor voltage V 1 mA before and after applying an ESD voltage of 8 kV (charge capacity 150 pF, discharge resistance 330 ⁇ ) to the multilayer varistor from the electrostatic discharge simulator is measured. Then, the change rate ⁇ V 1 mA is obtained by subtracting the value of the varistor voltage V 1 mA before applying the ESD voltage from the value of the varistor voltage V 1 mA after applying the ESD voltage. Further, to evaluate the average crystal grain size D g of ZnO crystal grains 1 by intercept method from the observation image by using an electron microscope.
- the varistor voltage V 1 mA of sample A is 5.8 V, which is lower than the varistor voltages of sample B and sample C.
- the non-linearity ⁇ of the sample A is superior to that of the sample B, and is almost equal to that of the sample C.
- FIG. 5 is a graph showing the voltage dependence of the capacitance C in Samples A to C.
- ⁇ C of sample B and sample C has a large voltage dependency, and the capacitance decreases with an increase in the electric charge rate. As shown in (Table 1), ⁇ C at an electric charge rate of 50% reaches approximately ⁇ 14% for both Sample B and Sample C. On the other hand, ⁇ C of sample A is about + 0.5%, and ⁇ C is clearly smaller than samples B and C, and the voltage dependency of capacitance C is extremely small.
- FIG. 6 shows the result of element distribution of Sr element and Co element in the grain boundary layer 2 of the voltage nonlinear resistor 4 using high resolution TEM and EDS.
- FIG. 6 shows the results of line analysis of the concentrations of Sr element and Co element along line 6-6 shown in FIGS. 1B and 1C.
- the thickness (width) of the grain boundary layer 2 in the 6-6 line is about 7 nm, and the grain boundary layer 2 contains an oxide containing Sr and Co at a high concentration.
- the thickness of the grain boundary layer 2 varies depending on the part, and has a distribution of about 1 nm to 10 nm.
- the precipitation amount of the oxide particle 3 is 2.1 atm% with respect to the quantity of all the ZnO powders.
- the voltage nonlinear resistor 4 as the varistor layer 11, it is possible to reduce the varistor voltage, increase the ESD resistance, and extremely reduce the voltage dependency of the capacitance.
- the multilayer varistor using the voltage nonlinear resistor according to the present invention has a low varistor voltage and very excellent ESD resistance. Moreover, the voltage dependency of the capacitance is small. Therefore, it is particularly useful as a varistor suitable for ESD countermeasures in various electronic devices.
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Abstract
Description
以下に、上述の製造方法にて作製された積層バリスタ14と、従来の電圧非直線性抵抗体を用いて作製された積層バリスタについて詳細に説明する。
2,22 粒界層
3 酸化物粒子
4 電圧非直線性抵抗体
11 バリスタ層
12 内部電極
13 外部電極
14 積層バリスタ
Claims (14)
- N型の複数のZnO結晶粒子と、
前記N型の複数のZnO結晶粒子間に形成され、アルカリ土類金属を含んだ酸化物を含む粒界層と、
前記粒界層を介して前記N型の複数のZnO結晶粒子間に配置されたP型半導体である酸化物粒子と、を備えた、
電圧非直線性抵抗体。 - 前記粒界層を構成する前記酸化物に含まれた前記アルカリ土類金属はSr、Ca、Baよりなる群から選ばれる、
請求項1記載の電圧非直線性抵抗体。 - 前記酸化物粒子は前記粒界層と同一の材料で形成されている、
請求項1記載の電圧非直線性抵抗体。 - 前記粒界層はペロブスカイト構造の固溶体であり、
前記酸化物粒子はペロブスカイト構造の固溶体である、
請求項1記載の電圧非直線性抵抗体。 - 前記粒界層の厚みが1nm以上、10nm以下である、
請求項1記載の電圧非直線性抵抗体。 - 前記複数のZnO結晶粒子の平均結晶粒子径は0.5μm以上、2μm以下である、
請求項1記載の電圧非直線性抵抗体。 - 前記非直線性抵抗体に含まれるZnOの1molに対して、AlをAl2O3に換算して0.0001mol以上、0.003mol以下、含有する、
請求項1記載の電圧非直線性抵抗体。 - 一対の内部電極と、
前記一対の内部電極間に形成されたバリスタ層と、
前記一対の内部電極とそれぞれ電気的に接続された一対の外部電極と、を備え、
前記バリスタ層は、
N型の複数のZnO結晶粒子と、
前記N型の複数のZnO結晶粒子間に形成され、アルカリ土類金属を含んだ酸化物を含む粒界層と、
前記粒界層を介して前記N型の複数のZnO結晶粒子間に配置されたP型半導体である酸化物粒子と、を含む電圧非直線性抵抗体で構成された、
積層バリスタ。 - 前記粒界層を構成する前記酸化物に含まれた前記アルカリ土類金属はSr、Ca、Baよりなる群から選ばれる、
請求項8記載の積層バリスタ。 - 前記酸化物粒子は前記粒界層と同一の材料で形成されている、
請求項8記載の積層バリスタ。 - 前記粒界層はペロブスカイト構造の固溶体であり、
前記酸化物粒子はペロブスカイト構造の固溶体である、
請求項8記載の積層バリスタ。 - 前記粒界層の厚みが1nm以上、10nm以下である、
請求項8記載の積層バリスタ。 - 前記複数のZnO結晶粒子の平均結晶粒子径は0.5μm以上、2μm以下である、
請求項8記載の積層バリスタ。 - 前記非直線性抵抗体に含まれるZnOの1molに対して、AlをAl2O3に換算して0.0001mol以上、0.003mol以下、含有する、
請求項8記載の積層バリスタ。
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CN116655369A (zh) * | 2023-06-19 | 2023-08-29 | 陕西科技大学 | 一种仅包含单个双肖特基晶界势垒的三层结构压敏陶瓷及其制备方法和应用 |
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