WO2016125520A1

WO2016125520A1 - Semiconductor element and method for manufacturing same

Info

Publication number: WO2016125520A1
Application number: PCT/JP2016/050205
Authority: WO
Inventors: 浩平深町
Original assignee: 株式会社村田製作所
Priority date: 2015-02-06
Filing date: 2016-01-06
Publication date: 2016-08-11
Also published as: JP6739353B2; JPWO2016125520A1; DE112016000618T5; CN107210105A; CN107210105B

Abstract

A semiconductor element which comprises: a ceramic element that contains sintered ceramic particles; and a first external electrode and a second external electrode that are respectively arranged on the end faces of the ceramic element. The sintered ceramic particles are composed of a perovskite compound that contains at least Ba and Ti, and have an average particle diameter of 0.4-1.0 μm. When a region in a cross-section of the semiconductor element is selected and observed with a scanning electron microscope, the contact ratio of the sintered ceramic particles as calculated on the basis of the total of the peripheral lengths of the sintered ceramic particles present within the region, the total of the peripheral lengths of the pores present within the region, the outer peripheral length of the region and the contact lengths of the sintered ceramic particles present within the region is 45% or more.

Description

Semiconductor device and manufacturing method thereof

The present invention relates to a semiconductor element and a manufacturing method thereof, and more particularly to a barium titanate-based semiconductor element and a manufacturing method thereof.

Since barium titanate-based semiconductor ceramics have a positive temperature characteristic, they are widely used in semiconductor elements such as a positive temperature coefficient thermistor (PTC thermistor).

For example, Patent Document 1 discloses a temperature characterized by discontinuously dispersing and adhering child particles made of metal particles that are in ohmic contact with the mother particles to the surface of the mother particles made of semiconductor particles having nonlinear temperature characteristics. A method for producing characteristic-functional composite particles is described. The composite particles described in Patent Document 1 are not subjected to high-temperature sintering, and the composite particles are dispersed in a solvent and applied, or as a green compact. It can be used as such.

Patent Document 2 discloses an insulating ceramic substrate, a thermistor thick film having a positive resistance temperature characteristic formed of a semiconductor ceramic sintered body formed on the insulating ceramic substrate, a thermistor thick film in contact with the thermistor thick film. A positive temperature coefficient thermistor is described, comprising at least one pair of electrodes facing each other across at least a part of the film, wherein the thermistor thick film has a resistivity at room temperature of less than 10 kΩ · cm. . The positive temperature coefficient thermistor described in Patent Document 2 can widen the contact area between crystal grains in the semiconductor ceramic constituting the thermistor thick film, and can reduce the resistance.

Patent Document 3 discloses a barium titanate-based semiconductor ceramic having an average ceramic particle size of 0.9 μm or less. Patent Document 3 describes that barium titanate semiconductor ceramics having an average ceramic particle size in the above range have a small specific resistance at room temperature and an excellent withstand voltage strength. Patent Document 3 discloses that the above-mentioned barium titanate-based semiconductor ceramic has a particle size of 0.1 μm or less, a crystal structure of cubic, a lattice constant of 4.020 angstroms or more, and a small amount of semiconductor. It is described that a barium titanate powder in which an agent is solid-solved or a product obtained by calcining the barium titanate powder is used as a raw material powder and is fired.

Japanese Patent Laid-Open No. 9-100169 International Publication No. 2012/111386 JP-A-11-116327

PTC thermistors are used in a wide variety of electronic devices to protect against overcurrent. With the recent increase in functionality of electronic devices, a PTC thermistor capable of handling particularly a large current has been demanded, and a PTC thermistor element having high withstand voltage characteristics has been developed. In order to improve the withstand voltage characteristics of the PTC thermistor, semiconductor ceramics constituting the PTC thermistor are made fine (Patent Document 3). However, as a result of repeated studies by the present inventor, it has been clarified that there is a problem that the specific resistance at room temperature of the PTC thermistor increases due to the formation of fine particles.

On the other hand, Patent Document 2 describes that the resistance is reduced by increasing the contact area between crystal grains in the semiconductor ceramic. However, the crystal particles described in Patent Document 2 have a large particle size with an average particle size of 2 to 38 μm.

An object of the present invention is to provide a semiconductor device having a high withstand voltage characteristic and a low specific resistance at room temperature, and a method for manufacturing the same.

In order to achieve the above-mentioned object, the present inventor conducted research while paying attention to the physical properties of perovskite type compound particles which are starting materials for manufacturing a semiconductor element. As a result, by controlling the specific surface area of the perovskite-type compound particles and the ratio of the c-axis length to the a-axis length (tetragonal) c / a of the crystal lattice of the perovskite-type compound particles, ceramics constituting the semiconductor element The inventors have found that it is possible to achieve both the fine particle formation of the ceramic sintered body particles contained in the element body and the improvement of the contact ratio of the ceramic sintered body particles, and have completed the present invention.

According to a first aspect of the present invention, a ceramic body including ceramic sintered body particles;
A first external electrode disposed on a first end face of the ceramic body,
A semiconductor element including a second external electrode disposed on a second end face of the ceramic body,
Ceramic sintered body particles are perovskite type compounds containing at least Ba and Ti,
The average particle size of the ceramic sintered body particles is 0.4 μm or more and 1.0 μm or less,
The total perimeter L _{G of} ceramic sintered body particles present in one region, calculated by observing one region selected in one cross section of the semiconductor element with a scanning electron microscope, Total L _NC of the perimeter of pores (pores) existing in the region, outer peripheral length L _S of one region, and the following formula

In represented, based on the value of the contact length L _C of the ceramic sintered particles present in one area, the following formula

A semiconductor element in which the contact ratio of the ceramic sintered body particles calculated by the above is 45% or more is provided.

The contact ratio of the ceramic sintered body particles is preferably 45% or more and 80% or less.

The semiconductor element described above may be a stacked semiconductor element in which one or more first internal electrodes and one or more second internal electrodes are arranged inside a ceramic body. At this time, the first internal electrode is electrically connected to the first external electrode at the first end face of the ceramic body, and the second internal electrode is connected to the second end face of the ceramic base body at the second end face. Electrically connected to the external electrode. The first internal electrode and the second internal electrode may be Ni electrodes.

According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor element,
Preparing perovskite-type compound particles containing at least Ba and Ti;
Forming a green chip containing perovskite-type compound particles;
Obtaining a ceramic body by firing a green chip;
Forming a semiconductor element by forming external electrodes on both end faces of the ceramic body,
The specific surface area of the perovskite type compound particles is 4.0 m ² / g or more and 14.0 m ² / g or less,
A method is provided wherein the ratio c / a of the c-axis length to the a-axis length of the crystal lattice of the perovskite type compound particles is 1.005 or more and 1.009 or less.

The specific surface area of the perovskite type compound particles is preferably 4.0 m ² / g or more and 11.0 m ² / g or less.

In the above method, the step of forming the green chip containing the perovskite type compound particles,
Producing a ceramic green sheet containing perovskite type compound particles;
Applying a conductive paste for internal electrodes on the main surface of the ceramic green sheet;
A step of obtaining a laminate by laminating a plurality of the ceramic green sheets coated with the internal electrode conductive paste;
And placing a ceramic green sheet not coated with the internal electrode conductive paste on the upper and lower sides of the laminate and pressing the ceramic green sheet, and cutting to a predetermined size to obtain a green chip. By such a method, it is possible to manufacture a stacked semiconductor element in which internal electrodes are arranged inside a ceramic body. The above-mentioned internal electrode conductive paste may contain Ni metal powder as the conductive powder.

The semiconductor element according to the present invention has a high withstand voltage characteristic and a low specific resistance at room temperature due to the above configuration. Moreover, the manufacturing method of the semiconductor element which concerns on this invention can manufacture the semiconductor element which has a high withstand voltage characteristic and has a low specific resistance at room temperature by having the said structure.

FIG. 1 is a schematic cross-sectional view of a semiconductor device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a modification of the semiconductor device according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of another modification of the semiconductor device according to one embodiment of the present invention. 4, in one section of the ceramic body is a diagram showing a total L _G around the length of the ceramic sintered particles present in the SEM observation region. 5, in one section of the ceramic body is a diagram showing a total L _NC of perimeter of the pores existing in SEM observation region. FIG. 6 is a diagram showing the outer peripheral length L _S of the SEM observation region in one cross section of the ceramic body.

Hereinafter, a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. However, the embodiment shown below is for the purpose of illustration, and the present invention is not limited to the following embodiment. The dimensions, materials, shapes, relative arrangements, and the like of the constituent elements described below are not merely intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. In addition, the size, shape, positional relationship, and the like of components illustrated in each drawing may be exaggerated for clarity of explanation. The dimension of each member does not necessarily indicate the following values accurately, but has tolerances.

[Semiconductor element]
FIG. 1 is a schematic cross-sectional view of a semiconductor element 1 according to this embodiment. The semiconductor element 1 according to this embodiment is a PTC thermistor. A semiconductor element 1 shown in FIG. 1 is disposed on a ceramic body 2, a first external electrode 31 disposed on a first end surface 21 of the ceramic body 2, and a second end surface 22 of the ceramic body 2. Second external electrode 32.

(Ceramic body)
The ceramic body 2 includes ceramic sintered body particles. The sintered ceramic particles are made of a ceramic material in which a donor element is added to barium titanate. The ceramic sintered body particles are a perovskite type compound containing at least Ba and Ti. The perovskite-type compound includes, in addition to Ba and Ti, at least one element selected from the group consisting of rare earth elements excluding Pm, Tm, Yb and Lu and / or a group consisting of Nb, W, Sb and Ta. It may contain at least one element selected. Hereinafter, at least one element selected from the group consisting of rare earth elements excluding Pm, Tm, Yb and Lu is at least one element selected from the group consisting of “element α”, Nb, W, Sb and Ta Is also referred to as “element β”. The elements α and β are donors (semiconductor agents) for imparting PTC characteristics to the ceramic body 2. The ceramic sintered body particles may include only one of the above-described element α and element β, or may include both elements α and β.

The ceramic body 2 preferably contains 99.5 mol parts or more and 100.5 mol parts or less of Ba when the total mol portion of Ti and β is 100 mol parts. When the content of Ba is 99.5 mol parts or more and 100.5 mol parts or less, the room temperature specific resistance of the ceramic body is lowered, and high withstand voltage characteristics can be obtained. The ceramic body 2 may contain the above-described element α and / or element β in addition to Ba and Ti. The ceramic body 2 contains the element α and / or the element β in such an amount that the total content of the elements α and β in the ceramic body 2 is 0.020 mol part or more and 0.500 mol part or less. Is preferred. When the total content of the element α and the element β is 0.020 mol part or more, suitable PTC (positive temperature coefficient) characteristics can be imparted to the ceramic body 2. When the total content of the elements α and β is 0.500 mol part or less, the specific resistance of the ceramic body 2 can be lowered.

The ceramic body 2 may further contain Si derived from a sintering aid described later. The ceramic body 2 may contain 3 mol parts or less of Si with respect to 100 mol parts of Ti.

The ceramic body 2 may further contain Zr that can inevitably be mixed in the manufacturing process. Zr may occur due to the use of zirconia balls as a grinding and dispersion medium when preparing a ceramic slurry described later. The ceramic body 2 may contain 0.01 mol part or more and 1 mol part or less of Zr with respect to 100 mol parts of Ti.

The average particle diameter of the ceramic sintered body particles contained in the ceramic body 2 is 0.4 μm or more and 1.0 μm or less. When the average particle size is 0.4 μm or more, a low specific resistance can be achieved. When the average particle size is 1.0 μm or less, the semiconductor device 1 can achieve high withstand voltage characteristics. The average particle diameter of the sintered ceramic particles can be calculated by observing a cross section of the semiconductor element with a scanning electron microscope (SEM) and performing image analysis.

In the semiconductor element 1 according to the present embodiment, even if the average particle size of the ceramic sintered body particles is small due to the large contact area between the ceramic sintered body particles included in the ceramic body 2, the room temperature is low. The specific resistance at (25 ° C.) can be lowered. In this specification, the contact rate of the ceramic sintered body particles is used as an index for evaluating the contact area between the ceramic sintered body particles. The contact ratio of the ceramic sintered body particles can be calculated by the procedure described below. First, the semiconductor element 1 is polished to expose a cross section, and the cross section is observed with a scanning electron microscope (SEM). The cross section to be observed with the SEM is not particularly limited, and an arbitrary cross section may be selected. The cross section is obtained by, for example, polishing the semiconductor element 1 in the LT plane (plane perpendicular to the W direction) to about 1/2 W point (about half the W dimension of the semiconductor element). The cross section of the semiconductor element may be parallel to. In the cross section of the semiconductor element 1, the region to be observed with the SEM is not particularly limited, but may be, for example, a region sandwiched between internal electrodes in the vicinity of the central portion of the ceramic body 2. The size and magnification of the observation region can be set as appropriate so that the number of ceramic sintered particles in the measurement region can be counted from about 70 to about 200. By analyzing the obtained SEM image, the total circumference L _{G of} the ceramic sintered body particles existing in the observation area, the total circumference L _NC of the pores existing in the observation area, and the observation area The outer perimeter length L _S is obtained. Examples of the results of _obtaining L _G , L _NC and L _S by image analysis are shown in FIGS. Total L _NC around the length of the pores shown in Figure 5, the length of the portion not in contact with the adjacent ceramic sintered particles of perimeter of the ceramic sintered particles (hereinafter, "non-contact length It can be regarded as the sum of “ As shown in FIG. 6, the outer peripheral length L _S of the observation region is in contact with the ceramic sintered particles present in the observation region among the peripheral lengths of the ceramic sintered particles located at the outermost edge of the observation region. It consists of the total length of the parts that are not. Based on the obtained values of L _G , L _NC and L _S , the length of the portion in contact with the adjacent ceramic sintered body particles in the peripheral length of the ceramic sintered body particles existing in the observation region ( hereinafter, the sum is L _C of called "contact length"). L _C is represented by the following formula.

Based on the obtained L _C and L _NC values, the contact ratio of the ceramic sintered body particles is obtained. The contact ratio of the ceramic sintered body particles can be calculated using the following formula.

The higher the contact ratio of the ceramic sintered body particles, the larger the contact area between the ceramic sintered body particles. In the semiconductor element 1 according to this embodiment, the contact ratio of the ceramic sintered body particles is 45% or more. When the contact ratio is 45% or more, the specific resistance at room temperature (25 ° C.) can be lowered even when the average particle diameter of the ceramic sintered body particles is small. The contact ratio of the ceramic sintered body particles is preferably 45% or more and 80% or less. When the contact ratio is 80% or less, high PTC (positive temperature coefficient) characteristics can be achieved.

The dimensions of the ceramic body 2 are not particularly limited, and can be set as appropriate according to the application. The dimension of the ceramic body 2 may be, for example, L dimension 2.0 mm × W dimension 1.2 mm × T dimension 1.0 mm. In the present specification, as shown in FIG. 1, the direction from the first end face 21 to the second end face 22 of the ceramic body 2 is the “L direction”, and the direction perpendicular to the L direction in the horizontal plane. Is called the “W direction”, and the direction perpendicular to the L direction and the W direction is called the “T direction”. The dimension of the ceramic body 2 in the L direction is referred to as “L dimension”, the dimension in the W direction as “W dimension”, and the dimension in the T direction as “T dimension”.

As shown in FIG. 2, the semiconductor element 1 according to the present embodiment is a stacked semiconductor in which one or more first internal electrodes 41 and one or more second internal electrodes 42 are arranged inside a ceramic body 2. It may be an element. In the present specification, the first internal electrode 41 and the second internal electrode 42 may be collectively referred to as “internal electrodes”. The first internal electrode 41 is electrically connected to the first external electrode 31 at the first end face 21 of the ceramic body 2, and the second internal electrode 42 is the second end face 22 of the ceramic body 2. And electrically connected to the second external electrode 32.
The first internal electrode 41 extends from the first end face 21 of the ceramic body 2 toward the second end face 22, and the second internal electrode 42 extends from the second end face 22 of the ceramic body 2. It extends toward the first end face 21. The first internal electrodes 41 and the second internal electrodes 42 are alternately arranged so as to face each other inside the ceramic body 2. In the modification shown in FIG. 2, two first internal electrodes 41 and two second internal electrodes 42 are arranged inside the ceramic body 2, but the number of internal electrodes is not limited to this. And can be appropriately set according to desired characteristics. The number of internal electrodes (the total of the first internal electrode 41 and the second internal electrode 42) may be, for example, about 2 or more and 50 or less. The distance between the adjacent first internal electrode 41 and second internal electrode 42 is not particularly limited, and can be appropriately set according to a desired application. The distance between the adjacent first internal electrode 41 and second internal electrode 42 may be, for example, about 10 μm to 200 μm.

The composition of the internal electrode is not particularly limited, and may be set as appropriate according to the application. The first internal electrode 41 and the second internal electrode 42 may be, for example, Ni electrodes that exhibit good ohmic properties with respect to a barium titanate-based semiconductor.

In the semiconductor element 1 according to this embodiment, a glass layer 5 may be formed on the surface of the ceramic body 2 as shown in FIG. The glass layer 5 has a function of improving environmental resistance and element strength. The composition and thickness of the glass layer 5 are not particularly limited, and may be set as appropriate according to the application. In the modification shown in FIG. 3, the first internal electrode 41 and the second internal electrode 42 are disposed inside the ceramic body 2, but the semiconductor element 1 according to the present embodiment is limited to this configuration. However, the configuration may be such that no internal electrode is provided. In the modification shown in FIG. 3, plating layers 61 and 62 (described later) are formed on the surfaces of the first external electrode 31 and the second external electrode 32. The semiconductor element 1 according to the present embodiment is It is not limited to this structure, The structure which does not have a plating layer may be sufficient.

(External electrode)
The semiconductor element 1 according to the present embodiment includes a first external electrode 31 disposed on the first end surface 21 of the ceramic body 2 and a second external surface disposed on the second end surface 22 of the ceramic body 2. Electrode 32. The first external electrode 31 and the second external electrode 32 may be formed so as to extend to a part of the side surface of the ceramic body 2 as shown in FIG. In the present specification, the “side surface” of the ceramic body 2 refers to a surface other than the first end surface 21 and the second end surface 22 of the ceramic body 2. In the present specification, the first external electrode 31 and the second external electrode 32 may be collectively referred to as “external electrode”. The composition and configuration of the external electrode can be appropriately set according to the type of the ceramic body 2 or the internal electrodes (the first internal electrode 41 and the second internal electrode 42) when present. The first external electrode 31 and the second external electrode 32 may have, for example, a multilayer structure in which NiCr, NiCu alloy, and Ag are sequentially stacked.

In the semiconductor element 1 according to the present embodiment, plating layers 61 and 62 may be formed on the surfaces of the first external electrode 31 and the second external electrode 32 as shown in FIG. The plating layers 61 and 62 have a function of improving solder wettability and heat resistance during mounting. The composition of the plating layers 61 and 62 can be appropriately selected according to the composition of the external electrode, and may be, for example, a Sn plating layer, a Ni plating layer, or a combination of two or more thereof. In the modification shown in FIG. 3, the first internal electrode 41 and the second internal electrode 42 are disposed inside the ceramic body 2, but the semiconductor element 1 according to the present embodiment is limited to this configuration. However, the configuration may be such that no internal electrode is provided. In the modification shown in FIG. 3, the glass layer 5 is formed on the surface of the ceramic body 2, but the semiconductor element 1 according to the present embodiment is not limited to this configuration. The structure which does not have may be sufficient.

[Method for Manufacturing Semiconductor Device]
Hereinafter, although an example of the manufacturing method of the semiconductor element which concerns on this embodiment is demonstrated below, the manufacturing method of the semiconductor element which concerns on this invention is not limited to the method shown below. The method for manufacturing a semiconductor device according to the present embodiment includes a step of preparing perovskite type compound particles, a step of forming a green chip containing perovskite type compound particles, and a step of obtaining a ceramic body by firing the green chip. And forming a semiconductor element by forming external electrodes on both end faces of the ceramic body. In this embodiment, for example, a method for manufacturing a stacked PTC thermistor having an internal electrode will be mainly described. However, the method for manufacturing a semiconductor element according to the present invention is not limited to the following method. Absent.

First, perovskite compound particles containing at least Ba and Ti (hereinafter, also referred to as “raw perovskite compound particles”) are prepared as raw materials for the ceramic body constituting the semiconductor element. The perovskite type compound particles as the raw material may contain at least one element selected from the group consisting of rare earth elements excluding Pm, Tm, Yb and Lu and / or Nb, W, Sb and Ta in addition to Ba and Ti. It may contain at least one element selected from the group consisting of: Each raw material of the perovskite type compound particles is weighed so that the composition of the ceramic sintered body particles contained in the ceramic body constituting the finally obtained semiconductor element becomes the target composition. The composition of the target ceramic sintered body particles is as follows. When the ceramic element body including the internal electrode is dissolved and quantitative analysis is performed by, for example, ICP-AES (Inductively-Coupled-Plasma-Atomic-Emission-Spectrometry), It may be a composition represented by the formula (1).

In the formula, α is at least one element selected from the group consisting of rare earth elements excluding Pm, Tm, Yb and Lu, and β is at least one selected from the group consisting of Nb, W, Sb and Ta Elements. The content molar part of Ba, α, α + β, Ti + β is defined as m _Ba , m _α , m _{(α + β)} , m _{(Ti + β),} and m = (m _Ba + m _{(α + β)} ) / m _{(Ti + β)} is defined as the molar ratio. To do. Under this definition, when the total mole part of Ti and β is 100 mole parts, m _Ba is 99.50 ≦ m _Ba ≦ 100.5, and the range of m _{(α + β)} is 0.020 ≦ m _{(α + β)} ≦ 0.500, and m is 0.995 ≦ m ≦ 1.005.

As raw materials for preparing perovskite type compound particles, Ba, Ti, chlorides of elements α and β, hydroxides, oxides, carbonates, alkoxides and the like can be used as appropriate. As shown in the above formula (1), the ceramic sintered body particles contained in the ceramic body constituting the finally obtained semiconductor element contain the elements α and / or β as donors (semiconductor agents). The raw material perovskite type compound particles may contain neither element α nor element β, or the total amount of element α and / or element β necessary for obtaining ceramic sintered particles having a desired composition may be included. It does not have to be included. In these cases, the amount of element α and / or β chloride, hydroxide, oxide, carbonate, alkoxide, ionized aqueous solution, etc. necessary for preparation of the ceramic slurry described later can be adjusted to the desired composition. it can.

The method for preparing the raw material perovskite type compound particles is not particularly limited, and a solid-phase synthesis method or a hydrothermal synthesis method such as a hydrothermal synthesis method or an oxalic acid method is appropriately used depending on the desired specific surface area and c / a. You can choose. The raw material perovskite type compound particles may be prepared, for example, by the procedure described below. Each of the above-mentioned raw materials weighed is put into a ball mill together with PSZ (partially stabilized zirconia) balls and pure water. At this time, a sintering aid such as SiO ₂ may be added as appropriate. The raw materials in the ball mill are sufficiently mixed and pulverized by a wet process and dried to obtain a mixed powder. The mixed powder is calcined at a temperature of 800 ° C. or higher and 1100 ° C. or lower to obtain raw material perovskite type compound particles as calcined powder. The calcination temperature can be appropriately set according to the specific surface area of the target perovskite type compound particles and the value of c / a.

The specific surface area of the raw material perovskite compound particles is preferably 4.0 m ² / g or more and 14.0 m ² / g or less. When the specific surface area is 4.0 m ² / g or more, the ceramic sintered body particles in the ceramic body constituting the obtained semiconductor element can be made a small particle diameter having an average particle diameter of 1.0 μm or less. When the specific surface area is 14.0 m ² / g or less, the number of grain boundaries between the sintered particles in the ceramic body can be reduced, and the contact ratio of the sintered particles can be increased. As a result, the specific resistance at room temperature of the semiconductor element can be lowered. The specific surface area of the perovskite compound particles is more preferably 4.0 m ² / g or more and 11.0 m ² / g or less. When the specific surface area is 11.0 m ² / g or less, the specific resistance value at room temperature of the obtained semiconductor element can be further reduced. The specific surface area of the perovskite compound particles can be measured by a gas adsorption method such as a BET method.

Raw material perovskite type compound particles have a highly tetragonal crystal structure. By using perovskite type compound particles having a highly tetragonal crystal structure as a raw material, the specific resistance of the semiconductor element at room temperature (25 ° C.) can be lowered. The ratio c / a of the c-axis length to the a-axis length of the crystal lattice of the raw material perovskite compound particles is preferably 1.005 or more and 1.009 or less. When c / a is 1.005 or more, the specific resistance value of the semiconductor element at room temperature can be further reduced. c / a is more preferably 1.006 or more and 1.009 or less. When c / a is 1.006 or more, the specific resistance value of the semiconductor element at room temperature can be further reduced. The c / a of the raw material perovskite compound particles can be calculated by conducting a qualitative analysis using a powder X-ray diffractometer and performing a Rietveld analysis. The raw material perovskite type compound particles contain one or more rare earth elements as donors.

Next, a green chip containing raw material perovskite type compound particles is formed. When manufacturing a stacked PTC thermistor having an internal electrode as a semiconductor element, a step of forming a green chip containing perovskite compound particles includes a step of producing a ceramic green sheet containing perovskite compound particles, and a main part of the ceramic green sheet. A step of applying a conductive paste for internal electrodes on a surface, a step of obtaining a laminate by laminating a plurality of ceramic green sheets coated with a conductive paste for internal electrodes, and a conductivity for internal electrodes above and below the laminate. And placing a ceramic green sheet to which a paste has not been applied, press-bonding, and cutting to a predetermined size to obtain a green chip.

First, a ceramic green sheet containing perovskite type compound particles is prepared according to the following procedure. An organic binder, a dispersant and water are added to the raw material perovskite type compound particles and mixed with zirconia balls for several hours to obtain a ceramic slurry. In addition, when the raw material perovskite type compound particles do not contain both element α and element β, or the total amount of element α and / or element β necessary for obtaining ceramic sintered particles having a desired composition When the ceramic slurry is not included, a predetermined amount of chloride, hydroxide, oxide, carbonate, alkoxide, ionized aqueous solution, or the like of the element α and / or β may be added as a donor during the preparation of the ceramic slurry.

The above-mentioned ceramic slurry is formed into a sheet by the doctor blade method and dried to produce a ceramic green sheet. The thickness of the ceramic green sheet is preferably 10 μm or more and 50 μm or less.

Next, a conductive paste for internal electrodes is applied on the main surface of the ceramic green sheet. First, conductive powder such as metal powder and an organic binder are dispersed in an organic solvent to prepare a conductive paste for internal electrodes. As the conductive powder, for example, metal powder such as Ni metal powder can be appropriately used.

¡Apply this internal electrode conductive paste on the main surface of the ceramic green sheet. The coating thickness of the internal electrode conductive paste is set so that the thickness of the internal electrode in the finally obtained semiconductor element is 0.5 μm or more and 2 μm or less. The conductive paste for internal electrodes may be applied by a method such as screen printing.

Next, a plurality of ceramic green sheets coated with the internal electrode conductive paste are laminated to obtain a laminate. The number of laminated ceramic green sheets coated with the internal electrode conductive paste may be set according to the number of internal electrodes that the finally obtained semiconductor element should have.

Next, ceramic green sheets not coated with the internal electrode conductive paste are disposed on and under the laminate, for example, 20 sheets at a time, and subjected to pressure bonding, with predetermined dimensions so that the dimensions after firing become a desired value. Cut to get green chips. The size of the ceramic body obtained by firing the green chip may be, for example, L size 2.0 mm × W size 1.2 mm × T size 1.0 mm.

When manufacturing a semiconductor element having no internal electrode, a plurality of ceramic green sheets not coated with the internal electrode conductive paste are stacked, pressed, and cut to a predetermined size to produce a green chip. It's okay.

Next, the ceramic body is obtained by firing the green chip. First, prior to firing, the green chip is degreased at a temperature of 300 ° C. to 450 ° C. for 10 hours to 15 hours in an air atmosphere. The green chip after the degreasing treatment is 0 at a temperature of 1000 ° C. or higher and 1300 ° C. or lower in a reducing atmosphere such as H ₂ / N ₂ / H ₂ O mixed gas, Ar / H ₂ , N ₂ / H ₂ / H ₂ O, or the like. Baking for 5 hours or more and 3 hours or less to obtain a ceramic body.

In some cases, the obtained ceramic body is glass-coated and heat-treated at a temperature of 600 ° C. or more and 900 ° C. or less in an air atmosphere to form a glass layer on the surface of the ceramic body, and at the same time, Reoxidation may be performed.

Next, external electrodes are formed on both end faces of the ceramic body. First, prior to the formation of the external electrode, the ceramic body is barrel-polished. External electrodes are formed on both end faces of the ceramic body after barrel polishing. The composition and formation method of the external electrode are not particularly limited, and can be appropriately selected according to the purpose. For example, the external electrode can be formed by sputtering Cr, NiCu alloy and Ag in this order on both end faces of the ceramic body. Alternatively, the external electrode may be formed by applying a paste containing a resin component and a metal (such as Ag) and baking it at an appropriate temperature. A plating layer may be formed on the surface of the formed external electrode by a method such as electrolytic plating. The composition of the plating layer can be appropriately selected according to the composition of the external electrode, and may be, for example, a Sn plating layer, a Ni plating layer, or a combination of two or more thereof. In this way, the semiconductor element according to this embodiment is obtained.

The semiconductor elements of Comparative Examples 1 and 2 and Examples 1 to 9 were produced by the following procedure. The semiconductor elements of Comparative Examples 1 and 2 and Examples 1 to 9 are all laminated PTC thermistors.

[Comparative Example 1]
First, BaCO ₃ , TiO _2, and La ₂ so that the composition of the ceramic sintered body particles contained in the ceramic body constituting the finally obtained semiconductor element is a composition represented by the following formula (2). O ₃ was weighed. In Comparative Example 1, each raw material was weighed so that α = La, m _Ba = 100, m _α = m _La = 0.2, and m = 0.999.

Each of the above-mentioned raw materials weighed was put into a ball mill together with PSZ (partially stabilized zirconia) balls and pure water, sufficiently mixed and pulverized in a wet manner, and dried to obtain a mixed powder. This mixed powder was calcined at a temperature of 800 ° C. or higher and 1100 ° C. or lower to obtain raw material perovskite type compound particles as calcined powder. The obtained perovskite compound particles had a specific surface area of 2.1 m ² / g and c / a of 1.010. The specific surface area of the raw material perovskite type compound particles was measured using a Macsorb (registered trademark) manufactured by Mountec Co., Ltd. under a degassing temperature of 250 ° C. The c / a of the raw material perovskite type compound particles was determined by conducting a qualitative analysis using a powder X-ray diffraction apparatus (RINT2500 manufactured by Rigaku Corporation) and performing a Rietveld analysis.

An organic binder, a dispersant and water were added to the obtained raw material perovskite type compound particles and mixed with zirconia balls for several hours to obtain a ceramic slurry. This ceramic slurry was formed into a sheet by a doctor blade method and dried to prepare a ceramic green sheet having a thickness of 30 μm.

Next, Ni metal powder and an organic binder were dispersed in an organic solvent to prepare a conductive paste for internal electrodes. This internal electrode conductive paste was applied on the main surface of the ceramic green sheet by screen printing. The coating thickness of the internal electrode conductive paste was adjusted so that the thickness of the internal electrode in the finally obtained semiconductor element was 0.5 μm or more and 2 μm or less. The ceramic green sheet coated with the internal electrode conductive paste and the ceramic green sheet not coated with the internal electrode conductive paste are included so that 24 internal electrodes are included and the distance between the internal electrodes is 30 μm. To obtain a laminate. Five ceramic green sheets not coated with the internal electrode conductive paste are placed on the upper and lower sides of this laminate and pressed, and the dimensions after firing are L dimension 2.0 mm × W dimension 1.2 mm × T dimension. A green chip was obtained by cutting into a size of 1.0 mm.

This green chip was degreased at 300 ° C. for 12 hours in an air atmosphere. The green chip after the degreasing treatment was baked at a temperature of 1000 ° C. or higher and 1300 ° C. or lower for 2 hours in a reducing atmosphere using a H ₂ / N ₂ / H ₂ O mixed gas to obtain a ceramic body.

The obtained ceramic body was glass-coated and heat-treated at a temperature of 800 ° C. or lower in an air atmosphere, thereby forming a glass layer on the surface of the ceramic body and simultaneously re-oxidizing the ceramic body.

The ceramic body on which the glass layer was formed was barrel polished. External electrodes were formed by sputtering Cr, NiCu alloy and Ag in this order on both end faces of the ceramic body after barrel polishing. An Sn plating layer was formed on the surface of the formed external electrode by electrolytic plating. In this way, a semiconductor element of Comparative Example 1 was obtained.

[Comparative Example 2 and Examples 1 to 9]
Semiconductor devices of Comparative Example 2 and Examples 1 to 9 were manufactured in the same procedure as Comparative Example 1 except that perovskite type compound particles having specific surface areas and c / a values shown in Table 1 described later were used as raw materials. .

For each of the semiconductor elements of Comparative Examples 1 and 2 and Examples 1 to 9, the average particle diameter and contact rate of the ceramic sintered body particles were measured. The average particle size of the sintered ceramic particles was measured by the following procedure. First, the semiconductor element is polished to about 1/2 W point (about half the W dimension of the semiconductor element) in the direction of the LT plane (plane perpendicular to the W direction), and the semiconductor element cross section parallel to the LT plane is exposed. I let you. This cross section was observed using a scanning electron microscope (Hitachi SU-8040) under the conditions of an acceleration voltage of 1 kV and a magnification of 10,000 times to obtain an SEM image. The size of the region (observation region) observed by SEM was set to a size that allows counting of 80 to 200 ceramics sintered body particles. This SEM image was subjected to image analysis using an analyzer (“A Image-kun” manufactured by Asahi Kasei Engineering Co., Ltd.), and the area of ceramic sintered body particles in the SEM image was determined. An equivalent area equivalent circle diameter (Heywood diameter) calculated based on the obtained area was defined as the particle diameter of the ceramic sintered body particles. The average value of the particle diameters of the ceramic sintered body particles completely contained in the observation region was defined as the average particle diameter of the ceramic sintered body particles. In this example, the average particle diameter of the ceramic sintered body particles was obtained in the above-mentioned semiconductor element cross section, but the same result can be obtained even when the average particle diameter is obtained in other semiconductor element cross sections. You can think of it.

The contact ratio of the ceramic sintered body particles was measured using the same cross section as that of the semiconductor element used for obtaining the average particle diameter. Of the cross section of the semiconductor element, the portion sandwiched between the internal electrodes in the vicinity of the central portion of the ceramic body 2 was observed with a scanning electron microscope (SEM). The cross section to be observed with the SEM is not particularly limited, and an arbitrary cross section may be selected. The cross section is obtained by, for example, polishing the semiconductor element 1 in the LT plane (plane perpendicular to the W direction) to about 1/2 W point (about half the W dimension of the semiconductor element). The cross section of the semiconductor element may be parallel to. In the cross section of the semiconductor element 1, the region to be observed with the SEM is not particularly limited, but may be, for example, a region sandwiched between internal electrodes in the vicinity of the central portion of the ceramic body 2. The dimension of the observation region of SEM was set to a dimension that allows the number of sintered ceramic particles to be counted from 80 to 200 at an observation magnification of 10,000. The resulting SEM image, and image analysis using an analysis apparatus (manufactured by Asahi Kasei Engineering Corporation "A picture kun"), the total L _G around the length of the ceramic sintered particles present in the observation _region, the observation region The total peripheral length L _NC of the pores existing inside and the outer peripheral length L _S of the observation region were determined. Examples of the results of _obtaining L _G , L _NC and L _S by image analysis are shown in FIGS. 4 to 6, respectively. Based on the obtained values of L _G , L _NC and L _S ,

The total L _C of the contact length of the ceramic sintered particles present in the observation area using the determined. Based on the values and _{L NC} of obtained _{L C,} the following formula

Was used to determine the contact ratio of the ceramic sintered body particles.

For each of the semiconductor elements of Comparative Examples 1 and 2 and Examples 1 to 9, the specific resistance at room temperature (25 ° C.) was measured by the 4-terminal method. The above measurement results are shown in Table 1.

From Table 1, Examples 1 to 1 in which the specific surface area of the raw material perovskite type compound particles was 4.0 m ² / g or more and 14.0 m ² / g or less and c / a was 1.005 or more and 1.009 or less. 9, the average particle diameter of the ceramic sintered body particles contained in the obtained semiconductor element can be 0.4 μm or more and 1.0 μm or less, and the contact ratio of the ceramic sintered body particles is 45% or more. I understand that I was able to. On the other hand, in Comparative Example 1 in which the specific surface area of the raw material perovskite compound particles was less than 4.0 m ² / g and c / a was greater than 1.009, the ceramic sintered body contained in the obtained semiconductor element The average particle diameter of the particles was larger than 1.0 μm, and the contact ratio of the ceramic sintered body particles was less than 45%. Further, in Comparative Example 2 in which the specific surface area of the raw material perovskite compound particles was less than 4.0 m ² / g, the contact ratio of the ceramic sintered body particles contained in the obtained semiconductor element was less than 45%. It was.

As shown in Table 1, the semiconductor elements of Examples 1 to 9 in which the average particle size of the sintered ceramic particles was 0.4 μm or more and 1.0 μm or less and the contact rate was 45% or more were 71 Ω at room temperature. -The specific resistance value was as low as cm or less. Further, the semiconductor elements of Examples 1 to 9 had high withstand voltage characteristics of 1000 V / mm or more. Further, the semiconductor elements of Examples 1 to 8, in which the specific surface area of the raw material perovskite compound particles was 4.0 m ² / g or more and 11.0 m ² / g or less, had a lower specific resistance of 32 Ω · cm or less at room temperature. The value is shown. On the other hand, the semiconductor element of Comparative Example 1 in which the average particle diameter of the ceramic sintered body particles was larger than 1.0 μm and the contact rate was less than 45% had low withstand voltage characteristics of less than 1000 V / mm. In addition, the semiconductor element of Comparative Example 2 in which the contact ratio of the ceramic sintered body particles was less than 45% exhibited a high specific resistance value exceeding 80 Ω · cm at room temperature.

The semiconductor element according to the present invention has both a high withstand voltage characteristic and a low specific resistance value at room temperature, and can be suitably used in a wide range of applications.

DESCRIPTION OF SYMBOLS 1 Semiconductor element 2 Ceramic body 21 First end surface of ceramic body 22 Second end surface of ceramic body 31 First external electrode 32 Second external electrode 41 First internal electrode 42 Second internal electrode 5 Glass layer 61, 62 Plating layer

Claims

A ceramic body including ceramic sintered body particles;
A first external electrode disposed on a first end surface of the ceramic body,
A semiconductor element including a second external electrode disposed on a second end face of the ceramic body,
The ceramic sintered body particles are perovskite type compounds containing at least Ba and Ti,
The ceramic sintered body particles have an average particle size of 0.4 μm or more and 1.0 μm or less,
Total perimeter L G of the ceramic sintered body particles present in the one region calculated by observing one region selected in one cross section of the semiconductor element with a scanning electron microscope , The total peripheral length L NC of the pores existing in the one region, the outer peripheral length L S of the one region, and the following formula

Based on the value of the contact length L C of the ceramic sintered body particles present in the one region represented by

The semiconductor element whose contact rate of the said ceramic sintered compact particle | grain calculated by is 45% or more.
The semiconductor element according to claim 1, wherein a contact ratio of the ceramic sintered body particles is 45% or more and 80% or less.
The semiconductor element is a stacked semiconductor element in which one or more first internal electrodes and one or more second internal electrodes are disposed inside the ceramic body,
The first internal electrode is electrically connected to the first external electrode at the first end face of the ceramic body;
3. The semiconductor element according to claim 1, wherein the second internal electrode is electrically connected to the second external electrode at the second end face of the ceramic body.
The semiconductor element according to claim 3, wherein the first internal electrode and the second internal electrode are Ni electrodes.
A method for manufacturing a semiconductor device, comprising:
Preparing perovskite-type compound particles containing at least Ba and Ti;
Forming a green chip containing the perovskite type compound particles;
Obtaining a ceramic body by firing the green chip;
Forming a semiconductor element by forming external electrodes on both end faces of the ceramic body,
The perovskite compound particles have a specific surface area of 4.0 m 2 / g or more and 14.0 m 2 / g or less,
A method in which the ratio c / a of the c-axis length to the a-axis length of the crystal lattice of the perovskite type compound particles is 1.005 or more and 1.009 or less.
The method according to claim 5, wherein the perovskite compound particles have a specific surface area of 4.0 m 2 / g or more and 11.0 m 2 / g or less.
Forming a green chip containing the perovskite type compound particles,
Producing a ceramic green sheet containing the perovskite type compound particles;
Applying a conductive paste for internal electrodes on the main surface of the ceramic green sheet;
Laminating a plurality of the ceramic green sheets coated with the internal electrode conductive paste to obtain a laminate; and
A ceramic green sheet not coated with the internal electrode conductive paste is disposed on and under the laminated body, and is bonded and cut to a predetermined size to obtain a green chip. The method described.
The method according to claim 7, wherein the internal electrode conductive paste contains Ni metal powder as the conductive powder.