DE1646752B2 - SEMICONDUCTOR COMPONENT MADE OF METAL OXYDE AND A GLASS-LIKE BINDER - Google Patents

Description

Semiconductor component with good properties in terms of its specific resistance and its Lifespan,

The invention will now be explained in detail with reference to the drawings; in these shows

F i g. 1 is a sectional view of one embodying the invention semiconducting component,

F ig 2 is a diagram of the current-voltage curve of the ISIN halbteitendcn in Fig, 1 reproduced component,

F i g. 3 is a Schm'Uansicht of a further, the invention embodying arrangement,

F i g. Figure 4 is a top view of another arrangement embodying the invention;

F i g. 5 is a sectional view of yet another arrangement embodying the invention;

F i g. 6 shows a diagram of the current-voltage characteristic of the in FIG. 5 reproduced component,

FIG. 7 is a sectional view of a further arrangement embodying the invention and FIG.

F i g. Figure 8 is a top view of another arrangement embodying the invention.

Let us first refer to FIG. 1 referred to. Particles of a substance 103, which is powdered tin dioxide (SnO ₂ ), are embedded as a semiconducting material in a vitreous binder 102. This semiconducting layer is formed in such a way that the mixture of the semiconducting material 103 with the material consisting of a vitreous powder is applied to the surface of an iron plate 104 and then dried by heating. The glazed sheet iron plate 104 serves both as an electrode and as a heat-resistant substrate surface. An electrode 101 consisting of an electrically conductive coating is applied to the aforementioned semiconducting layer.

The following is an example of the production process for the above-described arrangement embodying the invention will be explained. The composition that of a powdered frit material (hereinafter referred to as A) as a binder and consisting of powdered tin dioxide (hereinafter referred to as B) as the semiconducting material Mixture emerges from the following list:

45

material Volume percentage Powdered frit material: A ...
Powdered SnO ₂ : B 85
15th

The percentage of the metal oxide can / ₀ ° vary depending on the desired value of the specific resistance in the range of 10 to 35th The average grain size of A is preferably about 1 micron and that of B is at most about 5 microns. A grain size larger than this impairs the dispersibility of the particles and leads to difficulties in the formation of the layer, since the layer becomes porous in this case. On the other hand, a smaller grain size is desirable, since this improves the dispersibility, achieves a more stable electrical resistance behavior and facilitates shaping. However, it must be ensured that the condition is met to choose the grain size of A smaller than that of B. If the grain size of A is larger than that of B, the particles of the frit material are covered with metal oxide particles and can each other no longer touch each other, so when heated there is no formation of a cumulative layer.

Next, the powders A and B combined in this ratio are thoroughly mixed in a suitable mixer or stirrer. In this example, the mixture of A and B, to which a volatile liquid such as diacetone alcohol A or an equivalent amount of octyl alcohol had been added, was mixed in a ball mill for 12 hours. Half a day to a full day comes into consideration as a suitable period of time for this mixing procedure. With a shorter period of time, the particles are not sufficiently dispersed, while with a longer period of time the differences between the grain size of A and that of B are blurred, so that the The condition is no longer met that the core size of substance A is larger than that of B. The powder so thoroughly harvested and dispersed is essentially in a molar state, the liquid serving as a dispersant. The mixture is applied to the surface of the heat-resistant substrate using the silk screen method, although this procedure represents a preferred method of applying the substance, but this circumstance is not to be interpreted in a limiting sense of the invention. The purpose of the heating is to fuse the particles of vitreous binder together without, however, dissolving the particles of metal oxide in the vitreous material, and also to cause the binder to adhere to the substrate to form a smooth-surfaced layer. In this way, at least on their surface, the metal oxide particles go into a solid solution in the vitreous binder, as a result of which the surface layer effect of the surfaces of the metal oxide particles is reduced. This improves the electrical contact between the binder and the semiconducting material and gives the layer a uniform specific ohmic resistance. The lowest possible heating temperature is preferred. Accordingly, a frit material should be selected that is less viscous even at a low temperature, ie a frit material that has a low softening point. Table 1 below shows the composition of the vitreous material used in this exemplary embodiment.

Table 1

55

60 components

SiO ₂ .
B ₂ O ₃ .
ZnO.
BaO.
CaO.
MgO
Na ₂ O
K ₂ O.
TiO ₂ .
Al ₂ O ₃
Fe ₂ O ₃
PbO.

Weight percent

20.01
28.58
18.33
14.34
0.74
0.016
10.84
4.05
2.31
0.41
0.009
0.012

The softening point of this frit material was about 600 to 64o ⁰ C. As the substrate, a sheet iron plate was used approximately the same thermal expansion coefficient as the glass-like binder. The heating could be done in an electric furnace without difficulty. This means that the heating process can take place in a normal room atmosphere without the need for special measures, since the tin dioxide (SnO ₂ ) used as a semiconducting material is very stable at temperatures around 640 ° C in the air and since the substrate used is the same Has a coefficient of thermal expansion like the glass-like material. The sol-like mixture of A and B is applied to the substrate and heated within a period of about 20 minutes after immersion in an electric furnace at 650 ⁰ C, wherein the liquid component is evaporated, leaving behind the powder mixture on the substrate. The mixture applied to the substrate is kept at this temperature (650 ° C.) for about 5 minutes, followed by a cooling time of about 20 minutes, after which the entire operation is ended. If a 130 mesh per inch (130 mesh) silk screen is used to screen the powder having a grain size of about 1 micron, a layer about 20 microns thick can be formed in one heating cycle. In addition, a further layer can be applied to the already formed layer, if this should be desired for certain purposes. Since the glass is of considerable viscosity, there is no fear that the first layer of the glass could melt or change its thickness at the temperature of 650 ° C. during the short period of 5 minutes. F i g. 2 shows the current-voltage characteristic of the semiconducting layer formed in this way, the direct voltage being applied across electrodes 101 and 104. The excellent straightness of the characteristic curve shows that the layer has a specific ohmic resistance. This layer has a current carrying capacity of considerable height and is easily heat-resistant.

F i g. 3 shows another arrangement, embodying the invention, in which titanium dioxide (TiO ₂ ) is used instead of the tin dioxide of the previous embodiment. In the illustration of FIG. 3, the binder 301 is a vitreous material with a softening point of 550 to 58O ° C., in which the powdered TiO _{2 is} dispersed. Transparent electrodes 303 and 304 from each other are separately provided on a glass substrate 305 having a softening amounts to 680-700 ⁰ C. A semiconducting layer consisting of the binding agent 301 and the particles of the bisecting substance 302 is formed over the electrodes and over the substrate including the space between the two electrodes. The in F i g. The embodiment shown in FIG. 1 is intended as a resistance in the direction of the layer thickness, whereas in the embodiment according to FIG. 3 the electric current is intended to flow in the lateral direction in the viewing direction of the figure. Another feature of this embodiment is that the vitreous layer is formed on the surface of a glass or a vitreous substrate. The procedure in the manufacture of this component and the requirements with regard to the grain size are the same as in the previous embodiment. As far as the substrate is concerned, only sheet iron plates, ceramic or similar materials come into consideration as materials for this in the embodiment described first, while glass can also be used in the last embodiment. Two requirements must be met in order for it

ίο a glass can be used as a substrate. the one of them is that the softening point of the binder is lower than that of the substrate. this is an essential precondition because molding is impossible if the substrate is heated earlier softens as the binder. The other requirement concerns the cubic expansion coefficient of the substrate, which must be approximately the same as that of the vitreous binder. If the Coefficients of expansion in the materials

ao differ from each other, so are formed in that Substrate cracks or at least lose the cracks as a result of the tension forces occurring during cooling Electrodes 303 and 304 their conductivity due to the deforming mechanical stress. In table 2 are the cubic expansion coefficients and the softening points in the context of this exemplary embodiment binder and substrate used.

Table 2

Expansion coefficient softening point

binder
Sheet glass
(Substrate)

270 ΙΟ- ^7th
(270 to 300) x 10 " ⁷

approximately 580 ° C 650 to 700 ⁰ C.

In this embodiment, was heated to 630 ⁰ C. The transparent electrodes (Nesa electrodes) 303 and 304 do not lose their conductivity when heated.

F i g. 4 shows a further embodiment of the invention, in which the component has a shape suitable for a potentiometer. Transparent electrodes 401 and 402 are formed on a heat-resistant substrate 403 (made of glass or ceramic material). The semiconducting layer 404, which consists of a binder containing a powdered metal oxide, is applied to the substrate and to electrodes. In the arrangements embodying the invention, not only tin dioxide (SnO ₂ ) or titanium dioxide (TiO?) Come into consideration as semiconducting material, as was used in the above embodiments, but it can also be another semiconducting metal oxide, see above for example WO ₃ , Sb ₂ O ₈ , Cr ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₃ and mixtures of any two or more of these oxides.

It does not need to be emphasized that the invention does not apply to the embodiments described above is limited, but also embodied in manifold modified arrangements can be as required by the respective purpose.

646 752

As has already been explained above, in the following, in the context of further implementation

components semiconducting through the invention are based on another aspect of the invention

create, in which the particles of a semiconducting are entered.

Metal Oxides Embedded in a Vitreous Binder In accordance with this aspect of the invention, these are. Thanks to the fact that the 5 above-described metal oxide powder is a powdered substance component that provides the component with the conductive insulating material or several such insulating materials, it is mixed with a metal oxide, and the dispersion of the metal oxide gives this component a high resistance particle facilitate. In the context of this ability to withstand heavy use by external forms of execution of the invention one comes to influences and is resistant to ambient temperatures io extremely durable semiconducting components with a considerable height, so that even with uniform properties that an ohmic production no complicated and expensive resistance in the semiconductor area (10 ⁵ to 10 ⁸ ohm operating equipment or special measures centimeters) and increased dielectric strength are required. Thus, within the scope of the exhibit. With regard to the insulating invention to be mixed in, semiconducting components with an ohmic material, the only requirement is that there is a thermal resistance to which a specific resistance is stable, since this material is only used in the semiconductor area (namely in the range of 10 ⁵ a Incomplete dispersion or an error of up to 10 ⁸ ohm centimeters) is based, created to prevent distribution of the metal oxide particles and the specific resistance obtained in the individual case in no way contributes to the conductivity of the component from the relative volume fraction of the metal oxide 20. In this case, too, the grain size depends on the binder. Choosing glass powder smaller than that of the metal oxide. In short, the powder and also the insulating material. In the case of the semiconducting components according to the invention, the powder can be easily mixed, applied and heated using a process, the individual steps of which are essentially the same as the following process steps: Glass with an embodiment of the invention has been described, average grain size of less than 1 mi. An embodiment of such, crowning the invention with a powdered semiconducting metal-embodying arrangement is to be mixed below under oxide, the average grain size of which is explained with reference to the drawings , size is less than 5 microns but is greater than 30 In the illustration of FIG. 5 contains a vitreous metal oxide binder designated as that of the glass, with the proportion of the reference number 102 being 10 to 35 percent by volume as a semiconducting material particles of a powdered and with the mixture together with an additive mass 103 of tin dioxide (SnO ₂ ) and particles in the form of a volatile liquid to the point of being a powdered mass 104, which is in the form of a sol-like state; 35 BaTiO ₃ is and is mixed in to facilitate a process step in which this mixture in dispersing and distributing the semiconducting Ma-Form of a layer on the surface of a heat terials 103 and applied to the dielectric resistant substrate, its strength to increase the component. The mixture consisting of the melting or softening point higher than the powders 102, 103 and 104 becomes the softening point of the glass; and a method 40 in the form of a layer on the surface of an iron step in which this layer of the mixture is applied to a plate 105 and dried by heating. The glazable iron plate 105 serves as an electrode and softening point of the glass, but lower than that at the same time as a heat-resistant substrate. An electrical substrate consisting of the melting point or softening point of the heat-resistant electrically conductive coating. According to the method according to the invention 45 electrode 101 is applied to the aforementioned semiconducting layer, the heating can be carried out in a room atmosphere. The composition of the fitting material that has been powdered without taking any special precautions (hereinafter referred to as A with regard to the external conditions to be met), from the powdered tin dioxide (hereinafter referred to as. Also, is caused by the fact that it is referred to as B) and from the powdered BaTiO _3, the grain size of the glass powder is selected to be smaller 50 (hereinafter referred to as C) existing gel that of the metal oxide powder, a smooth and firm amount is obtained from the subsequent set-up layer. The fact that the.
Grain size of the glass and the metal oxide powder

is less than 1 or 5 microns, prevents the material

Layer becomes porous and ensures a sufficient 55

of dispersing the metal oxide particles in the as ^,. _ .... . ,.
w _ffl L * «,,. ηΗ« η fii ™ wnHi, «*»! en Hi * Hp.r. Powdered exterior material: A

Binder serving glass, thus making the

Volume percentage

65

15 20

position of resistances with uniform and equal- ^ epu vertes miu _? .
allows lasting properties and at the same time powdered ßanu ₃ . L ,.
the formation of layers is made much easier. So 60

can be used in a very simple way semiconducting construction- The percentage of SnO ₂ can depending on the other-

Elements with a specific resistance in the half-target value of the specific resistance lead range (10 ⁵ to 10 ⁸ ohm centimeters) are manufactured in favor of or at the expense of the percentage of fritting. materials vary in the range of 10 to 35 ° / _0.

The semiconducting components 65 according to the invention with regard to the grain sizes of B and C in the Versind even at temperatures considerably higher than that of A, the same preconditions apply Resistant to moisture and other external influences, as with the previous design influences very resistant. examples. Also the method of mixing

209 525/455

ίο

and mixing the mixture, the constituents or Al ₂ O ₃ , but can also be any other

of the frit material and the heating process are substances (such as SiO ₂ ) that involve one

here essentially the same as in the context of the significantly higher value of the electrical resistance

of the previous embodiments. F i g. 6 stands as the aforementioned metal oxides and one

shows the current-voltage characteristic curve of the melting point which is thus higher than that of the vitreous binder

shaped semiconducting layer, where the equiv.

voltage applied across the electrodes 101 and 105. As explained above, who according to

is. The straightness of the characteristic curve indicates that the second aspect of the invention semiconducting structural

the layer has an ohmic resistance. elements created in which particles of a half-

This layer also has a current load of conductive metal oxide and particles of an oxide

availability of considerable height. a higher specific resistance than that

F i g. FIG. 7 shows a further embodiment which, in the metal oxide in a vitreous binder, is essential to the arrangement of FIG. 3 equals, hold are. In addition to the in the context of the first aspect of the invention, powdered Al ₂ O _{3 in the addition of TiO 2} particles, however, is given in connection with the preceding embodiments to facilitate dispersion. In detail, the features described in this form are an increased di-case in the binder 301 to a vitreous electrical strength and an even more uniform material with a softening point of 550 to specific resistance, which is sufficient to 58O ° C, the semiconducting Material 302 is a powdered, fine dispersion of the semiconducting particles back-TiO ₂ and, as a dispersant 303, powdered 20 is to be fed.

Contains Al ₂ O _3. Electrodes 304 made of SnO ₂ Semiconducting components of this type can be and 305 are produced in a separate arrangement on the surface of the glass substrate 306 without difficulty using a process whose individual process steps are as follows: softening point at 680 to 700 ° C. The semiconducting 25 consisting of a process step in which a powdered glass powders 301, 302 and 303 with an average grain size of less layer fills the gap between the two electrodes than 1 micron with a powdered semiconducting two electrodes. In its other structural metal oxide and with a powdered, one higher characteristic, this embodiment essentially resembles the specific resistance than the metal oxide with reference to FIG. 3 described oxide is mixed, whereby the through-planes. 30 average grain sizes of the metal oxide and that

In Fig. 8 shows a further arrangement which has a higher specific resistance than the metal body. This arrangement of oxide containing oxide smaller than 5 microns is essentially the same as the embodiment which, however, is larger than that of the glass, the proportion F i g. 4, although a dispersion medium of the metal oxide is added to the mixture to a level of 10 to 35 percent by volume. In the illustration of FIG. 8 35 amounts and wherein the mixture is on the heat-resistant substrate 403 (in the case of the addition in the form of a volatile liquid until it can be ceramic material or glass to achieve a solar-like state) transparent electrodes 401 and 402 ; a process step in which this mixture is provided. Over the substrate and the electrodes in the form of a layer on the surface of a hitzeist then extruded semiconductive layer resistant substrate 40 is applied whose reference numeral is designated 404th Melting or softening point is higher than

In these embodiments too, the softening point of the glass is used; and a process semiconducting material step not only tin dioxide (SnO ₂ ), in which this layer of the mixture on a or titanium dioxide (TiO ₂ ) into consideration, but it can be heated to a temperature that is higher than that, as already stated above 45 softening point of the glass, but lower than a semiconducting metal oxide such as the melting or softening point of heat-WO ₃ , Sb ₂ O ₃ , Cr ₂ O ₃ , Fe ₂ O ₃ , V ₂ O ₅ or Bi ₂ O ₃ as well as stable substrate. Any mixtures of such metal oxides act by this process. The advantages that can be achieved have already been explained in the context of the first. Furthermore, the selection of the insulating aspect of the invention is limited and the dispersant or dispersant is by no means limited to BaTiO _3, so therefore not repeated here.

1 sheet of drawings

¹ T)

Claims (5)

to mix with each other, the grain sizes of the Claims: powder particles of the metal oxide and the glass powder between 50 and 100 microns and the glass powder L. Semiconductor component made of metal oxides and the same or a larger grain size than the powder, which has vitreous binder, which has particles of the metal oxide SnO ₈ , TiO ₈ , sintering produce a composite body whose specific Sb ₈ O ₆ , WO ₃ , Cr ₈ Oj ,, Fe ₈ q _a , V ₈ O ₆ and / or Bi _a 0 ₃ , fischer resistance several powers of ten below the in the vitreous binder (102) are dispersed unit lies. and that the grain size of the powder particle (103) io In the manufacture of the known semiconducting If the metal oxides are larger than the grain size of the glasses, cumbersome precautions must also be taken Glass powder, taken to create a suitable atmosphere 2. A method for producing the in claim 1 ensure so that an oxidizing of the metal powder claims Semiconductor component, identified particles are not carried out and are characterized by the high Br by a process step in which 15 temperature-related degradation notes during sintering Glass powder with an average grain size can be prevented. Also are size less than 1 micron with powder particles Metals highly mechanically resistant of a semiconducting metal oxide is mixed, and can therefore with the current state of whose average grain size is less difficult than crushing or granulating technology 5 microns, but larger than the grain size - 20 pulverize beyond a certain limit. Oversize of the glass powder, the proportion of the metal - this is what it prepares in the case of the known conductive glasses oxyde amounts to 10 to 35 percent by volume and great difficulty in obtaining a predetermined value of the whereby the mixture must be precisely adhered to together with an additive specific resistance, A volatile liquid until reaching a known it is already electrically conductive Sol-like state is carried out, a 25 powder particle in an organic resin or a process step in which this mixture is embedded in the form of plastic, which serves as a binder for a layer on the surface of a heat-resistant powder particle. However, these either have the substrate applied, the melting point of which, if they are fully embedded in the binder, is lower or the softening point is higher than the one another, an imperfect contact, which leads to the softening point of the glass powder, and a non-linear contact Voltage-current characteristic leads, driving step, in which this layer of the mixture or, if less binder is used, one is heated to a temperature that is higher, insufficient strength and service life,
than the softening point of the glass powder, but the object of the invention is to provide a semiconductor lower than the melting or softening point element of the type mentioned with a special heat-resistant substrate, the layer 35 being connected to the substrate with a ^{resistance of 10 5} to 10 ^{8 ohm centimeters.} create. 3. The method according to claim 2, characterized in that this object is drawn according to the invention in that the mixture additionally dissolves an oxide that powder particles of the semiconducting metal powder (104) is added, the specific oxydes, namely SnO ₂ , TiO ₂ , Sb ₂ O ₆ , WO ₃ , Cr ₂ O ₃ , resistance is higher than that of the semiconducting +0 Fe ₂ O ₃ , V ₂ O ₅ and / or Bi ₂ O ₃ , in the vitreous metal oxide (103). Binders are dispersed and that the grain size 4. The method according to claim 3, characterized in that the powder particles of the metal oxides are greater than «lie indicates that the oxide is BaTiO ₃ , grain size of the glass powder. If appropriate, Al ₂ O ₃ and / or SiO ₂ can also be involved. another oxide powder are provided, its 5. The method according to claim 3 or 4, characterized in that 45 grain size is also larger than that of the glass that a glass powder with powder powder. By the specified grain size reference particles a semiconducting metal oxide and with gene and through the dispersion of the powder particles an oxide powder, whose specific resistance of the metal oxide in the vitreous binder, what is higher than that of the semiconducting metal oxide and means that a small amount of metal oxide has a the grain size of which is larger than that of the glass powder, 50 greater amount of binder is mixed, is obtained but smaller than 5 microns, is mixed and a semiconductor device in which relatively large metal die Powder particles of the metal oxide and the oxide powder particles in a homogeneous structure of the glass powder are well dispersed in the glass powder, are embedded like binder. In this way whereupon the mixture is heated. good mechanical properties of the 55 conductor component and still a good contact between the individual powder particles, so that the Semiconductor component receives uniform and easily reproducible properties. A specific resistance in the semiconductor area, namely IO ⁵ to 10 ⁸ ohm- The invention relates to a semiconductor component of 60 centimeters, can be reached safely and also his Metal oxides and a vitreous binder. Value to be selected. Moreover, offer themselves It is known ("Technical Ceramics", VEB-Verlag no difficulties in terms of production, because metal technology Berlin, 1954, p. 109), easily brought to the fine powder sizes in the production of oxide Semiconductor resistances inorganic plasticizing can be used here in the range of less than medium to use. 65 5 microns. The glass powder particles should be a It is also known (German Auslegeschrift to have a grain size of about 1 micron. The proportion of 062 401), for the production of versatile metal oxide amounts to about 10 to 35 volume composite bodies Glass powder and metal oxide powder percent. So you get one that is easy to manufacture