DE2928256C2 - - Google Patents

Description

The invention relates to a laminated body and a Process for its production.

Electrically conductive layers, coatings and thin films or layers metal oxides are known. These were great Scope in the production of, for example, display devices such as liquid crystal displays det, with some of the required electrodes transparent must be so that the visibility of the displayed informa tion is not prevented by an observer. Comparisons see for example US-PS 38 14 501. The for this purpose the most commonly used metal oxides are the oxides of indium, tin, and of indium and tin together, d. H. Indium tin oxide or - from the English expression “Indium-tin-oxide” derived as ITO. The aforementioned US patent shows Pattern made of transparent electrically conductive material in a liquid crystal display device, the conductive Material indium oxide or tin oxide or a combination of these Materials is.  

Another application of transparent electrical conductors exists for electrodes for gate structures that are on half conductor devices, such as charge coupled Imaging devices are manufactured.

In both applications, both as an image device and as a Show device was the practice that the line pattern separately posed. Usually the pattern was created by that one parted metal oxide material and then photolithographi cal process used to the metal oxides in the ge wanted to bring shape, though various other possible solutions, such as printing, were also used. An example of that the latter possibility is in DE-OS 24 11 872 be wrote.

If a line pattern of, for example, indium tin oxide separately on an image or display device is formed, so at least two different ones Path or path types created for light, which on the Device falls. With one path type, the light is on beam once or twice through the thickness of the indium tin oxide whether it is reflected or not. The other This is the path type that does not run through an indium tin oxide layer Light typically shines through over a longer distance an air-filled room. The difference between the refraction indices of air and indium tin oxide as well as the difference in the number of interfaces traversed by a light beam, depending on the traversed path, creates a disturbance or "deformation" of the scanned or reflected image. The present invention redu graces these differences considerably, the giving disturbance or "deformation" is reduced.  

GB-PS 13 99 961 relates to a transparent conductor track structure on a substrate. Tin is used as the conductive material and indium oxide are proposed. The composite body this document is obtained by first printed the substrate with a paste in the desired pattern, said paste comprising a heat-decomposable carrier the entire substrate has a layer of an oxidizable Applies metal oxide material, the substrate coated in this way heated in an oxidizing atmosphere, the carrier of the Paste decomposes and the inorganic part contained therein together with the layered layers applied to the paste range can be removed from the metal oxide layer and then these particles and the metal on them oxide particles removed. Here you get a merged set body, consisting of a substrate on which in ge desired pattern the transparent conductor structure is brought. The body contains no zone of isolating Material, as is the case with the object of registration.

The US-PS 29 32 590 relates to transparent, elec trically conductive indium oxide layers on a temp sensitive carrier. The main point of the known Teaching is the application of the layer in a way that the temperature-sensitive carrier is not damaged.

The US-PS 29 32 590 also describes the controlled deposition of metallic indium and tin and the subsequent thermal Oxidation to produce thin transparent electrically conductive Covers. However, this US patent does not describe that Forming a pattern of electrical conductors on an isolie end layer, as provided according to the invention.  

In US-PS 29 71 867 a composite body is described, which has strips of transparent, electrically conductive and non-conductive material on a glass base. As can be seen from FIG. 1 of the document, transparent, electrically conductive strips 14 are arranged on the base 10 , which are separated from one another by transparent, non-conductive separating strips 16 . Tin oxide or indium oxide, for example, is used as the conductive material. Antimony oxide or titanium oxide or mixtures of tin oxide and other oxides are suitable as the non-conductive, transparent material.

With the composite body according to US-PS 29 71 867 should be avoided with strip-shaped coatings provided bodies are optically disadvantageous because the Lines that separate the conductive stripes from the uncoated ones striped areas according to the bodies of that time State of the art irritate the observer (cf. column 1, Lines 39ff). It is essential that the production of the Strip relative materials, suitable relative thicknesses, Have absorption coefficients and refractive indices (cf. Column 2, lines 34ff).

Based on this prior art, the invention lies The task is based on a laminate with the characteristics of the preamble of claim 1 to provide the disadvantages avoids the prior art and in particular the Aus formation of fine conductor structures.

This problem is solved with the characteristics of the characteristic Part of claim 1.  

The invention thus sees a pattern made of transparent electrically conductive material, namely deposited on a substrate, a semiconductor device or the like, wherein the pattern is made of electrically conductive material in an otherwise continuous layer of transparent Insulating material is included, which is essentially the same refractive index as the electrically conductive Ma has material, and further the location (overall) in has essentially the same thickness. Similar optical Paths are provided for light that passes through the conductor leads and for light, which through the insulating material runs because length and propagation time differences for light running through the two different types of material rays are small.

In the preferred exemplary embodiment, the insulating material is an indium oxide, in particular In ₂ O ₃ . So that the ratio of the resistance value of the insulating material to the resistance value of the conductive material is high, the insulating indium oxide is preferably made relatively free of impurities and with a substantially stoichiometric composition. Impurities and the lack of oxygen ions generate free charge carriers and are therefore undesirable.

Zones of the layer made of insulating material are modified, around them in a pattern according to the desired conductor to make patterns electrically conductive. In the preferred Embodiment uses tin as a dopant for modes fication of the insulator material used.

Both tin and indium are initially on the substrate or the device in metallic form deposited. The tin will be the pattern you want for the electrical conductor provided accordingly. The tin will then diffused into the indium and the  The material system is then oxidized.

Metals are significantly higher with Purity available as, for example, metal oxides. Thereby, that you start with metallic tin and indium, can the purities of ver in carrying out the invention materials used are brought into line with the needs of semiconductor technology where even small ones Amounts of contaminants worsen the device cause parameters.

Another advantage of the present invention is that smaller electrical line widths can be achieved than was previously possible. This is because that the line pattern is first in a thin layer Doping metal such as that mentioned above Tin, which is much thinner than the finally trained leaders. Tin layers can be on smaller conductor widths are etched because the smaller for the etching time greatly reduces the underetching.

Further advantages, aims and details of the invention result itself in particular from the claims and from the description of exemplary embodiments with reference to the drawing; in the drawing demonstrate

Figures 1A-1E. Schematic diagrams in cross-sectional views of the various stages in the formation of conductors according to a preferred embodiment of the invention.

The preferred embodiments will now be described in detail. In Fig. 1A, a base 10 (substrate) is shown, on which a layer 12 is deposited from a doping metal. The base 10 can, for example, be a glass substrate, such as is used as a cover plate for a liquid crystal display device, to which transparent electrodes are applied. Another example of the base 10 may be a semiconductor integrated circuit device, such as a CCD image or imaging device, where transparent conductors are used in the gate structure. In the preferred exemplary embodiment, the deposited doping metal is metallic tin. Preferably, high purity tin can be used in cases where the base is, for example, a semiconductor device, as mentioned above, and where the properties of the semiconductor device can be adversely affected by impurities in the tin. Metallic tin with a purity up to 99.999% can be obtained without further res and used in the practice of the invention.

In the preferred embodiment, the metallic tin is preferably deposited using the known spraying or sputtering method. A suitable power level for the HF sputtering of the tin is approximately 150 watts. A suitable gas pressure for the argon contained in the sputter chamber is 8 · 10 ^-6 m ± 2 · 10 ^-6 m Hg column.

Instead of sputtering, however, any of the various common methods for depositing layer 12 metals from tin can be used if desired. These other methods include, for example, the following: plating, plasma coating, vacuum vapor deposition, pyrolytic coating, thermal evaporation and electron beam evaporation.

A preferred thickness for a finished sheet of transparent material made in accordance with the invention is approximately 0.1 µm (1000 angstroms). This thickness is a compromise and provides an adequately high conductivity for the conductive zones of the finished layer and an adequately high resistance value for the insulating zones of the finished layer in electronic applications, for example display or image devices, together with one high light transmission. For a finished layer thickness of 0.1 µm, the preferred thickness or thickness for the deposited layer 12 made of tin is 7.5 · 10 ^-3 µm ± 2.5 · 10 ^-3 µm. It can thus be seen that in the preferred exemplary embodiment, the layer 12 made of doping metal has a thickness of only 10% or less of the thickness of the finished layer.

After the layer 12 of doping metal is deposited on the base 10 , as in FIG. 1A, the layer 12 is shaped into a corresponding pattern. The result is shown in FIG. 1B, where individual doping metal elements 14 on base 10 are shown, positioned on the base at the locations desired for the conductors. A variety of individual elements 14 are shown in FIG. 1B. The man skilled in the art recognizes that the invention can be used in the same way in cases where a desired line pattern has only a single, uniform conductor structure.

If the doping metal is tin, the individual elements 14 are preferably produced according to the desired conductor pattern by conventional photolithic processes. For example, a suitable photoresist material for this purpose is manufactured by Eastman Kodak Company in Rochester, New York, USA under the trademark Kodak No. 809. The photoresist is preferably baked at a relatively low temperature, for example not more than 90 ° C, to prevent the diffusion of tin into the photoresist. A suitable etchant for the tin is a mixture of 12.5 g ammonium fluoroborate, 2.25 l concentrated nitric acid, 0.2 l concentrated fluoroboric acid and 150 l deionized water. Using this etchant, the elements 14 can be formed in the tin in approximately 20 seconds.

It is well known that patterns made by photolithographic processes are limited in their dimensions due to the undercut created by the etchants. In the described method for producing the desired electrical conductor pattern, the pattern is produced from a layer 12 , the thickness of which is 10% or less of the thickness of the finished layer of transparent material. It then clearly appears that a conductor pattern with a finer definition (smaller line widths and smaller line-to-line spacing) can be produced photographically in connection with the present invention than is the case where a pattern in one layer to be produced, which has the greater thickness of the finished layer of transparent material. The latter case represents the state of the art situation where layers of conductive metal oxides are etched to produce the desired pattern of electrical conductors.

Although photolithographic methods for forming the elements 14 in the desired line pattern are preferred, other possibilities can be used in accordance with the invention. According to one example, the doping metal can be deposited via a mask, in which way the elements 14 of FIG. 1B are formed directly. This possibility can be expedient if the elements 14 are to be built on a base which has sharp corners or steps to which the elements 14 are to be adapted. In a further example, the doping metal can be arranged in a printing ink which is applied to the base by screen printing in the desired pattern. The use of one or the other of these two methods of forming the elements 14 can be the result of reducing the number of steps required to form a finished layer, since an undefined layer of doping metal, such as the layer need not be deposited 12 of Fig. 1A.

As shown in Fig. 1C, the dopant metal elements 14 , once formed, are covered with a layer 16 of a Sn or In metal layer which is both oxidizable into a transparent insulating material if it is relatively pure and into a transparent conductive one Material, when combined with a suitable doping metal, is oxidizable. Metallic indium with a purity of at least 99.9% by weight is the preferred oxidizable material for use with tin when practicing the invention. As in the case of forming the layer 12 of dopant metal in Fig. 1A ver applied tin, greater purity of the indium can before its Trains t, especially in cases where the base is example, a semiconductor device, and where the properties of the semiconductor device adversely affected by impurities can be influenced in the indium. Metallic indium with a purity of up to 99.999% by weight is readily available and can be used in the practice of the invention.

There is another reason for using indium with a relatively high purity. Oxidized indium is said to serve as an insulator in a finished layer of transparent material in accordance with the invention. Impurities in the indium tend to deliver free charge carriers and thereby reduce the electrical resistance value of the indium oxide. The extent to which the reduced resistance of the insulating indium oxide due to defects is a problem depends in part on the application of the invention. If the finished display system is relatively large, with the desired pattern for the conductive zones having relatively large conductors with a relatively large spacing, satisfactory workability can also be obtained with a relatively low ratio of the resistance value of the insulating material to the resistance value of the conductive material. For applications on the other hand in connection with microelectronic circuits and extremely high-precision definition of small conductors, it is preferred to obtain a ratio of the resistance value of the insulating material to the resistance value of the conductive material as high as is practical. In the latter case, the greater the purity of the metallic indium used, the greater the ratio of the resistance values will be. A ratio of the resistance value of the insulating material to the resistance value of the conductive material up to 10 ⁶ was obtained in the practice of the present invention, using indium with a purity of 99.999 wt .-%.

In the preferred embodiment, the metallic indium is preferably deposited using conventional spraying methods. A suitable power level for the HF sputtering of the indium is approximately 175 ± 25 watts. A suitable gas pressure for the argon contained in the spray chamber is 8 · 10 ^-6 m ± 2 · 10 ^-6 m Hg column.

However, instead of the spraying process, any other of the various methods of metal deposition, if desired, can be used to deposit the layer 16 from indium. As discussed above in connection with the discussion of tin deposition processes, these other processes include, for example, the following: plating, plasma plating, vacuum vapor deposition, pyrolytic plating, thermal evaporation, and electron beam evaporation.

For this preferred embodiment, where the finished layer of transparent material has a thickness of approximately 0.1 µm, and where the layer 12 of tin, as shown in Fig. 1A, 7.5 x 10 ^-3 µm ± 2.5 x 10 ^-3 µm thick, the preferred thickness for the indium layer 16 is about 0.07 µm.

The layer 16 of indium must cover the entire area or area on the base 10 , ie the area in which a coating of transparent material is desired. Since the deposition of the layer 16 from indium may have covered parts of the base 10 over which a coating of transparent material is not desired, photolithographic forming methods can be used to remove indium from these parts. This would be the case, for example, where access to contacts on an underlying semiconductor device must be available, specifically for the connection to an intermediate circuit that is not provided by the method according to the invention. In this case, the layer 16 of indium is preferably produced using the same photoresist material and the same etchant as described above with reference to the formation of the elements 14 according to FIG. 1B. It takes approximately two minutes to etch this indium layer 16 using the etchant mentioned above.

After the elements 14 made of doping metal are covered with a coating of oxidizable metal Sn or In 16 , as shown in FIG. 1C, the doping metal is diffused into the oxidizable metal. This can be accomplished in an oven that has either an inert or a reduced atmosphere. When the materials are the preferred dopant, tin, and the preferred oxidizable material, indium, the diffusion or alloying is preferably accomplished by heating in a reducing atmosphere of approximately 85% nitrogen and 15% hydrogen.

FIG. 1D shows the result of the diffusion of tin into the indium in the zones 18 over the entire depth of the layer 20 . The zones 18 of the layer 20 correspond to the desired pattern for the electrical conductors, whereas the remaining parts of the layer 20 are taken up by insulating material.

The definition of the line pattern to which the alloy material zones 18 correspond is limited by the need to maintain a certain minimum distance for insulation between the conductors. The distance obtained between the zones 18 of alloy material depends both on the distance between the elements 14 made of doping metal, as shown in FIGS . 1B and 1C, and also on the way in which the diffusion of the modified one Material in the oxidizable material is executed. The distance between the adjacent edges of the elements 14 made of doping metal, as shown in FIGS. 1B and 1C, is preferably at least ten times the thickness with which the layer 16 of oxidizable material is deposited. For a layer 16 with a thickness of, for example, 0.07 μm, the preferred distance between the elements 14 is preferably at least 0.7 μm or approximately 1 micron. This lower limit of the distance coincides with the minimum line-to-line distance which is reasonably obtainable for a 0.07 µm layer by photolithographic techniques.

The extent to which the doping metal is diffused into the oxidizable material is partly determined by the parameters of the heating operation used to generate the diffusion. In the preferred embodiment, the alloy formation of the tin and indium is achieved at a temperature of 200 ± 20 ° C for 30 ± 10 minutes. The diffusion must be limited, since heating for too long a period of time or too high a temperature or for both a period of time that is too long and a high temperature ultimately results in either the conductors being too close to one another, or are distributed uniformly in the doping metal over the entire layer 20 of FIG. 1D. In any case, the desired line pattern would be effectively eliminated. Heating at lower temperatures or shorter times, or both, can prevent a sufficiently good mixing of the indium and tin in the zones 18 of the layer 20 .

The person skilled in the art recognizes that the above-described series of processes for producing the material system of FIG. 1D are not exclusive, if also preferred. For example, layer 16 made of indium can first be deposited directly onto base 10 before layer 12 made of tin. After the layer 16 is formed from indium, the tin layer 12 can be deposited and formed photolithographically, moved on top of the indium layer 16 using known lift-off methods and using a photoresist mask to protect the indium from the etchant. Once the tin has diffused into the indium, the result is as shown in Fig. 1D.

The structure shown in FIG. 1D is converted to that shown in FIG. 1E by heating the layer 20 in oxygen or air to oxidize it. The unmodified oxidizable material is converted to transparent insulating material in the finished layer 22 of FIG. 1E. The modified material of zones 18 of FIG. 1D is converted into transparent electrically conductive material of zones 24 in FIG. 1E.

If the oxidizable metal is indium, the transparent insulating material formed is an indium oxide. It is believed that complete oxy dation gives a stoichiometric indium oxide (In ₂ O ₃ ) which is preferable because of the higher resistance. If the doping metal is tin, the indium-tin alloy is converted to indium-tin oxide, a well-known transparent electrical conductor.

It is believed that the stoichiometric composition of the In ₂ O ₃ is ensured by heating for a sufficient time to a sufficiently high temperature. Heating in air at 480 ± 20 ° C for 30 to 120 minutes appears to give satisfactory results.

The transparent layer 22 made of metal oxide material grows in thickness during the oxidation. A metal layer originally approximately 0.07-0.08 µm thick results in an oxide layer 22 according to FIG. 1E of approximately 0.1 µm thick. The layer growth factor (metal / metal oxide) is approximately 1.35 to 1.45.

One goal is the thickness of the indium and tin layers to control a composition after processing Obtain indium tin oxide which is approximately 90 mol% indium oxide and Contains 10 mol% of tin oxide. This is the generally accepted one Composition for the best conductive indium tin oxide.

Typical measured values for the refractive index of the indium oxide ranged from 1.7 to 1.8. Measured values for the The refractive index of the indium tin oxide ranged from 1.9 to 2.0. Ge measured values for the resistance value of the indium oxide were in the range of 1000 ohm.cm to 10,000 ohm.cm, whereas the resistance value of indium tin oxide produced by the invention, ranged from 0.01 ohm.cm to 0.02 ohm.cm.

Modifications of the invention are readily possible for the person skilled in the art. For example, tin, if relatively pure, can be used as the oxidizable material to form transparent insulator material. Antimony can be used as a dopant to modify the tin oxide into a conductor material. Furthermore, cadmium can be diffused into the tin as a doping metal, which serves as an oxidizable material. The oxidation of the cadmium-tin alloy gives the compound cadmium stannate (Cd ₂ SnO ₄ ), which is known to be highly conductive. Those skilled in the art will also recognize that the invention is not limited to a single sheet of transparent material containing zones of conductive material. If desired, a plurality of such layers can be formed in a stack. It may be expedient to separate the layers that enclose the conductor material, and this can be done by other layers of only insulating material.

Claims (4)

1. Laminated body, consisting of an insulating substrate and structures made of transparent, electrically conductive material and transparent insulating material arranged between the conductive structures, characterized by the following manufacturing steps:

• a) applying a first layer of a doping metal known per se in accordance with a desired pattern to an insulating substrate ( 10 );
• b) full-surface deposition of an oxidizable metal layer of Sn or In with a purity of at least 99.9% thereon;
• c) diffusion treatment of the layer structure in an inert or reducing atmosphere; and
• d) subsequent oxidation treatment to form the transparent insulating and conductive zones ( 22, 24 ).

2. Body according to claim 1, characterized in that the Oxidizable metal layer consists of In and Sn as a dotie metal serves. 3. Body according to claim 1, characterized in that the oxidizable metal layer consists of Sn and Sb or Cd as Doping metal is used.   4. A method for producing the composite body according to one of claims 1 to 3, in which a material according to the desired pattern is first applied to the base, characterized in that

• a) a first layer of a doping metal known per se is applied in accordance with the desired pattern,
• b) an oxidizable metal layer of Sn or In with a purity of at least 99.9% is deposited over the entire surface,
• c) the layer structure is subjected to a diffusion treatment in an inert or reducing atmosphere and then
• d) an oxidation treatment is carried out to form the transparent conductive and insulating zones.