EP1516374A1

EP1516374A1 - Reduction in the contact resistance in organic field effect transistors with palladium contacts by the use of nitriles and isonitriles

Info

Publication number: EP1516374A1
Application number: EP03729898A
Authority: EP
Inventors: Ute Zschieschang; Hagen Klauk; Günter Schmid; Marcus Halik; Efstratios Terzoglu
Original assignee: Infineon Technologies AG
Current assignee: Infineon Technologies AG
Priority date: 2002-06-27
Filing date: 2003-06-02
Publication date: 2005-03-23
Also published as: US20050133782A1; US7151275B2; WO2004004022A1; DE10228772A1

Abstract

The invention relates to a semiconductor device with a semiconductor path made from an organic semiconductor material, a first contact for the injection of charge carriers into the semiconductor path and a second contact for the extraction of charge carriers from the semiconductor path, whereby a layer of a nitrile or an isonitrile is arranged between the first contact and the semiconductor path and/or between the second contact and the semiconductor path. The nitrile or isonitrile acts as charge transfer molecule which facilitates the transfer of charge carriers between contact and organic semiconductor material. The contact resistance between the contact and organic semiconductor material can thus be significantly reduced.

Description

description

Reduction of contact resistance in organic field effect transistors with palladium contacts by using nitriles and isonitriles

The invention relates to a semiconductor device having a semiconductor path of an organic semiconductor material, a first contact for injecting charge carriers into the semiconductor path and a second contact for extracting charge carriers from the semiconductor path, and a method for producing such a semiconductor device.

Semiconductor chips have found wide use in a variety of technical applications. However, their production is still very complex and expensive. Although silicon substrates can be thinned down to very small layer thicknesses, they become flexible. However, these methods are also very expensive, so that flexible or curved microchips are only suitable for demanding applications in which increased costs can be accepted. The use of organic semiconductors offers the possibility of cost-effective production of microelectronic semiconductor circuits on flexible substrates. One application is, for example, a thin film with integrated controls for liquid crystal displays. Another field of application is transponder technology, where so-called tags, for example, store information about a product.

Field effect transistors are used as switches in electronic circuits. In each case, a semiconductor arranged between a source and a drain electrode arranged in each case made of an electrically conductive material acts as an insulator in the switched-off state of the transistor, while under the influence of the field of a gate electrode in the switched-on state of the transistor. Duct carrier channel forms. In this case, electrical charge carriers are injected into the semiconductor layer at the source contact and extracted from the semiconductor layer at the drain contact, so that an electric current flows from source to drain through the semiconductor layer or through the charge channel generated in the semiconductor layer.

Because of the different Fermi levels of semiconductor material and contact material, an asymmetric diffusion process of the charge carriers occurs at the contact surface of the two materials. Due to the different energy of the Fermi levels of the two materials there is an energy difference, which is compensated by the transfer of charge carriers. As a result, an interface potential builds up, which counteracts a transfer of the charge carriers between the two layers when an external potential difference is applied. Thus, a potential barrier arises, which must be overcome by the charge carriers when entering from the electrically conductive contact into the semiconductor material or at the exit from the semiconductor material into the electrically conductive contact. The tunnel current, which results from tunneling through the charge carriers through the potential barrier, is the lower, the higher or wider the potential barrier is. A low tunnel current corresponds to a high contact resistance. In the case of semiconductor components based on inorganic semiconductors, the contact resistance is increased by doping the inorganic semiconductor in a boundary layer oriented toward the contact surface. The doping modifies the energy of the Fermi level in the inorganic semiconductor, that is, the difference between the Fermi levels of contact material and semiconductor material decreases. As a result, there is either a reduction in the potential barrier, which makes it possible for a significantly larger number of charge carriers to overcome the potential barrier and to flood the opposing material or to narrow the potential barrier, which increases the probability of tunneling of charge carriers. gladly increased by the potential barrier. In both cases, the contact resistance decreases.

In the production of field effect transistors based on amorphous or polycrystalline silicon layers, the doping of the contact regions takes place by the introduction of phosphorus or boron into the silicon layer near the source and drain contacts. The phosphorus or boron atoms are incorporated into the silicon network and act as charge donors or charge acceptors, which increases the density of the free charge carriers and thus the electrical conductivity of the silicon in the doped region. This causes a reduction in the difference between the Fermi levels of contact material and doped semiconductor material. The dopant substance is only in the area of the source and

Discharge contacts introduced into the silicon, but not in the channel region, in which under the influence of the field of the gate electrode. Charge carrier channel forms. Since phosphorus and boron form covalent bonds with the silicon, there is no danger of diffusion of these atoms into the channel region, so that low electrical conductivity in the channel region is still ensured.

If the doping of the contact regions is sufficiently high, the tunneling probability already at rest is so great that the transition between the contact material and the inorganic semiconductor material loses its blocking capability and becomes highly conductive in both directions.

Organic semiconductor field effect transistors are of interest for a variety of electronic applications requiring extremely low manufacturing costs, flexible or unbreakable substrates, or the fabrication of transistors and integrated circuits over large active areas. For example, organic field effect transistors are useful as pixel controls in active matrix displays. Such screens are commonly used with amorphous or polycrystalline field-effect transistors. ner silicon layers produced. The temperatures of usually more than 250 ° C required for the production of high-quality transistors based on amorphous or polycrystalline silicon layers require the use of rigid and fragile glass or quartz substrates. Owing to the relatively low temperatures at which organic semiconductor based transistors are fabricated, usually less than 100 ° C, organic transistors allow the production of active matrix displays using inexpensive, flexible, transparent, unbreakable polymer films with significant advantages Glass or quartz substrates.

Another field of application for organic field effect transistors is the production of very inexpensive integrated circuits, such as those used for active identification and identification of goods and goods. These so-called transponders are usually manufactured using integrated circuits based on monocrystalline silicon, which leads to considerable costs in the construction and connection technology. The production of transponders based on organic transistors would lead to enormous cost reductions and could make transponder technology a worldwide breakthrough.

One of the major problems in the application of organic field effect transistors is the relatively poor electrical properties of the source and drain contacts, that is, their high contact resistances. The source and drain contacts of organic transistors are usually produced using inorganic metals or with the aid of conductive polymers, so as to ensure the highest possible electrical conductivity of the contacts. Most organic semiconductors that are suitable for use in organic field effect transistors have very low electrical conductivities. For example, Pentazene, which is widely used for the production of organic field effect transistors is a very low electrical conductivity of 10 ^{~ 14} ^~ Ω ^• ^"" cm ^-1. If the organic semiconductor has a low electrical conductivity, there is therefore a large difference between the Fermi levels of electrically conductive contact material and organic semiconductor material at the contact surface. This leads to the formation of a high potential barrier with a low tunneling probability for the passage of charge carriers. Therefore, source and drain contacts often have high contact resistances, which is why high electrical field strengths at the contacts are required to inject and extract charge carriers. The limiting factor is therefore not the conductivity of the contact itself, but the low conductivity of the semiconductor regions adjacent to the contacts into which the charge carriers are injected or from which the charge carriers are extracted.

Therefore, in order to improve the electrical properties of the source and drain contacts, high electrical conductivity of the organic semiconductor in the regions adjacent to the contacts is desired to reduce the difference in Fermi levels between organic semiconductor and contact material, and thus the To lower contact resistance. On the other hand, a high electrical conductivity of the organic semiconductor in the channel region has a negative influence on the properties of the transistor. An appreciable electrical conductivity in the channel region inevitably leads to high leakage currents, that is to relatively high electric currents in the off state of the field effect transistor. However, for many applications, low leakage currents in the range of 10 ^"12 A or less are essential, and high electrical conductivity also causes the ratio between maximum inrush current and minimum off current to be too low Many applications require the largest possible ratio of inrush current to off current in the range of 10 ⁷ or greater, since this ratio reflects the modulation behavior and gain of the transistor Channel region is therefore required a low electrical conductivity of the organic semiconductor, while in the region of the source and drain contacts a high electrical conductivity is necessary to improve the contact properties between the organic semiconductor material and the material of the contacts.

The electrical conductivity of many organic semiconductors can be increased by the introduction of suitable dopants as in inorganic semiconductors. However, the achievement of potential selectivity in doping is problematic. The dopants are not bound to a particular position in the organic semiconductors and are free to move within the material. Even if the doping process can originally be restricted to a certain area, for example the areas around the source and drain contacts, migration of the doping substances through the entire organic semiconductor layer occurs later, in particular under the influence of the electric field that exists between the Source and drain contact is applied to operate the transistor. The diffusion of the dopant within the organic semiconductor layer inevitably increases the electrical conductivity in the channel region.

I. Kymissis, CD Dimitrakopoulos and S. Purushothaman, "High-Performance Bottom Electrode Organic Thin-Film Transistors" IEEE Transactions on Electron Devices, Vol. 48, No. 6, June 2001, pp. 1060-1061 describe a semiconductor device with reduced contact resistance, where on

First, a monomolecular layer of 1-Hexadecanthiol is applied to chromium / gold electrodes and then a layer of pentacene is applied as an organic semiconductor material on this. This arrangement makes it possible to substantially reduce the contact resistance for the charge transfer of the charge carriers between the electrode and the semiconductor path. The molecules of 1-hexadecane molecules arranged at the interface between the contact and the organic semiconductor thiol act as charge transfer molecules. They are in direct contact both with the contact material and with the organic semiconductor layer. Because of their molecular structure, the charge transfer molecules can force a transfer of charge carriers between the contact material in which there is an excess of carriers and the organic semiconductor layer in which there is a lack of charge carriers. In this way, in the region of the source and drain contacts, a charge carrier excess in the organic semiconductor layer can be brought about, whereby the contact resistance is significantly reduced. The thiol groups of 1-hexadecanethiol form a covalent bond to the surface of the gold contacts, causing local fixation of the molecules. Therefore, even under the influence of a field applied between the source and drain electrodes, the charge transfer molecules do not migrate into those sections of the organic semiconductor path in which the channel region is formed.

However, gold has the disadvantage that it usually adheres very poorly to inorganic layers, such as on silicon dioxide. In order to improve the adhesion of the gold contacts, therefore, a thin layer of chromium or titanium is often applied as an adhesion promoter immediately before the deposition of the gold layer. However, this has the disadvantage that the structuring of the metal layer necessary for the production of the contact structures is made more difficult. Further, thiols are also not suitable as charge transfer molecules, since sufficient bonding strength can not be achieved to all metals which are suitable for the production of contacts in order to prevent diffusion of the thiols out of the interface between contact and semiconductor material.

The object of the invention is therefore to provide a semiconductor device having a semiconductor path of an organic semiconductor material, a first contact for injecting charge carriers into the semiconductor path, and a second contact for extracting charge carriers from the semiconductor device. route, which has a low contact resistance for the transfer of charge carriers between contact and semiconductor line.

The object is achieved in a semiconductor device of the type mentioned above, in that a monomolecular layer of a nitrile or an isonitrile is arranged between the first contact and the semiconductor path and / or between the second contact and the semiconductor path.

Nitriles and isonitriles can form complexes with a large number of metals used as material for contacts in the semiconductor devices described above. If the nitrile or the isonitrile is applied to the surface which later forms the contact surface with the semiconductor line, the molecules are therefore coordinated to the surface to form a complex. This ensures, on the one hand, good contact with the material of the contacts and, on the other hand, fixation of the molecules at the contact surface so that they are in a field that is between

Source and drain electrode is applied, do not diffuse into the sections of the semiconductor path, in which the duct is formed.

As a semiconductor route, a line route between two contacts is referred to, which is composed of an organic semiconductor material. The charge carriers, electrons or holes, are injected into the semiconductor path at the first contact, pass through the semiconductor path and are extracted again from the conductor path at the second contact. As organic semiconductor material, all organic materials which have semiconductor properties can be used per se. Examples of suitable compounds are condensed aromatics such as antrazene, tetracene or pentacene, polymeric aromatic compounds such as polyvinylene or polynaphthalene derivatives, polythiophene-based electrical semiconducting compounds, for example poly-3-hexylthiophene-2, 5-diyl, or electrically semiconducting Compounds based on polyvinylthiophene or polyaniline. In addition to the compounds mentioned, it is also possible to use other organic semiconductor compounds. The or ^¬ ganic semiconductor materials may have a doping up, such as camphor sulfonic acid or polystyrene. However, the doping in the semiconductor may diffuse only to a limited extent or preferably not. The semiconductor path can consist of homogeneous only one organic semiconductor material. However, it is also possible to provide a semiconductor path consisting of different sections, each composed of different organic semiconductor materials.

The materials used for the production of the semiconductor line of the semiconductor device according to the invention are easily accessible and can in part also be obtained from commercial suppliers. The organic semiconductor materials or precursors for the preparation of the organic semiconductor materials are usually readily soluble in organic solvents and can therefore be provided in dissolved form or as a suspension and applied in liquid form to a substrate. In this way, the semiconductor path of the semiconductor device according to the invention can be produced, for example, by simple printing methods, which considerably simplifies and reduces the production of the semiconductor element. However, the deposition of the organic semiconductor material can also be carried out by other methods, for example by sublimation of the semiconductor material from the gas phase.

As material for the contacts, all materials are suitable which have a sufficiently high electrical conductivity. In principle, all metals are suitable, preferably palladium, gold, platinum, nickel, copper, aluminum, as well as electrically conductive oxides, such as, for example, ruthenium oxide and indium tin oxide, and also electrically conductive polymers, such as polyacetylene or polyaniline. The first and / or second contact of the semiconductor single Rich ^¬ tung is preferably constructed of palladium. Palladium, like gold, has excellent oxidation resistance and is also easy to deposit and structure. However, unlike gold, palladium adheres much better to all kinds of substrates, so that the additional use of a primer, such as chromium or titanium, is not required. Nitriles and isonitriles show a very good adhesion to palladium surfaces, so that no migration of these compounds takes place in the electric field. Thiols are unsuitable for fixation on palladium, since the palladium-sulfur bond is significantly weaker compared to the gold-sulfur bond and there is no local fixation of the molecules on the contact surface.

In order to achieve the lowest possible contact resistance for the transfer of the charge carriers between contact and semiconductor line, the layer of nitrile or isonitrile should be made as thin as possible. Preferably, the layer of nitrile or isonitrile is formed as a self-organizing rαonomolekulare layer. In this case, the surface of the contact is covered with a monomolecular layer, wherein the nitrile group or the isonitrile group binds to the surface of the contact. If the surface of the contact is fully occupied, no further compound is adsorbed and excess nitrile or isonitrile For example, it can be rinsed away with a suitable solvent.

Isonitriles cause the formation of a positive partial charge on the surface of the contact. As a result, the contact resistance can be significantly reduced. Both aromatic and saturated isonitriles are suitable, the aromatic compounds preferably comprising 6 to 10 carbon atoms. Individual hydrogen atoms on the carbon backbone can also be replaced by substituents, such as alkyl groups. Alkyl isocyanides preferably comprise 3 to 10 carbon atoms, the alkyl chain may be straight or branched. Furthermore, Iso ^¬ cyanide are suitable having cycloalkyl, to lower the contact resistance ^¬ standing. For both the aromatic and the saturated isocyanides, individual carbon atoms may be replaced by heteroatoms such as nitrogen or oxygen. Examples of isonitriles which are suitable for the semiconductor device according to the invention are 2,4-diisocyanotoluene, ethyl isocyanoacetate, 4- (2-isocyanoethyl) morpholine, n-butyl isocyanide, tert-butyl isocyanide, cyclohexyl isocyanide, 1- (isocyanidomethyl) -1H-benzotriazole , 2-methylpropyl isocyanide, phenyl isocyanide dichloride, 1, 1, 3, 3-tetramethylbutyl isocyanide, 4-toluenesulfonylmethyl isocyanide.

However, isocyanides are usually difficult to access synthetically. Preferably, nitriles are therefore used for the semiconductor device according to the invention. The most significant reduction in contact resistance is achieved when an aromatic nitrile compound is used as the nitrile. An aromatic nitrile compound is understood as meaning a compound which, in addition to the nitrile group, has at least one aromatic radical which is preferably derived from a phenyl group. Particularly preferred is the simplest member of this class, namely benzonitrile. Benzonitrile can form a positive partial charge by binding to the surface of the contact, which can be delocalized in the benzyl radical. In this way, a very stable system is obtained. The binding of the nitrile to the surface of the contact can take place both via the nitrogen atom of the nitrile group, as well as laterally via the π-system of the nitrile group. Possible binding mechanisms as well as the delocalization of the positive charge are shown schematically below.

In addition to benzonitrile, substituted benzonitriles are also suitable, for example, in order to bring about the reduction in contact resistance observed in the semiconductor device according to the invention. The substituents on the phenyl ring can be varied within wide limits. It is possible, for example, a substitution by alkyl groups or by halogen atoms or pseudohalides. For example, o-fluorobenzonitrile, p-fluorobenzonitrile, perfluorobenzonitrile or tetracyanoquinodimethane are suitable.

tetracyanoquinodimethane

Furthermore, one or more of the carbon atoms of the phenyl ring can be replaced by heteroatoms, in particular by nitrogen atoms. Suitable compounds are, for example, 2-cyanopyridine or 4-cyanopyridine.

In addition to the aromatic nitriles, aliphatic nitriles are also suitable, which bring about the observed reduction in contact resistance in the semiconductor device according to the invention. For aliphatic nitriles, however, the effect is usually less pronounced than for aromatic nitriles. Suitable compounds are, for example, acetonitrile, valeronitrile or tetracyanoethylene.

Hydrocyanic acid (HCN) and the isoelectronic carbon monoxide (CO) are also suitable.

The semiconductor device according to the invention can be very easily integrated into more complex components. So will in In a particularly preferred embodiment, the semiconductor device described above is supplemented by a gate electrode and a gate dielectric to form a transistor. The first contact of the semiconductor device then forms the source contact, while the second contact forms the drain electrode. Under the influence of the field generated by the gate electrode, a charge channel is then formed between the source and drain electrodes, in which a charge carrier transport takes place. For the gate electrode, the same materials as described above for the first and second contacts can be used. For insulating the gate electrode, it is possible to use customary materials, such as silicon dioxide, aluminum oxide or an insulating polymer, such as polystyrene, polyethylene, polyester, polyurethane, polycarbonate, polyacrylate, polyimide, polyethers, polybenzoxazoles or mixtures of these compounds and their derivatives.

The semiconductor element according to the invention can be produced very cost-effectively from easily accessible materials and is therefore particularly suitable for use in devices which are subject to high cost pressure, such as labels for the labeling of goods.

The invention therefore also provides a method for producing the semiconductor device described above, wherein a first and / or a second contact having an exposed contact surface is provided on a substrate. On the exposed contact surface, a nitrile or an isonitrile is applied, so that a layer of the nitrile or the isonitrile is obtained on the contact surface. Finally, an organic semiconductor material is deposited in such a way that a semiconductor path is obtained from the organic semiconductor material between the first contact and the second contact.

As the substrate, inflexible substrates may be used in the production of the semiconductor device of the present invention such as glass or quartz or silicon wafers. Preferably, however, flexible substrates are used, such as plastic films of, for example, polystyrene, polyethylene, polyester, polyurethane, polycarbonate, polyacrylate, polyimide, polyether or polybenzoxazoles or paper. Components of the semiconductor device may also already be defined on the substrate, for example a gate electrode which is insulated with a corresponding gate dielectric. Subsequently, the first and second contacts are defined on the substrate, using conventional methods for deposition and patterning. The metal from which the contacts are constructed can, for example, be evaporated by electron beam evaporation or be deposited by means of cathode jet atomization. However, other methods can also be used. The metal layer is then patterned, for example by photolithographic methods. The nitrile or the isonitrile is then applied to the contacts, wherein any methods can be used here. For example, the nitrile or the isonitrile can be applied from the gas phase by passing an air stream saturated with the nitrile or isonitrile over the surface of the contacts, so that the nitriles or isonitriles are bound to the surface of the contact. Preferably, however, the nitrile or the isonitrile is applied as a solution to the contacts. For this purpose, a solution of the nitrile or isonitrile is first prepared in a suitable solvent and then applied to the contacts. By diffusion, the molecules migrate from the solution to the surface of the contacts, where the molecules are bound via their nitrile group or isonitrile group. Excess solvent and nitrile or isonitrile can then be removed, for example by rinsing or centrifuging. The solution of the nitrile or isonitrile can be applied to the contacts by conventional methods. Suitable examples are spraying or dipping. Likewise, the solution of the nitrile or isonitrile on the surface of the substrate and the contacts are spin-coated, whereby the nitriles or isonitriles are selectively bound to the surface of the metallic contacts. Finally, it is also possible to apply the nitriles or isonitriles to the contacts by a printing process. After the contacts are printed with the solution of nitrile or isonitrile, then excess solvent must then be removed, for example by evaporation. In order not to make the layer of nitrile or isonitrile too thick, it is necessary to work with dilute solutions. Finally, the organic semiconductor is deposited, so that a semiconductor path between first and second contact is obtained. For this purpose, also common methods are used. For example, pentacene can be separated by sublimation in vacuo. But it is also possible to apply the organic semiconductor in dissolved form. For this purpose, the solution of the organic semiconductor can, for example, be sprayed on or spin-coated. It is also possible to apply the organic semiconductor by printing techniques.

In the embodiment of the method described above, the contacts were first deposited, and applied to this, after treatment with nitriles or isonitriles, the layer of the organic semiconductor material. As such, the layer of the organic semiconductor material could first be deposited and only then the contacts could be defined. In general, however, it is difficult to perform patterning of the contacts when they are disposed on the layer of the organic semiconductor material. This adversely affects the

Conductivity of the organic semiconductor layer and on the reproducibility of the properties of the semiconductor devices shown. The contacts are therefore preferably first produced and only then the organic semiconductor material is deposited on the contacts in order to define the organic semiconductor path in this way. The invention will be explained in more detail with reference to an accompanying drawing. Identical objects are designated by the same reference numerals. It shows:

FIG. 1 shows method steps which are carried out in the production of a field-effect transistor which comprises the semiconductor device according to the invention; FIG.

2 shows a graph in which the contact resistance is shown as a function of a voltage applied between gate and source for two different field-effect transistors.

FIG. 1 shows a sequence of the method steps which are carried out in the production of a field-effect transistor which comprises the semiconductor device according to the invention. First, as shown in FIG. 1A, a gate electrode 2 is defined on a substrate 1. This will be on the

Substrate 1, for example a polymer film, a layer of, for example, palladium deposited and then patterned by photolithographic techniques. The gate electrode 2 is then isolated by applying a layer of silicon dioxide, for example, as the gate dielectric 3. This gives the arrangement shown in FIG. 1B. On the gate dielectric 3, the source electrode 4 and the drain electrode 5 are now defined. For this purpose, as described in the illustration of the gate electrode 2, first a layer of, for example, palladium is deposited and then structured by photolithographic techniques to obtain, as shown in FIG. 1C, portions of palladium, which are the source electrode 4 and the drain electrode 5 correspond. A solution of benzonitrile in a suitable solvent is then applied to the surface formed from the surfaces of the source electrode 4, the drain electrode 5 and the gate dielectric 3 and left there for a certain period of time so that the benzonitrile moiety From the solution molecules can diffuse to the exposed surfaces of the source electrode 4 and the drain electrode 5 and are bound there. Finally, excess solvent and unbound benzonitrile are removed, for example by rinsing with a suitable solvent and subsequent drying, for example a stream of nitrogen. As shown in FIG. 1D, an arrangement is obtained in which benzonitrile molecules which form a monomolecular layer 6 are bonded to the surfaces of the source electrode 4 and the drain electrode 5. Finally, as shown in FIG. 1E, a layer of an organic semiconductor 7 is applied, which covers the source and drain electrodes (4, 5) provided with the monomolecular layer 6 and the section of the gate dielectric 3 arranged between these electrodes.

example

A flexible polyethylene naphthalate film is cleaned with acetone and isopropanol and then a thin layer of titanium is deposited on the film. The titanium layer is patterned by photolithography and wet chemical etching in dilute hydrofluoric acid to define the gate electrodes of the transistors. Subsequently, a thin layer of silicon dioxide is deposited as a gate dielectric for the transistors by cathode-beam sputtering and patterned by photolithography and wet-chemical etching. Thereafter, palladium is deposited by either thermal evaporation, electron beam evaporation, or by cathode ray sputtering and also etched by photolithography and wet chemical etching in a highly dilute mixture of hydrochloric acid and nitric acid to define the source and drain contacts of the transistors. The substrate thus prepared is immersed in a 5% solution of benzonitrile in xylene for 5 minutes to cover the palladium surfaces with a benzonitrile monolayer. Excess benzonitrile is rinsed off in a rinsing step with hexane. After drying the substrate is by means of thermal evaporation, a thin layer of pentacene deposited as an organic semiconductor layer.

As a comparison, the same operations were performed, but the palladium surfaces were not covered with benzonitrile. For both transistor arrangements, the resistance was subsequently measured as a function of the voltage applied between source and drain. The obtained measurement curves are shown in FIG. The curve a shows the change of the resistance for the

Transistor, whose contacts were not treated with benzonitrile, while the curve (b) shows the change in contact resistance for a transistor whose source and drain electrodes were treated with benzonitrile. By treating the palladium contacts with benzonitrile, the contact resistance can be reduced by about a factor of 2.

LIST OF REFERENCE NUMBERS

1 substrate 2 gate electrode

3 gate dielectric

4 source electrode

5 drain electrode

6 monomolecular layer 7 organic semiconductors

Claims

1. Semiconductor device with a semiconductor path from an organic semiconductor material, a first contact for injecting charge carriers into the semiconductor path and a second contact for extracting charge carriers from the semiconductor path, characterized in that between the first contact and the semiconductor path and / or between the second contact and the Semiconductor section is arranged a layer of a nitrile or an isonitrile.

2. The semiconductor device according to claim 1, wherein the first and / or second contact is constructed from palladium.

3. Semiconductor device according to claim 1 or 2, wherein the layers of the nitrile or the isonitrile is formed as a self-assembling monomolecular layer.

4. A semiconductor device according to any one of the preceding claims, wherein the nitrile is an aromatic nitrile.

5. The semiconductor device according to claim 4, wherein the aromatic nitrile is a substituted or unsubstituted benzonitrile.

6. The semiconductor device according to one of claims 1 to 3, wherein the nitrile is an aliphatic nitrile.

7. Semiconductor device according to one of the preceding claims, wherein the semiconductor device is supplemented by a gate electrode and a gate dielectric to form a field effect transistor.

8. A method for producing a semiconductor device according to one of claims 1 to 7, wherein a first and / or a second contact is provided on a substrate, which has an exposed contact surface, a nitrile or an isonitrile is applied to the exposed contact surface, so that a layer of the nitrile or the isonitrile is obtained on the contact surface, and an organic semiconductor material is deposited, so that between the first contact and the second contact a semiconductor path is obtained from an organic semiconductor material.

9. The method according to claim 8, wherein the nitrile or the isonitrile is applied as a solution on the contact surface of the first and / or the second contact.