Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-07-01
2004-12-07
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S373000, C528S423000, C528S398000, C427S581000
Reexamination Certificate
active
06828406
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention lies in the organic semiconductor technology field. More specifically, the invention relates to an organic polymer having electrical semiconductor properties, compounds from which the polymer can be prepared, a semiconductor component which comprises the organic polymer, and a process for the production of the semiconductor component.
Semiconductor chips are widely used in a variety of technical applications. Their production is still very complicated and expensive. It is true that silicon substrates can be thinned down to very small layer thicknesses so that they become flexible. However, these processes are likewise very expensive, so that flexible or curved microchips are suitable only for demanding applications in which high costs can be accepted. The use of organic semiconductors offers the possibility of economical production of microelectronic semiconductor circuits on flexible substrates. One application is, for example, a thin film comprising integrated control elements for liquid crystal screens. A further application is transponder technology, where information about a product is stored on so-called tags.
Organic semiconductors can be very easily structured, for example by printing processes. However, the use of such organic semiconductors is at present still limited by the low mobility of charge carriers in the organic polymeric semiconductors. This is at present not more than 1-2 cm
2
/Vs. The maximum operating frequency of transistors, and hence of the electronic circuit, is limited by the mobility of the charge carriers, holes or electrons. It is true that mobilities of the order of magnitude of 10
−1
cm
2
/Vs are sufficient for driver applications in the production of TFT active matrix displays. However, the organic semiconductors are not yet suitable for high-frequency applications. For technical reasons, wireless information transmission (RF-ID systems) can be effected only above a certain minimum frequency. In systems which draw their energy directly from the alternating electromagnetic field and hence also have no voltage supply of their own, carrier frequencies of 125 kHz or 13.56 MHz are widely used. Such systems are used, for example, for identifying or labeling articles in smart cards, ident tags or electronic stamps.
Processes in which semiconducting molecules, for example pentacene or oligothiophenes, can be deposited as far as possible in an ordered manner have been developed for improving the charge carrier transport in organic semiconductors. This is possible, for example, by vacuum sublimation. Ordered deposition of the organic semiconductor leads to an increase in the crystallinity of the semiconductor material. As a result of the improved &pgr;—&pgr; overlap between the molecules or the side chains, the energy barrier for the charge carrier transport can be reduced. By substituting the semiconducting molecular units with bulky groups in the deposition of the organic semiconductor from the liquid or gas phase, it is possible to produce domains which have liquid crystalline properties. Furthermore, synthesis methods in which as high a regioregularity as possible is achieved in the polymers by the use of asymmetric monomers have been developed.
International PCT publication WO 97/10193 describes aromatic compounds substituted by ethynyl groups. These compounds have the following general formula.
Here, Ar represents an aromatic group which may also be substituted by an inert substituent, R, in each case independently of one another, represent hydrogen or an alkyl or aryl group which in each case may also carry an inert substituent; L denotes a covalent bond or a group which links a group Ar to at least one other group Ar; n and m denote an integer of at least 2; and q denotes an integer of at least 1. The monomer can polymerize with formation of polymers which have high thermal stability. The polymer, which may also be a copolymer, comprises units of the following structure:
in which the groups Ar′ are formed from the (R—C≡C)
n
Ar and Ar(C≡C—R)
m
segments of the above compound by Bergmann cyclization, and the groups R and L have the abovementioned meaning.
In addition to the unit shown above, the copolymer may have units of the following structure:
in which Ar′ and R have the abovementioned meaning.
Electrically semiconducting polymers are required, for example, in field effect transistors or electronic components which are based on a field effect. A description of such a configuration can be found, for example, in M. G. Kane, J. Campi, M. S. Hammond, F. P. Cuomo, B. Greening, C. D. Sheraw, J. A. Nichols, D. J. Gundlach, J. R. Huang, C. C. Kuo, L. Jia, H. Klauk, T. N. Jackson, IEEE Electron Device Letters, Vol. 21 No. 11 (2000), 534, or D. J. Gundlach, H. Klauk, C. D. Sheraw, C. C. Kuo, J. R. Huan, T. N. Jackson, 1999 International Electron Devices Meeting, December 1999.
For an application of organic polymers in field effect transistors or similar electronic components, it is necessary for the polymer to behave like an insulator when no electric field is applied, while it exhibits semiconductor properties or forms a conduction channel under the influence of an electric field. For example, polyphenylenes or polynaphthalene derivatives have such properties. However, owing to their insolubility, these are not processible, i.e. field effect transistors cannot be produced using these compounds.
The polymers described in WO 97/10193 have insulator properties and can be used, for example, as a dielectric in computer chips. These polymers cannot be used in electronic components, such as, for example, organic field effect transistors, since they acquire electrical semiconductor properties only as a result of doping. Doping is unspecific, which is why a field effect transistor produced from this polymer can no longer be switched off.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for the production of organic polymers with high charge carrier mobility due to &pgr;-conjugated crosslinking groups, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which are suitable for the production of organic field effect transistors.
With the foregoing and other objects in view there is provided, in accordance with the invention, an organic polymer which has electrical semiconductor properties and has a backbone of phenylene groups and a structure of the formula I
in which
E
1
and E
2
each represent any desired terminal group or a free electron;
S
m
represents a group which is electrically semiconducting or which produces electrical semiconductor properties in the polymer, it being possible for the groups S
m
in the polymer to be identical or different;
Ar represents a fused-on aromatic or heteroaromatic radical which shares a carbon bond with the phenylene groups of the backbone of the polymer;
R
n
represents any desired radical by which Ar can be substituted, it also being possible for a plurality of radicals R
n
, which may be identical or different, to be bonded to Ar, and it also being possible for the radicals R
n
to be bonded to one another with the formation of a conjugated &pgr; system; and
n represents an integer from 1 to 10
6
.
In the polymers according to the invention, groups which already have semiconductor properties or which impart semiconductor properties to the polymers are arranged in the polymer skeleton in a certain spatial arrangement relative to one another. The polymer skeleton is composed of conjugated &pgr; bonds. This gives rise to a conduction path in the backbone of the polymer which is formed by phenylene groups, along which path charge carriers are transported. The charge transport in the polymer according to the invention is shown in the following formula II.
On the one hand, the charge carriers can move from one group S
m
to the next group S
m
by a hopping mechanism as in the case of the materials described above, such as
Haasmann Roland
Halik Marcus
Schmid Günter
Walter Andreas
Greenberg Laurence A.
Locher Ralph E.
Stemer Werner H.
Truong Duc
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