Active solid-state devices (e.g. – transistors – solid-state diode – Organic semiconductor material
Reexamination Certificate
2002-03-07
2004-07-27
Yamnitzky, Marie (Department: 1774)
Active solid-state devices (e.g., transistors, solid-state diode
Organic semiconductor material
C257S410000, C257S411000, C438S099000, C428S901000
Reexamination Certificate
active
06768132
ABSTRACT:
TECHNICAL FIELD
This invention relates to organic thin film transistors having improved performance. More particularly, the invention relates to organic thin film transistors having a substituted acene semiconductor and a self-assembled monolayer between the semiconductor and gate dielectric.
BACKGROUND
Organic semiconductors are of great interest for a variety of applications such as low-cost electronics. Organics can be synthesized to incorporate the necessary electronic properties for a wide variety of devices, and also can be constructed to allow low-cost, roll processing that is not currently possible for crystalline silicon microelectronics.
One area of concern in organic electronic devices is the quality of the interface formed between the organic semiconductor and another device layer. Previous efforts to control the semiconductor/dielectric interface have included the use of hexamethyldisilazane (HMDS) and silane coupling agents on silicon oxide surfaces. Complex deposition processes involving long times in a vacuum have been used to coat octadecyltrichlorosilane (OTS) onto thermally-grown silicon dioxide gate dielectric materials to affect transistor performance. The materials useful in this process have several disadvantages, including sensitivity to water in the atmosphere and on the surface of a dielectric layer, instability due to crosslinking within the material in competition with the bonding reaction to the dielectric layer, and difficulties in achieving reproducible film properties. EP 1041652 A2 describes the use of several surface treatments to enhance the crystalline domain size of solution cast oligothiophenes on SiO
x
for thin film transistors (TFTs), although measured mobility values were generally lower than the untreated controls.
SUMMARY
Briefly, the present invention provides an organic thin film transistor (OTFT) comprising a self-assembled monolayer interposed between a gate dielectric and an organic semiconductor layer, the monolayer being a product of a reaction between the gate dielectric and a precursor to the self-assembled monolayer, the precursor comprising a composition having the formula:
X—Y—Z
n
,
wherein X is H or CH
3
;
Y is a linear or branched C
5
-C
50
aliphatic or cyclic aliphatic connecting group, or a linear or branched C
8
-C
50
group comprising an aromatic group and a C
3
-C
44
aliphatic or cyclic aliphatic connecting group;
Z is selected from —PO
3
H
2
, —OPO
3
H
2
, benzotriazolyl (—C
6
H
4
N
3
), benzotriazolylcarbonyloxy (—OC(═O)C
6
H
4
N
3
), benzotriazolyloxy (—O—C
6
H
4
N
3
), benzotriazolylamino (—NH—C
6
H
4
N
3
), —CONHOH, —COOH, —OH, —SH, —COSH, —COSeH, —C
5
H
4
N, —SeH, —SO
3
H, —NC, —SiCl(CH
3
)
2
, —SiCl
2
CH
3
, amino, and phosphinyl; and n is 1, 2, or 3 provided that n=1 when Z is —SiCl(CH
3
)
2
or —SiCl
2
CH
3
; and wherein the organic semiconductor layer comprises a material selected from an acene, substituted with at least one electron-donating group, halogen atom, or a combination thereof, or a benzo-annellated acene or polybenzo-annellated acene, which optionally is substituted with at least one electron-donating group, halogen atom, or a combination thereof.
The present invention also provides an organic thin film transistor comprising a self-assembled monolayer interposed between a gate dielectric and an organic semiconductor layer, the monolayer being a product of a reaction between the gate dielectric and a precursor to the self-assembled monolayer, the precursor comprising a composition having the formula:
X—Y—Z
n
,
wherein X is H or CH
3
;
Y is a linear or branched C
5
-C
50
aliphatic or cyclic aliphatic connecting group, or a linear or branched C
8
-C
50
group comprising an aromatic group and a C
3
-C
44
aliphatic or cyclic aliphatic connecting group;
Z is selected from —PO
3
H
2
, —OPO
3
H
2
, benzotriazolyl (—C
6
H
4
N
3
), benzotriazolylcarbonyloxy (—OC(═O)C
6
H
4
N
3
), benzotriazolyloxy (—O—C
6
H
4
N
3
), benzotriazolylamino (—NH—C
6
H
4
N
3
), —CONHOH, —COOH, —OH, —SH, —COSH, —COSeH, —C
5
H
4
N, —SeH, —SO
3
H, —NC, —SiCl(CH
3
)
2
, —SiCl
2
CH
3
, amino, and phosphinyl;
and n is 1, 2, or 3 provided that n=1 when Z is —SiCl(CH
3
)
2
or —SiCl
2
CH
3
; and wherein the organic semiconductor layer comprises a semiconductor of the formula:
wherein each R group is independently selected from electron-donating groups, halogen atoms, hydrogen atoms, and combinations thereof, provided that not all R groups are hydrogen; m is 1, 2, 3, or 4; each R
9
and R
10
is independently H or any R group; and any combination of two adjacent R groups may together form a five or six carbon cyclic aliphatic or aromatic group; provided that neither R
2
with R
3
nor R
6
with R
7
form part of a six-member aromatic ring; and provided that when m is 1 neither R
9
nor R
10
form part of a six-member aromatic ring.
As used herein, “electron-donating group” means C
1
-C
24
alkyl, alkoxy, thioalkoxy, or combinations thereof, which may be substituted or unsubstituted and “substituted” means, for a chemical species, substituted by a group that does not interfere with the desired product or process, e.g., substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), etc.
Various thin film transistor construction options are possible. For example, the source and drain electrodes may be adjacent to the gate dielectric with the organic semiconductor layer over the source and drain electrodes, or the organic semiconductor layer may be interposed between the source and drain electrodes and the gate dielectric.
In another aspect, the present invention provides a method of making a thin film transistor comprising the steps of providing a substrate, providing a gate electrode material on the substrate, providing a gate dielectric on the gate electrode material, providing a self-assembled monolayer (SAM) adjacent to the gate dielectric, the monolayer being a product of a reaction between the gate dielectric and a precursor to the self-assembled monolayer, applying an organic semiconductor layer on the monolayer, and providing a source electrode and a drain electrode contiguous to the organic semiconductor layer. The precursor is as described above with the organic thin film transistor article. The organic semiconductor layer also is as described above with the organic thin film transistor article. An integrated circuit comprising organic thin film transistor articles is also provided.
It is an advantage of the present invention to provide organic thin film transistors with one or more improvements over known devices that lack the features of the present invention. With the invention, improvements in properties such as threshold voltage, subthreshold slope, on/off ratio, and charge-carrier mobility can be achieved. The improvements in device performance provided by the present invention enable the production of more complicated circuits having faster switching speeds and simpler processing conditions. This invention also enables the production of larger circuit elements having comparable performance to devices with very small features. Devices with larger feature sizes can be less expensive as they do not require expensive precision patterning processes.
Other features and advantages of the invention will be apparent from the following detailed description of the invention and the claims. The above summary of principles of the disclosure is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The following detailed description more particularly exemplifies certain preferred embodiments utilizing the principles disclosed herein.
DETAILED DESCRIPTION
Generally, a thin film transistor includes a gate electrode, a gate dielectric on the gate electrode, a source electrode and a drain electrode adjacent to the gate dielectric, and a semiconductor layer adjacent to the gate dielectric and adjacent to the source and drain electrodes. More specifically, an organic thin film transistor (OTFT) has an organic semiconductor layer. Such OTFTs are known in th
Boardman Larry D.
Dunbar Timothy D.
Kelley Tommie W.
Muyres Dawn V.
Pellerite Mark J.
3M Innovative Properties Company
Kokko Kent S.
Yamnitzky Marie
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