Metal oxide precursors, coating compositions containing same, and use thereof

Abstract

The present invention relates to metal oxide precursors comprising i) at least one metal atom selected from the group consisting of In, Ga, Zn and Sn, ii) at least one non-photocrosslinkable ligand and iii) at least one photocrosslinkable ligand, to liquid coating compositions comprising the precursors, and to their use.

Claims

1. A liquid coating composition, comprising at least one metal oxide precursor, which is a coordination complex comprising: i) at least one metal atom selected from the group consisting of In, Ga, Zn and Sn; ii) at least one non-photocrosslinkable ligand; and iii) at least one photocrosslinkable ligand wherein the at least one photocrosslinkable ligand is selected from the group consisting of an acrylate, a methacrylate and an allyl; at least one solvent; and at least one photoinitiator.

2. The liquid coating composition according to claim 1, wherein the at least one non-photocrosslinkable ligand is selected from the group consisting of an oxo radical, a hydroxyl radical, an alkoxy radical, a nitrate radical and a halide radical.

3. The liquid coating composition according to claim 2, comprising, as at least one non-photocrosslinkable ligand, at least one oxo radical and at least one alkoxy radical.

4. The liquid coating composition according to claim 1, comprising, as the at least one non-photocrosslinkable ligand, an oxo, an alkoxy and at least one selected from the group consisting of a nitrate and a halide.

5. The liquid coating composition according to claim 1, wherein the at least one metal atom is In.

6. A metal oxide precursor having formula:
[In.sub.6(?.sub.6-O)(?.sup.2-OR).sub.12-xCl.sub.6(R).sub.x].sup.2? wherein: R represents a C.sub.1-10 alkyl, R represents acrylate or methacrylate, and x represents 1-10.

7. A metal oxide precursor having formula:
[In.sub.6(?.sub.6-O)(?.sup.2-OR).sub.12-x(NO.sub.3).sub.6(R).sub.x].sup.2? wherein: R represents a C.sub.1-10 alkyl, R represents acrylate or methacrylate, and x represents 1-10.

8. The liquid coating composition according to claim 1, comprising phenylbis(2,4,6-trimethyl benzoyl)phosphine oxide as the photoinitiator.

Description

EXAMPLE 1

Synthesis of [In6(?6-O)(?2-OR)12-xCl6(R)x]2? with R=Methacrylate

(1) 50 mg [In.sub.6(?.sub.6-O)(?.sub.2-OMe).sub.12Cl.sub.6].sup.2?[NH.sub.2Me.sub.2].sup.2+ were dissolved in 1 mL of 1-methoxy-2-propanol (anhydrous). Then 26 mg of methacrylic acid were added and the mixture was stirred at room temperature for 10 minutes. The resulting mixture was centrifuged, and the centrifugate was evaporated down and dried.

Production of the Coating Composition

(2) The solid obtained was dissolved in 1-methoxy-2-propanol, to give a solution having a concentration of 100 mg/mL in respect of the precursor. As photoinitiator, 8% by weight of Irgacure 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) was added. This solution was subsequently diluted in a volume ratio of 1:2 with 1-methoxy-2-propanol.

Production of Structured Layers

(3) The solution was applied to a substrate by spincoating and subsequently exposed with UV light with a wavelength ?=365 nm, selectively by means of a mask, on a mask aligner. In the course of the subsequent development, the unexposed portions were removed with a developer (1-methoxy-2-propanol). This left the unexposed portions. The structures obtained were converted by means of a UVO treatment with radiation of wavelength ?=184 nm and 254 nm and thermal reaction at 350? C. into structures containing indium oxide.

EXAMPLE 2

Synthesis of [In6(?6-O)(?2-OR)12-x(NO3)6(R)x]2? with R=Methacrylate

(4) 50 mg [In.sub.6(?.sub.6-O)(?.sub.2-OMe).sub.12(NO.sub.3).sub.6].sup.2?[NH.sub.2Me.sub.2].sup.2+(MeOH).sub.2 were dissolved in 1 mL of 1-methoxy-2-propanol (anhydrous). Then 26 mg of methacrylic acid were added and the mixture was stirred at room temperature for 10 minutes. The resulting mixture was centrifuged, and the centrifugate was evaporated down and dried.

Production of the Coating Composition

(5) The solid obtained was dissolved in 1-methoxy-2-propanol, to give a solution having a concentration of 100 mg/mL in respect of the precursor. As photoinitiator, 8% by weight of Irgacure 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) was added. This solution was subsequently diluted in a volume ratio of 1:2 with 1-methoxy-2-propanol.

Production of Structured Layers

(6) The solution was applied to a substrate by spincoating and subsequently exposed with UV light with a wavelength ?=365 nm, selectively by means of a mask, on a mask aligner. In the course of the subsequent development, the unexposed portions were removed with a developer (1-methoxy-2-propanol). This left the unexposed portions. The structures obtained were converted by means of a UVO treatment with radiation of wavelength ?=184 nm and 254 nm and thermal reaction at 350? C. into structures containing indium oxide.

COMPARATIVE EXAMPLES

(7) Synthesis of a precursor with exclusively Photocrosslinkable Groups

(8) A solution was made from 25 mg of In(III) isopropoxide (manufacturer: Alfa Aesar) per 1 mL of methacrylic acid. The mixture was boiled under reflux at 100? C. for 1 hour. The resulting mixture was centrifuged, and the centrifugate was evaporated down and dried. NMR measurements show exclusively methacrylate groups, i.e. photocrosslinkable ligands.

Production of the Coating Composition

(9) The residue obtained was dissolved in 1-methoxy-2-propanol, to give a solution having a concentration of 33 mg/mL in respect of the precursor. As photoinitiator, 8% by weight of Irgacure 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) was added.

Production of Structured Layers

(10) The solution was applied to a substrate by spincoating and subsequently exposed with UV light with a wavelength ?=365 nm, selectively by means of a mask, on a mask aligner. In the course of the subsequent development, the unexposed portions were removed with a developer (1-methoxy-2-propanol). This left the unexposed portions. The structures obtained were converted by means of a UVO treatment with radiation of wavelength ?=184 nm and 254 nm and thermal reaction at 350? C. and 550? C., respectively, into structures containing indium oxide.

(11) In both examples the layers were produced by spincoating with the following parameters: 100 ?l of coating composition were applied at 3000 rpm over 30 seconds to a silicon wafer having an SiO.sub.2 layer thickness of 230 nm and pre-structured source and drain contacts made from ITO. Thermal conversion took place on a hotplate.

(12) Electrical characterization was carried out in both cases with a Keithley 2612 System source meter with Keithley 3706-NFP System switch/multimeter. The samples were measured at room temperature under an N.sub.2 atmosphere. Characterization was carried out after the temperature treatment. The (pre-structured) gate, source and drain contacts here were connected to the apparatus via tungsten measurement tips. A voltage profile between gate electrode and source electrode between ?20 and +30 V was run, and the current which flowed between source electrode and drain electrode was recorded. This data can be used to calculate the mobility values as follows:

(13) ${?}_{\mathrm{lin}}=\frac{?I_D}{?V_G}\frac{L}{{\mathrm{WC}}_i{V}_D}$${?}_{\mathrm{sat}}=\frac{2L}{{\mathrm{WC}}_i}{\left(\frac{?\left(\sqrt{I_D}\right)}{?V_G}\right)}^2$
where I.sub.D and V.sub.G are the current between drain and source and the voltage applied at the gate, respectively. L and W correspond to the length and width of the channel, and C.sub.i is the dielectric constant of the dielectric. The higher the mobility value, the better the material.

(14) Further characteristic properties are the switch-on voltage (V.sub.ON), which describes the point at which current flow between source electrode and drain electrode begins; this value ought to be very close to 0 V. I.sub.ON is the maximum current flow between source electrode and drain electrode (measured here with a gate voltage of 30 V); this value ought to be very high. The ratio (I.sub.ON/I.sub.OFF) describes the ratio between I.sub.ON and the current flow in the switched-off state (below V.sub.ON); this value ought to be very high.

(15) The table set out below summarizes the electrical characterization data.

(16) TABLE-US-00001 TABLE ?.sub.lin ?.sub.sat T.sub.anneal V.sub.On I.sub.On [cm.sup.2/ [cm.sup.2/ Material [? C.] [V] [mA] I.sub.On/I.sub.Off Vs] Vs] Hybrid ligand 350 ?0.5 0.55 6 ? 10.sup.6 3.08 1.12 Ex. 1 Hybrid ligand 350 0.5 0.4 6 ? 10.sup.6 2.24 0.82 Ex. 2 Methacrylate 350 4 2.8 ? 10.sup.?3 1.6 ? 10.sup.4 0.013 0.014