Organic semiconductor device having an active dielectric layer comprising silsesquioxanes
View Patent ↗An organic field effect transistor (FET) is described with an active dielectric layer comprising a low-temperature cured dielectric film of a liquid-deposited silsesquioxane precursor. The dielectric film comprises a silsesquioxane having a dielectric constant of greater than 2. The silsesquioxane dielectric film is advantageously prepared by curing oligomers having alkyl(methyl) and/or alkyl(methyl) pendant groups. The invention also embraces a process for making an organic FET comprising providing a substrate suitable for an organic FET; applying a liquid-phase solution of silsesquioxane precursors over the surface of the substrate; and curing the solution to form a silsesquioxane active dielectric layer. The organic FET thus produced has a high-dielectric, silsesquioxane film with a dielectric constant of greater than about 2, and advantageously, the substrate comprises an indium-tin oxide coated plastic substrate.
1. A process for making an organic FET comprising:
providing a substrate suitable for an organic FET;
applying a liquid-phase solution including at least one silsesquioxane precursor over the surface of the substrate, wherein said at least one silsesquioxane precursor has phenyl, methyl or dimethyl pendant groups; and
curing the solution to form a dielectric film of silsesquioxanes, said film having a dielectric constant of at least about 2.
2. The process of claim 1 , in which the step of curing comprises heating the substrate and solution to a temperature of less than 150° C.
3. The process of claim 1 , further comprising a step of cleaning the substrate before the solution of silsesquioxane precursors is applied.
4. The process of claim 3 , in which the step of cleaning is achieved by rinsing with acetone, methanol, or de-ionized water.
5. The process of claim 3 , in which the step of cleaning is achieved by reactive ion etching a surface of the substrate with oxygen plasma.
6. The process of claim 1 , in which the step of applying the liquid-phase solution comprises spin-casting.
7. The process of claim 1 , wherein said at least one silsesquioxane precursor has phenyl pendant groups.
8. The process of claim 1 , wherein said at least one silsesquioxane precursor has methyl pendant groups.
9. The process of claim 1 , wherein said at least one silsesquioxane precursor has dimethyl pendant groups.
10. The process of claim 1 , wherein said at least one silsesquioxane precursor is an alkyl(methyl)phenyl oligomer.
11. A process for making an organic FET, comprising:
providing a substrate suitable for an organic FET;
applying a liquid-phase solution including at least one silsesquioxane precursor over the surface of the substrate; and
curing the solution to form a dielectric film of silsesquioxanes, said film having a dielectric constant of at least about 2, wherein said substrate is coated with indium tin oxide.
12. The process of claim 1 , wherein said substrate comprises polyethylene terphthalate.
13. A process for making an organic FET, comprising:
providing a substrate suitable for an organic FET;
applying a liquid-phase solution including at least one silsesquioxane precursor over the surface of the substrate;
curing the solution to form a dielectric film of silsesquioxanes, said film having a dielectric constant of at least about 2; and
treating said high-dielectric constant film with a silane-reagent.
14. The process of claim 13 , wherein said silane reagent is selected from the group X—Si(OR 1 ) m (R 2 ) n , where the values for m and n are from 0 to 3 and m+n=3; R 1 is an alkyl group having from 1 to 6 carbon atoms; R 2 is an alkyl group having from 1 to 16 carbon atoms or an halogen group; and X is a substituent selected from a substituted or unsubstituted aryl, F 3 C(F 2 C) 9 CH 2 —, the group NH(Si)(CH 3 ) 3 ; and a saturated or unsaturated alkyl or alkoxycarbonyl having from 6 to 20 carbon atoms.
15. The process of claim 13 , wherein said silane reagent is selected from F 3 C(F 2 C) 9 CH 2 —Si(OCH 3 ) 3 ; C 8 H 17 Si(OCH 3 )(CH 3 ) 2 ; C 6 H 5 Si(OCH 3 ) 3 ; C 18 H 37 Si(OCH 3 ) 3 ; CH 2 CH—C(O)—O—(CH 2 ) 3 Si(OCH 3 )(CH 3 ) 2 ; F 3 C(F 2 C) 9 —Si(Cl) 3 ; Cl—CH 4 SiCl 2 CH 3 ; and (CH 3 ) 3 SiNHSi(CH 3 ) 3 .