Color inhibitor for quaternary ammonium hydroxide in non-aqueous solvent

1. A composition comprising:

a quaternary onium hydroxide in a non-aqueous solvent, wherein the quaternary onium hydroxide has a concentration in the range from about 20% by weight to about 50% by weight of the composition;

imidazolidine-2,4-dione, wherein the imidazolidine-2,4-dione has a concentration in the range from about 10 to about 5000 parts per million of the composition, and

a water content of less than 0.5% by weight of the composition by Karl Fischer titration.

2. The composition of claim 1 wherein the quaternary onium hydroxide comprises an onium ion having a general formula (II):

wherein in formula (II), A is a nitrogen or phosphorus atom, R 1 , R 2 , R 3 and R 4 are each independently a branched or unbranched alkyl group containing from 1 to about 20 carbon atoms, a branched or unbranched hydroxyalkyl or an alkoxyalkyl group containing from 1 to about 20 carbon atoms, substituted or unsubstituted aryl groups or hydroxyaryl groups containing from 6 to 18 ring carbon atoms, when substituted, said substitution comprises one or more substituent selected from any of the foregoing alkyl, hydroxyalkyl or alkoxyalkyl groups, or R 1 and R 2 or R 3 together with A may form a heterocyclic group provided that if the heterocyclic group contains a C=A group, R 3 is the second bond.

3. The composition of claim 2 wherein the quaternary onium hydroxide in formula (II) is a quaternary ammonium hydroxide.

4. The composition of claim 2 wherein at least one of the alkyl groups in formula (II) contains 3 or more carbon atoms.

5. The composition of claim 1 wherein the non-aqueous solvent comprises one or more selected from propylene glycol (PG), butylene glycol (BG), ethylene glycol (EG), triethylene glycol (TEG), formamide (FA), and glycerol (GLY).