The invention provides diketopyrrolopyrrole (DPP)
quaternary ammonium salt compounds, which are disclosed as the
structural formula in the specification, wherein N-R2 is disclosed in the specification, and R1 is Cl, Br, F, I, CF3, CN, tBu, CH3, H, 2,6-F2, NH2, NO2, OH, CHO, COOH, 3,4-Cl2, or 3-F-5-CH3; n is a whole number
ranging from 1 to 18; and x is Br, F, Cl, I, HSO3, HSO4, HCO3, CF3CO3, H2PO4, OTf, OTs or BF4. The compounds have stable structure, and can not cause the phenomena of
coating fogging and the like at higher temperature; the big conjugate pi bond in the compounds can be adsorbed on the
copper layer surface more easily, and the N center can inhibit the deposition of
copper ions more efficiently; and thus, the compounds can be used for leveling as an
electroplating leveling additive.