Electrochemical Corrosion Inhibition System for Photoresist Stripper for New Copper FPD Manufacturing
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0990-B08-26
Electrochemical Corrosion Inhibition System for Photoresist Stripper for New Copper FPD Manufacturing Seiji Inaoka1, and Sang In Kim2 1 Mallinckrodt Baker, Tyco Healthcare, 1904 JT Baker Way, Bldg 122, Phillipsburg, NJ, 08865 2 Mallinckrodt Baker, Tyco Healthcare, Pyeongtaek, Korea, Republic of
ABSTRACT Development of photoresist stripper with copper compatibility is challenging as conventional corrosion inhibitors do not protect the metal as expected. Copper corrosion inhibition mechanism of newly developed photoresist stripper is proposed that significantly reduces copper corrosion with small amount of corrosion inhibitor. INTRODUCTION New FPD devices with new Cu or Cu-alloy technology are being developed with the expectation to take advantage of lower electrical resistance of Cu compared to conventional Al. The lower resistance of metal is particularly beneficial when the display device becomes larger in size or higher in resolution. Conventional bulk photoresist strippers were developed to be compatible with the conventional metal (Al or Al-alloy) and are not fully compatible with Cu or Cu-alloy. Copper corrosion is described as an electro-chemical oxidation of Cu [1], and its corrosion rate is affected by the solubility of Cu oxide that formed on surface. Solubility of Cu oxide is affected by pH of the solution, with higher solubility in acidic and basic condition while the solubility is low in neutral pH [2]. Conventional photoresist stripper is based on alkaline compound (such as organic amines) that would attack Novolac resin to dissolve the photo-resist film. In order to lower the Cu corrosion rate while keeping the high pH, it is necessary to reduce either formation of Cu oxide, or its solubility. While triazole or phenolic compounds are widely used as corrosion inhibitor for Cu, its corrosion inhibition performance is not optimized in non-aqueous basic circumstances. A new chemistry that effectively reduces Cu corrosion has been desired.
EXPERIMENT The base photoresist stripper composition was used throughout the experiment. The composition is non-aqueous and has polar organic solvents and alkanolamine. The type of alkanolamine, as well as its amount in the composition was comparable to that of conventional (not Cu compatible) photoresist stripper. The experimental solutions were prepared by adding small amount of additives to the base stripper composition. The Components A and B are organic compounds that may contain C, H, O and N. Triazole and Phenolic additives were also tested for comparison. Blanket Cu wafers (~4000≈ thickness) were used to determine etch rate by processing with each composition. The wafer was immersed in the experimental composition for 15 minutes at 70˚C, with stirring rate of 200rpm. Cu layer thickness was measured before and after the processing by ResMap 4-point probe (Creative Design Engineering). Surface potential of Cu in experimental solutions was measured with respect to a reference Ag/AgCl electrodes (Gamry Instruments, Inc.) using conventional multimeter.
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