Research About Analytical Techniques Of Trace Impurities Of The High-purity Hydrofluoric Acid And Tetramethylammonium Hydroxide

Process-chemicals are one of key basic chemical materials. They are mainly usedin the fabrication process of integrated circuit and discrete device which is used forchip cleaning, corrosion, and wafer cleaning. The main content of this paper is how tobuild a reliable analytical technique which is suitable for detecting trace anions,arsenic, metal ions in high-purity hydrofluoric acid and trace methanol, metal ions inhigh-purity tetramethyl ammonium hydroxide.The main difficulty of trace impurities analysis in the process-chemicals is thesubstrate concentration is too high and the test ion concentration is too low. For thedetection of trace anions in high-purity hydrofluoric acid, this paper firstlyinvestigated the effect of numbers of evaporation, state of evaporation, and salt on theremoval of matrix fluoride ions and the recovery of ions to be analyzed.50%concentration （wt%） hydrofluoric acid sample was evaporated consecutively threetimes without salt, then the residual liquid was injected into ion chromatography todetermine the content of phosphate, sulfate ion. The phosphate and sulfate ionsmethod detection limits （DLs） were0.4mg/kg,0.3mg/kg, respectively; recoverieswere90.1%and104%; relative standard deviation （RSD）, respectively,7.67%,9.20%.For the detection of trace arsenic in high-purity hydrofluoric acid, this paperfirstly applied salt oxidation method to remove the effect of matrix F^-, and usedhydride generation atomic fluorescence spectrometry （HG-AFS） to determine the Asconcentration. And it investigated the effect of oxidant ratio, salt, concentrations ofhydrochloric acid and reducing agent. On the condition of oxidizer （HCl：HNO₃=1:4）and salt,50%concentration （wt%） hydrofluoric acid sample was evaporatedconsecutively three times, then the residual liquid was reduced to be AsH3under theconditions of10%hydrochloric acid medium,20g/L thiourea,15min reaction time,10%hydrochloric acid carrier and20g/L of KBH₄. The arsenic DLs was0.07μg/kg;recovery was95.1%and104%; RSD was8.65%.The detection of residual methanol in tetramethyl ammonium hydroxide firstlyapplied headspace gas chromatography. This paper investigated the effect ofheadspace equilibrium temperature, equilibrium time, sample volume, TMAH matrixon the determination of residual methanol.5ml5%（wt%）TMAH was loaded in a 20ml headspace vial, and was analyzed at80℃headspace equilibrium temperaturefor30min. The standard curve of this method is suitable for the range of10³00mg/kg for the methanol; the recovery was99.6%, RSD was2.16%.Considering the polyatomic interferences in the detection of trace metal ions inthe high-purity hydrofluoric acid and tetramethyl ammonium hydroxide, InductivelyCouple Plasma Mass Spectrometry （ICP-MS） with the technology of dynamicreaction cell （DRC） was used. This paper investigated the mode selection of eachmetal ion. The DLs of metal ions for hydrofluoric acid and tetramethyl ammoniumhydroxide were0.05³ng/kg，0.1⁴.1ng/kg; recoveries were91%¹16%,92%to114%; RSD were1.3%to4.1%,1.5%to4.7%, respectively.