Novel one-step aqueous solutions to replace pregate oxide cleans

Abstract

We have developed a number of novel solutions to use for one-step pregate oxide cleaning; they are based on tetraalkylammonium hydroxides of varying alkyl chain lengths, namely tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH). We added these surfactants together with ethylenediaminetetraacetic acid (EDTA) into the RCA SC-1 cleaning solution to enhance the efficiency of cleaning. With the exception of the TBAH solution, the cleaning efficiency of these solutions toward particles was 4%-7% higher than that of the conventional RCA method. Our cleaning methods have better efficiency toward the removal of Fe, Na, Ca, Cu, and Mn contaminants. We found that the conventional RCA method results in 10(9)-10(10) atoms/cm(2) of Cu and Mn after cleaning. The electrical breakdown field of MOS capacitors was enhanced when using the new cleaning method. The literature model for surface adsorption and double-layer formation explains the cleaning behavior of the tetraalkylammonium ion-containing solutions. The removal of surface particles and metallic contaminants and the degree of surface roughness agree with the model's predictions. We believe that the best solution for use in one-step cleaning-one that comprises EDTA and TPAH-can replace the traditional RCA cleaning method. This new method has great potential for pregate oxide cleaning because it has the advantages of faster cycle times, lower costs, and greater efficiency.