Papers by Author: Steven Verhaverbeke

Abstract: In thin film photovoltaic silicon stacks, the sun facing contact needs to be transparent and textured. Typically transparent metal oxides are used for this purpose. When using sputtered ZnO as the transparent conducting contact typically an acid etch is used to texture etch the surface. This texturing enables light trapping in the cell and greatly enhances the photoresponse. Traditionally dilute HCl has been used for this purpose. In this paper we present the work on a novel etchant for this purpose consisting of HNO₃ and Acetic Acid. This greatly enhances the texturing and hence the light trapping in the cell.

Abstract: As device features scale down to 90nm and Cu/low-k films are employed for back end interconnects, post etch and ash residue cleaning becomes increasingly challenging due to the higher aspect ratio of the features, tighter CD control requirements, sensitivity of the low-k films, and the requirement for high wet etch selectivity between CuxO and Cu. Traditional solvent based cleaning in wet benches has additional issues such as wafer cross-contamination and high disposal cost [1, 2]. We have developed a novel aqueous solution (AQ) based single wafer cleaning process to address these challenges. The results of physical characterization, process integration electrical data, and process integration reliability data such as electromigration (EM) and stress migration data are presented. The main conclusions can be summarized as follows: (1) The single wafer cleaning process developed on the Oasis™ system can clean post etch residues and simultaneously clean the wafer front side and backside metallic contaminants; (2) In terms CuxO and Cu wet etch selectivity, CD loss control, the Oasis™ aqueous single wafer clean process is superior to the bench solvent cleaning process; (3)The Oasis aqueous cleaning process shows no undercut below etchstop due to the very low Cu etch amount in one cleaning pass, therefore the electromigration and stress migration performance of the aqueous Oasis processed wafers is clearly better than that of the solvent bench processed wafers.