Fabrication Of A Nonwoven Polishing Pad For The Polishing Of Silicon Wafers Using Polyethylene Terephthalate, Polypropylene And Polyvinyl Alcohol Fibers

Silicon wafers are used to produce circuits in the electronic industry. The wafers go through a number of preparation stages before the circuits are drawn on the wafers and one of the stages includes the polishing stage. This polishing stage uses specially designed polishing pads. Pads are usually made of polyester, polyurethane, fluorine or wool. The substrate can either be woven or nonwoven where the woven are used for heavy polishing of wafers and are characterized by the low porosity. The foam based type can be used to produce the softer materials along with the nonwoven materials. The successful removal of used slurry and wafer particles from the pad-wafer interface will depend on the ability of the slurry to escape. The methods for producing current pads include the foam method electro-spinning and colloidal production methods. Some pads include embedded particles such as halite, which can be dissolved during their use to create the porous structure. The project aims to develop a nonwoven polishing pad that can be used to polish silicon wafers using a cheaper method. The materials used were polyester, polypropylene fibres and polyvinyl alcohol fibres. Polyvinyl alcohol fibers is a water-soluble fibre and can be used to create voids in a matrix by dissolving when it comes into contact with water. The solubility of the polyvinyl alcohol fibers is due to the high number hydroxyl groups in the polymer. Polyester is a fibre with high tenacity and good abrasion resistance. Pores in this pad will be formed by dissolving polyvinyl alcohol fibers fibres. Samples were produced using a carding machine for web laying purposes and the resulting cross-lapped web to produce a web with a density of100g/m2before the web was superimposed to form fabrics with the required density. The densities of the fabrics to be used in the experiment were to be the300g/m2,500g/m2and750g/m2. After superimposing, the fabrics the samples were passed through a needle-punching machine that was running at30hz. Samples were then heated to improve the strength retention during the removal of polyvinyl alcohol fibers. The best sample was selected from the various samples that were produced and further treated to prepare them for polishing. Using the air permeability, count, tensile strength and elasticity the best pad was selected for polishing of samples. The500g/m2samples were chosen for polishing as they showed a balance in their properties.