Chapter 4 - Particle Removal by Surfactants During Semiconductor Cleaning

Abstract

Particle removal during semiconductor processing is very crucial to meet the requirements of device reliability and yield. Several process steps are involved during semiconductor manufacturing, and cleaning steps are necessary before and after each processing step to make the wafer surface ready for the next process. As wafers may have different kinds of surfaces and particulate contaminants, the cleaning should be carefully optimized to provide the necessary physical forces and/or chemical forces. In this chapter, two major semiconductor processing steps are discussed for the application of surfactants in removing particles: wafer cleaning and PCMP (post–chemical mechanical planarization) cleaning. There are several issues or challenges to remove the particles from these processing steps. Surfactants play a critical role in preventing the redeposition of the particles during the cleaning process by modifying surfaces to have repulsive interaction forces between particles and wafer surfaces. Some typical surfactants used for the semiconductor cleaning process and their characteristics are discussed. Various mechanisms involved in particle removal by surfactants are explained. They also play an important role in Si wafer cleaning in controlling the etch rates by adsorbing on the wafer surface. A PCMP cleaning is necessary to remove the slurry particles attached to the different substrates (such as dielectrics, metals, III–V materials) after the CMP process. These particles are removed by adding suitable surfactants to the cleaning solutions. The role of surfactants in particle removal depends on the type of substrate. A variety of surfactants used for the PCMP cleaning process are also discussed.