Collaborative Research: ECLIPSE-CHIPS: Avoiding Contamination by Controlling Charging and Transport of Particles in Plasmas under Modulation and Afterglow Conditions

University Of Iowa, Iowa City IA

Investigators

Abstract

This award is made in response to Dear Colleague Letter 24-130, as part of the ECosystem for Leading Innovation in Plasma Science and Engineering (ECLIPSE) interdisciplinary program. In semiconductor manufacturing, small solid particles, such as dust particles, are a source of contamination. Microchips made from silicon wafers are ruined when a particle lands on its surface during one of the manufacturing steps. Many of these steps involve a plasma to etch or deposit thin films. During these steps, small particles of nanometer or micron size can flake from chamber walls, or grow in the plasma itself, and then fall to the wafer and contaminate it. In this project, a recently invented method of mitigating this contamination is explored to gain an understanding of the physical processes involved towards developing even better mitigation methods. These methods involve applying an electric charge to the particles before they fall on the wafer, and using electric forces to lift and eliminate the particles before they contaminate the wafer. This project includes K12 outreach, course development, and training of both undergraduate and graduate students. This collaborative research effort by the University of Iowa and Appalachian State University focuses on the plasma afterglow, which is the condition lasting a few milliseconds after turning off the radio-frequency electrical power that had sustained the plasma. It is during an afterglow that particles can fall to a wafer and contaminate it. An afterglow occurs also during the off-time in modulated-power operation, which is commonly used in manufacturing. During the afterglow, the particle’s electric charge changes rapidly. It was recently discovered that the residual charge can be controlled by applying voltages to electrodes in the plasma chamber during the afterglow, thereby allowing an electric force to lift the particles and reduce the number that fall to the wafer. In this project, understanding of processes in the afterglow will be expanded by performing experiments and simulations. In the experiments, particle charge and movement during modulated plasma operation will be measured by video microscopy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.