Frederick William Kern

Ultrasonic Cleaning of Surfaces: An Overview

Removal of submicron particles from silicon-wafers presents an enormous challenge to the semiconductor industry. Ultrasonic cleaning is an established method for removing micron-size microcontaminants or larger from hard surfaces. This paper presents an overview of the sonic cleaning research as applied to microcontamination control. The paper also presents new recent results on submicron particle removal.

A Fluid Dynamic Study of a Microcontaminant Particles Removal Process

Flow visualization techniques are used to study microcontaminant particles removal using drag and centrifugal forces (wafer rinsing). This removal process is an effective and commonly used method in the semiconductor industry. Understanding the flowfield around the rotating wafers is essential in determining the effectiveness and efficiency of the process. Flow visualization is used to observe the effect of rotational speed, jet flow rate and nozzle type on the flow pattern on the wafers. Optical and novel chemical flow visualization techniques are used. The qualitative and quantitative results show that the rotating wafers were completely covered with a water-film (that provides the drag force) only at certain values of the governing parameters. An empirical correlation between the water-film coverage and the operating parameters is introduced. A three-dimensional turbulent time-dependent prediction procedure for swirling flows is used to predict the flow around the wafers. Predictions of the trajectories of the water droplets issued from a peripheral jet into the flowfield between two rotating disks are also performed and the results presented.

Metal Removal by Wafer Spin Cleaning Process with Advanced Chemical Distribution System

In this report we studied the single wafer spin cleaning system. We found that spin cleaning efficiency increases as the flux of chemical is increased, as the cleaning time was extended. From the metal removal test, we found that we can greatly reduce both cleaning time and chemical consumption at the same time as compare to batch process. Furthermore, we found that spin cleaning efficiency is dependant on a combination of the two parameters, chemical flux and cleaning time. We have optimized the proper nozzle position for complete coverage of the wafer surface by analyzing the fluid dynamics of the liquid on the wafer surface during spin treatment.