Laser isotope purification of lead for use in semiconductor chip interconnects

Abstract

Lead, used throughout the electronics industries, typically contains small amounts of radioactive /sup 210/Pb (a daughter product of the planet's ubiquitous /sup 238/U) whose /sup 210/Po daughter emits an /spl alpha/-particle that is known to cause soft errors in electronic circuits. The /sup 210/Pb is not separable by chemical means. This paper describes the generic Atomic Vapor Laser Isotope Separation (AVLIS) process developed at the Lawrence Livermore National Laboratory (LLNL) over the last 20 years, with particular emphasis on recent efforts to develop the process physics and component technologies required to remove the offending /sup 210/Pb using lasers. We have constructed a developmental facility that includes a process laser development area and a test bed for the vaporizer and ion and product collectors. We will be testing much of the equipment and demonstrating pilot-scale AVLIS on a surrogate material later this year. Detection of the very low alpha emission even from commercially available low-alpha lead is challenging. LLNL's detection capabilities will be described. The goal of the development of lead purification technology is to demonstrate the capability in FY97, and to deploy a production machine capable of up to several MT/y of isotopically purified material, possibly beginning in FY98.